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

Creep tests have been conducted on six commercial GFRP bars, pertaining to three different manufacturers, under two levels of sustained service load (nominally 15% and 30% of the ultimate tensile strength). The test duration was 10000 hours (417 days). At the end of the test duration, the samples were tested statically to infer upon their residual tensile properties. It is evident that GFRP bars with lower fiber content and/or bigger diameter exhibit higher levels of creep strain than their counterparts of high fiber content and smaller diameter. Residual tensile property tests show barely any change as to the bars’ longitudinal tensile properties. Microstructural analysis indicates that there is no degradation in the matrix or the fiber-matrix interface, within the GFRP bars after the lengthy duration.

Different strategies can be used to repair, rehabilitate and strengthen existing structures. Techniques based on Fiber Reinforced Polymer (FRP) materials appear to be innovative alternatives to traditional solutions because of their high tensile strength, lightweight, and ease of installation. One of the most common and useful FRPs is Carbon Fiber Reinforced Polymer (CFRP) sheets and anchors attached to strengthen the section through addition of tensile capacity. The purpose of this study was to develop a technique for assessing the strength of anchors for quality control. A method for assessing the quality of CFRP anchor installation was developed using plain concrete beams reinforced externally with CFRP sheets attached with epoxy and CFRP anchors. Under loading on the beam, a tensile force was developed in the CFRP sheets and a shear force on the CFRP anchors. The forces in the CFRP anchors were defined by the load applied to the beam and compared with forces based on measured stress in CFRP sheets.

The application of the conventional anchoring system used for steel wires is likely to reduce the efficiency of the CFRP tendon. Therefore, need is to develop anchor appropriate to CFRP tendon. This study selected the compression-type anchor among the three types of anchor. Tapered section was adopted for the external diameter of the sleeve to alleviate the concentration of stress occurring under compression, and the performance of the anchor was observed with respect to the length of the taper. The experimental results showed that the performance of anchors is sensitive to dimensions of the sleeve and the compression force. The sleeve presenting stress softening section was seen to reduce the concentration of stress. The finite element analysis and experimental results enabled to derive dimensions of the sleeve improving the efficiency of CFRP tendon, and dimensions of the sleeve enhancing the anchor performance of CFRP tendons with different diameters are proposed.

Several tests were conducted to evaluate the shear performance of beams strengthened externally with carbon fiber reinforced polymer (CFRP) laminates and CFRP anchors. Results are presented for five tests conducted on 24-in.(610-mm) deep reinforced concrete T-beams constructed and tested at Phil M. Ferguson Structural Engineering Laboratory at the University of Texas at Austin. Monotonically increasing load was applied to the reinforced concrete members at a shear span-to-depth ratio of three (a/d = 3) until failure. Overall, a 40-45% increase in shear strength was observed when anchored CFRP laminates were installed on the RC members. In all cases, CFRP anchors prevented a premature de-bonding failure in the CFRP laminates, thus increasing the useable capacity of the CFRP laminates. Theoretical calculations predicting the shear strength of the retrofitted concrete members were carried out and compared with the measured strengths of the members.