Dahlke Manor

Dahlke Manor

Engineering Judgment Report

Fire Rating of 3-HR and 2-HR rated assemblies EJ#1

Client Name: Peter Meijer Architect, PC

Client Address: 605 NE 21st Avenue Portland, OR

Date: 3/3/2021

Dahlke Manor – Engineering Judgment Report

R00163-001A Dahlke Manor 3HR rated C_Channel EJ#1-REV0E-FDC.docx codeul.com | 2

Table of Contents 1 Project Overview ........................................................................................................................................ 3

2 Applicable Codes, Standards, and Guides ................................................................................................. 3

3 Discussion .................................................................................................................................................. 3

3.1 Approach ............................................................................................................................................. 3

4 Proposed Design ........................................................................................................................................ 3

5 Assembly Analysis ...................................................................................................................................... 7

5.1 W/D Comparison of C-Channel and W-Beam ...................................................................................... 7

6 Summary .................................................................................................................................................. 11

7 Conclusion ............................................................................................................................................... 11

8 Appendix .................................................................................................................................................. 12



1 PROJECT OVERVIEW

Dahlke is a 9-story residential apartment tower of Type IA construction with a 1-story lower story attached

community space, located in Portland, Oregon serving low-income residents. It will be under the jurisdictional

review of the City of Portland. The proposed scope of work is a 1-story 700 SF addition for a kitchen and break

room associated with the Community Room.

New Structural channels are part of construction scope of work to create openings in existing masonry walls.

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 Engineering Judgment (EJ) letter for the 3-hour protection of

structural channels and 2-hour protection of angle sections supporting floor construction at the existing walls.

2 APPLICABLE CODES, STANDARDS, AND GUIDES

• 2019 Oregon Structural Specialty Code (OSSC)

• 2019 Oregon Fire Code (OFC)

3 DISCUSSION

3.1 Approach

• The proposed beam assembly has been analyzed in accordance with 2014 OSSC §703.3 Alternative

Methods for Determining Fire Resistance.

• The proposed design is compared to the 3-hour fire rated channels per ISOLATEK CAFCO IFRM.

• Portions of the tested assembly are modified to suit the unique design condition. The modification is analyzed

for equivalency using published fire test data and acceptable fire science principles.

4 PROPOSED DESIGN

The proposed assemblies of C12x30, C12x25, and L8x8x3/8 as well as the 1/2" plates & L6”x4"x5/16" (against

ceiling) members are being installed (see Fig 1, 2, 3, 3b, 4 and 5). For this EJ, all of the members will be

examined in detail and compared in a Table against the ISOLATEK designs and all steel members attached to

these C-Channel will be protected. The C-Channel members are considered primary structure. Per 2019

OSSC Table 601, are required to be minimum 3-HR. fire rated for the construction Type. The Angle sections

are roof support members and required to be 2-HR rated per 2019 OSSC Table 601. The L8x8x3/8 assembly

contains a L4x4x3/8 angle section. Protection will be consistently applied to the attached 1/2" plate projections

and L-angle attached to the horizontal beam (See EJ#2). As a conservative measure, the L4x4x3/8 weight will

not be added as part of the complete assembly evaluation. It is assumed that the proposed assembly will be



exposed to fire on the left side and the assembly will require continuous protection from three sides with

shielding on the concealed side (against Concrete or CMU wall) not requiring protection.

Fig 1: C-Channel Locations.

Fig 2: C-Channel C12x30 -3Hr Rating



Fig 3: C-Channel C12x25-3Hr Rating

Fig 4: Angle L8x8x3/8-2Hr Rating

See EJ#2

C12x25 and steel plate combined to be

heated on 4 sides



Fig 4b: Proposed assembly of wall plate.-2Hr

Fig 5: Angle L6x4x5/16-2Hr Rating

See EJ#2 for

IFRM Protection

L6x4x5/16

Protected by 2 Hr

See EJ#2

for IFRM

Protection



5 ASSEMBLY ANALYSIS

The proposed assembly of C-Channel C12X25 and C12x30 is intended as a primary structural member. The

proposed assembly of angles L8x8x3/8 and L6x4x5/16 are intended as a secondary structural member.

Compared to the C10x30 member in the ISOLATEK CAFCO assembly as shown in figure 6.

Figure 6: ISOLATEK CAFCO WB3-4 Protection

5.1 W/D Comparison of C-Channel and W-Beam

The proposed assembly has an inherent fire resistance greater than the tested beam, W/D comparison:

1.01>0.96. We have compared the beam as proposed along with the test configuration. See Fig. 6 and 7

below.

C10x30 ASTM

W/D Ratio = 0.96

Heated Perimeter of C12”x25

C-Channel Total Heated Perimeter = 23.0

Weight per foot from Figure 6

Calculated W/D Ratio = 1.08



Heated Perimeter of C12”x30

C-Channel Total Heated Perimeter = 23.5”

Weight per foot from Figure 6


Heated Perimeter of 1/2"x12"x2' plate against wall (Fig. 4b)

Steel Plate = 12+(2)1/2” =13

Total Heated Perimeter = 13”

Weight per foot =20.4 lb/ft


Heated Perimeter of L8”x8”x3/8”

Angle Iron = 2*(8”+3/8”)

Total Heated Perimeter = 16.75”

Weight per foot (20.1lb/ft) from Figure 7


Heated Perimeter of L6”x4”x5/16”

Angle Iron = 6+5/16”


Weight per foot (10.3lb/ft)


Heated Perimeter of Combined C12x25 & 1/2"x16"x1'9” knife plate (Fig. 3)

Steel Plate = 16+1/2”+8=24.5

C12x25 (exposed) 35”-8=27


Weight per foot (27.13 + 25) =52.13 lb/ft




Fig.7. C-Channel Dimensions



Fig.8. Weight of L8x8x3/8”

Member Weight(lb/ft) Perimeter D (in) W/D Mils

C10x30 30 28.8 (3 Sides-Beam) 0.96 324

C12x25 25 23.0 (3 Sides) 1.08 324

C12X30 30 23.5 (3 sides) 1.28 324

C12x25 &

12x16x1/2”

Knife Plate

52.13 51.5 (4 sides) 1.01 324

12x12 1/2”

Wall Plate (2-Hr)

20.4 13 (3 sides) 1.56 157

L8x8x3/8 (2-Hr) 20.1 16.75 (2 sides) 1.2 157

L6x4x5/16 (2-Hr) 10.3 6.315 (1 side) 1.63 157

Table.1. W/D ratios

Evaluated against the Isolatek published rating table (Fig.6), the proposed steel assemblies have larger W/D

ratios than the C-channel in the tested configuration. Additionally, the members will be partially concealed and

most are attached directly to a concrete wall that will act as a heat sink, which will extend the time to heat the

member to failure per ASTM E119 criteria.



6 SUMMARY

While evaluating fire resistance requirement of members, different sized beams are compared against each

other through a factor referred to as the W/D Ratio. The weight per unit length of a member is divided by the

length of exposed heated perimeter area to determine the inherent fire resistance of a member. Lower W/D

ratios correspond with thinner steel members that will be subject to earlier failure when heated.

During this evaluation, ISOLATEK CAFCO IFRM protection of miscellaneous shapes was included, where the

minimum required W/D ratio (0.96) of the C-Channel in the assembly is less than the proposed (calculated)

minimum member W/D ratio (1.08). The tested C-Channel requires 324 MILS (Fig. 6) of intumescent protection

to provide 3-hour fire-resistance (Figure 6). The proposed C-Channel has greater inherent fire-resistance

because of a large W/D ratio and is only heated from 3 sides as opposed to 4 in the compared design.

Protection thickness is provided for 3Hr. Also, the 1/2"x16"x1'9” knife plate connected to the C12x25 as a

combined assembly in Table 1.

The angle sections L8x8x3/8 & L6"x4"x5/16" are only required to be 2-HR rated, this requires 157 MILS (Fig. 6)

of intumescent protection.

Note: Any GWB provided in the field over the assembly will increase the overall rating of the assemblies.

HSS-4x4x5/16” Stongback protection to be prescriptively protected as a primary support member (3 hours per

Table 601. (No EJ Required) per X790. (See Appendix below)

7 CONCLUSION

When the steel ledger/beam assemblies are protected with Intumescent paint as listed in Table 1 above, the

assemblies evaluated in the letter will meet the 2 or 3 hour requirements for fire-resistance per the OSSC.

Franklin Callfas

Principal/Fire Protection Engineer

Code Unlimited



8 APPENDIX

HSS-Post Protection

UL Design-SFRM for HSS Strong Backs

Documents

Dahlke Manor