Dynamic response of bridges to multiple truck loading

Abstract

An analytical procedure called the iterative dynamic substructuring method (IDSM) is described for determining the response of a beam-slab bridge system traversed by multi-axle trucks. The trucks are idealized as systems of beams mounted on springs and the bridge as a grid. The IDSM applies mode superposition analysis to the bridge and truck as separate structures connected only at the time-dependent contact points. The bridge is subjected to forces equal to the time-dependent forces on the truck springs, while the truck is subjected to "ground" motion displacements. Since the forces in the spring and the ground motion are interdependent, an iterative procedure is necessary to achieve compatibility of forces and displacements at the contact points.The IDSM is employed to study the response to multiple vehicle loading of the Conestogo River bridge which was field tested by the Ontario Ministry of Transportation and Communications. The purpose of the analysis is to compare single with multiple vehicle loadings under various conditions of truck speeds and positions. The results are used to assess the validity of the reduction in impact factors applied to multiple vehicle loading in the Ontario Bridge Code.L'article decrit une mtthode dite "mtthode iterative d'Ctude dynamique par decomposition en sous-structures," applicable l'etude du comportement d'un pont poutre-dalle franchi par des camions B essieux multiples. Le pont est assimilt j. un grillage, tandis que les camions sont reprtsentCs comme des systkmes de poutres montees sur des ressorts. La mCthode de decomposition applique la technique de superposition modale au pont et au camion en les considerant comme des structures distinctes en contact seulement aux joints d'appui du camion, dont la position est fonction du temps. D'une part, l'ouvrage est sollicit6 par des forces egales aux forces dans les ressorts qui sont variables dans le temps; d'autre part, le camion est soumis aux deplacements correspondant aux mouvements du "sol." Puisque ces forces et ces dCplacements sont interdependants, on doit recourir a une methode itCrative pour satisfaire aux conditions de compatibilite des m&mes forces et deplacements aux points de contact.Les auteurs appliquent leur mCthode de dCcomposition I'analyse du pont de la riviere Conestogo sous charges roulantes multiples, pont qui a d t j i fait I'objet de mesures directes en nature par les ing6nieurs du Ministere des Transports et Communications de l'ontario. On veut, par cette recherche analytique, comparer les actions d'un v6hicule isolt et de plusieurs vkhicules sous des conditions diverses quant 5 leurs vitesses et a leurs precisians. Les resultats permettent de justifier la reduction des coefficents d'irnpact que prtvoit le reglement ontarien de calcul des ponts dans le cas d e charges roulantes multiples.[Traduit par la revue]Can. I. Civ. Eng., 8. 392-401 (1981)

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Analytical Modeling of Bridge-Road-Vehicle Dynamic Interaction System

“…The vehicle models consist of one degree of freedom (DOF; Chatterjee et al, 1994), two DOFs (Genin and Chung, 1979), or multiple DOFs (Veletsos and Huang, 1970;Wang et al, 1992). The types of bridges studied include single span bridges (Gupta and Trail-Nash, 1980), multispan continuous bridges (Hawk and Ghali, 1981;Green and Cebon, 1994;Chatterjee et al, 1994), cantilever bridges (Veletsos and Huang, 1970), and suspension bridges (Chatterjee et al, 1994). Table 1 summarizes the theoretical work performed by various researchers since 1970.…”