Study on the Mechanical Properties of Perforated Steel Plate Reinforced Concrete.

In this paper, the mechanical properties of perforated steel plate reinforced concrete were studied. Through the compression test of the specimen, the failure mode, the compressive ultimate bearing capacity, and the stress−strain curve of the specimen were obtained. The results show that the compressive strength of perforated steel plate reinforced concrete is twice that of the same grade of plain concrete; through the pull-out test of the specimen, the failure mode and the ultimate uplift bearing capacity were obtained. The finite element software ANSYS was used to simulate the perforated steel plate reinforced concrete specimen, and the results show that the model is reliable. Through the range analysis method, the influence degree of the three factors of the thickness of the perforated steel plate, the hole diameter, and the hole spacing on the compressive strength and the ultimate bearing capacity of the pull-out was studied, and the optimal solution was obtained. The analysis results show that the order of the three factors on the compression and pull-out tests is: the plate thickness of the perforated steel plate > the hole diameter > the hole spacing; the optimal combination of the compressive strength of the perforated steel plate reinforced concrete specimen is that the thickness of the perforated steel plate is 0.75 mm, the diameter of the perforated steel plate is 15 mm, and the spacing of the perforated steel plate is 5 mm; the optimal combination of the ultimate bearing capacity of the pull-out is that the thickness of the steel plate with holes is 1.0 mm, the diameter of the steel plate with holes is 15 mm, and the spacing of the steel plate with holes is 15 mm.

Study on Mechanical Properties of Multi-Cavity Steel-Concrete Composite Beam.

This paper proposes a new form of composite beam: a multi-cavity steel-concrete composite beam. This composite beam uses internal perforated steel plate to connect the concrete with the steel structure, and shear connectors are no longer required, which is more suitable for industrial production. The mechanical properties of a multi-cavity steel-concrete composite beam in industrial applications are studied to avoid failures. In this paper, two multi-cavity steel-concrete composite beams with a size of 2500 mm × 200 mm × 300 mm were prepared, in which the angle of internal porous steel plate was set as 60° and 75°, respectively. A full-scale static load test was conducted on the beams to research its deformation and failure modes. The finite element software ANSYS was used to perform finite element modeling of multi-cavity steel-concrete composite beams and to analyze the influence of concrete strength, steel strength, porosity, and the angle of internal porous steel plate on the mechanical properties of composite beams. The results are as follows: before the composite beam reaches its serviceability limit state, its deformation basically shows a linear change; with the increase of load, the plastic deformation is gradually obvious, which can still provide a certain bearing capacity in the failure stage; the bearing capacity of the composite beam is positively correlated with the strength of concrete and steel, while negatively correlated with the porosity and the angle of internal porous steel plate; composite beams have large bearing capacity, good ductility and integrity.

Study on Self-Leveling of Foamed Concrete for Long-Distance-Tunnel-Gas-Pipeline Backfill.

In the foamed-concrete-backfilled-gas-pipeline project, the fluidity of foamed concrete has a great impact on the construction quality. This research studied the fluidity of foamed concrete through laboratory tests. By changing the water−cement ratio, admixtures, additives, foaming-agent content and other test parameters, foamed concrete with different fluidities was prepared, and the effects of the above parameters on the fluidity of foamed concrete were analyzed. At the same time, the construction equipment was improved in the three steps of transportation, production and pouring. The results show the factors affecting the fluidity of foamed concrete are, in order of importance, foaming-agent content > water−cement ratio > water-reducer content > admixture content. According to the orthogonal-test results, the control scheme meeting the fluidity requirements of the actual engineering project had gains as follows: the water−cement-ratio range from 0.5 to 0.6, the amount of admixture from 35% to 40%, the water-reducer content at 1% and the foaming-agent content from 3% to 3.5% so as to ensure the automatic leveling of foamed concrete under the best flow state.

Effect of Maintenance and Water-Cement Ratio on Foamed Concrete Shrinkage Cracking.

This is a study on how to reduce shrinkage and improve crack resistance of foamed concrete. By selecting different curing temperatures and humidity, six different curing conditions were analyzed. The shrinkage deformation and maximum crack width of foamed concrete blocks with water-cement ratios of 0.4 and 0.5, under six curing conditions, were measured by a comparator and optical microscope, and the cracking time was recorded. The effects of curing temperature, humidity and water-cement ratio on the shrinkage and crack resistance of the foamed concrete were analyzed by comparing the experimental results of each group. We studied the primary and secondary order of the three factors affecting the drying shrinkage of foamed concrete. The results show that: temperature is the primary factor that changes the drying shrinkage performance of foamed concrete, followed by the water-cement ratio, and finally humidity. The interaction of these three factors is not obvious. The shrinkage of foamed concrete increases with the increase in temperature; increasing the humidity of curing can control the water loss rate of foamed concrete and reduce shrinkage. Lower humidity and higher temperature will make cracks appear earlier; with an increase in the water-cement ratio, the initial cracking time is shortened and the cracking property of foamed concrete is improved.

An Electrical Resistivity Method of Characterizing Hydromechanical and Structural Properties of Compacted Loess During Constant Rate of Strain Compression.

Hydromechanical and structural properties of compacted loess have a significant impact on the stability and reliability of subbase and subgrade, which needs to be quickly determined in the field and laboratory. Hence, an electrical resistivity method was used to characterize the hydromechanical and structural properties of compacted loess during constant rate of strain compression. In the present work, compacted loess samples with a dry density of 1.7 g/cm3, a diameter of 64 mm, a height of 10 mm and different water content ranging from 5-25% were prepared. The constant rate of strain (CRS) tests were conducted by a developed oedometer cell equipped with a pair of horizontal circular electrodes (diameter of 20 mm) and vertical rectangular electrodes (width of 3.5 mm) to determine the electrical resistivity of compacted loess. The results showed that as average water content increases, plastic compression indices increase from 0.220 to 0.350 and the elastic compression indices increase from 0.0152 to 0.030, but they decrease to 0.167 and 0.010 and yield stress decreases from 381.28 kPa to 72.35 kPa. Moreover, as vertical strain increases, the variation trend of average formation factor and average shape factor for the lower water content decreases but increases for the maximum water content, and the anisotropy index first decrease and then tend to increase slightly, which indicates that the structural properties of unsaturated and saturated samples during compression exhibits different trend and the anisotropy of samples tend to be stable as vertical strain increases. As the water content increases, the average formation factor and average shape factor decrease, but the anisotropy index first decreases then increases, suggesting that water content has a significant impact on these electrical indices. More important, The coefficients of average formation factor decrease from 33.830 to -1.698 and the coefficients of average shape factor decrease from 8.339 to -0.398 as water content increases, whereas there is less variation for the coefficient of anisotropic index with a value of 2.190. An equation correlating average formation factor and water content and vertical strain is regressed to characterize the hydromechanical properties of compacted loess by measuring its impedance, which can be used to evaluate the stability of compacted loessic ground and subgrade.

Epidemics in interconnected small-world networks.

Networks can be used to describe the interconnections among individuals, which play an important role in the spread of disease. Although the small-world effect has been found to have a significant impact on epidemics in single networks, the small-world effect on epidemics in interconnected networks has rarely been considered. Here, we study the susceptible-infected-susceptible (SIS) model of epidemic spreading in a system comprising two interconnected small-world networks. We find that the epidemic threshold in such networks decreases when the rewiring probability of the component small-world networks increases. When the infection rate is low, the rewiring probability affects the global steady-state infection density, whereas when the infection rate is high, the infection density is insensitive to the rewiring probability. Moreover, epidemics in interconnected small-world networks are found to spread at different velocities that depend on the rewiring probability.