冻融循环作用后钢筋混凝土梁受弯性能试验研究

为研究冻融循环作用后的钢筋混凝土梁受弯性能，对经历0、50、100、125次冻融循环的混凝土立方体试块进行抗压强度试验；设计并制作了48根钢筋混凝土梁试件，分别经历0、50、100、125次冻融循环后进行静力受弯性能试验；分析混凝土质量损失率、相对动弹性模量、相对抗压强度等参数与冻融循环次数的关系。研究冻融循环次数、混凝土强度等级对钢筋混凝土梁受弯性能的影响。结果表明：混凝土试块质量、相对动弹性模量和立方体抗压强度均随冻融循环次数的增加而下降，高强度等级混凝土可延缓冻融循环造成的破坏；部分设计适筋混凝土梁经历冻融循环作用后发生超筋破坏。推导了受弯梁经历冻融循环作用后发生超筋破坏的界限配筋率计算式，并通过试验验证了其正确性；冻融循环作用后钢筋混凝土梁的开裂弯矩、受弯承载力仍可采用现行混凝土结构设计规范相关理论计算。

Experimental study on flexural behaviors of RC beams after freeze-thaw cycles

In order to investigate the flexural behaviors of RC beams after freeze-thaw cycles, cubes compressive strength test of concrete after 0, 50, 100 and 125 freeze-thaw cycles were made, and static flexural experiments of 48 RC beams after 0, 50, 100 and 125 freeze-thaw cycles were made. Relationships of mass loss rate, relative dynamic elastic modulus, relative compressive strength and number of freeze-thaw cycles were analyzed. The influences of freeze-thaw cycles on the flexural behaviors of RC beams with different concrete grades were studied. The results show that concrete prisms’ mass, relative dynamic elastic modulus and compressive strength decrease with the increasing of number of freeze-thaw cycles, and high-strength grade concrete could slow down the damage caused by freeze-thaw cycles. Some appropriate designed RC beams exhibit over-reinforced failure mode after freeze-thaw cycles. Boundary reinforcement ratio of RC beams after freeze-thaw cycles was derived, and verified by experiment. Current code for design of concrete structure about calculation of cracking load and ultimate load are still suitable for RC beams after freeze-thaw cycles.