Nowadays, girders with corrugated webs are used in bridges as an efficient alternative to conventional girders with flat stiffened webs. Particularly in bridge girders with corrugated webs (BGCWs), the corrugated webs are the main elements for bearing the shear forces. Instead of prismatic BGCWs, tapered BGCWs are currently used mainly due to their structural efficiency, providing at the same time aesthetical appearance. Available literature shows that tapered BGCWs may be classified into four typologies. Among these typologies, Case I is the most common case appearing commonly near to the intermediate supports of continuous bridges. Accordingly, in this paper, the finite element (FE) method is employed to investigate the inelastic behavior of tapered BGCWs of Case I, following to the fundamental behavior of such girders published recently by the current authors. Previously validated 3-D nonlinear FE models are developed and used in this study. The paper seeks, first, at finding the validity limit of the previously proposed design strengths for the tapered BGCWs with respect to the girder’s initial imperfection. This is made by considering different initial imperfection amplitudes. Accordingly, it is found that the proposed equation is valid with initial imperfections of hw1/200; hw1 is the height of the long vertical edge of the web panel. However, the accuracy increases for initial imperfections similar to the web thickness (tw) for cases of tw≥hw1/200. Then, it investigates the effect of the aspect ratio of the web panels, different flange inclination angles and flange slenderness ratios. Finally, the paper checks the authors’ previously proposed design model using the results of the generated parametric studies. Overall, the outcomes of this study are expected to provide more insight into the behavior of tapered BGCWs and enable accurate prediction of the shear capacity of this special type of BGCWs.