【摘要】：鋼結(jié)構(gòu)在工程界的廣泛應(yīng)用使得鋼結(jié)構(gòu)的修復(fù)加固成為一項(xiàng)經(jīng)常性的工作，由于FRP加固技術(shù)的高強(qiáng)高效、良好的耐疲勞性能以及適應(yīng)性強(qiáng)等特點(diǎn)使得FRP加固鋼結(jié)構(gòu)技術(shù)應(yīng)用越來越普遍。另一方面，由于表面裂紋是鋼結(jié)構(gòu)中重要缺陷之一，而且表面裂紋的擴(kuò)展對(duì)鋼結(jié)構(gòu)的運(yùn)營存在安全隱患，因此，對(duì)FRP加固鋼結(jié)構(gòu)中表面裂紋的疲勞擴(kuò)展行為進(jìn)行研究具有重大的科學(xué)意義和工程應(yīng)用價(jià)值。 本文以采用本課題組發(fā)明的碳纖維薄板（Carbon Fiber Laminate，簡稱CFL）加固含表面裂紋的鋼板為研究對(duì)象，探討了CFL加固鋼板中表面裂紋的應(yīng)力強(qiáng)度因子計(jì)算方法及其疲勞擴(kuò)展規(guī)律。本文的主要研究內(nèi)容及結(jié)論如下： 1）對(duì)疲勞裂紋擴(kuò)展理論及應(yīng)力強(qiáng)度因子的有限元算法進(jìn)行分析，提出了將J積分與特殊單元相結(jié)合的有限元計(jì)算方法，以解決裂紋尖端的奇異性問題。 2）利用有限元軟件ABAQUS，建立了三點(diǎn)彎曲載荷下含表面裂紋鋼板的三維計(jì)算模型。通過將表面裂紋應(yīng)力強(qiáng)度因子的有限元計(jì)算結(jié)果與Newman-Raju公式計(jì)算值的比較，探討了裂紋前緣第一層單元的邊長L與裂紋深度a之比L/a、圍繞裂紋前緣的單元層數(shù)D、每層單元?jiǎng)澐址輸?shù)E以及沿裂紋前緣方向劃分份數(shù)S等對(duì)有限元計(jì)算結(jié)果的影響，給出了最優(yōu)有限元參數(shù)值，從而確立了表面裂紋前緣應(yīng)力強(qiáng)度因子的計(jì)算方法。 3）探討了裂紋形狀比a/c、相對(duì)長度c/W和CFL厚度tC對(duì)加固效果（應(yīng)力強(qiáng)度因子KI下降率，ROD）的影響。研究結(jié)果表明，θ=0°處ROD隨a/c或c/W增長而增加；θ=90°處ROD隨著a/c增長先迅速減小后趨于穩(wěn)定，但隨著c/W增長先減小后迅速增長；CFL加固效果隨著CFL厚度增加而增加，但是這種增長趨勢(shì)在tC≤0.4mm前較明顯，超過該厚度后ROD增長逐漸趨于平緩。 4）成功地將“Beach-mark”法應(yīng)用于三維表面疲勞裂紋的擴(kuò)展實(shí)驗(yàn)，并對(duì)具有不同裂紋參數(shù)a/c、a/t的受三點(diǎn)彎曲荷載作用下含三維表面裂紋的鋼板試件實(shí)施了疲勞裂紋擴(kuò)展實(shí)驗(yàn)研究，得到了CFL加固和未加固試件在彎曲疲勞荷載作用下的a~N和c~N實(shí)驗(yàn)曲線。 5）對(duì)受彎鋼板中三維表面裂紋的疲勞擴(kuò)展規(guī)律進(jìn)行了探討。研究結(jié)果表明：①CFL加固受彎試件中表面裂紋在長度和深度方向的擴(kuò)展規(guī)律都能用Paris模型進(jìn)行描述；未加固試件裂紋長度方向的擴(kuò)展規(guī)律也可用該模型很好地描述，但裂紋深度方向的擴(kuò)展卻不滿足Paris模型；②通過數(shù)據(jù)擬合得到了未加固試件裂紋長度方向、加固試件裂紋長度和深度方向的三維表面裂紋疲勞擴(kuò)展速率的半經(jīng)驗(yàn)公式；③CFL加固能抑制表面裂紋的擴(kuò)展，降低其疲勞擴(kuò)展速率。
[Abstract]:The widespread application of steel structure in engineering field makes the repair and strengthening of steel structure become a regular work, because of the high strength and high efficiency of FRP reinforcement technology, Due to its good fatigue resistance and strong adaptability, steel structure strengthened by FRP is more and more widely used. On the other hand, because the surface crack is one of the important defects in steel structure, and the propagation of surface crack has hidden danger to the operation of steel structure, therefore, It is of great scientific significance and engineering application value to study the fatigue propagation behavior of surface cracks in steel structures strengthened by FRP. In this paper, the method of calculating the stress intensity factor of the surface crack in the steel plate strengthened by CFL and its fatigue propagation rule are discussed. The carbon fiber sheet (Carbon Fiber Laminate, (abbreviated as CFL) is used to strengthen the steel plate with surface cracks as the research object. The main contents and conclusions of this paper are as follows: 1) the theory of fatigue crack growth and the finite element method of stress intensity factor are analyzed, and a finite element method combining J integral with special element is proposed. In order to solve the singularity problem of crack tip. 2) using finite element software Abaqus, a three-dimensional model of steel plate with surface crack under three-point bending load is established. By comparing the finite element results of the stress intensity factor of surface cracks with the calculated values of Newman-Raju formula, The influence of the ratio of the edge length L of the first layer element of the crack front to the crack depth a, the number of the element layers around the front edge of the crack, the partition number E of each layer and the fraction S along the front edge of the crack on the finite element calculation results are discussed. The optimal finite element parameter value is given. The calculation method of the stress intensity factor at the front edge of the surface crack is established. 3) the effects of the crack shape ratio a / c, the relative length C / W and the thickness of CFL t C on the reinforcement effect (the stress intensity factor Ki drop rate and the ROD) are discussed. The results show that the ROD increases with the increase of a / c or c / W at 0 擄, and the ROD decreases rapidly and then stabilizes with the increase of a / c at 胃 / 90 擄, but decreases first and then increases rapidly with the increase of c / W, and the reinforcement effect increases with the increase of CFL thickness. However, the growth trend is obvious before TC 鈮，

本文編號(hào)：2194067