International Concrete Abstracts Portal

An innovative corrosion-free system for short- and medium-span bridgesconsisting of precast prestressed concrete truss girders and cast-in-situ concrete deckhas been developed. Advantages of the new system include reduced self-weight andenhanced durability. The girders consist of top and bottom concrete flanges connectedby precast vertical and diagonal members made of fiber reinforced polymer (FRP) tubesfilled with concrete. Glass FRP dowels and corrosion-resistant steel stud reinforcementare used, respectively, to connect the vertical and diagonal members to the concreteflanges. The flanges are pretentioned with carbon FRP tendons. The deck slab isreinforced with corrosion-resistant steel bars in the bottom transverse layer and withglass FRP bars in the bottom longitudinal and the top layers. The girders may be post-tensioned with external carbon FRP tendons to balance the slab weight and to providecontinuity in multi-span bridges. The general details of the system and an experimentalevaluation of its critical components, namely, the FRP tubes and the truss connection,are presented. Three types of FRP tube and four types of connection are investigated.The results of testing eight connection specimens under static loading are presented.The tests have shown superior performance of the connection when filament woundtubes and continuous double-headed studs are used.

Glass, carbon, and hybrid (glass/carbon) fabric reinforced polymer (FRP)restrainers were developed and tested as an alternative to steel restrainers to reducebridge hinge movement during earthquakes. The FRP bridge restrainers weredynamically tested on a representative in-span hinge, in the large-scale structureslaboratory at the University of Nevada, Reno (UNR). Work included: (1) Strain rate testson both FRP strips and FRP/concrete bond; (2) FRP restrainer development and testing;(3) Comparisons between FRP, steel, and shape memory alloy (SMA) restrainers; (4)Development and evaluation of a simple restrainer design method. Findings confirm thepotential use of FRP restrainers as a viable option to steel as a restraining device forbridges. Results include: (1) FRP strength is strain-rate insensitive; (2) FRP/concretebond strength is a function of concrete shear strength and is strain-rate sensitive; (3)FRP restrainers are easily constructed and installed; (4) A proposed restrainer designmethod that considers the bridge structure dynamic characteristics is demonstrated tobe both simple and realistic.

During major earthquakes, buildings which have inadequate lateral strengthmay be subjected to severe damage or total collapse. To prevent such failures,buildings that are vulnerable against earthquakes must be strengthened. In reinforcedconcrete buildings inserting adequate amount of reinforced concrete infills is aneffective strengthening technique. Another promising technique is to strengthen theexisting hollow clay tile infill with diagonally placed CFRP sheets. In this technique,CFRP sheets are extended to the frame members. The connection between CFRP sheetsand frame members is provided by CFRP anchors. In this strengthening technique, theeffectiveness is dictated by the CFRP anchors. In this study, by means of the preparedtest setup, the pull-out strength capacities of CFRP anchors are measured. The effectsof concrete compressive strength, anchor embedment depth, anchor hole diameter,and number of fibers (CFRP sheet width) on the tensile strength capacity of CFRPanchors were studied.

In this paper, a precast concrete sandwich panel system with high thermalresistance and optimum structural performance was developed. Fiber-reinforcedpolymer was used to provide the connector in this panel system. Each connector wasprefabricated in a V-shape with both end hooks providing anchorage in the reinforcedconcrete wythes. The developed shear connecting system is described, along with itsperformance and advantages. An experimental investigation of the connecting systemwas conducted. The experimental program included pure-shear testing of push-offspecimens with a variety of wythe connectors, flexure testing of full-scale specimenswith FRP connectors, and testing of FRP material. The developed shear transfer anddegree of composite were evaluated and the observed behavior of the members ispresented. Design criteria are given for use by engineers and others to apply withappropriate engineering judgment.

Fiber reinforced polymers (FRP) are investigated in this study in comparisonwith a new class of materials, textile reinforced mortars (TRM), for shear strengtheningand/or seismic retrofitting of concrete structures. Textiles comprise fabric meshesmade of long woven, knitted or even unwoven fiber rovings in at least two (typicallyorthogonal) directions. Mortars – serving as binders – contain polymeric additives inorder to have improved strength properties. In this study, experimental investigationswere carried out in order to provide a better understanding on the effectiveness of TRMversus FRP jackets as a means of increasing: (i) the axial capacity of concrete throughconfinement; and (ii) the load-carrying capacity of shear-critical reinforced concreteflexural members. From the results obtained it is strongly believed that the proposedTRM strengthening technique is a viable alternative to the already successful FRPstrengthening technique.