Flexural cracks in steel fiber-reinforced lightweight aggregate concrete beams reinforced with FRP bars

Fourteen plain and steel fiber-reinforced lightweight aggregate concrete (LWC) beams with two types of fiber reinforced polymer (FRP) reinforcing bars were tested under a four-point bending load with different reinforcement ratios, bar diameters and clear span lengths to evaluate their cracking behavior. The test results showed that using steel fiber-reinforced lightweight aggregate concrete (SFLWC) and increasing the clear span length mitigated the maximum crack width at low load levels, while increasing the reinforcement ratio tended to decrease the maximum crack width during the entire loading period. At service load, all CFRP-reinforced beams satisfied the crack width criteria of 0.7 mm, while more than half of the GFRP-reinforced specimens exhibited unconservative crack widths. Crack width prediction equations in the current design codes in the US, China, and Canada were compared based on the experimental results. The original average crack spacing equation recommended by GB 50608 was modified considering the effect of bar position. Furthermore, using the method of probability and statistics, the relationships between the maximum crack width and the average crack width for the tested beams were investigated. Accordingly, a rational alternative crack width model was proposed for CFRPand GFRP-reinforced beams incorporating the effects of lightweight aggregates and steel fibers.