Tectonic design of elastic timber gridshells

This paper aims to 'bridge the gap' between engineers and architects for a better understanding of the design process of elastic timber gridshells. The purpose is to inspire architects to develop innovative timber structural forms informed by engineering knowledge. This paper is organised in two parts: the first part is a theoretical reflection on the concept of tectonic and on the combined application of architectural and structural knowledge; the second part is dedicated to the review and definition of the various decisions and consequences during the design and construction of elastic timber gridshells.This work is financed by FEDER funds through the Competitively Factors Operational Programme - COMPETE and by national funds through FCT –Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007633. The support of the Foundation for Science and Technology (FCT) through doctoral fellowship SFRH/BD/104677/2014 is grateful. The support of the Aarhus University through the financial support for participation in this conference

Elastic timber gridshells - structures with an integrated design

A timber gridshell is a special type of structure that establishes a new framework for lightweight construction. It is possible to create a wide variety of shapes and geometries, therefore guaranteeing an enormous architectural freedom. However, given the variety of forms and the difficulty they can present, it is necessary to use different tools and information to support this complex process.The present paper explores the interaction between the information and the different tools used by architects and engineers during the designing and construction process of an elastic timber gridshell, by presenting a real case study with 42m(2)(6,5mx6,5m) after being erected, built with the intent to explore the design and constructive process together with integrated form finding methods. In the paper, both the architect's and the engineer's optimization goals are performed on the same case study. The designing process will be presented and the construction of the elastic gridshell will be described.Una malla estructural de madera es un tipo especial de estructura que establece un nuevo marco para la construcción ligera. Es posible crear una amplia variedad de formas y geometrías, garantizando así una enorme libertad arqui-tectónica. Sin embargo, dada la variedad de formas y la complejidad que pueden presentar es necesario utilizar difer-entes herramientas e información para avalar este complejo proceso. El presente trabajo explora la interacción entre la información y las diferentes herramientas utilizadas por arquitectos e ingenieros durante el proceso de diseño y construcción de una malla elástica de madera, presentando un caso de estu-dio real con 42m2 (6,5mx6,5m), después de la elevación, construida con la intención de explorar el diseño y el proceso constructivo junto con métodos de integración de “form finding”. En el trabajo, los objetivos de optimización tanto del arquitecto como del ingeniero se realizan sobre el mismo caso de estudio. Se presentará el proceso de diseño y se descri-birá la construcción de la malla elástica.This work is financed by FEDER funds through the Competitively Factors Operational Programme - COMPETE and by national funds through FCT -Foundation for Science and Technology within the scope of the project POCI01-0145-FEDER-007633. The support of the Foundation for Science and Technology (FCT) through doctoral fellowship SFRH/BD/104677/2014 is grateful

Positron lifetime measurements on neutron‐irradiated InP crystals

Neutron‐irradiated InP single crystals have been investigated by positron‐lifetime measurements. The samples were irradiated with thermal neutrons at different fluences yielding concentrations for Sn‐transmuted atoms between 2×1015 and 2×1018 cm−3. The lifetime spectra have been analyzed into one exponential decay component. The mean lifetimes show a monotonous increase with the irradiation dose from 246 to 282 ps. The increase in the lifetime has been associated to a defect containing an Indium vacancy. Thermal annealing at 550 °C reduces the lifetime until values closed to those obtained for the as‐grown and conventionally doped InP [email protected] ; [email protected]

Reliability based robustness of timber structures through NDT data updating

This work presents a framework for reliability-based assessment of timber structures / members using data gathered from non-destructive test results. These results are used for modeling an update of the mechanical characteristics of timber, using Bayesian methods. These methods are suitable to be used for parameter estimation and also allow updating model uncertainties. From the updated model, decisions upon the life-cycle reliability of existing structures may be taken and maintenance or strengthening actions may be considered. In this work, results gathered from ultrasound testing, Resistograph® and Pilodyn® conducted on chestnut wood specimens were used, as well as correlations between those results and compression strength parallel to the grain tests’ results. The resistant characteristics are also updated assuming deterioration models applied to specific key elements of the structure, thus, being possible to evaluate reliability based in time dependent factors, as well to categorize that structure in terms of robustness.COST E55, STSM-6269Fundação de Ciência e Tecnologia, FCT, through project SFRH/BD/62326/2009

On the use of NDT data for reliability-based assessment of existing timber structures

The objective of this paper is to address the possibilities of using non-destructive testing (NDT) data for updating information and obtaining adequate characterization of the reliability level of existing timber structures and, also, for assessing the evolution in time of performance of these structures when exposed to deterioration. By improving the knowledge upon the mechanical properties of timber, better and more substantiated decisions after a reliability safety assessment are aimed at. Bayesian methods are used to update the mechanical properties of timber and reliability assessment is performed using First Order Reliability Methods (FORM). The results show that different degrees of belief in the updating data may significantly influence the reliability level. The updating data to be used are NDT results obtained with ultrasound, resistance drilling and pin penetration equipments. The tests were conducted on chestnut wood (Castanea sativa Mill.) specimens, and were combined with tests to determine the compressive strength parallel to the grain. The uncertainty of the different NDT results is modeled by Maximum Likelihood estimates. Resistance distributions functions are considered to analyze the difference before and after updating by NDT, showing that lower variations may typically be obtained with the new information. Moreover, updating of the parameters in different deterioration models is considered in order to be able to evaluate the time dependency of the reliability, and information of NDT is also used to calibrate these models. The proposed approach is used for reliability assessment of different structural timber systems. Reliability of the structural system is assessed regarding the failure consequences of individual elements defined as key elements which were determined by their influence on the cross section loss. The results given by the pin penetration tests were the most similar to the reference experimental model with statistic parameters given by the results of destructive tests. The resistance drilling and ultrasound updating schemes led to higher level of reliability than the reference model values, therefore these updating data should be considered with caution, as they can result in unsafe results for the reliability compared to the reference models.Fundação para a Ciência e a Tecnologia (FCT

Is the biology of breast cancer changing? A study of hormone receptor status 1984-1986 and 1996-1997

Using archived tumours, those from 1984-1986 and 1996-1997 underwent immunohistochemistry for hormone receptors and grade analysis. A significant shift towards more ER-positive and low-grade disease was found; this appears to reflect screening practices, but could still influence survival