Building Design and Construction Handbook - Merritt - Ventech!

CONCRETE CONSTRUCTION 9.101
TABLE 9.22 Minimum Concrete Cover, in., for Beams and Girders
Exposed to Earth or weather
CastCastin-place
Precast Prestressed in-place
Bar size No. concrete concrete concrete concrete
3, 4, and 5 11 ⁄2 11 ⁄4 11 ⁄2 11 ⁄2
Not exposed to weather or in
contact with ground
Precast
concrete
Prestressed
concrete
5 ⁄8 1 1 ⁄2
6 through 11 2 1 1 ⁄2 1 1 ⁄2 1 1 ⁄2 d b* 1 1 ⁄2
14 and 18 2 2 1 1 ⁄2 1 1 ⁄2 1 1 ⁄2 1 1 ⁄2
Stirrups Same as above for each size 3 ⁄8 1
* d b � nominal bar diameter, in.
WALLS
Generally, any vertical member whose length and height are both much larger than
the thickness may be treated as a wall. Walls subjected to vertical loads are called
bearing walls. Walls subjected to no loads other than their own weight, such as
panel or enclosure walls, are called nonbearing walls. Walls with a primary function
of resisting lateral loads are called shear walls. They also may serve as bearing
walls. See Art. 9.89.
9.68 BEARING WALLS
Reinforced concrete bearing walls may be designed as eccentrically loaded columns
or by an empirical method given in the ACI 318 Building Code. The empirical
method may be used when the resultant of the applied load falls within the middle
third of the wall thickness. This method gives the capacity of the walls as
2
kLc u nw c g�
� ��
P � �P � 0.55�ƒ�A 1 � (9.82)
32h
where ƒ�c � specified concrete compressive strength
� � strength-reduction factor � 0.70
Ag � gross area of horizontal cross-section of wall
h � wall thickness
Lc � vertical distance between supports
k � effective length factor
When the wall is braced against lateral translation at top and bottom:
k � 0.8 for restraint against rotation at one or both ends
k � 1.0 for both ends unrestrained against rotation
When the wall is not braced against lateral translation, k � 2.0 (cantilever walls).