DATA SHEET 3 Concrete Masonry Lintels MARCH 2013

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1 Concrete Masonry Association Australia PO Box, P: Artarmon F: NSW Disclaimer: The Concrete Masonry Association of Australia Limited is a non-profit organisation sponsored by the concrete masonry industry in Australia to provide information on the many uses of concrete masonry products. Since the information provided is intended for general guidance only and in no way replaces the service of professional consultants on particular projects, no liability can be accepted by the Association for its use. Remember, when working with cement and concrete/mortar or manufactured or prefabricated concrete products, ALWAYS follow the manufacturer's instructions and seek advice about working safely with the products from the manufacturer, your nearest WorkCover Authority or Worksafe Australia. Concrete Masonry Lintels This data sheet has been prepared by the Concrete Masonry Association of Australia for use by qualified and experienced structural engineers. The information is based on limit state design and is applicable specifically to concrete masonry with properties as set out in Clause and loads set out in Clause. How to Navigate this Data Sheet Any words in colour (eg, Figure ) can be clicked to take you to it. To return to where you were, click the Previous View Button in your Acrobat Reader Masonry Properties The design tables are based on masonry components with the following properties: Masonry units having a characteristic unconfined compressive strength (f' uc ), for units with face-shell bed, of MPa or MPa when tested in accordance with AS/NZS.. Mortar is of type M (or type M if required for durability) ie, either a C:L:S mix or a C:S mix plus methyl cellulose water thickener or equivalent. Grout shall have a characteristic cylinder compressive strength (f' c ) of. MPa. Note the maximum value of grout strength (f' cg ) used for design is. times f' uc ie,. x. =. MPa. Where possible pre-mixed grout should be used and, when ordering, specified that it is for grouting blockwork with a minimum cement content of kg/m. If the grout is to be site-mixed, it should be mixed in a tilting drum paddle mixer and must flow freely without separation of the aggregate. The aggregate should be rounded gravel where available and preferably mm to mm in size. The following proportions should be used: Cement part Hydrated lime up to part Mortar sand parts Aggregate parts Reinforcement is to be N-grade with a yield strength (f sy ) of MPa. Design Basis The loads, load combinations and load factors shall be in accordance with AS/NZS.. The serviceability design of lintels is based on a maximum span/deflection ratio of or mm deflection, whichever is the lesser. The long-term elastic modulus (E) has been taken as f m. The design properties and strengthreduction factors are in accordance with AS Masonry structures. DATA SHEET Concrete Masonry Lintels MARCH

2 Lintel Capacity Top bar/s cogged down into core N Fitments at mm centres Design Tables Capacity Tables are based on the practical consideration that the loading will usually be from trusses or similar roof or floor supports, at uniform centres, bearing on and tied down to the lintel. Hence, the Tables are for point loads at mm centres acting in both downward and upward directions. They take into consideration both shear and bending and allowance has been made for the self-weight of the lintel. Where the depth of masonry, (including the lintel and the height of masonry in running bond above the lintel) is at least equal to the span of the lintel and there is sufficient length of wall adjacent to the opening to act as a buttress, then the lintel will act as an arch and loads on the masonry may be ignored. The Tables are given for both simplysupported and continuous lintels as detailed in Figure. However, these Tables do not apply where the bottom reinforcement continues straight through from the adjacent wall. Capacity Tables are given for the full range of thicknesses and depths shown in Figure. The Tables cover bar sizes N, N and N for one and two bars, where two can fit, ie - and -mm wide lintels. Bottom bar/s cranked up to suit knock-out block before cogged down into core Knock-out block Eight sets of Design Tables are provided to cover the following: Table MPa block, single bars, simply-supported lintel. Table MPa block, single bars, continuous lintel. Table MPa block, double bars, simply-supported lintel. Table MPa block, double bars, continuous lintel. Table MPa block, single bars, simply-supported lintel. Table MPa block, single bars, continuous lintel. Table MPa block, double bars, simply-supported lintel. Table MPa block, double bars, continuous lintel. SIMPLY-SUPPORTED LINTEL Wall bar in grouted core Top bar/s carried minimum of beyond supports each side N Fitments at mm centres Bottom bar/s cranked up to suit knock-out block before cogged down into core Knock-out block Wall bars in grouted cores Worked Example A Worked Example is included to demonstrate the steps required when performing a manual calculation. It also serves the purpose of confirming the basis of the Tables. The Tables also cover different strength grades of blocks, namely, MPa and MPa blocks. CONTINUOUS LINTEL Figure Reinforcement Anchorage Details for Simply-Supported and Continuous Lintels DATA SHEET Concrete Masonry Lintels MARCH

3 LINTEL BLOCK THICKNESS mm mm mm LINTEL DEPTH All lintels fully grouted All lintels fully grouted All lintels fully grouted mm. Lintel to bar underside. Lintel to bar underside. Deep lintel cut to depth to bar underside to bar underside to bar underside to bar underside mm. Block on end with one end and web cut out inside fitment. / lintel inside fitment. Deep lintel cut to depth inside fitment to bar underside to bar underside to bar underside mm. Knock-out inside fitment. Deep lintel inside fitment. Deep lintel inside fitment. Lintel to bar underside to bar underside to bar underside. Knock-out. Knock-out. Double-U or. H-block mm. Half-height. Lintel inside fitment. / lintel inside fitment. Deep lintel cut to depth inside fitment to bar underside to bar underside to bar underside. Knock-out. Knock-out. Double-U or. H-block mm. Full-height inside fitment inside fitment inside fitment. Lintel. Deep lintel. Deep lintel NOTE: Design Tables are given for N, N and N bars for all thicknesses. For and thick blocks, Tables are for one and two bars top and bottom (except -deep lintels). All ligatures are N at mm centres. Figure Construction Details of Lintels covered by the Design Tables DATA SHEET Concrete Masonry Lintels MARCH

4 TABLE MPa Blocks, Single Bars, Simply-Supported Lintel Block thickness Lintel depth Bar details -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B [Go to Table Index] Load capacity (kn/m) in downward direction Load capacity (kn/m) in upward direction DATA SHEET Concrete Masonry Lintels MARCH

5 TABLE MPa Blocks, Single Bars, Continuous Lintel Block thickness Lintel depth Bar details -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B [Go to Table Index] Load capacity (kn/m) in downward direction Load capacity (kn/m) in upward direction DATA SHEET Concrete Masonry Lintels MARCH

6 TABLE MPa Blocks, Double Bars, Simply-Supported Lintel Block thickness Lintel depth Bar details -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B Load capacity (kn/m) in downward direction Load capacity (kn/m) in upward direction [Go to Table Index] DATA SHEET Concrete Masonry Lintels MARCH

7 TABLE MPa Blocks, Double Bars, Continuous Lintel Block thickness Lintel depth Bar details -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B Load capacity (kn/m) in downward direction Load capacity (kn/m) in upward direction [Go to Table Index] DATA SHEET Concrete Masonry Lintels MARCH

8 TABLE MPa Blocks, Single Bars, Simply-Supported Lintel Block thickness Lintel depth Bar details -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B [Go to Table Index] Load capacity (kn/m) in downward direction Load capacity (kn/m) in upward direction DATA SHEET Concrete Masonry Lintels MARCH

9 TABLE MPa Blocks, Single Bars, Continuous Lintel Block thickness Lintel depth Bar details -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B [Go to Table Index] Load capacity (kn/m) in downward direction Load capacity (kn/m) in upward direction DATA SHEET Concrete Masonry Lintels MARCH

10 TABLE MPa Blocks, Double Bars, Simply-Supported Lintel Block thickness Lintel depth Bar details -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B Load capacity (kn/m) in downward direction Load capacity (kn/m) in upward direction [Go to Table Index] DATA SHEET Concrete Masonry Lintels MARCH

11 TABLE MPa Blocks, Double Bars, Continuous Lintel Block thickness Lintel depth Bar details -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N only -N only -N only -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B -N T&B Load capacity (kn/m) in downward direction Load capacity (kn/m) in upward direction [Go to Table Index] DATA SHEET Concrete Masonry Lintels MARCH

12 Worked Example Brief Calculate the permissible net upwards and downwards distributed loads that may be exerted on a. m continuous lintel as described below: Note: All clause and table references to AS Concrete blocks: Width mm, Depth mm, Strength grade MPa Main reinforcement: N bar in the top and N bar in the bottom Ligatures: N centres (External depth mm) Hangers: R V (Internal depth mm) Masonry Properties Masonry unit characteristic unconfined compressive strength f uc =. MPa Units are hollow Block type factor k m =. Table. Equivalent blockwork strength f mb = k m (f uc ). Cl..(a)(i) =. x.. =. MPa or f mb =. MPa Table. Mortar joint height h j = mm Masonry unit height h b = mm Ratio of block to joint thickness h b /h j = / =. Block height factor k h =. Table. Characteristic masonry strength f m = k h f mb Cl..(a)(i) =. x. =. MPa Concrete Grout Properties Concrete grout specification Concrete grout shall comply with AS and have: a minimum of portland GB or GP cement content of kg/m ; a maximum aggregate size of mm; sufficient slump to completely fill the cores; and a minimum compressive cylinder strength of MPa. Specified characteristic grout cylinder strength f c = MPa > MPa OK AS Clause.. Design characteristic grout strength f cg = min [(. x f uc ),.] AS Clause. = min [(. x ),.] = min [.,.] =. MPa Main Reinforcement Properties Main reinforcement yield strength f sy = MPa Main reinforcement shear strength (dowel action) f vs =. MPa Clause. Number of main tensile reinforcing bars N t = Diameter of main tensile reinforcing bars D dia.t = mm A st = N t (. D dia.t / ) (approx) = x. x / = mm Cont DATA SHEET Concrete Masonry Lintels MARCH

13 Fitment Properties Fitment yield strength f sy.f = MPa Number of legs of ligature N f = Diameter of C ligature fitment reinforcement D dia.c = mm Fitment area A sv = N f (.D dia.c /) = x. x / =. mm Fitment spacing s = mm Dimensions Width of lintel B = mm Depth of lintel D = mm Density of reinforced concrete masonry γ mas =, kg/m Depth of W or V hanger of top steel (From top of block to underside of supported reinforcement) d = mm Inside dimension of C ligature fitment (From top of supporting reinforcement to underside of supported reinforcement) d = - - = mm Deflection Parameters Limiting deflection Δ a = min (, L/) Elastic modulus E =, f m =, x. =, MPa Deflection coefficients for continuous lintel K def = / =. Deflection coefficients for simply supported lintel K def = / =. Moment of inertia (based on gross section) I = BD / = x / =. x mm Cont DATA SHEET Concrete Masonry Lintels MARCH

14 Net Upwards Load Effective depth for upwards load d = D - d + D dia.t / = - + / = mm Design area of main tensile reinformcement A sd = min[.(.f m )bd/f sy, A st ] Cl. = min[(. x. x. x x /), ] = min[, ] = mm Shear capacity φv = φ(f vm b w d + f vs A st + f sy.f A sv d/s) Cl. =.[(. x x ) + (. x ) + ( x. x /)]/ =.( ) =. kn Bending Moment Capacity φm = φf sy A sd d[ -.f sy A sd d/(.f m bd)] Cl. =. x x x [ - (. x x )/ (. x. x x )] /,, =. kn.m Clear Span L c =. m Edge distance to the vertical anchorage reinforcement L au =. m Span for calculation of shear L vu = L c =. m For shear due to uplift, the critical section of the beam is at the face of the support. Span for calculation of bending moment L mu = L c + L au =. + ( x.) =. m For bending due to uplift, the beam will span between the closest vertical reinforcing bars that are fully anchored into the lintel/bond beam and the concrete slab below the wall. Span for calculation of deflection L Δu = L c + L au =. + ( x.) =. m For deflection due to uplift, the beam will span between the closest vertical reinforcing bars that are fully anchored into the lintel/bond beam and the concrete slab below the wall. Spacing of trusses exerting load on the lintel S u =. m Factor to account for increased shear due to point loads close to a support k vu = (L vu + S u )/L vu = (. +.)/. =. This factor allows for the fact that a point load from a roof truss, supporting load over a distance of S u, may be positioned immediately adjacent to the critical section. Thus increasing the shear force over the value applicable to the uniformly distributed case. Cont DATA SHEET Concrete Masonry Lintels MARCH

15 Factor to account for increased moment due to point loads close to a support k mu = (L mu + S u )/L mu = (. +.)/. =. This factor allows for the fact that a point load from a roof truss, supporting load over a distance of S u, may be positioned at the centre of the span, thus increasing the bending moment over the value applicable to the uniformly distributed case. Factor to account for increased deflection due to point loads close to a support k Δu = (L Δu + S u )/L Δu = (. +.) /. =. This factor allows for the fact that a point load from a roof truss, supporting load over a distance of S u, may be positioned at the centre of the span, thus increasing the deflection over the value applicable to the uniformly distributed case. Limiting deflection Δ a = min(, L c /) = min(, /) =. Load capacity (limited by shear) W vu = φv/(l vu k vu ) = x./(. x.) =. kn/m Load capacity (limited by bending moment) W mu = φm/(l mu k mu ) = x./(. x.) =. kn/m Load capacity (limited by deflection) W Δu = Δ a E I/(K def L Δ Δu k Δu ) =. x, x. x / (. x, x.) = kn/m The allowable deflection has been based on the clear span, rather than the span between the vertical anchorage reinforcement. Load capacity (limited by shear, bending moment or deflection) W lu = min (W vu, W mu, W Δu ) = min (.,., ) =. kn/m Factor on dead loads contributing to resistance γ R =. AS.: Factored self-weight contributing to failure W su = γ R. γ mas B D =. x. x, x x /,, =. kn/m Externally applied load capacity (adding self weight) W u = W lu + W su =. +. =. kn/m Using Tables Select Table: MPa blocks, single bars, continuous lintel Use Table Read Table: -mm wide block, -mm deep lintel, N bar T&B, opening size. m Externally applied upward load capacity W u = kn/m Note: Net Upwards load In some cases due to rounding up or down, load capacity (kn/m) values in a upward direction shown in Table to Table may be understated (ie conservative) by approximately.%. This anomaly has resulted from AS.: increasing the permanent load factor γ R contributinhg to resistance from. to.. For most practical purposes Cont this difference could be ignored. DATA SHEET Concrete Masonry Lintels MARCH

16 Net Downwards Load Effective depth for downwards load d = d + d. D dia.t = + (. x ) = mm Design area of main tensile reinforcement A sd = min[. (. f m ) b d/f sy, A st ] Cl. = min[(. x. x. x x / ), ] = min [, ] = mm Shear capacity φv = φ(f vm b w d + f vs A st + f sy.f A sv d/s) Cl. =.[(. x x ) + (. x ) + ( x. x / )]/ =.( ) =. kn Bending Moment Capacity φm = φf sy A sd d[ -.f sy A sd /(. f m b d)] Cl. =. x x x [ - (. x x )/(. x. x x )]/ =. kn.m Clear Span L c =. m Edge distance to the centre of bearing L ad =. m Span for calculation of shear L vd = L c d =. ( x.) =. m For shear downwards, the critical section of the beam is at a distance, d, from each face of the support. Span for calculation of bending moment L md = L c + L ad =. + ( x.) =. m For bending due to downwards load, the beam will span between the positions in the supporting masonry that has sufficient bearing strength to support the load. Span for calculation of deflection L Δd = L c + L ad =. + ( x.) =. m For deflection due to downwards load, the beam will span between the positions in the supporting masonry that has sufficient bearing strength to support the load. Spacing of floor bearers or other supports exerting load on the lintel S d =. m Factor to account for increased shear due to point loads close to a support k vd = (L vd + S d )/L vd = (. +.)/. =. This factor allows for the fact that a point load from a floor bearer or other support, supporting load over a distance of S d, may be positioned immediately adjacent to the critical section, thus increasing the shear force on the over the value applicable to the uniformly distributed case. Cont DATA SHEET Concrete Masonry Lintels MARCH

17 Factor to account for increased moment due to point loads close to a support k md = (L md + S d )/L md = (. +.)/. =. This factor allows for the fact that a point load from a floor bearer or other support, supporting load over a distance of S d, may be positioned at the centre of the span, thus increasing the bending moment over the value applicable to the uniformly distributed case. Factor to account for increased deflection due to point loads close to a support k Δd = (L Δd + S d )/L Δd = (. +.)/. =. This factor allows for the fact that a point load from a floor bearer or other support, supporting load over a distance of S d, may be positioned at the centre of the span, thus increasing the deflection over the value applicable to the uniformly distributed case. Limiting deflection Δ a = min(, L c /) = min(, /) =. Load capacity (limited by shear) W vd = φv/(l vd k vd ) = x./(. x.) =. kn/m Load capacity (limited by bending moment) W md = φm/(l md k md ) = x./(. x.) =. kn/m Load capacity (limited by deflection) W Δd = Δ a EI (K def L ΔΔd k Δd ) =. x, x. x (. x, x.) = kn/m The allowable deflection has been based on the clear span, rather than the span between the centres of bearing. Load capacity (limited by shear, bending moment or deflection) W ld = min(w vd, W md, W Δd ) = min(.,.,.) =. kn/m Factor on dead loads contributing to failure γ F =. AS.: Factored self weight contributing to failure W sd = γ F. γ mas B D =. x. x, x x /,, =. kn/m Externally applied load capacity (subtracting self weight) W d = W ld - W sd =. -. =. kn/m Using Tables Select Table: MPa blocks, single bars, continuous lintel Use Table Read Table: mm wide block, mm deep lintel, N bar T&B opening size. m Externally applied downward load capacity W u = kn/m Note: Net downwards load In some cases due to rounding up or down, load capacity (kn/m) values in a downward direction shown in Table to Table may be overstated (ie non conservative) by approximately.%. This anomaly has resulted from AS.: increasing the permanent load factor γ F contributing to failure from. to.. For most practical purposes this difference could be ignored. DATA SHEET Concrete Masonry Lintels MARCH