A Study on Seismic Response Analysis of Long Spanned Systems Subjected to Multiple Excitations Having Large Displacement

TUIS研究了大型三维结构如厂房管道系统和框架结构的试验响应分析，在这项基础性工作中，重点研究了这些系统在多个地震激励下同时从不同方向加载时的动力行为。以一个长约18.0m的带法兰的三维管道模型为典型结构，利用大型振动台和可为管道提供轴向位移载荷的致动器进行振动试验。通过本次试验，对管道弯头的位移响应特性和法兰部分的弯矩特性进行了评价。在工作台激励过程中，当轴向附加较大幅度荷载时，约束等固定部位的地震应力和响应力明显增大。此外，与无轴向载荷的情况相比，第一、二阶振型频率和相应的节距变得更大。轴向加载后，管道直段的位移响应显著增加。这一数值远大于振动台在共振激励下的响应。在轴向位移载荷作用下，翼缘部分出现较大的弯矩。这一弯矩值在轴向振动共振时保持相当稳定，但在垂直方向的共振激励下观察到该值的主要波动。

Tuis study deals with the experimental response analysis of large scaled three dimensional structures such as plant piping systems and frame type structures.In this basic work, particular intension is focused on the dynamic behavior of these systems due to multiple seismic excitations simultaneously given load from different directions. A mock-up three dimensional piping model having about 18.0m length with flanges was taken as a typical structure and vibration test was performed by using large scaled shaking table and also actuator which can provide axial displacement loading to the piping. From this testing, characteristics related to displacement response of the piping elbow and bending moment of the flange part were evaluated.Followings are main results obtained from this experimemtal investigation.1. When large amplitude loading was additionally given to the axialdirection during table excitation, seismic stress and response force on the fixed portions such as restraints clearly increased. Also, 1st and 2nd model frequencies and corresponding dainpings became larger compared with the case having no axial loading.2. Displacement response of the straight portion of the piping remarkably increased after the axial loading. This value was much larger than the response at the resonant excitation by the shaking table.3. Large bending moment appeared at the flange portion when axial displacement loading was provided. This bending moment value kept quite stable at the axial shaking resonance, however, dominant fluctuation of the value was observed at the resonance excitation from the perpendicular direction.