本文選題：受約束蜂窩梁　切入點(diǎn)：不均勻溫度分布　出處：《山東大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：火災(zāi)下受約束鋼梁的懸鏈線效應(yīng)是指:隨著溫度的升高,由于鋼梁的熱膨脹變形受到約束,鋼梁內(nèi)產(chǎn)生軸力;隨著溫度的進(jìn)一步升高,鋼梁發(fā)生大撓度變形,梁內(nèi)軸力由壓力轉(zhuǎn)變?yōu)槔Σ⒗^續(xù)承擔(dān)外荷載的現(xiàn)象。考慮受約束鋼梁的懸鏈線效應(yīng)可有效發(fā)揮結(jié)構(gòu)潛能,顯著提高構(gòu)件的臨界溫度。但目前對(duì)鋼梁懸鏈線效應(yīng)的研究集中于數(shù)值研究,且多是基于均勻溫度假設(shè),尚沒有成熟的理論分析方法。本文首先采用經(jīng)驗(yàn)證的有限元模型分析了火災(zāi)下受約束鋼梁懸鏈線效應(yīng)受力機(jī)理。結(jié)果表明,火災(zāi)下鋼梁經(jīng)歷三個(gè)階段:壓彎階段、屈曲后階段及懸鏈線階段,鋼梁受力機(jī)制由梁受彎承載機(jī)制轉(zhuǎn)變?yōu)閼益溇�拉力承載機(jī)制;截面不均勻溫度分布引起的熱彎效應(yīng)增大了鋼梁的撓度;與實(shí)腹梁相比,蜂窩梁腹板所起的作用很小,可以忽略。其次研究了不同參數(shù)對(duì)火災(zāi)下受約束鋼梁懸鏈線效應(yīng)的影響,考慮的參數(shù)有溫度梯度、荷載比、軸向約束剛度比、跨高比、開孔率、孔間腹板寬度及孔偏心。結(jié)果表明,荷載比、軸向約束剛度比及跨高比對(duì)火災(zāi)下受約束蜂窩鋼梁的懸鏈線效應(yīng)有較大影響,小荷載比及大跨高比蜂窩梁更適宜考慮懸鏈線效應(yīng);而開孔率、孔間腹板寬度及孔偏心對(duì)火災(zāi)下蜂窩梁的受力性能影響十分有限。最后基于平衡方程、本構(gòu)方程及幾何方程提出了一種適用于火災(zāi)下受約束蜂窩鋼梁懸鏈線效應(yīng)的簡(jiǎn)化分析方法。考慮了蜂窩梁孔洞上下方腹板對(duì)軸力的貢獻(xiàn)及進(jìn)入懸鏈線階段時(shí)孔洞上方截面由壓應(yīng)力轉(zhuǎn)變?yōu)槔瓚?yīng)力的應(yīng)力路徑影響。將簡(jiǎn)化分析方法計(jì)算結(jié)果與有限元分析結(jié)果進(jìn)行比較,從梁內(nèi)約束軸力、跨中撓度及特征溫度三個(gè)方面評(píng)估了該方法的準(zhǔn)確性。結(jié)果表明,本文提出的簡(jiǎn)化分析方法預(yù)測(cè)的結(jié)果與有限分析得到的結(jié)果吻合良好,并可用于分析火災(zāi)后期受約束蜂窩鋼梁的受力性能。當(dāng)不考慮蜂窩梁腹板對(duì)軸力的貢獻(xiàn)時(shí),該方法預(yù)測(cè)的軸力偏小;當(dāng)不考慮升溫過程中截面由壓應(yīng)力轉(zhuǎn)變?yōu)槔瓚?yīng)力的應(yīng)力路徑影響時(shí),該方法在懸鏈線階段預(yù)測(cè)得到的撓度偏大。
[Abstract]:The catenary effect of restrained steel beam under fire is that with the increase of temperature, the thermal expansion deformation of steel beam is restrained, and the axial force is produced in the steel beam, and with the further increase of temperature, the large deflection of steel beam occurs. Considering the catenary effect of restrained steel beam, the potential of the structure can be effectively realized by changing the axial force from the pressure to the tensile force and continuing to bear the external load. But the research on catenary effect of steel beam is focused on numerical research, and most of them are based on the assumption of uniform temperature. There is no mature theoretical analysis method. Firstly, the finite element model is used to analyze the mechanism of catenary effect of restrained steel beam under fire. The results show that the steel beam under fire goes through three stages: compression and bending stage. In post-buckling stage and catenary stage, the stress mechanism of steel beam changed from flexural loading mechanism to catenary tension bearing mechanism, the thermal bending effect caused by non-uniform temperature distribution of section increased the deflection of steel beam. The influence of different parameters on catenary effect of restrained steel beam under fire is studied. The parameters include temperature gradient, load ratio, axial restraint stiffness ratio, span height ratio, open hole ratio, etc. The results show that load ratio, axial restrained stiffness ratio and span height ratio have great influence on catenary effect of restrained honeycomb steel beam under fire, and small load ratio and long span height are more suitable to consider catenary effect than honeycomb beam. However, the effect of opening ratio, web width and eccentricity of holes on the behavior of honeycomb beams under fire is very limited. Finally, based on the equilibrium equation, A simplified analysis method for catenary effect of restrained honeycomb steel beams under fire is proposed by constitutive equation and geometric equation. The contribution of upper and lower webs of honeycomb beams to axial force and the hole at catenary stage are considered. The influence of the stress path of the upper section from compressive stress to tensile stress is obtained. The calculated results of simplified analysis method are compared with the results of finite element analysis. The accuracy of the proposed method is evaluated from three aspects: confined axial force, mid-span deflection and characteristic temperature. The results show that the predicted results of the simplified analysis method proposed in this paper are in good agreement with the results obtained from the finite analysis. It can be used to analyze the behavior of confined honeycomb steel beams in the later stage of fire. When the contribution of web to the axial force is not considered, the axial force predicted by this method is small. When the influence of the stress path from compressive stress to tensile stress is not taken into account in the heating process, the deflection predicted by this method in catenary phase is larger than that in the catenary stage.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU391;TU352.5

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