Stiffness Assessment of Cracked Reinforced Concrete Beams Based on a Fictitious Crack Model

Chunyu Fu,Yin Zhu,Dawei Tong 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.2

A fictitious crack model is introduced into cracked reinforced concrete beams to assess the changing beam stiffness under loads. Firstly, nonlinear concrete stress distributions near cracks are built based on the model. Then the stress of the steel bar at the cracked section is considered as cohesive stress. The concrete and steel stresses are substituted into the equilibrium equations of forces to solve the concrete stress. Based on the solution, the section inertias are estimated by iterating the calculation of the cracking open displacement, and finally the beam stiffness is assessed. Experimental data from seven concrete beams after cracking are adopted to validate the effectiveness of the proposed method, and the results show that the fictitious cracks ahead of actual cracks increase their depth with the load, which will raise the neutral axis and change the inertias of cracked sections and their neighboring sections. These changes are taken into account in the stiffness assessment, so the results predicted by the proposed method are shown to coincide well with the nonlinear deflections measured in the experiments.

Heliocoverpa armigera single nucleocapsid nucleopolyhedrovirus ORF52 is a ChaB homologous gene involved in per os infection

Chunyu Zhu,Fangliang Zheng,Sugai Yin,Hongsheng Liu,Yan Liu,Maosheng Zhang,Shuqin Xiong 한국유전학회 2014 Genes & Genomics Vol.36 No.6

The baculovirus ChaB proteins are conservedin all completely sequenced Lepidopteran NPVs and areannotated as putative DNA binding proteins. In our previousstudy, ORF51, a ChaB homologue from Helicoverpaarmigera single nucleocapsid nucleopolyhedrovirus(HearNPV) was found to be involved in budded virusproduction and DNA replication. In the present study, wecharacterized ORF52 (Ha52), the other ChaB homologousgene in HearNPV. 50-RACE revealed that Ha52 was transcribedfrom a conventional late promoter transcriptionalinitiator motif (TAAG) located 25 nucleotides upstream ofATG. Expression analysis demonstrated that HA52 proteinwas expressed from 48 to 96 h post infection. Western blotanalysis of virions from both budded viruses (BVs) andocclusion-derived viruses (ODVs) indicated that HA52 wasa structural component of nucleocapsid from ODV. Tostudy the function of Ha52 in the life cycle of HearNPV,Ha52-knockout and Ha52-restored viruses were generatedby the Bac-to-Bac system. Growth curve analyses showedthat the level of BV production in cells infected with Ha52null virus was similar to those infected with wild-typebacmid derived virus. However, bioassay showed thatdeletion of Ha52 significantly decreased the per os infectivityof HearNPV. Taken together, our results indicatedthat, unlike the previously characterized baculovirual ChaBgenes, Ha52 may be involved in HearNPV per os infection.

Synergistic Effect of PVA Fiber and PTB Emulsion on Mechanical Properties of Cementitious Composites for Damage Repair in Operating Tunnels

Chunyu Zhang,Mengjun Chen,Rentai Liu,Xiuhao Li,Jia Yan,Zhijing Zhu,Fengshuai Fan 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.12

Operating tunnels are often located in complex geological conditions and are prone to various types of damage. Even after structural repair, the repaired material may be vulnerable to secondary damage. It is difficult to effectively repair operating tunnel damage. Hence, developing high-performance repair materials for tunnel structures is critical. This study aimed to develop repair materials by studying the synergistic effects of fiber and polymers. The effectof polyvinyl alcohol (PVA) fiber and PTB (COMPAKTUNA.PRO) emulsion on the compressive strength (40 × 40 × 40 mm, GB/T 17671-2020), flexural strength (40 × 40 × 160 mm, GB/T 17671-2020), uniaxial tensile properties (330 × 60 × 13 mm, JC/T 2461-2018), bond strength (40 × 40 × 160 mm, JC/T 2537-2019), rapid chloride migration coefficient (ϕ100 × 50 mm, GB/T 50082-2009), porosity (40 × 40 × 40 mm, SY/T 6490-2014), and scanning electron microscopy (less than 1 cm3, GB/T 27788-2020) was analysed. The test was completed in the laboratory of our school, and the average value of three specimens per mix ratio was taken. The results indicate that both PVA fiber and PTB emulsion addition reduce the compressive strength but significantly increase the flexural strength, tensile strength, and ultimate tensile strain of cementitious composite. The compressive-to-flexural strength ratio decreases, and the uniaxial compression toughness index increases. The cementitious composites exhibit good integrity after damage. The influence of the PVA fiber is more potent than that of the PTB emulsion. The PTB emulsion increases the impermeability and bonding strength of the cementitious composite and can improve the disadvantages caused by adding the PVA fibers. The bridging effect of the PVA fiber and the membrane-forming effect of the PTB emulsion together influence the performance and cause a synergistic effect to achieve superposition and complementation of advantages. The optimal content of the PVA fiber and PTB emulsion under the synergistic effect can be obtained. The findings can provide a theoretical basis for the optimal design and practical application of restoration materials.

Mechanisms and kinetics of zinc and iron separation enhanced by calcified carbothermal reduction for electric arc furnace dust

Jiayong Qiu,Shui Yu,Jiugang Shao,Kaiqi Zhu,Dianchun Ju,Chunyu Chen,Dexing Qi,Fei Wang,Ni Bai,Rui Mao,Xiaoming Wang 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.4

A high basicity charge prepared with electric arc furnace dust (EAFD), carbonaceous reducing agent and CaO is proposed. The mechanisms of enhancing separation of zinc and iron by calcified carbothermic reduction of the high basicity charge were analyzed by combining thermal analysis kinetics and experiment. The influences of roasting temperature, carbon ratio (nc/no, molar ratio of carbon in graphitic carbon powder to oxygen in EAFD), and CaO dosage on phase transition and dezincification ratio in EAFD were investigated. The results show that the intermediates Ca2Fe2O5 and Fe0.85−xZnxO can be produced from the zinc-iron separation of zinc ferrate during the process of calcified carbothermic reduction of EAFD. Addition of CaO and C results in the following transition pathways: ZnFe2O4+ CaO→Ca2Fe2O5+ZnO→Ca2Fe2O5+Zn(g)→CaO+Fe; Fe0.85−xZnxO+CaO→Ca2Fe2O5+FeO+ZnO→CaO+Fe+Zn(g). In the range of nc/no of 0.4–1.2 and roasting temperature of 1,000–1,100 °C, the addition of CaO can promote reduction and dezincification. Based on the Kissinger-Akahira-Sunose (KAS) and Coats-Redfern methods, the kinetic results show that the calcified carbothermic reduction process can be divided into three stages: initial stage (α=0–0.3), middle stage (α=0.3–0.45), and final stage (α=0.45–1.0). The average activation energy of the initial stage is 305.01 kJ·mol−1, and the reaction mechanism is one-dimensional diffusion. The average activation energy is 315.67 kJ·mol−1 for the middle stage and 288.22 kJ·mol−1 for the final stage. The chemical reaction equation is found to be the most suitable mechanism in the medium and final stages. It is also found that the addition of CaO can reduce the average activation energy by about 32 kJ·mol−1 and shorten the intermediate stage of the reaction.

Management strategy for Spodoptera frugiperda (Lepidoptera:Noctuidae) in mountain maize planting areas in China

Yao Yao,He Yanyan,Zhang Lilan,Wang Kun,Li Bin,Du Guangzu,Zhu Chunyue,Yi Xiaocui,Liu Yiyi,Zi Shengjiang,Chen Bin,Xiao Guanli 한국응용곤충학회 2023 Journal of Asia-Pacific Entomology Vol.26 No.4

The fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), is a major maize pest worldwide and has caused huge economic loss. To explore the control tactics of S. frugiperda in mountain maize planting fields, studies were performed in China from 2020 to 2021 for screening the S. frugiperda-resistant maize variety, seed coating agents, chemical insecticides, and biological agents. The results showed that 75 g/hm 2 Emamectin benzoate had better controlling efficacy (with a control efficacy of 91.05% at 1d) than other chemicals, so it was recommended in the high incidence period of pests. Compared with other seed coating treatments, 50% Lumi ngwei TM625FS (with a control efficacy of 76.19% at 10d) was the best seed coating against S. frugiperda. The biological control “Telenomus remus + Picromerus lewisi” and “T. remus + Eocanthecona furcellata” had good control efficacy on S. frugiperda with 76.01%, 64.10% at 20d, respectively. Additionally, there were lower numbers of S. frugiperda in maize variety GuiDan6, BaoYu9, and YanBaiYu8. In summary, this research rec ommended four effective pest management strategies (GuiDan6-resistant maize variety, 50% Lumingwei TM625FS-seed coating agents, 5% emamectin benzoate-chemical pesticide, and “T. remus + P. lewisi”-biological control) in mountain maize planting fields. The study provided effective control strategies for

Fabrication of non-wetting surfaces on aluminum

Hiroki Habazaki,Katsutoshi Nakayama,Akira Koyama,Tomohiro Inoue,Chunyu Zhu,Yoshitaka Aoki 한국표면공학회 2018 한국표면공학회 학술발표회 초록집 Vol.2018 No.6