Hans G. Natke· James T. P. Yao

Structural Safety Evaluation Based on System Identification Approaches

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Methods in Clinical Pharmacology Norbert Rietbrock and Barry Woodcock

Advances in Solid State Physics

Advances in Structure Research by Diffraction Methods

Vieweg --------------------"

Hans G. Natke . James T. P. Vao

Structural Safety Evaluation Based on

System Identification Approaches

Proceedings of the Workshop at Lambrecht/Pfalz

M Springer Fachmedien Wiesbaden GmbH

This volume contents the proceedings of the Workshop on Structural Safety Evaluation Based on System Identification Approaches, held in Lambrecht/Pfalz June 29th to July 1 st 1987, Organized

by H. G. Natke, Curt-Risch-Institut, TU Hannover.

A II rights reserved

© Springer Fachmedien Wiesbaden 1988 Originally published by Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig 1988

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photo­copying, recording or otherwise, without prior of permission of the copyright holder.

ISBN 978-3-528-06313-9 ISBN 978-3-663-05657-7 (eBook) DOI 10.1007/978-3-663-05657-7

Contents

Preface (H.G.Natke/J. T.P. Yao) ................................. .

Damage Descriptions and Basic Requirements ......................... 7

Cracked Cross Section Measurement in Rotating Machinery B. O. Dirr, D. Hartmann, B. K. Schmalhorst

9

System Identification ......................................... 29

Utilization of Experimental Investigations in the Process of Tower Structures

Dynamic Identification R. Ciesielski, J. Kawecki

On the Determination of the Number of Effective Modes from Vibration

30

Test Data ................................................. 49

M. Link

Structural System Identification from Modal Information J.-G. Beliveau

System Identification Using Nonlinear Structural Models P.Jayakumar, J. L. Beck

Identification of Hysteretic Structural Behaviour from Strong Motion

69

82

Accelerograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 103 C.· Y. Peng, W. D. Iwan

Calibration of Nonlinear Constitutive Laws for Elastic-Plastic Analysis in Presence of Creep Strains A. Nappi, A. Gavazzi

118

Inelastic Modeling and System Identification ......................... 142 Y. K. Wen, H.-S.Ang

Identification of Equivalent Linear Systems .......................... 161 C. Paliou, M. Shinozuka

Reliability of an Identification System for Predicting Incipient Capsize Due to

Chaotic Rolling Motion of a Ship ................................. 182 E. Yarimer, L. N. Virgin

Correlation of Analysis and Test in Modeling of Structures: Assessment and Review ....... . 195

S. R. Ibrahim

Localization Techniques ....................................... 212

G. Lallement

A Two Stage Identification Approach in Updating the Analytical Model of Buildings ................................................. 234

M. A. M. Torkamani, A. K. Ahmadi

Interaction between System Identification and Damage Evaluation ........... 265

Reliability Based Factor of Safety for Unmanned Spacecrafts T. De Mollerat, C. Vidal, M. Klein

Parameter Identification for Reliability in Markov Cumulative Damage

Processes ..................... . P. Voltz, F. Kozin

A System Identification Approach to the Detection of Changes in Structural

Parameters ................................ .

M. S. Agbabian, S. F. Masri, R. K. Miller, T. K. Caughey

266

313

341

Time Domain Identification of Linear Structures .. . . . . . . . . . . . . . . . . . . . .. 357 V. C.Matzen

Fuzzy Data Processing in Damage Assessment ......................... 381 H. Furuta, M. Shiraishi

Concepts ................................................. 393

A Systems Approach to Fire Safety Engineering J.A.Purkiss

394

Experimental Vulnerability Detection in Civil Structures .... . . . . . . . . . . . . .. 414

P.lbanez

The Machinery Vibration and Wear Advancement Identification and Forecasting

C.Cempel .... 415

Bridge Inspection by Dynamic Tests and Calculations Dynamic Investigations of Lavant Bridge ............................................ 433

R. G. Flesch, K. Kernbichler

System Identification Approaches in Structural Safety Evaluation ........... 460 H. G. Natke, J. T. P. Yao

Structural Damage Assessment Using a System Identification Technique ....... 474 J.-Ch. Chen, J.A. Garba

Summary of Workshop Discussion

J.-L.Beck (Recorder) ......................................... 494

Concluding Remarks and Recommendations

H.G.Natke/J.T.P.Yao ........................................ 498

Preface

H. G.Natke, J. T.P. Yao

Preface

The idea of this workshop originated during a collaborative

research project by the Editors, who share a common interest

in safety evaluation based on theoretical and experimental

structural analysis. We believe that "Safety Evaluation

Based on System Identification Approaches" is an important a detailed topic in engineering applications

and critical consideration. Civil

were emphasized at this workshop.

and needs

engi neeri ng appl i cati ons Nevertheless, the inter-

disciplinary nature of this subject matter requires commu­

nication among experts with various backgrounds and ex­

perience.

It was not felt necessary to give an introduction to

the topics as covered herein. For a detailed description

of these topics, the interested reader can refer to several

textbooks and surveys as listed at the end of this preface. The role of system identification is shown in Fig. 1 and an extended identification methodology for safety

evaluation is illustrated in Fig. 2 (from the paper by H. G. Natke and J. T. P. Yao in the Proceedings).

W Cl:C ::::> •... f-: <i: z: lJ..: 0:

W: f-. <i: f-: Vl: . : Li._ f I~-I ,: I

. I i7l: I >-: I

EXCITATION RESpONSE.

;i: I z: L -r COLLECTiON OFl <i : ibOOITIONAL OATA..J~.r.=:==-='=~=c=~

pO'SSH'iL"E Aerlof,is':', : .. EXPERIENCED ENGR ........... ·:.·O··:E:C::IS::I·O·:N:JA· 'N' 'A' L'y' ·S·I·S·.' .. ° NORMAL OPERATION :-.. : .----=~-:-=~___, ° SPECIAL MEASURES: ESTIMATEO ···r············· -r ....

............................. : SYSTEM EQUATIONS :. , ............ "': ESTIMATED :

·CHARACTERISTICS .... -:RELIABILlTY· .. _RELIABILITY ECONOMICAL EXPE:C"TE·O···· ... ~--------' :.~.NA,LY?.I~ ... : FUNCTION CONSIOERATION FUTURE EXCITATION

FIG.1 SYSTEM IOENTIFICATION METHOOOLOGY

w a:

2

~ :' ........................................ .. ~ : EXCITATION r.:::::~=-:==-------, RESPONSE z : ~-.-~-~~~~~

FIG.2 EXTENDED SYSTEM IDENTIFICATION METHODOLOGY FOR-COMPLEX AND HIGHLY NONLINEAR STRUCTURES

In Fig. 1, the current system identification methodology

and its application are shown schematically. Usually,

excitation and response data are measured and processed

for use in system identification studies. Results of

these studies are used by experienced engineers, who use the

resulting mathematical equations for additional structural

analyses including reliability calculations. In the ex­

tended system identification methodology as shown sche­

matically in Fig. 2, we propose to include the identifica­

tion of limit states with the additional input data such

as inspection results, laboratory test data, and results

of nondestructive evaluations. Such data may be either

crisp or fuzzy, which may require new techniques for data

3

processing. In addition we propose the development of

expert systems including data bases and inference machines

as consultative aid to the experienced engineers who are

decision makers. An add,'t,'onal h' emp as,s is placed on the need for an ,'mproved model 'th k w, nown confidence.

Fig. 3 contains a list of the topics treated. Initially

we should know the definition and description of damage.

Looking at the usual mathematical models in their discrete

(with respect to local coordinates) form such as finite

elements or multi-body models, any changes in their para­

meters (physical or modal) may serve the purpose for the

detection of structural modifications, which are caused

by damage. Some of the required parameters cannot be

measured directly. How certain are we in making such

statements? I~hat are the most suitable quantities? I~hat

are the optimum testing (including measurement) conditions?

These questions should be addressed in detail before

the tools for the detection and localization of structure

modifications by identification methods are discussed

in general.

The discussion of system identification approaches is

included in Item No.2 in Fig. 3. Section 2.1 may be

conceived as direct modal identification. Updating math­

ematical models (2.3) using measured or identified quan­

tities is an important topic in order to obtain models

with known confidence. Here the a priori knowledge coming

from system analysis can be included. Instrumentation

and data processing are important parts of identification,

since the quality of the results depends on them.

The interaction between the results of system identifica­

tion (estimated modifications) and damage evaluation is

discussed in Item No.3. Here probabilistic methods and

related mathematics such as fuzzy sets are presented.

4

WORKSHOP

ON STRUCTURAL SAFETY EVALUATION

BASED ON SYSTEM IDENTIFICATION APPROACHES

1. DAMAGE DESCRIPTIONS AND BASIC REQUIREMENTS

1.1 STRUCTURAL CONSIDERATIONS

1.2 PARAMETERS (SENSITIVITY)

1.3 DM1AGE INDICES

1.4 TEST REQUIREMENTS

2. SYSTEM IDENTIFICATION

2.1 IDENTIFICATION OF LINEAR SYSTU1S

2.2 IDENTIFICATION OF NONLINEAR SYSTEMS

2.3 UPDATING OF ANALYTICAL MODELS

2.4 INSTRUIHNTATION, DATA PROCESSING

3. INTERACTION BEHJEEN SYSTU~ IDENTIFICATION

AND DAMAGE EVALUATION

3.1. STOCHASTICS

3 • 2 FUZZ Y SETS

3.3 PATTERN RECOGNITION, EXPERT SYSTE~1S

4. CONC E PTS

4.1 LINEAR MODELS

4.2 NONLINEAR MODELS

Fig. 3 List of the topics

5

Under Item No.4 in Fig. 3, concepts of damage evaluation

are discussed. Ideally both linear and nonlinear models

should be considered. However, only linear models are

presented herein.

In the above-mentioned categories the papers are classi­

fied in an arbitrary manner. Several papers cover more

than one item. The reader will find several topics cov­

ered by many authors, and other topi cs wi thout coverage.

This may be interpreted as an indication of the state of the art.

The aim of the workshop was to bring together several

researchers in different fields of experience in order

to

(a) document the state of the art,

(b) discuss the topics from different viewpoints, and (c) obtain recommendations regarding future work.

We wish to express our sincere gratitude to

Stiftung Volkswagenwerk, Hannover, FRG,

National Science Foundation, Washington, D.C., USA,

Rheinland-Pfalz, Staatskanzlei, Mainz, FRG, Deutsche Lufthansa AG, Ingenieurdirektion, Hamburg, FRG,

Dornier GmbH, Friedrichshafen, FRG,

for their encouragement and generous support, without

which the workshop would not have been possible.

In addition the organizers want to thank all participants for their active interest and valuable contributions.

References

1. J. T. P. Yao: Safety and Reliability of Existing

Structures; Pitman Publ. Inc.,

Boston, London, Melbourne, 1985

6

2. H. G. Natke (Ed.): Identification of Vibrating Struc-

3. H. G. Natke:

4. H. G. Natke (Ed.):

5. F. Kozin, H. G. Natke:

tures; CISM Courses and LEcture

No. 272 , S p r i n 9 e r , Wi en. New Y or k ,

1982

EinfUhrung i n Theorie und Praxis

der Zeitreihen- und

Vieweg,

1983

Braunschweig,

Modal analyse;

Wiesbaden.

Application of System Identification

in Engineering; CISM Courses and

Lecture No. 296, Springer. Wien,

New York, wi 11 appear

System Identification Techniques;

Structural Safety 3 (1986) 269 - 316.