【正文】 ing to the dint function with the structure good, having the small defomation, few of control joint,going smoothly fort,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 prestressing and vertical prestressing is not considered. The spans of the bridge are 26+246+26m,main beam is respective designed, each suit has one box two room and three traffic ways, the width of the bridge surface is 14m. The major girder applies Full scaffold construction , symmetric equilibrium construction . The procedure of the design is listed below: The first step as to dimension the structural elements and details of which it is posed, 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 secondparabolic curve, for secondparabolic curve is generally similar to the change of continuous bridge’s bending moments along. The section at the support is strengthened by the provision of thickened webs , bottom slabs and a cross beam , the thickness of the bottom slab and the top slab is . 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 position can be done by using the pute results. According to the internal force posited, the evaluated 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 prestressing and secondary force due to prestressing, first dead loads and temperature, bearing displacement, and so on. The last steps is checking the main cross section. the work includes the loadcaring capacity ultimate state and the normal service ability ultimate state as well as the main section’s being out of shape. In addition , the torsion of box girder, wind loads, seismic loads and the dynamic 西南交通大學(xué)本科畢業(yè)設(shè)計 （論文） 第Ⅸ 頁 properties aren’t taken into account during the design. Key Words: grade separated Prestressed concrete continuous girder bridge Secondary force Full scaffold construction 目 錄 第 1 章 緒論 ........................................................... 1 .......................................... 1 畢業(yè)設(shè)計的目的與意義 ............................................. 3 第 2 章 橋跨總體布置及結(jié)構(gòu)尺寸擬定 ...................................... 4 尺寸擬定 ......................................................... 4 橋孔分跨 ...................................................... 4 截面形式 ...................................................... 4 梁高 .......................................................... 5 細(xì)部尺寸 ...................................................... 6 主梁分段與施工階段的劃分 ......................................... 7 分段原則 ...................................................... 7 具體分段 ...................................................... 7 主梁施工方法及注意事項 ........................................ 8 第 3 章 荷載內(nèi)力計算 .................................................. 10 恒載內(nèi)力計算 .................................................... 10 活載內(nèi)力計算 .................................................... 12 橫向分布系數(shù)的考慮 ........................................... 12 活載因子的計算 ............................................... 15 計算結(jié)果 ..................................................... 17 第 4 章 預(yù)應(yīng)力鋼束的估算與布置 ........................................ 18 力筋估算 ........................................................ 18 計算原理 ..................................................... 18 預(yù)應(yīng)力鋼束的估算 ............................................. 21 預(yù)應(yīng)力鋼束的布置 ................................................ 26 第 5 章 預(yù)應(yīng)力損失及有效應(yīng)力的計算 ..................................... 26 預(yù)應(yīng)力損失的計算 ................................................ 27 摩阻損失 ..................................................... 27 . 錨具變形損失 ................................................ 28 . 混凝土的彈性壓縮 ............................................ 31 ................................................. 34 ................................................. 35 有效預(yù)應(yīng)力的計算 ................................................ 39 第 6 章 次內(nèi)力的計算 ................................................... 40 徐變次內(nèi)力的計算 ................................................ 40 預(yù)加力引起的二次力矩 ............................................ 40 溫度次內(nèi)力的計算 ................................................ 42 支座位移引起的次內(nèi)力 ............................................ 44 第 7 章 內(nèi)力組合 ....................................................... 45 承載能力極限狀態(tài)下的效應(yīng)組合 .................................... 45 正常使用極限狀態(tài)下的效應(yīng)組合 .................................... 48 第 8 章 主梁截面驗算 .................................................. 52 截面強度驗算 .................................................... 55 截面應(yīng)力驗算 .................................................... 57 正截面和斜截面抗裂驗算 ....................................... 57 法向拉應(yīng)力 .................................... 錯誤 !未定義書簽。本章簡介其發(fā)展： 由于普通鋼筋混凝土結(jié)構(gòu)存在不少缺點：如過早地出現(xiàn)裂縫，使其不能有效地采用高強度材料，結(jié)構(gòu)自重必然大，從而使其跨越能力差，并且使得材料利用率低。這樣就可以抵消外荷載作用下混凝土產(chǎn)生的拉應(yīng)力。 預(yù)應(yīng)力混凝土橋梁是在二戰(zhàn)前后發(fā)展起來的，當(dāng)時西歐很多國家在戰(zhàn)后缺鋼的情況下，為節(jié)省鋼材，各國開始競相采用預(yù)應(yīng)力結(jié)構(gòu)代替部分的鋼結(jié)構(gòu)以盡快修復(fù)戰(zhàn)爭帶來的創(chuàng)傷。雖然跨徑太大時并不總是用預(yù)應(yīng)力結(jié)構(gòu)比其它結(jié)構(gòu)好，但是，在實際工程中，跨徑小于 400 米時，預(yù)應(yīng)力混凝土橋梁常常為優(yōu)勝方案?，F(xiàn)在，我國已經(jīng)有了簡支梁、帶鉸或帶掛梁的 T構(gòu)、連續(xù)梁、桁架拱、桁架梁和斜拉橋等預(yù)應(yīng)力混凝土結(jié)構(gòu)體系。但是，在橋梁結(jié)構(gòu)中，隨著預(yù)應(yīng)力理論的不斷成熟和實踐的不斷發(fā)展，預(yù)應(yīng)力混凝土橋梁結(jié)構(gòu)的運用必將越來越廣泛。雖然連續(xù)梁有很多優(yōu)點，但是剛開始它并不是預(yù)應(yīng)力結(jié)構(gòu)體系中的佼佼者，因為限于當(dāng)時施工主要采用滿堂支架法，采用連續(xù)梁費工費時。 60 年代初期在中等跨預(yù)應(yīng)力混凝土連續(xù)梁中，應(yīng)用了逐跨架設(shè)法與頂推法；在較大跨連續(xù)梁中，則應(yīng)用更完善的懸臂施工方法，這就使連續(xù)梁方案重新獲得了競爭力，并逐步在 40—200 米范圍 西南交通大學(xué)本科畢業(yè)設(shè)計（論文） 第 2 頁 內(nèi)占主要地位。目前，連續(xù)梁結(jié)構(gòu)體系已經(jīng)成為預(yù)應(yīng)力混凝土橋梁的主要橋型之一。因此有人將兩種結(jié)構(gòu)結(jié)合起來，形成一種連續(xù) —剛構(gòu)體系。