The accurate finite element analysis of subregions of large structures is difficult to carry out because of uncertainties about how the rest of the structure influences the boundary conditions and loadings of the subregion model. This dissertation describes the theoretical development and computer implementation of a new approach to this problem of modeling subregions. This method, the specified boundary stiffness/force (SBSF) method, results in accurate displacement and stress solutions as the boundary loading and the interaction between the stiffness of the subregion and the rest of the structure are taken into account. This method is computationally efficient because each time that the subregion model is analyzed, only the equations involving the degrees of freedom within the subregion model are solved. Numerical examples are presented which compare this method to some of the existing methods for subregion analysis on the basis of both accuracy of results and computational efficiency. The SBSF method is shown to be more accurate than another approximate method, the specified boundary displacement (SBD) method and to require approximately the same number of computations for the solution. For one case, the average error in the results of the SBD method was +2.75% while for the SBSF method the average error was -0.3%. The comparisons between the SBSF method and the efficient and exact zooming methods demonstrate that the SBSF method is less accurate than these methods but is computationally more efficient. In one example, the error for the exact zooming method was -0.9% while for the SBSF method it was -3.7%. Computationally, the exact zooming method requires almost 185% more operations than the SBSF method. Similar results were obtained for the comparison of the efficient zooming method and the SBSF method. Another use of the SBSF method is in the analysis of design changes which are incorporated into the subregion model but not into the parent model. In one subregion model a circular hole was changed to an elliptical hole. The boundary forces and stiffnesses from the parent model with the circular hole were used in the analysis of the modified subregion model. The results of the analysis of the most refined mesh in this example had an error of only -0.52% when compared to the theoretical result for the modified geometry. The results of the research presented in this dissertation indicate that the SBSF method is better suited to the analysis of subregions than the other methods documented in the literature. The method is both accurate and computationally efficient as well as easy to use and implement. The SBSF method can also be extended to the accurate analysis of subregion models with design changes which are not incorporated into the parent model. / Ph. D.

No description available.

In this thesis, frontal subroutines are implemented to a plane frame analysis program for execution on the IBM PC. The resulting program solves for the unknown joint displacements of frame structures with large numbers of degrees of freedom by utilizing a peripheral back-up storage; which can not be analyzed directly in core. A comparison of the frontal solver and the out-of-core band solver is presented. / M.S.

Current aircraft noise guidelines are based primarily on outdoor sound levels. However, human perception is highly related to indoor response, particularly for residences. A research project has been conducted that provides insight into how typical residential dwelling envelopes affect sound transmitted indoors. A focus has been placed on the effect of residential dwelling envelopes on subsonic civil aircraft noise. Typical construction types across the United States have been identified and used to develop model predictions of outdoor-to-indoor transmission loss. While it was initially hypothesized that these construction types could be grouped by climate region, it was found that these constructions are better grouped according to their outermost construction layer. Further, the impact of systematically altering construction variables (such as the construction materials used and the ratio of window area to wall area) has been investigated. Results will be used to better understand trends for expected noise reduction for typical construction types around the United States. Additionally, comparisons have been made between the effect of older and more modern wall construction techniques on whole-house performance.

Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Structural analysis is examined in order to identify its essential information requirements, its fundamental tasks, and the essential functionalities that applications which support it should provide. The special characteristics of the information content of structural analysis and the algorithms that operate on it are looked into and exploited to devise data structures and utilities that provide proper support of the analysis task within a local environment, while presenting the opportunity to be extended to the context of a distributed network-based collaboratory as well. Aspects regarding the distribution of analysis parameters and methods are analysed and alternatives are evaluated. The extentions required to adapt the local data structures and utilities for use in a distributed communication network are developed and implemented in pilot form. Examples of collaborative analysis are shown, and an evaluation of the overhead involved in distributed work is performed. / AFRIKAANSE OPSOMMING: 'n Ondersoek van die struktuuranalise-taak word uitgevoer waarin die kerninligtingsbehoeftes en fundamentele take daarvan, asook die vereisde funksionaliteit van toepassings wat dit ondersteun bepaal word. Die besondere eienskappe van struktuuranalise-inligting en die algoritmes wat daarop inwerk word ondersoek en benut om data strukture en metodes te ontwikkel wat die analise-taak goed ondersteun in In lokale omgewing, en wat terselfdertyd die moontlikheid bied om sodanig uitgebrei te word dat dit ook die taak in 'n verspreide samewerkingsgroepering kan ondersteun. Aspekte van die verspreiding van analiseparameters en metodes word ondersoek en alternatiewe oplossings word evalueer. Die uitbreidings wat nodig is om die datastrukture en metodes van die lokale omgewing aan te pas vir gebruik in verspreide kommunikasienetwerke word ontwikkel en in loodsvorm toegepas. Voorbeelde van samewerking-gebasseerde analise word getoon, en die oorhoofse koste verbonde aan analise in 'n verdeelde omgewing word evalueer.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2005. / In the inverse finite element method (iFEM), given a finite element model of a structure and imperfect displacement measurements, the external loads acting on the structure can be assessed. The basic idea behind iFEM is the optimization of a quadratic cost function of the difference between the measured and estimated values, with a high cost corresponding to a high precision of the measurements. In the present research it is firstly shown how the iFEM theory was broadened to accommodate for strain measurements through the construction of cost matrices to express the cost associated with the estimation of the response. The main focus of the research falls however on the influence that the measurement set-up has on the quality of the iFEM estimates. Only a limited number of measurements may be available, therefore it is essential to plan the measurement set-up carefully to obtain the highest quality of estimates. The number of measurements and the precision required to obtain a realistic result from an iFEM analysis is also a factor which plays a role and varies for different types of measurements. A numerical method for systematic sensitivity study of the measurements set-up without involving the actual measurement data, is presented. Two examples consisting of structures with both displacement measurements and strain measurements being taken, are presented. It illustrates how the sensitivity study method can be used to plan a more effective measurement set-up.

Thesis (MScEng)--Stellenbosch University, 2003. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: A critical evaluation of provisions for imposed loads in the South African Loading Code for design of structures, SABS 0160-1989 (SABS), by comparison with other codes was performed earlier. The evaluation revealed the SABS loading code to be generally non-conservative in its provisions for imposed loads for a range of general and specialist occupancy classes. The SABS provision for imposed loads for inaccessible roofs was found to be substantially non-conservative in comparison with the other codes. An investigation into the imposed load for inaccessible roofs is subsequently performed in order to establish a scientific rationale through which the codified design values may be measured effectively. Due to the lack of information and the large uncertainties involved in the imposed roof load, stochastic treatment of the loads is implemented. This is in line with the stochastic modelling of loads as implemented in general. The approach applied is to select a type of building that can be regarded as a generic example of buildings to which these loads apply, and to discretisize the load into the various sub-mechanisms that translate into the imposed roof load. The probabilistic models for the load mechanisms are then quantified, either through physical load surveys, or through conducting an expert survey for those variables which are not observable. The use of expert opinion as a resource for information is not readily accessible in terms of yielding scientifically defendable results. Therefore, the expert survey is performed as a calibrated experiment whereby weights were calculated for the individual experts' opinions and their opinions combined accordingly. The probabilistic models for the load mechanisms are then translated into load effects by taking into account the physical process resulting in the load effects. By applying these mechanisms in such a way as to maximise the said load effects, equivalent uniformly distributed loads (EUDL's) were calculated for each mechanism. The probabilistic models obtained in terms of the EUDL's pose an easily accessible format through which existing load models and codified provisions can be evaluated. These load models are then utilised to evaluate the SABS provisions in terms of the level of reliability catered for by SABS ultimate limit-state design criteria. It is concluded that the SABS conservatively provides for maintenance loads on the roof, while the reliability for construction loads is non-conservative for large tributary areas and highly non-conservative for small areas. The load models so obtained can further be applied for structural reliability assessment. / AFRIKAANSE OPSOMMING: "n Kritiese evaluasie van die voorskrifte vir opgelegde belastings in die Suid- Afrikaanse Selastingskode vir die ontwerp van strukture, SASS 0160-1989 (SASS) deur 'n vergelyking met ander kodes is vroeër uitgevoer. Die evaluasie het getoon dat die SASS in die algemeen onkonserwatief is in sy voorsiening vir opgelegde belastings oor 'n bereik van algemene en spesialis okkupasie tipes. Die SASS voorskrif vir opgelegde belastings vir ontoeganklike dakke is hoogs onkonserwatief in vergelyking met die ander kodes. 'n Ondersoek na die opgelegde belasting vir ontoeganklike dakke word gevolglik uitgevoer met die doelom 'n wetenskaplike rasionaal daar te stel waardeur die gekodifiseerde voorskrifte effektief gemeet kan word. As gevolg van die gebrek aan inligting en groot onsekerhede betrokke by die opgelegde dakbelasting word stogastiese modellering geimplimenteer. Die aanslag wat gevolg is, is om 'n tipe gebou te selekteer wat beskou kan word as verteenwoordigend van die geboue waarvoor hierdie belastings van toepassing is, en om die belasting te diskretiseer in die verskeie lasmeganismes wat die opgelegde dakbelasting voortbring. Die waarskynlikheidsmodelle vir die lasmeganismes word dan gekwantifiseer, óf deur fisiese opnames, óf deur die uitvoering van 'n ekspertopname vir daardie veranderlikes wat nie waarneembaar is nie. Die gebruik van ekspert opinie as "n bron van inligting is nie maklik toeganklik in terme daarvan om wetenskaplik verdedigbare resultate te lewer nie. Daarom is die ekspert-opname uitgevoer soos 'n gekalibreerde eksperiment waardeur relatiewe gewigte bereken word vir die individuele eksperts en hulopinies daarvolgens gekombineer word. Die waarskynlikheidsmodelle vir die lasmeganismes word dan omgeskakel in laseffekte deur in agneming van die fisiese proses wat die las-effek voortbring. Deur die lasmeganismes op só 'n manier toe te pas dat die betrokke las-effekte gemaksimeer word, word ekwivalent uniforme belastings (EUS's) bepaal. Die waarskynlikheidsmodelle in terme van EUS's bied "n maklik toeganklike formaat waardeur bestaande lasmodelle en gekodifiseerde voorskrifte evalueer kan word. Die lasmodelle word gevolglik gebruik om die SASS voorskrifte te evalueer in terme van die vlak van betroubaarheid wat gehandhaaf word deur SASS limiet-staat ontwerp kriteria. Dit is bepaal dat die SASS konserwatief voorsiening maak vir onderhoudslaste op die dak, maar onkonserwatief tot hoogs-onkonserwatief is vir konstruksie laste. Die bepaalde lasmodelle kan verder toegepas word in strukturele betroubaarheids analise.

Call number: LD2668 .T4 1986 L43 / Master of Science / Civil Engineering

M.Sc. (Computer Science) / The purpose of this disssertation is to study methods to represent structures in three-dimensions. Due to the fact that chemical molecules are mostly complex three-dimensional structures, we used chemical molecules as our application domain. A literature study of current chemical information systems was undertaken. The whole spectrum of information systems was covered because almost all of these systems represent chemical molecules in one way or another. Various methods of three-dimensional structure representation were found in our literature study. All of these methods were discussed in the context of its own application domain. Structure graph grammars were examined and explained in detail. A small object-based system with structure graph grammars as the underlying principle was developed. We speculated on the use of such "intelligent" graph grammars in structure interpretation and identification. Further research in this area was also identified.

M.Tech. / South African government is one of the countries in the world that has delivered the highest number of houses to the poor through various delivery mechanisms to fulfill her vision to adequate housing for all as reflected in the National Housing Policy framework. Since 1994, about One Million Eight Hundred and Seventy Seven Thousand Nine Hundred and Fifty Eight (1 877 958) houses has been delivered. People’s Housing Process is a state-assisted, self help housing programme and about 3% of the total houses built were delivered through the PHP housing delivery programme. The Government’s goal is, subject to fiscal affordability, to increase housing delivery on a sustainable basis to a peak level of 350 000 units per annum until the housing backlog is overcome (South Africa’s National Housing code policy, 2000:5). The government focused on quantitative housing delivery with qualitative shortcomings. However the focus has now shifted to the quality of the end product delivered. Defects in houses manifest themselves primarily through cracking, dampness, detachment, and water leakages. Defects may be patent or latent, and could be discovered through checking, observations and tests. This research work is a study of structural qualities of houses delivered through PHP. The study investigated the causes of structural inadequacies in PHP houses focusing in the Gauteng Province of South Africa. The findings show that different types of structural defects occurred in houses delivered through PHP scheme, these defects include roof leakages, cracks in walls, wall not being straight and defects in roof trusses. The cause of these defects was as a result of poor quality control mechanism put in place by the Department of Housing.