New ACI 533 guide on general design and construction aspects of precast concrete tunnel segments

American Concrete Institute (ACI) is aiming to publish its first guide (ACI 533.2R) on general aspects of precast tunnel segments. This paper presents salient features of the guide including the most recent developments on major aspects of design, manufacturing and construction. This document is drafted based on the knowledge and the experience gained on projects in Asia, Europe, and North America, and available national and international recommendations. Procedures to perform structural design during production, transportation, construction and final service stages are explained. Details of segmental ring geometry and systems, concrete strength, curing, and reinforcement detailing are discussed. Gasket design, segment connection devices, anchorage systems, tolerances, measurement and dimensional control, and repair of defects are among other topics that are covered. This document also addresses durability and degradation mechanisms of tunnel linings and their mitigation methods. While some parts of this guide may only consider the procedures adopted by ACI, they can be extended to other national and international codes and used worldwide.