Effect of main reinforcement on box girder flexural and shear behavior

Abstract

The primary goal of the current study is to determine, in a lab setting, how the main longitudinal reinforcement ratio affects the behavior and load capacity of single-cell box girders made of reinforced concrete. Three specimens were cast and tested, each with a length of 1600 mm, top and bottom slab has a uniform thickness of 50 mm, an upper flange width of 430 mm, a bottom flange width of 300 mm, and a height of 230 mm. The three box girders are reinforced by having three distinct ACI 318–19 reinforcing ratios: the minimum, the maximum, and average of them, i.e., the reinforcing ratios were 0.0033, 0.0184, and 0.00591, respectively. All three specimens were subjected to 2-concentrated forces. For the tested box girders, the cracking load, crack pattern, failure load, deflection, average strain values on the concrete surface, strain values in steel bars, and failure mode were recorded and discussed. Experimental work has proven that increasing the ratio of the main steel reinforcement from minimum to maximum, passing through the average between them, i.e. 79-425%, leads to higher load capacity by about 66.67-99% and midspan deflection decrease by about 28-36%. It was also concluded that steel reinforcement yield occurred at both minimum and average main reinforcement resulting in flexural failure. While at the maximum of the main reinforcement, yield did not urge but rather a failure occurred in another place which is the shear, whose stirrups suffered from yield this time