Development of Mixed Column Base of Square CFT Structures Considering Constractability

本文提出了一种新型柱基础，对其结构性能进行了试验研究，并对其最大强度和初始刚度的估计进行了讨论。所提出的柱基础的思想是在两种传统方法的基础上发展起来的。另一种是裸型；柱嵌入一定长度的钢筋混凝土基础梁中。另一种是裸型；柱通过地脚螺栓和底板与基础梁连接。前者具有较大的刚度和强度，结构性能较好，但施工过程较为复杂；钢筋的安装必须在基础梁的混凝土浇筑之前进行。后者与预埋式相比，刚度和强度较小，但施工方便，施工成本较低。本文提出了半嵌入式CFT柱基础。研究发现：1)柱筒局部屈曲对柱筒性能影响不大；2)埋置长度较长的试件滞回线呈现稳定的主轴形状，而埋置长度较短的试件则呈现挤压形状。3)所提出的极限强度计算与试验值吻合较好。4)将半预埋柱基础初始刚度设为两种阻力机构；I)转动刚度by。地脚螺栓和底板。前者具有较大的刚度和强度，结构性能较好，但施工过程较为复杂；钢筋的安装必须在基础梁的混凝土浇筑之前进行。后者与预埋式相比，刚度和强度较小，但施工方便，施工成本较低。本文提出了半嵌入式CFT柱基础。研究结果表明：1)柱筒局部屈曲对柱筒性能影响不大；2)埋置长度较长的试件滞回线呈现稳定的纺锤形，而埋置长度较短的试件则呈现挤压形。3)所提出的极限强度计算与试验值吻合较好。4)将半预埋柱基础初始刚度设为两种阻力机构；1)地脚螺栓与底板的转动刚度；2)钢筋混凝土基础梁的抗弯刚度与抗撬阻力之和。5)上述机构提供的初始刚度较好地估计了实验值。少

In this paper, a new type of column base is produced of which the structural performance have been investigated experimentally, and the estimation of the maximum strength and initial stiffness is discussed. The idea of the proposed column base has been developed from the two conventional methods. The other is the bare type; the column is embedded into the reinforced concrete foundation beam with a certain length. The other is the bare type; the column is connected to the foundation beam by the anchor bolts and a base plate. The former shows the larger stiffness and strength, and the better structural performance, but the procedure of the construction is rather complicated ; the erection of the steel must be done before the concrete casting of the foundation beams. The latter has smaller stiffness and strength compared to the embedded type, but it is easy to construct, and the cost of construction is less. The semi-embedded type of CFT column base proposed in this paper.The research fin … More dings are as follows :1) Local buckling of the column tube did not much affect the behavior2) The hysteresis loops of specimens with longer embedded length showed the stable spindle shapes, but those with shorter length showed the pinched shape.3) The proposed calculation for the ultimate strength showed a good evaluation to the experimental values.4) The initial stiffness of a semi-embedded column base was provided into two resisting mechanisms; i) rotational stiffness by. the anchor bolts and base plate. The former shows the larger stiffness and strength, and the better structural performance, but the procedure of the construction is rather complicated; the erection of the steel must be done before the concrete casting of the foundation beams. The latter has smaller stiffness and strength compared to the embedded type, but it is easy to construct, and the cost of construction is less. The semi-embedded type of CFT column base proposed in this paper.The research findings are as follows :1) Local buckling of the column tube did not much affect the behavior2) The hysteresis loops of specimens with longer embedded length showed the stable spindle shapes, but those with shorter length showed the pinched shape.3) The proposed calculation for the ultimate strength showed a good evaluation to the experimental values.4) The initial stiffness of a semi-embedded column base was provided into two resisting mechanisms; i) rotational stiffness by the anchor bolts and base plate, ii) the sum of bending stiffness and prying resistance of reinforced concrete foundation beam.5) The initial stiffness provided by the mechanisms mentioned in 4) well estimated the experimental values. Less