Frequently Asked Questions

The ANSI/RMI Specification requires that all rack columns need to be anchored. Meaning both the aisle column and the interior or rear columns should be anchored on all frames according to the instructions from the manufacturer and applies to all rack frames at all times. If there is a specific application where the racks cannot be anchored, the user needs to get permission from the manufacturer’s engineer to waive the requirement. Anchors are required to resist many forces at the base of the columns and to keep the position of the rack column.

The rack manufacturer should be able to give the information on the proper quantity and size of anchors for the installation of its rack frame. This information should accompany installation instructions or on installation drawings. A ½” diameter anchor with the proper embedment depth is usually the anchor bolt used for medium sized pallet racks in non-seismic areas. If there is any uncertainty as to the anchoring requirement, the rack user or installer should contact the designer or the manufacturer in regards to the anchoring requirement for that specific application.

Some lightweight storage rack applications may be installed on surfaces other than concrete. Examples are wood decking, bar grating or other materials, but a qualified design engineer must review the means for anchoring or attaching. The rack user needs to provide a qualified design engineer with the necessary loads and configuration, and any other information that is required, to evaluate the ability of the floor system to support the rack column loads and the method for attaching or anchoring the rack.

The ANSI/RMI Specification shows the maximum out-of-plumb ratio for a loaded rack column as 1/2” per 10 feet of height. Columns whose out-of-plumb ratio exceeds this limit need to e be unloaded and re-plumbed. Any damaged parts should be repaired or replaced. This ratio could be used for straightness as well. The out-of-straightness limit between any two points on a column should not exceed 0.05” per foot of length (1/2” per 10 feet).

An out-of-plumb or out-of-straight condition will reduce the capacity of a rack column. The reduction could be significant. A rack that is out-of-plumb from top to bottom or a rack column that is not straight might become further out-of-plumb or out-of-straight when it is loaded.

The out-of-straight limit is given to prevent excessive “bows” or “dogleg” conditions that may exist in a rack column. A column could be plumb from top to bottom but have an unacceptable bow at mid-height (see figure (a)), or a 20 ft. high column could be out 1” from top to bottom, which could be acceptable using a simple top-to-bottom out-of-plumb measurement, but the entire out-of-plumb could be between the floor and the 5 ft. level (see figure (b)). This dogleg condition would be quite harmful. This condition could be resulted by fork truck impact. The column could have a sine wave shape and be out of straight as shown in figure(c). A column could become bent and exceed this limit as well (see figure (d)). As re-written the specification now prevents these situations from being acceptable if they exceed the 0.05" per foot out of straight limit.

At normal design working loads, beams are commonly designed to accommodate vertical deflections that do not exceed 1/180 (or 0.55 percent) of the horizontal beam length as measured with respect to the ends of the beams. Some users might specify a lesser-deflection requirement for visual appearance or cosmetic purposes. Still other users with systems intended to use more precise automated storage and retrieval equipment may specify a lesser-deflection requirement. (See ANSI/RMI Specification section 5.3, Commentary section 5.3).

Column protectors are commonly used to protect rack columns from possible collision damage in traffic aisles of rack storage systems. The nature of column protection might depend on the particular rack system and the vehicles which are used to service it. With inattentive operation, columns could be struck by man-operated forklift trucks directly or by over-hanging loads being carried by those vehicles.

It is not always feasible to build, install, and operate rack systems that are immune to dynamic operational abuse. Column-protectors, fenders, bumpers, or deflectors are often installed in front of each exposed rack column to attempt to keep such misuse from damaging the rack columns; aisle guides may also be used to attempt to keep a man-operated forklift from going astray; or reinforcement may be added to the exposed aisle-side columns with additional column sections, other reinforcing steel or other materials to improve their impact resistance. Automated or wire-guided vehicle systems are typically constrained on their intended path and are thus less likely to damage traffic-aisle rack columns. Users should consult their rack supplier about the various available protections, considerations, and options. (See ANSI/RMI, Specification section 1.4.9 and Commentary section 1.4.9).

Pallet racks are originally designed for configurations that the owner requested. These configurations are shown on the Load Application and Rack Configuration Drawings supplied to the owner. Changing the racks to a configuration that was not considered in the design may cause an unsafe condition. A qualified engineer needs to review any change to the bay configuration that is different from the original design configurations.

The RMI Specification states, “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.” If the damage were to re-occur, the application of the racks needs to be reviewed to see if modifications could be made to lessen the severity or the frequency of the damage. Forklift driver training is also essential.

Yes. The rack frame bracing consists of horizontal and/or diagonal members that join the front column to the back column. These members are very carefully designed by the rack manufacturer to stabilize the rack frame in the cross-aisle direction and to support each of the individual columns, also, in the cross-aisle direction. Damage to these components could jeopardize the stability of the frames and could degrade the strength of the column.

If a frame brace is damaged, the main priority should be to immediately unload the area supported by the damaged component and to prevent placement of loads into that area. In the case of the frame braces, it may be the bays on either side of the upright which are damaged.

Contact the manufacturer’s representative for an engineering evaluation of the effects of the damage to the structural integrity of the rack, of the damage. Only after an evaluation, after repairs if necessary are competently completed, and after approval of the work is done should the rack section be returned to service.

The detail used to make an acceptable repair should be designed or reviewed by a qualified design engineer and installed by people qualified to make the repair. The rack repair needs to be reviewed for compliance to the ANSI/RMI MH 16.1 Specification. A good repair will result in a structural member or connection that is at least as strong as the original.

When welding is prescribed, the welders should be certified for the types of welded joint required.

If there are any concerns about structural problems with the storage rack system, the main priority should be to safely and immediately unload the area supported by the damaged component and to prevent loads from being placed into that area. Then, the manufacturer’s representative must be contacted for an engineering evaluation of the problem. If the manufacturer cannot be identified, an independent engineer, experienced in the design of storage racks, should be retained for an evaluation.

All storage rack systems are designed for the specified load in any location, and it is typically assumed by the designer that the rack system will be loaded and unloaded in a random fashion during its lifetime. An appropriate approach to fully load a pallet rack is to start at the bottom middle of the rack row and to work outwards and upwards. Research has shown that a generally appropriate protocol for loading a rack system is to store the heaviest product on the floor or lower levels toward the middle of the rack and then to work outward to the ends of the rows and then upward. Due to inventory systems and control, this might not always be possible, but it is usually the most appropriate loading method for a given structure.

If the reason for extending the height of the pallet rack upright frames includes a change in the existing beam elevations or the addition of one or more bean levels, the design configuration of the rack is being changed Before making any such changes to the configuration or loads, the original and proposed rack design should be reviewed by the original manufacturer or by a qualified design professional.

All rack components and connections need to be checked with the new loads and the revised configuration to ensure that all the requirements of the ANSI/RMI Specification are satisfied for the new configuration and loads. The splice connection used should adequately transfer all loads from the frame extension to the existing frame. The frame extension must have proper bracing and be compatible with the beams or other components that will connect to it for the new configuration. In certain cases individual column extensions may be acceptable. If the rack configuration or load change is made and the extensions are added, it may be necessary to revise or replace the information on the load plaques and the rack application drawings.

If the reason for extending the frames is for non-structural purposes, the design review may not be required. If the racks are being extended to add cross-aisle ties for any reason, the design must be reviewed because the cross-aisle design model of the racks will be altered. If the racks are being extended for the purpose of tying the racks to the building, the design should be reviewed and the building design engineer must approve the connections. Any rack frames that are damaged need to be properly repaired or replaced before the extensions are added.

It is necessary to install the frames oriented as the manufacturer recommends. However, there may be cases that the orientations are not identified as important design considerations.

When the orientation of the frames is not design critical the diagonal brace orientation in the bottom upright panels run from lower front to upper rear so that the diagonal braces go into tension should the base portion of the aisle column be damaged. This orientation means that the aisle column usually has both a horizontal and a diagonal brace coming into the base portion of the aisle column for extra stiffness.

The other thought would be to have the diagonal braces in the bottom upright panels run from upper front to lower rear so that the diagonal braces will not be damaged or their welds broken if the base portion of the aisle post is damaged. The choice is a matter of personal preference. There are no studies to prove that one is better than the other and both cases have excellent track records.

To minimize damage to the aisle posts, your rack supplier will typically recommend heavy-duty bottom braces, deflector angles, backer posts, post protectors, or some combination thereof.

No. Wire decking is not designed to be walked on or stood upon. Walking and/or standing on a wire deck creates both dynamic (moving and varying) and concentrated loads. Wire decking is designed and assigned a load carrying capacity based on carrying uniformly distributed, static loads. While there is a safety factor designed and built into wire decking, dynamic and concentrated loading as a result of walking or standing on a wire deck is a use which falls outside of its intended purpose. In addition, the surface of a wire mesh deck is irregular and flexible and the open areas within the mesh could cause a person to trip. Furthermore, when subjected to lateral motion decks may slide upon the supporting rack beams or tip upward and become dislodged when loaded in a concentrated fashion on the outer extremities (beyond the outermost support members).

Wire decks are intended as an accessory to a pallet rack. The dimensions of the wire deck should correspond with the rack upon which the decks are to be installed. There are a large number of different rack manufacturers and a wide variety of beam styles and designs. If the dimensions are wrong, the wire deck may not fit on the rack or may fit but be unsafe. Commonly, wire deck manufacturers require a buyer to submit dimensional specification of the rack prior to production. This protects both the manufacturer and the buyer as well as assures that there is agreement upon precisely how the wire decks are to be utilized.

It is also a best practice to supply the wire deck manufacturer with the load capacity rating of the rack system so the wire deck can be designed and built to meet the capacity of the rack system. The system is only strong as its weakest link. The deck capacity is specified to mirror that of the load beams of the rack system, for example a beam pair rated at 5,000 lbs. will require two wire decks rated at 2,500 lbs. each.

(a) The most common type of wire deck is a waterfall style. The waterfall is the overlapping of the top deck wires running over and down the face of the support beams, like a waterfall. They usually have three to four support members or channels designed to fit in the step of the beam and support the load resting on the deck. A waterfall deck for a box or structural beam is the same as above, however, the support members or channels are flattened or flared at the ends where they rest on the top of the rack beam.

(b) Another popular type of wire deck, similar to the above, is a flush or instep deck fitting step beams only. This deck sets on the step ledge between the beams, flush with the top of the beams. This type can be flat or have formed instep waterfalls. The purpose of the design is to avoid potential snag points and to leave the rack beam face unobstructed.*

(c) Also available is a non-waterfall deck that could span across the top of the front and rear load beams but does not waterfall down. This style of deck is not recommended for non-step beams due to the configuration being unstable.*

* When applying types (b) and (c) above, it is recommended that the decks be fastened to the beams or the beams tied to prevent beam spread resulting in the deck dropping.

(a) The storage rack system owner should establish and implement a program of regularly scheduled storage rack system inspections. The inspections would need to be performed by a qualified person familiar with the storage rack design and installation requirements retained or employed by the storage rack system owner. Storage rack must be inspected periodically to check for any damage or abuse and immediately after any event that occurs that may result in damage to the rack. The frequency of inspections should be up to the owner’s discretion, depending on the conditions of use. As a minimum, inspections should be performed annually. The inspection schedule and results of the inspection should be documented and retained.