External bonding of steel plates has been used to strengthen deficient reinforced-concrete structures since the 1960s. In recent years, fiber-reinforced polymer (FRP) plates have been increasingly used to replace steel plates due to their superior properties. A key issue in the design of an effective retrofitting solution using externally bonded plates is the end anchorage strength. This paper first presents a review of current anchorage strength models for both FRP-to-concrete and steel-to-concrete bonded joints under shear. These models are then assessed with experimental data collected from the literature, revealing the deficiencies of all existing models. Finally, a new simple and rational model is proposed based on an existing fracture mechanics analysis and experimental observations. This new model not only matches experimental observations of bond strength closely, but also correctly predicts the effective bond length. The new model is thus suitable for practical application in the design of FRP-to-concrete as well as steel-to-concrete bonded joints.

Anchorage strength models for FRP and steel plates bonded to concrete

A uniaxial model for concrete confined with fiber-reinforced polymers (FRP), but also with steel jackets or conventional transverse reinforcement, is presented. The model, which is suitable to be i...

FRP-Confined Concrete Model

This paper presents the problem definition and guidelines of a set of benchmark control problems for seismically excited nonlinear buildings. Focusing on three typical steel structures, 3-, 9-, and 20-story buildings designed for the SAC project for the Los Angeles, California region, the goal of this study is to provide a clear basis to evaluate the efficacy of various structural control strategies. A nonlinear evaluation model has been developed that portrays the salient features of the structural system. Evaluation criteria and control constraints are presented for the design problems. The task of each participant in this benchmark study is to define (including sensors and control algorithms), evaluate, and report on their proposed control strategies. These strategies may be either passive, active, semiactive, or a combination thereof. The benchmark control problems will then facilitate direct comparison of the relative merits of the various control strategies. To illustrate some of the design challenges, a sample control strategy employing active control with a linear quadratic Gaussian control algorithm is applied to the 20-story building.

/pdf/benchmark-control-problems-for-seismically-excited-nonlinear-eiid7z4rnd.pdf

Benchmark Control Problems for Seismically Excited Nonlinear Buildings

Seismic Rehabilitation of Existing Buildings

FRP-confined concrete in circular sections: Review and assessment of stress-strain models

The rehabilitation of RC columns jacketed with carbon fiber-reinforced plastic (FRP) composites for improving shear strength, confinement, and ductility has received considerable attention. However, research for improving the shear capacity of beam-column T-joints using FRP composite materials is still in the early stages. The present paper describes the experimental results of 14 1/3-scale tests of concrete beam-column joints. The variables considered were the composite system, the fiber orientation, and the surface preparation. The tests have demonstrated the viability of carbon FRP composites for their use in improving the shear capacity of the joints as evidenced by the experimental results. Based on these experimental results, a design aid was developed for T-joints with inadequate confinement and shear reinforcement.

Shear Strengthening of RCT-Joints Using CFRP Composites

Reinforcing bar couplers are used in prefabricated bridge elements and bridge systems for accelerated bridge construction. Grouted splice sleeve connectors are used in bridge substructures because of the enhanced construction tolerances they offer. This paper presents a simplified modeling strategy for seismic assessment of precast bridge columns connected to precast footings using grouted splice sleeve connectors. A computational model was developed and validated using three half-scale bridge subassemblies tested to failure. Cyclic quasi-static loading was applied to two precast subassemblies and one cast-in-place specimen. The connectors were located in the footing, for the first precast alternative, and in the column end for the second precast alternative along with debonding of reinforcing bars in the footing. Force-based beam-column elements with fiber sections were used to construct the computational model based on plastic hinge weighted integration; the model included low-cycle fatigue and ...

Seismic Analysis of Precast Concrete Bridge Columns Connected with Grouted Splice Sleeve Connectors

.................................................................................................................................. iii ACKNOWLEDGMENTS.............................................................................................................. iv TABLE OF CONTENTS................................................................................................................ v LIST OF FIGURES.......................................................................................................................vii LIST OF TABLES ......................................................................................................................... ix

Performance-Based Evaluation of Exterior Reinforced Concrete Building Joints for Seismic Excitation

The writers evaluated the confinement that was provided by glass fiber-reinforced polymer (GFRP) spirals in concrete columns under axial load. Given that GFRP spirals are resistant to chloride-induced corrosion, the option of replacing steel spirals with GFRP spirals was explored to determine whether this would reduce the corrosion of the vertical steel bars in hybrid columns. The writers investigated the axial load behavior of 10 spirally reinforced concrete columns. Six of the 254-mm diameter columns were confined with a GFRP spiral and four were confined with a steel spiral. Some of the columns that were confined with a GFRP spiral utilized steel vertical bars (hybrid columns), whereas others utilized GFRP vertical bars (all-GFRP columns). The stress-strain and load-displacement behavior of all columns was studied. Analytical expressions predicted the axial load capacity of the hybrid and all-GFRP-reinforced concrete columns. Axial compression tests of all-steel-reinforced and hybrid specimens subjected to accelerated corrosion were also carried out. The latter exhibited a smaller corrosion rate, similar axial load capacity, and equal or higher ductility relative to steel corroded columns.

Axial Load Behavior of Concrete Columns Confined with GFRP Spirals

| PCI Journal 80 Accelerated bridge construction incorporates innovative techniques and materials to efficiently reduce construction time and traffic disruption. It also improves work-zone safety for workers and commuters. Prefabrication of bridge structural components is a highly effective technique and is one of the accelerated bridge construction methods promoted by the Federal Highway Administration under the category of prefabricated bridge elements and systems. Several bridges have been built or rehabilitated using accelerated bridge construction methods. Examples in Utah include the Interstate 15 (I-15) Core Provo Center Street interchange, the Riverdale Road over Interstate 84 (I-84) bridge, and the I-15 South Layton interchange. Precast concrete deck panels, substructures, and superstructures have been frequently used in accelerated bridge construction. Connections between such reinforced precast concrete elements are among the most critical components of the structure. Researchers are investigating the adequacy of various connection configurations, especially in moderate to high seismic regions. These connections not only have to conform to accelerated bridge construction standards in terms of construction delivery time but must also resist earthquake-induced deformations and stresses. Lateral load capacity, displacement ductility, and reparability are three significant criteria for any connection considered in seismic regions. In this paper, a column–to–cap beam joint is investigated using ■ Although grouted splice sleeve connectors facilitate the construction of precast concrete bridges and accelerate construction, seismic bridge design codes prohibit their use in column plastic hinges.

http://www.pci.org/uploadedFiles/Siteroot/Publications/PCI_Journal/2015/September/PCI-Journal-September-2015-Discussion.pdf

Chris P. Pantelides

Papers

Shear Strengthening of RCT-Joints Using CFRP Composites

Seismic Analysis of Precast Concrete Bridge Columns Connected with Grouted Splice Sleeve Connectors

Performance-Based Evaluation of Exterior Reinforced Concrete Building Joints for Seismic Excitation

Axial Load Behavior of Concrete Columns Confined with GFRP Spirals

Seismic evaluation of grouted splice sleeve connections for reinforced precast concrete column-to-cap beam joints in accelerated bridge construction