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Chen H.,Institute of Engineering Mechanics
13th International Conference on Fracture 2013, ICF 2013 | Year: 2013

Fracture analysis is a high non-linear problem and affected by uncertainties. Because of the limitation of observing technology, accuracy boundary condition can hardly be obtained. Normally, a stochastic model can be used. The difference between reality and numerical model is deemed as disturbance. This paper presents a three-dimension dynamic stability analysis of crack growth under disturbance in boundary condition by using particle discretization scheme finite element method. The model is a thin epoxy plate with two anti-symmetric notches located in the middle, under uni-axial tensile in longitudinal direction. Two types of disturbance are considered: (i), the disturbance is added to the initial cracks' configuration. The disturbance is modeled by adjusting the position, size and shape of the notches. It shows that changes of the notches' size and position have significant influence on crack growth in the investigated cases; (ii), the disturbance is applied to the displacement boundary condition, which is far from initial cracks. The variability of crack paths of different model sizes under the same disturbance is estimated. The results of the numerical experiment indicate that as the model size increases, the influence of the disturbance becomes weaker. The Saint-Venant principle still holds in the studied crack growth problem.. Copyright © (2013) by International Conference on Fracture.

Tao Z.,Institute of Engineering Mechanics
International Journal of Digital Content Technology and its Applications | Year: 2012

Event study, which is popular in finance and accounting, is adopted to measure the effect of an earthquake on stock market. In the case of the 2011 off the Pacific coast of Tohoku Earthquake, the constant mean return model and the market model are adopted for the whole Japanese stock market and some typical stocks respectively. The result indicates that abnormal returns from the whole market are negative and significant, at level 0.01, only in the next four days of this event; however, in fourteen typical stocks of automobiles and motorcycles manufacture, electronic goods, transportation, lifeline and insurance, those from Tokyo Electric Power Company Inc., Honda Motor Co. Ltd., Nissan Motor Co. Ltd. and Fuji Heavy Industries Ltd. are negative and significant, at level 0.01, in the next ten days.

Stasiuk G.,Institute of Engineering Mechanics
Key Engineering Materials | Year: 2012

The aim of the proposed studies is the development of the carbon/carbon composite with prescribed elastic properties. To achieve this, a microstructure optimisation problem for estimation of the microstructure with prescribed stiffness is formulated. The design variables of the posed problem are the local fibers distribution and porosity. The volume fractions of the fibers and pores in the whole microstructure are fixed. Material properties of the local microstructure of the composite are calculated using virtual models. Semi-analytical homogenization procedures were used for the development of these models. Modeling results are compared with elastic properties obtained experimentally by tension and compression test and ultrasonic studies of the bulk material. Approach to design microstructure for three point bending test is proposed. © (2012) Trans Tech Publications.

Qu Z.,Institute of Engineering Mechanics | Kishiki S.,Osaka Institute of Technology
Gongcheng Lixue/Engineering Mechanics | Year: 2015

An unconstrained gusset connection is proposed for buckling restrained braces in reinforced concrete frame structures in order to eliminate the detrimental frame action because of the interaction between the gusset plate and the adjoining reinforced concrete columns and beams, which may impair both the connection performance and the aseismic performance of the structural system. The local damage control by means of adjusting the longitudinal rebards in concrete beams is also adopted to further ensure the performance of the gusset connection. The results of quasi-static tests show that the proposed damage control scheme is able to relocate the beam end plastic hinge to outside the gusset region and thus protect the connection from being deteriorated. ©, 2015, Tsinghua University. All right reserved.

Qi W.-H.,Institute of Engineering Mechanics | Bo J.-S.,Institute of Disaster Prevention | Liu H.-S.,Institute of Engineering Mechanics
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

The current formula can not calculate the fundamental periods of the sites containing soft soil layers accurately. In order to solve the problem, a fundamental period formula for a horizontal layered site, on which the effect of soil layer construction is considered, is deduced based on the vibration theory. According to the rules of natural vibration periods being equal, a single layer site is simplified into a SDOF system by means of the lumped mass method, and the equivalent height coefficient between their heights is deduced. A horizontal multi-layer site can be simplified into a SDOF system based on any one soil layer, and the height of the SDOF system is equal to that of the soil layer multiplied by the equivalent height coefficient. The natural vibration period of the SDOF system is called contributing fundamental period of the soil layer here, and the fundamental period of the site should be equal to the square root of sum square (SRSS) of the contributing fundamental periods of all the soil layers in the site, and its formula is also deduced. The test results show that (a) the proposed formula can reflect the effect of soil layer construction on fundamental periods of sites very well, and (b) by comparing the calculated fundamental periods with the test ones of 5 engineering sites by use of the microtremor method, the proposed formula is of higher accuracy and reliability than the current formula. A conclusion is drawn that the deduced formula can be adopted to estimate the fundamental period of a layered horizontal site.

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