1桩基计算(钻孔灌注桩)选用桩径为两米的钻孔灌注桩,混凝土选用C25水下,钢筋选用R235钢筋,已知混凝土在桩身的弹性模量42.610cEMPa。桩基的设计荷载计算计算每一根桩承受的荷载:1、一孔的反力:117372.563686.282NKN2、计算盖梁重量反力:2878NKN3、计算系梁重量反力:3110.611.425185.52NKN4、计算单根墩柱的重量:4114.3NKN作用在桩顶部的反力:12344864.08NNNNNKN5、计算桩基的每米重量:22.02578.544qKNM6、计算可变荷载产生的反力:(1)计算可变荷载两跨产生的反力:51441.78NKN(三列车)'5153.10NKN(单侧人群荷载)(2)计算可变荷载单跨产生的反力:6807.78NKN(三列车)'658.14NKN(双侧人群荷载)(3)制动力:372.06186.032TKN作用在支座中心的反力和桩顶部的距离为:0.0421.856.8212m7、计算桩顶上作用的外力:2max4864.081441.78153.16458.96NKN(双孔)min4864.08807.858.145730.00NKN(单孔)186.3HKN'660.256.8210.251485.39MNTNKNM8、地面处作用在桩顶的外力max6458.9678.546537.5NKNmin5730.0078.545808.54NKN186.03HKN01458.39186.031.01671.42MKNM3计算桩基长度因为假定的图层为单一图层,所以可按照容许承载力的单桩经验公式来计算初步的桩长,最大冲刷线以下的灌注桩桩长为h,计算公式如下:002231[]{[](3)}2iiNUlmkhU:桩的周长,因为用旋转式钻机施工,成孔直径需增加5cm,所以2.056.44Um。i:桩外壁的摩阻力的极限值,取70MPa。Li:图层厚度,单位为米。:为桩入土深度考虑的修正系数,取0.75。0m:清底系数为考虑孔底沉淀厚度,取0.80。A:桩底截面面积,223.14ARm0[]:土层桩底的容许承载力,取400KPa。2k:深度修正系数,取值4.0。2:土层的重度,取值为11.8KN/2m。3h:一般冲刷线下方的深度。41[]6.44(9.51)700.750.83.14[4004.011.8(9.513)]3476.05314.322Nhhh桩底最大垂直力为:max6537.59.5178.5439.273476.05314.32Nhh计算得:h=13.85m,取14m。所以整理得,地面以下钻孔灌注桩的长度为23.15m。[]3476.05314.32147876.537284.4239.27147834.19NKNKN综上所述,钻孔灌注桩轴向承载力满足需要。桩基的内力计算(m法)1、计算桩基的计算宽度1b1(1)0.9(2.01)2.7fbkdm2、桩基的变形系数15mbEI式子中,722.610/hEKNm,440.04910.7856Idm,41000/mKNm受弯构件的0.67hEIEI,所以157100002.70.4560.672.60.785610m计算桩的换算深度为:0.45623.5110.722.5hh故按照弹性桩计算。3、计算地面下深度为z处的桩身截面上的弯矩值Mz,以及5水平压应力zx的计算作用在地面处桩基顶部的外力:06537.5NKN0186.03HKN01671.42MKNM(1)桩身截面弯矩00zmmHMAMB其中mA,mB等无纲量系数可在表中查到,桩身截面的弯矩分布图如下:zzhmAmB0mHA0mMBzM0.220.104.000.099600.9997440.631670.991711.620.440.204.000.196960.9980680.351668.181748.530.880.404.000.377390.98617153.961648.301802.261.320.604.000.529380.95861215.971602.241818.211.750.804.000.645610.91324263.381526.411789.792.191.004.000.723050.85089294.981422.191717.172.851.304.000.767610.73161313.151222.831535.983.291.504.000.754660.68694307.871148.171456.044.392.004.000.614130.40658250.54679.57930.115.482.504.000.398960.14763162.76246.75409.516.583.004.000.193050.0759578.76126.94205.707.683.504.000.050810.0135420.7322.6343.368.774.004.000.000050.000090.020.150.17(2)计算桩身的水平压力zx20011zxxxHMhAhBbb桩身的水平方向压力分布图如下:6Mz02468100.00500.001000.001500.002000.00MzMzzzxAxB201xHzAb301xMzBbzx0.000.002.44071.62100.000.000.000.440.202.11791.290913.3533.3446.690.880.401.80271.000622.7351.6874.411.100.501.65040.870426.0156.2082.211.320.601.50270.749828.4258.0986.511.540.701.36080.638930.0357.7587.781.750.801.22370.537330.6855.1985.871.980.901.09360.444831.0251.6982.722.191.000.97040.361230.4546.4376.884.392.000.1470-0.07579.25-19.51-10.266.583.00-0.0874-0.0947-8.24-36.58-44.818.774.00-0.1079-0.0149-13.56-7.67-21.23桩身截面强度计算与配筋验算根据上式,截面最大弯矩值在1.32zm处,所以验算该截面的强度即可。该处的内力值为1818.21MKN6537.578.451.326641.17NKN桩柱内部竖直方向配筋按000.2匹配。7所以220020.262.84sAcm配置的钢筋选则27根直径为18cm的二级钢筋,所以268.72sAcm下面计算桩基的换算面积A02202100.0068723.2094nsAAnAm桩基的换算模量即W0223330100.0068720.910.81342421ssnArWrmR计算桩长pl0.46523.5110.724h所以计算40.7(10)6.14plm0001671.420.256537.5MemN计算12010.22.70.755()serr021.150.011.11312lr所以取值为1计算偏心距增大系数2012011()1.0421400/()2slerrr即01.0420.250.261e分别取值g=0.88,000.211.5cdfMPa'195sdfMPa8所以'0'11.50.020.8819511.50.02195cdsdcdsdBfDgfBDeAfCfAC查表取值,当0.96时,A=2.5890,B=0.4011,C=2.2012,D=0.7446所以计算00.159em22'030566.726641.17cdsddArfCrfNKN33'004880.971818.21cdsddBrfDgrfNeKN综上所述,验算的灌入桩正截面受压承载力满足所需要求。5.14.5墩顶纵向水平位移验算1、计算桩基在地面位置处的水平方向位移0x和转角000033xxHMxABEIEI当4h时,Z=0时,查表得到2.44066xA1.621xB所以3375(0.456)0.672.60.78561012.9810EI2275(0.456)0.672.60.78561028.4610EI9计算05582.51671.422.441.6210.86612.981028.4610xmmmm以上计算结果完全符合m法的计算准则05582.51671.42(1.621)1.750580.00046228.461062.410rad2、计算墩柱顶部纵向水平位移