Determining the strained state of structures by using the optical fiber monitoring system through the example of transport infrastructure facilities

Purpose This paper is concerned with the development and validation of an ingenious model of the optical fiber monitoring and diagnostics system for long structural elements of buildings and structures, whose accuracy and high-speed response parameters enable its use at transport infrastructure facilities being under alternate live load with different frequencies of both their own and constrained oscillations.The proposed solutions undergo testing by using simulation modeling and numerical analytic solutions to structural element straining problems according to the rules of deformed rigid body mechanics. For the linearization of sought-for functional dependences in defining equations and their subsequent solution, a numerical method is proposed that allows selecting an approximation interval subject to the curvature parameter and points of inflection location. Design/methodology/approach As tools for achieving the purpose in hand and solving the accompanying problems, the following is used: the radial method for presenting unknown displacement functions in the defining equations system as power series sections by time and spatial coordinate; the numerical method for functional dependence linearization; simulation modeling methods for receiving numerical results of determining displacement at structure points. Findings The pursued study shows that the use of the proposed optical fiber monitoring and diagnostics system while monitoring and diagnosing the state of long beam elements of buildings and structures, including a railway track in major traffic arteries, will make it possible to opportunely reveal and detect component deterioration, emergence and further development of a wide range of defects and deviations from the design position, assess the operation of the major nodes of beams or columns, system internal damping, stationary and nonstationary straining processes. Originality/value The developed approach based on the aggregation of the possibilities of optical fiber monitoring systems, equations defining the dynamic behavior of rods and beams when exposed to external actions, radial method for presenting unknown values as power series sections, numerical method for sought-for function linearization in time intervals whose values depend on the curvature parameters enables to determine the strain-stress state of real structures and elements and also tune up the monitoring system by means of simulation modeling in the computing environment before it is actually installed at the construction facility. A comparative analysis of the results received in the course of defining equations solution, simulation modeling of the operation of the proposed monitoring system and full-scale experiment shows a good agreement between the numerical results and the opportunity for multifactor monitoring implementation in any conditions of buildings and structures operation.