A comparative analysis of energy dissipation and equivalent viscous damping of RC columns subjected to uniaxial and biaxial loading

Abstract

a b s t r a c tThe hysteretic behaviour of RC columns has been object of many experimental studies over the past years. However, the majority of these studies are focused on unidirectional loading. An experimental program was carried out where 24 columns were tested for different loading histories, under uniaxial and biaxial conditions. The experimental results are presented in this paper and are discussed in terms of global column behaviour, and particularly with regards to energy dissipation and damping capacity. The energy dissipation capacity of the columns was evaluated in terms of cumulative dissipated energy, comparing uniaxial and biaxial test results, and individual cycle dissipated energy. Ultimately, an equation relating the normalised dissipated energy with the displacement ductility is proposed. The equivalent viscous damping was analysed by comparing the uniaxial with biaxial test results, demonstrating the high influence of the load path in the biaxial response of RC columns. Proposals for estimating the equivalent viscous damping given by other authors are compared with the experimental results. Finally, simplified expressions are proposed to estimate equivalent viscous damping in RC columns under biaxial loading.

Comparative efficiency analysis of different nonlinear modelling strategies to simulate the biaxial response of RC columns

“…The general characteristics of the specimens and testing conditions are summarized in Table 1. A more detailed description of the columns' geometry, material properties, reinforcement details and test results is reported in (Rodrigues et al, 2012). The general characteristics of the specimens and testing conditions are summarized in Fig.…”

“…A detailed review of the available models is presented in CEB (1996) and Fardis (1991). In addition to the fi ber models (Petrangeli et al, 1999;Taucer et al, 1991;Spacone et al, 1992), other analytical models are available, following the concepts of classical plasticity (Pecknold, 1974), Mroz multisurface plasticity (Takizawa and Aoyama, 1976;Powell and Chen, 1986;Galal and Ghobarah, 2003), Bouc-Wen (Wen, 1976), hysteresis modelling (Romão et al, 2004;Kunnath and Reinhorn, 1990;Casciati, 1989;Wang and Wen, 2000), bounding surface plasticity Fardis, 1991a, 1991b;Bousias et al, 2002), or lumped damage models Florez-Lopez, 2002, 2003;Mazza and Mazza, 2008), among others. The available test results for biaxial bending are not as extensive and the development and calibration is not exhaustive.…”

“…The determination of the effects of earthquakes on buildings generally requires the consideration of two horizontal component loads in columns, which tend to induce larger demands than onedirectional actions. In many situations, biaxial demands on columns also result in the torsional response of buildings, namely as a result of in-plane structural irregularities (Romão et al, 2004).…”

Displacement-based design procedure of damped braces for the seismic retrofitting of r.c. framed buildings

“…Moreover, the mean value of the hysteretic energy dissipated through all cycles is expected to yield lower values of the equivalent damping. For this reasons, in order to minimize the difference with the response of the equivalent linear system, a better estimation of the equivalent viscous damping can been derived through experimental tests (Rodrigues et al 2012) and nonlinear dynamic analyses (Pennucci et al 2011;Mazza and Vulcano 2014b). In the present work, in a first approximation, as the Jacobsen approach can underestimate the inelastic displacements due to the overestimation of the equivalent damping, a reduction factor κ is considered in Eq.…”

Evaluation of Damage in Reinforced Concrete Columns Under Biaxial Loading

“…Thus, the present study focus on the assessment and comparison the DIs given by those expressions as well as by three other expressions (11) to (13) herein proposed. In all these expressions, DI biaxial is the biaxial damage index, DI x and DI y refer to the damage indices calculated for each independent direction, E x and E y are the cumulative dissipated energy calculated for each independent direction, and λ is a constant parameter experimentally calibrated.…”