• Computers and Concrete
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• v.22 no.2
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• pp.133-142
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• 2018

The deterioration of existing bridges has become a major problem around the world. In the paper, a new model and an associated stress checking method are proposed for concrete box girders strengthened by external prestressing. The new model called the spatial grid model can analyze all the spatial behaviors clearly by transforming the box girder into discrete orthogonal grids which are equivalent to plate elements. Then the three-layer stresses are employed as the stress checking indices to evaluate the stress state of the plate elements. The initial stress check before strengthening reveals the cracked and potential cracking areas for existing bridges, making the strengthening design more targeted and scientific; the subsequent stress check after strengthening evaluates the strengthening effect and ensures safety. A deficient bridge is selected as the practical example, verifying the accuracy and applicability of the proposed model and stress checking method. The results show that principal stresses in the middle layer of plate elements reflect the main effects of external prestressing and thus are the key stress checking indices for strengthening. Moreover, principal stresses check should be conducted in all parts of the strengthened structure not only in the webs. As for the local effects of external prestressing especially in the areas near anchorage and deviator, normal stresses check in the outer and inner layers dominates and local strengthening measures should be taken if necessary.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.23-32
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• 2022

Although PSCB girder bridges account for 4% of the bridges in use on highways, they do not account for much, but 98% of PSCB girder bridges are 1^st type and 2^nd type of bridge. Also, the total length of the PSCB girder bridge is 16% (192km) of the total length of the highway bridge. Thus, the PSCB girder bridge can be one of the bridge types where maintenance is important. In order to analyze the damage types of PSCB girder bridges, a detailed analysis was conducted by selecting 62 places (477 spans) precision safety diagnosis reports considering ratio of the construction method and snow removal environment exposure class. Analysis of report and a field investigation was conducted, and as a result, most of the causes of deterioration damage were caused by rainwater (salt water) flowing into the bridge pavement soaking in between the top flange and the interface. After concrete slab deteriorate occurred then bridge pavement cracking and breaking increased and exfoliation of concrete occurred by corrosion and expansion of the reinforcing bars occurred. In addition, the cause of cracks in the longitudinal direction on the bottom of the top flange is considered to be cracks caused by restrained drying shrinkage. In conclusion, for reasonable maintenance considering the characteristics of PSCB girder bridges, it should be suggested in the design aspect that restrained drying shrinkage crack on top flange. Also, it is believed that differentiated maintenance method should be proposed according to snow removal environment exposure class.

• Computational Structural Engineering
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• v.20 no.1 s.75
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• pp.71-77
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• 2007

• Computational Structural Engineering
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• v.17 no.4 s.66
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• pp.29-34
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• 2004

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.680-689
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• 2011

A dynamic analysis procedure is developed to provide a comprehensive estimation of the dynamic response spectrum for locomotive's wheels running over a Pre-Stressed Concrete (PSC) box girder bridge on the Korea high speed railway. The wheel force spectrum with the bridge behavior are analyzed as the dynamic procedure for various running speeds (50~450km/h). The high-speed railway locomotive (KTX) is used as 38-degree of freedom system. Three displacements(vertical, lateral, and longitudinal) and three rotational components (pitching, rolling, and yawing). For one car-body and two bogies as well as five movements except pitching rotation components for four wheel axes forces are considered in the 38-degree of freedom model. Three dimensional frame element is used to model of the PSC box girder bridges, simply supported span length of 40m. The irregulation of rail-way is derived using the exponential spectrum density function under assumption of twelve level tracks conditions based on the normal probability procedure. The dynamic responses of bridge passing through the railway locomotive with high-speed analyzed by Newmark-${\beta}$ method and Runge-Kutta method are compared and contrasted considering the developed models of bridge, track and locomotive comprehensively. The dynamic analyses of wheel forces by Runge-Kutta method which are able to analyze the forces with high frequency running on the bridge and ground rail-way are conducted. Additionally, wheel forces spectrum and three rotational components of vehicle body for three typical running speeds is also presented.

• Earthquakes and Structures
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• v.11 no.4
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• pp.681-699
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• 2016

Steel box girders have two webs and two flanges on top that are usually connected with shear connectors to the concrete deck and are also known as tub girders. The end diaphragms of such bridges comprise of a stiffened steel plate welded to the inside of the girder at each end. The diaphragms play a major role in transferring vertical and lateral loads to the bearings and substructure. A review of literature shows that the cyclic behavior of diaphragms under earthquake loading has not been studied previously. This paper uses a nonlinear finite element model to study the behavior of the end diaphragms under gravity and seismic loads. Different bearing device and stiffener configurations have been considered. Affected areas of the diaphragm are distinguished.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3D
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• pp.421-431
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• 2011

In this paper, actual bridges constructed with SMA (Stone Mastic Asphalt) deck pavement and virtual bridges substituted the deck pavement with polymer concrete under the same conditions were statically analyzed to investigate applicability of the thin polymer concrete bridge deck pavements. PSC (prestressed Concrete) girder bridge, steel box girder bridge, PSC box girder bridge, and RC (Reinforced Concrete) rahmen bridge constructed with the SMA deck pavement were analyzed and compared to evaluate various types of the bridge. The bridge deck and pavement were assumed to be fully bonded and the stress and deformation during the construction were ignored while those due to pavement weight and vehicle loading were analyzed. According to the analysis results, the stress and deformation of the bridges using the polymer concrete due to the pavement weight were smaller than those using the SMA because of smaller self weight due to lighter unit weight and thinner thickness of the pavement. The stress and deformation of the bridges using the polymer concrete due to the vehicle loading were larger than those using the SMA because of the smaller area moment of inertia due to the thinner pavement thickness. In case that the pavement weight and vehicle loading applied simultaneously, the stress and deformation of the bridges using the polymer concrete were smaller because effect of self weight reduction was more dominant. Investigation of performance of the bridge deck pavement and analysis of economical efficiency are warranted.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.2
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• pp.139-149
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• 2000

In the preliminary design stage of prestressed concrete (PSC) box girder bridges, the design factors decided by inexperience designer could heavily affect to the results of final design. There is a possibility that the design ends up with an excessively wasteful design. To achieve an economical design with preventing an excessive design, the optimal design technique has been developed using ADS optimal program and SPCFRAME in this study. The objective function for the optimal design problem is the material cost of box girders and constrained functions are constituted with design specifications and workability. The Sequential Unconstraint Minimization Technique (SUMT) is used for the optimal design in this study. We designed an uniform cross-section bridge and an ununiform cross-section bridge in the same design condition by optimal design technique developed in this study. Analyzing the results obtained for various tendon layouts, we suggest a standard tendon layout which gives the most effective structural behavior.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.674-679
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• 1998

In designing the prestressed concrete box-bridge, the dead load, prestressing force, creep and shrinkage of concrete are the main factors which influence the camber and deflection of segmental concrete structure under construction. Among these factors the creep and shrinkage are the functions of the time-dependent property which, therefore, must be considered with time. The prediction model for estimating creep and shrinkage of concrete has been suggested by ACI, CEB/FIP, JSCE and KSCE design code and EMM, AEMM, RCM, IDM and SSM has been suggested for analytical method in consideration of the time-dependent characteristics. In this study, the creep test was carried out for four curing ages of concrete which were applied to the prestressed concrete structure at a construction site, and the results of test were compared to the values of creep prediction by the design code. Also the creep test of step-wise incremental stresses were performed and were compared to analytical methods.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.73-82
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• 2022

The study presents a three-dimensional approach to simulate the nonlinear behavior of a 72 m long Ultra High Performance Fiber Reinforced Concrete (UHPFRC) pre-stressed box girder for a pedestrian bridge in Busan, South Korea. The concrete damage plasticity (CDP) model is adopted to model the non-linear behavior of the UHPFRC material, in which the material properties are obtained from uniaxial compressive and tensile tests. The simulation model based on the proposed stress-strain curve is validated by the results of four-point bending model tests of a 50 m UHPFRC pre-stressed box girder. The results from the simulation models agree with the experimental observations and predict the flexural behavior of the 50 m UHPFRC pre-stressed box girder accurately. Afterward, the validated model is utilized to investigate the flexural behavior of the 72 m UHPFRC pre-stressed box girder. Here, the load-deflection curve, stress status of the girder at various load levels, and connection details is analyzed. The load-deflection curve is also compared with design load to demonstrate the great benefit of the slender UHPFRC box girder. The obtained results demonstrate the applicability of the nonlinear finite element method as an appropriate option to analyze the flexural behavior of pre-stressed long-span girders.