Civil Engineering Reference
In-Depth Information
refers readers instead to the CEB-FIP Model Code. Currently, the main
design documents are the American code ACI 318-83 (revised 1986), the
Canadian code CAN-A23.3-M84, the CEB-FIP Model Code and the CIRIA
Guide 2. Of these, the CIRIA Guide gives the most comprehensive
recommendations and is the only one that covers the buckling strength of
slender beams.
The transition from ordinary-beam behaviour to deep-beam behaviour is
imprecise; for design purposes, it is often considered to occur at a span/
depth ratio of about 2.5 (Kong, 1986b). Although the span/depth ratio
l/h
is
the most frequently quoted parameter governing deep-beam behaviour, the
importance of the shear-span/depth ratio
l/h
was emphasised many years ago
(Kong and Singh, 1972) and, for buckling and instability, the depth/
thickness ratio
l/h
and the load-eccentricity/thickness ratio
l/h
are both
relevant (Garcia, 1982; Kong
et al.,
1986).
1.2
History and development
Classic
literature reviews
have been compiled by Albritton (1965), the
Cement and Concrete Association (C&CA) (1969) and Construction
Industry Research and Information Association (CIRIA) (1977), which have
been supplemented by the reviews of Tang (1987), Wong (1987) and
Chemrouk (1988). These show that the early investigations were mostly on
the elastic behaviour. Of course, elastic studies can easily be carried out
nowadays, using the standard finite difference and finite element techniques
(Coates
et al.,
1988; Zienkiewicz and Taylor, 1989). However, a serious
disadvantage of elastic studies is the usual assumption of isotropic materials
obeying Hooke's law; hence they do not give sufficient guidance for
practical design.
It was not until the 1960s that systematic
ultimate load tests
were carried
out by de Paiva and Siess (1965) and Leonhardt and Walther (1966). These
tests were a major step forward in deep beam research. They revealed a
concern for empirical evidence which reflected the philosophy of the
European Concrete Committee (CEB, 1964) which stated that 'the Comité
Européen du Béton considered that the 'Principles' and 'Recommendations'
should be fundamentally and solely based on experimental knowledge of the
actual behaviour…' The lead provided by these pioneers was subsequently
followed by many others in different parts of the world (reviews by CIRIA,
1977; Chemrouk, 1988).
In the late 1960s an extensive long-term programme was initiated by
Kong and is still continuing at the University of Newcastle upon Tyne; tests
to destruction have so far been carried out on over 490 deep beams, which
included large specimens weighing 4.5 t. each (
Figure 1.1
and Kong
et al.,
1978; Kong and Kubik, 1991) and slender specimens of height/thickness
ratio
h/b
up to 67 (Kong
et al.,
1986).
