On the contrary, the ultimate moment capacity of the cell reinforcement

(vertical reinforcement) in a combined joint and cell reinforced masonry

construction utilizes the concrete strength to resist the compression

forces. The method of calculating ultimate moment of the vertical

reinforcement is the same as that presented in the Section 5-1 and 5-2 of

NAVFAC P-397 which is similar to that presented in the American Concrete

Institute standard, Building Code Requirements for Reinforced Concrete.

(b) The ultimate shear stress in joint masonry walls is computed

by the formula:

EQUATION:

Vu = Vu/An

(127)

where,

vu = unit shear stress, psi

Vu = total applied design shear at db/2 from the

support, lb/in

An = net area of section, in2/in

In all cases, joint masonry walls, which are designed to resist blast

pressures, shall utilize shear reinforcement which shall be designed to

carry the total shear stress. Shear reinforcement shall consist of; (1)

bars or stirrups perpendicular to the longitudinal reinforcement, (2)

longitudinal bars bent so that the axis or inclined portion of the bent bar

makes an angle of 45 degrees or more with the axis of the longitudinal

part of the bar; or (3) a combination of (1) and (2) above. The area of the

shear reinforcement placed perpendicular to the flexural steel shall be

computed by the formula:

vubs

EQUATION:

Av =

(128)

[phi]fy

where,

Av

=

area of shear reinforcement, in2

b

=

unit width of wall, in

s

=

spacing between stirrups, in

fy

=

yield stress of the shear reinforcement, psi

[phi]

=

strength reduction factor equal to .85

When bent or inclined bars are used, the area of shear reinforcement shall

be calculated using:

Vubs

EQUATION:

Av =

(129)

[phi]fy (sin [alpha] + cos[alpha])

2.08-207