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NCMA TEK
National Concrete Masonry Association
an information series from the national authority on concrete masonry technology

ALLOWABLE STRESS DESIGN OF TEK 17-1B

Structural (2001)
CONCRETE MASONRY LINTELS
Keywords: allowable stress design, design examples, lintels,
openings in walls
Uniform Load
INTRODUCTION

Lintels and beams are horizontal structural members de-

signed to carry loads above openings. Although lintels may be Triangular Load
constructed of concrete masonry units, precast or cast-in-place
concrete, or structural steel, this TEK addresses reinforced
Concentrated Loads
concrete masonry lintels only. Concrete masonry lintels have the
advantages of easily maintaining the bond pattern, color, and
surface texture of the surrounding masonry and being placed Uniform load over portion
without need for special lifting equipment. of span
Concrete masonry lintels are sometimes constructed as a
portion of a continuous bond beam. This construction pro-
Lintel
vides several benefits: it is considered to be more advanta-
geous in high seismic areas or areas where high winds may be Clear span
expected to occur; control of wall movement due to shrinkage
or temperature differentials is more easily accomplished; and Effective span
Effective span = clear span + effective depth of lintel, d, but
lintel deflection may be substantially reduced.
need not exceed distance between centers of support (for
simply supported)
DESIGN LOADS
Figure 1Typical Lintel Load Components
Vertical loads carried by lintels typically include: (1) dis-
tributed loads from the dead weight of the lintel, the dead weight masonry wall laid in running bond,
of the masonry above, and any floor and roof loads, dead and sufficient wall height above the lintel to form a 45o triangle,
live loads supported by the masonry; and (2) concentrated at least 8 in. (203 mm) of wall height above the apex of the
loads from floor beams, roof joists, or other beams framing into 45o triangle,
the wall. Axial load carried by lintels is negligible. minimum end bearing (4 in. (102 mm) typ) is maintained,
Most of these loads can be separated into the four types control joints are not located adjacent to the lintel, and
illustrated in Figure 1: uniform load acting over the effective sufficient masonry on each side of the opening to resist
span; triangular load with apex at mid-span acting over the lateral thrust from the arching action. The designer should
effective span; concentrated load; and uniform load acting consider two cases. First, there should be a sufficient
over a portion of the effective span. The designer calculates the shear area of the masonry to resist the horizontal thrust,
effects of each individual load and then combines them using and second, there must be enough masonry to resist the
superposition to determine the overall effect, typically by in-plane overturning moment on the masonry adjacent to
assuming the lintel is a simply supported beam. the opening. In unreinforced masonry, this means using
vertical loads to offset overturning. In reinforced ma-
Arching Action sonry, vertical steel can be used to resist overturning. As
For some configurations, the masonry will distribute ap- an alternative, the lintel could be a discrete length of a
plied loads in such a manner that they do not act on the lintel. larger continuous bond beam to provide adequate re-
This is called arching action of masonry. Arching action can be straint. For a series of wall openings, the designer should
assumed when the following conditions are met (see also consider the offsetting effect of thrust from adjacent
Figure 2): openings.

TEK 17-1B 2001 National Concrete Masonry Association (replaces TEK 17-1A)
Lintel Loading
The loads supported by a lintel depend on whether arch- 4 x wall thickness + width of bearing area of beam
ing action can occur or not. If arching occurs, only the self Beam
weight of the lintel, the weight of the wall below the arched
portion, and concentrated loads are considered. Otherwise, the
self weight, the weight of the wall above the lintel, roof and floor
loads, and concentrated loads are considered. Self weight is
a uniform load based on lintel weight (see Table 2).
When arching occurs, the wall weight supported by the 30 30

lintel is taken as the wall weight within the triangular area below
the apex (see Table 3). This triangular load has a base equal to the
effective span length of the lintel and a height of half the effective
span. Any superimposed roof and floor live and dead loads are Lintel
neglected, since they are assumed to be distributed to the Clear span
masonry on either side of the lintel. When arching is not present, Effective span
the full weight of the wall section above the lintel is considered, (see Figure 1)
as are superimposed loads. Figure 3Distribution of Concentrated Load
Concentrated loads are assumed to be distributed as For Running Bond Construction
illustrated in Figure 3. The load is then resolved onto the lintel as
a uniform load, with a magnitude determined by dividing the
concentrated load by this length. In most cases, this results in a DESIGN EXAMPLE
uniform load acting over a portion of the lintel span.
When a lintel or other beam supports unreinforced masonry, Design a lintel for a 12 in. (305 mm) normal weight concrete
Building Code Requirements for Masonry Structures (ref. 1) masonry wall laid in running bond with vertical reinforcement
limits lintel deflection to the clear lintel span divided by 600 or to at 48 in. (1.2 m) o.c. The wall configuration is shown in Figure 4.
0.3 in. (7.6 mm) to limit damage to the supported masonry. Check for Arching Action. Determine the height of ma-
sonry required for arching action. Assuming the lintel has at
Table 2Lintel Weights, lb/ft (kN/m)a least 4 in. (102 mm) bearing on each end, the effective span is:
L = 5.33 + 0.33 = 5.67 ft (1.7 m).
Nominal lintel Nominal wall thickness, in. (mm) The height of masonry above the lintel necessary for
height, in. 8 (203) 10 (254) 12 (305) arching to occur in the wall (from Figure 2) is h + 8 in. (203 mm)
(mm) LIGHTWEIGHT CMU = L/2 + 8 in. = 3.5 ft (1.1 m).
8 (203) 51(0.75) 65 (0.95) 79 (1.2) Because there is 18.0 - 7.33 = 10.67 ft (3.3 m) of masonry
16 (406) 103 (1.5) 130 (1.9) 158 (2.3) above the lintel, arching is assumed and the superimposed
24 (610) 154 (2.3) 195 (2.9) 237 (3.5) uniform load is neglected.
Design Loads. Because arching occurs, only the lintel and
NORMAL WEIGHT CMU wall dead weights are considered. Lintel weight, from Table 2, for
8 (203) 58(0.84) 73 (1.1) 88 (1.3) 12 in. (305 mm) normal weight concrete masonry units assuming
16 (406) 116 (1.7) 146 (2.1) 176 (2.6) an 8 in. (203 mm) height is,
24 (610) 174 (2.5) 219 (3.2) 264 (3.9) Dlintel = 88 lb/ft (1.3 kN/m)
a
Face shell mortar bedding. Unit weights: grout = 140 pcf For wall weight, only the triangular portion with a height
3
(2,242 kg/m ); lightweight masonry units = 100 pcf (1602 of 3.5 ft (1.1 m) is considered. From Table 3 wall dead load is,
3
kg/m ); normal weight units = 135 pcf (2,162 kg/m ). 3 D wall
= 68 lb/ft2 (3.5 ft ) = 238 lb/ft (3.5 kN/m) at the apex.
Maximum moment and shear are deter-
mined using simply supported beam relation-
Superimposed wall load
ships. The lintel dead weight is considered a
8 in. (203 mm) minimum
uniform load, so the moment and shear are,
Mlintel = wL2/8 = (88)(5.7)2/8 = 357 ft-lb
h = Effective span (0.48 kN-m)
45 2 Vlintel = wL/2 = (88)(5.7)/2 = 251 lb (1.1 kN)
Wall For triangular wall load, moment and
Lintel height shear are,
End bearing
Mwall = wL2/12 = (238)(5.7)2/12 = 644 ft-lb
4 in. (102 mm) (0.87 kN-m)
minimum (typ) Vwall = wL/4 = (238)(5.7)/4 = 339 lb (1.5 kN)
Since the maximum moments and shears
for the two loading conditions occur in the
Clear opening
same locations on the lintel, the moments
Effective span (see Figure 1)
and shears are superimposed by simple
Figure 2Arching Action addition:
 1,000 lb/ft (14.6 kN/m) superimposed uniform load Case 2, No Arching Action. Using the same example,
recalculate assuming a 2 ft (0.6 m) height from the bottom of the
12 in. (305 mm) CMU lintel to the top of the wall. For ease of construction, the entire
fm = 1500 psi (10.3 MPa) 2 ft (0.6 m) would be grouted solid, producing a 24 in. (610 mm)
deep lintel.
Since the height of masonry above the lintel is less than
5 ft 4 in. (1.6 m) 18 ft 3.5 ft (1.1 m), arching cannot be assumed, and the superimposed
(5.5 m)
load must be accounted for.
Window 4 ft (1.2 m) Dlintel = 264 lb/ft (3.9 kN/m), from Table 2. Because the lintel is
24 in. (610 mm) deep, there is no additional dead load due to
3 ft 4 in. (1.0 m) masonry above the lintel.
Dtotal = 264 lb/ft + 1,000 lb/ft = 1,264 lb/ft (18.4 kN/m)
Figure 4Wall Configuration for Design Example Mmax = wL2/8 = (1,264)(5.7)2/8 x 12 in./ft = 61,601 in.-lb (7.0 kN-m)
Vmax = wL/2 = (1,264)(5.7)/2 = 3,602 lb (16.0 kN)
Mmax = 357 + 644 = 1,001 ft-lb = 12,012 in-lb (1.4 kN-m) From Table 4, a 12 x 24 lintel with one No. 4 (M 13)
Vmax = 251 + 339 = 590 lb (2.6 kN) reinforcing bar and 3 in. (76 mm) or less bottom cover is
Lintel Design. From Table 4, a 12 x 8 lintel with one No. 4 adequate.
(M 13) bar and 3 in. (76 mm) or less bottom cover has adequate
strength. In this example, shear was conservatively computed REFERENCES
at the end of the lintel. However, Building Code Requirements 1. Building Code Requirements for Masonry Structures, ACI
for Masonry Structures (ref. 1) allows maximum shear to be 530-99/ASCE 5-99/TMS 402-99. Reported by the Masonry
calculated using a distance d/2 from the face of the support. Standards Joint Committee, 1999.

Table 3Wall Weights a

Wall weights (lb/ft2) for wall thicknesses, in. (mm), of:

Grouted Lightweight units Normal weight units
cells 4 (102) 6 (152) 8 (203) 10 (254) 12 (305) 4 (102) 6 (152) 8 (203) 10 (254) 12 (305)
None 16 23 30 36 41 21 31 40 48 55
48 in. o.c. 19 29 38 46 54 24 36 48 58 68
40 in. o.c. 20 30 39 48 57 25 38 49 60 70
32 in. o.c. 21 32 42 52 61 26 39 52 63 74
24 in. o.c. 23 35 46 57 67 28 42 55 69 81
16 in. o.c. 26 40 54 67 80 31 48 63 79 94
Full grout 37 57 78 98 119 42 64 87 110 133
a
Assumes face shell mortar bedding. Unit weights: grout = 140 pcf (2,242 kg/m3); lightweight masonry units = 100 pcf (1602 kg/
m3); normal weight units = 135 pcf (2,162 kg/m3). kN/m2 = lb/ft2 x 0.04788
Table 4Allowable Shear and Moment Capacities for Concrete Masonry Lintels (width x height) a
Bottom cover, in. (mm):
No. 1.5 (38) 2 (51) 2.5 (64) 3 (76)
Steel of Vall Mall Vall Mall Vall Mall Vall Mall
size bars lb in.-lb lb in.-lb lb in.-lb lb in.-lb
8 x 8 lintels
No. 4 1 1,730 20,460 1,580 17,650 1,440 14,990 1,290 12,510
No. 5 1 1,710 23,170 1,560 19,890 1,420 16,810 1,270 13,930
No. 6 1 1,690 25,220 1,550 21,550 1,400 18,120 1,250 14,930
No. 4 2b 1,730 25,460 1,580 21,860 1,440 18,480 1,290 15,320
No. 5 2b 1,710 28,140 1,560 24,030 1,420 20,190 1,270 16,620
10 x 8 lintels
No. 4 1 2,190 23,810 2,000 20,570 1,810 17,500 1,630 14,620
No. 5 1 2,160 27,170 1,980 23,360 1,790 19,780 1,600 16,430
No. 6 1 2,140 29,760 1,950 25,480 1,770 21,470 1,580 17,720
No. 4 2 2,190 29,990 2,000 25,790 1,810 21,840 1,630 18,140
No. 5 2 2,160 33,430 1,980 28,600 1,790 24,080 1,600 19,870
12 x 8 lintels
No. 4 1 2,640 25,400 2,420 23,140 2,190 19,790 1,970 16,560
No. 5 1 2,610 30,820 2,390 26,530 2,160 22,490 1,940 18,710
No. 6 1 2,580 33,930 2,360 29,090 2,130 24,540 1,910 20,300
No. 4 2 2,640 34,130 2,420 29,390 2,190 24,920 1,970 20,740
No. 5 2 2,610 38,300 2,390 32,820 2,160 27,670 1,940 22,880
 Table 4Allowable Shear and Moment Capacities for Concrete Masonry Lintels (width x height) (continued)a
Bottom cover, in. (mm), of:
No. 1.5 (38) 2 (51) 2.5 (64) 3 (76)
Steel of Vall Mall Vall Mall Vall Mall Vall Mall
size bars lb in.-lb lb in.-lb lb in.-lb lb in.-lb
8 x 16 lintels
No. 4 1 4,090 61,110 3,950 58,820 3,800 56,540 3,650 54,250
No. 5 1 4,070 92,550 3,930 89,050 3,780 85,560 3,630 80,860
No. 6 1 4,060 109,740 3,910 103,210 3,760 96,830 3,610 90,600
No. 4 2b 4,090 107,750 3,950 101,420 3,800 95,240 3,650 89,200
No. 5 2b 4,070 123,960 3,930 116,510 3,780 109,240 3,630 102,150
10 x 16 lintels
No. 4 1 5,170 61,630 4,980 59,330 4,790 57,040 4,610 54,740
No. 5 1 5,140 93,500 4,960 89,970 4,770 86,450 4,590 82,940
No. 6 1 5,120 127,610 4,930 120,080 4,750 112,720 4,560 105,540
No. 4 2 5,170 119,870 4,980 115,360 4,790 110,700 4,610 103,740
No. 5 2 5,140 144,910 4,960 136,290 4,770 127,870 4,590 119,650
12 x 16 lintels
No. 4 1 6,240 62,030 6,020 59,720 5,790 57,420 5,570 55,110
No. 5 1 6,210 94,210 5,990 90,670 5,760 87,130 5,540 83,600
No. 6 1 6,190 131,170 5,960 126,190 5,740 121,220 5,510 116,250
No. 4 2 6,240 120,880 6,020 116,340 5,790 111,800 5,570 107,270
No. 5 2 6,210 164,010 5,990 154,330 5,760 144,860 5,540 135,620
8 x 24 lintels
No. 4 1 6,460 97,900 6,310 95,590 6,160 93,280 6,010 90,980
No. 5 1 6,440 148,990 6,290 145,440 6,140 141,900 5,990 138,360
No. 6 1 6,420 207,830 6,270 202,840 6,120 197,860 5,980 192,880
No. 4 2b 6,460 190,850 6,310 186,300 6,160 181,760 6,010 177,220
No. 5 2b 6,440 264,990 6,290 255,050 6,140 245,260 5,990 235,600
10 x 24 lintels
No. 4 1 8,150 98,600 7,960 96,280 7,780 93,970 7,590 91,650
No. 5 1 8,130 150,260 7,940 146,700 7,750 143,140 7,570 139,580
No. 6 1 8,100 209,870 7,920 204,850 7,730 199,840 7,540 194,830
No. 4 2 8,150 192,650 7,960 188,080 7,780 183,510 7,590 178,940
No. 5 2 8,130 292,290 7,940 285,280 7,750 278,290 7,570 271,290
12 x 24 lintels
No. 4 1 9,840 99,130 9,620 96,800 9,390 94,470 9,170 92,150
No. 5 1 9,820 151,220 9,590 147,640 9,370 144,070 9,140 140,490
No. 6 1 9,790 211,410 9,560 206,370 9,340 201,330 9,110 196,300
No. 4 2 9,840 194,010 9,620 189,420 9,390 184,830 9,170 180,240
No. 5 2 9,820 294,730 9,590 287,680 9,370 280,650 9,140 273,620
a
Grade 60 reinforcement. Metric equivalents: f'm = 1,500 psi (10.3 MPa); N = lb x 4.44822; N.m = in.-lb x 0.112985; No. 4 bar (M 13); No. 5
(M 16); No. 6 (M 19). Table values differ from TEK 17-1A due to change in Em (ref. 1).
b
For 8 in. (204 mm) lintels with two bars, low lift grouting is recommended for adjacent jambs to ensure proper grout flow and consolidation.

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