EXPERIMENTAL AND COMPUTATIONAL INVESTIGATION OF FIRE BEHAVIOR OF RESTRAINED REINFORCED CONCRETE COLUMNS - PART II

Year 2017, Volume: 18 Issue: 2, 121 - 136, 15.12.2017

Ataman Haksever

Abstract

In
the eighties the work was particularly focused in SFB (SonderForschungsBereich: A special fire research activity for
structural elements in Braunschweig Technical University, 1971-1986) on
the development of a universal material model for normal concretes in case of
fire. Through a comprehensive mathematical description of  the rheological phenomena at elevated
temperatures, the relaxation behavior of restrained col­umns could be
successfully predicted. It aimed at clarifying the difference, which took place
between the deformation behavior as well as restraint forces of calculated and
measured reinforced concrete columns (RFC) under fire conditions. Such a
material model was developed, in fact, through close cooperation of subprojects
A and B3 of SFB.

Naturally,
the use of such material model requires an immense computational treatment.
Theoretical studies have shown, however, that this is worthwhile, because only
by this process the fire behavior of structural concrete elements can be taken
into account satisfactorily. It should be stressed here that a material model
can gain confidence only if it has been tested successfully under different
boundary conditions. In particular, the model must apply for the assessment of
the fire behavior of structural elements in large scale.

In
this regard relaxation tests on reinforced concrete columns under different
boundary conditions have been carried out in the special furnace of SFB. The
heating of the reinforced concrete columns have been made with respect to ISO830-fire
as well as to a simulated natural fire condition. The following sections
describe the tests and also their theoretical investigation.

Keywords

Structural fire safety, reinforced concrete columns, fire resistance, relaxation, fire behavior

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