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Experimental study on bridge–track system temperature actions for Chinese high-speed railway

Lou P., Zhu J., Dai G., Yan B.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 2

451--464

EN

Atmospheric temperature and directed solar radiation have a significant effect on the temperature field of high-speed railway (HSR) concrete bridge and ballastless track structure. However, temperature actions are random process of which distribution laws are difficult to explore, and existing statistical methods for structure temperature analysis are still not precise. So far, there are few researches for annual temperature spectra and design codes for bridge–track system. Based on the one-year observation data, this paper investigated the temperature actions for Chinese HSR bridge–track structure. By utilizing reliability high moment theory, a statistical method which could built virtual distribution was put forward. Based on the renewed study, the effects of waterproof for deck were taken into consideration, a temperature action model was proposed which is suitable for both bridge and track structure. In addition, for track structure, the previous temperature load models were modified. Apart from that, by proposing the concepts of temperature uniform and fluctuant spectra, the research evaluated service performance of structure. Finally, the distribution regularities of uniform temperature spectra were fitted by Fourier series, and the relationship between structural and atmospheric uniform temperature was established (formula (25)). As a result, according to 50 years recorded atmospheric temperature data, the prediction model of the structure extreme temperature was suggested, and by taking the recurrence interval of 100, 150 and 300 years, the extreme temperatures of the system are 52.23, 54.34 and 57.77 °C.

2

Full-scale field experimental investigation on the interfacial shear capacity of continuous slab track structure

Dai G., Su M.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 3

485--493

EN

This paper presents the experimental observations and results of six full-scale field ballastless track structure specimens, and tested under longitudinal and transverse shear load. The tests aimed to examine the interfacial shear capacity of the continuous slab track structure and investigate the interfacial bond–slip behaviour. The results show that bond strength of the two interfaces which were on the top and bottom of mortar layer, respectively, have a large difference. Until the top interface of the mortar layer fractured, no slip displacement was observed in the bottom interface. In addition to the experimental study, a finite element model using nonlinear interface elements was employed to simulate the tests. The numerical calculated capacity agreed well with the experimental results, showing that the proposed bond–slip law is reliable. Finally, the track slab's evenness with the bond–slip effect under the dynamic load was studied.

3

Numerical study on thermal stress cutting of silicon wafer using two-point pulsed laser

Liu J., Lu J., Ni X., Dai G., Zhang L., Chen Y.

Optica Applicata

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2011

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Vol. 41, nr 1

247--255

EN

Laser cutting using the controlled fracture technique has great potential to be used for the separation of brittle materials. In this technique, thermal stress is used to induce the crack and the material is separated along the moving direction by extending the crack. In this paper, based on the heat transfer theory, a three-dimensional thermoelastic finite element model which contains a pre-existing crack is established for a two-point pulsed Nd:YAG laser cutting silicon wafer. The mechanism of crack propagation is investigated. Meanwhile the effects of laser power and the distance between the two laser spots on the development of thermal stress are investigated. The numerical results show that the thermal stress is affected by laser power and the distance between the two laser spots, an increase in the laser power for the same distance between the two laser spots or a decrease in the distance between the two laser spots with constant laser power can induce the increase in the cutting speed.