Piloto, P.A.G.; Ramos Gavilán, A.B.; Zipponi, Marco; Marini, Alberto; Mesquita, L.M.R.; Plizzari, Giovanni
This research presents the fire resistance of Partially Encased Beams (PEB). Fire resistance was determined by means of twelve experimental tests, according to European standard EN1363-1, for different load levels and shear conditions between stirrups and web steel. Three tests were also performed at room temperature for load bearing resistance. The experimental setup was designed for this purpose, using a small fire resistance furnace and portal reaction frame. Details about the specimens tested, the instruments used and the characteristics of the materials, are also presented. Load-deflection and load-strain results were determined at room temperature. Deflection and temperature measurements were determined...
Ramos, Luis F.; Marques, Leandro; Lourenço, Paulo B.; Roeck, G.; Costa, Alfredo Campos; Roque, João C. Almendra
The paper addresses two complex case studies of modal and structural identification of monuments in Portugal: the ClockTower of Mogadouro and the Church of Jerónimos Monastery, in Lisbon. These are being monitored by University of Minho with vibration, temperature and relative air humidity sensors. Operational modal analysis is being used to estimate the modal parameters, followed by statistical analysis to evaluate the environmental effects on the dynamic response .The aim is to explore damage assessment in masonry structures at a nearly stage by vibration signatures, as a part of a health monitoring process that helps in the preservation of historical...
Lopes, H.; Santos, J.V. Araújo dos; Soares, C.M. Mota; Guedes, R.M.; Vaz, M.A.P.
This paper presents a structural damage location method that decreases the number of spatial differentiations needed to compute modal curvature ﬁelds. The method is numerically and experimentally applied to isotropic and laminated rectangular plates, respectively. A speckle shear interferometer is used to measure the rotation ﬁelds of the laminated plate, while the isotropic plate is analysed by ﬁnite elements. It was found that the Gaussian differentiation is the most suited technique to compute the curvature ﬁelds. It is also demonstrated the superior performance of the curvature method using measured rotation ﬁelds instead of measured displacement ﬁelds.
Nogueiro, Pedro; Silva, Luís Simões da; Bento, Rita; Simões, Rui
Composite joints, considering the composite action of steel and concrete, exhibit, in general, high
strength and high ductility. As a consequence, the use of this type of joint has been increasing in many
countries, especially in those that are located in earthquake-prone regions. In this paper, a hysteretic model
with pinching is presented that is able to reproduce the cyclic response of steel and composite joints. Secondly,
the computer implementation and adaptation of the model in a spring element within the computer code
Seismosoft is described. The model is subsequently calibrated using a series of experimental test results for
composite joints subjected to cyclic loading. Finally,...
Nogueiro, Pedro; Silva, Luís Simões da; Bento, Rita; Simões, Rui
In this paper, a hysteretic model with pinching is presented that is able to reproduce realistically the cyclic response of generic steel joints. Secondly, the computer implementation and adaptation of the model in a spring element within the computer code SeismoStruct is described. The model is subsequently calibrated using a series of experimental test results for steel joints subjected to cyclic loading. Finally, typical parameters for the various joint configurations are proposed.
Santos, J.V. Araújo dos; Lopes, H.; Vaz, M.A.P.; Soares, C.M. Mota; Freitas, M.J.M. de
Three methods for the damage localization of impact damage in laminated composite plates, based on their vibrational characteristics, are presented in this paper. These methods use double pulse TV holography with acoustic excitation for mode shapes acquisition and the differences in translations, rotations and curvatures. The rotations and curvatures are obtained by numerical differentiation of mode shapes translations using a differentiation/smoothing technique. The methods are applied to a carbon fiber reinforced epoxy rectangular plate, free in space, subjected to two cases of impact damage. It is shown that the method based on curvatures allows the localization of both cases of...
Vila Real, P.M.M.; Piloto, P.A.G.; Franssen, J.-Marc
The behaviour of Steel I-Beams exhibiting lateral-torsional buckling at elevated temperature has been studied by means of experimental and numerical analysis. The authors in an earlier paper have presented an analytical formula for the buckling resistance moment in the fire design situation. This new proposal, different from the actual proposal of the Eurocode 3 Part 1.2 has been validated in this work by comparison with the results from a set of 120 experimental and numerical tests performed on IPE 100 beams, submitted to temperatures varying from room temperature to 600 °C. The numerical simulations have been based on the measured...
Mesquita, L.M.R.; Piloto, P.A.G.; Vaz, M.A.P.; Vila Real, P.M.M.
Lateral unrestrained steel beams when subjected to high temperatures may collapse in service by lateral torsional buckling. This instability state may be predicted in the resistance, temperature and time domain. In this work the beam strength is determined in the temperature domain from a batch of numerical and experimental tests, with a specified degree of utilisation and a typical accident temperature rise.
The experimental set-up is a reaction portal frame especially designed for beam elements under elevated temperatures. The specimens were heated by means of electroceramic resistances and a fibre mat specimen cover is used to increase the thermal efficiency. The...
Vila Real, P.M.M.; Lopes, N.; Silva, L.S.; Piloto, P.A.G.
This paper presents a numerical study of the behaviour of steel I-beams subjected to fire and a combination of axial force and bending moments. A geometrical and material non-linear finite element program, specially established in Liege for the analysis of structures submitted to fire, has been used to determine the resistance of a beam-column at elevated temperature, using the material properties of Eurocode 3, part 1–2. The numerical results have been compared with those obtained with the Eurocode 3, part 1–2 (1995) and the new version of the same Eurocode (2002).
The results have confirmed that the new proposal for Eurocode...
Vila Real, P.M.M.; Cazeli, R.; Silva, L.S.; Piloto, P.A.G.
When a beam is bent about its greatest flexural resistance axis it may twist and move laterally, before it reaches its strength limit in bending. Although this problem of lateral-torsional buckling of steel beams at room temperature has well established solution, the same problem at elevated temperature has not. The lateral-torsional buckling of steel I- beams have been numerically investigated from room temperature up to 700 °C, with the aim of assessing the effects of the residual stresses in this mechanism of failure.
A geometrically and materially non-linear finite element program i.e., a general model, has been used to determine the...
Vila Real, P.M.M.; Lopes, N.; Silva, L.S.; Piloto, P.A.G.; Franssen, J.-Marc
Two new formulae for the design of beam-columns at room temperature have been proposed into Eurocode 3, prEN 1993-1-1 (2002), and are the result of great efforts made by two working groups that
followed different approaches, a French-Belgian team and an Austrian-German one. Under fire conditions the
prEN 1993-1-2 (structural fire design) presents formulae, for the design of beam-columns based on the
prENV 1993-1-1 (1992). In order to study the possibility of having, in part 1-1 and part 1-2 of the Eurocode 3,
the same approach, a numerical research was made using the finite element program SAFIR, developed at the
University of Liege for the...
Lopes, N.; Silva, L.S.; Vila Real, P.M.M.; Piloto, P.A.G.
The possibility of having, in parts 1-1 and 1-2 of Eurocode 3, the same approach for the design of beam-columns and
for lateral–torsional buckling, was investigated by the authors in previous papers using a numerical approach, where it
was concluded that those assumptions could be made.
In the present paper, a new approach for lateral–torsional buckling has been used with the formulae for the design of
beam-columns at elevated temperature based on prEN 1993-1-1 combined with the formulae from prEN 1993-1-2. In
both cases the results obtained are much better than the current design expressions, when compared with those obtained
in the numerical calculations.
Rosa, Sérgio; Pinho, Fernando T.
The laminar flow of Newtonian fluids in axisymmetric diffusers has been numerically investigated to evaluate the pressure-loss coefficient
as a function of Reynolds number, diffusion angle and expansion ratio. The numerical simulations were carried out with a finitevolume
based code using non-orthogonal collocated grids and second order accurate differencing schemes to discretize all terms of the
The calculations were carried out for Reynolds numbers between 2 and 200, diffusion angles from 0 to 90 and expansion ratios of 1.5
and 2 and the data are presented in tabular form and as correlations. A simplified 1D theoretical analysis helped explain the various
contributions to the...
Escudier, Marcel; Rosa, Sérgio; Poole, Rob
New experimental data are presented and discussed for fully developed pipe flow of shear-thinning, viscoelastic polymer solutions in the transitional regime between laminar and turbulent flow. The data confirm that such transitional flows exhibit significant departures from axisymmetry in contrast to the fully developed pipe flow of Newtonian fluids or both laminar and turbulent flows of such drag-reducing liquids. The azimuthal structure of the asymmetry is investigated together with its axial development and also the velocity fluctuation levels. These data do not lead to an explanation for the asymmetry but do suggest that the influence of the flow geometry both...
Valin Rivera, J.L.; Monteiro, J.M.; Lopes, H.; Vaz, M.A.P.; Palacios, Francisco; Gonçalves, Edison; Garcia del Pino, Gilberto; Pérez, Jorge Ricardo
The purpose of this article is to study the application of the holographic interferometry techniques in the structural analysis of submarine environment. These techniques are widely used today, with applications in many areas. Nevertheless, its application in submarine environments presents some challenges. The application of two techniques, electronic speckle pattern interferometry (ESPI) and digital holography, comparison of advantages and disadvantages of each of them is presented. A brief study is done on the influence of water properties and the optical effects due to suspended particles as well as possible solutions to minimize these problems.
Lopes, H.; Guedes, R.M.; Vaz, M.A.P.
In this work a numerical-experimental method is used to study the dynamic behavior of an aluminum plate subjected to a small mass
impact.The out-of-plane displacements,due to transient bending wave propagation,were assessed for successive time instants,using
double pulse TV-holography,also known as pulsed ESPI.
Araújo, A.L.; Lopes, H.; Vaz, M.A.P.; Soares, C.M. Mota; Herskovits, J.; Pedersen, P.
In this paper two non-destructive methods for elastic and piezoelectric parameter estimation in active plate structures with surface bonded piezoelectric patches are presented. These methods rely on experimental undamped natural frequencies of free vibration. The first solves the inverse problem through gradient based optimization techniques, while the second is based on a metamodel of the inverse problem, using artificial neural networks. A numerical higher order finite element laminated plate model is used in both methods and results are compared and discussed through a simulated and an experimental test case.
Carneiro, J.O.; Melo, F.J.M.Q. de; Rodrigues, J.F.D.; Lopes, H.; Teixeira, Viriato
A vibration analysis for the determination of the natural frequencies and the associated eigenmodes of a pipe elbow with end-flanges or tangent terminations was performed. A numerical investigation of this problem was achieved with a semi-analytic definition finite ring element and a commercial finite element code. To assess the accuracy of the numerical solution for the elbow vibration, an experimental modal analysis was performed on a curved and on a straight pipe. The responses were processed by a data acquisition system which performs a fast Fourier transform on the time histories to convert them from a time to frequency domain,...
Ribeiro, J.E.; Monteiro, Jaime; Vaz, M.A.P.; Lopes, H.; Piloto, P.A.G.
The goal of this work was the development of other experimental techniques to measure residual stresses, as an alternative to the hole-drilling method with strain gauges. The proposed experimental techniques are based on the use of Moiré interferometry and in-plane electronic speckle pattern interferometry (ESPI). Both are field techniques allowing the assessment of in-plane displacements without contact and high resolution. Grating replication techniques were developed to record high-quality diffraction gratings onto the specimen's surfaces. An optical set-up of laser interferometry was developed to generate the master grating (virtual). An in-plane ESPI set-up was also designed and implemented to measure displacements...
Rodrigues, J.F.D.; Lopes, H.; Melo, F.J.M.Q. de; Simões, J.A.
In this paper we describe the experimental
characterization of the modal parameters of asynthetic com-
posite femur model widely used in biomechanical research
studies.The objective of the experimental procedure was to
identify the natural frequencies and modes hapes of anun-
constrained (free–free) femur.