Elements with a porous structure are quite common in nature. They are also starting to gain more and more recognition in mechanical engineering. They allow you to achieve the desired stiffness and strength with a significant reduction in weight and relatively acceptable geometric dimensions. However, unlike solid materials, they require more complex engineering calculations carried out in design and simulation processes. The article presents the possibility of using the lower bound method (characteristic method) to determine the limit load capacity of porous structural elements. The concept of limit load capacity is presented and an attempt to use it to solve the problem of pressing a rigid punch into a porous structure. Isotropy of the structure was assumed. The issue is considered in the context of the possibility of using it to estimate the strength of structures obtained with Fused Deposition Modeling method.