FAQs

In 1997 the RMI issued a new standard for storage rack. 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 standard was also established.

To satisfy these requirements the RMI developed a program by which any rack manufacturer, member or nonmember, could submit a standard set of data and information about their racks, testing information and sample calculations for review. The RMI facilitated the submittal of this information to two randomly selected, independent, pre-qualified, storage rack design engineers for their review and approval that the testing, calculations and resulting component capacities were in accordance with the 1997 RMI Standard.

The RMI then issued a seal (the R-Mark) that the rack company can use on published capacity charts and, in conjunction with a Professional Engineer’s seal, on special designs to indicate that the components and design are in accordance with the RMI Specification.

Since 1997, the RMI Specification was updated in 2002 (ANSI MH16.1-2004), 2008 (ANSI MH16.1-2008), 2012 (ANSI MH16.1-2012), 2019, and in 2021 (ANSI MH16.1-2021), which is the current version.

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, from any of the member companies or from the RMI website at www.mhi.org/rmi.

The Rack Manufacturers Institute published a document titled “Considerations for the Planning and Use of Industrial Steel Storage Racks” in 2012. This document covers such topics as Planning, Purchasing Consideration, Installation, Use and Inspection, Maintenance of storage rack, and has been updated several times over the years.

The safe and efficient use of racked storage facilities depends on a number of factors. It is with these factors in mind that the document was written. It was prepared to give advice to the warehouse operator, who may not be a specialist in technical matters, or in the detail design related to the storage facility.

Users should be diligent in creating safe and effective systems. The implementation of safe and effective systems will help avoid injury to persons and property. Safety should always be the number one priority in the use of any system.

Storage systems using pallets, pallet racking and mechanical handling equipment, will contribute best to safety objectives when well designed, diligently maintained and used carefully, as intended. A copy of the document can be purchased at http://www.mhi.org/rmi.

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, from any of the member companies or from the RMI website at www.mhi.org/rmi.

The International Building Code requires all racks to be designed based on the requirements of the applicable ANSI/RMI standard. These standards are the only recognized U.S. standards for design, testing, and utilization of industrial storage racks. Therefore, racks that do not conform to these standards may not be as safe as racks that do conform. Also, if there should ever be an accident or other incident involving the storage racks, a responsible rack user would likely want to show that the racks have been designed to meet the recognized and code required standard.

Racks that do not conform to the ANSI/RMI Standards may not be as safe as racks that conform to the standard. The Rack Manufacturer’s Standard is the only recognized U.S. standard 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.

The RMI recommends purchasing racks that clearly meet the requirements of the ANSI/RMI Standard.

More information about industrial metal shelving may be found on the Storage Manufacturers Association web site – www.MHI.org/SMA.

Examine the rack to see if there are any identifiable manufacturer’s stickers, embossed stamps or stenciled markings. If none are present, take pictures of the racking, including close-ups of the beam connectors, base plates, both the horizontal and diagonal bracing and the upright column. Send your request, along with the pictures to the managing executive of the RMI, whose information can be found at http://www.mhi.org/rmi/. The information can then be distributed to the members of the RMI for help in trying to identify the rack manufacturer.

Click here to view cantilever standard details.

Most rack manufacturers produce unique and proprietary components. In particular, column shapes and hole punching patterns along with the mating beam end connectors are designed to interface specifically with each other. While some different manufacturer’s products may seem somewhat compatible, they are not interchangeable. Mixing of products from various manufacturers may cause fit and/or function issues and may void the original equipment warrantee. The beam-to-column connection properties are of vital importance in the proper structural analysis of the rack system. These properties are typically determined through testing. It cannot be automatically assumed that products from different manufacturers can be connected together without any adverse effects. For these reasons a registered design professional shall determine if the rack components can be connected.

In order to arrest a fall, the system must absorb a large force. OSHA requires the fall protection system and attachment points be able to safely support 5,000 pounds of force. Most rack systems are not designed as fall protection system attachment points. However, there are places on rack systems that may be able to stand up to that level of force and there are places that may not.

If it is desired that the rack system be used as a fall protection system attachment point, a registered design professional should be consulted.

Steel storage rack is a family of products constructed of steel that is used in a single or multilevel storage system in single or multi-bays consisting of vertical columns or posts and horizontal supports. Trussed bracing and beam to column connections are often used to resist horizontal loads. The horizontal supports are generally loaded with product, and the system can be one of a number of different types (Standard Pallet Rack, Stacker Rack, Drive-in or Drive-Thru racks, etc,).

There are additional seismic design requirements for racks accessible to the public, which often result in different component sizes than a rack which is not accessible to the general public because of the higher importance factor. If a rack is being installed in a low-seismic region, then additional design requirements may not be needed. There are safety products, maintenance, and inspection schedules that an owner may wish to use specifically for racks open to the general public. FEMA 460 Seismic Considerations for Steel Storage Racks Located in Areas Accessible to the Public contains many suggestions for special considerations for racks accessible to the general public.

There are a number of risks associated with the use of steel rack components that have been exposed to elevated temperatures or were housed in a facility during a fire incident. Information pertaining to the maximum temperature that the steel was exposed to, how long the temperature was sustained, and the period of time over which the components were cooled is critical in assessing whether the rack components are salvageable for continued use. The temperature of Cold-formed steel increases faster than structural steel due to its reduced thickness. Recent testing of common thicknesses and grades of cold-formed steel indicate that there is a noticeable degradation in its mechanical properties (yield strength, ultimate strength, elastic modulus, etc.) between 570°F - 1110°F (300°C - 600°C). If storage rack components experience temperatures within this range and were loaded, one would expect to see distortion in the steel sections. Some deformation may also result from thermal expansion stresses. The cooling period of rack components that have been exposed to elevated temperatures is also critical to the steel’s microstructure. A steel’s microstructure can be permanently altered after a fire. Steel that is rapidly cooled or quenched, potentially through the activation of a sprinkler head during a fire, may result in its increased brittleness. This is not a favourable development as the performance of rack structures, particularly during a seismic event, rely on the material’s ductility for energy dissipation and deformation capacity. Given the above, it is recommended that rack components that are exposed to temperatures above 480°F (250°C) be inspected and tested at the direction of a professional engineer or be taken out of service and discarded.

Low temperatures cause a reduction in steel’s ductility. Low temperature service is considered to be when the structure is subjected to a lowest anticipated service temperature (LAST) of less than -76° F. Studies have found that, above -76° F, ductility does not deteriorate significantly. Knowing this, if the service temperature of the space where the rack is used will be below -76° F, it is advised to consult with a Professional Engineer so they can analyze the system, applying the necessary factors of safety for extreme temperature.

Warehouse owners should also be aware that the performance of dynamic system components, such as pushback carts or pallet-flow tracks, may be affected by cold temperature. Owners should consult with the dynamic storage manufacturers regarding low temperature use.

The manufacturer of storage rack that is exposed to low temperature needs to avoid severe stress concentrations at any of the welded connections, which is the most effective means of providing fracture-resistance construction. (Reference AISC Steel Construction Manual 15th Edition Commentary Section A3.1a)

Ref – “Material properties of cold-formed steel under subzero temperatures” Cold-Formed Steel Research Consortium Colloquium, Oct. 2020

Material Properties of Cold-formed Steel Under Subzero Temperatures

Storage racks have shelves upon which merchandise product is stored. Merchandise Product is either placed on pallets that, in turn, are placed on the shelves, or merchandise product in the form of individual boxes or containers are stacked directly on the shelves. To prevent or minimize the falling hazard posed by merchandise product stored overhead, and to achieve the life-safety performance level that is desired, a dual approach is recommended:

1) Prevent merchandise product “fall-through” --- where pallets and merchandise productshould not be permitted to fall downward through one shelf to the shelf or the ground floor below, and

2) Prevent merchandise product “toppling” --- where pallets and individual merchandiseproduct should not be permitted to overturn or slide, such that they fall from the shelves onto the aisles below.

To help keep pallet loads from falling through (“fall-through”) or between the pallet beams, containment on the shelf can be accomplished with the use of welded-wirerack decking; spaced wood boards; spaced metal channels, angles, or plates; or perforated metal decking. Whatever The method solution is employed should prevent fall-through when the unit load has moved as much as ½ the frame depth, in theis not supported by both beams in the cross-aisle direction, or as much as the sum of the unit load clearances in the down-aisle direction.

To help secure individual merchandise product stored on pallets, one can use stretch-wrapping, shrink-wrapping, banding, and/or integral-box pallets. In Seismic Design Category D, E, or F the loads should be wrapped or otherwise contained, such that the pallet can be tilted to 20 degrees without the product falling off the pallet. This containment may also be warranted in other areas where desired. See the Pallet pallet Tilt tilt Test test figure:

To secure merchandiseproduct, placed on shelves, but not stored on pallets, from sliding, overturning, or “toppling,”, particularly in warehouse stores open to the public, one can use restraining bars, restraining chains or cables, netting, or slip and overturning-resistant containers or boxes. It is the responsibility of the owner to ensure that the stored product will not fall through the shelves or topple (or spill – pushed through) into the aisles.

For product that is part of Storage Group S, located in Seismic Design Categories D, E, or F and with a At a minimum floor storage height in excess of four times the least dimension of the floor footprint of the individual stored loads, the product designed as a part of Storage Group S, and located in Seismic Design Categories D, E, or F, shall shshould be stored on a, seismically designed rack structure.

Copies of the most recent edition of the ANSI/RMI Standard For The Design, Testing and Utilization of Industrial Steel Storage Racks, Commentary, ANSI/RMI Standard for Industrial Storage Rack Decking and other useful information are available directly from the Rack Manufacturers Institute or from the RMI website at www.mhi.org/rmi.

No, all tests are not mandatory; however, ANSI MH16.1-2021 Standard for the Design, Testing and Utilization of Industrial Steel Storage Racks does require that stub column tests be done as detailed in Section 13.2 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, a connection cyclical test as specified in Section 13.5 is required.

The remaining tests in Section 13 are optional tests that may be used to evaluate the effects of components on the overall behavior. This section also states that the tests can be used when there are factors affecting the design of the racks that are difficult to account for analytically. When rational analytical methods can be used, these other tests are not required.

The RMI defines the height-to-depth ratio for a single row of pallet rack to be the ratio of the height from the floor to the top surface of the top load-supporting beam level divided by the depth of the frame. The depth needs to be measured from the outside of the column to the outside of the column at the floor. 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 MH16.1 Standard in Section 12.1 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. All of these ratios and requirements are for a typical rack frame. If a set back leg or slope leg upright were to move the center of gravity from the frame’s midpoint, these ratio limits do not apply, and a rack engineer should approve the configuration. Slope or setback legs should generally be avoided in single rows.

The ANSI/RMI Standard 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 must be unloaded and re-plumbed. Any damaged parts must be repaired or replaced. This ratio could be used for straightness also. In other words, 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 can be significant. A rack that is out-of-plumb from top to bottom or a rack column that is not straight is likely to 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 very harmful. This condition could be caused 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 also become bent and exceed this limit (see figure (d)). As re-written the standard now prevents these situations from being acceptable if they exceed the 0.05" per foot out of straight limit.

No, the RMI standards, do not cover sloped floors. If the loaded rack is not installed to result in the ½” in 10’ maximum out-of-plumb it is not in compliance with the RMI Rack Standard. Only the Engineer of Record, after being advised of the lean, can recommend a remedy to the out-of-plumb, by shimming, grouting or verifying by calculation that the racks are still within their design parameters to carry the loads in their leaning position.

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.

It is important 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 also 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 is to have the diagonal braces in the bottom upright panels run from upper front to lower rear so that the diagonal braces won’t be damaged or their welds broken if the base portion of the aisle post is damaged. The choice is basically a matter of personal preference. There are no studies which 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 often recommend heavy-duty bottom braces, deflector angles, backer posts, post protectors, or some combination thereof.

Upright bracing members can be omitted to create openings. However, this should be included in the initial design and fabrication by the rack manufacturers.

It is also possible to retrofit existing uprights with openings. However, this is a substantial structural change to the uprights and must be reviewed by a qualified design professional. Removal of bracing may also require modifications to the surrounding bracing, columns, or both.

Click here to view a list of anchoring issues.

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 Standard states that rack installations should display load plaques. Building and safety inspectors may require that plaques be installed.

Click here to view cantilever standard details.

ANSI MH16.1-2021 is a revision of ANSI MH16.1-2012(R2019). A summary of the major revisions is shown in the standard and listed below:

• Reorganization of the document to align with guidance in ISO/IEC Directives, Part 2, specifically moving requirements previously in Section 1 elsewhere in the document, adding Normative References to Section 2 (previously Section 10, “References to the Text”), and adding Terms and Definitions to Section 3 (previously “Nomenclature” in the Foreword)
• A requirement for post-installation inspection conducted by the owner has been added (see 4.3)
• New stability design requirements similar to the requirements in ANSI/AISI S100 or ANSI/AISC 360 replace the effective length method for stability design outlined in previous editions (see 7.2)
• Seismic provisions (7.4) were revised to align with ASCE/SEI 7-2016, including:
• Revision of redundancy factors for multiple rows (see 7.4.3)
• Revision of the 𝐹𝑎 and 𝐹𝑣 coefficients for the D-Default site class (see 7.4.4)
• Revision of the 𝐹𝑎 and 𝐹𝑣 coefficients for the D-Default site class (see 7.4.4)
• New design procedure for perforated columns that includes a new definition of net section using reduced strips to represent the hole lines. Torsional properties are now to be calculated using rounded corners and a distortional buckling check is required for those sections subject to distortional buckling. The equation for 𝑄 effect on the column strength has changed (see 8.2)
• New section on pallet support design (see 9.5)
• New section on frame tie and cross-aisle tie design (see 10.4
• New provisions for base plate and anchor design where the seismic overstrength consideration is required (see 11.3)
• Interpretation of the cyclic tests for connectors has been added (see 13.5)
• The base fixity test (see 13.6) and frame bracing test (see 13.7) have been added
• The portal test and the upright frame test in the 2012 revision were removed from the 2021 revision
• The new provisions in Sections 8 and 13 are the result of the work of Dr. Pekoz, his international colleagues, and the Specification Advisory Committee
• Also in the new standard is a table cross-referencing the section changes between the two documents

ANSI MH16.1-2023 is a revision of ANSI MH16.1-2021. A summary of the major revisions is shown in the standard and listed below:

• Seismic provisions were revised to align with ASCE/SEI 7-2022, including:
  • Referencing free to use ASCE 7 Hazard Tool online software to obtain seismic design ground motion data
  • Elimination of Fa and Fv factors
  • Increase in number of site soil types
  • New methods to obtain the seismic response coefficients.
• Revisions have been made to the cantilever testing provisions and to the cyclic beam-to-column testing provisions. Either test can be used to determine beam design spring constants.

The Rack Manufacturers Institute (RMI) of MHI released a standard pertaining to the design, testing and utilization of industrial steel cantilevered storage racks in 2016. The standard, ANSI MH16.3-2016, Standard for the Design, Testing and Utilization of Industrial Steel Cantilevered Storage Racks, applies to free-standing and top-tied cantilevered storage racks made of cold-formed or hot-rolled steel members, and includes guidance on cantilevered storage rack with accessories, such as decked shelves, shed roofs and canopies. The standard is intended to harmonize the provisions for cantilevered storage racks with the International Building Code (IBC) definition of Steel Storage Racks and other relevant industry standards by reference. The standard is available for purchase at MHI.org/RMI and the ANSI website.

The current version of the Cantilever Rack Standard (ANSI MH16.3-2016) allows loads to be evenly distributed to the number of arms supporting the load. For example, if a 20 foot long, 10,000 pound product bundle is stored on four arms spaced 60 inches apart in the down-aisle direction, the users may divide the weight of the bundle by 4, giving 2,500 pound per arm, assuming that the bundles would be placed symmetrically on the 4 arms and that the product bundle is relatively rigid. However, this method can under-estimate the load per arm because the bundles may be relatively flexible or the load may be offset so that more load is distributed to one of the end arms beneath the load. For this example, a flexible bundle with severe offset placement could cause the maximum load on one of the end arms to exceed 4,000 pounds. The following figures illustrate this point:

For this reason, the industry intends to add a new Product Loads section in the next edition of the standard as follows, and considers this to be best practice: The product load on the cantilever rack shall be determined by any one of the following three methods. Method 3 is only permissible if the arms supporting the product bundle are equally spaced and the total bundle length is not greater than the number of arms multiplied by the arm spacing:

Method 1: The owner specifies a load per arm to the designer. In this method, it is the owner’s responsibility to account for bundle weight, size, stiffness, and placement tolerance relative to the arm layout. The column shall be designed for the sum of the arm loads.

Method 2: The rack designer calculates the distribution of product load from a bundle to the support arms based on load bundle details provided by the owner. The product load distribution to the support arms shall account for an asymmetric down-aisle and cross-aisle loading tolerance and relative stiffness of the product and the support arms. The column shall be designed for the sum of the arm loads.

Method 3: The rack designer uses product loads specified below:

P_arm=1.3W/n

P=W/n

where:

P_arm is the product load per arm for the design of the arms components;

P is the product load per arm for the design of the column and base beam components;

W is the total weight of the bundle or pallet;

n is the number of arms under the load.

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, and the NFPA code. 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.

The materials required for a building permit normally include the details of the proposed rack system and its use, the various loads for which it has been designed, the “calculations” from an engineering analysis prepared and “sealed” by a registered design professional, demonstrating the structural integrity of the proposed system and its conformance with all applicable building code provisions, details of the fabrication and installation processes, information about the building in which the rack system will be housed and used. The building information may include relevant information about the characteristics of the floor slab, the below-slab soils, and about the building structure if connections to the building are proposed. Typically the owner works with the rack supplier to assemble and process this information through the permitting process. There may be costs associated with the development and processing of this information through the local permitting process and for a building permit itself. The magnitude of these costs and how they are shared are matters of negotiation between the owner and the rack supplier and may relate to the size, complexity, and site-specific requirements of particular projects.

Yes, it is NFPA 13: Installation of Sprinkler Systems. The current edition can be purchased through www.NFPA.org. This standard gets updated every three years.

The Society of Fire Protections Engineers offers a list of geographical Chapters on their website http://www.sfpe.org/?page=Chapters

Each chapter is different as some offer a listing of resources and some just a contact person.

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 the design may create an unsafe condition. A qualified engineer should review any change to the bay configuration that is different from the original design configurations.

New rack should always be designed in accordance with the current ANSI//RMI standards. 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 standards. 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 standards. It is up to the discretion of the building official to allow the use of new rack the same as the existing rack without any component revisions. See International Existing Building Code (IEBC) 2021 Section 302 for additions to existing systems.

Repairs to any structural element of an existing rack structure should comply with the requirements of the RMI/ANSI standards 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.

Additional information regarding damaged rack can be found in the “Guideline for the Assessment and Repair or Replacement of Damaged Rack” published by the Rack Manufacturers Institute. A copy can be purchased at http://www.mhi.org/rmi/.

If the reason for extending the height of the pallet rack upright frames involves a change in the existing beam elevations or the addition of one or more beam levels, the design configuration of the rack is being changed. Prior to 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 must be checked with the new loads and the revised configuration to ensure that all the requirements of the ANSI/RMI Standard are satisfied for the new configuration and loads. The splice connection used must 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 some 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 should 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 must be properly repaired or replaced before the extensions are added.

Most rack manufacturers produce unique and proprietary components. In particular, column shapes and hole punching patterns along with the mating beam end connectors are designed to interface specifically with each other. While some different manufacturer’s products may seem somewhat compatible, they are not interchangeable. Mixing of products from various manufacturers may cause fit and/or function issues and may void the original equipment warrantee. The beam-to-column connection properties are of vital importance in the proper structural analysis of the rack system. These properties are typically determined through testing. It cannot be automatically assumed that products from different manufacturers can be connected together without any adverse effects. For these reasons a qualified design engineer shall determine if the rack components can be connected.

All storage rack systems are designed for the most unfavorable loading condition possible and it is commonly assumed by the rack designer that the storage rack system will be loaded and unloaded in a random fashion, with the specified loads in any location during its lifetime. Best practice, however, would be to load a pallet rack commencing at the bottom middle of the rack row and to continue outwards and upwards during the loading operation.

Research has shown that a generally appropriate protocol for loading a rack system is to store the heaviest product on the floor or lower storage levels at the middle of the rack row and then to work outward towards the ends of the rows and then upward. Due to inventory systems and control, this may not always be possible, but it is often the most appropriate loading method for a given structure.

The average load rating defines the average product load per row of rack. The maximum load rating defines the maximum weight of a single unit or bay of product that must be supported by an individual, beam, column, or upright element.

Historic editions of the ANSI/RMI MH16.1 Standard prescribed an effective length factor, which accounted for statistical underloading of storage racks. The ANSI/RMI MH16.1-2021 Standard now requires the underloading to be stated in the form of an average load.

A rack’s stability and down-aisle seismic forces are directly dependent on the average product load in a row.

Average loads must be specified as part of the contract documents by the rack owner and appear on both the load plaques and the Load Application and Rack Configuration drawings and calculations.

Specifying average loads can result in a more economical rack design by preventing the stability and down-aisle seismic from being unnecessarily conservative. The RMI Specification allows the average load to be used for computation of the rack stability and down-aisle horizontal forces because these are system effects influenced by the total load in the interconnected structural system, rather than an individual bay.

A uniformily distriburted loads is any static load which is evenly distributed over the entire surface on the rack storage level. This means that the product being stored on the storage level must cover the entire storage area from side-to-side and front-to-back. Storage rack capacity ratings are typically based on a uniformly distributed load storage on the storage level, unless specified otherwise.

The definitions are as follows:
Concentrated Load - any static load which is not uniformly distributed over the entire area of the storage level, eg. a container with two runner bars extending along its entire depth (concentrated line load)

Point Load - any static load that is concentrated to particular points on the storage level, eg. a container with multiple, small leg bases (point load)

Items such as lighting systems, sprinkler systems, fire extinguishers, converyors, etc. are sometimes attached to storage rack, particularly in pick modules. These loads are frequently included in the total dead load of the rack structure. If substantive, the user must bring these additional loads to the attention of the registered design professional.

In cases where these ancillary items are attached to existing rack systems, the loads must be reviewed by the rack manufacturer or registered design professional.

In the analysis of storage racks, the height of the storage rack is measured from the floor to the top loaded storage level. It may be prudent, however, for the registered design professional to consider the height of the rack to be the height of the rack frame if future reconfiguration of the top loaded storage level by the rack user is likely.

Structural design requirements are continually being modified in the building codes and by new research. If a storage rack is not altered in any way from the way it was originally designed and certified, then the building codes allow the original design load capacity to be used. If the storage rack is altered, then the storage rack must be re-evaluated based on the current adopted building code.

Often times, evaluating existing rack under current codes results in less capacity than that for which it was once approved. This is not only because of the changes to the design requirements but also because less technical information might be known about the rack now than was known at the time of fabrication. If thorough documentation of material properties is not available, then a site survey can be performed to collect as much information as possible. Certain material properties and manufacturer’s testing data might not be obtainable by a site survey. Conservative assumptions may be made where information is unknown. A qualified structural engineer should be consulted.

If an existing rack must be re-certified without the benefit of complete technical documentation, then it can be expected that the racks will be down-rated.

If there are any concerns regarding the structural integrity of a storage rack system, the first priority of the owner must be to immediately isolate the affected portions of the rack and prevent loads from being placed in that area. The rack manufacturer’s representative should be contacted for an engineering evaluation of the problem so that a repair or replacement of rack components is initiated. If the rack manufacturer cannot be identified or is no longer in operation, a qualified design engineer should be retained to assess the rack structure.

Yes, damaged rack frame braces are certainly a concern. The rack frame bracing consists of horizontal and/or diagonal members that join the front column to the rear column. These members are very carefully designed by the rack manufacturer to stabilize the rack frame in the cross-aisle direction and to restrain each of the individual columns, also, in the cross-aisle direction. Any damage to these components can jeopardize the stability of the frames and degrade the strength of the column.

If a frame brace is damaged, the first priority should be to isolate the affected area(s) of the rack structure and prevent loads from being placed in that area. The rack manufacturer should be contacted immediately afterwards for an engineering evaluation of the rack so that the appropriate areas can be safely unloaded. In the case of the frame braces, the affected area may be the rack bays on either side of the frame which is 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 such an evaluation, after repairs if necessary are competently completed, and after approval of the work by a qualified design engineer is provided, should the affected portions of the rack system be returned to service.

Additional information regarding damaged rack can be found in the “Guideline for the Assessment and Repair or Replacement of Damaged Rack” published by the Rack Manufacturers Institute. A copy can be purchased at http://www.mhi.org/rmi/.

An acceptable repair to a damaged rack component is one that is designed or reviewed by a qualified design engineer for compliance to the ANSI /RMI MH16.1 Standard and installed by personnel who are qualified to undertake the repair work. An acceptable repair will result in the storage system being placed back into service once the rack system and/or the repaired components have been restored to at least their original design capacity.

When a welded field repair on a rack system prescribed, repairs should be supervised by a supervising engineer and welding performed by a certified welder so that the work is performed in accordance with applicable American Welding Society (AWS) standards.

Additional information regarding damaged rack can be found in the “Guidelines for the Assessment and Repair or Replacement of Damaged Rack” published by the Rack Manufacturers Institute. A copy can be purchased at http://www.mhi.org/rmi/.

At design working loads, load beams are typically designed to limit vertical deflections to 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 may specify a requirement for less deflection based on visual appearance or cosmetic purposes. Users of rack systems that use more precise automated storage and retrieval equipment may require smaller limits in beam deflection. (See ANSI/RMI MH16.1 Standard section 9.3).

To prevent accidental disengagement of a beam connection, ANSI/RMI MH16.1, Section 9.4.3 requires that beams subject to machine loading have a connection locking device (or bolts) that does not fail through distortion or a reduction of its carrying capacity when subjected to an upward force of 1,000 lbf. It is important that the locking devices be properly installed and remain engaged.

A properly installed beam-to-column connection, with an engaged locking device, will not become dislodged when subjected to a minor upward force (1,000 lbf or less). Every manufacturer of storage racks has one or more unique beam-to-column connections. The detailed requirements of the assembly of the connection and the connection strength and stiffness are the result of each individual manufacturer’s physical testing of that connection. The installation and maintenance of the rack, including the beam-to-column connection should be in accordance with the rack manufacturer’s instructions. This information may be provided on the project specific Load Application and Rack Configuration drawing or within the rack manufacturer’s literature.

Yes. The storage rack system owner should establish and implement a program of regularly scheduled storage rack system inspections. The inspections should 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 should 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 (for example after an earthquake). Periodic inspection of the anchor bolt installation may be required. The frequency of inspections should be up to the discretion of the owner, 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.

More information can be found in the standard ANSI MH16.1-2021 Design, testing, and Utilization of Industrial Storage Racks, and in the Considerations for the Planning and Use of Industrial. The ANSI/RMI Standard may be purchased from RMI in their website www.mhi.org/rmi.

Section 12.3.8. of the RMI/ANSI MH 16.1 Standard requires “The design shall consider any locations where operations would require horizontal or vertical safety barriers to prevent product from falling.”

There can be systems in place to protect areas within or around the structure from products that could accidentally fall. Often, these locations are areas where people could be situated, or areas where falling product could cause other types of property damage or present a safety hazard. These areas should be identified by the owner and brought to the attention of the registered design professional. Proper barriers, if required, should be supplied and installed. These requirements will vary depending on the products, the operation, and the configuration of the structure.

The ANSI/RMI Standard may be purchased from RMI in their website www.MHI.org/RMI.

As mentioned in the Considerations for the Planning and Use of Industrial Steel Storage Rack, tunnel bays are storage rack bays without lower beam levels. Tunnel bays enable people or material handling equipment to pass through the rack at the floor level, perpendicular to the storage rack aisles, to allow movement to adjacent aisles without having to drive to the end of the rack row. Tunnel bays are often used at building egress doorways.

The location of tunnel bays should be determined by both the registered design professional and the facility operator. Tunnel bays could require special design considerations, including the following:

a) Longer rack rows could require more than one tunnel bay location per row.
b) When the tunnel bay has more load than the adjacent tunnel bay(s).
c) When tunnel bays are at the end of a row, the row-end frame could require strengthening due to the longer column length and multi-tiered bracing effects.
d) The clearance height of tunnel bays needs to allow for personnel and vehicles, including material handling equipment masts, to pass through the tunnel without contacting the lower tunnel beam.
e) Tunnel bays designed to accommodate vehicle traffic are often wider than standard bays and could require special impact protection to protect the rack columns.
f) The bottom shelf of the tunnel bay could require decking or other horizontal guarding as protection from objects falling through the racks.
g) Tunnel bays for building egress are sometimes half bays.

The ANSI/RMI Standard may be purchased from RMI in their website www.MHI.org/RMI.

A pick module, or rack-supported platform, is a rack structure comprised of vertical frames and horizontal beams that typically has one or more elevated platform levels used for both storing product and order fulfillment.   The term “pick” refers to selecting one or more products from one of the storage levels to fulfill an order.   Originally, pick modules were used for replenishing the stock at a company’s store, but over the past 20 years have increasingly been used to fulfill on-line orders shipped direct to customers.  Pick modules are used by authorized or trained personnel and are not open to the general public.

The type of storage in pick modules varies and includes pallet flow, case flow, shelving-style storage and more recently a variety of robotic applications.    Due to the elevated deck levels to accommodate personnel, as well as conveyors or other material conveyance equipment, pick modules have a few special design considerations.   The decked levels that will be used by personnel or will be supporting equipment or materials must be designed for live load.   Pick modules typically contain two or more stairways, guardrails and kick plates to provide safe working conditions.

More information can be found in Section 12.3 of the RMI/ANSI MH 16.1. The ANSI/RMI Standard may be purchased from RMI in their website www.MHI.org/RMI.

The pick module stairs, handrails and guardrails are required to comply with Section 12.3 of ANSI MH16.1, which is the referenced standard for storage rack in the building code. These structures are not open to the public and are only to be used by authorized and trained order pick personnel and, therefore, have specific storage rack design requirements.

The ANSI/RMI Standard may be purchased from RMI in their website www.MHI.org/RMI.

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.

More information can be found in the Sections 4.10 and 12.2 of the RMI/ANSI MH 16.1. The ANSI/RMI Standard may be purchased from RMI in their website www.MHI.org/RMI.

Horizontal separation is required in Section 7.4.11 of RMI/ANSI MH 16.1and recommended in the RMI Considerations for the Planning and Use of Industrial Steel Storage Racks Section 2.16, for the more active seismic regions, because the structures will sway differently during this ground motion. It is required to minimize the potential damage of these two structures from impacting each other during any ground shaking.

The ANSI/RMI Standard may be purchased from RMI in their website www.MHI.org/RMI.

Most rack manufacturers produce unique and proprietary components. In particular, column shapes and hole punching patterns along with the mating beam end connectors are designed to interface specifically with each other. While some different manufacturer’s products may seem somewhat compatible, they are not interchangeable. Mixing of products from various manufacturers may cause fit and/or function issues and may void the original equipment warrantee. The beam-to-column connection properties are of vital importance in the proper structural analysis of the rack system. These properties are typically determined through testing. It cannot be automatically assumed that products from different manufacturers can be connected together without any adverse effects. For these reasons a qualified design engineer shall determine if the rack components can be connected.

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.

Copies of the most recent edition of the ANSI/RMI Standard For The Design, Testing and Utilization of Industrial Steel Storage Racks, Commentary, ANSI/RMI Standard for Industrial Storage Rack Decking and other useful information are available directly from the Rack Manufacturers Institute website at www.mhi.org/rmi.

(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, resembling a waterfall. They usually have three to four support members or channels designed to fit within the step of the beam and support the load resting upon the deck. A waterfall deck for a box or structural beam is the same as above with the exception that 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. It can be flat or have formed instep waterfalls. The purpose of the design is to avoid any potential snag points and to leave the rack beam face unobstructed.*

(c) Also available is a non-waterfall deck that may 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 which could result in the deck dropping.

Wire decks are intended as an accessory to pallet rack. The dimensions of the wire deck must correspond with the rack upon which the decks are to be installed. There are a relatively 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. Generally wire deck manufacturers require a buyer to submit dimensional standard of the rack prior to production. This protects both the manufacturer and the buyer and 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 that the wire deck can be designed and built to meet or exceed the capacity of the rack system. Short of that the system is only strong as its weakest link. Generally speaking 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.

There should be a method provided to keep the decks from falling thru the beams. For decks not designed to capture the beam, an alternate securing method is recommended to prevent the deck from falling thru. Methods of securing decks include, but are not limited to, screwing, riveting or some other provision to prevent beams from spreading under load. The deck manufacturer in conjunction with the rack manufacturer can provide specific details.

No, wire decking is not designed to be walked 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 standing or walking on a wire deck is a use which falls outside its intended purpose. In addition, the surface of a wire mesh deck is flexible and irregular and the open areas within the mesh may 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).

Physical load testing of this condition dictates that the load rating should not be increased. Although it may be intuitive to think that the pallet is capable of transferring product load directly to the supporting rack beam(s), which was proven in the laboratory to not be the case. The pallet’s specific construction details and overall physical condition may adversely impact how the product load gets shared between the rack beams and the decking.

Some lightweight storage rack applications may be installed on surfaces other than concrete, such as wood decking, concrete on metal deck, bar grating or other materials.  It is important to consider the rack loads, rack layout, required floor strength and stiffness and coordination for proper anchoring.

Several steps are required to do this.  The rack engineer should provide point loads for the dead, product, seismic and live load cases, the rack configuration, and the limits on rack deflection.  The qualified floor system engineer must review the above information and confirm the floor system’s capacity to support the storage rack safely within strength and deflection requirements.  The rack engineer and floor system engineer must coordinate to determine details of anchoring or attachment to the floor system.

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. (See Chapter 11, ASCE 7 and Sections 7.4.6 and 7.4.7 of the RMI 2021 Standard for more information). 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 type, size, 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.

The RMI Standard does not provide requirements for floor flatness or levelness. Sections 4.11.1 and 4.11.2 of the 2021 RMI Standard explains the out-of-plumb and out-of-straight limits of rack columns. If a warehouse floor has flatness or levelness irregularities that result in out-of-plumbness or out-of-straightness of a rack column, this is commonly remedied by the use of shims. Section 11.2 of the 2021 RMI Standard explains the requirements for shims.

In today’s construction practices, when specifying and measuring the surface flatness (roughness, wash boarding, or bumpiness) and levelness (tilt, pitch, or slope) of a poured concrete floor, the F-numbering system is used in lieu of the former straightedge (⅛-of-an-inch-in-10-feet) method. The F-numbering system was developed by the Edward W. Face Company in conjunction with the ACI Committee 117. By profiling the floor surface, both a flatness value, FF, and a levelness value, FL, can be determined. More information about the F-Number System can be found here.

It is recommended that an owner consult with the manufacturers of their VNA trucks, AGV’s, reach trucks, etc, in order to determine the required flatness and levelness of the concrete slab in their warehouse.

No, the RMI standards, do not cover sloped floors. If the loaded rack is not installed to result in the ½” in 10’ maximum out-of-plumb it is not in compliance with the RMI Rack Standard. Only the Engineer of Record, after being advised of the lean, can recommend a remedy to the out-of-plumb, by shimming, grouting or verifying by calculation that the racks are still within their design parameters to carry the loads in their leaning position. Shim requirements can be found in RMI Section 11.2.

The entire RMI Standard is based on the loaded racks being no more than ½” in 10’ of height deviation from the true parallel with gravity. It must be understood that warehouse floors are presumed to be level. However, racks are sometimes installed on sloping floors and the material handling equipment is riding on those sloping floors. It is incumbent upon the building owner to make the rack designer aware of any slope and the extent of the slope. If the racks are installed perpendicular to the floor, the notional loads and additional forces due to the slope should be included in the rack design.

Yes, the following methods were presented to the SEAOSC (Structural Engineers Association Of Southern California) membership. These methods were presented during a series of seminars held in March 2003 and available from SEAOSC.

Equivalent Footing - The allowable load is determined by assuming a “saw-cut” square unreinforced section and then applying the conventional working stress method of analysis.
Integral Footing –, The strength of a slab on grade is determined by using empirical equations developed by the American Concrete Institute. (Design and Construction of Concrete Slabs on Grade, ACI SCM-11(86), American Concrete Institute, Detroit, 1986.)
Empirical Method - Method of analysis based on studies that compare the load test results to computer analysis. (Shentu, L., Jiang, D., Hsu, T. (1997). “Load Carrying Capacity for Concrete Slabs on Grade.” Journal of Structural Engineering, ASCE, January 1997, pp 99-103.)

The ANSI/RMI Standard requires that all rack columns (including short columns) shall be anchored. This means that both the aisle column and the interior or rear columns must be anchored on all frames according to the instructions from the manufacturer and applies to all rack frames all the time. If there is a specific application where the racks can’t be anchored, the user should 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 maintain the position of the rack column.

Should pallet racks with frames 8 feet tall or shorter be anchored? Yes, anchor the rack. People should NOT, but have been seen climbing and hanging on to the beams and rack frames. These situations and other unforeseen circumstances may cause even short racks to overturn. These unforeseen circumstances make anchoring even short pallet racks prudent.

The rack manufacturer should be able to provide 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. ½” or 5/8” diameter anchors with the proper embedment depth are the most commonly used anchor bolts for medium sized pallet racks in low seismic areas. If there is any uncertainty as to the anchoring requirement, the rack user or installer should contact the designer or the manufacturer regarding the anchoring requirement for that specific application.

Not necessarily. Racks must always be anchored to the floor as shown on the Load Application and Rack Configuration drawings. RMI Section 4.2 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.

Research has shown that a wedge anchor may be placed 3.0 bolt diameters (center-to-center) away from an empty hole without reducing the pullout-capacity of the anchor. If the empty hole is filled with dry-pack mortar a wedge anchor may be installed within 1.5 bolt diameters (center-to-center) of the hole. (Use the larger wedge anchor diameter when determining the spacing required in the event the anchors are a different diameter.)

Ref – “Effect of Abandoned Holes on Capacity of Wedge Bolts” ASCE Journal
of the Structural Division, April 1982

https://www.researchgate.net/publication/331431827
_Abandoned_Hole_Effect_on_Ultimate_Strength_of_Mechanical_Anchors_in_Tension

Yes, the overstrength factor must be considered for anchor bolts in rack projects assigned to seismic design category C or higher.  See Section 11.3.2 of the RMI 2021 Standard.

The control joints and saw cuts are not considered edge of slab given they have concrete on either side and the vertical surface of the slab joint is prevented from spalling. Note: (Tests and research have been conducted by some anchor manufacturers and the results suggest anchors embedded adjacent to control joints can carry forces similar to cracked concrete.)

The slab is considered to have a free edge if the slab edge is against soil, the slab edge is at an expansion joint or the slab edge is against asphalt. In these cases, the free edge of the slab could spall when the anchor is loaded in tension or during installation. The anchors need to be designed accordingly when located adjacent to a free edge.

Column protectors are often used to protect rack columns from possible collision damage in traffic aisles of rack storage systems. The nature of column protection may depend on the particular rack system and the vehicles which are used to service it. With inattentive operation, columns may 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 such 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 normally 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, Standard Section 4.4 and Commentary Section 4.4).

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 Standard Section 4.5 states that rack installations should display load plaques. Building and safety inspectors may require that plaques be installed. .

Copies of the most recent edition of the ANSI/RMI Standard For The Design, Testing and Utilization of Industrial Steel Storage Racks, Commentary, ANSI/RMI Standard for Industrial Storage Rack Decking and other useful information are available directly from the Rack Manufacturers Institute at www.mhi.org/rmi.

Areas in Seismic Design Category B and above face the potential of earthquakes to varying degrees, magnitudes, and probabilities. Areas in Seismic Design Category A do not have enough seismic activity to warrant a design check for that loading case. 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, Standard Section 7.4, and Commentary Section 7.4).

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 ANSI/RMI MH16.1 all utilize the Seismic Design Categories in their seismic design.

There is a United States Geological Survey (USGS) website available, for free, that will provide the seismic design parameters based on the site location. This web site may be found at – https://asce7hazardtool.online/ or https://www.seismicmaps.org/.

The Standard utilizes spectral response seismic design maps that reflect seismic hazards on the basis of contours. These maps were developed by the USGS.

The soil classification will affect the design of the storage rack.

For example, the importance of knowing the soil information is as follows: Given, S_S = 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-default 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.

Horizontal separation is required in Section 7.4.11 of RMI/ANSI MH 16.1 and recommended in the RMI Considerations for the Planning and Use of Industrial Steel Storage Racks Section 2.16, for the more active seismic regions, because the structures will sway differently during this ground motion. It is desirable to minimize the potential damage of these two structures from impacting each other during this ground shaking.

The ANSI/RMI Standard may be purchased from RMI in their website www.MHI.org/RMI.

Redundancy was first introduced to storage rack design requirements in the 2012 RMI Standard for Seismic Design Categories D, E and F. A structure is considered redundant if it has multiple possible paths for a load to take. A more redundant structure is preferrable over a less redundant structure because if one component in the system fails, there are other components that can potentially resist that load and keep the structure from collapsing. The RMI standard allows the seismic demands on components to be scaled according to how redundant the structure system is. Interconnecting multiple uprights in the cross-aisle and down-aisle direction as described in the RMI Standard can potentially reduce the redundancy factor.

For product that is part of Storage Group S, located in Seismic Design Categories D, E, or F and with a At a minimum floor storage height in excess of four times the least dimension of the floor footprint of the individual stored loads, the product designed as a part of Storage Group S, and located in Seismic Design Categories D, E, or F, shall shshould be stored on a, seismically designed rack structure.