Taxonomy Parameters
1. Main structural system
- Buildings constructed of rubble stone in cement mortar walls
- Mortar mix is usually 1:6 or leaner
- Walls are generally thick at about 410 to 500 mm in average
- Walls usually have two wythes
2. Height range
Single story
3. Seismic design level
- Poor construction quality and workmanship
- No seismic enhancement measures
- Building designed to withstand gravity loads
4. Diaphragm type
- Roof/floor with insufficient in-plane stiffness
- Poor connection of the roof/floor to the lateral load resisting system
5. Structural irregularity
- Regular in plan and elevation
6. Wall panel length
- Wall length is less than or equal to 12 times the wall thickness
7. Wall openings
- Opening width in a wall between two consecutive cross walls is less than 0.35 times (0.25 times) the wall length in single-story (multi-story) building
8. Foundation type
- Prevents large foundation deformations and anticipated failures
9. Seismic pounding risk
- Seismic gap between buildings at least 4% of the height of the shorter building where the expected collision occurs
10. Effective seismic retrofitting
- Original structure, which undertook or not minor non-structural improvements and/or maintenance
11. Structural health condition
- Building is damaged or materials deteriorated so that seismic behavior is significantly affected
12. Non-structural components
- Building has non-structural components that can produce human casualties and economic losses such as: parapets, ceilings, tiles, pipes, infill, etc.
Failure Modes
Corner Failure
Corner failure mainly occur in heavy stone masonry walls. The corners are pushed out and subjected to partial collapse. Cause of this failure mode are poorly interlocking of the wall and mortar with poor quality.
Non-Structural Failure
Overturning or damage of non-structural components (e.g. parapets, chimneys, etc.) due to lack of adequate anchorage/confinement.
Diaphragm Failure
Collapse or failure of floor/roof. Possible causes include inadequate connection of floor/roof to the lateral resisting system (e.g. walls, frames), insufficient in-plane stiffness (e.g. unbraced timber/steel trusses) of the floor/roof, etc.
Test
In Plane – Combined Shear/Flexural Failure
Walls are divided into piers (i.e. vertical elements) and spandrels (i.e. horizontal elements) by openings (i.e. windows and doors) in the wall. This failure mode is a combination of shear, flexural rocking, and shear sliding failure.
In Plane – Flexural Rocking Failure
Walls are divided into piers (i.e. vertical elements) & spandrels (i.e. horizontal elements) by openings (i.e. windows and doors) in the wall. Flexural rocking usually occurs when material shear capacity is high, piers are slender, and compressive stress is low in the wall. Flexural cracking develops at the heel of the pier, leading to rotating behavior of the wall about the toe.
In Plane – Shear Failure
Walls are divided into piers (i.e. vertical elements) and spandrels (i.e. horizontal elements) by openings (i.e. windows and doors) in the wall. Diagonal cracking can develop in piers with relatively small aspect ratio (i.e. effective height by width ratio), leading to degraded strength of and potential shear sliding resulted offsets and overturn of the wall.
In Plane – Shear Sliding
Walls are divided into piers (i.e. vertical elements) and spandrels (i.e. horizontal elements) by openings (i.e. windows and doors) in the wall. When pointing mortar fails under shear, horizontal or stair-stepped diagonal cracks are generated, which allow sliding to occur. This may lead to potential offsets and overturn of the wall.
Out of Plane Failure
Overturning of masonry walls leading to partial or full collapse of the wall, which may have combined tension failure of in-plane pier portions of perpendicular walls. Possible causes are lack of structural integrity to achieve box-like behavior (e.g. no band beams, flexible diaphragms, etc.), and/or mortar has poor cohesion and tension capacity.
