不同技术状况等级下公路桥梁限载

Weight limits for highway bridges under different technical condition ratings

以现行《公路桥涵养护规范》(JTG H11—2004)为依据,提出一种考虑桥梁实际技术状况等级的钢筋混凝土简支梁桥限载分析方法,并推算了不同时期规范中桥梁在不同技术状况等级下的典型车辆限载建议值;以结构可靠度理论和现行规范设计表达式为基础,以设计活恒载比为基本参数建立了公路桥梁限载简化分析模型;以现行桥梁设计规范抗力标准值为基准确定了不同技术状况等级桥梁对应的抗力修正系数;应用公路桥梁限载分析程序分别计算了按《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTJ 023—85、JTG D62—2004和JTG 3362—2018)设计的桥梁在不同技术状况等级下的限载系数;依据设计汽车荷载标准值效应限值与典型车辆荷载效应等效假定,提出了钢筋混凝土简支梁桥的限载建议值。分析结果表明:在相同的技术状况和安全等级下,JTJ 023—85规范中汽车-超20级和汽车-20级桥梁限载较JTG D62—2004规范中安全等级一级的公路-Ⅰ级和公路-Ⅱ级高,最大差值分别为1.2和5.0 t;JTG 3362—2018规范中公路-Ⅰ级和公路-Ⅱ级的桥梁限载明显高于JTJ 023—85和JTG D62—2004规范,最大差值分别为13.8和8.6 t,且技术状况等级越高,桥梁限载差值越大;不同时期规范中桥梁初始设计抗力的差异导致其在相同技术状况等级下的典型车辆限载不同,在按技术状况等级对在役桥梁制定限载措施时,应考虑不同时期设计规范的影响。

In accordance with the current Code for Maintenance of Highway Bridges and Culverts(JTG H11—2004), a weight limit analysis method for reinforced concrete(RC) simply supported beam bridges was proposed by considering the actual technical condition ratings. Moreover, the typical vehicle weight limits for bridges under different technical condition ratings recommended in codes in different periods were determined. Based on the structural reliability theory and design expressions in the current code, a simplified analytical model of weight limits for highway bridges was established by taking the design live-to-dead load ratio as the fundamental parameter. The nominal resistances in the current bridge design code were used as the basis for determining the corresponding resistance correction factors for bridges under different technical condition ratings. A program for the weight limit analysis of highway bridges was used to calculate the weight limit factors of bridges under different technical condition ratings designed in accordance with the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTJ 023—85, JTG D62—2004, and JTG 3362—2018). The recommended weight limits of RC simply supported beam bridges were proposed under the assumption that the standard effect limit of design vehicle load was equivalent to the typical vehicle load effect. Analysis result shows that under the same technical condition rating and safety level, the bridge weight limits with ratings of truck-S20 and truck-20 in the JTJ 023—85 code are higher than those with safety levels of highway-Ⅰ and highway-Ⅱ in the JTG D62—2004 code, and the maximum differences are 1.2 and 5.0 t, respectively. The bridge weight limits with ratings of highway-Ⅰ and highway-Ⅱ in the JTG 3362—2018 code are significantly higher than those in the JTJ 023—85 and JTG D62—2004 codes, and the maximum differences are 13.8 and 8.6 t, respectively. Moreover, the higher the technical condition rating, the greater the difference between the bridge weight limits. The differences in the initial design resistance of bridges in codes in different periods lead to different typical vehicle weight limits under the same technical condition rating. When formulating the weight limit measures for existing bridges according to their technical condition ratings, the influences of design codes in different periods should be considered. 6 tabs, 2 figs, 32 refs.