【作者】 叶征伟；

【导师】 项贻强；

【作者基本信息】 浙江大学 ， 桥梁与隧道工程， 2012， 博士

【摘要】 随着高速公路建设进入山区,高墩大跨连续刚构桥越来越多,风荷载和风载内力逐渐成为控制此类桥梁设计的主要因素。一方面,现有的桥梁风环境研究成果多是针对平原地区进行的,而山区地形复杂多变,局部风环境影响因素多,风特性与平原区相比有很大差异,深入研究山区桥位风环境是山区桥梁抗风设计的前提；另一方面,现有的桥梁抗风研究成果多是针对悬索桥或斜拉桥进行的,针对高墩大跨连续刚构桥的抗风研究并不充分。本文以跨径98+5×185+98m、最大墩高180m的三水河大桥这一实际工程为背景,在现有研究的基础上开展山区桥位风环境及高墩大跨连续刚构桥风效应研究,主要研究内容及成果如下：采用不同于现有研究成果的抽样时间间隔、极值风速分布概型及风速样本整理方法,推导了考虑风速风向联合概率分布确定基本风速的计算公式,并对三水河大桥桥位附近气象站连续34年的风速风向观测资料进行了统计分析和对比。结果表明：不区分风向的传统统计分析方法对基本风速有所高估,现行规范建议的基本风速高估较多,基本风速推算宜考虑风速风向的联合概率分布,且抽样时间间隔越短越经济合理。建立了包括三水河大桥桥位和邻近气象站在内的大尺度数字地形模型,采用数值模拟技术研究了桥位风环境,与物理风洞试验结果进行了对比；提出了基于数值风洞技术由气象站基本风速推求桥梁设计风速的方法,推算了三水河大桥的设计基准风速并进行了分析对比。结果表明：数值风洞风剖面结果和物理风洞结果有一定偏差,但二者整体趋势的一致性较好；桥位复杂的地形环境对风场的干扰影响很大,部分风向部分桥墩风剖面不满足幂指数变化规律；来流风与河谷走向接近一致时,位于河道中的桥墩风剖面接近规范中的B类地表值；同一位置不同风向角下桥梁设计基准风速有可能存在较大差异,相同风向角下设计基准风速沿桥梁长度方向分布可能也不均衡。采用数值模拟方法研究了不同风攻(偏)角和有无护栏情况下桥梁不同断面的三分力系数,与物理风洞试验结果进行了对比,总结了桥梁断面气动力系数随不同影响因素的变化规律；在此基础上进一步探索了双幅桥的气动干扰机理,分析了不同干扰因素对上下游桥三分力系数的影响。研究表明：数值模拟对上游桥阻力系数精度较高,对下游桥阻力系数及上下游桥的升力系数和扭矩系数误差稍大,但总体上与物理风洞试验结果吻合较好；对阻力系数而言,来流风对上游桥的作用为较大的推力,而对下游桥的作用为相对较小的吸力,阻力系数随风攻角变化较小,随梁高增大而增大,受护栏影响显著；上下游桥升力系数和扭矩系数也受风攻(偏)角、梁高和有无护栏等因素的影响而变化。气动干扰效应对双幅下游桥的影响很大,总体上干扰效应随风攻角的变化规律不明显,随双幅桥间距减小而增大,随结构尺寸增大而增大；气动干扰效应对双幅上游桥也有一定影响,但影响相对较小。定量分析比较了国内外有关规范对高墩大跨连续刚构桥横桥向风荷载计算的差异,并以算例与抖振分析结果进行了对比；基于高墩大跨连续刚构桥的特点及横桥向一阶振型,考虑平均风荷载和结构脉动风荷载背影响应及共振响应,给出了方便工程应用的计算高墩大跨连续刚构桥墩底横桥向弯矩和剪力等效风荷载及风载内力的实用简化计算公式,并通过典型算例验证了简化方法的精度及适用性。对比分析表明：高墩大跨连续刚构桥基频较低,脉动风惯性力的影响不可忽略,现行规范风荷载计算时未考虑脉动风惯性力的影响,计算结果偏小较多；高墩尤其超高墩桥梁的桥墩风荷载很大,其对墩底内力的影响甚至可能超过主梁,应引起足够重视。更多还原

【Abstract】 With the entering of expressway into mountainous area, there are more and more long-span continuous rigid frame bridges with tall piers, and wind load and internal force of wind load have gradually become the major factors of this kind of bridge design. However, on the one hand, the existing research results on bridge wind environment are conducted on flat plain, yet mountainous area has more complicated terrain and the part wind environment has more influential factors. Therefore, the wind characteristic in mountainous area is very different from that in plain. The in-depth research on wind environment of bridge site is the prerequisite of bridge wind-resistant design in mountainous area. On the other hand, existing research results on wind resistance of bridge are targeted at long-span suspension bridges or cable-stayed bridges. The wind resistance research on long-span continuous rigid frame bridges with tall piers is not sufficient. Based on a typical actual engineering San-shui-he Bridge with span of 98+5×185+98 m and maximum high pier of 180m as background, research on bridge site wind environment in mountainous area and wind effect of long-span continuous rigid frame bridge with tall piers were conducted on the basis of existing researches in this thesis. The main research results are as follows:By different sample interval, extreme wind speed distribution possibility and wind speed sample sorting methods from existing research, the calculation formulas to determine basic wind speed were deduced in consideration of joint probability distribution of wind speed and direction. Through the statistical analysis of the wind speed and wind direction observational data in continuous 34 years of weather station around the bridge site, the different basic wind speed gained by different methods were given and compared in the paper. The results show that the traditional analytical method, which does not distinguish wind direction, overestimates the basic wind speed. The basic wind speed of the current code recommendation is overestimated too much. The basic wind speed deduction should take joint probability distribution of wind speed and direction into consideration, and the shorter sample interval is the more economic and reasonable it is.A large scale digital terrain model including the bridge site and nearby weather stations was established in the paper. On the digital model, the bridge site wind environment was studied, and the results of it were compared with that of physical wind tunnel trail. A method to estimate the bridge design standard wind speed through the basic wind speed of weather station by CFD (computational fluid dynamics) technology was proposed, and be used to calculate the design standard wind speed of San-shui-he Bridge. The results show that the wind profiles of the numerical wind tunnel have a certain deviation with the physical wind tunnel results, yet the consistence of the two’s overall tendency is good. The complicated terrain of bridge site in mountainous area has great interference influence on the wind field. The wind profiles in different wind direction and different location have great variation, and part of them cannot meet the power exponent change laws. When coming wind is in consistent with valley direction, the wind profile of the bridge piers in down watercourse are close to that of B type terrain in codes. The bridge design standard wind speed at the same location might have great variation in different wind direction, and its distribution along the bridge length would be uneven even in the same wind direction.The aerostatic coefficients of different bridge cross sections under various wind attack angles or directions and the situation with or without guardrails were studied by CFD. The results were compared with that of physical wind tunnel trail, and the change laws of the aerostatic coefficients with different influential factors were summarized. On this bases, the aerodynamic interference mechanism of double width bridge was explored, and the effects of different interference factors on aerostatic coefficients of the bridge in up and down stream were summarized. The results show that the aerostatic coefficients gained by CFD have high accuracy in upstream bridge resistance coefficient and relatively larger error in downstream bridge resistance coefficient and lift coefficient and torque coefficient of bridge in up and down stream. However, the overall results are in good agreement with the physical wind tunnel test results. For resistance coefficients, the effect of coming wind to upstream bridges is strong push, and to downstream bridges is relatively weak suction. It is affected small by wind attack angle, and becomes bigger with increase of the girder section’s height, and be affected largely by guardrail. Lift coefficients in up and down stream and torque coefficients will change with the influence of the wind attack angle (or wind direction), dimension of section, guardrail and other factors. The aerodynamic interference effect has great impact on double width downstream bridge. On the whole, the change rule of interference effect with wind attack angle is not very clear, but increase with the decrease of the gap and increase with the growth of the structure sizes. The aerodynamic interference effect has certain impact on upstream bridge, but the impact is relatively small.The differences of transverse wind load calculation about long-span continuous rigid frame bridges with tall piers in foreign and domestic standards were quantitatively analyzed and compared, and were further compared with buffeting analytical results by a numeric example. Based on the characteristic of tall pier continuous rigid frame bridge and its first model out-of-plane, considering average wind effects and background responses of fluctuating wind and its resonant responses as well, a practical analytical formulas was proposed in this paper, which aimed at calculating the equivalent wind loads of transverse bending moment and shear force of pier-bottom on continuous rigid frame bridge with tall piers. By two examples, the accuracy and applicability of simplified method were tested. Comparative analysis show that, because the fundamental frequency of the long-span continuous rigid frame bridge with tall piers is low, the resonant response effects should not be neglored. The wind load calculated using present code was generally underestimated due to the neglect of the resonant response effects. The wind loads on pier of high pier bridges, extra high pier bridges in particular, is very large, which impact on pier bottom internal force could even surpass the girder wind loads. It should be paid sufficient attention in design of these kinds of bridges.更多还原