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- Shear Testing of Topologically Optimised Web Cover Plates in Splice Connections – Experiment Design and ResultsPublication . Ribeiro, Tiago; Bernardo, Luís; Nepomuceno, Miguel; Maugeri, Natale Antonio; Longo, Paolo; Domenico, Dario DeTesting shear-resisting plates in steel connections is one of the most challenging laboratory undertakings in steel construction, as the most common experimental layout design includes simulating the connection with its adjoining members. This significant hindrance gained particular magnitude as the need to test prototypes of topologically optimised shear cover plates became more pressing. Indeed, new code-compliant topology optimisation approaches for steel construction have recently been offered, and physically non-linear analyses have been demonstrated to be vital for assessing these elements. Hence, a rapid and reliable experimental process has become a fundamental necessity. To answer this need, a novel layout is herein proposed, in which topologically optimised and previously numerically examined bolted shear plates of a well-known steel joint were tested. The results allowed for the definition of the material trilinear model for use in subsequent numerical analysis, as well as the validation of the numerical simulation results. The discrepancy between the previously mathematically anticipated and empirically determined ultimate resistance did not exceed 1.7%.
- The influence of self-compacting steel fibre reinforced concrete infill on the flexure strength and ductility of masonry wallsPublication . Oliveira, Luiz Pereira de; Bernardo, LuísThis paper presents an experimental study on the influence of longitudinal reinforcement ratio and steel fibre volume in self-compacting concrete infill on the strength and ductility of reinforced masonry walls subjected to flexure. Flexure tests were performed as four-point bending tests on twelve walls. The analysis of the concrete infill contribution to the walls capacity is made considering recent recommendations for steel fibre reinforced concrete design. A ductility index was defined and applied to study the ductility behaviour of the masonry walls. The analysed variables are the longitudinal reinforcement ratio and the steel fibre volume in the concrete infill.
- Betão estrutural de agregados leves de resistência normal e alta: dos estudos laboratoriais à produção no local - Caso de estudoPublication . Nepomuceno, Miguel; Bernardo, Luís; Pinto, HugoNeste artigo descreve-se um estudo experimental que se desenvolveu em duas fases, compreendendo, na primeira fase, o estudo e a produção laboratorial de betões estruturais de agregados leves de argila expandida com classes de densidade seca entre 1,8 e 2,0 de acordo com a EN 206-1 e quatro classes distintas de resistência à compressão compreendidas entre os 20 MPa e os 65 MPa e, na segunda fase, a produção e aplicação do betão em condições semelhantes às de um estaleiro de pré-fabricação na betonagem de 26 vigas de betão armado com secção retangular e diversas taxas de armadura de flexão. Com esse objetivo foram estudadas e produzidas em laboratório quatro séries de betão: a Série 1 (20 a 25 MPa), a Série 2 (40 a 45 MPa), a Série 3 (50 a 55 MPa) e a Série 4 (60 a 65 MPa). Para a produção dos betões foram selecionados os cimentos CEM II/B-L32,5N e CEM I 42,5R, duas adições de microssílica, uma adição de fíler calcário, um superplastificante, uma areia natural rolada, dois agregados grossos de granito britado e um agregado leve de argila expandida com máxima dimensão de 12,7 mm. Os betões produzidos podem ser designados de “sand-lightweight concrete” de acordo com o ACI 318, uma vez que apenas se usou areia natural como agregado fino. A metodologia adotada para o estudo da composição baseou-se no método das curvas de referência, nomeadamente aquelas propostas por Faury, correntemente usadas em Portugal para o betão vibrado. Neste artigo são descritos os materiais selecionados, são apresentadas as composições estudadas, o processo de produção e curas dos betões, os resultados obtidos nos ensaios no estado fresco e endurecido e são ainda discutidos alguns parâmetros relevantes para a análise efetuada no âmbito do presente estudo, nomeadamente as correlações entre a resistência à compressão, a razão água-ligante e a massa volúmica. É ainda comparada a variabilidade dos resultados entre os betões produzidos em laboratório e em estaleiro de pré-fabricação. Os resultados obtidos revelaram que é possível produzir satisfatoriamente betões estruturais de agregados leves de elevada resistência em estaleiro de pré-fabricação com distribuição homogénea, sem segregação, mesmo para aplicações estruturais em vigas de betão armado.
- Neutral Axis Depth versus Ductility and Plastic Rotation Capacity on Bending in Lightweight-Aggregate Concrete BeamsPublication . Bernardo, Luís; Nepomuceno, Miguel; Pinto, HugoThis article presents an experimental study on the evolution of the neutral axis depth at failure in the critical section with the flexural ductility and plastic rotation capacity of reinforced concrete (RC) lightweight-aggregate concrete (LWAC) beams. For this, the results of a previous experimental program involving RC LWAC beams tested in flexure until failure are used. The variable studies were the concrete compressive strength (between 22.0 and 60.4 MPa and dry density between 1651 and 1953 kg/m3) and the longitudinal tensile reinforcement ratio (between 0.13% and 2.69%). The flexural ductility and the plastic rotation capacity of the RC LWAC beams are characterized by a ductility index and a plastic trend parameter, respectively. The influence of the variable studies, as well as the relation of the flexural ductility and plastic rotation capacity with the values for the neutral axis depth at failure are analyzed and discussed. Some conclusions are drawn which can be useful for the design of RC LWAC beams for flexure. In particular, it is shown that the practical rule of limiting the neutral axis depth at failure to ensure ductile behavior, as used in normal-weight aggregate concrete beams, is also valid for RC LWAC beams.
- Experimental results for topologically optimised steel joints under tensionPublication . Ribeiro, Tiago; Bernardo, Luís; Nepomuceno, Miguel; Maugeri, Natale Antonio; Longo, Paolo; Domenico, Dario DeDevelopments on code-compliant Topology Optimisation methodologies for the steel construction industry have recently been proposed. Also, it has been found that topologically optimised steel bolted connection parts – which behave non-linearly to a very significant degree of damage – do not waive physically non-linear analyses to assess an ultimate capacity that can be lower than what is predicted by the optimisation procedure linear analyses. These two circumstances brought urgency to the experimental testing of such optimised parts. The herein depicted experimental programme assessed topologically optimised and previously numerically analysed bolted parts of a well-known steel connection. The results allowed redefining the material trilinear model to be used in further numerical analysis and, very significantly, validated the numerical simulations results as well as the application of Eurocode formulae for connections component resistance. The difference between the previous numerically predicted ultimate resistance and the experimentally defined did not exceed 2.6%.
- Plastic rotation capacity of lightweight-aggregate concrete beamsPublication . Bernardo, Luís; Nepomuceno, Miguel; Pinto, HugoThis article describes a study on the plastic behaviour of lightweight-aggregate concrete beams. The experimental results of nineteen simply supported beams previously tested by the authors were used in this study. The experimental plastic rotation capacity of the tested beams was characterized by a parameter called Plastic Trend Parameter (PTP). The main variables studied were the concrete compressive strength and the longitudinal tensile reinforcement ratio. It was found that plastic rotation capacity slightly increases as the concrete compressive strength increases. An appropriate range for the longitudinal tensile reinforcement ratio to ensure plastic rotation capacity is proposed. The results of this study were also compared with the requirements from some codes of practice. From this analysis, it was shown that ACI Code requirements give more guaranties as far as plastic rotation capacity is concerned, when compared with European codes.
- Cement-based grouts for masonry consolidation with high content of limestone filler, metakaolin, glass powder and ceramic wastePublication . Nepomuceno, Miguel C. S.; Bernardo, Luís; Oliveira, Luiz Pereira de; Timóteo, Rúben de OliveiraThis article reports an experimental research on the influence of high-volume mineral additions on the rheological, physical and mechanical properties of cement-based grout for stone masonry structures consolidation. Binary grout mixtures were produced by replacing 50% weight of cement by limestone filler, metakaolin, glass powder and ceramic waste. Grout flow properties, rheological parameters, bleeding water, bulk density and injectability were evaluated. Grout physical and mechanical properties were also tested. New methodology previously used in mortars was applied to interpret flow behaviour. Results showed that a high-volume mineral addition in cement-based grout is compatible with the required fresh and hardened properties.
- Avaliação experimental da ductilidade à flexão de vigas de betão de agregados levesPublication . Pinto, Hugo; Bernardo, Luís; Nepomuceno, MiguelO presente artigo descreve um estudo experimental que teve por objetivo avaliar a ductilidade à flexão de vigas de betão armado produzidas com betão de agregados leves de argila expandida com resistências à compressão entre os 20 e os 60 MPa e massas volúmicas secas de 1650 a 1950 kg/m3. No total foram ensaiadas até à rotura dezanove vigas de 2,6 metros de comprimento e secção transversal retangular média de 0,15 m x 0,30 m, com diferentes taxas de armadura longitudinal de tração. As vigas foram simplesmente apoiadas perto das extremidades e sujeitas a duas cargas concentradas idênticas, simetricamente distribuídas a terços de vão. A zona central das vigas (entre as cargas aplicadas) encontrava-se sob flexão pura e, para prevenir a rotura por corte na zona perto dos apoios, foram colocados estribos em quantidade suficiente, deixando livre a zona central. A ductilidade foi avaliada através da definição de índices de ductilidade. As variáveis principais neste estudo foram a resistência à compressão do betão de agregados leves e a taxa de armadura longitudinal de tração. Neste estudo é apresentada uma análise comparativa entre as vigas produzidas em termos de ductilidade à flexão. O estudo evidenciou que, de entre as duas variáveis analisadas, aquela que mostrou maior influência na ductilidade foi a taxa de armadura longitudinal de tração. Foi também possível observar uma ordem de grandeza para o limite máximo de taxa de armadura longitudinal compatível com um comportamento dúctil à flexão das vigas analisadas.
- Use of refurbished shipping containers for the construction of housing buildings: details for the structural projectPublication . Bernardo, Luís; Oliveira, Luiz Pereira de; Nepomuceno, Miguel; Andrade, Jorge Miguel AlmeidaConstruction using refurbished shipping containers is a recent building system, with already many successful examples around the world. This system presents a huge potential in the field of sustainable construction provided by the recycling of used containers. This paper aims to contribute to a better knowledge of this construction system in what concerns to the structural project. The general constitution of two maritime shipping containers is presented as well as some aspects of their structural behavior. For this purpose, numerical analyses were performed using a finite elements analysis program. Normative aspects for the structural project are also presented. This paper also presents the analysis of a case study with the use of refurbished shipping containers to build a single-family house. The evaluation of the strength of the refurbished shipping containers to building actions is carried out. It is shown that such evaluation is not easy because some mechanical parameters of noncommercial steel section of the elements that compose the shipping containers are unknown. Nevertheless, this study shows the feasibility of this building system.
- Evaluation of Self-Compacting Concrete Strength with Non-Destructive Tests for Concrete StructuresPublication . Nepomuceno, Miguel; Bernardo, LuísSelf-compacting concrete (SCC) shows to have some specificities when compared to normal vibrated concrete (NVC), namely higher cement paste dosage and smaller volume of coarse aggregates. In addition, the maximum size of coarse aggregates is also reduced in SCC to prevent blocking effect. Such specificities are likely to affect the results of non-destructive tests when compared to those obtained in NVC with similar compressive strength and materials. This study evaluates the applicability of some non-destructive tests to estimate the compressive strength of SCC. Selected tests included the ultrasonic pulse velocity test (PUNDIT), the surface hardness test (Schmidt rebound hammer type N), the pull-out test (Lok-test), and the concrete maturity test (COMA-meter). Seven sets of SCC specimens were produced in the laboratory from a single mixture and subjected to standard curing. The tests were applied at different ages, namely: 1, 2, 3, 7, 14, 28, and 94 days. The concrete compressive strength ranged from 45 MPa (at 24 h) to 97 MPa (at 94 days). Correlations were established between the non-destructive test results and the concrete compressive strength. A test variability analysis was performed and the 95% confidence limits for the obtained correlations were computed. The obtained results for SCC showed good correlations between the concrete compressive strength and the non-destructive tests results, although some differences exist when compared to the correlations obtained for NVC.