第六章 裂縫寬度及變形驗算

第六章正常使用極限狀態(tài)計算7.1抗裂性驗算7.1.1正截面抗裂性驗算A．荷載在短期效應組合作用下的抗裂性正截面抗裂性驗算以跨中截面受拉邊正應力控制，在荷載短期效應組合作用下，應滿足：為在荷載短期效應組合作用下，截面受拉邊的應力表7-1短期效應組合作用下的抗裂驗算截面3L1/8B-BL/4L/2MG1k5676.888818366.4424-669.89985023.5009MG2k2234.09977057.4557-264.47792029.3554MQ1k2142.9555579.04991606.24462354.5339W1.83357765.038588489662.31552261.8287885σst5.29624445.142377284770.17916694.9380774σpc5.508677111.141556031.456544910.161559σst-σpc-0.212443-5.99911874448-1.277338-5.223551結果表明截面的σst-σpc<=0.168Mpa正截面抗裂驗算滿足要求。B．荷載在長期效應組合作用下的抗裂性為在荷載短期效應組合作用下，截面受拉邊的應力表7-2長期效應組合作用下的抗裂驗算截面3L1/8B-BL/4L/2MG1k5676.888818366.4424-669.89985023.5009MG2k2234.09977057.4557-264.47792029.3554MQ1k2142.9555579.04991606.24462354.5339W1.83357765.038588489662.31552261.8287885σst4.87550015.10100005888-0.0705564.4745779σpc5.508677111.141556031.456544910.161559σst-σpc-0.633117-6.04055597007-1.527111-5.687001結果表明截面的σst-σpc<=0.168Mpa正截面抗裂驗算滿足要求。7.1.2斜截面抗裂性驗算斜截面抗裂應對構件斜截面混凝土主拉應力σtp進行驗算，A類構件應滿足表7-3斜截面抗裂驗算參數截面3L1/8B-BL/4L/2σpe1120.85511373.09991052.1991049.111Ap0.0083440.0333660.00250020.0175114Np(N)9347896645806566726325800183741115VG1K-162.62222987.89961258.755713.309VG2k-66.9855929.6166504.79994.85VQ1k182.1155330.2177363.2055213.96b1.311.3411SoApb0.003333600.00333360.001I1.13155.18421.75981.1258Sin0.174500.1570.2013表7-4斜截面抗裂驗3L1/8計算點A(m^2)y(m)S(m^3)dσpcσcxtσtp上梗肋處2.28060.48491.10586630.18491.9541.1143-0.35-0.271558形心處2.44560.2910.71167701.7164771.1716447-0.255999-0.037336下梗肋處1.80.71711.2907880.51714.78040.6946558-0.46433-0.044668B-B計算點A(m^2)y(m)S(m^3)dσpcσcxtσtp上梗肋處2.28060.97112.21469910.67113.3384.84987721.3101-0.331227形心處4.0688330.76113.096788705.95475.95471.8319004-0.518443下梗肋處2.521.12892.84482280.76711.51784.08144451.6828558-0.604338L/4計算點A(m^2)y(m)S(m^3)dσpcσcxtσtp上梗肋處2.28060.5811.32502290.2810.10163340.12773331.0706223-1.008666形心處3.14580.3611.135633400.4630.4630.9175992-0.714884下梗肋處1.890.861.62540.651.29891.23838891.3133223-0.832778L/4計算點A(m^2)y(m)S(m^3)dσpcσcxtσtp上梗肋處2.28060.48441.10472230.18441.222-0.1183380.3585993-0.422664形心處2.6450.33440.884488803.3733.3730.2871005-0.024226下梗肋處1.80.71561.2880880.51569.3915.6424770.4181111-0.030881計算結果表面各截面=1.68Mpa均符合要求變形計算7.2.1使用階段的（跨中）擾度計算部分預應力混凝土A類構件使用階段的擾度計算，去剛度Bo=荷載短期效應組合下的擾度Ms=15130.134Mpa,L=36000mm自重產生的擾度值按等效均布荷載做用情況計算：=+=7052.863KN·m=2354.539KN·m消除自重產生的饒度，并考慮擾度長期影響系數后，使用階段饒度為計算結果表明，使用階段的撓度滿足規(guī)范要求。7.2.2預加力引起的反拱計算及預拱度的設置預加力引起的反拱近似的按等截面梁計算，剛度?。築o=式中，Mp為半跨范圍M1圖的重心對應的預加力引起的彎距圖縱坐標Mpaypn為距支點L/3處預應力鋼筋重心的換算截面重心的距離ypn=0.4662ysn為距支點處L/3非預應力鋼筋重心的換算截面重心的距離ysn=0.7023得:Mp=取=2.0代入數據得111.88559mm由于預加的力產生的長期反拱值大于按荷載短期效應組合計算的長期撓度，所以可不設置預拱度。7.2.3持久狀