Antonio De Luca

Structural Evaluation of Full-Scale FRP-Confined Reinforced Concrete Columns

The external confinement of RC columns by means of externally bonded fiber-reinforced polymer (FRP) laminates is a well established technique for strengthening and retrofitting purposes. This paper presents a pilot research that includes laboratory testing of full-scale square and rectangular RC columns externally confined with glass and basalt-glass FRP laminates and subjected to pure axial load. Specimens that are representative of full-scale building columns were designed according to a dated American Concrete Institute (ACI) 318 code (i.e., prior to 1970) for gravity loads only. The study was conducted to investigate how the external confinement affects peak axial strength and deformation of a prismatic RC column. The results showed that the FRP confinement increases concrete axial strength, but it is more effective in enhancing concrete strain capacity. The discussion of the results includes a comparison with the values obtained using existing constitutive models.

Reinforced Concrete with FRP Bars: Mechanics and Design

The American Concrete Institute (ACI) Committee 440 fiber-reinforced polymer (FRP) reinforcement for concrete members is about to see full market acceptance and implementation after 22 years. This book is mainly intended for practitioners and the focus is on ACI technical literature that covers the fundamentals of performance and design of concrete members with FRP reinforcement and reinforcement detailing. The book is a valuable resource for researchers and graduate students to guide their studies and creative work. Only internal, nonprestressed FRP reinforcement are included in the book, prestressing and near-surface-mounted reinforcement applications are excluded. The authors of the book assume that the reader is already familiar with concrete as a material and reinforced concrete as a construction technology (i.e., fabrication, analysis, and design). The book is divided into three parts that are described to follow the typical approach to design of conventional reinforced concrete in detail. The first part of the book covers materials and test methods and the second part covers analysis and design. The third part of the book presents some design examples using a two-story medical facility as a case study.

Single-Parameter Methodology for the Prediction of the Stress-Strain Behavior of FRP-Confined RC Square Columns

The study presented in this paper proposes a new theoretical framework to interpret and capture the mechanics of the fiber-reinforced polymer (FRP) confinement of square reinforced concrete (RC) columns subjected to pure compressive loads. The geometrical and mechanical parameters governing the problem are analyzed and discussed. A single-parameter methodology for predicting the axial stress–axial strain curve for FRP-confined square RC columns is described. Fundamentals, basic assumptions, and limitations are discussed. A simple design example is also presented.

Analysis of RC Hollow Columns Strengthened with GFRP

Reinforced concrete (RC) hollow piers in bridges withstand high moment and shear demands ensured with reduced mass and lower stress on foundations compared with solid piers. Failure of hollow columns is typically affected by premature buckling of reinforcing bars and concrete cover spalling. At present, no guidelines are available for the design of their upgrade, and few research investigations can be found on hollow columns strengthened by using fiber-reinforced polymer (FRP) materials. This paper discusses an experimental program carried out on purely compressed RC hollow columns externally wrapped with glass-fiber-reinforced polymer (GFRP). Three specimens were tested: one specimen was unstrengthened and used as the benchmark; the other two specimens were GFRP-wrapped with different confining reinforcement ratios. Each specimen was designed according to dated codes (i.e., prior to 1970) accounting only for gravity loads. In particular, steel longitudinal bars cross section and steel tie-spacing were designed with the minimum amount of longitudinal reinforcement and minimum tie area at maximum spacing. Tests results highlight that the GFRP-jacket mainly provided ductility increases before low strength increments could be obtained. Refined and simplified numerical models for hollow square RC columns, previously proposed by the authors, herein extend to hollow rectangular members. Comparisons of experimental results and theoretical predictions on the basis of both refined and simplified confinement models were performed and showed good agreement. In the case of the simplified model, a value for the effective ultimate FRP strain was suggested.

In-Situ Load Testing: A Theoretical Procedure to Design a Diagnostic Cyclic Load Test on a Reinforced Concrete Two-Way Slab Floor System

The objective of this paper is to showcase to an engineer who is considering performing a diagnostic cyclic load test a theoretical procedure for determining the patch load, which when applied to a two-way reinforced concrete (RC) slab floor system would generate internal forces at critical locations equal to those resulting from the uniformly distributed load. This procedure should also help the practitioner to define a representative model of the structure and to update the magnitude of the target load at the end of each loading and unloading cycle by means of a real-time evaluation of boundary conditions and slab stiffness. The routine to design a cyclic load test is described theoretically first and then validated with the results of a load test on a concrete two-way RC slab floor system. Introduction The current role of testing within structural engineering has gained increasing importance, as it can now be applied to every phase of the structure’s life because of innovative materials and new design approaches. By focusing on either the preliminary testing of a new structure or the necessary control checks prior to assessing the strength of an existing one, in-situ load testing can determine the real behavior of the structure under the existing loading conditions. Accordingly, researchers can have an overall, accurate understanding of the mechanical properties of the structural members. In the United States of America, the current American Concrete Institute (ACI) 318 Building Code [1] provides requirements for load testing of concrete structures. ACI Committee 437 [2] proposes a diagnostic cyclic load (DCL) testing procedure consisting of the application of patch loads in a quasi-static way to the structural member according to loading and unloading cycles. Patch load magnitude and distribution shall simulate the uniformly distributed load defined in the ACI 318 Building Code. The DCL protocol [3,4] defines three acceptance criteria that can be easily computed, in real time, for any structural member by simply checking its behavior under the test load (see Fig. 1 for necessary notation). Repeatability and Permanency represent the behavior of the structure during two identical load cycles; Deviation from linearity represents the measure of the nonlinear behavior of a member being tested. Repeatability = 100 95 B B max r A B max r % % Δ − Δ × ≥ Δ − Δ ; (1) Permanency = 100 10 B r B max % % Δ × ≤ Δ ; (2)