Advanced Materials Research Vols. 255-260

Abstract: The characterstics of corrosion is important to asseess structure safety, however, because of the complexity of corrosion, it is hard to see papers anout it. In order to study the characterstics of corrosion specimen surface, two methods are used to obtain corrosion specimens, one method is constant temperature and humidity, the other is natural corrosion. Then roughness tester is used to detect the profile of corrosion specimen surface, and the surface characterization is analyzed by fractal theory. Through the experimnet, we find the law of power relationship between fractal dimension and the depth of localized corrosion, so it will help to solve the difficulty of safety assessment for in-service steel structure.

Abstract: Because of the complexity of corrosion, the law of uniform corrosion and localized corrosion is still not clear,so it is difficult to assess their impact on the structure safety. In order to differ them and find their own law, we obtain a lot of corrosion specimens by ways of constant temperature and humidity, and then detect the size of corrosion pits by roughness tester. After that, the method for calculating the thickness of uniform corrosion and localized corrosion is proposed. Then the method is used to analyze the experiment data. The result indicates the thickness of uniform corrosion and localized corrosion all increase with the rate of corrosion, and they all show a power relationship with corrosion rate, so it will provide a basis for distinguishing them in safety assessment.

Abstract: A great many of experiments has shown that reinforced concrete (RC) structures suffered from spalling in fire. However, at present there are still no convincing spalling predicting models available due to the inhomogeneous nature and complicated thermo-hydro-mechanical interactions in concrete at elevated temperatures. In order to evaluate the fire resistance of RC structures which are subjected to concrete spalling, a thermal analysis procedure is developed which considers the effects of spalling on the growth of temperature in RC members. The predicted temperatures are then used to model the structural behaviour. The spalled portion of concrete is modelled as "void", which has no thermal and mechanical properties. A series of parametric studies carried out on RC structural members with different boundary conditions shows that the influence of spalling on fire resistance is very significant apart from the RC slabs subject to higher laterally restraint.

Abstract: Based on the static test of large-scaled prestressed steel concrete frames, the behavior of crack were tested and investigated. In this paper, according to theory of reinforced concrete members, Code for design of concrete structures(GB 50010-2002)and code ACI 318—05, the formulas of cracking moment considering secondary axial forces were deduced and verified by test results. Conclusion can be drawn as follow: the calculation errors of formulas derive from theory of reinforced concrete members is small, generally less than 6%; the errors of formulas referring to Code for design of concrete structures(GB 50010-2002)is about 10%, which is satisfy the needs of engineering and simply to be calculated; Cracking moment calculated by formulas referring to code ACI 318—05 is less than test result, it is unsafe for engineering application.

Abstract: In order to understand the differences of swelling forces tested by three conventional methods and discuss the swelling force attenuation law with allowance of a small amount of swelling deformation, the swelling force tests of Baise expansive soil were carried out by anti-inflation pressure method using uniaxial oedometer. In addition, the swelling force tests with allowance of deformation base on the same principle of pressure expansion method were performed. The results of swelling force on the samples with two water contents and the same dry density indicated that the maximum, medium and minimum of swelling force were tested by swelling anti-pressure method, the balance pressure method and the pressure expansion method, respectively; In addition, the relationship between swelling force and expansion deformation was a negative exponential; The increase in water content of the expensive soil during practical conditions was restrained by the overburden pressure. The research results can provide the references for reasonably choosing the swelling force testing methods and the design of the expansive soil subgrade.

Abstract: According to the temperature changes of corrugated webs steel beam in fire at different time, 3 different kinds of shear buckling modes and the changes of elastic buckling critical stress of corrugated web steel beam are analyzed in the fire, considering the effect of fire high temperature on structure elasticity modulus. The computed expressions of partial shear elastic critical buckling stress, elastic critical buckling stress of general buckling mode and critical stress of elastic relevant buckling in the fire are presented in the paper. Numerical results show that fire high temperature has obvious effect on elastic shear critical buckling stress changes of corrugated web steel beam.

Abstract: Based on the fundamental theory of electrochemical anodic polarization, simulated concrete is doped with corrosion inhibitor to prevent corrosion by chloride ion in the marine environment. Thus, with reference to the potential-time curves obtained in different concrete environments and construction conditions, the early dynamic state of active transition of rebar passive films in concretes can be quickly characterized. According to the experiments, the characteristics of passive active transition are synchronous with rebar corrosion. This helps to systematically study the influence of different components of concrete and external media on the durability of the concrete structure. The strong alkaline environment of the concrete is useful in controlling corrosion rate of reinforcing bar. As one of the additional protective measures of the durability of the concrete structure, corrosion inhibitor’s long-term performance contains uncertainty.

Abstract: Construction accident precursors(CAPs) are potential upcoming accident signals and offer the possibility for improving safety management performance. Case-based reasoning (CBR) as an artificial intelligence(AI) tools can be used to improve the efficiency and quality of CAPs identification. This paper developed a system framework for identifying CAPs on construction sites using CBR. There were ten indicators, including six problem indicators and four solution indicators were identified to describe the CAPs case between the accident characteristics and corresponding precursors. Especially, a technique case-based adaptation was implemented in the adaptation stage of CBR called inner CBR and three indicators were identified to describe the adaptation case. Eventually, the CAPs identification system framework was presented and a case study based on actual accident case from US Department of OSHA was used to illustrate how to seek CAPs.This research provides a new way to acquire more useful information from historical accident records in order to improve safety on construction sites for future ongoing project.

Abstract: Large structures weighing system is upgrading the structure simultaneously using several jacks. After structure leaves the ground, the hydraulic control check valve is used for hydraulic lock, and pressure sensor that under each jack measures the jack cavity pressure. Data is collected by PLC system to obtain the force situation of each jack. With the moment of inertia calculation, center of gravity coordinates of the plane is obtained, the weighing system involves in the hydraulic system, control system, data acquisition and transmission. As the jack wall friction and the leakage factors, in the measuring process, pressure sensor reflects little, and measurement errors appear. In this research, experimental research data has been used to obtain empirical formula under varying pressures, error has also been corrected in weighing measurement system in order to get high precision weighing data. The results are in good agreement after comparing this theory with results measured by weight sensor.

Abstract: The acid mine drainage pollution is the worldwide difficult problem induced by mining industry. Based on the investigation and analysis of acid sewage quality component in some mine wastewater reservoir, the interaction and corrosion mechanism are studied between acid mine drainage and anti-seepage curtain, the technological ideas about how to improve and enhance the corrosion resistance of curtain are put forward, providing reference for predicting engineering durability and reinforcement. The corrosion mechanism research shows that the cement frequently take place the decompose and polyreaction because of the double action of solventing out and chemical dissolution during the AMD corroding, it changes the molecular structure inside the curtain and the composition of its framework, so as to lead to the structure loosing, the permeability increasing, and the cement strength reducing, and thus affecting the anti-seepage property and durability of the curtain seriously.