1. WHAT IS SNYDER’S VST AND CAPTOR SEISMIC SYSTEMS DESIGN FIGURES?
The seismic restraint system offered by Snyder meets System meets IBC 2006 / CBC 2007 code with seismic loads ≤ .445g SDC (Seismic Design Category) "D" - Fa=1.0, Fv=1.5, Ss=1.4, S1=0.5). If the requirement is greater than these design coefficients then you will need to contact Snyder to see if a system can be provided to meet the requirements for the site. This may change the price of the standard seismic system offered in Snyder’s Industrial Tank Price List.
See question 9 for further explanation of Seismic Design Category (SDC).
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2. WHAT IS IBC AND CBC AND HOW DOES IT AFFECT ME?
IBC stands for International Building Code. CBC stands for California Building Code.
If you are in California, then the new California Building Code of 2007 (CBC 2007) took effect on January 1, 2008.
All plans submitted to the state of California for permit on January 1st, 2008 or later, will be planchecked and constructed in accordance with the CBC 2007. As such, new calculations meeting CBC 2007 will be required for tank seismic restraint systems. If plan is submitted for plancheck on Dec. 31, 2007 or earlier, it will be planchecked and constructed in accordance with the previous CBC 2001 code.
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3. IS THE IBC AND CALIFORNIA BUILDING CODE (CBC) THE SAME THING? IF NOT, WHAT ARE THE DIFFERENCES, WHICH CODE SHOULD I FOLLOW WHEN DESIGNING PROJECTS IN CALIFORNIA?
Yes, but with amendments. The California Building Standards Council (CBSC) went through extensive review of the IBC and the California legislature adopted it by law as the new CBC in 2007, making it effective January 1, 2008. This is the code you must now follow depending on when the local jurisdiction you are working in adopts it.
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4. WHAT ABOUT OTHER STATES OTHER THAN CALIFORNIA?
Other states may have already or may be soon adopting IBC 2006. Typically many states follow the lead of California on seismic system design requirement. As of March 2008 at least 20 states have already adopted IBC 2006. Many other states are using previous versions of IBC (either 2000 or 2003) and in the process of adopting IBC 2006. You will need to check with local authorities for requirements for your area and when they take effect.
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5. WHAT DOES THE CODE REQUIRE WITH REGARD TO EQUIPMENT ANCHORAGE?
The California / International Building Codes require all stationary equipment to be anchored to its supporting structure (CBC 2007, Section 1613a & IBC 2006, Section 1613). In addition, much of this equipment must have calculations to validate its method of anchorage (ASCE 7-05, Section 13). For floor mounted equipment the requirement is for equipment that weighs 400 pounds or more or is over 60 inches in height.
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6. HOW DO I KNOW IF SNYDER’S SYSTEM WILL BE ACCEPTED?
With IBC 2006 / CBC 2007 the seismic design coefficients are site specific so each zip code may have different requirements. Our standard calculations are based on the design coefficients of a specific zip code in California (see seismic design coefficients in question 1). To determine if our standard calculations will be accepted we recommend you present a copy of our standard seismic design calculations to the contractor and/or engineering firm and have them review the calculations for acceptance. If the calculations are not acceptable then you will need to have the
contractor and/or engineering firm provide information on the design coefficients required for the project so they can be reviewed by Snyder.
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7. WHAT IF I’M BEING ASKED TO PROVIDE A WET STAMP?
Original Wet Stamp calculations are listed in Snyder’s price book as a purchased option for vertical tanks, double wall Captor tanks and cone bottom tanks. The wet stamps are broken down into three categories – Standard Calculation, Site Specific (VST/Captor), and Site Specific (CBT). The standard calculation is the calculation we already have done for a specific site that may work for your projects site. If, however, you require a “site specific” calculation which requires changes to the standard calculation then you would use the Site Specific calculation pricing. These site
specific calculations will be provided in the same format at the standard calculation only they will be adjusted for the specific site design coefficients. If a “non-standard” format calculation is required please contact Snyder as these will need to be quoted on a case-by-case basis as priced by the Engineer contracted to provide the calculations.
A copy of our standard calculation can be provided (PDF format) at no charge by contacting your Snyder Regional Sales Manager or Customer Service.
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8. TODAY'S DATE IS BEYOND THE “EXPIRED” DATE ON THE STRUCTURAL STAMP, IS THE CALCULATION STILL VALID?
The calculation is valid as long as the date on the calculation is prior to the expired stamp. The expiration date as related to the date of the permitted drawings, applies to the Engineer of Record's stamp.
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9. WHAT IS A SEISMIC DESIGN CATEGORY?
The old Uniform Building Code (UBC) 1997 used maps with numbered zones, 0, 1, 2, 3, 4. These maps are practically obsolete (1969 was the last year such a map was put out). The new IBC 2006 code uses Seismic Design Category (SDC). A SDC is a classification assigned to a structure based on its occupancy or use (referred to as Occupancy Category) and on the level of expected soil modified seismic ground motion. This can be expressed schematically as follows:
[Occupancy Category] + [Soil modified seismic ground motion] → SDC
| Seismic Design Category (SDC) |
What does it mean? |
|
A |
Very small seismic vulnerability |
|
B |
Low to moderate seismic vulnerability |
|
C |
Moderate seismic vulnerability |
|
D |
High seismic vulnerability |
|
E and F |
Very high seismic vulnerability and near a major fault |
To determine the seismic design category you need to determine the Ss and S1 using maps or calculation tool. If you are working on a specified project then have the contractor or engineering firm responsible for the specification provide you with these figures.
Ss = the maximum considered earthquake spectral response acceleration at short periods (0.2 seconds)
S1 = the maximum considered earthquake spectral response acceleration at 1 second period.
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10. WHAT SIZE PAD DO I NEED FOR THE SEISMIC RESTRAINT SYSTEM?
The diameter of the pad required is outlined in the standard VST and/or Captor calculations. Please review the calculations and find the pad drawing that applies to the tank you are using or quoting for your project. The pad design is based on the default value allowed by code. It may be possible to use a smaller pad size if soil conditions are known. This would have to be done by the engineer on site.
The thickness of the pad will need to be determined by a local design engineer based on the soil conditions; however the pad should be thick enough for the anchor embedment outlined in the standard calculations.
Please note that if you need a site specific seismic calculation or a non-standard calculation, then the pad size may differ substantially from what is shown in the standard calculation.
