The aim of this paper is to determine the short-term and long-term mechanical properties of lightweight concrete with sintered aggregate. The ecological aggregate comes from recycling ashes from power plants, which yield granules after processing. The research was planned based on two concrete mixes. A series of strength and rheological tests was carried out in the Building Structures, Geotechnics and Concrete Laboratory of the Building Research Institute (ITB). As a result of these tests, the following parameters were determined: secant modulus of elasticity and cylindrical strength of concrete, cubic strength of concrete, axial tensile strength, tensile strength at splitting, flexural strength and concrete strains due to creep and shrinkage. An unusual process of development of the modulus of elasticity was observed. Despite this, floor slabs designed from the discussed concrete show slight deflections compared to slabs made of plain concrete. It turns out that the current standard models correctly approximate the results of rheological tests in the case under consideration. Knowledge of the tested parameters is necessary when designing prestressed structures and adopting proven values for static calculations when designing complex structures, including prestressed elements made of discussed lightweight concrete with sintered aggregate.

This article compares the analytical results from two models, based on the theory of hereditary creep strain, with experimental results on the rheological properties of lightweight sintered aggregate concrete under cyclically varying loads. In a previous article, the authors analyzed the adequacy of standard models for the same test results. Because the use of standard models is very complex and does not improve the approximation of test results without additional calibration, the authors suggest reconsidering the use of hereditary models for LWAC. The application of four such long-term models was analyzed. Among these models, the Arutiunian theory of hereditary creep with aging and the modified hereditary theory with Bažant aging function yielded quantitatively and qualitatively correct results. The application of hereditary creep theory allowed for the formulation of the total strain as a superposition of strain increments, obtained by an integral equation. This equation was applied to a series of constant stress increments and decrements, as in the case of cyclic loading, and it was mathematically described in segmented form. Knowledge of the properties of LWAC and useful long-term models is essential for the design of prestressed structures made of lightweight aggregate concrete subjected to time-varying loads.

The aim of this work is to determine the short-term and long-term mechanical properties of lightweight concrete with relatively new sintered aggregate, as knowledge of these parameters is essential to the design of prestressed structures. The problem can be placed in a broader ecological context, because the aggregate comes from recycled power plant ash. This research study was planned based on two concrete mixtures that were already used in previous publications, as the aim of this work was to conduct comparative research by using other methods. In particular, the aim was to investigate the long-term properties of lightweight concrete by using standard methods and appropriate equipment, such as creep-testing machines. As a result of these studies, the secant modulus of elasticity, cylindrical strength, cubic strength, axial tensile strength, splitting tensile strength, bending strength, and shrinkage and creep strain were determined. This study confirmed the short-term properties of concrete obtained in previous studies but did not confirm the results regarding shrinkage and creep. These results turned out to be much higher, which means that these values should not be tested by non-standard methods. An unusual process of development of the elastic modulus and axial tensile strength was observed, and the reasons for these phenomena were described.

This paper presents an experimental determination of the long-term mechanical properties of lightweight concrete with sintered aggregate under cyclic loading and the corresponding analytical standard models. The research was designed around two concrete mixtures. Multiple tests were conducted at the Building Structures, Geotechnics and Concrete Laboratory of the Building Research Institute (ITB), using various equipment including creep-testing machines and tensometric measurements of sample deformations. As a result of these tests, in addition to strength properties, the following time-dependent parameters were determined: the secant modulus of elasticity, shrinkage strains, and creep-recovery strains under cyclic loading. For the parameterization and modeling of constitutive equations, an analysis of creep strains under cyclic loads was carried out, taking into account the integral hereditary law according to the Boltzmann superposition principle and the long-term models formulated according to the following standards and pre-standards: Eurocode 2 (2004), Model Code 2010, Model Code 2020, and Eurocode 2 (2023). The results from the individual models were compared with the test results using the rules for evaluating correction factors for models determined according to Eurocode 2 (2023). It was concluded that the development of creep strain is correctly modeled by the aforementioned standard methods, albeit with the aforementioned correction factors. One of the research objectives was to determine whether the ratchetting phenomenon could be observed during creep of the tested concrete under cyclic loading; however, due to the very low level of plastic deformation, this phenomenon was not detected. The research confirmed the suitability of lightweight concrete with sintered aggregate for use in cyclically loaded concrete structures.

The article presents experimental research and numerical analysis of a building partition in frame construction. The subject of the analysis were sections of the building partition consisting of cold-bent steel profiles and plasterboard cladding. The experiment was carried out using a four-point bending test and recording a continuous load-displacement curve until failure. Next, a computational model based on the finite element method was developed to simulate the experiment. The results from the experimental tests were then compared with that obtained from the numerical analysis. The validation of the numerical model demonstrated a high level of agreement in terms of load-displacement characteristics. The use of numerical analyses provides an alternative to time-consuming experimental tests for estimating displacements of building partitions in frame construction