دانلود رایگان مقاله انگلیسی ارزیابی رانش باقیمانده احتمالی SMRFs با میراگرهای ویسکوز خطی و غیر خطی - الزویر 2018

abstract

Maximum Residual Interstory Drift Ratio (MRIDR) is one of the most important Engineering Demand Parameters (EDPs) for evaluating the safety of structures after the occurrence of an earthquake. This EDP is used as an index to decide about the retrofit or demolition of structures. The main purpose of this study is to evaluate the effects of using linear and nonlinear Fluid Viscous Dampers (FVDs) on the MRIDR response of steel Special Moment Resisting Frames (SMRFs) with FVDs. Moreover, two vertical distributions of damping coefficients including Uniform Distribution (UD) and Interstory Drift Proportional Distribution determined based on the first mode deformations (IDPD) are compared for the structures considered. The values of median MRIDR capacity, median SaRD, corresponding to different MRIDR levels are determined by performing Incremental Dynamic analyses (IDAs). After computing the median SaRD for a specified MRIDR level and its corresponding logarithmic standard deviation, the Mean Annual Frequency (MAF) of exceeding that MRIDR level (λRD) is computed. Based on the results, the values of median SaRD for structures with linear FVDs are higher than those for structures with nonlinear FVDs, and hence the values of λRD corresponding to structures with linear FVDs are lower than those for structures with nonlinear FVDs. In addition, for structures with a soft story, using IDPD to determine damping coefficients results in higher median SaRD values, and hence lower λRD values.

7. Conclusions

In this study, probabilistic residual drift assessment of steel SMRFs with linear and nonlinear FVDs was conducted. For this purpose, three SMRFs and two vertical distributions of damping coefficients including Uniform Distribution (UD) and Interstory Drift Proportional Distribution determined based on the first mode deformations (IDPD) were considered. To evaluate the effect of damper nonlinearity, four values of velocity exponent, i.e., α = 0.25, 0.5, 0.75 and 1.0, were assumed. Moreover, four MRIDR levels were considered for performing IDAs. Then, the median MRIDR capacities (median SaRD) of the structures equipped with linear and nonlinear FVDs were estimated, and their corresponding fragility curves were developed. After developing fragility curves for different levels of MRIDR, by combining them with their corresponding seismic hazard curve, MAFs of exceeding different levels of MRIDR (λRD) were calculated. The conclusions of this study are summarized as follows:

• The structures equipped with linear FVDs (i.e., α = 1.0) have higher median SaRD values compared with those obtained for the corresponding structures with nonlinear FVDs (i.e., α = 0.25, 0.5 and 0.75). Moreover, among the structures with nonlinear FVDs, as the value of α increases, the median SaRD increases correspondingly. For example, according to the results for the 3-story-h1-1.4-UD structure, in the worst case, the Residual Drift Margin Ratio (RDMR) corresponding to α = 0.25 and MRIDR = 2.0% is 0.663 times that corresponding to α = 1.0.

• For each of the three structures considered, the lowest value of MAF of exceeding each MRIDR level (λRD) belongs to the structure with linear FVDs, and by decreasing the value of α, the value of λRD increases correspondingly.