José M. Cardoso Teixeira

Using linear model for learning curve effect on highrise floor construction

The evolution of repetitive scheduling methods led to the introduction of the learning concept in construction planning. It is common knowledge that performing the same activity repeatedly, and in the same conditions, takes less and less time as the activity is repeated (Gates and Scarpa, 1972). This phenomenon is clear in many construction activities and is known as learning experience or learning effect. The increase in productivity is mainly due to the increasing knowledge acquired by work repetition. Graphic representation is through a learning curve that admits duration decreases as the activity is repeated, according to a predictable and constant learning rate. The Linear Model of logarithmic coordinates (log10Y  =  log10A – nlog10X) was applied to two repetitive construction processes, frequently used in Portuguese construction. The intent was to examine its applicability and efficiency in predicting future performances, and the interest in incorporating the model in new planning methodologies for repetitive construction. In both cases, learning processes were created.

Training needs in construction project management: A survey of 4 countries of the EU

Abstract Knowledge on construction project management is a key issue in todays construction industry across Europe. This applies to the whole range of project participants from inception to conclusion of construction undertakings thereby involving professionals focusing in distinct perspectives yet working for a common goal. Several countries in Europe, with special relevance to the UK, have developed substantial knowledge in this topic through academic courses, professional training and experience of practitioners. Other countries have not achieved this stage but the need to prepare professionals to work in the open European market is impelling efforts for convergence in this matter. This article reports a survey on professional training needs in four European countries presently partnering in a Leonardo da Vinci project on management of construction infrastructure projects. The survey was carried by a questionnaire administered to a set of organisations of the construction cluster of the four countries...

Construction site environmental impact in civil engineering education

The environmental impact of construction activity has gained increasing importance in the last few years and become a key subject for civil engineering education. A survey of Portuguese higher education institutions shows that concern with this topic is mostly directed at the impact of large construction projects and especially focused on their operational stage. The impact of construction sites of smaller projects in urban areas tends to merit less attention, despite their importance for citizens and other economic activities taking place in the neighbourhood. Typical negative impacts include noise and dust production, traffic increase, shortage of parking space, visual impacts, etc. Site management is a typical course in most Portuguese undergraduate curricula for civil engineering, the syllabus of which should cater for the above concerns. This paper reports a survey on negative impacts of construction sites in urban areas and presents a set of related subjects that should be considered in civil engineering curricula.The environmental impact of construction activity has gained increasing importance in the last few years and become a key subject for civil engineering education. A survey of Portuguese higher education institutions shows that concern with this topic is mostly directed at the impact of large construction projects and especially focused on their operational stage. The impact of construction sites of smaller projects in urban areas tends to merit less attention, despite their importance for citizens and other economic activities taking place in the neighbourhood. Typical negative impacts include noise and dust production, traffic increase, shortage of parking space, visual impacts, etc. Site management is a typical course in most Portuguese undergraduate curricula for civil engineering, the syllabus of which should cater for the above concerns. This paper reports a survey on negative impacts of construction sites in urban areas and presents a set of related subjects that should be considered in civil engineering curricula.

A model for identifying owner's needs in the building life cycle

AbstractBuilding life cycle is a process which covers not only the construction phase but also the feasibility, the de- sign and the operation phases. Identifying the owners needs in all phases of this process is of paramount importance for achieving satisfactory results for the building project. Additionally, the owners needs should be fulfilled by the work scope of every stakeholder involved in the project. Nevertheless, these needs are not always adequately considered in building projects. Thus, the purpose of the research reported in this paper has been to develop a model that allows for the identification of the owners needs in all phases of the building life cycle. The article presents a six level classifica- tion system for the information required in the project and a two-dimensional model that maps the life cycle and the logical actions to be undertaken in each phase. The model has been corroborated and improved by applying the Delphi technique to a panel of ten experts in two rounds. The prac...

Cost overrun in construction projects in developing countries, Gas-Oil industry of Iran as a case study

AbstractCost overrun in construction projects is a common issue affecting project performance, and Gas-Oil construction projects in Iran are no exception. This paper presents the results of a questionnaire conducted to identify and evaluate the relative importance of the significant factors contributing to the Gas-Oil construction industry of Iran as a case study for developing countries. The survey respondents included project owners, contractors and consultants involved in Iranian Gas-Oil construction projects. The results of the survey revealed that the main causes of cost overrun in this industry include inaccurate cost estimations, improper planning, frequent design changes, inadequate labour/skill availability, inflation of costs of machinery, labour, raw material and transportation prices. The first three factors are the project consultants’ responsibility and the appointment of qualified consultants and personnel training are strongly recommended to alleviate cost overrun. The paper also reviews a...

A CFD Study of a pMDI Plume Spray

Asthma is an inflammatory chronic disease characterized by airway obstructions disorders. The treatment is usually done by inhalation therapy, in which pressurized metered-dose inhalers (pMDIs) are preferred devices. The objective of this paper is to characterize and simulate a pMDI spray plume by introducing realistic factors through a computational fluid dynamics (CFD) study. Numerical simulations were performed with Fluent® software, by using a three-dimensional “testbox” for room environment representation. A salbutamol/HFA-134a formulation was used for characterization, whose properties taken as input for the CFD simulations. Spray droplets were considered to be composed by ethanol, salbutamol and HFA-134a. Propellant evaporation was taken into consideration, as well as, drag coefficient correction. Results showed an air temperature drop of 3.3 °C near the nozzle. Also, an increase in air velocity of 3.27 m/s was noticed. The CFD results seem to be in good agreement with Dunbar (1997) data on particle average velocity along the axial distance from the nozzle.

Exergy Efficiency Optimization for Gas Turbine Based Cogeneration Systems

The authors would like to express their acknowledgments for the support given by the Portuguese F01mdation for Science and Technology (FCT) through the PhD grant SFRH/BD/62287/2009. This work was financed by National Funds-Portuguese Foundation for Science and Technology, under Strategic Project and PEst-OE/EME/UI0252/2011 and also the PEst-C/EME/UI4077/2011.

A Green City: Impossible Dream or Necessity?

Two out of three Europeans live in towns and cities, and this number is (still) increasing. By attracting more inhabitants, urban areas are facing new challenges, particularly in terms of social and environmental issues. Meeting the challenges of increasing urban pressure may rest on citizens’ active involvement and cross-commitment promoted by local authorities, simultaneously exploring and respecting the social, cultural and heritage structures – the city’s identity. Some cities face more demanding challenges than others. There are other factors associated with the identity process, where the culture and history tend to be relevant indicators, especially in historic cities. Reinforcing the bonds of local identity may facilitate the citizens’ engagement in the common effort to build an environmental and sustainable city. The city of Guimaraes faces such challenges. In this context, the European Green Capital Award, which yearly distinguishes a European city based on its environmental, economics and life quality efforts, encouraging best practices sharing, corresponds to certifying a certain city management paradigm.

Design Optimization of a Solar Dish Collector for Its Application With Stirling Engines

Solar concentric dish collectors and Stirling engines with cavity receivers are commonly considered for this purpose due to the high efficiency for converting solar radiation into mechanical energy. The study and design of a solar collector of this type, and of its cavity receiver, require solving a mathematical model that take into account the geometric, optical and thermal behavior of all components. With an adequate sizing, not only the useful energy produced on the solar device will meet the energy required for the process, but also the absorber temperature will be the needed for the operation of the Stirling engine. This paper focuses on the construction of a mathematical model that represents the operational performance of a concentric solar dish with cavity receiver for its applications in Stirling engines. The purpose is to develop a designing tool for optimization and for quantifying the effect of changing the values of design parameters over any specific output behavior or the overall performance of the system. The parameters in the optimization include: geometrical variables, i.e., the solar dish diameter, the receiver aperture diameter or the focal length; and optical variables, i.e., rim and incident angles, and irradiation interception factor. The objective is to minimize the solar dish collector cost and calculate the heat available to the Stirling engine, contained in the receiver cavity, to be converted in to mechanical energy. The numerical model was coded in the MatLab® programming language. The results of the simulation disclosed a model able to predict, adequately, the optical and thermal behavior of the described system, so that the model can be used to study the operation and also to design parameters. The optimal results disclosed the configuration of a solar collector dish with a rim angle of about 41° and for a dish diameter of 6.58 m and an aperture receiver of 0.12 m for a minimum cost of 4717 €. It was also concluded that the maximum temperature reached in the absorber of a receiver cavity, is limited mainly by the geometric relationships between the dish diameter, receiver aperture diameter and the aperture ratio, and it is possible to obtain an ideal thermal efficiency of 64%.Copyright

CFD Simulation of Two-Phase Flow in a Large Scale Venturi Scrubber

Venturi scrubbers are very attractive devices for gas cleaning in industrial facilities, from small scale textile plants to large scale power plants. They may also be used combining the cleaning capabilities with cooling and humidification process.The difficulty in studying venturi scrubbers arises from the complexity of its flow. It is a multiphase mixture of gas, droplets, and dust particles with multiple interactions between the various phases including: liquid atomization, droplet breakup, collision and coalescence, in addition to interactions between liquid droplets and dust particles.Amongst the various (phenomenological) models that have been proposed, the authors have developed an integral boundary layer model, applicable to the diverging section of the venturi. This has proved to be very successful in predicting the pressure drop for a wide range of venturis.Because phenomenological methods have limits on the performance prediction when the venturi geometry or the operation condition changes, attempts have been made to implement other computational models in venturi scrubbers. Computational Fluid Dynamics techniques can provide detailed information of the flow pattern in the venturi. The present paper reports the development of an Eulerian-Lagrangian model for the two phase flow in a large-scale venturi with a diameter ratio of 122.5/250 mm and the half angles for the converging and diverging sections are 17° and 5°, respectively.The experimental data are published elsewhere and are used in the present work to validate the CFD model presented.© 2013 ASME