International Concrete Abstracts Portal

External, prestressed carbon fiber reinforced polymer (CFRP) straps can be used to enhance the shear strength of existing reinforced concrete beams. In order to effectively design a strengthening system, a rational predictive theory is required. The current work investigates the ability of the modified compression field theory (MCFT) to predict the behavior of rectangular strap strengthened beams where the discrete CFRP strap forces are approximated as a uniform vertical stress. An unstrengthened control beam and two strengthened beams were tested to verify the predictions. The experimental results suggest that the MCFT could predict the general response of a strengthened beam with a uniform strap spacing < 0.9d. However, whereas the strengthened beams failed in shear, the MCFT predicted flexural failures. It is proposed that a different compression softening model or the inclusion of a crack width limit is required to reflect the onset of shear failures in the strengthened beams.

This paper deals with the shear strengthening of reinforced concrete (RC) beams using externally bonded (EB) fiber-reinforced polymers (FRP). The parameters that have the greatest influence on the shear behavior of RC members strengthened with EB FRP and the role of these parameters in current design codes are reviewed. The effect of transverse steel on the shear contribution of FRP was found significant and yet is not captured by any existing codes or guidelines. Therefore, a new design method is proposed, which considers the effect of transverse steel as well as to other influencing factors on the shear contribution of FRP (Vfrp). The accuracy of the proposed equations is verified by predicting the shear strength of experimentally tested RC beams using data collected from literature.

This paper deals with the assessment of a design formulation to predict the end debonding load in reinforced concrete (RC) elements strengthened with externally bonded reinforcement (EBR) in fiber reinforced polymer (FRP). The debonding loads recorded during several bond tests have been collected and the reliability of three relationships furnished by literature and codes to calculate the end plate debonding load has been assessed. Then, the experimental data have been used to assess a new relationship for the end plate debonding load according to the ‘design by testing’ procedure suggested in European codes. In particular, numerical factors for calculating mean values and percentiles for the end plate debonding load have been calibrated. Moreover, different factors have been assessed for the preformed and cured in-situ EBR FRP systems that have been distinguished in order to better exploit the performance of the latter ones.

A pedestrian bridge in Albstadt, Germany showed immense corrosion damages of the steel reinforcement. The damages were so immense that the bridge had to be torn down due to a lack of load-bearing capacity and, therefore, replaced by a new bridge. The architectural design follows a slender construction principle, thus, by using the new composite material textile reinforced concrete (TRC) a slender concrete superstructure is achieved. By using non-corrosive textiles, concrete covers can be reduced to a minimum of only some millimetres and cross-sections are minimized. The paper describes the design, structural analysis, load-bearing behavior and production processes of a 97 m (3819 in.) long TRC pedestrian bridge. The whole construction is subdivided into six prefabricated parts, each offering a maximum length of L=17.20 m (677 in.) and a maximum span of Ls=15.05 m (593 in.). The cross-section, which is a T-beam, has a height of only H=0.435 m (17 in.) resulting in a slender bridge construction with a slenderness ratio of H:Ls = 1:35.

Precast lightweight concrete panels reinforced with Glass Fiber Reinforced Polymer (GFRP) bars are an ideal candidate for adoption in the construction of bridge decks using Accelerated Bridge Construction (ABC). ACI 440.1R guidelines do not provide guidance for the use of lightweight concrete with GFRP bars. Tests have been carried out to evaluate the performance of normal weight and lightweight concrete precast panels reinforced with GFRP bars. The ultimate load capacity of the panels was compared to one-way shear capacity specified in the ACI 440.1R guidelines. The reduction factor for shear specified in the ACI 318 building code for lightweight concrete was used to modify the capacity predicted by the ACI 440.1R guidelines for sand lightweight precast concrete panels. Normal weight concrete panels achieved 1.8 to 2.2 times the ACI 440 predicted capacity and lightweight concrete panels achieved 1.6 to 1.9 times the modified ACI 440 shear capacity.