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The design of reinforced concrete beams involves the selection of design parameters such as beam dimensions and reinforcement details which result in a safe and economical section. This process of design consists of three stages: preliminary design, structural analysis, and detailed design which includes the selection of dimensions, reinforcement, and stirrups. The design process is an iterative one where considerable judgement and experience are required. This is an ideal situation for the application of expert system technology. A knowledge based expert system called BEAMDES was developed for the flexure design of reinforced concrete beams in accordance with ACI 318-83 specifications. The expert system was developed using the micro-computer based expert system shell, Insight 2+. BEAMDES can be used to design both rectangular and tee sections. The beams can be simply supported, cantilevered, or continuous. The results obtained from BEAMDES were tested against several example problems for both supported and continuous beams. It was found that the designs recommended by the system were similar to those of the examples. / Master of Science

A study was performed to compare the linear static analysis and concrete design capabilities of two structural analysis and design programs - MicasPlus and STAAD III. Four structures were considered including a four span continuous beam, a two story 3-D frame, a seven story 3-D frame, and a fourteen story 3-D frame. The study compared the accuracy of the programs as well as their functionality. In the evaluation of the accuracy of analysis results, factors such as support reactions, nodal displacements, and element end forces were compared. The evaluation of the concrete design capabilities was based on comparing the reinforcement recommended by the two programs for beams and columns. For beam design, steel reinforcing bar selections for positive moment, negative moment, and shear reinforcing were compared. For column design, the cross sectional area of steel chosen by each program was compared. Factors considered in the evaluation of functionality included: user interface, ease of use, ease of learning, quality of output, documentation, flexibility, and analysis and design capabilities. / Master of Science

This study has evaluated the degradation processes which will potentially affect the reinforced concrete structures of a nuclear power generation facility during and beyond its original design life. This task was undertaken in consideration of the feasibility of extending the life of nuclear power plants beyond their current license expiration dates. Following the identification of deterioration mechanisms which are expected to occur, an inspection system was developed to correctly assess and document the condition of the reinforced concrete components during their service life. Twenty-eight out of thirty-nine possible degradation modes are deemed likely to affect Surry’s reinforced concrete structures. The majority of these modes are visually evident in their incipient stages. Currently available nondestructive testing methods were assessed to determine their applicability to detect modes which are not visually evident or to determine the extent of deterioration due to other modes. It was found that many nondestructive testing methods are currently lacking in reliability, portability, or ease of application. Consequently, the developed inspection program is based primarily on visual inspections performed by qualified inspectors. This report was prepared under the authority of Virginia Power Company in conjunction with the Surry Unit One life extension study. It is the conclusion of this report that reinforced concrete degradation will in no way impair the usefulness or safety of the concrete structures of a nuclear facility during the 40 year design life provided actions are taken to implement a concrete inspection program similar to that which is described within. This program will allow the detection of potentially critical situations thereby directing the maintenance and repair activities necessary to insure the feasibility of extended life. / Master of Science

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / Introduction South Africa is currently experiencing a significant increase in infrastructure investment. Forecasts by BMI-BRSCU have shown that the building and construction industry is expected to grow considerably to 2010, before languishing slightly to 2015. This growth will be driven in particular by investment in non-residential building (41% growth) and construction (73% growth) activities. Even beyond 2015 however, the demand will still be high on the construction industry to provide infrastructure for South Africa’s growing population. South Africa is also facing a serious shortage of engineers, technicians and other skilled workers in the construction industry. This places high demands on designers and contractors to provide services and to realise projects in ever-reducing time periods and at less cost. These conditions have made it increasingly difficult to maintain the required quality of construction in an industry where mistakes can lead to disastrous consequences. Recent advances in structural materials, structural systems and the way in which projects are handled, now enables a new look at the possibilities of combining pre-fabrication with on site work. This method, known as Hybrid Concrete Construction (HCC), has the potential to revolutionize the South African construction industry if applied correctly. Local research into this technique is however required and it is the aim of this thesis to draw attention to this subject. Key Findings Hybrid Concrete Construction (HCC) can be applied to any structural project, it will however not necessarily be successful. A structure needs to be adapted from the very start to suit a particular construction method. This ensures that all the advantages of the selected construction method may be achieved. Adapting a structure to a different construction method requires a mutual understanding and commitment from all project participants, including the architect, engineer, contractor and client. HCC also requires a certain degree of repetition in a project to be financially viable. A theoretical cost exercise was performed where only the material and erection costs were considered. In this exercise, HCC was found to be slightly less expensive than other construction methods for the Office Building of more than 10 storeys. HCC was also found to be significantly faster than other construction methods for the Office Building of more than 3 storeys. The time calculation was however based on the simplified time estimates from one source. Because of HCC’s shorter estimated construction period, the client can expect to earn revenue from a much earlier date. This decreases the relative cost of a HCC project. This advantage, however, needs to be quantified for chosen South African projects. On-site safety is still an important issue with HCC projects. Labourers are not accustomed to this construction method and it may be necessary to alter current skill development programs to include a crane safety course. The training of qualified riggers and crane operators should receive priority if HCC is to develop in South Africa. This preliminary investigation has shown that Hybrid Concrete Construction (HCC) can be feasible for the South African market. Further investigation is however required to determine the parameters for which HCC would be the preferred construction method. Recommendations Based on the findings and conclusions of this investigation, the following recommendations are made. The following actions should be undertaken by individual South African companies: · Develop relationships with external project partners · Train competent riggers and crane operators The South African concrete industry should invest in the following actions: · Invest in mass-producing precast concrete facilities · Develop a central database of South African projects with information on time, costs, project concepts and layouts to be used as a guideline for decision making · Develop local guidelines for the production and application of self compacting concrete · Compile guidelines for the design and construction of HCC and precast concrete construction in South Africa · Develop a local hidden corbel type connection to its full potential

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Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Precast concrete has been used for decades in the construction industry, locally as well as internationally. Rapid urban development and the need for shorter construction periods for building and infrastructure projects have however encouraged more use of precast concrete construction. The improved speed of construction, high quality and less labour requirements that precast offers makes it an effective type of construction method for modern development. The utilization of various precast concrete systems has been frequently used in the international construction industry, making it a very popular construction method. It was however found that one of the major drawbacks or concerns with the use of precast concrete is the connections between the precast elements. In-situ construction does not have this problem, because it is designed to a monolithic structure or building. It was identified that if the connections in precast buildings or structures are designed or constructed in an insufficient way, it can lead to severe structural problems and even failure. This highlights the importance the design and construction of precast concrete connections have on the overall stability, strength and robustness of the structure. Precast concrete buildings are not merely separate precast elements, connected together to eventually form the same principals of in-situ construction. Precast concrete and connection design is considered to be a specialist field and requires the sufficient expertise and knowledge to understand the structural system and all its different aspects. The precast connection’s function is not merely to transfer loads, but also to develop continuity and ensure monolithic behaviour of the entire precast concrete structure (Englekirk 2003). The most important or desirable structural functions of precast connections are; (i) direct transfer of loads (load paths and flow or forces), (ii) develop structural continuity and integrity, (iii) distribution of concentrated loads, (iv) allow for movements and unintended restraints and lastly to (v) ensure efficient rigidity and robustness for the connection. It can be seen that there is many factors that contribute to the overall design and construction phases of precast concrete connections. The aim of this study is to identify and investigate aspects that influence the design and construction of precast concrete connections. This study will mainly focus on precast concrete and precast connection preferences of participants in the South African construction industry. During this study, industry participants (contractors and consultants) were asked to identify certain aspects and concerns associated with precast concrete and precast connection construction. These answers were used to develop guidelines and preferences that can be used by industry participants to improvise and effectively manage the precast construction, mainly focussing on the connections between the precast elements. / AFRIKAANSE OPSOMMING: Voorafvervaardigde beton word al vir dekades gebruik in die konstruksiebedryf, plaaslik sowel as internasionaal. Vinnige stedelike ontwikkeling en die behoefte vir korter konstruksie tydperke vir die struktuur en infrastruktuur projekte het egter die gebruik en implementasie van voorafvervaardigde beton konstruksie laat toeneem. Die verbeterde spoed van die konstruksie proses, 'n hoë gehalte produk en minder arbeid vereistes wat voorafvervaardiging bied maak dit dus 'n effektiewe tipe konstruksie metode vir moderne ontwikkelings. Die benutting van verskeie voorafvervaardigde beton sisteme en elemente word reeds herhaaldelik gebruik in die internasionale konstruksiebedryf, wat dit vervolglik ʼn baie populêre en effektiewe sisteem maak. Dit is egter bevind dat een van die groot struikelblokke of probleme met die gebruik van voorafvervaardigde beton is die verbindings tussen die voorafvervaardigde elemente. In-situ beton konstruksie het dus nie hierdie probleem nie, want dit word ontwerp om 'n monolitiese beton struktuur of gebou te vorm. Dit was immers geïdentifiseer dat as die verbindings in ʼn voorafvervaardigde gebou of struktuur, ontwerp word deur ʼn ontoereikende manier, dit kan lei tot ernstige strukturele probleme en selfs strukturele faling. Dit beklemtoon dus die belangrikheid wat die ontwerp en konstruksie proses van voorafvervaardigde beton verbindings het op die algehele stabiliteit, sterkte en robuustheid van die struktuur. Voorafvervaardigde beton geboue en strukture kan nie slegs beskou word as aparte voorafvervaardigde elemente wat met mekaar verbind word om eventueel dieselfde beginsels van insitu konstruksie te vorm nie. Voorafvervaardigde beton en verbinding ontwerp word beskou as 'n spesialis veld en vereis dat die ontwerper die nodige kundigheid en kennis van die strukturele stelsel en al sy verskillende aspekte verstaan. Voorafvervaardigde beton verbindings se funksie is nie net om toegepaste kragte oor te dra nie, maar ook om strukturele kontinuïteit te ontwikkel en te verseker dat monolitiese gedrag gehandhaaf word vir die hele voorafvervaardigde beton struktuur (Englekirk 2003). Die mees belangrike strukturele funksies van voorafvervaardigde beton verbindings sluit die volgende in; (i) verseker direkte oordrag van toegepaste kragte (vloei van kragte), (ii) ontwikkeling van strukturele kontinuïteit en integriteit, (iii) die verspreiding van puntbelastings, (iv) moet voorsiening maak vir die bewegings in die voorafvervaardigde element en konneksie self en laastens (v) verskaf doeltreffende rigiditeit en robuustheid vir die konneksie sone. Dus kan daar afgelei word dat daar baie faktore is wat bydra tot die algehele ontwerp en konstruksie fases van voorafvervaardigde beton verbindings. Die doel van hierdie studie is om aspekte te identifiseer en te ondersoek wat die ontwerp en konstruksie van aspekte beton verbindings wel beïnvloed. Die studie sal hoofsaaklik fokus op voorafvervaardigde beton en verbindings voorkeure van persone in die Suid-Afrikaanse konstruksiebedryf. Tydens die studie was persone in die industrie (kontrakteurs en konsultante) ook gevra om sekere aspekte en kwellings wat verband hou met voorafvervaardigde beton asook die verbindings te identifiseer. Die antwoorde wat verkry was uit die industrie deelnemers kan toepaslik gebruik om word riglyne en voorkeure op te stel wat vervolglik gebruik en toegepas kan word in die konstruksie bedryf van Suid Afrika. Die riglyne kan effektief gebruik word om voorafvervaardigde beton asook die verbindings te verbeter en persone in die konstruksie bedryf in te lig oor voorkeure en toepassings van hierdie metode.

The results of an experimental investigation are presented which examine the seismic adequacy of pre-1970 reinforced concrete (RC) corner beam-column joints and the efficacy of carbon fiber-reinforced polymer (CFRP) composites for both pre- and post-earthquake retrofit of such joints. Four full-scale corner beam-column-slab subassemblages built with identical dimensions and pre-1970 reinforcement details were subjected to a reverse-cycle bidirectional displacement history consisting of alternate and simultaneous cycles in the two primary frame directions before and/or after retrofit. Two of the specimens were first subjected to severe and moderate levels of damage, respectively, then repaired by epoxy injection, and strengthened by adding a #7 reinforcing bar within the clear cover at the column inside corner and by externally bonding multiple layers of carbon fabric to form a carbon-epoxy retrofit system. Two other specimens, one of which had a significantly lower concrete compressive strength, were strengthened in their as-built condition. The CFRP scheme was improved in light of the findings as the experimental program progressed. Pre-1970 RC corner beam-column joints were found to be severely inadequate in meeting seismic demands because of column bar yielding, joint shear failure, loss of anchorage of beam bottom bars, failure of column lap-splices, and the resulting loss of stiffness and strength that dominate their behavior even at relatively low interstory drift levels. Bidirectional loading played a significant role in such response. It was shown, however, that such joints can be strengthened easily both before and after earthquake damage by using CFRP composite schemes. Regardless of the level of existing damage and concrete strength, a "rigid" joint behavior up to interstory drift ratios of at least 2.4% and joint shear strength factors ranging from 1.06 to 1.41√MPa were achieved; such shear strength factors are larger than the value of 1.00√MPa recommended for use with seismically designed, code-conforming corner beam-column joints. A ductile beam hinging mechanism was achieved and energy dissipation capacity was improved efficiently for joints with concrete strengths ranging from 26 to 34 MPa. The subassemblage with significantly low-strength concrete (15 MPa) had low overall lateral stiffness and reduced reinforcement anchorages which prevented the formation of beam hinging. In cases of such low-strength concrete, more invasive operations may be required so that the improved joint shear strength can be mobilized. It is recommended that bidirectional loading be always considered in both pre- and post-retrofit evaluation of corner joints.

The purpose of this study was to evolve how to reduce the manifestation of poor decisions that always produce defects and rework. The purpose of the study is predicated on the fact that good decision-making is a fundamental element of improved project delivery in the construction industry. Such decisions determine the accomplishment of performance parameters in each project. However, suboptimal performance, which is pervasive in the construction industry, is often linked to team decisions. To remedy decision-making pitfalls, the concept of Choosing by Advantages (CBA) is promoted by lean construction researchers. CBA is a decision-making system that assists project parties in deciding a course of action among competing alternatives. Case study research design was used for this project to discover the decision-making process adopted by project teams. The results from the study achieved through cross-case analysis shows that concrete defects and rework is often caused by the project team’s decision-making process, which is influenced by the members of the project team because of lack of experience, poor working conditions, and lack of education. The results also show that the decision-making mechanism of the project teams is influenced by the construction method, specification, cost, quality and time. The outcome of the project team’s decision-making process when choosing a concrete type often causes the concrete defects and rework, which can be eliminated through the application of CBA when choosing a concrete type. The application of CBA when choosing concrete type from two alternatives, ready mixed concrete and site batched concrete is driven by the project team. It was discovered from all three cases that ready-mixed concrete had a better score than site-batched concrete when using CBA to compare these two alternatives. The results show that ready-mixed concrete had less chances of causing concrete defects and rework when used or applied per the correct specifications or methods which are detailed in the engineering drawings of the structure. The study proposes that the project team should adopt CBA to improve their decision-making process on site especially when working with concrete.