• Structural Engineering and Mechanics
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• v.64 no.2
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• pp.213-223
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• 2017

Bridges are lifeline and integral components of transportation system that are susceptible to seismic actions, their vulnerability assessment is essential for seismic risk assessment and mitigation. The vulnerability assessment of bridges common in Pakistan is very important as it is seismically very active region and the available code for the seismic design of bridges is obsolete. This research presents seismic vulnerability assessment of three real case simply supported multi-span reinforced concrete bridges commonly found in northern Pakistan, having one, two and three bents with circular piers. The vulnerability assessment is carried through the non-linear dynamic time history analyses for the derivation of fragility curves. Finite element based numerical models of the bridges were developed in MIDAS CIVIL (2015) and analyzed through with non-linear dynamic and incremental dynamic analyses, using a suite of bridge-specific natural spectrum compatible ground motion records. Seismic responses of shear key, bearing pad, expansion joint and pier components of each bridges were recorded during analysis and retrieved for performance based analysis. Fragility curves were developed for the bearing pads, shear key, expansion joint and pier of the bridges that first reach ultimate limit state. Dynamic analysis and the derived fragility curves show that ultimate limit state of bearing pads, shear keys and expansion joints of the bridges exceed first, followed by the piers ultimate limit state for all the three bridges. Mean collapse capacities computed for all the components indicated that bearing pads, expansion joints, and shear keys exceed the ultimate limit state at lowest seismic intensities.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.563-568
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• 2003

High-speed railway bridges subject to effect of dynamic loads by interaction between vehicle load which run specially fast and behavior of bridges. Such dynamic load effects result in fluctuations and fatigues to each elements as well as whole conduct of bridges. and is influenced in life of bridges. For these reason. Analysis and estimation of data about dynamic behavior of bridges occupies important factor in that estimate the remaining life of bridges and select the maintenance. repair and retrofit. In this paper. Analysis for the dynamic behavior of bridges using displacement and acceleration data that is actuality measure data to the bridges of Seoul-Susan high speed railroad test section has been made.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.111-135
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• 2015

Bridge behavior under passing traffic loads has been studied for the past 50 years. This paper presents how to model congestion on bridges and how the maximum dynamic stress of bridges change during the passing of moving vehicles. Most current research is based on mid-span dynamic effects due to traffic load and most bridge codes define a factor called the dynamic load allowance (DLA), which is applied to the maximum static moment under static loading. This paper presents an algorithm to solve the governing equation of the bridge as well as the equations of motions of two real European trucks with different speeds, simultaneously. It will be shown, considering congestion in eight case studies, the maximum dynamic stress and how far from the mid-span it occurs during the passing of one or two trucks with different speeds. The congestion effect on the maximum dynamic stress of bridges can make a significant difference in the magnitude. By finite difference method, it will be shown that where vehicle speeds are considerably higher, for example in the case of railway bridges which have more than one railway line or in the case of multiple lane highway bridges where congestion is probable, current designing codes may predict dynamic stresses lower than actual stresses; therefore, the consequences of a full length analysis must be used to design safe bridges.

• Journal of the Korean Society for Railway
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• v.8 no.1
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• pp.41-50
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• 2005

Steel -Concrete Composite two girder railway bridges applying high performance steel with extra thick plate have economic and aesthetic advantages due to the simplification of manufacturing and construction process. However, steel bridges are seldom adopted in domestic railway bridge, since steel bridges are not efficient as R.C bridges considering dynamic characteristics and noise, etc. While highway bridges do not have lower horizontal bracing and larger interval of diaphragm cross beam, railway bridges install lower horizontal bracings to control the torsion due to heavy eccentrical line load. Accurate finite element analysis were performed with the parameters of existence of bracing and bracing shape, with the cross beam interval and stiffness, etc. To find out the effects of secondary members such as horizontal bracings and diaphragms, static md dynamic analysis have been performed by using finite element method. In this study, few member plate-girder bridges are analyzed with variable span lengths to examine the dynamic behavior and limits of damping. And though lateral bracings are members against torsion, but lateral bracing's absence is no big problem. Time history analysis using mode superposition method makes proof of this result.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.310-315
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• 2001

In this study, railway plate girder bridges are modeled in detail for finite elements within 3-dimension and analyzed by SAP 2000N, a commercial finite element analysis tool. Especially, loads of trains gained by statistical averages of measured true loads of trains are used for analysis. When the loads are adapted, the numerical dynamic responses are very close to real measurements. Resonant speed areas by train types are evaluated from the results of numerical analyses by different driving speeds of trains. For dynamic numerical analysis of railway bridges, reasonable guides are also discussed.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.954-959
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• 2011

The intensity of train load in the railway bridges is relatively large and continues to repeat. Also, the speed of vehicles is very fast. For these reasons, analyses for dynamic response under train load are necessary in the railway bridges. In other words, the dynamic characteristics of steel-composite bridges under train loads should be investigated considering effects of dynamic responses such as vibrations, repeated displacements and acceleration of bridge members. Therefore, in this study, static and dynamic analyses for the steel box girder bridges and I-girder bridges are carried out. Based on analyses results, we investigated and compared dynamic response considering the impact factors of domestic and foreign design specifications.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.43-49
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• 2012

In the design of high speed railway bridges is important a impact factor as a tool of assessing the dynamic capacitys of bridges. However, the impact factor(or dynamic amplification factor, DAF) of high speed railway bridges may essentially be changeable because the dynamic response is affected by the long train length(380 m), number of axles and high speed velocity(300 km/h)(Korea Train eXpress: KTX). Therefore, on this study will be examined the dynamic capacity and stability of the typical PSC Box Girder of high speed railway bridge. At first, the static/dynamic analysis is performed considering the axle load line of KTX based upon existing references. Additionally, the KTX moving load is transformed into the dynamic time series load for conducting various parameter studies like axle length, analytical time increment, velocity of KTX. The time history analysis is repeatedly performed to get maximum dynamic responce by varying axle load length, analytical time increment, velocity of KTX. The study shows that dynamic analysis has resonable results with optimal axle load length(0.6 m) and time increment(0.01 sec.) and maximum DAF and dynamic resonance happens at 270 km/h velocity of KTX.

• Structural Engineering and Mechanics
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• v.46 no.5
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• pp.713-734
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• 2013

Bridges are vital components of the railroads. High speed of travel, the periodic and oscillatory nature of the loads and the comparable vehicle bridge weight ratio distinguish the railway bridges from the road bridges. The close proximity between estimations by some numerical methods and the measured data for the bridge-vehicle dynamic response under the moving load conditions has boosted the confidence in the numerical analyses. However, there is hardly any report regarding the responses of the railway bridges under the effect of the trains entering from the opposite directions while running at unequal speed and having dissimilar geometries. It is the purpose of this article to present an analytical method for the dynamic analysis of the railway bridges under the influence of two opposing series of moving loads. The bridge structural damping and many modes of vibrations are included. The concept of modal superposition is used to solve for the system motion equations. The method of solution is indeed a computer assisted analytical solution. It solves for the system motion equations and gives output in terms of the bridge deflection. Some case studies are also considered for the validation of the proposed method. Furthermore, the effects of varying some parameters such as the distance between the bogies, and the bogie wheelset distance are studied. Also, the conditions of resonance and cancellation in the dynamic response for a variety of vehicle-bridge specifications are investigated.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.1
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• pp.103-115
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• 1994

The dynamic earthquake analysis of plane cable-stayed bridge structures was formulated and implemented into a computer program which analyzes plane cable-stayed bridge structu- res subjected to initial cable tensions, member dead and live loads and seismic loads. Cable-stayed bridges were modelled as multi-degrees of freedom systems with lumped- mass. Various earthquake responses such as dynamic deflection, bending moment, shear force and cable tension were investigated by the dynamic analyses in the form of the time history analysis. The time history analysis was based on the mode superposition method. The study revealed that Fan-l type cable-syayed bridges is generally superior to other types for the earthquake proof even though aspects of deflection and section force of each type presents respective advantages and disadvantages. The study provided a method to design the sections of cable-stayed bridges under seismic loads with various design parameters related to structural types. The study is expected to be useful for effective design of cable-stayed bridges with conside- ration of earthquake.

• Structural Engineering and Mechanics
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• v.41 no.4
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• pp.539-558
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• 2012

The diagnosis of bridge serviceability is carried out by a combination of in-situ visual inspection, static and dynamic loading tests and analyses. Structural health monitoring (SHM) using information technology and sensors is increasingly being used for providing a better estimate of structural performance characteristics rather than above traditional methods. Because the mechanical behavior of bridges with various kinds of damage can not be made clear, it is very difficult to estimate both the damage mode and degree of damage of existing bridges. In this paper, the sensitivity of both static and dynamic behaviors of bridges are studied as a measure of damage assessment through experiments on model bridges induced with some specified artificial damages. And, a method of damage assessment of bridges based on those behaviors is discussed in detail. Finally, based on the results, a possible application for structural health monitoring systems for existing bridges is also discussed.