Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Structural design standards based on the principles of structural reliability are gaining worldwide acceptance and are fast becoming the new basis for structural safety verification. The application of these principles to establish a standardised basis for structural design using partial factor limit states design procedures is done in the European Standard for the Basis of Structural Design EN 1990 from which it is adapted to the South African Standard Basis of Design for Building and Industrial Structures SANS 10160-1. South Africa (SA) is on the advent of adopting the European Concrete Design Standard EN 1992-1-1 (EC2) as the equivalent standard for local use. This investigation seeks to provide a transparent quantitative reliability basis for the SA’s adoption of EC2, as well as provide for its subsequent implementation under local conditions and practice. The investigation kicks-off with a critical review of the reliability framework for structural resistance. The review establishes the relationships between the key elements of the framework, shedding light on issues SA needs to consider as it adopts EC2. Important issues for SA to consider include (1) target levels of structural performance ( -values), (2) partial factors, (3) model uncertainties, and (4) quality control. Design for shear resistance was investigated in greater detail by comparison of EC2’s Variable Strut Inclination Method (VSIM) for stirrup design against alternative approaches, namely, (1) South Africa’s currently operational SANS 10100-1 procedure, and (2) the fib Model Code 2010 first Level of Approximation (LoA I) and fib LoA III, which are based on the Modified Compression Field Theory (MCFT). Unbiased capacity predictions from the MCFT-based sectional analysis Program Response-2000 (R2k) served as LoA IV best-estimate results during this assessment. Results of this investigation showed that EC2 offers higher capacity predictions in excess of 1 MPa of stirrup reinforcement, with significantly higher predictions in the range of 1 to 2 MPa. A reliability performance assessment was therefore commissioned to assess safety regimes in terms of achieved reliability across a parametric range of the amount of stirrup reinforcement (from 0.45 to 2.0 MPa). The First Order Reliability Method (FORM) was implemented as part of the reliability performance assessment of the EC2’s VSIM design procedure. The model uncertainty for shear resistance (stirrup failures) was characterised according to a database of published stirrupreinforced concrete beam shear tests. Three cases of the Model Factor for shear resistance were derived from the experimental database for alternative shear resistance prediction models; two of which formed part of basic investigations conducted using the conventionally formulated performance function, and the other was integrated as part of an independent validation procedure using R2k predictions to obtain the reliability model. Results obtained from the basic reliability model ( -values) generally indicated lower levels of reliability with an increase in stirrup reinforcement and concrete strength, compared to those estimated from the R2k-based reliability model ( -values). The disparity between and -values revealed that systematic effects affect each model’s ability to predict the expected value of true shear resistance . There is reasonable evidence to suggest that the predictions of can be improved by accounting for each model’s peculiar sensitivity to concrete strength, consequently providing more representative estimates of . However, in the interim, and -values, respectively, represent reasonable lower and upper bound estimates of the performance of EC2’s VSIM design procedure. / AFRIKAANSE OPSOMMING: Die beginsels van struktuur betroubaarheid word wêreldwyd aanvaar as basis vir struktuur ontwerp standaarde en die versekering van voldoende struktuur veiligheid. Hierdie beginsels word in die Europese Standaard Basis of Structural Design EN 1990 toegepas om gestandaardiseerde partiële faktor gebaseerde limietstaat ontwerp prosedures daar te stel, van waar dit aangepas is vir die Suid-Afrikaanse Standaard Basis of Design for Building and Industrial Structures SANS 10160-1. Suid-Afrika (SA) staan op die punt om die Europese beton ontwerp standaard EN 1992-1-1 (EC2) aan te neem as die ekwivalente standaard vir plaaslike gebruik. Hierdie ondersoek het as doel om ‘n deursigtige kwantitatiewe betroubaarheidsbasis daar te stel vir die aanneming van EC2 as SA standaard en om voorsiening te maak vir die implementering daarvan onder plaaslike toestande en –praktyk. Die ondersoek begin met ‘n kritiese oorsig van die betroubaarheidsraamwerk vir strukturele weerstand. Die oorsig stel die verhouding vas tussen sleutel elemente van die raamwerk en werp lig op aspekte wat SA moet oorweeg in die aanneming van EC2. Belangrike aspekte vir oorweging sluit (1) teiken betroubaarheidsvlakke vir struktuur gedrag ( -waardes), (2) partiele faktore, (3) model onsekerhede en (4) kwaliteitsbeheer in. Skuif weerstandsontwerp is in groter detail ondersoek deur die EC2 se Veranderbare Stut Hoek Metode (VSHM) vir skuifbeuel ontwerp te vergelyk met alternatiewe benaderings, naamlik, (1) Suid Afrika se huidig operasionele SANS 10100-1 prosedure, (2) fib Model Code 2010 se sogenaamde eerste Vlak van Benadering (VvB I) en fib VvB III, gebaseer op die Aangepaste Drukveld Teorie (ADT). Onbevooroordeelde kapasiteit voorspellings van die ADT-gebaseerde snit analise program “Response-2000 (R2k)” is in die evaluering gebruik as VvB IV bes benaderde resultate. Die ondersoek toon dat EC2 hoër kapasiteit voorspel vir skuifbeuel bewapening tot 1 MPa en beduidend hoër kapasiteite voorspel vir skuifbeuel bewapening tussen 1 en 2 MPa. ‘n Betroubaarheidsprestasie studie is vervolgens geloots om die veiligheid in terme van behaalde betroubaarheid te bepaal oor ‘n parametriese bereik van 0.45 tot 2.0 MPa skuifbeuel bewapening. Die Eerste Orde Betroubaarheids Metode (EOBM) is implementeer as deel van die betroubaarheidsprestasie beoordeling van die EC2 VSHM ontwerp prosedure. ‘n Databasis van gepubliseerde skuifbeuel-bewapende betonbalk skuiftoetse is gebruik om die model onsekerheid vir die verskillende skuifweerstandsmodelle statisties te beskryf. Drie Model Faktore is uit die eksperimentele databasis afgelei, twee waarvan gebruik is in basiese ondersoeke met die konvensioneel geformuleerde prestasie funksie en die derde as deel van ‘n onafhanklike bevestigingsprosedure gebaseer op R2k voorspellings. Resultate wat verkry is uit die basiese betroubaarheidsmodel ( -waardes) was laer (meer konserwatief), en het ook vinniger afgeneem met ‘n toename in skuifbeuel bewapening as die waardes wat uit die R2k-gebaseerde betroubaarheidsmodel ( -waardes) verkry is. Die verskil tussen β en β -waardes toon dat sistematiese effekte die vermoë van elk van die modelle beïnvloed om die verwagte waarde van die werklike skuifweerstand V te voorspel. Daar is redelike bewyse om aan te voer dat die voorspellings van V verbeter sal kan word deur elke model se unieke sensitiwiteit teenoor betonsterkte in ag te neem, om sodoende meer verteenwoordigende β waardes te verkry. Intussen verteenwoodig die β en β -waardes onderskeidelik redelike onder- en bogrens skattings vir die prestasie van EC2 se VSHM ontwerp prosedure.

<p>The strut-and-tie method (STM) is a powerful tool used for the design of D-regions (disturbed regions) of reinforced concrete structures. Many typical bridge substructure components consist of D-regions and require the use of the STM for design. Implementation of the STM is more complex than typical design methods, and engineers are often unfamiliar with the design process. As a result, designing using the STM is more time consuming than traditional design methods. The Indiana Department of Transportation (INDOT) identified a need for a tool that assists with the design of typical bridge substructure components using the STM. STEP (Strut-and-Tie Evaluation Program) is a computer program created to fulfill this role. To use the computer program, engineers input geometric conditions, material properties, and reinforcement information for a structural component. STEP uses this information to develop a strut-and-tie model and perform STM design procedures. A graphical representation of the model and a summary of the design results are provided as program outputs for the user.</p> <p> </p> <p>STEP, created using Excel VBA, is intended to aid in the design of multi-column bent caps and integral and semi-integral end bent caps. Within this thesis, an overview of the STM is provided, including the basic procedures for designing using the STM. An introduction to Excel VBA is also presented. The document describes the layout and formatting of the computer program, required user inputs, and program outputs. Furthermore, limitations and assumptions within the computer program for the substructure components are also included. Finally, design examples focused on the use of STEP for the design of a five-column bent cap and an integral end bent cap are presented. This document can be used as a resource for engineers when designing bridge substructure components using STEP. </p>

This study presents and illustrates a methodology to calculate the capacity of an existing reinforced concrete bridge under a non-conventional blast load due to low and intermediate pressures. ATBlast program is used to calculate the blast loads for known values of charge weight and stand off distance. An excel spreadsheet is generated to calculate ultimate resistance, equivalent elastic stiffness, equivalent elastic deflection, natural period of the beam, the maximum deflection, and the maximum rotation in the support for a simple span solid slab and T-Beam bridges. The allowable rotation could be taken as to two degrees. Naval Facility Engineering Command (NAVFAC) approach was adopted, where the inputs were material properties, span length, and area of reinforcement. The use of the Fiber Reinforced Polymer for increasing the capacity of an existing bridge is also presented in this study. Parametric studies were carried out to evaluate the performance of the solid slab and T-Beam bridges under the assumed blast load. / by Firas A. Abdelahad. / Thesis (M.S.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, FL : 2008 Mode of access: World Wide Web.

This thesis investigates the behaviour of hollow and concrete filled steel columns fabricated from thin steel plates. The columns are investigated under axial, uniaxial and biaxial loading. The currently available international standards for composite structures are limited to the design of concrete filled steel columns with compact sections and yield stress of steel up to 460 N/mm2. This thesis consists of both experimental and analytical studies and design recommendations for future use. Three comprehensive series of experimental tests are conducted on hollow and concrete filled steel columns. The principal parameters that have been considered in the test programmes are the slenderness of the component plates, the yield stress of the steel and the loading conditions. In the first test series, three slender hollow steel columns and three slender composite columns are tested under uniaxial loading. The steel utilised is mild steel. High strength steel is utilised in the second test programme. In this test series four stub columns, eight short columns and eight slender columns are tested, each set consists of four hollow and four composite columns. Short columns are tested under axial loading to investigate the confinement effect provided by the steel casing. Slender columns are tested under uniaxial loading to investigate the coupled instability of local and global buckling. The third test programme is quite novel and considers the behaviour of hollow and concrete filled steel columns fabricated with high strength structural steel plate and subjected to biaxial bending. In this test eight short columns and ten slender columns each of them consisting of hollow and composite columns are investigated under biaxial loading. Analytical models are developed herein to elucidate the behaviour of the hollow and composite columns considering cross section slenderness, yield stress and loading conditions. An iterative model considering the coupled global and local buckling in the elastic and plastic range incorporating material nonlinearities is developed to investigate the behaviour of slender columns fabricated from mild steel. An improved deformation control model is developed to investigate the behaviour of slender high strength steel columns considering the confinement effect and local and post-local buckling in the elastic and plastic range. Then a numerical model for biaxial bending is developed to study the behaviour of short and slender concrete filled high strength steel columns under biaxial loading incorporating interaction buckling considering material and geometric nonlinearities. The scope of the thesis presents a wide range of experimental and theoretical studies of an extremely novel nature. It demonstrates the benefit of confinement and the consideration of local and post-local buckling in the elastic and plastic range. It is hoped that this research will contribute to the area of composite steel-concrete structural applications.

Self compacting concrete (SCC) is first developed in Japan in the late 1980s in order to overcome the consolidation problems associated with the presence of congested reinforcement. It is also termed as a high performance concrete, as it can flow under its own weight and completely fill the formworks. As the fresh properties of SCC are quite important, mix design of a SCC is performed by considering various workability related fresh properties. Therefore, a well designed SCC should satisfy all requirements of a hardened concrete, besides its superior workability properties. The aim of this research is to assess the effects of some basic ingredients of SCC on the fresh properties of SCC. This will be performed by applying design of experiment techniques and obtaining significant statistical models, which will give valuable information about the effects of the model parameters on the rheology and fresh state characteristics of SCC. In this research program, four different variables / use of fly ash replacement, use of high range water reducing admixture (HRWRA), use of viscosity modifying admixtures (VMA) and water-cementitious material ratio, are considered as the variables of the experimental design. Central Composite Design (CCD), a design of experiment technique, is employed throughout the experimental program and a total of 21 mixtures of concrete are cast. Slump flow, V-funnel, L-box, sieve segregation, initial and final setting time tests are performed, furthermore / to investigate the effects of these variables to the rheology of SCC, relative plastic viscosity and relative yield stress, which are the parameters of Bingham Model are measured with the help of a concrete rheometer. As a result of the experimental program, the fresh state properties of SCC are expressed by mathematical equations. Those equations are then used in order to explain the effects of fly ash replacement, HRWRA and VMA concentration, and the w/cm ratio on the fresh state properties of SCC. According to the derived models, it is stated that the water-cementitious material ratio of the concrete mixture is the most effective parameter on the flowability and passing ability of SCC beside the other parameters utilized in this research as its coefficient was the highest in the related models.

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The aim of this study was to investigate the quantifiable planimetric design efficiency of residential buildings designed to be built with &amp / #147 / Autoclaved &AElig / rated Concrete&amp / #148 / (AAC) panels. Focus was on the effects of plan shape, plan size and layout organization and the modularity of vertical AAC wall panels on the planimetric design efficiency of residential buildings. To this end, relevant analyses were conducted on 30 residential building projects obtained from the design office of an AAC panel manufacturing firm in T&uuml / rkiye, AKG Gazbeton. The lengths, widths and areas of building elements (quantitative data) were then calculated from the production drawings of these building. A total of fifteen ratios, which were considered relevant to the study as indicators of design efficiency, were computed by using this quantitative data. This was followed by the construction of frequency distribution tables and histograms showing the variations of the computed ratios. At the final phase, Analyses of Variance (ANOVA) were conducted to determine the source of variation and Chi-Square tests conducted to determine whether or not the distributions could be considered &amp / #145 / normal&amp / #146 / . According to the results of the study, it was found that plan shape and plan size of building projects together with their layout organizations, were the main influential factors on the efficiency of their wall and floor areas. It was also found that the modularity of vertical wall panels used in these buildings was another important factor to be considered in planimetric design efficiency.

This thesis investigates the behaviour of hollow and concrete filled steel columns fabricated from thin steel plates. The columns are investigated under axial, uniaxial and biaxial loading. The currently available international standards for composite structures are limited to the design of concrete filled steel columns with compact sections and yield stress of steel up to 460 N/mm2. This thesis consists of both experimental and analytical studies and design recommendations for future use. Three comprehensive series of experimental tests are conducted on hollow and concrete filled steel columns. The principal parameters that have been considered in the test programmes are the slenderness of the component plates, the yield stress of the steel and the loading conditions. In the first test series, three slender hollow steel columns and three slender composite columns are tested under uniaxial loading. The steel utilised is mild steel. High strength steel is utilised in the second test programme. In this test series four stub columns, eight short columns and eight slender columns are tested, each set consists of four hollow and four composite columns. Short columns are tested under axial loading to investigate the confinement effect provided by the steel casing. Slender columns are tested under uniaxial loading to investigate the coupled instability of local and global buckling. The third test programme is quite novel and considers the behaviour of hollow and concrete filled steel columns fabricated with high strength structural steel plate and subjected to biaxial bending. In this test eight short columns and ten slender columns each of them consisting of hollow and composite columns are investigated under biaxial loading. Analytical models are developed herein to elucidate the behaviour of the hollow and composite columns considering cross section slenderness, yield stress and loading conditions. An iterative model considering the coupled global and local buckling in the elastic and plastic range incorporating material nonlinearities is developed to investigate the behaviour of slender columns fabricated from mild steel. An improved deformation control model is developed to investigate the behaviour of slender high strength steel columns considering the confinement effect and local and post-local buckling in the elastic and plastic range. Then a numerical model for biaxial bending is developed to study the behaviour of short and slender concrete filled high strength steel columns under biaxial loading incorporating interaction buckling considering material and geometric nonlinearities. The scope of the thesis presents a wide range of experimental and theoretical studies of an extremely novel nature. It demonstrates the benefit of confinement and the consideration of local and post-local buckling in the elastic and plastic range. It is hoped that this research will contribute to the area of composite steel-concrete structural applications.

No description available.