【《某变截面预应力混凝土连续梁桥预应力钢束的估算和布置计算》2100字】

第页共33页某变截面预应力混凝土连续梁桥预应力钢束的估算和布置计算1预应力钢束的估算和布置1.1计算原则在预应力混凝土连续梁中，预应力钢筋共计有三种，分别为纵向、横向、竖向预应力筋。其中纵向预应力钢筋根据弯矩包络图计算并布置，横向预应力钢筋根据单位宽度桥面板计算并布置，如计算配筋仅需设置普通钢筋，则可不设置横向预应力钢筋；竖向预应力钢筋根据主梁主应力计算与验算结果设置。本设计为全预应力设计，主要考虑纵向预应力钢筋的计算与布置问题。1.2材料性能参数C50，主要强度指标为：fck=32.4MPa,ftk=2.65MPa强度设计值：fcd=22.4MPa,ftd=1.83MPacE=3.45×104MPac2、25φj15.2的钢绞线，其强度指标为：fpk=1860MPa抗拉强度设计值：fpd=1260MPap弹性模量：E=1.95105MPap3、造钢筋采用HRB335钢筋，其强度指标为抗拉强度标准值：fsk=335MPa抗拉强度设计值：fsd=280MPa1.3预应力钢筋数量的确定及布置连续梁预应力钢束的配置不仅要满足构造要求，还应考虑以下原则：1、应选择适当的预应力束的型式与锚具型式，对不同跨径的梁桥结构，要选用预加力大小恰当的预应力束，以达到合理的布置型式。2、应力束的布置要考虑施工的方便，也不能像钢筋混凝土结构中任意切断钢筋那样去切断预应力束，而导致在结构中布置过多的锚具。3、预应力束的布置，既要符合结构受力的要求，又要注意在超静定结构体系中避免引起过大的结构次内力。4、预应力束的布置，应考虑材料经济指标的先进性，这往往与桥梁体系、构造尺寸、施工方法的选择都有密切关系。5、预应力束应避免合用多次反向曲率的连续束，因为这会引起很大的摩阻损失，降低预应力束的效益。6、预应力束的布置，不但要考虑结构在使用阶段的弹性力状态的需要，而且也要考虑到结构在破坏阶段时的需要。7、预应力筋应尽量对称布置8、应留有一定数量的备用管道，一般占总数的1%。9、锚距的最小间距的要求。便计算，选取结构的一半，对控制点截面进行钢筋估算，对称布置。为满足抗裂要求，所需有效预加应力为（5-1-1）估算钢筋数量时，可近似采用毛截面几何性质。Ms为荷载短期效应弯矩组4-2-2Ms值；W为截面抵抗矩531。表5-3-1毛截面特性值及有效预加应力跨数单元位置Ac(m2)ycx(m)ycs(m)Jc(m4)Wx(m3)ep(m)e'p(m)Ms(kN·m)Npe（kN）第一跨1边支座9.551.100.905.234.750.950.750.0000.0007L/87.931.200.804.513.761.050.659941.5368160.1295米处7.931.200.804.513.761.050.6512206.2210019.011L/47.941.210.814.583.801.060.6615238.9512414.6153L/88.001.240.834.913.961.090.6816009.2412629.119L/28.111.300.875.544.251.150.7212547.569352.48225L/88.271.390.946.554.701.240.794632.0473196.43273L/48.481.511.028.025.301.360.87-7388.01-4646.6317L/89.931.581.2211.477.271.431.07-23601.5-1365934中支座11.11.631.3714.418.821.481.22-42745.1-2341341L/89.251.521.089.136.011.370.93-7679.29-4753.6续表5-3-1第二跨47L/48.231.370.926.304.591.220.7716211.8411384.4533L/88.001.240.834.903.961.090.6833607.0026516.760跨中7.931.200.804.513.761.050.6538566.6631655.973变截面38.231.370.926.304.591.220.7716211.8511384.485中支座11.051.631.3714.418.821.481.22-42745.1-23413第三跨93变截面28.481.511.028.025.301.360.87-7388.01-4646.61115米处7.931.200.804.513.761.050.6512206.2210019.0113变截面17.931.200.804.513.761.050.659941.5368160.12118边支座9.551.100.905.234.750.950.750.0000.000Ap1=139mm2fpk=1860MPa,σcon=0.75fpk=1395MPa,20%估算。表中“-”5-3-2表5-3-2钢筋束根数计算表跨数单元位置npm束数单束钢筋数总钢筋数Ap第一跨1边支座0.000.0099810.0117L/852.605.8499810.01195米处64.597.1899810.01111L/480.038.8999810.011153L/881.419.0599810.01119L/260.296.7099810.011225L/820.612.2999810.011273L/4-29.95-3.33-99810.011317L/8-88.05-9.78-2191890.02634中支座-150.93-16.77-2191890.026续表5-3-2第二跨41L/8-30.64-3.40-99810.01147L/473.398.1599810.011533L/8170.9418.992392070.02960跨中204.0722.672392070.02973变截面373.398.1599810.01185中支座-150.93-16.77-2191890.026第三跨93变截面2-29.95-3.33-99810.0111115米处64.597.1899810.011113变截面152.605.8499810.011118边支座0.000.0099810.011表5-3-3各截面累计角度位置θp1（度）累计角度θp2（度）累计角度θp3（度）边支座000L1/8（变截面1）000L1/40023L1/8864L1/213.8645L1/82013.543L1/4（变截面2）31.621207L1/8323636中支座323636L2/83247.853L2/4（变截面3）4355.5703L2/8546270跨中5462705-1-1φ8085mm，预应力筋锚固长度la=110d=110×15.2=1672mm=1.672m。预应力筋纵向曲线位置及各截面具体配筋情况见施工图中的相关配筋图。图5-3-1预应力混凝土连续梁配筋方式2截面几何性质计算CAD绘制相关净截面图及换算截面图，然后导入到MIDAS截面特性值Excel表格中进行整合计6-1-1。表6-1-1净截面几何特性值截面An(m2)Jn(m4)yns(m)ynx(m)ep(m)W（m3）WsWxWp边支座9.55.2240.91.10.155.8044.74934.827L1/87.884.4960.81.20.3425.6203.74713.146L1/47.8934.5530.8031.210.7255.6703.7636.2803L1/87.8934.5390.8021.2110.9445.6603.7484.808L1/28.0645.5050.8681.3070.8856.3424.2126.2205L1/88.2256.5250.9331.3960.5596.9944.67411.6733L1/48.3787.9671.0271.5050.5747.7585.29413.8807L1/89.8211.3521.2181.5661.0419.3207.24910.905中支座10.93914.2591.3791.6211.19510.3408.79611.932L2/89.2049.111.0941.5170.5538.3276.00516.474L2/48.1876.280.9181.3750.9736.8414.5676.4543L2/87.8824.7780.8151.2551.0295.8633.8074.643跨中7.8094.3860.7871.2131.0325.5733.6164.2506-1-16-1-2土面积，附到原截面图中，重新计算几何特性值，得到表6-1-2(6-1-1)(6-1-2)已知表6-1-2换算截面几何特性值截面A0(m2)J0(m4)y0s(m)y0x(m)ep(m)W（m3）WsWxWp边支座9.7555.2410.8951.1050.1455.8564.74336.145L1/88.1354.5330.8111.1890.3315.5893.81213.695L1/48.1494.6890.8261.1870.7025.6773.9506.6793L1/88.1494.7670.8321.1810.9145.7304.0365.216L1/28.3195.7010.8951.280.8586.3704.4546.6455L1/88.486.6120.951.3790.5426.9604.79512.1993L1/48.9738.170.9891.5430.5368.2615.29515.2437L1/810.41511.9711.1581.6260.98110.3387.36212.203续表6-1