Experimental Study on Elasto-Plastic Behavior of Steel Reinforced Concrete Space Frames

为了建立钢筋混凝土结构抗震能力的评价方法，对钢筋混凝土空间框架在等轴向推力和反复双轴弯剪作用下的弹塑性性能进行了试验研究。框架试件由一根柱和四根沿两个方向排列的梁组成，模拟了实际建筑框架中的梁柱组合。构件的截面由h型钢制成（柱：2H-148x30x6x9，梁：H-180x50x6x9）， 4个主要钢筋包裹在混凝土中。在试验中，首先在柱顶施加恒定垂直荷载，在y方向上施加梁尖恒定梁荷载，后者模拟长期荷载。然后，反对称，交替重复剪切荷载施加在梁的尖端在x方向模拟地震荷载。实验参数选取如下：垂直载荷比（0.2、0.4）；与长期荷载相对应的梁荷载强度和形态；破坏模式（柱破坏型和板破坏型）。试验的新发现如下：柱失稳试件；(1)柱在连接板处发生剧烈扭结变形，竖向荷载无法持续，在加载的最后阶段，由于P-效应导致强度急剧下降；(2)纵向梁荷载作用下，上、下柱端部均出现损伤，而平面荷载作用下，损伤集中在下柱端部；(3)双轴弯曲降低了变形能力，但提高了极限强度。面板破坏试件；(4)梁柱连接处的钢板承受较大的塑性应变，但由于梁约束对混凝土的破坏不大；(5)滞回线为稳定的主轴型，无论是重复加载引起的退化，还是P-效应引起的强度退化，都没有柱破坏试件严重。少

Elasto-plastic behavior of steel reinforced concrete (SRC) space frames subjected to constant axial thrust and repeated biaxial bending with shear is investigated exprimentally, in order to establish an evaluation method for the earthquake resistance ability of SRC structures. Frame specimen consists of a column and four beams arranged in two directions, which modilizes beam-and-column subassemblage in a real building frame. Cross sections of members are made of H-steel(column:2H-148x30x6x9, beam:H-180x50x6x9) and 4 main reinforecements encased in concrete. In the test, constant vertical load at the column top and constant beam loads at tips of beams in y-direction are first applied, the latter simulating the long-term load. Then, antisymmetric, alternately repeated shear loads are applied at tips of beams in x-direction simulating the earthquake load. Experimental parameters are selected as follows: vertical load ratio (0.2 and 0.4); intensity and pattern of beam loads corresponding t … More o the long-term load; and failure modes (column-failure type and panel-failure type). New findings obtained from the tests are as follows: As to column-failing specimens; (1) The column deforms with a sharp kink at the connection panel, and the vertical load cannot be sustained, because of the drastic strength deterioration due to P- effect in the final stage of loading; (2) Damage is observed at ends of both upper and lower columns in speciments with beam loads in y-direction, while it concentrates at the top end of the lower column in the specimen subjected to planer loading; (3) Biaxial bending decreases the deformation capacity, but increases the ultimate strength. As to panel-failing specimens; (4) Steel panel at the beam-to-column connection is subjected to large plastic strains, but damage on concrete is not much observed due to beam restraints; (5) Hysteresis loop is a stable spindle-type, and either degradation due to repeated loading or strength deterioration due to P- effect are not so severe as in the case of the column-failing specimens. Less