Circular reinforced concrete columns with spiral reinforcement exhibit an increased ductility and resistance due to the confinement effect. Many experimental investigations and theoretical studies related to this topic are focused on columns under axial load, while those for eccentric load are seldom. The scope of the paper is to present a developed calculation model of resistance for eccentrically loaded confined circular concrete columns. The model assumptions extend procedures of the ACI and Eurocode to the confined concrete case. In order to determine the resistance of columns in the form of the force-moment interaction diagrams, a special procedure is elaborated and described in detail. The peak stress and corresponding strain for axially loaded confined concrete is calculated using the Richart’s model. Then, an increase of ultimate strength capacity due to confinement is related to the axial strain level. The more the eccentricity, the less the confinement effect is engaged in the column resistance. The contribution of spiral reinforcement in the bearing capacity is the greatest in concentrically loaded columns and it vanishes at the point where axial strain in the concrete column is equal to zero, which initially governed the beneficial effect of the spiral reinforcement. A sample interaction diagram is obtained for the selected design case and compared with the diagram for unconfined column.

The paper analyses 100 multi-family residential buildings with basements made in traditional technology, with a usable area from 604.50 m2 to 2315.00 m2, built between 1952 and 1958 in the Masovian Voivodship. For the analysed buildings, individual elements were inspected once a year and their technical condition was determined. The research was conducted in 2018–2022 and focused on three selected buildings. The results of the study carried out by the authors were used to determine the degree of their aging using the visual method and to compare the results with those obtained from computational methods, e.g., time methods: linear, non-linear, parabolic. The main emphasis in the article is on faulty repairs of buildings, often without proper supervision and the impact of this phenomenon on the accelerated aging of buildings. Although the faulty repairs are common, they are omitted in the methods of predicting the aging of buildings. The paper also presents the analysis of the repair management carried out on the basis of post-inspection recommendations. The results of the conducted analysis confirm that the visual method is the most accurate to determine the degree of wear and tear of the building due to the possibility to determine its actual condition, considering account of the renovations carried out and their quality. The value of the degree of technical wear of selected buildings Sz was similar for visual and time methods.

The presented research program is focused on harnessing lunar regolith as raw material for the production of aggregates and concrete-like composites on the Moon. The proposed complex technological solution covers technology of lunar aggregate production, lunar concrete-like composites, shape of a lunar habitat, a type of its structure and erection technique. Each element of the proposed solution is supported by tests or calculations. In authors’ opinion magnetic separation seems to be the most promising technology of lunar aggregate production, habitats should be in egg-shaped form and the structure should be 3D printed as a Voronoi mesh. The research program was conducted using scientifically proven lunar soil simulants which were thoroughly tested by the authors. Production of lunar aggregate and subsequently concrete-like composite based on it is inevitable. The authors’ proposed approach to the erection of lunar habitats is fully based on in-situ resource utilization philosophy increasing its feasibility. Necessary future research areas were pointed out.

When testing soil parameters, the measured parameter values are only approximations of the true values. The measurand is determined based on metrological uncertainties or using statistical models for analysing data. Some parameters of the soil state present strong correlations, but others do not always provide simple correspondences. Multiple correlations between geotechnical parameters can provide a new perspective regarding the mutual relations between these parameters and may improve the fit of different soil parameters in geotechnical design procedures. Statistical modelling based on observed data generally involves a comparison between theoretical expectancies and practical surveys. Multidimensional regression models are useful for revealing the influences of several independent variables on one dependent variable. Statistical parameters and a quantitative approach can be used to define the relationships between several factors. Presented results claim that triple depended correlations may bring some corrects in relationships of soil parameters as against to double depended correlations. The differences in coefficients of determination are significant. Three variables involved stronger correlations.

The saturated metasandstone is taken as the research object, and the uniaxial compression characteristics of the saturated metasandstone are simulated by means of the artificially made saturated sandstone samples. By checking the parameters of the Particle Flow Code (PFC) numerical simulation of loading and unloading seepage stress coupling, the effects of the conductivity coefficient, the pipe diameter, the apparent volume of the domain and the time step on the calculation results are analyzed. When PFC is used for numerical simulation of seepage stress coupling, the conductivity coefficient K can be taken as 0.010. When the pipe diameter is 1.0 mm, the apparent volume of the current domain is 1 x 10–6 m3, the water pressure distribution inside the sample is relatively uniform. The influence of time step on the compressive strength and peak strain of the specimen can be almost ignored. Under the action of water pressure, the compressive strength of the intact rock like sample and the rock like sample with cracks decreases, and the compressive strength of the sample decreases gradually with the increase of water pressure. When the inclined angle of fracture is the same, the seepage pressure is the same, and the confining pressure is the same, the compressive strength of the specimen also increases with the increase of the initial axial stress level during unloading. When the confining pressure and the osmotic pressure are the same, the unloading effect makes the crack development of the specimen faster and more complete, the specimen is more fragmented and multiple parallel shear bands develop.

Take the metamorphic sandstone as the reference object, by making rock like samples with fractures, the conventional triaxial loading and unloading test and PFC numerical simulation of rock like sample with single fracture were conducted, and the effects of the loading path, inclined angle of fracture, axial stress level during unloading, initial confining pressure during unloading on the compressive strength, peak strain and crack propagation evolution of the samples were considered. The compressive strength of the specimen under triaxial unloading is smaller than that under triaxial loading. The peak strain of the specimen under triaxial unloading is also smaller than that under triaxial loading. The specimen is more prone to brittle failure. When the axial stress level is the same during unloading, with the increase of the initial confining pressure during unloading, the difference of the compressive strength of the specimens with different inclined angles of fracture gradually decreases. Under the condition of uniaxial compression and triaxial compression, the failure of all specimens is tensile failure, and the shear failure is the main one during unloading.

The prefabricated concrete frame structure system has advantages such as short construction period and good seismic performance, but its deformation and energy dissipation capacity are poor under earthquake action, making it prone to damage. By improving the analysis and simulation functions of existing finite element analysis for prefabricated structures, the engineering applicability of the analysis algorithm has been improved. Then, a finite element model has been established for collaborative optimization, and a parameterized optimization scheme that meets the seismic reduction requirements has been obtained. The results show that the optimization method proposed in the study has a better effect in seeking the minimum cost, and meets the design requirements of the specification. The optimization scheme of prefabricated concrete frames designed by the research institute based on finite element analysis can efficiently optimize various parameters, greatly improving the structure energy dissipation and seismic performance.

In this study, the fresh and hardened performance and durability of one-part ground granulated blast furnace slags (GGBFS) activated by solid CaO and Na2CO3 were discussed, and their hydration process and microstructure development were analyzed accordingly. Results showed that when the water-to-binder ratio was 0.32, the alkali-activated slag (AAS) paste exhibited lower flowability, higher yield stress and plastic viscosity. As the content of CaO and Na2CO3 increased, the yield stress, plastic viscosity, and compressive strength of AAS after hardening all increased. For the durability of the hardened sample, AAS with high content of activator have higher shrinkage strain and chloride ion flux. The microscopic analysis results indicated that AAS containing CaO and Na2CO3 exhibited more intense hydration heat release and rapid microstructure development in the early stage, thereby promoting the improvement of strength. The use of CaO and Na2CO3 to activate GGBFS has enormous application potential in solid waste utilization and carbon emission reduction, which can reasonably replace traditional Portland cement (PC) as a new generation of sustainable cementitious materials.

Excessive settlement or differential settlement of subgrade will lead to the deterioration of line operational conditions, the reduction of passenger comfort, and even endanger the safety of traffic. Therefore, it is of great significance to study the settlement prediction of subgrade. In order to predict the settlement of foundation under the next level of loading earlier during the embankment construction process, a new method of predicting settlement of soft soil subgrade is proposed. Firstly, based on monitoring results of soft soil foundation, the consolidation parameters of soil layer are back-calculated according to the three-point method. Then, combined with the theory of the consolidation degree of graded loading, the formula that can predict settlement under different loading conditions are derived. Eventually, the practical application of the method is verified by the prediction and comparative analysis of measured settlements based on engineering examples. The result of research shows that the method can predict the foundation settlement after loading during construction of engineering fill. This method has obvious advantages over the traditional curve fitting method and can guide the actual engineering construction.

This study focuses on the complex dynamics of heat dissipation within diaphragm walls during concrete hydration, crucial in construction engineering. Experimental measurements from three sites in Poland, featuring diaphragm walls of varying thicknesses, ranging from 1 to 1.5 meters, were compared to a numerical model. The model, using a Finite Difference Method, incorporated stages of execution of adjacent panels and their thermal influence. The results closely mirrored the measured temperatures, validating the accuracy of its predictions. Despite minor discrepancies, mostly within ±3°C, the method effectively approximated real-life scenarios. Suggestions for model enhancements include incorporating the effect of concrete admixtures and refining the modeling of sequential panel execution. The thermal soil parameters, their possible range, and their impact on hydration heat dissipation in deep foundations emerged as crucial insights. This research serves as a foundation for deeper investigations into early-age behavior in deep foundations, aiming to extend the analysis to stress and strain domains to unravel characteristic cracking patterns observed in diaphragm walls.