Full Scale Reinforced Concrete Beam-Column Joints Strengthened with Steel Reinforced Polymer Systems

This paper presents the results of an experimental campaign performed at the Laboratory of Materials and Structural Testing of the University of Salerno (Italy) in order to investigate the seismic performance of reinforced concrete (RC) beam-column joints strengthened with steel reinforced polymer (SRP) systems. With the aim to represent typical façade frames' beam-column subassemblies found in existing RC buildings, specimens were provided with two short beam stubs orthogonal to the main beam and were designed with inadequate seismic details. Five members were strengthened by using two different SRP layouts while the remaining ones were used as benchmarks. Once damaged, two specimens were also repaired, retrofitted with SRP, and subjected to cyclic test again. The results of cyclic tests performed on SRP strengthened joints are examined through a comparison with the outcomes of the previous experimental program including companion specimens not provided with transverse beam stubs and strengthened by carbon fiber-reinforced polymer (CFRP) systems. In particular, both qualitative and quantitative considerations about the influence of the confining effect provided by the secondary beams on the joint response, the suitability of all the adopted strengthening solutions (SRP/CFRP systems), the performances and the failure modes experienced in the several cases studied are provided

Reinforced concrete beams strengthened with SRP/SRG systems: Experimental investigation

Steel reinforced polymer (SRP) and steel reinforced grout (SRG) have emerged as promising and cost-effective technologies for the external strengthening of RC structures. Although the first studies date back to 2004, so far the literature related to the flexural strengthening of RC slabs/beams with steel tapes is rather limited. As a result, the application of such materials on a real structural member may be discouraged and, conversely, the use of carbon/glass FRP alternative systems may be preferred. The study presented in this paper contributes to filling this knowledge gap by presenting the results of 10 four-point bending tests performed on RC slabs strengthened with SRG/SRP systems. Test results have provided valuable information in terms of maximum forces, deformability and failure modes by varying number of layers and density of the steel tape. In particular, it has been shown that, disregarding the nature of the matrix (inorganic or polymeric), the presence of the external strengthening significantly increased the flexural strength of slabs, with percentage increases over the control (unstrengthened) member ranging from a minimum value of 27%, when using a single layer of low density tape, to a maximum of 106% in the case of SRP system with one layer of high density sheet. Preliminary analytical studies were also performed in order to investigate the possibility of extending to the SRP/SRG systems the applicability of formulations currently reported in some national and international guidelines for the flexural strengthening of RC members with FRP sheets

Concrete Confined by FRP Systems: Confinement Efficiency and Design Strength Models

Issue 4, Jun

Proceedings of the OpenSees Days - 2nd Italian Conference

Conference held at the University of Salerno (10-11 June 2015

Seismic retrofitting of RC columns with FRP systems: design relationships

"full paper" sul CD allegato agli Att

Strain models for FRP-confined concrete

In this paper, a study on the ultimate axial strain of the fiber-reinforced polymer (FRP) confined concrete is presented. To this aim, a large database was assembled from the scientific literature including results from compression tests performed on over 450 FRP-confined concrete cylinders. The experimental data were then used to calibrate, through simply best-fit procedures, some of the most accredited predictive strain models available in the literature; the efficiency of the found relationships was then compared with that of the formulations proposed by other authors. Finally, the reliability of a novel strain model was also investigated and compared to the other considered relationships

Results from cyclic tests on high aspect ratio RC columns strengthened with FRP systems

A limited number of experimental studies have been performed on FRP-confined columns having rectangular cross section with high aspect ratio. The experimental study presented herein addresses this knowledge gap by investigating performances, under constant axial load and cyclically reversed horizontal force, of full scale rectangular (300 × 700 mm) RC columns externally confined by using Fiber Reinforced Polymers (FRPs) or strengthened with FRP wraps and steel profiles. The study is a part of a wider experimental campaign also including tests on square (300 × 300 mm) columns whose details have been already published elsewhere. Test results discussed herein aim to evaluate the influence on the column performance of relevant parameters, such as: unconfined concrete strength, longitudinal steel reinforcement (smooth or deformed rebars), strengthening system (FRP confinement with or without steel profiles); axial load level and number of FRP layers. Finally, the effectiveness of the used strengthening techniques is investigated through the comparison with the performances obtained in the case of square members