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DAHLKE MANOR (EJ #2)
Engineering Judgment Report
Fire Rating of 6" x 6" x 3/8" HSS Member
Client Name: Peter Meijer Architect, PC
Client Address: 605 NE 21st Avenue, Portland, OR 97232
Date: 3/3/2021
Engineering Judgment Report
R00163-001A Dahlke Manor HHS Beam EJ #2-Rev1d.docx codeul.com | 2
Table of Contents 1 Project Overview ........................................................................................................................................ 3
2 Applicable Codes, Standards, and Guides ................................................................................................. 4
3 Approach .................................................................................................................................................... 4
4 Proposed Design ........................................................................................................................................ 4
5 Assembly Analysis ...................................................................................................................................... 7
5.1 W/D Comparison of HSS and W-Beam ............................................................................................... 9
5.2 Evaluation ........................................................................................................................................... 9
6 Conclusion ............................................................................................................................................... 11
Engineering Judgment Report
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1 PROJECT OVERVIEW
Dahlke Manor is an existing 9-story residential apartment building located at 915 NE Schuyler St, Portland. The
building has approximately 115 apartments and is of Type IA construction. There is also a 1-story portion on the
west side of the building including the main lobby, maintenance room(s), and amenity space.
Planned renovation work includes a small extension, upgrading of the finishes, and the installation of new HSS
6x6x3/8 structural beams in the lobby [Figure 1]. These beams will support the existing roof structure in locations
of proposed new openings. Existing walls are 8" hollow brick masonry or 8" hollow concrete block and meet 3-
hour minimum rating for Type 1A construction. The existing ceiling structure is 4 1/2" concrete slab above
concrete pre-block and beam system, providing a 2-hour rated assembly. See Appendix A for original permit
drawings and photo of existing ceiling structure for reference of the existing structure.
Code Unlimited has been asked to provide an Engineering Judgment (EJ) letter for this condition.
Figure 1: Proposed locations of the new HSS 6”X6”X3/8” beams
Engineering Judgment Report
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2 APPLICABLE CODES, STANDARDS, AND GUIDES
• 2019 Oregon Structural Specialty Code (OSSC)
• 2019 Oregon Fire Code (OFC)
3 APPROACH
• The proposed assembly has been analyzed in accordance with 2019 OSSC §833.3 Alternative Methods
for Determining Fire Resistance.
• We have evaluated the proposed beam assemblies against a fire rated beam assembly tested by
Underwriters Laboratories (UL N614).
4 PROPOSED DESIGN
The primary function of the HSS members is to support the existing roof of the lobby. Intumescent protection will
be provided. The proposed member assembly consists of 6x6x3/8 HSS sections. There are two beams, one
supported by an L-Ledger and - one beams will be bolted with a flat steel plate to the exterior CMU wall with the
connection (See EJ#1) and beam both being protected with a minimum thickness of 115 Mils intumescent
coating on all sides.
Figure 2: Proposed assembly of 6" x 6” x 3/8” HSS sectional view.
Engineering Judgment Report
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Figure 3a: Proposed assembly of 6" x 6” x 3/8” HSS
Figure 3b: Proposed assembly of 6" x 6” x 3/8” HSS.
See EJ#1 for IFRM Protection
See EJ#1 for
IFRM Protection
L6x4x5/16
Protected by 2 Hr
Engineering Judgment Report
R00163-001A Dahlke Manor HHS Beam EJ #2-Rev1d.docx codeul.com | 6
Figure 3c: Proposed assembly of 6" x 6” x 3/8” HSS.
See EJ#1
for IFRM
Protection
Engineering Judgment Report
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5 ASSEMBLY ANALYSIS
The proposed assembly of HSS 6” x 6” x 3/8” is an alternate to the W6x25 used in the test assembly N614 as
shown in Figure 3. The proposed design and UL N614 are compared in Table 1.
See Evaluation Section
Engineering Judgment Report
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Figure 4: UL N614 Assembly
Engineering Judgment Report
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Table 1: Comparison between Tested and Proposed beam assembly
Element UL Assembly Design No. N614 Proposed Assembly
Steel Member • W6 x 25 (W/D=0.83) • HSS 6x6x3/8” (W/D=1.13
(4-sided protection)
Exceeds tested
Normal Weight Concrete
• 146 pcf
• Existing roof construction
Steel Floor and Form Units
• 1-1/2, 2, 3 in. fluted type, welded to beam.
• N/A to review
Intumescent Coating
• IFRM thickness 115 Mils • Spray thickness 115 Mils
Fire-Resistance Rating
• 2-Hour • 2-Hour (minimum)
5.1 W/D Comparison of HSS and W-Beam
W/D ratios provide a means of evaluating different structural members for the purpose of fire protection rated
resistance. Larger W/D Ratios intuitively provide a longer resistance to temperature rise and failure through
excessive heating per SFPE Handbook. The larger the W/D ratio (or A/P with HSS member), the fewer fire
protection layers need to be added to achieve the required fire resistance rating.
5.2 Evaluation
The listed wide flange structural steel beam with ASTM designation W6x25 (Heated on 3 sides), has a W/D
ratio of 0.83, with 2-hour fire rating as shown in Figure 5. The proposed assembly of HSS 6” x 6” x 3/8” has
W/D ratio of 1.13(4-sided exposure), as shown in figure 6. The UL design includes Mineral Wool stuffed above
flutes in the steel concrete form to protect against any gaps at the top of beam. The project has elected to
protect the HSS members with IFRM on all sides with a reduced W/D ratio as shown in Fig. 6.
Engineering Judgment Report
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Figure 5: W/D ratio for W6x25
Figure 6: W/D ratio for HSS 6” x 6” x 3/8” (Protected on 4-sides)
The HSS member has an inherent fire resistance greater than the tested W beam. W/D comparison:
1.13 > 0.83.
Engineering Judgment Report
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6 CONCLUSION
When evaluated the proposed steel tube beam has a higher W/D ratio and provides greater heat resistance
than the UL tested beam. Intumescent protection will provide protection for the beam protected on all sides.
Therefore, the proposed design for the HSS members in the lobby will maintain the required 2-hour rating as
compared and detailed in this letter against the UL fire assembly, while maintaining a minimum 2-hour rating
required for floor support per OSSC Table 601.
Franklin Callfas
Principal/Fire Protection Engineer
Code Unlimited