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- Bending resistance of partially encased beams: experimental tests at elevated temperaturePublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.The bending performance of 27 Partially Encased Beams (PEB) is compared at different temperature levels using the four-point bending test setup. Tests consider only one composite cross section, two beam lengths and two different shear conditions for stirrups. The performance of PEB is also compared to bare steel I beams (IPE). Experimental measurements confirmed that temperature is not perfectly constant over the length of the heated beams, presenting strong gradients at extremities. Progressive damage of concrete occurred during experiments. The bending resistance of PEB at room temperature is much higher than bare steel beams and the bending stiffness is approximately 15% higher, being the post buckling deformation quite different. The reduction of the bending resistance of PEB at elevated temperature is not inversely proportional to the increase of the temperature. All tested beams attained lateral torsional buckling for deformed shape mode, with exception to those tested at 600 °C.
- Temperature assessment on fire resistance experiments of partially encased beamsPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Twelve fire resistance tests, grouped in four series, were developed using partially encased beams (PEBs) without concrete slab, for different load levels and shear condition. PEBs were built with standard hot rolled IPE100 profile and reinforced concrete between flanges. Fire resistance was determined for standard ISO834 nominal fire curve, using small fire resistance furnace and portal frame. Temperature was measured in three different sections along PEB length (S1, S2, S3), for three different materials (steel, concrete and reinforcement). Average temperature in each section and material was compared with the average temperature over length. Each series presented similar results, with good reproducibility. Special focus was given to critical temperature. The maximum temperature difference between sections and the average temperature of element length is smaller than 3.2%, 5.1%, 6.3% and 11.2%, for test series 1, 2, 3 and 4, respectively. Temperature is not uniform in cross-section. After the initial heating stage, temperature revealed a constant difference of approximately 150°C between temperatures measured inside and outside, defining two main temperature evolutions. Temperatures measured outside revealed always higher temperature level.
- Three dimensional simulation of partially encased beams at elevated temperaturesPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Partially Encased Beams (PEBs) are composite steel and concrete elements in which the web of the steel section is encased by reinforced concrete. The experimental investigation was already verified under fire and under elevated temperatures [1-2]. The bending resistance for three bending point configuration, at four temperature levels (20, 200, 400 and 600 ºC) is determined, based on the three dimensional finite element model, with precise detail of each component (steel profile, reinforcement, stirrups and concrete). The solution method is incremental and iterative (arc length), based on geometric and material non-linear analysis (ANSYS), using reduced integration method. The model considers perfect contact between steel and concrete. The material model assumes plasticity. The imperfection mode was based on the elastic stability solution, also performed with finite element method (ANSYS). Two types of stirrups were considered: welded to the web (PEBA) and welded to the flanges (PEBB), three different lengths (2.5, 4.0 and 5.5 m) and three types of cross section dimensions were simulated, based on the dimensions of IPE100, IPE200 and IPE300 steel profiles. A total of 72 models were simulated, showing conservative results with respect to the simple calculation method of EN1994-1-2. The bending resistance of the numerical results was determined for different force events, giving the opportunity to compare the ultimate bending moment. Results are in accordance to the new formula presented by Vila Real et al. [3] and adapted to composite beams.
- Experimental investigation of the fire resistance of partially encased beamsPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Zipponi, Marco; Marini, Alberto; Mesquita, L.M.R.; Plizzari, GiovanniThis 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 under ISO834 fire exposure. Results reveal the dependence of fire resistance on load level. An increase in 37% on load level is responsible for a decrease in 28% on fire resistance. Tests developed for the highest load level present similar fire resistance, independently of the shear condition; however, tests with welded stirrups present higher critical time. The main experimental results are presented and discussed. Particular emphasis was given to changes in temperature for each material, and on the global thermo-mechanical behaviour of this composite steel and concrete element.
- High temperature tests on partially encased beamsPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.; Gonçalves, CarlosPartially encased beams (PEB) are composite steel and concrete elements that present several advantages with respect to steel bare elements. This paper presents a set of experimental tests developed using two different beam lengths and two different shear conditions between stirrups and web (W – welded and NW – not welded), at high temperature (200, 400, 600 ºC) and room temperature. The composite section was built-up with IPE100 steel profile and reinforced concrete between flanges. The deformed shape mode and the bending resistance were compared for different temperature levels and stirrup shear conditions (W and NW). The behaviour of PEB was also compared with bare steel at room temperature. Most of the beams attained the ultimate limit state by lateral torsional buckling (LTB), with exception for those tested at 600 ºC, which collapsed by the formation of a plastic hinge (PH).
- Temperature analysis on fire resistance experiments of partially encased beamsPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Twelve fire resistance teslS, grouped in four series, were developed using partially encased beams (PEB) WitllOut concrete slob, for different load levei and shear connection. PEB were built witll standard bot rolled IPEJOO profile and reinforced concrete between flanges. Fire resistance was determined for standard 1S0834 nominal beating curve, using small fire resistance fumace and portal trame. Temperature was measured in Ihree differenl sections along PEB lengtll, for three differenl materiais (steel, concrete and reinforcemenl). Average temperature in each section and material was compared lo lhe average over length lemperature. Each series presented similar resuHs, wilh good reproducibility. Special focus was given to crilical temperature. The maximum temperature difference between sections SI, S2, S3 and lhe averoge elemen! lengtll temperature is smaller than 3.2% for tesl scries 1. For test series 2, 3 and 4 lhe maxirnum lemperature difference is smaller Ihan 5.1 %, 6.3% and 11.2%, respectively. Temperature is no! uniform in cross-section. Afler the ini!ial heating stag;e, temperature revealed a constan! difference ofapproximately IS0'C between temperatures measured inside and outside, defining two main temperature evolutions. Temperatures measured outside revealed a1ways higher temperature leveI.
- Bending resistance of partially encased beams at elevated temperature: advanced calculation modelPublication . Piloto, P.A.G.; Almeida, David; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Partially Encased Beams (PEBs) are composite steel and concrete elements in which the web of the steel section is encased by reinforced concrete. The experimental investigation of the bending resistance was already verified in fire and under elevated temperature (Paulo A. G. Piloto el al., 2013a) (Paulo A. G. Piloto el al., 2013b). The three-dimensional finite element solution, with precise detail of each component (steel profile, reinforcement, stirrups and concrete) was used to determine the bending resistance under three point bending configuration. Four temperature levels were tested (20, 200, 400 and 600 degrees C) and three lengths were considered (2.5, 4.0 and 5.5 m), using three different cross section types, based on the dimensions of IPE100, IPE200 and IPE300 steel profiles. Two distinct types of welded stirrups were simulated (PEBA with "C" shape stirrups welded to the web and PEBB with "I" shape stirrups welded to the flange). The solution method is incremental and iterative (arc length), based on geometric and material non-linear analysis (ANSYS), using reduced integration method. Results are in accordance to the new formula presented (P. M. M Vila Real et al., 2004) and adapted to partially encased beams. The bending resistance was not significantly influenced by the type of welded stirrup
- Push-out tests for partially encased beams at elevated temperaturePublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.; Barreira, Luísa
- Bending resistance of partially encased beams at elevated temperature: advanced calculation modelPublication . Piloto, P.A.G.; David, Almeida; Ramos Gavilán, Ana Belén; Mesquita, L.M.R.Partially Encased Beams (PEBs) are composite steel and concrete elements in which the web of the steel section is encased by reinforced concrete. The experimental investigation of the bending resistance was already verified in fire and under elevated temperature (Paulo A. G. Piloto el al., 2013a) (Paulo A. G. Piloto el al., 2013b). The three-dimensional finite element solution, with precise detail of each component (steel profile, reinforcement, stirrups and concrete) was used to determine the bending resistance under three point bending configuration. Four temperature levels were tested (20, 200, 400 and 600 degrees C) and three lengths were considered (2.5, 4.0 and 5.5 m), using three different cross section types, based on the dimensions of IPE100, IPE200 and IPE300 steel profiles. Two distinct types of welded stirrups were simulated (PEBA with "C" shape stirrups welded to the web and PEBB with "I" shape stirrups welded to the flange). The solution method is incremental and iterative (arc length), based on geometric and material non-linear analysis (ANSYS), using reduced integration method. Results are in accordance to the new formula presented (P. M. M Vila Real et al., 2004) and adapted to partially encased beams. The bending resistance was not significantly influenced by the type of welded stirrup.
- Experimental bending tests of partially encased beams at elevated temperaturesPublication . Piloto, P.A.G.; Ramos Gavilán, Ana Belén; Gonçalves, Carlos; Mesquita, L.M.R.This paper presents the result of an experimental research about the lateral torsional buckling instability during bending tests of Partially Encased Beams (PEB) at elevated temperature. A set of twenty seven four-point bending tests, grouped in ten series, were carried out to analyse the influence of relative slenderness, beam temperature and the shear bond conditions between concrete and steel in bending. In addition, this study compares the behaviour of PEB and bare steel beam under bending at room temperature. PEB specimens are based on IPE100 steel profiles, with two different lengths 2.4 m (medium series) and 3.9 m (large series), tested in bending using simple supporting conditions and exposed to different temperatures levels of 200 °C, 400 °C, and 600 °C. Two different shear bond conditions, between steel profile and lateral concrete, were analysed at 400 °C: one series with connectors formed by welded stirrups to the web and another series with natural adherence between steel and concrete, not welded stirrups. PEB attained lateral torsional buckling as deformed failure mode at the ultimate limit state, except for the case of PEB tested at 600 °C that results in a plastic hinge failure. The bending resistance was determined for the maximum load event (F u ) and for the displacement limit corresponding to L/30 (F L/30 ) and compared with the results of the Eurocode 3 part 1–2 simple calculation method, considering an adaptation of its formulae to PEB. The expected reduction in bending resistance at elevated temperature is in good agreement with the experimental reduction factor, when the deformation criterion is used.