António Gago - Academia.edu (original) (raw)

Papers by António Gago

Case Studies in Construction Materials

History of Construction Cultures, 2021

This paper presents the main characteristics of the Portuguese timbrel vault, known in Portugal a... more This paper presents the main characteristics of the Portuguese timbrel vault, known in Portugal as "abobadilha" or "abobadilha alentejana", after the region Alentejo where most examples are found. This research is part of an extensive study that culminates in a set of experimental and computational tests which aims to determine appropriate design rules for this type of structure. The rules, shapes and proportions of the timbrel vaults are compared with the geometric features of those described in European treaties of the 18th and 19th centuries. Experimental loading tests were performed on two simple timbrel vaults, the results of which are summarized in the present paper. The numerical model (based on the discrete element method) is intended to be used in the simulation of real structures, anticipating their structural capacity, without the need to perform new experimental tests. A comparison of the experimental results and the predictions obtained is also presented.

Structural Analysis of Historical Constructions, 2016

Seismic Tests on the S. Vicente de Fora Model

This paper contains an overview of the seismic strengthening interventions in school buildings, w... more This paper contains an overview of the seismic strengthening interventions in school buildings, within the scope of the School Building Modernization Programme. The selection of the schools to be retrofitted was based in the analysis of the time-frame for structural design codes in Portugal and the correspondent evolution of the construction practices and materials. This analysis led also to the identification of five building groups – “historical”, masonry wall with RC slabs, “no code” RC; “low code” RC, and other less typified building solutions (e.g.: precast RC). The major problems for each of the former five school building groups are generally presented. Some of these problems stem from the absence or use of outdated structural design codes, aggravated by constructive or detailing flaws. The implemented seismic strengthening procedures are outlined through a brief presentation of a collection of cases that exemplify the interventions in all the former main school building groups.

In this work diagonal compression tests and triplet tests on rubble stone masonry specimens are d... more In this work diagonal compression tests and triplet tests on rubble stone masonry specimens are described and the results obtained presented. For the tests carried out different dimensions of masonry specimens were adopted and two different types of mortar were used in the specimen’s construction, namely hydraulic and air lime mortar. The general objectives of the work presented herein are to determine: i) initial shear strength (cohesion) of masonry via diagonal compression test and ii) initial shear strength, or cohesion and coefficient of friction by triplet test. This study was developed within the scope of the national research project SEVERES (www.severes.org).

... Prior to that, longitudinal cracks appeared in the arch ring beneath the inside edges of the ... more ... Prior to that, longitudinal cracks appeared in the arch ring beneath the inside edges of the spandrel walls. ... However, as mentioned in the report, longitudinal cracks ap-peared in the arch ring beneath the inside edges of the spandrel walls. ...

This work presents the preliminary results for a retrofitting technique to use on the seismic rei... more This work presents the preliminary results for a retrofitting technique to use on the seismic reinforcement of ancient structures (buildings and others). The technique involves the replacement of masonry walls exterior or interior plasters or renders, with a retrofitting material that will significantly enhance the out-of-plane and in-plane mechanical behaviour of such walls, with major significance for the seismic response of the intervened structure. The reinforcement material (UHPPl) must respect the physical features and traits of the substratum in which it will be applied, as also its mechanical characteristics have the specific need to be consistent with the same substratum.

Rafter roofs, either gabled or hipped, were the traditional way to cover buildings in Portugal un... more Rafter roofs, either gabled or hipped, were the traditional way to cover buildings in Portugal until the second half of the sixteenth century. Foreign architects and engineers, who designed in the late sixteenth century some Portuguese large buildings, inspired local designers and new types of roof structures, allowing covering large spans, were adopted at the beginning of the seventeenth century. In what concerns roof structures, São Roque Church, in Lisbon, built in 1584, was one of the cases that greatl y influenced the Portuguese civil engineering. The main nave of São Roque Church is 17 meters wide and the traditional roof structures were not able to overcome such span. For that, the Italian architect Fillipo Terzi based his design in a roofing structure widely used in Italy, the “Palladiana” truss roof, but until then, unknown in Portugal. This “innovation” had become known by the Portuguese architects, engineers and building masters and in eighteenth century it was used when ...

Journal of Materials Engineering and Performance, 2021

This article describes the research carried out to assess the efficiency and mechanical performan... more This article describes the research carried out to assess the efficiency and mechanical performance of aluminum alloys to be used in the production of hysteretic dissipative brace devices for the seismic protection of old reinforced concrete buildings. Two different standard aluminum alloys were considered: the 6082 and the 5083 alloys, supplied with the T6 and H111 tempers, respectively. Features such as the inelastic deformation capacity and energy dissipation under cyclic loading were evaluated from experimental results and several performance indexes were computed. Additionally, four heat treatments (tempers) were applied to the 6082 alloy, namely: two tempers considering solubilization followed by two different aging cycles (AG); and two tempers considering two different annealing treatments (AN). The influence of these tempers on the mechanical behavior of the 6082 alloy was assessed through monotonic tensile and cyclic tension-compression tests. The results and discussion about the mechanical performance of each of the tested alloys and tempers are also presented. A comparative analysis between mechanical performance of the standard alloys and the tempered 6082 alloys demonstrates the potential benefits induced by these tempers. The 6082 alloy annealed at 350 °C for 120 min (6082-AN350/120) has proved to be a promising solution in terms of its damage capacity and energy dissipation, representing a cost-effective solution in the production of extruded profiles with non conventional cross sections.

Composites Part B: Engineering, 2018

This article presents the results of an extensive experimental programme investigating the struct... more This article presents the results of an extensive experimental programme investigating the structural performance for in-plane loads of old masonry walls strengthened using a specific technique that consisted of applying a CFRP mesh embedded within a shotcreted render. In this article the expression old masonry refers to rubble stone masonry with lime-based mortar but it is believed that the strengthening technique can also be applied to other types of old masonry (e.g. solid or almost solid clay or concrete brick masonry). The reinforcing composite material, called CFRP reinforced render (CFRP-RR), is characterized by the use of a CFRP mesh and the shotcreted pre-mixed mortar, lime-based, specific for the rehabilitation of old masonry load bearing walls. This material is applied to one or both faces of the masonry walls, thus improving both the inplane and out-of-plane behaviour for horizontal loads (the latter benefits are described in Ref. [1]). The experimental programme consisted of the in-plane testing of full-scale physical models of walls, herewith called specimens. These were subjected to reversed cyclic horizontal loads (simulating earthquake loads) with constant vertical loads (simulating gravity loads). The comparison between the experimental results of the nonreinforced with the reinforced (strengthened) specimens allowed the quantification of the inherent benefits in terms of structural performance under earthquake actions.

International Journal of Architectural Heritage, 2018

This article describes the initial development stages of a structural window frame system for the... more This article describes the initial development stages of a structural window frame system for the in-plane seismic strengthening of load-bearing masonry wall buildings. The solution implemented ultimately aims to stiffen (and strengthen) the opening such that the wall would behave as if there were no opening. This is achieved by installing a structural steel window frame composed of a profile forming a closed ring inside the opening, properly tied to the surrounding masonry wall. The strengthening concept was validated by means of a series of tests in which two approximately 1:2 geometric scale physical specimens with a similar central opening were cyclically tested to failure. One of these specimens (UMW) was unreinforced whereas the other (RMW) had a UPN profile internal ring tied at the corners and at mid-length and mid-height of the opening by means of threaded rods with chemical anchors. The material of these walls was common rubble masonry with lime-based mortar and render. The experimental results show that the strengthening technique leads to a significant increase in strength and in-plane deformation capacity, as well as in terms of cumulative dissipated energy at collapse. Nonlinear numerical specimens of the tested walls were also developed and calibrated.

Bulletin of Earthquake Engineering, 2017

The present paper aims to contribute to the knowledge concerning the seismic assessment of load b... more The present paper aims to contribute to the knowledge concerning the seismic assessment of load bearing masonry buildings with reinforced concrete slabs. The final goal of the present research was to propose a simple, yet accurate, methodology to assess the seismic safety of existing masonry buildings. The methodology here presented was based on the so-called ICIST/ACSS methodology with major improvements such as the extension to load bearing masonry wall buildings and the consideration of the effects of one of the most common strengthening solutions for masonry walls, here referred to as reinforced plastering mortar, as well as the possibility of considering four levels of increasing refinement: global, by alignment, by wall panel and by wall element. An extended research was performed on the existing methodologies to evaluate the seismic structural risk of load bearing masonry buildings, briefly describing methodologies similar to the one proposed, namely all of those that have in common the fact that they are based in the physical comparison between the resisting and acting shear forces at all storeys and along the two orthogonal horizontal directions. A case study is presented to check the applicability of the proposed methodology. The case study showed that the proposed methodology is relatively simple to apply and has a sufficiently good accuracy when compared with alternative methodologies. The degree of refinement of the analysis (global, by alignment, by wall panel and by wall element) must be taken into consideration and successively more complex analyses may be required when the results of simpler analyses are inconclusive.

Journal of Building Engineering, 2017

The following paper presents the most recent results of a research programme carried out to, amon... more The following paper presents the most recent results of a research programme carried out to, among other purposes, develop an innovative anchoring system for old masonry buildings. Despite the recognized importance of connections and anchoring systems, there is little experimental information about their strength and stiffness when installed in the masonry walls of old buildings. Therefore, one of the important goals of the research programme mentioned was the experimental characterization of the proposed anchoring system. The main characteristic of the proposed system, which makes it different from others, is an internal spherical steel element where the rod is connected. This steel eleme nt, called hinge, allows no orthogonality between the steel anchor plate and the tie rod, which makes it suitable for uneven connections between orthogonal walls and/or walls and floors. Besides this particular characteristic, the proposed system demonstrates all the capabilities of the traditional anchoring systems, namely, it can be used to strengthen the connection between orthogonal masonry walls or to ensure the connection of constructive elements (floors, roofs, stairs, etc.) to masonry walls. Moreover, numerical simulations with non-linear finite elements models were performed, aimed at reproducing the experimental tests for other load conditions or different wall thicknesses. The prime objective of the experimental and numerical studies was to assess the actual behaviour of the anchoring system and to establish appropriate design rules, which are also presented in this paper.

Construction and Building Materials, 2017

h i g h l i g h t s An innovative strengthening solution for loadbearing masonry wall buildings. ... more h i g h l i g h t s An innovative strengthening solution for loadbearing masonry wall buildings. The strengthening efficiently is dependent on bonding and anchorage behaviour. The experimental campaign allowed the validation of an end anchorage detail. The same campaign also served to prove that continuous bonding is ensured.

Composites Part B: Engineering, 2016

Fire performance is often identified as a difficult obstacle to overcome in designing lightweight... more Fire performance is often identified as a difficult obstacle to overcome in designing lightweight sandwich panels suitable for use in building applications. Fireproofing generally increases the weight and cost of sandwich panels, reducing the field of application of such solutions. This study presents the fire performance evaluation of different non-loadbearing sandwich wall assemblies, based on the fire resistance test methods recommended by EN 13501-2, EN 1363-1 and EN 1364-1. The main objectives of the present study are: (i) to evaluate the fire performance of different core materials; (ii) to evaluate the fire performance of different fireproofing materials; (iii) to classify the fire resistance of different wall assemblies; and (iv) to design a sandwich panel which withstands a 60 min fire exposure without compromising its integrity (E) and thermal insulation (I) capabilities. Expanded polystyrene foam (EPS), polyethylene terephthalate foam (PET), cork agglomerate (CA) and stone wool (SW) were tested as core materials. Fireproofing gypsum boards (FG) and magnesium oxide boards (MGO) were tested as fireproofing materials. The skins of all sandwich panels tested were glass fibre reinforced polymers (GFRP). Cork agglomerate cores exhibited the lowest thermal decomposition rate under fire exposure and cork agglomerate core sandwich wall assemblies proved to withstand fire exposure for the intended duration, presenting the required performance, even dismissing the use of fireproofing boards.

Journal of Building Engineering, 2016

In recent times, the construction market has seen a very significant increase in the demand of pr... more In recent times, the construction market has seen a very significant increase in the demand of prefabricated solutions of nonstructural elements, such as sandwich panels for buildings walls. Due to the inherent low weight, good mechanical behaviour, ease of assembly and cost-effectiveness, these types of wall assemblies are especially competitive in construction of single-family houses or one unit dwelling structures. However, the low fire resistance of many of these solutions, such as sandwich panels with expanded polystyrene core or polyethylene terephthalate foam core, precludes their use in buildings with more than one floor. The substandard fire resistance is generally due to the fact that the constituent materials are combustible or, at least, their properties are extremely sensible when subjected to high temperatures or flame. Given the isolation properties, good mechanical damping and fire resistance, cork agglomerate can be used as the core material for sandwich panels. However, this material is heavier than the other materials commonly used as core for sandwich panels. In order to deal with this drawback, it is necessary to choose a material for the panel facings that could fulfil the mechanical requirements and the condition not excessively increase the panel weight. The use of a glass fibre reinforced polymer seemed a suitable solution for the facing component. Therefore, the proposed wall assembly solution consists in a sandwich panel with cork agglomerate core and glass fibre reinforced polymer facings. The scope of this work was the assessment of the feasibility of a new configuration of vertical (wall) sandwich panels that could, not only be a cost effective solution for prefabricated construction, but also provide good mechanical performance and fire resistance. This sandwich wall panel configuration was tested for characterisation of its mechanical behaviour, resistance to impact and to fire. The results of the experimental campaign carried out are presented in this manuscript along with some conclusions about the suitability of this solution as sandwich wall panel for buildings façades.

In this work an experimental campaign with flat-jacks on old masonry buildings is presented and d... more In this work an experimental campaign with flat-jacks on old masonry buildings is presented and discussed. The tests were carried out on load bearing masonry walls of an 18 th century building of Lisbon downtown. They aimed the evaluation of the rubble stone masonry deformability properties in compression and compressive strength (double flat-jack test) and the shear strength parameters (shear flat-jack test). This study was developed within the scope of the Portuguese research project SEVERES (www.severes.org).

RESUMO Neste artigo utilizaram-se os resultados de um ensaio experimental realizado na ponte de B... more RESUMO Neste artigo utilizaram-se os resultados de um ensaio experimental realizado na ponte de Bargower, tendo em vista dois objectivos essenciais: i) verificar a capacidade de um modelo numérico de elementos finitos para a simulação do comportamento real de estruturas de alvenaria e ii) calibrar os parâmetros dos modelos não-lineares adoptados. O ensaio experimental referido, conduzido até à rotura da ponte, é simulado através de elementos finitos bidimensionais considerando dois níveis de discretização: i) um modelo simplificado onde o efeito do enchimento no extradorso do arco é simulado por molas horizontais de comportamento não-linear; ii) um modelo mais sofisticado onde o enchimento no extradorso é incluído explicitamente na malha de elementos finitos. Em ambos os casos, considera-se que os blocos que constituem o arco têm comportamento elástico linear; as juntas entre blocos do arco são simuladas através de interfaces de espessura nula e sem resistência à tracção. No modelo ...