Study on Development and Application of Steel Tube filled with Expansive Concrete to Energy Dissipative Braced Frame

为了改善耗能支撑框架中支撑的力学性能，采用中心扁筋钢管膨胀混凝土作为支撑构件，对筒内膨胀混凝土进行了试验研究。试验结果和讨论可概括如下：1.作为耗能支撑框架的支撑构件，由于化学预应力的作用，该筒在高拉或高压荷载作用下仍能保持很高的刚度。在膨胀能力方面，水/(水泥+硅灰+膨胀剂)=20~30%，Ex/(C+S+Ex)≧=55%的膨胀混凝土具有很高的膨胀能力。并提出了钢管屈服时混凝土的化学预应力估算公式，使钢管混凝土在三年半的时间内保持化学预应力。管内W/(C+S+Ex)=20~30%的膨胀混凝土的表观轴向初始刚度与不掺膨胀剂的普通混凝土的杨氏模数相同。给出了混凝土和钢管受压或受拉特性的理想化。为了将这种钢管应用于真正的消能支撑框架，我们给出了这种钢管膨胀混凝土支撑构件的受压或受拉设计强度和条件。

The purpose of this study is to improve the mechanical properties of the braces in a energy dissipative braced frame by using the expansive concrete filled steel tube with a flat bar in center as the brace member.We carried out some experiments on the expansive concrete in the tube. The results and discussions of the experiments may be summarized as follows :1. As a brace member of the energy dissipative braced frame, this tube may keep very high stiffness under a high tension or high compression load owing to the chemical prestress.2. On the expansive capacity of this tube, the expansive concrete with Water/(Cement+Silica fume+Expansive admixture) =20〜30% and Ex/(C+S+Ex)≧ 55% has a very high expansive capacity. And we proposed the estimation formulae of the chemical prestress of the concrete at yield of the steel tube, and then the concrete in the tube was keeping the chemical prestress during three and a half years.3. The apparent axial initial stiffness of the expansive concrete with W/( C+S+Ex) = 20〜30% in the tube is as same as the Young's modulus of the usual concrete without the expansive admixture. And then we showed the idealization of the compression or tension characteristics of the concrete and the steel tube.4. For an application of this tube to true energy dissipative braced frame, we showed the compression or tension design strength and condition of this brace member with the expansive concrete filled tube.