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Improvement of Hysteretic Energy Dissipation of Concrete Members by Multi-yielding Longitudinal Reinforcement

通过多屈服纵向钢筋改善混凝土构件的滞回耗能

基本信息

批准号：
07455221
负责人：
WATANABE Fumio
金额：
$ 4.93万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

A new reinforcing method to improve the inelastic behavior of reinforced concrete was proposed. The method combines use of high-strength and ordinary-strength longitudinal bars. When the column is subjected to bending moment, the ordinary strength longitudinal bars yield first and then the high-strength bars yield later in large post-yield range. Up to the stage of yielding of the high-strength bars, the column does not show significant degradation of load-carrying capacity. To confirm the advantages of the new reinforcing method, flexural analyzes on reinforced concrete columns with different grades of longitudinal bars were conducted. The results of the analysis indicate that the combined use of different grades of longitudinal bar improves the inelastic behavior of reinforced concrete columns. An experimental research work on the proposal was also conducted to verify the effectiveness. The parameters used were the ratio of the amount of high-strength reinforcement to that of ordinar … More y-strength reinforcement, the axial load level on the column and bi-directional loading.A new type of prestressing strand, graded composite strands, has been developed. The seven-wire strand consists of three high-strength wires (a yield stress of 1400 MPa) and four ordinary-strength wires (400 MPa). The high-strength wires provide prestressing force along the member axis even under large deformations. The ordinary-strength wires, which yield during the prestressing operation, are expected to contribute to hysteretic energy dissipation. Therefore, these graded composite strands make precast connections have many of the desirable characteristics of monolithic connections. The effectiveness of the strands is verified by loading tests on beam-to-column connections. Eight external beam-to-column connections were constructed and tested. Four specimens were connected by ordinary prestressing stands and the others were connected by the graded composite strands. The parameters used were the amount of prestressing force introduced and the distance of the location of prestressing strands from the centroidal axis of the beam section. The test results indicate that specimens with graded composite strands had much larger hysteretic energy dissipatiion than did the specimens with the ordinary strands.Another series of loading tests were carried out on column-to-foundation connections post-tensioned by 'graded composite prestressing steel bars'. The steel bar cross section consists of two parts : normal strength and high strength. Thus, it has a monotonic load-deformation relationship which is better modeled by a trilinear than a bilinear approximation. This nonlinear behavior results in energy dissipation. Nine column-to-foundation connections were constructed using the graded composite steel bars or ordinary prestressing steel bars. However, the test results revealed that the graded composite steel bars were not so effective to increase hysteretic energy dissipation capacity. Less

提出了一种新的改善钢筋混凝土弹塑性的加固方法。该方法结合了高强度和普通强度纵筋的使用。在较大的后屈服范围内，在弯矩作用下，普通强度纵筋先屈服，高强纵筋后屈服。直到高强钢筋屈服阶段，柱的承载能力没有明显的退化。为了验证这种加固方法的优越性，对不同等级纵筋的钢筋混凝土柱进行了抗弯分析。分析结果表明，不同等级纵筋的组合使用改善了钢筋混凝土柱的弹塑性性能。为验证该方案的有效性，还对该方案进行了实验研究。所用参数为高强钢筋与普通…的配筋量之比提出了一种新型的预应力钢绞线--级配复合钢绞线。七股钢丝由三根高强度钢丝(屈服应力为1400兆帕)和四根普通强度钢丝(400兆帕)组成。即使在大变形的情况下，高强度钢丝也能沿杆件轴线提供预应力。在预应力作用过程中屈服的普通强度钢丝有望起到滞回耗能的作用。因此，这些渐变的组合钢绞线使得预制连接具有许多整体连接所需要的特性。通过对梁柱节点的加载试验，验证了钢绞线的有效性。建造了8个外部梁柱节点并进行了试验。其中4个试件通过普通预应力架连接，其余试件通过渐变组合绞线连接。所使用的参数是引入的预应力量和预应力股位置与梁截面质心轴的距离。试验结果表明，与普通钢绞线相比，采用梯度复合钢筋的柱-基础节点具有更大的滞回耗能能力。钢筋横截面由普通强度和高强度两部分组成。因此，它具有单调的载荷-变形关系，这种关系用三线性近似比双线性近似更好地模拟。这种非线性行为导致了能量耗散。9个柱-基础节点采用分级组合钢筋或普通预应力钢筋。但试验结果表明，级配复合钢筋在提高滞回耗能能力方面效果不佳。较少