Materials Performance

OCT 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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OCTOBER 2018 MATERIALSPERFORMANCE: VOL. 57, NO. 10 41 the maintenance plan will need to be customized and the inherent value of the plan communicated to the owner. Service Life Analysis, Life Cycle Costing, and Asset Management ACI 365.1R 6 describes three types of service life: Technical, Functional, and Economic. Technical service life is the time in service until a defined unac- ceptable state is reached, such as spalling of concrete, unacceptable safety level, or failure of elements. Examples of the technical end of service life include (a) structural safety is unacceptable due to material degradation or exceeding the design load-carrying capacity, (b) severe material degrada- tion, such as extensive corrosion of steel reinforcement, and (c) excessive deflection under service load due to decreased stiffness. Functional service life is the time in service until the structure no longer fulfills the functional requirements or becomes obsolete due to change in functional requirements. Examples include (a) the need for increased clearance, higher axle and wheel loads, or road widening, (b) aesthetics become unacceptable—for example, excessive corrosion staining, and (c) functional capacity of the structure is no longer sufficient—for example, a football stadium with insufficient seating capacity. Economic service life is the time in service until replacement of the structure or part of it is more eco- nomical than keeping it in service. Examples include (a) maintenance requirements exceed available resource limits, and (b) replacement to improve economic opportunities—for example, replacing an existing parking garage with a larger one due to increased demand. If one is considering the service life of a concrete sidewalk, it is replaced when it becomes aesthetically unpleasing, uneven, or sufficiently rough to become a tripping hazard. If one is considering the service life of a concrete nuclear reactor containment vessel, the considerations for service life opti- mization become much more critical. Designing the concrete structures for optimum service life involve many factors such as the concrete quality, the service environment, the attention to detailing, and the protective systems employed. Consideration of the tradeoffs between initial cost, inspection, monitoring, maintenance, downtime, and decommissioning over the service life of the structure is one description of life cycle costing where having a higher initial cost with lower maintenance costs is compared to other alter- natives. Asset management is consideration of the life cycle costs of the components of a system such as treatment and distribution of a municipal water system including the intake of raw water, treatment to make it pota- ble, delivery to points of usage, and treatment of the waste water, all of which include many individual com- ponents of machinery, pipelines, etc. Service life analysis, life cycle cost- ing, and asset management will con- tinue to expand in complexity and usage to address corrosion-related issues. Maintenance Incorporated into BIM Building Information Modeling (BIM) is a process involving the generation and management of digital represen- tations of physical and functional characteristics of construction and is rapidly being accepted as a tool for construction design, scheduling, pro- curement, and management. In BIM, a three-dimensional model is devel- oped of the structure and construc- tion sequence overlaid to avoid time conflicts (a fourth dimension) and optimize costs (a fifth dimension). BIM also covers spatial relationships, light analysis, geographic information, and the quantities and properties of building components (for example, manufacturers' details). A logical extension of BIM is to also include the asset management and deconstruction of the structure throughout the building's service life. Combining all these properties into a model reduction of corrosion issues is a natural consequence, such as through improved detailing, better water management, and service life modeling.

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