05-12-14 Regular Meeting of La Porte City Council

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REQUEST FOR CITY COUNCIL AGENDA ITEMREQUEST FOR CITY COUNCIL AGENDA ITEM May 12, 2014May 12, 2014AppropriationAppropriation Agenda Date Requested:Agenda Date Requested: N/A N/A Bob Eng Bob Eng Source of Funds:Source of Funds: Requested By: Account Number:Account Number: Planning & Development Planning & Development Department: Amount Budgeted:Amount Budgeted: Report:Resolution:Resolution:Ordinance:Ordinance: Amount Requested:Amount Requested: Other: Budgeted Item:Budgeted Item:YESYESNONO Attachments :Attachments : 1. Memo1. Memo--Building Codes Appeals Board Building Codes Appeals Board approvalapproval 2. Ordinance2. Ordinance 3. Ordinance showing changes3. Ordinance showing changes 4. Wind Load Comparison Table4. Wind Load Comparison Table SUMMARY & RECOMMENDATIONSSUMMARY & RECOMMENDATIONS The City recently adopted the 2012 Editions of both the International Residential Code (IRC) and the International The City recently adopted the 2012 Editions of both the International Residential Code (IRC) and the International Building Code (IBC) from the previous 2009 Editions regulating the design and construction of buildings and Building Code (IBC) from the previous 2009 Editions regulating the design and construction of buildings and structures within the City limits.structures within the City limits. The 2012 adopted International Residential Code established a wind speed criteria for design, based upon a series The 2012 adopted International Residential Code established a wind speed criteria for design, based upon a series of maps that vary by proximity to the coast. The City adopted a local amendment specifying that a wind design of of maps that vary by proximity to the coast. The City adopted a local amendment specifying that a wind design of 120 mph would be used in lieu of choosing a wind speed number from a map. The chosen IRC design wind speed 120 mph would be used in lieu of choosing a wind speed number from a map. The chosen IRC design wind speed affects the design of a structure as a variable in the design calculations. The 2012 IRC allows two separate affects the design of a structure as a variable in the design calculations. The 2012 IRC allows two separate methodologies for utilizing this wind speed in calculating the design wind forces based upon formulas of the methodologies for utilizing this wind speed in calculating the design wind forces based upon formulas of the American Society of Civil Engineers (ASCE). The first allowable method is based on the ASCE 7American Society of Civil Engineers (ASCE). The first allowable method is based on the ASCE 7American Society of Civil Engineers (ASCE). The first allowable method is based on the ASCE 7American Society of Civil Engineers (ASCE). The first allowable method is based on the ASCE 7----5 (year 2005) 5 (year 2005) 5 (year 2005) 5 (year 2005) formula and the second newly adopted method is based on the ASCE 7formula and the second newly adopted method is based on the ASCE 7--10 (year 2010) formula. These two 10 (year 2010) formula. These two formulas appear similar but utilize the wind speed variable quite differently. Therefore the adopted 120 mph wind formulas appear similar but utilize the wind speed variable quite differently. Therefore the adopted 120 mph wind speed cannot be used interchangeably in the calculation of the resultant design wind forces. To achieve the speed cannot be used interchangeably in the calculation of the resultant design wind forces. To achieve the equivalent of the 2009 effective 120 mph wind speed for the use in the formula utilizing ASCE 7equivalent of the 2009 effective 120 mph wind speed for the use in the formula utilizing ASCE 7--10, it would need 10, it would need to be specified to at least 150 mph under the 2012 amendment. to be specified to at least 150 mph under the 2012 amendment. The International Building Code specifies the use of only the ASCE 7 The International Building Code specifies the use of only the ASCE 7--10 formula for wind load calculations and 10 formula for wind load calculations and the proposed amendment drops the 120 mph wind specified by the current Ordinance and replaces it with 150 the proposed amendment drops the 120 mph wind specified by the current Ordinance and replaces it with 150 mph. Using 150 mph wind speeds in the procedure outlined by ASCE 7mph. Using 150 mph wind speeds in the procedure outlined by ASCE 7--10 is nearly the equivalent of using 120 10 is nearly the equivalent of using 120 mph with the older ASCE 7mph with the older ASCE 7--5 formula used with the 2009 codes. 5 formula used with the 2009 codes. The Planning Department is recommending, as approved by the Building Code Appeals Board, the amendments The Planning Department is recommending, as approved by the Building Code Appeals Board, the amendments to the Ordinance, which relate to wind design speed and the associated charts and notes referenced by the 2012 to the Ordinance, which relate to wind design speed and the associated charts and notes referenced by the 2012 IRC and IBC.