【正文】 全截面重心到上緣距離毛截面扣除管道面積凈截面毛截面鋼筋換算面積換算截面面積截面慣性矩毛截面扣除管道面積忽略凈截面毛截面鋼筋換算面積忽略換算截面面積五、 主梁驗(yàn)算（1） 承載能力極限狀態(tài)驗(yàn)算本橋?yàn)楦咚俟分行】鐝綐?，設(shè)計(jì)安全等級為Ⅰ級。需要驗(yàn)算的截面有：邊跨L/4截面、邊跨L/2截面、邊跨右支點(diǎn)截面、中跨L/4截面、中跨L/2截面、中跨右支點(diǎn)截面。 根據(jù)布筋情況，預(yù)應(yīng)力筋的重心距受拉區(qū)邊緣的距離： 截面有效高度: 檢查是否符合下面條件： ；；； ；；； ，故混凝土受壓區(qū)高度按下式計(jì)算： 所以，該構(gòu)件混凝土受壓區(qū)高度符合要求。邊跨其余控制截面承載能力極限狀態(tài)驗(yàn)算見表51。根據(jù)公式進(jìn)行截面抗剪強(qiáng)度上、下限復(fù)核，即 公式中參數(shù)含義詳見《公預(yù)規(guī)》 計(jì)算結(jié)果表明，截面尺寸滿足要求。（二）正常使用極限狀態(tài)驗(yàn)算公路橋涵的持久狀況應(yīng)按正常使用極限狀態(tài)的要求，對構(gòu)件進(jìn)行抗裂性的驗(yàn)算。本設(shè)計(jì)對正彎矩比較大的邊跨跨中截面、中跨跨中截面；負(fù)彎矩比較大的邊跨右支點(diǎn)截面、中跨右支點(diǎn)截面進(jìn)行抗裂驗(yàn)算。其余截面驗(yàn)算見表53。其它控制截面的斜截面抗裂性也符合此檢算公式，故在此不一一列出。計(jì)算是作用（或荷載）取其標(biāo)準(zhǔn)值，汽車荷載應(yīng)考慮沖擊系數(shù)。以邊跨1/4截面為例進(jìn)行正截面混凝土壓應(yīng)力驗(yàn)算計(jì)算由作用（或荷載）標(biāo)準(zhǔn)值產(chǎn)生的混凝土法向壓應(yīng)力：一期恒載+二期恒載+移動(dòng)荷載+沉降組合+溫度荷載= 計(jì)算由預(yù)加力產(chǎn)生的混凝土法向拉應(yīng)力： 受壓區(qū)混凝土的最大壓應(yīng)力為：+==＜==（滿足要求）其余截面驗(yàn)算見表54，表55表54 邊跨控制截面正截面混凝土壓應(yīng)力驗(yàn)算表格單位邊跨1/2截面邊跨3/4截面邊跨右支點(diǎn)截面是否符合要求是是是表54 邊跨控制截面正截面混凝土壓應(yīng)力驗(yàn)算表格單位中跨1/4截面中跨1/2截面中跨3/4截面中跨支點(diǎn)截面是否滿足是是是是2. 預(yù)應(yīng)力鋼筋的拉應(yīng)力驗(yàn)算使用階段預(yù)應(yīng)力混凝土受彎構(gòu)件預(yù)應(yīng)力鋼筋的拉應(yīng)力應(yīng)符合下列規(guī)定：其中 = == =1860此處為換算截面重心軸到受拉區(qū)邊緣的距離，應(yīng)為最外層鋼筋中心處的混凝土拉應(yīng)力。以邊跨1/4截面為例進(jìn)行檢算。表57 邊跨控制截面混凝土主壓應(yīng)力驗(yàn)算邊跨跨中截面邊跨3/4截面邊跨支點(diǎn)截面上梗腋處是否滿足是是是下梗腋處894580501790是否滿足是是是表58 邊跨控制截面混凝土主壓應(yīng)力驗(yàn)算中跨1/4截面中跨跨中截面中跨3/4截面中跨支點(diǎn)截面上梗腋處是否滿足是是是是下梗腋處是否滿足是是是是（4） 可變荷載作用下主梁撓度驗(yàn)算 本設(shè)計(jì)用midas civil 2010 軟件建立的有限元模型中，可變荷載引起的撓度變化如表59所示。受彎構(gòu)件在使用階段的撓度應(yīng)該考慮荷載長期效應(yīng)的影響，乘以撓度長期增大系數(shù)。小結(jié)經(jīng)過三個(gè)多月對橋梁的完整設(shè)計(jì)，我對橋梁設(shè)計(jì)有了進(jìn)一步的理解和深化。整個(gè)設(shè)計(jì)過程中，我都以橋梁課本、橋梁規(guī)范為依據(jù)，并結(jié)合專業(yè)基礎(chǔ)課中有關(guān)原理和計(jì)算方法。從設(shè)計(jì)結(jié)果來看，該橋基本符合實(shí)際工程。 致謝歷時(shí)將近兩個(gè)月的時(shí)間終于將這個(gè)設(shè)計(jì)做完，在設(shè)計(jì)過程中遇到了無數(shù)的困難和障礙，都在老師和同學(xué)的幫助下度過了。另外，在本設(shè)計(jì)的檢算部分，得到了林麗霞老師精心的指導(dǎo)，在此致以真誠的感謝。感謝我的同學(xué)和朋友，在畢業(yè)設(shè)計(jì)過程中相互探討有爭議的步驟，還在設(shè)計(jì)的撰寫和排版過程中提供熱情的幫助。同時(shí)，還幫助我們改變一些處理事情時(shí)懶散的習(xí)慣。在設(shè)計(jì)過程中，我的動(dòng)手能力和資料搜集能力也得到了提升。掌握其使用的要領(lǐng)，運(yùn)用到設(shè)計(jì)當(dāng)中去。 畢業(yè)設(shè)計(jì)結(jié)束了，通過設(shè)計(jì)，我深刻領(lǐng)會(huì)到學(xué)習(xí)的重要性，畢業(yè)設(shè)計(jì)不僅僅能幫助我們檢驗(yàn)大學(xué)四年的學(xué)習(xí)成果，更多的是可以幫助我們更加清楚的認(rèn)識(shí)自我，磨練我們的意志與耐性，這會(huì)為日后的工作和生活帶來很大的幫助。s structural design process, such tendencies: more intensity considered in the design and durability consider less attention intensity limit to the use of state without limit state, and throughout the life cycle of the most important when it is precisely the use of performance。 does not conform to the structure dynamic and prehensive economy requirements.Bridge safety, durability, the main reason for poor 1) Construction and management of low level More bridges at home and abroad destruction and the sudden collapse of the bridge has been engineering more concerned about security issues. The general view is that the current project is barbaric incident management and construction caused by corruption. For the short term, such as the destruction and collapse of a sudden, mostly because of construction quality did not meet specifications and design requirements, typical problems include inadequate and construction materials intensity of failure。 some concrete strength grade too low to protect slice through small diameter steel micromanage , a thin crosssection ponents of these structures have weakened the durability, it would seriously affect the safety of the structure. Many bridges, although the design specifications meet the requirements of the strength of only 5 to 10 years because of the durability of the problems affecting structural safety. Structural Durability shortage has bee one of the most realistic security issues, from design to construction and materials, such as angle of measures to strengthen the durability of the structure.Of the environment and the use of different conditions, different design of the structural system will target different aspects of the layout and structure requirements. Norms can not cover in detail the design staff should solve the various problems in the updated norms faster can also adapt to new understanding, new technologies, new materials, rapid development of the structure of the new requirements. Therefore, reasonable and reliable addition to the structures is designed to meet the requirements of norms, and to design a structure to the correct understanding of nature, rich experience and accurate judgments.And the need to improve efforts in the direction 1) Should pay more attention to the durability of structural problemsBridge in the construction and use of the process, will be subject to environmental, and the erosion of harmful chemical substances, and to bear vehicles, wind, earthquake, fatigue, overloading, human factors, such as external role, and bridge materials used by the selfdegradation of performance will continue , resulting in the structure of the different degrees of damage and deterioration. In the field of longspan bridges, and from the country since the 1980s, the construction of a large number of cablestayed bridge, although so far there collapse or serious damage to the few examples, but has more bridges because of the durability of cable to the problem advance for cable, and this not only affects the use of increased economic losses.Needs to be pointed out is that many of these problems and did not conduct a reasonable durability of the design, which has also prompted renewed awareness of durability of the bridge.