A new finite element methodology for the mathematical modeling of reinforced concrete multispan bridges, under static and dynamic loadings

Reinforced concrete bridges are key components of the surface transportation network of the United States. It is therefore crucial that they continue to function following a damaging magnitude earthquake and maintain both structural integrity and accessibility. Recent reports on earthquake bridge damage clearly indicate a crucial nonlinear soil/bridge interaction that affects the structural behavior of the bridge. The reported damages range from column failures to severe cracks of the bridge decks and even overturning of abutments. Neglecting these nonlinear interaction effects can lead to large errors in predicting ultimate loads or bridge capacity.;The present study deals with the following new developments: (1) A new composite flat shell element that incorporates the following features: (a) A composite finite element to combine the behavior of the steel and the concrete using a scheme suggested by T. J. R. Hughes based on Mindlin's theory which accounts for transverse shear deformations. (b) A new trilinear stress cross-section algorithm to simulate the crack formation in the reinforced concrete, embedded in the new composite finite element. (c) A time step algorithm based on Newmark's method that incorporates the stress cross-section algorithm embedded in a cost-efficient predictor/corrector scheme, filtering high frequency residual modes. (2) A thorough comparative study on the performance of a new computer model incorporating the features above with existing computer models (GTSTRUDL, ADINA) and different computer environments such as the CRAY/XMP (supercomputer), ALLIANT/FX8 (mini-supercomputer) and the VAX11/780 (mainframe) computers. These comparative studies demonstrated a substantial improvement in modeling using the features outlined in (1) for a finite element computer model and clearly demonstrated the feasibility of completing an entire soil/bridge structure interaction analysis on computers of the ALLIANT class. (3) Validation of the above model for a real scale prototype of a typical three-span reinforced concrete box girder bridge was carried out using 4600 degrees of freedom.;The proposed new methodology for the modeling of reinforced concrete bridges was shown to perform well when subjected to loading using record seismograms from actual earthquakes. This model offers the only known comprehensive method to perform a nonlinear soil/bridge structure analysis which can be used to investigate collapsing mechanisms resulting from seismic wave excitations.