二次受力条件下基于塑性铰区扩展模式的钢筋混凝土柱的抗震性能研究

Concrete column is the key member in the construction framework which affects its safety and durability greatly. Enlarging concrete section by using new concrete, enveloping steel and strengthening with fiber-reinforced polymer（FRP）are three widely-used methods to strengthen concrete column, but these methods have their own disadvantages, such as construction complex and volume increase of enlarging section method, high technical needs and poor durability of enveloping steel, and the high cost and poor fire proof of FRP method. In order to improve the seismic performance, ductility and durability of concrete columns significantly while improving the bearing capacity greatly, a new method for strengthening concrete columns with ferrocement including steel bars (large diameter) have been put forward, and it show a good mechanical properties and practical both under axial compressive load and eccentric load. It also has a good performance on the seismic performance in the pre-research work. Due to the complexity of the experiment study on the pseudo-static response characteristic of the columns under cyclic loads, an experimental study was proposed on the pseudo-static response characteristic of the columns strengthened by ferrocement including steel bars under cyclic loads, with a view to explore the failure mode, hysteretic characteristics and energy dissipation mechanism thoroughly and deeply, and a feasible combination form of ferrocement including steel bars and strengthening method are obtained.

研发中的钢筋钢丝网砂浆加固混凝土柱方法，在轴压、偏压及往复加载试验中表现出优良的力学性能和实用性，轴压时提高承载力和延性，往复加载时提高试件耗能，且耐久性更好，其破坏形式也明显不同——试件表面形成又细又密的裂缝，且易于施工，材料费用较低，鉴于前期研究均是一次受力性能，本课题提出二次受力条件下钢筋钢丝网砂浆加固混凝土柱的往复加载试验，并进一步分析塑性铰性能改善与加固柱滞回耗能的关系。主要研究：二次受力情况下，表层砂浆裂缝开展情况与钢丝网砂浆关系分析；加固层与原柱不同配筋影响与施工工艺；典型试件钢筋钢丝网砂浆与碳纤维加固方法的对比；二次受力条件下往复加载的破坏形态和滞回耗能机理；基于塑性铰区扩展模式的塑性铰区性能改善与抗震性能改善的关系。预研（对比试验）结果显示，一次受力情况下，得益于钢丝网的优异配筋分散性，钢筋钢丝网砂浆加固柱在承载力有一定提高的基础上，其延性显著高于钢筋网及FRP加固试件。

对10组倒“T”型钢筋混凝土试件完成拟静力滞回往复加载后，在保持轴向荷载条件下用几种方式进行加固，再进行二次受力条件下的拟静力滞回往复加载试验，模拟实际情况下加固构件的受力状况和抗震性能，综合对比分析了几种加固方式的抗震性能。观察了各试件的裂缝开展情况，主要测量了纵筋的应变、试件不同高度处的侧移和往复加载的滞回曲线，计算了各试件的刚度退化、耗能及塑性铰区范围。研究得出，钢丝网由于优越的配筋分散性，使得加固试件能裂而不碎，承载力提高的同时，耗能最优，改善塑性铰区性能能提高构件滞回耗能能力；同时发现植筋能有效提高加固的各项数值；另外，通过直接加固和二次受力（模拟震损）对比试验，它们的极限承载力、耗能能力和位移延性系数都相当，因此钢筋加焊接钢丝网砂浆是有效加固震损结构的方法。