ANALYSING THE SEISMIC BEHAVIOUR OF SET BACK BUILDING BY USING E-TABS
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The document analyzes the seismic behavior of setback buildings using computer modeling and analysis. It describes creating 3D models of buildings with and without setbacks and analyzing them using time history analysis and response spectrum methods. The analyses show that setbacks increase seismic forces and deformations in buildings compared to those without setbacks. Irregularities from setbacks need to be considered carefully in seismic design according to building codes.
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ANALYSING THE SEISMIC BEHAVIOUR OF SET BACK BUILDING BY USING E-TABS
- 1. http://www.iaeme.com/IJCIET/index.asp 444 editor@iaeme.com International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 1, January 2017, pp. 444–451, Article ID: IJCIET_08_01_051 Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication ANALYSING THE SEISMIC BEHAVIOUR OF SET BACK BUILDING BY USING E-TABS Hema Venkata Sekhar Post Graduate Student, K. L University, Vaddeswaram-522502, A. P, India T. Venkata Das Asst Professor, K. L University, Vaddeswaram-522502, A. P, India ABSTRACT Objective: To study building behavior during earthquakes always depends on its strength, durability, stiffness and adequacy of the regular configuration of the structure. Methods: The analysis always depends on the forces and importance on the cost of analyzing the structure. Creating the 3D building model for both linear and non-linear dynamic method of analyses. Understanding the seismic behavior of Setback buildings and Co-relating the seismic behavior of the Setback building with that of a building without Setback finally comparing the seismic behavior of building with a setback at every two levels to that of the building with a setback at each floor level. Study the influence of vertical irregularity in the building when subjected to earthquakes. Findings: The present study is limited to reinforced concrete framed structure designed for seismic loads (DL, LL & EL). The seismic behavior of three 8-Storied buildings with and without setbacks was studied. The buildings were analyzed using Time History Analysis and Response Spectrum Method and. Novelty: The effect of Setback is studied considering the parameters such as Time Period, storey drifts, Displacements, Storey Shears, Bending Moments and Shear Forces and correlated with the building without a setback. Key words: Set Back Buildings, Linear and Non-Linear Analysis, Seismic Loads, IS: 1893- 2002, Dynamic Loads Cite this Article: Hema Venkata Sekhar and T. Venkata Das, Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs. International Journal of Civil Engineering and Technology, 8(1), 2017, pp. 444–451. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1 1. INTRODUCTION In the last 25years, the globe has experienced many Earthquakes of larger magnitudes leading to massive loss of lives and extensive physical destruction. Past experiences reveal that for the same magnitudes of earthquakes, the loss occurred in developing and underdeveloped countries are much more 1 .This may be attributed to the lack of awareness and technical knowledge related to the aspects of seismic hazard assessment and mitigation2 . Due to recent severe earthquakes, a lot of studies is required in the development of earthquake resistant structures. Earthquakes present a threat to public
- 2. Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs http://www.iaeme.com/IJCIET/index.asp 445 editor@iaeme.com safety and welfare in the significant portion everywhere. We cannot stop earthquakes but we can prevent ourselves from them, as earthquakes don’t kill human beings, but the buildings do. In the past decade, India has seen major earthquakes in the world3 . 1.1. GLOBAL DEFICIENCIES They are broadly classified as plan irregularities and vertical irregularities, as per the Code. Some of the identified irregularities are as follows4-6 : Plan Irregularities • Plane symmetry and eccentric mass from water tank crate Torsion irregularity • Common re-entrant corners. • Model discontinuity due to large openings or staggered floors, along with the deficiency of collector elements. • Out-of-plane offset for columns along the perimeter. • Nonparallel lateral load resisting systems (not observed in the building studied). Vertical Irregularities • Soft storey due to open ground storey. Stiffness irregularity • The mass irregularity was not observed in building studies. • Vertical plane geometric irregularity from set-back towers. • Along the perimeter of the building In-plane discontinuity for columns are observed • Weak storey due to open ground storey. The vertical geometric irregularity or set back is shown in Figure 1. Figure 1 Vertical Geometric Irregularity or Set back
- 3. Hema Venkata Sekhar and T. Venkata Das http://www.iaeme.com/IJCIET/index.asp 446 editor@iaeme.com 2. IRREGULARITIES IN STRUCTURES The configuration of the building is classified as regular or irregular in the mean of size and shape of the building, the arrangement of structural elements and with respective to weight. Regular building configurations are almost symmetrical (in plan and elevation) about the axis and have a uniform distribution of the lateral force-resisting structure such that, it provides a continuous load path for both gravity and lateral loads 7 . 2.1. Reasons for irregularities in buildings • Construction in Hilly areas • Modern/new trends in commercial complexes • Thickly populated areas 2.2. Classification of Irregularities The structural irregularities are categorized into three types as: • Plan Irregularities • Vertical Irregularities • Other Irregularities The details of all plans are shown in Figure 2-5. Figure 2 Plan Irregularities
- 4. Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs http://www.iaeme.com/IJCIET/index.asp 447 editor@iaeme.com Figure 3 Code Plan Irregularity Figure 4 Vertical Irregularities Figure 5 Code Vertical Irregularity 3. NUMERICAL STUDIES The regular and irregular buildings are prescribed by the building codes. Roughly all the Indian standards propose the static analysis for all symmetric structures which were chosen the class of buildings. Indian standards propose the shape of Buildings with the irregular utilization of static and dynamic analysis procedures such as Time History Analysis (THA) and Response Spectrum Method (RSM) 8 .
- 5. Hema Venkata Sekhar and T. Venkata Das http://www.iaeme.com/IJCIET/index.asp 448 editor@iaeme.com Earthquake-induced deformations are reduced by changing the storey height, which tends to focus at the flexible/ weak storey of the building. The focus on damage leads to more deformations in vertical members. The huge deformations in vertical members further lead to the collapse of the storey of the building. 3.1. DESCRIPTION OF SAMPLE BUILDING The plan layouts for the building models with and without Setbacks are shown in Figure 6-8. Figure 6. 3D View of model-1 Building without Setback Figure 7. 3D View of model-2 Building without Setback
- 6. Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs http://www.iaeme.com/IJCIET/index.asp 449 editor@iaeme.com Figure 8. 3D View of model-3 Building without Setback Symmetric Building Models Model 1: Building modeled with Re-entrant corner and without Setback. Model 2: Building modeled with Re-entrant corner and Setback at every two levels. Model 3: Building modeled with a Re-entrant corner at Setback at each level. The Lateral Seismic Shear Forces of View of Building for Model-1, Model-2 and Model-3 are shown in Table 1. Table 1 Lateral Seismic Shear Forces of View of Building for Model-1, Model-2 and Model-3 Story (Qi)(KN) Model-1 (Qi) (KN) Model-2 (Qi)(KN) Model-3 8 2223.83 401.33 390.53 7 4135.92 711.45 1137.63 6 5549.19 2444.47 2377.13 5 6526.02 3830.89 3718.51 4 7170.31 5253.79 4890.09 3 7502.84 6111.18 5688.13 2 7627.54 6621.97 6146.57 1 7670 6730 6270 3.2. PERFORMED ANALYSIS IN ETABS ETABS computer program will do the analysis and design of the building. The following are the modeling methods: 3.2.1. Equivalent Static Analysis The normal time period of the structure is ascertained by the expression, T=0.09H/√D given in Indian Standard code provision 1893-2002, whereas H=height and D= base measurement of the building9 . In this strategy the bearing of vibration and normal periods for every one of the models are same. The transverse burden count and its appropriation along the tallness are computed according to Seems to be: 1893-1984.Dead load plus 2.5% of live load is considered as a seismic dead weight/self weight10 .
- 7. Hema Venkata Sekhar and T. Venkata Das http://www.iaeme.com/IJCIET/index.asp 450 editor@iaeme.com 3.2.2. Response Spectrum Analysis (RSA) Reaction Spectrum Analysis of the building models is performed in ETABS. The transverse burdens created by ETABS match to the seismic zone V and the 8% damped reaction range given in IS: 1893- 200211 . 3.2.3. Time History Analyses of the Structure Time History investigation has been done additionally utilizing the Bhuj Earthquake record on January 26, 2001, otherwise called the seismic tremor in Kutch for acquiring the different floor reactions12 . 3.2.3.1. Time history analysis in ETABS • It defined as time history adding a command from a file. In this case, Bhuj earthquake records 2001 were applied in this program. • A separate analysis of the structure within adequate analysis is linked with the appropriate case studies i.e. linear direct integration time history. • From the defined time history function earthquake acceleration values are applied. • By calculating the mass and stiffness proportions the mentioned equations are given in a period of time with two successive modes of the structure. The program itself calculates the required damping coefficients from the sources given by the software11-12 . • Direct integration method is to be specified and adopt new mark’s direct integration method to solve the problem. • Run the analysis. The graphical representation of Significant Time History Function (Bhuj earthquake, 2001) in ETABS was shown in Figure 9. Figure 9. Significant Time History Function (Bhuj earthquake, 2001) in ETABS
- 8. Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs http://www.iaeme.com/IJCIET/index.asp 451 editor@iaeme.com 4. CONCLUSIONS • Generation of all forces due to unequal distribution of mass will be identified by critical setback ratio along the section of the plan and also in the vertical height of the building. • The ideal appraisals of basic difficulty proportions are RA and RH. The above evaluation conforms to the criteria given in gauges for sporadic structures are considered. • At last, we finish up from the outcomes unpredictable structures are to be treated with appropriate plan and ought to be trailed by all IS code procurements given the guidelines. • It can likewise be reasoned that alteration of quake codes geometric horizontal anomalies appear to be important to determine more preventive ordinates or apply more precise explanatory strategy to distinguish the seismic execution of difficulty building. Especially for structures with basic difficulty proportions assumes a critical part. REFERENCES [1] Kumar J L, Wright E W. Eathquake response of steel-framed multistory buildings with setbacks. Earthquake Engrg. and Struct. Dynamics, 1977 December; 5(1), 15-39. [2] Jhaveri D P. Earthquake forces in tall buildings with setbacks. Thesis of Doctor of Philosophy presented to the University of Michigan, Ann Arbor, 1967. [3] Kannan A E, Powell G H. DRAIN-2D: A general purpose computer program for dynamic analysis of inelastic plane structures. Report No. UCB/ EERC-73/6, Earthquake Engg. Res. Ctr., Univ. of California, Berkeley, Calif., April 13, 1973. [4] Korkut, K. Research on the seismic behavior of structures with mass concentrations or with variable width. Bauingenieur. 1984; 59, 235- 241. [5] Pekau O A, Green R. . "Inelastic structures with setbacks." Proc, Fifth World Conf. on Earthquake Engrg, 2, Rome, Italy, 1974, 1744- 1747. [6] Shahrooz B M, Moehle J P. Evaluation of seismic performance of reinforced concrete frame. J. Struct. Engrg, ASCE. 1989; 116(5), 1402-1421. [7] Shahrooz B M, Moehle J P. Experimental study of seismic response of R.C. setback buildings. Report No. UCB/EERC- 87/16, Earthquake Engrg. Res. Ctr., Univ. of California, Berkeley, Calif., 1987, Oct. 19. [8] Suzuki Z ed. (1971). General report on the Takachi-Oki earthquake of 1968. Keigsku Publishing Co., Tokyo, Japan, 1971. [9] Wood S L. Experiments to study the earthquake response of reinforced concrete frames with setbacks. Thesis submitted to the University of Illinois, at Urbana, 111, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 1986. [10] Pankaj Agrawal, Manish Shrikhande. Earth quake resistant design of structures. PHI Learning Pvt. Ltd., india, 01-Jan-2006 [11] Aditya Varma K.V, Manideep T and SS. Asadi. A Critical Comparison of Quantity Estimation for Gated Community Construction Project Using Traditional Method Vs Plan Swift Software: A Case Study. International Journal of Civil Engineering and Technology, 7(6), 2016, pp. 707– 713. [12] G.S. Sarma, SS. Asadi and S. Lakshmi Narayana, Creation of Web Based Decision Support Information System for Evaluation of Topographic Characteristics Using Remote Sensing & GIS and Visual Basic Programe. International Journal of Civil Engineering and Technology, 7(6), 2016, pp. 621–634 [13] Aranda, H., G. R. (1984). "Ductility demands for R/C frames irregular in elevation."Proc, Eighth World Conf. on Earthquake Engrg, IV, San Francisco, Calif., 559-566. 5. Arnold C. Building configuration: Characteristics for seismic design. Proc, Seventh World Conf. on Earthquake Eng., , Istanbul, Turkey, 1980; 6, 589-592.