Methods for measuring and modeling the process of prestressing concrete during tensioning/detensioning based on electronic distance measurements

摘要

Methods are disclosed for nondestructive testing and measuring the structural health of prestressed concrete structures, such as slabs, columns, girders, bridges, towers, elevated storage tanks, silos, cooling towers, wind power generation towers, liquefied gas storage tanks, nuclear power containment buildings, and the like. Measurements are made as the structure undergoes tensioning and detensioning operations. By measuring actual movements of cardinal points on the structure, in an absolute three-dimensional coordinate system, and comparing the measurements to a model—as tension on a tendon is changed—a margin of safety is assured. High accuracy measurements are made by electronic distance measurement (EDM) instruments over hundreds of meters, which yield coordinates of cardinal points with an uncertainty of the order of one part per million. The methods are proposed as possible alternatives to prior failures of post-tensioned concrete, including the Las Lomas Bridge, the Kapiolani Interchange On-Ramp, Turkey Point Unit 3 Nuclear Power Plant, and Crystal River Unit 3 Nuclear Power Plant. An extensive review of the most closely related prior arts is included.

主权项

1. A method for post-tensioning a concrete structure with steps comprising:
(a) programming a finite element model of the concrete structure, which when executed by a processor predicts coordinates of a plurality of points on the concrete structure as a function of a plurality of tensions applied to a corresponding plurality of tendons within the concrete structure; (b) developing a post-tensioning plan for applying the plurality of tensions, wherein the post-tensioning plan is a written document that specifies an order in which the plurality of tendons are tensioned and a tensioning force to be applied to each of the plurality of tendons; (c) identifying a plurality of cardinal points from the plurality of points on the concrete structure, wherein the identifying is based at least in part on the finite element model, the post-tensioning plan, the predicted coordinates of the plurality of cardinal points, and engineering experience; (d) attaching a plurality of retroreflectors to the concrete structure at locations corresponding to the plurality of cardinal points; (e) measuring at least a first range from a first electronic distance measurement instrument to a first cardinal point, a second range from a second electronic distance measurement instrument to the first cardinal point, and a third range from a third electronic distance measurement instrument to the first cardinal point, wherein
the first electronic distance measurement instrument is at a first location, the second electronic distance measurement instrument is at a second location, the third electronic distance measurement instrument is at a third location, andthe first location, the second location, and the third location are three different locations; (f) storing at least the first, second, and third ranges; (g) computing a first three-dimensional coordinate of the first cardinal point, based at least in part on the first, second, and third ranges; (h) applying a first tensioning force to a first of the plurality of tendons as specified by the post-tensioning plan; (i) measuring at least a fourth range from the first electronic distance measurement instrument to the first cardinal point, a fifth range from the second electronic distance measurement instrument to the first cardinal point, and a sixth range from the third electronic distance measurement instrument to the first cardinal point; (j) storing the fourth, fifth, and sixth ranges; (k) computing a second three-dimensional coordinate of the first cardinal point, based at least in part on the fourth, fifth, and sixth ranges; (l) modifying the post-tensioning plan based at least in part on the finite element model, the applied first tensioning force, the first three-dimensional coordinate, the second three-dimensional coordinate, and the engineering experience; and (m) applying a second tensing force to a second of the plurality of tendons as specified by the modified post-tensioning plan.