Consuelo Beschi

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.

Column and Joint Retrofitting with High Performance Fiber Reinforced Concrete Jacketing

A new technique for the strengthening of existing R.C. structures, based on the application of a high performance fiber reinforced concrete jacket, is investigated here. The aim of the research is to study the possibility of using this technique for the seismic retrofitting of existing columns and beam-column joints. Two full-scale tests have been performed: a column-to-foundation joint and a beam-column joint. The specimens have been loaded with static horizontal cyclic loads with increasing amplitude. The results show that with the adoption of this technique it is possible to significantly increase both bearing capacity and ductility of existing R.C. structures.

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%.

High Performance Fiber Reinforced Concrete Jacketing in a Seismic Retrofitting Application

A new technique for the strengthening of existing R.C. structures, based on the application of a high performance fiber reinforced jacket, is investigated herein. Aim of the research is to study the possibility of using this technique for the seismic retrofitting of existing columns. A full scale test has been performed on a column-foundation element. The specimen has been loaded with static cyclic action having increasing amplitude, up to failure. The results shows that with the adoption of this technique it is possible to significantly increase both bearing capacity and ductility of the existing R.C. structure.

Beam-Column Joint Retrofitting with High Performance Fiber Reinforced Concrete Jacketing

The possibility of strengthening existing R/C structures with a new technique based on the application of a High Performance Fiber Reinforced Concrete jacket is investigated herein, with the aim of studying the effectiveness of this technique for seismic retrofitting. The results of a beam-column joint full scale test simulating the behavior of existing beam-column joints are presented. The specimen have been subjected first to static loads and after to cyclic actions with increasing amplitude, up to failure. The tests demonstrated that, with the application of a HPFRC jacket, it was possible to remarkably increase the bearing capacity of the columns reaching also an adequate level of ductility, and the resistance of the beam column joints, with very little visible damage, thanks to the tensile strength contribution of HPFRC.