干濕環(huán)境下混凝土收縮與收縮應(yīng)力研究
發(fā)布時間：2018-09-12 15:43
【摘要】：干濕循環(huán)是導(dǎo)致混凝土結(jié)構(gòu)性能衰退最為嚴(yán)酷的環(huán)境條件之一。本文旨在研究干濕循環(huán)下混凝土收縮和收縮應(yīng)力的變化規(guī)律，建立相應(yīng)的計算方法。重點(diǎn)對干濕循環(huán)下混凝土收縮發(fā)展、混凝土內(nèi)部濕度場分布規(guī)律、混凝土抗拉徐變和典型混凝土結(jié)構(gòu)的收縮應(yīng)力等問題進(jìn)行了研究。 對3個強(qiáng)度等級混凝土（C30，C50，C80—分別代表普通強(qiáng)度、中等強(qiáng)度和高強(qiáng)混凝土），干濕循環(huán)下收縮和內(nèi)部相對濕度的發(fā)展進(jìn)行了同步試驗測量，試驗驗證了混凝土干縮濕脹的特性。干濕環(huán)境下混凝土收縮的發(fā)展與其內(nèi)部相對濕度發(fā)展具有很好的同步性，混凝土內(nèi)部相對濕度變化是其收縮變化的驅(qū)動力。建立了基于混凝土內(nèi)部濕度變化的收縮預(yù)測模型，模型結(jié)果能夠很好的預(yù)測干濕循環(huán)下混凝土收縮的發(fā)展。 建立了干濕循環(huán)下混凝土內(nèi)部濕度場的計算模型，并對模型所需參數(shù)：水泥水化耗水引起的濕度下降、干燥和濕潤階段混凝土水分?jǐn)U散系數(shù)和混凝土表面水分交換系數(shù)進(jìn)行了確定。采用大尺寸混凝土試件，對干濕循環(huán)下混凝土內(nèi)部不同位置處的相對濕度發(fā)展進(jìn)行了試驗測量。基于試驗測定結(jié)果，對干濕循環(huán)下混凝土內(nèi)部濕度場計算模型及相關(guān)模型參數(shù)進(jìn)行了驗證，模型結(jié)果和試驗結(jié)果吻合良好。 改進(jìn)了傳統(tǒng)環(huán)約束試驗方法，試驗測量了從混凝土澆筑開始鋼環(huán)內(nèi)表面環(huán)向應(yīng)變的發(fā)展，研究了混凝土強(qiáng)度等級，鋼環(huán)厚度和測量位置對試驗結(jié)果的影響。建立了基于環(huán)約束試驗的混凝土抗拉徐變系數(shù)的求解方法，依據(jù)環(huán)約束試驗結(jié)果，對3個強(qiáng)度等級混凝土的抗拉徐變系數(shù)進(jìn)行了確定。 基于彈性力學(xué)原理，建立了干濕循環(huán)下混凝土圓柱收縮應(yīng)力的計算模型，模型計算結(jié)果與有限單元法計算的結(jié)果吻合良好。對干濕循環(huán)制度、環(huán)境相對濕度、環(huán)境風(fēng)速和構(gòu)件尺寸等影響混凝土收縮應(yīng)力的因素進(jìn)行了分析；通過對收縮應(yīng)變的分解，，建立了干濕循環(huán)下混凝土路面板收縮應(yīng)力的計算模型，并對模型算法進(jìn)行了討論。模型計算結(jié)果與有限單元法計算的結(jié)果吻合良好。對混凝土強(qiáng)度等級、路面板長度等影響混凝土路面板收縮應(yīng)力的因素進(jìn)行了分析。
[Abstract]:Dry and wet cycle is one of the most severe environmental conditions that lead to the deterioration of concrete structure performance. The purpose of this paper is to study the change law of shrinkage and shrinkage stress of concrete under dry and wet circulation and to establish corresponding calculation method. The shrinkage and development of concrete under dry-wet cycle, the distribution law of moisture field in concrete, the tensile creep of concrete and the shrinkage stress of typical concrete structure are studied in this paper. The development of shrinkage and internal relative humidity of three strength grade concrete (C _ (30) C _ (50) C _ (80) on behalf of ordinary strength, medium strength and high strength concrete) under dry and wet cycles were measured simultaneously, and the characteristics of dry shrinkage and moisture expansion of concrete were verified by experiments. The development of concrete shrinkage in dry and wet environment has a good synchronism with the development of internal relative humidity. The change of relative humidity in concrete is the driving force of shrinkage change. A shrinkage prediction model based on the change of moisture in concrete is established. The results of the model can well predict the shrinkage development of concrete under dry-wet cycle. The calculation model of moisture field in concrete under dry and wet circulation is established, and the required parameters of the model are: the decrease of moisture caused by water consumption of cement hydration. The moisture diffusion coefficient of concrete and the moisture exchange coefficient of concrete surface were determined in drying and wetting stages. The development of relative humidity at different positions of concrete under dry and wet circulation was measured by using large size concrete specimens. Based on the experimental results, the calculation model of internal moisture field of concrete under dry-wet cycle and the related model parameters are verified. The results of the model agree well with the experimental results. The traditional ring confinement test method was improved to measure the development of the circumferential strain on the inner surface of the steel ring from the beginning of concrete pouring. The influence of the strength grade of concrete, the thickness of steel ring and the measuring position on the test results was studied. A method for solving the tensile creep coefficient of concrete based on ring confinement test is established. Based on the results of ring confinement test, the tensile creep coefficient of three strength grade concrete is determined. Based on the principle of elasticity, a model for calculating the shrinkage stress of concrete columns under dry and wet cycles is established. The results of the model are in good agreement with the results obtained by the finite element method (FEM). The factors influencing concrete shrinkage stress, such as dry-wet cycle system, environmental relative humidity, environmental wind speed and component size, are analyzed. The calculation model of shrinkage stress of concrete pavement slab under dry-wet cycle is established, and the algorithm of the model is discussed. The results of the model are in good agreement with that of the finite element method. The factors influencing the shrinkage stress of concrete slab such as concrete strength grade and pavement slab length are analyzed.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：TU528
本文編號：2239484
[Abstract]:Dry and wet cycle is one of the most severe environmental conditions that lead to the deterioration of concrete structure performance. The purpose of this paper is to study the change law of shrinkage and shrinkage stress of concrete under dry and wet circulation and to establish corresponding calculation method. The shrinkage and development of concrete under dry-wet cycle, the distribution law of moisture field in concrete, the tensile creep of concrete and the shrinkage stress of typical concrete structure are studied in this paper. The development of shrinkage and internal relative humidity of three strength grade concrete (C _ (30) C _ (50) C _ (80) on behalf of ordinary strength, medium strength and high strength concrete) under dry and wet cycles were measured simultaneously, and the characteristics of dry shrinkage and moisture expansion of concrete were verified by experiments. The development of concrete shrinkage in dry and wet environment has a good synchronism with the development of internal relative humidity. The change of relative humidity in concrete is the driving force of shrinkage change. A shrinkage prediction model based on the change of moisture in concrete is established. The results of the model can well predict the shrinkage development of concrete under dry-wet cycle. The calculation model of moisture field in concrete under dry and wet circulation is established, and the required parameters of the model are: the decrease of moisture caused by water consumption of cement hydration. The moisture diffusion coefficient of concrete and the moisture exchange coefficient of concrete surface were determined in drying and wetting stages. The development of relative humidity at different positions of concrete under dry and wet circulation was measured by using large size concrete specimens. Based on the experimental results, the calculation model of internal moisture field of concrete under dry-wet cycle and the related model parameters are verified. The results of the model agree well with the experimental results. The traditional ring confinement test method was improved to measure the development of the circumferential strain on the inner surface of the steel ring from the beginning of concrete pouring. The influence of the strength grade of concrete, the thickness of steel ring and the measuring position on the test results was studied. A method for solving the tensile creep coefficient of concrete based on ring confinement test is established. Based on the results of ring confinement test, the tensile creep coefficient of three strength grade concrete is determined. Based on the principle of elasticity, a model for calculating the shrinkage stress of concrete columns under dry and wet cycles is established. The results of the model are in good agreement with the results obtained by the finite element method (FEM). The factors influencing concrete shrinkage stress, such as dry-wet cycle system, environmental relative humidity, environmental wind speed and component size, are analyzed. The calculation model of shrinkage stress of concrete pavement slab under dry-wet cycle is established, and the algorithm of the model is discussed. The results of the model are in good agreement with that of the finite element method. The factors influencing the shrinkage stress of concrete slab such as concrete strength grade and pavement slab length are analyzed.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：TU528
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