• Architectural research
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• v.13 no.4
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• pp.53-60
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• 2011

Damage detection algorithms based on a one-dimensional beam model can detect damage within a beam span caused by flexure only but cannot detect damage at a joint with prescribed boundary conditions or at the middle part of a beam section where the neutral axis is located. Considering the damage at a welded joint of beam elements in steel structures and modeling the damage with twodimensional plane elements, this study presents a new approach to detecting damage in the depth direction of the joint and beam section. Three damage scenarios at the upper, middle, and lower parts of a welded joint of a rectangular symmetric section are investigated. The damage is detected by evaluating the difference in the receptance magnitude between the undamaged and damaged states. This study also investigates the effect of measurement locations and noise on the capability of the method in detecting damage. The numerical results show the validity of the proposed method in detecting damage at the beam's welded joint.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.131-138
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• 1998

Structural damage is used to be modeled through reductions in the stiffness of structural elements for the purpose of damage estimation of structural system. In this study, the concept of joint damage is employed for more realistic damage assessment of a steel structure. The joint damage is estimated damage based on the mode shape informations using neural networks. The beam-to-column connection in a steel frame structure is represented by a rotational spring at the fixed end of a beam element. The severity of joint damage is defined as the reduction ratio of the connection stiffness with respect to the value of the intact joint. The concept of the substructural identification is used for the localized damage assessment in a large structure. The feasibility of the proposed method is examined using an example with simulated data. It has been found that the joint damages can be reasonably estimated for the case with the measurements of the mode vectors subjected to noise.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.427-433
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• 2011

Chassis part in automotive body is affected by fatigue load at driving on the ground. Universal joint on this part is influenced extremely by the fatigue load. Fatigue life, damage and natural frequency are analyzed at universal joint under nonuniform fatigue load. The york part at universal joint is shown with the maximum equivalent stress and displacement of 60.755 MPa and 0.21086 mm as strength analysis. The possible life in use in case of 'SAE bracket' is the shortest among the fatigue loading lives of 'SAE bracket', 'SAE transmission' and 'Sine Wave'. The damage at loading life of 'SAE transmission' is the least among 3 types. The frequency of damage in case of 'Sine Wave' is 0.7 with the least among 3 fatigue loading life types but this case brings the most possible damage as 80% at the average stress of 0. Natural vibration at this model is analyzed with the orders of 1'st to 5'th and maximum frequency is shown as 701.73 Hz at 5'th order. As the result of this study is applied by the universal joint on chassis part, the prevention on fatigue damage in automotive body and its durability are predicted.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.35-46
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• 1998

Structural damage is used to be modeled through reductions in the stiffness of structural elements for the purpose of damage estimation of structural system. In this study, the concept of joint damage is employed for more realistic damage assessment of a steel structure. The joint damage is estimated damage based on the mode shape informations using neural networks, The beam-to-column connection in a steel frame structure is represented by a rotational spring at the fixed end of a beam element. The severity of joint damage is defined as the reduction ratio of the connection stiffness with respect to the value of the intact joint. The concept of the substructural identification is used for the localized damage assessment in a large structure. The feasibility of the proposed method is examined using an example with simulated data. It has been found that the joint damages can be reasonably estimated for the case with the measurements of the mode vectors subjected to noise.

• Structural Engineering and Mechanics
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• v.16 no.5
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• pp.581-595
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• 2003

Since the conventional direct approaches are hard to be applied for damage diagnosis of complex large-scale structures, a two-step approach for diagnosing the joint damage of framed structures is presented in this paper by using artificial neural networks. The first step is to judge the damaged areas of a structure, which is divided into several sub-areas, using probabilistic neural networks with natural Frequencies Shift Ratio inputs. The next step is to diagnose the exact damage locations and extents by using the Radial Basis Function (RBF) neural network with the second Element End Strain Mode of the damaged sub-area input. The results of numerical simulation show that the proposed approach could diagnose the joint damage of framed structures induced by earthquake action effectively and has reliable anti-jamming abilities.

• Smart Structures and Systems
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• v.5 no.4
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• pp.329-344
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• 2009

Ultrasonic chaotic excitations combined with sensor prediction algorithms have shown the ability to identify incipient damage (loss of preload) in a bolted joint. In this study we examine a physical experiment on a single-bolt aluminum lap joint as well as a three-dimensional physics-based simulation designed to model the behavior of guided ultrasonic waves through a similarly configured joint. A multiple bolt frame structure is also experimentally examined. In the physical experiment each signal is imparted to the structure through a macro-fiber composite (MFC) patch on one side of the lap joint and sensed using an equivalent MFC patch on the opposite side of the joint. The model applies the waveform via direct nodal displacement and 'senses' the resulting displacement using an average of the nodal strain over an area equivalent to the MFC patch. A novel statistical classification feature is developed from information theory concepts of cross-prediction and interdependence. This damage detection algorithm is used to evaluate multiple damage levels and locations.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.71-81
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• 2024

Fiber Reinforced Polymer (FRP) bars have now been widely adopted as an alternative to traditional steel reinforcements in infrastructure and civil industries worldwide due variety of merits. This paper presents a numerical methodology to investigate FRP bar-reinforced beam-column joint behavior under quasi-static loading. The proposed numerical model is validated with test results considering load-deflection behavior, damage pattern at beam-column joint, and strain variation in reinforcements, wherein the results are in agreement. The numerical model is subsequently employed for parametric investigation to enhance the end-span beam-column joint performance using different joint reinforcement systems. To reduce the manufacturing issue of bend in the FRP bar, the headed FRP bar is employed in a beam-column joint, and performance was investigated at different column axial loads. Headed bar-reinforced beam-column joints show better performance as compared to beam-column joints having an L-bar in terms of concrete damage, load-carrying capacity, and joint shear strength. The applicability and efficiency of FRP bars at different story heights have also been investigated with varying column axial loads.

• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.124-130
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• 2009

This study presents a finite element simulation of elastic waves for detecting anti-symmetric damages in an adhesively-bonded single lap joint. Plane strain elements were used for modeling adherents (aluminum) and adhesives (epoxy). Three types of damage were introduced: thickness reduction, elasticity deterioration, and voids in the adhesive layers, and two excitation and reception arrangements (ER1 and ER2) were used to investigate the detectability of the damage. The simulation showed that symmetrically located damage, such as a thickness reduction, can be detected by one excitation and one reception arrangement (ER1) and anti-symmetric damages, such as elasticity deterioration and voids, can be detected by modified two-point elastic wave excitation (ER2). Compared with the ER1 arrangement, the ER2 arrangement does not require a baseline signal for damage detection; hence, an efficient method of anti-symmetric damage detection in an adhesively-bonded single lap joint is proposed.

• Composites Research
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• v.25 no.2
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• pp.40-45
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• 2012

The comparison of the numerical results with those measured by the experiment showed good agreement. The design of composite joint which is the weakest part in the composite structures has become a very important research area since the composite materials are widely used in the aircraft and machine structure. In this paper, the new composite key joints that minimize the fiber discontinuity and strength degradation of adherend were proposed and their failure loads were evaluated. The failure index and damage area method were used for the failure prediction of the composite key joint. From the tests, the failure load of the composite key joint was 93% larger than that of a mechanical joint and the key joint whose slot depth and edge length were 0.88mm and 20mm had the largest failure load. Also, the analytic failure modes by the failure index and damage area were compared with experimental failure modes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.111-118
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• 2010

The joints are often the weakest areas in composite structures. In this paper, the thick aluminum-aluminum joint specimens and thick composite-aluminum single lap adhesive joint specimens were manufactured and the tensile tests were performed. The fracture mode of each specimen was investigated and the modified damage zone theory based on the yield strain was proposed and compared with experimental failure load of each mode. The failure loads of the thick aluminum-aluminum joint and composite-aluminum joint were predicted by the same failure criterion and they could be predicted to within 19.3% using the damage zone ratio method for all 14 cases investigated.