Impact Vibration Test Research Articles

Development of Indicator for Piled Pier Health Evaluation in Vietnam Using Impact Vibration Test Approach

Development of Indicator for Piled Pier Health Evaluation in Vietnam Using Impact Vibration Test Approach

Condition Monitoring and Quantitative Evaluation of Railway Bridge Substructures Using Vehicle-Induced Vibration Responses by Sparse Measurement

Bridge substructure failure has been responsible for numerous recorded bridge collapses, particularly for small- and medium-span bridges, so it is crucial to effectively monitor the performance of the bridge substructures for efficient maintenance and management. The current vibration-based approaches for quantitatively evaluating bridge substructures rely on in-situ experiments with a multitude of sensors or impact vibration test, making it challenging to implement long-term online monitoring. This paper proposes an accurate, low cost, and practicable method to achieve online quantitative monitoring of railway bridge substructures using only one vibration sensor and operational train-induced vibration responses. The newly derived flexible-base Timoshenko beam models, along with the random decrement technique and Levenberg–Marquardt–Fletcher algorithm, are employed to identify the modal parameters and quantitatively assess the condition of bridge substructures. The proposed method is numerically verified through an established 3D train-bridge-foundation coupling system considering different damage scenarios. In addition, a real-world application is also conducted on the 2nd Songhua River bridge in the Harbin–Dalian high-speed railway, aiming at examining the effectiveness and robustness of the method in condition monitoring of bridge substructure under a complete freeze-thaw cycle. The results indicate that the proposed methodology is effective in extracting the modal parameters and monitoring the state evolution of the bridge substructures, which offers an efficient and accurate strategy for condition monitoring and quantitative evaluation of railway bridge substructures.

Bearing condition assessment of a simply elastic supported beam based on impact vibration testing

The mechanical properties of bridge bearings gradually deteriorate over time, resulting from daily traffic loading and harsh environmental conditions. However, efficient detection of in-service bridge bearings is still challenging, especially in quantifying support stiffness. This study presents a bridge bearing condition assessment framework of a simply elastic supported beam based on impact vibration testing and structural flexibility identification. Firstly, the dynamic response equation of a simply supported beam with elastic boundary constraints is established. The modal orthogonality of Euler-Bernoulli beams and the corresponding overall matrix of undetermined coefficients are derived using the separate variable method. Subsequently, the flexibility matrix of the simply elastic supported beam is derived and verified in the cases of forward and inverse analysis, respectively. Furthermore, the vertical and rotational stiffness of the bearings are established based on the structural flexibility matrix. Finally, experimental verification is performed to identify the flexibility and the vertical support stiffness of the simply elastic supported beam based on impact vibration tests. The results indicate that the proposed the bearing condition assessment framework can straightforwardly quantify support stiffness.

Hinge Joints Performance Assessment of a PC Hollow Slab Bridge Based on Impact Vibration Testing

Hinge joint performance during the operation of prefabricated prestressed concrete (PC) hollow slab bridges is critical to ensure their lateral collaborative working condition and safe serviceability. Traditional performance identification of hinge joints mainly relies on manual inspection, which is inefficient and inaccurate. At the same time, existing indexes (such as acceleration and strain) can only qualitatively detect the damage to hinge joints. This study proposes a novelty detection method based on impact vibration testing to rapidly perform the quantitative assessment of the working condition of the hinge joints. The relationship between hinge joint performance and lateral load distribution (LLD) is first derived in detail by theoretical analysis. And then, the quantitative analysis of collaborative performance is converted to the identification of the LLD influence line, which is innovatively established by the lateral flexibility of the hollow slab bridge. The effectiveness of the proposed method is verified through a multibeam model using ABAQUS software, and the lateral collaborative working relationship between slabs is simulated using the connector elements. Furthermore, the LLD influence lines and hinge joints performance of a PC hollow slab Yanhu Bridge are evaluated based on the impact vibration testing with sensor lateral arrangement strategy. The detection results show that the proposed method can quickly and accurately identify the damage location and the stiffness loss of hinge joints.

Structural behavior and vibration characteristics of geopolymer composite lightweight sandwich panels for prefabricated buildings

In this study, two new types of geopolymer composite lightweight sandwich panels are developed for prefabricated buildings. The first one has Fiber-reinforced Geopolymer (FRG) composite skin layers and polyurethane (PUR) foam core, and the second one is based on the first panel but strengthened with Basalt fiber reinforced polymer sheet (BFRP). Experimental studies are conducted to investigate the structural behavior and vibration characteristics of these panels. The failure mechanisms and capacity of the developed lightweight sandwich panels under flexural and compressive loads are studied by experimental quasi-static tests. Experimental results from flexural and compressive loading tests match well those from analytical calculations. The experimental studies show that the lightweight sandwich panel has a competitive capacity for prefabricated buildings. The vibration characteristics of the developed lightweight sandwich panels are obtained by hammer impact vibration tests. The finite element models are developed to predict the vibration characteristics of the tested sandwich panels. The obtained natural frequencies and mode shapes from numerical analysis and experimental tests show that the developed finite element models can be used to predict the vibration characteristics of geopolymer composite lightweight sandwich panels accurately. The addition of BFRP sheet does not significantly change the vibration characteristics of the panels, but changes the failure mode of the developed sandwich panel from skin tension failure to PUR foam core shear failure.

Tahe effect of spring coefficients in the dynamic analysis model of the pile foundation structure in Binh Thuan seas, Vietnam

Now, the field experiments according to the non-destructive test method are developing widely in diagnostics and verification of structural engineering. To research and apply the impact vibration test, one of these non-destructive methods, the construction of the design dynamic analysis model is significant. The paper goes into research on the formulas to determine the dynamic spring coefficients according to Japanese and Vietnamese standards. Then, apply calculations for dynamic analysis models of pile foundations built in the Binh Thuan sea area. The impact vibration test in the field shows the appropriate formula for calculating the coefficient of dynamic springs in Binh Thuan, Vietnam.

Vibration‐Based Damage Evaluation of a Reinforced Concrete Frame Subjected to Cyclic Pushover Testing

This research investigated the changes in vibration characteristics of a simple reinforced concrete (RC) frame subjected to incremental cyclic pushover testing as a basis for detection, quantification, and localization of damage in RC frames using vibration data obtained before and after a seismic event. A half‐scale one‐story one‐bay plane frame was subjected to progressive damage through cyclic lateral loading to incrementally increasing drift ratios. Ambient and impact vibration tests were performed at each increment of drift ratio, and modal analyses of the acceleration responses obtained at seven locations on the frame were carried out with the acceleration responses measured at seven different locations on the frame to track changes in the dynamic characteristics. Linear degradation of the lowest two vibration frequencies was identified with increasing drift ratio, which was regarded as a promising result towards detection and quantification of damage. For localization, a flexibility‐based damage localization procedure, the damage locating vector (DLV) approach, was explored. Localization results mostly agreed with the observed damage, and the approach was found to have potential for use in prioritizing the suspected damage locations in the structure for detailed inspections.

Time‐varying frequency‐based scaled flexibility identification of a posttensioned concrete bridge through vehicle–bridge interaction analysis

Dynamic testing methods have been widely used in engineering practice for investigating dynamic properties of bridges; however, only basic dynamic parameters (i.e., natural frequencies, damping ratios, and unscaled modal shapes) can be identified, which are insufficient for condition assessment and health monitoring. To address this limitation, this article takes a three-span posttensioned concrete bridge as testbed; more useful structural parameters including mass-normalized mode shapes and scaled flexibility matrix are intended to be identified from moving vehicle-induced responses. For identifying scaled flexibility matrix, structural scaling factor between arbitrarily scaled mode shapes and mass-normalized mode shapes needs to be calculated firstly. In this article, time-varying frequencies of vehicle–bridge interaction (VBI) system were adopted for structural scaling factor identification, and the sensitivity of parameters identification error on calculated scaling factor was also investigated. The effectiveness of the proposed method was verified by in situ measurements of the studied three-span concrete bridge. In field testing, static load test and classical impact vibration testing were performed on this bridge for verifying the correctness of the proposed method. The good agreement between predicted deflections by using the scaled flexibility and reference values illustrates the reliability of the proposed method.

<b>Automatic Identification Method for Natural Frequency of Bridge Piers by Microtremor Measurement at Both Sides on Top of Pier</b>

The natural frequency of a bridge pier is used as an index to evaluate the soundness of pier foundations. However, using conventional approaches, it is sometimes difficult to obtain the natural frequency derived from microtremor, because the peak of the Fourier spectrum of the bridge piers derived from the microtremor does not appear clearly in many cases compared with that derived from the impact vibration test. In this paper, we propose a method that can automatically identify the natural frequencies using only derived from microtremor measurement results at both sides on the top of piers, without renewing the latest result of impact vibration test.

An advanced vision-based deformation measurement method and application on a long-span cable-stayed bridge

An advanced vision-based method focusing on fast and accurate deformation measurement was developed. First, computing speed and sub-pixel matching accuracy were improved by modifying the feature extraction process and optimizing the elimination mechanism of random sample consensus. An impact vibration test on a beam was designed to verify this improvement. Second, a new displacement transformation equation that considers the location change of measuring points for oblique optical axis measurement was proposed, with its advantage verified through a specially designed translation test. Based on the above, software for synchronous multi-region tracing was developed and applied to monitor the mid-span deflection and multi-cable tensile force of the Su Tong Bridge, the second longest cable-stayed bridge in the world. The test results show the great application prospects of the proposed optical method for remote and non-target deformation measurement.

Mechanical and free vibration properties of clamshell particles/polyester composites

In this work, an experimental investigation was implemented to identify the effect of adding clamshell powder (CSP) into the polyester matrix on the tensile and impact properties along with vibration characteristics of the particulate composites towards using eco-friendly reinforcement phase. Different weight ratios of clamshell powder, ranged from 0 to 20 wt%, were loaded into the polyester resin with particle sizes ranged from 25 to 75 μm. Tensile, Charpy impact and free vibration tests were performed to the specimens fabricated from the neat polyester and CSP-filled polyester. The results showed that the inclusion of CSP into the polyester matrix could improve the tensile modulus of the polyester up to 50% when the CSP weight ratio equals to 12%. Meanwhile, the strain-to-failure, tensile and impact strengths showed decreasing trends with increasing the CSP filler content owing to the weak adhesion (bonding) strength between CSP and the polyester matrix. Maximum improvements in the fundamental natural frequency and damping ratio of CSP-filled polyester were 24% (at 12 wt% of CSP) and 21% (at 8 wt% of CSP), respectively. Based on the results, the clamshell powder could be used as a very cheap bio-filler material within the polyester matrix if the high stiffness composites with improved damping properties are required.

Identification of modal parameters in a lightly damped system based on impact vibration testing: Application of exponential window and removal of its effect

The experimental environments for impact tests are simple to construct compared to other vibration tests in experimental modal analysis. However, given that sufficient sampling time is necessary for the response to attenuate, the following two problems arise: The first is that work efficiency is lowered. The second is that the measurement time increases, which makes it more susceptible to noise. To solve these problems, it is common to shorten the sampling time and apply an exponential window to reduce the leakage error of the frequency response function (FRF). Although studies on the influence on the FRF exist, identification accuracy for damping characteristic and the influence on the residue have not discussed. In this study, the influence on the modal properties obtained and the accuracy of the results are clarified using numerical examples based on a circle fit and method using simultaneous equations of the real and imaginary parts of the FRF. Finally, the identification results were compared and made sure that the method using simultaneous equations of the real and imaginary parts of FRF can identify modal properties with high accuracy. This method is effective for improving the working efficiency and reducing the influence of noise.

Evaluation of mechanical/dynamic properties of polyetherimide recycled polymer concrete for reducing rail slab noise

In this work, polymer concrete with recycled polyetherimide (PEI) was used to reduce the rail slab noise. Among recycled plastic, PEI is a low-density material which can enhance the damping capability of the polymer concrete. PEI recycled polymer concrete (PRPC) was fabricated with respect to the ratio of the epoxy resin, aggregate and PEI. In order to evaluate the mechanical/dynamic properties of the PRPC, experimental tests were performed. The flexural strength of the PRPC was obtained using a 3-point bending test. Also, the frequency dependent variation of the dynamic stiffness and loss factor of the PRPC were measured by a impact vibration test. The surface between the epoxy resin and PEI was characterized using x-ray photoelectron spectroscopy and scanning electron microscope. Ultimately, PRPC with 25 wt% epoxy resin and 2 wt% PEI showed 0.0193 highest damping value and 32.15 MPa flexural strength which was 3.2% less than the flexural strength of the polymer concrete without PEI.

High-speed stereo-digital image correlation using a single color high-speed camera.

A simple and practical high-speed stereo-digital image correlation (stereo-DIC) technique using a single off-the-shelf high-speed color CMOS camera is described in this work. By using the high-speed color CMOS camera and suitable optical filters, the recorded color images can be directly separated into red and blue channel sub-images with negligible color cross-talk between sub-channel images, which offers evident efficiency and accuracy advantages over the existing technique we proposed recently [Opt. Lasers Eng.95, 17 (2017)OLENDN0143-816610.1016/j.optlaseng.2017.03.009]. These separated sub-channel images can then be processed by regular stereo-DIC to retrieve the desired kinematic fields on the test object surface. The accuracy and precision of the established high-speed stereo-DIC system were characterized by measuring the displacements of a stationary object, and the results show good agreement with theoretical predications. To show the broad utility and practicality of the proposed method, three typical experiments, involving (i) transient displacement and velocity measurement of a rotating fan; (ii) full-field vibration measurement of a rectangular aluminum panel; and (iii) transient 3D surface shape, displacement, and strain fields measurement of a balloon during the whole explosion procedure, were carried out. The results show that, by using a proper high-speed color camera, high-speed 3D shape, displacement and deformation measurements can be realized in a cost-effective and easy-to-implement manner. The proposed technique demonstrates great potential in impact engineering, explosion, and vibration tests.

Review of single-camera stereo-digital image correlation techniques for full-field 3D shape and deformation measurement

Single-camera stereo-digital image correlation (stereo-DIC) techniques have gained increasing attentions and demonstrated excellent prospects in the experimental mechanics community owing to their prominent advantages of cost-effectiveness, compactness, and the avoidance of the complicated camera synchronization. Using additional optical devices, e.g. a diffraction grating, a bi-prism or a set of planar mirrors, pseudo stereo images of a test sample surface can be recorded with a single camera. By correlating these stereo images using DIC, full-field three-dimensional (3D) shape and deformation can be retrieved. This review comprehensively summarizes the historical development, methodologies, strengths and weaknesses of the diffraction grating-based, prism-based, four-mirror-adaptor-based single-camera stereo-DIC techniques, and the recently proposed novel full-frame single color camera-based stereo-DIC technique for full-field 3D shape and deformation measurement. The optical arrangements, principles and calibration procedures of these single-camera stereo-DIC techniques are described in detail. Since high-speed deformation measurement is efficiently achieved by combining the single-camera stereo-DIC with one high-speed camera, single-camera stereo-DIC techniques show great potential in impact engineering, vibration and other dynamic tests.

Application of Impact Vibration Test Method for Bridge Substructure Evaluation

The bridge foundations are constructed mainly below ground or water level. The rehabilitation of a foundation is difficult, and the results of evaluation of structural conditions are usually inaccurate. Furthermore, there are many cases that after natural disasters such as earthquakes, typhoons and floods, it is required to rapidly evaluate bridge substructure conditions for a judging decision on being able to open the bridge to traffic or not. Impact vibration test method has been developed to deal with such problems. Impact vibration test method is a non-destructive dynamic test method which allows to evaluate structural conditions of bridge substructures promptly with a good soundness. In this study, firstly, impact vibration test method, which is one of the utilizable non-destructive tests on the scouring of bridge substructure, is presented. Then, application of the test method for substructure evaluation of a bridge in Vietnam is introduced. The soundness and effectiveness of test method is also discussed.

Impact vibration test of monopile foundation model in dry sand

Measurements on full-scale offshore wind turbines have shown that the horizontal foundation stiffness for monopiles is underpredicted by current design methods. This paper presents a 1:20 model scale test of a monopile foundation for offshore wind turbines, installed in dry laboratory sand. The test is performed under fully controlled laboratory conditions, with low-stress soil effects minimised by overburden pressures applied by a vacuum system. Soil–pile interaction stiffness is indirectly measured by eigenfrequencies in a free vibration test, with vibration initiated by a horizontal impact load to the top of the pile. The purpose of the test is to provide a benchmark for evaluation of calculation methods for laterally loaded monopile foundations. Results for system eigenfrequency and system damping are presented along with measurements of small-strain stiffness for the laboratory sand. Pile displacement profiles are derived for different oscillation amplitudes, on the basis of a numerical beam model, accelerometer and strain gauge measurements. A relationship between small-strain soil stiffness and eigenfrequency is identified. The measured system eigenfrequencies and system damping are found to depend on the applied surcharge pressure and the displacement amplitude.

Impact vibration test of monopile foundation model in dry sand

Impact vibration test of monopile foundation model in dry sand

The Research on Impact Vibration Test Method for Bridge Piers

This paper conducts an analytical research on the use of bridges, and discusses how the vibration of bridges is affected by the healthiness of piers. Meanwhile, Impact Vibration Test Method is introduced, by which the modal parameter of bridges can be tested. A lot of dynamic tests of piers are conducted by using this method. By analyzing data and identifying modal information of piers, this paper made a conclusion on the general law of the impact each parameter has on characteristic frequency of the piers. The bridge finite-elemental model is constructed according to the actual structure of piers, the impact vibration test load stimulated, then computed and analyzed with the dynamic time-history method. Bases on the comparison between test result and frequency of Time-domain transverse velocity received the results of the analyses identify the frequency spectrums, the validity of the Impact Vibration Test Method is verified.

진동시험에 의한 방파제 케이슨의 동특성 평가 및 수치해석 모델의 검증

In this study, impact vibration tests are applied to analyze the vibration characteristics of caisson-type breakwater, and the results obtained from vibration tests are compared with numerical simulation results considering fluid-soil-structure interaction effects to verify the feasibility of a numerical analysis model. It is found that natural frequencies are reduced as amount of 1.7-4.3% after additional parapet structure is added to increase the height of breakwater, and the same results was observed from the numerical simulation study. Through the comparison, it was verified that the vibration tests and numerical simulation study can be applied to evaluate the vibration characteristics of caisson-type breakwater.