1、(6)底面以下深度z处桩截面的弯矩无量纲系数查附表3、7zAMBM118.09AM360BMMZ13600.30.70.29010.9938234.25791357.7752392.03310.61.40.529380.9586162.51448345.0996407.61410.92.10.689260.8860781.39471318.9852400.37991.22.80.761830.7741589.9645278.694368.65851.53.50.754660.6408189.1178230.6916319.80941.84.30.684880.4988980.87748179.
2、6004260.47792.25.20.53160.3202562.77664115.29178.06662.66.10.354580.1754641.8723563.1656105.03837.10.193050.0759522.7972727.34250.139278.30.050810.013546.0001534.874410.8745549.40.000050.000090.0059050.03240.038305(7)桩顶水平位移及转角其中、查附表1416,取,;(8)桩身最大弯矩及最大弯矩位置计算由公式(4-70)得由及查附表13得,故由及查附表13得(9)桩身配筋计算及桩身材料
3、截面强度验算a)纵向钢筋面积桩内竖向钢筋按含筋率0.2%配置:(下面还未算完)现选用10根的HRB335级钢筋:,桩柱采用的混凝土,。b)计算偏心距增大系数因为长细比:所以偏心距增大系数:c)计算截面实际偏心距d)根据公路桥涵地基与基础设计规范(JTG D63-2007)求得轴向力的偏心距:其中:并设则以下采用试算法列表计算ABCD0.792.09260.59821.59381.14962492391.0418410.82.12340.58981.63811.12122421.0125520.812.1540.5811.68111.09342340.979079由上表可见,当时,与实际的很接近
4、,故去0.80为计算值。e)计算截面抗压承载力满足要求。三、桩基础习题4-11某桥台为多排桩钻孔灌注桩基础,承台及桩基尺寸如图。纵桥向作用于承台底面中心处的设计荷载为:N=6400KN;H=1365kN;M=714kN.m。桥台处无冲刷。地基土为砂性土,土的内摩擦角;土的重度;桩侧土摩阻力标准值,地基比例系数;桩底土基本承载力容许值;计算参数取。试确定桩长并进行配筋设计。1.桩长的计算桩(直径1.5m)自重每延米计算时取以下数据:桩的设计桩径1. 5m,桩周长.,。所以得现取, 2.桩的内力计算(1)桩的计算宽度(P133)已知:则系数k按照此式计算:,。其计算长则为:,故按弹性桩计算。(3)
5、桩顶刚度系数值计算故取, 查附表17,18,19得。由式(4-86d)得:(4)计算承台底面原点O处位移、式(4-92)、式(4-93)得:,(5)计算作用在每根桩顶上作用力按式(4-97)计算:竖向力水平力弯矩(6)桥台处无冲刷桩身内力与桩顶相等。(7)深度z处桩截面的弯矩及桩身最大弯矩计算a.局部冲刷线以下深度z处桩截面的弯矩计算无量纲系数有附表3、附表7分别查得,1093.40AM782.41BM782.410.960.289650.99363316.70331777.4261094.1291.920.526030.95726575.161202748.96981324.1312.880
6、.678740.87987742.134316688.41911430.5533.840.73880.76503807.80392598.56711406.3714.810.713540.62469780.184636488.76371268.9485.770.620920.47411678.913928370.94841049.8627.050.43420.28334474.75428221.688696.44238.330.231810.13062253.461054102.1984355.65949.610.076280.0369483.40455228.90223112.306811.
7、210.000010.000040.0109340.0312960.04223b.桩身最大弯矩及最大弯矩位置由得:,故由,查附表13得, (8)桩身配筋计算及桩身材料截面强度验算按照h=13米计算桩(直径1.5m)自重每延米(已考虑浮力)788.84BM788.84783.81511100.518755.1251330.286694.07671436.211603.48631411.29492.78051272.965373.99691052.911223.5099698.2642103.0383356.499329.13975112.54430.0315540.042488a.纵向钢筋面积选用12根直径20的HRB335级钢筋。桩柱采用C20混凝土,b.计算偏心距增大系数c.计算截面实际偏心距d.根据公路桥涵地基与基础设计规范(JTG D632007)求得轴向力的偏心距:其中,并设,则()0.972.61580.38652.2290.7251116.18011121.0373230.982.64240.37172.25610.7061110.7254
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