Performance Investigation of Concrete Manhole Inlets

In the process of manufacturing manhole inlets, strengthening rebars are placed at each side around the holes that are precast through formwork. Manufacturers have found it more economical by first casting the inlets and then forming the holes by coring. To give more flexibility to a later coring, in terms of location and size of the holes, manufacturers requested to eliminate the strengthening rebars. This raises a concern as to the structural performance of the cored inlets. For this reason, 15 tests were conducted on six specimens of manhole inlets to evaluate and compare the structural performance of specimens with cast holes versus cored holes. It was concluded that the specimens with cast holes performed better than those with cored holes in both serviceability and ultimate load capacity. The coring construction without strengthening rebars is not acceptable. Recommendations were made for both cored-hole and cast-hole constructions.