桥梁自振特性与承载能力分析

桥梁结构自振特性与结构承载能力有着内在联系;自振频率与桥跨刚度、结构挠度检验系数存在一定关系。通过结构响应模态振型振幅的比较,可以对结构横向联系使用状况进行损伤识别。通过实测桥梁结构阻尼比的变化,可以对结构边界条件、结构材料阻尼特性的改变进行分析判断。本文结合两座桥梁自振特性的跟踪测试,对桥梁自振特性和承载能力之间的关系进行分析。     

采用振冲碎石桩处理软基的方法

文章介绍了振冲碎石桩在某软弱地基置换加固中的成功应用,为今后类似地基采用振冲碎石桩进行置换加固的设计、施工与检测提供经验。     

Comparison of vibration response prediction on the main deck of a catamaran using experimental,numerical and correlated mode shapes

This work analyses the influence of three types of modal matrices on the prediction of vibration response (virtual sensing), at unmeasured degree of freedoms (DOFs), on a catamaran’s main deck: (1) uncorrelated finite element (FE), (2) correlated FE and (3) experimental modal matrices.A multi-objective genetic algorithm (MOGA) framework was developed to handle the optimization and prediction processes. This framework introduces a new metric called Time–Frequency-Error Response Assurance Criteria (TFERAC) to assess the prediction quality. This metric also allows estimating the best set of modal acceleration vectors, which is a critical step in the virtual sensing process.As a case study, only 06 accelerometers and 13 vibration modes (within each modal matrix) were used in the virtual sensing. The MOGA framework’s performance was evaluated using a variance analysis test (ANOVA) between measured and predicted response signals.Results showed that: (1) any one of the modal matrices could be used successfully for virtual sensing on the main deck, that is, there is no need to use correlated FE or experimental modal matrices; (2) the newly proposed metric TFERAC leads to smaller errors in the prediction of both vibration time series and vibration spectra;(3) it is possible to perform a virtual sensing on a ship’s main deck using a limited number of sensors and a numerical modal matrix without being correlated with experimental data.     

Modeling and calculation of acoustic radiation of underwater stiffened cylindrical shells treated with local damping

Damping materials are widely used and playing an essential role in reducing the vibration and noise of various ships and underwater vehicles. In practical engineering, damping materials are often applied over the structural surface of ships and underwater vehicles. They are generally distributed not evenly in the whole area, but locally in some vital regions. The stiffened cylindrical shell is the most representative configuration for the main structure of underwater vehicles. Therefore, research on modeling and calculation of underwater acoustic radiation from stiffened cylindrical shells locally treated with damping has high practical value. This paper introduces a mixed analytical-numerical acoustic-vibration interaction method to achieve efficient calculation of the vibration and acoustic radiation from a locally damped cylindrical shell immersed in water. Two kinds of vibration and noise reduction measures are proposed for the damping treatment of a large-scale stiffened cylindrical shell structure. Calculation and analysis are carried out for both measures. The results can provide reference for developing the technology of reducing vibration and noise from ships and underwater vehicles via damping treatment.