Page 313 - Forensic Structural Engineering Handbook

10.2 CAUSES OF FAILURES

Case History 10: Wood Truss Erection 10.48
Case History 11: Column Reinforcing Steel Bracing 10.49
Case History 12: Bridge Demolition 10.50
HOW TO AVOID TEMPORARY STRUCTURE FAILURES? 10.55
ATTRIBUTION 10.55
REFERENCES 10.55
ADDITIONAL USEFUL LITERATURE 10.55

INTRODUCTION

More failures occur during construction than during the service lives of structures after
their completion, and most of those construction failures involve temporary structures.
To architects, engineers, lawyers, and even to some contractors, temporary structures in
construction are not as familiar as permanent structures, such as buildings and bridges. For
the engineer to design effective, economical, and safe temporary access or support struc-
tures, he or she has to have an understanding of not only loads, strength, and stability, but
also the business and practice of temporary works in order to know where, when, how, why,
and by whom temporary works are used.
For the forensic engineer to conduct an intelligent investigation of a construction failure
involving temporary structures, she or he, too, has to have an understanding of not only
loads, strength, and stability, but also the business and practice of temporary works in order
to recognize the possible sources and nature of problems. Therefore, much of this chapter is
devoted to design philosophies, to an overview of the design-construction processes, and to
the applicable design and construction codes, standards, and regulations as they relate to
temporary structures. The rest of the chapter includes presentations of several case histories.
For a short overview of the subject of temporary works, the reader is directed to the
four-page article, Temporary Structures in Construction—USA Practices. 1

CONSTRUCTION FAILURES

In the United States, as well as throughout the world, disturbingly large numbers of structural
failures occurs during construction. Advances in construction technology, newly developed
materials, increasingly fine-tuned designs, and the construction of more daring structures, as
well as the pressure of time and cost-cutting driven by competition, are all contributing fac-
tors. But the most frequent direct causes of failures are human factors: oversight; carelessness;
incompetence; breakdown of organization; poor management and communication; disregard
of codes, standards, and specifications; and general nonadherence to good practice.
There appears to be a disconnect between the practices of one group, the designers-of-
record—who by necessity distance themselves from the construction of the project—and
the objectives and capabilities of the other group, the constructors—who by contract must
perform under the constraints of agreed time and money.
More structures fail during construction than in service after completion; and many, if
not most, of the construction disasters occur as the result of the failure of temporary struc-
tures. A tacit attitude seems to prevail in the design-construction industry: “these things”
are temporary only, hence generally less important, therefore greater risks are acceptable
than in permanent structures. But a dollar or a life lost at a construction site is no less valu-
able or less tragic than its loss elsewhere. More than 1200 construction workers lose their
lives and many others are injured each year in the United States. According to some