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This research investigated a pavement system on steel bridge decks that use epoxy resin (EP) bonded ultra-high performance concrete (UHPC). Through FEM analysis and static and dynamic bending fatigue tests of the composite structure, the influences of the interface of the pavement layer, reinforcement, and different paving materials on the structural performance were compared and analyzed. The results show that the resin bonded UHPC pavement structure can reduce the weld strain in the steel plate by about 32% and the relative deflection between ribs by about 52% under standard axial load conditions compared to traditional pavements. The EP bonding layer can nearly double the drawing strength of the pavement interface from 1.3 MPa, and improve the bending resistance of the UHPC structure on steel bridge decks by about 50%; the bending resistance of reinforced UHPC structures is twice that of unreinforced UHPC structure, and the dynamic deflection of the UHPC pavement structure increases exponentially with increasing fatigue load. The fatigue life is about 1.2 × 107 cycles under a fixed force of 9 kN and a dynamic deflection of 0.35 mm, which meets the requirements for fatigue performance of pavements on steel bridge decks under traffic conditions of large flow and heavy load.

There is a limitation to apply air content in fresh concrete as the only index to pre-control frost resistance of cast-in-place concrete. By using an air void analyzer (AVA), the research investigated the influence laws of factors including water-cement ratio, addition amount of fly ash, vibration time, and time-dependent behaviors on a series of characteristics of fresh cement mortars. These characteristics include content, spacing factor, specific surface area (SSA), and size of air voids. The results demonstrated that when the air content was in the range of 7≈8%, the water-cement ratio insignificantly influenced the air-void structure. As fly ash can adsorb the air void, so its addition substantially reduced the content of large air voids and make the size distribution of voids more uniform. Compared with poker vibration, high-frequency vibration exhibited better effects in more uniformly distributing the air voids in the mixture. As large air voids escaped and split, the air content decreased, which was in favor of reducing the air-void size and the air-void spacing factor; Air-void structure in the mixture underwent complex change over time. On the whole, the air-void structure showed the following change trend: small air voids combined to large ones, air voids escaped, the number of air voids and the air-void SSA declined, and the air-void spacing factor enlarged. Therefore, while preparing concrete in practical engineering, it is particularly necessary to consider the adsorption effect of admixture, the time-delay effect of air-entraining agents, and the time-dependent behaviors of air voids, so as to control air-void parameters of hardened concrete.

With the advent and development of Industry 4.0 and 5.0, manufacturing modes have changed and numerous newly complicated and integrated village-level industrial parks have emerged in the Southeast of China, where several enterprises are gathered in the same multistory building. The number of floors and surrounding enterprises can have an impact on accident risk. To reduce the overall risk level of industrial parks, the layout of enterprises with different risks needs to be well designed and optimized. However, to date, limited studies have been conducted to emphatically consider safety and optimize the enterprise layout at an industrial area level, and most studies focus on the cost of the layout. Therefore, this study proposed three biobjective mathematical optimization models to obtain the trade-off between minimizing risk and maximizing rental profit. Risk factors include the enterprise location and the association risk; the enterprise inherent safety risks are not considered. To solve this problem, a specific linearization strategy was proposed and an epsilon-constraint method was applied to obtain Pareto-optimal solutions. Subsequently, an industrial park in Shunde, China, was considered as a case study to verify the performance of the proposed models and methods. Finally, a sensitivity analysis of critical parameters was conducted. The critical factors influencing the objective functions were also analyzed to provide valuable managerial insights.

To better understand thermal behaviors, combustion kinetic characteristics and dynamic releasing processes of gaseous products of four components separated from asphalt binder, thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) tests were conducted on each component at different heating rates, and both differential and integral methods were utilized to discuss their combustion kinetics characteristics, respectively. Results indicate that combustion processes of four components include the volatilization of light components in stage 1 and the combustion of charring layer in stage 2. Main mass losses of saturates and aromatics occur in stage 1, but the mass loss percentages of resins and asphaltenes in the two stages are almost equal. Thermal stability of four components is successively increased from saturates to aromatics, resins and asphaltenes. Also, there is a lag of combustion process due to more incomplete decomposition of each component at a higher heating rate. Temperature range of each combustion stage is widened as the heating rate is raised. Thermal decompositions of resins and asphaltenes are less affected by the heating rate than those of saturates and aromatics. Additionally, activation energy in each component combustion stage is calculated and collated by differential and integral methods, which are suitable to discuss combustion kinetics characteristics of four components and evaluate their thermal stability. Finally, the release rate and amount of gaseous products are increased at a higher heating rate. Combustion properties of asphalt materials are further understood at the component level.

Background The wishbone flower or Torenia fournieri Lind., an annual from tropical Indochina and southern China, is a popular ornamental plant, and many interspecific (T. fournieri × T. concolor) hybrid lines have been bred for the international market. The cultivated lines show a pattern of genetic similarity that correlates with floral color which informs on future breeding strategies. This study aimed to perform genetic analysis and population structure of cultivated hybrid lines comparing with closely related T. concolor wild populations. Methods We applied the retrotransposon based iPBS marker system for genotyping of a total of 136 accessions from 17 lines/populations of Torenia. These included 15 cultivated lines of three series: Duchess (A, B, C); Kauai (D, E, F, G, H, I, J); Little Kiss (K, L, M, N, P) and two wild T. concolor populations (Q and R). PCR products from each individual were applied to estimate the genetic diversity and differentiation between lines/populations. Results Genotyping results showed a pattern of genetic variation differentiating the 17 lines/populations characterized by their specific floral colors. The final PCoA analysis, phylogenetic tree construction, and Bayesian population structural bar plot all showed a clear subdivision of lines/populations analysed. The 15 cultivated hybrid lines and the wild population Q that collected from a small area showed the lowest genetic variability while the other wild population R which sampled from a larger area had the highest genetic variability. Discussion The extremely low genetic variability of 15 cultivated lines indicated that individual line has similar reduction in diversity/heterozygosity from a bottleneck event, and each retained a similar (but different from each other) content of the wild genetic diversity. The genetic variance for the two wild T. concolor populations could be due to our varied sampling methods. The two wild populations (Q, R) and the cultivated hybrid lines (I, K, M, N, P) are genetically more closely related, but strong positive correlations presented in cultivated lines A, C, E, M, and N. These results could be used to guide future Torenia breeding. Conclusions The genetic variation and population structure found in our study showed that cultivated hybrid lines had similar reduction in diversity/heterozygosity from a bottleneck event and each line retained a similar (but different from each other) content of the wild genetic diversity, especially when strong phenotypic selection of floral color overlaps. Generally, environmental factors could induce transposon activation and generate genetic variability which enabled the acceleration of the evolutionary process of wild Torenia species. Our study revealed that wild Torenia populations sampled from broad geographic region represent stronger species strength with outstanding genetic diversity, but selective breeding targeting a specific floral color decreased such genetic variability.

Through laboratory testing, this research studied the connection between air-void structures of hardened concrete and fresh concrete and discussed the effects of the air-void structure on the salt-frost durability of the concrete. The results demonstrate that, in comparison with fresh concrete, the air-void spacing factor shows a close correlation with hardened concrete air-content and decreases in the form of a power function as the air-content increases. When the fresh concrete air-content is more than 6% and the hardened concrete air-void spacing factor is less than 0.18 mm, the influence of parameters of air-void structure on the salt-frost resistance of the concrete reduces. The air-void spacing factor more significantly affects the salt-frost resistance of the concrete compared with air content and the correlation reaches 0.93. Therefore, air-content and air-void spacing factor are recommended for dual control.

This study discussed influences of surface states of concrete on salt-frost durability. By using the Capillary suction of Deicing solution and Freeze-thaw test method(CDF), the effects of factors, such as solution saturation in capillary, surface property and load coupling were compared and analyzed. It is found that drying shrinkage exerts greater effects on salt-frost resistance of the concrete in comparison with solution saturation in capillary. According to the CDF test standard recommended by RILEM, the salt-frost test results of the surface formed with the partitions in the laboratory overestimate salt-frost resistance of the concrete in the actual situation. Scaled mass of the top surface of the molded concrete due to salt frost is about 50% larger than that of the surface formed with the partitions. Coupling effects of repeated load and salt-freezing cycles can aggravate salt-frost damages of the concrete. Keywords: Salt-freezing cycle, Saturation, Surface property, Load coupling