ANALYSING THE SEISMIC BEHAVIOUR OF SET BACK BUILDING BY USING E-TABS
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Transcript of ANALYSING THE SEISMIC BEHAVIOUR OF SET BACK BUILDING BY USING E-TABS
http://www.iaeme.com/IJCIET/index.asp 444 [email protected]
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
Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs
http://www.iaeme.com/IJCIET/index.asp 445 [email protected]
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
Hema Venkata Sekhar and T. Venkata Das
http://www.iaeme.com/IJCIET/index.asp 446 [email protected]
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
Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs
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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.
Hema Venkata Sekhar and T. Venkata Das
http://www.iaeme.com/IJCIET/index.asp 448 [email protected]
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
Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs
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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.
Hema Venkata Sekhar and T. Venkata Das
http://www.iaeme.com/IJCIET/index.asp 450 [email protected]
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
Analysing The Seismic Behaviour of Set Back Building by Using E-Tabs
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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.