Publications

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2019
Flat slab strenghtening techniques against punching-shear, Lapi, M., Ramos A. P., and Orlando M. , Engineering Structures, Volume 180, p.160-180, (2019) AbstractWebsite
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2018
Efeito do confinamento e da redistribuição de momentos no comportamento de lajes fungiformes, Faria, Ricardo, Marreiros Rui, Ramos António, and Antunes Gonçalo , Encontro Nacional Betão Estrutural 2018, 7-9 Nov., LNEC, Lisboa, (2018)
Influência da distribuição transversal de armaduras longitudinais junto ao pilar na resistência ao punçoamento, Faria, Ricardo, Jesus Catarina, Marreiros Rui, and Ramos António , Encontro Nacional Betão Estrutural 2018, 7-9 Nov., LNEC, Lisboa, (2018)
Resposta da ligação pilar-laje fungiforme sujeitas a ações horizontais cíclicas reforçadas com estribos, Almeida, André, Ramos António, Marreiros Rui, Lúcio Válter, and Faria Ricardo , Encontro Nacional Betão Estrutural 2018, 7-9 Nov., LNEC, Lisboa, (2018)
Assessment of SFRC flat slab punching behaviour – Part I: monotonic vertical loading, Gouveia, Nuno D., Faria Duarte M. V., and Ramos António Pinho , Magazine of Concrete Research, p.1-46, (2018) AbstractWebsite

This paper presents a study of the behaviour and load capacity of Steel Fibre Reinforced Concrete (SFRC) flat slabs under monotonically increased concentrated vertical loads. The SFRC was used only in the local region of the slab-column connection, as the rest of the slab was cast using normal concrete (NC) without fibres. The six experimental test specimens had a thickness of 150 mm with different longitudinal reinforcement ratios, using a non-uniform distribution over the slab width. The concretes used were made with different Dramix® 4D 65/60 BG steel fibre contents (0%, 0.5 %, 0.75% and 1.0% volume content). The slab tests were complemented by flexural tests on notched-beams. This made it possible to determine the tension behaviour of the different concretes used, through a linear post-cracking behavior and inverse analysis. The inverse analysis made it possible to define the stress-crack opening relationship that characterize the tension behaviour of SFRC and to relate it to the observed behaviour and load capacity of the tested slabs. The tests results show that the tensile behaviour of the SFRC plays an important role in the behavioural and load capacity of the slabs and that it can be considered relevant to physically based models.

Assessment of SFRC flat slab punching behaviour – part II: reversed horizontal cyclic loading, Gouveia, Nuno D., Faria Duarte M. V., and Ramos António Pinho , Magazine of Concrete Research, p.1-17, (2018) AbstractWebsite

This paper presents an experimental study of four flat slab specimens subjected to combined vertical and horizontal cyclic loading. Steel fibre-reinforced concrete (SFRC) was used only in the local region of the slab–column connection, while the rest of the slabs were cast using normal concrete. The specimens measured 4·15 m × 1·85 m × 0·15 m and were connected to two steel half columns by 0·25 m × 0·25 m rigid steel plates, prestressed against the slab using steel bolts, to ensure monolithic behaviour. The specimens were tested using an innovative test setup system that accounted for important factors, such as the ability of bending moment redistribution, line of inflection mobility and assured equal vertical displacements at the opposite slab borders, and symmetrical shear forces. Results show that the presence of SFRC in the slab–column connection region is effective in increasing the deformation capacity of slab–column connections, allowing the increase of horizontal drift ratios.

Experimental and theoretical evaluation of punching strength of steel fiber reinforced concrete slabs, Gouveia, Nuno D., Lapi Massimo, Orlando Maurizio, Faria Duarte M. V., and Ramos António M. P. , Structural Concrete, Volume 19, Issue 1, Number 1, p.217-229, (2018) AbstractWebsite

This paper deals with the experimental and theoretical evaluation of punching shear capacity of steel fiber reinforced concrete (SFRC) slab–column connections. Five experimental specimens with a thickness of 160 mm, different fiber volume contents (0, 1.0, and 1.5%) and different flexural reinforcement ratios (0.75 and 1.5%) have been tested. The experimental results were evaluated using a physical–mechanical model based on the critical shear crack theory (CSCT). The model has given a good approximation of experimental punching shear strengths. In general, tests have highlighted a significant increase in load and deformation capacity of fiber reinforced concrete slab–column connections in comparison with reinforced concrete connections.

Reversed horizontal cyclic loading tests of flat slab specimens with studs as shear reinforcement, Isufi, Brisid, Ramos António Pinho, and Lúcio Válter , Structural Concrete, (2018) AbstractWebsite

The results of a series of experiments on four reinforced concrete flat slab specimens with shear studs and a control specimen without any shear reinforcement are presented. The specimens were tested under constant gravity loads and reversed horizontal cyclic displacements. The main test variables were the applied gravity load and the number of perimeters of studs. One of the specimens was tested in two phases to study the postearthquake behavior. Results showed a considerable improvement of the deformation capacity of specimens with studs compared to the reference specimen. In agreement with previous research, increasing the applied gravity shear ratio resulted in a lower experimental drift capacity. It is shown that a better explanation of the observed ultimate drifts can be made by considering also the flexural capacity and the extent of shear reinforcement. The specimen tested in two phases exhibited considerable residual capacity, even after severe horizontal loading.

Performance assessment of flat slabs strengthened with a bonded reinforced-concrete overlay, Lapi, M., Fernandes H., Orlando M., a Ramos, and Lúcio V. , Magazine of Concrete Research, Volume 70, Number 9, p.433-451, (2018) AbstractWebsite
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2017
Accelerated action of external sulfate and chloride to study corrosion of tensile steel in reinforced concrete, Silva, M. A. G., Cunha M. P., Pinho Ramos A., Sena da Fonseca B., and Pinho F. F. S. , Materiales de Construcción, Volume 67, Issue 328, (2017)
Applied element method simulation of experimental failure modes in RC shear walls, Cismasiu, Corneliu, Ramos António Pinho, Moldovan Ionut D., Ferreira Diogo F., and Filho Jorge B. , Computers and Concrete, Volume 19, Issue 4, p.365–374, (2017) Abstract

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Punching shear behavior of edge column connections in continuous flat slabs, Einpaul, Jürgen, Vollum Robert, and Ramos António , Proceedings of the 39th IABSE Symposium – Engineering the Future, Vancouver, Canada, (2017)
R/C flat slab connections under lateral loading, Lapi, Massimo, Isufi Brisid, Orlando Maurizio, and Ramos António , XVII Convegno ANIDIS – L´Ingegneria Sismica in Italia, Pistoia, Italy, p.8 pp-, (2017)
Reforço ao punçoamento de lajes fungiformes com lâmina complementar de betão, Fernandes, Hugo, Lúcio Válter, and Ramos António , Revista Portuguesa de Engenharia de Estruturas, Volume III, Issue 5, p.63-72, (2017)
Reforço de lajes fungiformes com armadura transversal pós-instalada usando diferentes técnicas de ancoragem, Inácio, Micael, Ramos António, and Faria Duarte , Revista Portuguesa de Engenharia de Estruturas, Volume III, Number 3, p.63–74, (2017) Abstract

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Reversed lateral cyclic loading test of two flat slab specimens with punching shear stud reinforcement, Isufi, Brisid, Ramos António, and Lúcio Válter , ICCE 2017 International Conference of Civil Engineering, Tirana, Albania, p.9 pp, (2017)
Strengthening of RC slabs with reinforced concrete overlay on the tensile face, Fernandes, Hugo, Lúcio Válter, and Ramos António , Engineering Structures, Volume 132, p.540 - 550, (2017) AbstractWebsite

Abstract Strengthening of concrete structures with a new concrete layer has been commonly used for columns, beams and slabs. This technique is economic and efficient for structural strengthening since it uses the same base materials, steel and concrete. It is usually applied on the compressed face of the concrete element due to concrete’s recognized behaviour under compression, posing several challenges to control cracking and resistance when applied on the tensile face. For assessing the performance of the strengthening method, twelve slab specimens were designed and tested monotonically. The main parameters to assess in this work were the debonding behaviour and load, and the relationship between the latter and the relative displacements at the interface of the two concrete layers. The performance of the strengthened structures strongly relies on the interaction of the two concrete layers, with this being the main subject of the research about overlaid concrete. The load transfer capacity of the interface depends on the interface shear strength, which in turn is highly dependable on substrate roughness, cleanliness and curing conditions of the newly added layer. Interface performance may be improved by using steel connectors crossing the interface, properly anchored on both layers. The importance for these elements grows as the existing concrete is more deteriorated, since adhesion strength will decrease with lower quality concrete. This paper presents the experimental research for the application of bonded concrete overlays on the tensile face of reinforced concrete slabs, mainly aimed at office buildings and parking facilities, where spatial clearances or inaccessibility to the lower side of the slabs are recurrent. A ductile behaviour upon debonding was achieved for the specimens with reinforcement crossing the interface, and a debonding load up to three times that of the reference specimens without reinforcement crossing the interface.

Utilização de betão de elevada resistência em lajes fungiformes, Inácio, Micael, Almeida André, Lúcio Válter, and Ramos António , Revista Portuguesa de Engenharia de Estruturas, Volume III, Issue 5, p.27-36, (2017)
On the distribution of shear forces in non-axisymmetric slab-column connections, Einpaul, J., Vollum R. L., and Ramos A. P. , High Tech Concrete: Where Technology and Engineering Meet - Proceedings of the 2017 fib Symposium, p.841-848, (2017) Abstract
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Strengthening of RC slabs with reinforced concrete overlay on the tensile face, Fernandes, Hugo, Lúcio Válter, and Ramos António , Engineering Structures, Volume 132, Number Supplement C, p.540 - 550, (2017) AbstractWebsite
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2016
Análise Experimental ao Punçoamento de Lajes Fungiformes em BRFA Sujeitas a Ações Vertical e Horizontal Cíclica, Gouveia, Nuno, VIULA FARIA Duarte M., and Ramos António Pinho , Encontro Nacional Betão Estrutural 2016, Coimbra, p.1–14, (2016) Abstract

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Comparison of flat slab strengthening techniques against punching-shear, Lapi, Massimo, Martini Daniele, Zagli Emilio, Orlando Maurizio, Ramos Antonio, and Spinelli Paolo , Proceedings of The New Boundaries of Structural Concrete 2016, NBSC2016, Italy ACI Chapter, Capri, Italy, (2016) Abstract

Punching-shear capacity of slab-column connections in existing R/C structures may be inadequate to bear design loads, so strengthening works are required. The lack of punching resistance may be due to detailing, design or building errors; in other cases, such lack is due to a change of use, which requires an increase of resistance. Different techniques have been developed for strengthening R/C slabs against punching: enlargement of the support, gluing external fibre reinforced polymers or casting a bonded concrete overlay (BCO) on the slab's top surface, insertion of post-installed steel bolts, application of fibre reinforced polymers cords as shear reinforcement. In the paper, the authors apply the Critical Shear Crack Theory (CSCT) to all of these techniques and evaluate their efficacy with reference to a case study.

Comportamento de Lajes Fungiformes Sujeitas a Acções Horizontais Cíclicas, Ramos, António Pinho , Construção Magazine, Issue 76, p.44-45, (2016)
Flat Slabs under Cyclic Reversed Horizontal Loads, Almeida, André, Lúcio Válter, and Ramos António , 3rd NOVA-Yamaguchi International Seminar – Earthquake Resistant Structures, Caparica, (2016)
Punching behaviour of RC flat slabs under reversed horizontal cyclic loading, Almeida, André F. O., Inácio Micael M. G., Lúcio Válter J. G., and Ramos António Pinho , Engineering Structures, Volume 117, p.204–219, (2016) AbstractWebsite

The aim of this work is to study the behaviour of reinforced concrete flat slab structures under combined vertical and horizontal cyclic loading. A total of five specimens were cast and tested: a control specimen was punched without eccentricity, one specimen was tested under constant vertical loading and monotonically increased eccentricity until failure and the remaining three were tested under constant vertical load, at different shear ratios, and cyclic horizontal loading with increasing horizontal drift ratios. All slabs were similar, measuring 4.25×1.85×0.15m3. The reinforced concrete slab specimens were connected to two steel half columns by 0.25×0.25m2 rigid steel plates, prestressed against the slab using steel bolts, to ensure monolithic behaviour. The cyclic tests were performed using an innovative test setup that allows bending moment redistribution, line of inflection mobility, assures equal vertical displacements at the North-South borders and symmetrical shear forces. Results show that cyclic horizontal actions are very harmful to the slab–column connection, resulting in low horizontal drifts and energy dissipation.