I-75 Over State Rd. 441 - Alachua, FL

The Problem

Damage to Bottom Flange

The bridge, located on I-75 over State Road 441 near Alachua, Florida, is 178 ft. long and has four simple spans. The main span is 48 ft. long and consists of a 7 inch thick concrete deck supported by nine AASHTO Type II pre-stressed concrete girders spaced at 6 ft. centers. The bridge is designed to carry three lanes of AASHTO HS-20 loading. The bridge was severely damaged when a vehicle transporting pre-manufactured homes struck the girders. The collision resulted in extensive damage of several girders.


Views of Damage

The exterior girder and the first interior girder sustained the most damage. These girders exhibited severe shear cracking and section loss, as well as pre-stressing loss in two strands.

Load testing evaluation revealed deficiencies in flexural and shear capacities requiring immediate attention. The bridge, being located on I-75 with heavy daily traffic, created an emergency situation. The option of closing one lane in order to perform conventional repairs or to replace the two damaged girders was undesirable. Furthermore, the traffic on SR-441 was also heavy with no easy detour routes available.

The situation called for an innovative alternative for bridge rehabilitation instead of lengthy conventional repair methods or costly replacement of the girders. The MAS2000 Fiber Wrap System was proposed to restore the strength of the girders to their original condition.

The Solution

Girder after Patching

The MAS2000 Fiber Wrap System repair technique was designed to accommodate the change in flexural and shear strengths of the girders and re-establish the stiffness of the section. The damaged girders were analyzed using a non-linear finite element program developed by SDR engineers. The results of the analysis were used to design the optimum restoration solution.

Upon arrival at the remote location, the repair crew discovered a complication involving contamination of the concrete due to oil bleeding down from the surface of the bridge. SDR overcame the poor bonding problem by using special degreasing chemicals and a specially suited epoxy adhesive.

The cross section was first restored to its original shape using high quality concrete capable of achieving full strength within 24 hours. The section restoration was followed by surface preparation according to SDR specifications. The MAS2000 Fiber Wrap System was then applied to the concrete girders over a distance of 20 ft., resulting in a complete restoration of the girders. The original appearance of the structure was restored and enhanced through painting the laminates with a specially designed ultraviolet (UV) coating.


Structure After Repair (Prior to Final Coating Being Applied)