NEHRP Recommended Provisions STRUCTURES Masonry Design
SEISMIC DESIGN OF MASONRYSTRUCTURESNEHRP Recommended ProvisionsMasonry Design Context in the NEHRP Recommended Provisions Masonry behavior Reference standards Seismic resisting systems Component design Quality assurance SummaryInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 1Objectives of Module Basics of masonry behavior Basics of masonry specification The MSJC code and specification and their relationship to the NEHRP Recommended Provisions documentsEarthquake design of masonry structures andcomponents using the 2005 MSJC code andspecificationExample of masonry shear wall designInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 2Context in the NEHRP RecommendedProvisions Design seismic loads– Load combinationsChap. 5– Loads on structuresChap. 5– Loads on components & attachmentsChap. 6 Design resistancesChap. 11– Strength design (mostly references the 2002 MSJC)Instructional Material Complementing FEMA 451, Design Examplesunits ofconcrete orfired clayDesign of Masonry Structures 12 - 3. typicaltypicalmaterialsmaterials inforcingbarsInstructional Material Complementing FEMA 451, Design ExamplesFEMA 451B Topic 12 HandoutsDesign of Masonry Structures 12 - 4Essential Elements of SimplifiedDesign for Wall-type Structures Starting point for design Design of vertical strips in walls perpendicular tolateral loads Design of walls parallel to lateral loads Design of lintels Simplified analysis for lateral loads Design of diaphragms DetailingmortargroutInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 5Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 6Masonry Structures 1
Starting Point for Wall-type MasonryStructuresEssential Function of Walls inResisting Gravity LoadsNo beams or columns(Example of direction ofspan)Bearing walls resistaxial loads (concentricand eccentric) asvertical stripsVertical reinforcement of#4 bars at corners andjambsHorizontal reinforcementof two #4 bars in bondbeam at top of wall, andover and under openings(two #5 bars with span 6ft)Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 7Essential Function of Walls inResisting Lateral ForcesWalls parallel to lateralforces act as shear wallsBond beams transferreactions from walls tohorizontal diaphragms andact as diaphragm chordsNonbearing walls resistconcentric axial load asvertical stripsInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 8Effect of OpeningsEffectivewidth of stripAStrip AEffectivewidth of stripBEffectivewidth of stripCStrip BStrip CWidth BWidth CVertical strips of walls perpendicular to lateralforces resist combinations of axial load and out-ofplane moments, and transfer their reactions tohorizontal diaphragmsWidth AInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 9Effect of OpeningsOpenings increase original design actionson each strip by a factor equal to the ratioof the effective width of the strip divided bythe actual width: Effective Width B Actions in Strip B Original Actions Actual Width B Instructional Material Complementing FEMA 451, Design ExamplesFEMA 451B Topic 12 HandoutsDesign of Masonry Structures 12 - 11Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 10Design of Vertical Strips inPerpendicular WallsMoments and axial forces due tocombinations of gravity and lateralloadM PeM Pe/2M windInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 12Masonry Structures 2
Design of Vertical Strips inPerpendicular WallsФPnDesign of Parallel WallsMoments, axial forces, and shears dueto combinations of gravity and lateralloadsMoment-axial forceinteraction diagram(with the help of aspreadsheet)PVhMu, PuФMnInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 13Design of Parallel WallsMoment-axial forceinteraction diagram(with the help of aspreadsheet)Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 14Design of Parallel WallsSufficient lateralcapacity comes fromwall density.Shearing resistance:Φ PnVn Vm Vs M Vm 4.0 1.75 u An fm' 0.25 Pu Vu dv Mu, PuΦ MnInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 15Instructional Material Complementing FEMA 451, Design ExamplesDesign of LintelsDesign of LintelsMoments and shears due togravity loads:(Example ofdirection of span)Mu Shear design: Provideenough depth so that shearreinforcement is notneeded.w l28wlVu 2Design of Masonry Structures 12 - 16Flexural design:Neutral axisdAs Muφ fy 0.9 dAsInstructional Material Complementing FEMA 451, Design ExamplesFEMA 451B Topic 12 HandoutsDesign of Masonry Structures 12 - 17Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 18Masonry Structures 3
Distribution of Shears to Shear WallsClassical Analysis of Structures withRigid Diaphragms Classical approach Locate center of rigidity Treat the lateral load as the– Determine whether thediaphragm is “rigid” or“flexible”– Carry out an appropriateanalysis for shearsInstructional Material Complementing FEMA 451, Design ExamplesInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 19Simplified Analysis of Structures withRigid Diaphragms8 ft 8 ft40 ftstiffness, which isproportional to plan lengthNeglect plan torsion8 ft40 ft8 ft8 ft40 ftV8 ft8 ftVrightInstructional Material Complementing FEMA 451, Design Examples40 ft V( 40 8 8 8 ) ft total( 8 8 8 ) ft V ( 40 8 8 8 ) ft totalInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 21Classical Analysis of Structures withFlexible Diaphragms8 ft8 ftVleft 8 ftDesign of Masonry Structures 12 - 20Simplified Analysis of Structures with RigidDiaphragms Consider only the shearing40 ftVsuperposition of a loadacting through the center ofrigidity and a torsionalmoment about that center ofrigidity 5Vtotal8 3Vtotal8Design of Masonry Structures 12 - 22Classical Analysis of Structures withFlexible Diaphragms40 ft Distribute shears accordingto tributary areas of thediaphragm independent ofthe relative stiffnesses ofthe shear wallshalfhalf8 ft8 ftV40 ft8 ft8 ft8 ftVrightInstructional Material Complementing FEMA 451, Design ExamplesFEMA 451B Topic 12 HandoutsDesign of Masonry Structures 12 - 231Vtotal21 Vtotal2Vleft Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 24Masonry Structures 4
Diaphragm DesignSimplified Diaphragm Analysis Diaphragm shears are resisted by total depth or bycover (for plank diaphragms). Diaphragm momentsare resisted by diaphragm chords in bond beams.Design for the worse of the two cases:40 ftL/28 ft5/8V1/2V8 ftV40 ft8 ft3/8V1/2VM w L2 / 8V wL/28 ft8 ftwInstructional Material Complementing FEMA 451, Design ExamplesInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 25Masonry BehaviorDetails Wall-diaphragm connections Design of lintels for out-of-plane loads between wall- On a local level, masonry behavior is nonisotropic,nonhomogeneous, and nonlinear. On a global level, however, masonry behavior can bediaphragm connections Connections between bond beam and walls Connections between walls and foundation Instructional Material Complementing FEMA 451, Design Examplesidealized as isotropic and homogeneous.Nonlinearity in compression is handled using anequivalent rectangular stress block as in reinforcedconcrete design.A starting point for masonry behavior is to visualizeit as very similar to reinforced concrete. Masonrycapacity is expressed in terms of a specifiedcompressive strength, fm′, which is analogous to fc′.Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 27Masonry Behavior Stress-Strain Curvefor Prism Under Compressionf unitf mortarPrismMortarStrainInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 28Review Masonry Basics Basic terms Units Mortar Grout Accessory materialsMasonry unitf prismFEMA 451B Topic 12 HandoutsDesign of Masonry Structures 12 - 26Design of Masonry Structures 12 - 29––––Reinforcement (may or may not be present)ConnectorsFlashingSealants Typical detailsInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 30Masonry Structures 5
Basic TermsHeadjoints Bond patterns (looking at wall): Concrete masonry units (CMU):BedjointsRunning bond1/3 Running bondStack bondDesign of Masonry Structures 12 - 31Masonry Units– Specified by ASTM C 62 or C 216– Usually solid, with small core holesfor manufacturing purposes– If cores occupy 25% of net area,units can be considered 100% solidInstructional Material Complementing FEMA 451, Design ExamplesInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 32Masonry Mortar Clay masonry units:Design of Masonry Structures 12 - 33Masonry Mortar Mortar for unit masonry is specified by ASTM C 270 Three cementitious systems– Portland cement – lime mortar– Masonry cement mortar– Mortar cement mortarInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 34Masonry Mortar Within each cementitious system, mortar is specifiedby type (M a S o N w O r K):– Going from Type K to Type M, mortar has anincreasing volume proportion of portland cement. Itsets up faster and has higher compressive and tensilebond strengths.– As the volume proportion of portland cementincreases, mortar is less able to deform whenhardened.– Types N and S are specified for modern masonryconstruction.FEMA 451B Topic 12 Handouts– Specified by ASTM C 90– Minimum specified compressivestrength (net area) of 1900 psi(average)– Net area is about 55% of gross area– Nominal versus specified versusactual dimensions– Type I and Type II designations nolonger existFlemish bondInstructional Material Complementing FEMA 451, Design ExamplesInstructional Material Complementing FEMA 451, Design ExamplesMasonry UnitsDesign of Masonry Structures 12 - 35 Under ASTM C270, mortar can be specified byproportion or by property. If mortar is specified by proportion, compliance isverified only by verifying proportions. For example:– Type S PCL mortar has volume proportions of 1 partcement to about 0.5 parts hydrated mason’s lime toabout 4.5 parts mason’s sand.– Type N masonry cement mortar (single-bag) has onepart Type N masonry cement and 3 parts mason’ssand.Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 36Masonry Structures 6
Masonry MortarMasonry Mortar Under ASTM C270, mortar can be specified The proportion specification is the default.by proportion or by property:– Proportion specification is simpler -- verifyin the field that volume proportions meetproportion limits.– Property specification is more complex: (1)establish the proportions necessary toproduce a mortar that, tested at laboratoryflow, will meet the required compressivestrength, air content, and retentivity (abilityto retain water) requirements and (2) verifyin the field that volume proportions meetproportion limits.Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 37 Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 38GroutGrout Grout for unit masonry is specified by ASTM C 476 Two kinds of grout:– Fine grout (cement, sand, water)– Coarse grout (cement, sand, pea gravel, water) ASTM C 476 permits a small amount of hydrated lime,but does not require any. Lime is usually not used inplant – batched grout.Instructional Material Complementing FEMA 451, Design Examples Unless theproperty specification is used, no mortar testing isnecessary.The proportion of water is not specified. It is determinedby the mason to achieve good productivity andworkmanship.Masonry units absorb water from the mortar decreasingits water-cement ratio and increasing its compressivestrength. Mortar need not have high compressivestrength.Design of Masonry Structures 12 - 39Grout Under ASTM C476, grout can be specifiedby proportion or by compressive strength:– Proportion specification is simpler. Itrequires only that volume proportions ofingredients be verified.– Specification by compressive strength ismore complex. It requires compressiontesting of grout in a permeable mold (ASTMC 1019).Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 40Grout If grout is specified by proportion, compliance isverified only by verifying proportions. For example:– Fine grout has volume proportions of 1 part cement toabout 3 parts mason’s sand.– Coarse grout has volume proportions of 1 part cementto about 3 parts mason’s sand and about 2 parts peagravel. Unless the compressive-strength specification is The proportion of water is not specified.The slump should be 8 to 11 in. Masonry units absorb water from the groutdecreasing its water-cement ratio andincreasing its compressive strength. Highslump grout will still be strong enough.used, no grout testing is necessary.Instructional Material Complementing FEMA 451, Design ExamplesFEMA 451B Topic 12 HandoutsDesign of Masonry Structures 12 - 41Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 42Masonry Structures 7
MASONRY DESIGN CODES IN THE USAccessory MaterialsHorizontally oriented expansion joint undershelf angle:WeepholesFlashingShelf angleSealant gap 3 / 8 in.Instructional Material Complementing FEMA 451, Design ExamplesANSI process (balance of interests, letter ballots, resolution ofNegatives, public visionsMSJCmodel codesSpecificationICCreference those(QA,Other ng Code)execution)(NFPA)local authoritiesadopt those modelcodesBuilding Code(legal standing)(contract between society and the designer)Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 43Design of Masonry Structures 12 - 442005 MSJC CodeWhat is the MSJC Code andSpecification. ?MSJCSpecificationCh. 1, General RequirementsACI(ACI 530-05)(ACI 530.1-05)2005 MSJCCode andSpecificationASCE(ASCE 5-05)(ASCE 6-05)(part of a civilcontract betweenowner andcontractor)TMS(TMS 402-05)(TMS 602-05)Ch. 2,AllowableStressDesignCh. 3,StrengthDesign“Masonry StandardsJoint Committee”Instructional Material Complementing FEMA 451, Design Examples2.1, General ASD2.2, URM2.3, RMDesign of Masonry Structures 12 - 45Ch. 4,PrestressedMasonryCh. 5,EmpiricalDesign3.1, General SD3.2, URM3.3, RMInstructional Material Complementing FEMA 451, Design ExamplesRelation Between Code andSpecificationCh. 6,VeneerCh. 7,GlassBlock6.1, General6.2, Anchored6.3, AdheredApp.A,AACDesign of Masonry Structures 12 - 46Role of fm′ Concrete: Code:– Design provisions are given in Chapters 1-7 andAppendix A– Sections 1.2.4 and 1.14 require a QA program inaccordance with the specification– Section 1.4 invokes the specification by reference. Specification:– Verify compliance with specified fm′– Comply with required level of quality assurance– Comply with specified products and executionInstructional Material Complementing FEMA 451, Design ExamplesFEMA 451B Topic 12 HandoutsDesign of Masonry Structures 12 - 47– Designer states assumed value of fc′– Compliance is verified by compression tests oncylinders cast in the field and cured under idealconditions Masonry– Designer states assumed value of fm′– Compliance is verified by “unit strength method” orby “prism test method”Instructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 48Masonry Structures 8
Example of Unit Strength Method(Specification Tables 1, 2)Verify Compliance with Specified fm′ Unit strength method (Spec 1.4 B 2):– Compressive strengths from unit manufacturer– ASTM C 270 mortar– Grout meeting ASTM C 476 or 2,000 psi Prism test method (Spec 1.4 B 3):– Pro -- can permit optimization of materials– Con -- require testing, qualified testing lab, andprocedures in case of non-complying resultsInstructional Material Complementing FEMA 451, Design Examples Clay masonry units (Table 1):– Unit compressive strength 4150 psi– Type N mortar– Prism strength can be taken as 1500 psi Concrete masonry units (Table 2):– Unit compressive strength 1900 psi– Type S mortar– Prism strength can be taken as 1500 psiInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 49Application of Unit Strength Method(Spec Tables 1, 2)Comply with Specified Products andExecution Products -- Specification Article 2: Design determines required material specification:– Units, mortar, grout, accessory materials– Designer states assumed value of fm′– Specifier specifies units, mortar and grout that willsatisfy “unit strength method” Execution -- Specification Article 3– Inspection– Preparation– Installation of masonry, reinforcement, grout,prestressing tendons Compliance with fm′ can be verified with no tests onmortar, grout, or prismsInstructional Material Complementing FEMA 451, Design ExamplesInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 51Organization of MSJC CodeChapter 11.1 – 1.6 Scope, contractdocuments andcalculations, specialsystems, referencestandards, notation,definitions1.7 Loading1.8 Material properties1.9 Section properties1.10 Deflections1.11 Stack bond masonry1.12 Corbels1.13 Details of reinforcement1.14 Seismic designrequirements1.15 Quality assurance program1.16 ConstructionInstructional Material Complementing FEMA 451, Design ExamplesFEMA 451B Topic 12 HandoutsDesign of Masonry Structures 12 - 53Design of Masonry Structures 12 - 50Design of Masonry Structures 12 - 52Code 1.8, Material Properties Chord modulus of elasticity, shear modulus, thermal expansion coefficients, and creep coefficients for clay,concrete, and AAC masonryMoisture expansion coefficient for clay masonryShrinkage coefficients for concrete masonryInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 54Masonry Structures 9
Code 1.9, Section Properties Use minimum (critical) area for computing memberstresses or capacities– Capacity is governed by the weakest section; forexample, the bed joints of face-shell bedded hollowmasonryInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 55Organization of MSJC CodeChapter 11.1 – 1.6 Scope, contractdocuments andcalculations, specialsystems, referencestandards, notation,definitions1.7 Loading1.8 Material properties1.9 Section properties1.10 Deflections1.11 Stack bond masonry1.12 Corbels1.13 Details of reinforcement1.14 Seismic designrequirements1.15 Quality assurance program1.16 ConstructionInstructional Material Complementing FEMA 451, Design ExamplesDesign of Masonry Structures 12 - 57Organization of MSJC CodeChapter 11.1 – 1.6 Scope, Contractdocuments andcalculations, specialsystems, referencestandards, notation,definitions1.7 Loading1.8 Material properties1.9 Section properties1.10 Deflections1.11 Stack bond masonry1.12 Corbels1.13 Details of reinforcement1.14 Seismic designrequirements1.15 Quality assurance program1.16 ConstructionInstructional Material Complementing FEMA 451, Design ExamplesFEMA 451B Topic 12 HandoutsDesign of Maso
Provisions Design seismic loads – Load combinations Chap. 5 – Loads on structures Chap. 5 – Loads on components & attachments Chap. 6 Design resistances Chap. 11 – Strength design (mostly references the 2002 MSJC) Instructional Material Complementing FEMA 451, Design Examples Design of Masonry Structures 12 - 5 grout steel reinforcing .
FEMA 451, NEHRP Recommended Provisions: Design Examples 6-6 6.1 DEVELOPMENT OF SEISMIC LOADS AND DESIGN REQUIREMENTS 6.1.1 Seismicity Using Provisions Maps 7 and 8 [Figures 3.3-3 and 3.3-4] for Berkeley, California, the short period and one-second period spectral response acceleration parameters SS and S1 are 1.65 and 0.68, respectively. [The 2003 Provisions have adopted the 2002 USGS .
Structural/Seismic Risk Consultant PO Box 3250 Memphis, TN 38173 901-488-9951 rwhowe@earthlink.net Seismic Code developments Process (USGS NEHRP Provisions ASCE 7 IBC) 2008 USGS national seismic hazard map developments (done) 2009 NEHRP Provisions developments (done) ASCE 7-10 / IBC 2012 incorporation of 2009 NEHRP
Masonry lintel design is a critical part of an efficient structural masonry solution. The design of masonry . Figure 2: Steel lintel at bearing Figure 3: Masonry lintel intersection masonry jamb. 2020. Lintel design criteria for all tables below: - Masonry design is based on f'm 2500 psi, strength design, and is designed using NCMA .
seismic hazard maps, the NEHRP Recommended Provisions seismic design maps, site effects, directionality effects, and the NEHRP Recommended Provisions response spectrum. FEMA 451B Topic 5a Notes Seismic Hazard Analysis 2 Instructional Material Complementing FEMA 451, Design Examples Seismic Hazard Analysis 5a - 2
Home Walls Masonry Walls Roof-to-Masonry-Wall Connections Roof-to-Masonry-Wall Connections In older houses with masonry walls it is common to find a 2x8 lumber plate that is bolted or strapped flat like a plate to the top of the masonry wall. The trusses or rafters are then connected to this plate. In older homes the connection may be
masonry school, it would have been a major issue for tilt-up construction. Masonry adapts well to almost any terrain while tilt-up requires a flat surface and sometimes considerable in-fill. Still, there was probably additional site work that would have increased the masonry school cost. (2) The masonry school had a greater window area.
retrofitting an existing masonry wall for increased loads. Masonry Properties: Shear and flexural masonry strength is dependent on the specified compressive strength (f'm) of the existing masonry assembly. The value of f'm, in turn, is dependent on the combination of the net compressive strength of the masonry units and the mortar type.
Awards for housing design provide the opportunity to reward, celebrate and encourage the best in residential design. They also provide the opportunity to learn about new forms of living environment and the potential quality of development which housing developers and designers can deliver. Such issues are of paramount importance as the quality of living environments has a significant impact on .
