Experimental tests were performed on a stack of cuboidal steel elements and its mathematical model was developed. Each cuboidal element was made of rolled profiles. Such stacks are the part of temporary supports that can be used to eliminate deflections of buildings. Stacks were loaded eccentrically through the inaccurate position of a jack. Moreover, two types of geometrical imperfections could be noticed. They included inaccurate contact between the stack elements and initial relative displacements of profiles that formed cuboidal elements. A mathematical model was developed to describe deformations of the stack and its parameters were determined by analysing test results. The eccentricity of the applied force had a slight impact on the stack stiffness, which was considerably reduced by geometrical imperfections. The imperfection covering initial relative displacements of rolled profiles inside cuboidal elements had the greatest impact on the stiffness. It could cause even a 10-fold drop in the stack stiffness when compared with the theoretical stiffness resulting from the stiffness of the stack section, and the stiffness dropped by ca. 3.5 times when the imperfection included the inaccurate contact between the cuboidal elements. Finally, the occurrence of both types of geometrical imperfections generated the real stiffness more than ten times lower than the theoretical stiffness that did not take into account imperfections.

One method of rectifying tilted buildings is by lifting them unevenly using hydraulic jacks. These jacks are loaded both monotonically and cyclically during the rectification process. It has been shown that the change in jack length is the sum of the change in the piston slide out and the change in the jack’s cylinder length, which is supported by a parallelepiped element. Laboratory tests were conducted to investigate the piston slide out and the change in the jack’s cylinder length under both monotonically and cyclically loaded conditions. The results indicated that the piston slide out forms a hysteresis loop. In contrast, the change in the jack’s cylinder length does not exhibit a hysteresis loop and is a non-linear function of the load. A structural model of the jack was proposed, consisting of three components: a linearly elastic component connected in parallel to the component where the frictional force occurs, and a component with non-linear elastic characteristics connected in series with them. Displacements of the linear elastic component, characterized by a constant stiffness, occur as long as the external load exceeds the internal frictional force. The value of the frictional force in this model increases with the load. The stiffness of the non-linear elastic component increases proportionally to the load.

The prospect of establishing a human presence on the Moon has transitioned from the realm of science fiction to an achievable goal. The long-term objective of the Artemis program is to establish a habitat on the Moon that would enable crews to remain on the lunar surface for extended periods. The developmental pathway for such facilities culminates in structures that are manufactured and constructed predominantly from materials sourced on the lunar surface, in alignment with the In-Situ Resource Utilization (ISRU) concept. This paper presents a conceptual lunar habitat that was created by covering 17 m diameter crater in the Mare Tranquillitatis with a structure made from a lunar regolith-based geopolymer. Five shapes of the covering lid were analysed, including: two concave domes with rises of 0.5 m and 1 m; a flat circular slab; and two convex domes with rises of 0.5 m and 1 m. Structural analysis was performed using the Finite Element Method, employing material data from existing literature as well as original strength tests of alkali-activated material based on lunar regolith simulants conducted by the authors. Each model of structure was subjected to dead loads and varying levels of internal air pressure. The numerical analysis revealed the advantages of concave-shaped structures, where internal pressure induced compressive stress within the cross-section, thereby mitigating the risks of air leakage and decompression of the habitat and taking advantage of material in which compressive strength is higher than tensile strength.

The removal of building deflections consists of uneven raising of buildings with piston hydraulic jacks. A stack of parallelepiped steel elements is situated under jacks during defl ection removal for technological reasons. The stack has decisive influence on the stiffness of the supports. Tests of the stack of parallelepiped elements loaded with increasing and decreasing force were designed and carried out. Three characteristic phases were identified based on the tests. The maximum stiffness in particular phases was, respectively 13.1, 63.1 and 10.1% of theoretical stiffness.

Dry stack structural elements are characterized by nonlinear stiffness that arises from geometric imperfections of their components and the absence of any bonding between them. Moreover, such elements dissipate energy under cyclic loading because of their internal structure. The authors considered dry stack structural elements loaded with a bending moment to propose a relatively simple mathematical model of dry stacks composed of only three elements. The model consists of a linear spring, a nonlinear spring, and a spring with hysteresis in series. In this model, the first element describes the idealized properties of a dry stack element, while the second and third elements correspond to the influence of geometric imperfections and the behaviour of dry joints. Furthermore, the authors described a procedure for determining the parameters of the model based on test results. The proposed solution was verified via experimental studies of temporary support structures consisting of a stack of cuboid elements and a hydraulic jack typically used in the process of building rectification. This study showed that the proposed model adequately describes both the nonlinearity and the energy dissipation under a cyclic bending moment.