Papers by Keyword: Ambient Excitation

Abstract: Prefabricated house is a new kind of temporary structure. It has the advantages of extensibility and diversity, and it is also easy to assemble and disassemble. This paper performed the dynamic characteristic test of 4 prefabricated houses of light-weight steel structure on the site by using SVSA, and got the natural frequencies, damping ratios and vibrational modes of these structures. To study the effects of infill walls to the dynamic characteristic of structures, two different modes were built. By comparing the results of numerical evaluation and actual data, the paper analyzed the dynamic characteristic of prefabricated houses of light-weight steel structure. Analysis suggests that the vibrational modes of prefabricated houses of light-weight steel structure are in shear shape, and the damping ratios are between 0.6% and 2%. The infill walls and the pull rods between columns can shorten the natural period of structures, so the computation period should be reduced in the aseismatic design.

Abstract: Modal identification technique is an effective measure of health diagnosis, structural rehabilitation, retrofitting and strengthening or optimization design of structures and materials in structural engineering field. The modal identification theories of random decrement technique and time-series method under ambient excitation are presented in this paper. The two methods are combined to become a joint algorithm for identifying modal parameters effectively. The numerical simulations of a three-layer architecture are carried out to verify the feasibility and practicability of the joint algorithm.

Abstract: This paper introduces the modal parameter identification method of a reinforced concrete block foundation under ambient excitation. On this basis, the dynamic characteristics of a stone cutting machine foundation are obtained by modal test under different operating conditions, and test results reveal that the main cause of abnormal vibration lies in lower dynamic stiffness of the whole structure. With the comparison of dynamic response between pre-reinforcement and post-reinforcement, reinforcement effects of high pressure grouting technique and pre-stressed bolt applied to restrain foundation vibration are verified effectively.

Abstract: To study validity of power spectrum density peak method which be used to identified modal parameter of concrete bridge under ambient excitation, number simulation of one Pre-stressed concrete bridge is carried out.3D model of the bridge is established by FEM software , FEM analysis and time-history analysis of 3D model of PC continuous beam bridge are carried out.During the simulation,practical factors such as acceleration measuring and white noise are taken into account. In the only case of the output signal modal parameter of bridge can be identified. Six-order modal parameters of the structure are identified by the number simulation which the average error is less than 5%. It is revealed that power spectrum density peak method is suitable for bridges monitoring and diagnosis, with important practical engineering application value.

Abstract: Dynamic test of double curved arch bridge based on environmental incentives. And Peak value method stochastic subspace identification method is used for modal analysis, and bridge modal parameters are obtained. The results were compared with the finite element software Midas civil, and results are consistent. The test shows that the bridge modal parameters can be identified in the environmental stimulus response. Measured frequency is lower than the finite element calculation of frequency; it means the bridge stiffness is lower. The identified dynamic properties can be served as the basis in the finite element model updating, damage detection, condition assessment and health monitoring of the bridge.

Abstract: In the condition of environmental excitation and the modal parameters can be identified to only use response data. Based on the improved stochastic subspace identification method, can avoid the fitting error from asynchronous samples, which can integrate asynchronous multi-groups response samples into synchronous pulsing response data, Finally, the identification results of different system order number was utilized to construct stable map to acquire more accurate identification and avoid lost root or duplicate root than the conventional method.

Abstract: A ship is a large and multifunctional marine structure operating on the sea. In practice, the environmental noise on a ship has many complicated components and they influence the vibration of the ship structure. Besides the stochastic excitations such as waves and winds, there are also propeller- and host-induced harmonic excitations. In this paper, NExT/ERA algorithm program and a ship model have been made to realize the modal parameters identification of ship structure in the presence of both white noise and harmonic excitations. Moreover, whether the signal filtering technology has a great effect on the results of modal analysis is discussed. In order to study and analyze the influence of the harmonic excitations, experiments under different signal-to-noise ratio (SNR) conditions have been carried out. This has a guiding significance to the engineering practice.

Abstract: Abstract: A vibration analysis of light flexible steel footbridge is investigates in this paper, which is based on dynamic testing. The finite element model of the footbridge was established. In this paper the reason is also analyzes which causes the vibration characteristic from the ambient excitation and its own structural features. Key words: Footbridge; Vibration Analysis; Dynamic Testing; Modal Analysis; Ambient Excitation;

Abstract: Pipelines are regarded as the most cost-effective and the safest choice for transporting oil in bulk. In this study, the significance and necessity of conducting damage detection for onshore pipelines is firstly stated. Then, the limitations of current measures in use in pipeline industry and the inherent difficulty of applying vibration-based damage detection techniques (VBDT) to pipeline structures are addressed. This study focuses on exploring the applicability of an advanced VBDT method, HHT method, to the condition assessment of onshore pipelines. The feasibility and effectiveness of HHT method is verified through numerical study. The result shows that for the cases with single or multi segments of damage which are of the same type or of different types coexist in the structure, the HHT method is capable of providing very good results for the damage detection of pipeline system under ambient excitations. The obtained Hilbert spectrum gives very explicit presentation of the structural response’s energy distribution in both time and frequency domain, the marginal spectrum offers satisfactory result not only for locating the damaged area but also for a rough estimate of damage severity.

Abstract: With the continuous development of national economy and the construction technology, a lot of large-span spatial structures with unique form and complex construction are emerging. The health monitoring system that mainly used in bridge structure is applied in large-span spatial structures gradually. Parameter identification and damage alarming are the core technology of health monitoring. In this paper some structural modal parameter identification methods based on ambient excitation are introduced. Finally, for large span structures with characteristics of low-intensive modes, the response data based on large span structures for modal parameter identification method was summed up, and the critical issues for further research in this field are also presented.