Alessia Monaco

Validation of a Shear Model for RC and Hybrid Beams with Two Different Inclinations of Transversal Reinforcement

The validation of an analytical model recently proposed for evaluation of the shear capacity in Reinforced Concrete (RC) beams containing multiple inclination of transverse stirrups is presented. The model is a suitable extension of that currently proposed in Eurocode 2 for the evaluation of the shear resistance, and it is derived by means of the the variable-inclination stress-field theory based on Nielsen’s plastic approach. Experimental and numerical data available in the literature on Hybrid Steel-Trussed Concrete Beams (HSTCBs) are used for model validation and result discussion. Finally, also the comparison with a different analytical approach for the assessment of the shear resistance of HSTCBs is provided.

Experimental Investigation of the Shear Response of Precast Steel-Concrete Trussed Beams

AbstractThe results of an experimental campaign of three-point bending tests on precast composite beams, named hybrid steel–trussed concrete beams (HSTCBs), are provided. HSTCBs are typically constituted by a precast steel truss embedded in a block of concrete cast in place. Two series of specimens were manufactured, designed such that shear failure would occur, and tested under positive and negative bending moment. The experimental results obtained showed that fragile shear failure occurred in almost all cases, evidencing the crisis of the compressed concrete strut involved in the collapse mechanism. Yielding of the steel members provided ductility to the system, especially in those cases in which the mechanical properties of the concrete were adequate and allowed the failure of the strut to be delayed. Some of the more accredited expressions for prediction of shear resistance available in the literature were used to assess the shear capacity and compared against those experimentally obtained for all spe...

Effect of FRP strengthening on the flexural behaviour of calcarenite masonry walls

The use of fiber-reinforced polymers (FRP) for structural strengthening has become increasingly popular in recent years. Several applications of FRP have been proposed and applied, depending on the target of the technique, kind and/or material of the structural member. In particular, because of their great tensile strength, FRP materials are commonly used to enhance the out-of-plane behaviour of masonry walls, allowing to increase their strength, ductility and improving safety against overturning. For these reasons, FRP laminates are often applied in vulnerable ancient buildings in seismic areas to reinforce façades and walls with poor structural features. However, some issues arise when adopting composites in historical constructions, the most related to the aesthetical impact of laminates and compatibility between FRP and masonry. Consequently, a correct evaluation of the reinforcement percentages for strength and ductility purposes is crucial, as well as the effective increase of structural performances. This paper presents a numerical-analytical approach able to reproduce the flexural behaviour of out-of-plane loaded masonry walls. The model is based on a simplified representation of the member, the latter modeled as a cantilever beam. Mechanical non-linearity is introduced by means of moment–curvature relationships, deduced with proper constitutive laws of masonry and by taking into account the ultimate debonding strain of FRP. Second order effects are considered by adopting an iterative step-by-step procedure. Comparisons are made in terms of moment–curvature and load–displacement curves with experimental data available in the literature and with non-linear finite element analyses, showing both good agreement. Finally, parametric considerations on the reinforcement percentages are made in terms of strength and ductility.

Cyclic behavior of composite truss beam-to-RC column joints in MRFS

In the present paper, the cyclic behavior of beam-to-column joints made up of Hybrid Steel Trussed Concrete Beams (HSTCBs) connected to Reinforced Concrete (RC) piers is investigated. HSTCBs are a typology of composite beam generally constituted by a steel truss with end zone added rebars embedded within a block of concrete cast in place. HSTCBs represent a structural solution for light industrialization in the civil constructions; the main advantages in their use are the higher construction speed with the minimum site labor, the possibility of covering wide spans with low depths and a final economical convenience. For these reasons, they are also increasingly adopted within seismic framed structures. In the present study, the examined joints are representative of framed RC structures subjected to seismic actions and designed according to the current Italian standard code. Cyclic tests are performed and interpreted by means of analytical and numerical models with the aim of verifying the strength capacity and ductility of the system, focusing on both the global behavior and the force transmission between steel truss and concrete in the joint region.

Effect of FRP Wraps on the Compressive Behaviour of Slender Masonry Columns

In the last decade, Fibre Reinforced Polymer (FRP) wrapping technique has become a common method to retrofit masonry piers or columns with poor structural performances. The passive confinement effect induced by the external wrap allows increasing the compressive strength and ductility of the member. Several studies highlighted as the efficacy of this technique is affected by several key parameters, including the shape of the transverse cross section, stress intensification at the strength corner of sharp sections, amount and mechanical properties of adopted composite. Despite this technique has been widely studied from both theoretical and experimental point of view, most of studies focused on short columns and little information is available on the influence of second order effects on its structural efficacy. This paper presents a simplified method able to assess the effect of FRP confinement on slender columns. A preliminary evaluation of the constitutive law in compression of FRP confined masonry is made and the best-fitting model is adopted to model masonry in compression. Sectional analysis is performed by including the tensile strength of masonry and considerations are made on the increase of ultimate moment and curvature. Finally, the effect of column slenderness is considered using a simple numerical procedure, making it possible to calculate the allowable slenderness ratios as a function of the maximum drift, taking into account both strength and stability.

Computational study of failure of hybrid steel trussed concrete beams

AbstractThis study investigates the failure behavior of hybrid steel trussed concrete beams (HSTCBs) under three-point bending through a series of finite-element (FE) simulations. The FE model empl...

Analytical prediction of the flexural response of external RC joints with smooth rebars

An analytical model in a closed form able to reproduce the monotonic flexural response of external R.C. beam-column joints with smooth rebars is presented. The column is subjected to a constant vertical load and the beam to a monotonically increasing lateral force applied at the tip. The model is based on the flexural behavior of the beam and the column determined adopting a concentrated plasticity hinge model including slippage of the main bars of the beam. A simplified bilinear moment-axial force domain is assumed to derive the ultimate moment associated with the design axial force. For the joint a simple continuum model is adopted to predict shear strength and panel distortion. Experimental data given in the literature are utilized to validate the model. Finally, the proposed model can be considered a useful instrument for preliminary static verification of existing external R.C. beam-column joints with smooth rebars.