Reliability assessment of structural concrete with special reference to shear resistance

[摘要] ENGLISH ABSTRACT: Structural design standards based on the principles of structural reliability are gainingworldwide acceptance and are fast becoming the new basis of structural safety verification.The application of these principles to establish a standardised basis for structural design usingpartial factor limit states design procedures is done in the European Standard for the Basis ofStructural Design EN 1990 from which it is adapted to the South African Basis of DesignStandard for Building and Industrial Structures SANS 10160-1. The basis of designrequirements stipulated in EN 1990 and SANS 10160-1 apply to all aspects of structuraldesign: This includes reliability levels of structural performance and their differentiation andmanagement; identification of various limit states and design situations; the specification ofall the basic variables; separate treatment of actions and material-based resistance. However,application of these requirements is then primarily focused on actions whilst the provision forstructural concrete is then left to the materials based design standards.This two-part thesis describes a systematic assessment of the degree to which the applicationof the reliability framework presented in the basis of design requirements has been achievedin the present generation of structural concrete design standards. More importantly, attemptsare made to identify ways in which the process can be advanced. Special attention is drawnto issues that are specific to South African conditions and practice in structural concrete.Part One of the thesis focuses on the key elements of the reliability framework presented inEN 1990 and traces to what extent the requirements have been propelled through the designstipulations of the Eurocode Standard for Design of Concrete Structures EN 1992-1-1. Theimplications of the different reference level of reliability between the Eurocode default valueof ß = 3.8 and that characteristic of South African practice ß = 3.0 through various issuesare highlighted. The use and advantage of explicit treatment of reliability performance onreliability management related to some aspects of quality control are explored. A criticalaspect is the shear prediction model providing unconservative estimates of shear resistance.Part Two of the thesis focuses on characterising the model factor of the EN 1992-1-1 shearprediction model for members requiring design shear reinforcement. This is done by acomparison to a compiled experimental database with special focus on situations with highreinforcement ratios. The significance of the modelling uncertainty in shear prediction is verified by this comparison. The use of the more conceptually rational modified compressionfield theory (MCFT) to improve on the quality of shear predictions is investigated and provesto yield more precise values with lower scatter hence making it a more reliable tool forpredicting shear. The MCFT can then be used as reference for the reliability calibration andpossible improvement for the Eurocode procedure.

[发布机构] Stellenbosch University