Der Bausektor wird von Politik und Öffentlichkeit als einer der größten Verbraucher von Ressourcen und als Verursacher hoher CO2-Emissionen wahrgenommen und steht deshalb bereits seit längerem im Fokus von Klimaschutz- und Nachhaltigkeitsdiskussionen. Zur Unterstützung der im „Grünen Deal“ der EU und im Klimaschutzgesetz (KSG) der Bundesrepublik vorgezeichneten ambitionierten Ziele hat der DAfStb eine Roadmap „Nachhaltig bauen mit Beton“ erarbeitet. Diese beinhaltet konkrete kurz- und mittelfristige Maßnahmen zur Umsetzung der Nachhaltigkeitsziele, aus denen dann weitere langfristig angelegte Vorhaben (Forschung, Richtlinien, Normung) entwickelt werden.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

A fully automated computer program is developed for the optimum design of steel space trusses acting compositely with a concrete slab placed on top. The program sizes the truss members to meet the requirements of the load and resistance factor design specification of the American Institute of Steel Construction using the load combinations of ANSI. Earthquake loading is not considered. The optimum size is based on minimum cost, regarding the amount of welding required at the joints and of the member itself. The total cost is based on all steel work in the truss. Once the truss configuration has been defined, and it has been ensured that linear elastic behavior exists, the structure is analyzed for the construction process, to make sure that no overstressing will take place in any structural element at any time during construction and service. The analysis and design principles are presented and an actual design case is solved. (Abstract shortened with permission of author.)

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Exponential growth of the global wind turbine market has led to a significant increase in the capacity of wind turbine generators. Modern turbines require higher support structures as higher wind speeds combined with longer blades are necessary to increase their generating capacity. The standard 80-90 m tower is thus not economically viable anymore. Transportation logistics of large steel towers has led to concrete towers becoming a viable option. There are currently no design codes dealing exclusively with the design of concrete wind turbine towers. The aim of this project is to investigate and highlight important aspects of the design process of a normally reinforced high strength concrete wind turbine tower. The tower was designed using nonlinear finite element modelling as a design tool to accurately design the tower for various loads and load cases. An analytical design method was developed that can be used in the preliminary design stage. Finally, the importance of the soil-structure interaction was investigated through a sensitivity analysis. It was found that the formation of cracks greatly affected the stiffness of the structure and that the reduction in stiffness increased the deflection significantly. It was also found that a structure that has sufficient strength to resist the ULS loads may not necessarily comply with the maximum deflection limit for the SLS. The concrete strength class required was not only determined by the maximum compression stress the concrete would experience, but also by the stiffness required to ensure that the tower frequency is within the turbine’s working frequency. The dynamic behaviour of the tower was also affected by the formation of cracks. The fundamental frequency of the tower was reduced by 46% after the SLS loads were applied. It was found that the soil preparation for the foundation plays a vital role in ensuring that the tower frequency is not reduced to a level where it falls outside the turbine working frequency. / AFRIKAANSE OPSOMMING: Die eksponensiële groei van die globale wind turbine mark het gelei tot ʼn beduidende toename in die opwekkingskapasiteit van wind turbine kragopwekkers. Moderne turbines benodig hoër ondersteuningstrukture om hulle opwekkingskapasiteit te verhoog en daarom is die standaard 80-90 m toring nie meer geskik nie. Die vervoer logistiek van groot staal torings het daartoe gelei dat beton torings ʼn lewensvatbare opsie geword het. Daar is huidiglik geen ontwerpkodes wat uitsluitlik handel met die ontwerp van beton wind turbine torings nie. Die doel van hierdie projek is om die ontwerp proses van ʼn bewapende hoë sterkte beton wind turbine toring te ondersoek en belangrike aspekte uit te lig. Die toring word ontwerp deur ʼn nie-liniêre eindige element model te gebruik as ʼn ontwerp hulpmiddel, om die toring akkuraat te ontwerp vir verskeie laste en lasgevalle. ʼn Analitiese ontwerpmetode is ontwikkel wat gebruik kan word in die voorlopige ontwerpfase. Laastens is die grond-struktuur interaksie ondersoek deur ʼn sensitiwiteitsanalise. Daar is gevind dat die vorming van krake die styfheid van die struktuur aansienlik beïnvloed en dat die vermindering in styfheid die defleksie beduidend vermeerder. Daar is ook gevind dat ʼn struktuur wat voldoende sterkte het om die uiterste lastoestande te weerstaan, nie noodwendig voldoen aan die maksimum defleksiegrens vir die diens lastoestande nie. Die beton sterkte klas wat benodig is, is nie net bepaal deur die maksimum druk spanning wat die beton sal ondervind nie, maar ook deur die styfheid wat vereis word om te verseker dat die toring se frekwensie binne die turbine se werksfrekwensie val. Die dinamiese gedrag van die toring is ook beïnvloed deur die vorming van krake. Die fundamentele frekwensie van die toring is verlaag met 46% nadat die diens lastoestande toegepas is. Daar is gevind dat die grond voorbereiding vir die fondasie ʼn belangrike rol speel om te verseker dat die toring se frekwensie nie verlaag word tot ʼn vlak waar dit buite die turbine se werksfrekwensie val nie.

published_or_final_version / abstract / Civil Engineering / Master / Master of Philosophy

published_or_final_version / abstract / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Philosophy

Damage to reinforced concrete bridges due to carbonation and chloride induced corrosion is widespread in South Africa and prone in environments where carbon dioxide is at high levels as well as in marine environments where chlorides are present. Performance specifications are therefore essential in order that structural concrete can be designed and constructed to the required standards ensuring that the long term durability can be maintained. This dissertation includes a review of SANRAL‘s current durability specifications. The specifications are critiqued in terms of the testing methodology followed as well as strength and environmental exposure considerations, and recommendations are made for improving the specifications. The literature review, outlines the background to both carbonation and chloride induced corrosion to reinforced concrete bridges , considering the fundamental causes of deterioration of concrete caused by carbonation and chloride ingress and repair costs during their service life. The South African Durability Index tests are presented and reviewed, in particular the laboratory testing apparatus and procedures. In addition, the index tests are compared with durability test methods currently being used internationally. The background and previous durability specifications used in South Africa on road bridges as well as details of research into specifications to ensure durable concrete with specific emphasis on curing of concrete is summarised. The indications are that performance based specifications for concrete on bridge structures internationally follow similar criteria to the specifications currently being adopted by SANRAL. Both performance and prescriptive specifications used usually depend on the risk that a constructor needs to carry. Importantly both cement extenders to ensure long term durability and penalties are applied in performance based durability. SANRAL‘s current durability specifications are reviewed and both the negatives and positives are presented for the various sections. Amendments to the Committee of Land Transport Officials (COLTO) standard specifications are recommended address shortcomings. The latest project specifications used on SANRAL contracts incorporating target requirements for cover and oxygen permeability are evaluated. These impose penalties if targets are not achieved, while limits are placed on chloride conductivity values for various blended binders. Data is also included for the sorptivity index values on the five projects which may analysed and target values can be set and implemented in future. Descriptions of the five projects with regard to durability specifications, their environmental exposure condition and concrete mix designs are presented. Five projects in KwaZulu-Natal, are used as case studies for durability tests and specifications. The only distinct difference in the specifications is that the three projects commencing in 2006 and early in 2007 had the target values for water sorptivity whereas for the project, sorptivity values are only reported on. Durability index testing results at each of the sites from the trial panels, additional test cubes (cast for coring and testing of durability indexes) as well as coring and testing from the bridge structures are presented. A major change is coring and testing of samples from trial panels and additional test cubes on the site instead of coring of the structure. The information is drawn together and relationships are determined between the various durability indexes as well as to strength. It is evident that the quality of concrete as constructed in the structure which is reflected by the durability index results is different to that produced in the test cubes and trial panels. It is deduced that while more care is being taken to produce quality concrete on the sites, certain aspects of the specifications need revision in order to remove confusion as well as to ensure that the concrete in the structure meets the target requirements. Finally it is noted that climate change is having an impact on design of bridge infrastructure, and while the surveys undertaken at Ethekwini and Msunduzi Municipalities shows that carbon dioxide levels being recorded are still average levels, worldwide there has been an increase in CO2 levels and further modifications to specifications in future may be required. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

The purpose of this mixed methods qualitative case study is to gain a deeper understanding about the factors that contribute to and/or hinder women’s participation in the construction industry by examining women’s experiences within one very industry-specific, male-dominated nontraditional occupation (NTO)—the concrete industry. In this study I utilized a combination of methods including interviews and survey research, as well as case analysis of an organization specifically involved with this population, the Women In Concrete Alliance (WICA). This investigation identifiesd some of the reasons why women’s participation remains low, discusses some of ways that the private, public, and educational sectors have set out to address those shortages, how women working in the field felt feel about those initiatives based upon their experiences, and what systems of support these women draw upon to remain active in a male-dominated profession. As women’s associations within NTOs are one relatively formal potential means of support for women facing occupational isolation, this study also examines different types of organizations to which women working in NTOs belong (e.g. membership, educational, advocacy, trades). I want to know in what ways the organizations benefit members; how the organizations support themselves or are supported financially.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / A hierarchical non-linear model was developed for the time-dependent shrinkage behaviour of South African concretes, from historical laboratory data. The fit of fifteen growth curve models to the shrinkage-time profiles was evaluated and MCDA was used to identify the best model. The three parameters of the chosen growth curve model were modelled in terms of covariates (relating to concrete raw materials, concrete composition and shrinkage testing conditions) by multivariate multiple regression to produce the WITS model. The model largely conformed to existing knowledge about the factors affecting concrete shrinkage. Published models for concrete shrinkage were compared to the WITS model regarding their predictive ability with respect to the South African data set. The WITS model performed the best across a variety of graphical and numerical goodness-of-fit measures. The importance of the study is two-fold:  The concept of hierarchical non-linear modelling has been applied for the first time to the modelling of the time-dependent properties of concrete.  This is the first comprehensive model to bring together laboratory data on the shrinkage of concrete generated in South Africa over a span of thirty years.