Seismic Evaluation of Steel Moment Resisting Frames (MRFs)—Supported by Loose Granular Soil

Soil underneath a structure might affect the behavior and the overall response of the structure in seismic events. The role of loose soil conditions and the inclusion of soil-structure interaction (SSI) in the analysis are important issues that need to be addressed. Since steel structures are light, two configurations designed as spatial and perimeter are considered to study the effect of soil on the steel structural frames for the same building. The paper provides a parametric analysis on the influence of SSI on the overall performance of MRFs (Moment Resisting Frames) according to the provisions of Saudi Building Code (SBC) [1]. A case study has been developed in which spatial and perimeter moment resisting frames of 12, 6 and 3 stories residential buildings are designed using Saudi Building Code (SBC) prescriptions. A modal response spectrum analysis has been carried out to see the influence of SSI on the fundamental period of vibration, top story displacement and inter-story drift limitations. Moreover, a static non-linear analysis has been performed to investigate the performance of frames, thus allowing to identify the influence of SSI on the structural design of steel MRFs.

滑坡速度计算及涌浪预测方法探讨

滑坡滑动速度的计算是涌浪预测的基础。在考虑滑坡入水条块受水阻力的基础上,对计算滑速的美国土木工程师协会推荐公式和运动方程方法进行改进,并以三峡库区秭归县下土地岭滑坡为例,计算了滑坡下滑过程中的平均速度及各条块的加速度、速度,对比分析了考虑水阻力前后加速度、速度大小、变化规律,并计算了滑坡下滑激起的初始涌浪高度。结果表明,考虑滑坡入水条块所受的水阻力,更符合滑坡运动过程中的实际受力情况。且水阻力对于滑坡运动的加速度、速度有较大影响,没有考虑水的阻力时,随着入水条块的增多,加速度先增大后减小,且变化趋势不会反弹;考虑水阻力后,由于水阻力大小和滑坡速度及坡面的迎水面积均相关,在两种因素综合作用下,加速度有可能在出现减小趋势后再增大。