Earthquake Resistant Performance of Reinforced Concrete Building Retrofitted by Multi-Story Steel Braces

进行了多层钢支撑加固钢筋混凝土平面框架的低周反复荷载试验。两个试件按实际建筑的四分之一比例进行了试验，该试件有三个跨度为1000 mm的开间，两个高度为800 mm的楼层，在中心开间放置多层钢支撑。以含多层钢支撑钢筋混凝土单元框架的破坏形式为试验参数。第一个试件的设计是为了发展由于多层钢支撑的上拔而引起的基础旋转。与此相反，2号试件设计为导致第一层钢支撑底部的弯曲破坏，这是由支撑的RC拉伸边缘柱中的整个纵向钢筋的屈服和桥接钢支撑水平弦杆与RC基础梁之间的锚固钢筋的拔出引起的（称为类型3的破坏）。钢支撑横截面为H形，宽60 mm，深60 mm，采用焊接法制作， ...更多信息 ng厚度为6 mm的平板。混凝土是用金属浇铸模在水平位置浇铸的。圆柱体试验混凝土抗压强度为30 MPa，采用两台油压千斤顶在框架试件中心单独施加顶部侧向力，保持各柱轴力不变。对于2号试件的基础，通过PC筋连接到RC反应层。对于设计为引起多层支撑上拔的1号试件，钢支撑下的两个基础不与楼板连接，而是通过在钢筋混凝土轴压基础之间插入圆形钢筋和设置在反应楼板上的钢反应板来承受侧向反力;对于1号试件，在顶部偏移角为0.2%时，基底功能发生上拔。顶偏角为0.7%时，柱体形成倒塌机制，边梁端部和底层裸柱底部出现弯曲屈服。1号试件在顶偏角为1%时达到最大强度后，由于这些铰区的混凝土受压破坏，其抗侧力逐渐衰减。考虑边梁和基础梁对上拔的约束作用后，试验中由支撑底部转动控制的抗侧力与快速分析计算结果吻合较好。对于2号试件，在顶部偏移角为0.3%时，支撑的RC边缘柱中的所有纵向钢筋在拉伸下屈服。在顶偏角为1%时，抗侧力达到最大值，梁端形成塑性铰。此后，由于混凝土受压破坏和钢支撑两侧柱底纵筋断裂，侧力急剧下降。少

Reversed cyclic loading tests were carried out for RC plane frames strengthened by multi-story steel braces. Two specimens with a quarter scale to actual buildings were tested which had three bays with each 1000 mm span length and two stories with the height of 800 mm, placing multi-story steel braces at the center bay. The failure type of RC unit frame containing multi-story steel brace was chosen as a test parameter. Specimen No. 1 was designed to develop the rotation of base foundation due to the uplift of multi-story steel braces. On the contrary, Specimen No. 2 was designed to result in flexural failure at the base of steel brace in a first story which is caused by both yielding of whole longitudinal bars in a RC tensile edge column of the brace and pull-out of anchorage bars bridging between horizontal chord of steel brace and RC foundation beam (called as the failure of Type 3). Cross section of a steel brace was H-shape with 60 mm width and 60 mm depth, which was built by weldi … More ng flat plates with 6 mm thickness. Concrete was cast in the horizontal position using metal casting form. Concrete compressive strength was 30 Mpa by cylinder tests.Top lateral force was applied alone at the center of the frame specimen by two oil jacks, keeping each column axial force constant. For footings of Specimen No. 2 were connected to RC reaction floor by PC tendons. For Specimen No. 1 designed to cause the uplift of multi-story braces, on the other hand, two footings under the steel brace were not connected to the floor, but lateral reaction force was supported through round steel bar inserted between RC footing subject to axial compression and steel reaction plate settled on reaction floor.For Specimen No. 1, uplift of base function occurred at the top drift angle of 0.2 %. Collapse mechanism was formed at the top drift angle of 0.7 %, developing flexural yielding at the end of boundary beans and the bottom of first story bare columns. Lateral resistance capacity in Specimen No. 1 decayed gradually due to concrete compressive failure at these hinge regions after attaining the maximum strength at the top drift angle of 1 %. Lateral resistance capacity dominated by base rotation of multi-story braces in the test agreed well with that computed by quick analysis taking the confining effect of both boundary beams and foundation beams on uplifting into account. For Specimen No. 2, all longitudinal bars in RC edge column of a brace yielded in tension at the top drift angle of 0.3 %. Lateral force resistance reached the maximum, forming plastic hinges at all beam ends at the top drift angle of 1 %. Hereafter lateral resistance diminished abruptly by the concrete compressive failure and the fracture of column longitudinal bars at the bottom of both edge columns of steel brace. Less