本文選題：混凝土 + 徐變模型��； 參考：《哈爾濱工業(yè)大學(xué)》2016年博士論文

【摘要】：混凝土徐變是指在荷載持續(xù)作用下,混凝土變形隨持荷時(shí)間延長(zhǎng)而增大的現(xiàn)象。徐變不但影響混凝土結(jié)構(gòu)構(gòu)件的正常使用性能,而且高應(yīng)力徐變會(huì)影響混凝土結(jié)構(gòu)構(gòu)件的承載能力�，F(xiàn)有混凝土受壓徐變模型適用范圍偏窄,無(wú)法預(yù)估高強(qiáng)混凝土試件徐變和高應(yīng)力構(gòu)件徐變;尚未建立考慮徐變影響的混凝土受壓應(yīng)力-應(yīng)變?nèi)�(xiàn)方程,無(wú)法考慮徐變對(duì)混凝土試件峰值壓應(yīng)變的影響;缺乏對(duì)混凝土徐變卸載瞬時(shí)應(yīng)變恢復(fù)和滯后應(yīng)變恢復(fù)規(guī)律的認(rèn)識(shí),無(wú)法準(zhǔn)確分析軸壓柱持荷過(guò)程中截面應(yīng)力重分布及受壓鋼筋對(duì)柱徐變的影響�；谏鲜隹紤]開(kāi)展研究工作,完成了齡期28d時(shí)軸心抗壓強(qiáng)度20.9MPa~40.9MPa、應(yīng)力水平0.154~0.725、加載齡期30d~512d、持荷時(shí)間39d~589d的188個(gè)混凝土受壓試件徐變?cè)囼?yàn)及徐變后的受壓破壞試驗(yàn)�；谠囼�(yàn)數(shù)據(jù),完善了混凝土徐變模型,探索了卸載后徐變?cè)嚰?yīng)變恢復(fù)規(guī)律,建立了考慮徐變影響的混凝土受壓應(yīng)力-應(yīng)變?nèi)�(xiàn)方程。具體分述如下:(1)基于國(guó)內(nèi)外徐變?cè)囼?yàn)數(shù)據(jù),分別建立了混凝土立方體抗壓強(qiáng)度、加載齡期、環(huán)境溫度、環(huán)境相對(duì)濕度、構(gòu)件理論厚度對(duì)徐變的影響系數(shù)公式。應(yīng)用上述公式,將54個(gè)混凝土試件的線(xiàn)性徐變?cè)囼?yàn)數(shù)據(jù)轉(zhuǎn)化為齡期28d時(shí)標(biāo)準(zhǔn)立方體抗壓強(qiáng)度30MPa、加載齡期28d、環(huán)境溫度20℃、環(huán)境相對(duì)濕度60%、構(gòu)件理論厚度50mm這一基準(zhǔn)條件下的徐變?cè)囼?yàn)數(shù)據(jù),繼而提出基準(zhǔn)條件下的線(xiàn)性徐變計(jì)算模型。將0.35作為線(xiàn)性徐變和非線(xiàn)性徐變分界點(diǎn),將0.76作為收斂型非線(xiàn)性徐變和發(fā)散性非線(xiàn)性徐變的分界點(diǎn)。對(duì)應(yīng)力水平介于0.35~0.76的非線(xiàn)性徐變,基于134個(gè)混凝土試件的非線(xiàn)性徐變?cè)囼?yàn)數(shù)據(jù),提出隨應(yīng)力水平提高呈指數(shù)函數(shù)增大的非線(xiàn)性徐變?cè)龃笙禂?shù)計(jì)算公式。從而擴(kuò)大了所建立徐變模型的適用范圍,可實(shí)現(xiàn)混凝土標(biāo)準(zhǔn)立方體抗壓強(qiáng)度15MPa~180MPa、徐變加載齡期1d~3650d、環(huán)境溫度-20℃~80℃、環(huán)境相對(duì)濕度3%~100%、理論厚度20mm~270mm、應(yīng)力水平0~0.76混凝土試件徐變的分析與計(jì)算。(2)基于114個(gè)試件徐變后卸載試驗(yàn)數(shù)據(jù),發(fā)現(xiàn)當(dāng)混凝土強(qiáng)度一定時(shí),瞬時(shí)應(yīng)變恢復(fù)系數(shù)(瞬時(shí)應(yīng)變恢復(fù)與徐變加載瞬時(shí)應(yīng)變的比值)隨應(yīng)力水平的增大而減小,滯后應(yīng)變恢復(fù)穩(wěn)定時(shí)間隨應(yīng)力水平的增大而延長(zhǎng),滯后應(yīng)變恢復(fù)與卸載前發(fā)生的徐變應(yīng)變呈正比,滯后應(yīng)變恢復(fù)隨時(shí)間的推移而減緩。建立了瞬時(shí)應(yīng)變恢復(fù)和滯后應(yīng)變恢復(fù)的相關(guān)計(jì)算公式,并將其用于考察軸壓柱在持荷過(guò)程中截面應(yīng)力重分布及受壓鋼筋對(duì)柱徐變的影響。(3)基于188個(gè)混凝土試件徐變后受壓破壞試驗(yàn)數(shù)據(jù),提出了混凝土試件經(jīng)歷徐變后繼續(xù)加載至受壓破壞四階段應(yīng)力-應(yīng)變?nèi)�(xiàn)方程和經(jīng)歷徐變后卸載至零再加載至受壓破壞六階段應(yīng)力-應(yīng)變?nèi)�(xiàn)方程。經(jīng)歷不同應(yīng)力水平徐變的試件受壓破壞時(shí)峰值應(yīng)力處對(duì)應(yīng)的總應(yīng)變約在2400×10-6~4500×10-6之間,相對(duì)于同批次同齡期參比用試件短期加載峰值壓應(yīng)變提高20%~120%。建立了合理考慮徐變影響的混凝土試件峰值壓應(yīng)變的計(jì)算公式,為合理應(yīng)用高強(qiáng)熱軋鋼筋作為受壓鋼筋提供了參考依據(jù)。
[Abstract]:Concrete creep is the phenomenon that the deformation of concrete increases with the prolonged loading time under the continuous load of the concrete. The creep not only affects the normal performance of the concrete structural members, but also the high stress and creep will affect the bearing capacity of the concrete structural members. The existing concrete compression and creep model has narrow application range and can not predict the high strength. The creep of concrete specimens and the creep of high stress components have not been established, and the effect of creep on the compressive stress-strain curves of concrete has not been established, and the effect of creep on the peak compressive strain of concrete specimens can not be considered, and the lack of understanding of the instantaneous strain recovery and the hysteresis strain recovery of concrete creep and unloading can not accurately analyze the holding of axial compression columns. The stress redistribution of the section and the influence of the reinforced bar on the creep of the column in the process of loading. Based on the above consideration, the axial compression strength 20.9MPa~40.9MPa, the stress level 0.154~0.725, the loading age 0.154~0.725, the loading age 30d~512d, the 188 concrete compression test of the loading time 39d~589d and the compression failure test after the creep are completed. Based on the test data, the concrete creep model is perfected, the strain recovery law of the creep specimens after unloading is explored, and the stress strain full curve equation of concrete under the influence of creep is established. The detailed description is as follows: (1) based on the data of the creep test at home and abroad, the concrete cube compressive strength, loading age and environment are established respectively. The formula of the influence coefficient of temperature, relative humidity and theoretical thickness of component to creep is used to convert the linear creep test data of 54 concrete specimens into standard cube compressive strength 30MPa for age 28d, loading age 28d, ambient temperature 20, ambient humidity 60%, and component theoretical thickness 50mm. According to the creep test data, the linear creep calculation model under the reference condition is put forward. 0.35 is used as the boundary of the linear creep and the nonlinear creep, and 0.76 is the demarcation point of the nonlinear creep and the divergent nonlinear creep of the convergent type. The nonlinear creep of the force level is between the 0.35~0.76 and the nonlinear creep of the 134 concrete specimens. By changing the test data, the formula of the nonlinear creep enlargement coefficient which increases with the increase of the stress level is proposed. Thus the application range of the creep model is expanded, and the compressive strength of the concrete standard cube is 15MPa~180MPa, the age of creep loading is 1d~3650d, the ambient temperature is -20 C ~80 C, and the environmental relative humidity is 3%~100%, On the analysis and calculation of the creep of the thickness 20mm~270mm and the stress level 0~0.76 concrete specimens. (2) based on the data of the unloading test after the creep of the 114 specimens, it is found that the instantaneous strain recovery coefficient (the ratio of instantaneous strain recovery to the instantaneous strain of the creep) decreases with the increase of the stress level when the concrete strength is fixed, and the lag strain is restored to stability. Time is prolonged with the increase of stress level, and the hysteresis strain recovery is proportional to the creep strain before unloading, and the hysteresis strain recovery slows with the passage of time. The correlation calculation formula of the instantaneous strain recovery and the hysteresis strain recovery is established, and is used to investigate the stress redistribution and the compression steel of the axial compression column during the loading process. The influence of the reinforcement on the creep of the column. (3) based on the creep test data of 188 concrete specimens after creep, the full curve equation of the stress-strain curve and the six stage of the stress strain of the concrete specimen after the creep are continued to be loaded to the four stage of the compression failure and the stress strain curve equation after the creep after the creep to zero reloading to the compression failure. The total strain corresponding to the peak stress is about 2400 x 10-6~4500 x 10-6 when the stress level creep is subjected to the compression failure, and the calculation formula for the peak pressure stress of the concrete specimen with the influence of the creep is set up for the reasonable application of the high strength hot rolling for the reasonable application of the calculation formula of the peak pressure stress of the concrete specimen with the influence of the creep. The reinforcement provides a reference for the reinforced bar.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TU528
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本文編號(hào)：1928038