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HomeMy WebLinkAboutStructual Assesment Report for Gazebo Structural Assessment Report Gazebo 3875 Hallock Lane Mattituck, New York August 17, 2022 Prepared For: Richard Martino 3875 Hallock Lane Mattituck, NY 11952 AI-ALT Project No. 22106.00 OF NEIV y 5 PL N 9 ` O z cc m LU A 092153 9�FESSIONP Prepared by: Alvin Tabar Ai-Alt Structural Engineering PLLC Professional Engineer d/b/a New York State License No.092153 Ai-Alt 25 Melville Park Road Suite 229H Melville, NY 11747 www.ai-alt.com Structural Assessment Report-Gazebo a g e I ii AI-ALT File No. 22106.00 August 17,2022 Table of Contents 1. Executive Summary 1 2. Structural Background 2 3. Structural Conditions Assessment 3 4. Southold Town Code and 2020 Residential Code of New York State 7 S. Structural Requirements for the Legalization of the Existing Gazebo 8 6. Summary of Recommendations 9 Appendix A—Wind,Snow and Seismic Loads A-1 ® www.ai-alt.com Structural Assessment Report-Gazebo _ 1 AI-ALT File No. 22106.00 August 17,2022 1. Executive Summary The existing Gazebo structure is an installation associated with the one-family dwelling located at 3875 Hallock Lane, Mattituck, New York. It was constructed circa 2005 without obtaining a building permit from the Town of Southold,the Authority Having Jurisdiction (AHJ).The Gazebo is a one-story detached structure with a gross floor area of approximately 360 square feet, including the approximately 135 square feet of uncovered balcony space with protective railing overlooking the Long Island Sound.The existing Gazebo floor with stone finish is elevated from the natural grade and is comprised of wood subflooring on wood joists and girders construction supported by 10" diameter concrete piers founded around 5 feet below the existing grade.The Gazebo has octagonal shape walls framed utilizing wood studs with plywood sheathing and clad with natural stone. It has large open windows on six (6) sides with entry openings on the other two (2) opposing sides for entry from the main pathway and for access to the balcony. Similarly, the structure has octagonal roof shape comprised of wood framing and sheathing that slope downward and covered with fiberglass shingles. The ceiling follows the profile of the roof and has stucco finish. Our visual observations did not reveal any advance stage of deterioration or sign of excessive distress to the structural members and the foundation of the existing Gazebo.The early sign of decay on the main girder supporting the balcony can be remedied to further the end-of-life stage of the existing Gazebo, if desired. Section 144-8 paragraph"c"of the Southold Town Code requires that accessory structure such as the Gazebo having gross floor area greater than 100 square feet shall require a building permit prior to commencing with the installation work.We understand that the existing Gazebo structure with gross floor area of approximately 360 square feet was constructed without the necessary permit. On this regard, structural drawings to be prepared by a Professional Engineer registered in the State of New York shall be submitted to the Town of Southold along with other plans and documents required to bring the Gazebo to compliance with the mandates of governing codes. www.ai-alt.com Structural Assessment Report-Gazebo a g e 2 AI-ALT File No. 22106.00 August 17, 2022 2. Structural Background 2.1.Description of the Structures The existing Gazebo has octagonal shape walls framed utilizing wood studs with plywood sheathing and clad with natural stone. It has large open windows on six (6) sides with entry openings on the other two(2)opposing sides for entry from the main pathway and for access to the balcony.Similarly, the structure has octagonal roof shape comprised of wood framing and sheathing that slope downward and covered with fiberglass shingles, see Photos 1 & 2. The ceiling follows the profile of the roof and has stucco finish, see Photos 3 &4. .X t "t 'n Photo 1. ExistingGazebo Photo 2. Stone Cladding g MEW Photo 3. Interior Ceiling Photo 4. Stone Cladding The existing Gazebo floor with stone finish is elevated from the natural grade and is comprised of wood subflooring on 2x8 wood joists at 16"spacing and 4x6 plus 2x4 laminated girders,supported by 10" diameter concrete piers founded around 5 feet below the existing grade,see Photos 5 through 6. www.ai-alt.com Structural Assessment Report-Gazebo : .a, �-,, e 3 AI-ALT File No. 22106.00 August 17, 2022 IY Photo 5. Wood Girders and Pier Foundation Photo 6. Balcony Pier Foundation 3. Structural Conditions Assessment On the 11th of August 2022,Alvin Tabar, P.E., Principal of Ai-Alt visited the property to carry out non- destructive visual structural observation of the Gazebo. The scope of the observation was limited to the current structural conditions that were visible from accessible areas without performing any destructive probes or tests. 3.1.Existing Gazebo Structure 3.1.1.Main Frame The main structural frame of the existing Gazebo appears to be in good condition with only superficial cracks on the stucco finish observed at the entry from the main pathway, see Photo 7. No cracks in the stucco finish at the ceiling that can be observed by a naked eye during the site visit,see Photos 8 through 10. 16 p k Photo 7. Cracks in Stucco Finish at Entry Photo 8. Stucco Finish at the Ceiling ® www.ai-alt.com Structural Assessment Report-Gazebo P .a ; P 4 AI-ALT File No. 22106.00 August 17,2022 V,{ Photo 9.Stucco Finish at the Ceiling Photo 10. Stucco Finish at the Ceiling The are no significant cracks on the interior stucco finish observed during the site visit. This is indicative that no structural distress of the wood stud wall behind the the panel sheathing,see Photos 11 and 12. aY x n4 i r Photo 11. Interior Wall Stucco Finish Photo 12. Interior Wall Stucco Finish Similarly,the exterior stone veneer seemed to be in good order as observed during the site visit. The are no major cracks at the joints and appeared to be no repair work or rejointing performed since it was built almost two (2) decades ago,see Photos 13 and 14. www.ai-alt.com Structural Assessment Report-Gazebo a g ,., 5 AI-ALT File No. 22106.00 August 17, 2022 -b Z'. t�F 1 t C� .r Photo 13. Exterior Stone Cladding Photo 14. Exterior Stone Cladding The floor remains relatively flat, an indication that there are no excessive sagging of the supporting joists and girders below, see Photos 15 and 16. There is no significant vibration observed on the floor when "heel-drop tests" were performed. The heel-drop test was conducted by having an individual stand in a strategic location on the floor, raise his heels approximately two(2) inches and then drop them to generate an impact due to his own weight on the floor to induce structural vibrations. The low vibration amplitudes observed are positive indication of the relatively high stiffness of the existing floor construction. b; _ Photo 15.Stone Floor Finish Photo 16.Stone Floor Finish A degree of deterioration was observed at the edge girder that supports the balcony. This appears to be an early stage of natural wood decay or rotting of wood due to exposure weather, ® www.ai-alt.com Structural Assessment Report-Gazebo P :- g; e 6 AI-ALT File No. 22106.00 August 17, 2022 see Photos 17& 18. Replacing this part of the structure will further extend the-end-of-life point of the existing Gazebo. Other wood members have no sign of deterioration as observed from the underside of the floor,see Photos 19 and 20. Photo 17. Main Girder Support at Balcony Photo 18. Main Girder Support at Balcony 7. Photo 19.Joists and Girders Support Photo 20.Joists and Girders Support 3.1.2. Foundation The foundation is comprised of fourteen (14) cast-in-place concrete piers poured using Sonotube®, eight(8) of which are situated at corners of the above octagon walls.Whereas, four(4) are located at each corners of the three-sided balcony while the remaining two (2) piers are located at the center portion of the Gazebo supporting the main girder that traverses from east to west corners of the above octagon walls. There is no excessive differential settlement observed during the site visit,which suggests that there is no significant settlement of the installed piers all through these years since the original construction of the Gazebo. No major cracks or sign of failure are observed on the exposed portion of the piers,see Photos 21 and 24.This is an evidence that there is hardly any lateral movement of the structure due to past high wind and or seismic events. www.ai-alt.com Structural Assessment Report-Gazebo , e 7 AI-ALT File No. 22106.00 August 17, 2022 k. i Photo 21. Exposed Portion of Existing Piers Photo 22. Exposed Portion of Existing Piers 7 AM 99 7Q mV� Il �� r L Photo 23. Exposed Portion of Existing Piers Photo 24. Exposed Portion of Existing Piers 4. Southold Town Code and 2020 Residential Code of New York State The provisions of the 2020 Residential Code of New York State(2020 RCNYS)govern the construction of accessory structure such as a gazebo in conjunction with the local Southold Town Code. Section 144-8 paragraph"c"of the Southold Town Code requires that accessory structure having gross floor area greater than 100 square feet shall require a building permit prior to commencing with the installation work. We understand that the existing Gazebo structure with approximately 360 square feet gross floor area was constructed without such permit. On this regard, to bring the Gazebo structure into compliance with the governing codes and standards,structural drawings prepared by a ® www.ai-alt.com Structural Assessment Report-Gazebo : i7 c 8 AI-ALT File No. 22106.00 August 17, 2022 Professional Engineer registered in the State of New York shall be submitted to the Authorities Having Jurisdiction (AHJ). The existing structural components shall be checked against the loadings in accordance with the "Minimum Design Loads for Buildings and Other Structures" (ASCE 7-16) and other effective standards per 2020 RCNYS to justify its structural adequacy. 5. Structural Requirements for the Legalization of the Existing Gazebo Structural design calculations shall be prepared to substantiate the structural adequacy of the existing Gazebo structure.Any members found to be structurally inadequate shall be remedied and enhanced to ensure their sufficiency to withstand the code required loadings. The Gazebo shall be checked against the following: 5.1.Basis of Design 5.1.1.Structural Design Criteria Codes and Standards a. "2020 Residential Code of New York State" b. "2020 Building Code of New York State" c. "Minimum Design Loads for Buildings and Other Structures" (ASCE 7-16) d. "Building Code Requirements for Structural Concrete" (ACI 318-14) e. "National Design Specifications (NDS)for Wood Construction" (NDS-2018) Live Loads: 40 psf except 60 psf at balcony Snow Loads a. Ground snow load, Pg: 25 psf b. Flat roof snow load, Pf: 20 psf c. Importance factor, Is: 0.8 d. Snow exposure factor, Ce: 0.9 e. Thermal factor, Ct: 1.2 f. Exposure B, Partially Exposed, Risk Category I Wind Loads a. Ultimate Design Wind Speed (Vuit): 118 mph b. Nominal Design Wind Speed (Vasd): 92 mph c. Structural Risk Category: I d. Wind Importance Factor, Iw: 1.0 e. Wind Exposure: B f. Internal pressure coefficient: +/-0.18 ® www.ai-alt.com Structural Assessment Report-Gazebo P la g e 9 AI-ALT File No. 22106.00 August 17, 2022 Seismic Loads a. Site Class: D (Default—Stiff Soil) b. Risk Category: I c. Seismic Design Category: B d. Occupancy Importance Factor, IE: 1.0 e. Design Spectral Response Acceleration at Short Periods,Sos 0.187g Acceleration at 1-Second,SM 0.079g Note:Seismic Design Need not be considered per Section R301.2.2 of 2020 RCNYS. 6. Summary of Recommendations To comply with the requirements of the Southold Town Code and the 2020 RCNYS for this project, the following scope of work shall be carried out: a. Perform structural analysis and design of the as-built Gazebo structure to demonstrate structural adequacy of its structural components to withstand the code required loadings. Prepare remediation details to enhance the capacities of insufficient members, if any. b. Prepare final structural drawings representing the as-built condition of the Gazebo and the enhancement work, if required,which are sufficiently complete and understandable to be submitted for approval to the appropriate reviewing agencies. ® www.ai-alt.com Structural Assessment Report-Gazebo Appendix A-1 AI-ALT File No. 22106.00 August 17, 2022 Appendix A—Wind,Snow and Seismic Loads www.ai-alt.com A This is a beta release of the new ATC Hazards by Location website.Please contact us with feedback. ® The ATC Hazards by Location website will not be updated to support ASCE 7-22.Find out why. OTCHazards by Location Search Information / Zle ``3 � New Lend 1 Address: 3875 Hallock Ln,Mattituck,NY 11952,USA 121 ft Coordinates: 40.9955445,-72.5859632 Sta Montauk Elevation: 121 ft rt c Timestam p: 2022-08-17T 19:38:53.357Z Hazard Type: Wind 'i( Go gMap data©2022 Google ASCE 7-16 ASCE 7-10 ASCE 7-05 MRI 10-Year 76 mph MRI 10-Year 79 mph ASCE 7-05 Wind Speed A 120 mph You are in a wind-borne debris region. MRI25-Year 86 mph MRI25-Year 89 mph MRI50-Year 98 mph MRI50-Year 99 mph MRI100-Year 105 mph MRI 100-Year 109 mph Risk Category 1 118 mph Risk Category 1 124 mph Risk Category 11 127 mph Risk Category II A 134 mph You are in a wind-borne debris region if you are Risk Category III A 136 mph also within 1 mile of the coastal mean high water If the structure under consideration is a healthcare line. facility and you are also within 1 mile of the coastal mean high water line,you are in a wind-borne debris Risk Category III-IV A 144 mph region.If other occupancy,use the Risk Category 11 basic wind speed contours to determine if you are in h the structure under consideration is a a wind-borne debris region. healthcare facility and you are also within 1 mile of the coastal mean high water line,you are in a wind-borne debris region.If other occupancy, Risk Category IV A 141 mph use the Risk Category 11 basic wind speed You are in a wind-borne debris region. contours to determine if you are in a wind-borne debris region. The results indicated here DO NOT reflect any state or local amendments to the values or any delineation lines made during the building code adoption process.Users should confirm any output obtained from this tool with the local Authority Having Jurisdiction before proceeding with design. Please note that the ATC Hazards by Location website will not be updated to support ASCE 7-22.Find out why. Disclaimer Hazard loads are interpolated from data provided in ASCE 7 and rounded up to the nearest whole integer.Per ASCE 7,islands and coastal areas outside the last contour should use the last wind speed contour of the coastal area—in some cases,this website will extrapolate past the last wind speed contour and therefore,provide a wind speed that is slightly higher.NOTE:For queries near wind-borne debris region boundaries,the resulting determination is sensitive to rounding which may affect whether or not it is considered to be within a wind-borne debris region. Mountainous terrain,gorges,ocean promontories,and special wind regions shall be examined for unusual wind conditions. While the information presented on this website is believed to be correct,ATC and its sponsors and contributors assume no responsibility or liability for its accuracy.The material presented in the report should not be used or relied upon for any specific application without competent examination and verification of its accuracy,suitability and applicability by engineers or other licensed professionals.ATC does not intend that the use of this information replace the sound judgment of such competent professionals, having experience and knowledge in the field of practice,nor to substitute for the standard of care required of such professionals in interpreting and applying the results of the report provided by this website.Users of the information from this website assume all liability arising from such use.Use of the output of this website does not imply approval by the governing building code bodies responsible for building code approval and interpretation for the building site described by latitude/longitude location in the report. A This is a beta release of the new ATC Hazards by Location website.Please contact us with feedback. 8 The ATC Hazards by Location website will not be updated to support ASCE 7-22.Find out why. L1TC Hazards by Location Search Information New Haven ° New London a Address: 3875 Hallock Ln,Mattituck,NY 11952,USA Bridgeport 121 ft . Coordinates: 40.9955445,-72.5859632 Stamford o Elevation: 121 ft Riv Timestamp: 2022-08-17T19:53:14.781 Z Hazard Type: Snow k Long island Go gle Map data©2022 Google ASCE 7-16 ASCE 7-10 ASCE 7-05 Ground Snow Load 25 Ib/sqft Ground Snow Load 25 Ib/sgft Ground Snow Load 25 Ib/sqft The results indicated here DO NOT reflect any state or local amendments to the values or any delineation lines made during the building code adoption process.Users should confirm any output obtained from this tool with the local Authority Having Jurisdiction before proceeding with design. Please note that the ATC Hazards by Location website will not be updated to support ASCE 7-22.Find out t why_ Disclaimer Hazard loads are interpolated from data provided in ASCE 7 and rounded up to the nearest whole integer. While the information presented on this website is believed to be correct,ATC and its sponsors and contributors assume no responsibility or liability for its accuracy.The material presented in the report should not be used or relied upon for any specific application without competent examination and verification of its accuracy,suitability and applicability by engineers or other licensed professionals.ATC does not intend that the use of this information replace the sound judgment of such competent professionals, having experience and knowledge in the field of practice,nor to substitute for the standard of care required of such professionals in interpreting and applying the results of the report provided by this website.Users of the information from this website assume all liability arising from such use.Use of the output of this website does not imply approval by the governing building code bodies responsible for building code approval and interpretation for the building site described by latitude/longitude location in the report. A This is a beta release of the new ATC Hazards by Location website.Please contact us with feedback- 0 The ATC Hazards by Location website will not be updated to support ASCE 7-22.Find out why. OTC Hazards by Location Search Information New Haven +� Address: 3875 Hallock Ln,Mattituck,NY 11952,USAi Bridgeport 121 ft U Coordinates: 40.9955445,-72.5859632 Stamford o Elevation: 121 ft R!verhead Timestamp: 2022-08-17T19:53:41.574Z y Hazard Type: Seismic k Long Island Reference Document: ASCE7-16 Go gie Map data 02022 Google Risk Category: I Site Class: D MCER Horizontal Response Spectrum Design Horizontal Response Spectrum Sa(g) Sa(g) 0.25 0.15 0.20 0.15 0.10 0.10 0.05 0.05 0.00 0.00 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Period(s) 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Period(s) Basic Parameters Name Value Description SS 0.175 MCER ground motion(period=0.2s) St 0.05 MCER ground motion(period=l.Os) SMS 0.28 Site-modified spectral acceleration value SMt 0.119 Site-modified spectral acceleration value SDS 0.187 Numeric seismic design value at 0.2s SA SD1 0.079 Numeric seismic design value at 1.0s SA Additional Information Name Value Description SDC B Seismic design category Fa 1.6 Site amplification factor at 0.2s Fv 2.4 Site amplification factor at 1.Os CRS 0.941 Coefficient of risk(0.2s) CRt 0.925 Coefficient of risk(1.0s) PGA 0.095 MCEG peak ground acceleration FPGA 1.6 Site amplification factor at PGA PGAM 0.152 Site modified peak ground acceleration TL 6 Long-period transition period(s) SsRT 0.175 Probabilistic risk-targeted ground motion(0.2s) SsUH 0.186 Factored uniform-hazard spectral acceleration(2%probability of exceedance in 50 years) SsD 1.5 Factored deterministic acceleration value(0.2s) S1 RT 0.05 Probabilistic risk-targeted ground motion(1.0s) S1 UH 0.054 Factored uniform-hazard spectral acceleration(2%probability of exceedance in 50 years) S1 D 0.6 Factored deterministic acceleration value(1.0s) PGAd 0.5 Factored deterministic acceleration value(PGA) The results indicated here DO NOT reflect any state or local amendments to the values or any delineation lines made during the building code adoption process.Users should confirm any output obtained from this tool with the local Authority Having Jurisdiction before proceeding with design. Please note that the ATC Hazards by Location website will not be updated to support ASCE 7-22.Find-out-why. Disclaimer Hazard loads are provided by the U.S.Geological Survey Seismic Design Web Services. While the information presented on this website is believed to be correct,ATC and its sponsors and contributors assume no responsibility or liability for its accuracy.The material presented in the report should not be used or relied upon for any specific application without competent examination and verification of its accuracy,suitability and applicability by engineers or other licensed professionals.ATC does not intend that the use of this information replace the sound judgment of such competent professionals, having experience and knowledge in the field of practice,nor to substitute for the standard of care required of such professionals in interpreting and applying the results of the report provided by this website.Users of the information from this website assume all liability arising from such use.Use of the output of this website does not imply approval by the governing building code bodies responsible for building code approval and interpretation for the building site described by latitude/longitude location in the report.