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Vibration Tests (vibration + test)
Selected AbstractsA Comparative Study of Modal Parameter Identification Based on Wavelet and Hilbert,Huang TransformsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 1 2006Banfu Yan Special attention is given to some implementation issues, such as the modal separation and end effect in the WT, the optimal parameter selection of the wavelet function, the new stopping criterion for the empirical mode decomposition (EMD) and the end effect in the HHT. The capabilities of these two techniques are compared and assessed by using three examples, namely a numerical simulation for a damped system with two very close modes, an impact test on an experimental model with three well-separated modes, and an ambient vibration test on the Z24-bridge benchmark problem. The results demonstrate that for the system with well-separated modes both methods are applicable when the time,frequency resolutions are sufficiently taken into account, whereas for the system with very close modes, the WT method seems to be more theoretical and effective than HHT from the viewpoint of parameter design. [source] The value of the Rydel-Seiffer tuning fork as a predictor of diabetic polyneuropathy compared with a neurothesiometerDIABETIC MEDICINE, Issue 6 2004T. Kästenbauer Abstract Aims The aim of the study was to investigate the predictive value of the Rydel-Seiffer tuning fork for detecting diabetic neuropathy and to compare it with an electronic neurothesiometer. Methods In 2022 consecutive diabetic subjects, peripheral polyneuropathy was diagnosed by vibration perception threshold (VPT) at the tip of both great toes using a 128-Hz tuning fork and a neurothesiometer, by simple bedside tests and by the presence of neuropathic symptoms. These evaluations were further combined to diagnose peripheral nerve dysfunction (abnormal bedside tests) and symptomatic neuropathy. VPT was also measured in 175 non-diabetic control subjects to define normal values. Results VPT was normal in 1917 subjects and abnormal in 105 (5.2%) patients when measured by the tuning fork. Patients with an abnormal vibration test were significantly (P < 0.0001) older than subjects with a normal vibration sense, while diabetes duration and HbA1c of the former were also significantly elevated. The same was true for the percentages of an abnormal 10-g monofilament test (66.7% vs. 7.2%, P < 0.0001) and a missing Achilles' tendon reflex (68.6% vs. 24.8%, P < 0.0001). Finally, the VPT measured by the neurothesiometer was 2.5 times higher in patients with an abnormal tuning fork test (32.0 ± 9.8 vs. 12.5 ± 6.4 V, P < 0.0001). The plot of the difference of both methods against their mean yielded a good agreement of the two VPT measurements, and the tuning fork had a high sensitivity and positive predictive value for the diagnosis of abnormal bedside tests and for symptomatic neuropathy. Conclusion The tuning fork reliably detected peripheral neuropathy in comparison with the neurothesiometer. A tuning fork is a useful screening test for diabetic neuropathy. [source] Numerical simulation of reservoir sediment and effects on hydro-dynamic response of arch damsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2001Chuhan Zhang Abstract Based on the dynamic theory for saturated porous media by Biot (Journal of the Acoustical Society of America 1956; 28: 168,178), a numerical model is presented to analyse the reflection behaviours of reservoir sediment and compared with those from the visco-elastic model. It is concluded that the two models give very similar results of reflection coefficient , within the frequency range of interest. Then, using the two models, the change of the reflection coefficients , with various sedimentation parameters and excitation frequencies are studied in detail. The results are further used in the analysis of response functions of hydro-dynamic pressures on, and structural displacements of the Xiang Hong Dian arch dam, for which some results from a field vibration test are available. It appears that effects of water compressibility with sediment reflection on hydro-dynamic pressures and structural response are not significant for this specific case. Copyright © 2001 John Wiley & Sons, Ltd. [source] A frequency domain technique for maintaining resonance condition during sine dwell vibration testing of packagesPACKAGING TECHNOLOGY AND SCIENCE, Issue 6 2000Vincent Rouillard Abstract When a package undergoes progressive damage during a sine dwell vertical vibration test, its dynamic characteristics, such as stiffness and damping, will change. This will result in variation of its resonance frequency during a test. This paper demonstrates that tracking the resonance by feedback control of the excitation frequency during resonance dwell tests is essential. Furthermore, this paper shows the differences in the results obtained from dwell tests with uncontrolled and controlled excitation frequencies. A computer-based resonance tracking system was developed and used together with a commercial vibration table to experimentally verify the benefits of such a technique. Copyright,©,2000 John Wiley & Sons, Ltd. [source] HDR devices for the seismic protection of frame structures: Experimental results and numerical simulationsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2009Laura Ragni Abstract As part of a national research programme an experimental campaign was carried out on a real scale mock-up consisting of a steel,concrete composite frame equipped with dissipative bracings, based on high damping rubber (HDR) devices. Free vibration tests, followed by force-controlled and displacement-controlled cyclic tests were performed. The experimental tests were aimed at studying the dynamic response of the coupled system in order to demonstrate the effectiveness of HDR devices in increasing the stiffness and dissipation capacity of the frame and investigating the ability of the constitutive HDR model proposed by the authors to predict the dynamic response of the coupled system. Copyright © 2009 John Wiley & Sons, Ltd. [source] A buffered impact damper for multi-degree-of-freedom structural controlEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2008Kuinian Li Abstract The results of an experimental investigation into the use of a buffered impact damper for controlling the dynamic response of an MDOF (multi-degree-of-freedom) structure are presented in this paper. Free and forced vibration tests of a three-DOF test structure equipped with a buffered impact damper are performed to evaluate the resulting damping effect and impact characteristics. The effect of damper parameters, such as clearance, and excitation type on the performance of the impact damper is also investigated. The performance of the buffered impact damper is compared with that of an equivalent conventional rigid impact damper. It is found that the buffered impact damper not only significantly reduces the peak contact force and the associated accelerations and noise generated by collisions but can also substantially enhance the damping effect over a wide range of frequencies, encompassing the natural frequencies of the test structure. Copyright © 2008 John Wiley & Sons, Ltd. [source] System identification applied to long-span cable-supported bridges using seismic recordsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2008Dionysius M. Siringoringo Abstract This paper presents the application of system identification (SI) to long-span cable-supported bridges using seismic records. The SI method is based on the System Realization using Information Matrix (SRIM) that utilizes correlations between base motions and bridge accelerations to identify coefficient matrices of a state-space model. Numerical simulations using a benchmark cable-stayed bridge demonstrate the advantages of this method in dealing with multiple-input multiple-output (MIMO) data from relatively short seismic records. Important issues related to the effects of sensor arrangement, measurement noise, input inclusion, and the types of input with respect to identification results are also investigated. The method is applied to identify modal parameters of the Yokohama Bay Bridge, Rainbow Bridge, and Tsurumi Fairway Bridge using the records from the 2004 Chuetsu-Niigata earthquake. Comparison of modal parameters with the results of ambient vibration tests, forced vibration tests, and analytical models are presented together with discussions regarding the effects of earthquake excitation amplitude on global and local structural modes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Identification of structural and soil properties from vibration tests of the Hualien containment modelEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2005J. Enrique Luco Abstract Measurements of the response of the ¼-scale reinforced concrete Hualien (Taiwan) containment model obtained during forced vibration tests are used to identify some of the characteristics of the superstructure and the soil. In particular, attempts are made to determine the fixed-base modal frequencies, modal damping ratios, modal masses and participation factors associated with translation and rocking of the base. The shell superstructure appears to be softer than could have been predicted on the basis of the given geometry and of test data for the properties of concrete. Estimates of the shear-wave velocity and damping ratio in the top layer of soil are obtained by matching the observed and theoretical system frequency and peak amplitude of the response at the top of the structure. The resulting models for the superstructure and the soil lead to theoretical results for the displacement and rotations at the base and top of the structure which closely match the observed response. Copyright © 2004 John Wiley & Sons, Ltd. [source] Dynamic performance of twin curved cable-stayed bridgesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2004C. Gentile Abstract The dynamic behaviour of two curved cable-stayed bridges, recently constructed in northern Italy, has been investigated by full-scale testing and theoretical models. Two different excitation techniques were employed in the dynamic tests: traffic-induced ambient vibrations and free vibrations. Since the modal behaviour identified from the two types of test are very well correlated and a greater number of normal modes was detected during ambient vibration tests, the validity of the ambient vibration survey is assessed in view of future monitoring. For both bridges, 11 vibration modes were identified in the frequency range of 0ndash;10Hz, being a one-to-one correspondence between the observed modes of the two bridges. Successively, the information obtained from the field tests was used to validate and improve 3D finite elements so that the dynamic performance of the two systems were assessed and compared based on both the experimental results and the updated theoretical models. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||