THESIS ON CRITICAL EVALUATION OF ETHIOPIAN BUILDING CODE STANDARD 2

Abstract

Design of a concrete structure is a step by procedure beginning with estimation of the loads acting on the structural system, preliminary proportioning of relative stiffness’s of the structural system, carrying out a detailed and often iterative general structural analysis, followed by the sizing or proportioning of the members and concluding with the detailing process. While engineers are usually well trained in analysis procedures and the basic mechanics of structural concrete, there is not a general methodology for detailing. This often presents the designer with numerous difficulties. The different codes and standards propose empirical recommendations for some specific applications. However the design standards cannot include the innumerable details that may arise. Structural design and construction has the objective to build safe durable, serviceable, economical and aesthetic structures. The translation of design into correspondingly high quality structure necessitates good detailing and construction practices. The limit state method design primary aim is to minimize the probability of failure to an acceptable low value. In this context attainment of limit state is called failure. Limit states imply those conditions where by a structure ceases to fulfill the functions for which it has been designed. By using limit states method (allowing for inelasticity and moment redistribution) with partial safety factors, with higher strength materials, for higher stresses, modern structures are designed. And also methods of analysis and design have become more sophisticated and accurate and the benefit of conservation in built in approximate methods is no longer available. Therefore these results in taller structures and longer spans more slender members and thinner slabs and walls and are built at faster pace. They are therefore more flexible (in terms of deflections) and are more crack prone as compared with the old structures which used to be low in height had thicker(stockier) members were lightly stressed and were built at slower place. Thus serviceability criteria assume for greater importance in modern structures. As a result of the introduction of limit state method of design for reinforced 15 concrete structures and the concept of development length has become extremely important as many of the design requirements are to be met through detailing. The design and building processes would subjected to substantial impact from construction details. Also it affects concrete structure durability and maintenance. Around concrete structures the problems arising are attributable to design stage and due to lack of or errors in construction details. Their share is 50% and 50%. Knowledge in four areas synthesized for good detailing: 1) Knowledge on structural concrete engineering underlying theory 2) Professional practice in on-site. 3) Laboratory trials information from experiments. 4) Forensic engineering studies experience. Detailing practices, construction practices, quality control in construction, building failures causes and prevention of cracks/leakage in buildings etc. are all large enough topics. Not all these topics strictly within the scope of this book (Detailing manual). As such an attempt is made here only to draw attention to some of the major and most common causes of failure pertaining to the design(and construction) of reinforced concrete buildings. In Detailing generally included are the properties of single and bundled bars, selection of beam reinforcement, and crack control requirements, development length of bars and minimum radii of bends. Therefore this book will be useful to concrete design engineers, field engineers and students of civil engineers