考慮內(nèi)充氣體與外部膜材共同作用的ETFE氣枕力學(xué)性能及風(fēng)致響應(yīng)研究
發(fā)布時(shí)間：2018-08-25 19:32
【摘要】：ETFE氣枕式膜結(jié)構(gòu)是本世紀(jì)初才開(kāi)始大量出現(xiàn)的新型圍護(hù)結(jié)構(gòu)。目前,有學(xué)者針對(duì)ETFE氣枕的力學(xué)性能與分析方法展開(kāi)研究并取得了一定進(jìn)展。然而,已有研究?jī)H涉及ETFE氣枕的形態(tài)分析和荷載分析等靜力學(xué)內(nèi)容,尚未觸及ETFE氣枕的自振特性和風(fēng)致響應(yīng)分析等動(dòng)力學(xué)問(wèn)題。ETFE氣枕在風(fēng)荷載作用下的動(dòng)力問(wèn)題涉及兩類(lèi)耦合：一是內(nèi)充氣體與ETFE薄膜的共同作用,二是氣枕與外部風(fēng)場(chǎng)的流固耦合。第一類(lèi)耦合的實(shí)質(zhì)是如何充分考慮內(nèi)充氣體對(duì)ETFE氣枕動(dòng)力特性的影響,而第二類(lèi)耦合的實(shí)質(zhì)是如何更準(zhǔn)確地計(jì)算外部流場(chǎng)的附加質(zhì)量、氣動(dòng)阻尼與氣承剛度效應(yīng)。 本文以實(shí)現(xiàn)耦合作用下的ETFE氣枕風(fēng)致動(dòng)力響應(yīng)分析為出發(fā)點(diǎn),基于理論推導(dǎo)、試驗(yàn)研究及數(shù)值模擬等手段對(duì)ETFE氣枕動(dòng)力分析中的關(guān)鍵技術(shù)問(wèn)題進(jìn)行了系統(tǒng)研究,主要內(nèi)容及創(chuàng)新包括： (1)推導(dǎo)了充氣膜結(jié)構(gòu)內(nèi)充氣體與外部膜材的共同作用方程,提出基于共同作用模型的充氣膜結(jié)構(gòu)數(shù)值分析方法并進(jìn)行了算例驗(yàn)證。在張拉膜平衡方程中引入內(nèi)壓項(xiàng)得到外部膜材的動(dòng)力學(xué)方程,基于勢(shì)流假定得到描述內(nèi)充氣體運(yùn)動(dòng)的波動(dòng)方程,然后引入界面協(xié)調(diào)條件并將結(jié)構(gòu)、流體方程聯(lián)立得到了充氣膜系統(tǒng)的共同作用方程。對(duì)兩類(lèi)典型充氣膜結(jié)構(gòu)進(jìn)行了數(shù)值模擬,驗(yàn)證了共同作用模型在充氣膜結(jié)構(gòu)分析中的準(zhǔn)確性和適用性。 (2)提出基于內(nèi)壓和膜面形狀測(cè)量的氣枕形態(tài)確定方法并用于ETFE氣枕的形態(tài)測(cè)試和加載測(cè)試,測(cè)試及分析結(jié)果表明該方法有效、可行。提出ETFE氣枕共同作用有限元模型的建立方法并進(jìn)行了靜力試驗(yàn)驗(yàn)證。定義了ETFE氣枕的破壞模式與承載力確定準(zhǔn)則并探討了尺寸、矢跨比、膜面厚度對(duì)承載力-內(nèi)壓曲線的影響。結(jié)果表明：ETFE氣枕內(nèi)壓對(duì)外荷載十分敏感,荷載作用位置對(duì)氣枕的變形和內(nèi)壓影響明顯。在設(shè)計(jì)內(nèi)壓范圍內(nèi),存在一個(gè)最優(yōu)氣壓使得ETFE氣枕具有最大承載力；尺寸、矢跨比及膜面厚度等參數(shù)變化會(huì)顯著影響氣枕的承載力。 (3)基于非接觸視頻測(cè)試并將峰值法、互譜法與指數(shù)擬合法相結(jié)合獲得了ETFE氣枕的模態(tài)參數(shù)及其隨內(nèi)壓和跨度的變化規(guī)律,研究了ETFE氣枕的自由振動(dòng)模式、頻率分布及阻尼特點(diǎn)。在此基礎(chǔ)上進(jìn)行了ETFE氣枕的自振特性參數(shù)分析,研究了內(nèi)壓、矢跨比、跨度、膜厚及外部空氣對(duì)氣枕模態(tài)參數(shù)的影響規(guī)律。結(jié)果表明：測(cè)試氣枕的1階振型均為左右擠壓振動(dòng),但后續(xù)模態(tài)的振型有所不同；ETFE氣枕在靜風(fēng)環(huán)境下屬于低阻尼結(jié)構(gòu),模態(tài)阻尼比隨內(nèi)壓升高非線性下降；氣枕固有頻率隨著內(nèi)壓升高而非線性增加,隨跨度增加而迅速減小,且分布更為密集。內(nèi)壓與跨度變化對(duì)氣枕的模態(tài)振型影響有限；膜材厚度、矢跨比變化對(duì)氣枕低階和高階模態(tài)頻率的影響效果不同；考慮外部空氣影響后的氣枕濕模態(tài)頻率較干模態(tài)頻率減小,外部空氣對(duì)氣枕動(dòng)力特性的影響隨氣枕跨度增加而顯著增大。 (4)驗(yàn)證了線性勢(shì)流單元在ETFE氣枕非線性、大變形隨機(jī)振動(dòng)分析中的適用性和準(zhǔn)確性,為氣枕流固耦合動(dòng)力分析奠定基礎(chǔ)。將CFD模擬的剛性氣枕表面風(fēng)壓時(shí)程加載于共同作用有限元模型進(jìn)行非線性隨機(jī)振動(dòng)分析,研究了ETFE氣枕在隨機(jī)風(fēng)荷載下的振動(dòng)模式及膜面響應(yīng)的分布特點(diǎn)。結(jié)果表明：風(fēng)荷載作用下氣枕振動(dòng)表現(xiàn)出極強(qiáng)的整體性,上、下層膜面在內(nèi)充氣體的聯(lián)系下呈豎向整體擺動(dòng)。氣枕上層膜的響應(yīng)峰值向迎風(fēng)側(cè)偏移,沿風(fēng)向呈非對(duì)稱(chēng)分布；氣枕下層膜響應(yīng)因僅受均布?jí)毫ψ饔枚瞥蕦?duì)稱(chēng)分布。 (5)基于結(jié)構(gòu)-流體同步數(shù)值建模技術(shù)建立了包含整個(gè)建筑的ETFE氣枕流固耦合分析模型,計(jì)算了考慮流固耦合作用的ETFE氣枕風(fēng)致響應(yīng),討論了流固耦合作用對(duì)ETFE氣枕響應(yīng)時(shí)程、空間分布、功率譜及風(fēng)振系數(shù)的影響。定義了ETFE氣枕的流固耦合效應(yīng)系數(shù),并給出其在工程常見(jiàn)風(fēng)速、內(nèi)壓、矢跨比和跨度下的變化規(guī)律和取值范圍。研究表明：ETFE氣枕在風(fēng)荷載下的流固耦合效應(yīng)主要表現(xiàn)為外流場(chǎng)對(duì)氣枕動(dòng)力響應(yīng)的單向影響,氣枕運(yùn)動(dòng)引起的流場(chǎng)改變十分微弱。流固耦合作用引起了較大的氣動(dòng)阻尼,抑制了ETFE氣枕的風(fēng)致振動(dòng)。流固耦合作用下ETFE氣枕的響應(yīng)譜表現(xiàn)為以低頻振動(dòng)為主的寬頻帶分布,與無(wú)耦合結(jié)果差異明顯,這表明有、無(wú)流固耦合作用下氣枕的風(fēng)致振動(dòng)機(jī)制有所區(qū)別,前者以風(fēng)荷載作用下的強(qiáng)迫振動(dòng)為主,而后者以結(jié)構(gòu)與流場(chǎng)的共振響應(yīng)為主。ETFE氣枕的流固耦合效應(yīng)系數(shù)受風(fēng)速、內(nèi)壓、矢跨比及跨度影響顯著；在工程常見(jiàn)的風(fēng)速、內(nèi)壓、矢跨比及跨度范圍內(nèi),氣枕流固耦合效應(yīng)系數(shù)的取值范圍分別為0.62-0.725、0.6-0.83、0.58-0.87及0.56～0.89。 本文以共同作用模型的理論推導(dǎo)和試驗(yàn)驗(yàn)證為基礎(chǔ),并考慮氣枕與外部風(fēng)場(chǎng)間的流固耦合作用實(shí)現(xiàn)了ETFE氣枕的風(fēng)致動(dòng)力響應(yīng)數(shù)值模擬和全過(guò)程分析,研究了ETFE氣枕的靜、動(dòng)力性能及流固耦合特點(diǎn),為氣枕工程設(shè)計(jì)提供了有益參考。
[Abstract]:ETFE air-cushion membrane structure is a new type of envelope structure which appeared in large quantities at the beginning of this century. At present, some scholars have made some progress on the mechanical properties and analysis methods of ETFE air-cushion. However, the existing research only involves the static analysis of ETFE air-cushion, such as morphology analysis and load analysis, and has not touched the natural vibration of ETFE air-cushion. The dynamic problems of ETFE air cushion under wind load involve two kinds of coupling: the interaction between the inner air cushion and the ETFE film, and the fluid-solid coupling between the inner air cushion and the external wind field. The essence of the second type of coupling is how to calculate the additional mass, aerodynamic damping and stiffness effect of the external flow field more accurately.
Based on the theoretical derivation, experimental study and numerical simulation, the key technical problems in the dynamic analysis of ETFE air sleepers are systematically studied in this paper. The main contents and innovations are as follows:
(1) The interaction equation between the inflatable membrane and the external membrane is deduced, and a numerical analysis method based on the interaction model is proposed for the inflatable membrane structure. Wave equation is introduced, interface compatibility condition is introduced, and the interaction equation of gas-filled membrane system is obtained by combining structure and fluid equation. Two typical gas-filled membrane structures are numerically simulated to verify the accuracy and applicability of the interaction model in the analysis of gas-filled membrane structures.
(2) A method for determining the shape of the air-cushion based on the measurement of internal pressure and membrane surface shape is proposed and applied to the shape test and loading test of the ETFE air-cushion. The test and analysis results show that the method is effective and feasible. The results show that the internal pressure of ETFE pillow is very sensitive to external load, and the location of load has obvious influence on the deformation and internal pressure of the pillow. Parameters such as size, sagittal span ratio and film thickness will significantly affect the bearing capacity of air cushion.
(3) Based on the non-contact video test and the peak value method, the cross-spectrum method and the exponential fitting method are combined to obtain the modal parameters of the ETFE air cushion and their variation with internal pressure and span. The free vibration mode, frequency distribution and damping characteristics of the ETFE air cushion are studied. The results show that the first mode shapes of the test sleepers are left-right extrusion vibration, but the subsequent mode shapes are different; the ETFE sleepers belong to low damping structure in static wind environment, and the modal damping ratio decreases nonlinearly with the increase of internal pressure. With the increase of internal pressure and span, the influence of the change of internal pressure and span on the modal vibration mode of the air sleeper is limited; the effect of the change of membrane thickness and rise-span ratio on the low-order and high-order modal frequencies of the air sleeper is different; the wet modal frequencies of the air sleeper considering the influence of external air are higher than that of the dry mode. When the state frequency decreases, the influence of external air on the dynamic characteristics of air cushion increases significantly with the increase of air cushion span.
(4) The applicability and accuracy of the linear potential flow element in the nonlinear and large deformation random vibration analysis of the ETFE air cushion are verified, which lays the foundation for the fluid-structure coupling dynamic analysis of the air cushion. The results show that the vibration of the air cushion under wind load shows a strong integrity, and that the upper and lower membrane surfaces oscillate vertically and wholly under the connection of the inner inflatable. The response peak value of the upper membrane of the air cushion shifts to the windward side and distributes asymmetrically along the wind direction. It is symmetrical distribution only under uniform pressure.
(5) Based on the structure-fluid synchronous numerical modeling technique, a fluid-structure coupling analysis model of ETFE air-cushion is established, and the wind-induced response of ETFE air-cushion considering fluid-structure coupling is calculated. The influence of fluid-structure coupling on response time history, spatial distribution, power spectrum and wind-induced vibration coefficient of ETFE air-cushion is discussed. The results show that the fluid-structure coupling effect of ETFE air-cushion under wind load is mainly manifested by the unidirectional influence of the external flow field on the dynamic response of the air-cushion, and the fluid-structure coupling effect caused by the movement of the air-cushion is very weak. The response spectrum of the ETFE sleeper under the fluid-solid coupling is broadband with low-frequency vibration as the dominant component, which is obviously different from that without coupling. This shows that the mechanism of the wind-induced vibration of the sleeper under the fluid-solid coupling is different, and the former is strong under the wind load. The fluid-structure coupling effect coefficients of ETFE gas sleepers are significantly affected by wind speed, internal pressure, rise-span ratio and span. In the common Wind speed, internal pressure, rise-span ratio and span range, the fluid-structure coupling effect coefficients of ETFE gas sleepers are 0.62-0.725, 0.6-0.83, 0.58-0.87 and 0.58-0.87 respectively. .56 ~ 0.89.
Based on the theoretical derivation and experimental verification of the interaction model and considering the fluid-structure interaction between the air cushion and the external wind field, the wind-induced dynamic response of the ETFE air cushion is numerically simulated and analyzed. The static, dynamic and fluid-structure coupling characteristics of the ETFE air cushion are studied, which provides a useful reference for the engineering design of the air cushion.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TU383
本文編號(hào)：2203881
[Abstract]:ETFE air-cushion membrane structure is a new type of envelope structure which appeared in large quantities at the beginning of this century. At present, some scholars have made some progress on the mechanical properties and analysis methods of ETFE air-cushion. However, the existing research only involves the static analysis of ETFE air-cushion, such as morphology analysis and load analysis, and has not touched the natural vibration of ETFE air-cushion. The dynamic problems of ETFE air cushion under wind load involve two kinds of coupling: the interaction between the inner air cushion and the ETFE film, and the fluid-solid coupling between the inner air cushion and the external wind field. The essence of the second type of coupling is how to calculate the additional mass, aerodynamic damping and stiffness effect of the external flow field more accurately.
Based on the theoretical derivation, experimental study and numerical simulation, the key technical problems in the dynamic analysis of ETFE air sleepers are systematically studied in this paper. The main contents and innovations are as follows:
(1) The interaction equation between the inflatable membrane and the external membrane is deduced, and a numerical analysis method based on the interaction model is proposed for the inflatable membrane structure. Wave equation is introduced, interface compatibility condition is introduced, and the interaction equation of gas-filled membrane system is obtained by combining structure and fluid equation. Two typical gas-filled membrane structures are numerically simulated to verify the accuracy and applicability of the interaction model in the analysis of gas-filled membrane structures.
(2) A method for determining the shape of the air-cushion based on the measurement of internal pressure and membrane surface shape is proposed and applied to the shape test and loading test of the ETFE air-cushion. The test and analysis results show that the method is effective and feasible. The results show that the internal pressure of ETFE pillow is very sensitive to external load, and the location of load has obvious influence on the deformation and internal pressure of the pillow. Parameters such as size, sagittal span ratio and film thickness will significantly affect the bearing capacity of air cushion.
(3) Based on the non-contact video test and the peak value method, the cross-spectrum method and the exponential fitting method are combined to obtain the modal parameters of the ETFE air cushion and their variation with internal pressure and span. The free vibration mode, frequency distribution and damping characteristics of the ETFE air cushion are studied. The results show that the first mode shapes of the test sleepers are left-right extrusion vibration, but the subsequent mode shapes are different; the ETFE sleepers belong to low damping structure in static wind environment, and the modal damping ratio decreases nonlinearly with the increase of internal pressure. With the increase of internal pressure and span, the influence of the change of internal pressure and span on the modal vibration mode of the air sleeper is limited; the effect of the change of membrane thickness and rise-span ratio on the low-order and high-order modal frequencies of the air sleeper is different; the wet modal frequencies of the air sleeper considering the influence of external air are higher than that of the dry mode. When the state frequency decreases, the influence of external air on the dynamic characteristics of air cushion increases significantly with the increase of air cushion span.
(4) The applicability and accuracy of the linear potential flow element in the nonlinear and large deformation random vibration analysis of the ETFE air cushion are verified, which lays the foundation for the fluid-structure coupling dynamic analysis of the air cushion. The results show that the vibration of the air cushion under wind load shows a strong integrity, and that the upper and lower membrane surfaces oscillate vertically and wholly under the connection of the inner inflatable. The response peak value of the upper membrane of the air cushion shifts to the windward side and distributes asymmetrically along the wind direction. It is symmetrical distribution only under uniform pressure.
(5) Based on the structure-fluid synchronous numerical modeling technique, a fluid-structure coupling analysis model of ETFE air-cushion is established, and the wind-induced response of ETFE air-cushion considering fluid-structure coupling is calculated. The influence of fluid-structure coupling on response time history, spatial distribution, power spectrum and wind-induced vibration coefficient of ETFE air-cushion is discussed. The results show that the fluid-structure coupling effect of ETFE air-cushion under wind load is mainly manifested by the unidirectional influence of the external flow field on the dynamic response of the air-cushion, and the fluid-structure coupling effect caused by the movement of the air-cushion is very weak. The response spectrum of the ETFE sleeper under the fluid-solid coupling is broadband with low-frequency vibration as the dominant component, which is obviously different from that without coupling. This shows that the mechanism of the wind-induced vibration of the sleeper under the fluid-solid coupling is different, and the former is strong under the wind load. The fluid-structure coupling effect coefficients of ETFE gas sleepers are significantly affected by wind speed, internal pressure, rise-span ratio and span. In the common Wind speed, internal pressure, rise-span ratio and span range, the fluid-structure coupling effect coefficients of ETFE gas sleepers are 0.62-0.725, 0.6-0.83, 0.58-0.87 and 0.58-0.87 respectively. .56 ~ 0.89.
Based on the theoretical derivation and experimental verification of the interaction model and considering the fluid-structure interaction between the air cushion and the external wind field, the wind-induced dynamic response of the ETFE air cushion is numerically simulated and analyzed. The static, dynamic and fluid-structure coupling characteristics of the ETFE air cushion are studied, which provides a useful reference for the engineering design of the air cushion.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TU383
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