Post-Tensioned Slab Bridges Research Articles

Firsts Post-Tensioned Slab Bridges in Poland — the Bridge in Pawia Street in Lublin

Firsts Post-Tensioned Slab Bridges in Poland — the Bridge in Pawia Street in Lublin

Evaluation of fibre-reinforced polymer post-tensioned slab bridges using the Canadian Highway Bridge Design Code

Corrosion of steel reinforcement is a major concern for bridges throughout Canada, particularly where deicing salts are used. Fibre-reinforced polymers (FRPs) are not susceptible to corrosion, making them an attractive alternative to internal steel reinforcement for Canadian bridges. Due to the low stiffness of FRP materials, concrete members tend to have high deflections and large crack widths at service loads with serviceability limits governing their design. In addition, they tend to have lower shear capacities compared to similar steel-reinforced members. This study focuses on glass FRP (GFRP) reinforced slab strips cast with self-consolidating concrete (SCC) and post-tensioned with carbon FRP (CFRP) tendons to improve their serviceability, shear capacity, and deformability. The experimental results highlight the potential of an FRP reinforcement system for slab bridges combining passive GFRP reinforcement with prestressed CFRP tendons. The flexural performance of five FRP-reinforced slabs and one ste...

Evaluation of FRP Posttensioned Slab Bridge Strips Using AASHTO-LRFD Bridge Design Specifications

Deterioration of concrete structures caused by corrosion of steel reinforcement requires large capital investments in order to repair or replace existing structures which may or may not be nearing the end of their expected service lives. Fiber-reinforced polymer (FRP) reinforcement has emerged as a viable alternative to conventional reinforcement with lower life cycle costs. Serviceability typically governs the design of FRP structures because of the inherent low stiffness of FRP materials. As a result, concrete members tend to exhibit high deflections, large crack widths, and a reduction in shear capacity compared to similar steel-reinforced members. This study focuses on glass fiber–reinforced polymer (GFRP) reinforced slab strips cast with self-consolidating concrete (SCC) and posttensioned with carbon fiber–reinforced polymer (CFRP) tendons to improve the serviceability, shear capacity, and deformability of slab bridges. The flexural performance of five FRP slabs and one steel-reinforced control slab are compared to the design provisions of the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications.

Accelerating the Construction of a Highway Bridge in Ohio

The Ohio Department of Transportation (ODOT) created Strategic Initiative Number 9 to “build bridges smarter, faster and better.” One project undertaken by ODOT was to use a precast, post-tensioned slab bridge in place of a cast-in-place slab. To accommodate school schedules and a festival, the bridge was to be completed in 16 days. However, the bridge was actually completed in 19 days. Delays were due to weather, equipment problems, and confusion over plans and specifications. Contributing to the success of the project was the effective partnering between ODOT and the contractor, along with a high level of upfront planning. However it is necessary to address problems such as the lack of contingency plans and some unexpected issues that were overlooked in the planning phase.

Secondary Prestressing Moments in Rehabilitated Posttensioned Bridges

Typical rehabilitation procedures for posttensioned slab bridges involve removing concrete from the top surface of the bridge, replacing corroded reinforcement, and resurfacing with new concrete. These permanently change primary and thus secondary prestressing moments. Continuous posttensioned bridges often rely on secondary prestressing moments to counteract dead and live load moments over interior supports and thus changes caused by rehabilitation impact serviceability and, particularly, ultimate limit states. An analysis procedure is derived for computing the changes in prestressing moments caused by rehabilitation. The impact of rehabilitation on a two-span continuous voided-slab bridge is evaluated considering rehabilitation schemes where both spans are rehabilitated simultaneously, or where one span is completely rehabilitated before work commences on the other. Rehabilitation creates concentrated primary prestressing moments at the exterior supports and at interfaces between solid and voided regions that reduce or even reverse the secondary moment at the interior support. The two-span scheme virtually eliminates secondary prestressing moments and, contrary to intuition, the span-by-span scheme has a markedly greater impact.

Overload and Ultimate Load Behavior of Posttensioned Slab Bridge

A three-tenths-scale model of a posttensioned slab bridge is constructed in a laboratory and tested in the overload and ultimate load ranges. Dimensions of the slab are 16.9 × 5.33 × 0.23 m. In addition to uniformly distributed longitudinal posttensioning, a band of tendons is located in a narrow region directly above the supporting columns. A large array of strain gauges, linear variable differential transformers, and load cells serve to gather data for each loading configuration. Results are presented for a series of overloads that are placed on the slab in a variety of critical locations. Ultimate positive bending moment is imposed on one span and an ultimate negative moment is applied to the slab in the region of the supporting columns. Complementary nonlinear finite-element analyses of the overload and ultimate loadings are also presented. Results show that the posttensioned slab bridge supported a load-causing moment equivalent to 4.8 times the factored moment of an AASHTO MS 18 loading.

Post-Tensioned Slab Bridge with Banded Transverse Tendons

A large, two-span 3/10 scale model of a posttensioned slab bridge is constructed in a laboratory. The moderately thick slab rests directly on columns without bent caps. Dimensions of the slab are 16.9-by-5.33-by-0.299 m. In addition to uniformly distributed longitudinal posttensioning, a band of tendons is placed in a narrow region directly above the supporting columns. A large array of strain gages, linear variable differential transformers, and load cells serve to gather data. Response of the structure is monitored for dead, live, and prestressing loads. Both short- and long-term effects of these loads are of interest. Special attention is given to the distribution of strain in the slab because of transverse prestressing. American Association of State Highway and Transportation Officials lane loads are applied statically. Shear lag at the edges of the banded region is considered. Complementary finite element analyses of the slab responses to loadings are also presented.

Time-Dependent Behavior of Post-Tensioned Slab Bridge

A three-span flat slab bridge is instrumented during its construction and monitored for more than 2 years. The slab is moderately thick and rests directly on columns without bent caps. Posttensioning is employed in the longitudinal and transverse directions. Longitudinal posttensioning is uniformly distributed across the width of the bridge; transverse posttensioning is employed only in column regions. Strains in the field bridge are measured by a large array of gages attached to small reinforcing bars that are embedded in the concrete. Deflection data caused by dead load are acquired immediately after placing of concrete, after longitudinal prestressing, and for a period of 2.5 years. Comparisons of deflections and strains are presented for existing simplified analytical methods and actual bridge response. Results indicate that a simplified one-way procedure yields predictions that are not always consistent with experimental measurements for service load conditions.