Strength Problems of Low-Floor Urban Buses

The main characteristics of up-to-date urban buses are the low floor level, high capacity, and the many large-size doors. The longitudinal bending load bearing elements of the frame structures of thin window and door supports, suitable for today's popular line design pattern, are the sidewalls and beams without door openings. The main torsional load bearing element, on the other hand, is the master beam made up of the longitudinal beams by means of the floor cover and the lattice joint of the latter's lower flanges. Since the structural height of the longitudinal beams playing the critical role in load bearing is governed, at a certain minimum free height provided for, by the height of the floor level, reduction of the latter will have to be associated with that of their dimensions as well