Page 216 - Advanced Design Examples of Seismic Retrofit of Structures

Example of a Steel Frame Building With Masonry Infill Walls Chapter 4 209

Q s ¼action caused by effective snow load, which is assumed to be zero in
this example.

(2) Where the effects or actions of gravity loads and seismic forces counteract
each other, the action caused by gravity loads, Q G , shall be obtained in
accordance with Eq. (4.3):
Q G ¼ 0:9Q D (4.3)
The demands should be compared with the lower-bound capacity of the
frame members. Acceptance criteria for force-controlled actions in components
shall satisfy Eq. (4.4):

κQ CL > Q UF (4.4)
where:
Q CL ¼lower-bound strength of a force-controlled action of an element at the
deformation level under consideration;
Q UF ¼force-controlled action caused by gravity loads in combination with
earthquake forces; and
κ¼knowledge factor which is assumed to be 1.0 because the usual level of
knowledge exists about the example buildings including material properties,
as-built sketches, etc. According to the Instruction for Seismic Rehabilita-
tion of Existing Buildings (Code 360) [10], the target performance level
of the building is considered to be “Life Safety” (LS) and the level of
knowledge is “Preferred.” As a result, the knowledge factor of the building
is 1.00.
The results of the analysis show that the frame alone is adequate for tolerating
the load combinations due to gravity loads.

4.4.1.2 Walls
All the walls in the building are made of solid bricks with sand-cement
mortar; they are hence classified as infill walls according to ICERIFB [2]
(Fig. 4.10).

4.4.1.3 Mechanical Properties of Brickwork
According to ASCE 41 [1], the condition of masonry can be classified into three
groups:
l Good condition: masonry found during condition assessment to have mortar
and units intact, with no visible cracking.
l Fair condition: masonry found during condition assessment to have mortar
and units intact, but with minor cracking.
l Poor condition: masonry found during condition assessment to have
degraded mortar, degraded masonry units, or significant cracking.