A coupled boundary element/differential equation method formulation for plate-beam interaction analysis

In this work, a new boundary element formulation for the analysis of plate-beam interaction is presented. This formulation uses a three nodal value boundary elements and each beam element is replaced by its actions on the plate, i.e., a distributed load and end of element forces. From the solution of the differential equation of a beam with linearly distributed load the plate-beam interaction tractions can be written as a function of the nodal values of the beam. With this transformation a final system of equation in the nodal values of displacements of plate boundary and beam nodes is obtained and from it, all unknowns of the plate-beam system are obtained. Many examples are analyzed and the results show an excellent agreement with those from the analytical solution and other numerical methods. (C) 2009 Elsevier Ltd. All rights reserved.

Analysis of a semi-rigid connection for precast concrete

This paper presents a study of a specific type of beam-to-column connection for precast concrete structures. Furthermore, an analytical model to determine the strength and the stiffness of the connection, based on test results of two prototypes, is proposed. To evaluate the influence of the strength and stiffness of the connection on the behaviour of the structure, the results of numerical simulations of a typical multi-storey building with semi-rigid connections are also presented and compared with the results using pinned and rigid connections. The main conclusions are: (a) the proposed design model can reasonably evaluate the studied connection strength; (b) the evaluation of strength is more accurate than that of stiffness; (c) for a typical structure, it is possible to increase the number of storeys of the structure from two to four with lower horizontal displacement at the top, and only a small increase of the column base bending moment by replacing the pinned connections with semi-rigid ones; and (d) although there is significant uncertainty in the connection stiffness, the results show that the displacements at the top of the structure, and the column base moments present low susceptibility deviations to this parameter.

Artificial neural networks analysis of Sao Paulo subway tunnel settlement data

Artificial neural networks have been used to analyze a number of engineering problems, including settlement caused by different tunneling methods in various types of ground mass. This paper focuses on settlement over shotcrete- supported tunnels on Sao Paulo subway line 2 (West Extension) that were excavated in Tertiary sediments using the sequential excavation method. The adjusted network is a good tool for predicting settlement above new tunnels to be excavated in similar conditions. The influence of network training parameters on the quality of results is also discussed. (C) 2007 Elsevier Ltd. All rights reserved.

Dimension stone for building facades: methodology for structural design

The importance of a careful selection of rocks used in building facade cladding is highlighted. A simple and viable methodology for the structural detailing of dimension stones and the verification of the global performance is presented based on a Strap software simulation. The results obtained proved the applicability of the proposed structural dimensioning methodology which represents an excellent simple tool for dimensioning rock slabs used for building facade cladding. The Strap software satisfactorily simulated the structural conditions of the stone slabs under the studied conditions, allowing the determination of alternative slab dimensions and the verification of the cladding strength at the support.

A comparison between neodymium doped alumina samples obtained by Pechini and sol-gel methods using thermo-stimulated luminescence and SEM

Neodymium doped and undoped aluminum oxide samples were obtained using two different techniques: Pechini and sol-gel. Fine grained powders were produced using both procedures, which were analyzed using Scanning Electron Microscopy (SEM) and Thermo-Stimulated Luminescence (TSL). Results showed that neodymium ions incorporation is responsible for the creation of two new TSL peaks (125 and 265 degrees C) and, also, for the enhancement of the intrinsic TSL peak at 190 degrees C. An explanation was proposed for these observations. SEM gave the dimensions of the clusters produced by each method, showing that those obtained by Pechini are smaller than the ones produced by sol-gel; it can also explain the higher emission supplied by the first one. (C) 2010 Elsevier B.V. All rights reserved.

Methane generation in tropical landfills: Simplified methods and field results

This paper deals with the use of simplified methods to predict methane generation in tropical landfills. Methane recovery data obtained on site as part of a research program being carried Out at the Metropolitan Landfill, Salvador, Brazil, is analyzed and used to obtain field methane generation over time. Laboratory data from MSW samples of different ages are presented and discussed: and simplified procedures to estimate the methane generation potential, L(o), and the constant related to the biodegradation rate, k are applied. The first order decay method is used to fit field and laboratory results. It is demonstrated that despite the assumptions and the simplicity of the adopted laboratory procedures, the values L(o) and k obtained are very close to those measured in the field, thus making this kind of analysis very attractive for first approach purposes. (C) 2008 Elsevier Ltd. All rights reserved.

New prediction methods for CO2 evaporation inside tubes: Part I - A two-phase flow pattern map and a flow pattern based phenomenological model for two-phase flow frictional pressure drops

An updated flow pattern map was developed for CO2 on the basis of the previous Cheng-Ribatski-Wojtan-Thome CO2 flow pattern map [1,2] to extend the flow pattern map to a wider range of conditions. A new annular flow to dryout transition (A-D) and a new dryout to mist flow transition (D-M) were proposed here. In addition, a bubbly flow region which generally occurs at high mass velocities and low vapor qualities was added to the updated flow pattern map. The updated flow pattern map is applicable to a much wider range of conditions: tube diameters from 0.6 to 10 mm, mass velocities from 50 to 1500 kg/m(2) s, heat fluxes from 1.8 to 46 kW/m(2) and saturation temperatures from -28 to +25 degrees C (reduced pressures from 0.21 to 0.87). The updated flow pattern map was compared to independent experimental data of flow patterns for CO2 in the literature and it predicts the flow patterns well. Then, a database of CO2 two-phase flow pressure drop results from the literature was set up and the database was compared to the leading empirical pressure drop models: the correlations by Chisholm [3], Friedel [4], Gronnerud [5] and Muller-Steinhagen and Heck [6], a modified Chisholm correlation by Yoon et al. [7] and the flow pattern based model of Moreno Quiben and Thome [8-10]. None of these models was able to predict the CO2 pressure drop data well. Therefore, a new flow pattern based phenomenological model of two-phase flow frictional pressure drop for CO2 was developed by modifying the model of Moreno Quiben and Thome using the updated flow pattern map in this study and it predicts the CO2 pressure drop database quite well overall. (C) 2007 Elsevier Ltd. All rights reserved.

New prediction methods for CO2 evaporation inside tubes: Part II - An updated general flow boiling heat transfer model based on flow patterns

Corresponding to the updated flow pattern map presented in Part I of this study, an updated general flow pattern based flow boiling heat transfer model was developed for CO2 using the Cheng-Ribatski-Wojtan-Thome [L. Cheng, G. Ribatski, L. Wojtan, J.R. Thome, New flow boiling heat transfer model and flow pattern map for carbon dioxide evaporating inside horizontal tubes, Int. J. Heat Mass Transfer 49 (2006) 4082-4094; L. Cheng, G. Ribatski, L. Wojtan, J.R. Thome, Erratum to: ""New flow boiling heat transfer model and flow pattern map for carbon dioxide evaporating inside tubes"" [Heat Mass Transfer 49 (21-22) (2006) 4082-4094], Int. J. Heat Mass Transfer 50 (2007) 391] flow boiling heat transfer model as the starting basis. The flow boiling heat transfer correlation in the dryout region was updated. In addition, a new mist flow heat transfer correlation for CO2 was developed based on the CO2 data and a heat transfer method for bubbly flow was proposed for completeness sake. The updated general flow boiling heat transfer model for CO2 covers all flow regimes and is applicable to a wider range of conditions for horizontal tubes: tube diameters from 0.6 to 10 mm, mass velocities from 50 to 1500 kg/m(2) s, heat fluxes from 1.8 to 46 kW/m(2) and saturation temperatures from -28 to 25 degrees C (reduced pressures from 0.21 to 0.87). The updated general flow boiling heat transfer model was compared to a new experimental database which contains 1124 data points (790 more than that in the previous model [Cheng et al., 2006, 2007]) in this study. Good agreement between the predicted and experimental data was found in general with 71.4% of the entire database and 83.2% of the database without the dryout and mist flow data predicted within +/-30%. However, the predictions for the dryout and mist flow regions were less satisfactory due to the limited number of data points, the higher inaccuracy in such data, scatter in some data sets ranging up to 40%, significant discrepancies from one experimental study to another and the difficulties associated with predicting the inception and completion of dryout around the perimeter of the horizontal tubes. (C) 2007 Elsevier Ltd. All rights reserved.

Sources of Variations When Comparing Concrete Carbonation Results

Carbonation is one of the main concerns for concrete service life in tropical countries. The mechanism and materials that produce it have been widely studied as well as natural and accelerated methods to report and analyze it. In spite of reported investigations, there is a need for information that could allow an adequate interpretation of the results of the standardization process. This lack of information can produce variations not only in the interpretation but also in the predictions of service life. The purpose of this paper is to analyze and discuss variables that could be sources of error, especially when performing accelerated tests. As a result, a methodologies to minimize variations when interpreting and comparing results is proposed, such as specimen geometry and preconditioning, spacing, relative humidity, and CO(2) concentration.

Performance evaluation of dual-flush WC cistern in a multifamily building in Brazil

The performance assessment as to water consumption in WC cisterns has contributed to the development of flushing system technologies, which allow smaller flushing volumes. The purpose of this work is to assess the performance of the the low water consumption requirement of WC cisterns with dual flushing system (6/3L), when compared to 6L flushing volume WC cisterns in multifamily buildings. The research methodology consisted of a case study in a multifamily residential building with submetering system, by monitoring the total water consumption and the two flushing systems using water meters installed in WC cisterns. By means of a mathematical model, a comparison of the design flowrate in the main branch was carried out considering the two types of WC cisterns. The results indicated that the water consumption in the 6L WC cistern was 20% in relation to the total domestic consumption, whereas the water consumption observed in the dual-flush WC cistern (6/3L) was 16%. The dual flushing system (6/3L) presented about 18% consumption reduction impact as compared to the 6 L system. The design flowrate values in the main branch, obtained by the mathematical model, were 0.35 L/s for systems with 6 L WC cistern and 0.34 L/s with dual-flush WC cistern (6/3 L), that is, a reduction of similar to 3%. Practical application: The knowledge of the performance in field of dual-flush WC cistern contributes to industry to improve this system and to users to aid their choice of technologies aimed at water conservation, and so assisting to the development of sustainable buildings.

Assessment of energy efficiency in electric storage water heaters

Nowadays there are several ways of supplying hot water for showers in residential buildings. One of them is the use of electric storage water heaters (boilers). This equipment raises the water temperature in a reservoir (tank) using the heat generated by an electric resistance. The behavior of this equipment in Brazil is still a research object and there is not a standard in the country to regulate its efficiency. In this context, an experimental program was conducted aiming to collect power consumption data to evaluate its performance. The boilers underwent an operation cycle to simulate a usage condition aiming to collect parameters for calculating the efficiency. This 1-day cycle was composed of the following phases: hot water withdrawal, reheating and standby heat loss. The methods allowed the identification of different parameters concerning the boilers work, such as: standby heat loss in 24 h, hot water withdrawal rate, reheating time and energy efficiency. The average energy efficiency obtained was of 75%. The lowest efficiency was of 62% for boiler 2 and the highest was of 85% for boiler 9. (C) 2008 Elsevier B.V. All rights reserved.

Modeling of Distributed Control Systems in Intelligent Building based on Colored Petri Nets

Distributed control systems consist of sensors, actuators and controllers, interconnected by communication networks and are characterized by a high number of concurrent process. This work presents a proposal for a procedure to model and analyze communication networks for distributed control systems in intelligent building. The approach considered for this purpose is based on the characterization of the control system as a discrete event system and application of coloured Petri net as a formal method for specification, analysis and verification of control solutions. With this approach, we develop the models that compose the communication networks for the control systems of intelligent building, which are considered the relationships between the various buildings systems. This procedure provides a structured development of models, facilitating the process of specifying the control algorithm. An application example is presented in order to illustrate the main features of this approach.

Determination of particle concentration in the breathing zone for four different types of office ventilation systems

Many factors affect the airflow patterns, thermal comfort, contaminant removal efficiency and indoor air quality at individual workstations in office buildings. In this study, four ventilation systems were used in a test chamber designed to represent an area of a typical office building floor and reproduce the real characteristics of a modern office space. Measurements of particle concentration and thermal parameters (temperature and velocity) were carried out for each of the following types of ventilation systems: (a) conventional air distribution system with ceiling supply and return; (b) conventional air distribution system with ceiling supply and return near the floor; (c) underfloor air distribution system; and (d) split system. The measurements aimed to analyse the particle removal efficiency in the breathing zone and the impact of particle concentration on an individual at the workstation. The efficiency of the ventilation system was analysed by measuring particle size and concentration, ventilation effectiveness and the indoor/outdoor ratio. Each ventilation system showed different airflow patterns and the efficiency of each ventilation system in the removal of the particles in the breathing zone showed no correlation with particle size and the various methods of analyses used. (C) 2008 Elsevier Ltd. All rights reserved.

Comparison between detailed model simulation and artificial neural network for forecasting building energy consumption

There are several ways to attempt to model a building and its heat gains from external sources as well as internal ones in order to evaluate a proper operation, audit retrofit actions, and forecast energy consumption. Different techniques, varying from simple regression to models that are based on physical principles, can be used for simulation. A frequent hypothesis for all these models is that the input variables should be based on realistic data when they are available, otherwise the evaluation of energy consumption might be highly under or over estimated. In this paper, a comparison is made between a simple model based on artificial neural network (ANN) and a model that is based on physical principles (EnergyPlus) as an auditing and predicting tool in order to forecast building energy consumption. The Administration Building of the University of Sao Paulo is used as a case study. The building energy consumption profiles are collected as well as the campus meteorological data. Results show that both models are suitable for energy consumption forecast. Additionally, a parametric analysis is carried out for the considered building on EnergyPlus in order to evaluate the influence of several parameters such as the building profile occupation and weather data on such forecasting. (C) 2008 Elsevier B.V. All rights reserved.

Methods of Fourier optics in digital holographic microscopy

In this paper, processing methods of Fourier optics implemented in a digital holographic microscopy system are presented. The proposed methodology is based on the possibility of the digital holography in carrying out the whole reconstruction of the recorded wave front and consequently, the determination of the phase and intensity distribution in any arbitrary plane located between the object and the recording plane. In this way, in digital holographic microscopy the field produced by the objective lens can be reconstructed along its propagation, allowing the reconstruction of the back focal plane of the lens, so that the complex amplitudes of the Fraunhofer diffraction, or equivalently the Fourier transform, of the light distribution across the object can be known. The manipulation of Fourier transform plane makes possible the design of digital methods of optical processing and image analysis. The proposed method has a great practical utility and represents a powerful tool in image analysis and data processing. The theoretical aspects of the method are presented, and its validity has been demonstrated using computer generated holograms and images simulations of microscopic objects. (c) 2007 Elsevier B.V. All rights reserved.