• Structural Engineering and Mechanics
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• v.59 no.6
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• pp.1095-1120
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• 2016

This paper investigates the change of structural characteristics of steel cable-stayed bridges after cable failure. Cables, considered as the intermediate supports of cable-stayed bridges, can break or fail for several reasons, such as fire, direct vehicle clash accident, extreme weather conditions, and fatigue of cable or anchorage. Also, the replacement of cables can cause temporary disconnection. Because of the structural characteristics with various geometric nonlinearities of cable-stayed bridges, cable failure may cause significant change to the structural state and ultimate behavior. Until now, the characteristics of structural behavior after cable failure have rarely been studied. In this study, rational cable failure analysis is suggested to trace the new equilibrium with structural configuration after the cable failure. Also, the sequence of ultimate analysis for the structure that suffers cable failure is suggested, to study the change of ultimate behavior and load carrying capacity under specific live load conditions. Using these analysis methods, the statical behavior after individual cable failure is studied based on the change of structural configuration, and distribution of internal forces. Also, the change of the ultimate behavior and load carrying capacity under specific live load conditions is investigated, using the proposed analysis method. According to the study, significant change of the statical behavior and ultimate capacity occurs although just one cable fails.

• Structural Monitoring and Maintenance
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• v.9 no.4
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• pp.337-357
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• 2022

The objective of this study is to present a data-driven machine learning (ML) framework for predicting ultimate shear strength and failure modes of reinforced concrete ledge beams. Experimental tests were collected on these beams with different loading, geometric and material properties. The database was analyzed using different ML algorithms including decision trees, discriminant analysis, support vector machine, logistic regression, nearest neighbors, naïve bayes, ensemble and artificial neural networks to identify the governing and critical parameters of reinforced concrete ledge beams. The results showed that ML framework can effectively identify the failure mode of these beams either web shear failure, flexural failure or ledge failure. ML framework can also derive equations for predicting the ultimate shear strength for each failure mode. A comparison of the ultimate shear strength of ledge failure was conducted between the experimental results and the results from the proposed equations and the design equations used by international codes. These comparisons indicated that the proposed ML equations predict the ultimate shear strength of reinforced concrete ledge beams better than the design equations of AASHTO LRFD-2020 or PCI-2020.

• Structural Engineering and Mechanics
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• v.63 no.2
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• pp.195-206
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• 2017

This paper presents the parametric numerical analysis on the ultimate bearing capacity of the purlin-sheet roofs connected by standing seam clips. The effects of several factors on failure modes and ultimate bearing capacity of the purlins are studied, including setup of anti-sag bar, purlin type, sheet thickness and connection type et al. A simplified design formula is proposed for predicting the ultimate bearing capacity of purlins. Results show that setting the anti-sag bars can improve the ultimate bearing capacity and change the failure modes of C purlins significantly. The failure modes and ultimate bearing capacity of C purlins are significantly different from those of Z purlins, in the purlin-sheet roof connected by standing seam clips. Setting the anti-sag bars near the lower flange is more favorable for increasing the ultimate bearing capacity of purlins. The ultimate bearing capacity of C purlins increases slightly with sheet thickness increasing from 0.6 mm to 0.8 mm. The ultimate bearing capacity of the purlin-sheet roofs connected by standing seam clips is always higher than those by self-drilling screws. The predictions of the proposed design formulas are relatively in good agreement with those of EN 1993-1-3: 2006, compared with GB 50018-2002.

• KCI Concrete Journal
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• v.12 no.1
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• pp.113-120
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• 2000

This paper presents the behavior and strengthening effect of reinforced concrete rectangular beams strengthened using CFRP sheets with different strengthening level. In general, normally strengthened beams are failed by interfacial shear failure (delamination) within concrete, instead of by tensile failure of the CFRP sheets. The delamination occurred suddenly and the concrete cover cracked vertically by flexure was spalled off due to the release energy. The strengthened beams were stiffer than the control beam before and after reinforcement yielding. The ultimate load considerably increased with an increase of strengthening level, while the ultimate deflection significantly decreased. The tensile force of CFRP sheets and average shear stress of concrete at delamination failure were curvilinearly proportional to the strengthening level. Therefore, the increment of ultimate load obtained by strengthening was curvilinearly proportional to the strengthening level. The averaged horizontal shear stress of concrete at the interface ranges between (equation omitted) and (equation omitted) (in kg/$\textrm{cm}^2$) depending on strengthening level.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.59-69
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• 2018

In order to use the limit equilibrium theory, it is necessary to find a slip line under the ultimate failure condition. The strength reduction method using the Lagrangian finite element method defines the ultimate failure state at a time when the numerical solution cannot converge within the certain number of the iteration. When the coupled Eulerian-Lagrangian (CEL) method is used, however, such definition is inappropriate because the numerical solution of the CEL method can converge even under the ultimate failure condition. In this study, an objective condition designating the ultimate failure state in the finite element analysis adopting the CEL method was proposed. In the problem of the bearing capacity of the undrained soft ground subjected to the strip footing loading, we found that the rate of the plastic dissipated energy is highly sensitive at the load of the theoretical limit of the ultimate failure state.

• Geomechanics and Engineering
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• v.6 no.5
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• pp.469-485
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• 2014

A series of bearing capacity tests was conducted with eccentrically loaded model surface and shallow strip footings resting close to a slope to investigate behavior of such footings (ultimate loads, failure surfaces, load-displacement curves, rotation of footing, etc.). Ultimate loads of footing close to slope decreased with increasing eccentricity for both surface and shallow footings. Failure surfaces were not symmetrical, primary failure surfaces occurred on the eccentricity side (the slope side) and secondary failure surfaces occurred on the other side. Lengths of failure surfaces decreased with increasing eccentricity. Footings always rotated towards eccentricity side a few degrees. For eccentrically loaded footing, decrease in ultimate load with increasing eccentricity is roughly in agreement with Customary Analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.781-786
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• 2000

This paper presents the behavior and strenghening effect of reinforced concrete rectangular beams strengthened sing CFRP sheets with different strengthening level. In general, normally strengthened beams are failed by interfacial shear failure (delamination) within concrete, instead of by tensile failure of the CFRP sheets. The delamination occurred suddenly and the concrete cover cracked vertically by flexure was spalled off due to the release energy. The ultimate load considerably increased with an increase of strengthening level, while the ultimate deflection significantly decreased. The tensile force of CFRP sheets and average shear stress of concrete at delamination failure were curvilinearly proportional to the strengthening level. Therefore, the increment of ultimate load obtained by strengthening was curvilinearly proportional to th strengthening level.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.1013-1021
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• 2001

A series of rabbit common extensor tendon specimens of the humeral epicondyle were subjected to tensile tests under two displacement rates (100mm/min and 10mm/min) and different elbow flexion positions 45°, 90°and 135°. Biomechanical properties of ultimate tensile strength, failure strain, energy absorption and stiffness of the bone-tendon specimen were determined. Statistically significant differences were found in ultimate tensile strength, failure strain, energy absorption and stiffness of bone-tendon specimens as a consequence of different elbow flexion angles and displacement rates. The results indicated that the bone-tendon specimens at the 45°elbow flexion had the lowest ultimate tensile strength; this flexion angle also had the highest failure strain and the lowest stiffness compared to other elbow flexion positions. In comparing the data from two displacement rates, bone-tendon specimens had lower ultimate tensile strength at all flexion angles when tested at the 10mm/min displacement rate. These results indicate that creep damage occurred during the slow displacement rate. The major failure mode of bone-tendon specimens during tensile testing changed from 100% of midsubstance failure at the 90°and 135°elbow flexion to 40% of bone-tendon origin failure at 45°. We conclude that failure mechanics of the bone-tendon unit of the lateral epicondyle are substantially affected by loading direction and displacement rate.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.73-80
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• 1997

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.585-591
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• 1998

In the case of reinforced concrete beams strengthening by steel plate, sometimes these beams collapse due to the stress concentration at the ends of steel plates before the design expected failure. This kind of failure is called premature failure. This study analyzes the behavior of strengthened RC beams to control premature failure of these plated beams with either changing the geometries at the ends of plates or strengthening steel plates beside the ends. The results from the former cases show that, the effect of expanded plates sections at the ends was very small, and the beams which are rounded the ends of plates effectively increased the initial rip-off loads about 14% compared with control beam but the ultimate loads was almost same. However, the beams in the latter cases effectively increased the initial and the ultimate rip-off loads with changing failure mode, especially around 14~19% in the ultimate rip-off load comparing with control beam.