The establishment of the Sustainable Development Goals in 2015 claims for a deep paradigm shift in the way infrastructure structures are conceived. The evaluation of the impacts derived from the con- struction, the service and the end-of-life stages of an infrastructure is consequently in the spotlight of the research community. Being the construction sector as one of the main stressors of the environment, great attention has been recently paid to the structural design from the economic and the environmental point of view. However, sustainability requires to consider the social dimension as well. The evaluation of the social impacts of products is still at a very early stage of development, so the inclusion of social aspects in the design of structures is often overlooked. In this study, a comparison of life cycle assess- ment results is conducted on seven different design alternatives for a bridge in a coastal environment. Two approaches are followed: the first approach considers the economic and the environmental aspects of each design and the second approach includes the several social impacts specifically developed for the assessment of infrastructures. These social impacts account for four stakeholders, namely workers, consumers, local community and society. Results show that the inclusion of social aspects shall lead to different preferred options when compared with conventional, two-dimensional approaches. Here, the design with silica fume added concrete performs 11% better from a sustainability point of view when compared with the best solution resulting from a conventional assessment.

This study presents a shape optimization approach for sound barrier using the isogeometric boundary element method based on subdivision surfaces. The geometry model is constructed through the subdivision scheme, and different control polygons/meshes describing the same curve/surface are used for geometry representation, boundary element analysis and optimization. The gradient-based optimization is implemented to minimize the sound pressure in the reference region. By subdivision coarsening treatment, the secondary processing improves the direct optimization results in reducing the oscillation of the optimized structure. The influence of different subdivision schemes on the obtained optimized configurations is studied in detail, which shows the potential of the secondary reverse processing for engineering prototype design.

Gearboxes are widely used in several applications ranging from the automotive to the industrial and robotic sectors. A planetary gearbox is a special kinematic gear arrangement that, taking advantage of a planet carrier, ensures high reduction ratios together with a very small design. Therefore, they are widely employed for transmissions which require a high power density. There are several fields of applications including, but not limited to, mechatronic, automation and wind power generation. To improve the design of new solutions, for performing monitoring activities on actual gearboxes and for the definition of maintenance schedules, the availability of physical models able to accurately describe the behavior of the system, both in healthy and damaged conditions, would represent a great support. Experimental and numerical studies of the behavior of gearboxes are already available in the literature. Nevertheless, while the experimental approaches are valid only for the specific configuration tested, the numerical techniques show limitations related to the computational effort required. This paper presents an innovative approach for the characterization of the behavior of two different geared transmissions. It is based on a hybrid approach that combines finite elements (FE) with analytical formulations. In detail, the solver computes separately the macro deformation of the bodies (numerical solution based on a coarse grid) and the contacts (solved analytically avoiding the need of mesh refinements). The computational effort is reduced significantly without affecting the accuracy of the results significantly. This approach was used to investigate and understand the vibro-dynamical behavior of a back-to-back test rig (typically used for the characterization of the surface fatigue strength of gears) and of an indus- trial planetary gearbox. The results obtained for the healthy – not damaged – gearboxes were compared with experimental measurements for both configurations in order to validate the hybrid approach. Once the models were validated, the same methodology was eventually used to study the effects of typical gear failures and in specifically surface fatigue (pitting), on the vibrational response. The capability to reproduce the effect of damages with the model of a gearbox represents the first indispensable step of a Structural Health Monitoring strategy. State-of-art and challenges are analyzed and discussed in the paper.

The paper deals with the optimization of a single-storey timber building structure designed from timber portal frames connected with steel purlins, rails and façade columns. While the portal frames are made of the glued laminated timber with rectangular cross-sections, purlins, rails and façade columns are made of commercially available steel I-profiles. The portal frames are supported by square concrete pad foundations. The building structure is optimized by a mixed-integer non-linear programming (MINLP). The optimization model is developed. The objective function defines the material costs of the structure. The objective function is subjected to structural analysis and design constraints defined according to Eurocode standards. The Modified Outer-Approximation/Equality-Relaxation algorithm (OA/ER) and the linked multi-level strategy are applied. The optimization determines the minimum material costs of the structure, the optimal number of glulam frames and steel members and all standard/discrete cross- sections. A numerical example at the end of the paper shows the efficiency of the proposed optimization approach.

As classically proposed in the technical literature, the boundary element modeling of cracks is best carried out by resorting to a hypersingular fundamental solution – in the frame of the so-called dual formulation – since with the singular fundamental solution alone, the ensuing topological issues would not be adequately tackled. A more natural approach might rely on the direct representation of the crack tip singularity, as already proposed in the frame of the hybrid boundary element method, with implementation of generalized Westergaard stress functions. On the other hand, recent mathematical assessments indicate that the conventional boundary element formulation – based on Kelvin’s fundamental solution – is, in fact, able to precisely represent high stress gradients and deal with extremely convoluted topologies provided only that the numerical integrations be properly resolved. We propose in this paper that inde- pendent of the configuration, a cracked structure is geometrically represented as it would appear in real-world laboratory experiments, with crack openings in the range of micrometers. (The nanometer range is actually mathematically feasible, but not realistic in terms of continuum mechanics.) Owing to the newly developed numerical integration scheme, machine precision evaluation of all quantities may be achieved and stress results consistently evaluated at interior points arbitrarily close to crack tips. Importantly, no artificial topological issues are introduced, linear algebra conditioning is kept well under control, and arbitrarily high convergence of results is always attainable. The present develop- ments apply to two-dimensional problems. Some numerical illustrations show that highly accurate results are obtained for cracks represented with just a few quadratic, generally curved, boundary ele- ments – and a few Gauss–Legendre integration points per element – and that the numerical evaluation of the J-integral turns out to be straightforward and actually the most reliable means of obtaining stress intensity factors. Higher-order boundary elements lead to still better results.

With the rapid development of hypersonic vehicles in recent years, high-temperature seal technology has become more and more essential. Recently, a rope-sealed structure with braided ceramic fibres has been designed for hypersonic vehicles. The ceramic fibres in the structure have the characteristics of high temperature strength, so that they make the sealed structure suitable for working under a high temperature. Meanwhile, when subjected to an external force, braided fibres can produce a buffer force at the ceramic interface, so that it can maintain the good performance of the whole sealed structure. But up to now, only a few researches have been conducted on this kind of structures. In this paper, a simplified thermal–mechanical seepage coupling model is proposed to simulate the complicated physical process for this kind of structures. Meanwhile, a new numerical method called element differential method (EDM) is used to calculate the coupling problem because it has great advantages in solving multi-physics coupling problems. What is more, some experiments are used to obtain the leakages when the sealed structure is under service. And finally, by referring the experimental results, the authors establish a series of material parameter relationships for the sealed structure and also verify the reasonability of the proposed multi-physics coupling model.

A general approach that utilizes both spectral and extremal statistical methods are utilized to investigate the time series of flow-induced response behavior of a flexible horizontal cylinder subject to both random waves and constant current conditions. The cylinder model was 29 m long and had a slenderness ratio of approximately 760. The random waves were generated using a JONSWAP wave amplitude spectrum. In addition, for some tests, the cylinder was towed at two different speeds to simulate the combined loading of random waves and constant current conditions. The data were initially analyzed using standard spectral analyses to interpret the cylinder’s flow-induced response behavior and relate the findings to traditional deterministic parameters. Further analyses were performed using a generalized extreme value (GEV) distribution procedure that involved dividing the time series into blocks and fitting the block maxima of the extreme values in the measured response time series data. The Anderson–Darling (AD) test criterion and quantile plots were then used to assess whether the GEV distribution provides a satisfactory fit to the data capturing the statistical characteristics in the flexible cylinder’s flow-induced response behavior, which was stochastic in nature. For the data set analyzed, the extremal GEV methodology presented was observed to provide excellent results for the random wave cases and moderately good-to-good results for the combined random wave and constant current cases.