US-80 TEXAS STREET BRIDGE OVER RED RIVER

US-80 TEXAS STREET BRIDGE OVER RED RIVER

The US-80 Texas Street Bridge, built in 1934, is an historic bridge which carries US-80 over the Red River. The bridge is used primarily for local traffic traveling between the cities of Shreveport and Bossier City in Louisiana. The bridge consists of 45 spans with a total length of 2,895 ft. The approach spans consist of reinforced concrete T-beam girders and steel deck trusses. The main span is composed of three steel truss spans.

SDR’s scope of work included in-depth inspection of all structural elements; LRFR load rating analysis; identification of structurally-deficient elements, and design of structural strengthening. A three-dimensional finite element analysis was utilized to determine the internal forces on all structure members. SDR also provided construction support.

BAYOU LAFOURCHE BRIDGE TESTING

BAYOU LAFOURCHE BRIDGE TESTING

The Bayou Lafourche Bridge is located on US 80 over the Bayou Lafourche Diversion Canal in Louisiana. This project adopted the innovative approach of Accelerated Bridge Construction (ABC) for rapid construction of precast concrete I-girder bridges and marks the first time this process was implemented in Louisiana. This bridge consists of six prestressed concrete girders, supporting the full-depth pre-stressed deck panels. The panels were post-tensioned along the spans during construction. SDR was tasked with instrumentation plan development, installation, and load testing of the bridge in order to study behavior of the bridge at various stages of construction, as well as during service life.

A series of nine load tests were conducted to validate operation of the installed Structural Health Monitoring (SHM) system. Measurement of the bridge’s response to these loading tests created a benchmark for future evaluation of the bridge’s long-term performance.

BAYOU PIERRE BRIDGE LOAD TESTING

BAYOU PIERRE BRIDGE LOAD TESTING

The Bayou Pierre Bridge is located between Desoto and Red River Parishes in Louisiana. The bridge owner requested that SDR perform independent analysis and testing of the existing structure to examine the possibility of transporting a special permit vehicle, called the dragline, across the bridge. Unloaded, this vehicle weighs around 7,100 kips. When loaded, the vehicle weighs around 10,000 kips. Each span of this bridge consists of 10 prestressed concrete girders; the substructure consists of a concrete cap and steel piles.

Analysis was performed in accordance with AASHTO LRFD using SmartBridge Suite software. A refined 3D Finite Element Analysis was also performed. Analysis results concluded that the piles would experience settlement during the vehicle passing. The results also indicated the possibility of permanent cracking of the prestressed concrete girders; therefore, it was decided to continuously monitor the bridge during the passing of the dragline vehicle and to reduce the weight of the vehicle compared to the originally proposed weight.

For the load testing stage of the project, strain gauges were placed along the girders and piles to measure the stresses and forces in critical members. Linear variable differential transformers (LVDTs) were used to measure the settlement of the structure. A series of preliminary bridge tests were performed to determine the overall bridge response and the possibility of settlement; results were used to calibrate the FE model.

During passing of the Dragline, no damages that compromise the structural integrity of the bridge were witnessed. SDR performed a follow-up inspection which showed only minor spalling and damage, verifying the good structural health of the bridge after the passage of the dragline.

US-11 LAKE PONTCHARTRAIN BRIDGE

US-11 LAKE PONTCHARTRAIN BRIDGE

The US 11 Lake Pontchartrain Bridge is an historic bridge (built in 1928) carrying US-11 over Lake Pontchartrain. The bridge consists of 717 reinforced concrete spans and two steel movable spans, for a total length of 24,922 ft. Past inspections revealed heavy spalls and cracks on the bridge from deck to pile bent.

Major tasks carried out by SDR included: 

  • Performing in-depth inspection of the superstructure and substructure in order to determine the level and type of structural deficiencies designated in the structural inventory reports.
  • Performing chloride ion penetration analysis to determine the diffusion coefficient and expected service life of the bridge.
  • Load rating the bridge using traditional analysis as well as refined non-linear 3-D finite element analysis.
  • Conducting diagnostic field load tests and compiling an evaluation report with repair recommendations.
  • Rehabilitation design of the bridge, including design documents, CADD drawings, technical special provisions, and construction cost estimation.

SAN ANTONIO “Y”

SAN ANTONIO “Y”

The San Antonio “Y” includes post-tensioned segmental concrete box bridges with a combined length of 22 miles. Post-tensioning anchorages and tendons were inspected by SDR to assess existing corrosion and other deficiencies of the structure and to determine the severity and extent of the deficiencies. SDR’s team performed a detailed post-tensioning (PT) non-destructive testing (NDT) investigation to access the areas behind the anchorages and the PT tendons to locate voids and steel tendon corrosion. Voids and steel corrosion were discovered, analyzed, and presented to the Texas DOT in a comprehensive report with repair recommendations. The work included conducting the detailed inspection, evaluating existing conditions, recommending repair methods to address existing deficiencies, and conducting a load rating reflecting the existing bridge conditions.

ASSAWOMAN BAY BRIDGE

Assawoman Bay Bridge

The Assawoman Bay Bridge, Maryland, consists of 139 spans. Longitudinal, transverse and shear cracks were observed during past routine inspections of the prestressed concrete box beams and AASHTO girders. The first phase of the project consisted of conducting an extensive investigation to determine the cause of these cracks and their affect on the performance and durability of the bridge. The investigation consisted of performing a hands-on inspection of the bridge elements, invasive testing of selected locations, collection of core samples, and performing chloride ion content analysis along the bridge.

The results from chloride ion penetration analysis and testing indicated severe corrosion and deterioration in the main span and five box section spans. The AASHTO girder drop span was deteriorated to the extent that complete replacement of the span was necessary. Analysis of the existing damage showed significant deterioration, due to corrosion of both the box beams and the AASHTO girders, that required immediate structural repairs. The results of the investigation were presented in a report recommending replacement of the drop span and preventative maintenance such as sealing and painting concrete surfaces, epoxy injection of cracks and structural strengthening of selected AASHTO girders and box beams using carbon fiber reinforced polymers (CFRP). The construction work for the entire project was completed successfully within six months at a construction cost of approximately $1,800,000, considerably less than the $12M estimate prepared by another consultant.