Private Bridge Load Limit Calculation

Our HOA requires a professional to calculate the load limit for a private steel bridge that provides access to a subdivision for homeowners, emergency services, police etc. Expertise in structural engineering, load bearing calculations, and knowledge of steel structures is necessary. Understanding of private bridge use and construction is an added advantage. The bridge has been in place since about YR 2000. Our HOA has not been able to find drawings for the bridge. The bridge is constructed using RR car chassis---1-1/2 chassis---and is 60 feet long and 20 feet wide. The steel structure sits on concrete abutments both sides and spans a creek. We need to post a load limit. The attached RR car bridge design is very similar to what we have.