David Bertrand

Experimental analysis of the response of fresh wood stems subjected to localized impact loading

The forest is a well known and efficient natural protection solution against rockfall. To compensate for a loss of the forest’s protective function after windstorms or maintenance tasks, some of the felled trees can be left in an oblique position on the slope as wooden protection structures. No studies have been conducted on the efficacy of these devices and particularly their resistance to rock impacts and their energy dissipation capacity. The dynamic response of fresh stems to impact was analyzed by laboratory impact experiments with a Mouton-Charpy pendulum. The experimental results allowed the definition of different impact types related to the occurrence of nonlinear processes associated with partial rupture of wood fibers. The physics controlling the stem loading force and displacement were shown to be mainly associated with inertial effects during the early stages of the impact. Second, when the stem displacements become larger, the stem response becomes quasi-static. Based on these results, a practical approach for assessing the capacity of wooden structures made of fallen trees to resist rock impact was proposed and evaluated.

Predicting mechanical degradation indicators of silver fir wooden strips using near infrared spectroscopy

The management of ecological engineering structures making up a timber structure requires periodical evaluations, including the level of decay of the constituent parts of the timber structure. Methods exist to measure the level of decay in the laboratory or in the field. However, they are rarely suitable for the conditions of ecological engineering structures, or give partial information. The aim of this study was to predict two mechanical degradation indicators (

Assessing fragility of a reinforced concrete element to snowavalanches using a non-linear mass-spring model

Dw_{MOE}

Felled trees as a rockfall protection system, experimental study for numerical models calibration

DwMOE and

Physical vulnerability of reinforced concrete buildings impacted by snow avalanches

Dw_{MOR}

A reliability assessment of physical vulnerability of reinforced concrete walls loaded by snow avalanches

DwMOR) of silver fir (Abies alba) wooden strips during microbial decomposition using near-infrared spectroscopy (NIRS). For 1.5 years, the degradation of 180 squared wooden strips, 30 mm wide and 500 mm long, buried in a greenhouse near Grenoble, France (Altitude: 200 m) was monitored.