Marshall Roffino 3501 Fall 2008 Web

STRUCTURAL MATERIALS RESEARCH CATALOGUE TENSILE STRUCTURES

ARCH 3501 - ARCHITECTURAL DESIGN STUDIO 4 COLLEGE OF ARCHITECTURE TEXAS TECH UNIVERSITY - FALL 2008

STUDIO 703

TENSILE STRUCTURES

Tensile structures were first seen in the earliest forms of shelter, such as the tent. However it was Vladimir Shukhov who pioneered the use of tensile structures in the late 19th & early 20th centuries by doing many shell tower and pavillions such as the Elliptical Pavillion of the Panrussian Exposition in 1896. These structures began an era of tensile creations done by many well known architects and engineers such as Eero Saarinen, Santiago Calatrava, Frei Otto, and many others.

TENSILE STRUCTURES: LINEAR 3 DIMENSIONAL SURFACE-STRESSED MATERIALS CONSTRUCTION PROCESS

LINEAR STRUCTURES SANTIAGO CALATRAVA

The Chords bridge in Jerusalem, Israel was done by Santiago Calatrava in 2008. It is a cable stayed bridge composed of 66 steel cables. It has one angle, cantilevered tower supported by the cables. The goal of the bridge was to add a unique defining aspect to the jerusalem skyline. These tensile structures often have a great beauty to them, but can also be much more costly than a more simple and traditional solution. On this particular project many of the cities tax payers were skeptical on how much this project was costing them. Although these structures are more expensive than a standard concrete or compression bridge, there structural longevity and stability offsets the price jump. This bridge, although beautiful and streamlined, is extremely simplistic in comparison to the other types of tensile construction. Linear structures typically have a central mast, just as the chords bridge and many others,

3D STRUCTURES

A typical 3D tensile structure can be not only in tension, but in compression as well. When this occurs, as it has in the sculpture to the left, the inner members are in compression while the outer members are in tension, causing tensegrity. Another example of a 3D tensile structure is the “bicycle wheel” used as a structural roof. There are steel members in tension on a lower and upper deck forming a volume in between. This unique feature is what makes these types of tensile buildings different from a linear structure. Although these structures and buildings have a more complex shell, it makes for a more interesting shape. The inner ring of this structure is in tension while the outer ring is in compression.

SURFACE-STRESSED STRUCTURES

The Olympic Stadium in Munich, Germany done by the engineer Frei Otto for the 1972 Olympics is an example of a surface stressed structure that uses acrylic glass stablized by steel cables that are in tension. This new form of structure has opend up many new possibilities in the 20th and 21st centuries with its flexibility for new shapes and forms that traditional hard surfaced materials can not provide. It also gives a lightness quality that hard surfaced coverings can not provide, along with bringing in natural lighting to the space below. Another example of these membranes is the millenium dome. This structure, although it does not have the hyperbaloid effect that the Olympic park has, it has still has a stretched membrane that has been formed into a dome. These complex shapes take much planning and placement in order to get the perfect balance of tension so that the weight is distributed in the correct way to hold everything up.

OLYMPIAPARK MUNICH, GERMANY

The Olympic Stadium in Munich, Gemany is the largest tent like structure in the world. Its acrylic glass roof rolls accross the park replicating the grace and beauty of the Swiss Alps. However there is some controversy over what Frei Otto actually used as inspiration. Frei Otto based many of his designs off the things in nature that fascinated him. In this case, the pattern and repetition of many of the different tents are said to be like that of a spiderwed, rather than the slopes of the alps.

OLYMPIAPARK: HISTORY ARCHITECT FACTS

OLYMPIAPARK HISTORY EXPO ‘67

Although it is Frei Otto who is known for Olympiapark, it was Gunter Behnisch of Behnisch and Partner that came to Frei Otto for his opinion. Otto’s design was approved in 1968 and the project was finished for the 1972 olympics. What sparked Behnisch’s interest in Frie Otto was Otto’s and Rolf Gutbrod’s unique design of the German Pavillion in 1967. In fact, the Olympic Stadium is strongly based off of this design, only much larger.

OLYMPIAPARK ARCHITECT FREI OTTO

Frei Otto had a strong philosophy of architecture and nature being one together. As Otto put it, “The desire to create a deliberate design stands in contradiciton to the search for a shape which, while as yet undiscovered, is nevertheless subject ot the laws of naure.” Otto throughout his studied various minimal surfaces such as cobwebs, soap bubbles, and other tensioned membranes. He used these characteristics found in nature to inspire him to create interesting structures, such as the Olympic Stadium.

OLYMPIAPARK FACTS

69,000 seating capacity

436 km of cable strands at 11.7mm thick

85,000m2 translucent acrylic glass

Cable stayed masts 76 meters in height

MATERIALS

The design of the structure was intended to catch the viewers eye. The acrylic glass plates used for the roofing material of the tents is an opaque material that allows in light whiile giving protection from natural elements. The steel cable netting underneath the acrylic glass supports the roof and gives extra weight in order to properly tension the structure to make it air tight. The 76 meter masts are constructed of steel drums that grow in width towards the center and shrink in diameter towards the bottom connection and the top of the mast. Atop the mast sits a steel pulley system which allows the supporting cables to sit and be properly tensioned. There are concrete supports where the tensioned cables run into the ground.

CONSTRUCTION PROCESS

The construction progress for this project was extremely meticulous and orderly. After the masts were constructed, the cable netting system were layed and joined together on-site. They were then hoisted up and tensioned. The cable manufacturer fitted the clamps on the cables in the factory so it was easily assembled on-site. The anchoring system was placed in an underground diaphragm foundation which had to be precast before the cables were tensioned to their correct shape. After the cable netting was set in place, the acrylic glass was pre-cut and then placed in a grid and tensioned along with the cables. Otto designed a system of seals that make the stucture watertight and barely visible from beneath.

STUDY MODEL ONE

The Olympic Stadium in Munich, Gemany, done by the engineer Frei Otto for the 1972 Olympics, is an example of a surface stressed structure. This structure uses acrylic glass stablized by steel cables that are in tension. The idea was to symbolize the alps with its white transparent shield. This new form of structure has opened up many new possibilities in the 20th and 21st centuries with its flexibility for newshapes and forms that traditional hard-surfaced materials cannot provide.

STUDY MODEL ONE: MATERIALS HOW IT WORKS WHAT WE CAN DO NEXT TIME

STUDY MODEL ONE MATERIALS

Metal Rod

Metal Wire

Mesh Fabric

For our first study model, our main goal was to capture the general shape that the acrylic glass forms at the Olympic Stadium. In order to do this we need materials that were flexible and easily manipulatible in order to keep adjusting them to see how these intricate forms are created. We used flexible metal rods for the support of fhe roof and a larger, but also flexible rod for the mast. To study the shapes of roof, we used a transparent mesh fabric that was anchored to the metal supports and manipulate until the desired shape was formed. We used thin metal wire to twist for our connections.

STUDY MODEL ONE HOW IT WORKED

During the construction of the Olympic stadium, the masts, steel supports, and cable netting were first constructed and tensioned to the appropriate forms in order to add the pre-cut acrylic glass to produce the finished product. For this first study model we simplified the structural support to a few basic beams and columns that could support our fabric. We then manipulated the understructure with the fabric connected in order to study what shapes needed to be made in order to create the hyperbaloid shape used for the stadium.

STUDY MODEL ONE

WHAT CAN WE DO NEXT TIME?

After studying and manipulating these into different shape along with studying diagrams and documentation of the stadium, we pieced together a better and more realistic view of how the structure was constructed and what materials needed to be used in order to better replicate this intricate design. For the following study model we dove into more noble materials closer to the actual materials used in order to get a better perspective of proportion, weight distribution, and functionality.

STUDY MODEL TWO

The Olympic Stadium in Munich, Gemany, done by the engineer Frei Otto for the 1972 Olympics, is an example of a surface stressed structure. This structure uses acrylic glass stablized by steel cables that are in tension. The idea was to symbolize the alps with its white transparent shield. This new form of structure has opened up many new possibilities in the 20th and 21st centuries with its flexibility for newshapes and forms that traditional hard-surfaced materials cannot provide.

STUDY MODEL TWO: MATERIALS HOW IT WORKS WHAT WE CAN DO NEXT TIME

STUDY MODEL TWO MATERIALS

Steel Cable

Wooden Dowel

Steel Rod

For our second study model, out goals was to construct it on a much larger scale than the first in order to show more detail and nobility of the structural system of this building. For the masts we used a 1” diameter dowel that reached 2’-6” in height giving this model a 1:100 scale (actual mast size is approximately 250 ft). for the steel framing of the structure, we used 1/8” steel rods. We used brass picture hangers to simulate the lose connections or cables running from the structure to the ground. For our cables we used a thin metal twine that was approximately 1/32” in diameter. A wooden base was used in order to drill the masts into the base for support.

STUDY MODEL TWO HOW IT WORKED

For the construction of our model, we wanted to replicated as closely as possible the construction process of the actual structure. For the olympic stadium, the masts and the steel structural supports went up first and were tensioned. For our model, we soldered the structural members together to give in plenty of support, then attached the cabling system to the structure, and hoisted it up on the masts and tensioned it until it formed into the appropriate shape. The front structural beam was clamped onto the structural steel making it one cohesive piece. To attach the cables to the base we screwed-in eye-hooks into the wood to support the cables thus supporting the rods.

STUDY MODEL TWO

WHAT CAN WE DO NEXT TIME?

For this study model we primarily focused on the understructure of the tent to see how the connections were made and at what strength must the steel be to carry different loads. For the next model, we began to take into account the acrylic roof with the under cabling system. A more detailed approach was taken to further develope our knowledge of the structure and the nature of its system.

FINAL MODEL

FINAL MODEL: MATERIALS HOW IT WORKS WHAT WE CAN DO NEXT TIME

FINAL MODEL MATERIALS

Steel Front Support

Steel Mast

Nails

Steel Rod

Steel Cable

For our final model we wanted to explore some of the more detailed aspects of this structural system. We kept the same scale as the previsous model, but changed a few of the materials. For our mast we used a hollow steel tube that remained at a 1 inch thick diameter in order to replicated the true materials of the actual structure. In the previous study model the cables used were too strong in proportion to the weight of the structure. For this model we used a thinner 22 gage cable wire in order to add more tension to the structure. For the front steel support we used a solid steel rod for extra tension support. For the roofing material we used a thin synthetic acrylic plexy to simulate the actual acrylic glass. For the under-cabling system, nails and a thinner 28 gage wire were used.

FINAL MODEL HOW IT WORKED

The beginning process for this final model was similar to that of the previous study model. We connected the steel members, only this time by welding to obtain a stronger bond. We attached these to the steel front tension rod with similar fasteneres to that of the previous study model. Before hoising this structure up, we formed the scored and drilled acrylic plexy to the desired shape using heat. After hoisting the structure up and tensioned properly, the plexy was placed to fit and then the model was re-tensioned until everything was cohesive. to simulate the plexy fastening to the understructure we used nails puncturing through the glass connecting to the under wiring system.

FINAL MODEL

WHAT CAN WE DO NEXT TIME?

Although our final model was successful in portraying the information we wanted to display, there is still much more detail in joints, connections, and overall tensioners that we would have liked to explore more in another model. Understadning the complexity of this system is an on-going process in which must be studied intensively from many different angles in order to fully understand how the system functions as a cohesive unit.