变形饱和倒塌机理在泸定震害分析中的应用

结构地震倒塌机理是一个关键而又艰难的课题。通过震害分析和逻辑推论否定了目前支配世界各国抗震设计规范的“弱柱强梁”倒塌理论。基于震害调查、模型实验和理论分析,提出了替代“弱柱强梁”的“变形饱和”理论。对于常见的多层建筑,同一楼层中如果抗侧刚度差异很大的构件“混搭”,地震作用下,刚度大的构件将出现内力凝聚现象,即使侧移很小其分担的剪力也容易达到其承载力极限并发生脆性破坏,即“变形饱和”,从而触发结构整体倒塌。通过合理的结构布置,避免内力凝聚,使结构具有超强的抗震能力。基于变形饱和理论,对泸定地震中4栋典型结构的震害现象进行了详细分析和解释,既回答了震损建筑为什么破坏,也回答了样板建筑为什么不破坏,进而为设计具有超强抗震能力的建筑结构提供参考。相关方法还可用于韧性城乡建设中既有建筑的地震风险排查和评定。

Numerical study of fatigue damage of asphalt concrete using cohesive zone model

In order to investigate the fatigue behavior of asphalt concrete, a new numerical approach based on a bi-linear cohesive zone model （CZM） is developed. Integrated with the CZM, a fatigue damage evolution model is established to indicate the gradual degradation of cohesive properties of asphalt concrete under cyclic loading. Then the model is implemented in the finite element software ABAQUS through a user-defined subroutine. Based on the proposed model, an indirect tensile fatigue test is finally simulated. The fatigue lives obtained through numerical analysis show good agreement with laboratory results. Fatigue damage accumulates in a nonlinear manner during the cyclic loading process and damage initiation phase is the major part of fatigue failure. As the stress ratio increases, the time of the steady damage growth stage decreases significantly. It is found that the proposed fatigue damage evolution model can serve as an accurate and efficient tool for the prediction of fatigue damage of asphalt concrete.

电影《唐山大地震》人物悲喜情感转换

电影《唐山大地震》改编自加拿大华人女作家张翎的中篇小说《余震》。它以1976年发生在唐山丰南县的7.8级大地震这一真实的历史事件为底本,主要演绎了地震中李元妮一家人的悲欢离合。影片一改小说的悲伤忧郁的主题,在李元妮及女儿这两条线索的发展中都呈现出了在悲戚中温暖的情感基调,尤其是主要人物李元妮的角色演绎,在悲喜互衬的美学原则中升华了人物的情感境界,在貌似平淡的表情动作中内聚了情感的冲力,从而达到了令人动容的艺术效果。