512C.2 Existing Unreinforced Masonry Walls.

512C.2 Existing Unreinforced Masonry Walls.

512C.2.1 Flexural rigidity. Flexural components of deflection may be neglected in determining the rigidity of an unreinforced masonry wall.

512C.2.2 Shear walls with openings. Wall piers shall be analyzed according to the following procedure which is diagrammed in Figure 5C-2:

512C.2.2.1 For any pier:

1. The pier shear capacity shall be calculated as:

Va = vaAx (5C-19)

2. The pier rocking shear capacity shall be calculated as:

Vr = 0.5PDD/H (5C-20)

512C.2.2.2 Pier behavior. The wall piers at any level are acceptable if they comply with one of the following modes of behavior:

1. Rocking controlled mode. When the pier rocking shear capacity is less than the pier shear capacity, i.e., Vr < Va for each pier in a level, forces in the wall at that level, Vwx, shall be distributed to each pier in proportion to PDD/H.

For the wall at that level:

Vwx < ΣåVr (5C-21)

2. Shear controlled mode. Where the pier shear capacity is less than the pier rocking capacity, i.e., Vr<Va in at least one pier in a level, forces in the wall at the level, Vwx, shall be distributed to each pier in proportion to D/H.

For each pier at that level:

Vp < Va (5C-22)

and

Vp < Vr (5C-23)

If VpVr for one or more piers, such piers shall be omitted from the analysis, and the procedure shall be repeated for the remaining piers, unless the wall is strengthened and reanalyzed.

512C.2.2.3 Masonry pier tension stress. Unreinforced masonry wall piers need not be analyzed for tension stress.

512C.2.3 Shear walls without openings. Shear walls without openings shall be analyzed as for walls with openings except that Vr shall be calculated as follows:

Vr = (0.50PD+0.25Pw) D/H (5C-24)