本文關(guān)鍵詞： 長(zhǎng)期下?lián)?收縮徐變 RPC-NC復(fù)合截面 內(nèi)力重分布　出處：《湖南大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：大跨PC剛構(gòu)橋長(zhǎng)期下?lián)系膯?wèn)題十分突出,同時(shí)它與開裂形成惡性循環(huán),對(duì)結(jié)構(gòu)的運(yùn)營(yíng)安全和耐久性構(gòu)成很大威脅。受壓混凝土收縮徐變是大跨剛構(gòu)橋長(zhǎng)期下?lián)系淖钪饕?鑒于RPC(活性粉末混凝土)經(jīng)熱養(yǎng)護(hù)后強(qiáng)度高、收縮極小、徐變系數(shù)小的特點(diǎn),提出在負(fù)彎矩區(qū)箱梁底板、跨中箱梁頂板中加入預(yù)制RPC柱形成局部RPC-NC(普通混凝土)復(fù)合截面的方案來(lái)控制剛構(gòu)橋長(zhǎng)期下?lián)�。本文首先通過(guò)試驗(yàn)、理論、有限元分析探究了RPC-NC復(fù)合截面柱的應(yīng)力重分布現(xiàn)象及其對(duì)復(fù)合截面柱后期變形的降低作用,同時(shí)分析了剪力鍵的受力性能,進(jìn)而得到了復(fù)合截面RPC的合理面積比例。在此研究基礎(chǔ)上設(shè)計(jì)了全橋加入RPC柱的布置方案,建立了全普通混凝土、加預(yù)制RPC柱剛構(gòu)橋全橋有限元模型并進(jìn)行對(duì)比分析。主要結(jié)論如下:(1)通過(guò)試驗(yàn)、理論、有限元分析知,由于RPC和C50混凝土在收縮徐變性質(zhì)上的巨大差異復(fù)合截面將發(fā)生內(nèi)力重分布的現(xiàn)象,C50應(yīng)力隨時(shí)間將逐漸減小,復(fù)合截面柱的后期變形、名義徐變系數(shù)也會(huì)隨之減小;RPC的徐變系數(shù)可以取為CEB-FIP(1990)模式下同條件C50混凝土的15%進(jìn)行分析計(jì)算;布置剪力鍵鋼筋橫截面積為復(fù)合柱橫截面積的4%時(shí),剪力鍵布置安全、有效;實(shí)橋應(yīng)用中,布置RPC面積為復(fù)合截面總面積的40%比較合理、有效;(2)通過(guò)全橋有限元模型應(yīng)力、變形、預(yù)應(yīng)力損失的對(duì)比分析知,相對(duì)于全普通混凝土剛構(gòu)橋,加入預(yù)制RPC柱的剛構(gòu)橋十年收縮徐變所引起的豎向位移降低了54.5%,跨中長(zhǎng)期下?lián)系玫矫黠@改善;中跨跨中梁底普通混凝土、0號(hào)塊梁頂普通混凝土壓應(yīng)力略有增加,0號(hào)塊梁底普通混凝土、中跨跨中梁頂普通混凝土壓應(yīng)力減小,中跨應(yīng)力分布更加均勻;中跨底板后期束、負(fù)彎矩區(qū)頂板束由成橋后十年收縮徐變引起的預(yù)應(yīng)力損失沒(méi)有明顯變化;(3)加入預(yù)制RPC柱后,剛構(gòu)橋跨中長(zhǎng)期持續(xù)下?lián)蠝p小的主要原因是:剛構(gòu)橋負(fù)彎矩區(qū)箱梁底板、跨中附近箱梁頂板形成了局部的RPC-NC復(fù)合截面,局部復(fù)合截面發(fā)生應(yīng)力重分布導(dǎo)致普通混凝土壓應(yīng)力減小、后期名義徐變應(yīng)變減小,進(jìn)而減小了剛構(gòu)橋負(fù)彎矩區(qū)的結(jié)構(gòu)轉(zhuǎn)角、跨中附近的豎向位移;(4)通過(guò)參數(shù)分析建議在負(fù)彎矩區(qū)0~8號(hào)塊的箱梁底板,24~26號(hào)塊、跨中合攏段的箱梁頂板布置預(yù)制RPC柱。綜上可知加入適當(dāng)比例的預(yù)制RPC柱,可使剛構(gòu)橋成橋后的長(zhǎng)期下?lián)辖档?0%左右,明顯改善剛構(gòu)橋的長(zhǎng)期下?lián)蠁?wèn)題,對(duì)于實(shí)際工程有一定的參考價(jià)值。
[Abstract]:The problem of long term deflection of long span PC rigid frame bridge is very prominent. At the same time, it forms a vicious circle with cracking, which poses a great threat to the operation safety and durability of the structure. The shrinkage and creep of compressed concrete is the main cause of long term deflection of long span rigid frame bridge. In view of the high strength, minimal shrinkage and low creep coefficient of RPC (reactive Powder concrete) after thermal curing, the bottom plate of box girder in negative bending moment region is put forward. The method of forming local RPC-NC (ordinary concrete) composite section by adding prefabricated RPC columns to the roof of span box girder is used to control the long-term deflection of rigid frame bridge. The stress redistribution phenomenon of RPC-NC composite section column and its effect on reducing the late deformation of composite section column are studied by finite element analysis, and the mechanical properties of the shear bond are analyzed at the same time. Then the reasonable area ratio of composite section RPC is obtained. On the basis of this research, the layout scheme of adding RPC column to the whole bridge is designed, and the whole ordinary concrete is established. The finite element model of the whole bridge with prefabricated RPC column rigid frame bridge is compared and analyzed. The main conclusions are as follows: (1) through experiment, theory and finite element analysis, Due to the great difference between the shrinkage and creep properties of RPC and C50 concrete, the internal force redistribution will occur in the composite section. The C50 stress will gradually decrease with time, and the post-deformation of the composite cross-section column will occur. The creep coefficient of RPCs can be taken as 15% of C50 concrete under the same condition under CEB-FIP1990) mode, and the shear bond arrangement is safe and effective when the cross section area of shear key steel bar is 4 of the cross section area of composite column. In the application of real bridge, it is reasonable to arrange RPC area to be 40% of the total area of composite section. (2) through the comparative analysis of the stress, deformation and prestress loss of the finite element model of the whole bridge, it is found that compared with the full ordinary concrete rigid frame bridge, The vertical displacement caused by 10 years shrinkage and creep of rigid frame bridge with prefabricated RPC column is reduced by 54.5 and the mid- and long-term deflection of span is improved obviously. The compressive stress of ordinary concrete at the top of No. 0 block beam increases slightly, the compressive stress of ordinary concrete at the top of middle span beam decreases and the stress distribution of middle span is more uniform. There is no obvious change of prestress loss caused by shrinkage and creep of roof beam in negative moment region after 10 years of bridge completion. (3) after adding prefabricated RPC column, the main reason of long-lasting deflection reduction of rigid frame bridge span is: the bottom plate of box girder in negative moment zone of rigid frame bridge, The local RPC-NC composite section is formed in the roof of the box girder near the middle span. The stress redistribution of the local composite section results in the reduction of compressive stress of ordinary concrete and the decrease of nominal creep strain in the later stage, thus reducing the structural rotation angle of the negative moment zone of the rigid frame bridge. Through parameter analysis, it is suggested that prefabricated RPC columns should be arranged on the bottom plate of box girder in block 0 ~ 8 of negative bending moment, and on the roof of box girder in the closing section of span. In summary, the appropriate proportion of prefabricated RPC columns should be added. The long-term deflection of rigid frame bridge can be reduced by 50% or so, and the long-term deflection problem of rigid frame bridge can be improved obviously, which has certain reference value for practical engineering.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：U441;U448.23

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