US-Southeast Asia Symposium on Engineering for Natural Hazards Protection Edited byA. HS. Ang

432 Pages·2009·19.91 MB·English

Proceedings of the
U.S.-Southeast Asia Symposium on
Engineering for
Natural Hazards Protection
Manila, 1977
Any opinions, findings, conclusions
or recommendations expressed in this
pUblication are those of the author(s)
and do not necessarily reflecttheviews
of the National Science Foundation.
Edited byA. H-S. Ang
Department of Civil Engineering
College of Engineering
Universityof Illinois at Urbana-Champaign
1978
REPRODUCEDBY
NATIONAL TECHNICAL
INFORMATION SERVICE
u.S.DEPARTMENTOFCOMMERCE
SPRINGFIELD,VA.22161
_.- _._-------------------------------------------- -
Foreword
The US-Southeast Asia Symposium on Engineering for Natural Hazards
Protection was held at the Philippine International Convention Center in
Manila, Philippines on 26-30 September 1977, sponsored jointly by the
Philippine National Science Development Board, the University of the
Philippines System, and the U.S. National Science Foundation.
The Symposium consisted of a technical conference and a research
workshop. The present volume contains all the technical papers contributed
and presented at the Conference part of the Symposium.
It is through the joint support of the above sponsors that made the
Symposium in Manila possible. The U.S. contribution to the Symposium was
supported by the Division of International Programs of the National Science
Foundation under Grant INT 77-15418 to the Department of Civil Engineering,
University of Illinois at Urbana-Champaign, which included the funding for
the publication of the present volume of proceedings. The Volume represents
the collective technical contributions of the authors to the SUbject of
the Symposium; their individual efforts and written contributions are
gratefully acknowledged.
It is a great pleasure to acknowledge the organizational leaderships
of Dr. E. G. Tabujara of the University of the Philippines and Mr. R. P.
Venturina of the National Science Development Board; the successful
convening of the Symposium in Manila was, in large measure, due to their
efforts.
The assistance of Mr. Lynn Barry of the U. of I. Engineering Publica
tions during the pUblication of the Volume is greatly appreciated.
A. H-S. Ang
Urbana, Illinois
CONTENTS
Risk and Safety Analysis in Design for Natural
Hazards Protection
A. H-S. Ang and Y. K. Wen .•.•.•.•. 1
Risk and Decision in Engineering for Natural
Hazards Protection
E. H. Vanmarcke • . • . • • . • • • . • 18
Earthquake Risk Analysis for Metro Manila
Fr. Sergio S. Su, S. J.•.•.•. 33
Risk Analysis of Underground Lifeline Network Systems
M. Shinozuka, S. Takada, and H. Kawakami 44
Statistical Nature of Earthquake Ground Motions and
Structural Response
J. Penzien •••• 59
Stochastic Process Models of Strong Earthquake Motions
for Inelastic Structural Response
H. Kameda •.••.•.•.•.•.•.•.•.
Vulnerability Analysis of Natural Disaster Risks
for the Metro Manila Area
N. von Einsiedel •.•.• 86
Seismic Risk Analysis Including Attenuation Uncertainty
A. Der Kiureghian • • . • • • . • . • . • .
Probabilistic Solution to Hysteretic Systems Subjected
to Earthquakes
P. Karasudhi, C-C. Wu, and H. Takemiya. • • • • .• •.•.•. Ilffi
Seismic Analysis of Soil-Building Interaction Systems
p. Karasudhi, T. Balendra, and Seng-Lip Lee • . • . •.•.• 121
Seismic Response and Reliability of Mechanical Systems -
Effects of Uncertainty of Ground Motions
H. Shibata, T. Shigeta, and A. Sone .•.•.•.•.•.•.•. 133
Current Trends in the Seismic Analysis and Design
of Structures and Facilities
W. J. Hall ••••••.•.•.•.•.•.• 147
Development of Earthquake Resistant Design Method
Employing Ultimate Capacity Concept
H. Aoyama •••.•.•••.•••.•.•.•.•••.•.• 164
ii
Seismic Design of Masonry Structures
M. J. N. Priestley •.•.•••. 178
Problems in Wind Engineering
M. P. Gaus. • .•.•. 196
Turbulence and Wind Force Effects on Structures
R. H. Scanlan.•.•.•.•••. 229
Aerodynamic Responses of Bridge Structures Subjected
to Strong Winds
N. Shiraishi and M. Matsumoto•.•. 241
Recent Developments in the Formulation of Design Wind
Loads
R. D. Marshall . 256
Some Probabilistic Considerations on Wind Resistant
Design
M. Ito and Y. Fujino • . • . • . 272
Wind-Resistant Design Practices of Cable-Suspended
Bridges in Japan
M. Ito and N. Shiraishi.•.•. 287
The Development of Design Criteria for Extreme Events
Arising from Natural Hazards
G. R. Walker and K. P. Stark .• 295
Design Considerations for Resistance to Wind
A. N. L. Chiu .•.•.•.•. 310
The Prevention and Control of Landslides
S. L. Koh and W-F. Chen. • .•. 325
Hurricane Waves, Storm Surge and Currents: An Assessment
of the State of the Art
O. H. Shemdin and D. B. King 338
Management of Storm Surges and Floods in Manila Bay
F-F. Yeh •.•••. 353
Storm Surge Potentials of Selected Philippine
Coastal Basins
C. P. Arafiles and C. P. Alcances, Jr.•
Some Observations on the Damages Resulting from
the ~tindanao Earthquake of August 17, 1976
A. O. Hizon••.•.•••.•.•.•••.• 382
iii
Assessment of Seismic Damage in Existing Structures
J. T.P. Yao • • • . • .•.•. 388
Wind Damage Experiences: Failure Assessment,
Practices, Solutions
J. E. Minor •.• 400
Full Scale Pressure Probability Distributions and
Spectral Measurements on a Multi Storey Building
R. Feasey and D. H. Freeston . • . • . • . • . • 420
iv
1
RISK AND SAFETY M~ALYSIS IN DESIGN
FOR NATURAL HAZARDS PROTECTION
by
A. H-S. Ang and Y.K.Wen
University of Illinois at Urbana-Champaign
Syno;psis
An approach to the risk-based analysis of safety of structures and
facilities against the extreme forces of natural hazards is described.
The components of the basic methodology are outlined, and applications
to wind and earthquake are emphasized. References to more comprehensive
works are provided. The implications for design to insure a desired
level of protection (in terms of probability) against natural hazards
are indicated.
Introduction
In the design and planning of a structure or facility for resistance
against the extreme forces of natural hazards, such as earthquakes and
storm winds, the level of protection or safety required for its design
is undoubtedly the most important technical problem underlying the planning
process. Indeed, resolving the question of "how safe is safe enough?" is
central to proper engineering.
In this regard, it is important to recognize that safety, specially
for protection against natural hazards, cannot be assured with absoluteness.
Realistically, safety may be assured only within the context of some
acceptable risk. Either explicitly or implicitly, some risk is unavoid
able; few (if any) economies can afford to do otherwise. In short, within
limited resources, there is a limit to safety--this is particularly
apropos in the case of natural hazards protection.
Within this risk-based concept of structural safety, a quantitative
framework for developing safety criteria for design can be developed. The
basic risk methodology is summarized herein, and the applications of the
approach to natural hazards protection are discussed and developed, with
emphasis on wind and earthquake resistant designs.
Methodology for Risk and Safety Assessments
The adequacy of a structure or facility to withstand the maximum
environment to which it may be subjected over its useful life is of
principal concern in planning its design. Like most natural phenomena,
the occurrence of an extreme environmental hazard, such as hurricane or
earthquake at a particular site, is difficult to predict; an extreme even
may occur at random in time as well as in space. Moreover, the intensity
2
(i.e. destruction potential) may vary greatly from one event to another.
In this light, the maximum environment that may be expected over the
life of a structure or facility at a particular location would be difficult
to predict with any certainty. It is realistically possible only to deter
mine the potential intensity in terms of probability; specifically, for
example, the annual probability of exceedance. Accordingly, the "design
environment" may be prescribed with an associated exceedance probability.
During the occurrence of a given natural hazard, such as a hurricane
or earthquake, the disturbance is a function of time; again the character~
istics of this function may be highly variable from one event to another
and thus may be described as a random process. Moreover, in analyzing
the response of a given system to a given random process disturbance
(requiring dynamic response analysis), the methods of random vibration are
appropriate.
The adequacy of a structure or facility against the expected lifetime
maximum environment, of course, will depend also on the limiting response
capacity of the structure. The determination of this capacity will
invariably also contain uncertainty; consequently, the adequacy or safety
of a structure against a particular lifetime hazard may only be measured in
terms of its probability of failure.
In summary, the determination of the safety of a given or proposed
system, therefore, requires the following: (i) definition or specification
of the maximum environment that a facility may be SUbjected to over its
intended useful life; (ii) analysis of the response of the system under
the estimated lifetime environment; and (iii) determination of the limiting
response capacity of the system. Each of these items may be elaborated as
follows:
Determination of Lifetime Maximum Environment
The determination of the lifetime maximum environment requires an
analysis of the potential hazards expected in the particular locality or
site. This may be accomplished by first determining the probability
distribution of the short-term (e.g. one year) maximum environment at the
site, from which the long-term (i.e. lifetime) maximum environment may be
extrapolated through extreme-value statistical theory.
The procedure for determining the short-term (e.g. one year)
distribution will depend on the specific hazard under consideration, as
will be discussed subsequently for the cases of wind and earthquake. In
any case, having determined the distribution of the annual maximum'
environment, say FA(a), the annual exceedance probability of the intensity
level a is,
P(A > a) = 1 - F (a)
A
Graphically, such hazard probabilities may be portrayed qualitatively as
shown in Fig. 1.
3
Then, the distribution of the life-time (say, n years) maximum environment
becomes
For sUfficiently large n, Eq. 2 will approach some asymptotic form
of distribution (Gumbel, 1958). Although the rate of convergence (in
distribution) will depend on the short-term distribution FA(a), it is
reasonable to assume, in the case of structures and large systems, that
the life (in years, n) is sUfficiently long to permit the use of the
appropriate asymptotic form of the extremal distribution for the lifetime
maximum. On this basis, only the key parameters of the extremal distribu
tion need to be determined for a given site; in particular, these are the
modal value, u, and the dispersion parameter, a.
The modal value, u, is defined as,
Hence, u is the annual maximum with the return-period of n years; whereas,
a is (see Gumbel, 1958)
(4)
Since I-FA(a) is invariably determined numerically, the necessary derivative,
may be evaluated approximately as,
(6)
from which the parameter a may be evaluated through Eq. 4.
In short, therefore, the main problem in the definition of the lifetime
environment is in the determination of the distribution or exceedance prob
abilities of the short-term (annual) maximum environment. Having established
this, the parameters of the lifetime maximum environment 'can be evaluated
from information on the short-term environment as indicated in Eqs. 3 and
4, whereas the distribution form for the lifetime maximum would be the
appropriate asymptotic extremal distribution.
Response to Life-time Maximum Environment
Knowledge of the lifetime environment itself, of course, is not
sUfficient; relative to the consideration of structural safety, the real
damage potential of the environment must include the "maximum" response of
the structure or system in question. The response of a structure to the
4
anticipated lifetime maximum environment may be analyzed assuming that it
does not significantly deteriorate over its life. The disturbance during
a natural hazard event is invariably a fluctuating forcing function over
the duration of the event. The response of a system to such a dynamic
forcing function may be analyzed by the methods of random vibrations.
Such analyses will depend on the definition of failure and associated
characteristics of the system. Failure may be defined as the occurrence
of the first yielding; in which case, the response may be limited to
linear system analysis. However, if failure is defined as some state
approaching ultimate collapse of the structure or any of its parts, then
the nonlinear-inelastic behavior of the system must be considered.
In any case, the response to the lifetime maximum environment may be
denoted as,
R =R(a,q)
max
where, q =the parameters of the structure or system, and a =the lifetime
maximum environment. R will remain a random variable, with probability
max
distribution FR(r).
The methods of random vibration analysis, suitable for the above
purposes, will be reviewed subsequently below.
Limiting Response Capacity
For a given structure or system, there is a response level beyond
which the structure may fail; this is the limiting capacity of the
structure. For a linear system, this may be the limiting displacement
(or velocity, or acceleration) beyond which some damage will occur in the
structure. However, failure may be defined as a state approaching
collapse, in which case the capacity could be related to its energy
absorbing capacity. In any case, the limiting capacity must be defined in
terms consistent with the calculated response r. The corresponding
probability distribution then may be represented as
Assessment of Risk and Safety
In view of the fact that both the lifetime extreme environment, as
well as the capacity of a system may be described only to the extent of
the respective probabilities, the assessment of safety may be evaluated
in the context of risk and probability of failure. Specifically, the
lifetime probability of failure is of interest:
r
PF(T) FC(r) . fR(r)dr
a
or r
PF(T) [l-FR(r)] . fc(r)dr ('Ta)
a