Design practice at the present day trends toward more and more complex forms of the reinforced concrete frame. / Master of Science

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-04-18T12:05:11Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO_ANDRÉ LOPES.pdf: 5318919 bytes, checksum: 7fcd711cb764df5b1129609d50537bdd (MD5) / Made available in DSpace on 2016-04-18T12:05:12Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO_ANDRÉ LOPES.pdf: 5318919 bytes, checksum: 7fcd711cb764df5b1129609d50537bdd (MD5) Previous issue date: 2015-05-29 / FACEPE / Diante do desenvolvimento da construção civil nos últimos anos e do aumento da concorrência entre as empresas deste setor, faz-se necessário oferecer alternativas estruturais e construtivas que permitam maior eficiência e redução de custos nas execuções das obras. O desenvolvimento das tecnologias na área de informática vem propiciando cada vez mais condições para análises estruturais de alta complexidade, que estão materializadas em programas comerciais de cálculo estrutural, os quais tornam o dimensionamento das estruturas mais produtivo e estão cada vez mais importantes na rotina do engenheiro estrutural. Este trabalho apresenta um estudo técnico comparativo entre lajes nervuradas em concreto armado bidirecionais moldadas no local com fôrmas de polipropileno e unidirecionais pré-fabricadas treliçadas. Inicialmente, realizou-se um estudo paramétrico comparativo de esforços, deslocamentos e de custo de lajes com geometrias quadradas e retangulares em função de suas dimensões em planta. Em seguida, desenvolveu-se uma análise comparativa de um estudo de caso, onde se adotou um edifício modelo localizado na cidade de Caruaru-PE, o qual foi dimensionado empregando os dois sistemas construtivos de lajes abordados nesta pesquisa. Na análise do referido estudo de caso observou-se o comparativo de esforços, deslocamentos verticais e horizontais e estabilidade da estrutura, bem como, os custos dos elementos estruturais que compõem a estrutura do edifício analisado para os dois modelos de sistemas construtivos utilizados. As simulações das estruturas foram efetuadas utilizando modelos gerados em computador no software CYPECAD versão 2012a. Os cálculos dos esforços e deslocamentos, assim como o dimensionamento da estrutura, foram obtidos através do referido programa. Após o dimensionamento e a análise dos resultados, foram extraídos do programa os quantitativos referentes aos esforços cortantes, momentos fletores, deslocamentos, consumos de fôrmas, concreto e armadura. Em seguida, fez-se a composição do custo total da estrutura para cada sistema estrutural e efetuou-se a comparação entre os dois sistemas construtivos de lajes analisados neste trabalho. / With the development of civil construction in recent years and the increased competition between the companies in this sector, is made necessary provide structural and constructive alternatives that allowing greater efficiency and cost savings in the execution of works. The development of the technologies in computer science area comes increasingly providing conditions for structural analysis of high complexity, which are materialized in commercial programs of structural calculation, which make the sizing of more productive structures and are increasingly important in the structural engineer's routine. This work presents a comparative technical study between ribbed slabs bidirectional molded on site with polypropylene molds and lattice slabs unidirectional prefabricated in reinforced concrete. Initially was held a comparative parametric study of efforts, displacements and cost of slabs with square and rectangular geometries according to their dimensions in plant. Then developed a comparative analysis of a case study, which adopted a model building located in the city of Caruaru-PE, which has been sized using the two building systems of slabs covered in this research. In analysis of this study of case was observed the comparative of efforts, vertical and horizontal displacements and stability of the structure, as well as the costs of structural elements comprising the building structure analyzed for the two types of construction systems used. The simulations of the structures were made using computer generated models in CYPECAD software version 2012a. The calculations of the efforts and displacements, as well as the sizing of the structure, were obtained through this program. After the sizing and analysis of the results, were extracted from the program the quantitatives relating to shear efforts, bending moments, displacements, molds consumption, concrete and armor. Then, was made the composition of the total cost of the structure for each structural system and was executed the comparison between the two building systems of slabs examined in this work.

no / The recently published report on Rethinking Construction in the UK has highlighted the need to reduce on-site activities as part of its drive for greater efficiency, improved quality and greater certainty in the delivery of construction projects. For multi-storey buildings, the use of precast slabs in the floors - particularly if this can be done without the need for in-situ screeds - drastically reduces the volume of on-site concreting required. Although the use of precast hollow core slabs in steel framed buildings are common, their use in composite design with steel beams is relatively new. By designing the steel beams and precast hollow core slabs compositely, a reduction in beam size and overall floor depth can be achieved, which would lead to an overall reduction in construction cost. This paper summarises the recent developments and on-going research on composite construction with precast hollow core slabs.

O objetivo principal deste trabalho é sistematizar e automatizar o cálculo de lajes maciças e retangulares de edifícios, utilizando-se a Teoria das Charneiras Plásticas. Apresentam-se as formulações necessárias para a sua automatização. Aborda-se também a questão relativa às deformações nas lajes maciças em concreto necessidade de consideração das dependentes do tempo. Por fim, faz-se um estudo comparativo com o método elástico para dimensionamento de lajes maciças em concreto e com o sistema de lajes treliçadas, através de aplicações em dois pavimentos de lajes, analisando-se os aspectos técnicos e financeiros (custos) dos resultados. / The main purpose of this work is to systematize the building rectangular compact slab calculation, using the yield line theory. The necessary formulation is presented. Deflections of reinforced concrete slabs are also discussed, making evident that cracking and time dependent effects are important parameters to be considered. Finally, a comparison with the elastic method for compact slabs design and with the lattice slab systems is presented, considering two examples of building floors, taking into account technical and financial (expenses) aspects of the results.

Small organic ‘collector’ ligands play an important role in the recovery of platinum group minerals (PGMs) from the industrial platinum mining process via the froth flotation process, which separates finely ground minerals on the basis of relative hydrophobicity. Design of novel ligands to improve PGM recovery is an ongoing industrial interest. This thesis involves the application of computational chemistry techniques to gain a first-principles understanding of simple mineral-collector ligand interactions, with a view to applying this understanding to the design of novel collector ligands. Experimental techniques are also used, where appropriate, to validate computational modelling in order to gauge the applicability of computational chemistry to this field. Sperrylite (PtAs2), the world’s most common PGM, was used as a model for a typical platinum group sulfide mineral. Pentlandite ((Fe,Ni)9S8) and pyrite (FeS2), two base metal sulfide minerals commonly associated with PGMs, were used as competitor surfaces to gauge collector selectivity. α-quartz (SiO2) was used as to model silicaceous waste material, and pure platinum (Pt) as an internal standard to gauge Pt-collector interactions. Chapter 1 provides an overview of PGM mining with particular focus on the froth flotation process. A brief overview of the computational methods applied in this work is provided in Chapter 2. Chapter 3 presents modelling work based on assessing the various mineral and metal surfaces upon which ligands adsorption is modelled. Stable ‘working surfaces’ are defined by calculating surface energies for various low Miller index cleavages of the bulk unit cells of these solids. Surface stability with respect to slab depth is also assessed. A number of methods, including application of the virtual crystal approximation, a pairwise cluster expansion and explicit site modelling, are used to resolve the issue of positional disorder of the metal sites in pentlandite. This leads to the observation that pentlandite slabs with a higher concentration of Ni atoms at the mineral/vacuum interface are more stable. A global minimum energy bulk unit cell of pentlandite is described. Chapters 4 and 5 deal with the adsorption of collector and aqua ligands onto these surfaces, with Chapter 5 also reporting attempts at rational in-silico ligand design. A novel method for calculating the binding energy of anionic species in periodic systems via a work-function based correction is described and tested for both mono- and dianionic species. Modelling of ethyl xanthate (H5C2OCS2-) and xanthate-based analogues (H5C2XCS2-, where X=N, NH, NC2H5, S, CH, CH2) shows a trend of increased binding strength upon formation of dianionic species. Whilst this observation was supported (to a lesser degree) by geometrical parameters, the extension of the work-function based correction to deal with dianionic species tended to significantly overbind these ligands and so the work function correction was found to be inappropriate for use in models with a charge state greater than -1. Modelling of heterocyclic ligands on selected surfaces shows weaker adsorption than non-heterocyclic species due to unfavourable electronic effects of the delocalised heterocycle on the R-CS2- head group. Efforts in ligand design focussed on optimising the electronic properties of the tail group in the xanthate structure to provide maximum electron density to the CS2- system. The output from this process was p-methoxyphenyl dithiocarbamate (H2CO-C6H4-N=CS2²-), which performed well in computational models. Synthesis of this ligand, as well as protonated Nethyl dithiocarbamate (H5C2NHCS2-) failed, however, due to the intrinsic instability of monosubstituted dithiocarbamates. Attempts to validate modelling results using two experimental techniques are reported in Chapter 6. Firstly, cyclic voltammetry experiments using sperrylite, pentlandite and platinum working electrodes suspended in collector solutions of concentration 1x10-3 M are reported, which show some correlation between the order of calculated binding energies and the relative position of the oxidation potential for the formation of disulfide oxidation products, a process which is affected by surface adsorption. Correlation is best for ethyl xanthate and diisobutyl dithiophospinate, but poor for N,N-diethyl dithiocarbamate ((H5C2)2NCS2-). Secondly, microflotation experiments for the recovery of sperrylite, pentlandite and pyrite using various collector ligands were conducted. Results broadly agree with prior microflotation literature, but show no simple correlation between ligand binding energies and flotation recovery, suggesting that more complex factors than simple ligand/mineral adsorption are involved.

Wong Chi Kit. / "Architecture Department, Chinese University of Hong Kong, Master of Architecture Programme 2004-2005, design report." / Chapter PART 00 --- INTRODUCTION / Chapter PART 01 --- RESEARCH: Outdoor Space Definition / Chapter a. --- collection of Hong Kong Public Housing Estate / Chapter b. --- timeline of development / Chapter c. --- typology study / Chapter d. --- case study / Chapter PART 02 --- DESIGN: New Prototype Design for Adaptibility

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains x, 114 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 108-113).

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Multi-storey buildings with precast hollowcore concrete floor systems are very common in New Zealand and in many other countries, but the structural behaviour of such systems under fire exposure is not easy to predict because of the complex geometry, composite construction, and a wide range of possible support conditions. The 2006 version of the New Zealand Concrete Standard NZS3101 introduces new details for connection of hollowcore floor units to reinforced concrete supporting beams to improve seismic performance, but the fire performance of the new connection systems is unknown. Currently available methods for simulating fire performance of hollowcore slabs are not suitable for design purposes. Therefore, a simple yet sufficiently accurate simulation method needs to be developed. This study was carried out using a proposed simulation method to investigate the fire performance of hollowcore floor slabs with different connection details between the hollowcore units and their reinforced concrete supporting beams conforming to NZS3101. The proposed simulation method is examined on the platform of SAFIR, a non-linear finite element program that includes both thermal and structural analysis. The proposed simulation method was validated using available experimental results from a limited number of tests. It does not take account of shear and anchorage failures or spalling effects, so designers should consult other studies for this behaviour of hollowcore concrete flooring systems. By using the proposed simulation scheme in SAFIR, it is investigated whether the tensile membrane action established through beams parallel to the hollowcore units and different floor aspect ratios will enhance the fire resistance of hollowcore concrete flooring systems. From the simulation results it is concluded that rigid connections at both the ends and the sides of the hollowcore flooring systems to the supporting beams provide better fire resistance than rotationally flexible connections, and the fire resistance of hollowcore flooring systems can be increased by using stiffer supporting beams at the end of the slabs and also by decreasing the spacing between the beams parallel to the hollowcore units.