Effects of different test apparati and heating procedures on the bond properties of post-installed rebar connections under elevated temperatures

The use of chemical bonds to fasten reinforcement bars in existing concrete structures has been widely developed in the previous years, showing in many cases higher bond values compared to cast in rebars due to better performance of the adhesive mortar. However, at elevated temperatures the concrete-adhesive bond tends to weaken endangering the construction under a fire situation. The paper presents the result of an experimental campaign carried out at Scientific and Technical Center of Building and Politecnico di Milano laboratories on a post-installed connection using vinyl-ester polymer. This paper aims to investigate the behavior of rebar connections through chemical resin when subjected to high temperatures, with particular emphasis on the effects of water vaporization in the concrete and on the influence of heating procedures on the mortar post-curing. Two different pull-out test procedures were adopted, differentiating each other for the loading and heating sequences. Results showed that specimens with the same water content may present different thermal gradients; however, comparable mean temperatures along the bar are detected for the same values of applied load. Moreover, for a given temperature, the increase of bond strength with exposure time showed a convergence towards an asymptotic value

Simplified Design Method for Fire Resistance of Timber Connections

International audienc

Derivation of an innovative testing protocol for plastic anchors for fixing light façade claddings under seismic action

The safety of buildings located in seismic zones is related to the proper design of both the structural and the non-structural components. In recent seismic events, the collapse of the non-structural parts clearly demonstrated how they may represent a risk not only for the life safety but also the majority of the economical losses. Light cladding panels are a common solution to built façades in framed systems with rigid infills, particularly in reinforced concrete structures with masonry walls. They are usually fixed to the supporting structures by means of plastic anchors through angle brackets. Within this context, an experimental campaign was carried out to investigate their behaviour under seismic action. Starting from dynamic tests on real size façades, a new test protocol was proposed for the assessment of plastic anchors for fixing façade claddings. The scope of the present paper is to provide a theoretical background for the aforementioned test protocol

On the structural behavior of reinforced concrete walls exposed to fire

The present work deals with numerical simulations concerning the international benchmark "Vulcain tests on 3 Walls" regarding fire tests conducted in CSTB in Paris, France. To this aim, sequentially-coupled thermo-mechanical analyses have been performed on three reinforced concrete walls, characterized by different load levels and boundary conditions. The numerical results show that the imposed compressive load and boundary conditions significantly influence the magnitude of the displacements. In the case of simply supported walls, the wall with the lower load level exhibited a gradual and monotonic increase of the displacements at mid-height (both in the tests and in the numerical analyses), while the wall with the higher load level exhibited a displacement reversal due to second-order effects after approximately 60 minutes of fire exposure. This reversal, which was obtained in the analyses, was not observed in the test. Load bearing capacity of all the three specimen walls was maintained in such a way that the collapse did not take place during two hours of fire exposure