Li H.,China Earthquake Administration |
Li H.,Wuhan Institute of Earthquake Engineering |
Li L.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Feng Q.,China Earthquake Administration |
Feng Q.,Wuhan Institute of Earthquake Engineering
Journal of Earthquake Engineering and Engineering Vibration | Year: 2012
The effect of the long-period filter cut-off, Tc, on spectral displacements is analysed using the NGA database of the Pacific Earthquake Engineering Research Center. Long-period spectral displacements would be suppressed badly, if a short Tc is chosen. Strong ground motion accelerograms with reliable period up to at least 10s are selected to investigate the characteristics of displacement response spectra at long periods. The results indicate that the period, in which the spectral displacement culminates, is a significant parameter to control long-period spectral ordinates. This parameter can't be affected obviously by site condition and magnitude,but greatly depends on epicentral distance with linear relation. The maximum amplification factor of displacement spectrum fluctuates slightly, and can be treated as a constant. A transition region is suggested to insert between velocity-sensitive region and displacement-sensitive region to fit for displacement spectrum, and the values of some parameters are proposed in this paper.
Li G.-Y.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Zhao K.-L.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Lu Z.-D.,CAS Wuhan Institute of Rock and Soil Mechanics
Yantu Lixue/Rock and Soil Mechanics | Year: 2012
The size effect coefficients of side and tip resistance of large diameter rock-socketed pile under 20 different conditions are obtained by using FLAC3D. The size effect on ultimate bearing capacity of rock-socketed bored piles with diameters of up to 3.4 m for Tainxingzhou Bridge caused by the excavation has been analyzed. The results show that: (1) The smaller the surrounding rock strength, the size effect of ultimate end of the pile resistance and ultimate friction resistance become greater, and the smaller the size effect coefficient. When the surrounding rock strength is 1-5 MPa, the damage of surrounding rock during excavation is obvious; the size effect is obvious. When the surrounding rock strength increasing to 10 MPa, the damage of surrounding rock during excavation is not obvious, the size effect is significantly weakened. (2) Under the same rock strength, the larger the pile diameter, the larger the size effect of the extreme end of the pile resistance and ultimate friction resistance and the smaller the size effect coefficient. Compared with pile side resistance, the size effect is more pronounced and the size effect of tip resistance coefficient is slightly smaller. (3) The relationship between size effect coefficient of ultimate end of the pile resistance and ultimate friction resistance and pile diameter is well fitted with the hyperbolic function.
Yin D.,T. Y. Lin International China |
Xu W.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Duan X.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co.
Bridge Maintenance, Safety, Management and Life-Cycle Optimization - Proceedings of the 5th International Conference on Bridge Maintenance, Safety and Management | Year: 2010
Being bisected by many large rivers, most notably the Yangtze River and the Jialing River, the city of Chongqing needs a lot of major bridges to accommodate its ever growing traffic volume. The city has been very progressive in accepting new ideas and innovative bridge concepts. The city now has over 50 major bridges, including the world's longest box girder bridge, the 330 m span Second Shibanpo Bridge, opened to traffic in 2006 and the world's largest arch span, the 552 m span Chaotianmen Bridge, opened to traffic in 2007. © 2010 Taylor & Francis Group, London.
Chen Y.M.,Hohai University |
Wu H.Q.,Hohai University |
Sha X.B.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Liu H.L.,Hohai University
International Efforts in Lifeline Earthquake Engineering - Proceedings of the 6th China-Japan-US Trilateral Symposium on Lifeline Earthquake Engineering | Year: 2014
Liquefied and post-liquefied sand can be treated as a kind of fluid. Previous research has suggested that liquefied or post-liquefied sand is a shear-thinning non-Newtonian fluid. The flow characteristics of pre-liquefied sand under high pore pressure ratio are worth discussing. According to the theory of dropping ball viscosimeter, the test apparatus of flow characteristics of pre-liquefied sand is developed. The saturated sand was put in a model box. A water tank was linked with the bottom of the sand box. The height of water tank can be lifted to provide the excess pore pressure required in the sand soil. A steel sphere, embedded in the sand box, can move in the horizontal direction under a dragging force. Resistance and ball velocity were measured during dragging and meanwhile apparent viscosity is evaluated. The velocity of the sphere and excess pore pressure ratio were the main focuses in the tests. The results suggest that the apparent viscosity of the pre-liquefied sand decreases with the growth of the strain rate. The pre-liquefied sand is shear thinning non-Newtonian fluid, which is similar with liquefied and post-liquefied sand. The apparent viscosity of the pre-liquefied sand also decreases with the growth of the excess pore pressure ratio.
Su C.,Southwest Jiaotong University |
Ma J.,Southwest Jiaotong University |
Huang Y.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Hu Z.,Southwest Jiaotong University
Geotechnical Special Publication | Year: 2013
The building of a cross-sea bridge on deep, soft soil in the deep sea requires the thick, soft soil reinforcement in advance. To this end, centrifuge model tests on the composite pile foundation were conducted. In the tests, the pile lengths were 18 cm and 9 cm, respectively. The diameter was 8 mm, and the pile spacings were 3d, 5d and 8d, respectively. The test results indicate that the foundation settlement value with raft can be effectively reduced by the raft between stress balance layer and basement. Corresponding to pile length of 18 cm, the foundation settlement value with raft was 39.1% of the one without raft. When the pile length was 9 cm and the pile spacings were 3d, 5d and 8d respectively, foundation settlement values with raft were about 13.4%, 35.2%, and 52.9% of the settlement value without piles and raft. Settlement value with the pile spacing of 8d was almost the same with the raft foundation settlement without pile. Corresponding to the pile spacings of 3d, 5d, and 8d, when the pile length was 18 cm, the settlement values were 12.5%, 76.5%, and 90.1% of the one without piles, respectively. When the pile spacing was 8d, raft foundation settlement with pile length of 18 cm was 30% less than the settlement with pile length of 9 cm. According to the test results, relationship between settlement and pile spacing in two different conditions was based on whether the raft is involved. Through nine groups of centrifuge model test of foundation reinforcement with steel composite piles, settling characteristics and the effects of pile spacing, pile length and raft on foundation settlement were studied. The results of this study provide important reference for theory research and engineering applications of foundation reinforcement of extremely deep soft soil for sea-cross bridge. © 2013 American Society of Civil Engineers.
Bai Y.,Southwest Jiaotong University |
Zeng Y.,Southwest Jiaotong University |
Zhang X.,Southwest Jiaotong University |
Yan X.,Southwest Jiaotong University |
And 3 more authors.
Tunnelling and Underground Space Technology | Year: 2016
To simulate the unsteady airflow variations in the main tunnel, transverse alleyways and pilot tunnel of the rescue station as a train with emergency is speeding towards the rescue station, a numerical model using dynamic mesh technique for the train running to the rescue station was carried out. The dynamic variation analysis of velocity field and pressure field in the rescue station reveals some airflow behaviors. Experiments have been conducted in parallel and efforts have been done in order to verify the validity of the simulation by comparing with the experimental data. The results show, when the train runs towards the rescue station, the airflow variations perform complexly. Before the train decelerates, the positive pressure occurs in the whole rescue station, and the highest relative pressure occurs in the main tunnel, so the airflows in transverse alleyways blow from the main tunnel to pilot tunnel with 6.2 m/s of the highest average velocity. In the earlier stage of train's deceleration period, the airflows in transverse alleyways 1-4# reverse their direction and reach -2.5 m/s of the highest average velocity. When the train stops in the rescue station, the velocity of airflow in the evacuation platform area blowing from the rear to the front of the train varies between 9 m/s and 12 m/s, now the pressure difference between the main tunnel and the pilot tunnel is obviously less than that in the period of constant speed, and the airflows in transverse alleyways still blow from the main tunnel with higher pressure to the pilot tunnel with lower pressure, with 3.7 m/s of the highest average velocity. As the train stops further, the pressure difference diminishes gradually, so does the airflow velocities in the evacuation platform area and the transverse alleyways, which decreases to 3 m/s and 1.9 m/s respectively when the train has stopped for 5 min. It is suggested that more attention should be paid to the impact which the airflow field variation produced by a train urgently speeding to the rescue station has on the fire smoke diffusion. © 2016 Elsevier Ltd.
Li S.-Y.,Hunan University |
Sun W.-F.,Hunan University |
Sun W.-F.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Chen Z.-Q.,Hunan University
Zhongguo Gonglu Xuebao/China Journal of Highway and Transport | Year: 2013
To investigate the aerodynamic forces acting on the stay cable and the rivulet during rain-wind induced vibrations, a cable model with a diameter of 350 mm was made. And 5 cases of wind tunnel tests were carried out to measure wind pressures on the cable and rivulet by using forced vibration system. The effects of the rivulet and the test model vibrations on the mean and fluctuating wind pressure coefficients, the mean aerodynamic force coefficients and the power spectral density of fluctuating lift coefficients were systematically studied. Moreover, the validity of quasi-steady theory in rain-wind induced vibrations was checked out. The results indicate that quasi-steady theory can reflect the main characteristics of the wind forces on the cable and the rivulet; the oscillation of the rivulet and vertical vibration of the cable do not change their mean wind force coefficients, and there is a fast drop of mean lift coefficient at the attack angle of 60°; the oscillation of the rivulet on the cable surface heavily affects the fluctuating aerodynamic force coefficients, while the vertical vibration of the cable has a little influence; furthermore, the presence of the rivulet decreases the frequency of vortex shedding.
Li S.,Hunan University |
Sun W.,Hunan University |
Sun W.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Chen Z.,Hunan University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2014
In order to investigate the unsteady aerodynamic forces on the cable and the rivulet during rain-wind induced vibration, a cable model with a diameter of 350mm was made and tested in the wind tunnel tests to measure the pressure distribution on the test model by a forced vibration system developed by HD-2 wind tunnel. The drag and lift forces of the cable and the rivulet were then obtained by the pressure integration. Eight aerodynamic derivatives of the cable and the rivulet were identified respectively, and the unsteady aerodynamic forces on the cable and the rivulet were carefully studied. The results show that it is feasible to simulate the rivulet oscillation on the cable surface by rotating the test model. Positive values of aerodynamic derivatives of the cable and the rivulet are found when rivulet position angle is 60°, which corresponds to a sudden decrease of the mean lift coefficient of the cable. The unsteady aerodynamic forces obtained through aerodynamic derivatives agree well with the tested forces, which indicate that the unsteady aerodynamic forces can be adopted in theoretical analysis of rain-wind induced vibration.
Liu M.-Y.,Hubei Engineering University |
Wang S.,Hubei Engineering University |
Zhang Q.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co Ltd
Wuhan Ligong Daxue Xuebao/Journal of Wuhan University of Technology | Year: 2013
The schemes of non-navigable span inshallow water area of Hongkong-Zhuhai-Macau bridge use 85 m span steel-concrete composite continuous beams with 6~7 spans one continuous unit and the designed service life of the bridge will be 120 years. The bridge use the construction technology of large segment integral lifting, converting simply-support in continuous , fulcrum lifting-up and fallbacking, stretching prestress of bridge deck in negative moment area. The ANSYS software is used to build 3-D and refined finite model of composite continuous beams with single span to research force distribution of shear studs in lognitudinal and transverse direction of composite continuous beams under dead load and live load.The side span with the shear stdus under the most unfavorable load condition is choosed and spring element combin39 is used to calculate accurately drawing force of every shear stdus. The calculation results of comparison of two section types show that the shear stdus between concrete deck and steel box girder of section with longitudinal beam has better connectivity than section without longitudinal beam.
Chen W.,Huazhong University of Science and Technology |
Chen W.,Wuhan Polytechnic University |
Wang B.,Huazhong University of Science and Technology |
Zhan H.,China Zhongtie Major Bridge Reconnaissance and Design Institute Co. |
Zhou L.,Wuhan Polytechnic University
Kybernetes | Year: 2013
Purpose: Denoising of the vibration signal is crucial to identify a structure's damage. Based on noise frequency character, the "real" vibration signal can be gotten. The purpose of this paper is to propose a novel method for denoising a signal based on the wavelet transform. Design/methodology/approach: The vibration signal with noise which can be collected by wireless network is decomposed by wavelet transform. In order to select optimal level of wavelet decomposition, based on noise's frequency, power spectral density is used. A soft thresholding method based on minimum mean-variance is used for vibration signal de-noising with Gaussian noise. Findings: A novel method has been described in his paper. Based on the relationship between vibration signal's character and noise frequency, the way to get rid of noise is combined wavelet transform with power spectral density. Originality/value: In order to select optimal level of wavelet decomposition, based on noise's frequency, power spectral density is used. A soft thresholding method based on minimum mean-variance is used for vibration signal denoising with Gaussian noise. © Emerald Group Publishing Limited.