In-situ load testing of a WWII era timber Warren truss in the development of a structural health monitoring program.

• Confirming in-situ Structural Health Monitoring instruments are in working order. • Determine the in-situ properties of timber in real service conditions. • 3D, bimodular, orthotropic numerical model of a timber Warren truss structure. • Local in-situ load testing of a full-scale, heritage timber structure. • Identification of load and stress reversal within select timber members. This research paper presents the experimental results of an in-situ load-testing program within a WWII era, timber Warren truss structure located at Canadian Forces Base St-Jean, Quebec. Four point load tests were carried out on a 68 m long, Douglas fir timber truss instrumented with conventional electric strain gauges, distributed fibre optic sensors, and string potentiometers, among other instruments. These instruments makeup a larger, long-term structural health monitoring program implemented within the truss structure. The objectives of the local point load tests were to (1) confirm the in-situ monitoring instruments are in working order, (2) compare calculated mechanical properties with assumed properties, and (3) calibrate a numerical model capable of replicating truss response and compare to current modeling standards used within the Department of National Defence. Non-destructive testing, including moisture content and cable tension tests, was also conducted to determine existing material properties. Load testing and non-destructive testing results identified variations between the existing properties of the truss and the assumed properties of certain structural members, as well as identifying possible lower strength or stiffness values of stress-reversed members. Results also indicated the importance of analyzing timber as an orthotropic, bimodular material for reliability and conservatism, particularly in numerical modeling. Lastly, the results presented in this paper outline the importance of in-situ load testing with an aim to determine existing material properties for monitoring projects. Moreover, the identification of the existing properties and behaviour of the structure is fundamental in the development of a structural health monitoring program for emergency purposes. [ABSTRACT FROM AUTHOR]