Numerical investigation of old RC frames strengthened against earthquakes by high dissipation steel link elements

The use of dissipative steel link elements for the seismic strengthening of existing reinforced concrete (R/C) frames, which have been designed according to older regulations, can provide additional strength and stiffness but mainly, high energy dissipation capacity. The aim of this work is the numerical investigation of the effectiveness of these dissipative steel elements, as well as the understanding of the overall behaviour of the strengthened reinforced concrete frames. The numerical models are based on tests executed in the Aristotle University of Thessaloniki and presented in the previous paper of the same volume. All the specimens were designed following the regulations and construction practice of the period before 1980. The first specimen is a typical one bay, single storey R/C frame, while the two other specimens are identical to the first one, but strengthened by two different types of dissipative steel elements. The aforementioned concrete frames are accurately simulated numerically and the results are compared with the respective experimental ones. © 2010 Taylor & Francis Group, London

Numerical simulation of bending response of reinforced concrete and fibre-reinforced concrete beams

The aim of this work is to understand the behaviour of members made of fibre reinforced concrete (FRC). The members under study were fibre reinforced concrete beams with no conventional reinforcement, as well as fibre reinforced concrete beams with longitudinal and transverse reinforcement. For the FRC specimens, a high-strength cement mix with the addition of steel fibres, was used. Conventional reinforced concrete beams and reinforced concrete beams strengthened by an FRC jacket were also studied in the same terms, for comparison reasons. The beams were tested under either monotonic (static tests), fully cyclic (positive and negative bending moments), or one-direction cyclic (positive bending only) three- or fourpoint bending. The validity of each proposed numerical model for the behaviour the FRC beams is established by comparing the numerical predictions with the experimental results. © Civil-Comp Press, 2008

Experimental and numerical study of the behaviour of high dissipation metallic devices for the strengthening of existing structures

The use of steel bracing systems for the strengthening of existing reinforced concrete (RC) frames may lead to increase of both strength and stiffness. However, in most of the cases the main target is the increase of the energy dissipation capacity. This paper studies, both experimentally and numerically, the efficiency of a specific strengthening type which utilizes a small steel link element having an I-shaped cross-section connected to the RC frame through bracing elements. The energy is dissipated through the plastification of the steel link element. The case studied in this paper is a typical one bay, single storey RC frame constructed according to older code provisions, which is strengthened through two different types of steel link elements. The behaviour of the strengthened frames is studied with respect to the one of the original bare frame. The experimental study is supported by complete numerical simulations of the performed tests. To this end, detailed numerical models are formulated, which are able to follow the highly non-linear nature of the problem, involving the plastification of the steel rebars, the cracking and plastification of concrete and the plastic deformation and hysteretic response of the dissipative link elements