## Concept of buckling

### Definition of buckling

Side deformation curve of a structural element compressed by heavy load.

#### Extended description

We will give a practical example of what is buckling.
We take two pieces of dough, different wavelengths: one longer and one shorter.
We mold them with shape of rectangular section. We assume that each bar is a pillar; put them vertically on the table.
We print a vertical pressure on them with the same intensity of pressure in each one until we see how they start to deform.
Then stop tightening and observe that the shortest bar is that less has deformed, and the two have done so according to the plane's inertia minor, i.e., about the direction of the smallest side of the rectangular section.
What we have seen with this exercise, is a bar by buckling deformation.
Buckling depends on the section type, the length of the bar and the type of knot or link.
Buckling length
A bar buckling length is determined by the type of bond, whereas a deformation caused in a bar of articulated links, i.e., isostatic unitary.
The deformation by a biarticulada bar buckling is taken as a reference for comparison, as a unit.
The actual length of the bar, in this type of links, coincides with the length of buckling.
The graph shows the four classic types of gateway and its deformation by buckling.
We note that all bars have equal length L, and are subject to the same load P.
They have been arranged according to their deformations by buckling, from highest to lowest.
In the case of the recessed, free bar, we see that deformation is twice that in hinge bar.
Apparently, we deduce that rigidity is greater at higher hiperestaticismo links, before buckling.

### Concept of buckling

Buckling is a phenomenon of elastic instability which may occur in slender compressed elements, and which is manifested by the appearance of significant movements transverse to the main direction of compression.
In structural engineering the phenomenon appears mainly on pillars and columns, and translates into the appearance of an additional bending in the pillar when it is subjected to the action of axial stress of some importance.
The occurrence of deflection by buckling severely limited resistance in compression of a pillar or any slender piece. Eventually, from true value of axial load of compression, called the critical buckling load, elastic instability can occur and then easily deformation increase producing additional stresses that exceed the breaking strain, causing the ruin of the structural element. In addition to the regular flexional buckling there is torsional buckling or elastic instability caused by an excessive torque.
There are different ways or failure by buckling modes. Frequently there to verify several of them and ensure that loads are far from critical loads associated with each mode or manner of SAG for a structural element. Typical modes are:
• Flexional buckling. Buckling mode in which an element in compression are flecta laterally without rotation or changes in cross-section.
• Torsional buckling. Mode of buckling in which a compression element rotates around its center of cutting.
• Flexo-torsional buckling. Buckling mode in which an element in compression are flecta and rotates simultaneously without changes in cross-section.
• Lateral-torsional buckling. Mode of buckling of an element flexural involving deflection normal to the plane of bending and, simultaneously, rotation around the center of court
Flexional buckling
The pillars and latticework compressed bars may have different modes of failure based on its mechanical slenderness:
• The very slender pillars often fail by elastic buckling and are sensitive to both the local buckling own pillar as to overall buckling of the entire structure.
• On the pillars of slenderness average imperfections constructive as inhomogeneities are particularly important being able to present anelastico buckling.
• The pillars of very low slenderness fails due to excessive compression, until the buckling effects are important.

### Meaning of buckling

Buckling is the process and the outcome of SAG. This verb refers to the curve or bending that occurs in the middle of a beam or a wall due to compression. I buckling, therefore, is a notion common in the field of construction and laarquitectura.
You can qualify to buckling as a phenomenon which is due to the instability of certain materials to be subjected to a compression. The manifestation of the phenomenon is evident from a transverse deformation.
If such deformation increases up to overcome the resistance of the structure, there is a breakdown or collapse. Architects and engineers, must therefore analyse buckling to prevent compression to put at risk a construction.
There are different types of warping. You can talk of torsional buckling, flexional buckling and buckling lateral-torsional. Each classification depends on the way in which from a certain compression deformation occurs.
Refers to local buckling to appoint the displacement that occurs in an isolated component. Global buckling, on the other hand, takes place when the deformation of an estructurano is proportional to the loads and, therefore, the buckling occurs at a general level without that structural components have each its buckling load.
Let's look at an example of buckling. We have two columns of aluminum: one is three meters, and the other two meters. By placing a weight on top of them (i.e., using a vertical pressure on each column), we can observe how begin to deform. If we remove the weight, we will observe that the smallest column has suffered one minor strain. This is explained from the deformation by buckling.