Abstract

Strengthening systems for existing reinforced concrete (RC) structures are increasingly needed due to several problems such as degradation of materials over the time, underdesign, serviceability or seismic upgrading, or new code requirements. In the last decades, strengthening by fibers composite materials applied with various techniques (FRP, FRCM, NSM) were largely investigated and theoretical formulations have been introduced in national and international design guidelines. Although they are an excellent strengthening solution, steel plates may represent still a valid traditional alternative, due to low costs, ductile stress-strain behavior, simple and fast mounting with possibility of reusing the material. Guidelines for a correct design are still lack and, therefore, detailed models and design formulas are needed. In this paper, the bond behavior at the plate-concrete interface, which plays a key role for the effectiveness of the strengthening system, is analyzed by means of 3D finite element models calibrated on experimental results available in literature. Parametric analyses were carried out by changing some meaningful parameters.

Highlights

  • In [19], a series of bond tests on carbon fiber reinforced polymer (FRP) reinforcements bonded on concrete elements were reported and a modified form of the Holzenkämpfer’s model [22], based on fracture mechanism approach, to predict ultimate load referred to steel plate was proposed too

  • On the debonding load is very low. Within such a limited influence, can a validation on experimental results of bond tests available in literature, it has been itused be observed that an increase of the adhesive thickness, i.e., a reduction of the adhesive for carrying out parametric analysis and comparisons with theoretical formulations in stiffness

  • Sessing the reliability of extending to externally bonded steel plates the design formulations usually adopted for FRP plates

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Summary

Introduction

Most experimental results available in the scientific literature concern bond tests on FRP materials glued to concrete elements, while only few tests, not recent, were carried out on steel plate glued to concrete [5,6,7]. Bonded or bolted steel plates represented, the first example of external strengthening technique for existing RC elements and they were supplanted by FRP materials in the 1990s. The study represents the first step of a wider research involving both experimental The study represents the first step of a wider research involving both experimental tests and numerical analyses on steel plates externally glued on concrete elements and tests and numerical analyses on steel plates externally glued on concrete elements and aimed to verify the reliability of the actual approaches proposed for FRP plates for the aimed to verify the reliability of the actual approaches proposed for FRP plates for the steel ones too It is worth noting, that for FRP externally reinforcements, the forsteel ones too.

2.2.Literature
Modeling Approaches for Bonded Interface
The FE 3D model
Constitutive
Validation of the FE Models by Means of Comparisons with Experimental Results
Analysis of Bond Behavior by Means of Parametric Analyses
Findings
Conclusions

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