ACCUMULATION OF DAMAGES OF NEW CARRIAGE CONSTRUCTIONS, PERFORMANCE CAPACITY

Abstract

The article presents the results of experimental studies of the strength and deformability of load bearing structures made of wood under the action of static loads. In most major cities of Ukraine there are a huge number of buildings that have historical and architectural value. To preserve these structures for centuries, it is necessary to constantly receive such information about the state of their supporting structures for making timely decisions about reinforcement, replacement, overhaul, etc.

In the materials of building structures, changes occur during the period of operation associated with the appearance, development and accumulation of structural damage. These damages cause submicron and microcracks, which are the result of external mechanical effects on the structure and therefore the transition to the boundary state is the result of a slow accumulation of damage. Having developed a technique for registering damage, you can get a tool that allows you not only to monitor the current state of the structure, but also to predict the change in its bearing capacity over time.

In the period of operation there is a change in the structure of materials bearing structures The development of this process consists of several stages, the main of which are: deformation of interatomic bonds, nucleation of a sub-microcrack as a result of breaking macromolecules that form the walls of tracheids. This turns out to be suddenly and is accompanied by weak sound signals, resembling a micro explosion. The interaction of submicrocracks leads to their merging and the occurrence of microcracks, and the merging and increase of microcracks - to the occurrence of macrocracks (trunk crack), which leads to the destruction of the material. This dynamic process, depending on the size, nature and time of action of the load, may stabilize over time or, continuing, lead to the destruction of the structure.

Mechanical and electrical devices currently used (indicators, strain gauges and other devices) are not suitable for detecting and recording material damage. For this purpose, it is necessary to use non- destructive research methods that allow continuous observation of submicro- and micro-processes that take place in the structure of the material of the structure. Such methods for estimating the residual life are currently being successfully applied only in aviation and on important equipment (thermal, hydraulic, nuclear power plants, etc.) The processes are obvious.

There is a need to comprehensively investigate the issue of damage accumulation in wooden structures under load, and the associated processes of changing the cross-sectional area and carrying capacity and use the results of the study in the calculation of structures. This makes it possible to reduce the consumption of materials and make the sections of wooden structures more economical, and also allows you to avoid excessive margins.

The direction of improving the methods of designing and calculating wooden structures and determining the residual life of the main wooden structures of structures are not yet reflected in the technical literature. In this regard, it requires a comprehensive study.

To study the processes of damage accumulation in the material of construction, a method was used that does not destroy the structure. This is an acoustic emission method, which is associated with the propagation in the material of elastic waves caused by the dynamic local restructuring of its structure. Acoustic emission signals appear at the onset of micro and macro defects and accompany the entire process of material deformation. This allows you to diagnose the state of the structure, since the emission of sound vibrations can be detected at the stage when the structure as a whole is still operational.