Fire Resistive Design of Exposed Timber Structures.ppt ...€¦ · Structures • Fire Resistive types of exposed wood members ... masonry walls shall have a fire-resistance rating

Fire Resistive Design of ExposedFire Resistive Design of Exposed Timber Structures

Heavy Timber & One Hour FireHeavy Timber & One Hour Fire Rating

Paul C. Gilham, P.E., S.E.Western Wood Structures IncWestern Wood Structures, Inc.

“Th W d P d t C il” i R i t d P id ith Th“The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members Certificates of Completion for both AIAAIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

This program is registered with AIA/CES for continuing professionalThis program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, y g gdistributing, or dealing in any material or product.

Questions related to specific materials, methods, and services willQuestions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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© The Wood Products Council 2012© The Wood Products Council 2012

Fi R i ti D i f E d Ti bFire Resistive Design of Exposed Timber Structures

Learning Objectives1. Learn where exposed timber fire resistive construction is allowed in the

IBC. 2. Learn the characteristics of Heavy Timber Construction y3. Learn the methods of obtaining 1 hour fire resistive rating for exposed

timber members using IBC section 721.6.3 4 Learn the methods of obtaining 1 hour fire resistive rating for exposed4. Learn the methods of obtaining 1 hour fire resistive rating for exposed

timber members using NDS chapter 16

Fire Resistive Design of Exposed Timber Structures


Fire Resistive Design of Exposed TimberFire Resistive Design of Exposed Timber Structures

• Fire Resistive types of exposed wood members– Heavy Timber Construction

B k d f H Ti b C i• Background of Heavy Timber Construction• Minimum Sizes• Connections• Approved Uses

– One Hour Fire Rated Wood Members• IBC section 721.6.3• Details• NDS Chapter 16• Examplesp


IBC Construction Types (IBC 602)

Type I & Type II– Non-combustible materials except as permitted in section 603

i ll b ibl i l i iType III – Exterior walls are non-combustible materials, interior building elements are of any material permitted by the code. (Allows FRT framing in exterior walls)

Type IV – Exterior walls are non-combustible and interior building elements are solid or laminated wood without concealed spaces. (Allows FRT framing in exterior walls and 1-hour assemblies in interior partitions.)

Type V – Structural elements, exterior walls and interior walls are of any materials permitted by the code.y p y

Heavy Timber Construction

• Background of heavy timber construction.“Heavy-timber construction,” as applied to buildings, means that in

which walls are of approved masonry or reinforced concrete; And in which the interior structural elements, including columns, floors and roof construction, consists of heavy timbers with smooth flat

f bl d t id thi ti h j ti dsurfaces, assembled to avoid thin sections, sharp projections and concealed spaces; And which all structural members which support masonry walls shall have a fire-resistance rating of not less than three hours; And other structural members of steel or reinforcedthree hours; And other structural members of steel or reinforced concrete, if used in lieu of timber construction, shall have a fire resistance rating of not less than one hour.”

1943 national building code1943 national building code.

Heavy Timber ConstructionMinimum size of members (IBC table 602.4)

Member Nominal Solid Sawn GLULAMMember Nominal Solid Sawn GLULAM

Columns

Supporting Floor 8x8 7½” x 7½” 6¾” x 8¼”

Supporting Roof 6x8 5½” x 7½” 5” x 8¼”

BeamsFloor 6x10 5½” x 9½” 5” x 10½”Floor 6x10 5½ x 9½ 5 x 10½Roof 4x6 3½” x 5½” 3” x 7½”

Arches springing from floorfloor

Supporting floor 8x8/8x8 7½” x 7½” 6¾” x 9”

Not supporting floor 6x8/6x6 5½” x 7½”/5½” 5” x 8¼”/6”

Arches springing from top of wall

4 x 6 3½” x 5½” 3” x 6 7/8”

TTrusses

Floor 8x8 7½” x 7½” 6¾” x 9”Roof 4x6 3½” x 5½” 3” x 6 7/8”

Heavy Timber Construction• Floors.

– Without concealed spaces.– Sawn or glued-laminated planks, T&G or splined of not less than 3 in.

nominal, covered with 1” T&G laid crosswise or diagonally or 15/32” wood structural panels.

l k l h i i l d l h ll ik d ( il– Planks not less than 4 in. nominal on edge close together, well spiked (nail laminated) with 1” flooring or 15/32” wood structural panels.

– The lumber shall be laid so that no continuous line of joints will occur i fexcept at points of support.

– Floors shall not extend closer than ½ inch to walls. Such ½ inch space shall be covered by a molding fastened to the wall and arranged so that it

ill b h lli d h i ki f h flwill not obstruct the swelling and shrinking movements of the floor. Corbeling of masonry walls under floors may be used in place of of such molding.


• Roofs.– No concealed spaces.– Sawn or glued-laminated plank, T&G or splined not less than 2 in.

nominal or 1 1/8” wood structural panels or 3 in. nominal on edge close together, well spiked (nail laminated).

– Laid as required for floors


• Partitions– Of solid wood construction formed by not less than two layers of

1 i h t h d b d1-inch matched boards or – Laminated construction 4” thick– 1-hour fire resistance construction

– Where code provisions require fire separation such as at a corridor, 1-hour fire resistive construction must be used.

Heavy Timber Constructiony• Construction Details.

– Approved wall plate boxes or hangers at walls.pp p g– Girders & beams shall fit closely around columns and

adjoining ends shall be cross tied to each other or intertied by caps or ties.intertied by caps or ties.

– Where intermediate beams are used to support a floor, they shall rest on top of girders or shall be supported by ledgers or blocks securely fastened to the sides of theledgers or blocks securely fastened to the sides of the girders , or they may be supported by approved metal hangers into which the beams shall be closely fitted.E f i d d l h f b– Every roof girder and at least every other roof beam shall be anchored to its supporting member.

– Roof decks supported by a wall shall be anchored every pp y y20’ max.

Scappoose High School Gym

Mighty Ducks Ice Arena, Anaheim, CA

Lemay America’s Car Museum – Tacoma, WA

Port of Portland – Terminal 5

Table 503

Allowable Building Heights and Areas

Type of Constructionyp C

Type I Type II Type III Type IV Type V

A B A B A B HT A BH i ht (ft) UL 160 65 55 65 55 65 50 40Height (ft) UL 160 65 55 65 55 65 50 40

Group Stories (S)/Area(A)A-1 S UL 5 3 2 3 2 3 2 1

A UL UL 15,500 8,500 14,000 8,500 15,000 11,500 5,500A-2 S UL 11 3 2 3 2 3 2 1

A UL UL 15,500 9,500 14,000 9,500 15,000 11,500 6,000, , , , , , ,A-3 S UL 11 3 2 3 2 3 2 1

A UL UL 15,500 9,500 14,000 9,500 15,000 11,500 6,000A-4 S UL 11 3 2 3 2 3 2 1

A UL UL 15,500 9,500 14,000 9,500 15,000 11,500 6,000A-5 S UL UL UL UL UL UL UL UL UL

A UL UL UL UL UL UL UL UL ULB S UL 11 5 3 5 3 5 3 2B S UL 11 5 3 5 3 5 3 2

A UL UL 37,500 23,000 28,500 19,000 36,000 18,000 9,000E S UL 5 3 2 3 2 3 1 1

A UL UL 26,500 14,500 23,500 14,500 25,500 18,500 9,500F-1 S UL 11 4 2 3 2 4 2 1

A UL UL 25,000 15,500 19,000 12,000 33,500 14,000 8,500F-2 S UL 11 5 3 4 3 5 3 2F 2 S UL 11 5 3 4 3 5 3 2

A UL UL 37,500 23,000 28,500 18,000 50,500 21,000 13,000H-1 S 1 1 1 1 1 1 1 1 NP

A 21,000 16,500 11,000 7,000 9,500 7,000 10,500 7,500 NPH-2 S UL 3 2 1 2 1 2 1 1

A 21,000 16,500 11,000 7,000 9,500 7,000 10,500 7,500 3,000H-3 S UL 6 4 2 4 2 4 2 1

A UL 60,000 26,500 14,000 17,500 13,000 25,500 10,000 5,000H-4 S UL 7 5 3 5 3 5 3 2

A UL UL 37,500 17,500 28,500 17,500 36,000 18,000 6,500H-5 S UL 4 3 3 3 3 3 3 2

A UL UL 37,500 21,000 28,500 19,000 36,000 18,000 9,000

Table 503

Allowable Building Heights and Areas

Type of Constructionyp C

Type I Type II Type III Type IV Type V

A B A B A B HT A BH i ht (ft) UL 160 65 55 65 55 65 50 40Height (ft) UL 160 65 55 65 55 65 50 40

Group Stories (S)/Area(A)I-1 S UL 9 4 3 4 3 4 2 1

A UL 55,000 19,000 10,000 16,500 10,000 18,000 11,500 5,500I-2 S UL 4 2 1 1 NP 1 2 1

A UL UL 15,000 11,000 12,000 NP 12,000 11,500 6,000, , , , , ,I-3 S UL 4 2 1 2 1 2 2 1

A UL UL 15,000 10,000 10,500 7,500 12,000 11,500 6,000I-4 S UL 5 3 2 3 2 3 2 1

A UL 60,500 26,500 13,000 23,500 13,000 25,500 11,500 6,000M S UL 11 4 2 4 2 4 UL UL

A UL UL 21,500 12,500 18,500 12,500 20,500 UL ULR 1 S UL 11 4 4 4 4 4 3 2R-1 S UL 11 4 4 4 4 4 3 2

A UL UL 24,000 16,000 24,000 16,000 20,500 18,000 9,000R-2 S UL 11 4 4 4 4 4 1 1

A UL UL 24,000 16,000 24,000 16,000 20,500 18,500 9,500R-3 S UL 11 4 4 4 4 4 2 1

A UL UL UL UL UL UL UL 14,000 8,500R-4 S UL 11 4 4 4 4 4 3 2R 4 S UL 11 4 4 4 4 4 3 2

A UL UL 16,000 16,000 24,000 16,000 20,500 21,000 13,000S-1 S 1 11 4 2 3 2 4 1 NP

A 21,000 48,000 26,000 17,500 26,000 17,500 25,500 7,500 NPS-2 S UL 11 5 3 4 3 5 1 1

A 21,000 79,000 39,000 26,000 39,000 26,000 38,500 7,500 3,000U S UL 5 4 2 3 2 4 2 1

A UL 35,500 19,000 8,500 14,000 8,500 18,000 10,000 5,000

Building Element Type I Type II Type III Type IV Type V

TABLE 601

FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (hours)

A B Ad B Ad B HT Ad B

Primary Structural Frame(See Section 202)

3a 2a 1 0 1 0 HT 1 0

Bearing WallsExteriorf,g

Interior33a

22a

11

00

21

20

21/HT

11

00

Nonbearing walls and partitionsg pExterior See Table 602

Nonbearing walls and partitionsInterior 0 0 0 0 0 0

See Section 602.4.6

0 0

Floor construction and secondarymembers (see Section 202) 2 2 1 0 1 0 HT 1 0

Roof construction and secondaryymembers (see Section 202) 1½b 1b,c 1b,c 0c 1b,c 0 HT 1b,c 0

a. Roof supports: Fire-resistive ratings of primary structural frame and bearing walls are permitted to be reduced by 1 hour where supporting a roof only.

b i G 1 d S 1 i fi i f l b h ll b i d i l di i f f f i d d ki hb. Except in Group F-1, H, M and S-1 occupancies, fire protection of structural members shall not be required, including protection of roof framing and decking where every part of the roof construction is 20 feet or more above any floor immediately below. Fire-retardant-treated wood members shall be allowed to be used for such unprotected members.

c. In all occupancies, heavy timber shall be allowed where a 1-hour or less fire-resistance rating is requried.

TABLE 601

FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (hours)

Building Element Type I Type II Type III Type IV Type V

A B Ad B Ad B HT Ad B

Primary Structural Frame(See Section 202)

3a 2a 1 0 1 0 HT 1 0

Bearing WallsExteriorf,g

Interior33a

22a

11

00

21

20

21/HT

11

00

Nonbearing walls and partitionsg pExterior See Table 602

Nonbearing walls and partitionsInterior 0 0 0 0 0 0

See Section 602.4.6

0 0

Floor construction and secondarymembers (see Section 202) 2 2 1 0 1 0 HT 1 0

Roof construction and secondary

a. Roof supports: Fire-resistive ratings of primary structural frame and bearing walls are permitted to be reduced by 1 hour where supporting a roof only.

b. Except in Group F-1, H, M and S-1 occupancies, fire protection of structural members shall not be required, including protection of roof framing and decking where every part of the roof construction is 20 feet or more above any floor immediately below. Fire-retardant-treated wood members shall be allowed to be used for

ymembers (see Section 202) 1½b 1b,c 1b,c 0c 1b,c 0 HT 1b,c 0

every part of the roof construction is 20 feet or more above any floor immediately below. Fire retardant treated wood members shall be allowed to be used for such unprotected members.

c. In all occupancies, heavy timber shall be allowed where a 1-hour or less fire-resistance rating is required.

One Hour Fire Resistive TimberOne Hour Fire Resistive Timber Construction

IBC 721.6.3 NDS Chapter 16



• IBC Section 721.6.3.– Based on work by T.T. Lee at the National Research

C il f C d i h 1970Council of Canada in the 1970s.– Assumptions.

• 1 42 in /hr char rate1.42 in../hr char rate.• Reduction of strength and stiffness for 1.5 in. in the heated

zone ahead of the char front.• 8 factor used to account for reduction of strength and stiffness• .8 factor used to account for reduction of strength and stiffness.• Accounts for design to ultimate strength ratio.• Ignores increased rate of charring at corners.

One Hour Fire Resistive Timber Construction


• Equation 1 – relates size to time

t = (B-b)/2 = (D-d)/

E i 2 l Ul i h D i h

t (B-b)/2 (D-d)/

bdBD 22

• Equation 2 – relates Ultimate strength to Design strength

6bd

6BDkZ

• The code specified live load is to be used in calculating Z• The code specified live load is to be used in calculating Z


• Fire resistive rating of Timber members IBC Section 721.6.3 Beams– Beams

)db24(Zb54.2tf 4-sided exposure

d)

db4(Zb54.2tf 3-sided exposured

3.1Z For R < 0.530

RZ 3.07.0 For R > 0.5


• Fire resistive rating of Timber members per UBC Std. 7-7– ColumnsColumns

)bd3(Zd54.2t f

d

4-sided exposure

)b2

d3(Zd54.2tf 3-sided exposure

F K l/d < 11 F K l/d > 11

5.1ZFor Kel/d < 11

For R < 0.5

For Kel/d > 11

3.1Z For R < 0.5

RZ 3.09.0 For R > 0.5

RZ 3.07.0 For R > 0.5


• Additional details.1. Minimum nominal width = 6.”2. Connections and fastenings supporting members shall be

protected for equivalent fire resistance.3. Replace one core lamination with an extra tension lamination.4. Glued-laminated timber members shall be marked “Fire-rated

One-hour.”




• Fire resistive rating of Timber members per NDS Chapter 16Calculates the capacity of fire resistive members using same– Calculates the capacity of fire-resistive members using same mechanics as Lee.

– Assumes failure occurs when applied load exceeds member capacity based on reduced size and average ultimate stressbased on reduced size and average ultimate stress.

• i.e. D + L < K RASD

– Section properties are computed assuming an effective char rate, eff, at a given time tat a given time, t.

– Effective char rate accounts for rounding of the member at the corners and reduction of strength and stiffness of the heated zone.

– The code prescribed Live Load is to be used in the calculations.

One Hour Fire Resistive Timber ConstructionAd t f NDS Ch t 16 th dAdvantages of NDS Chapter 16 method.

1. All terms can be easily determined giving the designer a more complete sense of the performance of the member.

2. The method for designing fire rated compression members is consistent with the non-fire resistive designmembers is consistent with the non fire resistive design of compression members.

3. This method includes procedures for designing tension membersmembers.

4. This method provides procedures for designing members subjects to combined axial forces and bending moments such as arches or continuous truss chords.

5. This method provides procedures for designing timber decks.

6. Two-hour fire resistive members can be designed using these principles.


• Fire resistive rating of Timber members per NDS Chapter 16Reduced Cross Sectional Properties

Section Property Four sided exposure Three sided exposureArea A(t)= (B-2efft)(D-2efft) A(t)= (B-2efft)(D-efft)

Section Modulus S(t)= (B 2 t)(D 2 t)2/6 S(t)= (B 2 t)(D t)2/6Section Modulus S(t)= (B-2efft)(D-2efft)2/6 S(t)= (B-2efft)(D-efft)2/6

Moment of Inertia I(t)= (B-2efft)(D-2efft)3/12 I(t)= (B-2efft)(D-efft)3/12

h 21 Where:187.0

neff t

2.1 and: 5.1n in/hr


10 3/4 x 16 1/210‐3/4 x 16‐1/2


Fire resistive rating of Timber members per NDS Chapter 16Allowable Design Stress to Average Ultimate Strength Adjustment FactorsAllowable Design Stress to Average Ultimate Strength Adjustment Factors

1/k c Assumed COV KBending, Fb 2.1 1-1.645COVb 0.16 2.85

Tensile, Ft 2.1 1-1.645COVt 0.16 2.85

Compression Fc 1.9 1-1.645COVc 0.16 2.58

Buckling, E05 1.66 1-1.645COVE 0.11 2.03Buckling, E05 1.66 1 1.645COVE 0.11 2.03

One Hour Fire Resistive Timber ConstructionConstruction

• Fire resistive rating of Timber members per NDS Chapter 16

Design a one hour beam to span 20’-0”, spacing = 6’-0” o.c., qdead=25psf, qlive=100 psf

wtotal = 6(25+100) = 750 plf

M = wL2/8 = 37,500 ft. lbs.

Try a 5 1/8” x 15” GLULAM DF 24F-V4 CV =0.9827

S = bd2/6 = 192.19 in3

F’b = Fb * (CL or CV ) = 2400 * 0.9827 = 2358.48 psiM’ = F’b * S = 2358.48 * 192.19/12 = 37,772.53 ft-lbs. OK


Fire Check1. Choose required fire endurance2. Calculate depth of char3. Calculate reduced section property4. Calculate Average Ultimate Stress5. Calculate Allowable Capacity


1. Choose one hour fire endurance

)51(212.

3 a = ff * t = 1 8 in/hr * 1 hr = 1 8 in

.hr/in8.10.1

)5.1(2.1187.0eff

3. a eff t 1.8 in/hr 1 hr 1.8 in.

4. Sf = (b-2a)(d-a)2/6 = (5.125-3.6)(15-1.8)2/6 = 44.29 in3

5 F’ F (C C )(2 85) 6 721 69 i5. F’bf = Fb (CV or CL)(2.85) = 6,721.69 psi

6. M’f = F’bf * Sf = 6,721.69 * 44.29/12 = 24,808.56 ft. lbs. < 37,500 ft. lbs. NG


/ l lTry 5 1/8” x 19 ½” glulam 24F-V4

1. Sf = (b-2a)(d-a)2/6 = (5.125-3.6)(19.5-1.8)2/6 = 79.63 in3

2. F’bf = Fb (CV)(2.85) 2400(0.9573)(2.85) = 6,547.93 psi

3. M’f = F’bf * Sf = 6,547.93 * 79.63/12 = 43,449.83 ft. lbs. > 37,500 ft. lbs. OK

Birchwood Community Church Anchorage, Alaska


• Available Resources• www.apawood.org

Fire Resistive Design of Exposed Timber StructuresA il bl R• Available Resources

• www.awc.org– Technical Note 10 – Calculating the Fire Resistance of Exposed Wood

Members– Wood Construction Data 5 – Heavy Timber Construction

Fire Resistive Design of Exposed Timber StructuresFire Resistive Design of Exposed Timber StructuresSummary

Two methods of code approved fire protection are available using exposed timber membersare available using exposed timber members

Heavy timber conforming to IBC 602.4 utilizes large timber members and is based on positive experiencetimber members and is based on positive experience.

One hour fire ratings can be obtained using IBC section 721.6.3 or NDS Chapter 16


Thank You

Questions?

This concludes The American Institute of Architects Continuing Education Systems Co t u g ducat o Syste sCourse

Paul C. Gilham, P.E., S.E.Chi f E iChief EngineerWestern Wood Structures, [email protected]

Fire Resistive Design of Exposed Timber Structures.ppt ...€¦ · Structures • Fire Resistive types of exposed wood members ... masonry walls shall have a fire-resistance rating

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