PSI - Issue 70

Ajisha T T et al. / Procedia Structural Integrity 70 (2025) 27–34

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Table 4 Maximum IDR in percentage

Maximum IDR in percentage

Kocaeli

Landers

Loma Prieta

Northridge

Average

Model1 Model2 Model3

1.901 1.726 0.710

1.653 1.814 1.579

1.738 1.623 1.298

1.176 1.081 0.529

1.619 1.561 1.029

Table 5 Performance level of all models

Models

Inter storey percentage

drift

In Performance levels

Model1 Model2 Model3

1.69

LS – CP LS – CP IO- LS

1.561 1.029

6. Conclusion The conclusion of the study can be summarized as follows,

1. From static and response spectrum analysis, Model 1shows higher storey displacement and inter storey drift ratio than other models. Model 2 behaves similar to model 1 without any notable differences in the result between them. Model 3 shows an 8.71% decrease in storey displacement and a 13.3% decrease in Inter storey drift. All models have experienced a higher percentage of Inter storey drift at first outrigger level. The critical height of the structure is found ranging from 0.7H to 0.85H. 2. From Nonlinear time history analysis, Model 2 shows higher storey displacement and Model 1 shows higher inter storey drift. Model 3 shows a 12.42% decrease in lateral storey displacement and a 25.43% decrease in inter-storey drift. In contrast to response spectrum analysis, all models experienced a higher percentage of inter storey drift at the second outrigger level. Due to the nonlinear behaviour of the structure, the critical height is found throughout the height of all models ranging from 0.37H, 0.45H, and 0.73H. 3. Model 3 shows a 36.6% decrease in average inter-storey drift and 92.1% decrease in average top storey drift due to the presence of outrigger at the top storey. Relative stiffness and distance between two outriggers greatly influence the behaviour of stories between them. The nonlinear responses of the structure increase with increases in the height of the structure due to the participation of higher modes. 4. Scattering of acceleration of ground motion input for a longer period result in unpredictable behaviour on all models. The seismic behaviour of all models is different in different ground motion irrespective of its PGA values. Performance levels of model 3 are better compared to other models and their level lies between and immediate occupancy level and life safety. So, to analyze the seismic response of the structure, it is well recommended to perform non-linear time history analysis in designing high rise structures. References Brunesi,E.,Nascimbene,R.,and Casagrande, L.2016. Seismic analysis of high-rise mega-braced frame-core buildings..Eng. Struct. 115 pp 1-17. Dennis, C. K. Poon, Ling-En Hsiao, Yi Zhu, and Leonard Joseph. 2011. “NonLinear Time History Analysis for the Performance Based Design of Shanghai Tower”. Struct. Congr. Pp 1-17 Patil, D. M. and Sangle, K. K. 2015. “Seismic behaviour of different bracing systems in High rise 2-D steel buildings”. Struct. 3 pp 282-305. Patil, D. M. and Sangle, K. K. 2016. “Seismic behaviour of outrigger braced systems in High rise 2-D steel buildings”. Struct. 8 pp 1-16. Taranath, B. S. 2012. Structural analysis and design of tall buildings. New York:CRC Press.pp 1-18 Hi Sun Choi, Goman Ho, Leonard Joseph and Neville Mathias. 2017. Outrigger Design of High-Rise Buildings: An output of the CTBUH outrigger working group. Council on Tall Building and Urban Habitat: Chicago. pp 115-134 Alok Rathore, Dr. Savita Maru "A Performance Based Analysis of Outrigger Structural System for Vertical Irregular Tall Building". International journal of trends in engineering and research, Volume 4, Issue 12, December 2017. Premalatha J, Mrinalini M "Seismic Behaviour of a Multi-Storeyed Reinforced Concrete Irregular Building with Outrigger Belt Truss System". International Journal of Engineering and Advanced Technology, Volume-8, Issue-2S, December 2018. Al-Subaihawi, S.; Kolay, C.; Marullo, T.; Ricles, J.M.; Quiel, S.E.: Assessment of wind-induced vibration mitigation in a tall building with damped outriggers using real-time hybrid simulations. Eng. Struct. 205, 110044 (2020). Fang, C.; Spencer, B.F.; Xu, J.; Tan, P.; Zhou, F.: Optimization of damped outrigger systems subject to stochastic excitation. Eng. Struct. 191, 280 291 (2019).