GRD Journals- Global Research and Development Journal for Engineering | Volume 6 | Issue 6 | May 2021 ISSN- 2455-5703
Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems Doi Gulam Ashraf. F Department of Civil Engineering Sankalchand Patel College of Engineering (SPCE), Visnagar
Ashutosh D. Patel Department of Civil Engineering Sankalchand Patel College of Engineering (SPCE), Visnagar
Abstract This Study presents the performance of Flat Slab System when constructed with different lateral load resisting systems when located in high seismic area. Lateral load resisting system includes RC Shear wall and Bracings. Different types of Bracings like V type bracing, Inverted V type bracing, X type bracing and Buckling Resistant Bracing as well as Shear wall at different location is used and parameter such as Lateral Displacement, Storey Drift, Storey Stiffness and Storey Shear are been compared. Analytical model has been worked out in ETABS Software and performance of Flat slab with lateral load resisting system is examined. Keywords- Shear Wall, Bracings, Story Drift, Displacement, Story Shear, ETABS
I. INTRODUCTION In design and engineering practice, the selectively defined design of space, design of structure, speed and efficiency. The system consist of column resting directly on floor slab for which sufficient strength ductility should be provide. The absence of beamex the transferring of their role to the floor RC structure which gain in height and density of reinforcement in the part of hidden beam, the bearing capacity of the structural system. In the 1950s, flat plate construction-particularly for medium to high-rise office and residential buildings. Reinforced concrete flat plate construction has been and continuous to be used as an economical structural for many buildings. This system is suitable to resists gravity load but its seismic response is very poor. In high seismic regions, Flat plate structures are connect with either a beam-column moment frame or shear wall or bracing lateral resisting system. In the present report behavior of flat slab combined with shear wall and bracings subjected to lateral loading is studied using linear static co-efficient method. Building Systems a building following sub structure system to transfer the different types of loads. – Horizontal Sub Systems – Vertical Sub System – Lateral Sub Systems for High Rise Buildings A. Horizontal Sub Systems Horizontal sub system consists of structural elements such as Slab, Beams and small elements like drop panels in case of beamless floor or flat slab. These elements are monolithically casted so as to jointly resist the effects of applied loads (both gravity as well as lateral loads). Horizontal sub systems are of different types as slab-beam, flat plate, flat slab, waffle slab, grid floor, prestressed concrete slab etc. B. Vertical Sub Systems Vertical sub system collects the loads from the horizontal sub system and transmits it to earth through foundation. Column lies under this system. C. Lateral Sub Systems Vertical sub system collects the loads from the horizontal sub system and transmits it to earth through foundation. Column lies under this system. D. Flat Slab Flat slab buildings are very common now a days. Flat slabs with drop panels and column are commonly constructed as extra projections provide protection against punching shear and also decrease the heavy negative moment. If drop panel is not provided then that system is called Flat Plate system. In the 1985 Mexico City earthquake, 91 flat plate buildings collapsed and 44 were severely damaged due to punching failure. Punching shear strength of slab-column connection is of importance which is depends upon the gravity shear ratio. Exterior slab-column connections behave differently than interior slab-column connections. When flat slab is subjected to lateral load every joint transfer the moment. When it is subjected to gravity loads only then edge and corner column transfer moment and interior column may transfer moment when it is subjected to pattern loading or when span lengths are unequal. All rights reserved by www.grdjournals.com
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Flat plate system is very economical and provides spatial flexibility to the user. Some distinct advantages of flat slab system over other systems are as follows: 1) Low floor to floor height which also reduce the total building height, lower cladding costs and prefabricated services. 2) Low cost is also due to faster construction because form work is very easy. Rapid turnaround can be achieved by using early striking and flying system. The overall speed of construction will depend upon the construction of vertical elements. 3) When flat slabs are used without drops panels (thickened part of slab near column to resist punching shear) then it also provides flexibility to the occupier because there is no restriction on positioning of horizontal services and partitions. Flat slab system is best for using as office, restaurants and parking areas etc. 4) Good aesthetical appearance and more architectural flexibility of building. E. Shear Wall Shear wall is a structural member which is generally used to resist lateral forces i.e. parallel to the plane of the wall. Continuous concrete vertical wall serves both architecturally as partition and structurally to carry gravity and lateral load. Shear wall are used in building to resist shear wall ideally suit for tall buildings. Shear wall generally start at foundation level and continue to building height. They act vertical cantilever in the form of separate planner wall. Shear wall in building must be symmetrically located in plan to reduce ill effect of twice in building. In other words, Shear walls are vertical member of the horizontal force resisting system. Structurally, the finest position for the shear walls is in the centre of each half of the building. This is rarely practical, since it also uses the space a lot, so they are positioned at the ends. It is better to use walls with no or minimum openings in them. So, usually the walls around lift shafts and stairwells are used as shear wall. F. Bracing A braced frame is a structural system generally use in structure to resist the lateral load due to wind and earthquake. Which can work effectively both in tension and compression. The beams and columns that from the frame carry vertical load, and bracing carry vertical load. The position of braces, however, can be problematic as they can interfere with the design of faced and the position of openings. Building adopting high-tech or post-modernist styles have responded to this by expressing bracing as an internal or external design feature. Cross bracing can rise a building’s ability to withstand seismic movement. Bracing is important in earthquake resistant buildings because it helps to keep the structure standing. Cross bracing is usually seen through two diagonal supports placed in an X shaped manner; these support compression and tension forces. This method of construction maximizes the mass of the load a structure is able to support. It is a usual applied when constructing earthquake-safe buildings. Table 1: G+10 Storey Building Description Description Dimension Storey G+10 Storey Height 3m Column Size 700 x 700 mm Slab Thickness 150 mm Shear Wall thickness 228 mm Material Property Concrete grade M30 Steel Grade Fe500 Seismic Parameters Seismic Zone III and IV Soil type Medium Importance factor 1 Response reduction factor 5 Load Data 2 Live Load 3 KN/m 2 Dead Load 4.75 KN/m Type of support Fix
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 1: Flat Slab
Fig. 2: Flat Slab
G. Load Combinations Frame Following load cases are considered for design of building. 1) Dead Load (DL) 2) Live Load (LL) 3) Floor Finish 4) Earthquake Load along X direction (EQX) 5) Earthquake Load along Y direction (EQY) Due to the above cases, following load combination are considered for design of structural elements as per IS 1893, 2002. 1) 1.5 (DL+LL) 2) 1.2 (DL+LL±EQX) 3) 1.2 (DL+LL±EQY) 4) 1.5 (DL±EQX) 5) 1.5 (DL±EQY) 6) 0.9 DL ± 1.5 EQX 7) 0.9 DL ± 1.5 EQY All rights reserved by www.grdjournals.com
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
H. Building Configuration To study the behavior of Flat Slab under lateral load with different types of lateral load resisting system in Zone III and Zone IV is considered. Static co-efficient method is used in the analysis process. Structure considered in this analysis is used to be a public building with importance factor taken as 1.0. Bay size has taken as 5 meter in both the direction. Building size in plan is 25 m x 25 m.Typical height of the floor is taken 3 m.The size of column is taken as 0.7 m x 0.7 m. Thickness of slab and drop is taken as 150 mm and 225 mm respectively. Shear wall of thickness 228 mm is provided.
II. RESULT The result of Flat slab models with different lateral load resisting system is discussed in the following section. A. Storey Displacement
Fig. 3: story displacement of flat slab (zone 4)
Fig. 4: story displacement of flat slab (zone 4)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 5: story displacement of flat slab with bracing (zone 4)
Fig. 6: story displacement of flat slab (zone 3)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 7: story displacement of flat slab with shear wall (zone 3)
Fig. 8: story displacement of flat slab with bracing (zone 3)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
B. Storey Drift
Fig. 9: story drift of flat slab (zone 4)
Fig. 10: story drift of flat slab with shear wall (zone 4)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 11: story drift of flat slab with bracing (zone 4)
Fig. 12: story drift of flat slab (zone 3)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 13: story drift of flat slab with shear wall (zone 3)
Fig. 14: story drift of flat slab with bracing (zone 3)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
C. Storey Shear
Fig. 15: story shear of flat slab (zone 4)
Fig. 16: story shear of flat slab with shear wall (zone 4)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 17: story shear of flat slab with bracing (zone 4)
Fig. 18: story shear of flat slab (zone 3)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 19: story shear of flat slab with shear wall (zone 3)
Fig. 20: story shear of flat slab with bracing (zone 3)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
D. Storey Stiffness
Fig. 21: story stiffness of flat slab (zone 4)
Fig. 22: story stiffness of flat slab with shear wall (zone 4)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 23: story stiffness of flat slab with bracing (zone 4)
Fig. 24: story stiffness of flat slab (zone 3)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
Fig. 25: story stiffness of flat slab with shear wall (zone 3)
Fig. 26: story stiffness of flat slab with bracing (zone 3)
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Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems (GRDJE/ Volume 6 / Issue 6 / 012)
III. CONCLUSION The Seismic evaluation of flat slab buildings designed for gravity load and earthquake load, combined with or without shear wall and bracings is presented. In the thesis analysis on 11 story flat slab building is carried out using etabs with and without shear wall and bracing. Following conclusion. 1) The research conclude that flat slab behaves as strong column weak beam mechanism because first hinges is formed at slab connection and slab-beam member. 2) If the percentage of shear wall is increase then performance point is improved in flat slab building. 3) Fundamental time period is higher in flat slab compared to beam-column framed structure. 4) Maximum inter-story drift is reduce if the number of shear wall increase. It shows that behavior of flat slab with shear wall is governed by shear wall only. 5) To enhance the punching shear strength of flat slab, shear studs reinforcement can be used. It include shear strength and increase ductility of slab.
REFERENCE Dia Eddin Nassani, Ali Khalid Hussein, Abbas H Mohammed, “Comparative Response Assessment of Steel Frames with Different Bracing Systems under Seismic Effect”, Structures (ELSEVIER) – 2017, PAGES 229-242. [2] Sagaseta, L. Tassinari, M. Fernandez Ruiz, A. Muttoni, “Punching of flat slabs supported on rectangular columns”, Engineering Structures (ELSEVIER)2014, PAGE 17-33. [3] Bhavesh Rajesh Sahni, Dr. Prashant D. Hiwase, Prasad P. Dahale, “Seismic behavior of flat slab building with shear wall according to IS 1893:2016”, International Journal of Civil Engineering and Technology (IJCIET)– 2018, PAGE 955-963. [4] Manish Dubey, Dr. Pankaj Singh, Niraj Kumar Soni, Goutam Varma, “Seismic analysis of flat slab multi-storey Building with varying Shear wall”, International Research Journal of Engineering and Technology (IRJET)–2018, PAGE 36-42. [5] Nishant Verma, Aradhna Shrivastava, Vijay Kumar Shukla, “Behavior of Building having Flat Slab under Seismic Loading”, International Journal of Research and Analytical Reviews (IJRAR)-2019, PAGE 1419- 1428. [6] Kimleng Khy, Chatpan Chintanapakdee, Pennung Warnitchai, Anil C. Wijeyewickrema, “Modified response spectrum analysis to compute shear force in tall RC shear wall buildings”, Engineering Structures (ELSEVIER)-2018, PAGE 295-309. [7] Elyson A. P. Liberati, Marilia G. Marques, Edson D. Leonel, Luiz C. Almeida, Leandro M. Trautwein, “Failure analysis of punching in reinforced concrete flat slabs with openings adjacent to the column”, Engineering structures (ELSEVIER)-2018, PAGE 331-343. [8] Fatma M. Eid, Tayel Magdy and Ebada Ahmed, “New Methods to Resisting Punching Shear Stress in Reinforced Concrete Flat Slabs”, International Journal of Current Engineering and Technology- 2018, PAGE 313-321. [9] R. P. Apostolska, G. S. Necevska-Cvetanovska, J. P.Cvetanovska, N. Mircic. "Seismic Performance of Flat-Slab Building Structural Systems." National Information Centre of Earthquake Engineering [14 WCEE], IIT Kanpur. Available at: https://www.iitk.ac.in/nicee/wcee/article/14_05-01-0435.PDF [10] Hasanabbas Sheliya, Prof. Abbas Jamani, Prof. Mili Sankhala. "Comparative Study on Effect of Various Lateral Load Resisting Systems on Buildings with Flat Slab Systems." IJRAR 6.1 (2019): 232 - 247. [1]
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