Abstract
Earthquake collapse of substandard reinforced concrete (RC) buildings, designed and constructed before the development of modern seismic design Codes, has triggered intense efforts by the scientific community for accurate assessment of this building stock. Most of the proposed procedures for the prediction of building strength and deformation indices were validated by assembling databases of RC column specimens tested under axial load and reversed cyclic lateral drift histories. Usually a column structural behavior is assessed by considering all involving mechanisms of behavior, namely flexure with or without the presence of axial load, shear and anchorage. In the present paper a force-based fiber beam/column element was developed accounting for shear and tension stiffening effects in order to provide an analytical test-bed for simulation of experimental cases such as the lightly reinforced columns forced to collapse. Their peculiar characteristics are the outcome of the shear – flexure interaction mechanism modeled here based on the Modified Compression Field Theory (MCFT) and the significant contribution of the tensile reinforcement pullout from its anchorage to the total column’s lateral drift. These features are embedded in this first-proposed stand-alone Windows program named “Phaethon” -with user’s interface written in C++ programming language code- aiming to facilitate engineers in executing analyses both for rectangular and circular substandard RC columns.
Highlights
Most of the state-of-the-art on seismic design and assessment procedures proposed recently for common engineering practice require some kind of nonlinear analysis either static or dynamic
The so-called fiber beam elements (Figure 1) provide results that seem to be appropriate for studying the seismic behavior of reinforced concrete (RC) structures: moment-axial force (M-N) coupling is readily taken into account as well as the interaction between concrete and steel in the section
In order to determine the normal and the shear stresses for the i-th fiber / layer of a fiber section of a RC beam (Vecchio & Collins, 1988) a bi-axial fiber constitutive model is developed according to the Modified Compression Field Theory (MCFT) (Table 1)
Summary
Most of the state-of-the-art on seismic design and assessment procedures proposed recently for common engineering practice require some kind of nonlinear analysis either static or dynamic. In an actual frame element the end moment–rotation relation results from the integration of the section response This can be achieved directly with elements of distributed inelasticity (Filippou & Fenves 2004). For the latter approach, the so-called fiber beam elements (Figure 1) provide results that seem to be appropriate for studying the seismic behavior of RC structures: moment-axial force (M-N) coupling is readily taken into account as well as the interaction between concrete and steel in the section. One of the modeling strategies in order to incorporate the beam theory that includes shear into the fiber approach is related to the idea of adopting suitable constitutive relationships In this category belong fiber beam-column elements using smeared cracking models.
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