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There are three benefits to steel, and two of them are areas where it significantly outperforms aluminum.

Stiffness - The comparison of aluminum and steel emphasizes the importance of deflection.Contrary to popular belief, stiffness and strength are two entirely distinct qualities.For instance, nylon rope is quite strong but not at all stiff.

Although "stiffness" is a phrase we use frequently, "Modulus of Elasticity" is the engineering term used to describe it. By alloy, there is a little but noticeable difference. Steel typically has a psi of roughly 30,000,000 and aluminum is typically around 10,000,000. Once more, the crucial factor is how much a beam will deflect under load, not the precise figures. Generally speaking, for equal beams, an aluminum beam will deflect about three times as much as a steel beam under same circumstances.

Practical Durability -A third benefit of steel is what we call Practical Durability. This is not a measurable value. Rather, the pragmatic side of designing, making, using, misusing, and owning the equipment is practical durability (crane, trailer, press, whatever). This includes benefits such as easier welds and greater resistance to damage and abuse when building with steel.

Steel is often significantly less fatigue-prone. One problem with aluminum is that metal tends to develop fractures, especially when welds are made. It takes a lot more skill and specialized equipment to weld aluminum. Also, because aluminum is less resistant to wear and abuse than other materials, we usually advise adding more gussets and other joint support. The practical benefit of employing aluminum, particularly with aluminum trailers, is that.

Naturally, this does not imply that you shouldn't employ it.It just implies that the design and building process needs to be given a bit more consideration.

Engineering Concepts

The phrase "Modulus of Elasticity" in engineering refers to how much a beam will flex under a specific load. It is a characteristic of the substance; aluminum, steel, titanium, plastic, and wood all have a unique "Elastic" characteristic.

The "I," or "Area Moment of Inertia," is another related engineering concept that is frequently mentioned in talks about strength and stiffness.

This is related to the beam's size and cross sectional area.To put it briefly, it refers to the quantity of material, how it is distributed throughout the beam cross section, and how far away from the areas of the beam that are under the most stress. For descriptions that are more detailed, click on the links above.

In essence, these 2 concepts work together to define how "Stiff" every beam is. This is not "Strength" — but they are sometimes connected. Though that has a lot to do with it, the beam form is not the cause.Let's examine an illustration using a straightforward Gantry Crane top beam using finite element analysis (FEA).We'll compare steel and aluminum using this amusing engineering tool because it offers some fantastic visual perspectives. (As a side note, see Safety with a Crane and the larger one, Gantry Crane Failure Modes, to understand what occurs when a crane does collapse.)

Engineering Tools' Insight

We first construct two cranes. Build cranes in CAD rather than using real cranes. One crane has an aluminum top beam, whereas the other has a steel top beam. Steel is used for all of the legs, so we can plainly see how the top beam differs from the others. Afterwards, we'll dangle 2500 pounds from the center of each of the gantry beams. The arrangement for cranes and loading is shown in the image below.

Crane and load

Finite element analysis of 5" Steel I beam &  5" Aluminum I beam gantry 

FEA Setup

Each leg is constricted at the bottom. Although it's not quite true, we assume they are fixed for the sake of simplicity, since it will enough for the simple comparative study. Also, we bind (weld) the legs to the top beam, which is not quite accurate but adequate for the information we need.

Both of the upper beams in this initial test are 5′′ I-Beams.One beam is made of steel, while the other is made of aluminum.

The engineering technology known as FEA, or finite element analysis, allows us to realistically observe what occurs when we apply a load to an item. In the figure below, the colors represent the stresses in the beam. In this illustration, the colors blue and green are considered "safe". Red denotes danger, whereas Yellow denotes caution. Both aluminum and steel can be used with it. In order for us to see what is happening visually, the deflection in the image has been greatly inflated. (For a genuine crane, this kind of beam bending would not occur.)The two gantry cranes for our load look something like this.

5″ I-Beams

This image displays a 30X enlarged deformation scale. In other words, there is 30 times as much deflection as what you observe. This form of exaggeration helps us see what is truly happening more clearly. We can better see the differences between steel and aluminum because it is simpler to observe and the exaggeration is the same for both beams.

Less than 0.2 inches is the actual deflection of the steel beam. Because of the setup presumptions, you should treat these data with caution. The aluminum beam deflects by almost 0.5 inches. With the exception of the hot regions near the leg connection, stress levels are noticeably similar. The larger deflection, which the legs attempt to counteract, is what causes those spots. Obviously, it is impossible to weld steel legs to an aluminum top beam. But when a deflecting beam imparts some deflection to the connecting elements, this is an intriguing connection symptom. Remember this for later.

Practically speaking, if a gantry crane's top beam deflects by 0.5 inches, it might be challenging to transfer the load along the beam because you'd be hauling it up a relatively steep slope. A weight of 2,500 pounds is substantial. Although the deflection moves with the load and is a compensation, the situation is not ideal.

6″ Aluminum I-Beam

Let's swap out the 5" aluminum beam for a 6" aluminum beam in an effort to lessen deflection and strengthen the joints. This is what happened.

Comparison of 5" steel I beam gantry vs 6″ Aluminum I-Beam gantry 

Comparison of 5" steel I beam gantry vs 8″ Aluminum I-Beam gantry

We can clearly see that there is less deflection in the FEA image. The aluminum beam now has a thickness of roughly 0.3 inches, which is better but still higher than the steel I-Beam. Furthermore, less stress is excellent. And because there are fewer hot spots, there is less beam deflection. All of these actions are positive steps.

The higher "I," or "Area Moment of Inertia," is what causes the shift in beam deflection that we observe. Only the size has changed; the aluminum substance has not changed. Yet, that is only a portion of the beam; the rest of it is shorter. Moreover, the 6′′ I-Beam has a larger cross section.

We can now determine whether the 0.3" deflection is acceptable.

In some real-world situations, it might be, but for the purposes of our analysis, let's switch back to the top aluminum beam since its deflection is still greater than that of steel. We'll do this to demonstrate how the beams made of steel or aluminum differ in terms of flexibility.

8″ Aluminum I-Beam

The next typical size up for I-Beams is 8′′, thus our study will move on to that size. Please keep in mind that we are still making comparisons to 5′′ Steel I-Beams.

It is clear from this image that the 8′′ Aluminum I-Beam further minimizes joint stress and deflection. Hot spots are no longer present, and this time, deflection is slightly below our target for a 0.2-inch steel beam. Our comparison is successful.

The new 8′′ aluminum I-Beam is obviously considerably taller and has a larger cross section. The 8′′ I-Beam is also significantly wider than the 3′′ I-Beam because we use standard size material. All of these factors contribute to a difference that is not immediately obvious from the description of 5′′ or 8′′ beams.

Note also that the stress in the 8″ I-Beam is less, quite a bit less. What that really means is we have a lot more material than we need from a strength standpoint in order to achieve the deflection goal. Remember our objective is to compare steel or aluminum for the crane, yet it is also true for a trailer frame.

Deflection Comparison: Steel vs Aluminum Beam

What then have we discovered? This is a straightforward illustration of a design where deflection, not stress, is the determining element. If we reinforce the corners with suitable gussets, even the first example had respectable strength, as shown by the stress. Deflection is usually more of a concern for longer beams.

Not that aluminum is a poor choice for crane beams. The research above just emphasizes one of the limitations when contrasting a steel or aluminum beam. Also, it demonstrates some of the distinctions between using aluminum and steel for construction. A project's material selection is usually difficult since it requires balancing aspects including strength, loading conditions, weight, and suitable safety considerations. This is especially true when creating unique blueprints, such as the gantry crane in the above illustration. We support thoughtful, customized individualization, as shown. If you have any need of i beam gantry crane, please feel free to contact us.