【作者】 王世杰；

【导师】 孙全胜；

【作者基本信息】 东北林业大学 ， 林区交通工程， 2021， 博士

【摘要】 格构式高支架具有长细比较大、结构相对轻柔等特点,对风荷载的作用非常敏感。在台风区修建跨海大桥时,高耸格构式支架体系除受雷暴、大雾及潮汐等恶劣自然条件的影响外,还受大风、台风侵袭的影响,结构设计及施工技术均面临巨大挑战。在台风区保证格构式高支架的安全和稳定性能是桥梁工程界关注的课题之一。本文以福平铁路平潭海峡公铁两用大桥-大练岛特大桥新建工程中现浇公路梁桥格构式高支架为研究背景,通过风洞测力试验、粒子图像测速(PIV)试验、气弹模型试验、现场监测、数值模拟和理论计算相结合的手段对风荷载作用下格构式高支架的受力性能进行研究,以解决台风区格构式高支架的风工程问题。本文主要研究工作和成果如下:(1)基于ANSYS对四腿和六腿格构式支架进行有限元分析,采用修正后的有限元模型和时域法对格构式支架模态和顺风向风致响应进行分析,结果显示四腿单柱支架和六腿单柱支架的前6阶振型基本一致;多腿单柱格构支架前两阶振型的共振贡献比较显著,格构式高支架横桥向的侧向刚度大于纵桥向的侧向刚度;格构式高支架侧边和中线位置存在扭转和平动,而格构式高支架结构在横桥向风向角下的扭转不明显;格构式高支架在非对称荷载作用下,支架顶部的位移均方根增长幅值约为12%,存在明显的扭转效应;格构式高支架主要受力构件为竖向构件与斜杆,且高支架迎风面和背风面的斜杆由于扭转效应应力增幅比较明显。考虑上部结构后,四腿与六腿格构式支架的位移都均有大幅减小,表明上部结构的施加有利于结构的位移控制。(2)基于风洞测力试验测得格构高支架在不同流场和不同风向角下的静三分力系数。基于PIV技术,首次对高墩钢管支架模型水平平面流场和竖向平面流场进行流场可视化分析,定量分析了单柱和双柱支架的涡心漩涡强度和湍流度,得出风场风向对格构式高支架气动特性影响规律。研究表明格构式高支架在抗风计算时,阻力、升力和扭矩均变化明显,应充分考虑三个方向静风荷载的影响;在45°风偏角时漩涡运动剧烈,漩涡强度和湍动能强度最大,导致模型的气动力平均值和脉动值较大;六腿格构式高支架模型的涡心处漩涡强度和湍动能均比四腿格构式高支架模型小;格构式高支架各个构件间存在明显的构件干扰,数值模拟时应考虑空间三维特性。(3)根据分段估计法获得格构式高支架的三维设计风荷载,并将等效风荷载施加于四腿和六腿格构式高支架,得到风力等级与格构式高支架各节段位移的相关公式,而后采用单变量灰色预测模型DGM(1,1),得出格构式高支架施工拼装阶段在不同风等级作用下的位移,最后拟合出四腿与六腿格构式高支架风荷载等级与施工节段位移的计算公式。将计算结果与现场监测位移进行对比,结果表明分别采用建筑荷载规范与时域法计算时,各支架结构的位移较实际值偏大,与按等效风荷载计算值接近,采用等效风荷载计算更符合支架位移的变化规律。(4)基于格构高支架1:40全桥气弹模型试验,分析了不同风速和风向角等各参数下结构的振动响应。结果表明,格构式支架加速度响应和风速、高度均成正相关,在某些风向角下,横风向的位移响应与顺风向位移响应相当,甚至大于后者。获取风振系数并对扭转响应和扭转风荷载进行分析,左右横风向的角加速度响应基本对称且反相位,支架呈整体扭转,各风速下的扭转角加速度均方根基本都在0度风向角下最大,90度风向角时最小,并且随着风速的增大而增大。(5)提出采用最优化准则法对格构式高支架进行优化设计,得出格构式高支架立柱选择4根为最佳,节段长度宜控制在15m以内,且总高度不宜超过70m,立柱间距控制在7m～8m之间;在格构式高支架设计优化过程中,格构式高支架顶层位移限值起控制作用,需要更新节点风荷载时程和等效静风荷载,且节点风荷载时程影响大于等效静风荷载。更多还原

【Abstract】 Lattice high support has the characteristics of large slenderness ratio and strong flexibility,which is very sensitive to wind load.When building a cross-sea bridge in typhoon area,the high lattice support system is not only affected by harsh natural conditions such as the thunderstorm,heavy fog and tide,but also affected by strong wind and typhoon,so the structural design and construction technology are faced with great challenges.To ensure the safety and stability of lattice high support in typhoon area is one of the issues concerned by bridge engineering field.In this dissertation,taking the lattice high support of the newly constructed cast-in-place highway beam bridge,the Fuping Railway Pingtan Strait Road-Rail Bridge-Daliandao Grand Bridge,as the research object,the mechanical performance of lattice high support under wind load is studied by means of wind tunnel force test,particle image velocimetry(PIV)test,aeroelastic model test,field monitoring,numerical simulation and theoretical calculation,so as to solve the wind engineering problem of lattice high support in typhoon area.The main research work and results of this dissertation are as follows:(1)The ANSYS was used to establish the models of the four-legged and six-legged lattice support,and the modified finite element method and time-domain method were utilized to calculate and analyze the downwind wind-induced response of the lattice support.The results show that the first sixth-order vibration mode of the four-legged single-column support and the six-legged single-column support are basically the same.The resonance contribution of the first two modes of the multi-legged single-column lattice support is more significant,and the lateral stiffness of the lattice high support in the transverse direction is greater than the lateral stiffness in the longitudinal direction.There is torsion and translation at the sides and the center line of the lattice high support structure,while the torsion of the lattice high support structure under the transverse bridge wind direction angle is not obvious,under the action of asymmetrical load of the lattice high support,the displacement of the top of the support RMS increased by about 12%,and there is a significant torsion effect,the main load-bearing components of the lattice high support are vertical members and diagonal rods,and the inclined rods on the windward and leeward sides of the high support have a significant stress increase due to the torsion effect.After considering the superstructure,the displacements of both four-legged and six-legged lattice supports are significantly reduced,indicating that the superstructure is imposed to facilitate the displacement control of the structure.(2)The three component force coefficients of the model under different wind direction angles in uniform flow and turbulence were measured by wind tunnel test of the lattice high support scale model.Particle image velocimetry(PIV)was first used to visualize the horizontal plane flow field and vertical plane flow field of the high pier steel tube support model.the vortex intensity and turbulivity of the vortex center in the single-column PI V test and the double-column PIV test of the support model were quantitatively analyzed,and the law of the influence of the flow direction on high aerodynamic characteristics was obtained.Research shows that the resistance,lift and torque of the lattice high support have obvious changes in wind resistance calculations,and the influence of static wind loads in three directions should be fully considered,when β=45°.the vortex motion is violent,and the vortex intensity and turbulent kinetic energy intensity are the largest,as a result,the average aerodynamic force and pulsation value of the model are large.The vortex intensity and turbulent kinetic energy at the vortex center of the six-legged lattice high-support model are both smaller than those of the four-legged lattice high-support model,and there are obvious construction disturbances among the components of the lattice high support,and the three-dimensional characteristics of space should be considered in numerical simulation.(3)Three-dimensional design wind load of latticed high support based on piecewise estimation method,equivalent wind loads were applied to four-legged and six-legged lattice high supports,the correlation formula between the wind grade and the displacement of each segment of the lattice high support was obtained.The single variable grey prediction model DGM(1,1)was used to calculate the displacements of the high lattice support under the action of different wind levels in the erection stage of construction,finally,the calculating formulas of wind load grade and construction segment displacement of four-legged and six-legged lattice high support were fitted.By comparing the calculated results with the field monitoring displacement,the results show that the displacements of each support structure is larger than the actual values when calculated by the building load code and time domain method respectively,which is close to the calculated value according to the equivalent wind load,the calculation of equivalent wind load is more consistent with the variation law of support displacement.(4)Based on wind load test on the full bridge aero-elastic model the with reduced scale of 1:40 of lattice high support,the vibration responses of the structure under different parameters such as wind speed and wind direction angle were analyzed.The results show that the acceleration response of lattice support is positively correlated with wind speed and height,at some wind direction angles,the displacement response of the transverse wind direction is equal to or even greater than the downwind displacement response,and the wind vibration coefficient is obtained and the torsional response and torsional wind load are analyzed.The angular acceleration response of the left and right transverse wind direction is basically symmetric and anti-phase,the root mean square of torsion angular acceleration at each wind speed is basically the maximum at the wind direction angle of 0°,and the minimum at the wind direction angle of 90°,and it increases with the increase of wind speed.(5)The optimization criterion method was proposed to optimize the design of lattice high support,the following conclusions can be drawn as follows:it is better to choose 4 columns with high lattice structure,the segment length should be controlled within 15m,and the total height should not exceed 70m,moreover,the column spacing should be controlled between 7m and 8m,in the design optimization process of the lattice high support,the top displacement limit of lattice high support plays a controlling role,the wind load time-history and equivalent static wind load need to be updated,and the influence of wind load time-history is greater than the equivalent static wind load.更多还原