汶川大地震底框结构建筑物震害调查

四川汶川大地震灾区底框结构的震害调查中发现：在极震区，底框的坍塌和倾斜成为底框结构破坏的主要形式，底框部分破坏后，切断了地震力向上传递的通路，使得砖混部分破坏减小；随着地震烈度的降低，底框的坍塌减少，而上部砖混的坍塌增多。由于刚度突变，底框和上部砖混的结合处成为底框结构的薄弱环节：底框结构刚度大，上部砖混结构破坏；砖混结构刚度大，底框结构破坏。底框结构的破坏都表现出柱破坏的特点，而且底框梁截面高度特别大，更难实现“强柱弱梁”的设计目标。施工质量对底框结构抗震性能有重要影响，特别是混凝土、砂浆等材料的强度对抗震性能影响明显。

Reports on the damages of bottom reinforced concrete frame structures in great Wenchuan Earthquake

From the earthquake disaster investigation of bottom RC frame structures after Wenchuan earthquake,some good conclusions can be reached.In violent earthquake zone,the settlement and slope of bottom RC frame structures are the major failure type.After the bottom frame failure,the transfer access of earthquake action is cut,therefore failure of the up brick masonry decreases.With the earthquake intensity falls,the settlement of the bottom frame decreases,but the settlement of the up brick masonry increases.Due to the change of stiffness,the combination position between bottom frame and up masonry is weak: if the stiffness of bottom frame is big,the up brick masonry fails,otherwise the bottom frame fails.Failure of the bottom frame is always aroused by the columns,because the height of the beams is bigger,the design object of stronger column and weaker beam can not be realized.Construction quality,especially concrete and mortar quality,affects anti-seismic capability greatly.