Friction Model for Sliding Bearings under Seismic Excitation

In this article, an experimentally validated model is proposed in order to take into account main sources of performance degradation that could be experienced by friction-based devices during a seismic event. Particular attention is dedicated to the degradation of friction characteristics due to repetition of cycles and consequent temperature rise. This effect can be responsible for overestimate of the dissipation capacity of the device. The proposed model of frictional behavior is suitable for immediate implementation in generalized structural analysis codes and provides an important design tool for realistic assessment of the seismic response of structures equipped with friction-based isolators.     

Use of stone hammer tools and anvils by bearded capuchin monkeys over time and space: construction of an archeological record of tool use

Wild bearded capuchins (Sapajus libidinosus) in the cerrado (seasonally dry savannah-like region) of Brazil routinely crack open several species of palm nuts and other hard encased fruits and seeds on level surfaces (anvils) using stones as hammers. At our field site, their nut cracking activity leaves enduring diagnostic physical remains: distinctive shallow depressions (pits) on the surface of the anvil, and cracked shells and stone hammer(s) on or next to the anvil. A monthly survey of the physical remains of percussive tool use at 58 anvils in our study site over a 36-month period revealed repeated use, seasonal consistency, temporal variation, landscape-scale patterning, appearance of new hammers and transport of existing hammers to new anvil sites. Artefactual evidence of the temporal and spatial pattern of tool use collected in the survey is in correspondence with concurrent direct observation of monkeys using and transporting tools at this site. Shell fragments endure for years above ground, suggesting that they may also endure in the strata around anvil sites. The bearded capuchins provide an opportunity to study the construction of percussive tool sites suitable for archeological investigation concurrently with the behavior responsible for the construction of these sites. We suggest several lines of inquiry into tool sites created by capuchin monkeys that may be useful to interpret the archeological evidence of percussive tool use in early humans. Archeologists should be aware that transported stone materials and artificial durable landscape features may be the result of activity by non-human animals.     

Probabilistic life-cycle assessment and rehabilitation strategies for deteriorating structures: a case study

When it comes to existing buildings, the estimation of the structural residual bearing capacity is required to evaluate the potential for reuse/conversion. The level of detail and accuracy of surveys dramatically affect structural diagnostics. In order to optimise the experimental survey process, a simulation of the structural life-cycle may be useful.

Based on a previously developed approach of Monte Carlo simulation implemented with a damage law for the life-cycle analysis of newly designed constructions, this paper presents the method application to a historic roof steel structure. It aims to identify critical situations, assess the residual life of the system, and plan possible retrofit strategies for the building conversion.

The case study is a steel frame roof structure of the ex pig abattoir within the complex of the municipal slaughterhouse in Monza (close to Milan, Northern Italy) and protected from the Cultural Heritage Authority. The life-cycle of the structure is here investigated over different stages of the building lifespan along with the damages caused by aging and negligence. The construction was built in 1902, and abandoned in 1984. Therefore, the periods analysed are: from construction to disuse and from disuse to today. The second phase of life, still on going, has significantly sped up the degradation.

The probabilistic evaluation of failure times is discussed and the possible interventions scenarios in terms of costs, and after-maintenance reliability and safety are investigated.     

Quantitative characterization of archaeological bronzes based on thermal and compositional analysis

Pulsed thermography has been applied to the quantitative characterization of the insertions of two ancient bronzes, the Boxer at Rest and the Hellenistic Prince. The analysis of the thermographic signal time dependence performed by a specifically developed model enabled the evaluation of the insertions’ thickness and of elements which could provide indications about the procedure followed for their insertion. This could be achieved by exploiting a semi-empirical relation establishing the thermal diffusivity dependence on the total effective weighted concentration of Sn and Pb atoms obtained from the analysis of the values determined on samples containing different concentrations of Sn and Pb.