• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.117-118
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• 2009

A systematic procedure is proposed that can be used to assess the span of PSC girder bridge for a given condition. The proposed scheme adopts a graphical approach that represents a relationship between the number of prestressing tendons and the span, and is derived on a basis of safety assessment equations of the girder in each stage of fabrication and in service.

• Smart Structures and Systems
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• v.7 no.5
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• pp.393-416
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• 2011

Hybrid acceleration-impedance sensor nodes on Imote2-platform are designed for damage monitoring in steel girder connections. Thus, the feasibility of the sensor nodes is examined about its performance for vibration-based global monitoring and impedance-based local monitoring in the structural systems. To achieve the objective, the following approaches are implemented. First, a damage monitoring scheme is described in parallel with global vibration-based methods and local impedance-based methods. Second, multi-scale sensor nodes that enable combined acceleration-impedance monitoring are described on the design of hardware components and embedded software to operate. Third, the performances of the multi-scale sensor nodes are experimentally evaluated from damage monitoring in a lab-scaled steel girder with bolted connection joints.

• Structural Engineering and Mechanics
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• v.72 no.1
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• pp.99-111
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• 2019

To investigate the seismic performance of long-span partially earth-anchored cable-stayed bridge, a super long-span partially earth-anchored cable-stayed bridge scheme with main span of 1400m is taken as example, structural response of the bridge under E1 seismic action is investigated numerically by the multimode seismic response spectrum and time-history analysis, seismic behavior and also the effect of structural geometric nonlinearity on the seismic responses of super long-span partially earth-anchored cable-stayed bridges are revealed. The seismic responses are also compared to those of a fully self-anchored cable-stayed bridge with the same main span. The effects of structural parameters including the earth-anchored girder length, the girder width, the girder depth, the tower height to span ratio, the inclination of earth-anchored cables, the installation of auxiliary piers in the side spans and the connection between tower and girder on the seismic responses of partially ground-anchored cable-stayed bridges are investigated, and their reasonable values are also discussed in combination with static performance and structural stability. The results show that the horizontal seismic excitation produces significant seismic responses of the girder and tower, the seismic responses of the towers are greater than those of the girder, and thus the tower becomes the key structural member of seismic design, and more attentions should be paid to seismic design of these sections including the tower bottom, the tower and girder at the junction of tower and girder, the girder at the auxiliary piers in side spans; structural geometric nonlinearity has significant influence on the seismic responses of the bridge, and thus the nonlinear time history analysis is proposed to predict the seismic responses of super long-span partially earth-anchored cable-stayed bridges; as compared to the fully self-anchored cable-stayed bridge with the same main span, several stay cables in the side spans are changed to be earth-anchored, structural stiffness and natural frequency are both increased, the seismic responses of the towers and the longitudinal displacement of the girder are significantly reduced, structural seismic performance is improved, and therefore the partially earth-anchored cable-stayed bridge provides an ideal structural solution for super long-span cable-stayed bridges with kilometer-scale main span; under the case that the ratio of earth-anchored girder length to span is about 0.3, the wider and higher girder is employed, the tower height-to-span ratio is about 0.2, the larger inclination is set for the earth-anchored cables, 1 to 2 auxiliary piers are installed in each of the side spans and the fully floating system is employed, better overall structural performance is achieved for long-span partially earth-anchored cable-stayed bridges.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1001-1006
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• 2000

These should be constructed partially, because many prestressed concrete box girder bridges in situ have large cross section and long span. Therefore, accurate prediction of differences, both elapse time of each construction stage and exposure of atmosphere at each position of cross section, is very important. Though it is importance, engineers are apt to overlook it. This study predicted cracks due to shrinkage and stress concentration phenomenon by each construction stage and then, ascertained reduction of tensile stresses after applying retrofit scheme.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.309-321
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• 1997

The prediction of the dynamic response of a bridge resulting from passing vehicles across the span is a significant problem in bridge design. In this paper. the static and dynamic experiments are performed to understand the dynamic behavior of an actual two-span steel plate girder bridge. The road surface roughness of the roadway and bridge deck is directly measured by Intelligent Total Station. Numerical scheme to obtain the dynamic responses of the bridges in consideration of measuring road surface roughness and 3-D vehicle model is also presented. The bridge and vehicle are modeled as 3-D bridge and vehicle model, respectively. The main girder and concrete deck are modeled as beam and shell elements, respectively and rigid link is used for the structure between main girder and concrete deck. Bridge-vehicle interaction equations are derived and the impact factors of the responses for different vehicle speeds are calculated and compared with those predicted by several foreign specifications.

• Journal of Korean Society of Steel Construction
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• v.21 no.4
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• pp.403-411
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• 2009

In the present study, nonlinear earthquake analysis was carried out for a steel girder bridge that had been damaged by the 1995 Kobe earthquake. For such analysis, the use of hysteretic models describing flexure-axial and shear-axial interaction was suggested. The models were incorporated into a structural analysis program in terms of the joint elements representing hinge models, and then a simplified analysis scheme using the hinge models was employed for bridge piers. The analytical predictions of the flexure-axial interactive hinge model show a good correlation with those of the detailed fiber element model. In addition, the analytical predictions of the flexure-shear-axial interactive hinge model enable a displacement component to be separately captured. It is thus recognized that the present study can be a useful scheme for the healthy evaluation of the global displacement performance of piers subjected to earthquake excitation.

• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.75-82
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• 2008

A vibration-based damage-monitoring scheme is proposed that would generate an alarm showing the occurrence and location of damage under temperature-induced uncertainty conditions. Experiments on a model plate-girder bridge are described, for which a set of modal parameters was measured under uncertain temperature conditions. A damage-alarming model is formulated to statistically identify the occurrence of damage by recognizing the patterns of damage-driven changes in the natural frequencies of the test structure and by distinguishing temperature-induced off-limits. A damage index method based on the concept of modal strain energy is implemented in the test structure to predict the location of damage. In order to adjust for the temperature-induced changes in the natural frequencies that are used for damage detection, a set of empirical frequency correction formulas is analyzed from the relationship between the temperature and frequency ratio.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.669-674
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• 2007

To develop a promising hybrid structural health monitoring (SHM) system, a combined use of structural vibration and electro-mechanical (EM) impedance is proposed. The hybrid SHM system is designed to use vibration characteristics as global index and EM impedance as local index. The proposed health monitoring scheme is implemented into prestressed concrete (PSC) girder bridges for which a series of damage scenarios are designed to simulate various prestress-loss situations at which the target bridges car experience during their service life. The measured experimental results, modal parameters and electro-magnetic impedance signatures, are carefully analyzed to recognize the occurrence of damage and furthermore to indicate its location.

• Wind and Structures
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• v.16 no.4
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• pp.323-340
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• 2013

An active mass damper system for flutter control of bridges is presented. Flutter stability of bridge structures is improved with the help of eccentric rotational actuators (ERA). By using a bridge girder model that moves in two degrees of freedom and is subjected to wind, the equations of motion of the controlled structure equipped with ERA are established. In order to take structural nonlinearities into consideration, flutter analysis is carried out by numerical simulation scheme based on a 4th-order Runge-Kutta algorithm. An example demonstrates the performance and efficiency of the proposed device. In comparison with known active mass dampers for flutter control, the movable eccentric mass damper and the rotational mass damper, the power demand is significantly reduced. This is of advantage for an implementation of the proposed device in real bridge girders. A preliminary design of a realization of ERA in a bridge girder is presented.

• Steel and Composite Structures
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• v.37 no.2
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• pp.117-136
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• 2020

Curved steel-concrete composite box girder has been widely adopted in urban overpasses and ramp bridges. In order to investigate its mechanical behavior under complicated and combined bending, shear and torsion load, two large-curvature composite box girders with interior angles of 25° and 45° were tested under static hogging moment. Based on the strain and deflection measurement on critical cross-sections during the static loading test, the failure mode, cracking behavior, load-displacement relationship, and strain distribution in the steel plate and rebar were investigated in detail. The test result showed the large-curvature composite box girders exhibited notable shear lag in the concrete slab and steel girder. Also, the constraint torsion and distortion effect caused the stress measured at the inner side of the composite beam to be notably higher than that of the outer side. The strain distribution in the steel web was approximately linear; therefore, the assumption that the plane section remains plane was approximately validated based on strain measurement at steel web. Furthermore, the full-process non-linear elaborate finite element (FE) models of the two specimens were developed based on commercial FE software MSC.MARC. The modeling scheme and constitutive model were illustrated in detail. Based on the comparison between the FE model and test results, the FE model effectively simulated the failure mode, the load-displacement curve, and the strain development of longitudinal rebar and steel girder with sufficient accuracy. The comparison between the FE model and the test result validated the accuracy of the developed FE model.