To study the additional aerodynamic effect on a bridge girder under the action of wind-driven rain, the rainfall similarity considering raindrop impact and surface water is first given. Then, the dynamic characteristi...To study the additional aerodynamic effect on a bridge girder under the action of wind-driven rain, the rainfall similarity considering raindrop impact and surface water is first given. Then, the dynamic characteristics and the process of vortex and flutter generation of the segment models under different rain intensities and angles of attack are tested by considering several typical main girder sections as examples. The test results indicate that the start and end wind speeds,interval length and number of vortex vibrations remain unchanged when it is raining, rainfall will reduce the windinduced vortex response. When test rain intensity is large, the decrease of amplitude is obvious. However, after considering the rain intensity similarity in this study, all of actual maximum rain intensities after conversion approach the domestic extreme rain intensity of approximately 709 mm/h. It can be observed that rainfall has a limited influence on the dynamic characteristics of the structure and vortex vibration response. When the test rain intensity is 120 mm/h, the critical wind speed of the model flutter increases by 20%-30%. However, after considering the rain intensity similarity ratio, the influence of rainfall on the wind-induced flutter instability of the bridge girder may be ignored.展开更多
A comparative study of two pre-stressed girder bridges, one with AASHTO （American Association of State Highway and Transportation Officials） Type III girders and the other with new FIB （Florida l-beam） girders, is...A comparative study of two pre-stressed girder bridges, one with AASHTO （American Association of State Highway and Transportation Officials） Type III girders and the other with new FIB （Florida l-beam） girders, is presented. FIB girders are expected to provide increased lateral stiffness, higher load carrying capacity, cost-efficiency and better reliability. In this paper, the first bridge that is analyzed is a 3-span bridge designed with six AASHTO Type III girders, and the second bridge has four FIB girders with the same span length, width and girder depth. The bridges are analyzed for Florida state legal loads SU4 and C5. Both bridges are analyzed using a sophisticated finite element method. The deflections, moment envelopes, section capacity and live load rating of the two bridges are obtained and compared. FIB girders have higher vertical stiffness, higher section capacity providing higher load rating than the AASHTO girders.展开更多
针对现有门式起重机主梁挠度测量方法存在操作复杂、不够安全、停机检测时间长和精度不稳定等问题,文章提出一种基于双目摄影测量的主梁挠度快速、安全与精准测量方法。相机标定是双目摄影测量精度的最重要影响之一,在传统灰狼算法(grey...针对现有门式起重机主梁挠度测量方法存在操作复杂、不够安全、停机检测时间长和精度不稳定等问题,文章提出一种基于双目摄影测量的主梁挠度快速、安全与精准测量方法。相机标定是双目摄影测量精度的最重要影响之一,在传统灰狼算法(grey wolf optimizer,GWO)中引入余弦函数收敛因子以提升算法的全局和局部搜索能力,并使用基于欧式距离的比例权重策略加快算法收敛速度,获得改进灰狼算法(improved grey wolf optimizer,IGWO)。将改进算法应用于双目相机的标定参数寻优中,获得最优标定值。通过仿真与现场试验进行验证,结果表明:该方法标定精确且快速,挠度检测误差在1%以内,满足门式起重机挠度的工程测量要求。展开更多
基金Projects(20B062,19B054)supported by Excellent Youth Program of Hunan Education Department,ChinaProject(2019JJ50688)supported by Hunan Provincial Natural Science Foundation of ChinaProject(kq195004)supported by Changsha Science and Technology Bureau Project,China。
文摘To study the additional aerodynamic effect on a bridge girder under the action of wind-driven rain, the rainfall similarity considering raindrop impact and surface water is first given. Then, the dynamic characteristics and the process of vortex and flutter generation of the segment models under different rain intensities and angles of attack are tested by considering several typical main girder sections as examples. The test results indicate that the start and end wind speeds,interval length and number of vortex vibrations remain unchanged when it is raining, rainfall will reduce the windinduced vortex response. When test rain intensity is large, the decrease of amplitude is obvious. However, after considering the rain intensity similarity in this study, all of actual maximum rain intensities after conversion approach the domestic extreme rain intensity of approximately 709 mm/h. It can be observed that rainfall has a limited influence on the dynamic characteristics of the structure and vortex vibration response. When the test rain intensity is 120 mm/h, the critical wind speed of the model flutter increases by 20%-30%. However, after considering the rain intensity similarity ratio, the influence of rainfall on the wind-induced flutter instability of the bridge girder may be ignored.
文摘A comparative study of two pre-stressed girder bridges, one with AASHTO （American Association of State Highway and Transportation Officials） Type III girders and the other with new FIB （Florida l-beam） girders, is presented. FIB girders are expected to provide increased lateral stiffness, higher load carrying capacity, cost-efficiency and better reliability. In this paper, the first bridge that is analyzed is a 3-span bridge designed with six AASHTO Type III girders, and the second bridge has four FIB girders with the same span length, width and girder depth. The bridges are analyzed for Florida state legal loads SU4 and C5. Both bridges are analyzed using a sophisticated finite element method. The deflections, moment envelopes, section capacity and live load rating of the two bridges are obtained and compared. FIB girders have higher vertical stiffness, higher section capacity providing higher load rating than the AASHTO girders.
文摘针对现有门式起重机主梁挠度测量方法存在操作复杂、不够安全、停机检测时间长和精度不稳定等问题,文章提出一种基于双目摄影测量的主梁挠度快速、安全与精准测量方法。相机标定是双目摄影测量精度的最重要影响之一,在传统灰狼算法(grey wolf optimizer,GWO)中引入余弦函数收敛因子以提升算法的全局和局部搜索能力,并使用基于欧式距离的比例权重策略加快算法收敛速度,获得改进灰狼算法(improved grey wolf optimizer,IGWO)。将改进算法应用于双目相机的标定参数寻优中,获得最优标定值。通过仿真与现场试验进行验证,结果表明:该方法标定精确且快速,挠度检测误差在1%以内,满足门式起重机挠度的工程测量要求。
