International Journal of Civil Engineering and Technology (IJCIET) Volume 10, Issue 04, April 2019, pp. 1203–1210, Article ID: IJCIET_10_04_126 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJCIET&VType=10&IType=4 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication Scopus Indexed DYNAMIC ANALYSIS OF THE BASE ISOLATED TUBULAR TALL BUILDING SYSTEM (LEADRUBBER BEARING) IN ETABS Aamir Riyaz Dar P.G. Student, Department of Civil Engineering, Chandigarh University, Mohali, Punjab, India Simranjit Singh Assistant Professor Department of Civil Engineering, Chandigarh University, Mohali, Punjab, India ABSTRACT In case of dynamic analysis of tall buildings, the various important dynamic characteristics of tall building namely, the natural frequency (ω, radians/second) or simply time period (T, seconds),lateral displacement, base shear and overturning moment of tall buildings using ETABS software. In this paper, an approximate procedure is generated to perform the seismic analysis of simple and tubular tall building system with base isolation (lead-rubber bearings) system and the outcome compared with the results obtained without base isolation (lead-rubber bearing) of tall buildings. Base isolation system is basically a passive control device which decouples the super structure from substructure resting ground motion by insinuating structural elements with low horizontal stiffness between the structure and foundation. This analysis of G+29 rigid joint plane RCC frame has for four cases. First case is simple RCC frame with fixed base and with base isolation (LRB), second case is simple tube RCC frame with fixed base and with base isolation (LRB), third case is tube in tube system RCC frame with fixed base and with base isolation (LRB) and fourth case is bundle tube system RCC frame with fixed base and with base isolation (LRB) .The effectiveness of base isolation in every cases is compared with simple frame and tubular system cases. This analysis is done by using ETABS software and for design purpose of base isolated system 1893:2002 (part 1) and for seismic design of isolated structures (F.Naeim and J.M.Kelly). Key words: Base isolation, Lead-rubber bearing (LRB), Response spectrum analysis, Time period, Lateral displacement, Base shear, Overturning moment. Cite this Article: Aamir Riyaz Dar and Simranjit Singh, Dynamic Analysis of the Base Isolated Tubular Tall Building System (Lead-Rubber Bearing) in ETABS, International Journal of Civil Engineering and Technology 10(4), 2019, pp. 1203– 1210. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=4 http://www.iaeme.com/IJCIET/index.asp 1203 editor@iaeme.com Dynamic Analysis of the Base Isolated Tubular Tall Building System (Lead-Rubber Bearing) in ETABS 1. INTRODUCTION The tall structure is commonly characterized as one that is taller than the most extreme tallness which individuals are happy to stroll up; it thus requires mechanical vertical transportation. This incorporates a somewhat constrained scope of building utilizers, principally private condos, inns, and places of business, however at times including retail and instructive offices. A sort that has appeared recently is the blended use of buildings, which contains shifting measures of private, office, lodging, or business space. Tall structures are among the biggest structures fabricated, and their unit costs are generally high; their business and office capacities require a high level of adaptability. The establishment of tall structures bolster exceptionally overwhelming burdens, yet the frameworks produced for low-ascent structures are utilized, however augmented in scale. These incorporate solid caisson columns bearing on sake or expanding on uncovered sake itself. Bearing heaps and coasting establishments are additionally utilized. Multi-story structures are utilised for office, unpredictable, private pads, open focuses, and so on. There is requirement for multi-story working due to congestion of urban areas. There multi-story structures can be changed into tall structures so as to accomplish more floor space yet involves less land space. In the plan of tall structures, parallel burdens are wind load and seismic load. There are different parallel burden opposing frameworks, for example, supporting edge framework, minute opposing edge framework, outline bracket cooperating framework, shear divider framework, centre and outrigger framework and tubular framework. The tube is name given where you oppose the horizontal loads (seismic or wind) a building is intended to act like a three dimensional empty cylinder, cantilevered opposite to ground. The framework was present by Fazlur Rahman Khan. Tube frame development was first utilised in the Dewitt-Chestnut Apartment building, Structured by Khan and finished in Chicago in 1963.thus, most of the structures more than 40 stories built since the 1960s are of this basic sort. The most effective impact on building is mainly due to earthquakes in the resent past have given the intention about seismic protection to the building structure. This has given the confinement to different advanced techniques to protect the building structure from the earthquake. The base isolation system is one of the best technique in which base isolators are provided at the base of building which separates the building from ground motion provide stiffness to the building in vertical direction and flexibility in horizontal direction. 1.1. Regular Types of Structural System in Tall Buildings Unbending frame system Braced casing framework Shear wall system Coupled wall system Advanced structural tubular system Tubular system: - The tubular system or cylindrical framework is to organize the auxiliary components so that the formwork can oppose the forced loads on the structure proficiently particularly the horizontal burdens. This framework includes different components for example pieces, beams, supports, columns. The dividers and centres are locked in to oppose the sidelong loads, in the rounded framework the even loads are opposed by section and spandrel beams at the border dimension of the cylinders (tubes). http://www.iaeme.com/IJCIET/index.asp 1204 editor@iaeme.com Aamir Riyaz Dar and Simranjit Singh Sorts of tubular system Simple tube structure Tube in tube structure Bundle tube structure Braced tube structure The tube system idea depends on the possibility that a structure can be intended to oppose lateral loads by planning and designing it as hollow cantilever perpendicular to the ground in the least complex manifestation of the tube, the border of the outside comprises of firmly divided columns that are integrated with profound spandrel beams. The combination of beams and columns form a rigid frame that acts like composite heavy wall along the outside of the structure. 2. RESPONSE SPECTRUM METHOD Seismic analysis is the combination of both structural investigation and estimation of the response of a structure to earthquakes. It is one of the important segments of structural designing in locals where seismic tremors are predominant. For analysis described in this guide, you have static and dynamic loads. The dynamic properties of structure are modelled in ETABS using response spectral analysis. In this method, during earthquake the peak response of structure is found directly from earthquake response spectrum. The multiple modes of building response to an earthquake are taken in account and each model is combined in this method to estimate the total response of structure. This model combination is to be made by using either complete quadratic combination or square root of the square method. The model values in case response spectrum analysis should be in range of effective damping of isolated system or 30 present of critical, whichever is less. In this analysis synchronous excitation of the model is done in both horizontal directions by considering 100 present of ground motion and 30 present of the ground motion in perpendicular direction to calculate the design displacement of isolated system. 3. MODELING AND ANALYSIS OF BUILDING USING SOFTWARE (ETABS) The purpose of present study is to compare the overall structural performance of simple, tubular, and base isolated system for stabilization G+29 RCC building having symmetry along X and Y direction with rectangle shape 30mX20m in all models against seismic force. Using base isolation: -Story shear, Base shear and Story drift reduced after the lead rubber bearing (LRB) is provided as base isolation system. Using tubular system:-Allows greater flexibility, Regularity in the column, Seismic resisting system and identical framing for all floors in building frame. 3.1. Design of Lead Rubber Bearing As per IS: 1893:2016 and design procedure mentioned in reference [1] as follows: http://www.iaeme.com/IJCIET/index.asp 1205 editor@iaeme.com Dynamic Analysis of the Base Isolated Tubular Tall Building System (Lead-Rubber Bearing) in ETABS Table 1.Design specifications of LBR for simple and tubular RCC building models S.No. Properties of lead rubber bearing 1. Required stiffness ,U2 & U3 (linear properties) (kN/m) 2. Horizontal stiffness, U2&U3 (non-linear properties)(kN/m) 3. Vertical stiffness, U1 (kN/m) 4. Yield strength, F (kN) 5. Stiffness ratio (Post yield) 6. Effective Damping (KN-s/m) Simple RCC frame 7743.61 Tubular RCC frame 8123.117 2363.82 2486.17 2740420.35 2943387.35 41.9457 44 0.1 0.05 0.1 0.05 3.2. Model Specification Thirty story building was examined for validation. The various model plans of G+29 story building, where each model with fixed and base isolated system are shown in figure 2. Figure 1 Plan for G+29 storey models simple, tube in tube, bundle tube and simple tube. The various models composed of two building RCC frame systems (simple and tubular system) load, ground and building details are given as. Table 1. Load and ground properties for all building models Live load (kN/m) Super dead load (kN/m) Wall load (kN/m) Zone Soil profile http://www.iaeme.com/IJCIET/index.asp 3(kN/m) 3(kN/m) 15(kN/m) 4 Medium sites 1206 editor@iaeme.com Aamir Riyaz Dar and Simranjit Singh Table 2 Model details S.No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 9. 10. Model details NO. of story Area of building base grid Typical Story height (m) Bottom story height (m) Beam size (mm) Spandrel beam (mm) Column size (mm) Slab thickness Concrete grade Steel grade Zone factor Simple RCC Frame Fixed Base isolated 30 30 X 20 m 3m 4m 0.650 X 0.400 m No 0.8 X 0.8 m 0.150 m M35 Fe500 0.24 Tubular RCC Frames Fixed Base isolated 30 30 X 20 m 3m 4m 0.650 X 0.650 m 1.2 X 0.450 m 0.8 X 0.8 m 0.200 m M40 Fe500 0.24 4. RESULTS Max. Lateral displacement in mm The results are based on model analysis, where we have four different structures with unique specification of each model. The dynamic analysis of models with fixed base and base isolated is carried out by using response spectrum method. So, we have total eight models and we compare the results for time period, lateral displacement, base shear and overturning moment. 140 120 100 80 60 40 20 0 lateral displacement in x-direction lateral displacement in y-direction WITHOUT BASE-ISOLATION(LRB) Max. Lateral deflection in mm Figure 2 Maximum Lateral Deflection 200 150 100 50 Lateral deflection in xdiection 0 lateral deflection in ydirection WITH BASE-ISOLATION(LRB) Figure 3 Maximum Lateral Deflection http://www.iaeme.com/IJCIET/index.asp 1207 editor@iaeme.com TIME PERIOD (sec.) Dynamic Analysis of the Base Isolated Tubular Tall Building System (Lead-Rubber Bearing) in ETABS 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 TIME PERIOD OF BUILDING MODEL WITHOUT BASE ISOLATION (LRB) TIME PERIOD OF BUILDING MODEL WITH BASE ISOLATION(LRB) Max. BASE SHEAR (kN) Figure 4 Time Period 5800 5600 5400 5200 5000 4800 4600 4400 BASE SHEAR IN X-DIRECTION WITHOUT BASE ISOLATION(LRB) BASE SHEAR IN Y-DIRCTION WITHOUT BASE ISOLATION(LRB) WITHOUT BASE ISOLATIOON (LRB) Max. BASE SHEAR (kN) Figure 5 Maximum Base Shear 6000 5000 4000 3000 BASE SHEAR IN X-DIRECTION WITHOUT BASE ISOLATION(LRB) 2000 1000 0 BASE SHEAR IN Y-DIRCTION WITHOUT BASE ISOLATION(LRB) WITH BASE ISOLATIOON (LRB) Figure 6 Maximum Base Shear http://www.iaeme.com/IJCIET/index.asp 1208 editor@iaeme.com Aamir Riyaz Dar and Simranjit Singh Table 3 Overturning moment [without base isolation (LRB)] Sr.no. 1 2 3 4 Type Of Model Simple RCC frame Simple tube Bundle tube Tube-in-tube Eqx X-Dir kN-m 7.563E-06 6.563e-06 3.291E-06 6.596E-06 Y-Dir kN-m 360771.9617 384338.8825 327134.3302 384612.4253 Eqy X-Dir Y-Dir kN-m kN-m 377385.2781 7.321E-06 340410.645 7.534e-06 343416.695 3.1E-06 340830.432 7.569E-06 Table 4 Overturning moment [with base isolation (LRB)] Sr.no. 1 2 3 4 Type Of Model Simple RCC frame Simple tube Bundle tube Tube-in-tube Eqx X-Dir kN-m 1.05E-05 2.0998 1.18E-06 4.21E-06 Y-Dir kN-m 237256.59 300283.2398 273601.7191 274369.90 Eqy X-Dir kN-m 236008.79 265193.36 299131.67 263131.00 Y-Dir kN-m 9.89E-06 1.82714 1.07E-06 5.93E-06 5. CONCLUSIONS From the results following conclusion were arrived. Maximum lateral deflection increases after providing base isolation (LBR) in G+29 story simple RCC frame and tube in tube building model, but in case of simple tube and bundle tube building model the maximum lateral displacement shows very less increment in comparison to simple RCC frame and tube in tube building models show in fig. The time period in all models like simple RCC frame, simple tube, bundle tube and tube in tube decreases about 24%, 13%, 10% and 26% after providing base isolation (LBR) in models as shown in fig. After providing base isolation system (LBR) in every model base shear decreases between 10% to 30% as shown in fig which make the building stable against dynamic forces. The overturning moment also decreases after analysing the models due to base isolation system providing base isolation system (LBR) as shown in tables. Finally we conclude that after dynamic analysing of all the models of G+29 story frame buildings by the use of ETABS software every model shows different changing properties in both cases with and without base isolation. Hence, the earthquake impact is reduced by the use of lead rubber bearing is an effective base isolation technique. REFERENCES [1] Minal Ashok, Somwanshi and.Rina N. Pantawane, Seismic Analysis of Fixed Based and Base Isolated Building Structures, July 2015. [2] Zanaica L.,“Design of Storey-Isolation System in Multi-Storey Building” MEEES programmed, May,2007. [3] Prashika Tamang, Bijay Kumar Gupta et al. (2016), Study on earthquake resistant building-( Base Isolation). [4] Salic R. B., Garevski M. A. And Milutinovic Z. 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