• Structural Engineering and Mechanics
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• v.42 no.3
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• pp.291-311
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• 2012

The multi-span suspension bridge having double main cables in the vertical plane is investigated regarding endurance of live load distribution in the case of non-displaced pylon and pylon displacement. The coefficient formula of live load distribution described as the ratio of live load on the bottom cable to the top cable is obtained. Based on this formula, some function in respect of this bridge are derived and used to analyze its characteristics. This analysis targets the cable force, the cable sag and the horizontal displacement at the pylon top under live load etc. The results clarified that the performance of the live load distribution and the horizontal force of cables in the case of non-deformed pylon has a similar tendency to those in the case of deformed pylon, and the increase of pylon rigidity can increase live load distributed to the bottom cable and slightly raise the cable horizontal force under live load. However, effect on the vertical rigidity of bridge and the horizontal force increment of cables caused by live load is different in the case of non-deformed pylon and deformed pylon.

• Structural Engineering and Mechanics
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• v.34 no.5
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• pp.635-662
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• 2010

In this study, the effect of superstructure-abutment continuity on the distribution of live load effects among the girders of integral abutment bridges (IABs) is investigated. For this purpose, two and three dimensional finite element models of several single-span, symmetrical integral abutment and simply supported (jointed) bridges (SSBs) are built and analyzed. In the analyses, the effect of various superstructure properties such as span length, number of design lanes, girder size and spacing as well as slab thickness are considered. The results from the analyses of two and three dimensional finite element models are then used to calculate the live load distribution factors (LLDFs) for the girders of IABs and SSBs as a function of the above mentioned parameters. LLDFs for the girders are also calculated using the AASHTO formulae developed for SSBs. Comparison of the analyses results revealed that the superstructure-abutment continuity in IABs produces a better distribution of live load effects among the girders compared to SSBs. The continuity effects become more predominant for short span IABs. Furthermore, AASHTO live load distribution formulae developed for SSBs lead to conservative estimates of live load girder moments and shears for short-span IABs.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.288-293
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• 2008

The standard prestressed concrete I-girder bridge (PSC I-girder bridge) is one of the most prevalent types for small and medium bridges in Korea. When determining the member forces in a section to assess the safety of girder in this type of bridge, the general practice is to use the simplified practical equations or the live load distribution factors proposed in design standards rather than the precise analysis through the finite element method or so. Meanwhile, the live load distribution factors currently used in Korean design practice are just a reflection of overseas research results or design standards without alterations. Therefore, it is necessary to develop an equation of the live load distribution factors fit for the design conditions of Korea, considering the standardized section of standard PSC I-girder bridges and the design strength of concrete. In this study, to develop an equation of the live load distribution factors, a parametric analysis and sensitivity analysis were carried out on the parameters such as width of bridge, span length, girder spacing, width of traffic lane, etc. Then, an equation of live load distribution factors was developed through the multiple linear regression analysis on the results of parametric analysis. When the actual practice engineers design a bridge with the equation of live load distribution factors developed here, they will determine the design of member forces ensuring the appropriate safety rate more easily. Moreover, in the preliminary design, this model is expected to save much time for the repetitive design to improve the structural efficiency of PSC I-girder bridges.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.119-120
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• 2009

The Live load distribution factors currently used in the standard prestressed concrete I-girder bridge are just a reflection of overseas design standards. Therefore, it is necessary to develop an equation of the live load distribution factors fit for the design conditions of Korea, considering the standardized section and the design strength of concrete. In this study, the major variables to determine of distribution factors were selected and an equation of live load distribution factors was developed.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.535-542
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• 2006

In this study, the effects of cross beams on the lateral distribution of live loads in composite rolled H-beam girder bridges, were investigated through three-dimensional finite element analysis. The parameters considered in this study were the inertial moment ratio between the main girder and the cross beam, the presence of the cross beam, and the number of cross beams. The live load lateral distribution factors were investigated through finite element analysis and the customary grid method. The results show that there was no difference between the bridge models with and without a cross beam. The cross beam of the beam and frame types also showed almost the same live load lateral distribution factors. However, the finite element analysis showed that the concrete slab deck plays a major role in the lateral distribution of a live load, and consequently, the effect of the cross beam is not so insignificant that it can be neglected.

• Journal of Applied Reliability
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• v.16 no.2
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• pp.90-97
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• 2016

Purpose: Majority of bridges and roads in Gangwon Province have been carrying loads associated with heavy materials such as rocks, mining products, and cement. This location-specific live loads have contributed to the present situation of overloading, compared to other provinces in Korea. However, the bridges in Gangwon province are designed by national bridge design specification, without considering the location-specific live load characteristics. Therefore, this study focuses on the real traffic data accumulated on regional weighing station to verify the live load characteristics, including actual live load gross vehicle weight, axle weight axle spacings, and number of trucks. Methods: In order to take into account the location specific live load, a governmental weigh station (38th national highway Miro) have been selected and the passing truck data are processed. Based on the truck survey, trucks are categorized into 3 different shapes, and each shape has been idealized into normal distribution. Then, the resulting survey data are processed to predict the target maximum live load values, including the axle loads and gross vehicle weights in 75 years service life span. Results: The results are compared to the nationally used DB-24 live loads, and the results show that nationally recognized DB-24 live load does not sufficiently represent real traffic in mountaineous region in Gangwon province. Conclusion: The comparison results in the recommendation of location-specific live load that should be taken into account for bridge design and evaluation.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.234-239
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• 1992

Design live load and girder distribution factors play an important role in the current design procedures. The fraction of vehicle load effect transferred to a single member may be selected in accordance with current KBDC. However, the specified values, both design load and distribution factors involve considerable inaccuracies, These inaccuracies relate to the uncertainties of the structural analysis, especially any bias and scatter which drives from the use of simplified load distribution factors. In this study , based on several field measurement and finite element analysis, live load distribution effects of current KBDC are evaluated. The final values of the bias and coefficient of variation of "g"according to bridge type are determined. The bridge types are reinforced concrete slab, prestressed concrete girder and steel l-beam.el l-beam.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.1
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• pp.91-101
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• 2008

Structural analysis models to develop live load distribution factors of simply supported prestressed concrete I-girder bridge should have the precision of the analysis results as well as modeling simplicity. This is due to the numerous frequency of structural analysis needed while developing live load distribution factors. In this study, an appropriate structural analysis model is selected by comparing previous researchs studies and models used in practical design. Also, the influence by the flexural stiffness of barrier and diaphragm on the live load distribution had been analyzed through comparing the numerical analysis and experimental tests. As a result, the model that the eccentric girder and the barrier and diaphragm are connected to the deck plate was appropriate in satisfying both accuracy and simplicity for structural analysis of simply supported prestressed concrete I-girder bridge. However, the barrier was analyzed to have insignificant influence on the live load distribution in spite of its variation of stiffness. The eccentric diaphragm showed little influence at 25% or higher of flexural stiffness. From the results, a model that the girder is rigidly connected to the deck plate in consideration of the eccentricity, the barrier is ignored and the whole section of diaphragm is supposed to be valid without eccentricity is decided as the most appropriate structural model to develop the live load distribution factors of simply supported prestressed concrete I-girder bridge in this study.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.725-732
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• 2006

This study has been started for the development of a refined live load distribution formula that has safety and precision toward I type prestressed concrete girder bridge. This type of bridge is mainly applied to short span bridges that are $25{\sim}40m$ in length. Based on various structure analysis models that are currently being applied as preceding studies for the development of live load distribution method. an analysis of flexural stiffness ratio for barrier and diaphragm has been performed. As the result of parametric analysis for the changes in flexural stiffness ratio, the effect of barrier on load distribution showed as insignificant in all structural analysis models while analyzing the deflection distribution. Also. the deflection distribution of the models with stiffness of 25% in which the diaphragm eccentricity is accounted for as same as the models with stiffness of 100% in which the diaphragm eccentricity is unaccounted for. This results are verified through the comparison with a experimental data.

• Advances in concrete construction
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• v.3 no.4
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• pp.295-316
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• 2015

A bridge widening technology using steel-concrete composite system was developed and is presented in this paper. The widened superstructure system consists of a newly built composite steel-concrete girder with concrete deck and steel diaphragms attached to the existing concrete girders. This method has been applied in several bridge widening projects in China, and one of those projects is presented in detail. Due to the higher stiffness-to-weight ratio and the rapid erection of composite girders, this widening method reveals benefits in both mechanical performance and construction. As only a few methods for the design of bridges with different types of girders are recommended in current design codes, a more accurate analytical method of estimating live load distribution on girder bridges was developed. In the analytical model, the effects of span length, girder pacing, diaphragms, concrete decks were considered, as well as the torsional and flexural stiffness of both composite box girders and concrete T girders. The study shows that the AASHTO LRFD specification procedures and the analytical models proposed in this paper closely approximate the live load distribution factors determined by finite element analysis. A parametric study was also conducted using the finite element method to evaluate the potential load carrying capacities of the existing concrete girders after widening.