高强钢筋在混凝土结构中应用基础研究

1. Steel bar of HRB500 (yield strain reaches 0.003) and HRB600(yield strain reaches 0.0036) are added in Code for design of concrete structures and hot-rolled steel for reinforced concrete, respectively. However, the ultimate compressive strain of concrete prism from C20 to C80 subjected to short-term axial pressure varies from 0.001498 to 0.00225. When creep is considered, the compressive strain of concrete when the ultimate compression is reached will determine whether steel bars of HRB500 and HRB600 can achieve the compressive strength. Thus, the laws of different parameters to the compressive strain of the concrete prism from loading to failure after suffering creep will be investigated, and calculation method for steel bar of HRB500 and HRB600 as compressive reinforcements will be proposed in consideration of influence of creep. 2. Considering internal force redistribution, a new design method will be proposed for continuous beams and frames where occurrence of plastic hinges delays and plastic rotation capacity decreases due to 500MPa or 600MPa strength of steel bar as longitudinal reinforcement. 3. For anchor design method of headed bars, anchorage force distribution method of steel bar between cohesive action of steel bar and concrete in anchorage length range and bearing of headed bar pressure surface will be proposed, as well as local compression bearing capacity calculation method of concrete will be proposed which is densely covered with headed bar.

1、新一轮国标《混凝土结构设计规范》和《钢筋混凝土用热轧钢筋》分别增加了HRB500钢筋（屈服应变约0.003）和HRB600钢筋（屈服应变约0.0036）。C20到C80混凝土短期轴向加载下极限压应变为0.001498到0.00225。考虑徐变后，混凝土达到抗压极限时压应变值，决定HRB500及HRB600钢筋抗压强度能否充分发挥作用。为此，揭示各关键参数对混凝土经徐变后加载至破坏时压应变的影响规律，提出考虑徐变作用的HRB500、 HRB600用作构件中受压钢筋的设计计算方法。 2、针对配置500MPa、600MPa级钢筋作受拉纵筋的连续梁及框架，塑性铰出现推迟，塑性转动能力减小，提出其考虑内力重分布设计计算方法。 3、对钢筋锚固板锚固设计计算问题，提出钢筋规定的锚固力在锚固长度范围内钢筋与混凝土的粘结作用和锚固板承压面的承压作用间分配方法和密布锚固板下混凝土局压承载力计算方法。

HRB500钢筋和HRB600钢筋的屈服压应变大于混凝土短期受压破坏应变。在徐变后混凝土受压破坏应变可能会大于其短期受压破坏应变的设想指导下，完成了考虑不同参数影响的素混凝土棱柱体收缩徐变、徐变后卸载应变恢复、徐变后破坏试验，建立了一种适用范围更广的考虑各参数影响的混凝土徐变模型；提出了混凝土徐变后卸载应变恢复模型；建立了考虑徐变影响的混凝土加载-徐变-徐变后破坏全过程应力-应变全曲线方程；提出了混凝土受压破坏后总应变的计算方法。完成了56根配置HRB500、HRB600钢筋的混凝土短柱和16根配置HRB500、HRB600钢筋的足尺混凝土柱徐变及徐变后破坏试验，建立了考虑配筋影响的混凝土受压徐变模型；提出考虑配筋的混凝土柱徐变后破坏总应变的计算方法。完成了16根混凝土梁徐变及徐变后不卸载破坏试验，提出了考虑应变梯度影响的混凝土受压徐变模型和徐变后继续加载破坏总应变表达式。针对HRB500、HRB600钢筋作受拉纵筋的混凝土连续梁及框架梁端塑性铰出现推迟、塑性铰转动能力减小、受拉纵筋应变渗透引起的附加转角对弯矩调幅的影响更加明显等问题，完成了42个考察应变渗透影响的混凝土试件试验，建立了应变渗透对配置高强钢筋的混凝土框架梁端转角贡献计算模型；完成了HRB500、HRB600钢筋作受拉纵筋的24根两跨混凝土连续梁和12榀单层两跨混凝土框架弯矩调幅试验，提出了考虑各关键参数影响的配置HRB500和HRB600钢筋的连续梁和框架梁弯矩调幅设计计算方法。针对锚固力在钢筋直锚段和锚固板间如何分配不清楚及直锚段粘结剪应力对锚固板下局压承载力影响不清楚的突出问题，完成了150个带锚固板钢筋混凝土试件的拉拔试验（120个用于考察锚固力分配，30个用于考察锚固板下局压承载力）及6根配置锚固板钢筋的混凝土梁的试验（用于考察密布锚固板下局压承载力），建立了锚固力在钢筋直锚段粘结和锚固板承压间分配的计算公式，提出了单根钢筋锚固板及密布多根钢筋锚固板下混凝土局压承载力计算方法。