Trees (such as buildings) also need static checks and checks

The importance of periodic checks

The trees also “get sick”, with pathologies that can trigger phenomena of material degradation Compromising its stability, especially when it comes to large plants with substantial masses. THE’analogy with the degradation of concrete and armor irons of a buildingto give an example, it is not so far away.

It was not the case of the episode of Venice – where the tree fell for the only action of the own weight (circumstance in itself already significant regarding the state of degradation and potential risk not perceived) – but also the external stressesmainly of a windy natureinduce solicitations to the limit for the resistance of some trees, often in conjunction with extreme temporal events.

Hence the importance, which has already been implemented for some time by the territorial administrations, of periodically check the state of health of public trees. A similar attention deserves to be taken into consideration also by all those private owners of green areas To safeguard private safety, and eventually public if they are green areas occasionally open to the public.

The VAT protocol

In fact exist periodic control plans performed by specialized technical personnel (arbor growers) with the aim of evaluating the state of health of the plant and therefore also its safety. The most used protocol is the Vat (Visual Tree Assessment)conceived in 1994 by Prof. Pierre Raimbault for the visual evaluation of the stability of the tree, founded on biomechanical principles and on Anatomical characteristics of the radical apparatusalso understanding the previous events that characterized the life of the tree. The result, by entering the data on special tables, is L‘attribution of a class of propensity to failure (Cpc: negligible, low, moderate, high, extreme) that allows the owner or manager of the area to acquire full awareness of any risks and possible interventions to be pursued, designed to preserve public safety.

THE’visual analysis of the hair, trunk and punctually of the roots (with picozza and awl to put limited portions to light) allows arbor growers to identify external symptoms related to defects or anomalies of the internal part of the tree. The main ones are detected measures tree (height, circumference, etc …) as well as performing ansound inspection with a hammer, which will serve to fill in specific diagnosis cards.

The Resistograph test

Any defects detected qualitatively from the outside can be confirmed and deepened with specific instrumental analyzes. They are mainly of a non -invasive nature, such as the classic trial resistography To identify the variations in density between healthy wood and the decomposed oneand therefore evaluate the percentage of healthy or enchanted parts of a wooden element. The test, used in construction also for the evaluation of the wooden beams of floors and roofsis performed by means of a tool that measures the penetration of a needle in the trunk. The result is expressed by a graph that specifies the penetration force along the stratigraphy of inflammation of the metal tip inside the wood.

The sonic tomography

Another non -invasive test, useful to deepen the presence of internal anomalies, is the sonic tomographyfrom the principles completely similar to that used in Investigations on historical wall structures. Through theentry of sound waves inside the trunk, The crossing speed is evaluated: if it is high, it means that the internal material is homogeneous, if it is low it means that the wave has undergone deviations due to voids or defects. Tomography allows you to easily examine entire trunk sections.

The bus test

There is also a real Traction load testcall Pulling TestFor evaluate the mechanical resistance of the tree at the root level in situ. The test consists in applying a shooting force on the trunk, with a controlled way, equivalent to that of the wind. The force is exercised via a padrank or a winch connected to the rope fixed on a high share of the trunk; The load value is determined by a dynamometer connected to the rope.

As understandable, it is Controls and analysis of a qualitative nature which, although they manage to identify the internal anomalies with sufficient and appreciable precision, cannot be concluded with an evaluation without the minimum but physiological uncertaintyso much so that There is talk of “propensity for failure” with different levels of risk. The traction test, on the contrary, can offer greater numerical certainty on the real mechanical resistance of the tree.

With a process completely similar in the purposes to what should be periodically carried out on the structures of existing buildings, also The control over time of health and staticity of trees guarantees greater safety to users of green areas. As in construction, Periodic prevention is the most useful tool to prevent It collapses with fragile events characteristics, and therefore dangerous because they do not emit easily detectable notice.