Based on the assumption that rock strength follows the log normal distribution statistically, this paper establishes a damage constitutive model of rock under uniaxial stress conditions in combination with the Mohr–Coulomb strength criterion and damage mechanical theory. Experiments were carried out to investigate the damage evolution process of rock material, which can be categorized into nondamaging, accelerated growth, constant-speed, similar growth, and speed-reducing growth stages. The evolution process had a good corresponding relationship with the rock stress-strain curves. Based on the statistical damage constitutive model proposed in this paper, a numerical fitting analysis was conducted on the uniaxial compression testing data of laboratory sand rock and on experimental data from other literature, in order to validate the rationality of the constitutive equation and the determination of its parameters and to analyze the effect of internal friction variables on damage variables and compression strength. The research outcomes presented in this paper can provide useful reference for the theory of rock mechanics and for rock engineering.
Focusing on the specific needs of network management in video surveillance platform, but almost all of current systems is insufficient. The development of OOP and distributed computer technology, especially the improvement of technology based on Web and the J2EE framework give an effect way to implement the distributed unified network management system. This paper firstly introduces n mixed network management model based on SNMP and ICE protocol. And then integrating use of web technology, Spring business logic control technology, Hibernate data persistence technology, Ajax technology to design a distributed, multilayer, extendable structure base on J2EE. Finally, we present the implement of key modules on network management system in video surveillance platform. Experimental results show that the architecture design not only meet specific needs of the large scale access and scalability but also improve the flexibility of the network management system.
The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.
The assessment method of load carrying capacity for concrete rectangle section simple beam subjected to fire was presented. Comprehensively considering influencing parameters, load carrying capacity for reinforced concrete rectangle section simple beam was analyzed in a fire hazard by using numerical simulation program. A series of safety assessment regularities for the reinforcement pieces was put forward subjected to fire. The studied results indicate that: the ultimate moment for reinforcement concrete beam bridge tends to decrease linearly after 40 minute, the fire resistance of the reinforcement concrete rectangle section simple beam increase linearly with the increment of the concrete cover thickness; Therefore, the increment of concrete protective thickness is effective to fire resistance and safety grade for the reinforcement concrete beam.
The deflection for pre-stressing concrete thin-wall box girders bridges under action of multi-span loads exposed to fire was presented in this paper. Based on thermal and mechanics parameters, the fire and load model was designed, the space analysis procedure was performed to analyze the maximum deflection of each span during prophase and anaphase of extending-fire time, altogether 4 kind of load case. The studied results indicate: under condition of the whole span fire and load model of multi span, the mid-span deflection of the second span is down-warping during the fire prophase which its time is about 20 minutes, and up-warding or horizontal during the fire anaphase which its time is about 50 minutes; the deflection of the first and third span is down-warping with extending time during the whole fire time.
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