It is clear that the structural material is stone, but the type of stone masonry is unknown. The build-up of the wall may be hidden, as in the case of a plastered wall, or information about it is unavailable.


This is a stone masonry building, but there is a mix of technologies - street facade was built in dressed stone masonry and the other exterior wall is built using random rubble stone masonry (Halifax, Canada, S. Brzev)

It is clear that the structure is stone, but the type of stone is unknown. There is insufficient information or it is not possible to identify the exact type of stone.


Stone masonry building, Southern France (S. Brzev)



Stone masonry building, museum, Antibes, France (S. Brzev)

Plaster finish over sheet material such as fibre cement board or expanded polystyrene, fixed to metal or wood studs.



Stucco cladding over wood stud walls, Canada (S. Brzev)

Structural irregularity is a feature of a building's structural arrangement, such as one storey significantly higher than other storeys, an irregular building shape or a change of structural system or material, that produces a known vulnerability during an earthquake. The user can choose a maximum of two vertical and two plan irregularities for a building. However, if a building has two irregularities of the same type (plan/vertical), the user needs to prioritize them by identifying the primary irregularity first and the secondary irregularity next.

Ductility denotes an ability of a building structure to undergo significant deformations before the failure occurs in structural members or their connections. These large deformations (usually referred to as plastic or inelastic deformations) are accompanied by damage in some of the structural components. Structures which show ductile performance may experience permanent deformations after a major earthquake.

Ductility is one of the most important factors affecting building performance in an earthquake. In general, a building can be classified as ductile or non-ductile, depending on its expected seismic performance (based on the design and construction) before an earthquake, or its observed performance after an earthquake. It is difficult, if not impossible, to determine whether a lateral load-resisting system should be classified as ductile or non-ductile based on visual information only. It is also difficult to determine whether a system is ductile or non-ductile solely based on information about material of the lateral load-resisting system. For example, a reinforced concrete building can perform either in ductile or non-ductile manner, as explained in the related glossary terms. Unreinforced masonry buildings are generally expected to behave in a non-ductile manner, however reinforced or confined masonry buildings are expected to show ductile performance.

According to the conventional seismic design approach, buildings are designed for ductile performance. Alternatively, a building can be equipped with base isolation and/or energy dissipation devices. The objective of this approach is to avoid damage in structural components and building content in case of a major earthquake.


Ductile performance of a building is characterized by large horizontal deformations (lateral sway), as shown by the green curve, while non-ductile behaviour is characterized by smaller horizontal deformations and brittle damage or collapse of a building or its components, as shown by the red curve (C.V.R. Murty, Earthquake Tip 8, NICEE, India)