Tech Tip: Crane Structures in GRAITEC Advance Design

Written by: Achraf Ben Afia, Solution Technical Expert

Introduction

Crane structures are essential components in the construction field, serving as pivotal tools for lifting and maneuvering heavy materials and equipment during various phases of building projects. Their versatile applications extend beyond construction, finding key roles in manufacturing, warehousing, and logistics operations, where they streamline material handling processes and enhance operational efficiency.

Engineers tasked with designing and optimizing crane structures require advanced tools for accurate modeling and analysis. GRAITEC Advance Design provides a comprehensive solution, enabling engineers to precisely model cranes with moving loads, simplifying complex tasks and empowering efficient design processes.

In this article, we will look at how to model a crane structure in GRAITEC Advance Design, then we will explore finite element (FE) analysis results.

1 – Working example

Our working example is a tie-rod supported jib crane (see Figure 1). This structure is composed of a fixed base column, a beam (also called a boom), and a tie-rod that supports the beam. The connection between the column and the beam is a pinned connection that allows a rotational movement for the beam. The chain host is modeled as a moving punctual load of 10 kN, which can be placed anywhere along the beam (0.1m ≤ x ≤ 4.9m). In Advance Design the tie-rod is modeled with the element type “Tie,” which carries only tension loads. The objective will be to determine the absolute maximum bending moment in the beam and the absolute maximum tensile force developed in the tie-rod.

Figure 1: Jib crane example

2 – Define a crane line in Advance Design

After modeling all structural elements, we need to create a crane runway line that specifies the first and subsequent points of the rail. To do so, we click on “Objects,” then click on “Crane Runway.” We select both beam ends and press Enter (see Figures 2 and 3).

Figure 2: Define crane runway

Figure 3: Select beam ends

Next, we should click on “Crane” and define our crane parameters (see Figure 4).  In crane properties, we can set the number of wheel axles depending on our project. For our example, we only need one wheel axle as we have only one moving load. Check Figure 5 for crane properties and Figure 6 for wheel loads values.

Figure 4: Select crane

Figure 5: Crane properties

Figure 6: Wheel loads values

3 – Define crane loads

In order to define crane loads, we need to right click on “loadings” in the project browser, select a case family, and choose crane loads as illustrated in Figure 7. Then click Ok. Next, we simply left click on the generated “Crane loads” to show the properties panel, then click on the icon shown in Figure 8 in order to open the crane system definition.

Figure 7: Defining crane loads

Figure 8: Crane moving parameters

Once we open the crane system definition, we click on Auto-detect, then we can modify the “Range” to Imposed. Doing so, we can modify the start point, the end point, and the length of steps. The number of steps is calculated automatically. Check Figure 9 for parameters values used in this example. Finally, click Ok. We right click on crane loads, and we select “Automatic generation” (Figure 10).

Figure 9: Crane system parameters values

Figure 10: Automatic generation

The automatic generation option will generate moving loads (Figure 11), as well as envelopes for internal forces and supports reactions (Figure 12).

Figure 11: Generated moving loads

Figure 12: Generated Envelopes

4 – FE results

Now we are ready to run the FE analysis. In the project browser, we select “Analysis,” enable “FE calculation,” and click Ok.

4.1  Absolute maximum bending moment happening in the beam:
Advance Design facilitates the way to find the absolute maximum bending moment. After selecting the beam and using the envelopes, we can display the max and min envelope diagram (see Figure 13).

Figure 13: Min and max bending moment, My values

Moreover, we can determine the location of the load which causes the absolute maximum bending moment happening in the beam. For that, we need to generate the table: “Absolute concomitant linear elements envelopes on My” in the report generator (see Figure 14).  The table is shown in Table 1.

Figure 14: Absolute linear element envelope on My (Report generator)

Table 1: Absolute concomitant linear elements envelopes on My

From the table above, we can conclude that the absolute concomitant My value happening in the beam is  -11.1 kN.m, which happens due to the load case number 20. To determine the location of the load, we need to return to the list of load cases, and then we will find the location as it is illustrated in Figure 15. We can conclude that the location of the load that causes the absolute maximum bending moment in the beam is 2 meters.

Figure 15: My diagram for load case number 20 (load location: 2 m)

4.2  Absolute tensile force happening in the tie-rod:
The same process explained above applies to determine the absolute tensile force happening in the tie-rod. After selection of the tie-rod element, we can directly show the table “Absolute concomitant linear elements envelopes on Fx” (see Table 2).

Table 2: Absolute concomitant linear elements envelopes on Fx

From the table above, we can conclude that the absolute concomitant Fx value happening in the tie-rod is 50.18 kN.m, which happens due to the load case number 49. Again, to determine the corresponding location of this maximum Fx force, we go back to the load cases list in the FE results. We select the load case 49, and we can find that the location of the load in the beam (crane boom) is 4.9 m.

Figure 16: Fx diagram for load case number 49 (load location: 4.9 m)

Conclusion

In summary, GRAITEC Advance Design stands out as an excellent software choice for engineers tasked with modeling and designing crane structures. Its user-friendly interface ensures ease of use, while its robust capabilities enable efficient handling of complex moving loads scenarios. Engineers benefit from its powerful navigation through finite element results, making analysis and optimization straightforward. While the example studied in this article is quite simple, it’s important to note that the software is capable of dealing with more complex problems involving multiple wheels and a high number of loading steps.

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TRY IT FOR YOURSELF! Discover the all-in-one FEA/FEM software for structural engineers: GRAITEC Advance Design. Contact the GRAITEC industry experts for more information.

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