Civil Engineering Reference
In-Depth Information
P
load
time
T
1
4
3
2
settlement
S
Fig. 2.15
Curve of load-settlement time.
and the observation point can be set at the surface of the foundation. When measuring,
the level will be arranged at the place with same distances to the two observation points,
then place the leveling staff at the position of the points (on the surface of the foundation),
obtain the reading of the elevation at the same level, then the nonuniform settlement will
be acquired. With the same method, nonuniform settlement between any two observation
points can be acquired, and the present nonuniform settlement of the whole building will be
known.
2.4.4
Inspection of Masonry Cracks
There are many reasons for the occurrence of masonry cracks, such as settlement cracks,
temperature cracks, load cracks and cracks caused by natural disasters like fire and earth-
quake. These cracks have great influence on the bearing capacity, service performance and
durability of the masonry structure. Thus, the cracks should be inspected in an all-round
way. The inspection includes the position, amount, width, length, direction, pattern, and
stability of the crack.
It is simple to inspect the crack length. The work can be done using measuring tools like
ruler and steel tape. The crack width can be measured by the crack-width comparison card,
calibration magnifier, and special crack width-measuring instrument.
The positions, numbers, directions and patterns of the cracks can be inspected visually,
and marked on the elevation drawings of the wall and photographed.
The active cracks should be inspected regularly, and sticking plaster bandage on the cracks
is the simplest and most widely used way in current inspection. The stability of the cracks
can be determined by observing the cracks of the plaster bandage. If it is an active crack, the
largest width and length of the cracks at different times should be recorded at the positions
of the cracks. The change of the length could be recorded by regularly marking at the end
of each crack.
2.5
Structural Reliability Assessment
At present, there are two practical methods of reliability assessment: building structure
reliability assessment method and building damage degree assessment. A simple introduction
of the two methods is made in the following sections.
2.5.1
Building Structure Reliability Assessment Method
The structural reliability levels are determined by the state of building structure reliability
(safety, applicability, durability), which is defined as the “three levels and four grades”
assessment method.
