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.

WESTBANK EXPRESSWAY INSTRUMENTATION AND LOAD TESTING

The Westbank Expressway is a six-lane freeway extending from Westwood Drive in Marrero, Louisiana, to the Crescent City Connection Bridge across the Mississippi River in New Orleans, Louisiana. The primary purpose of the proposed ramp project is to complete the MacArthur Interchange and reduce the distance between successive westbound off-ramps and eastbound on-ramps by providing access ramps from the service roads to the elevated expressway. Along this six-mile portion of the expressway, damage has been documented to the existing structure, especially the inverted-T pier caps, in both the eastbound and westbound directions.

SDR was selected by LADOTD to perform the following tasks:

Perform detailed investigation of reinforced concrete caps and girder seat bearings.
Perform finite element analysis and stress analysis of the inverted T caps.
Perform instrumentation and load testing of representative caps.
Present repair recommendations.

In the load testing stage of this project, one expansion end and one fixed end of representative caps were chosen for monitoring. During the load testing process, linear variable differential transformers (LVDTs) and strain gauges were used to measure the crack opening and strains in the proximity of damaged and undamaged areas under truck loads.

As a result of load testing and numerical simulations, it was concluded that exterior girder hanger bars were deficient; therefore, strengthening recommendations using CFRP wraps, bars or post-tensioning bars were presented. It was also concluded that cracks in the inverted T caps did not affect their structural performance, but they should be sealed for durability purposes.

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

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”

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.

MARTA CN915 BRIDGE

The MARTA CN915 light rail bridge experienced cracking and various structural deficiencies. This project consisted of preparing bridge strengthening plans using carbon fiber polymer (CFRP) and installing a 128-channel remote monitoring data acquisition system. The instrumentation consisted of strain and temperature sensors and was distributed over four spans that formed one of the bridge’s continuous units. A full 3-D finite element analysis was performed prior to proceeding with the instrumentation plan. SDR also conducted onsite load testing and has been remotely monitoring the bridge behavior since 2008.

MACARTHUR INTERCHANGE US-90 BUSINESS PHASE I

Full evaluation of the completed bridge widening was carried out under a task for peer review, where several constructability and detailing issues were discovered. SDR performed a full 3-D finite element analysis of the existing bridge, including the inverted-T piers, as well as a bridge load test. After further evaluation it was determined that the widening plans were deficient and re-design was required. SDR was tasked with the design and production of final plans of all superstructure elements, including the prestressed U girders and LG girders, deck, inverted-T caps and columns, and all complex columns with unbalanced loads. In addition, due to the structural complexity of the existing inverted-T piers, SDR performed a special analysis to evaluate and determine the cut lines for accommodating the widening. The evaluation of existing cut lines was performed and new alignment was developed.

LULING BRIDGE (HALE BOGGS MEMORIAL BRIDGE)

This bridge is a five-span cable-stayed bridge supported by twin steel towers and four concrete piers. The concrete deck overlay is supported by an orthotropic deck system integrated with transverse floor beams supported by twin longitudinal trapezoidal steel box girders. The supporting cables originate from the steel towers and are anchored at twelve transverse steel trapezoidal cross girders. Twin longitudinal trapezoidal steel box girders are supported by these cross girders, towers, and piers.

The scope of work included:

Detailed inspection of the bridge’s condition, including existing fatigue prone details, and the extent of existing cracks.
Evaluate and rate the existing bridge superstructure, including all major load-carrying components and bearing seats.
Investigate the cause of fatigue cracks using 3-D finite element analysis.
Prepare the bridge rehabilitation design.
Develop appropriate construction staging/phasing schemes and Maintenance & Protection of Traffic Plan based on TMP Level IV.
Prepare construction cost estimates and schedule.

LA-70 OVER MISSISSIPPI RIVER (SUNSHINE BRIDGE)

The Sunshine Bridge, located in Donaldsonville, LA, is a steel truss bridge opened in 1964. The bridge includes a steel deck truss and five continuous main truss spans. The main truss is a five-span cantilever structure utilizing intermittent drop spans, covering a total length of 3,327 ft. and a width of 60 ft. The approach structure consists of a variety of steel beams and girder types in addition to a deck truss span consisting of 10 panels equally spaced at 34.3 ft. The substructure of the approach spans consists of steel bents.

The project scope included performing inspection, assessment, a detailed 3-D finite element analysis and load rating of the main truss, including gusset plates, deck truss, steel approach spans and substructure elements.

I-10 OVER CALCASIEU RIVER BRIDGE (LAKE CHARLES BRIDGE)

The I-10 bridge over Calcasieu River is a steel truss cantilever bridge, opened in 1952 in Lake Charles, LA. The bridge includes a steel main truss, four steel deck trusses, and ninety approach spans. The approach spans are comprised of steel girder spans and fracture critical spans (two-girder system with floor beams and stringers). The total bridge covers an approximate length of 6,617 ft. and a width of 62.67 ft.

The major scope of work included inspecting the entire bridge, determining the affect of section losses and deficiencies on load rating, building the 3-D finite element model for the truss spans using LUSAS, rating the truss members and gusset plates, load rating the approach spans using Virtis, load rating the substructure using RC-Pier, spreadsheets, and writing the final evaluation report with repair recommendations.