Reference for Seismic Calculations

NAWL distributes an RMI certified pallet rack product the is manufactured in China. Our seismic engineering data and specifications have been tested by Seismic Inc. and all information for preliminary calculations are available through the Seismic Inc website once you register.

US Seismic Zone Map

Sheet Thickness Tolerances

RMI Certified

Pallet storage racks were created to optimize warehouse and distribution center operations. As individual storage rack manufacturers developed new and competing products, the need for design and utilization standards and their implementation by the user and producer industries became obvious.

The Rack Manufacturers Institute (RMI) was established and incorporated in 1958 to deal with industry-wide issues. Among its initial activities was development of the first edition of an RMI standard, Minimum Engineering Standards for Industrial Steel Storage Racks, which was issued in 1964. It represented the first step in developing specifications and other products designed to suit the needs of users, manufacturers, and the engineering and code-enforcement communities.

From Fema-460 – September 2005

Click to download documents below:


Comprehensive Resources For Safe Rack Design, Use Detailed In RMI’s ProMat Education Session

The safe use of a storage rack system is key to the ongoing productivity of a warehousing operation. That’s why members of RMI will both share insights from the current standards for the design, testing and utilization of industrial steel storage racks and address related questions in “Rack Safety, Inspection and Repair,” a free, on-show floor seminar during ProMat 2019. The session will be held on Wednesday, April 10 from 11:15 a.m. to 12:00 p.m. in Theater F, located in the back right-hand corner of McCormick Place’s South exhibit hall.

Attendees will learn about the comprehensive catalog of resources offered by RMI that can be used to design and implement a safe rack system. These include:

  • The ANSI MH16.1-2012 Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks
  • The ANSI MH16.3-2016 Specification for the Design, Testing and Utilization of Industrial Steel Cantilevered Storage Racks
  • The ANSI MH26.2-2017 Specification for the Design, Testing and Utilization of Welded Wire Rack Decking
  • Considerations for the Planning and Use of Industrial Steel Storage Racks
  • Guideline for the Assessment and Repair or Replacement of Damaged Rack

Additionally, the session will feature an overview of the elements that should be included in rack inspections to help ensure a rack system remains in productive working order. Further, the recommended frequency of those inspections to ensure the integrity of the installation and its safe use will be discussed.

Presenters will also detail the types of accessories that can be deployed to further enhance the safety of a rack system by offering a measure of protection from impacts. Finally, the presentation will discuss how to assess rack damage and, if deemed necessary, how to decide between repairing or replacing the damaged components.

Those who are unable to attend the session in person may still access the presentation and its accompanying audio via a recording that will be made available online after ProMat concludes.

Looking for answers to industrial storage rack system safety questions prior to ProMat? Visit RMI’s page of frequently asked questions (FAQs).

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Rack System Enhancements That Further Mitigate Forklift Impacts

A previous blog entry reviewed a selection of optional guarding accessories. These add-ons are applied at the time of installation—or as a later retrofit—to aisle-side or end-facing rack columns (or to the floor in front of them) to minimize the damage caused by a forklift impact. For operations wishing to preserve the maximum amount of aisle clearance, however, there are a number of options available for safeguarding the rack uprights for impact. These impact protection modifications can be implemented with either structural or roll-form rack systems, as both are used in high lift traffic warehouse applications.

Outlined in RMI’s ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks, none of these design enhancements will prevent the rack from failing due to a major collision, nor should they be considered a replacement for proper and ongoing forklift driver training and management. Nevertheless, they greatly reduce the chances that a minor, day-to-day impact will cause a collapse. And, in the instance of an impact causing significant damage, they may extend the time needed to safely unload the rack and remove it from commission until it can be inspected and repaired by a certified rack engineer.

Depending on the application, one or more of these design enhancements may be added to a system. They are most frequently deployed on the aisle-facing columns of interior uprights or to both columns in end-of-row or tunnel-bay cross-over uprights, where collisions are more likely to occur.

  1. Double Columns. In structural and roll-formed rack applications, a second column may be welded to the front column. The additional column reinforces and strengthens the upright. It also provides some redundancy by redistributing the load stress if the front column is damaged due to impact.
  2. Column Inserts or Reinforcement. Reinforcement sections can be added externally or internally to increase the impact strength and load capacity of the column. These sections can be made from various materials, such as steel or wood. Further, they can be placed inside racking columns to provide added protection against impact damage.
  3. Heavy-Duty Bracing. Implementing heavier horizontal and diagonal bracing within the rack upright, particularly in the lower impact regions, can also help the upright resist damage caused by a forklift impact.
  4. External Column Protectors. There are many other column devices that can be added to provide some level of impact protection. Included are steel guards bolted to the floor, steel guards bolted or welded to the column, snap-on plastic and rubber shock absorbing devices, guard rails, floor rails, and more.
  5. Beam Uplift Protection. Most roll-formed rack beams are installed with studded-type or formed steel connectors with beams clicking into place with spring-type locking devices or clips. Should a forklift driver miscalculate the clearance of a pallet load opening and impact the beam above the load, the resulting contact can create an excessive upward force. This may exceed the spring lock capacity and potentially cause the beam to dislodge. For additional protection against beam uplift, secondary items—such as bolts and J-pins—can be added, locking the beam connections to provide enhanced restraint.

Again, when correctly assembled, maintained and used in an environment where properly trained forklift drivers operate with caution and care, the vast majority of steel storage racks designed to RMI standards will deliver a long, safe service life. For operations wishing to further protect their racking structure, however, these modifications can enhance its resistance to forklift impacts.

Looking for more rack protection accessories? Section 3.4.2 of RMI’s publication, “Considerations for the Planning and Use of Industrial Steel Storage Racks,” offers a detailed review of the options.

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RMI Seminar At ProMat To Address Rack Safety In The Age Of E-Commerce

With the holiday shopping season officially starting a week ago on Black Friday (or—in some cases—a week or two prior, as retailers offered special discounts ahead of Thanksgiving to get a jump on the competition for consumers’ dollars), the popularity of online shopping further cemented itself. According to the National Retail Federation (NRF) , multi-channel shopping jumped nearly 40% over the same period in 2017. More than 165 million Americans shopped in stores or online. Further, more than 89 million people shopped via a combination of both (order online/pickup at store; order at store kiosk/deliver to home; order via mobile device/ship to store; and so on). In all, the NRF says multi-channel shoppers outspent single-channel shoppers by an average of $93.

What does this have to do with the safe use of industrial steel storage racks? A lot. Because the changes in how people shop directly impacts the breadth, variety, unit sizes and volumes of inventory stored on and picked from rack in warehouses and distribution centers (DCs). And those changes in inventory and orders for it—a transition from bulk shipments to replenish retail stores to a profusion of individual items shipped to unique consumers in significantly smaller unit sizes—will fundamentally change the design and installation of racking systems in both existing and planned facilities.

The topic will be explored in depth during RMI’s free, on-floor seminar, “Warehouse Racking Systems for the E-Commerce World,” presented during ProMat 2019. The 45-minute session will be held on Wednesday, April 10, from 2:15 to 3:00 p.m. in Theater B—located in the back right-hand corner of McCormick Place’s South exhibit hall.

Via the presentation, prospective and current end users and owners of industrial steel storage racks will tour a variety of different rack styles and designs created to meet the requirements of the e-commerce and multi-channel retail world. The session will explain some of the key design points to consider when determining which racking style is both the best and safest solution for a given facility.

Included will be an overview of the various types of rack available and the types of e-commerce inventory storage and picking processes for which each is more ideally suited. The presentation will also detail multiple types of rack configurations, highlighting their degree of storage density, notable features and operation, and potential areas of concern when accessing loads. Included are discussions of:

  • Selective rack
  • Selective double deep rack
  • Drive-in and drive-thru racks
  • Double pallet drive-in rack
  • Push back rack
  • Pallet flow rack
  • Carton flow rack
  • Automated storage and retrieval system (AS/RS) rack
  • Pallet shuttle systems
  • Cantilever rack

The session also features mezzanine-supporting racks utilized for optimizing overhead space, plus pick modules and multi-level storage systems. Unable to attend the session in person? The presentation and its accompanying audio will be recorded and shared online after ProMat concludes.

Want to learn more about selecting industrial storage rack system for e-commerce or other applications? RMI offers Considerations for the Planning and Use of Industrial Steel Storage Racks, a best practices guide for warehouse operators looking to implement such a system.

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Hour-Long RMI Webinar Overviews Rack Safety 101

Several members of RMI recently hosted an online learning session to educate participants on the fundamentals of rack assembly, installation, operator training, inspections and maintenance. The “Rack Safety 101” webinar—available for free—highlights the best practices in industrial steel storage rack construction and utilization as an overview for viewers of the most critical aspects for consideration.

The webinar begins with an explanation of RMI’s ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks. It also reviews the R-Mark Certification program for manufacturers of industrial steel storage racks and of welded wire rack decking. Companies that have earned the R-Mark license have shown—via independent assessment—that the rack frame, beam and decking capacities calculated in the design’s load table were done so in accordance with the RMI/ANSI MH16.1-2012 specification.

Additionally, a tour of the multiple factors taken under consideration when calculating a rack design is presented. This portion of the webinar touches on details about the type of pallet to be used within the system, the clearances around the loads, the maximum pallet load height, the spacing between racks, the maximum reach height of material handling equipment intended to interface with the racks, and more. Other design and installation points include warehouse fire sprinkler systems, building codes, permitting processes, and seismic design considerations.

Operator training is another key section of the webinar. The presentation notes that all associates working around the racking and utilizing material handling equipment—such as forklifts—that interfaces with the racking must be trained on proper and safe use of the vehicles. Those working from order pickers at elevated heights must be trained in fall protection safety. Further, a list of the types of documentation and compliance required by the Occupational Safety and Health Administration (OSHA) is also presented.

To ensure that a racking system continues to function as it did on the day of installation, routine inspections of a number of areas throughout the structure are recommended—because a damaged rack, regardless of the degree of damage, will have reduced capacity. If damaged rack is not immediately unloaded and taken out of commission until it’s properly repaired, the risk of a collapse is significantly increased. Additional details are included in RMI’s Guideline for the Assessment and Repair or Replacement of Damaged Rack.

Finally, the webinar offers guidelines for facilities considering changing the configuration of their existing rack. Highlights include why to avoid mixing different brands of components, the importance of testing and documenting a new configuration, and why it’s critical that a qualified rack engineer is involved in the process. It closes with a 20-minute question-and-answer session taken from queries submitted by the webinar’s original participants.

Interested in learning more? Watch the full Rack Safety 101 webinar, here.

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Learn More About Warehouse Fire Sprinkler Codes And How They Impact Rack Design

As RMI’s representative on the National Fire Protection Association’s NFPA 13 committee that’s tasked with the creation and revision of national standards specific to the safe design of sprinkler systems, member Gary Smith knows warehouse fire sprinkler codes. He shared some of his insights about sprinkler system design approaches, system installation, and component options to prevent fire deaths and property loss during MODEX 2018, in the free, on-floor seminar “Warehouse Fire Sprinkler Codes and Impact on Storage Racks,” last April. (For those who were unable to participate in the 45-minute session—or who wish to review its content—the presentation and its accompanying audio have been recorded.)

The seminar overviews some of the most current warehouse fire statistics (1,200-plus annually in the U.S.), the associated direct property damages (an annual average of $155 million), and the two leading causes of warehouse fires (arson and electrical). It also walks through the evolution of the current warehouse fire sprinkler design and building codes that resulted from six separate, significant facility fires that occurred in the last two decades.

With 84% of warehouse structure fires being suppressed by wet pipe sprinkler systems, the method has proven to be one of the most effective ways to reduce potential damage and deaths. Yet, to ensure its proper operation, a sprinkler system’s in-rack design must allow the water to flow through the storage system in the most optimal manner. That’s why the presentation discusses three pertinent warehouse fire sprinkler design and building codes recommended by RMI:

Further, the seminar dives into the three areas that need to be considered by a fire protection engineer when determining which rules need to be followed when designing a warehouse’s fire suppression system: the type of items being stored (non-combustibles, plastics, furniture, paper and wood products, and more); the type and density of the rack and the pallets upon which the products are being stored; and heights of both the racks and the building.

Additionally, the presentation reviews some of the devices and accessories that can be added into a rack structure to ensure that the water flows through designated flue spaces, overhead clearances to prevent blocked water spray, and considerations for the location of in-rack sprinkler heads so as to avoid impacts from forklifts.

Looking for more information about fire suppression systems and their impact on rack design? Further details can be found in the “Building Departments and Fire Codes” section of RMI’s frequently asked questions (FAQs) page.

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Have Questions About Rack Design? Watch This RMI Educational Session

In a two-part presentation delivered by RMI during MODEX 2018, members shared insights about the current standards for the design, testing and utilization of industrial steel storage racks and answered multiple, common questions on the topic. Entitled “Rack Design: Resources and Frequently Asked Questions,” a synchronized recording of the slides and audio is available for those who were unable to sit in on the session, or wish to revisit the information.

The first part of the seminar guides participants through the purpose of RMI and its R-Mark Certification Program, as well as a comprehensive list of all applicable codes and standards. Highlighted are design standards for pallet rack, cantilever rack and wire mesh decking, load plaques, and load application and rack configuration drawings. Also covered are International Building Codes, National Fire Protection Association Standards, and specifications for sprinkler systems and seismic installations.

During the second portion of the session, some of the most often asked questions are reviewed and answered. Included are:

  • An explanation of the differences between a uniformly distributed load and a point load (and why it’s important to know the distinction).
  • The reason why all rack columns—aisle, interior and rear—should be anchored to the floor, as well as why footplates have multiple holes.
  • How out-of-plumb or out-of-straight column rack can negatively impact overall system capacity and safety.
  • Why it’s generally not a good idea to tie racks to the building structure.
  • An overview of height-to-depth ratio and when racks need to be stabilized with the addition of overhead ties.
  • The recommended clearances between pallet loads and why they are important.
  • What the acceptable range of vertical deflection in horizontal rack beams is.
  • Guidance for determining the load carrying capacities of wire decking.
  • An explanation of why wire decking should never be stood or walked upon.
  • Cautionary guidelines for those considering used or repurposed racking systems.

Have more industrial storage rack system design and installation questions? Visit RMI’s page of frequently asked questions (FAQs).

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Newest Racking Technologies And How To Pick The Safest Solution For Your Operation Explained In RMI’s MODEX Education Session

During MODEX 2018, held this past April in Atlanta, members of RMI presented a free, on-floor seminar to attendees. Entitled “Considerations for the Planning and Use of Industrial Steel Storage Racks,” the 40-minute session’s slides and audio were recorded for those who were unable to attend, or wish to revisit the information.

Via the presentation, potential and current end users and owners of industrial steel storage racks take a high-level, visual tour of a variety of different rack styles. The session also aims to explain some of the key points to consider when determining which racking type is both the best and safest solution for a given facility.

Included in the first portion of the presentation is an explanation of the differences between roll-formed and structural steel racks, including the pros and cons of each as well as the types of applications for which each is more ideally suited. It also details multiple types of rack configurations, highlighting their degree of storage density, notable features and operation, budget costs, and potential areas of concern when accessing loads with different types of forklifts. Included are discussions of:

  • Selective rack
  • Selective double deep rack
  • Drive-in and drive-thru racks
  • Double pallet drive-in rack
  • Push back rack
  • Pallet flow rack
  • Carton flow rack
  • Automated storage and retrieval system (AS/RS) rack
  • Pallet shuttle systems
  • Cantilever rack

The session also features mezzanine-supporting racks utilized for optimizing overhead space, plus pick modules and multi-level storage systems accessed by vertical reciprocating conveyors (VRCs). Additionally, a brief overview of accessories—such as wire mesh and steel channel rack decking, and protective column guard rails and rail guides—is included.

The second part of the seminar reviews key areas of consideration when assessing rack damage and determining whether a system can be safely repaired or if it should be replaced. Highlighted are examples of poor repairs and subsequent collapses, the responsibility of the owner to ensure the safe maintenance and operation of the system, and why each repair project must be evaluated and supervised by a qualified engineer in order to ensure compliance with current building codes. Used racking—and the reasons why it probably isn’t right for your operation—is also discussed.

Want to learn more about selecting industrial storage rack system for your operation and how to keep it in peak operating condition? In addition to the session, RMI has published two related documents: Considerations for the Planning and Use of Industrial Steel Storage Racks and Guideline for the Assessment and Repair or Replacement of Damaged Rack.

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Learn More About Rack Installation And Safety Inspections In RMI’s New Video

The responsibility for safe industrial steel storage rack ownership and usage does not end at installation. Instead, it’s an ongoing process that includes several elements—including regular, routine inspections—to ensure a safe workplace. To help both potential and current end users and owners gain a better understanding of proper rack installation and inspections, RMI has produced and released a new video.

Running for four minutes, the video details the potential issues that can arise from a poor installation, and why it is critical to follow the manufacturer’s load application and rack configuration (LARC) drawings and installation guidelines. Other installation best practices that minimize the risk of failure include:

Further, the video reviews the minimum recommended safety inspection frequency of once a year. Operations should consider inspecting racks more frequently if their facility has: high traffic volumes around end aisles and transfer aisles; lighter-duty racking systems that are more prone to damage; or areas with a history of damage that are more likely to be damaged again. Inspections should occur after a collision or seismic event, and should always be performed under the guidance of a qualified rack system engineer.

Likewise, the video notes that rack inspections are not solely the responsibility of a single person, but rather of everyone who works in the facility. All personnel should continuously keep an eye out for damage or other issues and notify management of such occurrences immediately. The key steps of performing a thorough rack safety inspection are also detailed.

This video is the second in a planned series of industrial steel storage rack videos; the next one will focus on best practices in rack maintenance and repair.

For more details about why your facility should consider scheduling rack safety inspections more frequently, click here.

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Point Versus Uniformly Distributed Loads: Understand The Difference

When placing loads of equal weight in storage racks, it’s important to remember that all pallets or loads are not created equal. Some pallets are designed with multiple boards—or stringers—spanning the bottom surface; others have a foot in each corner. Unusually shaped loads like steel coils or rolls of paper can also create problems. The pallet’s bottom construction contributes greatly to whether the load is uniformly distributed or resting atop specific points. That means the distribution of the load weight can be different, depending on the type of pallet underneath it or the specific type of product being stored on the rack system.

When placed in steel storage racks, a uniformly distributed load is one whose weight is evenly distributed over the entire surface of the rack’s beams or deck. A point load is a one with its weight significantly concentrated in one (or more) places on the rack’s beams or decks. For example, a steel coil stored directly on a rack beam can create a very concentrated point load; even if the steel coil weighs the same as a palletized load, the load beam will likely have to be heavier duty. (There’s also a third type of load distribution: a line load, which has only two or three boards across its bottom, which creates a more even distribution of weight than a point load, but less even distribution than a uniformly distributed load).

So what does this mean for rack safety? Placing a point load within a steel storage rack that has been designed solely to support uniformly distributed loads could cause one of two situations: excessive beam or deck deflection and/or failure.

Beam Deflection: When a rack design engineer determines the specifications for a pallet support beam, the maximum amount of permissible deflection—or bowing—is included in the calculations as noted in Section 5.3 of RMI’s ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks. The deflection limit equals the horizontal length of the beam divided by 180 (i.e. L/180). The safety risk arises if a point load is placed on a beam that has been engineered only to bear the weight of uniformly distributed loads. That’s because the concentration could cause the beam to deflect beyond its maximum allowable amount, leading to possible failure and potentially causing the load to fall.

Decking Failure: Typically made of welded wire with reinforcing channels, or corrugated steel, decking is often placed on pallet rack beams to span the distance between them. While this provides additional support for the pallet load, unless the decking has been properly engineered to accommodate point loads—as specified in RMI’s ANSI MH26.2-2017: Design, Fabrication, Testing and Utilization of Welded Wire Rack Decking—the concentrated point load could cause it to fail and the load to fall.

To ensure the safest pallet rack design, therefore, a qualified design engineer must be advised of the types of loads and the pallets upon which they will be placed for storage. In applications where multiple types of pallets may be stored within the same racking structure, the system should be engineered to support point loads as the most conservative—and safest—approach.

Have more steel storage rack questions? Get answers from RMI’s list of Frequently Asked Questions.

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What’s Height-To-Depth Ratio, And Why Is It Important?

To significantly minimize the risk of a single row of standard steel storage rack from becoming unstable and overturning due to a seismic event, wind or forklift impact, Section 8.1 of RMI’s ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks advises evaluating its height-to-depth (HTD) ratio.

In simple terms, the HTD ratio describes the ratio between how tall the rack is compared with how wide it is at its base. A rack that is 10 feet tall and 10 feet wide (a 1-1 HTD Ratio) will be much more stable (less likely to fall over) than a rack that is 10 feet tall and 1 foot wide (a 10-1 HTD ratio). To calculate the HTD ratio, divide the measured height of the pallet rack from the floor to the top surface of the highest load-supporting beam level by the depth of the frame. (The depth should to be measured at floor level, from the outside of the front column to the outside of the back column.)

If the calculated HTD ratio is 6 to 1 (or less), the rack base plates can be secured to the floor with normal anchoring. However, if the HTD ratio exceeds 6 to 1, the anchors and the base plates should be designed to resist an overturning force of 350 pounds applied to the uppermost beam level.

If it is determined that the HTD ratio is greater than 8 to 1, the Specification recommends that racks be stabilized using overhead, or cross-aisle, ties as an additional safety measure. These extend across the aisle to connect two frames together at the top for additional support and to minimize the risk of overturning. (Additionally, when overhead ties are needed, the frame heights are frequently further extended so as to avoid being hit by a load during placement or removal from the top pallet position of the rack.) If anchoring is used for racks of this high ratio, an engineer must certify the anchors’ design.

The HTD ratio specifications apply to both roll-formed and structural rack in a standard, single-row configuration (not back-to-back). Racks in a back-to-back configuration require the proper type and quantity of row spacers to secure the two frames together. If unsure, contact an engineer. A rack system designed with sloping or offset legs are subject to different engineering calculations and analysis. Slope leg or offset leg frames are not to be used in a single row application without an engineer certifying the design.

Looking for more insight into rack specifications? Download a copy of ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks.

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