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Evaluation of bearing capacity of multi-span spandrel-braced stone arch bridge based on static load test

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Gao H. , Duan H. , Sun Y. , Jian J. , Zhang J. , Liu H.

tom Vol. 68, nr 4

633--651

Stone arch bridge is an important type in the early bridge construction process because of its beautiful shape, material saving and economic rationality. However, stone material will deteriorate after long-term operation, which results in a decrease in strength and bearing capacity of stone arch bridge. The vehicle load is increasing at the same time. Therefore, accurate evaluation of bearing capacity of stone arch bridge is essential to ensure safety. In this article, a three-span open-spandrel stone arch bridge was taken as research object. Firstly, the bridge damages were investigated and analyzed in detail, and bridge service state was evaluated. Then, based on the evaluation results of disease damages and considering stone material deterioration, a refined finite element model of stone arch bridge was established to analyze bending moment, axial force, strain and deformation. Finally, static load test was carried out to test vertical deformation and stress of arch ring, horizontal displacement of pier, settlement of foundation and development of cracks. The results show that static load test is the most accurate method for evaluating bearing capacity of stone arch bridge. The evaluation accuracy of finite element model based on material correction is in the middle, and the evaluation accuracy of disease damage assessment is the worst. In practical work, bearing capacity of stone arch bridge can be evaluated by combining the three methods with high accuracy and comprehensive results.

Effects of zero-valent iron and enzymes on the anaerobic co-digestion of sewage sludge and corn silage

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Zhou H. , Cao Z. , Ying Z. , Liu J. , Hu T. , Zhang M. , Zhang J.

tom Vol. 46, nr 4

41--56

Anaerobic co-digestion of sewage sludge and corn silage with zero-valent iron powder (Fe0), cellulase, and papain as reinforcement means was conducted. COD-based feeding ratio of sewage sludge to corn silage was set to 2:1, the solids retention time (SRT) 20 day, digestion temperature 35 °C, and mixing speed 60 rpm. Removal rates of total COD during the control group, and Fe0, papain, cellulase, and papain, Fe0, and the two kinds of enzyme-added tests were 38.04, 41.02, 34.62, 34.55, 35.42, and 48.21%, respectively. The corresponding biogas production was 2.12, 2.62, 2.22, 2.41, 2.25, and 2.81 dm3/day, respectively. The results indicated the addition of cellulase, and papain could maximize the decomposition and hydrolysis of organic matter in sewage sludge and corn silage to volatile fatty acids. Fe0 could reduce the redox potentials of the anaerobic co-digestion, optimize the circumstances of the methanogenesis stage, accelerate biogas production, and improve biogas components. Fe0 and enzymes played a synergistic role in the anaerobic co-digestion system. Life cycle assessment indicated that the anaerobic co-digestion of sludge and corn silage co-substrates could benefit the economy, environment, and social development under the synergistic action of Fe0 and enzymes.