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Anchorage Performance of Hooked Bars in Reinfored Concrete Members

钢筋混凝土构件中钩状钢筋的锚固性能

基本信息

批准号：
07455214
负责人：
JOH Osamu
金额：
$ 4.8万
依托单位：
HOKKAIDO 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 1997
项目状态：
已结题

项目摘要

In the previous study, the authors classified the anchorage failure of 90-degree hooked bars in exterior beam-column joints at an intermediate story into three modes : a side split failure, a local compression failure and a raking-out failure (named by the authors newly.) The purpose of this study is to clarify anchorage performances for all failure modes, especially for the raking-out failure mode of 90-degree hooked beam bars in exterior beam-column joints.The part one of this report estimates anchorage behavior of the joints at an intermediate floor and proposed some anchorage strength evaluations on the basis of 63 test specimens. The remarks on the rakig-out failure are (1) the strength increased severely according to increase of column axial stress in range of the axial stress ratio less than about one third, (2) since the failure crack lines with a trapezoidal shape in horizontal cross section appeared, the effect of lateral joint reinforcement on the strength reduced in case of large thickness of cover concrete.The part two of this report says the anchorage behavior of joints at a top floor on the basis of 24 knee joint specimens. The conclusions are follows : (1) the anchorage mechanism depends on stress transmission from tail portion of hooks to adjacent column bars, (2) main influence factors on the anchorage strength sre tail length after bent portion, horizontal distances between tail and column bars and between tail bars and beam end, lateral reinforcement ratio in joint and concrete strength, and (3) evaluation formulas on anchorage strength and deformability were proposed.In the part three, the exterior beam-column joints at an intermediate floor were simulated by a non-linear finite element method for reinforced concrete members. The good simulation for the specimen with raking-out failure was obtained by using discrete crack elements and dowel action of column bars at the crack elements.

在前人的研究中，作者将中间层外梁柱节点90度钩杆锚固破坏分为三种模式：侧裂破坏、局部压缩破坏和耙出破坏（作者新命名）。本研究的目的是明确各种破坏模式下的锚固性能，特别是外梁柱节点90度钩形梁杆的耙出破坏模式。本文第一部分对中间底板节点的锚固性能进行了估计，并在63个试件的基础上提出了一些锚固强度评价。结果表明：(1)在轴向应力比小于1 / 3的范围内，随着柱轴向应力的增大，强度显著提高；(2)由于水平截面出现梯形破坏裂缝线，当覆盖层混凝土厚度较大时，侧缝加固对强度的影响减弱。本报告第二部分在24个膝关节试件的基础上，对某顶楼的关节锚固行为进行了研究。研究结果表明：(1)锚固机制依赖于锚杆尾端向相邻柱杆的应力传递；(2)影响锚固强度的主要因素为弯后尾长、尾杆与柱杆、尾杆与梁端之间的水平距离、节点侧配筋率和混凝土强度；(3)提出锚固强度和变形能力的评价公式。第三部分采用钢筋混凝土构件非线性有限元法对某中间楼盖外梁柱节点进行了数值模拟。采用离散裂纹单元和柱杆在裂纹单元处的销钉作用，可以较好地模拟试件的耙出破坏。