• Structural Engineering and Mechanics
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• v.53 no.2
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• pp.261-276
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• 2015

Structural damage and moving load identification are the two aspects of structural system identification. However, they universally coexist in the damaged structures subject to unknown moving load. This paper proposed a dynamic response sensitivity-based model updating method to simultaneously identify the structural damage and moving force. The moving force which is equivalent as the nodal force of the structure can be expressed as a series of orthogonal polynomial. Based on the system Markov parameters by the state space method, the dynamic response and the dynamic response derivatives with respect to the force parameters and elemental variations are analytically derived. Afterwards, the damage and force parameters are obtained by minimizing the difference between measured and analytical response in the sensitivity-based updating procedure. A numerical example for a simply supported beam under the moving load is employed to verify the accuracy of the proposed method.

• Journal of Mechanical Science and Technology
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• v.18 no.12
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• pp.2114-2124
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• 2004

In this paper, a structural damage identification method (SDIM) is developed for cylindrical shells and the numerically simulated damage identification tests are conducted to study the feasibility of the proposed SDIM. The SDIM is derived from the frequency response function solved from the structural dynamic equations of damaged cylindrical shells. A damage distribution function is used to represent the distribution and magnitudes of the local damages within a cylindrical shell. In contrast with most existing modal parameters-based SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM requires only the FRF-data measured in the damaged state. By virtue of utilizing FRF-data, one is able to make the inverse problem of damage identification well-posed by choosing as many sets of excitation frequency and FRF measurement point as needed to obtain a sufficient number of equations.

• Steel and Composite Structures
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• v.47 no.1
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• pp.121-134
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• 2023

This paper tested 11 concrete-encased concrete-filled steel tube (CFST) composite columns and one reinforced concrete column under combined axial compression and lateral loads. The primary parameters, including the loading system, axial compression ratio, volume stirrup ratio, diameter-to-thickness ratio of the steel tube, and stirrup form, were varied. The influence of the parameters on the failure mode, strength, ductility, energy dissipation, strength degradation, and damage evolution of the composite columns were revealed. Moreover, a two-parameter nonlinear seismic damage model for composite columns was established, which can reflect the degree and development process of the seismic damage. In addition, the relationships among the inter-story drift ratio, damage index and seismic performance level of composite columns were established to provide a theoretical basis for seismic performance design and damage assessments.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.181-206
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• 2022

This paper presents experimental modal analysis and static load testing results to validate the accuracy of dynamic parameters-based damage locating indices in RC structures. The study investigates the accuracy of different dynamic-based damage locating indices compared to observed crack patterns from static load tests and how different damage levels and scenarios impact them. The damage locating indices based on mode shape curvature and mode shape fourth derivate in their original forms were found to show anomalies along the beam length and at the supports. The modified forms of these indices show higher sensitivity in locating single and multi-cracks at different damage scenarios. The proposed stiffness reduction index shows good sensitivity in detecting single and multi-cracks. The proposed anomalies elimination procedure helps to remove the anomalies along the beam length. Also, the adoption of the proposed weighting method averaging procedure and normalization procedure help to draw the overall crack pattern based on the adopted set of modes.

• Steel and Composite Structures
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• v.24 no.4
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• pp.409-423
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• 2017

This paper presents an experimental study on damage evolution laws of solid-web steel reinforced concrete (SRC) T-shaped columns along the direction of the web under various loadings. Ten specimens with a scale ratio of 1/2 and a shear span ratio of 2.5 were designed and fabricated. The influences of various parameters, including the axial compression ratio, steel ratio, and loading mode, were examined. The mechanical performances including load-displacement curve and energy dissipation capacity under the monotonic and low cyclic loadings were analyzed. Compared with the monotonic loading, bearing capacity, ultimate deformation capacity, and energy dissipation capacity of the specimens decrease to some extent with the increase of the displacement amplitude and the number of loading cycle. The results show that the damage process of the SRC T-shaped column can be divided into five stages, namely non-damage, slight-damage, steadily-developing-damage, severe-damage and complete-damage. Finally, based on the Park-Ang model, a modified nonlinear damage model which combines the maximum deformation with hysteretic energy dissipation is proposed by taking into account the dynamic influence of the aforementioned parameters. The results show that the modified model in this paper is more accurate than Park-Ang model and can better describe the damage evolution of SRC T-shaped columns.

• Computers and Concrete
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• v.22 no.4
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• pp.395-405
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• 2018

In this paper, the performance of post-installed adhesive bonded anchor embedded in concrete is assessed using numerical simulations. This study aims at studying the influence of parameters on the performance of a chemically bonded anchorage system. Non-linear finite element modelling and simulations are carried out by properly using the material properties and phenomenon. Materials parameters such as characteristic length, fracture energy, damage criteria, tension retention and crack width of concrete and interface characteristics are carefully assigned so as to obtain a most realistic behaviour of the chemical anchor system. The peak strength of two different anchor systems obtained from present numerical studies is validated against experimental results. Furthermore, validated numerical models are used to study the load transferring mechanism and damage progression characteristics of various anchors systems where strength of concrete, strength of epoxy, and geometry and disposition of anchors are the parameters. The process of development of strain in concrete adjacent to the anchor and energy dissipated during the course of damage progression are analysed. Results show that the performance of the considered anchorage system is, though a combined effect of material and geometric parameters, but a clear distinction could be made on the parameters to achieve a desired performance based on strength, slip, strain development or dissipated energy. Inspite the increase in anchor capacity with increase in concrete strength, it brings some undesirable performance as well. Furthermore, the pullout capacity of the chemical anchor system increases with a decrease in disparity among the strength of concrete and epoxy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.969-974
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• 2004

Although guided-waves are very efficient for long-range nondestructive damage inspection, it is not easy to extract meaningful pulses of small magnitude out of noisy signals. The ultimate goal of this research is to develop an efficient signal processing technique for the current guided-wave technology. The specific contribution of this investigation towards achieving this goal, a two-stage Gabor pulse-based matching pursuit algorithm is proposed : rough approximations with a set for predetermined parameters characterizing the Gabor pulse and fine adjustments of the parameters by optimization. The parameters estimated from the measured signal are then used to assess not only the location but also the size of a crack existing in a rod. To validate the effectiveness of the proposed method, the longitudinal wave-based damage detection in rods is considered. To estimate the crack size, Love's theory for the dispersion of longitudinal waves is employed.

• Smart Structures and Systems
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• v.5 no.4
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• pp.427-442
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• 2009

In this paper, the acceptability of system identification results for health monitoring of instrumented bridges is addressed. This is conducted by comparing the confidence intervals of identified modal parameters for a bridge in California, namely Truckee I80/Truckee river bridge, with the change of these parameters caused by several damage scenarios. A challenge to the accuracy of the identified modal parameters involves consequences regarding the damage detection and health monitoring, as some of the identified modal information is essentially not useable for acquiring a reliable damage diagnosis of the bridge system. Use of strong motion data has limitations that should not be ignored. The results and conclusions underline these limitations while presenting the opportunities offered by system identification using strong motion data for better understanding and monitoring the health of bridge systems.

• Smart Structures and Systems
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• v.8 no.2
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• pp.157-172
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• 2011

A new method for both local damage(s) identification and input excitation force identification of beam structures is presented using the dynamic response sensitivity-based finite element model updating method. The state-space approach is used to calculate both the structural dynamic responses and the responses sensitivities with respect to structural physical parameters such as elemental flexural rigidity and with respect to the force parameters as well. The sensitivities of displacement and acceleration responses with respect to structural physical parameters are calculated in time domain and compared to those by using Newmark method in the forward analysis. In the inverse analysis, both the input excitation force and the local damage are identified from only several acceleration measurements. Local damages and the input excitation force are identified in a gradient-based model updating method based on dynamic response sensitivity. Both computation simulations and the laboratory work illustrate the effectiveness and robustness of the proposed method.

• Journal of Marine Life Science
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• v.9 no.1
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• pp.33-40
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• 2024

To understand the detrimental effects of triclosan on Java medaka (Oryzias javanicus) embryos, fertilized embryos were exposed to different concentrations (1, 10, 50, 100, 200, 400, 600, 800, and 1,000 ㎍ l^-1) of triclosan until hatching. Then, we examined the survival rate and developmental parameters as well as alterations in antioxidant constituents and DNA damage markers. The results showed dose-dependent mortality, hatching delays, and developmental abnormalities in the embryos. Additionally, there were significant increases in oxidative stress parameters and antioxidant responses, along with elevated DNA damage. These findings suggest that sublethal concentrations of triclosan induce toxic effects through oxidative stress on Java medaka embryos, as evidenced by changes in in vivo parameters and biochemical constituents.