本文選題：纖維混凝土梁 + 正截面抗彎承載力�。� 參考：《東北大學》2014年碩士論文

【摘要】：在混凝土基材中摻入纖維有利于提高混凝土結構的抗彎承載力、抗變形和抗裂能力。然而,隨服役時間延長,纖維混凝土梁會因混凝土碳化、鋼筋銹蝕和裂縫開展等原因,導致材料性能衰減,使得構件在服役過程中可能存在安全隱患,甚至尚未達到設計基準期就喪失正常使用功能。因此,有必要對纖維混凝土梁的時變可靠性進行分析。目前,關于混凝土梁時變可靠性研究大都集中于普通混凝土,由于纖維的加入使得構件內(nèi)部組分的復合效應更為復雜,理論分析難度更大,故該領域研究仍處于比較匱乏的階段。論文在混凝土結構可靠度理論的基礎上,將結構抗力視為隨機過程,考慮混凝土強度、截面有效尺寸、纖維增強系數(shù)及構件承載力等影響因素,推導了纖維混凝土梁正截面抗彎承載力和基于撓度控制的可靠性分析模型,并利用一次二階矩法進行實例計算,從強度和剛度兩個方面求取了纖維混凝土梁抗彎可靠性的可靠指標和隨機變量靈敏度。其次,基于混凝土材料強度、鋼筋截面面積、鋼筋和混凝土之間粘結系數(shù)、纖維增強系數(shù)以及計算模式不定性系數(shù)等多因素影響機制,引入鋼纖維影響系數(shù),推導了鋼筋鋼纖維混凝土梁正截面抗彎承載力、基于裂縫寬度控制和撓度控制的時變可靠性分析模型。以10年持續(xù)荷載作用下鋼筋鋼纖維混凝土梁抗彎試驗為基礎,討論了各隨機變量的時變規(guī)律,將等效抗力法和一次二階矩法相結合,求取了鋼筋鋼纖維混凝土梁的時變可靠指標和時變靈敏度。從鋼筋鋼纖維梁正截面抗彎承載力時變可靠性分析可知,鋼纖維的最佳摻量與相關研究成果吻合；外荷載越小,可靠指標越大,抗彎承載力越大；在服役初期,可靠指標先上升后下降。從基于裂縫寬度和撓度控制的可靠性分析可知,鋼纖維摻量越高,可靠指標越大,抗變形和裂縫的能力越強,與試驗結果吻合；外荷載越小,可靠指標越大,抗變形和裂縫的能力越明顯；在服役初期可靠指標下降明顯,隨服役時間延長,可靠指標下降趨于平緩,與試驗數(shù)據(jù)吻合。纖維混凝土梁抗彎性能可靠性分析可用于計算整體結構的失效概率和進行動態(tài)可靠性研究,為纖維混凝土抗裂性能及彎曲韌性的提高提供理論依據(jù)；同時對結構損傷維修、加固有一定的參考價值,為充分發(fā)揮材料潛能以及開發(fā)及應用提供理論支持。
[Abstract]:The addition of fiber in concrete substrates can improve the flexural bearing capacity, deformation resistance and crack resistance of concrete structures. However, with the extension of service time, fiber reinforced concrete beams may be damaged by carbonation of concrete, corrosion of steel bars and crack development, which may lead to the attenuation of material properties, which may lead to hidden dangers of safety in the service process. Loss of normal function even before the design benchmark period has been reached. Therefore, it is necessary to analyze the time-varying reliability of fiber reinforced concrete beams. At present, most of the researches on time-varying reliability of concrete beams are focused on ordinary concrete. Due to the addition of fiber, the composite effect of internal components is more complex, and the theoretical analysis is more difficult. Therefore, the research in this field is still in a relatively scarce stage. Based on the reliability theory of concrete structure, the structural resistance is regarded as a random process, and the influence factors such as the strength of concrete, the effective size of section, the fiber reinforcement coefficient and the bearing capacity of members are considered. The flexural bearing capacity of normal section of fiber reinforced concrete beam and the reliability analysis model based on deflection control are derived. The reliability index of flexural reliability of fiber reinforced concrete beams and the sensitivity of random variables are obtained from the aspects of strength and stiffness. Secondly, based on the influence mechanism of concrete material strength, section area of steel bar, bond coefficient between reinforcement and concrete, fiber reinforcement coefficient and uncertainty coefficient of calculation mode, the influence coefficient of steel fiber is introduced. A time-varying reliability analysis model based on crack width control and deflection control is derived for the flexural bearing capacity of steel fiber reinforced concrete beams. Based on the flexural tests of steel fiber reinforced concrete beams subjected to 10 years of continuous load, the time-varying laws of each random variable are discussed, and the equivalent resistance method and the first-order second moment method are combined. The time-varying reliability index and time-varying sensitivity of reinforced steel fiber reinforced concrete beams are obtained. From the time-varying reliability analysis of flexural bearing capacity of steel fiber beam, it can be seen that the optimum content of steel fiber is in agreement with relevant research results; the smaller the external load, the greater the reliability index, the greater the flexural bearing capacity; at the beginning of service, Reliable indicators rise first and then decrease. From the reliability analysis based on crack width and deflection control, it can be seen that the higher the content of steel fiber, the greater the reliability index, the stronger the ability of resisting deformation and crack, and the smaller the external load, the greater the reliability index. The ability of resisting deformation and crack is more obvious, and the reliability index decreases obviously at the beginning of service. With the extension of service time, the decrease of reliability index tends to be gentle, which coincides with the test data. The reliability analysis of flexural behavior of fiber reinforced concrete beams can be used to calculate the failure probability of the whole structure and to study the dynamic reliability, which can provide the theoretical basis for improving the crack resistance and flexural toughness of fiber reinforced concrete. Reinforcement has certain reference value and provides theoretical support for exerting the potential of materials and developing and applying.
【學位授予單位】：東北大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU37
，

本文編號：1878258