跨度128 m高速铁路系杆拱桥拱肋拟合预拱度研究

高速铁路系杆拱桥拱肋预拱度的设置方法决定着成桥后拱肋的线形及全桥受力情况。本文提出了一种新的拟合预拱度设置方法,弥补了规范中有支架悬链线拱肋施工预拱度设置的空缺。该方法所得数值与利用桥梁光电挠度仪进行现场实时监测得到的挠度相符,准确性高且保留了悬链线线形,便于施工。使用MIDAS/Civil建立有限元施工仿真模型计算在吊杆张拉工况下L/2拱肋各控制点考虑各种影响因素设置的预拱度,进一步验证了新的拟合预拱度设置方法。     

钢管混凝土系杆拱桥拱肋及吊杆施工监控

以在建郑州—万州铁路河南段一座128 m钢管混凝土系杆拱桥为工程实例,介绍了施工中拱肋及吊杆的监控要点。选取拱肋线形、拱肋应力、吊杆索力作为主要的监控对象,通过有限元分析,选取了拱脚、1/4拱、拱顶作为拱肋线形、应力的监控截面。根据工程实际情况,选择合适的仪器(HF-5B型桥梁光电挠度仪)进行数据采集,提高了测量精度。同时,结合虚功原理运用MIDAS/Civil建立了考虑现场实际的全桥仿真模型,获得了经实测数据验证的吊杆张拉影响矩阵,用于指导吊杆张拉,并将各施工阶段的实测值与有限元计算值进行对比,指导现场施工。结果表明,各施工阶段的拱肋线形、应力及调整后的吊杆索力均在合理范围之内,满足设计要求。     

Bandgap optimization for chiral acoustic metamaterials based on material selection method北大核心CSCD

［Objectives］This study seeks to expand the bandgap frequency band, reduce the bandgap starting frequency and analyze and optimize the bandgap parameters of acoustic metamaterials. ［Methods］The influence of geometrical and material parameters on the bandgap properties of acoustic metamaterials is analyzed, and a method for maximizing the bandgap width is proposed. The multi-objective optimization problem is converted into a single objective optimization problem by normalizing the bandgap frequency coefficients. Structural material conversion is achieved via the material selection optimization method, and the optimization equations of bandgap parameters are established on the basis of weight-lightening. For chiral acoustic metamaterials, the material properties (density and wave velocity) and geometric parameters (scatterer diameter, ligament thickness and coating thickness) are defined as design variables, and the comprehensive optimization of structural parameters and material selection of acoustic metamaterials based on weight-lightening are implemented. ［Results］The optimization results show that the bandgap width increases by 27.7% and the lower bound frequency decreases by 1048 Hz, thereby achieving the goal of expanding the bandgap width based on lightweight acoustic metamaterials. The acoustic transmission analysis of the finite chiral acoustic metamaterial structure is then carried out to verify the effectiveness of the proposed method. ［Conclusions］The results show that the goal of lightweight acoustic metamaterials can be effectively achieved by integrating the comprehensive optimization of structural parameters and materials. As such, this study provides references for the design of new-type acoustic metamaterials. © 2023 Authors. All rights reserved.