STRUCTURAL ANALYSES OF TWO TYPICAL MEDIUM-DUTY TRANSIT BUSES

Finite-element computer models were developed for two medium-duty transit buses: a 21-ft bus with 11 seats (22 passengers) and a 25-ft bus with 13 seats (26 passengers). Two models of each bus were derived: one with passenger seats fastened to the bus floor only and one with seats attached to both the bus sidewalls and the floor. The models were each analyzed under three cases of bus deceleration: with seat belts installed and used on all passenger seats, with seat belts installed on all seats but used by approximately half of the bus passengers, and with seat belts installed and used on the front seats only. Each load case was analyzed using seven bus floor angles from 0 to 30 degrees. The following conclusions were reached with respect to the structural responses of a typical medium-duty transit bus to bus deceleration: (a) maximum member stresses should generally be lower with full versus staggered seat belt use or versus front seat belt use only; (b) maximum member stresses should generally be higher with seats attached to both the sidewalls and the floor versus seats fastened to the floor only; (c) maximum member stresses could be relatively high in the seat anchorage members for wall- and floor-mounted seats and in the perimeter frame members for floor-mounted only seats; and (d) differences should be relatively small between the maximum member stresses for shorter versus longer medium-duty transit buses.