Papers by Author: Jun Deng

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Authors: Jian Li, Jun Deng
Abstract: Based on the similarity between knowledge discovery from data bases (KDD) and Structural health monitoring (SHM), and considered the particularity of SHM problems, a four-step framework of SHM is proposed. The framework extends the final goal of SHM from detecting damages to extracting knowledge to facilitate decision making. The purposes and proper methods of each step of this framework are discussed. To demonstrate the proposed SHM framework, a specific SHM method which is consisted by second order structural parameter identification as feature extraction and statistical control chart analysis of identified stiffness for feature analysis is then presented. Through clarifying the goal and hierarchy of extracting useful knowledge of SHM problems, the framework has potential to facilitate the further development of SHM.
Authors: Jun Deng, Jian Li, Xiao Yue Fang
Abstract: The existing long-span bridges deteriorate with time due to fatigue, overloading, corrosion and environmental effects. To date, condition evaluation of the existing long-span bridges is important to carrying out the activities related to maintenance, rehabilitation and replacement of bridges. In this paper, a methodology was developed to evaluate the condition of the existing long-span bridges. The analytic hierarchy process was combined with the fuzzy synthesis. A procedure is given for condition rating of the existing long-span bridges as well. A bridge as the example is evaluated by this method and the results show that the damage of the bridge is marginal, which is same as the conclusion obtained from the traditional methods.
Authors: Zhi Hong Xie, Pei Yan Huang, Gen Quan Zhong, Jun Deng
Abstract: Fiber Reinforced Polymer (FRP) has been effectively used for strengthening concrete beams. In this study, nonlinear finite element (FE) model of the beam strengthened with CFRP is established to analyze the debonding failure caused by the adhesive hollow defects. The constitutive relationship of the adhesive layer in the FE models is similar to Monti’s bi-linear mode. Three different locations of the hollows are considered in the FE models. The principal stresses in the concrete, the debonding stresses in the adhesive and the stress in CFRP are calculated. The results show that the effect of the locations of the hollow is marginal on the principal stresses in the concrete. When the hollow appears close to the interfacial end, the debonding stresses in the adhesive and the shear stress in the CFRP are significant, which easily causes the debonding failure.
Authors: Jun Deng, Pei Yan Huang
Abstract: The fatigue performance and durability of the reinforced concrete (RC) beams strengthened with fibre reinforced polymer (FRP) laminates is an advanced research topic in civil engineering. The crack propagation life is the dominant part of the whole fatigue life of the cracked RC members strengthened with FRP laminates under cyclic loads. In this paper, a theoretical and experimental study was conducted to investigate the rule of the fatigue crack propagation of the RC beams strengthened with carbon FRP (CFRP) under constant cyclic bending load. A total of 5 RC beams with sizes 1850×100×200mm strengthened with CFRP were tested. The results show that it is possible to divide the process of the crack propagation into three distinct phases, including crack initiation and then quickly propagation (Phase I), stable propagation and then rest (Phase II) and unstable propagation (Phase III). In accordance with Paris-Erdogan Law, a semi-empirical equation was developed to predict the crack propagation rate. The empirical coefficients of the equation were obtained from the fatigue test results. To validate this equation, the predicted fatigue life of crack propagation calculated by it is compared with the data obtained from tests. It shows the agreement is good.
Authors: Jun Deng, Jian Li, Xiao Yue Fang
Abstract: The assessment of the risk probability and risk consequence of existing long-span bridges has become a focus in both research and engineering applications. In this paper, a process to assess the risk consequence of existing long-span bridges is developed. The analytic hierarchy process was combined with the fuzzy synthesis. In accordance with the features of existing long-span bridges, risk consequences are classified and the model of the risk consequence is simulated. A bridge as the example is evaluated by this process and the results show that the risk consequence of the bridge is negligible. Combining the risk probability and risk consequence gives the comprehensive risk of this bridge is negligible.
Authors: Jun Deng
Abstract: One of the greatest drawbacks to predicting the behaviour of bonded joints has been the lack of reliable data on the mechanical properties of adhesives. In this study, methods for determining mechanical properties of structural adhesive were discussed. The Young’s modulus, Poisson’s ratio and tensile strength of the adhesive were tested by dogbone specimens (bulk form) and butt joint specimens (in situ form). The shear modulus and shear strength were test by V-notched specimens (bulk form) and thick adherend lap-shear (TALS) joint specimens (in situ form). The test results show that the elastic modulus provided by the manufacturer is too low, the dogbone specimen is better than the butt joint specimen to test the tensile strength and elastic modulus and the TALS joint specimen is better than the V-notched specimen to test the shear strength.
Authors: Hui Li, Jun Deng, Jun Hong Lin
Abstract: Since the expansion of the cement during curing was constraint by the steel tube, the concrete core in the self-stressing concrete-filled steel tubes (SSCFST) is under tri-axially compression before applying load, which increases the axial capacity of the SSCFST. In addition, Carbon fiber reinforced polymer (CFRP) wrapping can avoid bucking of the steel tube, increase the axial capacity and improve the durability of SSCFST. This study presents a theoretical study on axial capacity of the SSCFST wrapped with CFRP sheets. Several basic assumptions are proposed. The ultimate equilibrium method was employed to analyze the axial capacity, of which two limit states, including steel tube bucking and CFRP sheets rupturing were considered. The analytical results from an example show that the initial self-stress improves axial capacity of the SSCFST by about 30% and the CFRP reinforcement improves axial capacity by about 15%.
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