International Concrete Abstracts Portal

This volume contains 72 papers from the 10th International Symposium held in Tampa, FL. The papers address internally reinforced members, strengthening of columns, material characterization, bond, emerging fiber-reinforced polymer (FRP) systems, shear strengthening, fatigue and anchorage systems, masonry, extreme events, applications, durability, and strengthening. The papers emphasize the experimental, analytical, and numerical validations of using FRP composites and are aimed at providing insights needed for improving existing guidelines. The increasing maturity and acceptance of FRP is reflected by several papers that provide background information on the recent design codes and guidelines relating to blast and seismic repair. New frontiers of FRP research are explored, addressing emergin materials, and systems and applications for extreme events, such as fires and earthquakes, which will further consolidate FRP’s preeminent position. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-275

The results of an experimental investigation on the effects of prestressing on the flexural behavior of GFRP-reinforced SCC slabs are presented. A total of six one-way slab strips were tested up to failure, including one steel-reinforced control slab. The five remaining slabs were reinforced with GFRP bars, three of which also contained two CFRP post-tensioned tendons. Steel stirrups were included in one prestressed and one non-prestressed slab to ensure a flexural mode of failure. The slabs were tested under four-point bending. Results were compared to analytical models for ultimate flexural and shear capacity as well as load-deflection behavior. Prestressing effectively increased the cracking load and post-cracking stiffness of the FRP-reinforced slabs and significantly reduced crack widths at service loads. Slabs without shear reinforcement failed in shear in a brittle manner prior to reaching their full flexural capacity. All of the GFRP-reinforced slabs failed at higher loads than the control slab.

This paper presents a new concept for an FRP-Concrete composite floor system. The system consists of a moulded glass fiber reinforced polymer (GFRP) grating adhesively bonded to rectangular pultruded GFRP box sections as structural formwork for a concrete slab. Holes cut into the top flange of the box sections at a variable spacing allow concrete ‘studs’ to form at the grating/box interface. During casting, GFRP dowels are inserted into the holes to further connect the grating and box sections. Following preliminary component tests on two concrete blocks, experimental results show that the concrete filled grating provides a 100% increase in strain capacity when compared to a plain concrete block. It is therefore feasible to provide ductility to the complete system through the concrete in compression. Four push-out GFRP grating-box section specimens were then tested in double shear to assess the shear behavior of the proposed GFRP dowel shear connector in both partially concrete-filled and fully concrete-filled box sections. From the resulting load-slip curves, a progressive longitudinal shear failure was seen to be provided by such a connection. The experimental results indicate that this type of shear connection can provide robustness and reasonable ductility to the system. Research is now underway to test a complete prototype system under variable load conditions to examine whether the behavior is as predicted.

Concrete-filled GFRP tubes (CFFTs) with and without moment connections to concrete footings were tested. The study aims at exploring the combined effect of maximum shear and maximum moment, both occurring at the same location, on the ultimate strength of CFFTs, as well as moment connection behavior in general. Testing involved simply supported and cantilever bending specimens with varying shear spans and fixed end arrangements. End conditions consisted of either direct embedment into concrete blocks with steel dowels, or mechanical clamping. For the GFRP tubes used, the study concluded that the presence of shear at the location of maximum moment near the connection in a cantilever setup does not cause reduction in flexural capacity, relative to the pure bending strength of the CFFT. The study also revealed that achieving tensile rupture of the CFFT tube does not guarantee that the full potential moment capacity of the CFFT member is reached, as slip plays a key role at the moment connection.

The use of near surface mounted (NSM) fiber reinforced polymers (FRPs) is being increasingly recognized as a valid technique strengthening of concrete members. In case of elevated temperature or fire exposure however, the bond between the bars and the concrete will be lost very quickly due to the adhesive’s low glass transition temperature. Although recent studies have shown that the fire endurance of appropriately designed and insulated FRP strengthened RC members is satisfactory, the performance of FRP strengthening systems at high temperature remains largely unknown. To study the bond behaviour at elevated temperature between the NSM FRP bars and concrete a series of 18 double bond shear tests were performed at Ghent University. Results show that the failure load of NSM FRP strengthened concrete structures and the bond strength are influenced at values of temperature equal to or beyond the glass transition temperature. Failure mode changed by increasing the temperature.