STRUCTURAL EVALUATION OF RC T-BEAM BRIDGES THROUGH LOAD TESTING & FEA

STRUCTURAL EVALUATION OF RC T-BEAM BRIDGES THROUGH LOAD TESTING & FEA

Structural evaluation through load testing coupled with advanced Finite Element Analysis (FEA) is a powerful tool to load rate posted bridges with the aim of removing current postings. Based on SDR’s vast experience in structural evaluation and load testing, bridges can carry much higher loads than those estimated by design codes equations. Load testing captures actual behavior of the structure (load distribution) and accounts for strength enhancing factors not included in design

The load rating of LA 182 bridge over Berwick Bay is controlled by reinforced concrete T-beam spans. SDR was tasked with performing the structural evaluation though load testing of the T-beam spans with the aim of removing the current posting.
Test results and FEA reveal that, due to support conditions of the slab, partial fixed end moments are developed, causing significant reduction in mid-span moment compared to moment calculated assuming simple-beam action. Load rating of the bridge was carried out in consideration of the test findings and FEA results, resulting in an increase of load rating factor from 0.85 to 1.23.

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LOAD TESTING OF LA-1 OVER LOCKPORT CANAL

LOAD TESTING OF LA-1 OVER LOCKPORT CANAL

Structural evaluation through load testing, coupled with advanced Finite Element Analysis (FEA) is a powerful tool to load rate posted bridges with the aim of removing current posting. Based on SDR’s vast experience in structural evaluation and load testing, bridges can carry much higher loads than those predicted by design codes. Load testing captures actual behavior of the structure (load distribution) and accounts for strength enhancing factors not included in design.

The LA-1 bridge over Lockport Canal was built in 1959. The bridge load rating is controlled by the reinforced concrete slab spans. SDR was tasked with performing the structural evaluation though load testing of the slab spans with the aim of removing the current posting.

Test results, along with the FEA, reveal that due to the support conditions of the slab, partial fixed end moments are developed, causing significant reduction in mid-span moment as compared to moment calculated assuming simple-beam action. The slab behaved in two-way bending action rather than the one-way bending action used in conventional design and load rating. Load rating of the bridge was carried out in consideration of the test findings and FEA results, which resulted in a load rating factor increase from 0.75 to 1.22.

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WILLIAMS ROAD/SW 66 STREET OVER I-75 BRIDGE

WILLIAMS ROAD/SW 66 STREET OVER I-75 BRIDGE

The Williams Road/SW 66 Street bridge over I-75 in Ocala, Florida was built in 1989. The bridge consists of four (4) spans with a total bridge length of 272.5 ft. The superstructure comprises four (4) AASHTO Type III precast-prestressed concrete beams. The bridge was impacted by an over-height truck causing damage to exterior and interior beams. Damage to both beams was in the form of partial loss of concrete section in the bottom flanges and webs with exposed prestressing strands, but with no rupture of prestressing strands. During the inspection it was also found that the exterior beam had old repair at the right end of the beam, which exhibited signs of distress, e.g. cracking and delamination.


Repair of the beams included restoring the concrete section of the bottom flanges and webs, and applying externally bonded CFRP to confine the restored section and to provide redundancy to the shear strength. These repair methods allowed I-75 to remain open during construction.

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I-10 OVER US-19 IMPACT DAMAGE BRIDGE REHAB

I-10 OVER US-19 IMPACT DAMAGE BRIDGE REHAB

The I-10 over US 19 bridge is in the center of Jefferson County near Monticello, Florida. The bridge spans 243.33 ft. over US 19 and consists of four (4) spans. Two spans are 44.5 ft. long, comprising two Type III AASHTO beams for the exterior beams and three Type II AASHTO beams for the interior beams. Two spans are 77.16 ft. long, comprising seven Type III AASHTO beams.

Span 3 was impacted by an over-height truck, causing severe damage in the fascia beam (beam 7) and the interior beam (beam 6). The vehicle impact resulted in significant section loss, cracking, and rupture of prestressing strands. In-house developed software, Smart Bridge Suite, was used to analyze the superstructure, determining the impact of damage on the structural strength of the beams and to design the rehabilitation work.

Repair work included splicing ruptured prestressing strands, restoring concrete section using polymer-modified concrete, using externally bonded longitudinal CFRP sheets and transvers U-wraps. The use of advanced composite materials allowed the damaged beams to be repaired instead of replaced, while providing accelerated construction.

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LA-66 BIG BAYOU SARA BRIDGE

LA-66 BIG BAYOU SARA BRIDGE

Big Bayou Sara Bridge is an historic bridge (built in 1949) carrying LA-66 over Big Bayou Sara in West Feliciana Parish, Louisiana. The bridge main spans comprises five, 100 ft. steel pony trusses and the approach spans comprises five, 40 ft. steel I-beam spans with a total bridge length of 700 ft.


Services provided by SDR included in-depth inspection of the superstructure and substructure of the bridge, development of 3-D finite element models to determine internal forces, evaluation of the existing structure to determine deficient elements, design of a rehabilitation system for the superstructure and substructure, development of preliminary and final plans for construction, design of two-lane detour temporary steel bridge to be constructed on the north side of the existing bridge to maintain traffic during rehabilitation work on the existing bridge, development of cost estimation and schedule, and construction support.

REPAIR OF LA 27 BRIDGES OVER I-10

REPAIR OF LA 27 BRIDGES OVER I-10

Repair of 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 interior steel girders, partial deck replacement, splicing of fractured prestressing strands, restoration of 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 works, development of construction plans, and construction support.

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LA 27 CONSTRUCTION SUPPORT FLYER (1)
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LA-1 OVER I-49

LA-1 OVER I-49

LA-1 over I-49 bridge was built in 1989. The 403 ft. as-built bridge consists of four continuous, steel plate girder spans at 45 degrees skew.
SDR performed thorough document review, hands-on inspection, surveying, and detailed analysis. A topographic survey revealed that both abutments are experiencing excessive settlement and lateral movement resulting in transverse shear and uplift forces on the bearings at both abutments; increased reactions at intermediate bents, causing over-stress and excessive deformation of bearing pads; redistribution of loads to internal supports, which exerts more force on the foundations of internal bents; and additional negative moment, causing high tensile stresses and significant cracking of the deck.

SDR presented three alternatives to rehabilitate the bridge. The selected alternative consisted of adding two end spans of 100 ft. each to reduce the embankment height, and utilizing wraparound Mechanically Stabilized Earth (MSE) walls. In addition, SDR provided construction support.

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.

I-10 OVERPASS OVER US 165

I-10 Overpass Over US 165

On behalf of the LA DOTD, SDR was tasked with design of the high-traffic volume I-10 overpass, spanning 1,136 ft. and intersecting US 165. The criteria of the project required designing a bridge to withstand immense traffic demand, allowing for future widening as the traffic volume steadily increases over time and conforming with the existing infrastructure surrounding the overpass. The ten-span bridge consists of both 54 in. deep and 63 in. deep prestressed Louisiana I-shaped girders (LG-54 & LG-63), spaced 7.6 ft. and 9.7 ft apart, respectively. The exterior girders were designed with the non-composite section capacity equal to that of the interior girders to facilitate future widening of the bridge to grow with the increase of average daily traffic (ADT), facilitating the longevity of the structure. The bridge is designed to carry four lanes of traffic at design speeds of 70 miles per hour. The overpass incorporates optimum vertical clearance for both the arterial US 165 highway and the railroad it intersects. The bridge design also incorporates aesthetically-pleasing design cues in the implementation of ornamental bridge fencing and functionally sound, decorative bridge parapets.

LA-10 BEAVER CREEK BRIDGE

LA-10 Beaver Creek Bridge

SDR was tasked with emergency design for the replacement of a three-span prestressed concrete bridge that experienced irreparable damage due to flooding. The scope of the LA 10 over Beaver Creek bridge project, designed in just under two months, included finalized plans, cost estimation, surveying, load rating, and the submittal of comprehensive calculations books. The urgency of the project to restore the viability of the LA 10 corridor was met with sound engineering design and was submitted in a timely manner by the SDR team.


The newly-designed bridge has a total length of 200 ft. and a clear roadway width of 40 ft., an increase in width from the pre-existing bridge. The superstructure consists of six 36 in. deep Louisiana I-shaped girders (LG-36), acting in composite action with the 8.5 in. continuous concrete deck. The substructure consists of cast-in-place concrete caps and precast concrete piles. The bridge has an expected 40-plus-year lifespan to service the St. Helena Parish of Louisiana.

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