Applications of absolute extrinsic Fabry-Perot interferometer (EFPI) fiber optic sensing system for measurement of strain in pre-tensioned tendons for prestrained concrete

摘要

Abstract: The application of a state-of-the-art fiber opticsensing system for the quantitative analysis of strainin strands used in prestressed concrete is proposed.Compressive stress in concrete is used tocounterbalance any tensile force due to loading, whichmight lead to cracking or deflection. In pre-tensioningprestressed concrete, a tendon is tensioned beforeconcrete is placed and the prestress is transferred tothe concrete after it has cured by releasing thetension on the tendon. In linear prestressing it isoften required to determine the axial strain on thetendon during the initial procedure of pre-tensioning,so that the required longitudinal force to achievemaximum concrete strength, can be accuratelydetermined. Conventional techniques for this purposeinvolve the use of conventional foil strain gages,which are not only expensive to use, but are also knownfor their failure rate in high strain environments. Wediscuss the absolute extrinsic Fabry-Perotinterferometer (AEFPI) fiber optic sensing system formonitoring strain in pretensioned tendons while thistendon is being loaded. The experiments performed atthe Turner Fairbanks Federal Highway Administration atMcLean, Virginia exhibit the survivability of the EFPIsensor at strain in excess of 12,000 $mu$epsilon whilebeing attached to the tendon surface. The results arecompared to those obtained from a collocated foilstrain gage and excellent correlation is obtained.Applications of the AEFPI system to high performancesmart materials and structures are analyzed and futurework in this area is discussed. !9