Quantitative Damage States
In order to compare directly with HAZUS methodology, drift ratio is used as the quantitative damage indicator. Tables 7 through 9 show measured drift ratio (DR) from experimental results.
Parameters that influence the behavior mode of a reinforced masonry wall include aspect ratio, amount of flexural steel, amount of shear steel and masonry strength. HAZUS methodology presented in this paper focuses on low-rise masonry bearing walls. Most of the walls tested in the three experimental programs had axial loads consistent with low-rise construction. One of Ibrahim’s walls had an axial load of 250 psi and some of Shing’s walls (see Table 3) had axial loads of 200 or 270 psi. These levels of axial load would be consistent with medium-rise or high-rise construction. Despite this inconsistency between axial load used in some of the experimental tests and the low-rise HAZUS methodology used in this paper, axial load is not considered as a parameter in this study. Future work may incorporate effects of axial load in damage assessment.
For the experimental database examined, walls with aspect ratio less than 1 exhibited shear critical response, regardless of the amount of reinforcement present. The specimens falling in this category are 2, 3, 4 and 5 from Ibrahim’s test program.
When the aspect ratio was greater than or equal to 1, behavior can be either flexurally critical, shear critical or mixed mode. Ibrahim’s Wall 1 had an aspect ratio of 1, and exhibited shear critical behavior. All of Shing’s walls had an aspect ratio of 1. His Walls 1, 2, 10, 12 and 15 exhibited primarily flexural response (10 and 15 actually exhibited mixed response) and specimens 3, 4, 5, 7, 9, 13, 14 and 16 showed shear critical behavior. The specific behavior mode depended on the amount of flexural and shear reinforcing present in the wall. All of Eikanas’s walls exhibited flexural response.
Drift ratio versus the corresponding damage states are plotted in Figure 1. The flexurally critical specimens (1.0 < AR < 2.6, AR = 1.0) and shear critical specimens (AR = 1.0, AR < 1.0) are plotted separately. In these figures, numerical designations 1, 2, 3, 4 correspond to damage states Slight, Moderate, Extensive and Collapse, respectively.
In Figure 1, the aspect ratio (AR) is used as a discriminator. The aspect ratio is defined as the ratio of wall height divided by wall length, without regard to wall support conditions. Some
Table 7. Drift ratio – Shing.
researchers define an "effective” aspect ratio, which, for example, would be calculated as half the wall height divided by its length, when fixed-fixed support conditions exist. However, in order to keep the quantitative classification simple, and because the current experimental database is limited in size, only the aspect ratio is used in Figure 1.
Based on experimental results and results shown in Figure 1, quantitative damage states are classified as shown in Table 10.