Average Crack Spacing of Overlay-Strengthened RC Beams

Abstract

Abstract:The research is focused on evaluating the average crack spacing of overlay-strengthened reinforced concrete (RC) beams. The current equations in different structural codes for predicting the average crack spacing of RC beam with multilayered-reinforcing bars is proved to be inapplicable for overlay-strengthened RC beam, although these two kinds of beams are both with reinforcement in multi-layers. Therefore, a simple, practical and new analytical model that is capable of predicting the average crack spacing of overlay-strengthened beams is developed. An overlay-strengthened beam element is analyzed based on equilibrium and compatibility equations to formulate the average stresses of concrete, overlay and tension reinforcement. A series of verification comparisons with the experimental investigations, which involved various types of beam elements, are performed to verify the validity and reliability of the model. The proposed model performs satisfactorily with respect to measured response from the experimental database.Keyword: crack spacing; overlay; strengthening; interface; bond; multilayered-reinforcement BackgroundOverlaying is considered as a major retrofitting method for flexural and fatigue strengthening or retrofitting of concrete flexural members. As illustrated in Fig Cracks in overlay-strengthened RC structures may be expected because of the relatively low tensile strength of concrete and overlay materials and the use of high strength reinforcement in substrate and overlay. Cracking in overlay-strengthened RC structures has a major influence on structural performance, including tensile, bending and shear stiffness, energy absorption capacity, ductility and corrosion resistance of reinforcement. Moreover, the average crack spacing of overlaystrengthened beams plays an important role in transferred shear stress along overlay-substrate interface and normal stress generated in the substrate concrete in case when the premature debonding failure is investigated (Zhang et al. 2010;Wang and Ling 1998;Raoof and Hassanen 2000). It is, therefore, necessary to predict the cracking behavior of overlay-strengthened RC beam.Despite the fact that many design models have been provided by different structural codes or individual researchers with respect to average crack spacing of RC members with single or multilayered-reinforcement (JSCE 2007; EC2 2004; CSA 2004; NS 1992; CEB-FIP 1990;Broms 1965;Albandar and Mills 1974;Bặzant and Oh 1983;Rizk and Marzouk 2010;Dawood and Marzouk 2010;Marzouk et al. 2010;Rizkalla et al. 1983;Rizkalla and Hwang 1984), which are similar to overlay-strengthened RC member with reinforcement layers in the substrate and overlay, their applicability for overlay-strengthened beams has not yet been investigated.The main objective of this study is to develop a rational methodology for predicting the average crack spacing of overlay-strengthened RC beam. Firstly, the predicted average crack spacing based on existing models from several design specifications is compared with that from expe...

Experimental and Analytical Investigation of Crack Spacing and Width for Overlaid RC Beams at Elevated Temperatures

“…Decreasing crack spacing was observed with increasing total perimeter steel reinforcements in the overlay at all temperature levels. Zhang et al (2011) observed a similar tendency for PCM overlaid beams tested at room temperature. Based on their study, the average crack spacing increased with increasing tensile strength and effective tensile area of concrete and PCM but decreased with increasing the total perimeter of the tension reinforcements in the overlay and the bond strength of the concrete/steel and PCM/steel interfaces.…”

“…Therefore, it is necessary to predict the cracking behavior of overlaid RC beams. Different structural codes and researchers present models for predicting the crack spacing and width of RC members Zhang et al (2011) concluded that the existing codes are incapable of predicting the crack spacing of overlaid RC beams, and they proposed a new model by considering the equilibrium and compatibility equations between two adjacent cracks and verified the model using a large database. However, the applicability of the proposed model for overlaid beams at elevated temperatures has not yet been investigated.…”

Influence of steel fibers extracted from waste tires on shear behavior of reinforced concrete beams

“…Crack spacing depends on the bond between steel and concrete. It was decreased by increasing flexural reinforcement area and more specifically the perimeter of the flexural reinforcement 39‐42 . In this work, flexural reinforcement for all beams was kept constant, whereas the amount of fibers in the concrete was varying, and significant reduction in the crack spacing was observed with the increase in the fibers amount as shown in Figure .…”

“…It was decreased by increasing flexural reinforcement area and more specifically the perimeter of the flexural reinforcement. [39][40][41][42] In this work, flexural reinforcement for all beams was kept constant, whereas the amount of fibers in the concrete was varying, and significant reduction in the crack spacing was observed with the increase in the fibers amount as shown in Figure 10. Fibers were assumed to strengthen the matrix of concrete and also resist crack propagation with application of load.…”

Cracking Behavior of CFRP Laminate-Strengthened RC Beams with Premechanical and Postmechanical Environmental Damage

“…Cracking in strengthened RC structures has a major influence on structural performance, including tensile, bending and shear stiffnesses; energy absorption capacity; ductility; and corrosion resistance of the reinforcement. Moreover, the average crack spacing of strengthened beams plays an important role in the transfer of shear stress along the CFRP laminate-substrate interface with concrete and in the normal stress generated in the concrete substrate in the case when premature debonding failure, such as CFRP peeling or concrete cover separation, is investigated (Zhang et al 2011;Wang and Ling 1998;Raoof and Hassanen 2000).…”