Keywords: Discrete Staggered Shear Wall, High-Rise Building, Response Spectrum Analysis, Storey Drift.

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1 ISSN Vol.03,Issue.09 May-2014, Pages: Seismic Response of High-Rise Structure with Staggered Shear Wall AUNG MON 1, TIN TIN HTWE 2 1 Dept of Civil Engineering, Mandalay Technological University, Mandalay, Myanmar, aungmon25@gmail.com. 2 Dept of Civil Engineering, Mandalay Technological University, Mandalay, Myanmar, tthtwe@gmail.com. Abstract: This paper presents seismic response of high-rise structure with staggered shear walls. The proposed building is 25- storeyed vertical irregular rectangular shaped building in seismic zone 2, 3 and 4 is solved by dynamic response spectrum analysis. Structural members are designed according to ACI Code The structure is analysed by using ETABS software and dual system is used. Concrete cylinder strength of 3000 psi and steel yield stress of psi is used. When structure is analyzed without shear wall, stability check for structure is unsatisfactory for storey drift. Discrete staggered shear walls are positioned by two groups such as outside and inside places of the structure. Then the structure is analyzed and design checked with dynamic response spectrum method. Selection of suitable location is based on the results of storey drift and displacement. Finally, the most suitable shear wall location is selected from the structural point of view. Keywords: Discrete Staggered Shear Wall, High-Rise Building, Response Spectrum Analysis, Storey Drift. I. INTRODUCTION According to social and economical demands, presently, Myanmar needs various types of tall buildings. These buildings are the solutions to the problem of living population growth rate. In high-rise building, it is important to ensure adequate stiffness to resist lateral forces induced by wind or seismic effects. Concrete walls, which have high inplane stiffness placed at convenient locations, are often economically used to provide the necessary resistance to horizontal forces. This type of wall is called a shear wall. The walls may be part of a service core or stairwell, or they may serve as partitions between accommodations. They are usually continuous down to the base to which they are rigidly attached to form vertical cantilevers. Shear walls can reduce total deflection and also reduce moment in columns and floor members due to lateral loads. The beams connected to the shear wall need to have the larger member size. Shear wall acts as vertical cantilevers and fixed at the base. The thickness of shear wall should be optimum thickness. If the shear wall thickness is more than its requirements, the building weight will increase and then it will not be economical design. Shear wall is basically a member that is subjected to cantilever beam action with fixed end at the base. Therefore, the magnitudes of moment and horizontal shear are found to be maximized at the base and they become less as they become high. II. SHEAR WALL STRUCTURE Shear walls may be defined as planar vertical elements distinguished by their relative thickness and substantial length. Concrete or masonry continuous vertical walls may serve both architecturally as partitions and structurally to carry gravity and lateral loading. Shear walls are usually continuous down to the base to which these walls are rigidly attached to form vertical cantilevers. In reinforced concrete building, lateral force due to wind or seismic action can be effectively resisted by providing shear walls. These elements are fixed at their base by the foundations and like cantilever beams to brace the frame. Since stiffness of shear walls is many times greater than that of all columns combined, lateral load is largely carried to the foundation by these elements. To prevent twisting of the structure, the shear walls should be positioned symmetrically in the structure. Shear walls may be added: 1. Closely stairways or elevator shafts. 2. Where permanent partitions and the lack of flexibility for future modification can be tolerated. 3. Where the effects of shear walls are almost equally shared by columns. Resist the lateral loads for high-rise building : 1. Decrease both structure and non-structure damage. 2. Increase lateral stiffness. 3. Reduce moments in columns and floors due to lateral loads. 4. Reduce total deflection and story drift There are four types of shear wall. They are planar shear wall, couple shear wall, core shear wall and staggered shear wall. In proposed building, staggered shear wall is used such as diagonal shear wall SEMAR GROUPS TECHNICAL SOCIETY. All rights reserved.

2 III. PREPARATION FOR ANALYSIS AND DESIGN OF REINFORCED CONCRETE SUPERSTRUCTURE A. Site Location and Structural System The proposed structure is a twenty-five storey reinforced concrete residential building. Details of the superstructure are described below, - Height of structure =272ft - Length of structure =156ft - Width of structure = 124ft - Typical storey height = 10ft - Bottom storey height = 12ft - Shape of building =Vertical irregular - Location = Seismic zone 2, 3 and 4 - Type of occupancy = Residential B. Material Properties Material properties for structural data are; - Concrete cylinder strength = 3 kip/in 2 - Yield strength of main reinforcement = 50 kip/in 2 - Yield strength of shear reinforcement = 50 kip/in 2 - Modulus of elasticity for concrete = 3122 kip/in 2 - Poison s ratio = Coefficient of thermal expansion = in/in per degree F C. Loading Consideration The applied loads are dead loads, live loads, earthquake load and wind load. Dead loads consist of the weight of all materials and fixed equipment incorporated into the building. Floor finishing, ceiling, partitions are considered as superimposed dead loads. Loads that are almost always applied horizontally are called lateral loads. Earthquake and wind load are used according to UBC-97[4]. For dead load, - Unit weight of concrete = 150 lb/ft 3-9" thick brick wall = 100lb/ft 3-4.5" thick brick wall = 55lb/ft 3 - Weight of ceiling and finishing = 25 lb/ft 3 For live load, - Live load on floor = 40lb/ft 2 - Live load on stair case = 100lb/ft 2 - Live load on roof = 20lb/ft 2 -Weight of lift = 3 tons -Weight of water = 62.4 lb/ft 2 For wind load, - Exposure type = B - Wind speed = 80 mph - Effective height = 260ft - Important factor = 1 - Method used = Normal Force Method - Windward = Leeward = 0.5 For earthquake load, - Seismic zone = 4 - Zone factor = 0.4 AUNG MON, TIN TIN HTWE - Soil profile type = SD - Seismic important factor (I) = 1 - Ct value = Seismic source type = A - Ca = Cv = Response modification factor, R = Structural system = Dual system - Analysis = Response Spectrum Analysis D. Loading Combination Design codes applied are ACI and UBC-97. There are 14 number of load combinations DL DL+1.7LL DL+1.275LL+1.275WX DL+1.275LL-1.275WX DL+1.275LL+1.275WY DL+1.275LL-1.275WY DL +1.3WX DL -1.3WX DL +1.3WY DL -1.3WY DL LL SPECX DL LL SPECY DL SPECX DL SPECY IV. DESIGN RESULTS OF PROPOSED BUILDING A. Modeling of Non-Shear Wall Structure A twenty-five storied R.C building is chosen for the analysis. The height of the base and ground levels is 12 feet. Other stories are 10 feet high. Total height is 272feet. The building is located in the UBC seismic Zone 4.It is analyzed by the using ETABS software. Floor plan and three dimensional proposed building of the selected model are shown in Figure 1 and Figure2. Figure1. Plan of proposed building. B. Member Sizes of Structure Column (Base to Level 5) -30 x30,28 x28,26 x26 (Level5 to Level10) - 28 x28,26 x,26,24 x24 (Level10 to Level 15) -24 x24

3 Seismic Response of High-Rise Structure with Staggered Shear Wall (Level15 to Level 20) -22 x22 After analysing structure, storey drift of the structure must (Level20to Roof) -20 x20 be checked. Some storey drift are exceed the drift limitation Beam size -14 x24, 14 x22, 14 x20, 14 x18 value. Hence the structure is not stable and shear wall must -12 x20, 12 x18, 12 x16, 10 x14, 9 x12 be provided for the structure. Check for storey drift is as Slab - 4 shown in Table 1. D. Modelling of Shear Wall Structure In this study, the models are constructed with different contributions shear wall are used. The cross sectional dimensions of beams, columns and slabs are the same with the previous non-shear wall structure. The material properties, loading and other data for wind and seismic forces are also the same as the non-shear wall structure. The thickness of staggered shear walls is 6 in.the elevation of diagonal shear wall structures are shown in Figure 3. The stability checks are satisfactory and are listed in Table II. Figure2. 3D view of proposed building. C. Check for Storey Drift of Non-Shear Wall Structure TABLE I: Check for Storey Drift of Non-Shear Wall Structure Figure3. Elevation 4 and 7 of diagonal shear wall structure. TABLE II: Results for Stability Checks (Zone 4) V. COMPARATIVE ON ANALYSIS RESULTS FOR DIAGONAL SHEAR WALL STRUCTURE In this study, the design results for members are carried out load combinations based on ACI code. From analysis results, storey drift, Storey displacement, Torsion, storey

4 shear and storey moment on proposed building between zone 2, zone 3 and zone 4 are compared. A. Comparison of Storey Drift Comparisons of storey drift in X-direction and Y- direction are shown in Figures 4 and 5. AUNG MON, TIN TIN HTWE Figure6. Displacement in X-direction. Figure4.Storey Drift in X-direction. In comparison of storey drift X between zone 2, zone 3 and zone 4, drifts are increased slowly and maximum storey drifts are found in storey 17, 18, 19, 21 and 22 about 1.35 times from zone 2 to zone 3 and 1.23 times from zone 3 to zone 4 of storey drift X respectively. Figure7. Displacement in Y-direction Figure5. Storey drift in Y-direction In comparison of storey displacement Y between zone 2, zone 3 and zone 4, displacements are increased slowly and maximum storey drifts are found in roof about 1.35 times from zone 2 to zone 3 and 1.20 times from zone 3 to zone 4 of storey displacement Y respectively B. Comparison of Torsion Comparison of torsion with diagonal shear wall is shown in Figure 8. In comparison of storey drift Y between zone 2, zone 3 and zone 4, drifts are increased slowly and maximum storey drifts are found in storey 17, 18, 19, 21 and 22 about 1.35 times from zone 2 to zone 3 and 1.18 times from zone 3 to zone 4 of storey drift Y respectively. B. Comparison of Displacement Comparisons of displacement in X-direction and Y- directions are shown in Figures 6 and 7. In comparison of storey displacement X between zone 2, zone 3 and zone 4, displacements are increased slowly and maximum storey drifts are found in roof about 1.35 times from zone 2 to zone 3 and 1.20 times from zone 3 to zone 4 of storey displacement X respectively. Figure8. Torsion with Diagonal shear wall Structure.

5 Seismic Response of High-Rise Structure with Staggered Shear Wall In comparison of torsion between zone 2, zone 3 and zone 4, displacements are decreased slowly and maximum storey drifts are found in ground level about 1.35 times from zone 2 to zone 3 and 1.20 times from zone 3 to zone 4 of torsion respectively. C. Comparison of Storey Shear Comparisons of storey shear in X-direction and Y- direction are shown in Figure 9 and 10. Figure11. Storey moment in X-direction. In comparison of storey moment X between zone 2, zone 3 zone 4 of storey moment X respectively. Figure9. Storey shear in X-direction. In comparison of storey shear X between zone 2, zone 3 zone 4 of storey shear X respectively. Figure 10.Storey shear in Y-direction. In comparison of storey shear Y between zone 2, zone 3 zone 4 of storey shear Y respectively. Figure 12.Storey moment in Y-direction. In comparison of storey moment Y between zone 2, zone 3 zone 4 of storey moment Y respectively. TABLE III: Summary Results for Storey Drift, Displacement, Torsion, Storey Shear and Storey Moment D. Comparison of Storey Moment Comparisons of storey moment in X-direction and Y- direction are shown in Figure 11 and 12.

6 VI. CONCLUSION In this study, twenty-five storeyed reinforced concrete building with dual system was selected. Wind and seismic loadings are considered based on UBC-97.All structural members are designed in accordance with ACI Analysis is to be done by using ETABS software and the analysis procedure is dynamic approach. Firstly, the required data for the proposed building such as material properties, load combinations, frame sections, etc, are defined. And the static analysis is used to design the proposed building. Next, dynamic analysis is used to obtain the final results of proposed building in seismic Zone 4. From the comparative study for the proposed building designed in seismic Zone 2 when accidentally subjected to high seismic risk level of Zone 3 and Zone 4, the analyzed results of storey drift, storey shear and storey moment are increased about 1.35 times in Zone 3 and 1.65 times in Zone 4. In the effect of seismic forces on building, the increased percentage of Zone 3 is 1.35 times and Zone 4 is 1.65 times. VII. REFERENCES [1] Author H. Nilson, 1997, Design of Concrete Structures, McGraw-Hill Companies, Inc. [2] Smith, B.s and Coull, A Tall Building Structure: Analysis and Design, John Wiley & sons, Inc. [3] American Concrete Institute Building Code Requirements for Structural Concrete (ACI ). U.S.A. [4] Uniform Building Code Volume 2. Structural Engineering Design Provisions. U. S. A. International Conference of Building Officials. AUNG MON, TIN TIN HTWE