Qualitative Damage States

Because HAZUS fails to differentiate between flexurally critical and shear critical walls, it was necessary to create such a distinction when evaluating test results. Table 6 shows the classification selected.

For flexurally dominated behavior, initial yielding of flexural steel is associated with "Slight” damage. For this damage state repairs can be made relatively easily by grout injection and/or cos­metic repairs. The value of masonry strain used to define the end of the "Moderate” damage region (0.0025) is based on what the MSJC Code (2005) calls the "maximum usable strain”.

Table 6. Qualitative definition of damage states based on experimental results.

Damage States

Flexurally Dominated Behavior

Shear Dominated Behavior

Slight

First yield of vertical steel achieved

First yield of vertical steel achieved

Moderate

Masonry compressive strain 0.0025 achieved

Major diagonal cracking

Extensive

Toe crushing or ultimate load achieved

Ultimate load achieved

Complete

20% load degradation

20% load degradation

For shear dominated behavior, major diagonal cracks extend at an angle of approximately 45°, from the top of the wall toward its base. When large amounts of flexural reinforcement are provided, the vertical steel may not yield, and the first indication of damage will be diagonal cracking, and the wall enters the “Moderate” damage state after vertical steel yielding. Shing’s specimens 5, 7, and 16 exhibited this type of behavior.

“Complete” damage is defined as 20% strength degradation. Although collapse may not occur at load degradation of 20% (or larger), repair costs will typically be such that the structure is clas­sified as a total economic loss. Therefore the load degradation of 20% or larger is be considered “Complete” damage.