HomeMy WebLinkAboutFile Documents.121 E Hyman Ave.0149.2018 (83).ARBK WILSON STRUCTURAL ENGINEERING,
INC.
March 4th, 2020
Mr. Bob Horenn
Durango, Colorado !MOM970-247-1601<infoCa�bhstair.com> 2021
Re: Cayton Residence Stairs, Aspen, Colorado
WSE Proj. #: 01420 justinh
Dear Mr. Horenn:
At your request, we have analyzed the glass guards of the Grid 5 stairs and the stairs to
roof for the Cayton residence. The following is a list of assumptions that were made in our
structural analysis:
Design Criteria (per Table R301.5 of the 2015 International Residential Code):
• Concentrated Load = 200Ibs any direction, any location along top
• Uniform Load = 50p1f perpendicular to glass at top
• Load of 50Ibs on 1 square foot at any location on glass
• Height to top of glass or handrail = 36"
Laminated Tempered Glass Guards and Connections Minimum Requirements:
• The laminated tempered glass guards have the minimum design values:
► Modulus of Rupture Fr = 24,000psi (6,000psi allowable, using factor of safety of 4
per IRC)
► Material complies with Category II or CPSC 16 CFR Part 1201 or Class A of ANSI
Z97.1
• Each full segment of glass is engaged when the live loads are applied.
• The lag screws for connecting the guards have the minimum design values:
► Steel tensile strength = 60,000psi
• The lag screws meet the minimum size, embedment lengths, and spacing requirements
shown in the attached calculations.
• The glass standoffs (CRL #RSOB2134BS), handrails, connections, and base shoes with
taper-locs (CRL #9BL68D & CRL #LT96X) are located as described in the stair
drawings provided by B&H Stair.
• Per the ICC-ES evaluation report#ESR-3842, the glass standoffs (CRL
#RSOB2134BS), handrails, connections, base shoes with taper-locs (CRL #9BL68D &
CRL #LT96X), and weld blocks (CRL #LSWB21) used for this design are adequate to
resist the minimum required applied loads (listed above).
• Where handrails are used, there shall be a minimum of 2 handrail connection brackets
at each piece of glass (bracket locations by others shall meet spacing requirements
shown in ICC-ES evaluation report#ESR-3842).
• The existing stair, floor, and wall structure is adequate to support and resist all the
minimum required applied loads (listed above) from the glass guards and are of a size
to achieve the lag screw spacing and penetration shown in the attached calculations.
• The existing wood structural members have a specific gravity of 0.50 or greater.
48 County Rd. 250•Durango, CO 81301 • (970) 385-6774
Conclusion:
We found that the glass guards and connections require the following criteria to support the
minimum required applied live loads listed above:
• Glass thickness shall have a minimum nominal thickness of 0.6875" (11/16").
• For sections of glass without a top-rail or handrail connecting them, the minimum panel
width shall be 40". NOTE: There is one section of glass that is approximately 8" wide at
the uppermost stair landing that is exempt from the minimum width of 40". Provided it is
connected to the existing wall on one side with a piece of C.R.Laurence hardware either
continuously or within 12" from the top of the glass, and connected to the adjoining
section of glass with a piece of C.R. Laurence hardware within 12" from the top of the
glass.
• The base shoes will be connected to weld blocks per C.R.Laurence specifications, and
the weld blocks shall be spaced @ 12"o.c. as shown in the attached calculations and
connected to a continuous steel plate per C.R.Laurence specifications.
• The continuous steel plate shall be 6" wide x 5/16" thick grade A36 steel and shall be
connected to the existing wood floor/wall structure with lag screws as shown in the
attached calculations.
• Lag screws shall have a minimum thread penetration (not including tip) into the existing
wood floor/wall structures of 4".
Please do not hesitate to call if you or others wish to discuss these findings.
Respectfully,
444 4.4.
David L. Wilson, P.E.
Principal
48 County Rd. 250•Durango, CO 81301 • (970) 385-6774
WILSON STRUCTURAL ENGINEERING, INC.
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