Sustainable wood 1st

In general, it is considered from the Civil Engineering area that, in order to develop large-scale structural projects, it is necessary to use the latest technology in materials or those that are industrial. Frequently the origins of this profession are forgotten, which consists of the design of structures to support some type of load. That is, the job of a Civil Engineer is to be able to design a structure (house, building, bridge, road, etc.) and prevent it from collapsing during its useful life, either due to use loads or due to environmental effects such as earthquakes, tides, chemical attacks, etc. In that sense, any material that allows us to meet that objective, and with reasonable security and repeatability, that is, the material usually behaves in a similar way regardless of its production batch, can be used to build. It is important to emphasize that those materials that do not meet this condition are not advisable to build, since the variation of their characteristics can result in catastrophic consequences.

 

With all of the above in mind, today I would like to emphasize the role of wood in the discipline of Civil Engineering, as a material with potential and capacity to be widely used in structures. First, it is necessary to roughly explain what wood is and where we get it from. In essence, wood is a set of ordered plant cells that are dead, but still form a fundamental part (the pith) of a tree. In the tree we also find living wood, which is normally a layer between the pith and the bark, but we do not use it for structural purposes. To obtain structural wood, this is what is used to build, trees are cut down and then their different sections are processed. The structural wood is obtained mostly from the trunk of the tree. It is possible to classify wood into two broad categories: soft and hard woods. Broadly speaking, softwoods contain very large cells, which results in a sparse structure, and hardwoods contain small, compact cells, which results in a dense structure. Usually softwoods are those of industrial production, such as pine or eucalyptus, and hardwoods come from some species of native trees.

Now that we have defined the different types of woods, it is necessary to discuss their production. There are two sources through which wood is obtained, the first is native forest and the second is industrial plantations. Currently, approximately 75% of the wood is obtained from native forests. It is usually considered

to the use of products made of wood, as one with low environmental impact. Unfortunately, if the production of industrial plantations and the felling of native forests is not controlled or controlled, wood is no better than the production of cement or steel. To verify that the plantations and / or logging of native forests are carried out in a responsible manner, there are various certifications that ensure that these processes have a low impact on the environment. For this reason, it is important when choosing the supplier of wood for construction, to verify whether it is certified or not.

As the origin and impact of the structural wood industry has already been discussed, it is time to talk about the characteristics, or engineering properties, of wood. The first thing that needs to be raised is the resistance of the wood. Strength is the ability of a material to withstand external forces or deformations without breaking. Furthermore, the resistance of a material can be classified according to the type of force, or rather the position, to which it is subjected. We have, for example, the compressive strength, which corresponds to that when a material is compressed longitudinally. On the other hand, there is the resistance to traction, which occurs when the force is applied in the opposite direction to that of compression. Flexural strength is that which occurs when trying to bend a material, which is fixed at the ends. Finally, shear resistance is that which occurs when a material is subjected to simultaneous compression and bending loads. All materials have the ability to resist all the stresses mentioned above to a greater or lesser extent, depending on specific characteristics. Even within the same family of materials, we can find differences in strength, for example, between Radiata pine and Oregon pine. It must be taken into account which are the resistances to which our material is more apt when designing.

In particular wood is known as an anisotropic material.