Simplified System-Level Pavement-Stiffness Model for Box Culvert Load-Rating Applications

Abstract

Tens of thousands of aging, bridge-class, RC box culverts are in service in the United States. Within the context of establishing load rating for in-service RC box culverts, this paper introduces, calibrates, and applies a system-level pavement-stiffness model to a production-simplified, soil–structure interaction model used for calculating load demands. The proposed pavement-stiffness model uses system-level pavement data to account for the additional stiffness provided by the pavement structure to attenuate live load. The full cover-soil depth is modeled using linear-elastic finite elements per the production-simplified soil–structure interaction model, and the additional stiffness provided by the pavement structure is modeled using beam elements across the top row of finite-element nodes. Equivalent beam-modulus values for the system-level pavement-stiffness model were calibrated against results from a research-intensive, full-pavement model for various pavement types. A parametric study using the proposed model showed that the inclusion of pavement stiffness could increase the load ratings for both asphalt pavements with an intermediate thickness and concrete pavements, for both direct-traffic and low-fill RC box culverts. The effects of the system-level pavement-stiffness model on predicted live-load moment response were further evaluated using measured live-load moments from field live-load tests on in-service culverts. From these comparisons, the system-level pavement-stiffness model showed improved accuracy and precision of the live-load demand prediction. Finally, load-rating analyses performed for an illustrative sample of 24 in-service Texas RC box culverts under various pavement types showed improved rating factors from the system-level pavement-stiffness model compared to the production-oriented soil–structure interaction model without pavement stiffness and the AASHTO-recommended structural-frame model. The inclusion of the pavement stiffness when modeling in-plane live-load attenuation improves the RC box culvert load-rating results and can be implemented for systemwide infrastructure management.