空间网壳结构的节点-构件阻尼模型研究

Investigation of a joint-member damping model for single-layer latticed domes

目前尽管对已有的阻尼模型进行了大量研究,然而,经典黏性阻尼模型会过高估计阻尼力,无法真实地描述结构内未知的非线性的能量耗散,而非黏性阻尼模型应用于工程实践还存在诸多问题。针对网壳结构中的阻尼源,提出一种节点-构件阻尼模型,在节点处考虑节点与构件之间的摩擦阻尼效应,而构件的材料阻尼则认为与应力水平有关。以单层大跨空间网壳为例,对地震荷载作用下网壳结构的材料阻尼比进行评价,研究了不同阻尼模型对结构动力需求的影响。研究表明:1当材料能量耗散公式中的指数n取2.4时,该结构的平均材料阻尼比大约为0.45%~0.5%;2不同阻尼模型对网壳结构的动力需求、稳定性等参数影响显著,合适的阻尼模型的选择是对结构进行合理的抗震性能评估的前提条件,然而,在工程结构的动力分析中,这一事实往往被忽视;3提出的节点-构件阻尼模型的能量耗散主要依赖于材料的塑形变形能,从而在一定程度上消除了Rayleigh阻尼模型会过高估计结构内黏性阻尼力的缺陷。提出的这种阻尼模型,也可应用于其他形式的建筑结构体系(如平面网架)和建筑结构具有非比例黏性阻尼的情况。

At present the existing viscous damping models have been investigated by many researchers,while the damping force of a structure will be overestimated when these classical models are used in dynamic analyses,thus the nonlinear energy dissipation mechanism of the structure cannot be well described. Furthermore,there are many problems when the non-viscous damping models are applied in engineering practice. Aiming at the damping sources in single-layer latticed domes,a joint-member damping model is proposed,in which the friction damping effects at the joint are taken into account and the material damping is considered to be stress-dependent. Taking the single-layer latticed dome as the example,the structural material damping ratios are evaluated and the effects of the different damping models on the dynamic demands of the structure subjected to seismic ground motions are investigated. It shows that 1 the equivalent structural material damping ratio is about 0. 45% ~ 0. 5% when the exponent in the formula for material energy dissipation is taken to be 2. 4; 2 the damping models have significant effects on the dynamic demands and stability of a structure,and an appropriate damping model is critical for reasonably evaluating the seismic performance of a structure,which has not been well recognized in engineering practice; 3 the energy dissipation in the joint-element damping model depends heavily on the plastic deformation energy,thus to some certain extension,it can eliminate effects of the unrealistic high damping forces due to the adoption of the Rayleigh damping model. The damping model proposed in this paper can also be applied to other structural systems,e. g. flat grid structures and structures with non-proportional viscous damping.