超载下板柱节点破坏形式发生次序与直剪设计计算方法  

Failure Sequence of RC Flat Plate Structures under Overloads and Calculation Method for Direct Shear Design

作　　者：杜旭 DU Xu(Shanghai Tongjian-Qianghua Architecture Design,Ltd.,Shanghai 200072,China)

机构地区：[1]上海同建强华建筑设计有限公司,上海200072

出　　处：《结构工程师》2022年第4期29-35,共7页Structural Engineers

基　　金：住房和城乡建设部课题(2020-K-132)。

摘　　要：近期发生的部分板柱结构地下车库顶板坍塌事故中,柱顶呈现“秃头”形状而非冲切引起的锥体破坏形式,引发业内讨论。研究首先认为该破坏形式为弯曲参与的板直剪破坏。考虑冲切和直剪两种破坏形式,选择文献中相应的极限承载力计算表达式。设计典型的板柱结构地下车库顶板算例,包括5种覆土厚度(1 m、1.5 m、2 m、2.5 m和3 m)和2种板柱节点形式(设置托板和“托板+柱帽”),共计10种工况,比较超载下冲切和直剪破坏的极限承载力大小和破坏顺序。结果显示,直剪破坏时的超载为冲切破坏时的46%~68%,板的直剪破坏均先于冲切破坏发生,从而解释了破坏柱顶呈现“秃头”形状的原因。经验算,《装配式混凝土结构技术规程》(JGJ 1—2014)第7.2.2条中的方法具有合适的安全储备,建议用于板柱结构中板的直剪设计计算。Recently,several collapse accidents have been reported for top slabs of underground garages using reinforced concrete flat plate structures.In these accidents,the column tops appeared“bald”shape rather than cone shape traditionally caused by punching failure.This attracted extensive attentions in industrial and academic communities.In this study,first,direct shear failure involved with bending is considered to cause the“bald”shape of the column tops.Expressions in the literature were chosen to predict ultimate resistances for punching and direction shear failures.Then ten conditions were designed for the top slabs of the underground garages using flat plate structures,including five thicknesses of covering soil(i.e.,1,1.5,2,2.5 and 3m)and two slab-column connection forms(i.e.,drop-panel and“drop-panel+column-cap”).Ultimate resistances were calculated and compared for punching and direct shear failures.Results revealed that,the overloads for direct shear failure ranged from 46%to 68%compared to that of punching failure,which meant direct shear failure occurred prior to punching failure for the slab-column connections in all ten conditions.This explained why the column tops appeared“bald”shape.It was also suggested to use the formula in term 7.2.2 in Technical specification for precast concrete structures(JGJ 1—2014)for direct shear design for the top slabs of the underground garages using reinforced concrete flat plate structures.

关 键 词：板柱结构 板柱节点 直剪破坏 冲切破坏 设计方法 

分 类 号：TU318[建筑科学—结构工程]