LULING BRIDGE DECK OVERLAY AND REPAIRS

The Luling bridge, built in 1983, is an historic bridge in St. Charles Parish. The bridge is a cable-stay bridge, consisting of twin trapezoidal steel box girders with an orthotropic deck. Deck overlay and repairs were expected to be performed on this bridge. Cracks on the steel orthotropic deck, extending from the transverse web stiffeners, were observed during inspection of the bridge. The wearing surface was comprised of several different materials, including numerous asphalt mixtures and two reinforced concrete sections.

Detailed Finite Element analysis using shell elements was performed to study the state of stress at the onset of cracks under normal loading and fatigue loading. Analysis results revealed that the main cause of cracking is the rigid connection between deck and transverse stiffener. These concentrated stresses can be reduced by trimming the web stiffener. The full three-dimensional numerical model was also utilized for the main spans to check the strength of the cables and perform a LRFR load rating of the bridge under new overlay loads and during construction. A novel overlay section was developed, consisting of an Aramid/Glass FRP-Epoxy underlayment system, angular granite aggregate, and Steel Fiber Reinforced Concrete (SFRC).

US-61 I-10 REPAIR

The I-10 westbound on-ramp from US-61 in Louisiana is a curved steel-plate girder bridge. The bridge consists of four continuous spans with span lengths of 114 ft., 140 ft., 140 ft., and 115 ft. each. The exterior girder of the second span over I-10 eastbound was struck by an over-height vehicle, causing severe damage to the girder.
The superstructure consists of two curved steel plate girders with a curvature radius of 757.4 ft. The substructure consists of two concrete hammerhead bents and two steel bents.
The repair was performed by removing a segment of the second span at the splices, assembling the new segment on-site, and sliding in place a self-propelled modular transportation (SPMT) vehicle. This allowed for minimum highway closure.
SDR’s scope of work included design of repair, development of repair plans, and testing and monitoring. Load testing was performed before and after repair with continuous monitoring. Three-dimensional Finite Element analysis with staged-construction was deployed to design the repair and ensure the integrity of the bridge during each phase of construction

DR. AMIR BOTROS PRESENTED A WEBINAR ON LOAD RATING OF BEAM-SLAB BRIDGES WITH IRREGULAR GEOMETRIES

Beam-slab bridges with irregular geometries cannot be analyzed using AASHTO approximate methods of analysis. Accordingly, it is impractical or cumbersome to load rate beam-slab bridges with irregular geometries using AASHTOWARE Bridge Rating software. For such cases, refined analysis is required to obtain the internal forces developed in the structural members under the effect of vehicular live load. For conventional concrete and steel bridges, numerical models, utilizing elastic material properties and small deflection theory such as Finite Element Analysis, are most commonly used for structural analysis.
SDR has extensive experience and knowledge of Finite Element Analysis of beam-slab bridges with irregular geometries, as well as complex bridges, using different software packages. SDR has successfully completed modeling of numerous bridges for design and load rating projects.

INSTRUMENTATION AND LOAD TEST OF 10,000-KIP DRAGLINE ON BAYOU PIERRE BRIDGE

The Bayou Pierre bridge in Louisiana has five equal spans with a total length of 500 ft. The superstructure consists of 10 PPC girders, and the substructure consists of reinforced concrete caps and steel piles. The 10,000 kips (4,500 tons) DRAGLINE crossed the bridge under continuous monitoring using 46-axles SPMT, taking 85 minutes.
SDR was tasked to evaluate the strength of the bridge to withstand DRAGLINE loads, to instrument and load test the bridge before the DRAGLINE crossing, to continuously monitor the bridge during crossing, and to carry out hands-on inspection of all bridge elements after crossing.
3-D numerical models, including soil-structure interaction, were developed to estimate internal forces on the bridge elements under the weight of the DRAGLINE and transporters. The bridge was instrumented using linear variable differential transformers (LVDTs) and strain gauges. The diagnostic test loading was applied using a combination of counterweights and six 390-kip trucks to fully load two adjacent spans. Load testing included verifying the piles’ capacity, potential settlement, and residual settlement.
Results from analyses and testing determined the safe passing weight from 10,000 kips to 8,300 kips. Hands-on inspection of bridge following the crossing indicated excellent conditions of the bridge

REPAIR OF CR 514 BRIDGE OVER I-75 IN SUMTERVILLE, FLORIDA

Repair of the CR 514 Bridge over I-75 in Sumterville, Florida was completed by SDR. The bridge was struck by an over-height truck, causing severe damage to the exterior prestressed concrete girders, including rupture of several prestressing strands and a severe loss of concrete.
Before SDR’s involvement, it was decided to replace the girder. SDR was tasked with assessing the damage (using its in-house developed damage assessment tools) and impact on the structural integrity of the girders; design of the repair; and development of repair details.
Repair of the girders included splicing of ruptured prestressing strands, correcting the alignment and rotation of the bottom flange, restoring the concrete section, substituting ruptured stirrups using Near-Surface-Mounted technique; and applying externally bonded CFRP to confine the restored section and provide redundancy to the shear strength. The special repair techniques utilized allowed I-75 to remain open during construction.

REPAIR OF LA 27 BRIDGES OVER I-10

Repair of the LA 27 bridges over I-10 was completed by SDR. The overpass northbound concrete bridge and southbound steel bridge were both impacted by a truck, causing severe damage to both bridges. Repair work included the replacement of the exterior steel girder, heat straightening of the interior steel girders, partial deck replacement, splicing of fractured prestressing strands, restoration of the concrete section, and application of externally bonded Carbon Fiber Reinforced Polymers (CFRP). Repairs were completed while both bridges remained in operation.
SDR’s role included inspection of the damaged bridges, design of repair work, development of construction plans, and providing construction support