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A RCHITECTURAL S TRUCTURES : Office Hours F ORM, B EHAVIOR, AND D ESIGN A RCH 331 D R. A NNE N ICHOLS S PRING 2019 lecture twenty eight link to posted schedule http://faculty.arch.tamu.edu/anichols/schedule/ masonry construction:

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F2010abn

ARCHITECTURAL STRUCTURES: FORM, BEHAVIOR, AND DESIGN ARCH 331

  • DR. ANNE NICHOLS

SPRING 2019

twenty eight

masonry construction:

beams & columns

Masonry Construction 1 Lecture 28 Architectural Structures ARCH 331

lecture

www.theeagle.com F2012abn

Office Hours

Masonry Construction 2 Lecture 28 Architectural Structures ARCH 331

link to posted schedule

http://faculty.arch.tamu.edu/anichols/schedule/

F2008abn Masonry Construction 2 Lecture 28 Foundations Structures ARCH 331

Masonry Design

  • Masonry Standards Joint Committee

– ACI, ASCE, TMS – ASD (+empirical)

  • linear-elastic stresses

– LRFD added in 2002 – referenced by IBC – unreinforced allows tension in flexure – reinforced - all tension in steel – walls are also in compression

International Masonry Institute (Brian Trimble) Masonry Construction 3 Lecture 28 Foundations Structures ARCH 331 F2008abn

Masonry Beam & Wall Design

  • reinforcement increases capacity &

ductility

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Masonry Construction 4 Lecture 28 Foundations Structures ARCH 331 F2008abn

Masonry Design

BIA Teknote 17 series

grout unit t d n.a. STRAIN STRESS As fm kd s M Ts=Asfs fs/n m Cm=fmb(kd)/2 jd

bd A s  

  • fs is not the yield stress
  • fm is the stress in the masonry

F2008abn Masonry Construction 5 Lecture 28 Foundations Structures ARCH 331

Masonry Materials

  • units

– stone, brick, concrete block, clay tile

www.GlenGerybrick.com National Concrete Masonry Association F2008abn Masonry Construction 6 Lecture 28 Foundations Structures ARCH 331

Masonry Materials

  • mortar

– water, masonry cement, sand, lime – types:

  • M

higher strength – 2500 psi (ave.)

  • S

medium high strength – 1800 psi

  • N

medium strength – 750 psi

  • O

medium low strength – 350 psi

  • K

low strength – 75 psi

W R A O

National Concrete Masonry Association F2008abn Masonry Construction 7 Lecture 28 Foundations Structures ARCH 331

Masonry Materials

  • rebar
  • grout

– fills voids and fixes rebar

  • prisms

– used to test strength, fm

  • fire resistant

Ryan-Briggs Associates National Concrete Masonry Association

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Masonry Construction 8 Lecture 28 Foundations Structures ARCH 331 F2008abn

Masonry Materials

  • moisture resistance

– weathering index for brick – bond and detailing – expansion or shrinking from water

  • provide control joints
  • parapets, corners,

long walls

parapet with no control joint

F2008abn Masonry Construction 9 Lecture 28 Foundations Structures ARCH 331

Allowable Masonry Stresses

  • tension - unreinforced only

F2008abn Masonry Construction 10 Lecture 28 Foundations Structures ARCH 331

Masonry Walls

tension normal to bed joints tension parallel to bed joints Not allowed in MSJC code

strong units weak units

WALLS

F2008abn

  • flexure

– Fb = 1/3 f’m (unreinforced) – Fb = 0.45 f’m (reinforced)

  • shear, unreinforced masonry

– Fv =  120 psi

  • shear, reinforced masonry

– M/Vd  0.25: Fv = – M/Vd  1.0: Fv =

3.0

m

f  2.0

m

f  1.5

m

f 

Masonry Construction 11 Lecture 28 Architectural Structures ARCH 331

Allowable Masonry Stresses

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F2008abn Masonry Construction 12 Lecture 28 Foundations Structures ARCH 331

Allowable Reinforcement Stress

  • tension

a) Grade 40 or 50 Fs = 20 ksi b) Grade 60 Fs = 32 ksi c) Wire joint Fs = 30 ksi

  • *no allowed increase by 1/3 for

combinations with wind & earthquake

– did before 2011 MSJC code

F2010abn

MSJC: Fs = 20 ksi, 24 ksi or 30 ksi by type

Reinforcement, Ms

Masonry Construction 14 Lecture 23 Architectural Structures III ARCH 631

grout unit t d n.a. As T

s=Asfs

Cm=fmb(kd)/2 jd

F=0: M about Cm:

kd

2 kd b f f A

m s s

if fs=Fs (allowable) the moment capacity is limited by the steel

s 2 s s s

jf ρbd jd f A M  

F2010abn

Reinforcement, Mm

Masonry Construction 15 Lecture 23 Architectural Structures III ARCH 631

grout unit t d n.a. As T

s=Asfs

Cm=fmb(kd)/2 jd

F=0:

jk bd f 5 . jd 2 kd b f M

2 m m m

 

kd

MSJC Fb =0.33f’m

2 kd b f f A

m s s

if fs=Fs (allowable) the moment capacity is limited by the steel M about T

s:

F2010abn

Masonry Lintels

  • distributed load

– triangular or trapezoidal

Masonry Construction 16 Lecture 28 Foundations Structures ARCH 331

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Masonry Construction 15 Lecture 28 Foundations Structures ARCH 331 F2008abn

Strategy for RM Flexural Design

  • to size section and find reinforcement

– find b knowing f’m and fy – size section for some  < b

  • get k, j
  • get b & d in nice units

– size reinforcement (bar size & #): – check design:

s

jF M bd  

2

needs to be sized for shear also

jd F M A

s s  b b s s s

F jk bd . M f M jd F A M    

2

5

Masonry Construction 16 Lecture 28 Foundations Structures ARCH 331 F2008abn

Ultimate Strength Design

  • LRFD
  • like reinforced concrete
  • useful when beam shear is high
  • improved inelastic

model

– ex. earthquake loads

T 1c 0.80f’m C

2 c

1

Masonry Construction 17 Lecture 28 Foundations Structures ARCH 331 F2008abn

Masonry Columns and Pilasters

  • must be reinforced

Masonry Construction 18 Lecture 28 Foundations Structures ARCH 331 F2008abn

Masonry Columns and Pilasters

  • considered a column when

b/t<3 and h/t>4

  • b is width of “wall”
  • t is thickness of “wall”
  • slender is

– 8” one side – h/t  25

  • needs ties
  • eccentricity may be required
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F2011abn

 

2

70 65 25          h r F A . A f . P

s st n m a

 

                 

2

140 1 65 25 r h F A . A f . P

s st n m a

Masonry Columns

– allowable axial load

h/r  99 h/r > 99

h = effective length r = radius of gyration An = effective area of masonry Ast = effective area of column reinforcement Fs = allowable compressive stress in column reinforcement

Masonry Construction 21 Lecture 24 Foundations Structures ARCH 331 F2008abn Masonry Construction 20 Lecture 28 Foundations Structures ARCH 331

Masonry Walls (unreinforced)

– allowable axial stresses

h/r  99 h/r > 99

                

2

140 1 25 r h f . F

m a 2

70 25         h r f . F

m a

F2008abn Masonry Construction 21 Lecture 28 Foundations Structures ARCH 331

. 1  

b b a a

F f F f Design

  • masonry columns and walls

– h/r < 99 – h/r > 99

                

2

140 1 25 r h f . F

m a 2

70 25         h r f . F

m a m b

f F   33 .

and

t a b

F f f  

(unreinforced)

Masonry Construction 22 Lecture 28 Foundations Structures ARCH 331 F2008abn

Design

  • masonry columns and walls - loading

– wind loading – eccentric axial load – “virtual” eccentricity, e1

h P e w

eo P M V P w w eo P V P e1

P M e 

1

virtual eccentricity

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7

Masonry Construction 23 Lecture 28 Foundations Structures ARCH 331 F2008abn

Design

  • masonry columns and walls – with rebar

– wall reinforcement usually at center and ineffective in compression b b a

F f f  

provided a a

F f 

grout unit t d n.a. BENDING STRESS As fm M Ts=Asfs fs/n Cm=fmb(kd)/2 jd fa = P/A AXIAL STRESS

  

s m

T C P F for equilibrium:

Masonry Construction 24 Lecture 28 Foundations Structures ARCH 331 F2008abn

Design Steps Knowing Loads

  • 1. assume limiting stress
  • buckling, axial stress,

combined stress

  • 2. solve for r, A or S
  • 3. pick trial section
  • 4. analyze stresses
  • 5. section ok?
  • 6. stop when section is ok

Masonry Construction 26 Lecture 28 Foundations Structures ARCH 331 F2008abn

Final Exam Material

  • my list:

– systems

  • components & levels
  • design considerations

– equilibrium - F & M

  • supports, trusses, cables, beams, pinned frames,

rigid frames

– materials

  • strain & stress (E), temperature, constraints

Masonry Construction 27 Lecture 28 Foundations Structures ARCH 331 F2008abn

Final Exam Material

  • my list (continued):

– beams

  • distributed loads, tributary width, V&M,

stresses, design, section properties (I & S), pitch, deflection

– columns

  • stresses, design, section properties (I & r)

– frames

  • P, V & M, P-, effective length with joint

stiffness, connection design, tension member design

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Masonry Construction 28 Lecture 28 Foundations Structures ARCH 331 F2008abn

Final Exam Material

  • my list (continued):

– foundations

  • types
  • sizing & structural design
  • overturning and sliding

– design specifics

  • steel (ASD & LRFD)
  • concrete
  • wood
  • masonry