南京工業(yè)大學(xué)課程設(shè)計全預(yù)應(yīng)力混凝土梁設(shè)計

南京工業(yè)大學(xué)課程設(shè)計用紙南京工業(yè)大學(xué)課程設(shè)計用紙#全預(yù)應(yīng)力混凝土梁設(shè)計一．設(shè)計題目預(yù)應(yīng)力混凝土簡支T梁設(shè)計二．設(shè)計資料.橋梁跨徑與橋?qū)挊?biāo)準(zhǔn)跨徑：40m(墩中心距離)主梁全長：39.96m計算跨徑：39.0m橋面凈空：凈14+2X1.75m=17.5m.設(shè)計荷載：城一A級車輛荷載，人群荷載3.0kN/m,結(jié)構(gòu)重要性指數(shù)Y0=1.1。.材料性能參數(shù)(1)混凝土強度等級為C50,主要強度指標(biāo)為：強度標(biāo)準(zhǔn)值f=32.4Mpa,f=2.65Mpack tk強度設(shè)計值f=22.4Mpa,f=1.83Mpacd td強度模量 E=3.45x104MPac(2)預(yù)應(yīng)力鋼筋采用1X7標(biāo)準(zhǔn)型一15.2—1860—II-GB/T5224—1995鋼絞線，其強度指標(biāo)為：抗拉強度標(biāo)準(zhǔn)值f=1860MPapk抗拉強度設(shè)計值f=1260Mpapd彈性模量 E=1.95x105MPac相對界限受壓區(qū)高度自=0.4,g=0.2563b pu(3)預(yù)應(yīng)力錨具采用OVM錨具(4)普通鋼筋1)縱向抗拉普通鋼筋采用HRB400鋼筋，其強度指標(biāo)為抗拉強度標(biāo)準(zhǔn)值f抗拉強度標(biāo)準(zhǔn)值f=400MPask抗拉強度設(shè)計值f抗拉強度設(shè)計值f=330MPasd彈性模量E彈性模量E=2.0x105MPas相對界限受壓區(qū)高度自=0.53,g=0.1985b pu2)箍筋及構(gòu)造鋼筋采用HRB335鋼筋，其強度指標(biāo)為抗拉強度標(biāo)準(zhǔn)值f=335MPask抗拉強度設(shè)計值f=280MPasd彈性模量 E=2.0x105MPas.主要結(jié)構(gòu)構(gòu)造尺寸主梁高度h=2300mm,主梁間距S=2500mm,其中主梁上翼緣預(yù)制部分寬為1600mm，現(xiàn)澆段寬為900mm，全橋由7片梁組成，設(shè)7道橫隔梁。.內(nèi)力計算結(jié)果摘錄預(yù)制主梁（包括橫隔梁）的自重g=24.46kN/m1p主梁現(xiàn)澆部分的自重 g=4.14kN/m1m二期恒載（包括橋面鋪裝、人行道及欄桿）g=8.16kN/m2p（1）恒載內(nèi)力：恒載內(nèi)力計算結(jié)果 表1截面位置距支點截面的距離x（mm）預(yù)置梁自重現(xiàn)澆段自重二期恒載彎矩剪力彎矩剪力彎矩剪力MG1PK(kN?m)VG1PK(kN)MG1MK(kN?m)VG1MK(kN)MG2K(kN?m)VG2K(kN)支點00.00476.970.0080.730.00159.12變截面2000905.02428.05153.1872.45301.92142.80L/497503487.84238.49590.3440.371163.5779.56跨中195004650.460787.1201551.420（2）活載內(nèi)力：活載內(nèi)力計算結(jié)果 表2截面位置距支點截面的距離x（mm）A級車道荷載人群荷載最大彎矩最大剪力最大彎矩最大剪力MQ1K(kN?m)對應(yīng)V(kN)VQ1K(kN)對應(yīng)M(kN?m)MQ2K(kN?m)對應(yīng)V(kN)VQ2K(kN)對應(yīng)M(kN?m)支點00251.93251.930032.6932.690變截面2000472.44235.79215.711335.6559.8632.5637.13135.65L/497501762.50173.23175.321675.25230.6732.4617.74183.68跨中195002427.6621.6890.431724.75307.5714.267.89155.26(3)內(nèi)力計算組合：1)基本組合M=1.2(M+M+M)+1.4M+1.12Md GK1P GK1m GK2 Q1K Q2K

V=1.2(V+V+V)+1.4V+1.12Vd GK1P GK1m GK2 Q1K Q2K2)短期組合MM=(M+M+M )+0.7—Q1K+Ms GK1P GK1m GK2 1+R Q2K3)長期組合MM=(M+M+M )+0.4(—Q1K+M )LGK1P GK1m GK2 1+R Q2K截面位置項目基本組合Sd短期組合Ss長期組合sLMdVdMsVsMLVL(kN^m)(kN)(kN^m)(kN)(kN^m)(kN)支點最大彎矩0.001249.500.00907.140.00819.97最大剪力0.001249.500.00907.140.00819.97變截面最大彎矩2360.601138.531715.57823.391552.97740.63最大剪力3653.981115.542331.45815.391891.91735.27L/4最大彎矩9015.95708.986572.16499.265964.16433.34最大剪力8841.17695.426473.58485.855914.17428.20跨中最大彎矩12130.0046.328815.4827.827979.9813.46最大剪力10975.34135.448223.3864.477667.7535.49荷載內(nèi)力計算結(jié)果表3設(shè)計內(nèi)容：（一）預(yù)應(yīng)力鋼筋數(shù)量的確定及布置首先，根據(jù)跨中截面正截面抗裂要求，確定預(yù)應(yīng)力鋼筋數(shù)量。為滿足抗裂要求，所需的有效預(yù)加力為N, MWpe 1e0.85(+-p)

AWM為短期效應(yīng)彎矩組合設(shè)計值，由表3查得M=8815.48kN-m；估算鋼筋數(shù)量時，可y-689y-689.29mm，csA-0.968750x106mm2，y-1610.71mm，c cxJ=0.2649x1012mm4，W=0.1645x109mm3e為預(yù)應(yīng)力鋼筋重心至毛截面重心的距離，e=y-ap pcxp

假設(shè)a=150mm則e=1610.71-150=1460.71mmpp由此得到N>

pe8815.48x106164468286.8N>

pe8815.48x106164468286.80.85x(1460.71 + 968750164468286.8-=6360782.9N)擬采用*依2鋼絞線，單根鋼絞線的公稱截面面積量二139mm2，抗拉強度標(biāo)準(zhǔn)值f=1860MPa，張拉控制應(yīng)力取o=0.75f=0.75x1860=1395MPa，預(yù)應(yīng)力損失pk con pk按張拉控制力的20%估算。N

N

pe

(o -o)Aconsp6360782.9(1-0.2)x1395x139=41.0045,取48根。采用4束120y15.2預(yù)應(yīng)力鋼筋束,OVM-12型錨具，供給的預(yù)應(yīng)力筋截面面積Ap=48x139=6672mm2，采用*80金屬波紋管成孔，預(yù)留管道直徑為85mm。預(yù)應(yīng)力筋束曲線要素表 表4鋼束編號起彎點距跨中（mm）曲線水平長度（mm）曲線方程1019980y=250+4.80961x10-6x22400015980y=150+6.46146x10-6x23、4120007980y=150+7.06654x10-6x2各計算截面預(yù)應(yīng)力鋼筋束的位置和傾角計算截面截面距離跨中（mm）錨固截面19980支點截面19500變截面點17500L/4截面9750跨彼面0鋼束到梁底的距離（mm）1號束21702078.91722.9638.82502號束18001652.41277.6313.61003、4號束600497.5331.9100100合力點1292.51181.6916.8288.1137.5鋼束與水平線夾角1號束12.087911.804210.61715.953302號束12.964512.585310.99584.72180

（度）3、4號束7.14976.72294.938600平均值9.83809.45887.87252.66880累計角度（度）1號束00.28371.47086.134612.08792號束00.37921.96878.242712.96453、4號束00.42682.21117.14977.1497（二）截面幾何性質(zhì)計算部分預(yù)應(yīng)力各階段截面幾何性質(zhì) 表6階段截面A106mmys(mm)yx(mm)ep(mm)I102mm4W(X109mm3)W=IyssW=I：yx-xW=I/ep 'p階段1：鋼束灌漿、錨固刖支點1.432301010.741289.26107.660.730560.566650.722800.67858變截面0.991831083.951216.05299.250.642660.528480.592890.21476L/40.81105926.681373.321084.970.543920.396060.586960.51386跨中0.81105926.931373.071235.570.534520.389290.576810.43261階段2：現(xiàn)澆600mm連接段支點1.478121021.281278.7297.120.760220.594520.744380.78276變截面1.037511096.841203.16286.360.675120.561120.615510.23576L/40.85674992.831307.171019.090.612650.468680.617070.60119跨中0.85674992.751307.251169.750.613240.469120.617720.52452階段3：二期荷載、活載支點1.61313937.581362.42180.820.874520.641890.868750.48364變截面1.17251979.791320.21403.410.801920.607420.818461.98785L/40.99174874.831425.171137.070.721430.506210.824650.63446跨中0.99174867.851432.151294.650.726300.507130.836900.56100（三）承載能力極限狀態(tài)計算.跨中截面正截面承載力計算150x3+250a= =175mmp4h=h—a=2300-175=2125mmppb=200mm,上翼板厚度為150mm，考慮承托影響，其平均厚度為hf=150+[2x0.5x500x100/(2500-200)]=171.74mm上翼緣有效寬度取下列數(shù)值較小者b'<s=2500f

bf<L/3=3900%=13000mm(3)bf<"12hf,因承托坡度2二100^00二0.2<「3,故不計承托影響，hf按上翼緣平均厚度計算b'<200+12x171.74=2260mmf綜上，h,取2260mmf首先按公式fA<fb'h'判斷截面類型，代入數(shù)據(jù)計算得pdpcdfffA=1260x6672=8406720Npdpfb'h'=22.4x2260x171.7=8692140.8Ncdff因為8406720<8692140.8,滿足上式要求，屬于第一類T型，應(yīng)按寬度為b1的矩形截面計算f其承載力。由Ex=0的條件，計算混凝土受壓區(qū)高度丫fA

x=—p-Pfb'cdf1260x667222.4x2260=166.1mm<171.7mm<qh=0.4x2125=850mmb0將x=166.1mm代入下式計算截面承載能力M=fbx(h—X)=17170>yM=12130kNducdf0 2 0d計算結(jié)果表明，跨中截面的抗彎承載力滿足要求。2.斜截面抗剪承載力計算(1)距支點h.；2截面斜截面抗剪承載力計算首先進行截面抗剪強度上下限復(fù)核0.5x10-3afbh<yV<0.51x10-3:廠bh2td0 0d %cu,k0V為驗算截面處剪力組合設(shè)計值，按內(nèi)插法得距支點h2=1150mm處，V為1192.4d 2 d預(yù)應(yīng)力a2取1.25；驗算截面距支點1150處的截面腹板寬度b=550mm，取h=2125mm0求得：1336.8<YV=1311.64kN<4214.8kN0d斜截面抗剪承載力計算YV<V+V0dcspdV=1192.4kN,a=1.0,a=1.25,a=1.1,b=550mmd 12 3p=100(A+A pb p

bh)=0.5709Ap=—=0.001829svbSvV=aaa義0.45義10-3bh:(2+0.6p):廠pf=2106.24kNcs123 0 cu,ksvsd,v0=10.01。,0 =10.51。,0 =5.13。TOC\o"1-5"\h\zp1 p2 p3,4V=0.75x10-3xfZAsin0=843.39kNpb pd pd pV=V+V=2949.60kN>yV=1311.64kNducspd 0d說明截面抗剪承載力是足夠的。（2）變截面點處斜截面抗剪承載力計算首先進行抗剪強度上、下限復(fù)核：0.5x10-3afbh<yV<0.51x10-3x:廠bh2td0 0d cucu,k0其中V=1065.28kN,b=200mm,h仍取2125求得：486.09kN<yV=1171.81kN<1502.60kN0d計算表明，承載尺寸滿足要求，但需配置抗剪鋼筋.斜截面抗剪承載力按下式計算YV<V+V0dcspdV=aaax0.45x10-3bhJ(2+0.6ppfcs123 0 cu,ksvsd,vp=100(Ap=100(—pb p)=1.57bh0A

p=——sv-

svbSv=0.00503V=aaax0.45x10-3bhcs123-'(2+0.6p)?'廠pf=1423.41kN

cu,ksvsd,v0=10.6171。,0=10.9958。,0 =4.9386。p1 p2 p34V=0.75x10-3xfZAsin0=862.46kNpb pd pd pV=V+V=2285.87kN>YV=1171.81kN0d0d說明截面抗剪承載力滿足要求。（四）預(yù)應(yīng)力損失計算.摩阻損失o=o [1-e-（叫kx）]con摩擦損失計算表 表7截面鋼束號1234總計支點x(mm)0.480.480.480.480（弧度）0.004250.004750.005710.00571o2.482.652.992.9911.11變截面11x(mm)2.482.482.482.486（弧度）0.21960.02450.029490.02949o 11 12.7913.6715.3915.3914.31L/4截面x(mm)10.2310.2310.2310.236（弧度）0.090610.10120.12160.1216o 11 52.0155.5662.3862.3858.08跨中x(mm)19.9819.9819.9819.986（弧度）0.17700.19760.23760.2376o99.79106.44119.26119.26111.192.錨具變形損失012反摩擦的影響長度計算表 表8鋼束號1234o=o0 con1395139513951395o=o-o1 0 111295.211288.561275.741275.74Ao=(o-o)/Ld 0 10.0049940.0053270.0059690.0059691(mm)f1249.7512100.611431.311431.3錨具變形損失計算表 表9截面1234總計

鋼束號支點x(mm)480480480480Ao（MPa）124.83128.92136.47136.47o （MPa）120.04123.81130.07130.07505.32變截面 n x（mm）2480248024802480Ao（MPa）124.83128.92136.47136.47o （MPa）100.06102.50106.86106.86416.28L/4 r-2 x（mm）10230102301023010230Ao（MPa）124.83128.92136.47136.47o （MPa）22.6519.9314.3414.3471.28跨中 T2 x（mm）19980199801998019980Ao（MPa）124.83128.92136.47136.47o （MPa） 0.000.000.000.000.003.分批張拉損失o=a乙Ao a=E..E=5.6514 Ep pc Epp■c預(yù)應(yīng)力鋼筋束的張拉順序為：4T3T2T1.N為張拉控制力減去摩擦損失和錨具變形損pe失后的張拉力。預(yù)應(yīng)力分批張拉損失的計算見表。分批張拉損失計算表 表10截面張拉束號有效張拉力Npe（x103N）張拉鋼束偏心距e(mm)y計算鋼束偏心距e(mm)y個各鋼束應(yīng)力損失o14(MPa)支占八、、32130.800.00.0791.760.00.0791.760.00.018.4422115.920.0-363.14-363.140.0791.76791.760.03.643.6412122.50-789.6-789.64-789.64-363791.76791.7613.08-1.89-1.89總計13.081.7520.49變截面32122.950.00.0884.150.00.0884.150.00.026.6822133.090.0-61.55-61.550.0884.15884.150.011.1311.1312138.63-506.8-506.85-506.85-61884.15884.1512.773.763.76總計12.7714.9941.6732198.890.00.01273.320.00.01273.30.00.052.35

L/4222200.940.01059.721059.720.01273.31273.30.041.0141.0112202.33734.52734.52734.5210591273.31273.333.1536.7436.74總計33.1577.75130.1跨中32127.930.00.01273.070.00.01273.070.00.051.2822149.320.01273.071273.070.01273.01273.00.051.7951.7912160.411123.11123.071123.0711231273.01273.043.8543.8543.85總計43.8595.64146.924.鋼筋應(yīng)力松弛損失oo=v七＜0.52—pe一0.26)-opel5 fpepk鋼筋應(yīng)力松弛損失計算表 表11鋼束o(MPa)peo(MPa)15截面12341234支點1272.51255.51223.51204.8136.5534.2830.1227.77變截面1282.21266.11221.81195.137.8835.6927.1726.57L/41320.31286.41240.51152.243.2238.4532.3121.47跨中1259.21208.71180.11048.834.7728.2524.7510.455.混凝土收縮、徐變損失ol60.9[E￡(t,tJ+a.o0(t,t)]O= pcs、 0，Eppc、、 0，l6 1+15pppsNNMo=_p+」e——GKepeAJpJpnne2Pps=1+=f,i2=JAi2 n'n混凝土收縮、徐變損失計算表 表12

截面ePs(mm)PPPsNpe(kN)M自重(kN?m)a預(yù)（MPa）a自重（MPa）aPC(MPa)a16(MPa)支點106.70.004141.0218568.20.005.990.005.9967.1變截面299.90.005691.1328505.51260.128.58-0.827.7674.9L/41085.20.006732.6199473.45241.7510.46-8.22.2637.4跨中1198.10.006732.9203290.66989.0010.32-3.72-2.4916.876.預(yù)應(yīng)力損失組合應(yīng)力損失組合 表13截面a〃二a11+a12+a14(*)a1II=a15+a16(MPa)1234平均1234平均支點122.52140.26135.48154.22138.12105.44103.1799.01196.66101.07變截面112.85128.94137.24163.92135.74160.47158.28149.73149.16154.41L/474.66108.64154.47206.82136.15161.84157.07150.93140.09152.48跨中136.15150.29214.90266.18191.88152.19145.67142.17127.87141.98（五）正常使用極限狀態(tài)計算.全預(yù)應(yīng)力混凝土構(gòu)件抗裂性驗算正截面抗裂性驗算以跨中截面受拉邊的正應(yīng)力控制。在荷載短期效應(yīng)組合作用下應(yīng)滿足：a—0.85o<0st pca為在荷載短期荷載效應(yīng)組合作用下，截面受拉邊的應(yīng)力：stast由表M G1PKJast由表M G1PKJn16查得My+ G2Kn1x+0.7M(1+m+M Q1K Q2Ky0xJ/yn1'n1x=0.38929x109mm3Jyyn2Jyyn2sn2x=0.46911x109mm3J/y=0.50712x109mm30' 0x彎矩設(shè)計值由表1和2查得：=1551.42kN-mM =4650kN-m,M =787.12kN-m=1551.42kN-mG2KGG2KM =2427.66kN?m,M =307.57kN?m,1+^=1.1188Q1K Q2K將上述數(shù)值代入公式得：a=(st4650.47+28711+衛(wèi)+^x242766巫+軍0.389290.469110.27630)=25.25MPa°pc為截面下邊緣的有效預(yù)應(yīng)壓力：N Ne° =—p+—P—nxypcAJ nxnnN=°A=(° 一°一°)ApstpconsIsIIp二(1395-191.88一141.98)義6672,1000=7080.13kN,1000,7080.137080.13x1.23557,ZB°=( + ),1000得pc0.81105 0.38929=31.20MPa°一0.85°=—1MPa<0st pc計算結(jié)果表明，正截面抗裂性滿足要求。（2）斜截面抗裂性驗算斜截面抗裂性驗算以主拉應(yīng)力控制，一般取變截面點分別計算截面上梗肋、形心軸和下肋處在荷載短期效應(yīng)組合作用下的主拉應(yīng)力，應(yīng)滿足°<0.6f的要求。tp tk°,為荷載短期效應(yīng)組合作用下的主拉應(yīng)力°tp°——cx2°=±°cxpcM士—g1pkyJ n1n°tp°——cx2°=±°cxpcM士—g1pkyJ n1n1M G1mKJn2My±—n2+0.7M(1+旦)+M Q1K Q2Ky0vT=G1PKSJbn1+-G1mKSG2K+0.7v (1+m+v Q1K Q2K°Asin0n1Jbn2n2JbOpepeJbn1p-Sn1上述公式中車輛荷載和人群荷載產(chǎn)生的內(nèi)力值，按最大剪力布置荷載，即取最大剪力對應(yīng)的彎矩值，其數(shù)值由表3差得。恒載內(nèi)力值：M=905.02kN-mM=905.02kN-mG1PKM =153.18kN-mG1mKM=301.92kN-mG2K活載內(nèi)力值：M =472.44kN?mQ1KV =215.71kN?mQ1KV =72.45kN-mGImKM =59.86kN?mQ2KV=37.13kN?mQ2KV =428.05kN-m，G1PKV=142.8kN-mG2K1+目=1.1188截面點處的主要截面幾何性質(zhì)由表6差得：yy=1083.95mmn1sA=0.99183x106mm2n1

J=0.64266x1012mm4n1A=1.03751x106mm2n2J=0.67512x1012mm4n2y=1096.84mmn2sA=1.17251x106mm20J=0.80192x1012mm40y=979.79mm0s計算點幾何性質(zhì) 表14計算點受力階段A(x106mm2)1y(mm)x1d(mm)S(x109mm3)1上梗肋處階段10.4450001008.95933.950.31277階段20.3100001021.84946.840.31677階段30.310000904.79829.790.40263形心位置階段10.49679920.841000.45746階段20.49937804.79850.40189階段30.61096846.8400.51739下梗肋處階段10.193751016.05816.050.19686階段20.25011003.16803.160.25089階段30.25011120.2920.210.28016變截面處的有效預(yù)應(yīng)力G=0—0—0=1395—135.74—154.41=1104.85MPape conlIlIIN=0A=1104.85x6672/1000=7371.6kNPpep 'e=y=299.25mmpnpn預(yù)應(yīng)力筋彎起角度分別為：e=10.6171。0=10.9958。0 =4.9386。p1p2p1p2將上述數(shù)值代入，分別計算上梗肋、形心軸和下梗肋處的主拉應(yīng)力。a）上梗肋0=(

pc7371.67371.60=(

pc7371.67371.6x0.299250.991830.64266x0.93395),10000.801920.80192x1000=4.23+1.32+0.21+0.32=6.08MPa=4.23MPa905.02 153.180=4.23+ x0.93395+ x0.94684- 0.64266x1000 0.67512x1000301.92+0.7x472.441.1188+59.86+ x0.82979428.05x428.05x0.3127772.45x0.31677T= + +0.64266x0.2x10000.67512x0.2x1000

142.82+0.7x215.711.1188+37.13)x0.402630.80192x0.2x10001104.85義6672義sin7.8725。*0.312770.64266義0.2義106=1.04+0.17+0.37-2.21=-0.63MPa6.08 ?6.08o= ,( )2+(-0.63)2=-0.06MPatp2 \ 25形心軸處o=(

pcUo=(

pcU+7371.6x0.299250.991830.64266x0.1),1000=7.78MPa905.02 153.18o=7.78- x0.1- x0.085- 0.64266x1000 0.67512x1000=7.74428.05x428.05x0.45746 72.45x0.40189 + +0.64266x0.2x10000.67512x0.2x1000(142.8+0.7x215.711.1188+37.13)x0.402630.80192x0.2x10001104.85x6672xsin7.8725。 x0.517390.64266x0.2x1000=-1.55MPa7.47 :7.47 __o=——一，(——)2+(-1.55)2=-0.31MPatp2 2 2C)下梗肋處opc7371.6=opc7371.6=( +0.991837371.6x0.299250.64266x0.81605),1000=10.23MPaocx=10.23- 90502 x0.81605-—15318 xocx0.64266x1000 0.67512x1000=8.9MPa_428.05x0.19686 72.45x0.25089 (142.8+0.7x215.71/1.1188+37.13)x0.28016T=0.64266x0.2x1000+0.67512x0.2x1000+ 0.80192x0.2x10001104.85x6672xsin7.8723x0.196860.64266x0.2x106=-0.4MPao=-0.02MPatp變截面處不同計算點主應(yīng)力匯總表 表15計算點位置正應(yīng)力o(MPa)cx剪應(yīng)力T(MPa)主壓應(yīng)力o (MPa)cp上梗肋處6.08-0.63-0.06形心位置7.47-1.55-0.31下梗肋處8.9-0.4-0.02計算結(jié)果表明，形心處主拉應(yīng)力最大，其數(shù)值為o =-0.31MPa,小于限制值tp,max0.7f=2.65*0.7=1.855MPatk.變形計算(1)使用階段的撓度計算使用階段的撓度值，按短期荷載效應(yīng)組合計算，并考慮撓度長期影響系數(shù)％，對C50混凝土，n=1.425，剛度B=0.95EJ=0.95x3.45x104x0.72630x10i2e 0 c0=2.38x10i6N?mm2荷載短期效應(yīng)組合作用下的撓度值，可簡化為按等效均布荷載作用情況計算：5L2xMf=—x s48B05 39.962x8815.48=-x =61.6mm480.95x3.45x0.72630x104自重產(chǎn)生的撓度值按等效均布荷載作用情況計算：5L2xMf=——x GKG48B0539.962x(4650.46+787.12+1551.42)=—x 48 0.95x3.45x0.72630x104=48.8mm消除自重產(chǎn)生的撓度，并考慮撓度長期影響系數(shù)后，使用階段撓度值為f=n(f—f)=1.425x(61.6—48.8)=18.24mmlesG<L.1600=66.6mm計算結(jié)果表明，使用階段的撓度值滿足規(guī)范要求。(2)預(yù)加力引起的反拱計算及預(yù)拱度的設(shè)置預(yù)加力引起的反拱近似地按等截面梁計算，截面剛度按跨中截面凈截面確定，即取B=0.95EJ=0.95x3.45x104x0.53452x1012=1.75x1012N?mm20 Cn反拱長期系數(shù)采用n=2.0e預(yù)加力引起的跨中撓度為23M?Mf=-ne 1"~PPeB03 為跨中截面作用單位力P=1時，所產(chǎn)生的M圖在半跨范圍內(nèi)的面積：M12 1L23 =——M1216Mp為半跨范圍M1圖重心(距支點L3處)所對應(yīng)的預(yù)加應(yīng)力引起的彎矩圖縱坐標(biāo)M=NeP PpN=(o-a—°,〃)A=(1395—136.15—152.48)義6672,1000=7381.7NP con L1 LII P -e為距支點L：3處的預(yù)應(yīng)力束偏心距pe=y-apxopM=7381,7x103義（1424.17-294.6）=8338.15義106N-mP由預(yù)加力產(chǎn)生的跨中反拱為/c2x39960216x8838.15x106f=2x =201.61>nf=1.425x616.6p 1.75x1016 es=89.32mm由于預(yù)加力產(chǎn)生的長期反拱值大于按荷載短期效應(yīng)組合計算的長期撓度，所以可以不設(shè)預(yù)拱度。（六）持久狀況應(yīng)力驗算（1）跨中截面混凝土法向正應(yīng)力驗算NNeMMM+M+Mo二一p-—ppn1+——G1PK+——G1PK+G1mK Q1K Q2K<05fhAW W W W ckn1 snl sn1 sn2 OSo=o—o—o=1395—191.88—141.98=1061.14MPapeconsIN=oA=1061.14x6672.1000=7079.9kNp pep由表六查得：e=y=1235.57mmpn1 pn17079.97079.9x1.235574650.46 787.12o=[ - + + +kc0.81105 0.38929 0.389290.469121551.42+2427.66+307.57 ]1000=8.33<0.5f=0.5x32.4=16.2MPa0.507132）跨中截面預(yù)應(yīng)力鋼筋拉應(yīng)力驗算o=（o+ao）<0.65fppeepkt pkM+M+M+Mo= G1mK G2K Q1K Q2Kkt w0P

787.12+1551.42+2427.66+307.570.56100x1000=9.4MPao=o+

p peao=1061.14+5.65x9.04=1112.21<0.65f=1209MPaepkt,k pk3）斜截面主應(yīng)力驗算一般取變截面點分別計算截面上梗肋、形心軸和下梗肋處在標(biāo)準(zhǔn)值效應(yīng)組合下的主壓應(yīng)力，應(yīng)力滿足o787.12