It would be hard to believe that anyone who takes the time and makes the effort to stay abreast of events affecting their industry would not be aware of the monumental changes regarding the next edition of the International Residential Code (IRC) and fire sprinkler systems. However, just in case you accidentally picked up this magazine thinking it was Sports I Illustrated or you are in the waiting room of your doctor’s office and must choose between this magazine and Psychology Today, let me fill you in because you are already behind.

In September 2008, the IRC committee voted to include a new provision that requires single-family homes to be sprinklered. This, of course, has been the topic of articles, seminars, reports, and state legislation ever since, and through it all one thing is for sure: The installation of fire sprinkler systems in residential occupancies is here to stay. Challenges and amendments may have some impact initially, but I have learned one main thing during many years of being involved in the code-making process. Once something makes it into the book, it is very difficult to get it out, and with each edition that it remains, it becomes like curing concrete: The longer it sets, the stronger and more unmovable it will be.

YOUR OPTIONS
Now that this requirement is here, the question must be asked: “What are you going to do about it?”

You have a few options. The first is to ignore it and go on with business as usual—that is, if you still have a business. Let’s face it: With the economy shrinking like it has, the level of competition for the few available projects is very high, and many of us have experienced downsizing in one way or another. In fact, most of us are working to stay in business, much less thinking about growing one.

The second option is to recognize that while the construction market is smaller, an entirely new vertical has been opened. It is this option that presents a “glass half full” opportunity.

It has been reported that this new residential sprinkler market could conservatively create revenues more than $3 billion annually (see “Residential Fire Sprinkler Market Analysis“. That’s billion, with a B. It also is well documented that the fire protection industry will be strained to meet this demand as this new requirement grows by adoption.

The design and installation of residential fire sprinkler systems is not new to the fire protection industry, but it is new to the plumbing industry, which includes engineers as well as contractors. Who better to relieve that strain than those already familiar with residential construction and most of the materials associated with these types of systems but the plumbing industry? While residential fire sprinkler systems are not as complicated as commercial systems, there are major differences in the design approach as well as some of the equipment used. If this second option has sparked your interest and you have the energy to pursue something that may take time and some investment to master, I would encourage you to read on.

The rewards are plenty, but it will not be easy.

A LITTLE BACKGROUND
In brief, the history of residential fire sprinkler systems starts around 1930, but it did not really become formal until the 1950s and early 1960s. This was due predominately to the development of a new installation standard and, soon after that, the emergence of several new types of sprinkler technologies responding to the growing concern over residential fire loss. Manufacturers and contractors alike began to envision the immense benefits that these systems would provide toward alleviating the ongoing tragedy of human loss due to residential fires. Money and market share took it from there.

One of the first milestones identified during these early events was the development of an installation standard, similar to the commercial standard for installation, called NFPA 13: Standard for the Installation of Sprinkler Systems. Along the course of the standard development, creators recognized that the two major occupancy groups already established in the building codes would have to be addressed. These two groups are single-family and multifamily.

As such, we ended up with two installation standards. They were conveniently named NFPA 13D: Standard for the Installation of Sprinkler Systems in One- and Two family Dwellings and Manufactured Homes and NFPA 13R: Standard for the Installation of Sprinkler Systems in Residential Occupancies Up to and Including Four Stories in Height. Once these standards became available, the adoption process began, which lead to the historic September 2008 vote.

HOW DOES RESIDENTIAL SPRINKLER SYSTEM DESIGN DIFFER FROM COMMERCIAL?
Having these two standards in hand, you easily could conclude just by looking at them that together their thickness is not more than the single Chapter 8 of NFPA 13. Do not let that fool you. There are significant differences in the approach of residential design compared to commercial. Equally significant is the difference between NFPA 13D and NFPA 13R. It is these differences that need the most press and should be the starting point for anyone who is interested in learning more about residential fire sprinkler system design and installation.

Let’s start by focusing on NFPA 13D.

SPRINKLER HEAD LAYOUT
First and arguably the most important aspect of residential fire sprinkler systems, aside from water supply, is sprinkler head layout. Hundreds of different types of residential sprinklers are available today (see Figure 1), each with their own specific characteristics, including orientation, temperature rating, spray pattern, and minimum water and pressure demands. In fact, one of the most time-consuming tasks of residential design is finding the right head for the right application.

You easily can end up with four, five, or even more different types of heads in one home. Hence, you easily could spend as much as 50 percent of your design time just getting the sprinkler heads laid out.

That said, a closer look at what this process involves would be helpful.

One concept to understand in residential sprinkler head layout is the philosophy or goal behind the rules in the standard. What are we trying to accomplish? Commercial systems have a spectrum type of philosophy, if you will, spanning from life safety to property protection as its goal. Depending on the occupancy type, the goal may weigh more toward life safety than property protection or vice versa.

That’s not so in residential design. The goal for residential design is one thing and one thing only: life safety! The standards are written around the goal of giving people enough time to get out. While residential sprinkler system statistics conclusively prove that sprinklers provide a high level of property protection, the truth is that we do not care about the dwelling.

The rules and standards in NFPA 13D and NFPA 13R are based on the concept of sprinkler heads activating early in the fire growth, providing wall wetting and air cooling for 10 minutes (the required water supply duration) such that the rooms are tenable enough for evacuation. If this is the goal, it is obvious why the sprinkler head type, spacing, and location are so critical. This cannot be emphasized enough. You may find a sprinkler head that fits your needs on the very first cut sheet you open, but 28 years of experience tells me that this rarely happens. When it does, I am very skeptical about running off with my first choice without researching others just to make sure.

Another concept of residential sprinkler layout involves understanding the part that orientation and application play. As I stated earlier, there are hundreds of heads to choose from, so selecting the right one for the job means you first need to evaluate the space you are protecting. You will need to answer questions such as:

• Is the ceiling flat or sloped and if so, at what pitch?

• Are there any soffits, pockets, or other ceiling configurations that would inhibit the goal of early activation with high spray patterns?

Answering these questions will narrow your selection of sprinkler heads very quickly.

The process of laying out sprinkler heads involves a mix of rules from the standard, either NFPA 13D or NFPA 13R, and those found in the manufacturer’s data. Most of the time the manufacturer’s data supersedes the minimum requirements in the applicable standard, which is acceptable in that every NFPA standard includes in it an equivalency clause such as this: “Nothing in this standard is intended to prevent the use of systems, methods, or devices of equivalent or superior quality, strength, fire resistance, effectiveness, durability, and safety over those prescribed by this standard. Technical documentation shall be submitted to the authority having jurisdiction to demonstrate equivalency. The system, method, or device shall be approved for the intended purpose by the authority having jurisdiction.”

The challenge then becomes to accurately locate the sprinkler heads in accordance with the manufacturer’s requirements as well as any applicable minimums found in the standard. The effort required for this process is dictated by the complexity of the space.

As mentioned before, several factors determine the final location for a sprinkler head, and the designer must be familiar with these.

For example, let’s evaluate a simple layout in a single-family, single-story home using NFPA 13D. Figures 2 and 3 represent identical floor plans with two different head layouts. Both are in accordance with manufacturer’s data and NFPA 13D.

Notice the difference in head types as well as the head count.

System economics is driven predominately by head count. However, do not take this to mean that less heads always means less expensive.

Depending on the type of construction, the labor to pipe Figure 2 easily may offset the cost associated with the difference in head count shown in Figure 3. Keep in mind that these two layouts are based on flat ceilings, no ceiling fans or light fixtures, no soffits or coffered ceilings, control over the locations of heat vents, and geographically located in the southern half of the United States where freezing conditions are not an issue. Certainly it appears easy just looking at the finished layout, but all it takes is one or more of those previously mentioned conditions to exist for the layout to change drastically.

Also included in this head layout process are the rules involving the rooms or spaces requiring and, more importantly, not requiring sprinkler head coverage. Dealing with exceptions in codes and standards is always a challenge because the shades of gray show up.

This is usually not as prevalent in single-family, NFPA 13D systems as it is in NFPA 13R and NFPA 13 systems; however, where there is an architect, there is always more than just black and white. Along with the exceptions to coverage are those construction or architectural features that neither the standard nor the manufacturer addresses, and contrary to popular thinking, this is not more common in custom homes than tract housing. These types of situations make head layout very challenging and require assistance from those more familiar with the industry and developed resources such as fire protection engineers and manufacturer technical service departments.

RESIDENTIAL SPRINKLER HEAD LAYOUT IS AN ART
It can be mastered by anyone who has desire to learn. The better your understanding and working knowledge of residential construction techniques and materials, the more proficient you will be. I would encourage anyone interested in pursuing this industry to first purchase a copy of NFPA 13D and NFPA 13R. Second, find online resources including blogs and sprinkler industry articles, webinars, and books that will help you grow in your understanding and knowledge of residential sprinkler design and installation. Third, and probably the most important, is to join the sprinkler industry associations.

I have very little patience with and am skeptical of anyone, no matter how long you have been designing or installing toilets and sinks, who is going to get into this industry and not take it seriously.

This goes for engineers and contractors alike. Fire sprinklers are not something with which you dabble. I am very critical when it comes to engineers practicing outside of their discipline and contractors who think that pipe and water is all that there is to it!

If you have decided to participate in this growing industry and work for a piece of this huge pie, then welcome, but do it right! Getting involved in an association is one way of ensuring your success in this new venture. These associations are stocked full of resources and technical staffs who are looking for ways to help you do just that.

In my next article I will compare the two residential standards, NFPA 13D and NFPA 13R, and highlight the major differences between them.

Steven Scandaliato is a Fire Smarts Faculty member and Principal at SDG, LLC, a fire protection design and consulting company. With over 23 years of fire protection engineering, design and project management experience he holds a Level IV certification from NICET in Fire Sprinkler Layout and serves as a member of the NFPA 13, 101 and 5000 committees.

To view part three of the series visit “Residential Fire Sprinklers: Plumbing Contractor Competitive Advantage #1“

When the 2009 International Residential Code (IRC) arrives, with it will be the highly publicized requirement for all single family homes to have fire sprinkler systems installed in them. Previously we discussed the market and individual growth potential for residential plumbing contractors this new code will create. If we have convinced you, a residential plumbing contractor, that in fact, this opportunity is viable; the question now is, what next? Certainly questions of capital, resources, training and tools all fill the list. But, if you are like me, you are asking, “How do I sell this?” How do I convince my existing homebuilding client that, not only am I capable of providing both services, but it will be less expensive than two separate contractors doing the work?

To start with, let’s admit that most everyone would agree that it should cost less to get everything you need from one source, rather than to get only one thing you need from one source at a time. A quick glance at the popularity and success of big retail such as Wal-Mart or Best Buy will validate that. And while it may seem obvious that bundling services is cheaper than buying them separately, it is harder to distinguish this when the amounts that are being compared are relatively low. For instance, you normally don’t drive to a specialty battery store to buy AA batteries that cost $6.50 when you can get the same brand at the grocery store for approximately the same price or usually within a $1 while you are buying your groceries. The batteries at the battery store may even be less expensive (not likely, but possible) however, when the retail price of batteries is not that much to begin with, who is going to drive all over town to save a dollar. And while costs are always a strong part of decision making, the residual savings that you get by not spending the time to make the extra trip to the battery store will most likely outweigh the cost difference between the two stores supplying the batteries. Not to mention the convenience and stress reduction of having one more item off your “to do” list.

Now equate this example with those contractors vying for the installation of a residential fire sprinkler system. You have the fire protection contractor acting as the specialty store and the plumbing contractor acting as the “all in one” store. If an average tract home is 2500 square feet and the higher end of installed costs for a fire sprinkler system are $1.50 square foot, the installed cost would be $3,750. If the average sales price for this size tract house falls into the mid $200 thousands the fire sprinkler system would represent approximately 2% of the cost. The question is “can a plumbing contractor provide this system for less than a fire protection contractor?” While geographic factors such as unions will skew the numbers somewhat, it would be safe to answer this question with a resounding “yes”. The first and most obvious reason is the combination or overlapping of insurance, tools and resources. It would be very difficult to compete with a workforce that is trained to install toilets and sinks as well as risers and fire sprinklers, especially when many of the tools and materials used are the same. A second factor that would make this option even more definite would be if the fire sprinkler system is a multipurpose or combined type system. Meaning a system of valves and piping that feeds both domestic and fire sprinkler demand all together. The reduction in coordination issues alone would make this a very attractive choice for any home builder.

The third and not so obvious reason would reflect the nature of tract housing itself. Tract housing is all about volume and typical construction. I have termed it RPTV which stands for “Residual Profit on Typical Volume”. This represents profit that is not readily measurable, but is made as the result of “production line” thinking. It could be characterized as savings made from repetitive activities that require very little effort on your part or that of your clients. It can apply to the services you currently provide for your tract home builder, but can also apply to his services as well. The typical nature of this type of construction produces less and less supervision with each home built. I can attest to this first hand. While growing up in the homebuilding industry I experienced the transformation of our family business from tract housing to full custom homes. Without diverting into a dissertation on the differences, suffice it to say, it can be summed up in one word… Volume.

Let’s say the average cost of the plumbing contract for our 2,500 square foot tract home is $15,000 and the fire sprinkler system is $3,750. The total cost for each service without profit is $18,750. If both the plumbing contractor and the fire sprinkler contractor apply a 10% markup, the total price to the client is $20,625. Now, if you are a plumbing contractor providing both services it would be reasonable to expect your price to be at least 2% lower than this as your fixed expenses are now spread over a larger amount of revenue. This would put your sell price at approximately $20,210 which is a savings of roughly $415 to the client per house. Now, consider that your 10% profit per house should actually increase as your crews become more and more proficient with the installation of both systems, along with savings on bulk materials. When you multiply that profit over a couple of hundred homes a year the decision to expand your services to include fire sprinkler systems becomes much easier.

Do not forget, just like everyone else in the construction industry, home builders are looking for ways to do more or get more with the same amount. And if they do agree to pay more money it has to be towards something that they know will help them stand out from their competition. Tract home pricing is very competitive with margins averaging 8% to 10% at best. So other marketing tools are used. Usually these types of things come in the form of “buyer options”. This is where the buyer of the home may want to add certain options to the basic home he is buying such as a refrigerator, washer/dryer or upgraded carpet. The big difference is that these options are not “required” by codes or standards. The fire sprinkler system, on the other hand, is required by code and therefore is a hard cost that the home builder must account for. While he is looking for “bang for the buck” he is equally looking for companies that are going to make his life easier. Meaning, fewer coordination issues, no more sub-contractors than what he is already working with and someone who is managing their work without his supervision. By using an “all in one” plumbing contractor for both services he eliminates one more company he has to go into contract with, he needs only one phone number to deal with issues for either system, and there are fewer invoices to process, which keeps his overhead from increasing.

Trust me when I tell you, home builders put a high price on their time and how it is spent. They don’t want to deal with coordination problems or issues regarding permits or scheduling conflicts. They just want it done, on time, on budget and with attention to the same quality expected in custom home building. Home builders today are looking for every advantage they can find to either lower costs or provide more value for the same price. If domestic plumbing and fire sprinkler services are packaged up by a single source contractor, they will take a long hard look at the single source price. With a competitive price and the reduction of administrative expenses, there is real value to the home builder in getting there plumbing and fire sprinkler systems from the same “store”. Show the home builder how this works for them with the pricing in your own neighborhood and I am confident you will be successful as a single source provider.

In Part 5 of this series, “Residential Fire Sprinklers: Plumbing Contractor Competitive Advantage #3”, Jayson Drake, will discuss why multipurpose systems are the future of residential fire sprinklers, why plumbing contractors are uniquely qualified to install these systems and how this creates a clear competitive advantage.

Steven Scandaliato is a Fire Smarts Faculty member and Principal at SDG, LLC, a fire protection design and consulting company. With over 23 years of fire protection engineering, design and project management experience he holds a Level IV certification from NICET in Fire Sprinkler Layout and serves as a member of the NFPA 13, 101 and 5000 committees.

To view part two of the series visit “Plumbing Contractors Needed for Residential Fire Sprinkler Work“

Growing up in the home building business provides a very unique opportunity to learn about micro and macro economics without ever having to pay a single tuition bill. In fact, when taking these courses in college, I found myself arguing with the establishment most of the time, because not one of my instructors had ever experienced grossing $1 million one year and then struggling to stay in business with it for the next five. Mowing lawns to buy basketball shoes and cancelling family vacations, because interest rates changed as fast as the weather does. None of them had experienced living in a thriving community with great growth potential for several years to come and then see it completely stopped by a select group of community activists using a gas moratorium as a way to stop future growth. Now, several years later, ironically, a similar event has taken place, which is going to have one of the most significant impacts on the home building industry since 1.5 gallon toilets were mandated. Of course, I am speaking of the new IRC requirement for all new single and two family dwellings to have fire sprinkler systems installed.

The impact is estimated to be as high as $3 billion a year in potential revenue. Of course, there are those that are for this and those who are not. Nevertheless, it is here and the potential market that is now open to those who install fire sprinklers is also open to the plumbing industry as well. I say this because, contrary to many of the reports and articles written about this subject, the fire sprinkler industry is not large enough to absorb this type of demand. And, even with the pressure our capitalistic economy is currently feeling, demand for designers and installers of these systems is going to be very deliberate. So the question is, do you want to be a part of this market?

Before you answer, allow me to impart some observations that only someone in my position can share. First, I doubt anyone would argue with me about the significant differences there are between commercial and residential construction. Certainly this discussion alone would warrant several pages. However, when narrowed to the introduction of fire sprinklers to the home building process there are specific issues to consider. First, consider the fact that the plumbing industry can be characterized into three major groups. There are the large major mechanical contractors consisting usually of both HVAC and plumbing capabilities. These companies are found predominately on commercial types of projects, which require more than 2-3 man crews with construction schedules that can stretch out for months and many times years. Then there are those companies that concentrate on the residential markets. These would include multifamily as well as single family projects. These companies are usually much smaller than those involved in the commercial markets and tend to have smaller crews. The final group is those companies that have chosen to focus on the service side of the plumbing market. They are typically small to medium sized companies, less than 25 employees, and are structured to accommodate the general public’s plumbing service needs. They are not involved with new construction much, if any at all.

Of these three groups, it is the residential companies that are most prevalent and have the most opportunity to gain from the emerging residential fire sprinkler market. There are several simple reasons for this. First and foremost, they have the most to gain with the least amount of investment required. Let me explain. In residential construction, there are usually only five or six sub-contractors involved. They include the foundation, framing, mechanical, electrical, finish and painting contractors. Of course this will vary for several reasons, but for the purpose of this discussion these would be considered the core group for a home builder to contract with on a regular basis. Since the residential plumbing market is already very competitive the potential profit margins are very tight, especially when you consider the fact that average tract housing plumbing contracts only total $8 to $10k to begin with. So most residential contractors are looking for volume as well as the occasional custom home that comes along. Any chance one has to increase the base cost of their services means that while the actual margins may not increase, the amount of that margin allows opportunities for more rapid growth or internal capital improvements such as tools, trucks or even employee benefits.

Second, as long as I can remember, and my father before me and his father before him, every house that our family built had running water in it. What I mean by this is that plumbers have been on site for decades. Not so for fire sprinklers contractors. Plumbing contractors already have relationships built with current clients. They are familiar with home building trends, contracts and market conditions. The overwhelming majority of all fire sprinkler contractors in this country are commercial contractors. They do not have the years of experience with residential markets. Over the years, some have diversified into the residential markets but one thing is for sure, very few are capable, or for that matter, even want to participate in both markets. The reasons for this are the same reasons there are three groups of plumbing contractors. The bottom line costs are not as high as commercial construction and they have found that trying to accommodate both markets usually involves higher overhead which makes it harder to compete.

The third reason is the nature of the trade itself. It is pipe and water. Who better to adapt to this market than skilled labor that already knows how to work with the majority of the components involved with fire sprinkler systems. I have read several articles and reports from those on both sides of the residential fire sprinkler argument. And in response I say this: As a guy who started on his dad’s framing crew at age 14, going on to become the Vice President of the company and getting my Class A contractor’s license at age 21, only to end up as NICET IV fire sprinkler designer as well as a member of the NFPA committees that put the codes and standards for fire sprinklers into place, this is NOT hard. It will not take years of training and expense to merge the design and installation of fire sprinkler systems into an already successful residential plumbing contracting company.

While residential fire sprinkler systems have been required in select markets and geographic locations since the mid 1980’s, it has really only made its presence known in multi-family projects and even then it is fairly marginal. Today’s residential plumbing contractors have a very clear and distinct advantage coming into the residential fire sprinkler market. It would be prudent for them to consider this advantage as well as the education and training tools that are being made available by Fire Smarts and the Plumbing-Heating-Cooling Contractors Association (PHCC). 2011 when the IRC requirement comes into effect is not far off. And given the current economic conditions in the residential market, demand can only grow. Like my father always said, “people will always need a place to live”. For me, these are words to build a company by.

In Part 4 of this series, “Residential Fire Sprinklers: Plumbing Contractor Competitive Advantage #2”, Steven Scandaliato, SET, will discuss how plumbing contractors that provide both domestic water and fire sprinkler services have a competitive advantage by reducing the general contractor’s administrative burden, while increasing their own profit margin.

Steven Scandaliato is a Fire Smarts Faculty member and Vice President of Business Development of Telgian Corporation. With over 23 years of fire protection engineering, design and project management experience he holds a Level IV certification from NICET in Fire Sprinkler Layout and serves as a member of the NFPA 13, 101 and 5000 committees.

Continued from Seismic Design For Fire Sprinkler Systems – Part 3a: Practical Example

Before moving on, let’s examine a couple of options that can be considered with the layout that we now have. First, as indicated in NFPA 13 Chapters 9.3.5.3 and 9.3.5.4, the bracing used in one direction on one run of main can be counted as the opposite type of brace for an adjacent main in the perpendicular direction. For example, if we locate a lateral brace within 24 inches of the end of the bulk main on the 11-foot, 9-inch piece of pipe, it could be counted as the first longitudinal brace on the cross main. Figure 5 shows how this would affect the layout. Notice that the first longitudinal brace was eliminated because the next longitudinal brace required can be up to 80 feet away. However, you also can see that we really did not gain anything in terms of the number of braces needed. In this case we simply traded one brace location for another. Furthermore, we now have loaded the brace at the 11-foot, 9-inch piece with much more weight than the original brace location, which means we could end up having to size this brace much larger than the original brace location. This is a great example of how brace location is somewhat subjective and, if properly done, can offer a fair amount of flexibility to accomplish the overall goal of seismic design.

The last brace to be located is the 4-way brace. This is a bracing configuration that provides support in all directions specifically for vertical pieces of pipe. The requirements for 4-way bracing can be found in NFPA 13 Chapter 9.3.5.5: Risers. The requirements found here include a maximum 25 feet between braces, so if the riser piece being braced is longer than 25 feet, two braces must be installed, one of which must be located within 24 inches of the top. Remember also that size is not a consideration here. It applies to all pipe sizes. Further, the 4-way brace can be counted as the longitudinal brace for the first run of pipe coming off the top of the riser. In the case of our example, we could eliminate the longitudinal brace that is in the middle of the run of bulk main because we are within 40 feet of each end, and only one is required. The total weight on the brace is the same regardless, so this is a good option to use. Figure 6 shows how the design is affected.

Now that the bracing layout is complete, we can begin to determine the sizing of the components. This process is very similar to that of establishing the area of operation or remote area when performing hydraulic calculations. The total force that the system must resist is a function of the weight of the water-filled piping times the force factor that has been assigned by the engineer of record (see Part 1 of the series). As shown in Figure 7, we have clouded the piping that will be assigned to each of the lateral and longitudinal braces. Notice how it is equally distributed. Obviously, since there is an odd number of branchlines, one of the lateral braces needs to carry the weight of one extra branchline. The terminology used to describe these areas is referred to as the zone of influence or ZOI. Examples of how the ZOI is located for different system configurations can be found in NFPA 13 Figure A.9.3.5.6(a).

Once the ZOI has been established, determining the total weight for each zone is next. To calculate the total weight for a zone you add the weights of all pieces of pipe (as if filled with water). Several resources are available for this information. Most of the pipe manufacturers have these values for every pipe type they make. NFPA 13 provides the values for Schedule 10 and Schedule 40 in Table A.9.3.5.6. If you are using one of the specialty pipe sizes equivalent to Schedule 7, the values are found in the manufacturer’s data sheets. The conservative approach is to use the weights of Schedule 10 and 40 regardless of the actual pipe type used.

For the purpose of this example, let’s examine the most demanding zone, which is ZOI No. 1. Since the branchlines are typical, determine the weight for one of them and multiply by four. The weight of one branchline is approximately 133 pounds, so the total is 532 pounds. The total weight for the main piping that is part of this zone is 35.0 feet = 3-inch pipe ≈ 320 pounds. Thus, the total load for ZOI No. 1 lateral brace is Wp ≈ 850 pounds.

As mentioned previously, the resultant design load is a function of the total weight of water-filled pipe times the force factor expressed as Fp. It is important to note that the Fp from the International Building Code (IBC) and the Fp from the map found in NFPA 13 vary greatly, which causes a lot of confusion. For years, NFPA 13 has allowed a default value of 0.5 to be used. This is where the phrase “half the weight of water-filled pipe” came from. When IBC 2000 began to be adopted, many designers realized this discrepancy and have taken a completely different attitude toward seismic design of sprinkler systems. For example, the Fp for California based on NFPA 13 is 0.4. Using IBC and ASCE 7: Minimum Design Loads for Buildings and Other Structures, the Fp for California can be 1.35 or more. My advice is to use the IBC/ASCE 7 formula. It is obvious that the 0.4 that NFPA 13 offers is substantially lower than IBC and the default value, while greater than the value for California, will grossly oversize the components for areas like Colorado Springs, which can be as low as 0.17. As a reminder, the formula from ASCE 7 is expressed as

For the sake of our example I have used numbers that represent a location in Jonesboro, Ark., zip code 72404. Using the formulas referenced in IBC from Part 1 of this series we end up with a SSD of 1.317g. Since we have not considered height of the building in this example, we drop of the last part of the equation. Therefore, Fp = (0.4 x 1.0 x 1.317 x 850)/(3.5/1.5) = 192. If we use the default value of 0.5 we would end up with a resultant weight of 425 pounds (Fp = 850 x 0.5). That is a difference of more than 220 percent.

Finally one more factor is involved before we can size the components: the system component factor. This is a percentage that has been assigned by NFPA 13 to account for the fittings and sprinkler heads on the main and branchline piping within the ZOI. If you are using the 1999 edition of NFPA 13, the factor is allowed to be revised; however, if you are using the 2002 edition it shall be 15 percent, or 1.15 times Fp. This raises our value from 192 pounds to approximately 221 pounds.

Now that we have the force we can proceed with sizing the components. The most common type of brace material is steel pipe. However, several other popular materials are available. Tension cable is another method for bracing that provides the required resistance while sometimes being easier to install than rigid pipe and structural attachments. In the case of using cable or any other material not listed in the tables of NFPA 13, the manufacturers’ values must be used. As seen in NFPA 13 Table 9.3.5.8.9(a-c) several options are available depending on the type of brace, such as pipe, steel angles, steel flats, and rods.

Another very important factor is the angle at which the brace is situated in relation to the pipe it is bracing and the structure to which it is attached. For lateral bracing, the brace gets stronger as it nears 0 degrees. Notice that as the slenderness ratio grows, the maximum length of the component lengthens. Take 1-inch pipe for example. When the brace is 3 feet, 6 inches long it can withstand loads as high as 12,242 pounds when the angle is reduced from 90 degrees to 60 degrees or more. Obviously the brace can resist more weight the closer to perpendicular it is. Also, the longer the brace is, the less weight it can resist.

When sizing braces it is important to consider the reality of the project. Again, you want to provide as much flexibility with the actual installation as possible, so sizing the brace based on the worst-angle orientation (30 degrees to 44 degrees) is prudent. The length is a function of the type of system you are designing, that being its location with regard to structure. For instance, if the system is in a warehouse, the bracing most likely will be relatively short since the system piping will be located high in the structure. On the other hand, in a hospital the system will be located right above the ceiling with several obstructions above it and several feet from the top of the structure where the anchoring attachment must be located. If we assume the warehouse situation, our lateral brace could be 1-inch pipe up to 10 feet, 6 inches long. We can conclude that 221 pounds is well under the allowable 786 pounds.

After determining the brace type and size, the final step is to determine the type of attachment. NFPA 13 Figure 9.3.5.9.1 provides the available attachment arrangements and corresponding attachment types, which usually are dictated by the type of structure. Several more types of listed seismic attachments are available from the major hanger manufacturers, and I strongly recommend that you reference them in this process as well. Even in the past few years, several new types of attachments have become available, making it easier to deal with the types of structures being built today.

The previous steps then are used to determine the longitudinal braces as well. Remember, the only weight considered for longitudinal braces are the main piping. Branchlines are not considered. Also, in case your situation does not fall into the scope of the tables listed in NFPA 13, the standard does allow for other types of methods and materials as long as the system is designed by a registered professional engineer.

I hope that this series of articles has helped you understand seismic design for fire sprinkler systems. If you need further explanation, feel free to contact me. I also recommend contacting the local sales representative for the major hanger manufacturers. Several of them are represented on the hanging and bracing committee of NFPA 13 and surely would be able to answer specific issues as they arise. Three familiar manufactures (Tolco, Afcon, and Loos) offer software that streamlines this process. Two of them even integrate with AutoCAD.

Finally, let me remind those of you who have decided to practice fire protection engineering. You are responsible for the design criteria of a life safety system. While toilets and drains and warm and cold air are important, they are not life safety systems. Take this seriously and do your homework. Keeping a sprinkler system in place and able to perform in the case of a seismic event is of utmost importance. Like I always tell myself, “Just do it … right!”

Continued from Seismic Design For Fire Sprinkler Systems – Part 2c: Clearance and Sway Bracing

In the previous articles of this series I discussed the “if” and the “how” of seismic design for fire sprinkler systems. Let’s now take a look at an actual design and apply this knowledge in a practical example. For the sake of size and complexity, I’ll use a basic design; however, keep in mind the basics should be applied to each design no matter how complex it might be.

To begin, I recommend that you print out Figure 1 that will be referenced throughout. This is our basic system design. Using the step-by-step guideline that was provided in the first article, assume that this system falls into a seismic category C-F. Remember, if the building has been classified as an A or B it is exempt from seismic design.

It is the job of the engineer of record not only to designate the seismic category but also, if required, to provide the force factor that shall be used. This force factor now is going to be used to help in sizing the seismic bracing that is part of the overall seismic design. Seismic bracing is only one of the five design features that must be provided when doing seismic design for a system. While bracing is the most common, remember that the system must have rigid and flexible couplings located in specific locations, separation or expansion components at specific locations, and clearance provided as specific locations. Further, restraint for branchlines must be considered as well.

Using the example let’s first locate the lateral bracing that is required. (Remember, the requirements for lateral brace location are found in NFPA 13: Standard for the Installation of Sprinkler Systems Chapter 9.3.5.3.) The braces are spaced a maximum of 40 feet apart from each other with a brace required within the first 20 feet from each end of the run of main being considered. This is half the allowable distance between braces. Also, a brace must be located on the first piece of pipe from each end. This may sound confusing but considering that steel pipe comes in 21-foot, 24-foot, and 25-foot lengths, putting a brace on the first piece of pipe and within the first 20 feet of each end is not that hard to grasp.

However, let us say the first piece of pipe on a run of main is 14 feet long. Then the first brace has to be located within that first 14 feet. It cannot be located after that somewhere in the next 6 feet. Locate the braces on the cross main first. We will deal with the bulk main last. This main is 97 feet, 7 inches long from end to the last branchline on the end. If you divide 97 feet, 7 inches by 40 feet (maximum distance between braces) you can determine the minimum number of braces needed. Keep in mind that this is the minimum.

Several factors must be considered when determining how many braces actually are needed. For instance, if it is an exposed system with the piping near the roof deck or structure above, the bracing usually is spaced to its maximum as long as weight is not an issue, which we will see when we are sizing the braces. However, if the system is feeding pendants or is several feet lower than the structure, braces more than likely will need to be added to find locations to attach to the structure. When systems are hung lower other systems such as HVAC, electrical, and plumbing usually are above it, which makes it more difficult to locate a place where the braces can reach the top of the structure.

Hence: 97.58/40 = 2.4395. This means the minimum number of lateral braces required is 3. For the sake of example, consider this system to be unobstructed to structure. Our example ends up with something that looks like Figure 2. As you can see, the approximate locations fall into the allowances given in NFPA 13 Chapter 9.3.5.3. Again, if the starting pieces on each end where less than 20feet, the brace would need to be located somewhere on that first piece. Notice that the distances from the braces on each end to the middle brace both are within the 40 feet maximum.

The second step is locating the longitudinal braces. The requirements for longitudinal braces can be found in NFPA 13 Chapter 9.3.5.4. Again, we will concentrate on the cross main first. As you may recall, longitudinal braces affect only the main itself and do not have anything to do with the branchlines. Also, size is not an issue. The cross main could be 8 inches or 1 inch. Either way, longitudinal bracing is required.

The spacing requirements for longitudinal bracing are double that of the lateral bracing. The maximum spacing is 80 feet with a brace required within the first 40 feet, which is half the allowable distance between braces. To find the minimum number of longitudinal braces divide 97 feet, 7 inches by 80feet. Hence: 97.58/80 = 1.21975. So a minimum two braces are necessary to meet the requirements of NFPA 13 Chapter 9.3.5.4. Locate the longitudinal braces on the example layout. Remember that there must be a brace within the first 40 feet of each end of the run of main. As you can see in Figure 3, two braces are adequate. Notice the amount of over spacing. This is advantageous because it allows the fitters plenty of distance to relocate the braces from one end to the other in case obstructions are encountered yet still stay within the limits allowed.

Now that the lateral and longitudinal braces are located on this run of main, attention can be given to the bulk main feeding this cross main. As was previously described, lay out the lateral and longitudinal bracing for this run of main. It should look something like Figure 4. The overall length of this bulk main is 35 feet, 9 inches, so the minimum number of lateral braces required is one since it is less than 40 feet in overall length. The brace must be located within the first 20 feet of each end and must be on the first piece of pipe from each end.

A common question raised here is what to do about the 11-foot, 9-inch piece of pipe. If we put one brace within 20 feet of the system riser symbol, we have nothing on the 11-foot, 9-inch piece on the other end. Technically speaking, that is correct; however, given the fact that the entire run is less than 40 feet and the brace is located within 20 feet of each end, it generally is understood that the amount of weight will not be such that one brace cannot adequately provide the support required. In such a case it is recommended to locate the brace as close to center as possible so the weight is distributed as equally as possible.

The required longitudinal brace is also a single brace since the overall distance of the main is less than 80 feet. This brace also can be located toward the middle of the run so the weight is distributed equally. When a lateral and longitudinal brace end up relatively near each other, it is usually cost effective to use bracing components that are made specifically to accommodate both braces. This is one example where the vocabulary gets diluted, so be careful. This is not a 4-way brace as described in Part 2 of this series. Rather, it is a combination brace that allows for support in both the lateral and longitudinal directions. Notice that the symbols are not crossed but rather two individual symbols side by side. This is done on purpose because it can be confused with the next brace that we are going to locate, which is a 4-way brace.

Continued at Seismic Design For Fire Sprinkler Systems – Part 3b: Practical Example

Continued from Seismic Design For Fire Sprinkler Systems – Part 2b: Couplings and Seismic Separation

Clearance
The third design element involved with seismic restraint is clearance. This feature includes provisions for piping that penetrates specifically concrete and/or masonry floor/ceiling and wall assemblies. Do not confuse this with penetrations through rated assemblies that are framed with wood or steel studs with gypsum board. This section has nothing to do with assembly ratings or the requirements for sleeves or fire caulking. Those are usually a function of other specification requirements and should not be in this section of your specification or drawings notes.

Like separation, this feature is simple but very expensive. This section requires a specific nominal annular space to be provided around the pipe penetrating the assembly. A 1-inch annular space is required around 1-3- inch pipe. A 2-inch space is required around pipes that are 4 inches and larger. Core drilling a 10-inch-diameter hole for a 6-inch pipe is not something most fire protection contractors are very eager to do. This process can be quite involved, and the cost of core drilling is tied directly to the size of the hole.

However, there is a less expensive way to accomplish this penetration. You will recall that I previously mentioned that flexible couplings also could be used as a solution for clearance requirements. This is where couplings prove their worth. In lieu of large clearances, the standard allows for a flexible coupling to be installed on either side of the assembly within 12 inches of the face of the penetration. By providing these couplings, standard hole diameters may be used. My experience is that contractors prefer this method to providing the larger holes.

This section applies to all pipe sizes, so, like the separation requirements, consideration of the piping configuration is important. It is usually better to penetrate once into a concrete- or masonry-assembly room with main piping and then create a smaller tree-type system than it is to penetrate
several smaller holes into the space simply to maintain uniformity. A prudent plumbing designer would discuss these types of design features with the architect during the design development phase to try to minimize the amount and/or configuration of these assemblies as well as the overall sprinkler system cost. Doing so also may help you gain a level of favor with the installing contractor.

Sway Bracing
The fourth and most commonly referenced seismic restraint design feature is sway bracing. Unlike in other plumbing systems, the water and pipe that comprise fire protection systems are lifesaving features. While the majority will never activate, fire sprinkler systems must perform when needed or people and property will suffer. With that in mind, it becomes obvious why the bracing of fire sprinkler systems has its own rules for spacing, location, and force factor criterion.

The process for laying out sway bracing starts much like that for laying out sprinkler heads. There are three types of braces: lateral, longitudinal, and 4-way. Lateral bracing is required to be spaced at a maximum of 40 feet between braces. We also are required to install a brace within 20 feet of each end of the run of main, which is half the allowable distance between braces. Finally, we must have a brace on the first piece of pipe on each end of the main. Figure 3 depicts an example of lateral bracing.

When applying the rules to each run of main piping, you’ll want to try to maximize the distance between braces as much as possible. However, remember to leave room for the braces to be moved in either direction in case actual field conditions inhibit the fitter’s ability to install the brace at the location shown on the drawing. Also, as the distance between braces grows, so does the total weight that each brace will be required to resist. If you are in a high seismic category or if the site soil or building importance dictates a high force factor, maximizing the spacing may not be cost effective.

Once the lateral braces are located, you lay out the longitudinal braces. The maximum spacing for these braces is 80 feet. As with lateral braces, you are required to install a longitudinal brace within half the allowable distance between braces, meaning you must have one brace within 40 feet of each end of the run of main. Normally there will be fewer longitudinal braces than lateral.

The final bracing that is required is referred to as 4-way bracing. Industry terminology for this feature has been diluted, so for the purpose of clarification, 4-way bracing is not where both a lateral and longitudinal brace are located. Rather it is a bracing assembly that is used to restrict the movement of pipe that is installed in a vertical position such as the riser piping at the fire service entry into the building. As you can see in Figure 4, this bracing usually is installed in the horizontal position and has specific attachments that are designed to meet the intended installation configurations. The brace must be located within 24 inches of the top of the riser.

Like many of the requirements of this standard, nuances and exceptions can be applied. Both lateral and longitudinal braces can serve each other’s purpose if located within 24 inches of the end of the run of main (see Figure 5). Notice that the 4-way brace can be considered as the longitudinal brace as well. As a matter of design, I usually first lay out the bracing for each run of main independently, and then go back and consider the relocation of the braces at each end of the mains as a whole to apply these alternatives. Some designers have been taught to simply install a 4-way brace at every change of direction if sway bracing is required. Not only is this wrong, it is very expensive and does not accomplish the goal of seismic design. Bracing layout needs to be done with consideration of total weight and the ability of the fitter to actually have ceiling space to install the brace.

For example, in ceiling areas with an excessive amount of ductwork above the piping, it will be very difficult to run the sway brace up to the top chord of the structural member. If you have maximized the spacing, little can be done. Whereas if you have allowed for this condition ahead of time, the fitter can relocate the brace further down the main in one direction or the other without compromising the ability of the hanger to carry the weight that it was designed to resist. While it is not cheap, adding a brace to cut down the spacing is much less expensive than having field personnel trying to figure out how to make it work.

It is my hope that you see the importance of the “how” of the process of seismic design of fire sprinkler systems. As with any engineered system, especially life safety systems, understanding the overall goal and applying the standards by which we are intended to meet these goals is very important. Remember: Vince Lombardi said, “Excellence is achieved by mastering the fundamentals.”

Continued at Seismic Design For Fire Sprinkler Systems – Part 3a: Practical Example

Continued from Seismic Design For Fire Sprinkler Systems – Part 2a: The Objective of Seismic Restraint

Couplings
The first element is couplings. The general idea is to provide rigid couplings throughout the system except at locations where the piping is installed vertically. In fact, if flexible couplings are installed on piping running horizontally, a lateral sway brace is required to be included within 24 inches of the coupling. (Please note that this applies only to piping that is 2½ inches and larger.) So it stands to reason that you do not want to install flexible couplings anywhere other than where they are required.

Following are the coupling requirements as listed in NFPA 13 (2003). (Nos. 2 and 4 are taken from the 2002 edition.)

1. Within 24 inches (610 millimeters) of the top and bottom of all risers, unless the following provisions are met:
a. In risers less than 3 feet (0.9 meter) in length, flexible couplings are permitted to be omitted.
b. In risers 3-7 feet (0.9-2.1 meters) in length, one flexible coupling is adequate.

2. Within 12 inches (305 millimeters) above and within 24 inches (610 millimeters) below the floor in multistory buildings. When the flexible coupling below the floor is above the tie-in main to the main supplying that floor, a flexible coupling shall be provided on the vertical portion of the tie-in piping.

3. On both sides of concrete or masonry walls within 1 foot (0.3 meter) of the wall surface, unless clearance is provided in accordance with Section 9.3.4.

4. Within 24 inches (610 millimeters) of building expansion joints.

5. Within 24 inches (610 millimeters) of the top and bottom of drops to hose lines, rack sprinklers, and mezzanines, regardless of pipe size.

6. Within 24 inches (610 millimeters) of the top of drops exceeding 15 feet (4.6 meters) in length to portions of systems supplying more than one sprinkler, regardless of pipe size.

7. Above and below any intermediate points of support for a riser or other vertical pipe.

It is the practice in my company to include a sheet note on the drawings that says, “All couplings shall be rigid type unless noted otherwise.” In the design of the system, we use some type of symbol designation to indicate that the couplings are to be flexible. The coupling requirements are usually stricter in inrack sprinkler systems, standpipe systems, systems that are multilevel, and riser assemblies.

Seismic Separation
The second element involved is seismic separation. Building separation is a critical aspect of design for structural engineers. The building codes require buildings to be structurally separated once they reach a specific length and/or square footage. Where a building is separated, no part of the structure is connected at that point. In other words, while the building may appear to be one complete structure, it is structurally separate such that the two parts move independently of each other.

You usually can identify this occurrence by reviewing the structural drawings. You will find two column grid bubbles that are very close together, usually 12 inches apart. You will see two beams or other structural members running side-by-side, parallel to each other for the entire width of the building. If you look at the details you will see that no part of the structure at that point is connected. From the foundation up through the roof, the two parts are completely separate. The only thing that makes the building appear whole is the siding and roof coating that are applied.

A separation should not be confused with a building expansion joint. While an expansion joint is designed to allow the building to move, it certainly does not provide the magnitude of movement that a separation is designed to allow. Expansion joints also have coupling requirements, but NFPA 13 requires a specific type of assembly to be used with building separation. Many contractors and designers have seen pictures of this assembly, but I have found that few have investigated its purpose or actually used it.

This section includes only one statement, but its effects are far reaching. In fact, this one requirement can completely dictate the type of piping configuration you will use for the system. If this section is overlooked during the estimating process, complying with
the requirement in the field most likely will use up most of the profit. This section requires that separation assemblies with flexible fittings be installed, regardless of size, where piping crosses building seismic separation joints.

Figure 1 Gridded System

The magnitude of this requirement is best explained by considering a gridded system. This type of piping configuration involves the installation of a primary main on one side of the building and a secondary main on the opposite side. The mains are connected
with a series of branch lines that run perpendicular to each main (see Figure 1). Since seismic separation applies to all pipe sizes, a seismic separation assembly is required at every location that these grid branch lines cross a required separation. If you look at what this involves, you will better understand what is at stake (see Figure 2). Six 90-degree ells added to each branch line will be included in the hydraulic calculations, and their presence most likely will increase the branch-line size at least one size, making the system even more expensive.

The only currently known alternative to this assembly is a fitting assembly called a Metraloop, which provides the same movement in a more feasible manner. While the NFPA 13 assembly can take out as much as 5 feet or more depending on size, the Metraloop provides a more compact and easy-to-install alternative. While a grid usually is considered the most cost-effective piping configuration, you also should consider a series of center-feed, tree-type systems requiring only the bulk feed main to cross the separation once, rather than several times as with a gridded system. Remember: If you use the Metraloop, flexible couplings are required for its connection to the piping.

Continued at Seismic Design For Fire Sprinkler Systems – Part 2c: Clearance and Sway Bracing

Continued from Seismic Design For Fire Sprinkler Systems – Part 1d: A Word About Responsibility

In the first part of this series, I discussed the “if” aspect of seismic design for fire sprinkler systems. The article reviewed International Building Code (2003) Section 1614 where the requirement for seismic design is made and each of the six exemptions to this requirement. Now it is time to discuss how to actually do this in your sprinkler system designs.

Let’s first review the process thus far. IBC Section 1621 references a document called ASCE 7, which is published by the American Society of Civil Engineers and used by structural and civil engineers for building component design criteria, among other things. ASCE 7 Chapter 9.6, “Architectural, Mechanical and Electrical Components and Systems,” is where the exemption for fire sprinklers is found if the Seismic Category as determined in IBC is an A or B. (Remember that fire sprinkler systems in Seismic Category C cannot be exempt from the seismic restraint requirement because they are considered life safety systems and therefore are given a higher rating than standard mechanical and electrical systems.) Having determined that seismic design is required, the “how” of the process begins.

A Word About Terminology
While almost everyone is familiar with the concept of sway bracing, it is important to standardize the language of this design process. For years specifying engineers and other entities have referred to seismic design by simply stating “provide earthquake bracing as required” or “sway bracing shall be provided as required in NFPA 13 [Standard for the Installation of Sprinkler Systems]” or “when bracing is required, it shall be installed per NFPA 13.”

I must stress that you immediately remove any such canned or standardized language in your company’s specifications. Such vague wording is very misleading. Seismic design for fire sprinkler systems includes several components in addition to bracing. While bracing is one of the most familiar methods, it certainly does not provide the necessary restraint for a system to meet the level of performance intended.

The Objective of Seismic Restraint
Understanding the purpose behind seismic design is the next step in the process. As with other aspects of sprinkler system design, plenty of gray areas make following the rules difficult. I believe that a designer must understand the overall objective behind a code or standard to better provide a solution for those times when the rules do not readily apply.

The objective of seismic design for a fire sprinkler system is twofold. The first goal is to minimize stresses in piping by providing flexibility and clearances at points where the building is expected to move during an earthquake. The second is to minimize damaging forces by keeping the piping fairly rigid when supported by a building component expected to move as a unit during an earthquake, such as a floor/ceiling assembly. The idea is to design a system that gives and moves as the building is designed to move. You want the system rigid where the building is rigid and flexible where the building is flexible. According to the standards, the
systems attached to the structure of the building all should work together as one unit.

That being the case, let’s look at each element required to make this happen. NFPA 13 Chapter 9.3 is where all the standard installation requirements for seismic design can be found. The chapter is organized by each required category: couplings, separation, clearance, and sway bracing.

Continued at Seismic Design For Fire Sprinkler Systems – Part 2b: Couplings and Seismic Separation

Continued from Seismic Design For Fire Sprinkler Systems – Part 1c: Determining the Seismic Design Category of a Building

A Word About Responsibility
Prior to the introduction of the IBC, contract specifications were usually the vehicle used to require seismic restraint. Engineers would add language to the specifications indicating “earthquake bracing shall be provided per NFPA 13.” This usually meant the contractor would multiply the predetermined force factor by the weight of water-filled pipe in a zone of influence to size the braces. However, the method has changed; you now must take several variables and steps to evaluate and determine whether seismic protection is needed and, if so, the data required to properly size the components that will be used. This is the “how” in the process, which I will look at in the second article of this series.

Before we go any further, I believe a discussion regarding responsibility is warranted. Just like every other aspect of sprinkler system design, the criteria for seismic should be determined and provided to the contractors by the engineer of record. This certainly does not mean that contractors are not capable of learning this process and applying it correctly. They have been taking on the liability and exposure for the majority of the design criteria from the beginning. However, it is time that the engineers who have decided to practice in the discipline of fire protection take on the responsibility that goes with it. I am sure that many of you are rolling your eyes and beginning to complain about how all this is going to affect you. But before you do, let me point out that while going through the learning curve, I discovered something that will most likely help you digest this. Are you ready? Here it is: The structural engineers have been figuring this out as part of their design process for years. Just like many other items that fall under the engineer’s responsibility, the information needed in the course of this process is available from the other design team members (the structural engineer) at the time that the construction documents are prepared. So you see, it really should not take that much effort to determine a very important part of the required design criteria that the engineer of record should be providing.

As I said, meeting the installation requirements for seismic components in a sprinkler system is costly, and the matter needs to be given serious consideration during the bidding process. Therefore, the information needed, namely the “if” and the force factor to be used, should be included with the rest of the information that is required in the owner’s certificate found in NFPA 13 Chapter 4.3.

I think you’ll agree that this is an important process and one that will take some time to become familiar with. Whether you are in Orlando, Fla., the plains of West Texas, Boise, Idaho, or Yuma, Ariz., the evaluation of seismic protection is required. It is the design professional’s job to determine the Seismic Design Category that is assigned to a building, as well as provide the force factor that should be used if seismic protection is required, a process I will explain in the second part of this series.

Continued at Seismic Design For Fire Sprinkler Systems – Part 2a: The Objective of Seismic Restraint

Continued from Seismic Design For Fire Sprinkler Systems – Part 1b: IBC Requirements and Exemptions

Determining the Seismic Design Category of a Building
So how do you know if seismic protection is required? The process begins with assigning a Seismic Use Group to the building. This classification can be found by using IBC Table 1604.5. (The relevant portion of this table is found in Table 1.) The second part of the initial process involves an evaluation of ground motion. This can be determined using a general procedure or a site-specific one. The only exception to this is if the Site Class is determined to be F. This class mandates the site-specific procedure be used.

Using the general procedure, two maximum earthquake spectral response accelerations (short term and long term) must be considered as discussed. Remember that both time periods must be evaluated separately. A Site Class of A through F then is determined based upon the soil at the site per IBC Table 1616.5.1.1. This step is very important because a building’s Site Class directly dictates whether or not it has to be designed for seismic. Keep in mind that you can use the specific Site Class value from the table, or, if this information is not readily available for some reason, you are allowed to default to Site Class D. However, this classification more than likely will require you to provide seismic protection so do not be too quick in deciding to use this option. A quick call to the structural or civil engineer on the design team should provide this information.

As I noted previously, seismic protection for sprinkler systems can be costly. For example, a Site Class A allows a reduction of the spectral response acceleration values, which possibly would result in exempting seismic protection. The response values are adjusted based on the effects of the Site Class using formulas in IBC Sections 1615.1.2 and 1615.1.3:

Using the design response accelerations and Seismic Use Group, Tables 1616.3(1) and 1616.3(2) yield the Seismic Design Category (see Table 2).

Again, this must be evaluated for both the short- and long-term accelerations. These categories also use designations A through F. The most severe Seismic Design Category of the two time periods is used. The last step is determining whether seismic protection is required based on the assigned Seismic Design Category.

Now, if your head is in a tailspin at this point, don’t feel left out. Many of us have had to perform the process several times before grasping it. To help you understand this process, I’ve listed the steps below.

Continued at Seismic Design For Fire Sprinkler Systems – Part 1d: A Word About Responsibility