Field measurement of strong wind characteristics is of great significance for the development of bridge wind engineering. Located in east China, the Runyang Suspension Bridge (RSB) with a main span of 1490 m is the lo...Field measurement of strong wind characteristics is of great significance for the development of bridge wind engineering. Located in east China, the Runyang Suspension Bridge (RSB) with a main span of 1490 m is the longest bridge in China and the third longest in the world. During the last four years, the RSB has suffered from typhoons and strong northern winds on more than ten occasions. To determine the strong wind characteristics of the RSB, wind measurement data obtained from field tests during strong winds and data from the wind environment monitoring subsystem of the structural health monitoring system (SHMS) of the RSB were combined to analyze the wind speed and direction, variation in wind speed with height, turbulence intensity, turbulence integral length, wind friction speed and the power spectrum. Comparative studies on the characteristics of these different strong winds were carried out based on the current wind-resistant design specification for highway bridges. Results showed that some regularity in wind characteristics can be found in these different typhoons passing through the RSB. The difference between a strong northern wind and a typhoon is relatively clear, and in summer the typhoon is the dominant wind load acting on the RSB. In addition, there were some differences between the measured strong wind characteristics and the values suggested by the specification, especially in respect to turbulence intensity and turbulence integral length. Results provide measurement data for establishing a strong wind characteristic database for the RSB and for determining the strong wind characteristic parameter values of this coastal area in east China.展开更多
The wind-rain induced vibration phenomena in the Dongting Lake Bridge (DLB) can be observed every year, and the field measurements of wind speed data of the bridge are usually nonstationary. Nonstationary wind speed c...The wind-rain induced vibration phenomena in the Dongting Lake Bridge (DLB) can be observed every year, and the field measurements of wind speed data of the bridge are usually nonstationary. Nonstationary wind speed can be decomposed into a deterministic time-varying mean wind speed and a zero-mean stationary fluctuating wind speed component. By using wavelet transform (WT), the time-varying mean wind speed is extracted and a nonstationary wind speed model is proposed in this paper. The wind characteristics of turbulence intensity, integral scale and probability distribution of the bridge are calculated from the typical wind samples recorded by the two anemometers installed on the DLB using the proposed nonstationary wind speed model based on WT. The calculated results are compared with those calculated by the empirical mode decomposition (EMD) and traditional approaches. The compared results indicate that the wavelet-based nonstationary wind speed model is more reasonable and appropriate than the EMD-based nonstationary and traditional stationary models for characterizing wind speed in analysis of wind-rain-induced vibration of cables.展开更多
为了研究复杂地形的风场特性,同时获得实际桥址处的风参数,以喇叭口河谷地形为研究对象,进行了为期6个月的现场实测。河流在该区域由山区进入平坦地区,因此该类河谷既有山区峡谷特点又有平原的地貌特点,地形地貌复杂。实测过程中使用三...为了研究复杂地形的风场特性,同时获得实际桥址处的风参数,以喇叭口河谷地形为研究对象,进行了为期6个月的现场实测。河流在该区域由山区进入平坦地区,因此该类河谷既有山区峡谷特点又有平原的地貌特点,地形地貌复杂。实测过程中使用三维扫描式激光雷达在河谷内进行多点观测,依托当地1座双塔斜拉桥进行测点布置。沿桥轴线方向每隔141 m设置1个虚拟测风塔,总计4个虚拟测风塔,即可得到这4个测点处的风速剖面。最终得到喇叭口河谷内不同位置的风剖面,以及不同位置、不同高度处的平均风速和风向,分析得到该地形下的风场特性。研究结果表明:在一定高度处风速有加速现象,此现象主要发生于河谷中下部,其成因与来流风向变化及地形有关;喇叭口河谷地形风剖面比《公路桥梁抗风设计规范》(JTG T 3360-01—2018)(简称规范)所列的模型复杂,难以用现有模型进行描述,但仍可以用幂函数进行描述;受来流及周围地形地貌影响,高风速时桥面高度处跨中位置的风速要大于两侧风速;桥面高度处不同位置的风向受来流方向和地形的影响存在差异;大气风向为西北方时,谷内风向角由近地面到高空变化较大,大气风向为东南方时,谷内风向角垂直方向上差异较小。所得观测结果与目前规范对风特性的描述存在较大差异,可对规范内容进行补充,同时也可为复杂地形下的风特性预测提供参考。展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 50725828, 50908046, and 50978056)the National Science & Technology Pillar Program (No. 2006BAJ03B05)the PhD Program Foundation of MOE (No. 200802861012), China
文摘Field measurement of strong wind characteristics is of great significance for the development of bridge wind engineering. Located in east China, the Runyang Suspension Bridge (RSB) with a main span of 1490 m is the longest bridge in China and the third longest in the world. During the last four years, the RSB has suffered from typhoons and strong northern winds on more than ten occasions. To determine the strong wind characteristics of the RSB, wind measurement data obtained from field tests during strong winds and data from the wind environment monitoring subsystem of the structural health monitoring system (SHMS) of the RSB were combined to analyze the wind speed and direction, variation in wind speed with height, turbulence intensity, turbulence integral length, wind friction speed and the power spectrum. Comparative studies on the characteristics of these different strong winds were carried out based on the current wind-resistant design specification for highway bridges. Results showed that some regularity in wind characteristics can be found in these different typhoons passing through the RSB. The difference between a strong northern wind and a typhoon is relatively clear, and in summer the typhoon is the dominant wind load acting on the RSB. In addition, there were some differences between the measured strong wind characteristics and the values suggested by the specification, especially in respect to turbulence intensity and turbulence integral length. Results provide measurement data for establishing a strong wind characteristic database for the RSB and for determining the strong wind characteristic parameter values of this coastal area in east China.
文摘The wind-rain induced vibration phenomena in the Dongting Lake Bridge (DLB) can be observed every year, and the field measurements of wind speed data of the bridge are usually nonstationary. Nonstationary wind speed can be decomposed into a deterministic time-varying mean wind speed and a zero-mean stationary fluctuating wind speed component. By using wavelet transform (WT), the time-varying mean wind speed is extracted and a nonstationary wind speed model is proposed in this paper. The wind characteristics of turbulence intensity, integral scale and probability distribution of the bridge are calculated from the typical wind samples recorded by the two anemometers installed on the DLB using the proposed nonstationary wind speed model based on WT. The calculated results are compared with those calculated by the empirical mode decomposition (EMD) and traditional approaches. The compared results indicate that the wavelet-based nonstationary wind speed model is more reasonable and appropriate than the EMD-based nonstationary and traditional stationary models for characterizing wind speed in analysis of wind-rain-induced vibration of cables.
文摘为了研究复杂地形的风场特性,同时获得实际桥址处的风参数,以喇叭口河谷地形为研究对象,进行了为期6个月的现场实测。河流在该区域由山区进入平坦地区,因此该类河谷既有山区峡谷特点又有平原的地貌特点,地形地貌复杂。实测过程中使用三维扫描式激光雷达在河谷内进行多点观测,依托当地1座双塔斜拉桥进行测点布置。沿桥轴线方向每隔141 m设置1个虚拟测风塔,总计4个虚拟测风塔,即可得到这4个测点处的风速剖面。最终得到喇叭口河谷内不同位置的风剖面,以及不同位置、不同高度处的平均风速和风向,分析得到该地形下的风场特性。研究结果表明:在一定高度处风速有加速现象,此现象主要发生于河谷中下部,其成因与来流风向变化及地形有关;喇叭口河谷地形风剖面比《公路桥梁抗风设计规范》(JTG T 3360-01—2018)(简称规范)所列的模型复杂,难以用现有模型进行描述,但仍可以用幂函数进行描述;受来流及周围地形地貌影响,高风速时桥面高度处跨中位置的风速要大于两侧风速;桥面高度处不同位置的风向受来流方向和地形的影响存在差异;大气风向为西北方时,谷内风向角由近地面到高空变化较大,大气风向为东南方时,谷内风向角垂直方向上差异较小。所得观测结果与目前规范对风特性的描述存在较大差异,可对规范内容进行补充,同时也可为复杂地形下的风特性预测提供参考。
