Comparative Study of Various Seismic Analysis Methods for RC Structure

Abstract

A large number of RC frame buildings have been built in India in recent years. Huge number of similarly designed and constructed buildings exist in the various towns and cities situated in moderate to severe seismic zones of the country. Analysis and design of such buildings for static forces is a routine affair these days because of availability of affordable computers and specialized programs which can be used for the analysis. On the other hand, dynamic analysis is a time-consuming process and requires additional input related to mass of the structure, and an understanding of structural dynamics for interpretation of analytical results. Reinforced Concrete (RC) frame buildings are most common type of constructions in urban India, which are subjected to several types of forces during their lifetime, such as static forces due to dead and live loads and dynamic forces due to earthquake. To ensure safety against seismic forces of multi-storied building hence, there is need to study of seismic analysis to design earthquake resistance structures. In the present study a multi-storied framed structure is selected, And Linear seismic analysis is done for the building by static method (Equivalent Static Method) and dynamic method (Response Spectrum Method & Time history Method) using ETABS as per the IS-1893-2002-Part-1. As a result, the response of structure has been obtained for considered building models, based on each methods of analysis, and then the results are compared with each other.

Introduction

An earthquake is caused by the sudden release of energy due to tectonic plate movement, often resulting in destructive effects such as ground shaking, landslides, fires, and tsunamis. Buildings, especially tall structures, are particularly vulnerable due to resonant vibrations and inertia forces, which can cause stress concentrations, structural damage, or collapse.

The seismic behavior of reinforced concrete buildings needs careful analysis using appropriate methods. This study focuses on analyzing a 10-storey building (30m height) using three primary seismic analysis methods:

1. Equivalent Static Analysis

2. Response Spectrum Analysis

3. Time History Analysis

These methods were implemented using ETABS software based on IS 1893:2002 code guidelines.

Key Parameters of the Building Model:

• Plan dimensions: 16m x 16m

• Storey height: 3m

• Wall thickness: 230 mm

• Slab thickness: 150 mm

• Beam & column size: 450 mm x 450 mm

• Material: M-25 Concrete, Fe-500 Steel

• Seismic zone: Zone V (Z = 0.36)

• Soil type: Type II (Medium)

• Response Reduction Factor (R): 5

• Importance Factor (I): 1

• Analysis types: EQX, EQY, Spec X, Spec Y, THX, THY

Seismic Analysis Insights:

• Equivalent Static method is the simplest, assuming a fixed base and applying static lateral forces.

• Response Spectrum method considers dynamic properties like natural frequency and damping.

• Time History analysis uses real or synthetic earthquake records to simulate building response over time.

All methods are used to compute storey displacement and assess structural damage. Additionally, soil-structure interaction is acknowledged as critical for accurate seismic behavior assessment.

To reduce seismic effects, technologies like base isolators and various types of dampers (viscous, friction, tuned mass, magnetorheological) are suggested.

Conclusion

In this study, the seismic vulnerability of building is shown through an example building. The main object of this investigation is to study the effect of horizontal loading on reinforced concrete frames for three different analysis models i.e. (I) Model 1- Structure Analyzed by Equivalent Static Analysis, (II) Model 2- Structure Analyzed by Response Spectrum Analysis and (III) Model 3- Structure Analyzed by Time History Analysis. In this section only the conclusion obtained from the analysis result and their discussions are presented. This study leads to following conclusion. 1) As a result of comparison between three mentioned analysis it is observed that the displacement obtained by static analysis are higher than dynamic analysis including response spectrum and time history analysis 2) The spectral acceleration versus period is used to define the acceleration values in the both directions, i.e. THX and THY, to account for the directional uncertainty of the earthquake motions and the low probability of simultaneous occurrence of the maximum response for each direction, the time-history method allows a much more complete analysis because it provides the time evolution of any kind of result. For important structures time history analysis should be performed as it predicts the structural response more accurately in comparison with other two methods. 3) From results and discussion chapter, Linear static analysis of structures can be used for regular structures of limited height as in this process lateral forces are calculated as per code based fundamental time period of the structure. Linear dynamic analysis are an improvement over linear static analysis, as this analysis produces the effect of the higher modes of vibration and the actual distribution of forces in the elastic range in a better way. 4) Static analysis is not sufficient for high rise building and its necessary to provide dynamic analysis. The results of equivalent static analysis are approximately uneconomical because values of displacement are higher than dynamic analysis. 5) A quantitative comparison of the base shear for three models is presented. Their seismic performance during the seismic time period interval has been vary. Although the three analysis have different attributes, they all have acceptable performance and are expected to behave desirably in seismic events. 6) Suitable methods of analysis are provided in codes of practice; in general, the more complex and tall the building, the more stringent the analysis that is required. The linear time history method has huge potential to improve seismic performance in that dynamic amplification effects due to yielding are explicitly included in the evaluation.

References

[1] IS: 1893-2002 part-1 Code of Practice Criteria for Earthquake Resistant Design of Structures (Part 1 : General Provision and Buildings) [2] IS: 4326-1993 Code of Practice Earthquake Resistant Design and Construction of Buildings [3] IS: 13920-1993 Code of Practice Ductile Detailing of Reinforced Concrete Structures subjected to Seismic Forces [4] [1] MrunmayiGursale and P.S.Patil, Comparative parametric study of linear and nonlinear behavior of multistory structures, International Journal of Research in Engineering and Technology, Volume: 04 Issue: 04 | Apr-2015 [5] Pankag agrawal, Manish shrikhande, Earthquake resistant design of structure. [6] S.K. duggal, Earthquake resistant design of structure. [7] Chopara A. K, Dynamic of structure [8] IS 1893(part 1) (2002), Indian Standard Code of Practice for Criteria for Design of Earthquake Resistant Structures, Bureau of Indian Standards, New Delhi. [9] IS 456:2000, Indian Standard Code of Practice for Criteria for Plain and Reinforcement concrete, Bureau of Indian Standards, New Delhi [10] EERI, 1999, Earthquake Engineering, Lessons Learnt Over Time – Learning from Earthquakes Series: Volume II Innovative Recovery in India, [11] IITK-BMTPC Earthquake Tip, New Delhi, Research Institute, Oakland (CA), USA.Murty, C.V.R., 2004. [12] FEMA – 547. (2006). Federal emergency management Agency, ”Techniques for the seismic rehabilitation of existing buildings.” [13] Washington, D.C. FIB (2003).” Seismic Assessment and retrofit of reinforced concrete buildings: state of the art report – International (4), 552- 568. [14] IS 456 – 2016, Bureau of Indian standards, New-Delhi (2016), Code of practice for “Plain and Reinforced Concrete”. [15] IS 10262 – 2019, Bureau of Indian standards, New-Delhi (2019), Indian standard recommended guidelines for concrete mix design, [16] ACI 440. 1R(2007). American Concrete Institute (ACI) Committee 440 Farmington Hills, MI, Report on “Fibre-Reinforced Polymer (FRP) Reinforcement”, [17] ACI 440. 2R (2008). American Concrete Institute (ACI) Committee 440.Farmington Hills, MI. Guide for the “Design and Construction of externally bonded FRP Systems”, [18] ACI 544. 1R (2002), American Concrete Institute 544. Farmington Hills, MI, State of the Art report on “Fibre Reinforced Concrete”, [19] ACI 544. 5R (2010), American Concrete Institute 544, Farmington Hills, MI. Topic on the “Physical Properties and Durability of Fibre-Reinforced concrete”, [20] Alcocer, S.M. (1993), Journal of Structural Engineering, ASCE, Vol. 119, No. 5, app. 1413 – 1431, RC Frames Connections Rehabilitated by Jacketing,” [21] Alcocer, S.M. and Jirsa, J.O (1993). ACI Structural journal, Vol. 90, No.3, Topic on “Strength of Reinforced Concrete Frame Connections Rehabilitated by Jacketing”, [22] Austin, S; Robin, P. and Pan, Y. (1999). Cement and Concrete Research, Vol. 29, No. 7, pp. 1067- 1076. “Shear Bond Testing of Concrete Repairs”, [23] Bett, B.J; Klingner, R.E and Jirsa, J.O. (1988).”Lateral Load Response of strengthened and Repaired Reinforced Concrete Column”, ACI Structural Journal, Vol. 85. 5, pp. 499-508 [24] Beushausen, H and Alexander, M.G. (2008). “Bond Strength Development Concretes of Different ages”, Magazine of Concrete Research, Vol. 60, No.1, pp. 65. [25] Seible, F; Priestly, M.J.N; Hegemier, G.A; and Innamorato, D (1997) ASCE – Journal of Composites for Construction, 1 (2), 52-62. “Seismic Retrofit of RC Columns with Continuous Carbon Fiber Jackets”, [26] Saadatmanesh H, Ehsani MR and Jin L; (1997) ACI Structural Journal 94, Study on “Repairs of Earthquake – Damaged RC Columns with FRP Wraps”, [27] Saadatmanesh, H; and Ehsani, M.R. (1990) Journal of Structural Engineering, ASCE, 117, PP. 3417 – 3433. “Reinforced Concrete Beams Strengthened with GFRP plates I”, [28] Saadatmanesh, H; Ehsani, M.R; and Jin, L. (1996) “Seismic Strengthening of circular bridge pier models with fiber composite”, ACI Structural Journals, 93 (6), pp. 639-647. [29] Saxena, P; Toutanji, H; and Noumowe, A. (2008) “Failures Analysis of FRP –strengthened RC Beams”, Journal of composites for construct

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Copyright © 2025 Wahane Rasika Murlidhar, Phuke Rahul M.. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.