# Patch load on stiffened panel ?

• XaeroR35
In summary, the conversation discusses a need for help with analyzing a load scenario involving a stiffened panel with fixed and pinned edges. The panel has equally spaced stiffeners and a uniform patch load can be applied at any point. The speaker has attempted to use Roark's formulas, but they do not seem to be directly applicable. They have also shown two scenarios for reference. Another person points out that hand calculations may not always be possible for nontrivial plate problems, but the FEA analysis should be close to the correct answer. The speaker agrees and just wants to know if there is a way to do the calculation by hand.

#### XaeroR35

I need help analyzing a load scenario. I have a stiffened panel with fixed and pinned edges. There are fairly sturdy stiffeners equally spaced below the panel.

There is a uniform patch load (pressure) that can be applied at any point around the panel. I need to determine the resulting stress in the plate. I have tried to apply Roark’s formulas to this situation, but I don’t think they can directly apply. FEA analysis gives me much different results than using Roark’s formulas.

I am showing two scenarios in the picture below.

A: Load direction over a single stiffener.
B: Load spanning two stiffeners.

Any help would be appreciated.

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XaeroR35: I suppose Roark formulas are for something completely different from this scenario. Therefore, they would not be expected to be applicable nor give the same answer. There is not always a hand-calculation formula for nontrivial plate problems (unless you want to be conservative and basically ignore plate action). Do you not trust your FEA? It seems it would probably be close to the correct answer.

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Yes, I trust FEA. I just need to know if there is a way to do this calculation by hand.

## 1. What is a patch load on a stiffened panel?

A patch load on a stiffened panel is a type of external force or load that is applied to a panel that has been reinforced with stiffeners. This load can come from various sources such as wind, impact, or pressure, and it can cause stress and deformation on the panel.

## 2. How does a patch load affect a stiffened panel?

A patch load can cause stress concentrations on the stiffeners and can also result in buckling and distortion of the panel. It can also affect the overall structural integrity of the panel and its ability to withstand other types of loads.

## 3. What factors determine the severity of a patch load on a stiffened panel?

The severity of a patch load on a stiffened panel depends on the magnitude and direction of the load, the location of the load on the panel, and the stiffness and strength of the panel's stiffeners.

## 4. How is the strength of a stiffened panel evaluated under patch loading?

The strength of a stiffened panel under patch loading is evaluated using analytical methods, such as finite element analysis, and experimental testing. The panel's stiffness, buckling resistance, and ultimate strength are all factors that are considered in this evaluation.

## 5. What are some methods for mitigating the effects of patch loading on a stiffened panel?

Some methods for mitigating the effects of patch loading on a stiffened panel include increasing the stiffness and strength of the panel's stiffeners, using thicker or more resistant materials, and optimizing the panel's geometry and reinforcement layout to distribute the load more evenly.