IFMASS10

FAILURES OF STRUCTURES IN SERVICE

Aleksandar Sedmak

University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia

Jasmina Lozanović

University of Belgrade, Innovation Centre of the Faculty of Mechanical Engineering,

Belgrade, Serbia

1. INTRODUCTION

Despite great improvements in design, manufacturing, inspection and maintenance

procedures, failures of structures still occur, often with great human and economic loss.

Since this lecture provides an introduction to the subject of failure analysis, the general

methodologies involved in carrying out such an analysis are illustrated by two case

studies. Failure analysis can be an absorbing subject to those involved in investigating the

cause of an accident, but the capable investigator must have a thorough understanding of

mode of operation of the components involved, as well as knowledge of the possible

failure modes. A properly performed investigation should lead to a rational scenario of

the sequence of events occurred in the failure as well as to an assignment of respon-

sibility, either to the designer, the manufacturer, the operator or the maintenance and

inspection organization involved. A successful investigation may also result in

improvements in design, manufacturing, inspection and maintenance procedures.

Since prehistoric times, failures have often resulted in taking one step back and two

steps forward, but sometimes with severe consequences for the designers and builders.

This can be illustrated by the Code of Hammurabi, which was written in about 2250 BC

/1, 2/: “If a builder build a house for a man and do not make its construction firm, and the

house which he has built collapse and cause the death of the owner of the house, that

builder shall be put to death. If it causes the death of a son of the owner of the house, they

shall put to death a son of that builder. If it destroys property, he shall restore what ever it

destroyed, and because he did not make the house which he built firm and it collapsed, he

shall rebuild the house which collapsed at his own expense.”

The failure analysis of bridges, viaducts, cathedrals, pressure vessels, aircraft vehicles

and other structures resulted in better design, improvement of materials and construction

procedures. Mechanical components, such as wheels and axles, were improved through

empirical insights gained through experience, and these improvements worked out quite

well, but not always. An example of an evolved design that did not work out well is rela-

ted to the earthquake that struck Kobe, Japan, in 1995. That area of Japan had been free

of damaging earthquakes for some time, but had been visited frequently by typhoons. To

stabilize homes against the ravages of typhoons, the local building practice was to use a

rather heavy roof structure. However, when the earthquake struck, the collapse of heavy

roofs caused considerable loss of life and property damage. The current design codes for

this area have been revised to reflect a concern for both typhoons and earthquakes.

Stress analysis plays an important role both in design and in failure analysis. Ever

since the advent of the industrial revolution, concern about the safety of structures has