大跨胶合木拱桥人致振动及其优化控制

现代胶合木结构人行桥因轻质高强材料的使用而变得轻柔和低阻尼化,无论采取何种结构形式其基频均难以避开步行频率范围,桥梁将产生共振。为研究木结构人行桥的人致振动特性,舒适度评价和减振优化控制方法,进行了一座大尺寸胶合木拱桥模型的人致振动试验和ANSYS有限元仿真分析。分析结果很好地预测了多重调谐质量阻尼器(MTMD)的减振效率,与试验测试结果吻合良好,验证了该方法的可靠性和实用性,可以应用于木结构人行桥的振动优化控制。研究表明：空载时竖向基频小于3Hz、满载时(2人/m2)横向基频小于1.2Hz的木结构人行桥,需要分别检算其在单人和人群共振荷载作用下的竖向和横向加速度峰值是否小于舒适度容许值;采用固定位置集中加载(原地踏步)代替行人移动作用对人行桥激振,既能简化求解过程,又使结果略偏安全;MTMD在其参数经遗传算法优化后可以将木结构人行桥在共振频率附近较窄频带内的动力响应控制在容许范围内。

Human-induced vibration and optimal control of long-span glulam arch bridges

The modern glued-laminated timber (glulam) footbridge becomes flexible and low-damping due to the use of lightweight and high-strength materials. Although many structural styles have been taken, this kind of bridge is still easy to generate resonance because the fundamental frequency is very close to that of the pedestrian. To study the human-induced vibration performance, comfort assessment and optimal control of the glulam footbridge, human-induced vibration tests and finite element simulation were conducted on a large-scale arch model. The damping efficiency of multiple tuned mass dampers (MTMD) was well predicted and was in good agreement with experimental results. The research results can be applied to the optimal vibration control of the glulam footbridge. It is shown that the peak lateral and vertical acceleration of the glulam footbridge needs to be checked separately under single-or crowd-resonant loads for the comfort limits when the vertical fundamental frequency is less than 3 Hz without load or the lateral fundamental frequency under full load case (2 persons/m2) is less than 1.2Hz. The use of fixed-position centralized loading (in-situ stepping) instead of pedestrian movement to excite the footbridge can simplify the solution procedure and make the results more reliable. The dynamic response of the glulam footbridge in the narrow frequency near the resonance can be controlled within the allowable range when the parameters of MTMDs are optimized by genetic algorithm.