Indiana Administrative Code
Title 675 - FIRE PREVENTION AND BUILDING SAFETY COMMISSION
Article 15 - INDUSTRIALIZED BUILDING SYSTEMS
Rule 2 - Indiana Mobile Structures Code
Section 2-31 - In-transit design requirements

(a) Scope. This section covers the general requirements for designing the mobile chassis to fully withstand the adverse effect of transportation shock and vibration without degradation of the integrated structure or of its component parts and the specific requirements pertaining to the transportation system and its relationship to the structure.

(b) Definitions. "Chassis" means the entire transportation system comprising the following subsystems: drawbar and coupling mechanism, frame, running gear assembly and lights.

"Drawbar and Coupling Mechanism" means the rigid assembly (usually an "A" frame), upon which is mounted a coupling mechanism, which connects the mobile structure's frame to the towing vehicle.

"Frame" means the fabricated rigid substructure which provides considerable support to the affixed mobile structure both during transport and on-site; and also provides a platform for securement of the running gear assembly, and drawbar and coupling mechanism.

"Running Gear Assembly" means the subsystem consisting of suspension springs, axles, bearings, wheels, hubs, tires, and brakes, with their related hardware.

"Highway," includes all roads and streets to be legally used in transporting the mobile structure.

"Length," for purposes of transportation only, means the distance from the extreme front of the mobile structure to the extreme rear, including the drawbar and coupling mechanism, but not including expandable features that do not project from the body during transportation.

(c) General requirements for designing the structure to withstand transportation shock and vibration.

The cumulative effects of highway transportation shock and vibration upon a mobile structure may result in incremental degradation of its designed performance in terms of providing a safe, healthy and durable structure. Therefore, the mobile structure shall be designed, in terms of its structural, plumbing, mechanical and electrical systems, to fully withstand such transportation forces during its intended life.

Particular attention shall be given to maintaining watertight integrity and conserving energy by assuring that structural components in the roof and walls (and their interfaces with vents, windows, doors, etc.) are capable of resisting highway shock and vibration forces during primary and subsequent secondary transportation moves.

In place of an engineering analysis, either of the following may be accepted:

(d) Specific requirements for designing the transportation system.

General. The entire system (frame, drawbar and coupling mechanism, running gear assembly, and lights) shall be designed and constructed as an integrated, balanced and durable unit which is safe and suitable for its specified use during the intended life of the mobile structure. In operation, the transportation system (supporting the mobile structure and its contents) shall effectively respond to the control of the towing vehicle in terms of tracking and braking, while traveling at applicable highway speeds and in normal highway traffic conditions.

Specific requirements. The drawbar shall be constructed of sufficient strength, rigidity and durability to safely withstand those dynamic forces experienced during highway transportation. It shall be securely fastened to the mobile structure frame by either a continuous weld or by bolting.

The coupling mechanism (which is usually of the socket type) shall be securely fastened to the drawbar in such a manner as to assure safe and effective transfer of the maximum loads, including dynamic loads, between the mobile structure and the hitch-assembly of the towing vehicle. The coupling shall be equipped with a manually operated mechanism so adapted as to prevent disengagement of the unit while in operation. The coupling shall be so designed that it can be disconnected regardless of the angle of the mobile structure to the towing vehicle. With the mobile structure parked on level ground, the center of the socket of the coupler shall not be less than twenty inches (20") nor more than twenty-six inches (26") from ground level.

The chassis, in conjunction with the mobile structure, shall be designed and constructed to effectively sustain the designed loads consisting of the dead load plus a minimum of three (3) pounds per square foot floor load (example: free-standing range, refrigerator, and loose furniture), and the superimposed dynamic load resulting from highway movement but shall not be required to exceed twice the dead load. The integrated design shall be capable of insuring rigidity and structural integrity of the complete mobile structure and to insure against deformation of structural or finish members during the intended life of the structure.

The running gear assembly, as part of the chassis, shall be designed to perform, as a balanced system, in order to effectively sustain the designed loads set forth in this section and to provide for durable dependable safe mobility of the mobile structure. It shall be designed to accept shock and vibration, both from the highway and the towing vehicle and effectively dampen these forces so as to protect the mobile structure from damage and fatigue. Its components shall be designed to facilitate routine maintenance, inspection and replacement.

Location of the running gear assembly shall be determined by documented engineering analysis, taking into account the gross weight (including all contents), total length of the mobile structure, the necessary coupling hitch weight, span distance, and turning radius. The coupling weight shall not be less than twelve percent (12%) nor more than twenty-five percent (25%) of the gross weight.

Spring assemblies (springs, hangers, shackles, bushings and mounting bolts) shall be capable of withstanding all the design loads as outlined in this section without exceeding maximum allowable stresses for design spring assembly life as recommended by the spring assembly manufacturer. The capacity of the spring system shall assure, that under maximum operating load conditions, sufficient clearance shall be maintained between the tire and mobile structure frame or structure to permit unimpeded wheel movement and for changing tires.

Axles, and their connecting hardware, shall be capable of withstanding all of the design loads outlined in this section without exceeding maximum allowable stresses for design axle life as recommended by the axle manufacturer. The number of axles required to provide a safe tow and good ride characteristics shall be determined and documented by engineering analysis. Those alternatives listed in this section may be accepted in place of such an analysis.

Hubs and bearings shall meet the requirements of this section and good engineering practice. Both of these components shall be accesible for inspection, routine maintenance and replacement of parts.

Tires, wheels and rims shall meet the requirements of this section. Tires shall be selected for anticipated usage.

The number, type, size and design of brake assemblies required to assist the towing vehicle in providing effective control and stopping of the mobile structure shall be determined and documented by engineering analysis. Those alternatives listed in this section may be accepted in place of such an analysis.

Brakes on the towing vehicle and the mobile structure shall be capable of assuring that the maximum stopping distance from an initial velocity of twenty (20) miles per hour does not exceed forty feet (40').

Highway safety electrical lights and associated wiring shall conform to applicable federal requirements in terms of location and performance. The manufacturer shall have the option of meeting this requirement by utilizing a temporary light/wiring harness provided by the mobile structure transportation carrier.