Page 43 - Advanced Design Examples of Seismic Retrofit of Structures

Example of a Two-Story Unreinforced Masonry Building Chapter 2 35

(A) (B)

(C) (D)

(E) (F)
FIG. 2.21 Examples of damage to jack-arch roof. (A) Partial collapse of the last bay. (B) Incipient
collapse of the last bay. (C) Incipient collapse of the last bay. (D) Collapse of the last bay.
(E) Incipient collapse of one of the bays. (F) Severe cracking in the last bay. (Permission from
DRES.)
example of the cracks originated from unbalanced foundation settlements in a
URM building.

2.4.11 Partial Collapse of Jack-Arch Roofs
Jack-arch roofs, as one the most abundant roof systems in masonry buildings,
usually experience partial collapse at their end bays. This is because the foot-
arch beams (the first and last beams in the roof ) are not constrained to the walls,