Michael G. Oliva

Concrete Bridge Decks Constructed with Fiber-Reinforced Polymer Stay-in-Place Forms and Grid Reinforcing

A description is given of laboratory testing, initial test results, and continuing research to develop design procedures and plans for construction of a two-span highway overpass on US-151 in the state of Wisconsin using only a fiber-reinforced polymer (FRP) reinforcement system in the concrete bridge deck. The use of FRP reinforcing is being pursued to increase the durability of bridge decks and to reduce unit cost and time. The unique aspect of the new bridge is that it will use FRP stay-in-place formwork, placed over precast concrete I girders, to serve as formwork and as the bottom transverse reinforcement of the bridge deck. In addition, a heavy-duty prefabricated FRP grid will be used for the top layer of concrete reinforcing. Full-scale prototype laboratory testing is being used to develop design recommendations including effective distribution widths. From the spring to fall of 2003, a construction productivity study comparing the FRP deck construction sequence with that of identical adjacent steel reinforced deck will be conducted. Both bridges will be field load tested before opening to traffic. The FHWA Innovative Bridge Research and Construction Program is supporting the research and construction.

Pultruded FRP Plank as Formwork and Reinforcement for Concrete Members

A feasibility study in which the use of a commercially produced pultruded fiber reinforced polymer (FRP) plank for both permanent formwork and secondary or primary tensile reinforcement of a concrete structural member is described in this paper. To achieve satisfactory bond at the interface between the smooth surface of the FRP plank and the concrete, two kinds of aggregate, gravel and sand, were epoxy bonded to the planks. Concrete beams using the aggregate-coated FRP planks were fabricated and tested. Satisfactory bond between the FRP plank and the concrete was developed which was evidenced by numerous well-distributed flexural cracks, and ultimate capacities of the aggregate coated FRP plank specimens greater than the steel rebar reinforced control specimen. ACI 440 equations were found to provide good predictions of the flexural strengths but poor predictions of the shear strengths of the FRP plank reinforced beams. ACI 318 equations, however, provided good shear strength predictions.

Cost-Effective, Structural Stay-in-Place Formwork System of Fiber - Reinforced Polymer for Accelerated and Durable Bridge Deck Construction

This paper describes research on the evolution of a cost-effective, structural stay-in-place (SIP) formwork bridge deck system with an integrated modular three-dimensional fiber-reinforced polymer (FRP) reinforcement cage. Recent research conducted at the University of Wisconsin is reviewed to show the evolution of the reinforcing system to include an integral FRP SIP form. The evolution occurred through laboratory testing, which was followed by the design and construction of two bridge structures owned by the State of Wisconsin. Each structure used different FRP reinforcement and formwork. These projects pointed out the need for a competitive SIP formwork to be used in conjunction with FRP reinforcement. Two specimens with different FRP reinforcement and SIP formwork arrangements were tested. Full-scale deck slab specimens were tested by applying a simulated wheel design load to investigate the static response, ultimate capacity, and failure mechanism. The most economical FRP reinforcing system has been ...

Rapid-Construction Technique for Bridge Abutments Using Controlled Low-Strength Materials

The time required for building bridge abutments is one of the main obstacles facing rapid bridge construction. For typical span bridges, this can be remedied by using controlled low-strength materials (CLSM) as backfill materials placed behind full-height, precast concrete panels that are integrated with the CLSM backfill via steel anchors. The CLSM bridge abutments can be constructed in a short time as they require neither heavy machinery for excavation and compaction nor piling equipment. In addition to the speedy construction, the ability to use by-product material, such as fly ash and foundry sand, in CLSM backfill translates into greater economy and the potential for a sustainable design. This paper describes the behavior of an instrumented laboratory, large-scale CLSM bridge abutment with full-height, precast concrete panels that was subjected to a monotonically increasing sill pressure. The experiment showed that the CLSM bridge abutment is capable of carrying typical bridge loads with a large safety margin and with negligible deformations.

Experimental Study of Concrete Beam with FRP Plank as Formwork and Reinforcement

We perform an experimental study of concrete beam with pultruded fiber reinforced polymer(FRP) plank using as a permanent formwork and the tensile reinforcement. A satisfactory bond at the interface between the smooth surface of the pultruded plank and the concrete must be developed for the FRP plank and the concrete to act as a composite structural member. Two kinds of aggregate were bonded to the FRP plank using a commercially available epoxy. No additional flexural or shear reinforcement was provided in the beams. For comparison we test two types of control specimen. One control did not have any aggregate bonded to the FRP plank and the other control had infernal steel reinforcing bars instead of the FRP plank. The beams were loaded by central patch load to their ultimate capacity. The experimental results were compared to current ACI 318 (2005) and ACI 440 (2006) code predictions. This study demonstrates that the FRP plank has the potential to serve as formwork and reinforcing for concrete structures.

Strand Debonding for Pretensioned Bridge Girders to Control End Cracks

Characteristic cracks occur at prestressed bridge girder ends during prestress release due to the transfer of the prestress force to the concrete. This research investigated the quantitative and qualitative impact of strand debonding on cracking through nonlinear finite element analysis (FEA) and plant observations. The analysis included plastic behavior of concrete and stress redistribution after tension induced cracking. Prestressed bulb tee girders, 54, 72, and 82 in. (1372, 1829, 2083 mm) deep, were analyzed with 25, 35, and 50% of the strands debonded at the girder end. The tensile strains were used to judge cracking, and were compared with cases that had no debonding. The results showed that 25% debonding can completely eliminate the excessive concrete tension strains associated with cracks in critical locations. For cracks in other locations, related strains were considerably reduced with 25 to 35% debonding, and eliminated with 50% debonding. The selection of the strands to be debonded significantly impacts cracking. Recommendations on debonding strands and desirable bonded strand patterns are presented.

Reinforcement-Free Decks Using Modified Strut-and-Tie Model

This study presents a new method for predicting the strength of reinforcement-free bridge decks. The concept presented for the reinforcement-free bridge deck includes removing steel reinforcement, using compressive membrane action in the deck by tying concrete wide-flanged girders together, and introducing a polypropylene fiber to control shrinkage cracks. A modified strut-and-tie model (STM) that considers geometrical nonlinearity that can capture punching or flexural failure of the restrained bridge deck between the girders is proposed. The model provides a two-dimensional axisymmetric representation of the behavior of the reinforcement-free deck. Results from the proposed STM analysis method are compared to nonlinear finite element method (FEM) analysis results. Findings suggest that the proposed method is a practical and effective replacement for the time-consuming FEM analysis when the clear deck spans are 5ft or less.

Punching Shear Failure in Double-Layer Pultruded FRP Grid Reinforced Concrete Bridge Decks

The use of pultruded fiber reinforced polymer (FRP) grids is being investigated as tensile reinforcement in concrete bridge decks. Three full scale simply supported concrete slabs reinforced with double layer pultruded FRP girds representing long span bridge decks were tested. Punching shear was the critical failure mode. The punching shear capacity was compared to the University of Wisconsin punching shear equation, developed for the grid system on shorter spans by Jacobson (2004), and the punching shear capacity as given by ACI 440 (2006). The Jacobson equation conservatively predicted the capacity for slabs with edge restraint and accurately predicted the punching shear capacity for slabs without edge restraint. The ACI 440 (2006) punching shear equation underestimated the punching shear capacity of the slabs.

Impact of cast-in-place concrete column construction vibrations on sensitive occupancies

AbstractConstruction activities required to renovate or enlarge buildings cause vibration levels that could impede facility functionality. Facility and construction managers should have an understanding of the magnitude and frequencies of construction vibrations and how far their effects travel in a building. Vertical elements such as columns in a building transmit the vibrations into other floors. The pouring and vibrating of concrete columns are expected to create high vibrations and transmit them vertically. This paper investigates the vibrations caused by construction activities, particularly those caused by concrete column pours, during the construction of three RC buildings. The RMS of the velocities at varying frequencies and varying building locations was recorded. The vibration levels were compared with the vibration criteria previously set for human environments. Significant increases in velocities were observed during column pours, especially for low frequencies. For low frequencies, vibrations...