Equation for localized time-dependent scour at pier-like structures with eccentric inline arrangements

Excess scour developing around tandem and eccentric piers of side-by-side bridges may aggravate bridge failure. Thinking differently, this kind of pier-like structure combination may increase scour and shift sediments towards the bank which may help in self-dredging. Therefore, accurate estimation of temporal scour depth (d_st) around such piers is getting the utmost priority nowadays. However, very little work has been done in this regard. Most of the previous equations predict d_st only for isolated pier. In the present study, 2-3 piers were placed eccentrically inline in addition to isolated piers to empirically derive equations for accurately predicting d_st considering circular, triangular and square pier shapes. Present experimental results for isolated circular pier are validated using literature equations and also cross-validated with other literatures experimental data. Predictive equations are proposed for 2-3 piers with eccentrically inline arrangements, taking their intermediate spacing's as key variables. These equations are established based on dimensional analysis and non-linear regression. Overall analysis reveals that the estimated temporal scour depths based on the proposed integrated equation are closely within the ±80% accuracy band. The proposed equations can be used to accurately predict temporal scour for selected combinations of piers within the given experimental ranges.