A 51-story building in downtown Los Angeles that is equipped with a seismic monitoring accelerometric array recorded the Mw7.1 Ridgecrest, California earthquake of July 5, 2019. The building is a dual-core reinforced-concrete shear-wall and perimeter-column structure with ~ 80% of floors constructed as post-tensioned flat slabs, which makes it a trending design. Using system identification methods, spectral analyses, and coherence-phase angle computations, the recorded response data allowed the identification of dynamic response characteristics (fundamental frequencies of [NS] 0.21 Hz, [EW] 0.28 Hz, and [Torsional] 0.45 Hz, critical damping percentages < 2.5%, and associated mode shapes), as well as computation of drift ratios with maximum peaks of 0.145% for both NS and EW directions. The critical damping percentages are consistent with those recommended by LATBSDC (2017). There is no indication from the records that post-tensioned slab design played any role in altering the dynamic characteristics.

洛杉矶市中心一栋51层的建筑，装有地震监测加速度计阵列，记录了2019年7月5日加利福尼亚州里奇克莱斯特Mw7.1地震。该建筑是双芯钢筋混凝土剪力墙和周长柱约有80％的地板构造为后张拉平板，这使其成为一种趋势设计。使用系统识别方法，频谱分析和相干相角计算，记录的响应数据可以识别动态响应特性（[NS] 0.21 Hz，[EW] 0.28 Hz和[Tortional] 0.45 Hz的基本频率，临界阻尼百分比<2.5％，以及相关的振型），以及计算NS和EW方向最大峰值为0.145％的漂移比。临界阻尼百分比与LATBSDC（2017）推荐的百分比一致。从记录中没有迹象表明，后张板设计在改变动力特性方面起了任何作用。