Influence of near‐field ground motions with fling‐step and forward‐directivity characteristics on seismic response of stilted buildings in mountainous area

The Structural Design of Tall and Special Buildings Pub Date : 2024-03-21 DOI:10.1002/tal.2109

Ruifeng Li, Yingmin Li, Weihao Pan, Liping Liu

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Abstract

SummaryNear‐field ground motions with fling‐step and forward‐directivity characteristics contain large‐amplitude pulses in velocity history, causing severe damage to stilted buildings in mountainous areas. In this study, three groups of 20 near‐field ground motions with fling‐step and forward‐directivity characteristics and 10 far‐field ground motions were selected as seismic inputs. Nonlinear response history analysis (NLRHA) was performed on plane finite element models of two seven‐story stilted frame structures, one with steel braces in the stilted story and the other without steel braces in the slope direction. Structural seismic response obtained from NLRHA was discussed in terms of inter‐story drift ratio (IDR) and peak floor acceleration (PFA). In addition, damage to two structures was assessed using the modified Park–Huang damage model. The results show that stilted structures exhibit greater inter‐story ratios and damage index values under near‐field ground motions with fling‐step characteristics and forward‐directivity characteristics than far‐field ground motions, where the stilted story has the highest amplification ratio in both IDR and damage index among floors. Designers should pay sufficient attention to the influence of ground motions with fling‐step and forward‐directivity characteristics on seismic demands and damage to stilted structures. The peak inter‐story ratio and damage index of stilted structures with steel braces were significantly lower than that of stilted structures without braces, proving the validation of setting steel braces on reducing the seismic demands of stilted structures and improving structural seismic safety. Additional NLRHA performed using artificial pulses shows that the seismic response of stilted buildings is related to pulse periods of near‐field ground motions and the greatest seismic demands and damage are obtained when the pulse period is 1.5–1.6 times the fundamental period of the stilted building.

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具有平步和前导特性的近场地面运动对山区棚屋地震响应的影响

摘要具有平步和前向特性的近场地面运动在速度历史中包含大振幅脉冲，会对山区的棚屋建筑造成严重破坏。本研究选取了三组 20 个具有平步和前向特性的近场地面运动和 10 个远场地面运动作为地震输入。对两个七层高跷框架结构的平面有限元模型进行了非线性响应历史分析（NLRHA），其中一个在高跷层有钢支撑，另一个在斜坡方向没有钢支撑。从层间漂移比（IDR）和峰值楼层加速度（PFA）方面讨论了 NLRHA 得出的结构地震响应。此外，还使用修改后的 Park-Huang 损伤模型对两个结构的损伤进行了评估。结果表明，与远场地面运动相比，在具有阶梯特性和前向特性的近场地面运动下，高跷结构表现出更大的层间漂移比和破坏指数值，其中高跷层的层间漂移比和破坏指数在各楼层中都具有最高的放大比率。设计人员应充分重视平步地动和前向地动对棚架结构抗震要求和破坏的影响。设置钢支撑的棚架结构的层间比峰值和破坏指数显著低于未设置钢支撑的棚架结构，证明了设置钢支撑对降低棚架结构的抗震要求和提高结构抗震安全性的有效性。另外，利用人工脉冲进行的近地震动评估表明，高脚建筑的地震反应与近场地震动的脉冲周期有关，当脉冲周期为高脚建筑基本周期的 1.5-1.6 倍时，地震需求和破坏最大。

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The Structural Design of Tall and Special Buildings

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