The purpose of the experimental study is to investigate the relationship between effective width and the shear span under cyclic loading. When referring to slab participation in practical design, engineers usually ignored the effective width in negative moment.
According to the research  in 2012, the effective widths are different between short beams and slender beams. Furthermore, the slab participation is a drift-controlled problem, the effective width would increase with the drift ratio. To estimate the contribution of slab reinforcements in negative moment is the most important thing.
The test results indicate the initial stiffness of slender beams (a/d>2.5) in negative moment were higher than positive moment about 10%, and it was found that the slab participation in initial stiffness of slender beams were more obvious than the short beams (a/d<2.5). Probably, the shear span is one of the factors in slab participation in initial stiffness.
The effective width of short beams (a/d<2.5) with construction joint were wider than the beam without construction joint, and the effective width of slender beams were all full of the width. According to the effective width design of ACI 318-11 (4bw), it may not be conservative in negative moment.