Live Load Distribution Factors for a Lightweight Movable Bridge Deck System

Louisiana has approximately 160 movable bridges, mostly in the southern part of the state. The typical deck systems in these movable bridges are steel grids. Records show that steel grids have had maintenance issues. A precast lightweight concrete deck system for Louisiana’s movable bridges is presented. The deck configuration features a multi-rib T-beam configuration. Live load distribution factors (LLDFs) for flexure and shear are quantified so that the deck system can be designed using the traditional beam line analysis method. Several nonlinear finite element analyses were conducted to quantify worst case LLDFs for interior and exterior ribs. A variety of load positions and span configurations are examined. LLDFs for moment and shear vary from 0.63 to 0.87, and from 0.64 to 0.86, respectively. The LLDFs for flexure and shear provided in this paper offer a practical approach for designing this new deck system for movable bridges.