考虑全梁承载能力因素的RC桥梁限载取值

摘要

为确定85和04规范钢筋混凝土简支梁桥限载标准,系统分析了受弯和受剪抗力对桥梁限载系数的影响规律.首先,根据结构可靠度理论,提出了桥梁限载取值的一般分析方法.然后,以6～30m简支梁桥为例,通过比较85和04规范汽车荷载产生的跨中弯矩和支点剪力,选择三轴和五轴载重汽车作为典型限载车辆模型.在此基础上,以设计活恒载比值为基本参数,采用85和04规范钢筋混凝土受弯和受剪抗力设计表达式,分别计算了85规范汽车-20级和汽车-超20级以及04规范公路-Ⅰ级和公路-Ⅱ级桥梁的限载系数.结果表明,在同一限载安全等级下,按85和04规范设计的中、小跨径钢筋混凝土简支梁桥,其限载值均由受弯抗力控制,建议按受弯抗力确定此类桥梁的限载取值.%In order to determine the truck weight limits of simply supported reinforced concrete beam bridges designed with 85 and 04 editions of the code,the impact of the flexural and shear capacities on the coefficients of weight limit was analyzed for these bridges.Firstly,based on the structural reliability theory,a general simplified analytical model for determining the truck weight limits was proposed for RC beam bridges.Then,the simply supported beam bridges with the length ranging from 6m to 30m were selected,and the moments at mid-span and shear forces at supports caused by design load in 85 edition of the code were compared with those caused by design load in 04 edition for the purpose of determining the typical truck models.Finally,according to the general design expressions of the flexural and shear resistances of RC beam bridges as specified in 85 and 04 editions of the code,the basic parameters of live-to dead-load ratios were used to compute the coefficients of weight limit of bridges designed with q-20,q-s20,highway-Ⅰ,and highway-Ⅱ design loads,respectively.The results show that for short to medium span RC beam bridges designed with 85 and 04 editions of the code,the truck weight limits are controlled by the flexural capacities,which shall be used as the basis for determining the weight limit standards of these bridges.