Comparative Study on Static and Dynamic Analysis of a G+5 RCC Building as per IS 1893 (Part 1): 2016 on Serviceability Parameters

Comparative Study on Static and Dynamic Analysis of a G+5 RCC Building as per IS 1893 (Part 1): 2016 on Serviceability Parameters

Rahul Meena

M.E Scholar, Department of Civil Engineering, Jabalpur Engineering College, Jabalpur, India

R.K Grover

Professor, Department of Civil Engineering, Jabalpur Engineering College, Jabalpur, India

Abstract: Accurate estimation of seismic forces and structural response is essential for earthquake-resistant design. IS 1893 (Part 1):2016 allows the use of both Equivalent Static Analysis (ESA) and Response Spectrum Analysis (RSA) for regular medium-rise RCC buildings, though the responses obtained from these methods may differ. This study presents a comparative seismic analysis of a G+5 RCC building located in Seismic Zone III with medium soil conditions and 5% damping, modelled and analysed in ETABS as per IS 1893 provisions. Storey displacement and storey drift in both X and Y directions are evaluated under static and dynamic loading. The equivalent static base shear is observed to be higher than the unscaled dynamic base shear; therefore, response spectrum results are scaled to satisfy code requirements. The results indicate that ESA may not adequately represent the actual mass and stiffness distribution, leading to possible over- or underestimation of displacement and drift demands, whereas RSA provides a more realistic variation of seismic response along the height. The study concludes that although both methods are applicable for G+5 buildings, response spectrum analysis offers a more reliable assessment of seismic performance.

Keywords Equivalent Static Method, Response Spectrum Method, Base Shear, Storey Drift, Storey Displacement, ETABS, IS 1893

structures by incorporating natural periods, mode shapes, and modal mass participation. Despite the improved accuracy of dynamic analysis, the static approach remains commonly adopted for low- to medium-rise buildings due to its computational simplicity. Hence, a comparative assessment is required to examine the differences in seismic response predicted by these two methods for medium-rise RCC buildings.

1. OBJECTIVE OF THE STUDY
   • To conduct seismic evaluation of a G+5 reinforced cement concrete (RCC) building using the equivalent static method in accordance with IS 1893 (Part 1):2016.
   • To perform response spectrum analysis by incorporating the dynamic and modal characteristics of the structure.
   • To examine and compare seismic responses obtained from static and dynamic analyses in terms of storey displacement and storey drift in both X and Y directions.
   • To investigate the influence of base shear scaling on the outcomes of dynamic analysis.
   • To evaluate the suitability of equivalent static and response spectrum methods for the seismic assessment of medium-rise RCC buildings.
     1. INTRODUCTION

        Understanding the structural response of buildings is particularly important in regions susceptible to seismic activity. Reinforced cement concrete (RCC) frame structures form a significant share of Indias urban building stock, making seismic evaluation a critical aspect of structural design practice. IS 1893 (Part 1):2016 outlines procedures for assessing earthquake effects using both static and dynamic analysis methods.

        The Equivalent Static Method represents seismic action through simplified lateral forces derived from seismic weight and vertical distribution, while the Response Spectrum Method accounts for the dynamic behaviour of

2. SCOPE OF THE STUDY

   The scope of the present study is confined to the following aspects:

   • A regular G+5 reinforced cement concrete (RCC) moment-resisting frame structure.
   • Linear elastic seismic analysis carried out using ETABS software.
   • Seismic action defined in accordance with IS 1893 (Part 1):2016 for Seismic Zone III with medium soil conditions.
   • Evaluation limited to serviceability-based structural response parameters, namely storey displacement and storey drift.
   • Nonlinear behaviour, including material cracking, yielding, and plastic hinge development, is beyond the scope of this study.
3. METHODOLOGY

   A three-dimensional RCC building model was created in ETABS with consistent geometry, material properties, mass distribution, and loading parameters adopted for both static and dynamic analyses. Seismic actions were applied independently along the X and Y directions.

   1. Equivalent Static Method

      The design base shear was evaluated using codal parameters including zone factor, importance factor, response reduction factor, and the fundamental natural period of the structure. This base shear was then apportioned over the height of the building in accordance with the provisions of IS 1893.

   2. Response Spectrum Method

   For response spectrum analysis, modal properties were evaluated to obtain natural periods and mode shapes, and the design spectrum for medium soil with 5% damping was applied. Modal responses were combined using the SRSS method, and the dynamic base shear was scaled to match the equivalent static base shear as per IS 1893.

4. MODELLING
   1. Building Description

      The building analysed is a G+5 RCC moment-resisting frame with overhead water tank (OHT) and lift machine room (LMR), situated in Seismic Zone III. The structure has an overall height of about 20.3 m with a consistent storey height of 2.9 m. Beams and slabs were modelled using M30 grade concrete, while columns and shear walls were assigned M35 grade concrete. The base of the structure was assumed to be fixed, and semi-rigid diaphragm behaviour was assigned at all floor levels.

      Table 1 Building Description

   2. Material Properties

      Table 2 Material Properties

      Grade of Concrete for Beams	M30
      Grade of Concrete for Slabs	M30
      Grade of Concrete for Columns	M35
      Grade of Concrete for Shear Walls	M35
      Main Reinforcement	HYSD 500
      Shear Reinforcement	HYSD 415

   3. Section Properties

   Table 3 Beam & Column Properties

   Section	Name	Width (mm)	Depth (mm)
   Beam	B 150 X 300 M30	150	300
   Beam	B 150 X 400 M30	150	400
   Beam	B 230 X 450 M30	230	450
   Beam	B 230 X 500 M30	230	500
   Beam	B 230 X 600 M30	230	600
   Beam	B 300 X 600 M30	300	600
   Column	C 300 X 450 M35	300	450
   Column	C 300 X 600 M35	300	600

   Section	Name	Grade of Concrete (N/mm2)	Type	Thickness(mm)
   Slab	S125M25 General	M30	Thin Shell	125
   Slab	S200M25 OHT&LMR	M30	Thin Shell	200
   Slab	ST200 Staircase	M30	Membrane	200

    

   Table 4 Slab Properties

   Type of Structure	RCC Moment Frame
   Location	Mumbai
   Number of floors	G+5+OHT&LMR
   Height of Project	20.3m
   Length of Project	22.158m
   Width of Project	11.353m
   Typical height of Project	2.9m

   Figure 1 Building 3D view Figure 2 Building Plan view

   Table 5 Shear wall properties

   Section	Name	Grade of Concrete (N/mm2)	Type	Thickness (mm)
   Wall	SW 230	M35	Thin Shell	230
   Wall	SW 300	M35	Thin Shell	300

   Table 6 Seismic parameters

   Parameters	Value	Code Reference	Table / Clause
   Seismic Zone Factor	0.16	IS-1893 Part 1 (2016)	Table 3 Clause 6.4.2
   Soil Type	II	IS-1893 Part 1 (2016)	Table 4 Clause 6.4.2.1
   Importance Factor	1	IS-1893 Part 1 (2016)	Table 8 Clause 7.2.3
   Damping Ratio	0.05	IS-1893 Part 1 (2016)	Clause 7.2.4
   Response Reduction Factor	5	IS-1893 Part 1 (2016)	Table 9Clause 7.2.6
   Mass Source	D=1 L=0.25(Live Load<3) L=0.50(Live Load>3)	IS-1893 Part 1 (2016)	Table 10 Clause 7.3.1

   Table 7 Stiffness Reduction Parameters

   Element	Uncrack Model	Service Model	Strength Model
   Beam	I22:1, I33:1	I22:0.5, I33:0.5	I22:0.35, I33:0.35
   Column	I22:1, I33:1	I22:1, I33:1	I22:0.7, I33:0.7
   Slab	F11:1, F22:1, F12:1 M11:1, M22:1, M12:1	F11:1, F22:1, F12:1 M11:0.35, M22:0.35, M12:0.35	F11:1, F22:1, F12:1 M11:0.25, M22:0.25, M12:0.25
   Wall	F11:1, F22:1, F12:1 M11:1, M22:1, M12:1 V13:1, V23:1	F11:1, F22:1, F12:1 M11:1, M22:1, M12:1 V13:1, V23:1	F11:0.7, F22:0.7, F12:0.7 M11:0.1, M22:0.1, M12:0.1 V13:0.1, V23:0.1

   Figure 4 Supports

   Figure 3 Columns and Walls Figure 5 Support Restraints

   Individual modal responses were combined using the Square Root of the Sum of Squares (SRSS) method.

   The base shear values obtained from response spectrum analysis before scaling were:

   Table 9 Dynamic Base Shear

   DYNAMIC BASE SHEAR
   SPECX	393.6 KN
   SPECY	410.5 KN

   Figure 6 Semi Rigid Daiphragm

5. ANALYSIS AND VALIDATION

   Seismic evaluation of the G+5 RCC building was performed in ETABS using both the Equivalent Static Method (ESM) and the Response Spectrum Method (RSM), while maintaining identical modelling assumptions, material properties, mass distribution, and loading conditions. Earthquake loads were applied separately along the X and Y directions in compliance with IS 1893 (Part 1):2016.

   A. Equivalent Static Analysis

   Under the Equivalent Static Method, the design seismic base shear was evaluated using codal parameters including seismic zone factor, importance factor, response reduction factor, soil condition, and the fundamental natural period of the structure. The resulting total base shear was subsequently apportioned along the building height in accordance with the storey mass and elevation.

   The total design base shear obtained from equivalent static analysis was:

   These values were found to be considerably lower than the corresponding results obtained from the equivalent static analysis. To facilitate a consistent comparison of seismic response parameters, the response spectrum results were scaled such that the total dynamic base shear equaled the equivalent static base shear in both principal directions. Following this scaling procedure, the dynamic base shear values were modified to:

   Table 10 Base Shear Scaling

   STATIC BASE SHEAR		SCALE FACTOR	DYNAMIC BASE SHEAR
   EX	806.1	20090.88	SPECX	806.1
   EY	806.1	19263.9	SPECY	806.1

6. RESULTS AND DISCUSSION
   1. Storey Drift Comparison.

      Maximum storey drift values remain within the permissible limit of 0.004 times storey height as per IS 1893. Static analysis produces higher drift values in all storeys in X direction. In Y direction static analysis generally produces slightly higher drift values in upper storeys, whereas dynamic analysis shows higher drift in lower storeys. The value of drifts are taken from service model.

      Table 8 Static Base Shear

      STATIC BASE SHEAR
      EX	806.1 KN
      EY	806.1 KN

      These values were used as the reference base shear for comparison with dynamic analysis results.

   2. Response Spectrum Analysis

   Response spectrum analysis was carried out to assess the dynamic behaviour of the structure by accounting for the participation of multiple vibration modes. An initial modal analysis was conducted to obtain the natural time periods and corresponding mode shapes. The design response spectrum for medium soil conditions with 5% damping, as specified in IS 1893 (Part 1):2016, was adopted, and the

   Figure 7 Storey Drift in X

   Figure 8 Storey Drift in Y

   B. Storey Displacement Comparison

   Maximum top storey displacement in the X-direction is 30.843 mm (ESA) and 24.498 mm (RSA), indicating that the static method yields higher lateral displacement. In the Y-direction, RSA produces higher displacements in all storey except OHT & LMR compared to ESA, reflecting directional stiffness variation and higher-mode effects. Static analysis shows a more uniform but conservative displacement profile, whereas RSA captures realistic deformation behaviour. The values of displacement are taken from service model.

7. CONCLUSIONS

From the present stuy, the following conclusions are drawn:

1. The base shear obtained from the response spectrum analysis was observed to be lower than that from the equivalent static method. This difference arises because the dynamic analysis accounts for the contribution of multiple vibration modes in distributing seismic inertia forces, rather than assuming the structures response to be governed solely by the fundamental mode. Consequently, the combined modal response results in a reduced dynamic base shear. To ensure compliance with the provisions of IS 1893, the response spectrum results were subsequently scaled such that the total dynamic base shear matched the equivalent static base shear.
2. Equivalent static analysis resulted in higher storey displacement and drift in the X-direction.
3. Response spectrum analysis governed the displacement in all storeys except OHT&LMR in Y direction and also drift response in the Y-direction are higher at upper storey levels while equivalent static method produces higher drift in lower storeys thus RSA responses indicating the influence of dynamic effects.
4. Overall, response spectrum analysis provides a more accurate representation of seismic demand and is preferable for detailed seismic assessment of G+5 RCC buildings.

Figure 9 Storey Displacement in X

Figure 10 Storey Displacement in Y

REFERENCES

1. [1] Agarwal P. and Shrikhande M., Earthquake Resistant Design of Structures, New Delhi, India: PHI Learning Private Limited, 2011.
2. [2] American Concrete Institute, Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19), Farmington Hills, MI, USA: American Concrete Institute, 2019.
3. [3] Bagheri B., Firoozabad E. Salimi and Yahyaei M., Comparative study of the static and dynamic analysis of multi-storey irregular buildings, International Journal of Civil and Structural Engineering, vol. 6, no. 11, pp. 10451049, 2012.
4. [4] Bajpai Shobit, Grover R.K Earthquake Resistance Performance of a Multistorey RCC Frame Considering Two Different Positions of the Staircase. International Journal for Research in applied science and Engineering Technology, Volume 10, Issue , Sep 2022.
5. [5] Bureau of Indian Standards, IS 875 (Part 1): 1987 Code of Practice for Design Loads (Other Than Earthquake) for Buildings and Structures: Dead Loads, New Delhi, India.
6. [6] Bureau of Indian Standards, IS 875 (Part 2): 1987 Code of Practice for Design Loads (Other Than Earthquake) for Buildings and Structures: Imposed Loads, New Delhi, India.
7. [7] Bureau of Indian Standards, IS 1893 (Part 1): 2016 Criteria for Earthquake Resistant Design of Structures: General Provisions and Buildings, New Delhi, India.
8. [8] Bureau of Indian Standards, SP 16: 1980 Design Aids for Reinforced Concrete to IS 456, New Delhi, India.
9. [9] Duggal S.K., Earthquake-Resistant Design of Structures, 2nd ed., New Delhi, India: Oxford University Press, 2013.
10. [10] Gottala A. and Kishore N.S., Comparative study of static and dynamic seismic analysis of a multistoried building, International

    Journal of Science, Technology & Engineering, vol. 2, no. 1, pp. 173 180, 2015.

11. [11] Khan Mohammed Mohiuddin, Khan Mohammed Furqan Ali, Karimuddin Khaja and Charan K. Sai, Comparative Study of Linear Static and Linear Dynamic Method of Seismic Analysis of RCC Multistoried Building Using ETABS. International Journal for Research in Applied Science & Engineering Technology, Volume 10,

    Issue V, May 2022

12. [12] Mahmoud S. and Abdallah W., Response analysis of multi- storey RC buildings under equivalent static and dynamic loads according to Egyptian code, International Journal of Civil and Structural Engineering Research, vol. 2, no. 1, pp. 7988, 2014.
13. [13] Masatkar Varsha, Grover R.K Comparison of Low-Rise Open Ground Storey Framed Building in Different Earthquake Zones.International Research Journal of Education and Technology, Volume: 04, Issue: 04, April 2022.
14. [14] Meleka N., Hekal G., and Rizk A., Comparative study on static and dynamic analysis of structures, Engineering Research Journal, vol. 39, no. 4, pp. 277283, 2016.
15. [15] Singh Rohan, Grover R.K Comparative Study and Analysis of Conventional and Diagrid Building in Seismic Loading.Journal of Computational Analysis and Applications (Scopus indexing), Volume 33, No. 8, 2024.