2012.08.08 - masonry building design

MASONRY BUILDING

An Overview of Masonry Building Design Methods

Presented by Scott W. Walkowicz, P.E., NCEES

Walkowicz Consulting Engineers, LLC

SE University, August, 2012 www.LearnWithSEU.com 1

MASONRY BUILDING DESIGN

� To know the basic requirements for a masonry structured building� To know key changes in recent masonry code

updates

Learning Objectives

� To understand the specific defining limits and requirements related to different masonry elements

� To recognize the benefits of whole building or wall software

Copyright © 2012, Walkowicz Consulting Engineers, LLC 2

� Overview

� Software Overview

� Introduce the Example Building

Lintel Design

Seminar Outline

� Lintel Design

� Jamb Strip Design

� Bearing Wall Design


� Gravity and lateral loads

� Elements

� Sidetrack (s)….

Overview


� Gravity load path� First act on horizontal members:

� Roof or floor plates

� Transfer to beams

� Then to girders

Gravity and Lateral Loads

� Then to girders

� Then transfer to vertical elements� Columns

� Walls

� Terminate at foundations where they transfer to the earth


Diagram Credit: Luebkeman and PetingDiagram Credit: Luebkeman and Peting



� Buildings must also resist lateral loads� Wind

� Seismic

� Fluid


� Fluid

� Earth

� Act horizontally

� Cause sliding and/or overturning� Individual elements

� Building as a whole


� Lateral load path� First act on vertical surfaces perpendicular to

their direction

� Transfer load to horizontal supports


� Foundation

� Floor plates

� Roof plate

� Flow through horizontal supports to vertical elements parallel to the load’s direction

� Transfer through to foundation



Copyright © 2012, Walkowicz Consulting Engineers, LLC

Diagram Credit: IMI InternationalDiagram Credit: IMI International

9

� Joints

� Connections

� Walls

Columns

Elements

� Columns

� Piers

� Beams

� Pilasters


� Not going to design joints today…

� May avoid joints with horizontal reinforcement

When using joints:

Joints

� When using joints:� Place to minimize and control cracking

� Utilize vertical control joints

� Utilize vertical and horizontal expansion joints

� Move them off openings in structural wythes

� Locate them in drawings and detail them


� Not going to design connections today…

� Must connect the walls receiving load to the diaphragm

� A 25’ tall wall with 20 psf wind load

Connections

� A 25’ tall wall with 20 psf wind load generates 250 lbs./ft. at top connection

� If anchors are at 4’ = 1000 lbs./anchor

� Compression and

� Tension


� Must connect the diaphragm to the lateral load resisting elements

� Shear

� A 25’ tall building that is 100’ long with 2 –

Connections

� A 25’ tall building that is 100’ long with 2 –40’ long shear walls and 15 psf MWFRS load generates 190 lbs./ft. of shear at the diaphragm connection

� If anchors are at 4’ = 760 lbs./anchor


� Pay attention to capacity and stiffness

� Axial

� Tension

� Compression

Connections

� Compression

� Unbraced length

� Eccentricity

� Shear

� Flexural

� If bridging cavities or other voids with transverse displacement


� Vertical Element

� Horizontal length : Thickness > 3 : 1

� Used to enclose space

Walls



� Not a wall: Length = 3 * nom. thickness

Walls



� Wall example:

Walls


� Note:

� Within a wall…

� No confinement ties unless…

The reinforcement is being utilized

Walls

� The reinforcement is being utilized (through transformed section analysis) to resist axial compression


� An ISOLATED vertical member� Like at the corner of a Porte-cachere

� Not referring to seismic isolation

� Horizontal dimension : Thickness ≤ 3 : 1

Columns

� Horizontal dimension : Thickness ≤ 3 : 1

� Height : Thickness > 4 : 1

� Grouted solid – SD only


� Prescriptive confinement ties (≥ #2)

� Min. / max. longitudinal reinforcement

� Slenderness limit on height (ASD: 25 or SD: 30 * nominal dimension)

Columns

SD: 30 * nominal dimension)

� Minimum eccentricity (ASD: 0.1*dim.)


Columns


� Minimum Height and Maximum Length for an 8” nominal column thickness

22

Columns


� An ISOLATED vertical member� Not between windows

� Special case conceptually between walls and columns

� Strength Design only

Piers

� Strength Design only

� Load limit (0.3*An*f’m)

� Horizontal dimension : Thickness > 3 : 1 and ≤ 6 : 1

� Height : Length < 5 : 1

� No prescriptive confinement ties


Piers


� No specific definition

� Longitudinally reinforced

� May have transverse reinforcement

� Laterally braced at 32 x Thickness

Beams

� Laterally braced at 32 x Thickness

� Deflection control only to protect strength and serviceability

� l/600 for support of unreinforced masonry

� Do NOT require solid grout


� No specific definition

� Typically vertical spanning flexural element with walls spanning horizontally between

Pilasters

horizontally between

� Longitudinally reinforced

� May have confinement ties, if� Longitudinal reinforcement is utilized to resist axial

compression

� If unbonded and meet column criteria or to bond with wall wythe


� 2008 MSJC Adopted with 2009 IBC

� TMS now the lead sponsor

� Major changes� Relocation of certain information

Sidetrack… 1.

� Relocation of certain information

� Structural corbels allowed

� Removed 0.3” deflection for beams supporting unreinforced masonry

� Explicit Ieff requirements

� Light column provisions

� Self Consolidating Grout (SCG) added

� See “Transition Guide” published by TMS


� 2011 MSJC Adopted with 2012 IBC

� Major changes� Side by side layout with commentary

� 1/3 stress increase eliminated with stress

Sidetrack… 2.

� 1/3 stress increase eliminated with stress recalibrations

� ASD shear stress provisions significantly reworked

� Coordinated with ASCE 7-10

� AAC moved to Chapter 8 (from Appendix A)

� Design of Masonry Infill added as Appendix B


� Special Inspection

� Are they required?

� Put a list in the drawings?

What else?

Sidetrack… 3.

� What else?


Int’l Building Code


� Chapter 17

IBC 2009 Special Inspections


� Chapter 17



� Example Design of a Single-Story Building

� Masonry Structures Behavior and Design, 3rd Addition (Drysdale & Hamid)

Introduce the Example

Design, 3rd Addition (Drysdale & Hamid)


� 16.5 Example Design of a Single-Story Building (p. 655 ff)� 147’-4” x 96’-0”

� Single-story, T.O.M. = 18’-0” with no parapet


� Single-story, T.O.M. = 18’-0” with no parapet

� Small interior two-story office area

� Modify to Lansing, MI location

� Modify wind per ASCE 7-05

� Modify control joint layout to non-lintel ends per NCMA TEK 10-3


Graphic Credit: MIMGraphic Credit: MIM

Roof Framing Plan


West Elevation



43

North and South Elevations


Graphic Credit: MIMGraphic Credit: MIM44

North and South Elevations



45

� Hand Calculations

� Component

� Whole Building

Analysis Introduction


� A combination of calculations and tabulated data…

� Current code provisions and values?

� Less time requires simplification and

Hand Methods…

� Less time requires simplification and assumption

� Simplification and assumption lead to conservatism

� Conservatism leads to inefficiency

� Inefficiency adds cost and time to projects


� Structural Masonry Design System (SMDS)

� Enercalc

Quick Masonry

Component Software

� Quick Masonry

� Digital Canal

� Many others….

� We’ll use SMDS


� Some more accurate than others

� Some very inaccurate and even unconservative

Limited applications

Component Software

� Limited applications

� Multiple evaluations required


� Ram Elements

� RisaMasonry

� We’ll use Ram Elements…

And Ram Structural System

Whole Building Software

� And Ram Structural System


� Ram Elements for Masonry Design

� Build model in Ram Structural System

� Rapid generation

� Grid lines and Story Levels


� Grid lines and Story Levels

� Easy member and material designation

� Easy generation of openings

� Easy modification

� Generate Seismic and Wind Shear Story Loads

� Direct interface with Revit


� Ram Elements for Masonry Design

� Build model in Revit

� Technician generation

� Single model path with documentation


� Single model path with documentation model

� Bi-directional integration with Revit through Structural Synchronizer


� Build model in Ram Structural System

� Some drawbacks to consider� Wind loads may be higher than necessary

� Cannot designate walls as masonry


� Cannot designate walls as masonry

� Stories interrupt entire levels even when partial areas

� Out-of-plane pressures are not applied and do not transfer to RE (only story lateral forces and gravity loads)

� Once in RE will require some modifications


� Before we begin

� Must determine basic loads� Dead Load

� Live Load

All Methods…

� Snow Load

� Wind Load

� Seismic, etc…

� Then…

� We’ll look at several element designs using various methods


� Roof Dead Load:

� Roof membrane (60 mil EPDM): 0.4 psf

� Insulation (2” polyiso + ½” fiberboard): 1.7 psf

� Deck (1.5 B 22): 1.8 psf

Basic Loads

� Deck (1.5 B 22): 1.8 psf

� Joists (30K10 at 6’ o.c. – 12 plf): 2.0 psf

� Mech/Elect/Misc: 5.0 psf

� Total Dead Load: 10.9 psf

Say: 11.0 psf


� Roof Live Load (ASCE 7-05):

� 20 psf base live load (reducible)

� To the perimeter walls: Joist Tributary areas:

� 6’ spacing

58’ span maximum

Basic Loads

� 58’ span maximum

� 6’ x 58’/2 = 174 SF – not eligible for reduction

� Use 20 psf


� Roof Snow Load (ASCE 7-05):

� Pf = 0.7 x Ce x Ct x I x Pg

� Ce = 1.0 (Table 7-2, Partially exposed, Terrain Category B or C)

Basic Loads

� Ct = 1.0 (Table 7-3, standard roof performance)

� I = 1.0 (Table 7-4, Occupancy Category II, Table 1-1)

� Pg = 30 psf (Figure 7-1)

� Pf = 0.7 x 1.0 x 1.0 x 1.0 x 30 = 21 psf


� Wind Load - MWFRS (ASCE 7-05):

� Simplified Method

� Ps = λ x Kzt x I x PS30

� λ = 1.26 (Figure 6-2, Interpolated, Exposure C)

Basic Loads


� Kzt = 1.0 (Section 6.5.7.2)

� I = 1.0 (Table 6-1, Category II)

� PS30-C = 8.5 psf (Figure 6-2, Area C, 90 mph, flat roof)

� Ps = 1.26 x 1.0 x 1.0 x 8.5 = 10.71 psf


� Wind Load - MWFRS (ASCE 7-05) – In-plane loads:

� Analytical Method

� qz = 0.00256 x 0.882 x 0.85 x 902 x 1.0 = 15.55 psf

Basic Loads***

� qz = 0.00256 x 0.882 x 0.85 x 90 x 1.0 = 15.55 psf

� Ps = 15.55 x 0.85 x (0.8 + 0.5) = 17.2 psf***


� Wind Load - MWFRS (ASCE 7-05):

� East & West Walls

� V = (96’ x 18’/2 x 10.71 psf) / 2 = 4627 lbs./wall

� V = 4627 lbs. / 147.3’ = 31.4 plf

Basic Loads

� V = 4627 lbs. / 147.3’ = 31.4 plf

� North & South Walls

� V = (147.3’ x 18’/2 x 10.71 psf) / 2 = 7099 lbs./wall

� V= 7099 lbs. / 96’ = 74 plf

� Combine with appropriate out-of-plane loads


� Wind Load - Components and Cladding (Out of Plane Loads) (ASCE 7-05):

� Simplified Method

� Pnet = λ x Kzt x I x Pnet30

λ = 1.26 (Figure 6-3, Interpolated, Exposure C)

Basic Loads


� Kzt = 1.0 (Section 6.5.7.2)

� I = 1.0 (Table 6-1, Category II)

� Pnet30-C = +12.4/-13.6 psf (Figure 6-3, Area 4, 100 SF, 90 mph, flat roof)

� Pnet = 1.26 x 1.0 x 1.0 x -13.6 = -17.14 psf (neg. pressure controls - magnitude & direction)


� Wind Load (ASCE 7-05):

� Don’t forget to include edge and corner zone pressures in actual design…

Basic Loads


� Seismic Loads (ASCE 7-05):

� Michigan Location

� Light roof

� Modest building mass

Basic Loads

� Modest building mass

� Even with bearing wall/shear wall configuration:

� Wind will govern… no calc’s for example


� Hand Methods

� Wall Weight Only with Min. Roof Trib� wDL = (10.67’ x 41 psf) + (6’/2 x 9 psf) = 465 plf

� wLL = 6’/2 x 20 psf = 60 plf

w = 6’/2 x 21 psf = 63 plf

Lintel DesignLintel in Non-load Bearing Wall:

� wSN = 6’/2 x 21 psf = 63 plf

� wTL = 528 plf

� MTL = 528 x 10.672/8 = 7514 lb.-ft. = 90,168 lb.-in.

� VTL = 528 x 10.672/2 = 2817 lbs.

� NCMA TEK 17-01C: 8” x 16” with (1) #6

� NCMA Lintel Manual: 8” x 16” with (1) #4 and f’m = 2500 psi


� Hand Methods:� Strength of method:

� Fairly quick� No software investment� Decent results� Could incorporate triangular, reduced load due to arching


� Could incorporate triangular, reduced load due to arching

� Weaknesses of method:� This building probably has 6 different lintels….� No out-of-plane load consideration� No ability to add load/moment/torsion from anchored lintel� f’m = 1500 psi (only) or purchase NCMA Lintel Manual or

more involved hand calcs….� Pinned-Pinned only


� Component Software:

� Same loads and geometry as hand method

� Increase f’m to 2500 psi per local availability

� 8” x 16” with (1) #6 (no arching)


� 8” x 16” with (1) #6 (no arching)

� 8” x 8” with (2) #5’s (with arching)

� (No Control Joints to maintain thrust resistance)

� Proper height above opening

� No point loads within ‘triangle’


� Component Software:� Strength of method:

� Very quick� Minimal software investment� No software investment� Decent results


� Decent results� Easily incorporate benefits of arching� Easily allows trials of different materials and configurations

� Weaknesses of method:� This little building probably has 6 different lintels….� No out-of-plane load consideration� No ability to add load/moment/torsion from anchored lintel� Pinned-Pinned only


� Build in RSS and import the model into RE

� About 2 hours to build this model

� About 20 minutes to modify the model and set load combinations, etc…

Or build in RE directly


� Or build in RE directly

� Longer to generate due to nodal entry method

� Can do five story simple building in 8 hours

� Or jump to the wall module…

� 10 to 15 minutes for a wall segment

� Includes openings and all loads


� RSS model imported into RE



� Import the model into RE

� Assign materials, etc…

� Masonry (f’m = 2500 psi)

� Bar Joist Sections and Material


� Bar Joist Sections and Material


� Whole Building Software

� We’re only after lintel design right now…

� Don’t analyze the model!

� Select the appropriate wall stack




� A rendered look…




� Open the appropriate wall stack in Module




� Change the number of levels to (1) and adjust the height




� Create Load Cases and Combinations

� Add distributed Roof Live and Snow Loads

� e=0 to match other methods for now…


� e=0 to match other methods for now…

� Analyze without veneer lintel loads…

� Analyze without lateral loads…

� Lintel: 8” x 16” with (1) #4


� Look ahead:

� Add additional strips

� Adjust base fixity to “pinned”

� Will get a lot of “bang for our lintel buck”


� Will get a lot of “bang for our lintel buck”

� Ready for the “jamb strip” analysis (and others)


� Revisit RE Lintel Results: 8” x 16” with (1) #4

� Interesting…

� M = 4,544 lb.-ft. (flexure controls)

� SMDS without arching: M = 7,910 lb.-ft.


� SMDS without arching: M = 7,910 lb.-ft.

� SMDS with arching: M = 2,930 lb.-ft.

� So neither arching nor simple span are accurate???

� Actual moment somewhere in between?


� Whole Building Software:� Strength of method:

� Very efficient results� Automatically incorporates benefits of finite element force

distribution� Full out-of-plane load consideration


� Full out-of-plane load consideration� Full ability to add load/moment/torsion from anchored lintels

or other elements� Easily allows trials of different materials and configurations� Very quick to select multiple walls sequentially from 3-d model� Multiple level and fixity condition capability

� Weaknesses of method:� Moderate to high software investment� Not as quick for a single element unless really streamline input


� Whole Building Software� Add lateral out-of-plane pressure: -17.14 psf� Jamb strip(s) okay with (1) #6 in first 16” then

#6 at 40” or 72” o.c. in rest of wall� Or (2) #5’s in first 24” then more variety in

Jamb Strip DesignJamb Strip in Non-load Bearing Wall:

� Or (2) #5’s in first 24” then more variety in required spacing…

� Then…� Add in shear, eccentricity for gravity – no

change!� Could add veneer lintels, canopy reactions,

etc…


� Whole Building Software:� Strength of method:

� Already had the wall entered� Very efficient results� Automatically incorporates benefits of finite element force

distribution


distribution� Full out-of-plane load consideration� Full ability to add load/moment/torsion from anchored lintels

or other elements� Easily allows trials of different materials and configurations� Very quick to select multiple walls sequentially from 3-d model� Multiple level and fixity condition capability

� Weaknesses of method:� Moderate to high software investment� Not as quick for a single element unless really streamline input


� Component Software

� First: Calculate collected loads

� Assume same 16” strip as RE

� Assume window load distributes to jamb like RE


� Assume window load distributes to jamb like RE

� Wind Loads:

� Direct wind on jamb = -17.14 psf

� Window distribution = (-17.14 psf x 10’/2) / 1.33’

� Window distribution = -57.28 psf

� Total wind load on jamb = -74.42 psf

� Then apply gravity loads with eccentricity



� #6 @16” o.c. - No Good!

� #10 @ 8” o.c.!


� #10 @ 8” o.c.!

� Distribute over 48”… 38.57 psf

� #6 @ 24” or (3) bars in 48”

� Still not as efficient


� Component Software:

� Strength of method:� No software investment

� Rapid analysis for a single element

� Easily allows trials of different materials and configurations

Weaknesses of method:


� Weaknesses of method:� New data entry

� Less efficient results

� Limited out-of-plane load consideration

� No multiple level and limited fixity condition capability

� No ability to add load/moment/torsion from anchored lintels or other elements

� No in-plane shear included


� Hand Methods

� First: Calculate collected loads same as SMDS

� Probably ignore minor gravity loads and their eccentricity

� Multiple load combinations will take time…



� Drysdale takes 5 pages, less than 2 pages of hand calcs, or use

� Spreadsheet interaction diagram

� Few old charts and graphs

� Rigorous calcs equate to SMDS results

� Others more conservative depending on effort


� Hand Methods:

� Strength of method:� No software investment

� Excellent to decent results depending on ability and effort


effort

� Could incorporate any material, load and boundary conditions

� Weaknesses of method:� Not fast at all, no tabulated methods

� This building probably has multiple jamb strips….

� Multiple load combinations will cost time…


� Hand Methods

� First: Calculate loads and eccentricities� Cannot ignore gravity loads and their eccentricity


Drysdale takes 5 pages, less than 2 pages of

Load Bearing Wall DesignGeneral Field Strip in Bearing Wall:

� Drysdale takes 5 pages, less than 2 pages of hand calcs, or use

� Spreadsheet interaction diagram

� Few old charts and graphs

� Rigorous calcs equate to SMDS results

� Others more conservative depending on effort



� First: Calculate Loads

� Same as hand calcs except software does self-wgt.

� DL = 11 psf x 58’/2 = 319 plf


� DL = 11 psf x 58’/2 = 319 plf

� LLr = 20 psf x 58’/2 = 580 plf

� SnL = 21 psf x 58’/2 = 609 plf

� WL = -17.14 psf

� Gravity load eccentricity = -2”



� #5 @ 48” o.c. No Good

� #5 @ 40” o.c. OK


� #5 @ 40” o.c. OK



� Select the appropriate wall stack

� Make quick changes

� Same loads applied as SMDS


� Same loads applied as SMDS

� Include eccentricity for gravity

� Add in shear – no change!

� Could add canopy reactions or other point loads…




� Wire-frame model



� Rendered view

� Whole Building Software – Wall Module


� #5’s @ 40” o.c.


� Lintel:� Lintel design most shallow by SMDS with arching – is it

accurate?� Lintel design lightest steel at 16” depth by RE and NCMA

manual� 2 cs. grout and (1) #4 v. 1 cs. and (2) #5’s

Summary

� 2 cs. grout and (1) #4 v. 1 cs. and (2) #5’s� Not a bad selection to choose from� Hand: 15 minutes with tabulated values� Hand: 30 to 60 minutes to calculate� SMDS: 10 minutes� RE: Wall Module: 10 – 15 minutes but includes entire

wall� RE: 3D: Well… � Wouldn’t do that for a lintel


� Jamb Strip:� Much more efficient with RE� Hand: 30 to 60 minutes or more to calculate� SMDS: 20 minutes� RE: Wall Module:

Summary

RE: Wall Module:� Still the same 10 – 15 minutes from the lintel analysis� Includes all jamb strips, lintels, general field areas

� RE: 3D: Well… � Wouldn’t do that for one wall strip, either� But we’re getting closer… how many walls do you have?� RSS took about 2 hours to build model from start� RE import and modification took about 20 minutes� Wall Module modification use took about 5 minutes


� Load Bearing Wall:� Hand: 30 to 60 minutes or more to calculate

� SMDS: 10 to 15 minutes

� RE: Wall Module: 10 minutes, more if openings, etc…

Summary

etc…

� RE: 3D: Well… � Still wouldn’t do that for one wall segment

� But we’ve now used another part of the model

� RSS took about 2 hours to build model from start

� RE import and modification took about 20 minutes

� Wall Module modification and use took about 5 minutes


� Single elements� Can be done about as quickly in SMDS or RE as by

simplified hand methods

� Can be done more quickly in SMDS or RE than by full hand calculations

Conclusions

full hand calculations

� RE offers ability to consider aspects of design that others don’t

� RE Wall Module is as quick as SMDS for blank walls and

� RE Wall Module offers concurrent design of multiple elements if openings are present


� Multiple Elements

� The greater the number of elements the greater the design time savings with RE

� The greater the number of elements the greater the impact of efficiency on the project cost and schedule

Conclusions

impact of efficiency on the project cost and schedule and therefore the greater the project savings with RE

� And if you need to model floor and roof structures anyway…

� Use one model for the entire building


Questions and Discussion

� Scott W. Walkowicz, P.E., N.C.E.E.S.� [email protected]

� (517) 339-0314


Questions and Discussion

2012.08.08 - masonry building design

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