Colorado Department of Transportation. Applied Research & Innovations Branch
Abstract
This report presents three major aspects that are related to the evaluation of timber bridges with and without repair: i) laboratory testing, ii) finite element modeling, and iii) load ratings. In addition, worked examples are provided to demonstrate the implementation of research findings. The first part of the report explores the effectiveness of various retrofit techniques in improving the flexural behavior of structural timber. The second part presents the behavior of a timber bridge strengthened with lag bolts, carbon fiber reinforced polymer (CFRP) sheets, and hollow structural sections (HSS). The third part discusses load ratings for timber bridges repaired with HSS. A mechanics-based rating approach is proposed to holistically rate these bridges before and after the repair. The capacity of the girders with the steel beams is as high as 2.56 times that of the control girders. Likewise, the allowable stress of the timber is improved by a factor of 1.39 and 2.09 for flexure and shear, respectively. The effectiveness of the repair becomes pronounced when the deterioration level of the timber girders rises, and the geometric properties of the steel beams are a crucial consideration that alters the rating of the repaired girders. The placement of grouped steel beams is recommended to raise the efficacy of the repair system
