combined effects of multi-story buildings and brick veneer

Welcome to Architecture Exchange East 2013

Virginia Society AIA is a registered provider with the American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of completion for non-AIA members are available on request. This program is registered with the 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, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Architecture Exchange East 2013

Presented By:

Michael A. Matthews, P.E.

The Structures Group, Inc.

Architecture Exchange East 2013

Combined Effects of Multi-Story Buildings and Brick Veneer

Speaker Bio • Mike Matthews is President and CEO of The Structures

Group, Inc., a consulting engineering firm with its corporate office in Williamsburg, Virginia. He graduated from Virginia Polytechnic Institute & State University in 1982 with a degree in Civil (Structural) Engineering and received an MBA from the College of William and Mary in 1988.

• Mike is currently chairman of the ACEC/VA Professional Development Committee and former chair of the Codes and Regulations Committee. Mike has served on the VBCOA Region Eight Special Inspections Task Force and is one of the Co-Authors of National Practice Guidelines for the Structural Engineer of Record (CASE, Fourth Edition) and the Hampton Roads Regional Special Inspection Guidelines and Procedures (2003, 2006, and 2009 USBC Editions).

• The Structures Group, Inc. provides structural engineering, forensic analysis, special inspections, independent code review, and risk analysis services. The firm, as well as Mike, is currently licensed to practice engineering in eighteen (18) states, as well as the District of Columbia.

Our Goal Today Will Be To Illustrate:

• Differing expansion and contraction properties of masonry veneer and its backup

• Building code requirements regarding masonry veneer and expansion joints

• Pros and cons of commonly used masonry veneer expansion joint details

• Need for collaboration between Architects and Structural Engineers in developing construction documents and value engineering related to masonry veneer

The 2009 Edition of the Virginia Uniform Statewide Building Code (VUSBC) adopts and amends the 2009 Edition of the International Building Code (IBC)

Chapter 21 of the IBC refers to: Building Code Requirements for Masonry Structures (ACI 530-05) Section 1.8: Material Properties of ACI 530 defines the coefficients for:

• Temperature Expansion (Reversible) • Shrinkage (No curing shrinkage of clay brick) • Moisture Expansion

Volume Change of Clay Brick

As stated in Section 1.8 of ACI 530:

• Temperature Expansion (Reversible): kt

= 4 x 10-6 in/in/°F Example: ΔF = 100F H or L=100’ Δt = L(12)(100)(ΔF)(Ke) Expansion due to temperature Δt = 100(12)(100)(.000004)=0.48in

Volume Change of Clay Brick continued


• Moisture Expansion (Non-reversible): ke

= 3 x 10-4 in/in Example: H or L = 100’ Δe = L(12)(Ke) Expansion due to moisture Δe = 100(12)(.0003) = 0.36 in


Summary of volume change: • Expansion due to temperature

– Δt = 100(12)(100)(.000004)= 0.48in

• Expansion due to moisture

– Δe = 100(12)(.0003) = 0.36 in

• Total Expansion of Brick

– Δt + Δe = 0.84 in



Chapter 21 of the IBC refers to: Building Code Requirements for Masonry Structures (ACI 530-05)

Section 1.8: Material Properties of ACI 530 defines the coefficients for:

• Temperature Expansion (Reversible)

• Moisture Expansion (Reversible)

• Drying Shrinkage (Non-Reversible)

• Creep

Volume Change of Concrete Masonry (CMU)

CMU Backup

CMU Veneer


• Temperature Expansion (Reversible):

– kt = 4.5 x 10-6 in/in/°F

Example:

ΔF = 100F

H or L=33’

Δt = L(12)(ΔF)(Kt)

Volume Change of Concrete Masonry (CMU) continued

CMU Backup


• Drying Shrinkage (Non-Reversible):

– Km = 0.55 S1 ≈ ranges from 0.0002 – 0.00065 in/in (S1 : Total linear drying shrinkage of concrete masonry units determined in accordance with ASTM C426)

Example:

H or L=33’

Δm = K m L(12)

Drying Shrinkage = .000425(33)(12) = 0.17 in.


CMU Backup

CMU Veneer

Creep: Long-term deflection will be relative to instantaneous deflection from sustained loading. (Negligible) KL = 2.5 x 10-7 in/in/psi

Example:

Loads: Dead + Reduced Live (ASCE-7 Appendix C)

3rd Floor – 800 plf

2nd Floor – 1600 plf

1st Floor – 2400 plf

8” CMU reinforced with #6 bars at 24” on center

Creep: Δc = K l Ph/AE

3rd Floor – 0.0003 in

2nd Floor – 0.0008 in

1st Floor – 0.0011 in

Total Creep: Δc = 0.0003 + 0.0008 + 0.0011 = 0.0022 in



• Expansion due to Temperature Δt = 100(12)(33)(.0000045)=0.18 in.

• Drying Shrinkage = .000425(33)(12) = 0.17 in.

• Moisture Expansion (Reversible): Value not given by ACI 530

• Creep: Negligible

Total CMU wall Movement = Δt + Δm + ΔL

Temperature 0.18 inches

Shrinkage 0.17 inches

Creep 0.0022 inches

Total 0.3522 inches


Three directions of Wood Expansion and Shrinkage: • Tangential

• Radial

• Longitudinal

Volume Change of Wood

Moisture Shrinkage: Timber is manufactured today at 19% moisture content while equilibrium of timber is about 11% to 12%

• Tangential Shrinkage: Greatest Shrinkage

• Radial Shrinkage: Approximately 1/2 of tangential shrinkage

• Longitudinal Shrinkage: Very small and usually disregarded

Problem: Not knowing how wood grain is oriented

Volume Change of Wood continued

Simplified Method for Moisture Shrinkage Analysis: • Horizontal Lumber (Joists, Truss Chords, and Plates)

– Shrinkage of dimensional lumber Δs: 0.2% shrinkage per 1% change in moisture content (Δmc)

Example for horizontal members considering tangential and radial shrinkage:

• Vertical Members (Studs, Columns, Web Members, and Truss Webs)

– Shrinkage of dimensional lumber: negligible Δs ≈ 0


Joist Plate

Δs =(0.002) d Δmc d = 11.25 in (2 x 12 joist) Δmc = 8 (moisture change in wood from manufactured to equilibrium) Δs = (0.002)(11.25)(8) = 0.18 inches

Δs =(0.002) d Δms

d = 1.5 in (2 x plate) Δmc = 8 (moisture change in wood from manufactured to equilibrium) Δs = (0.002)(1.5)(8) = 0.024 inches

Temperature Expansion: Radial and tangential depend on specific gravity wood species

• Radial Expansion: αr = (18G + 5.5) * 10-6 per F

– Example: 10’-0” of southern pine (G = 0.55) experiencing 100F temperature change: Δ=0.18”

• Tangential Expansion: αT= (18G + 10.2) * 10-6 per F

– Example: 10’-0” of southern pine (G= 0.55) experiencing 100F temperature change: Δ=0.24”

• Longitudinal temperature change independent of specific gravity. Ranges from αL= 0.0000017 to 0.0000025 per F

– Example: 10’-0” of long board subject to (100F temperature change: Δ=0.03”


Moisture Expansion:

• Wood exposed to moisture will expand and shrink back towards its original size, reversing the wood shrinkage experienced.


Volume Change of Cast-in-Place Concrete

Three elements of movement involved in cast-in-place

concrete structures that need to be considered in design:

• Elastic Shortening

• Creep

• Shrinkage

Volume Change of Cast-in-Place Concrete continued


Chapter 21 of the IBC refers to: Building Code Requirements for Masonry Structures (ACI 530-05) Section 1.8: Material Properties of ACI 530 defines the coefficients for:

• Elastic Shortening • Creep • Shrinkage


Elements of Concrete Frame Shortening

Elements Time Dependent Load Dependent

Elastic Shortening X

Creep

Shrinkage X


Magnitude of long term concrete volume changes (Per ACI 209)

• Elastic Shortening: The instantaneous deflection in the concrete frame due to applied loads.

• Creep, νu : 2.35 times the instantaneous deflection experienced from sustained loading. Reaches approximately 90% of total anticipated creep in approximately 5 years.

• Shrinkage, (εsh): 780 γsh x 10-6 in./in., i.e. 0.078%. Reaches approximately 90% of total anticipated shrinkage in approximately 1 year.

Example:

H or L = 100’

Δs = L(12)(εsh)

Shrinkage = 100(12)(0.00078) = 0.94 in.

Creep and Shrinkage (Per ACI 209) Applied to creep coefficient and shrinkage strain to achieve more accurate volume change prediction.

• Curing Conditions – Specified Curing Processes

• Concrete Composition – Concrete Mix Design

• Geometry – Exposed Surface Areas

• Anticipated Loading – Specified Live/Dead Loads

– Specified Length of Time for Shoring


Volume Change of Steel

Shelf Angles and Shelf Angle Flashing

Volume Change due to Temperature • Coefficient of Expansion: 6.5 x 10-6 in./in./°F (Per the AISC Steel Manual)

– Example: 20’ long angle with 100 °F temperature change: Δ = 0.17 in

Volume Change of Steel continued

Expansion of steel shelf angles and metal flashing must be accounted for.

What Happens When Movement of the Veneer & Frame are not Accounted for

Examples of distress in masonry after construction

ACI 530 Section 6.2.2.3.1.2 - Anchored Veneer with a backing of wood framing shall not exceed the height above the noncombustible foundation given in Table 6.2.2.3.1.

Maximum Height of Anchored Veneer with Wood Backing

ACI 530 Table 6.2.2.3.1

Height at top plate Height at gable

30’-0” 38’-0”

Example No. 1 Brick Veneer with Wood Frame Backing

Example No. 1 Continued

Expansion of Brick Veneer and Shrinkage of Wood Frame are additive:

Brick Veneer Expansion: • Expansion due to temperature:

Δt = (33)(12)(100)(0.000004) = 0.16 in • Expansion due to moisture:

Δc = (33)(12)(0.0003) = 0.12 in

Total anticipated expansion of brick veneer: 0.28 inches

Example No. 1 continued


Wood Frame Shrinkage: Example: 9’-0” ceiling and 2’-0” floor wood truss framing for three (3) story building:

Per Floor: • (1) 2x sill plate; (2) 2x top plates; (2)

2x chords from wood truss (Total of (5) 2x plates per floor)

• Δs = (5 plates per floor)[(0.002)d Δms ] = 0.12 inches per floor

Total anticipated shrinkage of wood framing: 0.36 inches

Exterior Wall Δ

Brick Expansion 0.28”

Wood Shrinkage 0.36”

Total Movement 0.64”


Total movement to be accounted for: 0.64” = + 10/16” = + 5/8”


Example of distress where differential movement between wood frame and brick veneer was not accounted for

Example No.1 continued

Why did this happen?

Example No.1 continued

Example No. 2 Brick Veneer with Cast-in-Place Concrete Backing

21-story cast-in-place concrete structure with brick veneer located in Baltimore, Maryland


Short

enin

g o

f C

oncre

te F

ram

e:

+

4.2”

Expansio

n o

f M

asonry

:

+ 1.5”

Tota

l V

eneer

Movem

ent:

+ 5.7”


• 21 floors • 5.7 in total movement = approximately

0.27” of movement per floor • Therefore, shelf angels at each floor

• Shelf angles 3/8” thick and mortar joints were 1/2” thick

• 35% compressible filler included in joint below angle

• 3/4“ deep covering edge of angle lip prevents any expansion joint between

brick coursing • However, the Design Professional

allowed joints to be every other floor during value engineering


Example of distress resulting from poorly designed expansion joint


Example No. 3 Concrete Masonry Veneer

• Designed: Circa 2005 • Built: Circa 2006 • Distress: Circa 2011

Example of distress at expansion joints at alternating floors and welded flashing • Joints at alternating floors • Shelf angles are continuous and welded • Flashing is continuous and welded


Total Vertical Masonry Expansion: + 1.1 inches (CMU Veneer)

Formula: Δm = H * ε t Δ T

ε t :Temperature Expansion: 4.50 x 10-6 in/in /°F (CMU Veneer)

Δ T: Temperature Change (110) BIA: Maximum temperature of wall 140

+183’-3”

43


Total Concrete Frame Shortening (Ultimate Life): + 4.3 inches.

0.11

0.12

0.14

0.15

0.17

0.18

0.19

0.21

0.21

0.22

0.24

0.24

0.25

0.26

0.26

0.25

0.24

0.24

0.39

0.25

4.32

Note: 1. Concrete shortening calculation based on

ACI 318-99, ACI 209 R-92 and ASCE 7-98. 2. Concrete shortening is affected by concrete

creep, shrinkage, and elastic shortening per floor (inches).

3. Variations on concrete frame shortening result from variations in column layout, floor height, floor loading, and concrete length.

4. Concrete material properties taken from construction documents.

44



Short

enin

g o

f C

oncre

te F

ram

e:

+

4.3”

Expansio

n o

f M

asonry

:

+ 1.1”

Tota

l V

eneer

Movem

ent:

+ 5.4” Cumulative Calculated

Concrete & Masonry Veneer Vertical Movement (Ultimate Life) Total Anticipated Cumulative Concrete and Masonry Movement During the Ultimate Life of the Structure: + 5.4 inches

Specifications Section 04810 – Unit Masonry Assemblies

2.8 MISCELLANEOUS MASONRY ACCESSORIES A. Compressible Filler: Premolded filler strips complying with ASTM D

1056, Grade 2A1; compressible up to 35 percent; of width and thickness indicated; formulated from neoprene urethane or PVC.

3.9 CONTROL AND EXPANSION JOINTS

C. Provide horizontal , pressure relieving joints by either leaving an air space or inserting a compressible filler of width required for installing sealant and backer rod specified in Division 7 Section “Joint Sealants,” but not less than 3/8 inch.

1. Locate horizontal, pressure-relieving joints beneath shelf angles supporting masonry.

2. Compressible filler to be compressible to 35% of thickness. TSG Note: Compressible filler only allows for 1/4” expansion of 3/8” joint

9


• 3/8” (.375) vertical gap shown with sealant joint, backer rod, and compressible filler.

• Expansion joints to be located at every other floor. • Vertical movement for typical 18.16’ between expansion joints (7th and

8th floor) mid height of building 0.62 inch ~ 5/8” > 3/8”. 47

Expansion Joint Detail (From Architectural Drawings)


Typical Shelf Angle Detail Shown on Structural Drawings • No vertical expansion area shown between top of brick and bottom of angle. • Overhang of masonry from end of angle is not defined. • No gap is indicated between masonry and concrete floor slab. • L6 x 6 x 3/8 shelf angle supports 4” CMU.

8a

Section (From Structural Drawings) Section (From Structural Drawings)


Construction Documents:

Ten (10) levels with shelf angles (Denoted by Arrows).

-Total Allowable Vertical Expansion height with 35% compressible fill: 2.44 inches. -Total Allowable Vertical Expansion height without compressible fill: 3.75 inches.

49

Total Anticipated Vertical Expansion: +5.4 inches > Total Designed Vertical Expansion (w/o compressible fill): 3.75 inches.

Total Anticipated Vertical Expansion: +5.4 inches > Total Designed Vertical Expansion (w/compressible filler): 2.44 inches.


0.10

0.12

0.13

0.14

0.16

0.17

0.19

0.20

0.20

0.21

0.23

0.23

0.24

0.25

0.25

0.23

0.22

0.23

0.37

0.24

4.32

50


Total Concrete Frame Shortening (Over 5 years): + 4.1 inches.

Note: 1. Concrete shortening calculation based

on ACI 318-99, ACI 209 R-92 and ASCE 7-98.

2. Concrete shortening is affected by concrete creep, shrinkage, and elastic shortening per floor (inches).

3. Variations on concrete frame shortening result from variations in column layout, floor height, floor loading, and concrete length.

4. Concrete material properties taken from construction documents.


Short

enin

g o

f C

oncre

te F

ram

e:

+

4.1”

Expansio

n o

f M

asonry

:

+ 1.1”

Tota

l V

eneer

Movem

ent:

+ 5.2”

Total Cumulative Concrete and Masonry Movement (Over 5 years): + 5.2 inches. • Remaining Concrete and

Masonry Movement Over Life of Structure

- Ultimate Concrete Shortening: + 4.3 inches

- Concrete Shortening to Date: + 4.1 inches

• Remaining Concrete Shortening : + 0.2 inches

• Masonry Expansion: + 1.1 inches

Total Remaining Concrete and Masonry Movement Over Life of Structure: + 1.3 inches

11

Caution in Use of Generic Details BIA Technical Note 7 - Water Resistance of Brick Masonry Design and Detailing Details Require Project Specific Coordination

11

BIA Technical Note 28B - Brick Veneer

Caution in Use of Generic Details continued

11 Emphasis added by TSG

Caution in Use of Generic Details continued

11

Attention to Detail • Pay Attention to Construction Tolerances

Per ACI 117 “Structural Specifications for Tolerances for Concrete Construction and Materials” the lateral alignment for cast-in-place concrete members, including elevated slabs, is permitted to vary up to 1” from a specified line or point in the horizontal plane.

THANK YOU for attending

Combined Effects of Multi-Story Buildings and Brick Veneer

Presented By:

Michael A. Matthews, P.E.

The Structures Group, Inc.

Please remember to complete an evaluation form. You may leave the form on the table outside the room or with a room monitor.

combined effects of multi-story buildings and brick veneer

Design

masonry structures aci

volume change of clay

expansion jointspros

differing expansion

l12ke expansion

l12100fke expansion

summary of volume change

intotal expansion of