UT system : a structural system to build taller urban timber houses with aspired spatial flexibility

In past few years, in consequence to the continuous increase of urban densities and seeking for a more sustainable profile for construction, some new proposals for tall timber city housing have emerged. The development of new wood-based materials, like cross laminated timber (CLT), has made possible to believe to build high with timber. Demonstration buildings located in different locations around the world contribute to the development of this new concept of urban housing. With the exception of few recent proposals based on hybrid systems, majority of buildings so far built are fully based in the monolithic construction system offered by CLT panels. Despite all the advantages related with this monolithic system, two main important weaknesses related with architectural freedom have been pointed out: the excessive compartmentalization of inner spaces and the external expression of an extruded box with reduced openings. Inspired on new CLT/steel and CLT/concrete hybrid proposals and their advantages in comparison to the CLT monolithic system, a CLT/glulam hybrid construction system, named UT system (urban timber system), has been developed. CLT remains the main structural material in the UT system but, glulam linear elements are used to reduce the CLT walls both inside and in the building perimeter. Further, based in the bundled tube concept, UT system looks into the possibility of overcome eccentricity problems caused by non-symmetrical location of vertical cores and consequently, offers more design freedom. UT system is described and illustrated, considering concerns related with structural system, tall building specificities, construction sequences, architectural design possibilities, moisture effects, durability, fire resistance, acoustic performance and joints between timber elements.Fundação para a Ciência e a Tecnologia (FCT

MLCC na construção em altura

Na última década tem-se observado o aumento da procura por novas soluções estruturais em madeira para a construção em altura. Esta temática possui vários fatores de motivação, sendo o de maior importância o perfil sustentável associado à madeira. A madeira lamelada colada cruzada (MLCC) é o material de eleição uma vez que os sistemas construtivos em painéis mostram maior adequabilidade para este tipo de construção. O presente artigo apresenta um enquadramento desta recente temática, descrevendo os fatores motivadores e as principais barreiras ao seu desenvolvimento. Descrevem-se as principais características da MLCC analisando as suas potencialidades na construção de edifícios em altura apresentando e discutindo exemplos que recorrem a este novo material. É realizada uma breve descrição de quatro edifícios, nomeadamente o Stadthaus e o Bridport em Londres, o Forté em Melbourne’s Docklands, e o Via Cenni em Milão, de modo a desvendar os pontos fortes e as principais fragilidades deste sistema construtivo. Por fim, são apresentados dois casos de projetos em desenvolvimento, o Barents House e o FFTT system, os quais prometem, através de sistemas híbridos, serem capazes de conceber estruturas mais arrojadas.Fundação para a Ciência e a Tecnologia (FCT

A project contribution to the development of sustainable multi-storey timber buildings

Wood is a natural material, renewable, easily recyclable, and able to store carbon-dioxide, which makes tall timber buildings a solution with potential to answer the main sustainability targets. Cross laminated timber (CLT) has been pointed out as the best wood-based material to make this ambition a real thing. In order to understand why, this paper introduces the material and describe some demonstration buildings recently built. Based on diagnosed weaknesses of CLT buildings, it is presented an initial propose for a new CLT/glulam hybrid construction system, called Urban Timber (UT) system, which aims be able to support taller timber buildings. The main motivation was the development of a wood-based structural solution that provides more spatial flexibility and wider versatility for visual architectural expressions. The system is described and illustrated, considering concerns related with structural behavior, architectural value, structural connections and wood shrinkage.Fundação para a Ciência e a Tecnologia (FCT

Strategies to avoid humidity causing damages in tall timber buildings

The number of tall housing buildings using cross laminated timber (CLT) as the main structural material has been growing all around the world but especially in Europe. This kind of construction has already proven to be a solution with a sustainable profile and despite the conflicts with some building codes and some countries legislation, this construction material is able to shape safe structures. However, to get the full confidence of the public, several researches focused on main CLT restrictions are still under development, such as fire safety, strength of connections, structural behavior, acoustics and durability. This last point is of huge importance considering timber’s propensity for rotting and its known hygroscopic behavior. If humidity effects are not considered during the building design as well as the structure’s integrity the people’s wellbeing can be compromised. The content of the present paper aims to outline important recommendations concerning the reduction of humidity causing damages in tall timber buildings. For that, CLT/glulam hybrid construction system (Urban Timber system) is used to illustrate and describe suggested construction details of a timber building, from the foundations to the roof: the most cautious solution for foundations is to resort to reinforced concrete, in case of biological attacks or unexpected hazards; facades have to ensure the protection of timber structural elements from contact with moisture either through insulation materials or by glazed walls; windows in contact with timber ends should be able to prevent water to reach them; connection between timber elements must predict swelling/shrinkage movements of timber; at least an efficient rain water drainage has to be guaranteed by the balconies and the roof design

Three-leaf stone masonry repair and strengthening

This paper summarizes the results of an extensive test campaign over three-leaf stone masonry walls, aiming at studying the behavior of these kind of walls under compressive loading and the effects introduced by the most common strengthening techniques used for structural rehabilitation of heritage buildings. A total of ten three-leaf stone (granite) masonry walls were tested, plain or strengthened resorting to transversal tying with GFRP rods, injection of a lime based grout and both techniques applied simultaneously. In addition, it is also presented the characterization of the materials and of the three-leaf walls components (external and inner leaves). The results show that the strengthening techniques used in this work were effective in different ways.Fundação para a Ciência e a Tecnologia (FCT

On the strengthening of three-leaf stone masonry walls

This paper is devoted to the experimental characterization of the structural behaviour of three-leaf stone ma-sonry walls. The first part of the experimental results described here was presented during the last SAHC Conference (Oliveira et al. 2006). In total ten walls, plain and strengthened resorting to transversal tying, in-jection and both techniques applied simultaneously, were tested aiming at capturing the detailed structural be-haviour. Globally, all strengthening techniques described here showed to be effective in different ways.Fundação para a Ciência e a Tecnologia (FCT

Evidence of spontaneous spin polarized transport in magnetic nanowires

The exploitation of the spin in charge-based systems is opening revolutionary opportunities for device architecture. Surprisingly, room temperature electrical transport through magnetic nanowires is still an unresolved issue. Here, we show that ferromagnetic (Co) suspended atom chains spontaneously display an electron transport of half a conductance quantum, as expected for a fully polarized conduction channel. Similar behavior has been observed for Pd (a quasi-magnetic 4d metal) and Pt (a non-magnetic 5d metal). These results suggest that the nanowire low dimensionality reinforces or induces magnetic behavior, lifting off spin degeneracy even at room temperature and zero external magnetic field.Comment: 4 pages, 3 eps fig

A construção em taipa e os sismos

A reconhecida sustentabilidade da construção em taipa e o vasto património arquitectónico edificado segundo este processo construtivo são motivos, por si só suficientes, para justificar o crescente interesse pela construção taipa por parte das autoridades, investigadores, projectistas e empresas. Todavia, este tipo de construção apresenta tipicamente um deficiente desempenho sísmico, o que torna desaconselhada a adopção da taipa como solução estrutural em zonas de perigosidade sísmica não negligenciável. Neste contexto, o presente artigo descreve a construção em taipa bem como a sua importância cultural. Seguidamente, caracteriza-se o desempenho sísmico deste tipo de construções, com especial ênfase nos modos de rotura. Por fim, discutem-se possíveis modificações do processo construtivo para melhorar o desempenho sísmico das construções em taipa novas, bem como as técnicas de reforço sísmico e reparação para construções existentes

Characterization of compatible TRM composites for strengthening of earthen materials

The high seismic vulnerability of earth constructions has been evidenced by several recent earthquakes that occurred around the World with moderate to high magnitudes, namely Bam 2003, Pisco 2007 and Maule 2010. The seismic risk associated to earth constructions is further amplified by the fact that a great percentage of these constructions is built on regions with important seismic hazard. Thus, the preservation of the immense earthen built heritage and of the life of their inhabitants demands adopting innovative strengthening interventions. However, the success of such solutions requires fulfilling compatibility requirements, while its general use requires adopting affordable materials and low complexity technical solutions. In the last years, textile reinforced mortars (TRM) have been increasingly used to strengthen masonry structures due to their high structural effectiveness and compatibility. In the case of earth constructions, these composite materials are also expected to provide efficient strengthening, though specific component materials should be adopted. This paper presents an experimental program dedicated to the characterization of the composite behavior of two TRM composites proposed for strengthening rammed earth walls. The composites differ on the mesh used, namely a low cost glass fiber mesh and a nylon mesh acquired locally, while the same earth-based mortar was used in both cases. The experimental program involved testing the mortar under compression and composite coupons under tension. In general, the glass TRM presents higher strength and stiffness in tension, while the nylon TRM presents considerably higher deformation capacity. Finally, stress-strain relationships describing the composite behavior are presented for numerical modelling purposes.This work was partly financed by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of projects POCI-01-0145-FEDER-007633 and POCI-01-0145-FEDER-016737