Vaibhav Satishrao Shinde,
S.A. Bhalchandra,
- Student Department of Applied Mechanics, Government College of Engineering, Chhatrapati Sambhaji Nagar, Maharashtra, India
- Professor Department of Applied Mechanics, Government College of Engineering, Chhatrapati Sambhaji Nagar, Maharashtra, India
Abstract
The present work deals with the analysis of vertical geometric irregular structures, such as step
buildings and setback buildings, which exhibit stiffness irregularity at different locations. These
structures are analyzed using pushover analysis, a nonlinear static analysis method that provides
insight into the performance of buildings under seismic loading by incrementally applying lateral forces
until a target displacement is reached or the structure collapses. Stiffness irregularities in buildings
can significantly affect their seismic response, making it crucial to understand how different
configurations influence the overall performance. In this study, buildings with stiffness irregularity
located at various points along their height—specifically at the bottom, middle, and top—are evaluated.
The stiffness irregularity can result from various factors such as variations in column or beam
dimensions, changes in material properties, or abrupt changes in the structural system. From the data
obtained using pushover analysis, fragility curves are plotted for different damage states of the
structures. Fragility curves represent the probability of reaching or exceeding a certain damage state
as a function of seismic intensity measures, providing a probabilistic assessment of the seismic
vulnerability of the structures. A comparative analysis is carried out to assess the relative performance
of the step and setback buildings with different stiffness irregularities. It is found that step buildings
with stiffness irregularity located at the middle can transfer loads more effectively compared to those
with irregularity at the bottom. This is because the concentration of stiffness in the middle portion helps
in distributing the loads more uniformly, thereby enhancing the overall stability and reducing localized
damage. On the other hand, setback and step buildings with stiffness irregularity at the top may
experience less damage in the initial stages due to their ability to dissipate energy through higher
flexibility at the top. However, as the seismic intensity increases, these buildings become more
vulnerable to extensive or complete damage due to the larger displacements and increased demands on
the structural elements.
Keywords: Vertical irregularity, pushover analysis, fragility curves, irregular buildings, setback buildings
[This article belongs to Journal of Offshore Structure and Technology(joost)]
References
1. Barbat AH, Pujades LG, Lantada N. Seismic damage evaluation in urban areas using capacity
spectrum method. Soil Dynam Earthquake Eng. 2006; 28 (10–11): 851–865.
2. Chintanapakdee C, Chopra AK. Seismic response of vertically irregular frames: response history
and modal pushover analyses. J Struct Eng. 2004; 130 (8): 1177–1185. doi: 10.1061/(ASCE)0733-
9445(2004)130:8(1177).
3. Halder L, Paul S. Seismic damage evaluation of gravity load designed low rise RC buildings using
non-linear static method. Procedia Eng. 2016; 144: 1373–1380.doi:
10.1016/J.PROENG.2016.05.167.
4. Patel NK, Vasanwala SA. Propagating fragility curve for RC building via HAZUS methodology.
Mater Today Proc. 2020; 32 (Part 3): 314–320. . doi: 10.1016j.matpr.2020.01.399.
5. Shil P, Singhal S, Chourasia A, Ravindranatha. Seismic performance assessment of reinforced
concrete building with precast shear wall. In: Sitharam TG, Kolathayar S, Sharma ML, editors.
Seismic Hazards and Risk. Lecture Notes in Civil Engineering Vol. 116. Singapore: Springer; 2021.
pp. 95–107. doi: 10.1007/978-981-15-9976-7_10.
6. Paul S, Debnath S. Seismic damage evaluation of RC building using nonlinear static method. In:
Rao A, Ramanjaneyulu K, editors. Recent Advances in Structural Engineering, Volume 2. Lecture
Notes in Civil Engineering Vol. 12. Singapore: Springer; 2019. pp. 559–569. doi:
10.1007/978/981/13/0365-4_48.
7. Ravikumar CM, Babu Narayan KS, Sujith BV, Venkat Reddy D. Effect of irregular configurations
on seismic vulnerability of RC building. Architect Res. 2012; 2 (3): 20–26. doi:
10.5923/j.arch.2012023.01.
8. Federal Emergency Management Agency. US Department of Homeland Security. Hazus
Earthquake Model Technical Manual. Hazus 4.2 SP3. Washington, DC, USA: Federal Emergency
Management Agency; 2020.
9. Bureau of Indian Standards. IS-1893-2016 – Criteria for earthquake resistant design of structure.
New Delhi, India: Bureau of Indian Standards; 2016.
Journal of Offshore Structure and Technology
| Volume | 11 |
| Issue | 02 |
| Received | July 5, 2024 |
| Accepted | July 11, 2024 |
| Published | July 12, 2024 |