The Effect of Composite Floor Behavior on the Failure of Steel Moment-Resistant Connections

9416363 Leon在1994年1月17日加州北岭地震后，观察到钢框架中焊接抗弯连接断裂的独特失效。 这些失效可分为O结构失效，O主要与钢构件和焊缝中的延性和局部应变比设计中设想的大有关，或O冶金失效，O主要与焊接缺陷、焊接工艺差、宽翼缘构件厚截面韧性不足以及存在应力缺陷（如垫板）有关。 故障的主要原因的解决方案将决定必须修改的抗震设计规范的规定。 它还将决定钢框架所需的维修和修复的性质，因为改造策略将根据故障的主要原因而有所不同。 这个项目通过研究荷载和阻力两个方面的问题来解决结构行为的问题。 关于电阻，本研究将调查是否存在的复合楼板和屈服的发生在面板区区域的连接显着增加了局部应变附近的关键焊缝。 将进行分析-实验相结合的研究，重点关注焊接连接的局部行为，特别是底部梁翼缘附近的区域，大多数断裂发生在该区域。 实验计划将包括三个梁-柱子组件的测试，包括一个没有板，一个有板具有部分复合作用，一个有板具有完全复合作用。 三维非线性连续有限元分析将用于量化焊缝附近的局部应变以及混凝土/钢界面处部分复合作用对力传递的影响。 在荷载方面，本研究将通过使用能够跟踪水平和垂直加速度的三维、非线性、瞬态动态框架分析程序来解决地震期间结构中可能的力分布。 这项研究将对钢结构的设计产生深远的影响，如果它可以证明，目前的抗震分析和设计方法的钢框架抗侧力系统是不够的，因为他们通常排除了组合楼板对结构性能的影响。 这是一个北岭地震项目。 ***

9416363 Leon Unique failures by fracture to welded moment-resisting connections in steel frames were observed after the Northridge, California earthquake of January 17, 1994. These failures can be categorized either as Ostructural,O which is associated primarily with larger ductilities and local strains in the steel members and welds than is envisioned in design, or Ometallurgical,O which is associated primarily with weld defects, poor weld workmanship, lack of toughness in thick sections of wide- flange members, and the presence of stress risers such as backing plates. The resolution of the primary cause of the failures will determine the provisions of the seismic design specifications which must be modified. It will also dictate the nature of the repair and rehabilitation that will be required in steel frames, since the retrofit strategies will differ depending on the primary cause of failure. This project addresses the problem of structural behavior by examining both the load and resistance aspects of the problem. With respect to resistance, this research will investigate whether the presence of a composite floor slab and the occurrence of yielding in the panel zone region of the connection significantly increased the local strains near the critical welds. A combined analytical-experimental investigation will be conducted to focus on the local behavior of the welded connections, and in particular on the region near the bottom beam flange, where most of the fractures occurred. The experimental program will include tests of three beam-to-column subassemblages, including one with no slab, one with a slab having partially composite action, and one with a slab having fully composite action. Three-dimensional nonlinear continuum finite element analysis will be used to quantify the local strains near the welds and the effect on force transfer of partial composite action at the concrete/steel interface. With respect to loading, this research will address th e probable force distribution in the structure during the earthquake through the use of a three-dimensional, nonlinear, transient dynamic frame analysis program capable of tracking both horizontal and vertical accelerations. This research will have a profound effect on the design of steel structures if it can be demonstrated that current seismic analysis and design methodologies for steel frame lateral-resistance systems are inadequate, since they usually exclude the effect of the composite floor slabs on the structural behavior. This is a Northridge Earthquake project. ***