Nonlinear dynamic assessment of mid-rise light-frame wood shear walls under horizontal and vertical ground motions
Date
2024
Authors
Mohammadi, Hadiseh
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Abstract
This research complements recent studies on light-frame wood shear walls for mid-rise buildings by comparing the dynamic performance of multi-story shear walls constructed with discrete and continuous rod hold-down systems. For this purpose, a numerical model has been developed and series of comprehensive nonlinear time-history analyses are conducted in SAP2000 software. Maximum inter-story drifts are estimated and compared under different earthquake records. According to the numerical results, using continuous steel rod hold-down could reduce the maximum drift in the multi-story strong wall by over 40%. The maximum drift in the strong shear wall with discrete hold-down is 2.3%, while this value is 1.3% in the wall with continuous rod hold-down. The results show the better performance of continuous steel rod leading to lower inter-story drifts in all stories in both multi-story conventional and strong wall. Estimates of deflection and drift of a six-story strong wood shear wall using CSA O86:19, SDPWS 2021, are also compared with numerical modelling results. The estimates from CSA O86:19 is found to be conservative, with deflections 10% to 55% higher than the FE model, while SDPWS 2021 generally predicts lower deflections in upper floors compared to FE and CSA O86. It should be noted that while the results indicate that the deflection predictions from CSA O86:19 may be conservative in some stories, the drift predictions might not be.
According to parametric studies conducted using the development numerical model, higher aspect ratios could lead to increased axial forces in studs and hold-downs as expected, with a notable rise in tension for walls with an aspect ratio of 1.50 compared to those with 0.72. Numerical results in the walls with different numbers of stories (one, three, five and six stories) illustrate how demands are distributed vertically across different stories during an earthquake event, with the maximum force in the studs concentrated at lower story levels. Numerical results show that including vertical component of earthquake slightly increases lateral deflections and axial forces, with continuous rod systems showing smaller increases compared to discrete hold-downs. In terms of diaphragm effect, a significant reduction in lateral deflection of considered shear walls under monotonic load are noted due to out-of-plane stiffness effect of diaphragms especially at higher stories.
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Keywords
Mid-rise strong light-frame wood shear wall, High seismic risk areas, Lateral load-resisting systems, Continuous rod, Discrete hold-down, Nonlinear time history analysis, SAP2000