End Diaphragm Cracking of Box Girder Bridges due to Post-tensioning: Case Study

Adequate dimensioning and detailing of box girders end diaphragm is critical for proper performance of post‐tensioned bridges. Current design methods have led to highly congested anchorage zones with construction issues and cracking problems. In order to study the performance of anchorage zones, box girders end diaphragms were instrumented in the field. Strain gauges were used in order to capture stresses in reinforcing bars and strains within the concrete elements. End diaphragm cracking was observed during post‐tensioning for one of the investigated bridges. These cracks were not noticed during regular inspection because they occurred on the inner face of the diaphragm inside the box section. Skew angle of the end diaphragm is a governing factor affecting cracks distribution. The paper will discuss reasons for the developed cracks and highlight design recommendations.