This paper presents the application of multi-axis hybrid simulation for evaluating the seismic response of a rigid-frame bridge structure constructed with concrete-filled steel tube (CFST) columns subjected to combined horizontal and vertical ground motions. These types of bridges are believed to have superior seismic performance and better ability to withstand collapse when subjected to extreme multi-directional seismic loads. The case-study hybrid model was a 1:3 scaled bridge structure with three spans and double-column bents. The experimental element consisted of one CFST column while the rest of the bridge elements were modelled numerically in the computer. Two popular cross-section shapes of circular and square CFST columns were tested and compared. The structure was subjected to the horizontal (longitudinal) and vertical components of the Northridge ground motion with five increasing intensity levels to cover all scenarios ranging from frequent to very rare events during the lifecycle of the structure. A state-of-the-art hybrid testing facility, referred to as the multi axis substructure testing system, was used to simulate complex boundary effects on the physical specimen using mixed load/deformation modes. The bridge columns showed great levels of ductility and no sign of severe damage or loss of stability, while they were subjected to large axial force variations and lateral deformation demands during hybrid simulations. The superior seismic performance of CFST elements highlights their benefit in construction of more resilient bridges, particularly those with the vital roles in post-disaster operations.

中文翻译：

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水平和垂直地震动对钢管混凝土柱建造桥梁的混合模拟

本文介绍了多轴混合仿真在评估刚性钢管混凝土结构（CFST）柱在水平和垂直地震动共同作用下的地震响应中的应用。这些类型的桥梁被认为具有出色的抗震性能，并且在承受极端多向地震荷载时具有更好的抗倒塌能力。案例研究混合模型是具有三个跨度和双列弯曲的1：3比例桥结构。实验元素由一根CFST柱组成，其余的桥梁元素在计算机中进行了数值建模。对圆形和方形CFST柱的两种常用横截面形状进行了测试和比较。该结构经受了Northridge地面运动的水平（纵向）和垂直分量，强度增加了五个，以覆盖结构生命周期中从频繁到非常罕见的所有场景。先进的混合测试设备，称为多轴子结构测试系统，用于使用混合载荷/变形模式模拟物理样本的复杂边界效应。桥梁柱显示出高水平的延展性，没有严重损坏或稳定性下降的迹象，而在混合模拟期间，它们承受较大的轴向力变化和横向变形要求。CFST元件的出色抗震性能凸显了它们在建造更具弹性的桥梁方面的优势，