Location: St. Landry Parish, Louisiana, United States

PROJECT SUMMARY

This study evaluates the capacity of a trestle bridge to support crane lifting operations. The bridge geometry was provided by the contractor, and several analyses were conducted using the original trestle configuration. To enhance load distribution from the crane crawlers to the superstructure twin beams, a modified trestle geometry was proposed. 

The analysis was performed using a Kobelco CK 2500-II crawler crane with estimated lifting loads to determine the bearing pressure on both crawlers. It was found that a crane swing angle of 90 degrees resulted in the worst-case loading scenario, which was applied in all analysis cases. The crane was positioned in two orientations to determine the most critical loading conditions for the trestle bridge superstructure. 

Initially, the original trestle geometry was analyzed with the crane crawlers positioned parallel to the bridge span. The results indicated significant differences in the distribution of moment and shear forces between the twin beams due to the crawler’s eccentricity. To address this uneven force distribution, a modified trestle beam spacing was proposed and used for further evaluation. 

The modified trestle geometry was then analyzed with the crane crawlers positioned parallel to the span. The results showed that the superstructure, including both the longitudinal and transverse header beams, could safely support the applied loads. As a precautionary measure, it is recommended to mark guidance lines on the bridge surface for the crane operator to follow during lifting operations. 

Additionally, the modified trestle geometry was analyzed with the crane crawlers positioned perpendicular to the span. While the longitudinal beams were found to safely support the loads, the header beams failed to meet the required moment and shear capacities. Therefore, it is not recommended to position the crane in this orientation. 

Finally, pile loads were estimated for the case where the crane crawlers were positioned parallel to the span. A summary of both service and factored loads was provided to aid in the pile design.