1 CCR 301-25-8.0 - Construction

8.1 All metal surfaces that will be painted shall be chemically cleaned, etched, zinc phosphate- coated and zinc-chromate or epoxy primed or conditioned by an equivalent process. Particular attention shall be given to lapped surfaces, welded connections of structural members, cut edges, punched or drilled hole areas in sheet metal, closed or box sections, unvented or undrained areas, and surfaces subject to abrasion during vehicle operation.

8.2 The floor shall be at least 14-gauge, mill applied, zinc-coated steel sheet, and shall be on one plane. There shall be a main floor cross member of at least 10-gauge steel or equivalent extending the full width of the floor plate and permanently attached. There shall be a minimum of two intermediate floor cross members of at least 16-gauge steel equally between the main floor cross members and permanently attached.

8.02(a) Type A buses 14,500 GVWR or less, may use other metal or material with strength and corrosion resistance at least equivalent to all-steel construction as certified by the bus body manufacturer.

8.3 The subfloor shall be either five ply nominal 5/8 inches thick plywood, or a material of equal or greater strength and insulation R-value and it will equal or exceed properties of exterior-type softwood plywood C-D grade, as specified in National Bureau of Standards (NBS) Product Standard 1-83. Type A buses, 14,500 GVWR or less, shall have nominal 1/2-inch thick plywood or equivalent material equal to or exceeding the properties listed above.

8.4 Ceiling Panels: If the ceiling is constructed to contain lap joints, the forward panel shall be lapped by the rear panel, and the exposed edges shall be beaded, hemmed, flanged, or otherwise treated to eliminate sharp edges.

8.5 All body components shall be designed and constructed to avoid the entrapment of moisture and dust.

8.6 All openings between the chassis and passenger-carrying compartment made for any reason must be sealed.

8.7 On Type B, C, and D buses, the bus body shall meet the test standards of the Kentucky Pole Test as outlined in rule 8.8.

8.8 In addition to complying with FMVSS 220 test procedures, the body manufacturer shall record and report the downward vertical movement of the force at 0, 25, 50, 75, and 100% of the maximum force (both loading and unloading). The expected force- deflection curve is Illustrated schematically in Figure 1a. Low load nonlinearities may indicate joint confirmation; high load nonlinearities may indicate yielding structural members.

8.08(a) A second load cycle shall be performed following the procedure given in the first paragraph. The expected force-deflection curve is Illustrated schematically in Figure 1b. Any hysteresis following the initial shakedown will be revealed by this second cycle.

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Figure 1. Static Load Test Load-Deflection Curves

8.9 A diagonal (racking) load test shall be performed on Type A, B, C, and D school buses to ensure adequate shear stiffness and strength of the bus body. Details of the tests are provided below. A two-cycle loading sequence shall be conducted following the procedure described in Rule 8.08 of these rules.

8.09(a) Requirements: When a force equal to 1 1/2 times the GVW is applied to the edge of the roof of the vehicle's body structure through a force application plate as specified in (b), Test Procedures:

8.09(a)(1) The diagonal movement of the force at any point on the application plate shall not exceed 5 1/8 inches.

8.09(a)(2) Each emergency exit of the vehicle provided in accordance with FMVSS 217 shall be capable of operation as specified in that standard during the full application of the force and after the release of the force.

8.09(b) Test Procedures: Each vehicle shall be capable of meeting the requirements of (1) and (2) when tested in accordance with the procedures set forth below.

8.09(b)(1) The vehicle shall be supported on a rigid surface along the lower edge of the frame or along the body sills in the absence of a frame.

8.09(b)(2) The load shall be applied through a force application plate that is flat and rigid. The dimensions of the plate shall be chosen to ensure that the plate edges never make contact with the vehicle skin during testing. The typical width is 18 inches. A typical length is 20 inches less than the length of the vehicle's roof measured along its longitudinal centerline.

8.09(b)(3) Place the force application plate in contact with the edge of the vehicle roof. Orient the plate so that its flat, rigid surface is perpendicular to a diagonal line connecting the most distant points on an interior cross-section of the vehicle. The rear edge of the plate shall be positioned approximately 20 inches from the rear edge of the vehicle roof. A temporary stand may be used to support the plate until a force is applied.

8.09(b)(4) Apply an evenly distributed force in a diagonally downward direction through the force application plate at any rate not more than 0.5 inches per second, until a force of 500 pounds has been applied.

8.09(b)(5) Apply additional force in a diagonally downward direction through the force application plate at a rate of not more than 0.5 inches per second until the force specified in (a) has been applied and maintains this application of force.

8.09(b)(6) Measure the diagonal movement of any point on the force application plate that occurred during the application of force in accordance with Rule 8.09(b)5 and upon the emergency exits as specified in Rule 8.09(a)2 of these rules.

8.09(b)(7) Release all diagonal force applied through the force application plate and operate the emergency exits as specified in Rule 8.09(a)(2) of these rules.

8.09(c) Test Conditions: The following conditions apply to the requirements specified in Rule 8.09(b)(3).

8.09(c)(1) Temperature: the ambient temperature is any level between 32 degrees Fahrenheit and 90 degrees Fahrenheit.

8.09(c)(2) Windows and Doors: Vehicle windows, doors, and emergency exits are in the fully closed position and latched but not locked.

8.09(d) An alternative method of testing for the racking load test shall be as follows:

8.09(d)(1) The racking load shall be applied along a line connecting the most distant points on a transverse cross-section of the bus interior. It produces a shear distortion of the cross-section as shown in Figure 2.

A representative method of loading which employs a hydraulic jack to load a two-frame test assembly is Illustrated in Figure 2.

The maximum jack load for the two-frame assembly is determined by the following formula:

J = 2P J - maximum jack load for two-frame test assembly

P = load/frame where

P = DVW divided by N

DVW = dynamic vehicle weight

N = total number of bus body frames and DVW = DF x GVW

DF = dynamic factor, not less than 1.5

GVW = gross vehicle weight

Thus, for a DF = 1.5, a GVW = 22,000 pounds-force (lbf), and N = 11, the dynamic vehicle weight is DVW = 33,000 lbf, the load/frame is P=3000 lbf and the maximum jack load is j = 6000 lbf.

8.09(d)(2) When a complete bus body is rack loaded, the total load DVW must be distributed uniformly along the bus body. One method is to mount a series of hydraulic jacks along the length of the bus interior. Seats may be removed to facilitate jack mounting. The rack load will be considered to be uniformly distributed when the variation in the hydraulic jack readings is less than 10%. A maximum load for DVW shall be the sum of all jack readings.

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Figure 2: Transverse Cross Section Side View Arrangement of Hydraulic Jack for Rack-Loading of Two-Frame Assembly

8.09(d)(2)(A) The test may be performed on a complete bus body or on a representative section composed of at least two complete frames (body posts plus roof bows) and floor. Standard seats may be installed in the test section in a manner identical to that of the full bus body. Fabrication procedures for the test assembly shall be identical to normal bus body production.

8.09(d)(2)(B) A two-cycle loading sequence shall be conducted, with intermediate and final load and deflection readings recorded according to the procedure described.

8.09(d)(2)(C) The maximum deflection in line with the jack (A, maximum) shall not exceed four inches.

8.09(d)(3) Manufacturers shall specify which testing method was used and submit appropriate certification information as called for and 3.1 of these rules.

Notes

1 CCR 301-25-8.0

38 CR 07, April 10, 2015, effective 4/30/2015 46 CR 14, July 25, 2023, effective 8/14/2023 47 CR 19, October 10, 2024, effective 10/30/2024