No abstract

No abstract

No abstract

Abstract-The paper presents the results of physical modeling of the wind pressure. Systematic data are obtained for the pressure coefficient distribution over the sides of the differentsize building models under the airflow conditions. These conditions are provided by an obstacle situated in front of the building model. The obstacle has the same geometrical parameters as the building and is longitudinally and transversely displaced relative to the airflow direction.

No abstract

The paper presents the two-dimensional model of Portland cement curing based on the finite element method. The cement curing lasts for 2 days in the temperature gradient conditions ranging from 65 to −20 °C. A cement rod 7×70 cm in size was used for modeling the von Mises stress distribution. It is shown that in the temperature gradient conditions, the stress maximum in curing Portland cement shifts toward the hot edge of the cement rod and exceeds the minimum stress level more than two times. The stress growth at the interfaces between the concrete timber and the cement rod exceeds the stress maximum inside the latter. This stress distribution is connected with the heat flow generation and superposition of direct and reverse heat flows. Superposition of the negative heat flows generates the stresses at the interfaces, which are higher than those generated by the positive heat flows. The concrete timber and the interface fixation are the additional factors that increase the stress level at the interfaces and promote the cement fracture.

No abstract

The paper studies the strength properties of sand-cement rod with the water-cement ratios of 0.4, 0.44, 0.49 and 0.54 under thermal gradient conditions. Experimental research concerns the influence of the temperature gradient within 60 to –20 оС on the mechanical properties of the sand-cement mortar with the different water-cement ratio. It is shown that the strength gain rate of sand-cement specimens varies in different periods of curing. The strength index of the sand-cement rod also varies in the conditions of heat and mass transfer that is supported by the theoretical background. The indicated temperature gradient significantly affects the curing process of the sand-cement specimens. Lower intensity of the strength gain is observed in specimens after 4-hour curing. The increase in the curing time from 8 to 12 hours leads to more intensive strength gain starting from the third specimen, when positive temperature begins. After 8-hour curing, the strength gain rate grows starting from the fifth specimen. At last, 12-hour curing results in the higher rate of the strength gain. Further increase in the curing time can lead to the highest strength gain rate. The rupture point drops with increasing water-cement ratio for all the specimens, independently of their position in the rod. Investigation of these processes will provide a better understanding of the negative effect of thermal gradient on the concrete structures and allow finding ways to increase their service life.