Anabela Paiva

Sylvester equations for Laguerre-Hahn orthogonal polynomials on the real line

Matrix Sylvester differential equations are introduced in the study of Laguerre-Hahn orthogonal polynomials. Matrix Sylvester differential systems are shown to yield representations for the Laguerre-Hahn orthogonal polynomials. Lax pairs are given, formed from the differential system and the recurrence relation, that yield discrete non-linear equations for the three term recurrence relation coefficients of the Laguerre-Hahn orthogonal polynomials.

A contribution for the improvement in thermal insulation of tabique walls coated with metal corrugated sheets

Tabique is a traditional Portuguese building technique using timber and earth and was intensively applied until the 20th century. There is an impressive tabique heritage that requires maintenance and rehabilitation interventions. Taking into account the facts that technical and scientific publications related to this particular technique are lacking and that the technique is also applied worldwide, this research work is a very relevant one. This study aims at studying the thermal insulation behaviour of tabique walls and in particular, tabique walls coated using metal corrugated sheets and thermally reinforced with an insulation material. This type of building component is initially characterized and some building details concerning the metal corrugated sheet coating are described. An experimental work was conducted to determine the thermal transmission coefficient of the tabique wall samples. It was concluded that providing the tabique wall coated with metal corrugated sheets with a 3 cm extruded polystyrene board results in a thermal insulation improvement of 61%. These results revealed that the thermal insulation reinforcement of tabique walls is possible and it may be a straightforward building procedure because it can be achieved using the thermal insulation building materials that are currently being used. Therefore, the thermal insulation reinforcement of tabique walls seems feasible. Furthermore, the thermal insulation parameters obtained in this study are similar to the ones obtained for currently applied walls solutions in new buildings. This technical fact may provide guidance for the possibility of using solutions used in old buildings to meet the thermal comfort requirements expected in today’s times. The knowledge gained will also be useful to support future proposals of energy rehabilitation solutions. Practical implications: In this article, tabique construction and its relevance worldwide are discussed. This article highlights the building details concerning the use of metal corrugated sheet coating on tabique walls and evaluates the thermal insulation behaviour of this wall system. The outcomes indicate that it is possible to improve the thermal insulation of a tabique wall. The data obtained in this study may be valuable for repairing tabique walls and may also inspire innovative building solutions in modern industrial practice.

Earth-based construction material field tests characterization in the Alto Douro Wine Region

Abstract The Alto Douro Wine Region, located in the northeast of Portugal, a UNESCO World Heritage Site, presents an abundant vernacular building heritage. This building technology is based on a timber framed structure filled with a composite earth-based material. A lack of scientific studies related to this technology is evident, furthermore, principally in rural areas, this traditional building stock is highly deteriorated and damaged because of the rareness of conservation and strengthening works, which is partly related to the non-engineered character of this technology and to the knowledge loosed on that technique. Those aspects motivated the writing of this paper, whose main purpose is the physical and chemical characterization of the earth-based material applied in the tabique buildings of that region through field tests. Consequently, experimental work was conducted and the results obtained allowed, among others, the proposal of a series of adequate field tests. At our knowledge, this is the first time field tests are undertaken for tabique technology. This information will provide the means to assess the suitability of a given earth-based material with regards to this technology. The knowledge from this study could also be very useful for the development of future normative documents and as a reference for architects and engineers that work with this technology to guide and regulate future conservation, rehabilitation or construction processes helping to preserve this important legacy.

Characterization of tabique walls nails of the Alto Douro Wine Region

Abstract Tabique is one of the main Portuguese traditional building techniques which use raw materials as stone, earth andwood. In general, a tabique building component as a wall consist of a wooden structure made up of vertical boards connected to laths by metal nails and covered on both sides by an earth based material. This traditional building technology as an expressive incidence in the Alto Douro Wine Region located in the interior of Northern Portugal, added to the UNESCO’s Word Heritage Sites List in December 2001 as an ‘evolved continuing cultural landscape’. Furthermore, previous research works have shown that the existing tabique construction, in this region, reveals a certain lack of maintenance partially justified by the knowledge loosed on that technique, consequently this construction technique present an advanced stage of deterioration. This aspect associated to the fact that there is still a lack of scientific studies in this field motivated the writing of this paper, the main objectives are to identify and characterize the nails used in the timber connections. The nails samples were collected from tabique walls included in tabique buildings located in LamegoMunicipality, near Douro River, in the Alto Douro Wine Region. This work also intends to give guidelines to the rehabilitation and preservation of this important legacy.

Possible Applications of Corncob as a Raw Insulation Material

Some alternative applications of corncob as a raw thermal insulation material are presented in this research work. Usually, corncob has been treated as an agricultural waste. Finding practical applications of this waste in product manufacturing may preserve the environment and may also allow using more green technologies. Therefore, a corncob particleboard, a lightweight concrete for nonstructural purposes, and a lightweight concrete masonry unit (CMU) are the granulated corncob-based products proposed. These products are studied in terms of thermal performance, and some thermal parameters are delivered. The results obtained through the experimental study allowed to estimate the thermal conductivity of the granulated corncob and of the granulated corncob particle‐ boards. The values obtained were 0.058 and 0.101 W/m°C, respectively. A thermal transmission coefficient of 1.99 W/m2°C was obtained for the nonstructural corncob lightweight concrete, and it was concluded that the density and the thermal properties of this alternative solution are in accordance with the properties of the currently used expanded clay concrete. For the granulated corncob lightweight CMU, a value of 1.15 W/ m2°C was estimated. This shows that this agricultural waste may have potential as a thermal insulation product.

Benefícios económicos e ambientais inerentes ao uso de materiais estruturais naturais em habitações unifamiliares

In Portugal, the house building industry has mostly adopted reinforced concrete framed structures and clay brick-wall. The use of other structural materials, such as steel, timber, and stone-wall is still rather limited in this sector. Moreover, the use of earth-based construction techniques and solutions still remains limited to individual cases. Within this context, this paper describes an investigation on sustainable structural solutions for a typical single family house using natural materials. Three different structural solutions were compared, namely a reinforced concrete frame solution, a solution based on CEB (compressed raw earth blocks) masonry and timber structures for floors and roof, and a solution based on reusable materials, such as timber originated from the demolition of buildings. These alternative structural solutions were compared in terms of building costs, energy consumption and CO2 emissions. The study confirmed that the sustainable solutions had most advantages, particularly with regards to the environment.