A concise state-of-the-art survey of fiber-reinforced polymer (also known as fiber-reinforced plastic) composites for construction applications in civil engineering is presented. The paper is organized into separate sections on structural shapes, bridge decks, internal reinforcements, externally bonded reinforcements, and standards and codes. Each section includes a historical review, the current state of the art, and future challenges.

Fiber-Reinforced Polymer Composites for Construction—State-of-the-Art Review

Design-oriented stress–strain model for FRP-confined concrete

Minimum Design Loads for Buildings and Other Structures provides requirements for general structural design and includes means for determining dead, live, soil, flood, wind, snow, rain, atmospheric ice, and earthquake loads, as well as their combinations, which are suitable for inclusion in building codes and other documents. This Standard, a revision of ASCE/SEI 7-05, offers a complete update and reorganization of the wind load provisions, expanding them from one chapter into six. The Standard contains new ultimate event wind maps with corresponding reductions in load factors, so that the loads are not affected, and updates the seismic loads with new risk-targeted seismic maps. The snow, live, and atmospheric icing provisions are updated as well. In addition, the Standard includes a detailed Commentary with explanatory and supplementary information designed to assist building code committees and regulatory authorities. Standard ASCE/SEI 7 is an integral part of building codes in the United States. Many of the load provisions are substantially adopted by reference in the International Building Code and the NFPA 5000 Building Construction and Safety Code. Structural engineers, architects, and those engaged in preparing and administering local building codes will find this Standard an essential reference in their practice. Note: New orders are fulfilled from the second printing, which incorporates the errata to the first printing.

Minimum Design Loads for Buildings and Other Structures

A review of the present and future utilisation of FRP composites in the civil infrastructure with reference to their important in-service properties

Fiber-wrapping or encasement of concrete in fiber-reinforced plastic (FRP) shells significantly enhances strength and ductility of concrete columns. However, design of such hybrid systems requires an accurate estimate of the performance enhancement due to the confinement mechanism. Current design procedures are simple extensions of the models developed for conventional reinforced concrete columns. Previous studies have demonstrated that such models may not be conservative for FRP-encased concrete. A simple model is presented to predict the complete bilinear stress-strain response of FRP-confined concrete in both axial and lateral directions. The model is based on correlation between the dilation (expansion) rate of concrete and the hoop stiffness of the restraining member. The parameters of the model are directly related to the material properties of the FRP shell and the concrete core. The predicted stress-strain curves compare favorably with the results of the present study, as well as tests by others on both fiber-wrapped and FRP-encased concrete columns.

Model of Concrete Confined by Fiber Composites

External confinement of concrete by means of high-strength fiber composites can significantly enhance its strength and ductility as well as result in large energy absorption capacity. The confinement mechanism may include fiber-wrapping of existing columns as a retrofitting measure or encasement of concrete in a fiber reinforced plastic (FRP) tube for new construction. Proper design of such hybrid columns, however, requires an accurate estimate of the performance enhancement. Current design methods use simple extension of the models developed for conventional reinforced concrete columns. Results from a series of uniaxial compression tests on concrete-filled FRP tubes are compared with the available confinement models in the literature. The present study indicates that these models generally result in overestimating the strength and unsafe design. The study also shows a unique characteristic of confinement with fiber composites in that, unlike steel, FRP curtails the dilation tendency of concrete, as it re...

Behavior of Concrete Columns Confined by Fiber Composites

Confinement effectiveness of fiber reinforced plastic (FRP) jackets (shells) in concrete columns depends on several parameters, including concrete strength, types of fibers and resin, fiber volume and fiber orientation in the jacket, jacket thickness, shape of cross section, length-to-diameter (slenderness) ratio of the column, and the interface bond between the core and the jacket. In this paper effects of shape, length, and bond on FRP-confined concrete are studied. Square sections are shown to be less effective in confining concrete than their circular counterparts. Their effectiveness is measured by a modified confinement ratio that is a function of the corner radius and the jacket's hoop strength. Length effect in short columns of up to 5:1 is shown to be similar to ACI provisions for tied columns, i.e., 10% eccentricity and 20% strength reduction in pure compression. While chemical adhesive bond does not change the confinement effectiveness of the jacket, mechanical shear connectors can enhance the ...

Effect of Column Parameters on FRP-Confined Concrete

There is an urgent need for models that can accurately predict performance of fiber-wrapped concrete columns. Axial compression tests on a total of 45 carbon-wrapped concrete stubs of two batches of normal and high-strength concrete and five different number of wraps were used to verify a confinement model, which was originally developed for concrete-filled glass FRP tubes. Also, a nonlinear finite element model with a non-associative Drucker–Prager plasticity was developed. Both models compared favorably with test results. It was concluded that the adhesive bond between concrete and the wrap would not significantly affect the confinement behavior. Moreover, the same confinement model can be applied to carbon and glass fibers, as long as the model has incorporated the dilation tendency of concrete as a function of the stiffness of the jacket. However, it is of utmost importance to establish the effective hoop rupture strain of the wrap through a reliability analysis by setting proper confidence level for design purposes.

Tests and modeling of carbon-wrapped concrete columns

An effective use of fiber reinforced plastic (FRP) shapes in infrastructure is in the form of composite construction with reinforced concrete. A novel composite column is proposed that is similar to the classic concrete-filled steel tubes, except that steel has been replaced with a hollow FRP shell. The FRP shell, while an integral part of the structure, is also the pour form for concrete. The shell may be a filament-wound or a multi-layer FRP pipe with a layer of longitudinal fibers sandwiched between two piles of circumferential fibers. The proposed column offers high strength and ductility in addition to excellent durability. Behavior of the proposed column is studied by developing two analytical tools; a new passive confinement model for externally reinforced concrete columns, and a composite action model that evaluates the lateral stiffening effect of the jacket. Results are compared with recent studies of fiber-wrapped columns.

Amir Mirmiran

Papers

Model of Concrete Confined by Fiber Composites

Behavior of Concrete Columns Confined by Fiber Composites

Effect of Column Parameters on FRP-Confined Concrete

Tests and modeling of carbon-wrapped concrete columns

A new concrete-filled hollow FRP composite column