The Morphology Of Structure
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The Morphology of Structure
THE MORPHOLOGY OF STRUCTURES * by Vinzenz F.J. Sedlak Associate Professor and Director, Lightweight Structures Research Unit, School of Architecture, The University of New South Wales, Sydney Australia * updated in October 2003 from a published paper: SEDLAK, Vinzenz "The Morphology of Structure", Proceedings LSA’86 First International Conference on Lightweight Structures in Architecture, University of NSW, 1986 pp1164-1187
INTRODUCTION STRUCTURE: in the broadest sense any material object that is able to sustain loads (forces) may be called a structure (3, p.11). This includes objects in nature such as land and water, animals and plants, in the universe such as stars, planets, solar systems and galaxies, as well as man-made objects such as buildings, bridges, vehicles, furniture, appliances etc. Accoring to this definition principle criteria of a structure are therefore:
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the OBJECT, defined by its SHAPE and the MATERIAL it is made of, and the LOADING the object is subjected to. The shape of an object is its visible representation: it is what we see. The material of an object is often not visible at first view and may reveal itself only through its colour and surface texture. By touching an object texture and weight (loading) of its material can be experienced. In order to understand structure in its essence and its totality we must first consider shape, material and loading in turn and than combine them to form an integrated whole: structure. This process is described in subsequent sections of this paper. We will be concentrating on building structure, but while looking at buildings and the structures that make them stand up we should always be aware that buildings form only one part of the world of structure. In order to be universally valid our investigation must address itself to the much wider context of structure: much can be gained and learned from observing and understanding the basic principles which govern structure in nature and its organisation in other technological fields often leading to insight and subsequent improvement of structures utilised in building. In order to obtain such insight and then to be able to draw parallels with buildings we must first look out for those basic properties and attributes of shape, material, loading and structure which are common to a wide range of different structures and subsequently identify them. For this analytical process to occur and for the outcome to be understood we must first agree on a common terminology. That is a clearly identifiable, recurring set of definitions of those recognisable properties and attributes which are common and valid to all structures.
TERMINOLOGY BUILDING STRUCTURE, a specific type of structure, encloses and protects space from drastic changes in shape while resisting loads exerted on it by the elements of nature (wind, snow and earthquake), by the gravitational pull of the earth and by other influences such as temperature. That space usually accommodates people, animals, plants and goods. BUILDING is a part of the built environment which is relatively independent in its function and appearance. STRUCTURE is that part of a building that provides the support function in order to safeguard the overall functioning of the building. It consists of a STRUCTURAL CONTINUUM, a BOUNDARY which borders the continuum and SUPPORTS. Supports can be placed within the continuum or at the boundary. Depending on the complexity of make-up, the structure can be an ELEMENT STRUCTURE, a UNIT STRUCTURE, an AGGREGATE STRUCTURE or a COMPOSITE STRUCTURE. The CONTINUUM is that part of a structure that encloses (interior) space and is directly subjected to LOADING by external loads. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (2 of 51)28/08/2009 12:08:43
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LOADING of the continuum creates FORCES. Forces cause STRESSES within the elements of the structure. The continuum responds to loading by stressing. Stresses are channelled through the object and through its elements into the structural MATERIAL which reacts to stressing with SHAPE-CHANGE. At the SUPPORTS these stresses are collected and channelled into forces which are then transmitted through the supports to the ground or to another supporting medium where they are resisted by opposite forces activated by the supporting medium. In the case of an aggregate and composite structure the continuum is bordered by a BOUNDARY. The boundary makes up the extreme limits of the continuum and may consist of one or more structure elements. The STRUCTURE SYSTEM is the abstract model of that structure. A STRUCTURE ELEMENT is the smallest part of a structure which when connected to other structure elements makes up a continuum, a boundary or a support of that structure. (an example for an element in a continuum is a single beam in a series of floor beams). According to the make-up of the structure we differentiate between the following levels:
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ELEMENT STRUCTURE is a structure that consists of one structure element only. (eg. a single board providing a small bridge between two parts of a building; a single rope for lifting goods). Element structure consists of an element which is simultaneously its continuum, boundary and its support(s). UNIT STRUCTURE is an assembly of structure elements into an identifiable whole. (eg. a brick pier made from bricks, or a wall, or a floor, or a roof). Unit structure consists of a number of elements which make-up the its continuum, boundary and support(s). Usually a unit structure is made up of several different elements (an example is a timber floor unit using two different elements: bearers and boards). AGGREGATE STRUCTURE is any assembly of structure units. (eg. a house made up of walls, floors and roof). Aggregate structure consists of a continuum made up of structure units, a boundary and supports. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (4 of 51)28/08/2009 12:08:43
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COMPOSITE STRUCTURE is any assembly of identical or different aggregate structures (eg. a cluster of houses). Composite structure consists of several continua, each of which may be bordered by a boundary, a composite boundary encloses these continua, supports may be arranged at composite or at aggregate boundaries or, alternatively, continua may be directly supported.
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Additionally we define the following qualitative attributes: SUPPORT-FUNCTION is the very purpose of structure namely to accept forces and moments through loads, to transform, transport, and to transmit them (to the ground). file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (6 of 51)28/08/2009 12:08:43
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STRUCTURAL QUALITY is the integration of those essential properties of a structural system that are required for it to fulfil it's support-function. STRUCTURAL (SUPPORTING) BEHAVIOUR is the expression of structural quality of a structure system for a set of given loads and other influences. Structural quality is determined at the conceptual design stage while structural behaviour is principally determined at the engineering design phase of structural design. Consideration of structural quality during design of a building requires knowledge of structure systems. For the architect, knowledge of structure systems is essential as it enables him to conduct the conceptual design of a building in a comprehensive and adequate manner. Structural behaviour involves determination of loads and their intensities and choice of materials for construction. This is essentially the domain of the structural engineer. At a more general level, however, a basic understanding of structural behaviour is required from the architect in order to become an active participant in the structural design process rather than a passive bystander. Quality and behaviour of a structure forming a building cannot be isolated from each other but are intimately connected. Therefore, co-operation of the architect and engineer-designers is imperative during the conceptual design stage so that a building structure emerges, that is both, in tune with the overall architectural concept and safe and economical to construct and to use.
STRUCTURE SYSTEMS AND BUILDING DESIGN The "morphological" approach described in the following has proven to be a convenient analytical method to introduce structural systems while at the same time developing a closer understanding of the "structure" of structures and their many possible variations. At a subsequent stage, the morphological approach can also be utilised for design synthesis: the systematic, conceptual design of structure systems (2). In the present context, the morphological approach is an analytical tool that assists in the conceptual understanding of structural systems. As such it is a means to an end and as any such tool dependent on understanding of its operation and use. Prerequisite for it's use is systematic and rigorous application of logical steps. For practical purposes, the morphology can also be used to produce an organized OVERVIEW OF STRUCTURE SYSTEMS as is shown in the latter part of this paper. Morphological studies should be accompanied by the following: STAGE 1: Observation of buildings and objects (man-made and natural). The aim in observing buildings, structures and objects is immediate, conscious perception of the natural and built environments and development of the ability to recognise structural systems by deduction from the appearance of a particular building/object. During this stage photographs and sketches are important aids as well as information on a range of previous structural solutions for similar applications. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (7 of 51)28/08/2009 12:08:43
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STAGE 2: Investigation of principle types of structural systems The aim is qualitative recognition of principal structural behaviour of a chosen system -its structural quality- based on the study of equilibrium, and development of the student's ability to recognise and to understand structural quality in its essence. Qualitative knowledge of principle load/force distribution ie. internal forces and torques/moments (stresses) within structural elements in response to loading is required. This stage normally concludes the extent of structural knowledge required from the architect and, shared with the engineer, it becomes the stepping stone for the next stage, which is normally conducted by the engineer: STAGE 3: Confrontation with actual structural systems The aim is quantitative determination of essential values for load-bearing, stressing, and shape-change of a structure system based on studies of equilibrium and changes in shape dependent on types of loading. Subsequent aim is the development of the student's capability to assess the influences of parameter changes on stressing and shape-changing of structural systems. At this stage diagrams which illustrate quantitative changes in stress levels and deformations in response to changes in load intensity, and loading type and cross-sectional/ material properties are required.
THE MORPHOLOGY OF STRUCTURE According to Fritz Zwicky (1), a Swiss/American scientist and "inventor" of the morphological method: "Morphology is the study of the basic pattern of things". The morphological approach directed at a particular field of study helps to discover the intrinsic "structure" of this field in its totality. This is done by observing and analysing a representative range of existing samples in a systematic, logical and reproducible manner: The first step is to establish the field of investigation, in our case STRUCTURE. The second step is to identify a recurring set of recognisable principle attributes called PARAMETERS and the range of their possible VARIATIONS by observation and analysis of a representative range of existing examples (eg. buildings). The most convenient method to establish and display a morphology is a MORPHOLOGICAL TABLE, which is a matrix where parameters are listed in order of hierarchy in a column to the left and their corresponding variations in rows to the right. PARAMETERS
VARIATIONS
The third step is to check the validity of established parameters and variations by identification of an arbitrary range of new samples. This is also known as the ANALYSIS FUNCTION of the morphology. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (8 of 51)28/08/2009 12:08:43
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The fourth step is to create an entire range of structures, including known and hitherto unknown structures, by selectively combining different variations from all parameters in a series of successive steps. This process is known as the SYNTHESIS FUNCTION of the morphology and as such utilised for creative development of structure systems during the conceptual design stage of a building. (this paper does not deal with the fourth step) MORPHOLOGICAL PARAMETERS AND THEIR VARIATIONS In previous investigations of STRUCTURE we identified principle attributes (PARAMETERS), namely OBJECT, (SHAPE, MATERIAL) and LOADING. In addition we established a number of SUB-PARAMETERS, namely those relating to SHAPE : namely ELEMENT, AGGREGATE and COMPOSITE and those relating to LOADING and STRUCTURE: namely CONTINUUM, STRESSING, BOUNDARY and SUPPORTS. We will now investigate how they relate to each other and show their VARIATIONS.
1.
SHAPE
(for background information on the following including a detailed analysis of shape ("form") see (8, p.14ff) and (9)) Macro- and Microcosms are composed of material objects: Each material object has a shape. Shape refers to: 1. 2. 3.
the outside appearance of the object it's interior if the object is hollow it's "structure" (structure in this context refers to the arrangement of elements or components which make up the shape)
SHAPE GENERATION Every object is characterised by the process through which it was created. Every object is in a state of change. Dynamic Shapes are objects whose shape varies rapidly (eg. waterfall, cloth). Static Shapes are objects whose shape varies only very slowly (eg. mountain, building). We are aware of the following: file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (9 of 51)28/08/2009 12:08:43
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SHAPE GENERATION PROCESSES Change of shapes in NON-LIVING NATURE (eg. the evolution of landmasses on earth by folding and faulting of the earths crust, by volcanic activity; erosion of rock, mountains) Evolutionary shape-changes in LIVING NATURE (eg. evolutionary development of species; growth and decay of microbes, plants, animals and man). Shape generation by HUMAN ACTIVITY (shaping, forming of materials for objects which serve man in this quest for dominance of his environment eg. tools, machines, buildings, vehicles). PERCEPTION AND CLASSIFICATION OF SHAPES Geometric description of most shapes is difficult, if not impossible, due to their complexity. Only the simpler, regular shapes can be readily described (eg. sphere, cone, cube). Objects in living nature are usually described by shape characteristics of a specific species. Other means of "capturing" the shape of objects are by documentation, eg. sketching and drawing photography or photogrammetry mechanical shape-measurement models Shapes, however, can be successfully described morphologically. THE SHAPE OF OBJECTS Every material object has a mass, a volume and a surface. Its PROPORTIONS are, therefore, three-dimensional. However, for the purpose of this study, a different definition of proportion is more practical. In order to facilitate theoretical considerations we define PROPORTIONS OF AN OBJECT as follows: An object that is relatively large in one dimension (length) and relatively small in both other dimensions (width and height) is termed ONE DIMENSIONAL. It extends into a linear direction, it is LINEAR. An object that is relatively large in two dimensions (length and width) and relatively small in the third is termed TWO-DIMENSIONAL. It extends into a surface (area), it is SURFACE. An object that is relatively large in all three dimensions (length, width and height), or if little difference can be seen between all dimensions of the object, is termed THREE-DIMENSIONAL. It extends into three-dimensional space, it is SPATIAL. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (10 of 51)28/08/2009 12:08:43
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A three dimensional object that is infinitely small so that its proportions are not visible to the eye is termed POINT. Point implies that there is no visible extension in any dimension. A relatively very small spatial object that is in an assembly with other, much larger objects is often idealised and called POINT. Transition between one-, two- and three-dimensional proportions is often not clear cut: a one-dimensional object can grow into a two-dimensional one by extension of the second dimension or vice-versa. a two-dimensional object can grow into a three-dimensional one by extension of the third dimension or vice-versa. Objects which are of different size, but of similar proportions do not change their proportion. CURVATURE OF OBJECTS Apart from proportion, curvature of an object is a major parameter. LINEAR OBJECTS can be straight, angular or curved in one plane, or angular or curved in space
SURFACE OBJECTS can be plane, single curved, folded and double curved (domical = synclastic or saddle = anticlastic).
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SURFACE OBJECTS can have positive peaks or negative peaks (navel), folds or undulations.
SPATIAL OBJECTS are identified by the surface(s) which border(s) them. The surface can be a continuous unit (sphere) or a composite one: pointed, with edges and corners, faceted or with undulations. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (12 of 51)28/08/2009 12:08:43
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COMPOSITE OBJECTS Any one-, two- or three-dimensional object can be combined with other objects. Any object can also be composed of one-, two- or three-dimensional elements
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ELEMENT OBJECTS An object that is composed of a number of elements is termed a UNIT OBJECT. Each one of its elements may be one-, two- or threedimensional.
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An object that is composed of more than one unit object is called an AGGREGATE OBJECT. Each one of its units may be one-, two- or three-dimensional. An object that is an assembly of aggregate objects is termed COMPOSITE OBJECT. These aggregates may be one-, two- or three-dimensional. EXAMPLES Hammer Overall 1-D UNIT Elements1-D and 3-D Chair Overall 3-D UNIT Elements2-D and 3-D Balloon Overall 3-D UNIT Elements1-D, 2-D and 3-D Block of Overall 3-D UNIT Stones Elements1-D, 2-D and 3-D Aeroplane Overall 3-D AGGREGATE Units 2-D and 1-D Elements2-D and 1-D Multistorey Overall 3-D AGGREGATE Building Units 3-D Elements 2-D and 1-D We can now summarize the criteria (parameters) pertaining to SHAPE -which are valid for all shapes of objects without exception- in form of a MORPHOLOGICAL TABLE: PARAMETER
VARIATIONS
TYPE OF SHAPE
positive (proud) shape, negative (cavity) shape
TYPE OF OBJECT
particle, element, unit, aggregate, composite, macro
SIZE OF OBJECT
very small (molecular), small, medium, large, very large (macro)
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PROPORTION OF OBJECT
non dimensional (point), one dimensional (linear), two dimensional (surface), three dimensional (space)
CURVATURE OF THE OBJECT RELATED TO ITS PROPORTION LINEAR straight, angular in one plane, curved in one plane, angular in space, curved in space SURFACE
plane, folded, single curved, domical(double) curved, saddle (double) curved
SPATIAL
folded (edged), rounded (relates to surface)
TYPE OF SURFACE (OBJECT) SHAPE OF SURFACE
unit, composite smooth (unit), peaked (composite), folded (composite), undulated (composite)
TYPE OF PEAKS
positive (pointed), negative (navel)
TYPE OF FOLDS (UNDULATIONS)
straight, curved
Having analysed the morphology of shape we can now consider the next principle parameter:
2.
MATERIAL
The ability of an object to sustain loading is dependent on two factors: it's SHAPE and the MATERIAL it is made of. Objects can be made from different material substances: these can be gaseous, liquid, plastic, granular or solid, in various combinations and densities. Transitions between these states are often undefined, such as between solid and liquid states of ductile materials such as metal or water(ice). All materials can be subdivided into two groups depending on their capacity to sustain loading (stresses) as well as on the magnitude of shape-change when elements made from these materials are loaded: file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (16 of 51)28/08/2009 12:08:43
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Materials which display small shape-changes are called SHAPE-RESISTANT. Materials which display relatively large shape-changes are called NON-SHAPE RESISTANT. Solid materials are usually shape-resistant, while granulose, plastic, liquid and gaseous substances are usually non-shape-resistant. The majority of building materials are solid. Examples are timber, steel, concrete, masonry, plastics, glass, bricks etc. "Solid" materials are either RIGID or NON RIGID (flexible). Rigidity or "stiffness" of solid materials depends on their stress/deformation characteristic (eg. the magnitude of shape-change under a given loading) and also on the proportions of the element-object, it's "slenderness" (eg. for one-dimensional objects: thin and long against thick and short). Depending on the type of stress the material is subjected to we distinguish between tensile-, bending-, shear- or torsional stiffness. Depending on the relative permanence of shape-change in a solid material the stress/deformation characteristic of that material may either be called ELASTIC or PLASTIC. Elastic materials are those which deform under stress, but recover from this shape-change in time. Plastic materials are those which, when stressed, do not recover from shape changes but remain in a permanently deformed state. Depending on the time/deformation/failure characteristic of solid materials when under stress (eg. the degree of shape-change in relation to the duration of load application at failure) we distinguish between BRITTLE and DUCTILE materials.
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Rigid materials can resist AXIAL STRESSES such as compression and tension as well as NORMAL STRESSES such as shear and bending. Examples are steel in the form of rolled or cold formed section or plate, masonry, brick, concrete, timber and the range of products derived from them. Non-rigid (flexible) materials can resist mainly tensile stresses and to a lesser extent shear. Examples are steel in the form of wire, cable or thin sheet; cellulose, animal hair, plastic or glass in the form of fibre-rope or woven fabric. Granular, liquid and gaseous material substances are normally non-shape resistant they can, however, withstand loading (stresses) when they are subjected to uniform file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (18 of 51)28/08/2009 12:08:43
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pressure (eg. air in a balloon). Gases must be contained in enclosed spaces, liquids or granulates can be contained in open containers, when under the influence of gravity (eg. water in a container or in a lake, sand in a bag). Non-material substances such as electrical energy, magnetism and gravitational attraction and repulsion between masses can also transmit forces. Examples are atoms and solar systems.
3.
LOADING SYSTEMS
Loads, such as weight, wind, snow, earthquake, temperature, acting on a composite structure, such as a house, create stresses in an aggregate structure, such as a timber frame, which subsequently create stresses in its elements, such as posts, beams, studs etc., and these, in turn, create material stresses at a molecular level.
This system of external and internal forces is termed a LOADING SYSTEM. The presence of the loading system convert an object into a structure. We distinguish between the following LOADING SYSTEMS: file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (19 of 51)28/08/2009 12:08:43
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EXTERNAL and INTERNAL LOADS which can be applied as (idealised) point, line, surface or volumetric loads.
External forces are caused by loads (ACTIONS) which are resisted at the supports (REACTIONS).
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External and internal forces cause STRESSES within objects or elements.
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Element stresses cause stresses in minute material particles (MATERIAL STRESSES).
Stresses act in different directions depending on the load application and on the proportion of the object or element: STRESS DIRECTION. Stresses in objects or elements (OBJECT or ELEMENT STRESSES) may be directed: in one direction (MONOAXIAL), in two directions (BIAXIAL) or in three directions (TRIAXIAL). The following TYPES OF STRESSES occur and are accompanied by SHAPE-CHANGES: TENSION leading to stretching or elongation of the object or element; file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (23 of 51)28/08/2009 12:08:43
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COMPRESSION leading to shortening; BENDING leading to curving accompanied by compression on the concave side of the object/element and to tension on the convex side; TORSION leading to twisting of the object/element which is associated with circumferential necking object.
SHEAR leading to a local compression or indent on the object/element accompanied
by sliding along perpendicular planes of the element/
Object or element stresses are rarely of only one type (eg. tension only). Stressing of a component usually involves a range of composite stresses acting in different directions and with different intensities. Ref.(4) (sections 2.3 - 2.6) gives examples of the range of multi axial stressing of objects and elements.
4.
STRUCTURE SYSTEM
Under the influence of load an object, defined by its shape and material, becomes a STRUCTURE. In this study we are concerned with abstract models of structures: STRUCTURE SYSTEMS. Structure system may refer to ELEMENT STRUCTURE, UNIT STRUCTURE, AGGREGATE STRUCTURE or to COMPOSITE STRUCTURE.(we defined these types previously). The parameters used to describe the shape of an object are identical to the ones used to describe the shape of a structure system: PROPORTION and CURVATURE. We identify a STRUCTURE ELEMENT primarily through its PROPORTION and STIFFNESS regardless whether the element is part of either continuum, boundary or support . By morphological combination of four variations of proportion (point, linear, surface, spatial) with two variations for stiffness (rigid and non rigid or flexible) altogether seven useful element combinations result:
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POINT (stiffness does not apply) RIGID LINEAR NON-RIGID LINEAR
RIGID SURFACE NON RIGID SURFACE
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These are the known STRUCTURE ELEMENTS. Depending on their shape and stiffness, these elements can be subjected to different stresses acting in different stress directions. Structure elements are useful common identifiers when analysing or studying structure systems and their behaviour under load. Any structure system consists normally of at least three disticts components: a CONTINUUM (surface) which is bordered by a BOUNDARY with both, continuum and/or boundary requiring SUPPORT.
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Supports may be positioned:
EXTERNAL to the structure (suspended), PERIPHERAL at the boundary, INTERNAL within the continuum or in various COMBINATIONS.
Supports may be any of the following types: POINT RIGID LINEAR (beam, arch, truss or frame), NON-RIGID LINEAR (cable), RIGID SURFACE (wall, plate, slab or shell) or NON-RIGID SURFACE (membrane with sand or water filling).
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Finally, a most important consideration in the study of structure is stability. STABILITY refers to the ability of an element, unit or aggregate to limit shape-changes which are associated with loading to safe and (visually and practically) acceptable limits. It is the fundamental responsibility of the designer of structural systems to ensure stability of the proposed structure under all expected loading conditions. Unfortunately many architects do not possess adequate structural knowledge to resolve their designs in terms of stability and proposed buildings are often unstable under certain loads which the architect did not consider. In such cases it becomes the engineers task to correct these shortcomings. Models are convenient aids to stability studies and their use should be propagated during study and in professional practice. Stability is fundamental to all building design considerations and must forms part of the basic structural knowledge required by the architect. Depending on the type of structure element and structure system ADDITIONAL STABILISATION may be required. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (30 of 51)28/08/2009 12:08:43
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The following methods are possible: POSITIONING (re-arranging or adding) OF ELEMENTS (eg. bracing struts or cables, shear planes); STIFFENING OF CONNECTIONS between elements (RIGID JOINTS), APPLICATION OF ADDITIONAL LOAD/WEIGHT and/or PRESTRESS in the case of flexible structures (cable and membrane structures). The following types of stability occur:
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ELEMENT STABILITY refers to resistance of a slender, rigid structural element (eg. strut or slab/sheet) against buckling deformation, or to stability of a flexible cable by prestress or weight. UNIT STABILITY refers to stability of a structural unit (eg. post and beam system, linear cable system etc.) against falling over/larger deformations. Three basic methods are available for ensuring lateral stability of simple, linear assemblies: introduction of additional diagonal bracing, shear planes or rigid joints. AGGREGATE STABILITY refers to stability of a complete (three-dimensional) assembly. Lateral bracing, shear plans in walls and roofs are typical provisions for simple assemblies.
We can now summarise all parameters and their variations, those relating to MATERIAL, LOADING and STRUCTURE which we just discussed as well as SHAPE which we considered earlier in the combined MORPHOLOGICAL TABLE OF STRUCTURE.
MORPHOLOGICAL TABLE OF STRUCTURE PARAMETER
VARIATIONS
SHAPE: TYPE OF SHAPE
positive (proud) shape, negative (cavity) shape
TYPE OF OBJECT
particle, element, unit, aggregate, composite, macro
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SIZE OF OBJECT
very small (molecular), small, medium, large, very large (macro)
PROPORTION OF OBJECT
non dimensional (point), one dimensional (linear), two dimensional (surface), three dimensional (space)
CURVATURE OF THE OBJECT RELATED TO ITS PROPORTION LINEAR straight, angular in one plane, curved in one plane, angular in space, curved in space SURFACE plane, folded, single curved, domical(double) curved, saddle (double) curved SPATIAL folded (edged), rounded (relates to surface) TYPE OF SURFACE (OBJECT) SHAPE OF SURFACE
unit, composite smooth (unit), peaked (composite), folded (composite), undulated (composite)
TYPE OF PEAKS
positive (pointed), negative (navel)
TYPE OF FOLDS (UNDULATIONS)
straight, curved
MATERIAL: MATERIAL SUBSTANCE
solid, granular, plastic, liquid, gaseous
DEFORMATION CHARACTERISTIC
shape-resistant, non-shape resistant
MATERIAL TYPE
solids: such as timber, metals (steel, aluminium etc.), plastics, masonry and brickwork,concrete, glass, composites; gaseous: eg. air; liquids: eg. water, oil etc. and their combinations
LOADING SYSTEM: EXTERNAL LOADS
gravity(self-weight, dead-load), additionalweight of objects or persons (live-load), snow, wind
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,
earthquake, settlement, and their combinations
POSITION OF LOAD
point, line, surface, volumetric, and their combinations
INTERNAL LOADS
dimensional changes (temperature, lack of fit)
STRESSES
(loads within an object, an element or at element material level in response to external and/or internal loads) tension, compression, bending, shear, torsion, and their combinations as above, but applied to element tension, compression, shear, and their combinations on a molecular level
OBJECT ELEMENT MATERIAL DIRECTION OF STRESS
monoaxial (one-directional), biaxial (two-directional), triaxial (three-directional)
STRUCTURE SYSTEM: TYPE OF STRUCTURE
element, unit, aggregate, composite
PROPORTION OF STRUCTURE
linear, surface, spatial
IDENTIFICATION OF COMPONENT
continuum, boundary, support
CURVATURE OF COMPONENT
straight/plane, angular/folded, single curved, double domical curved, double saddle curved
PROPORTION OF ELEMENT
point, linear, surface, spatial
STIFFNESS OF ELEMENT
rigid, non rigid (flexible)
BOUNDARY/SUPPORT point, rigid linear, rigid solid, ELEMENT non rigid linear, non rigid surface, non rigid solid and combinations TYPE OF SUPPORT
point, line (rigid linear, non rigid linear), surface (rigid surface, non rigid surface)
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POINT SUPPORT CONDITION
fixed, pin(hinge), roller(ball), simple, cable (suspended), and combinations
POSITION OF SUPPORT
external, boundary, internal, and combinations
STABILITY at element, unit, aggregate level CONSIDERATION ADDITIONAL STABILISATION
none required, required (positioning of elements, rigid connections, load/weight(gravity), prestress, or combinations)
Subsequently we can also demonstrate the practical use of the morphological table by establishing an OVERVIEW OF STRUCTURAL SYSTEMS. In order to create the range of structural systems for buildings we utilise a convenient classification based on the predominant element type which makes up the continuum of the system. Rigid linear elements RL Linear elements mainly subjected to compression and/or bending (and shear) Non-rigid linear elements NRL Linear elements mainly subjected to tension Rigid surface elements RS Surface elements mainly subjected to tension (and shear) Non-rigid surface elements NRS Surface elements mainly subjected to tension (and shear) Rigid spatial elements RSP Spatial elements mainly subjected to compression and/or bending (and shear) Non-rigid spatial elements NRSP Spatial elements mainly subjected to tension (and shear) Discontinuous elements Any combination of the elements above (eg. tensegrity systems: RL and NRL) file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (35 of 51)28/08/2009 12:08:43
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In establishing the criteria for the following classification spatial (three dimensional) elements were omitted. The reasons for this omission are predominantly of a practical nature: rigid solid elements, such as bricks or stone (masonry) are mainly found in historical structures, non-rigid spatial elements, such as living cells, are mainly found in natural structures. Both these areas were considered to be peripheral when dealing with contemporary building and were eliminated for the sake of brevity and clarity. It must also be emphasised that for this classification neither boundary nor support elements were considered. This exclusion is valid because of the large number of possible variations of boundary and support for most structural continua. Furthermore it is both boundary and support, who, when varied or manipulated, lead to variations in shape of the structure using the same continuum and can therefore be considered to be variables.
OVERVIEW OF STRUCTURAL SYSTEMS (considering the CONTINUUM only and classified according to ELEMENT TYPE) 1.
STRUCTURES COMPOSED OF RIGID LINEAR ELEMENTS: RETICULATE STRUCTURES
1.1
Linear systems:
strut - column beam - truss arch post and beam frame multistorey & multi bay frame
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1.2
Surface systems:
single layer grid double layer (space) grid curved grid: grid shell
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1.3
Spatial systems:
3D - frames (multistorey) "tree" systems
2.
STRUCTURES COMPOSED OF NON RIGID LINEAR ELEMENTS: CABLE STRUCTURES
2.1
Linear systems:
2.11 2.12
non-prestressed: prestressed:
2.2
Surface systems:
2.21
non-prestressed:
2.22
prestressed:
2.3
Spatial systems:
suspended cable cable truss
parallel or radial suspended cable suspended cable net cable net
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2.31 2.32
non-prestressed: prestressed:
3D suspended cable net 3D cable net
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3.
STRUCTURES COMPOSED OF RIGID SURFACE ELEMENTS: RIGID SURFACE STRUCTURES
3.1
Linear systems:
3.11 3.12
with rigid plane surface elements: with rigid curved surface elements:
3.2
Surface systems:
3.21
with rigid plane surface elements:
3.22
with rigid curved surface elements:
3.3
Spatial systems:
3.31 3.32
with rigid plane surface elements with rigid curved surface elements
box beam tube beam
slab - plate folded surface shell folded shell
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4.
STRUCTURES COMPOSED OF NON -RIGID SURFACES: MEMBRANE STRUCTURES
4.1
Linear systems:
4.11
with surface supported membranes:
4.12
with point or line supported membranes:
4.2
Surface systems:
4.21
with surface supported membranes:
4.22 4.3 4.31
pneumatic or air structures: high pressure tubular beams, frames arches (prestressed) tents
low pressure envelopes: single - double skin high pressure envelopes with point and line supported membranes: external - internal support: mast mast and 'hump' arch Spatial systems: with surface supported membranes: balloon 4.32 with point or line supported membranes
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5.
STRUCTURES COMPOSED OF RIGID SPATIAL ELEMENTS (not considered)
6.
STRUCTURES COMPOSED OF NON RIGID SPATIAL ELEMENTS (not considered)
7.
STRUCTURES COMPOSED OF DISCONTINUOUS ELEMENTS: COMPOSITE STRUCTURES
7.1
Linear systems:
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7.11
7.12 7.13
7.14 7.15
with rigid linear/non rigid linear elements: continuos strut: (prestressed) column, cable truss, arch, frame discontinuous and continuous strut: (prestressed) cable truss, arch, frame (linear tensegrity) with rigid linear/rigid (plane) surface elements: skin/frame (box) beam, column, arch, frame with rigid linear/non rigid surface elements: strut supported (prestressed) membranes (surface tensegrities): (box) beam, column, arch, frame, skin/frame (non-prestressed) (box) beam, column, arch, frame with non rigid linear/rigid surface elements: cable/skin structures with non rigid linear/non rigid surface elements: cable reinforced membranes
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7.2
Surface systems:
7.21
with rigid linear/non rigid linear elements: continuous strut: (prestressed) cable truss grid discontinuous and continuous strut: (prestressed) cable truss grid (linear tensegrity) with rigid linear/rigid (plane) surface elements: skin/frame plate/slab, folded surface, shell with rigid linear/non rigid surface elements: strut supported (prestressed) membranes (surface tensegrities): plate/slab air structure/tent, folded surface air structure/tent, curved surface air structure/tent (shell), skin/frame (non-prestressed) structures (as above) with non rigid linear/rigid surface elements: cable/skin plate/slab, folded surface, curved surface (shell)
7.22 7.23
7.24
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7.25
with non rigid linear/non rigid surface elements: cable reinforced membrane
7.3
Spatial systems:
7.31
with rigid linear/non rigid linear elements: continuos strut: cable truss discontinuous and continuous strut: cable truss (tensegrity) with rigid linear/rigid (plane) surface elements:skin/frame (box) beams, bridges, towers with rigid linear/non rigid surface elements: strut supported membranes (surface tensegrities): (box) beams, bridges, towers skin/frame structures with non rigid linear/rigid surface elements: cable/skin structures with non rigid linear/non rigid surface elements: cable reinforced membranes
7.32 7.33
7.34 7.35
CONCLUDING REMARKS The previous pages outlined a rigorous approach to the organization of structure systems and their shape based on the morphological method . An overview of possible STRUCTURE SYSTEMS illustrates the wide range that are available to the creative designer. Current building construction practice utilises only a very narrow range of these possibilities. The predominant reason for this situation is lack of knowledge by the architectural and engineering professions about the range of alternative structural systems, their structural behaviour and how to best integrate them into building design. This situation affects the majority of schools of architecture and engineering: usually architects emphasise a general, all-encompassing approach to building design often at the expense of sufficient basic knowledge of building technology and usually engineers concentrate on the analytical quantitative approach to building structures often at the expense of adequate development of their conceptual structural design capacity. The morphological approach to the conceptual design of structure systems has been proven a successful tool in architectural training and teaching courses conducted by the author at the University of New South Wales and internationally over the past 17 years. Current trends world-wide point to a far wider variety of structures than during the past history of building. Major changes in approach to design and in the practice of building are now happening that will determine future directions for our professions in the next century. The technological progress made in associated fields, such as motorcar, ship, aircraft and spacecraft design and manufacture continues to influence construction practice and the range and depth of technological knowledge required from architects have increased accordingly. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (50 of 51)28/08/2009 12:08:43
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Architects and engineers must face these challenges. Prerequisite is adequate training in conceptual design of building structures based on systematic, logical and reproducible methods. Awareness of the full range of available shape and design options and better knowledge of structure systems will enable architects to design better buildings and will hopefully lead to a more appropriate, more adaptable and richer built environment and to economical buildings.
REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
ZWICKY, Fritz "The Morphological Method of Analysis and Construction" Courant Anniversary Volume, 1948. NORRIS, K.W. "The Morphological Approach to Engineering Design", Proc. of the Conference on Design Methods, Pergamon/MacMillan, 1963 OTTO, Frei (Ed.) "Tensile Structures" Vol.2., M.I.T.Press, 1969 (first published in German by Ullstein Fachverlag, Berlin, 1966) JUNKERS, K.P. "Einteilung der Konstruktionen" Diploma thesis, Faculty of Architecture, University of Stuttgart, 1973 SEDLAK, Vinzenz "A Morphology of Folded Surface Structures" Report on the RIBA Research Award, London, 1975. SEDLAK, Vinzenz "The Morphology of Structures", Lecture notes, School of Architecture, University of NSW, 1976-1985. SEDLAK, Vinzenz "On Structural Morphology" unpublished paper presented at the ANZAScA Conference "Environmental Control", Melbourne, 1977 OTTO, Frei; SCHAUR, Eda "Form-Force-Mass" IL 21, Institute for Lightweight Structures, University of Stuttgart, 1979 OTTO, Frei "Form" Concepts Vol.1 SFB 230, University of Stuttgart/University of Tübingen, 1984. SEDLAK, Vinzenz "The Morphology of Structure", Proceedings LSA’86 First International Conference on Lightweight Structures in Architecture, University of NSW, 1986 pp1164-1187
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THE MORPHOLOGY OF STRUCTURES * by Vinzenz F.J. Sedlak Associate Professor and Director, Lightweight Structures Research Unit, School of Architecture, The University of New South Wales, Sydney Australia * updated in October 2003 from a published paper: SEDLAK, Vinzenz "The Morphology of Structure", Proceedings LSA’86 First International Conference on Lightweight Structures in Architecture, University of NSW, 1986 pp1164-1187
INTRODUCTION STRUCTURE: in the broadest sense any material object that is able to sustain loads (forces) may be called a structure (3, p.11). This includes objects in nature such as land and water, animals and plants, in the universe such as stars, planets, solar systems and galaxies, as well as man-made objects such as buildings, bridges, vehicles, furniture, appliances etc. Accoring to this definition principle criteria of a structure are therefore:
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the OBJECT, defined by its SHAPE and the MATERIAL it is made of, and the LOADING the object is subjected to. The shape of an object is its visible representation: it is what we see. The material of an object is often not visible at first view and may reveal itself only through its colour and surface texture. By touching an object texture and weight (loading) of its material can be experienced. In order to understand structure in its essence and its totality we must first consider shape, material and loading in turn and than combine them to form an integrated whole: structure. This process is described in subsequent sections of this paper. We will be concentrating on building structure, but while looking at buildings and the structures that make them stand up we should always be aware that buildings form only one part of the world of structure. In order to be universally valid our investigation must address itself to the much wider context of structure: much can be gained and learned from observing and understanding the basic principles which govern structure in nature and its organisation in other technological fields often leading to insight and subsequent improvement of structures utilised in building. In order to obtain such insight and then to be able to draw parallels with buildings we must first look out for those basic properties and attributes of shape, material, loading and structure which are common to a wide range of different structures and subsequently identify them. For this analytical process to occur and for the outcome to be understood we must first agree on a common terminology. That is a clearly identifiable, recurring set of definitions of those recognisable properties and attributes which are common and valid to all structures.
TERMINOLOGY BUILDING STRUCTURE, a specific type of structure, encloses and protects space from drastic changes in shape while resisting loads exerted on it by the elements of nature (wind, snow and earthquake), by the gravitational pull of the earth and by other influences such as temperature. That space usually accommodates people, animals, plants and goods. BUILDING is a part of the built environment which is relatively independent in its function and appearance. STRUCTURE is that part of a building that provides the support function in order to safeguard the overall functioning of the building. It consists of a STRUCTURAL CONTINUUM, a BOUNDARY which borders the continuum and SUPPORTS. Supports can be placed within the continuum or at the boundary. Depending on the complexity of make-up, the structure can be an ELEMENT STRUCTURE, a UNIT STRUCTURE, an AGGREGATE STRUCTURE or a COMPOSITE STRUCTURE. The CONTINUUM is that part of a structure that encloses (interior) space and is directly subjected to LOADING by external loads. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (2 of 51)28/08/2009 12:08:43
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LOADING of the continuum creates FORCES. Forces cause STRESSES within the elements of the structure. The continuum responds to loading by stressing. Stresses are channelled through the object and through its elements into the structural MATERIAL which reacts to stressing with SHAPE-CHANGE. At the SUPPORTS these stresses are collected and channelled into forces which are then transmitted through the supports to the ground or to another supporting medium where they are resisted by opposite forces activated by the supporting medium. In the case of an aggregate and composite structure the continuum is bordered by a BOUNDARY. The boundary makes up the extreme limits of the continuum and may consist of one or more structure elements. The STRUCTURE SYSTEM is the abstract model of that structure. A STRUCTURE ELEMENT is the smallest part of a structure which when connected to other structure elements makes up a continuum, a boundary or a support of that structure. (an example for an element in a continuum is a single beam in a series of floor beams). According to the make-up of the structure we differentiate between the following levels:
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ELEMENT STRUCTURE is a structure that consists of one structure element only. (eg. a single board providing a small bridge between two parts of a building; a single rope for lifting goods). Element structure consists of an element which is simultaneously its continuum, boundary and its support(s). UNIT STRUCTURE is an assembly of structure elements into an identifiable whole. (eg. a brick pier made from bricks, or a wall, or a floor, or a roof). Unit structure consists of a number of elements which make-up the its continuum, boundary and support(s). Usually a unit structure is made up of several different elements (an example is a timber floor unit using two different elements: bearers and boards). AGGREGATE STRUCTURE is any assembly of structure units. (eg. a house made up of walls, floors and roof). Aggregate structure consists of a continuum made up of structure units, a boundary and supports. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (4 of 51)28/08/2009 12:08:43
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COMPOSITE STRUCTURE is any assembly of identical or different aggregate structures (eg. a cluster of houses). Composite structure consists of several continua, each of which may be bordered by a boundary, a composite boundary encloses these continua, supports may be arranged at composite or at aggregate boundaries or, alternatively, continua may be directly supported.
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Additionally we define the following qualitative attributes: SUPPORT-FUNCTION is the very purpose of structure namely to accept forces and moments through loads, to transform, transport, and to transmit them (to the ground). file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (6 of 51)28/08/2009 12:08:43
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STRUCTURAL QUALITY is the integration of those essential properties of a structural system that are required for it to fulfil it's support-function. STRUCTURAL (SUPPORTING) BEHAVIOUR is the expression of structural quality of a structure system for a set of given loads and other influences. Structural quality is determined at the conceptual design stage while structural behaviour is principally determined at the engineering design phase of structural design. Consideration of structural quality during design of a building requires knowledge of structure systems. For the architect, knowledge of structure systems is essential as it enables him to conduct the conceptual design of a building in a comprehensive and adequate manner. Structural behaviour involves determination of loads and their intensities and choice of materials for construction. This is essentially the domain of the structural engineer. At a more general level, however, a basic understanding of structural behaviour is required from the architect in order to become an active participant in the structural design process rather than a passive bystander. Quality and behaviour of a structure forming a building cannot be isolated from each other but are intimately connected. Therefore, co-operation of the architect and engineer-designers is imperative during the conceptual design stage so that a building structure emerges, that is both, in tune with the overall architectural concept and safe and economical to construct and to use.
STRUCTURE SYSTEMS AND BUILDING DESIGN The "morphological" approach described in the following has proven to be a convenient analytical method to introduce structural systems while at the same time developing a closer understanding of the "structure" of structures and their many possible variations. At a subsequent stage, the morphological approach can also be utilised for design synthesis: the systematic, conceptual design of structure systems (2). In the present context, the morphological approach is an analytical tool that assists in the conceptual understanding of structural systems. As such it is a means to an end and as any such tool dependent on understanding of its operation and use. Prerequisite for it's use is systematic and rigorous application of logical steps. For practical purposes, the morphology can also be used to produce an organized OVERVIEW OF STRUCTURE SYSTEMS as is shown in the latter part of this paper. Morphological studies should be accompanied by the following: STAGE 1: Observation of buildings and objects (man-made and natural). The aim in observing buildings, structures and objects is immediate, conscious perception of the natural and built environments and development of the ability to recognise structural systems by deduction from the appearance of a particular building/object. During this stage photographs and sketches are important aids as well as information on a range of previous structural solutions for similar applications. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (7 of 51)28/08/2009 12:08:43
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STAGE 2: Investigation of principle types of structural systems The aim is qualitative recognition of principal structural behaviour of a chosen system -its structural quality- based on the study of equilibrium, and development of the student's ability to recognise and to understand structural quality in its essence. Qualitative knowledge of principle load/force distribution ie. internal forces and torques/moments (stresses) within structural elements in response to loading is required. This stage normally concludes the extent of structural knowledge required from the architect and, shared with the engineer, it becomes the stepping stone for the next stage, which is normally conducted by the engineer: STAGE 3: Confrontation with actual structural systems The aim is quantitative determination of essential values for load-bearing, stressing, and shape-change of a structure system based on studies of equilibrium and changes in shape dependent on types of loading. Subsequent aim is the development of the student's capability to assess the influences of parameter changes on stressing and shape-changing of structural systems. At this stage diagrams which illustrate quantitative changes in stress levels and deformations in response to changes in load intensity, and loading type and cross-sectional/ material properties are required.
THE MORPHOLOGY OF STRUCTURE According to Fritz Zwicky (1), a Swiss/American scientist and "inventor" of the morphological method: "Morphology is the study of the basic pattern of things". The morphological approach directed at a particular field of study helps to discover the intrinsic "structure" of this field in its totality. This is done by observing and analysing a representative range of existing samples in a systematic, logical and reproducible manner: The first step is to establish the field of investigation, in our case STRUCTURE. The second step is to identify a recurring set of recognisable principle attributes called PARAMETERS and the range of their possible VARIATIONS by observation and analysis of a representative range of existing examples (eg. buildings). The most convenient method to establish and display a morphology is a MORPHOLOGICAL TABLE, which is a matrix where parameters are listed in order of hierarchy in a column to the left and their corresponding variations in rows to the right. PARAMETERS
VARIATIONS
The third step is to check the validity of established parameters and variations by identification of an arbitrary range of new samples. This is also known as the ANALYSIS FUNCTION of the morphology. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (8 of 51)28/08/2009 12:08:43
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The fourth step is to create an entire range of structures, including known and hitherto unknown structures, by selectively combining different variations from all parameters in a series of successive steps. This process is known as the SYNTHESIS FUNCTION of the morphology and as such utilised for creative development of structure systems during the conceptual design stage of a building. (this paper does not deal with the fourth step) MORPHOLOGICAL PARAMETERS AND THEIR VARIATIONS In previous investigations of STRUCTURE we identified principle attributes (PARAMETERS), namely OBJECT, (SHAPE, MATERIAL) and LOADING. In addition we established a number of SUB-PARAMETERS, namely those relating to SHAPE : namely ELEMENT, AGGREGATE and COMPOSITE and those relating to LOADING and STRUCTURE: namely CONTINUUM, STRESSING, BOUNDARY and SUPPORTS. We will now investigate how they relate to each other and show their VARIATIONS.
1.
SHAPE
(for background information on the following including a detailed analysis of shape ("form") see (8, p.14ff) and (9)) Macro- and Microcosms are composed of material objects: Each material object has a shape. Shape refers to: 1. 2. 3.
the outside appearance of the object it's interior if the object is hollow it's "structure" (structure in this context refers to the arrangement of elements or components which make up the shape)
SHAPE GENERATION Every object is characterised by the process through which it was created. Every object is in a state of change. Dynamic Shapes are objects whose shape varies rapidly (eg. waterfall, cloth). Static Shapes are objects whose shape varies only very slowly (eg. mountain, building). We are aware of the following: file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (9 of 51)28/08/2009 12:08:43
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SHAPE GENERATION PROCESSES Change of shapes in NON-LIVING NATURE (eg. the evolution of landmasses on earth by folding and faulting of the earths crust, by volcanic activity; erosion of rock, mountains) Evolutionary shape-changes in LIVING NATURE (eg. evolutionary development of species; growth and decay of microbes, plants, animals and man). Shape generation by HUMAN ACTIVITY (shaping, forming of materials for objects which serve man in this quest for dominance of his environment eg. tools, machines, buildings, vehicles). PERCEPTION AND CLASSIFICATION OF SHAPES Geometric description of most shapes is difficult, if not impossible, due to their complexity. Only the simpler, regular shapes can be readily described (eg. sphere, cone, cube). Objects in living nature are usually described by shape characteristics of a specific species. Other means of "capturing" the shape of objects are by documentation, eg. sketching and drawing photography or photogrammetry mechanical shape-measurement models Shapes, however, can be successfully described morphologically. THE SHAPE OF OBJECTS Every material object has a mass, a volume and a surface. Its PROPORTIONS are, therefore, three-dimensional. However, for the purpose of this study, a different definition of proportion is more practical. In order to facilitate theoretical considerations we define PROPORTIONS OF AN OBJECT as follows: An object that is relatively large in one dimension (length) and relatively small in both other dimensions (width and height) is termed ONE DIMENSIONAL. It extends into a linear direction, it is LINEAR. An object that is relatively large in two dimensions (length and width) and relatively small in the third is termed TWO-DIMENSIONAL. It extends into a surface (area), it is SURFACE. An object that is relatively large in all three dimensions (length, width and height), or if little difference can be seen between all dimensions of the object, is termed THREE-DIMENSIONAL. It extends into three-dimensional space, it is SPATIAL. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (10 of 51)28/08/2009 12:08:43
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A three dimensional object that is infinitely small so that its proportions are not visible to the eye is termed POINT. Point implies that there is no visible extension in any dimension. A relatively very small spatial object that is in an assembly with other, much larger objects is often idealised and called POINT. Transition between one-, two- and three-dimensional proportions is often not clear cut: a one-dimensional object can grow into a two-dimensional one by extension of the second dimension or vice-versa. a two-dimensional object can grow into a three-dimensional one by extension of the third dimension or vice-versa. Objects which are of different size, but of similar proportions do not change their proportion. CURVATURE OF OBJECTS Apart from proportion, curvature of an object is a major parameter. LINEAR OBJECTS can be straight, angular or curved in one plane, or angular or curved in space
SURFACE OBJECTS can be plane, single curved, folded and double curved (domical = synclastic or saddle = anticlastic).
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SURFACE OBJECTS can have positive peaks or negative peaks (navel), folds or undulations.
SPATIAL OBJECTS are identified by the surface(s) which border(s) them. The surface can be a continuous unit (sphere) or a composite one: pointed, with edges and corners, faceted or with undulations. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (12 of 51)28/08/2009 12:08:43
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COMPOSITE OBJECTS Any one-, two- or three-dimensional object can be combined with other objects. Any object can also be composed of one-, two- or three-dimensional elements
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ELEMENT OBJECTS An object that is composed of a number of elements is termed a UNIT OBJECT. Each one of its elements may be one-, two- or threedimensional.
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An object that is composed of more than one unit object is called an AGGREGATE OBJECT. Each one of its units may be one-, two- or three-dimensional. An object that is an assembly of aggregate objects is termed COMPOSITE OBJECT. These aggregates may be one-, two- or three-dimensional. EXAMPLES Hammer Overall 1-D UNIT Elements1-D and 3-D Chair Overall 3-D UNIT Elements2-D and 3-D Balloon Overall 3-D UNIT Elements1-D, 2-D and 3-D Block of Overall 3-D UNIT Stones Elements1-D, 2-D and 3-D Aeroplane Overall 3-D AGGREGATE Units 2-D and 1-D Elements2-D and 1-D Multistorey Overall 3-D AGGREGATE Building Units 3-D Elements 2-D and 1-D We can now summarize the criteria (parameters) pertaining to SHAPE -which are valid for all shapes of objects without exception- in form of a MORPHOLOGICAL TABLE: PARAMETER
VARIATIONS
TYPE OF SHAPE
positive (proud) shape, negative (cavity) shape
TYPE OF OBJECT
particle, element, unit, aggregate, composite, macro
SIZE OF OBJECT
very small (molecular), small, medium, large, very large (macro)
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PROPORTION OF OBJECT
non dimensional (point), one dimensional (linear), two dimensional (surface), three dimensional (space)
CURVATURE OF THE OBJECT RELATED TO ITS PROPORTION LINEAR straight, angular in one plane, curved in one plane, angular in space, curved in space SURFACE
plane, folded, single curved, domical(double) curved, saddle (double) curved
SPATIAL
folded (edged), rounded (relates to surface)
TYPE OF SURFACE (OBJECT) SHAPE OF SURFACE
unit, composite smooth (unit), peaked (composite), folded (composite), undulated (composite)
TYPE OF PEAKS
positive (pointed), negative (navel)
TYPE OF FOLDS (UNDULATIONS)
straight, curved
Having analysed the morphology of shape we can now consider the next principle parameter:
2.
MATERIAL
The ability of an object to sustain loading is dependent on two factors: it's SHAPE and the MATERIAL it is made of. Objects can be made from different material substances: these can be gaseous, liquid, plastic, granular or solid, in various combinations and densities. Transitions between these states are often undefined, such as between solid and liquid states of ductile materials such as metal or water(ice). All materials can be subdivided into two groups depending on their capacity to sustain loading (stresses) as well as on the magnitude of shape-change when elements made from these materials are loaded: file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (16 of 51)28/08/2009 12:08:43
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Materials which display small shape-changes are called SHAPE-RESISTANT. Materials which display relatively large shape-changes are called NON-SHAPE RESISTANT. Solid materials are usually shape-resistant, while granulose, plastic, liquid and gaseous substances are usually non-shape-resistant. The majority of building materials are solid. Examples are timber, steel, concrete, masonry, plastics, glass, bricks etc. "Solid" materials are either RIGID or NON RIGID (flexible). Rigidity or "stiffness" of solid materials depends on their stress/deformation characteristic (eg. the magnitude of shape-change under a given loading) and also on the proportions of the element-object, it's "slenderness" (eg. for one-dimensional objects: thin and long against thick and short). Depending on the type of stress the material is subjected to we distinguish between tensile-, bending-, shear- or torsional stiffness. Depending on the relative permanence of shape-change in a solid material the stress/deformation characteristic of that material may either be called ELASTIC or PLASTIC. Elastic materials are those which deform under stress, but recover from this shape-change in time. Plastic materials are those which, when stressed, do not recover from shape changes but remain in a permanently deformed state. Depending on the time/deformation/failure characteristic of solid materials when under stress (eg. the degree of shape-change in relation to the duration of load application at failure) we distinguish between BRITTLE and DUCTILE materials.
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Rigid materials can resist AXIAL STRESSES such as compression and tension as well as NORMAL STRESSES such as shear and bending. Examples are steel in the form of rolled or cold formed section or plate, masonry, brick, concrete, timber and the range of products derived from them. Non-rigid (flexible) materials can resist mainly tensile stresses and to a lesser extent shear. Examples are steel in the form of wire, cable or thin sheet; cellulose, animal hair, plastic or glass in the form of fibre-rope or woven fabric. Granular, liquid and gaseous material substances are normally non-shape resistant they can, however, withstand loading (stresses) when they are subjected to uniform file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (18 of 51)28/08/2009 12:08:43
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pressure (eg. air in a balloon). Gases must be contained in enclosed spaces, liquids or granulates can be contained in open containers, when under the influence of gravity (eg. water in a container or in a lake, sand in a bag). Non-material substances such as electrical energy, magnetism and gravitational attraction and repulsion between masses can also transmit forces. Examples are atoms and solar systems.
3.
LOADING SYSTEMS
Loads, such as weight, wind, snow, earthquake, temperature, acting on a composite structure, such as a house, create stresses in an aggregate structure, such as a timber frame, which subsequently create stresses in its elements, such as posts, beams, studs etc., and these, in turn, create material stresses at a molecular level.
This system of external and internal forces is termed a LOADING SYSTEM. The presence of the loading system convert an object into a structure. We distinguish between the following LOADING SYSTEMS: file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (19 of 51)28/08/2009 12:08:43
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EXTERNAL and INTERNAL LOADS which can be applied as (idealised) point, line, surface or volumetric loads.
External forces are caused by loads (ACTIONS) which are resisted at the supports (REACTIONS).
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External and internal forces cause STRESSES within objects or elements.
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Element stresses cause stresses in minute material particles (MATERIAL STRESSES).
Stresses act in different directions depending on the load application and on the proportion of the object or element: STRESS DIRECTION. Stresses in objects or elements (OBJECT or ELEMENT STRESSES) may be directed: in one direction (MONOAXIAL), in two directions (BIAXIAL) or in three directions (TRIAXIAL). The following TYPES OF STRESSES occur and are accompanied by SHAPE-CHANGES: TENSION leading to stretching or elongation of the object or element; file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (23 of 51)28/08/2009 12:08:43
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COMPRESSION leading to shortening; BENDING leading to curving accompanied by compression on the concave side of the object/element and to tension on the convex side; TORSION leading to twisting of the object/element which is associated with circumferential necking object.
SHEAR leading to a local compression or indent on the object/element accompanied
by sliding along perpendicular planes of the element/
Object or element stresses are rarely of only one type (eg. tension only). Stressing of a component usually involves a range of composite stresses acting in different directions and with different intensities. Ref.(4) (sections 2.3 - 2.6) gives examples of the range of multi axial stressing of objects and elements.
4.
STRUCTURE SYSTEM
Under the influence of load an object, defined by its shape and material, becomes a STRUCTURE. In this study we are concerned with abstract models of structures: STRUCTURE SYSTEMS. Structure system may refer to ELEMENT STRUCTURE, UNIT STRUCTURE, AGGREGATE STRUCTURE or to COMPOSITE STRUCTURE.(we defined these types previously). The parameters used to describe the shape of an object are identical to the ones used to describe the shape of a structure system: PROPORTION and CURVATURE. We identify a STRUCTURE ELEMENT primarily through its PROPORTION and STIFFNESS regardless whether the element is part of either continuum, boundary or support . By morphological combination of four variations of proportion (point, linear, surface, spatial) with two variations for stiffness (rigid and non rigid or flexible) altogether seven useful element combinations result:
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POINT (stiffness does not apply) RIGID LINEAR NON-RIGID LINEAR
RIGID SURFACE NON RIGID SURFACE
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These are the known STRUCTURE ELEMENTS. Depending on their shape and stiffness, these elements can be subjected to different stresses acting in different stress directions. Structure elements are useful common identifiers when analysing or studying structure systems and their behaviour under load. Any structure system consists normally of at least three disticts components: a CONTINUUM (surface) which is bordered by a BOUNDARY with both, continuum and/or boundary requiring SUPPORT.
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Supports may be positioned:
EXTERNAL to the structure (suspended), PERIPHERAL at the boundary, INTERNAL within the continuum or in various COMBINATIONS.
Supports may be any of the following types: POINT RIGID LINEAR (beam, arch, truss or frame), NON-RIGID LINEAR (cable), RIGID SURFACE (wall, plate, slab or shell) or NON-RIGID SURFACE (membrane with sand or water filling).
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Finally, a most important consideration in the study of structure is stability. STABILITY refers to the ability of an element, unit or aggregate to limit shape-changes which are associated with loading to safe and (visually and practically) acceptable limits. It is the fundamental responsibility of the designer of structural systems to ensure stability of the proposed structure under all expected loading conditions. Unfortunately many architects do not possess adequate structural knowledge to resolve their designs in terms of stability and proposed buildings are often unstable under certain loads which the architect did not consider. In such cases it becomes the engineers task to correct these shortcomings. Models are convenient aids to stability studies and their use should be propagated during study and in professional practice. Stability is fundamental to all building design considerations and must forms part of the basic structural knowledge required by the architect. Depending on the type of structure element and structure system ADDITIONAL STABILISATION may be required. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (30 of 51)28/08/2009 12:08:43
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The following methods are possible: POSITIONING (re-arranging or adding) OF ELEMENTS (eg. bracing struts or cables, shear planes); STIFFENING OF CONNECTIONS between elements (RIGID JOINTS), APPLICATION OF ADDITIONAL LOAD/WEIGHT and/or PRESTRESS in the case of flexible structures (cable and membrane structures). The following types of stability occur:
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ELEMENT STABILITY refers to resistance of a slender, rigid structural element (eg. strut or slab/sheet) against buckling deformation, or to stability of a flexible cable by prestress or weight. UNIT STABILITY refers to stability of a structural unit (eg. post and beam system, linear cable system etc.) against falling over/larger deformations. Three basic methods are available for ensuring lateral stability of simple, linear assemblies: introduction of additional diagonal bracing, shear planes or rigid joints. AGGREGATE STABILITY refers to stability of a complete (three-dimensional) assembly. Lateral bracing, shear plans in walls and roofs are typical provisions for simple assemblies.
We can now summarise all parameters and their variations, those relating to MATERIAL, LOADING and STRUCTURE which we just discussed as well as SHAPE which we considered earlier in the combined MORPHOLOGICAL TABLE OF STRUCTURE.
MORPHOLOGICAL TABLE OF STRUCTURE PARAMETER
VARIATIONS
SHAPE: TYPE OF SHAPE
positive (proud) shape, negative (cavity) shape
TYPE OF OBJECT
particle, element, unit, aggregate, composite, macro
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SIZE OF OBJECT
very small (molecular), small, medium, large, very large (macro)
PROPORTION OF OBJECT
non dimensional (point), one dimensional (linear), two dimensional (surface), three dimensional (space)
CURVATURE OF THE OBJECT RELATED TO ITS PROPORTION LINEAR straight, angular in one plane, curved in one plane, angular in space, curved in space SURFACE plane, folded, single curved, domical(double) curved, saddle (double) curved SPATIAL folded (edged), rounded (relates to surface) TYPE OF SURFACE (OBJECT) SHAPE OF SURFACE
unit, composite smooth (unit), peaked (composite), folded (composite), undulated (composite)
TYPE OF PEAKS
positive (pointed), negative (navel)
TYPE OF FOLDS (UNDULATIONS)
straight, curved
MATERIAL: MATERIAL SUBSTANCE
solid, granular, plastic, liquid, gaseous
DEFORMATION CHARACTERISTIC
shape-resistant, non-shape resistant
MATERIAL TYPE
solids: such as timber, metals (steel, aluminium etc.), plastics, masonry and brickwork,concrete, glass, composites; gaseous: eg. air; liquids: eg. water, oil etc. and their combinations
LOADING SYSTEM: EXTERNAL LOADS
gravity(self-weight, dead-load), additionalweight of objects or persons (live-load), snow, wind
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,
earthquake, settlement, and their combinations
POSITION OF LOAD
point, line, surface, volumetric, and their combinations
INTERNAL LOADS
dimensional changes (temperature, lack of fit)
STRESSES
(loads within an object, an element or at element material level in response to external and/or internal loads) tension, compression, bending, shear, torsion, and their combinations as above, but applied to element tension, compression, shear, and their combinations on a molecular level
OBJECT ELEMENT MATERIAL DIRECTION OF STRESS
monoaxial (one-directional), biaxial (two-directional), triaxial (three-directional)
STRUCTURE SYSTEM: TYPE OF STRUCTURE
element, unit, aggregate, composite
PROPORTION OF STRUCTURE
linear, surface, spatial
IDENTIFICATION OF COMPONENT
continuum, boundary, support
CURVATURE OF COMPONENT
straight/plane, angular/folded, single curved, double domical curved, double saddle curved
PROPORTION OF ELEMENT
point, linear, surface, spatial
STIFFNESS OF ELEMENT
rigid, non rigid (flexible)
BOUNDARY/SUPPORT point, rigid linear, rigid solid, ELEMENT non rigid linear, non rigid surface, non rigid solid and combinations TYPE OF SUPPORT
point, line (rigid linear, non rigid linear), surface (rigid surface, non rigid surface)
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POINT SUPPORT CONDITION
fixed, pin(hinge), roller(ball), simple, cable (suspended), and combinations
POSITION OF SUPPORT
external, boundary, internal, and combinations
STABILITY at element, unit, aggregate level CONSIDERATION ADDITIONAL STABILISATION
none required, required (positioning of elements, rigid connections, load/weight(gravity), prestress, or combinations)
Subsequently we can also demonstrate the practical use of the morphological table by establishing an OVERVIEW OF STRUCTURAL SYSTEMS. In order to create the range of structural systems for buildings we utilise a convenient classification based on the predominant element type which makes up the continuum of the system. Rigid linear elements RL Linear elements mainly subjected to compression and/or bending (and shear) Non-rigid linear elements NRL Linear elements mainly subjected to tension Rigid surface elements RS Surface elements mainly subjected to tension (and shear) Non-rigid surface elements NRS Surface elements mainly subjected to tension (and shear) Rigid spatial elements RSP Spatial elements mainly subjected to compression and/or bending (and shear) Non-rigid spatial elements NRSP Spatial elements mainly subjected to tension (and shear) Discontinuous elements Any combination of the elements above (eg. tensegrity systems: RL and NRL) file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (35 of 51)28/08/2009 12:08:43
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In establishing the criteria for the following classification spatial (three dimensional) elements were omitted. The reasons for this omission are predominantly of a practical nature: rigid solid elements, such as bricks or stone (masonry) are mainly found in historical structures, non-rigid spatial elements, such as living cells, are mainly found in natural structures. Both these areas were considered to be peripheral when dealing with contemporary building and were eliminated for the sake of brevity and clarity. It must also be emphasised that for this classification neither boundary nor support elements were considered. This exclusion is valid because of the large number of possible variations of boundary and support for most structural continua. Furthermore it is both boundary and support, who, when varied or manipulated, lead to variations in shape of the structure using the same continuum and can therefore be considered to be variables.
OVERVIEW OF STRUCTURAL SYSTEMS (considering the CONTINUUM only and classified according to ELEMENT TYPE) 1.
STRUCTURES COMPOSED OF RIGID LINEAR ELEMENTS: RETICULATE STRUCTURES
1.1
Linear systems:
strut - column beam - truss arch post and beam frame multistorey & multi bay frame
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1.2
Surface systems:
single layer grid double layer (space) grid curved grid: grid shell
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1.3
Spatial systems:
3D - frames (multistorey) "tree" systems
2.
STRUCTURES COMPOSED OF NON RIGID LINEAR ELEMENTS: CABLE STRUCTURES
2.1
Linear systems:
2.11 2.12
non-prestressed: prestressed:
2.2
Surface systems:
2.21
non-prestressed:
2.22
prestressed:
2.3
Spatial systems:
suspended cable cable truss
parallel or radial suspended cable suspended cable net cable net
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2.31 2.32
non-prestressed: prestressed:
3D suspended cable net 3D cable net
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3.
STRUCTURES COMPOSED OF RIGID SURFACE ELEMENTS: RIGID SURFACE STRUCTURES
3.1
Linear systems:
3.11 3.12
with rigid plane surface elements: with rigid curved surface elements:
3.2
Surface systems:
3.21
with rigid plane surface elements:
3.22
with rigid curved surface elements:
3.3
Spatial systems:
3.31 3.32
with rigid plane surface elements with rigid curved surface elements
box beam tube beam
slab - plate folded surface shell folded shell
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4.
STRUCTURES COMPOSED OF NON -RIGID SURFACES: MEMBRANE STRUCTURES
4.1
Linear systems:
4.11
with surface supported membranes:
4.12
with point or line supported membranes:
4.2
Surface systems:
4.21
with surface supported membranes:
4.22 4.3 4.31
pneumatic or air structures: high pressure tubular beams, frames arches (prestressed) tents
low pressure envelopes: single - double skin high pressure envelopes with point and line supported membranes: external - internal support: mast mast and 'hump' arch Spatial systems: with surface supported membranes: balloon 4.32 with point or line supported membranes
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5.
STRUCTURES COMPOSED OF RIGID SPATIAL ELEMENTS (not considered)
6.
STRUCTURES COMPOSED OF NON RIGID SPATIAL ELEMENTS (not considered)
7.
STRUCTURES COMPOSED OF DISCONTINUOUS ELEMENTS: COMPOSITE STRUCTURES
7.1
Linear systems:
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7.11
7.12 7.13
7.14 7.15
with rigid linear/non rigid linear elements: continuos strut: (prestressed) column, cable truss, arch, frame discontinuous and continuous strut: (prestressed) cable truss, arch, frame (linear tensegrity) with rigid linear/rigid (plane) surface elements: skin/frame (box) beam, column, arch, frame with rigid linear/non rigid surface elements: strut supported (prestressed) membranes (surface tensegrities): (box) beam, column, arch, frame, skin/frame (non-prestressed) (box) beam, column, arch, frame with non rigid linear/rigid surface elements: cable/skin structures with non rigid linear/non rigid surface elements: cable reinforced membranes
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7.2
Surface systems:
7.21
with rigid linear/non rigid linear elements: continuous strut: (prestressed) cable truss grid discontinuous and continuous strut: (prestressed) cable truss grid (linear tensegrity) with rigid linear/rigid (plane) surface elements: skin/frame plate/slab, folded surface, shell with rigid linear/non rigid surface elements: strut supported (prestressed) membranes (surface tensegrities): plate/slab air structure/tent, folded surface air structure/tent, curved surface air structure/tent (shell), skin/frame (non-prestressed) structures (as above) with non rigid linear/rigid surface elements: cable/skin plate/slab, folded surface, curved surface (shell)
7.22 7.23
7.24
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7.25
with non rigid linear/non rigid surface elements: cable reinforced membrane
7.3
Spatial systems:
7.31
with rigid linear/non rigid linear elements: continuos strut: cable truss discontinuous and continuous strut: cable truss (tensegrity) with rigid linear/rigid (plane) surface elements:skin/frame (box) beams, bridges, towers with rigid linear/non rigid surface elements: strut supported membranes (surface tensegrities): (box) beams, bridges, towers skin/frame structures with non rigid linear/rigid surface elements: cable/skin structures with non rigid linear/non rigid surface elements: cable reinforced membranes
7.32 7.33
7.34 7.35
CONCLUDING REMARKS The previous pages outlined a rigorous approach to the organization of structure systems and their shape based on the morphological method . An overview of possible STRUCTURE SYSTEMS illustrates the wide range that are available to the creative designer. Current building construction practice utilises only a very narrow range of these possibilities. The predominant reason for this situation is lack of knowledge by the architectural and engineering professions about the range of alternative structural systems, their structural behaviour and how to best integrate them into building design. This situation affects the majority of schools of architecture and engineering: usually architects emphasise a general, all-encompassing approach to building design often at the expense of sufficient basic knowledge of building technology and usually engineers concentrate on the analytical quantitative approach to building structures often at the expense of adequate development of their conceptual structural design capacity. The morphological approach to the conceptual design of structure systems has been proven a successful tool in architectural training and teaching courses conducted by the author at the University of New South Wales and internationally over the past 17 years. Current trends world-wide point to a far wider variety of structures than during the past history of building. Major changes in approach to design and in the practice of building are now happening that will determine future directions for our professions in the next century. The technological progress made in associated fields, such as motorcar, ship, aircraft and spacecraft design and manufacture continues to influence construction practice and the range and depth of technological knowledge required from architects have increased accordingly. file:///D|/BREEZE/Kuliah/Web%20Site/The%20Morphology%20of%20Structure.htm (50 of 51)28/08/2009 12:08:43
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Architects and engineers must face these challenges. Prerequisite is adequate training in conceptual design of building structures based on systematic, logical and reproducible methods. Awareness of the full range of available shape and design options and better knowledge of structure systems will enable architects to design better buildings and will hopefully lead to a more appropriate, more adaptable and richer built environment and to economical buildings.
REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
ZWICKY, Fritz "The Morphological Method of Analysis and Construction" Courant Anniversary Volume, 1948. NORRIS, K.W. "The Morphological Approach to Engineering Design", Proc. of the Conference on Design Methods, Pergamon/MacMillan, 1963 OTTO, Frei (Ed.) "Tensile Structures" Vol.2., M.I.T.Press, 1969 (first published in German by Ullstein Fachverlag, Berlin, 1966) JUNKERS, K.P. "Einteilung der Konstruktionen" Diploma thesis, Faculty of Architecture, University of Stuttgart, 1973 SEDLAK, Vinzenz "A Morphology of Folded Surface Structures" Report on the RIBA Research Award, London, 1975. SEDLAK, Vinzenz "The Morphology of Structures", Lecture notes, School of Architecture, University of NSW, 1976-1985. SEDLAK, Vinzenz "On Structural Morphology" unpublished paper presented at the ANZAScA Conference "Environmental Control", Melbourne, 1977 OTTO, Frei; SCHAUR, Eda "Form-Force-Mass" IL 21, Institute for Lightweight Structures, University of Stuttgart, 1979 OTTO, Frei "Form" Concepts Vol.1 SFB 230, University of Stuttgart/University of Tübingen, 1984. SEDLAK, Vinzenz "The Morphology of Structure", Proceedings LSA’86 First International Conference on Lightweight Structures in Architecture, University of NSW, 1986 pp1164-1187
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