全容式LNG储罐抗震性能的振动台试验及有限元研究

Shaking Table Tests and Finite Element Study of Seismic Performance of Full‑containment LNG Storage Tanks

摘要:

全容式液化天然气（LNG）储罐是燃气系统的重要组成部分，其抗震性能对城市天然气供应至关重要。本研究以 16×104 m3 的超大型全容式 LNG 储罐为原型，开展了 1∶14 缩尺全容式 LNG 储罐模型的振动台试验，并分析了其加速度响应分布和应变响应分布。同时基于有限元软件 ABAQUS 建立了考虑流固耦合的全容式 LNG 原型储罐有限元模型。再通过相同的有限元建模方法对缩尺模型进行建模，对比振动台试验中响应较大位置处的加速度和应变时程，从而验证了有限元建模方法的合理性。随后选取Ⅱ类场地的 3 条地震波作为地震激励，得到了全容式 LNG 储罐原型结构在 0.2g 地震动下的剪力分布和 0.4g 地震动下的结构响应，其中包括加速度响应分布，位移响应分布和应力响应分布，从而对结构的抗震性能和失效机制进行评估。研究结果表明：①在主要频段覆盖结构一阶固有频率的地震动和长周期速度脉冲型地震动激励下，结构的加速度响应和最大层间剪力均被明显放大；②混凝土外罐的薄弱位置是穹顶与侧壁的连接部位；③在长周期速度脉冲型地震动激励下，钢内罐除了发生“象足”屈曲外，还可能发生由液体大幅晃动所产生的“菱形”屈曲模式。

Abstract:

Full-containment liquefied natural gas (LNG) storage tanks are a critical part of gas supply systems, and their seismic performance is essential for ensuring urban natural gas supply. This study used an ultra-large full-containment LNG storage tank with a capacity of 16 × 104 m3 as the prototype to conduct shaking table tests on a 1∶14 scaled model of the full-containment LNG tank, and analyze its acceleration and strain response distributions. Meanwhile, a finite element model of the prototype tank, considering fluid-structure interaction, was established using finite element software ABAQUS. Then, the scaled model was modeled using the same finite element modeling approach. The acceleration and strain time histories at high-response locations in the shaking table tests were compared, thereby validating the reliability of the finite element modeling method. Subsequently, using three seismic waves from Site Class II as seismic excitations, the shear force distribution under 0.2g ground motion and structural responses—including acceleration, displacement, and stress distributions under 0.4g ground motion—of the full-containment LNG prototype tank were obtained to evaluate the tank's seismic performance and failure mechanisms. The results showed that: (1) under seismic excitations with dominant frequency bands covering the first-order natural frequency of the structure and long-period velocity pulse-type ground motions, both the structural acceleration response and maximum interstory shear force were significantly amplified. (2) The weak points of the concrete outer tank were at the connections between the dome and lateral wall. (3) Under excitations of long-period pulse-type ground motions, the steel inner tank may experience not only "elephant-foot" buckling but also "diamond-shaped" buckling modes caused by substantial liquid sloshing.