Sustainable shells: New African vaults built with soil-cement tiles

The Mapungubwe National Park Interpretive Centre, South Africa achieves economy of means, social improvement and low environmental impact in a remote World Heritage site. This paper outlines the design methodology and construction process for a series of thin shell domes and vaults in rural South Africa. We use the Valencian tradition of tile vaulting, a 700-year-old construction system, to create lightweight and durable buildings from thin soil-cement bricks. The load-bearing masonry is used to construct roof vaults achieving high structural strength with minimal material. The largest free-form vaults span 14.5m with an unreinforced masonry vault of 300mm thickness. We replaced fired-clay bricks with less energy-intensive stabilized earth tiles, which have a well-established tradition in sustainable practice. At Mapungubwe they are used to create sophisticated engineered forms by adapting a hand-press to locally manufacture tiles of sufficient strength. In addition to being structurally efficient, elegantly simple and environmentally sustainable, tile vaults have advantages for construction in developing areas. When compared to conventional construction, this system offers material and financial savings, waste reduction, and local employment with transferable outputs and skills for future projects. For this project, we introduced the structural masonry of tile vaults to South Africa, and for the first time we combined tile vaulting with locally made stabilized earth tiles that have low embodied energy. No steel reinforcing simplifies construction, lowers cost and reduces embodied energy. The vaults are built with minimal support, saving time, money and resources on formwork. The Centre represents a significant step forward in structure and material for sustainable construction

Reactive oxygen species and male reproductive hormones

Reports of the increasing incidence of male infertility paired with decreasing semen quality have triggered studies on the effects of lifestyle and environmental factors on the male reproductive potential. There are numerous exogenous and endogenous factors that are able to induce excessive production of reactive oxygen species (ROS) beyond that of cellular antioxidant capacity, thus causing oxidative stress. In turn, oxidative stress negatively affects male reproductive functions and may induce infertility either directly or indirectly by affecting the hypothalamus-pituitary-gonadal (HPG) axis and/or disrupting its crosstalk with other hormonal axes. This review discusses the important exogenous and endogenous factors leading to the generation of ROS in different parts of the male reproductive tract. It also highlights the negative impact of oxidative stress on the regulation and cross-talk between the reproductive hormones. It further describes the mechanism of ROS-induced derangement of male reproductive hormonal profiles that could ultimately lead to male infertility. An understanding of the disruptive effects of ROS on male reproductive hormones would encourage further investigations directed towards the prevention of ROS-mediated hormonal imbalances, which in turn could help in the management of male infertility

Dynamics of in-plane arch rocking: An energy approach

This study employs an analytical model to describe the rocking response of a masonry arch to in-plane seismic loading. Through evaluation of the rate of energy input to the system, the model reveals the ground motions that cause maximum rocking amplification. An experimental investigation of small-scale masonry arches subjected to past earthquake time histories is used to evaluate the analytical model and to explore arch rocking behaviour. The results demonstrate that rocking amplification can occur, but is highly sensitive to slight variations in the ground motion. Thus, the accuracy to which the arch response can be predicted is brought into perspective. The concept that the primary impulse of an expected ground motion is fundamentally important in predicting arch collapse is evaluated in light of the developed energy approach. Finally, a statistical method is proposed for predicting the probability of arch collapse during seismic loading

Roman masonry stairways. Geometry, construction and stability

This article focuses on the study of the so-called “Roman Masonry Stairways” which represent a rather common typology in historical buildings particularly in the Neapolitan area. The vaulted system of the numerous examples of Neapolitan open staircases consists of the use of the main elements of structural support, such as arches and vaults, underlining the close dialectical relationship between form and structure. Therefore, the analysis of the vaulted space is carried out in relation to functional requirements, materials and construction techniques within the articulation of the architectural figure [1]. This research proposes an interpretation of the static behavior of this type of staircase through simplifications that facilitate its analysis. In this paper reference is made to the case study of the stairway of Palazzo Persico in Naples, whose structural analysis is carried out in the theoretical framework of the Limit Analysis as applied by Heyman to masonries [2]. The main objective of the investigation is to demonstrate the static equilibrium of this structure and to understand its mechanical behavior. Before dealing with the analysis, the structural process was defined from different points of view, by interlocking formal, material and spatial aspects. The formal definition concerns its geometric configuration, while the material and spatial one concerns the elements that compose it and the relationship existing between them. Specifically, the staircase in issue is characterized by a cantilevered structural system with a planimetric scheme consisting of a 45° rotated square. Its vertices are rounded off by arches of circumference along the sides of which are placed the flights. The flights are cantilevered from the walls and connected by small vaults constituting the landings, as common for these masonry vaulted staircases. The aim of the work is to obtain an equilibrium solution that, being compatible with the loads, does not violate the limit condition of the material [3]. In other words, a solution for which there is no traction and where the compressive stresses are contained within the masonry. The structural analysis was performed taking into account the principles of limit analysis and by applying the Safe Theorem. Ultimately a static graphic analysis has been conducted