摘 要
本畢業(yè)設(shè)計主要是關(guān)于大跨度預(yù)應(yīng)力混凝土連續(xù)梁橋上部結(jié)構(gòu)的設(shè)計。預(yù)應(yīng)力混凝土連續(xù)梁橋以結(jié)構(gòu)受力性能好、變形小、伸縮縫少、行車平順舒適、養(yǎng)護(hù)工程量小、抗震能力強等而成為最富有競爭力的主要橋型之一。受時間和個人能力的限制，本次畢業(yè)設(shè)計沒有具體涉及到下部結(jié)構(gòu)、橫向預(yù)應(yīng)力及豎向預(yù)應(yīng)力的設(shè)計。
設(shè)計橋梁跨度為62m+104m+104m+62m,分為兩幅設(shè)計，單幅為單箱單室，橋面總寬25m，雙向4車道，上下行。主梁施工采用懸臂掛籃施工，對稱平衡澆筑混凝土。施工分為21個階段：第一階段：施工臨時支座并固結(jié)，澆筑墩頂0#段及邊跨直線段滿堂支架施工；第二階段至第十七階段：懸臂對稱平衡澆筑混凝土至最大懸臂端；第十八階段：邊跨合攏；第十九階段：中跨合攏,拆除掛籃設(shè)施，加載二期恒載；第二十施工階段：預(yù)留施工階段；第二十一階段：運營階段。本橋設(shè)5個支座，其中第3個支座為固定鉸接支座，其余均為活動鉸接支座。本設(shè)計中總共有9個臨時支座。
設(shè)計過程如下：
首先，確定主梁主要構(gòu)造及細(xì)部尺寸，它必須與橋梁的規(guī)定和施工保持一致，考慮到抗彎剛度及抗扭剛度的影響，設(shè)計采用箱形梁。主梁的高度呈二次拋物線變化，因為二次拋物線近似于連續(xù)梁橋彎距的變化曲線。墩頂截面通過腹板、底板的加厚以及設(shè)置橫隔梁強度得以加強，底板厚度呈二次拋物線變化，底板厚度為0.7變?yōu)?.3。腹板厚度呈直線變化，由0.75變?yōu)?.4。頂板厚度沿全橋保持不變,均為0.28m。
其次，利用BSAS電算軟件分析內(nèi)力結(jié)構(gòu)總的內(nèi)力(包括恒載和活載的內(nèi)力計算)。用于計算的內(nèi)力組合結(jié)果也由BSAS電算軟件計算而得，從而估算出縱向預(yù)應(yīng)力筋的數(shù)目，然后再布置預(yù)應(yīng)力鋼絲束。
再次，計算預(yù)應(yīng)力損失及次內(nèi)力，次內(nèi)力包括先期恒載徐變次內(nèi)力、先期預(yù)應(yīng)力徐變次內(nèi)力、后期合攏預(yù)應(yīng)力索產(chǎn)生的彈性次內(nèi)力、局部溫度變化次內(nèi)力。
然后進(jìn)一步進(jìn)行截面強度的驗算，其中包括承載能力極限狀態(tài)和正常使用極限狀態(tài)。在正常使用極限狀態(tài)驗算中包括計算截面的混凝土法向應(yīng)力驗算、預(yù)應(yīng)力鋼筋中的拉應(yīng)力驗算、截面的主應(yīng)力計算。

關(guān)鍵詞： 預(yù)應(yīng)力混凝土連續(xù)梁橋、次內(nèi)力、懸臂施工

Abstract
The graduate design is mainly about the design of superstructure of long-span pre-stressed concrete continuous box Girder Bridge . Pre-stressed concrete continuous Girder Bridge become one of main bridge types of the most full of competion ability because of subjecting to the dint function with the structure good, having the small defomation,few of control joint,going smoothly comfort,protected the amout of engineering small and having the powerfully ability of earthquake proof and so on. For time and ability limited, the design of the substructure, transverse pre-stressing and vertical pre-stressing is not considered.
The spans of the bridge are 62m+104m+104m+66m,main beam is respective designed, each suit has one box one room and four traffic ways of all, the width of the bridge surface is 25m.
The major girder applies cantilever hung-basket bearing, symmetric equilibrium construction .There are twenty-one steps in the working. The 0# member is worked in the first step , then form the second step to the seventeenth the other members is worked before they are jointed except the ones are siuated in the beside or middle of span and the substructure is worked in the steps; and then it’s jointed in the site of beside spans in the eighteenth step; and then mid-span is jointed in ninteenth step; and remove the hung-basket bearing then the second dead loads is in effect in the step; the tweentith stage: vacant construction stage; in the last step, the structure is running. There are five bearings, the third is fixed bearing, the left four are expansion bearings. In the design there are nine casual bearing.
The procedure of the design is listed below:
The first step as to dimension the structural elements and details of which it is composed, it can’t and certainly should without being fully coordinated with the planning and working phrases of the project. Considering the distorting stiffness and the bending stiffness, box birder goes as second-parabolic curve, for second-parabolic curve is generally similar to the change of continuous bridge’s bending moments along. The sectionat the support is strengthened by the provision of thickened webs , bottom slabs and a cross beam , the thickness of the bottom slab is changed in second-parabolic curve and the thickness of the web is changed in linearity, the former varies from 0.7m to 0.3m, the latter varies from 0.75m to 0.4m, the top slab’s thickness is 0.28m.
The second step is to use BSAS software to analyze internal gross force of the structures(including dead load and lived load), the internal force composition can be done by using the compute results. According to the internal force composited, the eva luated amount of longitudinal tendons can be worked out, then we can distribute the tendons to the bridge.
The third steps is to calculate the loss of pre-stressing and secondary force due to pre-stressing, first dead loads and temperature, bearing displacement, and so on.
The last steps is checking the main cross section. the work includes the load-caring capacity ultimate state and the normal service ability ultimate state as well as the main section’s being out of shape.

Key Words: Pre-stressed concrete c..