Monday, October 3, 2011

Earthquake Data for Canada

There is a site similar to USGS' for earthquake data in Canada available at:
Let us know if you are interested in having Anvil Fire update our Seismic Force Calculator App to include this information.

Sunday, September 25, 2011

Seismic design changes - 2012 IBC

DesignMaps Application and 2008 Design Data
USGS has released an updated DesignMaps application which is a great application.  However, before you start applying it to 2009 International Building Code please make sure to read their FAQ page which states:
This application should currently only be used to investigate which design values will likely be mandated in the future.

This recommendation by USGS is based on the hierarchy of the codes and standards, which is as follows:
2003 IBC2006 IBC2009 IBC2012 IBC
USGS 2002USGS 2002USGS 2002USGS 2008

The DesignMaps application utilizes information from the 2008 USGS National Seismic Hazard Maps information.   For 2008 the hazard values in the Central and Eastern U.S. have been reduced by 10-25% in many cases, and most 1-second period ground motion values for the Western U.S. have also been reduced, in some cases by as much as 30%.

Example differences between 2002 and 2008 Design Data
Lets look at a comparison of several values based on the 2002 vs 2008 hazard values.  (Examples based  Site Class 'D' and Occupancy Category of 'II').
Atlanta, GA (Lat 33.7489954, Lng -84.3879824)
Data SourceSsS1SdsSd1Sds Design CatSd1 Design Cat
2002 Design Data0.2260.0850.2410.137BC
2008 Design Data0.1850.0900.1970.144BC

Sacramento, CA (Lat 38.5815719, Lng -121.4943996)
Data SourceSsS1SdsSd1Sds Design CatSd1 Design Cat
2002 Design Data0.5910.2440.5230.311DD
2008 Design Data0.6750.2940.5670.355DD

Casper, WY (Lat 42.866632, Lng -106.313081)
Data SourceSsS1SdsSd1Sds Design CatSd1 Design Cat
2002 Design Data0.3700.0770.3710.123CB
2008 Design Data0.2770.0740.2910.118BB
As seen in the last example for Casper, Wyoming, seismic bracing for fire sprinkler piping is not required based on which design criteria is applied.  The Sds value is 21% less in the 2008 values.  So whether you utilize the 2002 or 2008 hazard data can make a significant difference on your project.

Anvil Fire's Seismic Force Calculation App provides values based on the 2002 hazard values published by USGS and is basically identical to the Java Ground Motion Parameter Calculator provided by USGS.  Consult with your AHJ, but at this time we recommend that you follow USGS's recommendation to only use the DesignMaps application to investigate the requirements of the future 2012 International Building Code.

For more detailed information on how to determine the seismic design forces for fire suppression systems, please read our blog post on Seismic Design For Fire Sprinkler Systems.

Sunday, August 14, 2011

Expanded Seismic Data for On-line App

So that our clients outside of the continental United States don't feel left out, we have expanded our seismic ground motion data to include:

  • Hawaii
  • Puerto Rico/U.S. Virgin Islands

This data is from the USGS and is applicable for designs applying ASCE 7-05 as referenced by the 2006 and 2009 editions of IBC.  Visit our on-line fire sprinkler seismic calculation app and try it out for these locations.

Thursday, July 28, 2011

Simple Engineering

A toothpaste factory had a problem: they sometimes shipped empty boxes, without the tube inside. This was due to the way the production line was set up, and people with experience in designing production lines will tell you how difficult it is to have everything happen with timings so precise that every single unit coming out of it is perfect 100% of the time. Small variations in the environment (which can’t be controlled in a cost-effective fashion) mean you must have quality assurance checks smartly distributed across the line so that customers all the way down the supermarket don’t get pissed off and buy someone else’s product instead.

Understanding how important that was, the CEO of the toothpaste factory got the top people in the company together and they decided to start a new project, in which they would hire an external engineering company to solve their empty boxes problem, as their engineering department was already too stretched to take on any extra effort.

The project followed the usual process: budget and project sponsor allocated, RFP, third-parties selected, and six months (and $8 million) later they had a fantastic solution — on time, on budget, high quality and everyone in the project had a great time. They solved the problem by using some high-tech precision scales that would sound a bell and flash lights whenever a toothpaste box weighing less than it should. The line would stop, and someone had to walk over and yank the defective box out of it, pressing another button when done.

A while later, the CEO decides to have a look at the ROI of the project: amazing results! No empty boxes ever shipped out of the factory after the scales were put in place. Very few customer complaints, and they were gaining market share. “That’s some money well spent!” – he says, before looking closely at the other statistics in the report.

 It turns out, the number of defects picked up by the scales was 0 after three weeks of production use. It should’ve been picking up at least a dozen a day, so maybe there was something wrong with the report. He filed a bug against it, and after some investigation, the engineers come back saying the report was actually correct. The scales really weren'’t picking up any defects, because all boxes that got to that point in the conveyor belt were good.

Puzzled, the CEO travels down to the factory, and walks up to the part of the line where the precision scales were installed. A few feet before it, there was a $20 desk fan, blowing the empty boxes out of the belt and into a bin. “Oh, that — one of the guys put it there ’cause he was tired of walking over every time the bell rang”, says one of the workers.

Saturday, July 16, 2011

Fire Pump Sizing App

We are pleased to offer a NFPA 20 fire pump sizing app to our clients.  This app allows you to quickly look up the minimum required suction, discharge, test header, number of hose valves, and relief valve size.  These are the recommended sizes and we recommend a quick phone call to discuss your project specific conditions.

Saturday, January 15, 2011

Seismic Design For Fire Sprinkler Systems

How do you know when seismic bracing is required for fire sprinkler piping?  Lets walk through the general procedure to determine if bracing is required.  (Hint - You can just go to our Seismic Calculator App and have much of the look up work done for you.)

Assuming that you are working in a jurisdiction that has adopted the International Building Code (IBC), you would start with section 1613.1 which states:
1613.1 Scope. Every structure, and portion thereof, including
nonstructural components that are permanently attached to
structures and their supports and attachments
, shall be
designed and constructed to resist the effects of earthquake
motions in accordance with ASCE 7, excluding Chapter 14 and
Appendix l1A. The seismic design category for a structure is
permitted to be determined in accordance with Section 1613
 Furthermore the International Mechanical Code (IMC) section 301.15 states:
301.15 Seismic resistance. When earthquake loads are applicable in accordance with the International Building Code, mechanical system supports shall be designed and installed for the seismic forces in accordance with the International Building Code.
Looking in the appendix of the 2009 edition of IBC (page 590), we can see that the 2005 edition of ASCE 07 (ASCE 07-05) is adopted.  So what is ASCE 07-05?  The name of the standard is "Minimum Design Loads for Buildings and Other Structures" and is published by the American Society of Civil Engineers (ASCE).

STEP TWO - Ss and S1 Design Ground Motions
As noted in IBC section 1613.1 above, we are going to use IBC section 1613 to determine our seismic design category.  The first step is determine how strong the forces will be at your site.  There are two types of forces to consider: Short Period (Ss) and 1-Second Period (S1).  These values are typically determined by the USGS and the official definitions are as follows:

  • Ss = mapped MCE, 5 percent damped, spectral response acceleration parameter at short periods
  • S1 = mapped MCE, 5 percent damped, spectral response acceleration parameter at a period of 1 second
  • MCE = Maximum Considered Earthquake effects
Most building codes use 0.2 second and 1.0 second to represent the approximate natural period of vibration of a short and tall building, respectively

The USGS provides and excellent Java based calculation program for looking up these and many other values based on lat/lng and zip code. Or you can just go to our Seismic Calculator App which is based on this same data and provides some addition capabilities.

If I asked which area of the country had the heights forces, I bet you would guess California.  However, the highest seismic forces for the continental United States are:
  • La Center, Kentucky (37.1, -89.0) with a Ss = 3.4079
  • Harrisburg, Arkansas (35.5, -90.6) with a S1 = 1.36927
  • * Based on USGS 2003 Conterminous US Design Ground Motion data on

The next step is to determine the Site Class.  Whether the ground is very stiff or very soft greatly affects the way the seismic forces are transferred to the structure.  In general, a stiff ground transfers the energy efficiently and a soft ground just absorbs the energy.  As such, the IBC provides a standard formula to adjust the S1 and Ss values determined above for your soil profile.  We strongly recommend that you consult with the Structural Engineer of Record since he already had to determine this class for his calculations.  That being said, the most typical soil type is 'D' or Still Soil Pile.

Table 1613.5.2 - Site Class Definitions
Site Class
Soil Profile Name
Soil shear wave velocity, Vs (ft/s)
Standard penetration resistance, N
Soil undrained shear strength, Su (psf)
Hard Rock
Vs > 5,000
2,500 < VS <= 5,000
Very Dense Soil and Soft Rock
1,200 < VS <= 2,500
N > 50
Sa >= 2,000
Stiff Soil Profile
600 <= VS <= 1,200
15 <= N <=50
1,000 <= Sa <= 2,000
Stiff Soil Profile
VS < 600
N < 15
Sa < 1,000

You then look up the site coefficients from IBC tables 1613.5.3(1) and 1613.5.3(2) below.  Note that you can apply a straight-line interpolation for intermediate values and this can make a significant difference.

Site ClassMapped Spectral Response Accleration at Short Period
Ss <= 0.25Ss = 0.50Ss = 0.75Ss = 1.00Ss >= 1.25
FNote bNote bNote bNote bNote b
  • (a) Use straight-line interpolations for intermediate values of mapped spectral response acceleration at short period, Ss.
  • (b) Values shall be determined in accordance with Section 11.4.7 of ASCE 7.

Site ClassMapped Spectral Response Acceleration at 1-Second Period
S1 <= 0.1S1 = 0.2S1 = 0.3S1 = 0.4S1 >= 0.5
FNote bNote bNote bNote bNote b
  • (a) Use straight-line interpolations for intermediate values of mapped spectral response acceleration at 1-second period, S1.
  • (b) Values shall be determined in accordance with Section 11.4.7 of ASCE 7.

Now that we know the expected forces (S1 and Ss) and adjustment factors (Fv and Fa), we need to crunch some numbers to determine the adjusted force factors per the following simplified IBC formulas:

(IBC equations 16-37 and 16-39 combined)

(IBC equations 16-36 and 16-38 combined)

Now that we know the adjusted design forces, we need to determine if these forces are great enough to require preventative actions.  Risk is related to the activity.  A hospital has a much higher risk than a temporary storage facility.  IBC recoginzes this in Tables 1604.56, 1613.5.6(1), and 1613.5.6(2) as follows:

IBC Table 1604.5 - Occupancy Category of Buildings and Other Structures
Occupancy CategoryNature of Occupancy
IBuildings and other structures that represent a low hazard to human life in the event of failure, including but not limited to:
  • Agricultural facilities
  • Certain temporary facilities
  • Minor storage facilities
IIBuildings and other structures except those listed in Occupancy Categories I, III, and IV
IIIBuildings and other structures that represent a substantial hazard to human life in the event of failure, including but no limited to:
  • Covered structures whose primary occupancy is public assembly with an occupant load greater than 300
  • Buildings and other structures with elementary school, secondary school or day care facilities with an occupancy load greater than 250
  • Buildings and other structures with an occupancy load greater than 500 for colleges or adult education facilities.
  • Health care facilities with an occupant load of 50 or more resident patients, but not having surgery or emergency treatment facilities.
  • Jails and detention facilities.
  • Any other occupancy with an occupant load greater than 5,000.
  • Power-generating stations, water treatment for potable water, waste water treatment facilities and other public utility facilities not included in Occupancy Group IV.
  • Buildings and other structures not include in Occupancy Category IV containing sufficient quantities of toxic or explosive substances to be dangerous to the public if released.
IVBuildings and other structures designated as essential facilities, including but not limited to:
  • Hospitals and other health care facilities having surgery or emergency treatment facilities.
  • Fire, rescue and police stations and emergency vehicle garages.
  • Designated earthquake, hurricane or other emergency shelters.
  • Designated emergency preparedness, communication, and operation centers and other facilities required for emergency response.
  • Power-generating stations and other public utility facilities required as backup facilities for Occupancy Category IV structures.
  • Structures containing highly toxic materials as defined by Section 307 where the quantity of material exceeds the maximum allowable quantities of Table 307.1.(2).
  • Aviation control towers, air traffic control centers and emergency aircraft hangers.
  • Buildings and other structures having critical national defense functions.
  • Water treatment facilities required to maintain water pressure for fire suppression.

Sds < 0.167gAAA
0.167g <= Sds < 0.33gBBC
0.33g <= Sds < 0.50gCCD
0.50g <= Ss1DDD

Sd1 < 0.067gAAA
0.067g <= Sd1 < 0.133gBBC
0.133g <= Sd1 < 0.20gCCD
0.20g <= Sd1DDD

Finally we have determined a Seismic Design Category based on the forces, adjustment factors, and occupancy of the building.  Based on the worst case seismic design category, we can go back to ASCE 07-05 and look at the following single paragraph:
13.1.4 Exemptions. The following nonstructural components are exempt from the requirements of this section: 
… 2.  Mechanical and electrical components in Seismic Design Category B.
So if Category A or B you are exempt, if C or D you need to provide bracing.

Look for the next post on calculating the forces on individual piping components in accordance with ASCE 07-05 paragraph