What is RMI?

"RMI" are the initials of The Rack Manufacturers Institute. The Rack Manufacturers Institute is an independent, incorporated trade association formed in 1958 and affiliated with the Material Handling Industry. The membership of the RMI is made up of companies which produce the vast majority of industrial storage racks installed in USA. The RMI promotes the safe design and use of storage racks and related structural systems such as Welded Wire Rack Decking through research, testing, preparation of specifications, educational programs, and meetings. The RMI is the American National Standards Institute (ANSI) accredited developer of storage rack standards and administers the R-Mark Certification Program.

What is the R-Mark?

In 1997 the RMI issued a new specification for storage rack (later updated to become the 2002 edition and more recently adopted by American National Standard ANSI MH 16.1-2004). Shortly thereafter, RMI created the R-Mark Certification Program as a way for storage rack users and customers to clearly identify that rack frame and beam capacities shown in a load table were calculated in accordance with the new standard. A way of identifying special projects that were designed in accordance with the new specification was also established.

How do I obtain copies of the ANSI/RMI Specifications? Does RMI have a website?

Copies of the most recent edition of the ANSI/RMI Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks, Commentary, ANSI/RMI Specification for Welded Wire Rack Decking, and other useful information are available directly from the Rack Manufacturers Institute (704-676-1190), from any of the member companies, or from the RMI website at: www.mhi.org/rmi.

What are the SIC and NAICS Code for Storage Racks and related items?

Beginning in the late 1930’s, Federal economic statistics for USA were collected and organized using the Standard Industrial Classification (SIC) System. In 1997, the SIC system was replaced by the North American Industry Classification System (NAICS) to normalize data-capture between USA, Canada and Mexico.

SIC and NAICS codes for racks and related items:
Products/NAICS Code SIC Code

  • Rack Accessories -- 33715EYYW 2542300
  • Drive In/Drive Through -- 33715E111 2542341
  • Cantilever -- 33715E121 2542343
  • Portable Racks/Frames -- 33715E131 2542345
  • Stacker Racks -- 33715E141 2542347
  • All Other (including Conventional) -- 33715E151 2542349

Are there any safety considerations for personnel accessing the area under the racking?

Section 8.4.5. of the RMI/ANSI MH 16.1 Specification and Commentary requires "The owner should specify to the designer any locations where operations may require horizontal or vertical safety barriers. These barriers shall prevent product from falling into those areas."

What should I do if I want to reconfigure my load beam elevations?

Pallet racks are originally designed for configurations requested by the owner. 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 that design may create an unsafe condition. A qualified engineer should review, for compliance with the current RMI/ANSI MH 16.1 design standard, any change to the bay configuration that is different from the original design. The new configuration will need to be added to the Load Application and Rack Configuration Drawing(s).

When a portion of a current rack structure is repaired, is it required to bring the unrepaired sections of the rack up to current ANSI/RMI specifications?

The RMI/ANSI MH 16.1 is the best technical storage rack design resource available today. It may be desirable to have the whole rack system evaluated to this standard.

Repairs to any structural element of an existing rack structure should comply with the requirements of the RMI/ANSI specifications for new construction. Existing structural elements of a rack structure that do not require repair and are not adversely affected by the repair of other structural elements may not be required to comply with the ANSI/RMI requirements for new structures. It might be prudent to contact the local building department to determine if a new review is necessary.

If more rack is added to an existing rack system, is the new rack required to be designed according to the current ANSI/RMI specifications?

New rack should always be designed in accordance with the current ANSI//RMI specifications. However, any existing rack that is unaffected by the addition of the new rack does not have to be modified to bring it up to the current specifications. If the new rack will affect the design of the existing portion, the whole affected part of the system must be reviewed for compliance with the current design specifications.

IBC-2012 code reference: Chapter 34, Section 3403.1.

What constitutes a UDL (Uniformly Distributed Load) and how does it apply to storage capacity ratings?

The definition of UDL - Any static load which is evenly distributed over the entire surface on the rack deck (Ref MH26.2). This means that the product being stored on the deck must cover the entire deck from side to side and front to back. General capacity ratings are based upon a UDL stored on the deck.

What is a concentrated or point load?

Concentrated Load - any static load which is not uniformly distributed over the entire surface of the decking section (Ref MH26.2 - 2004).

Point Load - any static load that is concentrated to particular points on the deck. (ie. A container with four small feet (point load) versus a container with two runner bars running the entire length of the container (concentrated load).

What happened to the old seismic zones (0 to 4)?

The zone designations are no longer used. This occurred with the introduction of the International Building Code in 2000 which affected the ANSI/RMI MH 16.1 Specification.

The old UBC seismic zones (0 to 4) were based upon the seismic ground motion, corresponding to a certain probability of occurrence within a zone. Therefore, all structures within a zone were designed for the same requirements.

What is currently used by the building codes to designate seismicity in lieu of the seismic zones?

The building codes use what is now referred to as Seismic Design Categories (SDC), which range from A to F, and are a function of the seismic hazard at the site, the type of buildings (or occupancies) built at the site and the soil data at the site, and is more representative of the site seismic characteristics. The Seismic Design Categories have been in existence since 2000. The building codes design manuals and the ANSI/RMI MH16.1 all utilize the Seismic Design Categories in their seismic design.

What is the importance of knowing the soil classification?

The soil classification will affect the design of the storage rack. For example, the importance of knowing the soil information is as follows: Given, SS = 0.2 and S1 = 0.08, if the soil is Site Class A or B, then the Seismic Design Category is A, and seismic design is not required. If the Soil is Site Class C or D (Site Class D is the default required to be used if the actual Site Class is not known), then the Seismic Design Category is B where seismic design is required.

Why should I purchase racks that conform to the ANSI/RMI Specifications?

Racks that do not conform to the ANSI/RMI Specifications may not be as safe as racks that conform to the specification. The Rack Manufacturer’s Specification is the only recognized U.S. specification for the design, testing and utilization of industrial steel storage racks. If there should ever be an accident or other incident involving the storage racks, a responsible rack user may want to show that its racks have been designed to meet this recognized standard.

What were the changes to ANSI MH16.1-2008 that resulted in ANSI MH16.1-2012?

The 2012 RMI Specification was modified in the following areas:

  • In Sections 2.1 and 2.2 the load combinations were modified to include the redundancy factor and seismic product load coefficient.
  • Section was added explaining the redundancy factor.
  • The seismic maps in Section were updated.
  • Information on the Seismic Design Categories utilized by the building code was added in Section
  • Section 2.6.4 regarding Connection Rotational Capacity was updated.
  • Section 2.6.6 was added on the seismic separation between rack and the building columns in Seismic Design Category D and higher.
  • The section on Beam-to-column connections was moved from Section 7 and added to Section 5, which deals with beam design.
  • Section 5.5 was added on Pallet Supports.
  • The maximum considered earthquake base rotation in Section 7.1.3 (formerly Section 7.2.3) was better defined.
  • Section 7.2 on Slab and Subgrade Evaluation was added.
  • Section 7.3 on Anchor Bolts was added.
  • Section 9.6.11 on Evaluation of Test Results was added.

What information should I know about the floor slab and the soil subgrade and why is this important?

It is the responsibility of the owner to make sure that the new or existing floor slab in the building will support the loads that are imposed on it by storage racks, fork trucks and any other equipment that may be present. The owner should consult with a qualified engineer who is able to evaluate the existing floor or design a new floor once the intended use of the building has been established and the expected loading on the floor has been determined.

The data required for designing a floor system or for evaluating an existing floor system should include information about the soil sub-grade. At a minimum, the designer typically needs the bearing capacity of the soil sub-grade expressed in pounds per square foot and the stiffness of the sub-grade (also known as the sub-grade modulus) expressed in pounds per cubic inch. Additional data such as the soil type may also be needed to evaluate slabs so that the soil site classification can be determined. This soil site classification can have a significant effect on the design of storage racks for earthquake resistance. This information should be given to the rack engineer and the building engineer, who is analyzing the floor slab.

The necessary slab data may include the strength of the concrete (compressive yield strength in pounds per square inch), the slab thickness, the strength and spacing of the steel reinforcement in the slab, the levelness and flatness of the floor, the joint locations, any other irregularities that may be present in the floor slab, and more. This data should also be given to the rack engineer and the building engineer who is analyzing the floor slab.

It will be beneficial to the owner to provide all of the information on the slab and the sub-grade because doing so could reduce the chance of having problems with the slab or rack structure and could result in a more economical rack and floor slab design for new construction. In many cases the building engineer may communicate directly with the rack engineer at the request of the owner. The rack engineer may give the building engineer the loads imposed by the rack, and there can be agreement on items such as the base plate size and the anchor bolt locations. Often the location of the rack anchor bolts can be coordinated with rebar placement in the floor to reduce or eliminate interference.

Why is it important to provide the rack designer with the average load per shelf as well as the maximum load per shelf for the rack structure?

The use of average load is only appropriate for the determination of the seismic down-aisle horizontal force. The use of average load is not to be used for static design.

For the down aisle seismic design, the RMI Specification allows the designer to use the average load to determine the horizontal seismic forces for the rack analysis. This can result in economy by preventing the down aisle seismic analysis from becoming overly conservative. The RMI Specification allows the average load to be used for computation of these horizontal forces because at the time of a seismic event only the loads that are actually in the rack at the time of the event will participate in swaying the racks.

The RMI Specification does not permit the use of the average load for computation of cross-aisle seismic forces because there could be an accumulation of heavier loads in one bay.

The user and designer are reminded that for the rack design, once the horizontal seismic forces are determined, the RMI Specification requires the racks to be designed for these forces in combination with the maximum gravity loads. The loads are to be combined using the appropriate load combinations.

How would I know if I need a building permit for my rack system?

Rack structural systems, not unlike building structures, are often subject to the building code review and permitting process. The pertinent building code is usually required by a municipality, county, or state. Most building codes which have been adopted and are being enforced include rack structures - e. g., the International Building Code, the NFPA, and the earlier UBC, BOCA, and SBC model codes. Those provisions often include the requirement of a local building permit. Occasionally, local requirements may differ slightly from the more generally-applied national and international building codes. The user should determine from local authorities which building code is applied and should report that information to the rack manufacturer.

How do I know if my rack system will require special design for seismic forces?

Rack structural systems, not unlike buildings, are often subject to the building code review and permitting process. Most communities face the potential of earthquakes to varying degrees, magnitudes, and probabilities. Particular seismic requirements are site-specific, and the user should bring to the attention of the rack manufacturer the specific local requirements, including applicable building codes, the specific installation location, any knowledge of the supporting concrete slab, and any information about the below-slab soils and their properties.

Rack systems should be designed, manufactured, installed, and used in accordance with the site-specific requirements of the site; these requirements may include seismic effects and may also include the characteristics of the building in which the rack system is housed. (See also, ANSI/RMI, Specification section 2.7, and Commentary section 2.7). To find the requirements for your job site contact the local building authority.

What should I know about height-to-depth ratio of single rows of rack?

The RMI defines the height to depth ratio for a single row of pallet rack to be the ratio of the distance from the floor to the top beam level divided by the depth of the frame. Normal anchoring as is used for double rows is usually adequate for racks whose ratio is 6 to 1 or less. If the height to depth ratio exceeds 6 to 1, the anchors and the base plates should be designed to resist overturning. The ANSI/RMI Specification in section 8.1 provides for the anchorage to resist an overturning force of 350# applied at the topmost shelf level (to an empty rack). If the LRFD method of design is used, this force should be treated as a live load and multiplied by 1.6.

If the height to depth ratio exceeds 8 to 1, the racks should be stabilized using overhead ties. If anchoring is used for this extreme case, the design of the anchors must be certified by an engineer.

Why should I install load plaques?

Load plaques serve as a constant reminder of the rated load capacity of the rack. Plaques may also serve as a record of the rack’s manufacturer. The ANSI/RMI Specification states that rack installations should display load plaques. Building and safety inspectors may require that plaques be installed.

Is there a national standard for the design, testing and utilization of welded wire rack decking?

Yes, ANSI standard MH26.2 - 2004 and can be purchased through www.MHI.org.

Is there an NFPA fire safety code regarding racking or wire decking?

Yes, NFPA 13: Installation of Sprinkler Systems, 2007 edition and can be purchased through www.NFPA.org.

Are all tests outlined in section 9 of the RMI specification mandatory?

No, all tests are not mandatory; however, the MH16.1-2012 Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks Section does require that stub column tests be done as detailed in Section 9.2 to determine the Q value of perforated rack columns. This is required because the effect of the holes on the column strength is difficult to determine analytically. Additionally, in Seismic Design Category D and above, a connection cyclical test as specified in Section 9.6 is required.

What is the requirement for beam connector locking devices for uplift force?

ANSI/RMI MH 16.1 Section 5.4.2 requires a locking device that prevents disengagement of the shelf beam when subjected to a 1000 lbs vertical uplift force. It is important that the locking devices be properly installed and remain engaged.

Should I tie single rows of rack to the wall?

It is generally not a good idea to tie racks to the wall because forces from the building can be transferred to the racks and because forces from the racks can be transferred to the building, although wall ties are sometimes used in low seismic areas. If wall ties are used, there must be proper coordination between the building engineer and the rack engineer to ensure that the ties and any transmitted forces will not damage the rack or the building structures.

The connection to the wall must be capable of transferring the required forces, and the connectors must be compatible with the wall material. The seismic analysis of the rack and the building being tied together is extremely complex, and the connection is best avoided. If the height to depth ratio is such that a single row needs extra stability, heavy- duty anchor patterns with larger base plates or cross aisle tie configurations could be used rather than wall ties.

Do all the holes in the baseplate require anchors?

Not necessarily. Racks must always be anchored to the floor as shown on the Load Application and Rack Configuration drawings. The RMI Specification requires at least one anchor per column. The rack manufacturer will often provide extra holes in the base plate as alternate holes that can be used in case floor reinforcing interference is encountered when drilling the floor.


Installation and Safety