There is a concern with worldwide deterioration of highway bridges, particularly reinforced concrete. The advantages of fiber reinforced plastic (FRP) composites over conventional materials motivate their use in highway bridges for rehabilitation and replacement of structures. In this paper, a systematic approach for analysis and design of all FRP deck/stringer bridges is presented. The analyses of structural components cover: (1) constituent materials and ply properties, (2) laminated panel engineering properties, (3) stringer stiffness properties, and (4) apparent stiffnesses for composite cellular decks and their equivalent orthotropic material properties. To verify the accuracy of orthotropic material properties, an actual deck is experimentally tested and analyzed by a finite element model. For design analysis of FRP deck/stringer bridge systems, an approximate series solution for orthotropic plates, including first-order shear deformation, is applied to develop simplified design equations, which account for load distribution factors under various loading cases. An FRP deck fabricated by bonding side-by-side box beams is transversely attached to FRP wide-flange beams and tested as a deck/stringer bridge system. The bridge systems are tested under static loads for various load conditions, and the experimental results are correlated with those by an approximate series solution and a finite element model. The present simplified design analysis procedures can be used to develop new efficient FRP sections and to design FRP highway bridge decks and deck/stringer systems, as shown by an illustrative design example.

A systematic analysis and design approach for single-span FRP deck/stringer bridges

Dynamic performance of existing high-speed railway bridges under resonant conditions retrofitted with fluid viscous dampers

Road transport and the related infrastructure are clearly an integral part of the economic, political and social development of the western world. Road pavements and bridges can be greatly damaged by excessively heavy vehicles. Great economies in the cost of road pavements can thus be achieved if truck and axle weights can be maintained within legal limits. Consequently, there has been a considerable research effort at European level on technologies for weighing trucks (and axles) while they are moving. The hope is that the accuracy of these so-called weigh-in-motion systems can be enhanced to such a level that they can be used directly for enforcement purposes. Bridge Weigh-in-Motion (B-WIM) systems are based on the measurement of the deformation of an existing bridge, and the use of these measurements to estimate the attributes of passing traffic. The purpose of this research is to enhance accuracy and usability of such B-WIM systems. B-WIM accuracy is heavily dependent on exact calibration, i.e., the correct choice of influence line or influence surface. A new method of influence line inference is presented. This matrix method has been developed to provide a fully automatic and accurately calibrated influence line from measurements of the bridge response to a truck of known weight. The B-WIM algorithm is extended to allow for the variation in the transverse position of the truck on the bridge. This involves moving from an influence line to an influence surface. Various methods were employed to calculate the transverse position of the crossing calibration vehicle. The calibration procedure to find the influence surface, solely from experimentally measured data, is presented. The accuracy of existing B-WIM systems is strongly affected by the number of vehicles present on the bridge during measurement. A B-WIM algorithm has been developed to cater for multi-vehicle events, thus removing unnecessary constraints regarding the operating environment of future B-WIM systems. The developed algorithms are verified using data from two test sites in Sweden and one in Vienna, Austria. A clear trend between erroneous results and the transverse position of the crossing vehicle is noted. The study suggests that the accuracy of B-WIM systems can be significantly enhanced through the use of a 2-D algorithm, based on the use of an influence surface. Adoption of the 2-D algorithm is also shown to allow the accurate determination of vehicle weights during multi-vehicle events. A detailed Finite Element model of an instrumented bridge and calibration vehicle is constructed and combined with a program that derives the interaction forces for bridge and vehicle models. These models are validated using measured data and a number of simulations performed which confirm the suitability of the 2-D B-WIM algorithm for such bridge types.

Bridge weigh-in motion : development of a 2-D multi-vehicle algorithm

Waffle slabs, also known as two-way ribbed flat slabs, are being used increasingly in modern construction to reduce dead weight and ensure efficient lateral distribution of loads. This paper presents the results of an experimental study of reinforced concrete waffle slabs with a square layout of ribs. Tests to failure were carried out on eight large-scale models with varied rib spacing and rib depth. The validity of the equivalent thickness concept was also examined by testing two related slabs. The results for the rigidities in the elastic-uncracked and elastic-cracked ranges were compared with predicted values obtained from three different methods. The theoretical analysis based on the conventional orthotropic plate theory gave satisfactory predictions but involves an elaborate procedure for determining the torsional rigidities. The equivalent thickness approach, which was modified to apply to the cracked as well as the uncracked ranges, gave moderately higher values for the rigidity than test results. An alternative simplified approximate method based on the effective modulus of elasticity is also proposed. Predictions for the rigidities by the proposed method were on the safe side and reasonably close to test results.

Rigidity and strength of orthotropic reinforced concrete waffle slabs

Those methods of bridge analysis that are developed basically for right bridges are also sometimes used for analyzing (skew bridges provided that the angle of skew is less than 20°. A critical review of this practice is presented in this paper, which also contains a recommended procedure for obtaining longitudinal moments with good accuracy in skew slab‐on‐girder bridges by this practice. It is shown that the errors in analyzing skew slab‐on‐girder bridges as right are not characterized by the angle of skew but by two dimensionless parameters, which depend upon the angle of skew, the spacing and span of girders, and their flexural rigidities relative to the flexural rigidity of the deck slab. Recommendations are given for the use of the simplified methods of analysis for skew slab‐on‐girder bridges. It is proposed that bridges having (S tan ϕ/L) less than 0.05 can be analyzed as equivalent right bridges, where S, L, and ϕ are the girder spacing, bridge span, and angle of skew, respectively.

Analysis of some skew bridges as right bridges

The book presents the theory and applications of the analytical techniques used in finding stresses in highway and other bridge decks. Current trends in bridge design and construction are discussed and are followed by the various analytical methods. The plate method is dealt with, initially by the basic derivation and solution of the plate equation. A chapter is devoted to the determination of the equivalent plate rigidities of various representative types of bridge deck. An approximate method of determination of bending moments for initial design is described. Various special applications of orthotropic plate theory are covered and the finite difference method for plates is described, including a summary of the dynamic relaxation method. The last four chapters deal with the stiffness method and its application: grillage and space frame analysis, the folded plate method, the finite element method, and the finite strip method. The book is intended for use by bridge designers and students with a particular interest in bridge engineering. /TRRL/

Bridge deck analysis

A method is presented based on articulated plate theory for the determination of the distribution of deflections, moments and forces in bridge decks made up of several beams. The analysis employs a single series solution of the plate equation. Design equations are presented in a simplified form. The solution covers the case of multibeam bridges with edge-stiffening beams. A method of selecting an optimum size of edge-stiffening beam is examined. Comparison is also made with previously reported tests on full size bridges.

Edge beam stiffening of multibeam bridges

The problem of designing a multibeam concrete bridge consisting of pretensioned beams, in which transverse distribution of the load is obtained by a combination of shear keys and transverse prestressing, is examined. It is shown that such a bridge may be designed by orthotropic plate theory with the choice of suitable flexural and torsional parameters. The flexural parameter is proved to be independent of transverse prestress and the torsional parameter increases with the value of transverse prestress. Experimental results are given for load tests of two model bridge desks. Comparison is also made with previously reported tests on a full-size bridge. Ultimate strength is also considered and an adaption of normal yield line theory is used to predict the ultimate loads of the two models.

Ricardo P. Pama

Papers

Bridge deck analysis

Edge beam stiffening of multibeam bridges

Design of Concrete Multibeam Bridge Decks