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Canadian Concrete Masonry Producers’ …

Canadian Concrete Masonry producers MasonryDesign GuidelinesCanadian Concrete Masonry producers AssociationEmpirical Masonry Design Guidelinesw c m DESIGN FOR Masonry BUILDINGS8-1 INTRODUCTIONThe empirical or Conventional Design for Masonry isbased on a simplified analysis of the loads and forcesacting on the structure. When this approach is utilized,the limitations of height, load location, seismic zone,wind loading, the size of any openings and lateral sup-port requirements must be resulting from this type of procedure are oftendescribed by such phrases as deemed to performbased on long-term experience .Engineered Analysis, results in a more cost effectivestructure in many instances and must be used wheneverthe limitations are chapter is a commentary on selected detailsof Clause 16, Masonry Design for Buildings(Limit States Design) does not purportto be a total design Concrete Masonry producers AssociationEmpirical Masonry Design Canadian Concrete Masonry producers association gratefully acknowledges the contributionsof the following:Dr.

Canadian Concrete Masonry Producers’ Association Empirical Masonry Design Guidelines w w w . c c m p a . c a EMPIRICAL DESIGN FOR MASONRY BUILDINGS

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1 Canadian Concrete Masonry producers MasonryDesign GuidelinesCanadian Concrete Masonry producers AssociationEmpirical Masonry Design Guidelinesw c m DESIGN FOR Masonry BUILDINGS8-1 INTRODUCTIONThe empirical or Conventional Design for Masonry isbased on a simplified analysis of the loads and forcesacting on the structure. When this approach is utilized,the limitations of height, load location, seismic zone,wind loading, the size of any openings and lateral sup-port requirements must be resulting from this type of procedure are oftendescribed by such phrases as deemed to performbased on long-term experience .Engineered Analysis, results in a more cost effectivestructure in many instances and must be used wheneverthe limitations are chapter is a commentary on selected detailsof Clause 16, Masonry Design for Buildings(Limit States Design) does not purportto be a total design Concrete Masonry producers AssociationEmpirical Masonry Design Canadian Concrete Masonry producers association gratefully acknowledges the contributionsof the following:Dr.

2 Drysdale, PhD., University, HamiltonR. Jiran, Branch, City of Shirlaw, Portland Cement association , Toronto, OntarioThis "Guide" is intended to facilitate the use of Concrete block construction in accordance with , Masonry Design for Buildings, (Limit States Design) Clause 16 While all possible care has been taken to ensure that the information contained herein is accurateneither the Canadian Concrete Masonry producers association nor any of the contributors can accept responsibility for any errors or Concrete Masonry producers AssociationEmpirical Masonry Design empirical Rules can be used for non-reinforcedMasonry height of loadbearing walls above the firststorey floor does not exceed 11 height of exterior non-loadbearing walls abovegrade does not exceed 20 metres and the 1 in 30years wind pressure does not exceed kN/m2.(Refer to Table , Ontario Building Code, forapplicable data). walls are not subject to lateral Ontario Building Code ( ) allows limitedusage on basis of "deems to" proven,performance.

3 (See Figure ) structure is not subjected to lateral pressureother than wind resultant vertical force of a load falls within themiddle third of the wall thickness. (See Figure ) is located within seismic zones 0 and1. (Refer to Table Ontario Building Code,for applicable data). empirical Rules can only be used for plain,non-reinforced Masonry . Note that joint reinforcingfor bonding or crack control and reinforcing insecondary structural elements such as short spanlintels, does not invalidate this design `A' and `B' fall within empirical `C' requires Engineered AnalysisFigure 1 MIDDLE THIRD RULEC anadian Concrete Masonry producers AssociationEmpirical Masonry Design GuidelinesALLOWABLE COMPRESSIVE the purposes of Table `A', the conversion from Netto Gross Area strength of standard units is as follows:See Tables `B' and `C' for allowable loads on standardstrength units. 15 MPa net is the standard strengthavailable from CCMPA Members See Section Units with a strength of 20 MPa and over areavailable on a made to order Masonry is constructed of different types orgrades of units or mortar, the allowable stress shall bebased on the weakest the wythes of a cavity wall are of differenttypes of material, it is recommended that only onewythe be loaded.

4 Where only one wythe is loaded, the allowable stress shall be based on the MASONRY20 MPa & overSolid - 20 MPaHollow MPaCAVITYWALLS olid MPaHollow MPaSNMORTARTYPESTABLE A:MAXIMUM ALLOWABLE COMPRESSIVE STRESSFOR NON-REINFORCED Concrete MASONRYBASED ON GROSS CROSS-SECTIONAL AREA (MPa)WALLTYPESUNIT TYPENET MPaGROSS allowable compressive stresses on Masonry ,based on gross cross-sectional area, are given in Table7 in Where concentrated loads occur,Clause allows maximum stresses to beincreased by 25% (But the total load on the masonrycannot exceed value allowable).Note that the latest specification for Concrete , designates strengths in terms of net Concrete Masonry producers AssociationEmpirical Masonry Design TYPENSUNIT TYPE(15 MPa)ALLOWABLESTRESS MPaUNIT B:ALLOWABLE LOADS FOR SOLID or SINGLE WYTHE Masonry (Standard Strength Concrete Block) (kN/m)TABLE C:ALLOWABLE LOADS FOR LOADED CAVITY WYTHE 2(Standard Strength Concrete Block) (kN/m)MORTAR TYPENSUNIT TYPE(15 MPa)ALLOWABLESTRESS MPaUNIT Unit means a structural Masonry unit with a net cross sectional area of at least 75% of its gross cross sectional area in any plane parallel to its bearing the exterior wythe is designed as a veneer, the values in Table `B' may be used for the loadbearing Concrete Masonry producers AssociationEmpirical Masonry Design D:ALLOWABLE COMBINED LOADS FOR BOTH WYTHES (kN/m)(Standard Strength Concrete Block)MORTAR TYPENSUNIT TYPE(15 MPa)ALLOWABLESTRESS ++++++90140190240290 TABLE E.

5 ALLOWABLE LOADS FOR HIGH STRENGTH SOLID UNITS(> 20 MPa)1 (kN/m)MORTAR TYPENSALLOWABLESTRESS F:WALL WEIGHT & MASS FOR STANDARD WEIGHT UNITS (2100 kg/m3)MORTAR TYPEWALL MASS(kg/m2)WALL WEIGHT(kg/m2)ALLOWABLESTRESS MPaUNITSIZEH ollow13817022326731075% High strength units are available on a made to order basis : Wall weight = mass x 1000 Canadian Concrete Masonry producers AssociationEmpirical Masonry Design GuidelinesLateral Masonry means Masonry of solid or hollow units that does not have cavities between the wythes, single wythe Masonry is included in this height or length of wall between horizontal or vertical lateral thickness may be reduced; the 140mm solid Masonry unit can be useda)in loadbearing applications, the maximum height at eave is and at the gable (See Figure )b)in exterior, non-loadbearing applications, with a maximum height of 3m but Type `S' mortar is partitions in buildings with small exterior openings or with unbalanced air pressures not exceeding 24 G.

6 HEIGHT & THICKNESS OF SOLID MASONRY1 TYPE OFWALLLOADBEARING(Solid or Hollow Units)EXTERIORNON-LOADBEARING(Solid or Hollow Units)PARTITIONS4 MAXIMUMh/t2 HEIGHT/THICKNESS RATIO h/t22019090 11 metres2019075 20 metres36757572 x actual thicknessMINIMUM WALLt3(mm)MINIMUM WYTHEt (mm)MAXIMUM TOTALHEIGHTL ateral support must be provided at either horizontal or vertical intervals not exceeding 20 times the actual wallthickness (t) except as partition walls, lateral support is required at cavity walls, the wall thickness shall be based on two thirds (2/3) the sum of both wythes but not lessthan the thickness of either wythe. This derived effective thickness (te) applies irrespective of the loadingof the that raked joints reduce the usable thickness and cannot be used where unit width is less than Concrete Masonry producers AssociationEmpirical Masonry Design + + + + + (te) (mm)MAXIMUMBUILDING HEIGHT 3(m)LATERALSUPPORT(m) wythe combinations are possible, 140 and 140mm will produce at te of and allows lateralsupport at use of width of thicker wythe to determine both wythes are solid units, one wythe may be 75mm (CAN3-S304, ).

7 Lateral support is required at but maximum building height is limited to 6m above first storey cavity walls, the effective thickness shall be based on two thirds (2/3) the sum of both wythes butnot lessthan the actual thickness of the greater NOT SUPPORTED AT THE TOP(CAN3-S304, Clause )PARAPETSA cantilevered wall cannot exceed a slenderness ratio (h/t) of four, unless horizontal lateral supportsare provided in accordance with the requirement of Table 8 in Code. (generally 20t or 20 te for cavity walls)WINDOW SILLSThe unsupported distance from sill to the floor below cannot exceed a slenderness ratio (h/t) of 3 but onlywhere the length exceeds the requirements of Table 8 in Code. (20t or 20te)Where lateral support is provided along the top or where the length of wall below the sill is equal orless than permitted, vertical supports are not H:EFFECTIVE THICKNESS & LATERAL SUPPORT FOR CAVITY WALLSFIGURE DESIGN FOR LATERAL SOIL from , Ontario Building grade depth measured from top of floor must be below frost Building Code gives lateral support requirementsCanadian Concrete Masonry producers AssociationEmpirical Masonry Design Concrete Masonry producers AssociationEmpirical Masonry Design GuidelinesALLOWABLE OPENINGS IN EXTERIOR WALLSw c m ( ) provides requirementsto avoidover stressing walls between openings for doors, windows and ends of wall due to reduced wall requirements apply to walls laterally supported at top and to wind loads is deemed sufficient where aspecified percentage of the wall remains.

8 The minimumlength depends on the slenderness ratio (h/t): as theratio increases ( the wall becomes more slender) therequired length of wall remaining the required percentage remainingis based on thelength between centre points of adjacent openings andbetween centre point of an opening and the end orreturn of a wall. (See Figure 4.) Where the length of wall remaining is less than 3t, the wall shall be designedas a column with lateral support at 1 PERCENTAGE OF WALLREQUIRED FIGURE ALLOWABLE 1 illustrates values from Table 9 ( ). interpolation is permitted h/t = 13: required wall= 35% of openings vary from 80% of total wall(where h/t = 10) to a minimum of 15% (where h/t = 20) Canadian Concrete Masonry producers AssociationEmpirical Masonry Design GuidelinesEmpirical Design ExampleFour Storey Residencew c m Concrete Masonry producers AssociationEmpirical Masonry Design GuidelinesFour Storey Residencew c m @ POINT`A'LA=Roof Dead Load + Roof Live Load + Wall Dead Load=[[8m ( kN/m2) + ( kN/m2)] + [ x kN/m2]]=[ kN/m + kN/m + kN/m]=[ kN/m + kN/m]La= kN/mLOAD @ POINT`B'LB=Floor Dead Load + Occupancy Load + Wall Dead Load + LA=[[ ( kN/m2) + ( kN/m2)] + ( x )] + kN/m]=[[ kN/m + kN/m + kN/m] + kN/m]=[ kN/m + kN/m]Lb= kN/mLOADS @ POINT`CLC=Floor Dead Load + Occupancy Load + Wall Dead Load + LB=[[ ( kN/m2) + ( kN/m2)] + ( kN/m2)

9 ] + kN/m]=[[ kN/m + kN/m + kN/m] + kN/m]=[ kN/m + kN/m]= kN/mDESIGN LOADS Roof Dead Load kN/m2 Roof Live Loadsdue to snow, ice and rain (Sudbury) kN/m2 Floor Dead LoadPrecast Concrete Slab kN/m2 Wall Dead Load20cm NW Hollow Block kN/m220cm NW 75% Solid Block kN/m2 Occupancy Load kN/m2 Canadian Concrete Masonry producers AssociationEmpirical Masonry Design Guidelinesw c m @ POINT`D'LD=Floor Dead Load + Occupancy Load + Wall Dead Load + LC=[[ ( kN/m2) + ( kN/m2)] + ( kN/m2)] + kN/m]=[[ kN/m + kN/m + kN/m] + kN/m]=[ kN/m + kN/m]LD= kN/mCONSTRUCTION MATERIAL SELECTIONS1st Floor 20cm 75% solid NW Concrete block @ 15 MPa strength with Type `S' mortar2nd Floor 20cm Hollow NW Concrete block @ 15 MPa strength with Type `S' mortar3rd Floor 20cm hollow NW Concrete block @ 15 MPa strength with Type `S' mortar4th Floor 20cm hollow NW Concrete block @ 15 MPa strength with Type `S' mortarCanadian Concrete Masonry producers AssociationEmpirical Masonry Design Guidelinesw c m OPENINGSHEIGHT/THICKNESS RATIOh/t = 2400/190 = say 13%Area of wall required is 35%(refer to chart on page 8-10)DISTANCE TO from centre of window to end of wall35% of = Distance = Distance > Minimum AllowableDistance OK!

10 Between opening centres35% of = Distance = Distance > Minimum AllowableDistance OK! from centre of door to end wall35% of = Distance = Distance > Minimum AllowableDistance OK!8-14


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