Bridge Timber Piles Load Rating under Eccentric Loading Conditions

Abstract

This study evaluates the load rating procedure that is currently used in rating timber piles supporting multiple-span simply supported bridges. For simplicity, these piles are often rated under concentric loads and the effect of bending in the piles is neglected. Recent studies have shown, however, that under highly eccentric live loads, the effect of bending moments in the piles are of great importance and could have a dramatic effect on the load rating of the piles. This paper proposes an alternative structural load rating method for timber piles based on the National Design Specifications, which takes the effect of combined compression-flexure behavior of piles into consideration. This method is used to conduct a parametric study to investigate the effect of several geometric and structural parameters on the load rating of bridge timber piles using three-dimensional finite element models of concrete-deck bridges supported on group of timber piles. The results show that the proposed load rating method produces significantly less ratings for piles with moderate-to-high levels of deterioration, as compared with that obtained by the conventional approach. Among the studied parameters, the pile length is found to have the most significant impact on the pile load rating.