Identification of Structural Damage in Civil Engineering

Civil engineering systems such as bridges, buildings, and dams are critical to survival and well-being of our society. Because of my education and background, the emphasis of these lectures is placed on the damage identification of existing structures.

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J.T.P. Yao Purdue UniYenity, W. Lalayette, U.S.A.

INTROOUC'riON Civil engineering systems such as bridges, buildings, and critical to survival and well-being of our society. tion and background, the emphasis of these

dams

are

Because of my educa-

lectures

is

placed

on

the

simplify

and

damage identification of existing structures. To make mathematical analyses, idealize

the

structural

system

it and

is its

necessary

to

environment. The design of a

structure follows an iterative process involving both structural analysis and

structural

design

using generalized mathematical models, whieh are

based on experienee and available knowledge in sion.

Using

field

data

design is made and the

and

the

engineering

profes-

other relevant information, a preliminary

idealized

mathematieal

H. G. Natke (ed.), Application of System Identification in Engineering © Springer-Verlag Wien 1988

model

is

analyzed

for

J.T.P. Yao

350

expected or specified loading conditions.

Based on these analytiral stu-

dies, the design may be revised and re-analyzed in all

until

design

criteria

an

iterative

manner

are satisfied. The rompleted design is then

constructed accordingly. For structures which have been construrted and are thus existing, it times

at

necessary

is

to assess their respective darnage states on the

basis of available information including measured and recorded experimental

data.

In

addition, it is desirable to evaluate the reliability of

these structures so that rational decisions can be made concerning neressary repairs, replacements, retirement, and other maintenance or rehabilitation procedures as shown in Fig. 1.

Time

Foeld Work



Operation

l~~--~------~

__t_____:: --r-f---'--..,-----'----, t

lnspectoon and Test Data

Office Werk

Conception Planning

r----- ,

Expected I Math M0d11l I EnvoronCond I for Structure 1 Response

•L------

Satety Evaluation Dlt I,Riti,LI t I

D

Domage R Resodual Strength

L

Rellabollty

Fog 1 : RoJe of Structural ldenllfocatoon I From Yao. 1985 I

351

Structural Darnage in Civil Engineering

Because (a) it is difficult to predict future loading conditions and (b)

material

properties are random in nature, stochastic processes have

been used to represent these quantities for probabilities.

the

structure

is

an

phase

extremely complex system.

because

the

real-

difficult

to

all the details in the mathematical model of a given structure.

Moreover, the damage path and failure behavior of most remain

failure

Even with the use of

finite element methods and modern computers, it is usually consider

of

However, the as-built structure is usually different from

the original mathematical model in the design world

estimation

large

structures

unknown because few experimental studies of full-scale structures

have been conducted to-date. For important structures, nondestructive dynamic tests are conducted for

the

estimation

of

dynamic

properties

of the as-built structure.

These test data are then used to obtain "impro