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This title provides an assessment of pre-stressed concrete, unbonded tendons, properties of materials, losses in pre-stress, suitable types of structures, design of floor and roof slabs of buildings using unbonded tendons, design of other structures using unbonded tendons, work on site and post-tensioning systems.
Abstract: Post-tensioning concrete technology increases the resistance of flexural concrete members. This technology allows for the production of slenderer sections, and sequentially less usage of material preserving the sustainability concept in construction engineering. Post-tensioning process can be done using bonded or unbonded steel tendons. The unbonded tendons are thought to have better resistance to corrosion for structures exposed to severe environmental conditions. The unbonded tendon's steel strands are painted with grease and covered with plastic sheathing to prevent the moisture from reaching the steel strands thus they can provide high corrosion resistance. According to the ACI 318-19 and other codes of practice, the stress in the unbonded tendon at the ultimate limit state is limited to less than or equal to the tendon's yield stress. On the other hand, the bonded tendon's stress at this state is determined to be more than or equal to the tendon's yield stress. This limitation for the unbonded tendons restrained the widespread usage of the unbonded system. Through this research, six-simply supported one-way slabs; two with bonded tendons, two with unbonded tendons and two with unbonded tendons and non-prestressing steel reinforcement are tested in flexure to failure. The post-tension slabs are of 4.0-meters in span and the flexural tests are carried in the AUC structural engineering laboratory in a four-point loading scheme. The ultimate stress of the unbonded tendons are measured at the failure stage. The results of both systems are compared against each other and against the provisions of the ACI 318-19. The unbonded post-tension slabs with non-prestressing steel reinforcement showed higher failure loads than the bonded and unbonded slabs without reinforcement. The ACI 318-19 provisions were critically reviewed versus the results of the experimental investigation. The review reveals that the limitation of the unbonded tendon's ultimate stress is not accurate and can be reviewed.
Prestressed concrete is widely used in the construction industry in buildings, bridges, and other structures. The new edition of this book provides up-to-date guidance on the detailed design of prestressed concrete structures according to the provisions of the latest preliminary version of Eurocode 2: Design of Concrete Structures, DD ENV 1992-1-1: 1992. The emphasis throughout is on design - the problem of providing a structure to fulfil a given purpose - but fundamental concepts are also described in detail. All major topics are dealt with, including prestressed flat slabs, an important and growing application in the design of buildings. The text is illustrated throughout with worked examples and problems for further study. Examples are given of computer spreadsheets for typical design calculations. Prestressed Concrete Design will be a valuable guide to practising engineers, students and research workers.
The book combines history with academic notes for use at the university level, presenting design examples from actual jobs with applications and detailing for the practicing engineer. Chapter 1 tells the history of post-tensioned concrete as only Ken Bondy can tell it. Chapters 2-8 are the notes Dirk Bondy uses to teach Design of Prestressed Concrete Structures at UCLA and Cal Poly-San Luis Obispo. Chapters 9-13 are design examples that address many of the decisions faced by practicing engineers on typical projects. Chapters 13-14 cover the art of detailing and observing the construction of post-tensioned concrete. This knowledge was obtained over many years of working on our own projects and listening and learning from the the pioneers of post-tensioned concrete. Chapter 15 covers the slab on grade industry, which represents more sales of post-tensioning tendons than all other post-tensioning applications combined. Chapter 16 discusses the challenging application of post-tensioning-external post-tensioning.