International Concrete Abstracts Portal

The structural reliability of concrete flexural members reinforced with fiber reinforced polymer (FRP) reinforcement is investigated. Reliability indices based on the equations for flexure in ACI 440.1R-03, which uses the load factors from ACI 318-99 are presented. Choice of a resistance factor for flexure for ACI 440.1R-06, which uses the load factors from ACI 318-02 is also presented. Flexural designs using either ACI 440.1R-03 or ACI 440.1R-06 provide sufficient reliability, with reliability indices between 3.5 and 4.8, with the older versions of ACI 440.1R yielding higher reliability. An analysis of curvature of the beams at failure showed that flexural members that fail by FRP reinforcement rupture have ductilities similar to those that fail by concrete crushing, indicating that FRP reinforcement fracture is not necessarily a more brittle failure mode than concrete crushing.

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

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.

Shear walls as an integral part of structures have revealed to be of prime concern following earthquake surveys over the past few years. It was observed that shear wall structures sustained less damage in comparison to structures that did not possess shear wall. Researchers on the basis of their post earthquake surveys concluded that shear wall buildings sustained damage as a result of design and construction work flaws. In this article test data of CFRP strengthened short RC walls is analyzed. Three RC shear walls, designed to fail in shear, were subjected to static and cyclic load tests in which the loading amplitude was gradually increased till specimen failure occurred. Two out of three walls were strengthened externally with the help of CFRP material and mesh anchors at the wall foundation joint. The experimental results analysis consists in cracking pattern, stiffness, ultimate load capacity, ductility and energy dissipation.