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Cheng G.,Survey and Design Institute | Chen G.,Survey and Design Institute Co.
Modern Tunnelling Technology | Year: 2013

Based on the actual construction of the Shizishi tunnel on the Lijiang to Panzhihua highway, which crosses over the Xinzhuang railway tunnel, the cracking and spalling of the lining in the railway tunnel was comprehensively analyzed through numerical simulation and observed phenomena. It was determined that the main factor of the newly-built highway tunnel's effects on the existing railway tunnel was blasting vibration, especially within the section with poorer quality. The reinforcement measures taken regarding the existing railway tunnel and treatment measures used for the newly-built highway tunnel are presented in this paper as a preliminary reference for similar projects.

Zhang S.,Survey and Design Institute Co. | Zhang S.,Hunan University | Shao X.,Hunan University | Cao J.,Hunan University | And 3 more authors.
Journal of Bridge Engineering | Year: 2016

An innovative lightweight composite deck (LWCD) is proposed for steel bridges to avoid premature fatigue cracking. The composite deck is composed of an open-ribbed orthotropic steel deck (OSD) and a thin ultrahigh-performance concrete (UHPC) layer. This study is based on a suspension steel bridge in China, namely, the Second Dongting Lake Bridge. The following investigations were performed: (1) preliminary finite-element analysis (FEA) was carried out to evaluate the vehicle-induced stress ranges (i.e., σ = σmax - σmin) of six typical fatigue-prone details; (2) parameter analyses were performed to investigate the effects of the shape of cutouts and the thickness of the floor beams; and (3) two fatigue tests, one that used a full-scale LWCD panel and another that used a LWCD beam specimen, were conducted to reveal fatigue performance of the OSD and the stud shear connectors, respectively. Results of the preliminary FEA show that, with the contribution of the UHPC layer, the vehicle-induced stress ranges at some fatigue details of the LWCD, such as the rib-deck plate welded joints and the splice welds of the longitudinal ribs, were reduced to be less than their constant-amplitude fatigue limits, which indicates theoretically infinite fatigue lives of these details. The parameter analyses reveal that the apple-shaped cutout had relative good fatigue properties among the four cutout schemes and that the thickness of the floor beams is recommended to be 14-18 mm. According to the fatigue tests on the composite panel specimen and on the composite beam specimen, both the open-ribbed OSD and the stud shear connectors exhibited satisfactory fatigue endurances, which were much greater than 2 million cycles. The current theoretical and experimental investigations reveal that the proposed open-ribbed LWCD has favorable fatigue performances. © 2016 American Society of Civil Engineers.

Ge Z.,South China University of Technology | Wang H.,Rutgers University | Yao H.,South China University of Technology | Zhang Q.,South China University of Technology | Zhang L.,Survey and Design Institute Co.
Journal of Testing and Evaluation | Year: 2016

Moisture transport in asphalt mixtures is influenced by the distribution and connectivity of air voids in the mixture. Therefore, characterization of air void structure is important for predicting moisture damage potential. The purpose of this paper was to detect the air void content of asphalt pavement using ground penetration radar (GPR) and then evaluate the moisture damage potential of asphalt mixtures with different air void contents. In particular, an innovative device, a dynamic water pressure tester (DWPT), was used to evaluate the resistance of asphalt mixture to moisture damage. A rotary loaded wheel tester (RLWT) was used to measure rutting resistance of asphalt mixture before and after being tested by DWPT. A linear relationship between air voids and the amplitudes of wave valley in the GPR signal was found. It suggested that the GPR waveform could be used to detect the air void content of asphalt pavement layers consistent with laboratory measurements. The relationship between air voids and rut depths measured with RLWT showed that an increase in air void content led to an increase in rut depth. Test results in the laboratory indicated that dynamic water pressure resulted in the greater reduction of strength and increase of rut depth if the asphalt mixture has higher air void contents. © 2016 ASTM Int'l all rights reserved.

Wang X.-F.,Changan University | Wang X.-F.,Survey and Design Institute Co.
Chang'an Daxue Xuebao (Ziran Kexue Ban)/Journal of Chang'an University (Natural Science Edition) | Year: 2011

In order to decide the optimal timing of the aspalt pavement preventive maintenance, a decision model was developed. Through analyzing the change of pavement performance after the maintenance treatment application, the model defined the pavement composite benefit, decided the analysis period and set up the four decision making indexes. An application example shows that the model can reflect the roles of various pavement performance indexes, objectively describe the characteristics of maintenance object; based on the four decision indexes (the composite benefit value, the equal annual cost, the benefit index, and the expected extension of life), the five decision principles can be formed, they are the minimum cost principle, the maximum composite benefit principle, the maximum unit cost benefit principle, the longest service term principle and the comprehensive balance principle; these principles may meet the needs of different decision makers, and the decision precision lies on the data of pavement performance.

Wang X.-F.,Changan University | Wang X.-F.,Survey and Design Institute Co. | Cao R.-J.,Jiangsu Transportation Research Institute
Chang'an Daxue Xuebao (Ziran Kexue Ban)/Journal of Chang'an University (Natural Science Edition) | Year: 2011

In light of the complexity of rubber asphalt modification mechanism, such means as scanning electron microscopy, infrared spectroscopy, differential thermal analysis, microscopic structure analysis, component analysis were adopted to study the components of the asphalt before and after modifying, and chemical analysis of rubber powder are adopted to study the modification mechanism of asphalt rubber blending system. The results indicate that the swollen rubber powder is mutually-adhered to form a network structure, and the matrix asphalt changes from homogeneous body into a two-phase continuous blending structure system constituted by rubber powder and asphalt; physical swelling dominates the system, accompanied by a little chemical reaction and with the prolongation of time, the chemical reaction becomes more obvious; the swollen rubber powder forms damping effects to improve the viscosity of rubber asphalt. The modification of asphalt comes from two aspects: firstly, the network structure formed by swollen rubber powder; secondly, the modification of the asphalt composition resulting from rubber powder desulphurization degradation. The natural rubber has better performance in modifying asphalt than synthetic rubber.

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