3 Chapters Upto Mid.docx

CHAPTER-1 INTRODUCTION 1.1 GENERAL The elementary purpose of all kinds of structural systems used in the building is to support gravity loads. The most common loads resulting due to effect of gravity are dead load, live load. Beside these vertical loads, buildings are also subjected to lateral loads caused due to wind, blasting or earthquake. Lateral loads can develop high stresses, produce sway movement or cause vibration to the structure. Therefore, it is very important for the structure to have sufficient strength against vertical loads together with adequate stiffness to resist inplane lateral forces, typically wind and seismic loads. Due to the economy point of view, in India like countries, most of the building structures are used reinforced structural systems. The lateral load resisting structural systems of a structure are: 

Bearing wall system: These walls are load bearing walls. This type of bearing walls is known as shear walls. This wall system is designed for both vertical as well as lateral loads. These systems may use some columns to support floor and roof vertical loads.

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Moment resisting frames: This type of systems provides a complete space frame throughout the building to carry vertical loads, and they use some of those frame elements to resist lateral loads. These are such type of frames in which the beams, columns, and joints resist lateral loads through flexure of members.

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Dual system: In this system, the frames provides a complete support for gravity loads, ad resistance to lateral loads is provided by a detailed moment resisting frame and shear wall.

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Tube system: It utilizes the entire building perimeter to resist lateral loads.

Now a day, most of the residential high-rise multi-storey residential building uses a shear wall for providing the lateral stiffness of building for heavy lateral loads like wind load, seismic load. Shear wall framed structure is the combined form of shear wall and rigid frame, which tend to deflect in shear mode and in the flexural mode. As per literature survey of India, most of the residential structures have only frame structures which don’t perform well under the action of lateral force like seismic and wind loads. In high seismic zones, the main focus should be on shear wall frame structures.

FRAMED STRUCTURE Frame structure can be defined as the combination of beams, column, and slab to rsist the lateral and vertical loads. These structures are basically used to reduce the large moments developing due to the applied loading. Types of framed structure:A. Rigid frame structure 

Pin ended



Fix ended

B. Braced frame structure 

Gabled frames

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Portal frames

Rigid frame structure The meaning of the word rigid means ability to resist the deformation. We can define the rigid frame structures as structures in which beam and columns are made monolithically and act together to resist the moments which are generating due to applied load. These types of frame structures resist the shear, moment and torsion more effectively than any other type of frame structures. In general, we can say that the rigid frames are not as stiff as shear wall construction and are considered more ductile and less susceptible to catastrophic earthquake failures when compared to the shear wall structure. 

Pin ended frames This system has pins as their support conditions. If it support conditions are removed, then this frame structure is considered to be non-rigid frame structure.

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Fix ended frames In such type of frames structural systems, the end conditions are usually fixed.

Braced frame structure In this frame system, generally, bracings are used between horizontal member (i.e. beams) and vertical member (i.e. columns) to increase their resistance against the lateral forces and sideway forces due to applied load. During lateral loading, this system provides more efficient resistance. The braced frames system is more effective than rigid frame system.

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Gabled frame system This frame system generally has the peak at their top and is used at that place where there are possibilities of heavy rain or snow.

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Portal frame system This frame system is quite often used for the construction of industrial and commercial building.

SHEAR WALL In the multistory building, the shear wall is a structural system composed of the braced panel along with slabs, beams, and columns to counter the effect of the lateral load acting on the structure. They are vertically oriented wide oblong beams that carry earthquake load to the foundation. These walls usually start at foundation level and are continuous throughout the building height and also provided along both length and width of the building. Shear wall thickness is as low as 150mm or as high as 400mm in high rise building. These walls require special detailing of reinforcement in the high seismic zone. Shear wall is a part of the multi-story structure which resists the laterally unbalanced forces like wind and earthquake forces. So these walls help in avoiding a total collapse of building built in the high seismic region. The shear wall which is meant to resist earthquake and wind forces shall be designed for ductility. Shear walls are used to provide when the centre of gravity of building area and loads acted on structure differs by more than 30%. Shear walls are provided to bring the centre of gravity and centre of rigidity in range of 30%, i.e. lateral forces may not increase much. There are two types of forces will be resisted say shear forces and uplift forces. Transfer of horizontal forces creates shear forces throughout the height of the wall between the top and bottom shear wall connections. On the shear walls, uplift forces exist because the horizontal forces are applied to the top of the wall. These uplift forces try to lift up from one end of the wall and push the other end down. In the case of bearing walls, walls have less uplift than non-bearing walls because vertical loads on the shear wall help them resist uplift. When the gravity loads can’t resist all of the uplifts shear walls need to hold down devices at each end. So this device provides the necessary uplift resistance. The construction of shear walls is simple, because reinforcement detailing of walls is relatively straight forward and easy to implement at the site of construction. Shear walls are very effective both in construction cost and effectiveness in minimizing earthquake damage to the structural and non structural elements also.

Generally shear walls are in planar form in the plan of the building. However, some planar walls are also used in the structural systems. Typical non-planar shear wall sections used in the building structures are given in Figure 1.1. The analysis of shear wall-frame structures is more complicated than normal frame structural systems. Shear walls are rectangle in cross section having one dimension is much larger than the other. Thin walled hollow RC shafts used around the elevator core of the structure also act as shear walls, and should be taken advantage of to resist earthquake forces. The Shear Wall sections are classified as:

Box Section

L – Section

W – Section

H - Section

U - Section

Fig.1 different types of sections of shear wall

TYPES OF SHEAR WALL Shear walls are of different types:

Reinforced Concrete Shear wall

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RC Hollow Concrete Block Masonry Wall

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Light-framed or Braced Wooden Walls with Shear Panels

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Steel Plate Shear Wall

T – Section

ADVANTAGES AND DISADVANTAGES OF SHEAR WALLS IN BUILDINGS From previous earthquakes records, it has been found that shear walls with properly designed and detailed buildings performed very well. However, the building structure with sufficient amount of all that were not especially detailed but had well distributed reinforcement was also performed well in the past earthquakes. The construction of shear walls is easy because reinforcement detailing of the wall is relatively straight forward and therefore easily implemented at the site. These walls are efficient in terms of construction cost and effectiveness in minimizing earthquake damage in structural and non- structural elements. But apart from advantage, there are some short of disadvantage that is it presents barriers which may interfere with architectural and service requirement. Also, lateral load resistance in shear wall buildings is usually concentrated on a few walls rather than on a large number of columns. ARCHITECTURAL ASPECTS OF SHEAR WALL Many reinforced concrete buildings with shear walls also have columns, these columns carry gravity load (self-weight + contents of buildings). Shear walls provide strength and stiffness to the building to the direction of orientation, and hence it reduces the lateral sway and damage of the building structure. The size of window and door opening in the shear wall should be small to ensure least interruption to the force passing through the walls. Opening should be symmetrically provided. To ensure that the effective cross-sectional area of a wall at an opening is sufficient to carry the horizontal earthquake force special design checks will be performed. The shear wall in a building must be symmetrically provided in the plan so that reduces the twisting of buildings. STEEL PLATE SHEAR WALL Since 1970’s, the steel plate shear wall (SPSW), also known as the steel plate wall (SPW), has been used as lateral force resisting system in a number of structures in Japan and North America . In earlier days, SPSWs were treated like vertically oriented plate girders and design procedures tended to be very conservative. Stiffeners were used to prevent web buckling or by selecting an appropriately thick web plate. For the design of an SPSW structure, the steel plate girder theory seems to be appropriate; a very important difference is the relatively high bending strength and stiffness of the beams and columns that are used as the boundary elements of the wall. These members are expected to have a significant effect

on the overall behaviour of a building incorporating this type of system and several researchers have focused on this aspect of SPWs. The quality of high dissipation of energy of the web plate under extreme cyclic loading has raised the prospect of using SPSWs as a promising alternative to conventional systems in high-risk seismic zones. A further benefit is that the diagonal tension field of the web plate acts like a diagonal braces in a braced frame and thus completes the truss action, which is known to be an efficient to control wind drift and shear resistance. The large ductility and high strength-to-weight ratio of structural steel make it an ideal material for earthquake resistant structures. In general, steel building structures are more flexible than RCC buildings. The main function of steel plate shear wall is to provide lateral strength to the building and to resist horizontal story shear and overturning moment due to lateral loads. In general, steel plate shear wall system consists of a web plate, two vertical boundary elements (i.e. columns) and horizontal boundary elements (i.e. floor beams). Together, the steel plate wall and two boundary columns act as a vertical plate girder as shown in Figure 1.2. The vertical columns act as flanges of the vertical plate girder and the horizontal floor beam act as transverse stiffeners in a plate girder and the steel plate wall acts as its web.

Fig1.2 (a). Steel plate shear wall

Fig1.2 (b). Steel plate shear wall

There are three different SPSW systems: 1. Un-stiffened, thin steel plate shear wall 2. Stiffened steel plate shear wall 3. Composite concrete steel plate shear wall

1) Un-stiffened steel plate

2) stiffened steel plate

3) Composite concrete plate shear wall Fig1.3 different SPSW systems

NECESSITY 

Shear walls are designed not to resist gravity / vertical loads (due to its self-weight and other living / moving loads) only, but they are also designed for lateral loads caused due to earthquakes / wind.

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The walls are structurally integrated with roofs / floors (diaphragms) and other lateral walls running across at right angles throughout the height of structure, thereby giving the three dimensional stability for the building structures.



Shear wall structural systems are more stable. Because, their supporting area (total cross-sectional area of all shear walls) with reference to total plans area of building structure, is comparatively more.

ADVANTAGES From a designer’s point of view, steel plate walls have become a very efficient and attractive alternative over other steel systems, or to replace reinforced concrete elevator cores and reinforced concrete shear walls. In comparative studies it has been shown that the overall costs of a building structure can be reduced significantly when considering the following advantages: 

A steel plate shear wall system, when designed and detailed properly, has relatively large energy dissipation capability with stable hysteretic behaviour, thus being very attractive for high risk earthquake zones.



As web tension field acts much like a diagonal brace, and SPW system has relatively high initial stiffness, and is thus very effective in limiting shear resistance and wind drift.

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In comparison to RC shear walls, SPWs are much lighter, which ultimately reduces the demand on columns and foundations, and reduces the seismic load, which proportionally reduce the overall mass of the structure.

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In comparison to RC shear wall construction, the erection process of steel building is significantly easier and faster, thus reducing the construction duration, which affecting the overall cost of a project.

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By using shop-welded, field-bolted SPWs, field inspection is improved and a high level of quality control can be achieved in SPSW construction.

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From architects point of view, the increased versatility and space savings because of the smaller cross-section used in SPWs as compared to reinforced concrete shear walls is a distinct benefit, especially in high-rise buildings, where reinforced concrete shear walls

requires large cross-section in lower floors which occupy a large proportion of the floor plan. 

All-steel construction with steel plate shear wall system is a practical and efficient solution due for cold regions, where concrete construction may not be feasible, as very low temperatures complicate the construction and freeze-thaw cycles can result in durability problems.

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In retrofitting of building, SPWs are typically much easier and faster to install as compared to reinforced concrete shear walls, which is a critical issue when building occupancy needs to be maintained throughout the construction time.

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In the event of inelastic response, steel panels can more easily repair and replace, otherwise simpler than for equivalent reinforced-concrete systems.

In comparison with conventional bracing systems in steel buildings, steel panels have the advantage of being a redundant, continuous system exhibiting relatively stable and ductile behaviour under severe cyclic loading (Tromposch and Kulak, 1987). This system is efficient because of its high stiffness of the plates acting like tension braces to maintain stability, strongly qualifies the SPW as an ideal energy dissipation system in high risk seismic regions, while providing an efficient system to reduce lateral drift and shear resistance. Thus, some of the advantages of using SPWs than conventional bracing systems are as follows: 

Reduces seismic force demand due to characteristics of higher SPW ductility and inherent redundancy and continuity.

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Accelerates structural steel erection by using shop-welded and field-bolted steel panels, and thus, less inspection and reduced quality control costs of overall project.

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Permits efficient design of lateral-resisting systems because large forces distributes evenly.

OBJECTIVES OF THE WORK The main objectives of the present study are 1. To compare the base shear, displacement, storey drifts and design results of RC and SPSW buildings using response spectrum analysis of different building structures. 2. To compare the results of reinforced concrete and earthquake-resistant design as per IS 456:2000 and IS 1893 (part-1) and steel plate building design as per IS 800:2007 corresponding to equivalent static analysis and response spectrum analysis 3. To analyze the thickness of steel plate shear wall system in two different zones (Zone IV &V) The purpose of this study is to evaluate thickness and comparative analysis and design of G+15 stories building with different plan sizes of building with and without shear wall at core location of building structure. All developed models can be used for both static and dynamic analysis. SCOPE OF THE STUDY From previous research, it has been found that around 60% of India lying in earthquake prone zone at which there is a need for an increase of understanding the behaviour of earthquake, construction, and development of earthquake resistant structures. Now a day’s building with steel plate shear wall is used because of its large energy dissipation capability with stable hysteretic behaviour, thus being very attractive for high risk earthquake zones. Now an adequate change in building code specifications should be made for the better performance of structure under hazardous conditions. And also play more attention towards strength rather than cost. However, if these building structures are properly designed they might prove to be more economical. In the present study, the analysis and design of G+15storey building subjected to dead, live, seismic and different loading combination according to Indian code using ETABS software and the best result of analysis and design are being demonstrated. Our considered different building structure configurations are 1. RC and steel buildings are considered having different plan sizes 2. Previously analysis of steel plate shear wall has been done by AISC Steel Design Guide 20 but in this study analysis is done by using Indian Code of Standards 3. Column was modeled as fixed to the base

ORGANIZATION OF THE THESIS The present work deals with the seismic analysis of RC frame structures and steel frame structures with and without using shear wall Chapter 1 deals with the general introduction about lateral load resisting structural systems, shear wall, its advantages and disadvantages in building. It also contains description of steel plate shear wall with advantages. Modeling approaches used for steel plate shear wall thoroughly studied objectives of the project, scope of the study. Chapter 2 deals with the literature survey carried to gain an idea of research work related to the project done by various researchers and scientists. Summaries of both analytical and experimental investigations are presented. Chapter 3 describes the methodology and analysis methods employed and at last design technique involved. Chapter 4 involves the problem formulation of the models. In this, we define about the material like concrete and steel, cross-sectional dimensions of different structural element (beam, column, slab, shear wall, & steel plate thickness), support conditions. Chapter 5 involves the results and discussions of analysis methods and design methods followed. Firstly, response spectrum analysis was carried for all models of different plan sizes with and without shear wall shear wall and the lateral displacement, drift of storey were compared. Lastly, steel plate shear wall having same thickness were analyzed according to IS 800:2007corresponding to response spectrum analysis. Chapter 6 covers the conclusion, future scope, and references of the project. Under conclusion, the comparative results of lateral displacement, storey drift, base shear and design result of all models with and without shear wall have been presented in a brief manner and references covers the papers, journals etc related o the project.

CHAPTER 2 LITERATURE REVIEW

Priya S Jain, (2015) [1] The aim of this paper was to comparative study of two types of steel plates i.e., Stiffened and Un-stiffened steel plate walls. In this research finite element analysis of 10 storey steel plate shear wall, both stiffened and un-Stiffened subjected to lateral forces were done by using ANSYS software. Again these lateral forces were calculated by modeling a 10 storey building with steel plate shear wall in ETABS and analyzed with combine effect of earthquake and wind. Building was analyzed for most critical load combinations and results the storey drift and storey shear forces. Further to perform non-linear analysis of same models, same forces were applied in the finite element analysis of stiffened and un-stiffened steel plate shear wall. For un-stiffened steel plate shear wall system three different thicknesses were taken as 8mm, 12mm, and 16mm. Also, comparison was done between unstiffened, stiffened steel plate shear wall with single strut and stiffened steel plate shear wall with double strut for the thickness of 3mm. From analysis, it was shown that the maximum storey drift of a building subjected to lateral loads obtained at mid height of building, as storey drift was minimum at base of building and goes on increasing until sixth floor, found to be maximum at sixth floor and it again starts decreasing from there until last floor. Also, result showed that maximum storey displacement varies linearly along with increase in height of the building and maximum storey displacement decreases with the increase in thickness of the steel plate. Anil kumar k., (2016) [2] The aim of this paper was to ascertain in which aspects each of building behaves i.e. strong or weak and what are effect of high rise building structure with different plan sizes under the effect of seismic forces and other forces which affect the stability and life of structures. In this research work three RCC buildings with different plan configurations as follows 1) Square, 2) Hexagonal, 3) Octagonal were considered and analyzed for the base reactions, axial forces, storey drift, storey stiffness, mode-Period etc. also Non linear static pushover analysis were carried out using ETABS2015. On the basis of this study it was unable to state that which one model is superior to other one, because each model has its own merits and demerits but this study reveals the effect of shapes of the structure in resisting various forces aginst their stability. There was future scope for research

to find the most suitable shape of structure which can resist seismic forces and other forces effectively. Pratik A. Bilomoria (2016) [3] In this research work low rise building comparison were considered for same seismic conditions for all the structures. Analysis results were compared to check the suitability of RCC, Steel and composite low rise building under same seismic conditions. Sections of RCC building elements were determined using IS 456 and that of steel structure were determined using IS1893. For composite building, due to unavailability of codes, sections were determined using ANSI codes. For section determination, firstly manual calculations have been performed and then applied in ETABS software along with same seismic and external loading conditions. These three buildings were compared on the basis of uniform factor of safety between 2 to 3. After the calculation of results it was concluded that instead of composite and steel structures, RCC structure should be selected for the low rise building construction, because of more deformations in steel structures and more stiffness in composite structures result in less convenient construction. There was further future scope of using CFST columns along with steel beams as a form of composite structure to know whether it can give better performance or not and also structure can be compared with different orientations of columns. Also, these aspects can be use for tall buildings with various options of composite structure. Sanisha Santosh, (2017) [4] The aim of this study was on improvement of shape of shear walls used in symmetrically high rise buildings. In symmetrical buildings, center of gravity coincides with center of rigidity so, that the shear walls are also placed symmetrically. In this study, the multi-storey building with G+14 and G+ 29 storeys with four different shapes (W, T, H, and U) of shear walls were considered for analysis on ETABS software. For the analysis of the building for seismic loading with two zones (zone-III & zone-V) were considered. Dynamic method (Response spectrum analysis) was used to analyze the storey drifts and base shear of the building in ETABS. Results concluded that on basis of storey drift and base shear value, G+14 building with W and U shaped shear wall showed better performance and G+29 building with W and H shaped shear wall showed better performance in both zone V and III. There was further future scope of study that the analysis of building carried out by changing the position of shear.

Divya A. Narkhede (2017) [5] The aim of this research work focus on review of comparison of shear wall and bracing system by using response spectrum method with the help of STAAD-Pro software. A symmetrical residential building of G+ 10 storeys were analyzed and comparison of response of shear wall and bracing system is done in this research work. As to minimize the damages caused due to earthquake, shear wall are efficient regarding cost and effectiveness. On other hand in steel buildings bracing system perform well and absorb great degree of energy which is exerted by earthquake. Structural performances of both systems are significant, but have unequal variations and behavior against earthquake load. The volume of work undertaken in this study was limited to know effective location and type of most efficient shear wall and bracing system. Study could be extended by comparison of shear wall and bracing system analysis by response spectrum method with the help of STAAD-Pro software, as STAAD-Pro gives accurate and quick results. Abhishek verma, (2017) [6] The aim of this study to explore the effectiveness of staggering of web plates on the reduction of vertical boundary elements and drift responses of steel plate shear wall during an earthquake event. Analysis has been done to determine the base shear reduction factor to match the over strength of staggered systems with conventional SPSWs. To compare the seismic response a design methodology was proposed for staggered SPSWs. 6th, 9th, and 20 storey staggered and conventional SPSEs with various aspect ratios were considered. These building models were modeled and analyzed in OpenSEES platform. Nonlinear static and dynamic analyses were performed to compare drift responses, hinge mechanism, and steel tonnage. Staggered SPSWs showed uniform drift distribution and reduction in inter storey drift and axial force demand on the vertical boundary elements. Results of dynamic analyses showed that when either wider or staggered web plates were used, vertical forces on footings of columns were reduced to about 50% to 60%. There was no significant increase in steel tonnage for high-rise SPSWs with web plates arranged in staggered configurations, Lower forces on the footing proportional to reduction of cost of foundation. SPSW may be more economical than its conventional counterpart if it’s designed by proposed methodology.

Jaimin Dodiya, (2018) [7] The aim of this research work was to do analysis of multistory building with shear wall using ETABS software. In seismic design of multistoried building, shear walls are most common structure used to make the structure earthquake resistant. These are constructed to resist the lateral loads caused by wind load and seismic loads. In the present work the lateral resisting structural system i.e., shear wall system considered for construction of 20 storey structure. Results obtained by comparing the different location of shear wall in multi-story building. From study, it is clear that if we provide shear wall in opposite direction in building, less will be displacement value for moderate seismic zone. Providing shear wall in opposite direction performs better and more efficient than all other cases. The provision of shear wall position in an appropriate location is necessary and advantageous for an existing or a new structure to perform better under lateral loads.

CHAPTER 3 METHODOLOGY Analysis needs to adopt the exact process to analyze a certain structural frame considering its corresponding characteristics related to earthquake as seismic analysis. Methods used for earthquake analysis of structural system are: 1. Review of existing literature related to our project work by different researchers. 2. Selection of types of structures. 3. Basic design data and general codal recommendations used in research paper 4. Apply the design guidelines to building without and with RC shear walls 5. Apply the design guidelines to design steel shear walls according to IS 800:2007 6. Modeling of the selected structures. 7. Comparison of steel plate shear wall and RC shear wall according to Indian Code 8. Determine the limited thickness that can be given to steel plate in SPSW system 9. Perform Equivalent static analysis & Dynamic Analysis on selected building models by using ETABS ANALYSIS AND DESIGN METHODS In the earthquake engineering, the seismic analysis is a major tool which is used to understand the response of building due to seismic excitations in a simpler manner. Seismic analysis is the recent development of building design, in the past; the buildings were designed just for gravity loads. It is a part of the structural analysis and a part of structural design where an earthquake is prevalent. In this project, we are using dynamic analysis of earthquake (response spectrum analysis) and in design; we compare the result of design by using static method and dynamic method of earthquake. Effect of design earthquake loads applied on structures according to IS 1893(Part 1):2002 can be considered in two ways, namely: 

Equivalent static method, and



Dynamic analysis method

Dynamic analysis can be performed in three ways 1. Response Spectrum Method, 2. Modal time history method, and 3. Time History Method

EQUIVALENT STATIC METHOD In this method, firstly the design base shear VB shall be computed for the building as a whole. Then, this VB shall be distributed to the various floor levels at the corresponding centers of mass. And, finally, this design seismic force at each floor level shall be distributed to individual lateral load resisting elements through structural analysis considering the floor diaphragm action. This method shall be applicable fir buildings with height less than 15m in seismic zone II. 1. Design base shear VB of a building shall be determined by: VB= AhW Where Ah = design horizontal acceleration coefficient value W = seismic weight of the building The design horizontal seismic coefficient Ah for a structure shall be determined by formula: 𝐴ℎ =

𝑍 𝐼 𝑆𝑎 2𝑅𝑔

Where, Z = seismic zone factor I = importance factor given in IS 1893(Part 1 to 5) for the corresponding structures R = response reduction factor, depending upon the perceived seismic damage performance of the structure, characterized by ductile or brittle deformations however the ratio I/R shall not be greater than 1. Sa /g = design acceleration coefficient for different soil types, normalized with peak ground acceleration, corresponding to natural period t of the structure 2. Seismic Weight The seismic weight of each floor is submission of its full dead load and appropriate amount of imposed load as specified. While computing the seismic weight of each floor of the building, the weight of columns and walls in any storey shall be equally distributed to the floors above and below the storey. The seismic weight of the whole building is calculated by submission of the seismic weights of all the floors. Any weight supported in between the storey shall be distributed to the floors above and below in inverse proportion to its distance from the floors.

3. Fundamental Natural Period The approximate fundamental translational natural time period of oscillation as mentioned in clause 7.6.2 IS 1893 (part 1): 2016 is given by a. For MRF buildings (without any masonry infill) Ta = 0.075h0.75 (for RC MRF building) Ta = 0.080h0.75 (for RC-Steel Composite MRF building) Ta = 0.085h0.75 (for steel MRF building) Where, h = height of the building in ‘m’. This excludes the basement storey, if it is connected with the ground floor decks or fitted in between the building column. b. Buildings with RC structural walls: 𝑇𝑎 =

0.075ℎ0.75 √𝐴𝑤

≥

0.09ℎ √𝑑

Where Aw = total effective area of walls c. All other buildings 𝑇𝑎 =

0.09ℎ √𝑑

Where h = height of building d = base dimension of the building at the plinth level along the considered direction of earthquake shaking, in m. 4. Distribution of Design Force: The design base shear, Vb computed in 1 shall be distributed along the height of the building as per the following expression, 𝑊𝑖 ℎ2 𝑖 𝑄𝑖 = ( 𝑛 ) 𝑉𝐵 ∑𝑗=1 𝑊𝑗 ℎ2𝑗 Where, Qi = design lateral force at floor i; Wi= seismic weight of floor i; hi = height of ith floor measured from the base; and n = numbers of storey in building, i.e., number of levels at which the masses are located.