Overton-15 3-hour Horizontal Assembly

Overton-15 3-hour Horizontal Assembly

Engineering Judgement Report

Client Name: Vallaster Corl Architects

Client Address: 711 SW Alder St, Portland, OR 97205

Date: 2/10/2019

3-hour Horizontal Assembly Engineering Judgement Report

Code Unlimited LLC [2] www.codeul.com

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

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

3 Discussion ..................................................................................................................................................... 4

3.1 Approach ................................................................................................................................................ 4

4 Proposed design ............................................................................................................................................ 4

5 Assembly Analysis ......................................................................................................................................... 6

5.1 ASTM E119 Criteria ............................................................................................................................... 6

5.2 Fire-Resistance Analysis ........................................................................................................................ 6

6 Summary ..................................................................................................................................................... 10

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



1 PROJECT OVERVIEW

Vallaster Corl Architects are designing a new 7-story residential building in Portland, Oregon. The project includes 5-stories of Type III-B construction over 2 stories of Type IA construction. The building is protected by automatic fire sprinkler system and fire alarm system throughout.

Structural members of Type IA construction that have direct connections to columns are considered primary structural members per §202 of the 2014 OSSC. Primary structural members are required to be 3-hour fire rated per Table 601. Currently, a structural beam is protected for 2-hours per UL design D503 in the Type IA floor assembly of the building. Code Unlimited has been asked to provide analysis of adding protection to the existing UL assembly to increase the fire rating to a 3-hour minimum fire-resistance.

2 APPLICABLE CODES, STANDARDS, AND GUIDES

2014 Oregon Structural Specialty Code (OSSC), including the recently adopted Appendix N which references the International Fire Code.



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 horizontal assembly is currently installed per UL D503 and is protected for a 2-hour fire rating. Fire-resistance of the assembly will be increased through the addition of 1 layer of 5/8” thick gypsum board.

It is analyzed to ensure a minimum of 3-hour fire-resistance is provided using published fire test data and acceptable fire science principles.

4 PROPOSED DESIGN

The proposed design consists of 4½” minimum normal-weight concrete (6” maximum thickness), steel decking and framing, steel framing at suspended ceiling, and 2 layers of 5/8” thick Type C gypsum board (Figure 1). This existing assembly is installed per UL D503 (2-hour fire rating). It will be modified with the addition of 1 layer of 5/8” Type C gypsum wallboard (GWB). Where the assembly is located over parking garages (Figure 3), 4” maximum of extruded polystyrene insulation (XPS) and 2 additional layers of 5/8” thick Type C gypsum boards are added to the base of the assembly (Figure 2). The protection of the of the horizontal assembly is continuous, to also provide protection at vertical connections. The structural beam is directly connected to columns and is therefore considered as a primary structure. Per 2014 OSSC Table 601, the primary structure is required to be minimum 3-hour fire rated. The proposed design provides a ceiling at height about 9 ft above the finished floor, which provides context for the proximity of fire exposure from below.

Figure 1: 3-hour fire-rated proposed beam assembly located at retail and lobby areas.



Figure 2: 3-hour fire-rated proposed beam assembly located over parking garages.

Figure 3: Framing plan to show the application of the proposed beam assembly where the red hatch delineates the application of the assembly shown in Figure 1 (retail and lobby areas) and the blue

hatch delineates the application of the assembly in Figure 2 (over parking garages).



5 ASSEMBLY ANALYSIS

5.1 ASTM E119 Criteria

The proposed assembly must provide protection for primary structural members. Protection is based on maintaining the criteria for testing fire rating of unrestrained beams established in ASTM E119 for a minimum of 3 hours. The criteria for support beams is that the temperature of steel members shall not exceed 1300 ºF (704 ºC) at any single point nor an average temperature of 1100 ºF (593 ºC).

5.2 Fire-Resistance Analysis

§704.3 permits rated membrane protection for primary structure other than columns, that do not support more than two floors or one floor and roof or support a load-bearing walls or a nonload-bearing wall more than two stories high. The proposed beam supports a single floor level only and no walls.

UL G512 is a 3-hour rated assembly where a structural beam is protected by membrane protection only. The test details protection adequate such that the structural beam does not reach an average temperature of 1100 ºF (593 ºC) or 1300 ºF (704 ºC) at any point for 3 hours given the installation of the assembly per UL G512 testing. The proposed structural beam, including the additional layer of protection provided by the layer of Type-C GWB, is compared below to the 3-hour fire rated unrestrained beam, UL G512 (Figure 4).



Figure 4: UL G512.



Table 1: Comparison between Tested and Proposed beam assembly

Element UL Assembly Design No. G512 Proposed Assembly (Figure 1)

1. Structural Material

Steel Beam: W8x35 minimum Steel Beam: W12x19 minimum

(Exceeds minimum depth)

2. Concrete type

Normal-Weight Concrete — Carbonate or siliceous aggregate, 150 + or - 3 pcf unit weight 4500 psi compressive strength.

Normal Weight Concrete — Normal weight concrete, carbonate or siliceous aggregate, 152 ± 3 pcf unit weight, 4000 psi compressive strength. Concrete thickness above top of steel floor units minimum 4-1/2 in.

(Exceeds minimum)

3. Steel Framing

Welded Wire Fabric — 6X6 — W1.4XW1.4.

Metal Lath — 3/8-in. rib, 3.4 lb/sq yd expanded steel; tied to each joist at every other rib and midway between joists at side lap, with 18 SWG galv steel wire. As an alternate, the form material for the concrete may be corrugated steel deck, 9/16 in. deep, of 28 MSG (min) galv steel, welded to supports 15 in. O.C. with welding washers. The concrete thickness shall be measured to the top plane of the steel deck. Corrugated steel deck to be used with Type 16K4 or larger joists only.

Steel Joists — Type 12J2 min size; spaced 24 in. O.C. and welded to end supports. Min size of joists for use with corrugated steel deck forms is 16K4.

Bridging — 1/2-in. diam continuous steel bar stock; welded to top and bottom chords of each joist.

Furring Channels — Min 0.020 in. thick (25 gauge) galv steel, 2-9/16 in. or 2-11/16 in. or 2-23/32 in. wide at top and 1-3/4 in. wide at bottom by 7/8 in. deep; spaced 24 in. O.C., perpendicular to joists, except at wallboard end joints as noted below. Two courses of furring channel positioned 6 in. O.C., 3 in. on each side of wallboard end joints. Channels secured to each joist with 18 SWG galv steel wire bent into double strand saddle ties. Channels spliced with adjoining pieces overlapped 6 in. and tied together with strand of 18 SWG galv steel wire at each end of overlap.

Steel Floor Units — Min. 2 in. deep, min. 20-gauge galv fluted steel floor units welded to supports. Welds spaced 12 in. OC. Supports spaced max. 10 ft OC. See Steel Floor and Form Units (CHWX) Category for names of manufactures.

Hanger Tab — No. 18 GSG galv steel, 2 in. wide by 3-1/2 in. long, hooked at one end for attachment over male side joint of floor units; other end provided with hole for attachment of hanger wire. Spaced alongside joints of floor units as required for hanger wire locations.

Hanger Wire — No. 12 SWG galv steel wire. Hanger wires spaced not over 48 in. O.C. along main runners and located at ends of main runners at walls.

Steel Framing Members — Main runners nom 12 ft long spaced 48 in. OC. Cross tees nom 4 ft long installed perpendicular to main runners and spaced 24 in. OC. Additional cross tees located 8 in. from and on both sides of each wallboard end joint.

Wall Angle — (Not Shown) — No. 26 MSG angle with 1-1/8 in. legs, nailed to the walls along perimeter of ceiling to support steel framing member ends and for screw-attachment of the gypsum wallboard.

(See summary below)



Element UL Assembly Design No. G512 Proposed Assembly (Figure 1)

4. Gypsum Board

(1) layer 5/8 in. thick 4 ft wide Type C gypsum board; installed with long dimension perpendicular to furring channels and side joints located midway between joists. Wallboard fastened to furring channels with 1 in. wallboard screws spaced 12 in. OC, 1-1/2 in. and 3 in. from butted side and end joints, respectively. End joints attached to double channels and protected on top with 2-3/4 in. wide strips of thick wallboard with joints of strips staggered 8 in. from side joints of the wallboard sheets. End joints of the sheets may be continuous or staggered and similarly fastened to double furring channels that extend 3 in. beyond each end of joint, and which are wire-tied to bottom chord of joists.

Screw, Wallboard — No. 6 Phillips-type, self-drilling and self-tapping, 1 in. long. Screw heads may be either exposed or covered with joint cement.

Finishing System — (Not Shown) — Wallboard joints may be either exposed or covered with fiber tape and joint compound, except where required for specific edge configuration. For tapered, rounded-edge wallboard, joints covered with fiber tape and joint compound. As an option, nom 3/32 in. thick gypsum veneer plaster may be applied to the entire surface of gypsum board. Joints reinforced.

(2) layers 5/8 in. thick, 4 ft wide Type C gypsum board, installed with long dimension perpendicular to cross tees with side joints centered along main runners. Wallboard fastened to each cross tee with five wallboard screws with one screw located at the mid-span of the cross tee, one screw located 12 in. from and on each side of the cross tee mid-span, and one screw located 1-1/2 in. from each wallboard side joint. Except at wallboard end joints, wallboard screws shall be located on alternating sides of cross tee flange. At wallboard end joints, wallboard screws shall be located 1/2 in. from the joint. Wallboard fastened to main runners with wallboard screws, 1/2 in. from side joints midway between intersections with cross tees (24 in. OC) End joints of adjacent wallboard sheets shall be staggered not less than 4 ft OC. Wallboard sheets screw-attached to leg of wall angle with wallboard screws spaced 12 in. OC.

Screw, Wallboard — Type S-12, 2 in. long, self-drilling and self-tapping, 0.163 in. thread diam, 5/16 in. diam heads.

Finishing System — (Not Shown) — Paper tape embedded in compound over joints and covered with additional compound. Exposed screw heads covered with compound. Edges of compound feathered out.

(Exceeds Minimum)

Fire Resistance

3-hours 3-hours (minimum)



6 SUMMARY

Primary Structural member (Beams) require protection for 3 hours per OSSC Table 601. §704.3 allows membrane protection to meet the protection requirements when the beams are not supporting a load bearing wall.

The basis of analysis of the proposed design is establishing that the horizontal assembly currently installed is 2-hour fire rated per UL D503. The ASTM E119 testing criteria requires maximum temperature to not exceed 1300 ºF at any point along the beam, or a maximum average temperature of 1100 ºF, during the 2-hour test. This is the failure criteria for the protection of the steel member and must be maintained through our analysis.

The fire-resistance of the proposed restrained beam will be 3 hours with the additional layer of 5/8” thick Type-C gypsum board. This is a conservative evaluation as restrained beams require less fire protection. They are less likely to fail during heating than unrestrained members which will deform or twist without restraint to building columns or concrete floor attachment.

The fire protection is to be continuous and provide protection horizontally and at vertical faces of mezzanine (GWB required wrap to floor elevation above-See attachments). This is compared against the fire rated unrestrained beam tested by Underwriter Laboratories. The UL rated assembly UL G512 (Figure 4) provides 3-hour fire rating to an unrestrained beam that utilizes (1) layer of 5/8” thick Type C gyp board membrane protection at the base of the assembly. Table 1 demonstrates the equivalency between the UL G512 assembly and the proposed design in the assembly components, where equivalent fire-resistance is achieved by addition of 5/8” thick Type C gyp board. Noted differences between the proposed and UL G512 assembly are the following: The floor assembly is 2” thicker than the tested, with the support beam directly under the slab (added heat dissipation for the beam). A deeper cavity will be provided with a minimum W12” beam vs W8” minimum for the UL design, extending the volume of air in the cavity. Additionally, the G512 assembly utilized clips directly attached to bar joists. The currently installed D503 assembly does not have the structural rigidity (bar joist and clips) of (G512) support, therefore a conservative tradeoff is used by adding the GWB layer. The additional layer of Type-C GWB adds rigidity to the ceiling system and additional fire protection to the assembly by doubling the GWB protection.

The ceiling System over the parking garage (Figure 2) will utilize the same principles for fire resistance as identified above, but will install 3 total layers of Type C GWB, two beneath the rigid insulation, below the existing 2-hour D503 assembly (fig. 2).

Type C—proprietary gypsum board—has a composition of glass fibers, shrinkage-compensating additives, and chemically bonded water molecules. When exposed to fire, the composites come into play in providing additional protection when compared to that of a Type X gyp board or a generic fire rated gypsum board. The glass fibers in the Type C increase the fire resistance of the wallboard by reducing the extent of cracks during the exposure of a fire. At high temperatures, the gypsum core shrinks due to water depletion and the shrinkage-compensating additives expand at about the same rate. Lastly, the chemically bonded water extends the fire-resistance of the gyp board by cooling down the membrane when exposed to fire. The additional composites in Type C gyp boards, as well as the contribution of Type C boards to the fire-resistance of fire rated assemblies, provides the justification that the addition of 1 layer of 5/8” thick Type C gyp board to the existing permitted primary structure will provide a minimum of 3-hour fire-resistance



7 CONCLUSION

Code Unlimited has reviewed the proposed protection of the restrained structural beam against the fire rated design UL G512. As demonstrated in Sections 5 and 6 of this report, the proposed assembly equivalency to UL G512 with a minimum of 2 layers of 5/8” thick Type C gypsum board attached to the base of the proposed assembly will provide the required fire-resistance, while compensating for the differences in GWB support system. The proposed design will comply with the required 3-hour fire-resistance per Table 601 of the 2014 OSSC, for protection of a primary structural beam member in Type IA construction.

The addition of (1) 5/8” thick Type C gyp board is based on the established 2-hour fire rating of the existing assembly per (UL D503) and meets 3-hour unrestrained beam protection (UL G512) through equivalency. The precedent of the additional fire rating is detailed through the Type C GWB contribution to numerous (2 and 3 hour) UL fire rated assemblies.

Therefore, the proposed design, when installed as detailed above, as evaluated in this report will provide a minimum 3-hour fire-resistance for the restrained beam as required by OSSC.

Franklin Callfas Principal/Fire Protection Engineer Code Unlimited

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