Damage to a rack frame or beam will reduce its load capacity. The greater the damage, the greater the reduction in the load carrying capacity. Damage to the frame bracing will reduce the capacity of the frame to withstand accidental impact to the front post and will also reduce the axial load carrying capacity of the frame. Damage to the beam/frame connection will reduce the load capacity of the beam.
There are two main Safety Codes that apply to the design, installation and maintenance of steel storage rack structures.
(a) Rack Manufacturer’s Institute (RMI) – Specification for the design, testing and utilization of industrial steel storage racks.
(b) SEMA Code of Practice for the design of static racking
The RMI Code states that “Upon any visible damage, the pertinent portions of the rack shall be unloaded immediately by the user and the damaged portion shall be adequately repaired or replaced”.
The SEMA specification allows for measurable amount of damage and provides a method of measuring the damage.
For damage to frames and bracing members:
- Any frame with a tear, split, buckle or bend should be replaced.
- A frame with a bend in the direction of the rack beam should be measured using straight edge 1.0 meters long. Placed against the concave edge, the gap between the edge and the rack at the bend should not exceed 5.00mm.
- For a frame bent in the plane of the frame bracing the maximum gap between the frame and the straight edge should not exceed 3.00mm.
- For a frame with damage in both directions deformation should be measured as above and the appropriate limits maintained.
- For bracing members bent in either plane the gap between the straight edge and the member should not exceed 10mm.
If the damage exceeds any of these tolerances the damaged member should be replaced or repaired. Any repairs to a rack frame must be done according to the manufacturer’s specifications or by a method approved by an engineer.
For damage to beams:
- Beams showing signs of cracks in the welds between the end connector and the beam section should be replaced.
- Beams with end connectors showing deformation should be unloaded and the supplier consulted.
- Beams will naturally deflect under normal loading to a maximum vertical deformation not to exceed the measure of the beam length in inches divided by 180 (L”/180). This deflection should disappear when the beam is unloaded. With the load removed, the maximum vertical deformation should not exceed 20% of the normal deflection while under load. The lateral deformation should not exceed 40 % of the normal vertical deflection under load.
If the damage exceeds any of these tolerances the damaged beam should be replaced. Damaged beams should not be repaired.