Ключевые слова: temperature stresses

Experience of concreting a massive monolithic foundation slab

https://doi.org/10.58224/2618-7183-2025-8-5-2
Аннотация
The large number of recipe and technological factors affecting the stress-strain state of concrete in the initial period of massive monolithic structures erection predetermines the expediency of using modeling of temperature fields and stresses with software packages based on analytical and numerical solutions when developing technological regulations for concreting. Improving the algorithm for calculating temperature fields and stresses taking into account the kinetics of concrete heat release, heat exchange conditions, ambient temperature and the stages of construction of structures is a pressing task. A comparison was made of calculated, laboratory and natural values of some parameters when concreting a foundation slab with a volume of 1642 m3, a surface area of 821 m2, and a thickness of 2 m. Concreting was completed in 13.5 hours with an average intensity of concrete mix placement of 122 m3/h, and a peak intensity of up to 240 m3/h. A method for calculating temperature fields and stresses taking into account the staged nature of construction has been developed in the MATLAB environment. It does not require rebuilding the geometry of the finite element model, adding nodes and elements during the process of laying new layers, and allows for the correct consideration of the dependence of the strength and deformation properties of concrete on the degree of its maturity. The results of calculated and measured temperature values excluding heating from solar radiation showed a discrepancy of up to 10 °C on the upper surface at some points in time. Some discrepancy between the calculated and experimental values of stresses and deformations with a qualitative coincidence in the nature of the curves is due to the neglection of shrinkage and rapid creep of concrete and poor study of the deformation properties of concrete with additives based on polycarboxylate esters at an early age.
PDF

Methodology for determining true temperature stresses during the construction of massive monolithic reinforced concrete structures

https://doi.org/10.58224/2618-7183-2024-7-3-5
Аннотация
The purpose of the article is to develop and test a simplified method for calculating temperature stresses during the construction of massive monolithic reinforced concrete structures. The essence of the method is to calculate the stress-strain state in standard FEM complexes (ANSYS, Abaqus , etc.) with constant physical and mechanical characteristics of concrete over time, followed by recalculation to true stresses, taking into account the dependence of the elastic modulus of concrete over time. The methodology is based on the hypothesis of equality of temperature deformations for structures with a constant and time-varying modulus of elasticity of concrete. The developed
methodology was tested on experimental data for a massive monolithic foundation slab. The calculation at a constant modulus of elasticity of concrete was carried out in the ANSYS software package. Conversion to true stresses was implemented by the authors in the MATLAB environment. A good agreement between the calculated stress values and the experimental values was obtained.
PDF