Each historic building or cultural heritage site requires proper care at every stage of its life cycle. Appropriate interventions aim to prevent building disasters and preserve invaluable cultural objects from ageing or deterioration processes. This article is a case study of mistakes made in various phases of a building’s life—in the design, execution, and use. The work aims to point out various aspects of the errors made during the building’s restoration. The conducted material research, computational analyses, laboratory tests, and documentation studies comprehensively consider the presented examples. The structural analysis of the buildings consists of its load-bearing capacity and its stability.

Non-destructive testing (NDT) methods are a diagnostic tool for evaluating the risk of failure or the need for repair and renovation. In analyzing constructions of high historical value, destructive diagnostic methods should be avoided. This study is a comprehensive NDT investigation of the masonry tower topped with a steel dome, a remnant of the overhead telecommunications network from the end of the 19th century. Visual inspection and research made it possible to assess the degree of damage to the structure. Stress–strain state analysis showed the sufficient load-bearing capacity of the steel dome. In addition, calculations have shown that the masonry tower is subjected to significant horizontal forces causing structure cracks.

In this study, qualitative tests were carried out to compare the behaviour of selected slabs exposed to short- and long-term loading. Full-scale models of the half-slab and hollow-core slab with dimensions of 6.30 m × 6.30 m, built of four different precast panels, were tested. The first two were semi-precast lattice girder slabs, the third semi-precast prestressed ribbed panels, and the last was composed of hollow-core panels. A common feature was the lack of joint reinforcement and the same modular width of 600 mm. The short-term load was applied sequentially in the first stage, and displacement was measured using an electronic method. In the second stage of long-term testing, the load was mainly applied to one part of the slab. Testing under short-term and long-term load allows determining the change in the performance of panel slabs over time. The panels maintained the ability of load redistribution based on their interaction despite the work of the longitudinal joints being only through the concrete cross-section. The behaviour of slabs with concrete topping shows more significant lateral interactions than elements connected only by shear key. Comparative calculations were made based on four computational models. Comparative analysis showed that the current design procedures lead to a safe but conservative estimation of the slab behaviour.

This paper presents a case study of structural damage resulting from the swelling of zinc slag used as a subbase layer beneath a commercial building. Although the material had been approved for construction, geotechnical, chemical, mineralogical and long-term geodetic investigations revealed that internal chemical reactions within the slag led to gradual volume expansion. Over ten years after construction, these changes resulted in significant floor uplift and structural issues, including wall cracking and floor deformation. The difference in floor level exceeds 100 mm, and the annual swelling during the last measurement period was more than 8 mm/year. The formation of secondary minerals (gypsum and ettringite) was identified as a key indicator of slag deterioration. Mineralogical assessments showed volumetric increases ranging from 25 to 51%, with higher swelling observed in areas with greater slag depths. The study highlights the limitations of current slag qualification methods and underscores the need for more rigorous testing methods to predict slag behaviour in field conditions. The findings offer valuable insights into construction practices involving industrial by-products and highlight the need for stricter standards to prevent future structural failures.

There are many reasons why engineering structures are at risk of losing their loading capacity during their long-term exploitation, which may lead to hazardous states. In such cases, structures must be strengthened. The most popular technique of strengthening is based on the use of composite materials—fiber-reinforced polymer (FRP) elements attached to the structure with the special resins. FRP elements are applied externally, often in hard to reach places, which makes it difficult to diagnose the durability and quality of such a connection. In this study, a combination of a modern thermographic method was proposed, which makes it possible to assess the degree of damage to the contact of the structure with the composite material along with the running platform (wheeled robot) equipped with a set of diagnostic sensors. The development potential of such a solution for subsequent projects was also indicated.