短暫狀況的正應(yīng)力驗(yàn)算

1、1 短暫狀況的正應(yīng)力驗(yàn)算1）構(gòu)件在制作、運(yùn)輸及安裝等施工階段由預(yù)制T梁?jiǎn)为?dú)受力，張拉時(shí)，混凝土強(qiáng)度等級(jí)為C50的90%，即C45。在預(yù)加力和自重作用下的截面邊緣混凝土的法向壓應(yīng)力根據(jù)公預(yù)規(guī)條應(yīng)符合下列要求：壓應(yīng)力： 拉應(yīng)力： ，與構(gòu)件制作、運(yùn)輸、安裝各施工階段混凝土立方體抗壓強(qiáng)度相應(yīng)的抗壓強(qiáng)度、抗拉強(qiáng)度標(biāo)準(zhǔn)值，本設(shè)計(jì)考慮混凝土強(qiáng)度達(dá)到時(shí)開(kāi)始張拉預(yù)應(yīng)力鋼束，則：則： 2）短暫狀況下（預(yù)加力階段）梁各截面上、下緣的正應(yīng)力上緣：下緣：其中，見(jiàn)表2-30，、截面特性取用表2-17中的第一階段的截面特性。表2-33示出了預(yù)加應(yīng)力階段混凝土法向應(yīng)力的計(jì)算過(guò)程。由表可知，上緣最大拉應(yīng)力位于邊梁變化點(diǎn)處，下緣

2、最大為，即預(yù)加力階段混凝土的壓應(yīng)力滿足應(yīng)力限制值的要求；混凝土的拉應(yīng)力通過(guò)規(guī)定的預(yù)拉區(qū)配筋率來(lái)防止出現(xiàn)裂縫，故預(yù)拉區(qū)只需配置配筋率不小于0.2%的縱向鋼筋即可。則預(yù)制T梁頂面上應(yīng)配縱向鋼筋：。翼緣中僅構(gòu)造鋼筋就滿足要求（15根）。 表2-33 預(yù)加應(yīng)力階段的法向應(yīng)力計(jì)算表梁號(hào)截面位置邊梁跨中上緣0.81401.08830.32163103.012155.60.014下緣0.81401.08830.55753103.012155.66.003上緣0.81400.99230.32193102.961617-0.73下緣0.81400.99230.55673102.9616176.438變化點(diǎn)上緣0

3、.81400.86010.32493144.24943.16-1.56下緣0.81400.86010.55943144.24943.167.011支點(diǎn)上緣1.24960.26010.43253111.0400.619下緣1.24960.26010.61863111.0403.7983號(hào)梁跨中上緣0.77861.06680.31903102.782286.880.778下緣0.77861.06680.52733102.782286.885.925上緣0.77860.97020.31293102.081715-0.15下緣0.77860.97020.51623102.0817156.492變化點(diǎn)上

4、緣0.77860.83850.31513143.441000.6-1.15下緣0.77860.83850.51803143.441000.67.194支點(diǎn)上緣1.2160.24360.42083110.8600.757下緣1.2160.24360.58193110.8603.8613）吊裝應(yīng)力驗(yàn)算采用兩點(diǎn)吊裝，吊點(diǎn)設(shè)在支座處，即兩點(diǎn)間距為28.90m。根據(jù)橋規(guī)4.1.10條規(guī)定，構(gòu)件在吊裝、運(yùn)輸時(shí)，構(gòu)件重力應(yīng)乘以動(dòng)力系數(shù)1.2或0.85，因此可分別按超重和失重兩種情況進(jìn)行吊裝應(yīng)力驗(yàn)算，此時(shí)截面特性型采用表2-17中的第二階段的截面特性。結(jié)果于表2-34。通過(guò)各控制截面的計(jì)算，可知：邊梁最大壓應(yīng)

5、力為6.674MPa<20.72 MPa，發(fā)生在超重狀態(tài)變化點(diǎn)截面下緣；最大拉應(yīng)力為1.699MPa<1.757 MPa，發(fā)生在失重狀態(tài)跨中截面上緣?？梢?jiàn)混凝土法向應(yīng)力滿足施工階段要求.3號(hào)梁最大壓應(yīng)力為6.808MPa<20.72 MPa，發(fā)生在超重狀態(tài)變化點(diǎn)截面下緣；最大拉應(yīng)力為2.212MPa>1.757 MPa，發(fā)生在失重狀態(tài)跨中截面上緣，由公預(yù)規(guī)7.2.8條可知，當(dāng)拉應(yīng)力，預(yù)拉區(qū)需配置配筋率不小于0.3%的縱向鋼筋，可見(jiàn)混凝土法向應(yīng)力均滿足施工階段要求。表2-34 T梁吊裝時(shí)截面上緣、下緣應(yīng)力計(jì)算梁號(hào)截面位置超重失重邊梁邊梁跨中上緣0.81401.08830.

6、32163103.012586.72198.711.3550.148下緣0.81401.08830.55753103.012586.72198.715.231.699續(xù)上表上緣0.81400.99230.32193102.961940.41649.340.275-0.63下緣0.81400.99230.55673102.961940.41649.345.8571.244變化點(diǎn)上緣0.81400.86010.55943144.241131.8962.0231.0520.748下緣0.81400.86010.55943144.241131.8962.0236.6740.748支點(diǎn)上緣1.24960

7、.26010.43253111.04000.6190.619下緣1.24960.26010.61863111.04003.7981.1823號(hào)梁跨中上緣0.77861.06680.31903102.782744.32332.622.2120.921下緣0.77861.06680.52733102.782744.32332.625.0582.131上緣0.77860.97020.31293102.0820581749.30.943-0.044下緣0.77860.97020.51623102.0820581749.35.8281.543變化點(diǎn)上緣0.77860.83850.31513143.441200.71020.61-0.517-1.089下緣0.77860.83850.