How does a tower crane work?

The Torre crane crane (often shorten simply with the word crane) I am machines of fundamental importance for the carrying out the works within a construction site. They are used to move, move and/or raise heavy objects in various points of the construction site and are necessary when the works are carried out on Important Plano-Altimetric extensions. A crane is built starting from a series of physical concepts and using some fundamental elements that guarantee resistance and stability during the exercise and rest phases.

What is a tower crane and how it is done

Although with the term crane they can be indicated different types of mechanical organs With different operation, in this article we will focus on the functioning of Torre crane crane: structures that develop mainly in height, equipped with an arm used for the movement of objects or material. This arm, which is an element with horizontal development, It has the right to move around the crane bodyallowing movements to plan with 360 ° corners: in this case we talk about rotation crane. To ensure sufficient Resistance and stability of the parties, each crane is equipped, in addition to its own metal support structure, of:

• A system of counterweight that balances the load at altitude;
• Adequate foundation system.

The foundation system

The foundation system of a crane is intimately connected with the operating mechanism that is established. We start from the fact that high structures subject to eccentric loads would require, in principle, the realization of deep foundations (also called Foundation poles) which are able to guarantee resistance towards the reversal mechanisms. However, making a pole is not always possible and, in principle, in specific applications it would be uneconomical: in fact, the post, once made, should remain fixed in the ground foreverwithout any future technical function.

To avoid the costs and complications of deep foundations, more practical solutions are used: Large surface plates in concreteoften even one meter high, capable of providing the weight necessary for stability against the reversal phenomenon. This, however, is not enough: the foundation plate is accompanied by one ballastthat is to say a weight died to be placed above the audience. In this way, the loads centered at the base are significantly amplified and, consequently, the eccentricity produced by loads at altitude are reduced.

The counterweight at high altitude

In the upper part, you immediately notice that The crane has two asymmetrical arms and, in one of the two (the shortest) there is always a element “heavy“ (usually prefabricated slabs of concrete). This counterweight It further reduces loading eccentricity and also balances the loads that act on the arm, limiting the flexions of the crane. However, in all those phases in which the crane is not in operation (i.e. it has not loaded), the counterweight is antagonist and partly produces an increase in the same eccentricity that would like to reduce.

The metal structure

The whole structure of the crane is built through metal pylonsusually made up of councils assembled with each other through bolted joints. The trellis represents the load -bearing bone of the crane And it is the element to which the task of transferring the loads from the point to altitude to the Foundation is charged. To do this, the system undergoes internally traction and compression efforts, which must be limited to the maximum eligible according to the resistance of the steel in play.

The physics behind the crane

Analyzed the elements of which a tower crane is made up, we now try to understand its operation. To be literally standing, a crane must be designed in such a way as to make The resulting of all the agents falls within the support base of the foundation plate. If this does not happen, then the crane cannot be in balance: in this case it would occur in a phenomenon of overturning from the side in which this is unbalanced. How to make this stay inside resulting loads? With ballast!

Any weight that acts is a force facing down: the result of this system of forces – that is, the sum of all the agents – will always be in an intermediate position between these and will approach the force with greater intensity. For this reason, ballast is designed to be A far greater weight than all the other weights that act. This is possible because:

• The steel pierced structure is light enough;
• The loads in play mobilized by the crane are limited and anyway minors compared to the weights of the crane body.

On the upper part, however, the task of balanced the forces involved is mainly given to counterweight. This balances the load to be moved by means of The physical principle of levers: in this case, The centerpiece of the lever is on the crane bodywhile the two forces that act on the lever have different intensity and arm (distance from the fulcrum). Therefore, it is possible to calculate how much counterweight it serves to balance the moving load. In doing so, however, there would be an important flexion of the crane when this is downloaded. Therefore, usually the counterweight project strategy is such as to have a flexion of the body of the crane equal in all the operating conditions. Then the ballast will be at the base of guaranteeing balance and resistance to the whole system.