According to the Rubber Manufacturer’s Association, the United States generated 3664 thousand metric tons of scrap tires in 2015. While most waste tires are repurposed, approximately 409.5 thousand metric tons were disposed in landfills. This study investigates an alternative use of the waste tires as a replacement of natural aggregates in concrete mixtures. This study investigated fresh concrete properties and compressive strength. Different coarse and fine aggregate rubber particle sizes were evaluated: 19-mm tire chips (TCs) and 30-mesh crumb rubber (CR). TCs were used to replace coarse aggregates, while CR was used to replace fine aggregate in the concrete mixtures in increments of 10% by volume. Concrete strength loss was reduced with a fine aggregate replacement with CR as opposed to greater losses of strength exhibited by a coarse aggregate replacement with TCs. Adequate strengths were achieved at replacement levels as high as 40% by volume with CR, whereas satisfactory strengths were achieved with only a 10% replacement of coarse aggregates with TCs. Acceptable strengths were obtained from mixtures utilizing a combination of the two rubber sizes. Cement content was observed to have greater influence on rubberized concrete compressive strength at lower rubber contents than higher levels.

Multispan continuous bridges have been widely used in navigable waterways. However, their susceptibility to progressive collapse as a result of vessel collision is not yet fully understood. Experimental studies of bridge collapses induced by vessel collision are costly, time-consuming, and often not feasible. This paper presents a numerical study on the progressive collapse of a multispan continuous bridge subjected to vessel collision. A high-fidelity finite-element model of a 14-span continuous bridge, including its prestressed concrete (PC) superstructures and reinforced concrete (RC) pier columns/piles, and the colliding barge was developed to investigate the bridge failure mechanism. The validation was carried out for PC superstructures and RC structural members of the bridge piers by using available drop-weight impact tests of PC and RC beams. Furthermore, evaluation of available forensic investigation data, such as photographs and a survey of collapsed spans/piers, indicated that the progressive collapse was well predicted by the numerical analysis. Results show that the bridge pier directly impacted by a vessel will fail in the lateral direction of the bridge span, whereas nonimpacted piers will fail in the longitudinal direction of the bridge span. Results also show that the number of collapsed spans/piers depends on underwater terrain conditions and that the failure of the slender pier columns and piles results from plastic-hinge bending.