Giovanni Metelli

Cyclic behaviour of a column to foundation joint for concrete precast structures

ABSTRACT This paper aims at presenting the results of two experimental tests concerning the cyclic behaviour of a dissipative column-to-foundation connection for precast concrete elements. The tested joints are characterized by the use of high strength threaded steel bars partially un-bonded in grouted sleeves and by steel support elements which allow an easy assemblage and centering of the column. The two specimens differ in bar number and bar diameter of the un-bonded high-strength bars adopted to restore the flexural continuity. The experimental results are compared to the response of a pocket foundation joint and they show a good performance of the joint in term of resistance, ductility, cycle stability and energy dissipation. The specimen damage is localized at the column base thus allowing a simple retrofitting after a seismic event.

Experimental and numerical studies on the behaviour of concrete sandwich panels

ABSTRACT Precast concrete panels are often used for the façades of modern warehouses and commercial malls. During the last two decades, they have generally been made of two concrete layers with interposed thermal insulating polystyrene boards. Traditionally, perimeter concrete ribs allow the weight of the external concrete layer to be transferred to the internal thus causing unavoidable thermal bridges which reduce the energy performance of the building. In the sandwich cladding panel, the two concrete layers can be linked by low-conductivity shear connectors crossing through the insulation layer, thus ensuring the overall thermal efficiency of the building. In this paper, the results of a wide numerical study on the behaviour of concrete sandwich panels realized with glass fibre-composite pultruded connectors are presented, focusing on the stresses and deformations caused by dead load, thermal actions and shrinkage.

HPFRC Jacketing of Non Seismically Detailed RC Corner Joints

In this article, the effectiveness of a High-Performance Fiber-Reinforced Concrete (HPFRC) jacket for the seismic retrofitting of existing RC corner beam-column joints is experimentally investigated. The results of cyclic experimental tests on full-scale corner beam-column sub-assemblies (two unretrofitted and two retrofitted) are presented and discussed in detail, focusing on the effectiveness of the adopted retrofitting technique. The RC test units were designed with structural deficiencies typical of the Italian construction practice of the 1970s: use of smooth bars, inadequate reinforcement detailing, such as lack of stirrups in the joint panel, and hook-ended anchorage. The results underlined that the joint panel strength impairs the seismic response of the sub-structure with a drift at incipient collapse not greater than 2%. The results showed that the application of thin HPFRC jackets appears a promising technique to strengthen poorly-detailed RC joints: the jacket was able to increase the shear strength of the joint by about 40%, with respect to the bare joint, limiting the damage of the retrofitted sub-assembly, which reached an ultimate drift of 6%.

Combining seismic retrofit with energy refurbishment for the sustainable renovation of RC buildings: a proof of concept

In this paper, an integrated approach targeting sustainability, safety and resilience is envisioned for the renovation of the post-Second World War RC buildings clustered in urban outskirts. The so...

The Repair of Timber Beams with Controlled-Debonding Steel Plates

In this paper a non-invasive technique for the repair of ancient wooden floors is presented. Steel plates are glued on one side only by epoxy-adhesive into longitudinal grooves in order to allow the free swelling and shrinkage of the wood in the direction transversal to the plate glueing surface, thus reducing the risk of plates’ delamination. A set of high strength steel nails guarantees the transmission of the load from the steel plates to the wooden beam in case of loss of adhesion due to fire or delamination. This technique was used to repair a precious beam in a wooden floor of the 15th century in Palazzo Calini (Brescia, Italy). The presented technique requires particular attention because it might be affected by the delamination of the glued reinforcement due to the stress concentration, which occurs at the end of the repairing element or at the cracks of the repaired beam.The main results of experimental and numerical studies focusing on the delamination phenomenon are also presented and discussed. They have shown that the risk of plate debonding can be markedly reduced by the capability of the sapwood to develop plastic strain. The wooden floor has been monitored for more than eleven years, confirming the effectiveness of the adopted technique. The monitoring has also shownthe importance of limiting the wooden moisture content variation to reduce the floor’s creep deflection.