DAHLKE MANOR (EJ #2)

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


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



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



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.



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



Figure 3c: Proposed assembly of 6" x 6” x 3/8” HSS.

See EJ#1

for IFRM

Protection



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



Figure 4: UL N614 Assembly



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.



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.



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

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DAHLKE MANOR (EJ #2)