design of reinforced masonry lintels. Reinforced masonry lintels must have all cores and other voids solidly

grouted. Precast reinforced concrete or structural steel lintels will be designed in accordance with ACI 318

and the AISC Steel Construction Manual, respectively, except the deflection limits contained in this chapter

will be followed. Torsion is not covered in this chapter. Where torsion is a major consideration, the designer

should consider precast reinforced concrete lintels with closed loop stirrups. The principles of this chapter

may be used for designing beams of reinforced masonry that are not lintels. Except as contained herein,

design criteria, section properties, material properties, design equations, and allowable stresses are contained

in chapter 5.

wall weight and from floor or roof framing. The lintel may also carry concentrated loads from the framing

members above.

whether arching action of the masonry above the opening can be assumed. When arching action occurs, the

lintel supports only the masonry that is contained within a triangle having sides which begin at the ends of

the lintel and slope upward and inward 45 degrees from the horizontal to converge at an apex above the

center of the lintel. See figure 8-1 for an illustration of this triangular lintel loading distribution. When the

lintel deflects into the opening over which it spans, the masonry above the triangle will arch over the lintel

and be supported by the more rigid walls on either side of the opening. For the arch to be stable, both ends

of the opening must have sufficient horizontal restraint to provide the confining thrust necessary to support

it laterally. Therefore, arching action should not be considered where the end of the arch and the lintel are

near a wall corner, near a control or building expansion joint, or in stacked bond walls. When arching action

can be assumed, the lintel will be designed to carry its own weight plus the weight of masonry within the

triangle above. Where uniform floor or roof loads are applied to the wall above the apex of the triangle, it

will be assumed that arching action will carry these loads around the opening and not load the lintel. When

uniform floor or roof loads are applied below the apex of the triangle, arching action cannot take place and

these loads will be carried downward and applied uniformly on the lintel. Also, when a uniform floor or roof

load is applied below the apex of the triangle, it will be assumed that all of the weight of the masonry above

the lintel is uniformly supported by the lintel.

above an opening will be distributed downward from the apex of a triangle which is located at the point of

load application. The sides of this triangle make an angle of 60 degrees with the horizontal. The load is

transferred as a uniform load over the base of the triangle. This uniform load may extend over only a portion

of the lintel. See figure 8-1 for an illustration of the distribution of concentrated loads on lintels.

inches.

(1) Span length. The assumed span for deflection calculations will be the distance between the centers

of supports, illustrated as dimension "L" on figure 8-1.

(2) Moment of Inertia. The moment of inertia for deflections will be the effective moment of inertia,

Ie, which will be determined as follows:

Ie = (Mcr/Mmax) 3Ig + [1 - (Mcr/Mmax) 3] Icr (in4)

(eq 8-1)

Where:

Mmax = The maximum moment in the member at the design load level, inch-pounds.

pounds.

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