環(huán)境和荷載共同作用下鋼筋混凝土橋梁疲勞性能研究
發(fā)布時間：2018-09-07 20:07
【摘要】：疲勞作為結(jié)構(gòu)脆性破壞的重要誘因已在工程領(lǐng)域引起重視,隨著交通流量和密度的攀升,混凝土橋梁的疲勞問題也逐漸顯現(xiàn),環(huán)境侵蝕因素的影響進一步加劇了橋梁結(jié)構(gòu)的疲勞劣化。因此,開展環(huán)境和荷載共同作用下鋼筋混凝土橋梁疲勞性能研究具有積極的現(xiàn)實意義。本研究在對實際橋梁疲勞荷載和應(yīng)力狀態(tài)進行研究計算的基礎(chǔ)上,有針對性地開展了設(shè)計荷載和調(diào)查荷載兩種應(yīng)力水平下鋼筋混凝土梁的疲勞試驗;進一步考慮環(huán)境因素影響,進行了設(shè)計荷載應(yīng)力水平下的銹蝕鋼筋混凝土梁疲勞試驗;對比分析了應(yīng)力水平和環(huán)境因素對混凝土梁疲勞極限循環(huán)次數(shù)和應(yīng)變演變的影響規(guī)律;提出了環(huán)境和荷載共同作用下的鋼筋混凝土梁截面疲勞應(yīng)力理論計算方法,并運用Matlab軟件編制了計算程序。方法中考慮了疲勞和環(huán)境因素作用引起的混凝土和鋼筋材料的損傷;通過條帶法體現(xiàn)了構(gòu)件層面的疲勞應(yīng)力計算方法與材料層面的區(qū)別,并反映了鋼筋與混凝土共同工作以及鋼筋混凝土受彎構(gòu)件中應(yīng)變的分布特征;通過銹蝕鋼筋與混凝土之間的應(yīng)變協(xié)調(diào)關(guān)系考慮了鋼筋與混凝土之間粘結(jié)性能退化的影響;引入疲勞和銹蝕引起的損傷對混凝土對本構(gòu)關(guān)系、鋼筋有效受力面積的影響,通過粘結(jié)單元的粘結(jié)力-滑移曲線考慮銹蝕引起的粘結(jié)力的退化,在ANSYS軟件平臺上實現(xiàn)了環(huán)境和荷載共同作用下鋼筋混凝土梁疲勞性能的有限元模擬,進一步揭示了應(yīng)力水平和銹蝕兩種因素對鋼筋混凝土梁疲勞性能的影響規(guī)律;最后,在總結(jié)已有試驗和理論研究成果的基礎(chǔ)上,對環(huán)境和荷載共同作用下的鋼筋混凝土橋梁疲勞壽命進行了初步評估。本研究形成的主要結(jié)論如下:通過中小跨徑鋼筋混凝土橋梁的疲勞應(yīng)力驗算,實際橋梁在現(xiàn)行公路橋梁設(shè)計規(guī)范設(shè)計荷載應(yīng)力水平下滿足規(guī)范要求,在實際調(diào)查荷載作用下已不滿足規(guī)范要求;普通鋼筋混凝土梁構(gòu)件層面的疲勞損傷機理與材料層面的機理存在差別,鋼筋混凝土受彎構(gòu)件的疲勞損傷可以分為兩個階段,疲勞壽命的前期(約占整個壽命的10%)主要受壓區(qū)混凝土的疲勞損傷控制,而疲勞引起的縱向鋼筋的損傷(表現(xiàn)為鋼筋有效受力面積的減小)主導(dǎo)并控制著構(gòu)件的整個疲勞過程;應(yīng)力水平的提高加速了構(gòu)件的疲勞損傷和劣化,應(yīng)力水平提高后,疲勞壽命大幅下降,但疲勞破壞前構(gòu)件的劣化程度相當。當應(yīng)力幅由設(shè)計荷載提高20%至調(diào)查荷載應(yīng)力水平時,試驗梁極限循環(huán)次數(shù)下降了31.2%~44.6%,疲勞破壞前構(gòu)件中鋼筋應(yīng)力的增長率由12.08%上升至12.3%;當應(yīng)力幅提高70%時,試驗梁縱向鋼筋的應(yīng)力增幅提高至15.5%,極限循環(huán)次數(shù)下降超過66%;銹蝕也大幅降低了梁的疲勞壽命,并加劇了梁體的劣化,但銹蝕對疲勞的影響起始于疲勞初始狀態(tài),不同銹蝕率下構(gòu)件的損傷速率相同。在試驗采用相同的設(shè)計荷載應(yīng)力水平下,銹蝕率約5%的鋼筋混凝土梁疲勞壽命較未銹蝕梁下降34.9%以上,疲勞破壞前其縱向鋼筋和混凝土應(yīng)變增長率與同應(yīng)力水平下未銹蝕梁相當;通過匯總本研究和同類試驗研究結(jié)果,得出設(shè)計荷載應(yīng)力水平下的未銹蝕梁和縱筋銹蝕率5%的銹蝕梁不存在疲勞破壞的風(fēng)險,調(diào)查荷載應(yīng)力水平下的未銹蝕梁運營后期存在發(fā)生疲勞破壞的風(fēng)險;如同時兩種因素的影響,我國混凝土設(shè)計規(guī)范中給定的應(yīng)力幅限值在實際荷載作用和銹蝕條件下已不能滿足實際橋梁的要求。
[Abstract]:Fatigue, as an important inducement of brittle failure of structures, has attracted much attention in the engineering field. With the increase of traffic flow and density, fatigue problems of concrete bridges gradually appear. The fatigue deterioration of bridge structures is further aggravated by the influence of environmental erosion factors. Based on the research and calculation of fatigue load and stress state of actual bridge, the fatigue test of reinforced concrete beams under design load and investigation load is carried out, and the design load stress water is carried out considering the influence of environmental factors. The fatigue test of corroded reinforced concrete beams under flat condition is carried out. The influence of stress level and environmental factors on the fatigue limit cycles and strain evolution of concrete beams is compared and analyzed. In this method, the damage of concrete and steel bar caused by fatigue and environmental factors is considered, the difference between the fatigue stress calculation method and material layer is reflected by strip method, and the joint work of steel bar and concrete and the distribution characteristics of strain in reinforced concrete flexural members are reflected. The strain compatibility relationship between concrete and reinforcement takes into account the deterioration of bond strength between reinforcement and concrete; the influence of damage caused by fatigue and corrosion on the constitutive relationship of concrete and the effective bearing area of reinforcement is introduced; the degradation of bond strength caused by corrosion is considered by the bond force-slip curve of bond element, and the degradation of bond strength caused by corrosion is considered in ANSYS software platform. The finite element simulation of the fatigue behavior of reinforced concrete beams under the combined action of environment and load is realized, and the influence law of stress level and corrosion on the fatigue behavior of reinforced concrete beams is further revealed. Finally, on the basis of summarizing the existing experimental and theoretical research results, the reinforced concrete beams under the combined action of environment and load are mixed. The main conclusions of this study are as follows: through the fatigue stress checking calculation of small and medium span reinforced concrete bridges, the actual bridge meets the requirements of the code under the design load stress level of the current highway bridge design code, and under the actual investigation load, it does not meet the requirements of the code; The fatigue damage mechanism of reinforced concrete beams is different from that of materials. The fatigue damage of reinforced concrete flexural members can be divided into two stages. The early stage of fatigue life (about 10% of the total life) is mainly controlled by the fatigue damage of concrete in the compressive zone, while the longitudinal damage of steel caused by fatigue (represented by steel). The increase of stress level accelerates the fatigue damage and deterioration of the components. After the increase of stress level, the fatigue life decreases greatly, but the deterioration degree of the components before the fatigue failure is comparable. When the stress amplitude increases from 20% of the design load to the stress level of the investigated load, The ultimate cycling times of the test beams decreased by 31.2%~44.6%, and the increase rate of steel stress in the members before fatigue failure increased from 12.08% to 12.3%; when the stress amplitude increased by 70%, the increase of longitudinal steel stress in the test beams increased to 15.5%, and the limit cycling times decreased by more than 66%; corrosion also greatly reduced the fatigue life of the beams and aggravated the deterioration of the beams. The fatigue life of reinforced concrete beams with corrosion rate of about 5% is 34.9% lower than that of non-corroded beams under the same design load stress level. The strain growth rate of longitudinal reinforcement and concrete before fatigue failure is higher than that of non-corroded beams. By summarizing the results of this study and similar tests, it is concluded that there is no risk of fatigue failure for the corroded beams with 5% corrosion rate of longitudinal bars and uncorroded beams at the same stress level, and the risk of fatigue failure for the corroded beams at the later stage of operation under the load stress level is investigated. Under the influence of various factors, the limit value of stress given in the code for concrete design in China can not meet the requirements of actual bridges under the actual load and corrosion conditions.
【學(xué)位授予單位】：交通運輸部公路科學(xué)研究院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U441.4
本文編號：2229287
[Abstract]:Fatigue, as an important inducement of brittle failure of structures, has attracted much attention in the engineering field. With the increase of traffic flow and density, fatigue problems of concrete bridges gradually appear. The fatigue deterioration of bridge structures is further aggravated by the influence of environmental erosion factors. Based on the research and calculation of fatigue load and stress state of actual bridge, the fatigue test of reinforced concrete beams under design load and investigation load is carried out, and the design load stress water is carried out considering the influence of environmental factors. The fatigue test of corroded reinforced concrete beams under flat condition is carried out. The influence of stress level and environmental factors on the fatigue limit cycles and strain evolution of concrete beams is compared and analyzed. In this method, the damage of concrete and steel bar caused by fatigue and environmental factors is considered, the difference between the fatigue stress calculation method and material layer is reflected by strip method, and the joint work of steel bar and concrete and the distribution characteristics of strain in reinforced concrete flexural members are reflected. The strain compatibility relationship between concrete and reinforcement takes into account the deterioration of bond strength between reinforcement and concrete; the influence of damage caused by fatigue and corrosion on the constitutive relationship of concrete and the effective bearing area of reinforcement is introduced; the degradation of bond strength caused by corrosion is considered by the bond force-slip curve of bond element, and the degradation of bond strength caused by corrosion is considered in ANSYS software platform. The finite element simulation of the fatigue behavior of reinforced concrete beams under the combined action of environment and load is realized, and the influence law of stress level and corrosion on the fatigue behavior of reinforced concrete beams is further revealed. Finally, on the basis of summarizing the existing experimental and theoretical research results, the reinforced concrete beams under the combined action of environment and load are mixed. The main conclusions of this study are as follows: through the fatigue stress checking calculation of small and medium span reinforced concrete bridges, the actual bridge meets the requirements of the code under the design load stress level of the current highway bridge design code, and under the actual investigation load, it does not meet the requirements of the code; The fatigue damage mechanism of reinforced concrete beams is different from that of materials. The fatigue damage of reinforced concrete flexural members can be divided into two stages. The early stage of fatigue life (about 10% of the total life) is mainly controlled by the fatigue damage of concrete in the compressive zone, while the longitudinal damage of steel caused by fatigue (represented by steel). The increase of stress level accelerates the fatigue damage and deterioration of the components. After the increase of stress level, the fatigue life decreases greatly, but the deterioration degree of the components before the fatigue failure is comparable. When the stress amplitude increases from 20% of the design load to the stress level of the investigated load, The ultimate cycling times of the test beams decreased by 31.2%~44.6%, and the increase rate of steel stress in the members before fatigue failure increased from 12.08% to 12.3%; when the stress amplitude increased by 70%, the increase of longitudinal steel stress in the test beams increased to 15.5%, and the limit cycling times decreased by more than 66%; corrosion also greatly reduced the fatigue life of the beams and aggravated the deterioration of the beams. The fatigue life of reinforced concrete beams with corrosion rate of about 5% is 34.9% lower than that of non-corroded beams under the same design load stress level. The strain growth rate of longitudinal reinforcement and concrete before fatigue failure is higher than that of non-corroded beams. By summarizing the results of this study and similar tests, it is concluded that there is no risk of fatigue failure for the corroded beams with 5% corrosion rate of longitudinal bars and uncorroded beams at the same stress level, and the risk of fatigue failure for the corroded beams at the later stage of operation under the load stress level is investigated. Under the influence of various factors, the limit value of stress given in the code for concrete design in China can not meet the requirements of actual bridges under the actual load and corrosion conditions.
【學(xué)位授予單位】：交通運輸部公路科學(xué)研究院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U441.4
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