Structural design and numerical analysis of a light-weight manhole lid using a carbon steel frame and double injection molding

In this study, a composite manhole lid composed of a carbon steel frame and a double injection composite material was proposed to solve the problem of the currently heavy manhole lids. First, the structural design of the carbon steel frame to be used for composite manhole lids was carried out. The lattice structure of the carbon steel frame for effective load distribution while reflecting the limiting factors was determined by using a structural analysis simulation. In addition, we tried to compare the manufacturing cost indirectly by the weight of the carbon steel frame and the number of welding points. Considering that the analytical result and the cost aspect of the stress and deformation were small at the given load among the considered shapes, the composite manhole lid with the hexagonal carbon steel frame lattice shape could be adopted into the proper design. This is 42% less in weight than conventional manhole lids, but the maximum stress or deformation is kept at the same level as existing iron lids.