无缝化改造的空心板桥受力性能
Mechanical performance of jointless retrofitted bridge with hollow-slabs

对某多跨空心板桥进行了无缝化改造,简支板改为双排支座连续板,桥台改为延伸桥面板桥台,取消了全桥的伸缩装置; 测试了实桥静动载,研究了无缝化改造后的多跨空心板桥受力性能; 应用有限元模型,计算了结构受力、承载力、引板受力及单、双排支座对结构力学性能的影响。测试结果表明:无缝化改造后的桥梁实测基频为8.60 Hz,高于改造前的5.37 Hz,4种车速下实测冲击系数最大值为1.11,小于《公路桥涵设计通用规范》(JTG D60―2004)的计算值1.36,应变与挠度校验系数均小于0.95,因此,无缝化改造提高了全桥整体性能,改善了行车条件。有限元分析结果表明:无缝化改造后桥梁基频的计算值为8.48 Hz,实测基频与计算基频比值为1.01,因此,改造后桥梁功能状况良好; 跨中截面的正弯矩明显降低,第2跨跨中降幅最大,达15.6%,但内支座处出现了负弯矩,同时剪力增大,最大增幅为18.2%; 跨中挠度明显降低,以第2、3跨降幅最大,达35.5%,桥梁整体刚度明显提高; 最大裂缝宽度计算值为0.15 mm,小于《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG D62―2004)(简称《桥规》)规定的0.20 mm,承载力、挠度和裂缝宽度验算均满足《桥规》要求; 支座排数对上部结构的受力影响较小,采用双排支座是可行的; 引板与地基的摩擦因数对引板和铺装层轴向力影响较大,对弯矩影响较小; 引板和铺装层最大拉应力分别为0.87、1.25 MPa,满足设计强度要求。
A multi-span bridge with hollow-slabs was retrofitted into a jointless bridge, in which the simple support slabs were converted into the continuous slabs with double row supports and the general abutments were converted into deck-extension abutments, thus, all movable deck joints of the bridge were eliminated. The static and dynamic load tests of jointless retrofitted bridge with multi-span hollow-slabs were carried out, and the mechanical performance of the bridge was studied. The finite element model was used to calculate the structural mechanical performance, bearing capacity and mechanical performance of approach slab, and to analyze the influence of single and double rows supports on the structural mechanical performance. Test result shows that after jointless retrofitting, the tested fundamental frequency of the bridge is 8.60 Hz and larger than 5.37 Hz before jointless retrofitting. The maximum tested impact factor is 1.11 of four vehicle speeds and smaller than 1.36 that is the calculated value by the General Specifications for Design of Highway Bridges and Culverts(JTG D60―2004). The verification coefficients of the strain and deflection are less than 0.95. Obviously, the jointless retrofitting enhances the integrality of the bridge and improves the driving comfortability. The finite element analysis result shows that after jointless retrofitting, the fundamental frequency of the bridge is 8.48 Hz, and the ratio is 1.01 between the tested fundamental frequency and calculated result, so the bridge is in good working condition. The positive bending moments of mid-span sections reduce significantly with a maximum value of 15.6% at the second span, while the negative bending moments appear at the inner-supports and the shear forces near the inner-supports increase with a maximum value of 18.2%. The mid-span deflections decrease obviously with a maximum value of 35.5% at the second and third spans, which indicates