For a nation subject to annual hurricanes and earthquakes, the question should be asked, how do buildings stand up under the strain of a natural disaster? While two very different approaches are taken to building designs to allow for either extreme wind speeds or high seismic (earthquake) events, the common thread is lateral forces. Acting horizontally, lateral forces try to push structures over. Without a lateral-force resisting system, buildings cannot stand against wind, seismic or other lateral forces.
In the United States, buildings are assigned one of four risk categories that determine general design criteria. An office building would typically be a Category 2. Hospitals, power generation / back-up facilities, earthquake / hurricane shelters and other structures critical to functioning in a major disaster are designated Category 4. While these categories are a nationwide standard, requirements for both high wind and high seismic design also include regionally specific design criteria and standards for lateral-force resisting systems that vary depending on the building category.
Preservation of life is the primary goal when designing a building in areas that experience high winds or earthquakes. When designing for wind the goal is a strong structure; when designing for earthquakes, the focus is on controlling building behavior.
As demonstrated by the main characters of the well-known children’s tale, “The Three Little Pigs,” building materials have a significant impact on a structure’s strength against high winds. Materials are selected based on their performance during different tests. One method, known as the missile test, uses a compressed air cannon to launch a 15-pound, 2×4 wood stud (missile) at an assembled wall sample at over 100 mph. With tests such as this in mind, it is understood as to why buildings in hurricane regions are commonly constructed having exterior wall systems of masonry or concrete for their mass and impact resistance. Other elements, like storm shutters and high-impact glass, are added to protect the windows and doors from flying debris damage.
For high wind design in a high-risk region, like along the Gulf Coast and Florida, a Category 2 building would be designed to stand up to between 150 to 180 mph winds. Buildings in Category 4, the highest designation, follow stringent and regionally-specific design standards to ensure critical buildings will take minimal damage from hurricanes and flying debris.
When working on high seismic building designs, it’s best to consider the paperclip. What makes the paperclip such a handy office supply is its ductility, i.e. the ability to bend without breaking or collapsing. High seismic designs strive for ductility in a building’s structural framework. The design can accommodate bending to absorb pressure from an earthquake without breaking by using ductile building materials. As a result, steel or concrete with steel reinforcements are frequently used in different structural systems like steel moment frames or concrete shearwalls.
High seismic design typically anticipates building damage and seeks to control the amount and location of damage with “fuses” or energy-absorbing structural members. While this adds complexity and emphasis on design details, the technique allows building designs to plan for a specific mechanism and prevent fatal damage. For example, understanding how a high-rise residential complex will react to lateral loads means the building can be designed to allow occupants to escape in the event of a disaster.
As mentioned above, seismic building requirements vary regionally. Ground motion intensity, or the strength of the lateral “G-forces” during an earthquake, is based on the location of fault lines and areas of seismicity throughout the nation. This regional consideration, along with the building type and associated risk category, dictate the code requirements needed for design.
A structural engineer’s focus is creating a building in which occupants are safe. In some regions that looks like designing a hospital fortified against high winds, in others it is an elementary school prepared to absorb the lateral forces of an earthquake.
About the Author
Greg Mosier, PE, SE
Greg is an Associate / Sr. Structural Engineer with nationwide design and construction administration experience in retail, office, residential and hospitality markets. With knowledge of applicable building codes and project work in moderate to high seismic regions, Greg provides structural design systems that respond to complex building challenges for owners while coordinating project details with architects, other design disciplines and contractors.
Safety and performance of concrete silos, particularly older silos, are often a concern to owners and operators of heavy industrial processing facilities. Blowout of silo walls and / or partial collapse of concrete silos are not uncommon. This article summarizes factors that contribute to concrete silo failure and defines methods to avoid instances that may compromise safety and operations at a facility.
Nature and Behavior of Stored Materials
In the agribusiness industry there are two broad categories of stored granular materials - free flowing bulk solids such as corn, wheat, soybeans and non-free flowing cohesive materials like DDGS, soybean meal and wheat middling. A fundamental question in the design of silos for storage of dry bulk solid materials is the determination of the pressures the material imposes on the silo structure. Methods for the determination of pressures in silo resulting from granular "free flowing" solids are relatively well understood and mandated by the American Concrete Institute (ACI) building standard, "Standard Practice for Design and Construction of Concrete Silos and Stacking Tubes for Storing Granular Material (ACI313-97 and 16) reported by the ACI Committee 313. Behavior and flow of non-free flowing or cohesive bi-product bulk solids is dependent on process dependent variables which are not easy to predict or quantify.
Cohesive materials can cause highly erratic flow patterns inside the silo which results in non-uniform load on the silo walls leading to bending (flexing) of the silo wall which may be unaccounted for if a silo was not intended to store such material. The cohesive or "non-free flowing" characteristics of such materials also results in "bridging" of the material or poor flow at discharge. Typically, a mechanical discharger, agitator or unloader auger is installed in silos to facilitate uniform and consistent flow. When the bridged material spans a hollow area, as the auger undercuts the material, the overhead bridges material can become unstable and fall leading to very high and unanticipated impact loads. The unanticipated loads can cause potential risk of silo wall or bottom failure to occur.
Unlike conventional single or multi-story buildings, concrete silos are often filled full - meaning they are subject to the full design live load. As a result, the subsoil beneath the silo foundation is often loaded to the limit set forth when a silo was originally designed and built. If the subsoil material is not uniform, or too compressible or if excess moisture or fluctuation of ground water affect its characteristics, the subsoil will not perform as planned. Excessive settlements can cause a variety of problems such as cracking and damage to the foundation, accumulation of water in the reclaim tunnels or serious damage to the silo roof.
Deficiency in Original Design and Construction of Silos
Numerous concrete silos in service were designed and built before modern design codes and standards were in place. Today older silos often fail to meet current design standards and require review to identify limitations. Silo construction can also have defects including, missing or misplaced rebar, poor concrete consolidation, original horizontal lift cracks, inadequate concrete mix, and insufficient concrete cover on rebar or rebar laps.
Over time, original defects can cause local or widespread deficiencies that most likely can compromise safe use of the silo. Further as silos age, weather-related damage to the silo walls becomes more pronounced, particularly if reinforcing design, concrete cover and/or concrete mix were not adequate in the original construction. Penetration of water through cracks combined with freeze-thaw cycles often cause damage and lead to gradual degradation of silo walls.
Operational Requirements and Misuse of Silos
The rate of discharge and turnover also play a role in concrete silos longevity. Unless concrete silos were intentionally designed to be more robust, life expectancy of such structures are shorter when they are subject to daily cycles of fill-empty and / or when flow rates are high.
For example, a marginally designed and constructed concrete silo at a port terminal with high turnover and high discharge rate is far more likely to show signs of distress (i.e., excessive cracking and degradation) than a similarly designed and constructed silo at a low turnover country cooperative grain elevator.
Misuse of concrete silos is often another factor that causes safety and structural problems. When silos designed to hold specific free-flowing commodities like corn or wheat are used for storage of cohesive non-free flowing bi-products such as soybean meal, one can often expect unanticipated problems on silo walls or silo bottom structures. Cutting new openings into the silo wall to load trucks, trains or fill flat storage buildings can also overload the silo wall. Another concern is use of multiple discharge outlets to reclaim grain, with or without use of a side tap which can overstress silo walls if it was not originally intended for such unloading arrangement.
Problems with hoppers are frequent and often take different forms. Concrete silos with self-cleaning or mass flow steel cone hoppers are typically the most problematic. In these silos, a steel hopper is welded directly to a steel ring embedded in the silo wall. Cracking and failure of the silo wall at hopper intersection is often caused by poor engineering, lack of attention to details, and construction deviations during the slipform process. For larger diameter concrete silos with self-cleaning steel hoppers the most reliable and cost- effective approach is to use a concrete ring beam supported by concrete pilasters or columns to which the steel cone hopper is attached.
Another common construction for a hopper is a sloping concrete slab constructed on top of granular fill leaning. The inclined slab is poured against the silo wall along the edges and rests on the reclaim tunnel roof slab at its lower end. Problems often relate to poor overall compaction of the fill causing the top edge of the concrete slab to push horizontally against the concrete silo wall causing structural damage and potentially compromising safety of the silo wall.
Silo Roof Issues
Generally, concrete silo roofs are slabs supported by either conventional steel beams or bar joists when the span is 60 feet or longer. Silo roofs are generally designed to carry standard equipment load plus snow / ice load and nominal code prescribed live load. Adequate slope of the roof is one of the culprits leading to ponding of water on the silo roof and sometimes penetration of water inside the silo which causes mold and degrades the stored material. In addition, large frozen lumps of corn or wheat can cause gravity flow problems leading to unanticipated asymmetric (eccentric) loads on silo walls.
Improper design or construction of anchorage between silo roof beams to the silo walls, and poor attention to reinforcing design details at silo roof openings and along the edge of the silo roof are also important considerations often ignored. Thus, steel roof beams have been known to slip at the bearings and fall inside the silo creating flow headaches and an unsafe roof until operators recognize what has occurred.
A common and widespread problem noticed by operators is concrete breaking off and falling along the edge of the silo roof. This problem poses serious safety concerns to personnel and potential risk to damage vehicles, equipment and utility lines adjacent to the silo wall. The issue is often due to inadequate anchorage of the silo roof to the silo wall and exacerbated by poor design or placement of reinforcing steel along the edge of the silo roof.
Silo Observation and Evaluation
Inspection by a qualified, experienced professional structural engineer can often diagnose problem(s) and recommend option(s) to mitigate the risk of a structural failure and prolong the life expectancy of a silo after proper remediation and/or reinforcement are implemented. Frequency of the silo inspection is a function of condition of the silo and associated problems, some of which have been mentioned in this article. For silos in fair structural condition, inspection is recommended every three years. Silos is poor condition should be inspected annually.
Concrete silos may often be overlooked from a maintenance standpoint. Along with normal wear and tear, initial design and construction mishaps may lead to increased safety risk and operational issues.
The following general signs often indicate the silo wall may need repair and / or reinforcing.
Concrete silos are commonly used to store a variety of commodities and bi-products in the agribusiness industry. When aging concrete silos are subject to loads and conditions for which they were not designed to handle, the noted deficiencies often accelerate the degradation and reduce the life expectancy of the silo unless it is properly repaired and reinforced.
About the Author
S. (Shawn) Shahriar, PhD, PE is a principal and Senior Structural Engineer with VAA, LLC located in Minneapolis MN. A member of and former Chair of ACI 3137 (Silo Code), Shawn has over 30 years of experience in design, construction, evaluation and remediation of concrete silos and bins used in the grain, feed, renewable energy, fertilizer, minerals, power and food industries. He has set company-wide technical standards and quality guidelines for VAA’s engineers, including continuing education and professional development for the firm’s structural engineers.
Associate / IT Manager Nat Schmidt credits the 2009 H1N1 pandemic with revealing vulnerabilities in corporate IT infrastructure. Since joining VAA in 2006, Nat had taken steps to improve the firm’s business operations, but the H1N1 crisis expanded the realm of possible events that could impact “business as usual.”
Grim statistics released during H1N1 from FEMA reporting forty percent of businesses don’t reopen after a disaster and the U.S. Small Business Administration indicating 90 percent of businesses fail within two years of a disaster further illustrated the need of a crisis plan.
With the go-ahead from then-CEO Scott Stangeland, PE, Nat and other VAA business support leaders formed a team to create a Business Continuity Plan. The Plan would put strategies in place for managing operations if a situation occurred that prevented employee access to a shared physical office.
“The time to try to figure out how to get through something is not when you’re in the middle of it,” says Nat. “It’s an investment in your future to have an infrastructure that allows you to be agile.”
The Plan includes procedures to mitigate threats and concrete steps to respond to events like fires, tornadoes, evacuations and pandemics. Employee safety is top priority, Nat stresses, but ensuring everyone can work away from the office is also a vital piece of the Plan. Key considerations included ensuring new technologies had cloud capabilities to aid in decentralizing the office and keeping the Plan as simple as possible.
The Plan was tested when VAA experienced an office flood in 2016. Due in large part to tools put in place by the Plan — such as redundant offsite servers and remote work capabilities — the firm had zero downtime during the event.
The Business Continuity Team regularly reviewed and updated the Plan to keep it ready for implementation. Having the Plan in place before the COVID-19 pandemic was a massive advantage as the firm prepared for the “new normal.” Having reliable assets in place such as stable vendors, dependable technology and resources to turn to for help was also critical to the firm’s COVID-19 response.
“Nat’s foresight and preparedness set us up for complete success moving to remote working at the onset of COVID-19,” says CEO, Jeff Schrock, PE. “I am proud of how he has led our IT systems, guiding us with ease into remote work and beyond. Truly an amazing accomplishment!”
While prepping for the unknown may seem daunting, Nat welcomes the challenge of combating potential problems.
“I enjoy trying to outrun fate,” he says. “I try to eliminate the ‘gotchas,’ so if our power gets turned off or the internet gets disconnected, I want to make sure we’re ready.”
Nat is always thinking about new technologies and initiatives, carefully considering how new tools can provide value to the firm and its clients. However, he cautions against introducing new technology for its own sake.
"It’s got to be something that’s going to make you a better employee, make us a better company and show our clients that we truly do care about their best interests,” he says.
In preparing for the possibility of an extended period of remote work, Nat offers these tips:
Repurpose Old Equipment
Provide unused or retired computers and other technology to employees for use in their home office.
Keep excess supplies on hand such as keyboards and headsets for employee use.
Lean on Past Experiences
Every experience comes with opportunities to learn. Think back on past situations and incorporate lessons learned into your planning.
Focus on Security
Hardware and software protections are essential to safeguard company and client data, but equally important is a knowledgeable workforce. Employees who undergo cyber security training are less likely to fall victim to phishing scams or other threats to company security.
Stay on Top of Trends
Be aware of what is happening in the news and how it could impact your business. Stay informed about industry standards and be proactive in planning for emerging threats.
Embrace Digital Tools
Get to know the features of your company’s digital tools. Many companies utilize online collaboration software. If your firm has an intranet or centralized location for information sharing, check it regularly to stay informed.
Consider holding meetings with team members or provide an open forum for staff discussion on a regular basis. Use video calling or chat features to check-in and answer questions.
Practice Video Call Etiquette
Don’t minimize your video window; it’s easy to forget others can see you and you may start doing distracting things. Mimic the same behavior you would in an in-person meeting.
Don’t be too hard on yourself; if something is frustrating, take a quick walk and gather your thoughts. It’s easy to feel overwhelmed, but remember: if you are experiencing something, chances are someone else is too. Know who your resources are and reach out if you need help. You’re not alone!
Exposure to electricity in the workplace killed an average of three people per week in 2018, according to data from the U.S. Bureau of Labor Statistics. This number doesn’t include the thousands of serious but non-fatal electrical injuries that occur every year. Although the National Fire Protection Association (NFPA) notes the number of such injuries has fallen steadily in recent years, the costs associated with these instances remain alarmingly high, from the victim’s medical costs and lost productivity to possible OSHA penalties. Factor in potential costs from litigation and negative press, and a single electrical injury can be well over six figures.
One of the primary causes of electrical injuries is arc flashes. To safeguard against arc flash hazards, it’s important to understand what an arc flash is and what safety measures need to be in place to minimize risks to employees and business operations.
An arc flash is a release of energy that happens during a fault, or short circuit, in an electrical system. Faults occur for several reasons, such as accidental contact with an energized wire, compromised insulation, or physical damage of components during normal operation or maintenance. If not rapidly extinguished, this type of short circuit produces an uncontrolled arc between two conductive surfaces. Under certain conditions, the high temperature of the arcing current can vaporize the conductors, resulting in an explosion of hot gases, molten metal and a pressure wave. Arc flashes can result in severe injuries from impact damage and burns to the body, including fatal third-degree burns.
Electrical safety-related work requirements for general industry are detailed in OSHA’s Code of Federal Regulations (CFR) Title 29, Part 1910, Subpart S, in Sections 1910.331–1910.335. These requirements describe several elements organizations must establish in their electrical safety program. The OSHA regulations are based on the NFPA standards NFPA 70, National Electric Code (NEC) and NFPA 70E. One element is the Arc Flash Risk Assessment. NFPA 70E requires an Arc Flash Risk Assessment be performed to identify and document potential arc flash hazards for all facilities with three-phase electrical power systems. This standard covers every type of commercial, industrial and institutional facility enterprise.
Arc flash risk assessments may be conducted by an electrical engineer or other qualified electrical workers with the experience and knowledge to document the electrical systems; build a digital model of the electrical systems; and analyze, interpret and communicate the results to workers.
The process typically starts with a site visit to document the existing electrical equipment and collect all necessary information to build a model of the electrical distribution system using a computer program such as SKM or ETAP. The digital model can be used to simulate a short-circuit event within each electrical enclosure to calculate the magnitude of an arc flash incident.
A typical Arc Flash Risk Assessment includes:
Some professionals may also provide findings for NEC violations and recommendations to meet proper installation requirements. In addition, they may optimize device settings to reduce dangerous levels of incident energy, discuss the results of the risk assessment with applicable personnel and review proper personal protective equipment (PPE) applications and lock-out / tag-out procedures.
The assessment results are compiled into a report with the study findings, arc flash labels, updated breaker settings and one-line diagrams; the final report and contents are typically certified by a licensed professional engineer.
An Arc Flash Risk Assessment must be reviewed and reanalyzed at least every five years or if a significant change is made to the system. It falls on the owner of the equipment to ensure the labels are updated and accurate to properly protect employees.
The equipment labels generated by an Arc Flash Risk Assessment provide information for workers to protect themselves from an arc flash, including nominal system voltage, the arc flash boundary and either a description of the required PPE or the incident energy (IE) level and corresponding working distance.
Employers are required to provide and maintain proper PPE for employees to wear while working on live equipment. The PPE necessary to protect someone working on a specific piece of equipment is based on that equipment’s IE level.
For IE exposure equal to 1.2 – 12 calories/cm², the NEC specifies PPE that includes arc-rated pants, long-sleeved shirt, gloves, jacket and baclava. An arc-rated face shield and hard hat, along with safety goggles, hearing protection and leather footwear are also required.
For IE exposure greater than 12 calories/cm² up to 40 calories/cm², the aforementioned PPE is required, with the addition of arc-rated flash suit pants, jacket and hood.
Working on equipment above 40 calories/cm² is prohibited at most facilities. While the NFPA doesn’t include PPE requirements for IE levels below 1.2 calories/cm², shock protection equipment is still required.
The first step to preventing arc flash-related injuries is an Arc Flash Risk Assessment. These studies provide vital information for equipment labels that inform workers about the hazards associated with specific equipment and what PPE is required to protect themselves while working on that equipment.
As a facility owner, you are responsible for the accuracy of the arc flash labels on your equipment, as well as worker training and the availability of proper PPE for employees. NFPA 70E provides specific requirements for facility owners, and failure to comply with these standards presents a substantial risk to workers and business operations. Above all, the cost to perform an Arc Flash Risk Assessment is minimal compared to the potential losses from an electrical injury event.
About the Authors
Morgan Anderson, EIT, Electrical Engineer
Morgan is an Electrical Engineer in Training (EIT) with four years of experience in electrical construction design, electrical equipment specifications and arc flash risk assessments. At VAA, she has assisted with and completed several arc flash risk assessments for multiple clients in the industrial and agribusiness sectors.
Devon Nelson, EIT, Electrical Engineer
Devon is an Electrical Engineer in Training (EIT) with more than four years of experience. Prior to his work at VAA, he spent nearly three years performing arc flash risk assessments across the United States, Canada and Central America for a Fortune 500 agribusiness and commodities trading company. At VAA, Devon prepares construction design plans and electrical equipment specifications for new facilities as well as proposes remediation strategies for electrically upgrading existing facilities.
 U.S. Department of Labor, Bureau of Labor Statistics. “National Census of Fatal Occupational Injuries in 2018,” News release, (December 17, 2019).
Next article: NFPA 61 & 652: DHA Requirements
Clients and Partners,
VAA began its transition to welcome employees back to the office on Tuesday, May 26. The below FAQs are to help answer inquiries you may have about our first-phase office integration during the COVID-19 pandemic.
VAA’s objective remains to create a safe work environment while providing a seamless transition in our workflow and work together to maintain our project responsibilities.
Visitors will be allowed to enter the office in limited situations where a business need dictates. Most employees continue to work remotely while some employees who showed interest have returned to the office. All VAA employees are encouraged to continue to use online capabilities to conduct business operations with clients.
Travel is restricted for VAA employees using parameters noted below.
Domestic critical travel may be allowed to meet project needs but must be approved in writing by a Partner.
Clients will be asked specific site questions for VAA employees to understand additional Personal Protection Equipment (PPE) requirements and / or other site guidelines related to COVID-19.
Pending site or facility location, a Partner may require a VAA employee to self-quarantine prior to returning to the office or additional travel.
VAA office employees will adhere to a health screen attestation prior to entering the building every day and agree to workplace expectations, including wearing a mask, social distance guidelines and exercising the CDC’s COVID-19 Guidelines related to personal hygiene and respiratory etiquette.
Contact your respective VAA Partner or project manager via phone or email.
We continue to be here for you and are so glad we are! Information of our status will be provided as developments occur. Thank you for your partnership.
Jeff Schrock, PE
This information will be updated as developments occur with COVID-19.
A formal goal-setting program is an asset in any corporate environment, with benefits for both individuals and companies overall.
S.M.A.R.T. goals – statements that are Specific, Measurable, Attainable, Realistic and Timely – have become the standard for organizational goal setting. Use of this method provides guidance for employees when proposing goals and allows managers to more accurately judge the feasibility and later the progress of those goals.
Once a goal-setting program is established, it’s critical to engage staff in the process. Here are a few tips to encourage thoughtful participation when creating and executing S.M.A.R.T goals:
Write It Out
Ask employees to write out their ideas before completing a formal document. Individuals are far more likely to remember the key details of a goal when asked to create it and write it down on paper.
Make It Fun
Allowing staff to explore a genuine interest or improve current skills of their choice leads to more engaged participants. If an individual has a key role in shaping their commitment, they will be more likely to accomplish it.
Keep It Accountable
Motivate staff with clear rewards for success and repercussions for little or no progress. Consider adding quarterly check-ins between the employee and direct supervisor. This will give employees built-in deadlines for progress and gives managers the chance to provide feedback throughout the year.
Encourage leadership support by communicating information about the S.M.A.R.T. goals systems in annual trainings. This is a chance to share the values of the program – accountability, personal development, self-motivation – as well as preliminary steps for implementation.
Trying something new is an opportunity to learn. The obvious learning opportunity is directly related to the goal. For example, an employee may set a goal to learn the latest version of a software program. In achieving proficiency in that program, they have learned a new skill. Even trying and failing comes with learning opportunities.
In addition to goal-related knowledge, participants are developing skills in goal setting and accountability that can benefit any position and any company. Everyone wants an employee comfortable setting goals and independently planning to achieve them.
As the goal-setting program becomes more established, employees and direct managers will learn how to effectively assess the feasibility of goals. Learning by doing, staff will gain a better understanding of what can be accomplished on an individual basis in the time allowed.
It is also important for managers to discuss goals with their employees and create attainable goals by planning for other priorities throughout the year. Practicing communication in your organization through goal setting will positively impact how employees on all levels share expectations for project work and related deadlines.
Goal setting raises the bar for performance in organizations and provides employees a natural opportunity to demonstrate leadership and self-motivation. By using a goal-setting program to create clear avenues toward accomplishment, companies will develop happier employees that grow into skilled leaders. As employees are promoted to leadership roles, their earlier interests may now benefit or be formally incorporated into organizational business plans.
People are the catalyst for growth. By supporting personal goals, employees are empowered to develop the core of a business. Contributing individual drive to overall business goals can open the door to improvements from expanded service offerings to fostering a culture of wellness.
Goal setting is a life-long skill. Continuing to encourage learning and self-motivation is a benefit to employees and, from a corporate perspective, will grow and enhance an organization.
Next Article: NFPA 61 & 652: DHA Requirements
A Dust Hazard Analysis (DHA) is a systematic review to identify and evaluate potential fire, flash fire, or explosion hazards associated with the presence of one or more combustible dusts and combustible particulate solids in a process facility. The National Fire Protection Association (NFPA) now requires DHAs to be performed on both new and existing facilities. The purpose of the DHA is to help owners / operators to prioritize management of dust hazards and generate plans to manage risks for deflagration.
Starting in 2016, DHAs were introduced as a requirement for new and existing facilities in NFPA 652.1 A DHA identifies and documents the areas of a facility where combustible dust hazard exists, then identifies existing safeguards in place as well as recommendations for additional safeguards where warranted including a plan for implementation.
Starting in 2017, the industry specific NFPA standards added the requirement for owner / operators to perform a DHA for all newly constructed facilities and retroactively on all existing facilities. The deadlines for completing DHAs on existing facilities are based on the applicable NFPA standard as follows:
NFPA 61 (2020 ed.): January 1, 20222
NFPA 652 (2019 ed.): September 7, 20203
NFPA 654 (2020 ed.): September 7, 20204
The NFPA also requires the DHA be reviewed and updated at least every five years.5
The International Building Code (IBC) incorporates many sections of the NFPA standards into its requirements. As of 2006, the IBC requires any facility handling or storing materials that can produce combustible dust to comply with NFPA 61.
The IBC added NFPA 652 as a requirement in its 2018 version and plans to add 654 in a future version. In the 2015 International Fire Code (IFC), NFPA 61 and 654 were added as explosion protection standards. A DHA is required if the Authorities Having Jurisdiction (state / county / city) have adopted IBC 2006 or IFC 2015 or newer as its governing code, unless specific exclusion of NFPA standards is referenced.
In addition, there may be local adoption of the NFPA standards that require a DHA regardless of what version of the IBC or IFC is enforced. Insurance companies are also starting to require completion of a DHA before underwriting a new facility or expansion of an existing facility.
In general, a DHA includes four major steps.
The NFPA does not provide a standard format for performing a DHA; however, it does include example formats in NFPA 61: Annex F and NFPA 652: Annex B.
These examples are intentionally vague to allow the user to match their chosen analysis format with the complexity and extent of the facility and its processes.
Once the DHA is assembled it will assist the owner in prioritizing the hazards and any mitigation plans to manage those hazards.
DHAs have only recently been added to IBC code, but are currently required in many jurisdictions and being requested by code officials. The DHA is a valuable tool for facility owners / operators to better understand actions to make their facility safer and cleaner for employees while providing a guideline for what hazards exist and the prior-ity in which they should be addressed.
The IBC and NFPA require compliance with the new DHA requirements. These requirements apply to new facilities, renovated facilities and even operational facilities not undergoing any modifications.
NFPA requires owner / operators demonstrate reasonable progress in the development of DHA each year leading up to the deadline for completion.11 A DHA can help identify where a facility is compliant or areas of concern and offer solutions.
It is important to begin work now to maintain compliance with NFPA and plan for work that arises due to the DHA. Safety should be a priority. The painful results of ignoring dust hazards can include serious injury or loss of life, as well as costly equipment failure and dust deflagration.
For more information, contact:
Next Article: Engineering an Exceptional Pile
Increasing crop yields per acre, inconclusive trade talks and low commodity prices slow the movement of corn and grain, leaving elevator owners to consider how best to add storage capacity while minimizing costs and protecting their product.
Installing a temporary storage system (commonly known as a ground pile) is faster and cheaper than building a steel or concrete bin, but several aspects need to be considered to ensure the best possible outcome.
Ground pile “structure” varies greatly, from ultra-temporary storage directly on the ground to piles sited on a gravel, asphalt or concrete surface. Some piles have no sidewalls, while others include 4' to 8' steel or concrete sidewalls that provide stability and allow grain to be piled higher.
Simply piling grain on the ground may seem like an easy storage solution, but it can end up costing elevator owners money. Soil is likely to mix with the bottom 18 – 24” of grain, resulting in product lost to contamination and rot.
Piles sited on gravel or aglime are better protected, but the bottom 12 – 18” are susceptible to moisture. A concrete surface, if properly constructed, provides the most durable and water-resistant option but it’s comparatively a larger investment. Though it may be cheaper intitially to not install pavement, the loss of product can often pay for these improvements.
Each plant’s storage needs are different and an effective ground pile design will account for a variety of factors, such as an owner’s budget, the amount of grain to be stored and the length of storage time.
Ground piles require a substantial amount of suitable land. Space for drainage, ditching and culverts needs to be factored in to site selection, as well as constraints such as proximity to a county highway right-of-way and / or compliance with local stormwater regulations.
For example, a pile of 1 million – 1.5 million bushels takes up roughly 1.5 – 2 acres (depending on sidewall height); factor in space for the walls, ditching and roadways and the actual footprint of the site is about 4.3 acres.
The topography of the site is also critical, and it’s possible that much earthwork will need to be performed to ensure proper drainage.
The process isn’t overly complicated, but there are some intricacies and factors to be aware of to make a good design. Developing a site grading plan can help minimize drainage issues and make sure the pile can be filled and reclaimed in an efficient manner.
Owners also need to determine how the additional storage impacts other features of the plant, such as relative locations of truck roadways and scales. Understanding how a ground pile fits within the site’s workflow and existing infrastructure ensures the plant continues to operate smoothly.
While year-to-year conditions such as yields, prices and availability of storage space drive the decision to add ground piles, the big question is what the return on investment will be and whether an owner will be able to recoup their costs.
The biggest benefit of ground piles is they provide a less expensive grain storage option than bins because they typically have no real structure. However, the site location, plant layout and how the pile will be filled and reclaimed all impact the project’s return on investment, which is often the ultimate factor in determining whether to add a ground pile.
While elevator owners generally have a good idea of how much grain they want to store and how to go about it efficiently, partnering with an experienced engineer can help owners obtain a cost-effective design tailored to their needs.
A knowledgeable engineer will ask specific questions and offer schematic design as well as big picture planning.
Taking in to account the site’s typography, plant infrastructure and workflow and owners’ business objectives is essential to creating the most successful storage solution to guard against the loss of product, time and revenue.
About the Author
Landon Pohl, PE
Landon is an Associate / Sr. Civil Engineer with 11 years of experience in designing grading plans, stormwater / site layouts and grain storage and loading facilities for industrial and agribusiness projects. A civil engineering point of contact for one of the Midwest’s well-known Fortune 500 companies specializing in agribusiness, his skill for managing his time and project details is clear in his work, from straight forward site planning and utility coordination to multidiscipline agribusiness and industrial efforts.
Next Article: Let It Snow! Let It Snow! How about the Loads?
Looking out a window after a heavy snowfall, it’s easy to find beauty in a freshly covered landscape – frosted trees in a peaceful blanket of white. Driving across the plains of Minnesota after a snowfall, it’s easy to see the power of nature partially burying fences and roadways as new snow swirls to threatening depths.
As we watch the nightly weather forecast, predicting and pinpointing the intensity and amount of snow can be a challenge. Wind transforms existing and falling snow into massive drifts as it blows, swirls and repositions snow on and around roofs and buildings. This repositioning can result in existing snow landing on the ground or lower roofs, canopies, adjacent buildings and even vehicles parked next to the building such as a semi-trailer backed into a warehouse dock door
Whether snow is angelic or angry, does drifting represent a threat to the buildings and structures you own, occupy and operate? Are codes and engineers “too conservative” in situations where the chance of structural failure seems low? It may not be an everyday occurrence, but when Jack Frost throws a fastball, it is crucial to know your facility or building can withstand the elements.
Structural engineers rely on building codes to provide criteria for their design. Codes tell us how much snow and snowdrift weight a building needs to support. They also offer methods for determining snow loading applied to specific roof configurations. In the United States, ASCE 7: Minimum Design Loads for Buildings and Other Structures is the national code that provides load requirements for general structural design, including snow loads. For our neighbors to the north, The National Building Code of Canada sets the loading requirements for designing structures.
Historical data documenting snow load totals, snowfall intensity, moisture content, wind speed and wind direction are the basis for ASCE 7. In mountainous areas and near major lakes and oceans, detailed local maps may be available to highlight county-by-county variations in potential snowfall amounts. Building codes, with their primary focus on public safety, will continue to evolve as more and better data is available and as climatic conditions change.
Building dimensions are significant because the length, or fetch, of a roof is the primary source of the snow that accumulates into windward and leeward drifts on buildings with multiple roof levels or parapets. Windward drifts occur when wind blows snow up against the higher portion of a building creating snowdrifts on the lower (windward) roof. Leeward drifts occur as snow blown from the higher roof deposits on the lower (leeward) roof. In addition, snowdrifts can form around roof obstructions such as penthouses, large mechanical units, solar arrays and rooftop gardens (green roofs). A proper structural design must account for all of these conditions.
What about sloping roofs? Can we slope a roof so we don’t need to design for snow loads? Roof slopes can impact snow load design, but usually don’t reduce the design load on the sloped roof very much. More often, sloped roofs add to the snow accumulation on an underlying roof or sliding snow from a sloped roof can cause damage to adjacent structures
The closer the ambient temperature is to freezing during a snowstorm, the higher the moisture content – and weight – of the snow. Very heavy snows can exceed the code mandated loads and cause serious damage or partial collapse of roofs. Abundant examples can be found in the northeast and east central states. Partial thawing of snow followed by rain or additional snow can significantly increase the applied loading as well.
Examples of extraordinary snowfalls that caused roofs to collapse
Engineers are often challenged or questioned about “over-designing” buildings. Truthfully, many buildings will never experience the loads they are designed for, however, when record snow falls occur and when huge, heavy drifts form, a proper design may be the only thing standing between you and a major business disruption.
About the Author
Keith Jacobson has been President of VAA since 2003 and supports the growth of the firm’s expanding engineering and design services to meet the evolving needs of clients. With over 25 years of structural engineering experience, he works with owners and design-build contractors to optimize building systems in commercial and heavy industrial markets. Beyond his cast-in-place, post-tensioned and precast concrete technical expertise, Keith is a member of ACI 362 – Parking Structure, ACI 350 – Environmental Engineering Structures, the Minnesota Concrete Council and ACEC/MN Board of Directors.
As more corporations adopt formal goal-setting programs, it is important to understand how to engage staff in the process and how goal-setting can be used effectively to benefit individuals and companies overall. S.M.A.R.T. goals – statements that are Specific, Measurable, Attainable, Realistic and Timely – have become the standard for organizational goal-setting. Use of this method provides guidance for employees when proposing goals and
allows managers to more accurately judge the feasibility and later the progress of those goals. With a goal-setting program and engagement tools in place, companies will begin to benefit from the growth and additional skills of their employees.
After establishing a goal-setting program, it is critical to engage employees and managers in the process. Here are a few tips to encourage thoughtful participation when creating and executing S.M.A.R.T goals:
1. Write It Out
As a part of the goal-setting process, ask employees to write out their ideas before completing a formal document. Studies have demonstrated there are many benefits related to handwriting original content. Individuals are far more likely to remember the key details of a goal when asked to create it and write it down on paper. Written goals provide more than a starting-point for progress assessment; employees will be more likely to independently plan for and progress toward their goals.
2. Make It Fun
Allowing employees to explore a genuine interest or improve current skills of their choice leads to more engaged participants. If an individual has a key role in shaping their commitment, they will be more likely to accomplish it. Additionally, consider offering a personal goal for each employee. This goal, often unrelated to workplace skills, allows for a balance of work and play, demonstrating the company values well-rounded individuals.
3. Keep It Accountable
To get the most out of a goal-setting program, follow through with individual outcomes by adding mandatory meetings to review goal progress. Motivate staff with clear rewards for success and repercussions for little or no progress. While it’s important to incorporate this into annual reviews, consider introducing quarterly check-ins between the employee and direct supervisor. This will give employees built-in deadlines for progress and
gives managers the opportunity to provide advice and feedback throughout the year.
An inevitable part of trying something new is an opportunity to learn. The obvious learning opportunity is directly related to the goal. For example, an employee may set a goal to learn the latest version of a software program. In achieving proficiency in that program, they have learned a new skill. Even trying and failing comes with learning opportunities. However, in addition to goal-related knowledge, participants are developing skills in goal-setting and accountability that can benefit any position and any company. Everyone wants an employee comfortable setting goals and independently planning to achieve them.
As the goal-setting program becomes more established, employees and direct managers will learn how to effectively assess the feasibility of goals. Learning by doing, staff will gain a better understanding of what can be accomplished on an individual basis in the time allowed. It is also important to teach managers to discuss goals with their employees and create attainable goals by planning for other priorities throughout the year. Practicing communication in your organization through goal-setting will positively impact how employees on all levels share expectations for project work and related deadlines.
Obtaining leadership support can be accomplished through annual trainings. During these discussions, information about the S.M.A.R.T. goals system and tips on goal-setting can be shared in a way that is both informative and persuasive. This is a chance to share the values of the program – accountability, personal development, self-motivation – as well as preliminary steps for implementation.
Goal-setting raises the bar for performance in organizations. As mentioned earlier, growing different aspects of employee interests into skills – both professional and personal – benefits employee wellness and the company overall. Individuals who feel a healthy work-life balance have a higher tendency to stay and progress through the company. Goal-setting provides employees a natural opportunity to demonstrate leadership and self-motivation; typically leading employees to earn promotions. By using a goal-setting program to create clear avenues toward accomplishment, companies will develop happier employees that grow into skilled leaders.
As employees are promoted to leadership roles, their earlier interests may now benefit or be formally incorporated into organizational business plans. People are the catalyst for growth. By supporting personal goals, employees are empowered to develop the core of a business. Contributing individual drive to overall business goals can open the door on improvements from expanded service offerings to fostering a culture of wellness.
Goal-setting is a life-long skill. Continuing to encourage learning and self-motivation is a benefit to employees and, from a corporate perspective, will grow and enhance an organization as a whole.
About the Author
Mary Pettit is a Human Resources (HR) Manager leading organizational development and leadership training; managing employee relations; and building strategies to retain and recruit key talent for VAA. She welcomes and values the opportunity to contribute ideas to company-wide business goals and aligning HR initiatives and monthly wellness activities to foster employee camaraderie. Earning her first HR certification in 2008, Mary has continued in the field with a PHR certification from the HR Certification Institute and a Society of Human Resource Management (SHRM)-CP Certification.
According to the National Fire Protection Association (NFPA), 50 combustible dust accidents occurred in the United States alone between 2008 and 2012. To continue improving and reducing hazard risk in agricultural facilities, the NFPA reviews and updates their guidelines every three years. The latest, 2016 edition of NFPA 652 Standards for Combustible Dust introduces the use of a Dust Hazard Analysis (DHA). This edition’s NFPA 652 update impacts existing and new facilities that combat dust-related hazards as a result of their processes. The NFPA now advises commissioning a DHA once every five years.
A DHA documents potential fire, flash fire and explosion (or dust deflagration) hazards. All potential hazards are placed in one of three general categories: Not a hazard, Maybe a hazard or Deflagration hazard. In existing facilities, a licensed professional will conduct a site visit to observe the process, categorize potential hazards and provide any recommended administrative or engineering safeguards to reduce the risk of deflagration. For new facilities or facility expansions, a licensed professional can assess and incorporate safety measures in designs based on the local jurisdiction and building codes.
When considering commissioning a DHA, reach out to the Authority Having Jurisdiction and a licensed professional. These entities will confirm which codes and guidelines are used in the jurisdiction and if a DHA is required for a project. To perform the DHA and offer practical solutions, engage a licensed professional that specializes in the industry, such as an architect, mechanical engineer or fire protection engineer. A qualified professional will be knowledgeable about the facility process and have a thorough understanding of local and state codes.
Often it is not the design but the lack of consistent maintenance in existing facilities that poses risk. When conducting a DHA, the difference between the Maybe a hazard and Deflagration hazard categories is frequently proper maintenance and scheduled inspections of the equipment and associated safety features. To effectively manage hazards in a facility, DHA inspections will look for the following safety practices:
Part of the NFPA 652 - Annex B states the “purpose of a DHA is to identify hazards in the process and document how those hazards are being managed.” For new construction, earlier is best for making hazard management design decisions. Recognizing and addressing dust hazards in the preliminary design phase of a project can lead to cost and time savings. Including features in the initial facility design like appropriate ventilation and use of a vacuum system for dust removal will reduce the need for future retrofits. Keep maintenance and hazard management integrated in a project by considering the following questions in early phases:
The continued development and updates of the NFPA guidelines are, at least in part, developed as a result of past, unaddressed facility hazards. As a preventative measure and code improvement, NFPA 652 recommends DHA inspections are conducted once every five years. However, only some state and local jurisdictions have adopted NFPA 652 as a requirement.
It is important to note the relationship between NFPA guidelines and the International Building Code (IBC). IBC dictates the industry standard and references other guidelines to bring new versions into their requirements. NFPA 652 is not yet directly referenced in the current IBC requirements. While this means DHA’s are not currently required by the IBC, there are a few compelling reasons to get ahead of the regulation.
About the Authors
As a Senior Designer at VAA, Doug regularly works with owners and design-build contractors to design feed mills, grain elevators and other agricultural bulk material handling and processing facilities from early stages of project conception through final design and construction. Doug’s 15 years of experience in agribusiness has translated into a comprehensive understanding of how different construction methods; material handling and process systems; and the NFPA affect design. His favorite part of the job is meeting with plant managers at their facility to understand challenges and work together towards improving operations.
Eric has two decades of domestic and international experience, including feed mills, grain export terminals, flour mills, bulk storage facilities and specialty slipform structures. Versatile in managing both engineering and construction efforts, he understands the details needed to fulfill design, constructability,
procurement and cost estimating activities. A member of the NFPA, Eric’s knowledge of material handling, mechanical and structural engineering is complemented by his technical skills in AutoCAD, P6 and Hard Dollar. Prior to joining VAA, Eric worked for a design-build contractor where he developed design concepts with clients and coordinated design and construction efforts with equipment vendors and subcontractors. Clients appreciate his global understanding of the design / construction process to accomplish operational goals and challenging facility requests.