International Concrete Abstracts Portal

This paper presents an experimental study on shear performance of concrete I-beams with fiber reinforced polymers (FRP) as internal reinforcement. A total of four beam tests were conducted, including one test without shear reinforcement and three tests with glass fiber reinforced polymers (GFRP) stirrups. In all specimens, GFRP bars were used as flexural reinforcement. The test variable was the ratio of shear reinforcement. In the test without stirrups, diagonal tension failure occurred. Failure due to rupture of the GFRP stirrups rupture was observed in the test with a shear reinforcement ratio of pw = 0.75% and web crushing failure occurred in the beam tests with pw = 1.26% and pw = 2.26% respectively. The experimentally obtained shear strengths were then compared to calculated design values using equations provided in the modified Eurocode 2, ACI 440.1R06, and CSAS806-2.

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 behavior of seventeen RC beams strengthened with FRP laminates mechanically fastened to their tension soffits with concrete anchor bolts is presented. The beams were tested in four-point bending on a 7.5 foot (2286 mm) span. Bolt diameter and spacing and FRP strip length were varied. The beams exhibited increases in yield moment ranging from 12.5% to 46%, and increases in ultimate moment from 30% to 75%, while displacement ductility ratios were 75% of values from un-strengthened control beams. The number of fasteners in the shear span had a greater impact on ultimate strength than did FRP strip length. Terminating the FRP strips in regions of larger bending moment resulted in an unexpected change of failure mode from concrete compression to shear. Measured strains in the FRP were less than those calculated assuming fully bonded conditions.

This paper presents an experimental investigation into the bond behavior between basalt FRP (BFRP) sheet and concrete substrate under coupled effects of freeze-thaw cycling and sustained load. Specially designed double-lap shear specimens were exposed to up to 200 freeze-thaw cycles with sustained load. After exposure, the specimens were tested to failure. Digital Image Correlation (DIC) test method was applied to capture the full-field strain in the study. Nonlinear constitutive law of FRP-concrete interface was determined based on full-field deformation and strain analysis. Test results show that freeze-thaw cycling leads to significant decreases in load carrying capacity, ultimate slip, shear strength and increases in effective stress transfer length of FRP-concrete interface. Additional damage is generated when the load condition is taken into account during freeze-thaw cycling test. Moreover, apparent changes in failure mode were found with the increasing number of freeze-thaw cycles.

In current International Codes for FRP Reinforced Concrete, an environmental reduction factor is applied to the tensile strength of GFRP bar to account for its long-term durability. In this paper, the approaches for the durability design of GFRP bars are discussed and corresponding limitations are addressed, followed by presentation of a newly developed design approach, which incorporates the effects of relative humidity, exposure temperature, and design life. By using time extrapolation and time-temperature shift approaches, a new equation for design strength of GFRP bar under various exposure time and temperature was proposed. The effect of moisture, in the form of relative humidity, was incorporated into the new equation by investigating the relationship between the relative humidity and concrete pore water. On the basis of reported durability data for E-glass/VE GFRP bars embedded in moist concrete, reduction factors linked to service life, temperature and relative humidity were obtained. By utilizing the new approach presented in this paper, more refined and accurate design values for long-term tensile strength of a GFRP bar could be achieved.