Kot carried out a structural assessment of conveyors in a maritime terminal. To do this, we carried out a static analysis of the components and their connections in accordance with the applicable standards and requirements. Read this article to find out more about this Succes story developed by the company's team!

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Introduction

Conveyors, better known as TRs in the engineering context, are widely used objects for transporting various types of solid and granular materials. Their applications can meet various demands.

Kot developed a study that aimed to carry out a structural assessment of these assets, using static and link analyses. Figure 1 shows an overview of these structures.

Figure 1: General view of the structures. [1]

To prevent contamination of the sea due to falling materials, containments were designed for the conveyors. The structural check carried out took into account the increased load caused by these additional structures.

Structure modeling

Starting the study, the first step was to model the conveyor in beam-column elements with the aid of the analysis program using the finite element method PROCAL 3D, developed by the company, in order to determine the acting stresses and strains, enabling structural analysis in relation to the applicable standards.

To help visualize the computer model, a 3D structural model was also generated using the VRML programming language, as shown in Figure 2.

Figure 2: 3D structural model - VRML. [1]

Definition of loads

Following on from this, the loads applicable to the structural assessment were defined, based on the recommendations of the ASCE 7-05 [2] and NBR 8800:2008 [3] standards. Some of the loads considered were:

• Own weight;
• Material loading;
• Tension in the belt;
• Overloading of roofs, walkways, platforms and stairs;
• Wind load;
• Chute clogging.

The criteria used to evaluate the member elements used in the structure are shown below:

• Utilization index: Evaluates the degree of stress to which a structural element is being subjected. It is determined from the ratio between the stress acting on each bar and the admissible resistance determined by the standard for steel structures;
• Permissible use index: This is the value defined by a standard, used as a reference for approving or disapproving the degree of stress of a structural element.

The permissible utilization index for member elements for all loads considered is 1.

Link analysis

Connecting elements enable parts of the structure to be joined to each other or to external elements. Welds, screws, threaded rods and bolts are the main means of connection.

All connections are commonly classified according to their rigidity, i.e. their ability to prevent the relative rotation of the connected parts. Two categories are possible according to this criterion:

• Flexible connection: No resistance to bending moments. In this case, only normal and shear forces are transmitted;
• Rigid connection: Characterized by the total restriction of bending moments. There is no considerable relative rotation after the load is applied.

These connections must be designed in such a way that their design strength is equal to or greater than the demand for the connection, withstanding all the acting actions and meeting all the requirements set out in NBR 8800: 2008 [3].

The criteria used to check the connections considered are listed below:

• Utilization index: Representsthe degree of stress to which the connection is being subjected. The connection is approved when its utilization index is less than 1.

Results

The static analysis of the conveyor structure was carried out to determine the impact of installing the material containment chute. Three different cases were considered, which are detailed below.

• 1st - Material clogging: The utilization rates obtained from this structure check are shown in Figure 3.

Figure 3: Result of static analysis in case of clogging. [1]

As can be seen in the figure, some elements failed the analysis.

2nd - Boundary Condition: The aim of this analysis is to determine the boundary condition of the structure, i.e. what is the maximum load of material that can be allowed in the containment channel. The result can be seen in Figure 4.

Figure 4: Result of static analysis in borderline case. [1]

It was therefore concluded that the structure was not ready for the installation of the gutters and reinforcements are needed.

3rd - Normal gutter operation: The aim of the analysis is to survey the elements that need to be reinforced in the structure so that the gutter can be installed. Figure 5 shows the results obtained in this last stage.

Figure 5: Result of the static analysis - Utilization rates. [1]

In the static analysis and connection analysis, it was found that the structure was not ready for the installation of the material containment chutes without prior modifications. As a result, Kot indicated some necessary actions to ensure the Structural Integrity the assets.

Conclusion

Although the solution for containing the material was of great value from an environmental point of view, the structural assessment acted to mitigate the risk of structural collapse by proposing improvements that should be made before implementing this containment system. 

It should be noted that Kot has a great deal of know-how in the area, having calculated hundreds of conveyors, being able to evaluate different operating contexts and contribute to its clients' results. Contact our team for more information!

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References

[1] Kot Collection.

[2] AISC 2005 - Specification for Structural Steel Buildings, Allowable Stress Design and Plastic Design, July 2006, American Institute of Steel Construction.

[3] ABNT, NBR 8800, Design of steel structures and steel-concrete composite structures for buildings, 2008;