STRC11 Masonry Part2 0716

Structural Engineering Exam Review Course

Masonry

Design of Masonry Structures (Part 2) Structural Engineering Review Course

STRC ©2015 Professional Publications, Inc.

© 2015 Professional Publications, Inc.

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Masonry

Masonry (Part 2)

Lesson Overview Masonry (Part 2) •

Design of Slender Walls

•

Design of Anchor Bolts

•

Quality Assurance, Testing, and Inspection

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Masonry

Masonry (Part 2)

Learning Objectives You will learn •

•

•

design of slender masonry walls under axial and out‐of‐plane flexural loads connections to masonry code requirements for inspection and masonry construction

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Masonry

Masonry (Part 2)

Learning Objectives You should already be familiar with •

structural analysis

•

mechanics of materials

•

ASD and SD fundamentals of bending and axial masonry design

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Masonry (Part 2)

Referenced Codes and Standards •

Building Code Requirements and Specification for Masonry Structures (MSJC, 2011)

•

International Building Code (IBC, 2012)

•

Minimum Design Loads for Buildings and Other Structures (ASCE/SEI7, 2010)

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Design of Slender Walls design basis (MSJC Sec. 3.3.5) •

•

•

Iterative design approach accounts for P-Δ effect. Maximum service deflection, δs, is limited by MSJC Eq. 3‐28 to δs = 0.007h.

•

•

If h/t ≤ 30, factored axial stress is limited to 0.2f′m. If h/t > 30, factored axial stress is limited to 0.05f′m.

For empirical masonry only, minimum wall thickness is 6 in for one‐story buildings and 8 in for multiple‐story buildings (MSJC Sec. 5.6.2)

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Masonry (Part 2)

Poll: Design of Slender Walls An interior load‐bearing wall in a two‐ story building is under empirical masonry design. What is the minimum wall thickness required? (A) 6 in (B) 8 in (C) 12 in (D) 14 in

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Masonry (Part 2)

Poll: Design of Slender Walls An interior load‐bearing wall in a two‐ story building is under empirical masonry design. What is the minimum wall thickness required? (A) 6 in

Per MSJC Sec. 5.6.2, the minimum required wall thickness is 6 in for one‐ story buildings, and 8 in for all others. The answer is (B).

(B) 8 in (C) 12 in (D) 14 in

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Masonry (Part 2)

Design of Slender Walls strength design (SD) method (MSJC Sec. 3.3.2) •

•

Typical reinforcement is centered in wall, so d = t/2. Equivalent reinforcement area accounting for axial load, Ase, is Pu  s fy  Ase  fy

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Masonry (Part 2)

Design of Slender Walls strength design (SD) method (MSJC Sec. 3.3.2) •

Figure 6.13 Flexural Capacity of a Slender Concrete Masonry Wall

Depth of stress block, a, is Pu  s fy  a 0.80bf m'

•

Design moment capacity, Mn, is  Pu

a   As f y   d   2  

 M n  (0.9) 



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Example: Strength Design Method Example 6.13



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Example: Strength Design Method



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Example: Retaining Wall Practice Problem 6.2



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Example: Retaining Wall



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Design of Slender Walls flexural demand on a slender masonry wall (MSJC Sec. 3.3.5) •

•

•

Wall is assumed to be simply supported and uniformly loaded.

When Mser < Mcr, deflection at midheight of the wall due to service‐level moment is

Critical section occurs at midheight of wall.

u

Factored moment, Mu, is

When Mser > Mcr, deflection at midheight of the wall due to service‐level moment is

u



wu h 2 8



Puf eu 2

 Pu u

MSJC Eq. 3‐26

5 

u 

ser h

MSJC Eq. 3‐29

48Em I g

5M cr h 2 48 EmgI



2



5h 2 ( Mser  crM ) 48 mcrE I

MSJC Eq. 3‐30

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Design of Slender Walls flexural demand on a slender masonry wall (MSJC Sec. 3.3.5) •

•

the modulus of rupture, f′r, for out‐of‐plane forces is given in MSJC Table 3.1.8.2 moment of inertia of the cracked section,   

I cr  n As

 Pu   fy

  t sp   2      ( d c) 2 d    c

s

bc 3 3

f y  Pu

0.64 mb

MSJC Eq. 3‐31

MSJC Eq. 3‐32



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Masonry (Part 2)

Slender Masonry Wall Analysis Figure 6.14 Analysis of a Slender Concrete Masonry Wall

Figure 6.15 Transformed Section of a Slender Concrete Masonry Wall



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Masonry (Part 2)

Example: Flexure on a Slender Masonry Wall Example 6.13



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Example: Flexure on a Slender Masonry Wall



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Design of Slender Walls maximum reinforcement limit for a slender masonry wall (MSJC Sec. 3.3.3.5.1) •

•

Strain in the extreme tension reinforcement is 1.5 times the strain associated with the reinforcement yield stress, fy. maximum strain in the extreme masonry compression fiber, εmu = 0.0025

•

unfactored gravity axial loads are included in the analysis using the combination P  D  0.75 L  0.525QE

•

equating compressive and tensile forces acting on the section yields Amax 



0.286

' m

P

fy

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Masonry (Part 2)

Design of Slender Walls Figure 6.16 Maximum Reinforcement Requirements for a Slender Concrete Masonry Wall



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Masonry (Part 2)

Example: Maximum Reinforcement for a Slender Wall Example 6.15



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Example: Maximum Reinforcement for a Slender Wall Example 6.15



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Example: Maximum Reinforcement for a Slender Wall



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Design of Slender Walls lateral deflection of a slender masonry wall under service loads •

•

Maximum permissible deflection, δs, at the midheight of the wall is δs = 0.007h.

ser



Pf e

wh   P s 8 2

•

The moment of inertia of a cracked section, Icr, is bc 3 2 cr se I  3  nA (d  c)

When Mser < Mcr, deflection at midheight of the wall due to the service loads, δ s, is s 

The service moment, Mser, is 2

•

•

5

h2

48 Em I g

MSJC Eq. 3‐29

When Mser > Mcr, deflection at midheight of the wall due to the service loads, δ s, is 5M ser h 2  s  48 EmgI 



ser

5h 2 ( M ser  M cr ) 48 mcrE I

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Masonry (Part 2)

Design of Slender Walls Figure 6.17 Elastic Analysis of a Slender Concrete Masonry Wall



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Example: Lateral Deflection of Slender Walls Example 6.16 •



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Example: Lateral Deflection of Slender Walls Example 6.16 •



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Design of Anchor Bolts placement details (MSJC Sec. 1.17) •

•

•

•

Figure 6.18 Anchor Bolts in Masonry

minimum clear distance between bolts is db or 1 in if db ≥ ¼ in, anchor must be embedded in grout minimum ½ in coarse grout or ¼ in fine grout required between bolts minimum lb= 4db ≥ 2 in per MSJC Sec. 1.16.6



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Design of Anchor Bolts anchor bolts in tension (MSJC Sec. 1.17) tension failure modes •

tensile yielding of the steel anchor

•

masonry tensile breakout

•

straightening of the hook for bent‐bar anchors



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Masonry (Part 2)

Design of Anchor Bolts anchor bolts in tension (ASD method) •

tensile yielding Bas  0.6 bAy F

anchor bolts in tension (SD method) •

 Bans   Ab yf

MSJC Eq.-2 2 •

•

masonry tensile breakout Bab  1.25 A pt

•

m

f'

MSJC Eq.-2 1

120 b  b b (l b e

MSJC Eq. 3-2

masonry tensile breakout (ϕ = 0.5) '  Banb   (4 A pt ) m f

•

MSJC Eq.- 3 1

bent bar hook straightening  Banp   1.5mbfb ' ed

bent bar hook straightening Bap  0.6mbfb ' e d

tensile yielding (ϕ = 0.9)

d )d

300  b (bl b

b

e

d )d



MSJC Eq. 3-4

MSJC Eq. 2-4 STRC ©2015 Professional Publications, Inc.


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Design of Anchor Bolts masonry tensile breakout

Figure 6.19 Masonry Breakout

Breakout occurs by pullout of a conically shaped section of masonry with an area of Apt – Ao where applicable.



of Anchor Bolt in Tension

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Masonry (Part 2)

Design of Anchor Bolts Figure 6.20 Overlap of Projected Areas

Figure 6.21 Projected Area Extends Beyond Wall Edge



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Masonry (Part 2)

Example: Anchor Bolts in Tension A flagpole is mounted horizontally on an 8 in CMU wall with four ½ in diameter (Ab = 0.20 in2) anchor bolts in a 7 in × 7 in layout. The connection must resist a moment and shear load from the flagpole. The ASD total tension load in both top anchors is 1500 lbf and the shear is 400 lbf. The SD tension in the top anchors is 2100 lbf and the shear is 560 lbf. The bottom anchors have no tension. The masonry strength is 1500 psi and the anchor bolt strength is 36 ksi. Are the anchor bolts are adequate in tension? STRC ©2015 Professional Publications, Inc.


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Masonry (Part 2)

Example: Anchor Bolts in Tension A flagpole is mounted horizontally on an 8 in CMU wall with four ½ in diameter (Ab = 0.20 in2) anchor bolts in a 7 in × 7 in layout. The connection must resist a moment and shear load from the flagpole. The ASD total tension load in both top anchors is 1500 lbf and the shear is 400 lbf. The SD tension in the top anchors is 2100 lbf and the shear is 560 lbf. The bottom anchors have no tension. The masonry strength is 1500 psi and the anchor bolt strength is 36 ksi. Are

The effective embedment length of an anchor bolt , lb, measured from the surface of the masonry to the bearing surface of the bolt head is

the anchor bolts are adequate in tension?

Apt   lb   (5 in)  78.5 in

lb  5 in

 4db [satisfies MSJC Sec. 1.17.6]  2 in [satisfies MSJC Sec. 1.17.6] The projected area of one bolt, Apt, before considering overlapping areas, is 2



2

2

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Masonry (Part 2)

Example: Anchor Bolts in Tension The horizontal spacing of the bolts, 2θ, is 2  2 arccos

s 7 in  2 arccos 2r 10 in

 91.1 For the top two anchor bolts, the overlapping area, Ao, is

The reduced projected area for the top two bolts, Ab, is Ab  2 ptA o  A

 (2)(78.5 in 2)  (14.8 in 2)  142 in 2

  2   sin2   r 2  180    91.1    sin9 1.1  (5 in) 2 180    2  14.8 in

Ao  



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Masonry (Part 2)

Example: Anchor Bolts in Tension ASD Method

For tensile strength governed by masonry breakout, the allowable strength of the four bolts, 2Bab, is given by MSJC Eq. 2‐1 as ' 2 Bab  1.25 A pt

m

Bas  0.6 bAy f

f'

 (1.25)(142 in 2 ) 1500  6.87 kips  T [satisfactory]

For tensile strength governed by tensile yielding of a steel anchor, the allowable strength of each anchor bolt, Bas, is given by MSJC Eq. 2‐2 as

lbf in 2

kips    (0.6)(0.20 in 2 ) 36  in 2    4.32 kips



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Example: Anchor Bolts in Tension The allowable strength of the two bolts is

SD Method

2 Bas  (2)(4.32 kips)

For tensile strength governed by the tensile yielding of a steel anchor, the design capacity, ϕBans, is given by MSJC Eq. 3‐2 as

 8.64 kips  T [satisfactory] The bolts are adequate for the tension force on the flagpole. The allowable tension force on one bolt in the absence of shear force, Ba, is Ba 

6.87 kips

 Bans   Ab yf kips    (0.9)(0.20 in 2 ) 36  in 2    6.48 kips

2

 3.44 kips



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Example: Anchor Bolts in Tension The design capacity of the two bolts, 2ϕBanb, is ' ' 2 Banb   (4 A pt ) m f

(0.5)(4)(142 in 2 ) 1500

 1000

lbf

lbf in 2

The bolts are adequate for the tension force on the flagpole. The design capacity of one bolt in the absence of shear force is  Ban 

11 kips

2  5.5 kips

kip

 11 kips [governs]  2 Bans  Tu [satisfactory]



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Design of Anchor Bolts anchor bolts in shear (MSJC Sec. 1.17)

Figure 6.22 Shear Failure Modes for Anchor Bolts

shear failure modes •

steel anchor shear yielding

•

masonry shear breakout

•

anchor bolt shear pryout

•

masonry shear crushing



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Design of Anchor Bolts anchor bolts in shear (ASD method) •

steel anchor shear yielding Bvs  0.36bAy f

•

MSJC Eq. 2‐9

masonry shear breakout Bvb  1.25 A pv

m

•

f'

MSJC Eq. 2‐6

anchor bolt shear pryout Bvpry  2 Bab  2.5ptA

•

f'

MSJC Eq. 2‐8

masonry shear crushing Bvc  350 4 mfb ' A



m

MSJC Eq. 2‐7

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Design of Anchor Bolts anchor bolts in shear (SD method) •

steel anchor shear yielding (ϕ = 0.9)  Bvns  0.6 A by f

•

•

MSJC Eq. 3‐9

anchor bolt shear pryout (ϕ = 0.5)  Bvnpry  2 Banb

masonry shear breakout (ϕ = 0.5) '  Bvnb   (4 A pv ) m f

  (8

MSJC Eq. 3‐6 •

pt

) f m'

masonry shear crushing (ϕ = 0.5)  Bvnc   (1050)4



MSJC Eq. 3‐8

f'A

mb

MSJC Eq. 3‐7

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Masonry (Part 2)

Design of Anchor Bolts masonry shear breakout

Figure 6.23 Masonry Breakout in Shear

Breakout occurs of a semi‐conically shaped section of masonry with area, Apv.



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Masonry (Part 2)

Example: Anchor Bolts in Shear A flagpole is mounted horizontally on an 8 in CMU wall with four ½ in diameter (Ab = 0.20 in2) anchor bolts in a 7 in × 7 in layout. The connection must resist a moment and shear load from the flagpole. The ASD total tension in both the top anchors is 1500 lbf, and the total shear load is 400 lbf (ASD) or 500 lbf (LRFD). The SD tension in the top anchors is 2100 lbf and the shear is 560 lbf. The masonry strength is 1500 psi and the anchor bolt strength is 36 ksi. There are no edge distance restrictions. Are the anchor bolts adequate in shear? STRC ©2015 Professional Publications, Inc.


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Masonry

Masonry (Part 2)

Example: Anchor Bolts in Shear A flagpole is mounted horizontally on an 8 in CMU wall with four ½ in diameter (Ab = 0.20 in2) anchor bolts in a 7 in × 7 in layout. The connection must resist a moment and shear load from the flagpole. The ASD total tension in both the top anchors is 1500 lbf, and the total shear load is 400 lbf (ASD) or 500 lbf (LRFD). The SD tension in the top anchors is 2100 lbf and the shear is 560 lbf. The masonry strength is 1500 psi and the anchor bolt strength is 36 ksi. There are no edge distance restrictions. Are the anchor bolts adequate in shear?

From the previous example, before considering overlapping areas, the projected area, Apt, of one bolt is 78.5 in2. The projected areas of the bolts overlap horizontally and vertically. From the previous example, the overlapping area between two bolts, Ao, is 14.8 in2. The reduced projected area for the four bolts, A′pt, is Ab  4 A  o4 A pt

 255 in 2 STRC ©2015 Professional Publications, Inc.


(4)(78.5  in 2) (4)(14.8in )2

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Masonry

Masonry (Part 2)

Example: Anchor Bolts in Shear ASD Method

For shear strength governed by the shear yielding of the steel anchor, the allowable strength of each anchor bolt , Bvs, is given by MSJC Eq. 2‐9 as  

Bvs  0.36bAy f  (0.36)(0.20 in 2) 36

 2.59 kips

kips 



For shear strength governed by masonry pryout, the combined allowable strength of all four bolts, 4Bvpry, is given by MSJC Eq. 2‐8 as 4 Bvpry  2.5 Apt'

in 2 

f'

m

(2.5)(255 in 2 ) 1500

 1000

lbf in 2

lbf kip

 24.7 kips



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Masonry (Part 2)

Example: Anchor Bolts in Shear For shear strength governed by masonry crushing, the allowable strength of each anchor bolt, Bvc, is given by MSJC Eq. 2‐7 as

 4 Bvpry  4 Bvs [satisfactory]

Bvc  350 4 mfb ' A

   

 350   4 1500 

4Bvc  (4)(1.46 kips)  5.84 kips

 lbf  (0.20 in 2)  2   in  

1000

The bolts are adequate for the shear force on the flagpole.

lbf kip

 1.46 kips [governs]



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Masonry

Masonry (Part 2)

Example: Anchor Bolts in Shear SD Method

The design strength of each anchor bolt in shear yielding, ϕBvns, is given by MSJC Eq. 3‐9 as  Bvns  0.6 A by f kips    (0.6)(0.9)(0.20 in )  36  in 2    3.89 kips 2

For shear strength governed by masonry pryout, the combined design capacity for all four bolts, ϕBvpry, is given by MSJC Eq. 3‐8 as  Bvpry  2 Banb   (8)ptA'

m

f'

 (0.5)(8)(255 in 2 ) 1500

lbf in 2

 39.5 kips



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Masonry

Masonry (Part 2)

Example: Anchor Bolts in Shear For shear strength governed by masonry crushing, the design capacity of each anchor, ϕBvnc, is given by MSJC Eq. 3‐7 as  Bvnc

lbf   2 1500 in 2  (0.20 in )    (1050) 4 mbf ' A  (0.5)(1050) 4  1000

4 Bvnc

lbf

kip

 2.18 kips [governs]  (4)(2.18kips)  8.72 kips  Vu [satisfactory]

The bolts are adequate for the shear force on the flagpole.



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Masonry

Masonry (Part 2)

Design of Anchor Bolts headed anchor bolts in combined shear and tension •

ASD method: comply with ba Ba

•



Bv

1

MSJC Eq. 2‐10

SD method: comply with baf  Ban

•

bv



bvf  Bvn

1

MSJC Eq. 3‐10

design capacity in shear and tension shall exceed the applied loads STRC ©2015 Professional Publications, Inc.


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Masonry

Masonry (Part 2)

Example: Headed Anchor Bolts in Tension and Shear A flagpole is mounted horizontally on an 8 in CMU wall with four ½ in diameter (Ab = 0.20 in2) anchor bolts in a 7 in × 7 in layout. The connection must resist a moment and shear load from the flagpole. The ASD total tension in both the top anchors is 1500 lbf, and the total shear load is 400 lbf (ASD) or 500 lbf (LRFD). The SD tension in the top anchors is 2100 lbf and the shear is 560 lbf. The masonry strength is 1500 psi and the anchor bolt strength is 36 ksi. There are no edge distance restrictions. Are the anchor bolts adequate for the combined tension and shear force?



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Masonry

Masonry (Part 2)

Example: Headed Anchor Bolts in Tension and Shear A flagpole is mounted horizontally on an 8 in CMU wall with four ½ in diameter (Ab = 0.20 in2) anchor bolts in a 7 in × 7 in layout. The connection must resist a moment and shear load from the flagpole. The ASD total tension in both the top anchors is 1500 lbf, and the total shear load is 400 lbf (ASD) or 500 lbf (LRFD). The SD tension in the top anchors is 2100 lbf and the shear is 560 lbf. The masonry strength is 1500 psi and the anchor bolt strength is 36 ksi. There are no edge distance restrictions. Are the anchor bolts adequate for the combined tension and shear force?

ASD Method

The applied tension force on one bolt, ba, is

T 1.5 kips  2 2  0.75 kips

ba 

The applied shear force on one bolt, bv, is

V 0.4 kips  4 4  0.1 kips

bv 



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Masonry

Masonry (Part 2)

Example: Headed Anchor Bolts in Tension and Shear For combined tension and shear, anchor bolts

SD Method

must comply with MSJC Eq. 2‐10.

The factored tension force on one bolt, baf, is

ba bv  1 Ba Bv 0.75 kips 3.44 kips



0.1 kips 1.46 kips

baf 

 0.29 [satisfactory]

Tu 2.1 kips   1.05 kips 2 2

The factored shear force on one bolt, bvf, is

bvf 

Vu 4





0.56 kips 4

 0.14 kips

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Masonry

Masonry (Part 2)

Example: Headed Anchor Bolts in Tension and Shear For combined tension and shear, anchor bolts must comply with MSJC Eq. 3‐10.

baf Ban 1.05 kips 5.5 kips





bvf Bvn

0.14 kips 2.18 kips

1  0.26 [satisfactory]



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(Part 2)


Masonry

Masonry (Part 2)

Quality Assurance, Testing and Inspection quality assurance plan (IBC Sec. 110, Sec. 1704.5, Sec. 1705.4, Sec. 2105, and MSJC Sec. 1.12) •

•

quality assurance plan developed by engineer of record (EOR) and incorporated into contract documents (CDs) testing agency appointed to sample any materials used

•

•

inspection agency appointed to perform inspections both agencies required to bring deficiencies to the attention of EOR, building official, and contractor



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Masonry

Masonry (Part 2)

Quality Assurance, Testing and Inspection types of inspections (IBC Sec. 110, Sec. 1704) •

•

periodic inspection: part‐time observation of work by inspector at stages of construction continuous inspection: full‐time observation of work by inspector

•

•

standard inspection: applicable to all projects special inspection: required for installation of critical components, performed by special inspectors with expertise



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Masonry

Masonry (Part 2)

Quality Assurance, Testing and Inspection level of inspection

depends on design process (empirical vs. engineered) used and risk category of building •

engineered masonry includes ASD, SD, and prestressed

•

empirical masonry is specified in MSJC Chap. 5

•

veneer (MSJC Chap. 6) and glass unit masonry (MSJC Chap. 7) are considered empirical



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Masonry

Masonry (Part 2)

Quality Assurance, Testing and Inspection risk category (IBC Sec. 110, Sec. 1604, Sec. 1705)

Risk categories are used to determine structural requirements based on occupancy. Table 6.3 Risk Category of Buildings



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Masonry

Masonry (Part 2)

Quality Assurance, Testing and Inspection inspection requirements •

Foundation inspection is required after footing is excavated and reinforcement is in place.

•

• •

•

Forms and materials should be in place for concrete footings. Slab and under‐floor inspections are required after reinforcement and building equipment are in place.

•

Building official may require other inspections. Final inspection is required after the completion of permitted work. Special inspections are not required for empirical masonry if the category is I, II, or III.



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Masonry

Masonry (Part 2)

Quality Assurance, Testing and Inspection levels of quality assurance (IBC Sec. 1705.4, MSJC Sec. 1.19) •

•

•

Table 6.4 Masonry Quality Assurance Requirements

Level A: requires verification of compliance with approved submittals (MSJC Table 1.19.1) Level B: requires periodic inspections (MSJC Table 1.19.2) Level C: additional requirements over Level B (MSJC Table 1.19.3)



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Masonry

Masonry (Part 2)

Quality Assurance, Testing and Inspection structural observation (IBC Sec. 1705.4) •

•

•

required for SDC D, E, and F and where basic wind speed Vasd ≥ 110 mph consists of visual observation, typically by EOR, for compliance with CDs in addition to normal inspections also required when stipulated by building official, EOR, or architect of record (AOR)



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Masonry

Masonry (Part 2)

Quality Assurance, Testing and Inspection structural observation required for SDC D, E, or F when

structural observation required where Vasd ≥ 110 mph when

•

risk category is III or IV

•

risk category is III or IV

•

structure height > 75 ft

•

structure height > 75 ft

•

SDE E, risk category I or II, and there are more than two stories



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Masonry

Masonry (Part 2)

Learning Objectives You have learned •

•

•

design of slender masonry walls under axial and out‐of‐plane flexural loads connections to masonry code requirements for inspection and masonry construction



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Masonry

Masonry (Part 2)

Lesson Overview Masonry (part 2) •

Design of Slender Walls

•

Design of Anchor Bolts

•

Quality Assurance, Testing, and Inspection



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STRC11 Masonry Part2 0716

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