The effect of length on stress-wave velocity in long pieces of Salzmann pine from existing structures.
Abstract
The use of non-destructive techniques (NDT) to estimate physical-mechanical timber properties is an effective way of assessing and conservation of built heritage. Some research works have applied NDTs in different species with different piece's dimensions and have showed good correlations between timber properties and the Time-of-Flight (ToF) with portable stress-wave devices. Nevertheless, there are certain parameters that need to be studied deeper, such as the effect of the pieces' dimensions on the ToF estimation. Usually, timber structures of existing buildings in Spain present large cross-section pieces as well as a cross-section variation along the piece. Frequently, in-situ assessments accessibility to structural members is complicated and measurements may only be made on 1 or 2 surfaces of the piece. The test material used in this research study consisted of 21 structural timber pieces (rafters) with 150x200 mm2 in average cross-section and 9.53 to 11.00 m in length of Salzmann pine species (Pinus nigra Arnold ssp. salzmannii (Dunal) Franco). The material comes from an existing structure built in 1768 (Royal Coliseum of Charles III in Aranjuez, Madrid, Spain).In this work, the ToF has been obtained from end to end and in different lengths ranging from 0.5 to 10.5 m at one edge of the piece and also their corresponding transmission velocities. In addition, stress velocity has been determined based on both the ToF corrected with time lag and the ToF in intermediate sections to avoid the local effect of the initial wave path.