CAJ | 학술논문

完成了7块火灾后两跨无黏结预应力混凝土单向连续板受力性能试验.基于试验结果,拟合出火灾后预应力混凝土连续板中无黏结筋剩余应力、极限应力的计算公式,提出了火灾后预应力混凝土连续板正截面承载力计算公式.根据火灾下温度场分布沿板厚方向将截面分条带,引入火灾后钢筋、混凝土本构关系,基于截面轴力、弯矩平衡,获得了火灾下预应力混凝土板任意截面的弯矩-曲率关系全曲线.基于支座变形协调方程,可用割线刚度法对支座反力进行迭代求解,计算板在外荷载(曲率荷载)与支座反力共同作用下的弯矩、挠度和支座位移,进而对截面曲率积分可求得连续板的变形.试验结果表明:初始有效应力越高、受火时间越长,火灾后连续板预应力钢丝应力损失越严重;保护层厚度越小、受火时间越长、荷载水平越大,火灾后板跨中截面承载力降低幅度越大;受火时间越长、荷载水平越大,板中支座截面承载力降低幅度越大.
완성료7괴화재후량과무점결예응력혼응토단향련속판수력성능시험.기우시험결과,의합출화재후예응력혼응토련속판중무점결근잉여응력、겁한응력적계산공식,제출료화재후예응력혼응토련속판정절면승재력계산공식.근거화재하온도장분포연판후방향장절면분조대,인입화재후강근、혼응토본구관계,기우절면축력、만구평형,획득료화재하예응력혼응토판임의절면적만구-곡솔관계전곡선.기우지좌변형협조방정,가용할선강도법대지좌반력진행질대구해,계산판재외하재(곡솔하재)여지좌반력공동작용하적만구、뇨도화지좌위이,진이대절면곡솔적분가구득련속판적변형.시험결과표명:초시유효응력월고、수화시간월장,화재후련속판예응력강사응력손실월엄중;보호층후도월소、수화시간월장、하재수평월대,화재후판과중절면승재력강저폭도월대;수화시간월장、하재수평월대,판중지좌절면승재력강저폭도월대.
An experiment was conducted on the mechanical performance of seven unbonded prestressed concrete (PC) continuous slabs after elevated temperature. The residual stress and the ultimate stress in unbonded stress wire in PC continuous slabs after elevated temperature were obtained by fitting the curve of experiment data, and the calculation method for normal section load-bearing capacity of PC slabs after elevated temperature was established. The section of the slab was divided into strips along its depth according to the distribution of temperature field.The stress-strain relationship of concrete and steel after elevated temperature was introduced, and the moment-curvature of PC slabs after elevated temperature was obtained on the basis of the equilibrium equations of force and moment on the slab section. The redundant support restriction of continuous slabs was removed,and the moment, deflection and support displacement of the slab imposed by load (curvature) and support reaction together were calculated respectively.The support reaction was calculated in secant stiffness matrix iteration method until the deflection compatibility equation at the support was satisfied, and the deflection of continuous slabs could be obtained with the curvature integral of the cross section. The experiment results have shown that the prestress losses in stress wire in slabs after elevated temperature increase with the rise of the effective prestress at ambient temperature and the heating time. The rate of load-bearing capacity degradation in mid-span section of PC slabs after elevated temperature increases with the rise of heating time and load level and the decrease of concrete cover, and the rate of load-bearing capacity degradation in inner support increases with the rise of heating time and load level.