考虑箍筋约束的预应力型钢高强砼梁延性分析

预应力型钢高强混凝土(PSRHC)梁具有承载力高、截面尺寸小等特点,适用于大跨度、重荷载的建筑结构.为掌握不同设计参数对PSRHC梁构件延性性能的影响,利用数值方法,进行了PSRHC梁静力性能的模拟及多参数分析.首先,基于截面纤维模型,建立了可考虑箍筋约束作用的PSRHC梁的静力全过程数值模拟方法,相关荷载-位移计算曲线与已有试验结果吻合良好.之后,研究了混凝土强度等级、受拉、受压钢筋用量、预应力筋用量、型钢翼缘及腹板厚度、箍筋间距及直径等因素对PSRHC梁延性的影响.结果表明:增大混凝土强度等级,增加受压钢筋及箍筋用量,可提高PSRHC梁的延性;增加受拉钢筋、预应力筋用量,增大腹板厚度,均使得延性降低;而翼缘厚度对延性的影响规律不明显.其中,箍筋间距由50 mm增加至200 mm时,延性系数降低约20.6%;箍筋直径由6 mm增大至10 mm,延性系数增大18%~34%.最后,结合数值试验结果,建立了包含体积配箍筋率及综合配筋指标两个参数的延性系数计算公式,利用此公式评估延性时以3.1作为界限值.

Ductility analysis of prestressed steel reinforced high-strength concrete beam considering hoop-confined effect

Prestressed steel reinforced high-strength concrete (PSRHC) beams possess high load-carrying capacity and small section dimension, which is applicable to long-span and heavy-load buildings. To investigate the various design parameters'' effects on the ductility of PSRHC beam members, the static behavior of PSRHC beam was simulated with numerical method and multi-parameter analysis was carried out. Based on the section fiber model, an analysis method, which could consider the confined effect of hoops, was firstly established to simulate the static behavior of PSRHC beams. Result shows that the analysis result has a good agreement with the test load-deflection curves. Then, the effect of parameters, including concrete class, amount of tension and compression rebar and prestress tendons, thickness of steel flange and web, and diameter and space of hoops, on the ductility of PSRHC beams was investigated. The results imply that: raising the concrete class, increasing the amount of compression rebar and hoops can improve the ductility of PSRHC beam members; increasing the amount of tension rebar, prestress tendons and thickness of steel web would decrease the ductility; and the effect of flange thickness is not obvious. When the hoop-space increases from 50 mm to 200 mm, the ductility coefficient decreases about 20.6%, and the diameter of hoop improves from 6mm to 10mm, the coefficient increases various from 18% to 34%. Finally, according to the simulation results, a regression formula, containing two parameters of hoops-volumetric ratio and complex reinforcement index, was proposed to evaluate the ductility of PSRHC members, and 3.1 was selected as demarcation value in this formula.