【摘要】：近年來(lái)由于各種人為因素或地質(zhì)災(zāi)害的影響,建筑物嚴(yán)重破壞的事故頻繁發(fā)生。重要的大跨度網(wǎng)殼結(jié)構(gòu),例如地區(qū)標(biāo)志性建筑,如果遭受特大地震、撞擊等意外危害時(shí)發(fā)生破壞,不僅會(huì)造成生命財(cái)產(chǎn)的重大損失,甚至還會(huì)有深遠(yuǎn)的政治影響。結(jié)構(gòu)設(shè)計(jì)的根本任務(wù)是保證結(jié)構(gòu)安全而防止結(jié)構(gòu)倒塌則是保證結(jié)構(gòu)安全的底線。對(duì)有大量人群聚集的大跨度建筑結(jié)構(gòu)進(jìn)行倒塌分析,采取防止動(dòng)力倒塌的措施,將逐步成為結(jié)構(gòu)設(shè)計(jì)的一項(xiàng)重要內(nèi)容。 造成建筑物失效破壞的突發(fā)事故既可是自然界中的突發(fā)地震,也可是意外的沖擊。本文以球面網(wǎng)殼為研究對(duì)象,具體包括單層網(wǎng)殼、雙層網(wǎng)殼兩種形式,以數(shù)值模擬和試驗(yàn)研究相結(jié)合的方法,分析了強(qiáng)震和沖擊荷載下網(wǎng)殼結(jié)構(gòu)的動(dòng)力響應(yīng)、失效模式,模擬了動(dòng)力倒塌的過(guò)程,并揭示了倒塌機(jī)理,主要內(nèi)容如下： (1)以結(jié)構(gòu)倒塌的數(shù)值模擬為基礎(chǔ),選用顯式動(dòng)力非線性程序LS-DYNA作為數(shù)值模擬平臺(tái)。對(duì)數(shù)值模擬的相關(guān)技術(shù)及其難點(diǎn)進(jìn)行了分析,自編制前處理子程序,采用了鋼材的彈塑性損傷本構(gòu)模型。建立了基于IDA方法的球面網(wǎng)殼的動(dòng)力倒塌的計(jì)算流程,提出了基于能量守恒的倒塌判斷準(zhǔn)則。 (2)通過(guò)對(duì)單層球面網(wǎng)殼結(jié)構(gòu)的動(dòng)力分析,定義了強(qiáng)震下網(wǎng)殼結(jié)構(gòu)的失效模式。研究了單層網(wǎng)殼結(jié)構(gòu)在強(qiáng)震下的動(dòng)力響應(yīng)和失效特征,重點(diǎn)模擬了結(jié)構(gòu)倒塌的全過(guò)程,從凹陷產(chǎn)生、擴(kuò)展的角度揭示了倒塌機(jī)理。對(duì)影響網(wǎng)殼結(jié)構(gòu)極限承載力的影響因素,如：矢跨比、屋面荷載、有無(wú)下部支承結(jié)構(gòu)進(jìn)行了分析。對(duì)荷載分布不對(duì)稱下的網(wǎng)殼結(jié)構(gòu)進(jìn)行了動(dòng)力倒塌分析。對(duì)空腹雙層網(wǎng)殼進(jìn)行了動(dòng)力全過(guò)程分析。 (3)提出了在網(wǎng)殼中增設(shè)開孔的雙鋼管約束屈曲支撐作為減震裝置,對(duì)其耗能能力進(jìn)行了分析。提出了在單層網(wǎng)殼、雙層網(wǎng)殼中,約束屈曲支撐布置的方式,對(duì)其減震效果進(jìn)行了分析。并對(duì)無(wú)約束屈曲支撐和有約束屈曲支撐的網(wǎng)殼的極限承載力進(jìn)行了對(duì)比分析。結(jié)果表明,約束屈曲支撐具有較好的減震效果,并能提高網(wǎng)殼的極限承載力 (4)通過(guò)縮尺模型振動(dòng)臺(tái)試驗(yàn),對(duì)網(wǎng)殼結(jié)構(gòu)在不對(duì)稱荷載作用下的動(dòng)力失效模式進(jìn)行了驗(yàn)證。結(jié)果表明：荷載不均勻分布會(huì)降低強(qiáng)震下網(wǎng)殼結(jié)構(gòu)的極限承載力。在設(shè)計(jì)過(guò)程中,應(yīng)充分考慮不對(duì)稱荷載對(duì)網(wǎng)殼動(dòng)力穩(wěn)定性的影響。 (5)研究了如落石等這種質(zhì)量較大、速度較小的沖擊荷載,對(duì)沖擊荷載進(jìn)行了分析。建立了網(wǎng)殼結(jié)構(gòu)沖擊響應(yīng)的計(jì)算模型,定義了網(wǎng)殼結(jié)構(gòu)在這種荷載作用下的失效模式,分析了各失效模式對(duì)應(yīng)的動(dòng)力響應(yīng)特點(diǎn),對(duì)失效機(jī)理進(jìn)行了研究。分析了當(dāng)網(wǎng)殼同時(shí)遭受兩點(diǎn)沖擊、三點(diǎn)沖擊的動(dòng)力響應(yīng),對(duì)三點(diǎn)沖擊下的網(wǎng)殼結(jié)構(gòu)的整體倒塌機(jī)理進(jìn)行了研究。結(jié)果表明：對(duì)于單點(diǎn)沖擊,對(duì)應(yīng)的失效模式為輕度損傷、局部凹陷、局部沖切破壞。當(dāng)沖擊質(zhì)量和速度均較小時(shí),沖擊能量較小,沖擊點(diǎn)處的桿件有輕微的損傷；當(dāng)速度較大時(shí),一般發(fā)生的是局部沖切破壞,當(dāng)質(zhì)量較大,速度適中時(shí),才會(huì)發(fā)生局部凹陷。網(wǎng)殼結(jié)構(gòu)在最不利兩點(diǎn)沖擊和三點(diǎn)沖擊下的失效機(jī)理為；由于局部凹陷形成、擴(kuò)展、聯(lián)通,導(dǎo)致結(jié)構(gòu)最后動(dòng)力倒塌。 (6)進(jìn)行了縮尺模型的網(wǎng)殼結(jié)構(gòu)的沖擊試驗(yàn),采用不同質(zhì)量的沖擊物對(duì)網(wǎng)殼結(jié)構(gòu)的不同節(jié)點(diǎn)進(jìn)行了沖擊測(cè)試,分析了整體結(jié)構(gòu)的動(dòng)應(yīng)力、動(dòng)位移及加速度,和有限元結(jié)果進(jìn)行了對(duì)比分析,研究了網(wǎng)殼結(jié)構(gòu)的動(dòng)力響應(yīng)特點(diǎn),驗(yàn)證了網(wǎng)殼結(jié)構(gòu)在低速?zèng)_擊下局部凹陷的失效模式。結(jié)果表明：沖擊區(qū)域測(cè)點(diǎn)的響應(yīng)明顯大于非沖擊區(qū)域的測(cè)點(diǎn),主肋節(jié)點(diǎn)測(cè)點(diǎn)的響應(yīng)大于其他測(cè)點(diǎn)的響應(yīng),說(shuō)明沖擊荷載產(chǎn)生的應(yīng)力波主要沿沖擊方向傳播,沿環(huán)形傳播的能量衰減的較快。不同沖擊點(diǎn)產(chǎn)生的結(jié)構(gòu)響應(yīng)也不同,主肋靠近頂點(diǎn)的節(jié)點(diǎn)、中間部位的節(jié)點(diǎn)為不利加載點(diǎn)。
[Abstract]:In recent years, due to various man-made factors or geological disasters, serious building damage accidents occur frequently. Important large-span reticulated shell structures, such as regional landmark buildings, will not only cause significant loss of life and property, but also have far-reaching political shadow if they are damaged by major earthquake, impact and other accidental hazards. The basic task of structural design is to ensure structural safety and prevent structural collapse is the bottom line of structural safety. Collapse analysis of large-span building structures with large crowds and measures to prevent dynamic collapse will gradually become an important part of structural design.
In this paper, the dynamic response of reticulated shells under strong earthquakes and impact loads is analyzed by means of numerical simulation and experimental study, which includes single-layer reticulated shells and double-layer reticulated shells. The failure mode is simulated, and the collapse mechanism is revealed. The main contents are as follows:
(1) Based on the numerical simulation of structural collapse, the explicit dynamic nonlinear program LS-DYNA is selected as the numerical simulation platform. The related techniques and difficulties of numerical simulation are analyzed. The pretreatment subroutine is compiled and the elastic-plastic damage constitutive model of steel is adopted. The dynamic collapse of spherical reticulated shell based on IDA method is established. Based on the calculation process, a collapse criterion based on energy conservation is proposed.
(2) Based on the dynamic analysis of single-layer reticulated spherical shells, the failure modes of reticulated shells under strong earthquakes are defined. The dynamic response and failure characteristics of single-layer reticulated shells under strong earthquakes are studied. The whole collapse process is simulated with emphasis. The collapse mechanism is revealed from the angle of depression and expansion. Influencing factors, such as rise-span ratio, roof load, and whether or not the lower supporting structure is analyzed. The dynamic collapse of reticulated shell under asymmetric load distribution is analyzed.
(3) The double steel tube restrained buckling braces with openings in reticulated shells are proposed as shock absorbers, and their energy dissipation capacity is analyzed. The results show that the restrained buckling braces have better damping effect and can improve the ultimate bearing capacity of reticulated shells.
(4) The dynamic failure modes of reticulated shells subjected to asymmetric loads are validated by scale model shaking table test. The results show that the ultimate bearing capacity of reticulated shells under strong earthquakes can be reduced by non-uniform load distribution.
(5) The impact loads with large mass and small velocity, such as rockfall, are studied, and the impact loads are analyzed. The calculation model of impact response of reticulated shells is established, the failure modes of reticulated shells under such loads are defined, the corresponding dynamic response characteristics of each failure mode are analyzed, and the failure mechanism is studied. The overall collapse mechanism of reticulated shells subjected to two-point impact and three-point impact is studied. The results show that the failure modes of reticulated shells subjected to single-point impact are slight damage, local depression and local punching failure. There is a slight damage to the bar at the impact point; when the velocity is high, the local punching failure usually occurs. When the mass is large and the velocity is moderate, the local depression will occur.
(6) The impact tests of reticulated shells with different mass impactors were carried out. The dynamic stress, displacement and acceleration of the whole structure were analyzed and compared with the results of finite element method. The dynamic response characteristics of reticulated shells were studied and the reticulated shells were verified. The results show that the response of the measured points in the impact area is obviously greater than that in the non-impact area, and the response of the main rib node is greater than that of the other measuring points. It shows that the stress wave produced by the impact load mainly propagates along the impact direction, and the energy attenuates rapidly along the ring. The structural response is also different. The nodes near the top of the main rib and the middle part are the unfavorable loading points.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU399;TU311.3

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本文編號(hào)：2181766