4,602 research outputs found
Analysis of damage building in the north region of Portugal
A damaged building in the North Region of Portugal is analysed.
Geotechnical characterisation of the soil foundation is presented. This soil has a low
bearing capacity and the water level is near the ground surface.
The reinforced concrete structural skeleton of this building consists of a mat foundation
and slabs joined by walls. The façades of the building are in air brick masonry.
Instrumental devices to measure the settlements of the building were installed. To
observe the behaviour of the developed cracks, a monitoring system was also applied.
The water table was observed with piezometers.
A tridimensional numerical linear-elastic analysis using a finite element computer
program considering soil-structure interaction is done. The soil is modelled using
springs distributed continuously and the values of the modulus of subgrade vertical
reaction are estimated from the geotechnical properties. The numerical results reveal the
deformations and the damages of the building. These results are compared with the field
observations.
A rehabilitation structural solution is analysed in order to decrease the differential
settlements and the soil pressure, and sustain the crack development.Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ECM/59033/2004 “CUTINSHEAR - Performance assessment of an innovative structural FRP
strengthening technique using an integrated system based on optical fiber sensors
Strategy to evaluate the stress-crack opening relationship of the SFRC
No presente trabalho é descrita a metodologia desenvolvida para a determinação
dos parâmetros de fractura do betão reforçado com fibras de aço, designadamente, a forma
da relação tensão-abertura de fenda e a energia subjacente ao processo de fendilhação deste
compósito. Para tal recorreu-se a resultados experimentais obtidos em ensaios de flexão
efectuados segundo as recomendações do TC 162-TDF da RILEM e foram desenvolvidos dois
modelos numéricos, um com base num modelo de secção e o outro utilizando elementos
finitos de interface para modelar a progressão da fenda.The methodology developed to determine the fracture parameters of the steel fibre
reinforced concrete is described in the present work. The shape of the stress-crack opening
displacement relationship and the fracture energy were assessed. For this purpose, the forcedeflection
relationships obtained in experimental tests carried out according to the
recommendations of the RILEM TC 162-TDF were taken and two numerical approaches were
developed, one based on the cross-section layer model and the other using interface finite
elements to model the crack opening propagation
Modelling the SFRC flexural behavior using a stress-strain relationship
No presente trabalho foi desenvolvida uma estratégia numérica de forma a avaliar
a possibilidade de ser definida uma lei tensão-extensão capaz de simular o comportamento
fendilhado do betão de custo competitivo reforçado com fibras de aço (BRFA) concebido no
âmbito de um projecto de investigação. Essa estratégia englobou dois modelos de
complexidade distinta. O primeiro, designado por modelo de secção, foi utilizado para, com
recurso a análise inversa e utilizando respostas força-flecha registadas em ensaios
experimentais, se determinarem os parâmetros que definem uma lei trilinear tensão-extensão
capaz de reproduzir as respostas experimentais com o rigor desejado. De seguida, esta lei foi
utilizada para definir o modo I de fractura da lei constitutiva da fenda, no âmbito de um
código computacional de análise não linear material de estruturas submetidas a estado plano
de tensão, suportado no método dos elementos finitos, onde o processo de fendilhação é
simulado por um modelo de fendilhação distribuÃda. Da aplicação dos dois modelos
constatou-se que o modelo de secção não permite definir a lei tensão-extensão pós pico (lei
de amolecimento) com o rigor necessário. Enquadrado numa análise inversa, o modelo
baseado no MEF foi de seguida utilizado para se determinar a lei de amolecimento do BRFA,
tendo-se constatado que essa lei não pode ser explicitada unicamente em função do conceito
de resistência equivalente, tal como sugere o RILEM TC 162-TDF.To assess the post-cracking stress-strain relationship for a developed cost
competitive steel fibre reinforced concrete (SFRC), a numerical strategy involving two
numerical models of distinct complexity was carried out. Inserted into an inverse analysis
framework, a cross-sectional-layer-model (CSLM) was used to evaluate the post-cracking
stress-strain relationship able of reproducing, with the desired accuracy, the force-deflection
relationship recorded in three-point bending tests carried out according to the RILEM
TC 162-TDF recommendations. This relationship was used as the strain softening law of the
fracture mode I crack constitutive law of a smeared crack model based on the strain
decomposition concept, under the framework of the finite element method (FEM). Applying
this model it was verified that the CSLM couldn't define a strain softening law able of
simulating, with the necessary accuracy, the fracture mode I of the SFRC. Using an inverse
analysis and the FEM model, the softening law for the SFRC analysed was evaluated. From
the values obtained for the definition of this law it was concluded that this law cannot be
exclusively dependent on the concept of equivalent flexural tensile strength, as RILEM TC
162-TDF recommends
Comportamento à tracção directa de elementos laminares de betão armado reforçado com fibras de aço
Quando comparado com o betão simples, o betão reforçado com fibras de aço, BRFA,
apresenta melhor comportamento à fendilhação e maior capacidade de absorção de energia. Em
consequência, a utilização de BRFA, em determinadas aplicações, pode ser uma mais valia em
termos técnicos e económicos. O presente trabalho tem como principal objectivo avaliar a
influência das fibras de aço no comportamento à tracção de elementos laminares de betão
armado. Os principais resultados experimentais e numéricos são apresentados e discutidos
Betão auto-compactável reforçado com fibras de aço para o reforço à flexâo de estruturas laminares
Com o objectivo de avaliar a influência da adição de fibras discretas de aço no reforço à flexão de estruturas laminares de betão auto-compactável, foi realizado um programa experimental que consistiu no ensaio de faixas de laje armadas com distinta percentagem de armadura longitudinal, mantendo-se constante uma percentagem de fibras de aço julgada adequada para estruturas com elevado grau de hiperestaticidade.Os autores agradecem o apoio da FCT por intermédio do Projecto FICOFIRE - POCTI/ECM/57518/2004 e da empresa Maprel – Empresa de Pavimentos e materiais Pré-Esforçados, Lda. O 1º Autor agradece o apoio financeiro obtido por intermédio da bolsa, ao abrigo do projecto acima referido. À Empresa Bekaert S.A. um reconhecimento pelas fibras gentilmente oferecidas
High strength and ductile fibrous concrete of enhanced fire resistance
In the present work a Fiber Reinforced Concrete of Enhanced Fire Resistance (FRCEFR)
was developed and its properties are characterized by experimental research. This concrete is
intended to have enough resistance for the most structural engineering applications and is
reinforced with a fibrous system to assure the necessary ductility and to improve its fire resistance.
Two types of fibers are used to accomplish the aforementioned requisites for the concrete. The
research performed for the selection of a nonmetallic fiber type for inclusion on the FRCEFR is
resumed. The experimental programs carried out to evaluate the residual compressive and flexural
behavior of the developed FRCEFR are presented and the main obtained results are analyzed. The
tests were executed at 28 days after FRCEFR have been exposed to the following distinct levels of
temperature: 250ºC, 500ºC, 750ºC and 1000ºC
Fibrous reinforcing system to increase the shear resistance of high strength concrete
The available research has evidenced that discrete steel fibers can increase significantly
the shear resistance of High Strength Concrete (HSC) structural elements when High Strength Fiber
Reinforced Concrete (HSFRC) is designed in such way that fiber reinforcing mechanisms are
optimized. In general, the increase of the concrete compressive strength is associated to an increase
of its compactness, resulting benefits in terms of durability, but a strong concern emerges related to
the integrity of this material, since it fails in a too brittle mode when submitted to high
temperatures. To contribute for the knowledge about the benefits provided by discrete steel fibers
when added to HSC applied to laminar structures, an experimental program composed of slab strips
submitted to shear loading configuration was carried out. Uniaxial compression tests with cylinders
of 150 mm diameter and 300 mm height, and bending tests with 600×150×150 mm3 beams were
executed to assess the compression and bending behavior of the developed HSFRC. To evaluate the
influence of the percentage of fibers in the shear resistance of laminar structures, three point loading
tests with slab strips of 800×170×150 mm3 dimensions were performed. Taking the obtained
experimental results, the applicability of the formulation proposed by RILEM TC 162-TDF was
evaluated. Test results showed that, even with relative low dosages of steel fibers, the increment in
shear resistance was significantly increased. The main obtained results in the research program are
presented and discussed in this paper.Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ECM/57518/200
Steel fibres for the shear resistance of high strength concrete beams
Available research on the use of steel fibres to increase the shear resistance of concrete structures
shows that the effectiveness of this type of reinforcement increases with the increase of the concrete
compressive strength, as long as the fibre rupture is avoided. Experimental research has also indicated
that the effectiveness of the fibre reinforcement for the shear resistance is more pronounced in shallow
beams than in deep beams. In terms of analytical research, some models have been proposed and,
recently, RILEM TC 162 TDF recommended an analytical approach for the prediction of the fibre
reinforcement contribution in terms of shear resistance of concrete beams.
The present work has the purpose to contribute for this topic, discussing the performance of
RILEM TC 162 TDF approach, by using the results obtained in an experimental program composed of
three point bending tests with shallow beams of high strength concrete (HSC).
Six different HSC compositions were developed, varying the dosage of steel fibres (0, 60 and
75 kg/m3) and concrete strength class. The experimental program also included tests to characterize
the flexural behaviour of the developed high strength steel fibre reinforced concrete (HSSFRC).
Using the force-deflection relationships obtained in the three point-notched beam bending tests,
and performing an inverse analysis, the values of the fracture mode I parameters of the HSSFRC were
determined. These values were used on the numerical simulation of the tests carried out with HSSFRC
beams failing in shear, under the framework of the material nonlinear finite element analysis, in order
to evince the influence of using a softening constitutive law for modeling the crack shear sliding.
In the present work, the experimental program and the numerical research are described, and the
main results are presented and discussed.Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ECM/57518/2004 “FICOFIRE : High performance fiber reinforced concrete of
enhanced fire resistance
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