Paulo Cachim | University of Aveiro (original) (raw)

Papers by Paulo Cachim

Journal of Building Engineering

Advances and Trends in Engineering Sciences and Technologies III, 2019

IOP Conference Series: Earth and Environmental Science, 2020

The construction of new buildings as well as its retrofitting processes should be ruled by sustai... more The construction of new buildings as well as its retrofitting processes should be ruled by sustainability concepts considered since the design and project phases. The materials and the construction processes used at each stage have a direct influence on the sustainability of the final solution at all parts of the “before use” stage of a building life cycle, namely: “pre-construction”, “product” and “construction process”. The aim of this paper is to compare three different construction solutions for flat roofs, commonly used in Portuguese buildings regarding their economical sustainability. All the solutions have the same functional equivalent, i.e. they are designed to have similar thermal, acoustical and fire protection performance. In order to evaluate the economical sustainability of the different construction solutions, the EcoSust methodology, based on the European standards framework, will be applied. According to this methodology the result of the economic performance is exp...

Journal of Structural Fire Engineering, 2019

Purpose Fire degradation is an extremely important risk that threatens timber structures. It is t... more Purpose Fire degradation is an extremely important risk that threatens timber structures. It is therefore normal that timber design codes include provisions for the design and verification of structures under fire loading. Eurocode 5 is no exception to this, but the simplified methods presented in the code show some inconsistencies, and the advanced method is not practical to use for design purposes. Artificial neural networks (ANNs) have the ability to model complex problems and have been used in a variety of construction engineering problems. They can learn from a subset of data, and then they can be used to predict the results for other input parameters. The purpose of this study is to present the possibility of the use of ANNs for the prediction of temperatures in rectangular timber cross sections, under fire exposure. Design/methodology/approach In this work, a multilayer feedforward ANN has been trained to predict the temperatures within a timber cross section, using as input ...

Materiales de Construcción, 2016

The durability of concrete structures is an important issue nowadays. Specifically in the case of... more The durability of concrete structures is an important issue nowadays. Specifically in the case of reinforced concrete bridges or other infrastructures one of the main form of environmental attack is the penetration of chloride ions, which leads to corrosion of concrete steel reinforcement. This study aims to evaluate the effect of the introduction of metakaolin and diatomite, two chemically and physically different pozzolans, on the resistance of concrete to the penetration of chlorides but also the effect on other properties of concrete, namely, its compressive strength and its porosity distribution. The results of this study show that the pozzolans physical and chemical characteristics have a strong influence on the pozzolans behavior and, consequently, on the concrete properties.

Advances and Trends in Engineering Sciences and Technologies II, 2016

Journal of Structural Fire Engineering, 2016

Purpose This paper aims to present the results of an extensive experimental programme on the fire... more Purpose This paper aims to present the results of an extensive experimental programme on the fire behaviour of timber beam-to-column shear connections, loaded perpendicularly to the grain. Design/methodology/approach The experimental programme comprised tests at normal temperature and loaded fire resistance tests on beam-to-column connections in shear. Twenty-four full-scale tests at normal temperature were performed covering nine different connection typologies, and 19 loaded fire resistance tests were conducted including 11 connections typologies. Findings The results of the fire resistance tests show that the tested typologies of steel-to-timber dowelled connections reached more than 30 and even 60 minutes of fire resistance. However, aspects such as a wider gap between the beam and the column, reduced dowel spacing, and the presence of reinforcement with self-drilling screws all have a negative influence on the fire resistance. Originality/value The experimental programme addres...

Nanotechnology, Sep 14, 2009

Using a sample holder with an integrated force sensor, a collection of carbon nanotubes filled wi... more Using a sample holder with an integrated force sensor, a collection of carbon nanotubes filled with Ga-doped ZnS, and spanning a broad window of lengths and diameters, has been mechanically studied inside a transmission electron microscope. The successful evaluation of the filled nanostructures was seen to depend on their slenderness ratio. Upon controlled removal of the encapsulated sulfide, the system considerably changed its response to uniaxial compressive stress. This report follows part 1 of the study which was instrument-focused and laid the ground to achieve consistent results with a novel type of nanomechanics setup for one-dimensional nanostructures (Costa et al, 2009 Nanotechnology. 40:405706).

Nanotechnology, Sep 14, 2009

The mechanical response of hybrid carbon nanotubes to applied uniaxial compressive forces has bee... more The mechanical response of hybrid carbon nanotubes to applied uniaxial compressive forces has been evaluated inside a transmission electron microscope. The initially crooked nanocolumnar materials had an average elastic modulus of 0.53 GPa, measured in situ via a device based on an atomic force microscope cantilever. To extract this property it was necessary to curtail several sources of error (contact sliding, electronic interferences, etc) and develop the methodology herewith outlined. Since the present study was carried out with a commercially available sample holder, these mechanical studies are pertinent to all those working with one-dimensional structures such as nanorods and nanowires.

Footbridge 2022, Madrid: Creating Experience, 2021

The current paper describes the structure and the dynamic behaviour of a footbridge built in Serr... more The current paper describes the structure and the dynamic behaviour of a footbridge built in Serralves Park at Porto, Portugal. The footbridge, named Tree Top Walk, is located in a slope in the park at the height of the top of the trees. Because it is in a slope, the footbridge develops with an irregular U-shape at a constant level. The total length of the footbridge is approximately 250 m. At its highest level, the height is 15 m.Approximately at one third of the course there is a passage between the two branches of the U. At this zone, there is a staircase that allows to reach the footbridge at the middle of its course, from the woods and a small amphitheatre at a level of 14 m. The structure of the deck is made with timber while the columns are made with steel covered with timber across their height and the connection between the columns and the deck is performed with timber struts placed in the longitudinal and transversal directions. Three of the columns are made with a circula...

Bridge Maintenance, Safety and Management, 2010

Buildings

The article investigates the temperature prediction in rectangular timber cross-sections exposed ... more The article investigates the temperature prediction in rectangular timber cross-sections exposed to fire. Timber density, exposure time, and the point coordinates within the cross-section are treated as inputs to determine the temperatures. A total of 54,776 samples of wood cross-sections with a variety of characteristics were considered in this study. Of the sample data, 70% was dedicated to training the networks, while the remaining 30% was used for testing the networks. Feed-forward networks with various topologies were employed to examine the temperatures of timber exposed to fire for more than 1500 s. The weight of the artificial neural network was optimized using bat and genetic algorithms. The results conclude that both algorithms are efficient and accurate tools for determining the temperatures, with the bat algorithm being marginally superior in accuracy than the genetic algorithm.

Journal of Building Engineering

Advances and Trends in Engineering Sciences and Technologies III, 2019

IOP Conference Series: Earth and Environmental Science, 2020

The construction of new buildings as well as its retrofitting processes should be ruled by sustai... more The construction of new buildings as well as its retrofitting processes should be ruled by sustainability concepts considered since the design and project phases. The materials and the construction processes used at each stage have a direct influence on the sustainability of the final solution at all parts of the “before use” stage of a building life cycle, namely: “pre-construction”, “product” and “construction process”. The aim of this paper is to compare three different construction solutions for flat roofs, commonly used in Portuguese buildings regarding their economical sustainability. All the solutions have the same functional equivalent, i.e. they are designed to have similar thermal, acoustical and fire protection performance. In order to evaluate the economical sustainability of the different construction solutions, the EcoSust methodology, based on the European standards framework, will be applied. According to this methodology the result of the economic performance is exp...

Journal of Structural Fire Engineering, 2019

Purpose Fire degradation is an extremely important risk that threatens timber structures. It is t... more Purpose Fire degradation is an extremely important risk that threatens timber structures. It is therefore normal that timber design codes include provisions for the design and verification of structures under fire loading. Eurocode 5 is no exception to this, but the simplified methods presented in the code show some inconsistencies, and the advanced method is not practical to use for design purposes. Artificial neural networks (ANNs) have the ability to model complex problems and have been used in a variety of construction engineering problems. They can learn from a subset of data, and then they can be used to predict the results for other input parameters. The purpose of this study is to present the possibility of the use of ANNs for the prediction of temperatures in rectangular timber cross sections, under fire exposure. Design/methodology/approach In this work, a multilayer feedforward ANN has been trained to predict the temperatures within a timber cross section, using as input ...

Materiales de Construcción, 2016

The durability of concrete structures is an important issue nowadays. Specifically in the case of... more The durability of concrete structures is an important issue nowadays. Specifically in the case of reinforced concrete bridges or other infrastructures one of the main form of environmental attack is the penetration of chloride ions, which leads to corrosion of concrete steel reinforcement. This study aims to evaluate the effect of the introduction of metakaolin and diatomite, two chemically and physically different pozzolans, on the resistance of concrete to the penetration of chlorides but also the effect on other properties of concrete, namely, its compressive strength and its porosity distribution. The results of this study show that the pozzolans physical and chemical characteristics have a strong influence on the pozzolans behavior and, consequently, on the concrete properties.

Advances and Trends in Engineering Sciences and Technologies II, 2016

Journal of Structural Fire Engineering, 2016

Purpose This paper aims to present the results of an extensive experimental programme on the fire... more Purpose This paper aims to present the results of an extensive experimental programme on the fire behaviour of timber beam-to-column shear connections, loaded perpendicularly to the grain. Design/methodology/approach The experimental programme comprised tests at normal temperature and loaded fire resistance tests on beam-to-column connections in shear. Twenty-four full-scale tests at normal temperature were performed covering nine different connection typologies, and 19 loaded fire resistance tests were conducted including 11 connections typologies. Findings The results of the fire resistance tests show that the tested typologies of steel-to-timber dowelled connections reached more than 30 and even 60 minutes of fire resistance. However, aspects such as a wider gap between the beam and the column, reduced dowel spacing, and the presence of reinforcement with self-drilling screws all have a negative influence on the fire resistance. Originality/value The experimental programme addres...

Nanotechnology, Sep 14, 2009

Using a sample holder with an integrated force sensor, a collection of carbon nanotubes filled wi... more Using a sample holder with an integrated force sensor, a collection of carbon nanotubes filled with Ga-doped ZnS, and spanning a broad window of lengths and diameters, has been mechanically studied inside a transmission electron microscope. The successful evaluation of the filled nanostructures was seen to depend on their slenderness ratio. Upon controlled removal of the encapsulated sulfide, the system considerably changed its response to uniaxial compressive stress. This report follows part 1 of the study which was instrument-focused and laid the ground to achieve consistent results with a novel type of nanomechanics setup for one-dimensional nanostructures (Costa et al, 2009 Nanotechnology. 40:405706).

Nanotechnology, Sep 14, 2009

The mechanical response of hybrid carbon nanotubes to applied uniaxial compressive forces has bee... more The mechanical response of hybrid carbon nanotubes to applied uniaxial compressive forces has been evaluated inside a transmission electron microscope. The initially crooked nanocolumnar materials had an average elastic modulus of 0.53 GPa, measured in situ via a device based on an atomic force microscope cantilever. To extract this property it was necessary to curtail several sources of error (contact sliding, electronic interferences, etc) and develop the methodology herewith outlined. Since the present study was carried out with a commercially available sample holder, these mechanical studies are pertinent to all those working with one-dimensional structures such as nanorods and nanowires.

Footbridge 2022, Madrid: Creating Experience, 2021

The current paper describes the structure and the dynamic behaviour of a footbridge built in Serr... more The current paper describes the structure and the dynamic behaviour of a footbridge built in Serralves Park at Porto, Portugal. The footbridge, named Tree Top Walk, is located in a slope in the park at the height of the top of the trees. Because it is in a slope, the footbridge develops with an irregular U-shape at a constant level. The total length of the footbridge is approximately 250 m. At its highest level, the height is 15 m.Approximately at one third of the course there is a passage between the two branches of the U. At this zone, there is a staircase that allows to reach the footbridge at the middle of its course, from the woods and a small amphitheatre at a level of 14 m. The structure of the deck is made with timber while the columns are made with steel covered with timber across their height and the connection between the columns and the deck is performed with timber struts placed in the longitudinal and transversal directions. Three of the columns are made with a circula...

Bridge Maintenance, Safety and Management, 2010

Buildings

The article investigates the temperature prediction in rectangular timber cross-sections exposed ... more The article investigates the temperature prediction in rectangular timber cross-sections exposed to fire. Timber density, exposure time, and the point coordinates within the cross-section are treated as inputs to determine the temperatures. A total of 54,776 samples of wood cross-sections with a variety of characteristics were considered in this study. Of the sample data, 70% was dedicated to training the networks, while the remaining 30% was used for testing the networks. Feed-forward networks with various topologies were employed to examine the temperatures of timber exposed to fire for more than 1500 s. The weight of the artificial neural network was optimized using bat and genetic algorithms. The results conclude that both algorithms are efficient and accurate tools for determining the temperatures, with the bat algorithm being marginally superior in accuracy than the genetic algorithm.