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:


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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Don’t Forget To Check Permitting Requirements For Your Proposed Rack Systems

Whether planning for a new rack system in a new location, or a new rack system in an existing location, the system cannot be installed until all applicable building codes have been satisfied. Further, a building permit must be issued for a particular system design that meets geographic location requirements while supporting the user’s load application. The local Authority Having Jurisdiction (AHJ) or building official will first need to verify that all code provisions will be satisfied before issuing a building permit and will issue a certificate of occupancy (CO) upon completion of the rack installation.

As for the basis of the permits themselves, many U.S. jurisdictions (but not all) utilize the 2015 International Building Code (IBC)—developed by the International Code Council—as their standard. The IBC references RMI’s ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks in section 2209.1 as the standard for safe design and installation of steel storage racks. Likewise, the National Fire Protection Association references the same specification in the NFPA 5000 Building Construction and Safety Code. Key areas of inspection can include verification of proper anchorage of the racks to the floor, field welding, proper flue spaces are maintained between the racks and between the products being stored, and egress distances.

Many projects are delayed by not addressing fire safety requirements during the planning process. In many cases fire protection requirements will significantly impact the design of the rack system, as well as what can be stored in it. The permit and inspection verify that a facility’s sprinkler system and racking are properly designed and will work together effectively, as per the NFPA 13 design standard for sprinkler system installation and the International Code Council (ICC) International Fire Code (IFC) regulations. IFC Section 2302 covers permits for High Piled Storage, which is defined as storage of combustible material in closely packed piles, or combustible materials on pallets, in racks or on shelves where the top of storage is more than 12 feet high.

In order to ensure a smooth project and to minimize surprises, it is a good idea to contact the local building and planning department ahead of time. This allows a facility owner to gain a better understanding of the requirements, costs and the typical timeline for plan review, permit processing, inspections, and completed project approval.

RMI offers published guidelines for operations to review before undertaking a rack project. Get your copy of Considerations for the Planning and Use of Industrial Steel Storage Racks today.

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Making A Tight Beam-To-Column Connection

To ensure that a pallet rack beam does not separate from an upright rack column as a result of either an impact or seismic event, RMI’s ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks specifies how a steel storage rack manufacturer should calculate the number of engaged locking mechanisms (such as pins, bolts, or other devices that resist disengagement).

In general, the more pins or bolts used to connect a beam to a column (typically ranging from two to four), the tighter the connection. This yields higher load capacity, as well as greater resistance to both vertical and lateral (or horizontal) forces. In high seismic zones, for example, racking should be engineered to not only hold a pallet load securely, but also to withstand the side-to-side motion caused by an earthquake. This ensures the rack system can withstand lateral forces and minimizes the chance of collapse.

Specific to racking systems loaded by forklift, Section 5.4 in MH16.1-2012 covers beam-to-column connections, noting:

Except for movable-shelf racks, beams subject to machine loading shall have connection locking devices (or bolts) capable of resisting an upward force of 1,000 pounds (453.6 kilograms) per connection without failure or disengagement.

Section 2.6.4 provides guidelines for determining the maximum rotational capacity of a beam-to-column connection in a seismic zone.

Every storage rack manufacturer utilizes one or more unique beam-to-column connections. The assembly requirements for both the connection and its strength and stiffness result from the manufacturer’s testing. As detailed in section 2.4.1 of the ANSI MH16.1-2012: Specification, three different tests can be applied when determining the proper number of beam-to-column connections to create the strongest structure:

Cantilever Test (Section 9.4.1) – Conducted to determine the beam-to-column connection’s moment capacity. Set-up includes one column segment and one beam segment connected to each another with a load applied downwardly in the plane of the frame at the cantilever end of the beam segment.

Portal Test (Section 9.4.2) – Another test to determine the beam-to-column connection’s ability to resist force and its rotational rigidity. Specifically, this test is used to obtain a joint spring constant needed for semi-rigid frame analysis. It utilizes two column segments connected by a single beam in between—creating a portal frame. The load is applied both laterally in the plane and to the corner of the portal frame in the direction parallel to the beam segment.

Cyclic Test (Section 9.6) – Specifically designed and conducted to determine the beam-to-column connection’s earthquake force resistance, inelastic rotational capacity and rotational stiffness, as well as its energy-dissipation properties, this test subjects the connections to cyclic (repeated) loading conditions. The test set-up creates a double cantilever, with two beam segments connected to a single column, and applies the load to the end of the beams in an alternating fashion.

Based on the results of the tests, the rack manufacturer will include specific beam-to-column connection instructions on the installation’s Load Application and Rack Configuration drawing.

Want to learn more about beam-to-column connections? Section 5.4 of the ANSI MH16.1-2012: Specification includes more details.

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Why Was The R-Mark Created?

As a voluntary program for manufacturers of industrial steel storage racks and of welded wire rack decking, RMI’s R-Mark Certification helps to assure storage rack users that they have selected a product designed, engineered and made by a reputable supplier. But why was such verification necessary in the first place?

The idea for a certification came from RMI member companies in 1999, around the same time that RMI’s ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks was first incorporated into the International Building Code (IBC) as the standard for the safe design and installation of steel storage racks. Prior to that, there were other rack design standards in the marketplace— it was difficult for potential rack buyers to determine which standard a given manufacturer followed. Therefore, RMI members created the R-Mark Certification program (although membership in the association is not a requirement for earning an R-Mark license).

To attain an R-Mark license, two independent, USA registered professional engineers—with experience and expertise in the design and application of racking systems—conduct a rigorous analysis of an applicant manufacturer’s design process. This includes verification that the testing, calculations and resulting component (rack frame, beam and decking) capacities shown in a unique design’s load table were performed in a manner consistent with the RMI/ANSI MH16.1-2012: Specification.

So the next time you see an R-Mark on an industrial steel storage rack or piece of welded wire rack decking, you can be confident that the manufacturer of those components and systems has the technical and manufacturing skills—as well as the ability—to produce products that meet RMI codes and standards.

There is a caveat, however, in that simply seeing an R-Mark applied to a component does not mean the system is safe. Rack owners must still have a qualified engineer review each application to ensure that the system design and components meet the requirements for the specific use and job site.

That’s because every rack installation is different. Load types and component structures can be constructed in a multitude of combinations. Seismic codes may or may not apply in a given location. State and local building requirements can vary from one zip code to the next. Or, a rack engineered and intended for one use might be misapplied or erroneously configured within another installation.

Ultimately, however, an R-Mark serves as an acknowledgement that the rack or decking manufacturer has the engineering skills and the manufacturing ability to produce products that meet the RMI/ANSI MH16.1-2012: Specification, and—if the project is completed under engineering supervision and the codes are properly applied—system purchasers have a high degree of assurance that their final installation will be both code-compliant and safe.

Is your industrial steel storage rack or welded wire rack decking made by an R-Mark Certified manufacturer? Find a complete listing of R-Mark certified companies here.

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