scholarly journals Effects of Precast Cladding Systems on Dynamic Characteristics of Steel Frame Buildings by Ambient and Free Vibration Tests

2017 ◽  
Vol 2017 ◽  
pp. 1-20 ◽  
Author(s):  
Jun Ma ◽  
Shinji Nakata ◽  
Akihito Yoshida ◽  
Yukio Tamura
Keyword(s):  
Free Vibration ◽  
Dynamic Characteristics ◽  
Steel Frame ◽  
Ambient Vibration ◽  
Test Cases ◽  
Vibration Method ◽  
External Wall ◽  
Wide Range ◽  
Cladding Panels ◽  
Vibration Tests

Full-scale tests on a one-story steel frame structure with a typical precast cladding system using ambient and free vibration methods are described in detail. The cladding system is primarily composed of ALC (Autoclaved Lightweight Concrete) external wall cladding panels, gypsum plasterboard interior linings, and window glazing systems. Ten test cases including the bare steel frame and the steel frame with addition of different parts of the precast cladding system are prepared for detailed investigations. The amplitude-dependent dynamic characteristics of the test cases including natural frequencies and damping ratios determined from the tests are presented. The effects of the ALC external wall cladding panels, the gypsum plasterboard interior linings, and the window glazing systems on the stiffness and structural damping of the steel frame are discussed in detail. The effect of the precast cladding systems on the amplitude dependency of the dynamic characteristics and the tendencies of the dynamic parameters with respect to the structural response amplitude are investigated over a wide range. Furthermore, results estimated from the ambient vibration method are compared with those from the free vibration tests to evaluate the feasibility of the ambient vibration method.

scholarly journals Evaluation of Steel Stairwell Dynamic Characteristics, Under Few Mass Configurations Using Ambient Vibration Method

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Ahmad Fahmy Kamarudin ◽  
◽  
Shahrul Niza Mokhatar ◽  
Mohammad Soffi Md Noh ◽  
Mohammad Azim Mohd Sulaiman ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Ambient Vibration ◽  
Vibration Method

Determination of the dynamic characteristics of the Colquitz River Bridge by full-scale testing

1996 ◽  
Vol 23 (2) ◽  
pp. 536-548 ◽  
Author(s):  
C. E. Ventura ◽  
A. J. Felber ◽  
S. F. Stiemer
Keyword(s):  
British Columbia ◽  
Dynamic Characteristics ◽  
Field Tests ◽  
Free Vibrations ◽  
Full Scale ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Ambient Vibration Tests ◽  
Vibration Tests ◽  
Full Scale Tests

This paper presents the results of full-scale tests performed at the Colquitz River Bridge near Victoria, British Columbia (B.C.), Canada, during September 1992 to determine the dynamic characteristics of the structure. The five-span bridge was completed in 1954 and is part of the Trans-Canada Highway. It is 82.68 m long and 11.89 m wide, and has six continuous steel girders supporting a 175 mm thick concrete deck. This particular bridge was chosen for testing because of its typical nature of many B.C. bridges, its location in an area of high seismic risk, and its excellent site accessibility. The tests included extensive measurements of ambient vibrations induced by traffic and other sources to determine the dynamic characteristics of the bridge. The most significant vertical and lateral mode shapes and associated periods of vibration were determined from vibration measurements at more than 50 different locations of the deck, piers, and abutments. Although a large amount of data were collected, they were quickly processed and analyzed with an innovative system developed at The University of British Columbia. One of the important features of this system is that it permits the identification of the principal modes of vibration immediately after the data have been collected. In addition to the ambient vibration tests, quick release pullback tests were conducted to verify modal frequencies determined from the ambient vibration tests and to determine the damping of the fundamental modes. These tests consisted of loading the bridge at a selected location with a force of about 90 kN and then releasing this load very quickly to induce free vibrations. The information obtained from the field tests was used to refine a computer finite element model of the bridge, which, in turn, was used to gain insight into the dynamic behaviour of specific components of the bridge. Further, this information was used later by the bridge owner to evaluate the bridge's expected response during an earthquake. Key words: steel bridges, dynamic response, full-scale tests.

Modal parameter identification of a long-span footbridge by forced vibration experiments

2017 ◽  
Vol 20 (5) ◽  
pp. 661-673 ◽  
Author(s):  
Q Wen ◽  
XG Hua ◽  
ZQ Chen ◽  
JM Guo ◽  
HW Niu
Keyword(s):  
Free Vibration ◽  
Frequency Response ◽  
Forced Vibration ◽  
Ambient Vibration ◽  
Modal Parameters ◽  
Response Functions ◽  
Modal Parameter ◽  
Modal Parameter Identification ◽  
Cable Stayed Bridge ◽  
Vibration Tests

Performing forced vibration tests on full-scale structures is the most reliable way of determining the relevant modal parameters in structural dynamics, such as modal frequencies, mode shapes, modal damping, and modal masses. This study describes the modal identification of a double-level curved cable-stayed bridge with separate deck systems for pedestrians and vehicles via forced vibration tests. The steady-state structural responses to sinusoidal excitations produced by an electrodynamic shaker are recorded under varying excitation frequencies, and the frequency response functions are established. The measured frequency response functions are curve fitted to estimate the modal parameters. The numerical simulation of frequency response function–based modal parameter identification of an elastically multi-supported continuous beam structure is carried out, and the emphasis has been placed on the evaluation of the effect of an additional shaker mass, excitation frequency step and range, multi-mode vibration, and noise on identification results. Finally, the modal parameters for the first lateral mode of a double-level curved cable-stayed bridge are identified by forced vibration experiments, and the results are compared with those from ambient vibration tests and free vibration tests. The effect of the unmeasured wind excitation on identification is discussed. It is shown that the effect of ambient vibration is minor for wind velocity of 3–5 m/s. The damping ratios identified by forced and free vibration tests are comparable, while those from ambient vibration are subject to large variations. The modal mass obtained from forced vibration tests is in good agreement with finite element prediction, which provides design basis for mass-type dampers.

scholarly journals EXPERIMENTAL STUDIES OF A STEEL FRAME MODEL WITH AND WITHOUT BUCKLING-RESTRAINED BRACES

2016 ◽  
pp. 33-52 ◽  
Author(s):  
Héctor Guerrero Bobadilla ◽  
Tianjian Ji ◽  
José Alberto Escobar
Keyword(s):  
Free Vibration ◽  
White Noise ◽  
Experimental Studies ◽  
Steel Frame ◽  
Shaking Table ◽  
Shaking Table Tests ◽  
Frame Model ◽  
Seismic Input ◽  
Low Intensity ◽  
Vibration Tests

This paper presents comparative experimental studies of a five-storey steel-frame model at a scale of 1/10 with, and without, buckling-restrained braces (BRBs). The building model was subjected to free vibration tests and shaking table tests. The latter were conducted using low-intensity white noise and seismic input. From the free vibration tests and shaking table tests with low-intensity white noise, it was found that the BRBs contributed a significant amount of damping. This happened to the model even at low levels of vibration. The shaking table tests with seismic input were conducted using seven earthquake records, taken in the lakebed zone of Mexico City with seismic intensities from pga=0.1g to 0.25g. At an intensity of pga=0.1g, the results show that the model fitted with BRBs had a significantly smaller response than the bare model, in terms of displacement, inter-storey drift, floor velocity and floor acceleration. The higher intensities were only applied to the model fitted with BRBs. The results indicate that the model with BRBs was able to withstand about 2.5 times the seismic intensity of the bare model, in terms of lateral displacement, inter-storey drift and Arias Intensity, as a measure of the energy contents of the movement. At the end of the tests, all BRBs were removed and the model remained in its original undamaged state.

Theoretical Analysis and Experimental Identification of a Vibration Isolator With Widely-Variable Stiffness

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Zhan Hu ◽  
Xing Wang ◽  
Hongxiang Yao ◽  
Guangyuan Wang ◽  
Gangtie Zheng
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Nonlinear Dynamic ◽  
Variable Stiffness ◽  
Vibration Isolator ◽  
Practical Applications ◽  
Wide Range ◽  
Nonlinear Dynamic Characteristics ◽  
Vibration Tests ◽  
The Hilbert Transform

This paper develops an adjustable high-static-low-dynamic (AHSLD) vibration isolator with a widely variable stiffness. By adjusting deformations of its horizontal springs, the natural frequency of the isolator can be substantially changed starting from a quasi-zero value. In this paper, the nonlinear static and dynamic analyses of the AHSLD isolator are presented. Effects of horizontal adjustments on the variation range of the stiffness and nonlinear dynamic characteristics are investigated. Good performance of the stiffness variation is validated by free-vibration tests. The wide-range variable stiffness from 0.33 N/mm to 23.2 N/mm is achieved in tests, which changes the natural frequency of the isolator from an ultra-low value of 0.72 Hz to 5.99 Hz. Besides, its nonlinear dynamic characteristics are also experimentally identified by applying the Hilbert transform. Both analytical and experimental results demonstrate the weakly hardening nonlinearity in the tested AHSLD isolator, which will not degrade its performance in practical applications.

scholarly journals CubeSat’s Deployable Solar Panel with Viscoelastic Multilayered Stiffener for Launch Vibration Attenuation

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Shankar Bhattarai ◽  
Hongrae Kim ◽  
Hyun-Ung Oh
Keyword(s):  
Solar Cells ◽  
Free Vibration ◽  
Dynamic Characteristics ◽  
Random Vibration ◽  
Solar Panel ◽  
Structural Safety ◽  
Vibration Attenuation ◽  
Vibration Tests

Ensuring the structural safety of a deployable solar panel under a severe launch vibration environment is one of the important factors for a successful CubeSat mission. A CubeSat’s deployable solar panel proposed in this study is effective to guarantee the structural safety of solar cells by attenuating launch loads owing to the superior damping characteristic achieved by a multilayered stiffener with viscoelastic acrylic tapes. The demonstration model of 3 U CubeSat’s deployable solar panel was fabricated and tested to validate the effectiveness of the proposed design. The basic dynamic characteristics of the solar panel were measured through free-vibration tests according to the various layers of the stiffener. Moreover, the characteristics of the deployed solar panel were measured and investigated under various temperatures to predict its capability under in-orbit operation. The effectiveness of the proposed design for launch vibration attenuation was demonstrated through qualification level sine and random vibration tests.

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