GNGTS 2013 - Atti del 32° Convegno Nazionale

Branco and Araùjo, 2010, performed an experimental program on simple log specimens, in order to assess the magnitude of friction developed along two timber notches subjected to in-plane lateral loads. Their experiments resulted in a static friction coefficient equal to 0.66 (Coefficient of Variation CoV=8.4%) and 0.64 (CoV=12.8%) for log walls subjected respectively to a vertical pre-compression of 3kN and 3.9 kN. Further friction experiments, resulting in a friction static coefficient equal to 0.67, have also been performed by Hirai et al. (2004) on timber log walls tied with vertical pre-tightened through bolts. In general, contributions available in literature highlighted the importance of friction phenomena in the definition of the global stiffness of shear log walls subjected to in-plane lateral loads. Nevertheless, based on requirements of Eurocode 5, it should be noticed that friction cannot be considered as a resistant mechanism in timber log shear walls. In this context, 24 specimens have been tested at the Department of Engineering and Architecture of the University of Trieste, Italy. The typical specimen consists of three 0.60 m long typical timber logs subjected to a horizontal pre-compression introduced by means of four pretensioned steel bolts (Fig 3a). During the tests, in the estimation of the average static friction coefficient m, different values of imposed pre-compression V L (10 kN and 20 kN) and geometries (e.g. thickness of logs/number of notches) of timber logs were taken into account. In particular, 12 tests have been performed on ‘Tirol’ 0.09 0.16 m 2 logs, whereas further 12 tests have been performed on ‘Schweiz’ 0.13 0.16 m 2 timber logs currently produced by Rubner Haus. In each test, after the application of the horizontal pre-compression to the specimens, the middle log was subjected to a vertical increasing force, and the corresponding vertical slip was measured. Fig. 3 – a) Experimental setup for static frictional tests performed on simple Blockhaus beam specimens; b) compressive behavior of ‘Standard’ joints. Failure mechanism; c) overview of ABAQUS/Standard numerical model; d) comparisons between S01 full-scale monotonic test results and ABAQUS/Standard simulations. 26 GNGTS 2013 S essione 2.1