發(fā)布時間：2018-06-28 22:37

  本文選題：混凝土 + 率效應(yīng)　； 參考：《武漢理工大學》2013年博士論文

【摘要】：混凝土結(jié)構(gòu)的強度、剛度和延性會受到加載速率的變化而產(chǎn)生顯著影響,因而混凝土率效應(yīng)特性和破壞機理也成為抗震安全評價中的關(guān)鍵性因素之一。本文在大量試驗基礎(chǔ)上對混凝土材料的率效應(yīng)及其發(fā)生機理進行了系統(tǒng)的研究。利用三軸儀對混凝土在水飽和狀態(tài)、有加載歷史和雙向受壓狀態(tài)下進行了動態(tài)抗壓試驗,對CT圖像進行了破壞機理分析,累計完成247個試件的加載試驗,共獲取168組有效數(shù)據(jù)。主要研究內(nèi)容如下： 第一,研究了水環(huán)境對混凝土率效應(yīng)特性的影響。對大氣自然濕度狀態(tài)下的混凝土和水飽和混凝土在10-5/S、5×10-5/s、10-4/S、5×10-4/S應(yīng)變速率下進行單軸抗壓試驗與4MPa、8MPa兩種圍壓下的常三軸抗壓試驗,分析了在不同應(yīng)變速率、不同圍壓下大氣自然濕度狀態(tài)和水飽和狀態(tài)下的混凝土強度、變形特性及彈性模量等物理力學參數(shù)及性能的變化特性,并就水介質(zhì)對混凝土率效應(yīng)特性的影響程度與規(guī)律給出了明確結(jié)論,建立了三軸強度率效應(yīng)經(jīng)驗公式。 第二,研究了不同荷載類型與加載歷史對混凝土率效應(yīng)特性的影響。對預(yù)靜載歷史和預(yù)循環(huán)加載歷史的混凝土試件在同應(yīng)變速率下進行單軸抗壓試驗,對比分析在不同預(yù)靜載加載歷史、預(yù)循環(huán)加載歷史和應(yīng)變速率下混凝土的峰值應(yīng)力、峰值應(yīng)變以及彈性模量等的變化規(guī)律。在高應(yīng)變速率(10-3/s)作用下,加載歷史對混凝土強度的影響作用減弱,當預(yù)靜態(tài)加載歷史幅值為60%的極限抗壓強度時彈性模量達到最大值。在低應(yīng)變速率(10-5/S)作用下,循環(huán)加載歷史對混凝土強度的劣化更加明顯。 第三,研究了單雙向應(yīng)力狀態(tài)下混凝土的率效應(yīng)特性。對大尺度混凝土試件進行了10-5/S、10-4/S和10-3/s應(yīng)變速率下單軸壓縮試驗和在一向側(cè)應(yīng)力為0MPa、8.3MPa、5.6MPa、8.3MPa下的雙軸壓縮試驗,對比并分析了混凝土的單軸受壓和混凝土在不同側(cè)應(yīng)力下強度、變形特性以及彈性模量等力學性能,對其變化規(guī)律給出明確結(jié)論。 第四,基于CT圖像分析了混凝土的破壞機理。通過CT實時對混凝土試件橫斷面在不同加載階段進行了11次掃描和第9、10、11次加載進行了從外向里的切面掃描,分析了混凝土的破壞機理。對水飽和混凝土動態(tài)損傷與破壞形態(tài)從細觀層面給出了清晰的描述,對其損傷與破壞機理給出了明確的解釋。
[Abstract]:The strength, stiffness and ductility of concrete structures will be significantly affected by the change of loading rate. Therefore, the concrete rate effect characteristics and failure mechanism have become one of the key factors in seismic safety evaluation. Based on a large number of experiments, this paper systematically studies the rate effect of concrete material and its occurrence mechanism. The dynamic compression tests of concrete under water saturation, loading history and biaxial compression were carried out by using a triaxial apparatus. The failure mechanism of CT images was analyzed. The loading tests of 247 specimens were completed, and 168 effective data were obtained. The main contents are as follows: first, the effect of water environment on concrete rate effect is studied. Uniaxial compression tests and constant triaxial compression tests of concrete and water-saturated concrete under natural atmospheric humidity at 10 ~ (-5) / S ~ (-5) 脳 10 ~ (-5) / s ~ (-5) 脳 10 ~ (-4) S strain rate and 4 MPA ~ (8 MPA) confining pressure were carried out, and different strain rates were analyzed. Physical and mechanical parameters such as strength, deformation and elastic modulus of concrete under different confining pressures under natural humidity and water saturation, The influence degree and law of water medium on concrete rate effect characteristics are given, and the empirical formula of triaxial strength rate effect is established. Secondly, the influence of different load types and loading history on concrete rate effect is studied. Uniaxial compression tests of concrete specimens with prestatic loading history and precyclic loading history were carried out at the same strain rate. The peak stresses of concrete under different prestatic loading histories, precyclic loading histories and strain rates were compared and analyzed. The variation of peak strain and elastic modulus. Under the action of high strain rate (10 ~ (-3) / s), the effect of loading history on the strength of concrete is weakened, and the modulus of elasticity reaches the maximum when the historical amplitude of prestatic loading is 60% of the ultimate compressive strength. Under the action of low strain rate (10 ~ (-5) / S), the degradation of concrete strength by cyclic loading history is more obvious. Thirdly, the rate effect characteristics of concrete under single and two-way stress are studied. The axial compression tests of 10 ~ 5 / S 10 ~ (-4) / S and 10 ~ (-3) / s strain rate for large scale concrete specimens were carried out, and the uniaxial compression tests of concrete under uniaxial compression and the strength of concrete under different lateral stresses were compared and analyzed. The deformation characteristics and elastic modulus of mechanical properties are discussed. Fourthly, the failure mechanism of concrete is analyzed based on CT images. The concrete cross-section was scanned by CT in real time at different loading stages, and the concrete failure mechanism was analyzed. The dynamic damage and failure form of water-saturated concrete is described clearly from the meso level, and its damage and failure mechanism is explained clearly.
【學位授予單位】：武漢理工大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TU528

【引證文獻】

相關(guān)期刊論文 前1條

1 鄒三兵;彭剛;胡偉華;;考慮圍壓的混凝土損傷特性試驗研究[J];水電能源科學;2014年11期

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本文編號：2079636