Key Laboratory of High speed Railway Engineering

Chengdu, China

Key Laboratory of High speed Railway Engineering

Chengdu, China
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Xiao L.,Southwest Jiaotong University | Xiao L.,Key Laboratory of High Speed Railway Engineering | Xiao L.,University of Tennessee at Knoxville | Li X.,Southwest Jiaotong University | John Ma Z.,Southwest Jiaotong University
Journal of Bridge Engineering | Year: 2017

Perforated shear connectors (PSCs) in steel-concrete composite joints are usually deeply embedded in concrete, and the perforated plate thickness varies significantly, which is different from those in a steel-concrete composite beam. In this study, two types of push-out tests (24 specimens in total) were conducted to compare the mechanical behavior of PSCs used in steel-concrete composite joints with that in composite beams. The testing variables include the push-out test arrangement, plate thickness, and concrete compressive strength. The experimental results are presented and discussed, focusing on the shear resistance, load-slip behavior, and failure modes. Finally, the experimental results were compared with existing shear resistance equations to evaluate their applicability for PSCs in composite joints. © 2016 American Society of Civil Engineers.

Wang Y.F.,Southwest Jiaotong University | Wang Y.F.,National Central University | Dong J.J.,National Central University | Cheng Q.G.,Southwest Jiaotong University | And 2 more authors.
Journal of Geophysical Research: Solid Earth | Year: 2017

To characterize the hypermobility mechanism of rock avalanches, a series of rotary shear tests at different shearing velocities (Veq) ranging from 0.07 m/s to 1.31 m/s and at a normal stress of 1.47 MPa were carried out on soil sampled from the basal facies of the Yigong rock avalanche that occurred in the Tibetan plateau in China. Through conducting these tests, the macroscale and microscale features of the deformed samples were analyzed in detail with the following valuable conclusions being reached: (1) soil subjected to rotary shear exhibits a clear velocity-dependent weakening characteristic with an apparent steady state friction of 0.13 being reached at Veq ≥ 0.61 m/s, (2) high-temperature rises and layers with high porosity were observed in the samples sheared at Veq ≥ 0.61 m/s, and (3) the cooperation of thermal pressurization and moisture fluidization induced by friction heating plays an important role in explaining the marked frictional weakening of the soil. In addition, the appearance of nanoparticles due to particle fragmentation should facilitate the weakening of the soil but is not the key reason for the marked frictional weakening. ©2017. American Geophysical Union. All Rights Reserved.

Wang P.,Key Laboratory of High speed Railway Engineering | Wang P.,Southwest Jiaotong University | Yang F.,Key Laboratory of High speed Railway Engineering | Yang F.,Southwest Jiaotong University | And 2 more authors.
Gongcheng Lixue/Engineering Mechanics | Year: 2017

By combining the random vibration Pseudo Excitation Method (PEM), symplectic mathematics of infinitely periodic sub-structures, and harmonic response finite element analysis, a prediction model of environment vertical vibration induced by a vehicle-track-tunnel coupled system is proposed which accounts for the frequency-dependent stiffness of the rail pad. Taking Nanjing's Metro Line 1 Project as the research object, a Martin-Davidenkov model, a type of equivalent linear visco-elastic model, was used to describe the relationship between soil loading and unloading and nonlinear stress-strain. Theoretical results of vertical acceleration of the surface soil are compared with the measured data, and they agree well in the whole frequency domain but have a maximum peak difference of 0.6 dB at the centre frequency of 50 Hz. The conclusion indicates that the track irregularity on the testing subway line is close to the calculated condition, and the prediction model for environment vertical vibration of the vehicle-track-tunnel coupled system has better predictive accuracy and efficiency in the frequency domain and its parameter selection method is reasonable. © 2017, Engineering Mechanics Press. All right reserved.

Wei K.,Key Laboratory of High speed Railway Engineering | Wei K.,Southwest Jiaotong University | Zhang P.,Key Laboratory of High speed Railway Engineering | Zhang P.,Southwest Jiaotong University | And 2 more authors.
Gongcheng Lixue/Engineering Mechanics | Year: 2017

Taking the rail pads of the thermoplastic polyurethane elastomer (TPEE) for example, the nonlinear curves between the static loads of TPEE rail pads and their corresponding compressed deformation were plotted by a universal testing machine. A rail-fastener finite element model used for the nonlinear static analysis was established to calculate the compressed deformation of rail pads and their corresponding static stiffness under the static vehicle weight and the preload of the rail fastener. Finally, the vertical vehicle-track coupled model was applied to investigate the influence of the constant stiffness, the frequency-dependent stiffness, the amplitude- and frequency-dependent stiffness of TPEE rail pads on the frequency-domain random vibration responses of the vehicle-track coupled system. Results indicate that the static stiffness of TPEE rail pads nonlinearly increases with the increase of their compressed deformation, and the static stiffness of TPEE rail pads ranges from 19.1 kN/mm to 37.9 kN/mm under 1/8 vehicle weight of 80 kN and rail fastener' preloading of 20 kN, with an average approximately equivalent to the hypothetically linear constant stiffness of 26.7 kN/mm in the national standard. Additionally, compared with the amplitude- and frequency-dependent stiffness of TPEE rail pads, their hypothetically linear constant stiffness leads to a severe underestimate of the random vibration levels of wheel-track coupled system at frequencies of 65 Hz~150 Hz. Thus, only if there are polymer materials with strong nonlinear stiffness in the vehicle-track coupled system, it is necessary to comprehensively consider its amplitude- and frequency-dependent stiffness; otherwise, it is difficult to accurately predict the frequency-domain responses of both the wheel-track coupled vibrations and the train-induced environment vibrations. © 2017, Engineering Mechanics Press. All right reserved.

Zhan Y.,Southwest Jiaotong University | Zhan Y.,Key Laboratory of High speed Railway Engineering | Zhao R.,Southwest Jiaotong University | Ma Z.J.,University of Tennessee at Knoxville | And 3 more authors.
Engineering Structures | Year: 2016

Concrete-filled steel tube (CFST) member is widely used for building, bridge and foundation structures because of its excellent performance. When a CFST member is subjected to axial loads, the filling concrete is confined by the steel tube, resulting in a tri-axial state of compression that improves its strength, stiffness and ductility. However, the cracking of concrete in tension zone would decrease this enhancement when the CFST member is subjected to flexure, especially when it is used as a major flexural member with large-scale section in bridges. To overcome this weakness, the prestressed CFST concept is investigated in this paper. Eight prestressed CFST beams with large-scale section (300 × 450 mm) were tested under bending. Two concrete strengths (C50 and C60) and two different degrees of prestressing (0.26 and 0.40) were studied in the experimental program. The full vibration and grouting method was introduced to gain a good performance of specimens. The perfobond rib shear connector was adopted to achieve the composite action. The flexural behaviors were verified by comparing with predictions from a proposed model considering the confinement effects. A simplified method is proposed to determine the ultimate moment capacity based on the plastic stress block hypothesis. Both experimental and analytical results show that the prestressed strands could significantly enhance the confinement effect of the core concrete under bending, which, in turn, improves the prestressed CFST beam performance in strength, stiffness and ductility. © 2016.

Zhao X.,Southwest Jiaotong University | Zhao X.,Key Laboratory of High speed Railway Engineering | Zhao X.,Purdue University | Salgado R.,Purdue University | Prezzi M.,Purdue University
Proceedings of the Institution of Civil Engineers: Geotechnical Engineering | Year: 2015

The use of combined anchoring systems for slope stability enhancement is becoming more frequent. In combined anchoring systems, active anchors (e.g. prestressed tiebacks) and passive anchors (e.g. soil nails) are used simultaneously to stabilise a slope. Although stability analysis of slopes with either active or passive anchors used separately is routine in engineering practice, experience with slopes in which these two types of anchoring systems are used in combination is considerably more limited. For example, there are questions concerning the load sharing between active and passive anchors. In this study, centrifuge tests are designed to investigate the contribution of passive anchors to the overall stability of a slope by monitoring the deformation and stress distributions in anchored slope models. Centrifuge model tests are carried out on six model slopes at the same acceleration of 100 g with different types of reinforcement: active anchors for four models and a combined anchoring system for two models. The experimental results show that the passive anchors in the combined anchoring system make an important contribution to the overall stability of the slopes. The tests are then used to verify a slope stability program that can consider both types of anchors acting together. © ICE Publishing: All rights reserved

Jiang G.-L.,Southwest Jiaotong University | Jiang G.-L.,Key Laboratory of High speed Railway Engineering | Wang L.-W.,Southwest Jiaotong University | Wang L.-W.,Key Laboratory of High speed Railway Engineering | And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

The deformation of bridge-approach foundation is the key factor to cause that of bridge abutment, so the study on the bridge-approach deformation contributes to the further study on abutment deformation. Based on the elastic theory, a formula for additional stress of bridge-approach foundation and adjacent surroundings under an arbitrary subgrade section load is derived. The distribution rules of additional stress of approach foundation under a standard railway embankment section load are obtained, and the response of the adjacent buildings to the approach foundation under the subgrade load is analyzed. On this basis, the rationality of the formula is verified by means of numerical simulation. The results show that the proposed method is clear in thought, mathematically logic, and easy in programming. It may provide the theoretical basis for calculation of additional stress and the theoretical support for the studies on abutment deformation.

Chen W.,Southwest Jiaotong University | Jiang G.,Southwest Jiaotong University | Wang Z.,Key Laboratory of High Speed Railway Engineering | Li A.,Key Laboratory of High Speed Railway Engineering
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2014

At present, many passenger dedicated lines are constructed or designed in China, which traverse through expansive soil regions regularly, such as Yun-Gui high-speed railway. To master the physical-mechanical parameters of the undisturbed expansive soils, a number of series tests are carried out for the intact expansive soil, and these samples were taken from different soil layers in Mile town of Yun-Gui railway. Based on it, taking the stage loading of high embankment as the object of study, the K0 oedometer tests of undisturbed expansive soil under stage continuous loading are performed on geotechnical digital systems (GDS) triaxial apparatus. The test result shows that the stress-strain curves of expansive soil is varies with ladder, and the relationship between secant modulus and stress is like sickle. The empirical formula recommended by Wroth could describe the relationship between K0(OC) and ηOCR (overconsolidation ratio) well for the overconsolidated expansive soil reasonably. Compared with the result in stage loading oedometer test, the compression of undisturbed expansive soil is found to rise in stage continuous loading oedometer test. The conclusion provides a reference and a guideline for analyzing the settlement of subgrade for high-speed railway in expansive soil regions.

Cui K.,Southwest Jiaotong University | Cui K.,Key Laboratory of High speed Railway Engineering | Lic W.,Southwest Jiaotong University
Materials Research | Year: 2016

In this paper, the mechanical, dry shrinkage and frost resistance performance of cement stabilized graded stone with framework and dense structure were investigated. A higher cement content owns a correspondingly better mechanical performance. With the different moisture content, the dry shrinkage and frost resistance performance of cement stabilized graded stone showed a similar improving and deteriorating trend. The specimens (sample 0, 1, 2, 3), with different moisture content (4%, 5%, 6%, 7%) in a 6% cement content, were measured and analyzed. A sample contained low moisture content has a relatively loose and dry mixtures, which owns a insufficient cement hydration reaction and low strength, finally leads to a weaker dry shrinkage resistance performance. Moreover, the high moisture content sample has a damp and flabby reaction procedure, which has a larger amount of moisture evaporation and further deteriorated dry shrinkage. The moisture content significantly influence the pore parameters of prepared samples, whose trend followed those of dry shrinkage and frost resistance performance. The pore size distribution of these composites shifted toward smaller pore size scope with a proper moisture content. In addition, scanning electron micrographs (SEM) showed that the denser microstructure of prepared cement stabilized graded stones.

Zhai W.,Southwest Jiaotong University | Wei K.,Key Laboratory of High speed Railway Engineering | Wei K.,Southwest Jiaotong University | Song X.,Southwest Jiaotong University | Shao M.,Southwest Jiaotong University
Soil Dynamics and Earthquake Engineering | Year: 2015

A field measurement of ground vibration was performed on the Beijing-Shanghai high-speed railway in China. In this paper, the experimental results of vertical ground vibration accelerations induced by very high speed trains running over a non-ballasted track on embankment with speeds from 300 to 410. km/h are reported and analyzed in detail for the first time. Characteristics of ground vibration accelerations in both time and frequency domains are analyzed based on the test data. It is shown that the periodic exciting action of high-speed train bogies can be identified in time histories of vertical accelerations of the ground within the range of 50. m from the track centerline. The first dominant sensitive frequency of the ground vibration acceleration results from the wheelbase of the bogie, and the center distance of two neighboring cars plays an important role in the significant frequencies of the ground vibration acceleration. Variations of time-response peak value and frequency-weighted vertical acceleration level of ground vibration in relation with train speed as well as the distance from the track centerline are also investigated. Results show that the time-domain peak value of ground vibration acceleration exhibits an approximately linear upward tendency with the increase of train speed. With the increasing distance from the track centerline, the frequency-weighted vertical acceleration level of the ground vibration attenuates more slowly than the time-domain peak value of the ground vibration acceleration does. Severe impact of high-speed railway ground vibration on human body comfort on the ground occurs at the speed of 380-400. km/h. The results given in the paper are also valuable for validating the numerical prediction of train induced ground vibrations. © 2015.

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