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  本文關鍵詞： FRP約束混凝土 本構關系 受壓斷裂能 斷裂 粘聚區(qū)模型 剝離　出處：《大連理工大學》2014年博士論文　論文類型：學位論文

【摘要】：在鋼筋混凝土結構的服役過程中,由于年限、周圍環(huán)境影響等原因,其結構性能出現退化。主要的表現有承載能力與剛度的降低、延性降低。另外一方面,隨著對結構安全等級認識的提高,一些按照原有規(guī)范設計的結構物已經不能適應新規(guī)范的要求。此外,結構使用用途的改變也有可能造成既有結構不能滿足使用要求。這些問題導致結構需要進行拆除重建或者加固改造。由于纖維增強復合材料具有輕質高強、耐腐蝕等優(yōu)點,近年來大量應用于加固工程結構的各種構件尤其是梁、柱。各國研究人員對FRP加固結構的性能進行了大量的實驗與理論研究,取得諸多成果。本文在前人研究的基礎上,重點對FRP約束混凝土的本構關系以及FRP加固混凝土梁的斷裂及FRP混凝土界面剝離過程進行了分析。得到了以下結果： (1)修正了Lam和Teng基于設計的應力-應變關系。首先通過Jefferson的混凝土破壞面方程推導了FRP約束混凝土的強度預測模型。該模型直接僅需混凝土單軸抗壓強度以及FRP拉斷應變；推導了基于損傷的應變公式。在強度與應變預測模型的基礎上,提出了修正的Lam和Teng應力-應變模型。與搜集的試驗數據比較表明,對于強度模型,本文模型與Rousakis和Karabinis模型、Wu和Zhou模型與試驗數據吻合最好；對于應變模型,本文模型、Wu等模型與Teng等模型與試驗數據吻合最好。進一步比較表明,本文提出的修正的Lam和Teng模型能夠很好地表達結構的整體行為。本模型可用于實際構件截面的應力分析。 (2)在Suzuki等以及Teng等工作的基礎上,基于受壓斷裂能的概念,提出了一種確定基于分析FRP約束混凝土應力-應變關系的數值方法。與試驗結果比較表明,該方法與試驗結果整體吻合良好。另外,分別對強約束小破壞應變、弱約束小破壞應變、弱約束大破壞應變三種情況研究了試件長度對FRP約束混凝土應力-應變關系的影響。分析結果表明,對于強約束類型FRP約束混凝土,其應力-應變關系不需要考慮試件長度的影響；對于弱約束類型FRP約束混凝土,其應力-應變關系必須考慮試件長度的影響。 (3)提出了一種斷裂力學方法來模擬FRP加固梁的斷裂與FRP-混凝土界面剝離過程。該方法采用虛擬裂縫模型模擬混凝土的斷裂過程,采用粘聚區(qū)模型模擬FRP混凝土界面的剝離,采用應力強度因子疊加原理與權函數方法建立了整體控制方程與裂縫口張開位移協(xié)調方程。通過本課題組的試驗數據驗證了本方法的有效性。另外,還對影響梁承載能力的各個因素進行了詳細的研究。研究結果表明,初始縫高比、梁高、混凝土強度等級對FRP加固混凝土梁的第一峰值荷載影響較大,FRP的厚度與高度對FRP加固混凝土梁的第二峰值荷載影響較大。研究還表明,相對于FRP厚度,FRP的寬度對FRP加固混凝土的承載能力影響更大。
[Abstract]:During the service of reinforced concrete structures, the performance of reinforced concrete structures is degraded due to the years of service and the influence of the surrounding environment. The main performance is the reduction of bearing capacity and stiffness, and the decrease of ductility. On the other hand, With the improvement of the level of structural safety, some structures designed according to the original code can no longer meet the requirements of the new code. The change in the use of the structure may also cause the existing structure to fail to meet the operational requirements. These problems lead to the need for demolition, reconstruction or reinforcement of the structure. Because fiber reinforced composites have the advantages of light weight, high strength, corrosion resistance, etc. In recent years, a large number of members, especially beams and columns, have been used in strengthening engineering structures. Many experimental and theoretical studies have been carried out on the performance of FRP reinforced structures by researchers from all over the world, and many achievements have been obtained. The constitutive relation of FRP confined concrete, the fracture of concrete beam strengthened by FRP and the process of FRP concrete interface exfoliation are analyzed in detail. The following results are obtained:. (1) the stress-strain relationship of Lam and Teng based on design is modified. Firstly, the strength prediction model of FRP confined concrete is derived by using the concrete failure surface equation of Jefferson. The model requires only uniaxial compressive strength of concrete and FRP tensile strain directly. The strain formula based on damage is derived. On the basis of strength and strain prediction model, the modified Lam and Teng stress-strain models are proposed. The model agrees well with the experimental data of Rousakis and Karabinis models Wu and Zhou models, and the model Wu et al., Teng model and experimental data of strain model are in good agreement with the experimental data. The further comparison shows that the proposed model is in good agreement with the experimental data. The modified Lam and Teng models proposed in this paper can well express the global behavior of the structure. This model can be used for the stress analysis of the actual member section. 2) based on the work of Suzuki et al and Teng, and based on the concept of compressive fracture energy, a numerical method for determining the stress-strain relationship of concrete confined by FRP is proposed. The method is in good agreement with the experimental results. The influence of specimen length on the stress-strain relationship of FRP confined concrete is studied in three cases of weak constraint and large failure strain. The results show that for FRP confined concrete with strong confinement, The stress-strain relationship does not need to consider the influence of specimen length, but for weakly constrained type FRP confined concrete, the influence of specimen length must be taken into account in the stress-strain relationship. In this paper, a fracture mechanics method is proposed to simulate the delamination process between the fracture and the interface of FRP strengthened beams. The virtual crack model is used to simulate the fracture process of concrete, and the cohesive zone model is used to simulate the exfoliation of the interface of FRP concrete. The stress intensity factor superposition principle and the weight function method are used to establish the integral control equation and the crack opening displacement coordination equation. The validity of the method is verified by the experimental data of our group. The factors that affect the bearing capacity of beams are also studied in detail. The results show that the initial joint height ratio, the beam height, The influence of concrete strength grade on the first peak load of FRP reinforced concrete beam is greater than that of the thickness and height of FRP-strengthened concrete beam. The study also shows that the thickness and height of FRP-strengthened concrete beam have great influence on the second peak load of concrete beam strengthened by FRP. Compared with the thickness of FRP, the width of FRP has more influence on the bearing capacity of concrete strengthened by FRP.
【學位授予單位】：大連理工大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TU37

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