Add capability to model distributed loads on shell element

[Kavan-Khaledi]

Motivation

Distributed loads on shell elements are commonly encountered in various engineering applications, such as self-weight or wind loads on thin structures, or gas pressure in pressure vessels and tanks. However, the current shell model does not support the functionality to model these distributed loads.

Design

A new ADKernel (ADDistributedLoadShell) is added to calculate the contribution to the residual from the distributed loads

Impact

• No impact on the exisiting features, tests ,...
• adds the capability to model distributed loads on shells