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Summary In precast technology, the effective design and construction are related to the behaviour of the connections between the structural members in order to cater for all service, environmental and earthquake load conditions. Therefore, the design and detailing of the connections should be undertaken consistently and with awareness of the desired structural response. In the research presented herein, an analytical expression is proposed for the prediction of the resistance of precast pinned connections under shear monotonic and cyclic loading. The proposed formula addresses the case where the failure of the connection occurs with simultaneous flexural failure of the dowel and compression failure of the concrete around the dowel, expected to occur either when (i) adequate concrete cover of the dowels is provided (d > 6 D) or (ii) adequate confining reinforcement (as defined in the article) is foreseen around the dowels in the case of small concrete covers (d

In precast technology, the effective design and construction is related to the behaviour of the connections between the structural members in order to cater for all service, environmental and earthquake load conditions. Therefore, the design and detailing of the connections should be undertaken consistently and with awareness of the desired structural response. In the research presented herein an analytical expression is proposed for the prediction of the resistance of precast pinned connections under shear monotonic and cyclic loading. The proposed formula addresses the case where the failure of the connection occurs with simultaneous flexural failure of the dowel and compression failure of the concrete around the dowel, expected to occur either when (a) adequate concrete cover of the dowels is provided (d > 6 D) or (b) adequate confining reinforcement (as defined in the article) is foreseen around the dowels in the case of small concrete covers (d < 6 D). The expression is calibrated against available experimental data and numerical results derived from a nonlinear numerical investigation. Emphasis is given to identifying the effect of several parameters on the horizontal shear resistance of the connection such as: the number and diameter of the dowels; the strength of materials (concrete, grout, steel); the concrete cover of the dowels; the thickness of the elastomeric pad; the type of shear loading (monotonic or cyclic); the pre-existing axial stress in the dowels; and the rotation of the joint. In addition, recommendations for the design of precast pinned beam-to-column connections are given, especially when the connections are utilised in earthquake resistant structures.

Remote welding provides new possibilities for highly productive and flexible joining of metal structures, especially in the automotive industry. This study presents an experimental investigation on the behavior of the lap welds’ geometrical characteristics with respect to the laser beam inclination. Two remote welding systems (RWSs) have been utilized: a large field RWS with a CO2 laser and a small field RWS with an Nd:YAG laser. The materials investigated include steels (noncoated, zinc-coated, and stainless) and an Al alloy. Conclusions are drawn related to the behavior of the process mechanism under different laser beam inclinations, useful for the industrial application of the process and for further research in the field.

Um projeto estrutural adequado é fundamental para que a satisfação dos requisitos fundamentais de uma estrutura sejam alcançados sob a ação de um sismo. Como é bem conhecido, o projeto de uma estrutura inclui três fases distintas, nomeadamente a conceção estrutural, a análise (cálculo de efeitos das ações, tendo também em consideração a ação sísmica) e o dimensionamento – verificação. A experiência baseada na história da engenharia sísmica e a experiência recente sobre o comportamento das estruturas de betão armado mostrou que, apesar da enorme evolução dos meios informáticos, a satisfação dos requisitos fundamentais do projeto sísmico não pode ser alcançada diretamente por meio de cálculos, tendo-se verificado que a observância de alguns conceitos básicos de projeto é mais importante. Este capítulo enfatizará a grande importância da primeira etapa do projeto, a chamada, conceção estrutural. Ou seja, cada análise tem que ser feita de acordo com uma conceção estrutural pré-concebida; várias decisões deverão ser tomadas a priori, antes de qualquer procedimento analítico, como por exemplo, minimizar incertezas relacionadas com a resposta sísmica da estrutura. publishersversion published

Laser beams can be used in many industrial applications including machining whereby it constitutes an alternative to traditional material removal techniques and can be used to process a variety of materials including metals, ceramics, glass, plastics, and composites. Laser machining is characterized by a number of advantages such as absence of tool wear, tool breakage, chatter, machine deflection and mechanically induced material damage, phenomena which are usually associated with traditional machining processes. However, as with all manufacturing processes, optimum operating parameters have to be determined. These include the laser power, the spot size of the focused laser beam, etc. In order to arrive at a set of optimum setting variables, either experiments can be conducted and optimum conditions can be found based on the results, or a process model can be created and evaluated for the selection of setting variables, which will optimize the desired performance measures. Analytical and numerical modeling have contributed to the understanding of laser processing, but there are still many questions to be answered. This paper attempts to give an overview of laser machining modeling and experimentation techniques, elucidating recent developments and research trends.

The term of 3D laser processing has been used so far to describe a group of different three-dimensional laser processing concepts. At each of these concepts the 3D aspect refers to a different manipulation of one or more laser beams, as to process and/or produce three-dimensional geometries by performing material removal, welding or heat treating. The most important concepts are focused mainly in laser machining and laser welding processes by incorporating one or two laser beams simultaneously. This paper overviews a number of these concepts that have been developed in research or industrial level, along with their advantages, drawbacks and fields of application.

This study presents an environmental analysis of a number of cutting and joining processes taking place during the ship hull repair. These processes include oxy-acetylene cutting, plasma arc cutting, shielded metal arc welding, flux core arc welding and submerged arc welding. The processes are modelled in terms of their environmental impact. The environmental-related inputs and outputs of each process are elaborated with a life cycle assessment tool. The impact on various aspects, such as human health, resource depletion etc., is assessed by the 'environmental priority strategy (EPS)' and the 'Eco-Indicator 99' impact assessment methods. Based on the results, a benchmarking of the cutting and welding processes is performed, in terms of their environmental impact.

This article briefly summarises experiments, including very recent work, at the NTU in Athens, on the connections of large precast reinforced concrete panels when subjected to monotonic, repetitive-dynamic and cyclic shearing actions. Conclusions as to the seismic behaviour of such connections are also presented. For monotonic loading, a theoretical model for predicting ultimate bearing capacity of the connections is shown schematically, accompanied by a design formula. The relevant behaviour under repetitive-dynamic loading is represented by a 'fatigue curve'. For rational seismic design of the connections, experimental data show cyclic-strain reactions, such as shear-force response, shear-stiffness degradation, hysteretic damping, ultimate (static) bearing capacity and residual strength. These lead to a proposed approximate behavioural model for possible use in computer analyses of composite walls, and to design values (together with degradation factors) for estimating the bearing capacity of v...