Concrete Filled Tube Braced Frame Testing

混凝土填充管（CFT）已被用作抗震结构的柱，因为它们比钢或钢筋混凝土具有显著的优势。混凝土填充物为钢筋提供抗压强度和刚度，并减少了局部屈曲的可能性。钢管提供模板，以尽量减少混凝土放置的成本，并加强混凝土的轴向拉伸，弯曲和剪切，以及提高其延性。CFT柱特别适合支撑框架，因为需要较大的轴向强度和刚度，而支撑框架构成了用CFT柱建造的大多数建筑物。虽然CFT柱对于支撑框架是理想的，但迄今为止所有的研究都集中在弯矩框架连接，CFT成员的组合加载和CFT单元的粘结应力上。支撑框架- cft柱连接从根本上不同于弯矩框架连接，因为它们向柱传递了相对较大的轴力，这些轴力必须在钢和混凝土之间分配。支撑框架的延性要求不同，因为耗散是通过支撑屈曲而不是梁的弯曲屈服来实现的。本研究将重点研究支撑梁- cft柱连接的设计。将确定几种具有经济和性能优势的原型连接，并详细介绍非线性连接；计算机将对连接进行分析。这些分析将评估预期的延展性和断裂潜力，确定关键位置，并确定每个原型连接的关注点。将选择最有希望的连接方案进行实验评估。将为这些选定的连接开发设计方法，并进行实验研究，以评估设计方案，验证延性和抗震性能。三个支撑-梁-柱连接组件将在非弹性循环荷载下进行测试。这些样本将采用中等规模的模型，以便为3至6层的建筑提供全尺寸的连接模拟，并为高层建筑提供中等规模的连接模型。

Concrete filled tubes (CFT) have been used as columns for seismic resistant construction, since they offer significant advantages over either steel or reinforced concrete. The concrete fill provides compressive strength and stiffness to the steel, and it reduces the potential for local buckling. The steel tube provides formwork to minimize the cost of the concrete placement and reinforces the concrete for axial tension, bending and shear as well as enhancing its ductility. CFT columns are particularly well suited for braced frames, since the large axial strength and stiffness are needed, and braced frames constitute the majority of the buildings constructed with CFT columns.While CFT columns are desirable for braced frames all research to date has focused on moment frame connections, combined loading of CFT members and bond stress in CFT elements. Braced frame-CFT column connections are fundamentally different than moment frame connections, since they transfer relatively large axial forces to the column, which must be distributed between the steel and concrete. The ductility demands are different in braced frames because dissipation is achieved through brace buckling rather than flexural yielding of the beams. This study will focus on the design of brace-beam-CFT column connections. Several prototype connections, which offer economic and performance advantages, will be identified, and detailed nonlinear; computer analyses of the connections will be performed. These analyses will evaluate expected ductility and fracture potential, identify critical locations, and identify concerns with each prototype connection. The most promising connection alternatives will be selected for experimental evaluation. Design methods will be developed for these selected connections, and an experimental study will be used to evaluate the design proposals and verify ductility and seismic performance. Three brace-beam-column connection subassemblages will be tested under inelastic cyclic loading. The specimens will be of moderately large scale so that they provide full scale simulation of connection in buildings of 3 to 6 stories and moderately large scale models of connections for tall buildings.