Abstract

Local scour around bridge piers is one of the main causes of bridge failure all over the world. Experimental and hydraulic models were carried out to investigate two types of scour reduction methods around a single cylindrical pier, namely pier's slots and collars. The efficiency of various types of pier slots and circular collars around the pier's base in reducing scour were studied. A new shape of a conical collar was developed by the authors and examined among other shapes. The results revealed that collars, in general, have more influence in reducing scour depth than slots made in the front and rear of bridge piers. The sigma slot acts better than other tested slots with reduction in the scour depths of 59.3% and 52.8% at the upstream and downstream of the pier, respectively. On the other hand, the conical collar appeared to be the most effective collar shape in reducing the scour around the bridge pier with a 61.1% reduction in the scour depth downstream of the pier. A 3-D Laser scanner was used to capture the bed topography at the end of each experiment and contour maps of the deformed bed was produced. A 1-D HEC-RAS model was developed with a single bridge pier to predict the scour depth around the pier with an attempt to introduce new values for the pier nose shape factor, K1, which describe the tested piers.

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