A bridge construction method comprising removing the trucks and wheels from a flatbed type railroad car to provide a bridge substructure, preparing support means upstanding from an area to be bridged for emplacement of the substructure, and emplacing the substructure on the support means over the area.

A light weight steel dolly connection plate on either side of two, three or more running gear dollies connect these individual dollies together and the dolly connection plate connects to the wood frame prefabricated building at the floor level thus forming the low level building carrier. Each dolly contains a single axle running gear. The flat steel dolly connection plate distributes the concentrated load to the all wood prefabricated building "box" without over stress. The individual dollies utilize conventional mobile home type running gear and are constructed of relatively light weight compact structural steel sections. The low level building carrier, over the distance of its contact and connection to the building floor, forms a very stiff "carrying bed" section adequately strong to support sections of the building which have reduced strength such as side walls containing door openings, etc. By increasing the number of dollies or the distance between individual dollies, measured along the longitudinal length of the building, the effective length of the stiffened carrying bed may be increased to provide adequate support for all sections of opening weakened wall which characterizes a given building floor plan.

A metal "A" frame structure capable, upon attachment, of towing a prefabricated building of, primarily, conventional frame construction. Metal "A" frame utilizes two identical leg members which attach to load distributing members that transmit the relatively heavy concentrated loads into the sides and front of the prefabricated building without introducing over stress. Interconnection of the various metal parts of the "A" frame is selectively accomplished by welding and bolting so that the "A" frame may be easily installed, removed and stored when not in use. The load distributing members which deliver the concentrated loads into the prefabricated building "box" may be adjusted in height, in the case of the front wall of the side walls in order to apply the loads at at the most structurally advantageous locations on the "box".

A storage rack with moveable lifting jacks. The rack includes horizontally extending members joined but spaced apart by a pair of upper and a pair of lower cross members. Two upright posts extend above the horizontally extending support members and are secured in place by the cross members. A powered lifting jack and a follower lifting jack each include tongues insertable between the horizontally extending support members at the opposite ends of the rack. The tongues are biased between the upper and lower cross members preventing the pivotal motion of the tongues which are mounted to wheels rotatably mounted to frames having hydraulic cylinder motors mounted thereatop. Piston rods are extendable from the hydraulic cylinder motors and are attached to the tongues to apply lifting force in an upward direction along an axis extending through the wheel axis of rotation applying lifting force to the opposite ends of the rack.

A simple trailer frame is provided which may be included within a structure, and which allows the frame or the structure to be easily and quickly converted into a mobile trailer on detachable wheel assemblies, without the need for tools. The components and assemblies are also quickly and easily removed from the structure without the need for tools. When the frame is used within a structure, once the structure is at its use site it need show very little evidence that it was a trailer. Also included in the frame is a towing member receiving member for quick and easy attachment and detachment of a towing member to the frame without the need for tools. A mechanical linkage may be provided in the frame in combination with wheel receiving members so that proper connection of the towing member to the frame locks the wheel assemblies in place on the frame. As a safety precaution, the design may also include a provision so that the towing member cannot be secured to the structure unless the wheel assemblies are fully and properly locked to the frame. Details of wheel assemblies, light assemblies and other trailer components which are quickly and easily removably attached to the trailer system or frame by a single individual without the need for tools are provided. Self-contained lifting and lowering components, such as jacks, may also be included as an integral part of the frame or the structure.