Effect of material uncertainties on dynamic responseof segmental box girder bridge

Suchart Limkatanyu 1 and Kittisak Kuntiyawichai 2

AbstractLimkatanyu, S. and Kuntiyawichai, K.Effect of material uncertainties on dynamic response ofsegmental box girder bridgeSongklanakarin J. Sci. Technol., 2007, 29(6) : 1537-1550

The main objective of this paper was to investigate the effect of material uncertainties on dynamicresponse of segmental box girder bridge subjected to a moving load, in this case a rapid passing trains.Literatures concerned with the design of segmental box girder bridge, the application of finite elementanalysis to model the segmental box girder bridge, and the minimum requirement for structural conditionsof the bridge were described and discussed in detail. A series of finite element analysis was carried out usingSAP2000 Nonlinear software. The effect was investigated by varying the Modulus of Elasticity by 5%, 10%and 15%. The results were then compared with the case of assumed uniform property which had alreadybeen checked for model accuracy using the Standard prEN 1991-2.

The results showed that, for the uniform case, the dynamic responses of the bridge gave the highestresponse at the resonance speed. When considering the non-uniform material properties (non-uniform case),the effect of material uncertainties appeared to have an effect on both displacement and accelerationresponses. Nonetheless, the dynamic factor provided in the design code was sufficient for designing the

ORIGINAL ARTICLE

1Ph.D. (Structural Engineering and Structural Mechanics), Asst. Prof., Department of Civil Engineering,Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla, Thailand, 90112 Thailand. 2Ph.D.(Structural Engineering), Asst. Prof., Department of Civil Engineering, Faculty of Engineering, Ubonratcha-thani University, Warinchamrap, UbonRatchathani, Thailand, 34190 Thailand.Corresponding e-mail: kittisak.ubu@gmail.comReceived, 22 August 2006 Accepted, 15 May 2007

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Effect of material uncertainties of segmental box girder bridge

Limkatanyu, S. and Kuntiyawichai, K.

segmental box girder bridge with either uniform or non-uniform material properties for the train speedsconsidered in this study.

Key words : segmental box girder bridge, dynamic response, rapid passing train,material uncertainties

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For thousands of years, human has usedbridges to cross any obstructions from traveling(e.g. river, road). Several types of bridges havebeen used and various types of bridge construct-ion techniques have been created (Xanthakos,1994). Novel and innovative construction tech-niques, however, are still needed. External-pre-stressed precast-concrete segmental hollow box-girder bridge is one of the major developments inbridge construction techniques over the last fewyears. This development was due to the highdemands on economical design, high durability,and fast and versatile construction. The greatadvantage of this construction technique hasrendered them the more desirable structures for

many large elevated highways and railway bridges,especially in Southeast Asia region. As opposed toclassical monolithic structures, a segmental bridgeconsists of "small" pieces stressed together byexternal tendons as shown in Figure 1.

With regards to railway bridges, one of themain design issues is related to the dynamic(moving) loadings, for which basic solutions weredescribed by Timoshenko, Young, and Weaver(1974), and fully discussed by Fryba (1972, 1996).Most engineering design codes for railway bridgeshave followed the approach using the dynamicamplification factor proposed in UIC (1979), FS(1997), IAPF (2001), and prEN 1991-2 (2002). Thisapproach takes into account the dynamic effects

Songklanakarin J. Sci. Technol.

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Effect of material uncertainties of segmental box girder bridge

Limkatanyu, S. and Kuntiyawichai, K.1549

Table 4. Comparison of the distribution of displacement response due to different variation ofmaterial properties.

Train Variation Min. Mean Max. Different between Different betweenSpeed of material Displacement Displacement Displacement Min. and Mean Mean and Max.(kph) property (m) (m) (m) response (%) (%)

100 Uniform - 0.004529 - - -5% 0.004413 0.004515 0.004604 2.26 1.9310% 0.004344 0.004519 0.004705 3.87 3.9515% 0.004316 0.004542 0.004840 4.98 6.16

150 Uniform - 0.004823 - - -5% 0.004506 0.004787 0.005083 5.87 5.8210% 0.004301 0.004813 0.005439 10.68 11.5215% 0.004299 0.004817 0.005444 10.71 11.52

Table 5. Comparison of the distribution of acceleration response due to different variation ofmaterial properties.

Train Variation Min. Mean Max. Different between Different betweenSpeed of material Acceleration Acceleration Acceleration Min. and Mean Mean and Max.(kph) property (m/s2) (m/s2) (m/s2) response (%) (%)

100 Uniform - 0.7098 - - -5% 0.6788 0.7139 0.7418 4.92 3.7610% 0.6555 0.7122 0.7658 7.96 7.0015% 0.6301 0.7108 0.7891 11.35 9.92

150 Uniform - 0.7214 - - -5% 0.6582 0.7144 0.7614 7.87 6.1710% 0.6054 0.7172 0.8111 15.62 11.5815% 0.6052 0.7176 0.8116 15.64 11.58

effects of dynamic loads and material uncertain-ties on the responses of the segmental box girderbridge are also sufficient for the accelerationresponse.

Conclusions

This paper presented the effect of materialuncertainties of concrete on the dynamic responseof segmental box girder bridge using the finiteelement software SAP2000 Nonlinear. Theanalyses deal with the material properties, i.e.uniform material properties (uniform case) andnon-uniform material properties (non-uniform case)

of the bridge. For the uniform case, the dynamicresponses of the bridge gave the highest responseat the resonance speed (V=174 km/hr) because ofthe resonance phenomena. When considering thenon-uniform material properties (non-uniformcase), the effect of material uncertainties appearsto have an effect on both displacement andacceleration response. There is an importantevidence from this study that the dynamic factorprovided in the design code is sufficient fordesigning the segmental box girder bridgecontaining either uniform or non-uniform materialproperties for the train speeds considered in thisstudy.

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Effect of material uncertainties of segmental box girder bridge

Limkatanyu, S. and Kuntiyawichai, K.

Acknowledgments

The authors would like to express theirsincere thanks to the Department of Civil Engi-neering, Prince of Songkla University and theDepartment of Civil Engineering, UbonratchathaniUniversity for providing research facilities fromwhich the authors were able to perform the presentresearch work.

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