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《基础工程》课程设计指导书柱下钢筋混凝土独立基础设计1)选择持力层因为下卧层有软弱层,故基础要浅埋,基础埋深d=2米。混凝土强度等级:C20,ft=9.60N/mm2钢筋级别:HRB335,fy=300N/mm2基础与覆土的平均容重:20.00kN/m3作用力位置标高:0.000m基础混凝土保护层厚度:45mm2)计算地基承载力特征值,并修正承载力特征值:标贯数为12,由此查表2-4计算可知:承载力fak=140)1012(1015140180=156kpa查表2-5有深度修正系数为2.0所以)5.0()3(dbffmdbaka=kpa6.216)5.02(2.2021563)计算基础所需底面尺寸有三种荷载设计值F1=735KNF2=1435KNF3=2035KN分项系数:1.35荷载标准值分别为FK1=544.44KNFK2=1062.96KNFK3=1507.41KN又有公式dfFbaK20方柱下基础底面选择方形,带入上面数据就有:对应的基础尺寸最小值为:1.7558m2.4534m2.9216m初选基础底面宽度b为:1.8m2.5m3m4)验算软弱层强度和沉降量基底处总竖向力Fk+Gk(KN)=dbFK220带入数据得总竖向力分别为:674.04KN1312.96KN1867.41KN基底平均压力Pk(kpa):2bGFPKKK带入数据得Pk分别为:208.038kpa210.074kpa207.490kpa可见:Pk均小于地基承载力特征值fa=216.6kpa,所以持力层承载力验算通过,后面由于调整沉降差改变了基础尺寸,再做验算。又有:43.16.5821ssEE,z/b分别为:67.18.132.15.23133查表2-7内插法计算θ=23+(25-23)/2*(1.43-3)=21.43tanθ=0.39247下卧层顶面的附加应力σz(kpa)为:22)tan2()(zbPbcdKz,带入数据计算分别为:31.464kpa44.993kpa52.445kpa下卧层自重应力σcz(kpa):下卧层kpazdczm2.20kpacz101)32(2.20又有下卧层标贯数6.6,所以kpafak8.112)106.6(5140180140修正承载力:kpadbffmdbaka6.294)5.02(2.2028.112)5.0()3(而σz+σcz=132.464kpa,145.993kpa,153.445kpa,均小于faz=294.6kpa,所以下卧层承载力验算通过。持力层土的变形模量Eo=8,泊松比u=0.4,柔性基础平均影响系数Wm=0.95*由于F2的相邻基础情况有两种,故记作F2113,F2123F1=734.6KN,F21=1434.6KN,F3=2034.6KN,F23=1434.6KNP36页:mnnbE021带入四组数据分别得:0.05542,0.0399,0.03325,0.0399P38页:00557.0684.011202LEjk所以,各个基础的沉降量kjkjjjFFS,带入数据有:56.69174mm,76.7582mm,102.958mm,80.6575mm查表2-6得相邻基础沉降差允许值0.002L=0.0026000=12mm,调整基础尺寸,修正后基础尺寸b(m)b1=1.8m,b2113=3.2m,b3=5.4m,b2123=3.4m修正后δnn(mm/KN)分别为:mnnbE0210.055416667,0.031171875,0.018472222,0.029338235修正后δJK(mm/KN)=0.005570423所以修正基础尺寸后沉降:kjkjjjFFS56.6917413mm,64.23682034mm,72.89115313mm65.50557699mm,沉降差均小于限值,符合要求。*具体下卧层沉降量计算见计算表39行至51行。根据改变后的基础尺寸,再验算前面的指标:基底处总竖向力Fk+Gk(KN)=dbFK220:674.041472.562673.811525.36基底平均压力Pk(kpa):2bGFPKKK208.038409143.804976991.694356131.9518134前计算得知:kpafa6.216,可见akfP持力层承载力验算通过。软弱下卧层顶面的附加应力σz(kpa)为:22)tan2()(zbPbcdKz,带入数据计算分别为:31.463915634.3162965524.87212731.95658231进而求得:101zczz132.463916135.3162965125.87213132.9565823前面计算得知:kpafa6.294,可见aczzf下卧层承载力验算通过。5)设计基础剖面,并计算配筋地基净反力设计值Pj(kpa),2bFPj带入数据可得结果分别为:226.85kpa,140.14kpa,69.79kpa,124.13kpa,综合考虑:5.2tan取h值分别为350mm,610mm,1050mm,650m,保护层厚度45mm,则ho=305mm,565mm,1005mm,605mm,002hb分别为1010mm,1530mm,2410mm,1610mm由此可见:b002hb求抗冲切面积A1,由公式:2001)24.02()24.02(hbbhbA得A1分别为0.5552m,1.9752m,5.8382m,2.2422m。所以ljlAPF,125.897KN,276.738KN,407.417KN,278.307KN而抗冲切力F(KN):00)4.0(7.0hhfFthp带入数据有:165.5693KN,320.031KN,468.1793KN,320.031KN由此可见Fl均小于对应的F值,抗冲切验算通过。04.021tanhb,所以tan值分别为:2.295081972.4778761062.48756222.479338843满足条件:5.2tan值分别为66.5,68.0,68.1,68.0;4)4.0()4.0(1234bbA:带入修正后的不同的基础地面尺寸得:(2m)0.772.527.252.85计算梯形的形心至柱边的距离:)4.0(6)4.02()4.0(0bbbL,带入数据得:0.4242m,0.8815m,1.6092m,0.9474m于是:01234lApMj,带入数据分别为:74.1KN*m,311.3KN*m,814.2KN*m335.2KN*m计算配筋:钢筋为HRB335级,fy=300N/mm2,09.0hfMAys,带入数据得四种底面的钢筋面积分别为:899.92mm,2040.62mm,3000.52mm,2051.82mm。选择钢筋:12@120(As=943mm2),20@150(As=2095mm2)24@150(As=3016mm2),20@150(As=2095mm2)其中括号内为实配钢筋面积。6)计算列表入下。7)施工图见图纸。钢筋混凝土柱下独立基础设计F1F2(1)F3F2(2)由于计算沉降F2有区别,故区分开选择持力层基础埋深d(m)2222重要公式备注计算地基承载力特征值(kpa)标贯击数101512特征值fak(kpa)140180156深度修正系数2加权平均重度20.2承载力特征值fa(kpa)216.6216.6216.6216.6fa=fak+ηd*rm*(d-0.5)基础底面尺寸(m)荷载F(KN)735143520351435FK(KN)544.4441062.9631507.4071062.963基础计算尺寸(m)1.7562.4532.9222.453b=sqrt(Fk/(fa-20*d))基础底面宽度b(m)1.802.503.002.50修正后基础尺寸b(m)1.803.205.403.40持力层及下卧层强度及沉降量验算荷载值Fk(KN)544.4441062.9631507.4071062.963基底处总竖向力Fk+Gk(KN)674.041472.562673.811525.36基底平均压力Pk(kpa)208.038143.80591.694131.952Pk=(Fk+Gk)/power(b,2)持力层承载力结论通过通过通过通过压缩模量Es18压缩模量Es25.6Es1/Es21.43软弱层距离z(m)3z/b1.671.201.00Es1/Es23θ23Es1/Es25θ25θ21.43tanθ0.3924711下卧层附加应力σz(kpa)31.46434.31624.87231.957σz=b²*(Pk–σcd)/(b+2*z*tanθ)²下卧层自重应力σcz(kpa)101下卧层rm20.2rm=σcz/(d+z)下卧层标贯数6.6下卧层fak(kpa)112.8下卧层承载力特征值faz(kpa)294.6faz=fak+2.0*rm*(d-0.5)σz+σcz132.464135.316125.872132.957均小于faz=294.6下卧层承载力结论通过通过通过通过持力层土的变形模量Eo8泊松比u0.4柔性基础影响系数Wc\Wo\Wm0.561.120.95Fn734.61434.62034.61434.6δnn(mm/KN)0.05540.03990.03330.0399δnn=(1-power(u,2))/Eo/b*WmδJK(mm/KN)0.00560.00560.00560.0056Δjk=(1-power(u,2))/Eo/3.1415/6沉降量(mm)56.69276.758102.95880.657s=δjjFj+δjkFk修正后基础尺寸b(m)1.803.205.403.40修正后δnn(mm/KN)0.05540.03120.01850.0293δnn=(1-power(u,2))/Eo/b*Wm修正后δJK(mm/KN)0.00560.00560.00560.0056Δjk=(1-power(u,2))/Eo/3.1415/6修正基础尺寸后沉降(mm)56.691764.236872.891265.5056相邻基础沉降差小于12mm基地附加压力po(KN/m2)226.73140.1069.77124.10柔性基础角点沉降s(mm)24.0026.3622.15s=(1-power(u,2))*Wc*F/b/Eo柔性基础中点沉降s(mm)47.9952.7244.31s=(1-power(u,3))*Wo*F/b/Eo柔性基础平均沉降量s(mm)40.7144.7237.58s=(1-power(u,4))*Wm*F/b/Eo下卧层土的压缩系数a0.35下卧层土的压缩模量Eo5600000l/b1111z/b1.6670.9380.5560.882应力系数ac0.1070.1830.2270.190附加应力σz(kpa)97.274102.53563.28994.208σz=4acσoz/b4.4442.5001.4812.353应力系数ac0.02230.06040.12330.0663附加应力σz(kpa)20.23533.85734.40932.929软弱层沉降量s(mm)58.75568.19648.84963.569s3=(a/(1+e))*σz*hi设计基础剖面及配筋计算地基净反力设计值Pj(kpa)226.852140.13769.787124.135基础有效高度ho(mm)3055651005605保护层厚度45mmbc+2ho1010153024101610抗冲切面积A1(m)0.5551.97
本文标题:柱下钢筋混凝土独立基础课程设计指导书
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