Applied Mechanics and Materials Vols. 166-169

Abstract: In this paper ABAQUS is used to establish three dimensional finite element(3D) model of WFBW, fracture behavior of “artificial crack” of the weld root is analyzed, the stress intensity factor(KⅠ) as a fracture mechanics parameters to calculate fracture behavior in the beam flange weld root. Results show that stress intensity factor varies cross the beam flange width. When selecting the same initial flaw length, the stress intensity factors of bottom flange weld root was significantly higher than in the top flange weld root. The K1 increases nearly linear with the increase of the initial flaw length. Comparison of 2D and 3D models, when the same initial flaw length, calculation of KⅠ by the three-dimensional model approximately as 1.5 times as that by two-dimensional model.

Abstract: Based on the local deformation theory, we study the mechanics behavior of anchorage interface of full-length bonded rock bolt by using a mathematics model (tri-linear model). With pull-out load increasing, the changing process of anchorage interface of full-length bonded bolt is divided into three stages in this paper: elastic stage, plastic softening stage and crack slipping stage. It is found that in the state of elastic, axis force decreases rapidly with bolt depth increasing, and when pull-out load is greater than elastic ultimate load, attenuation degree will slow for the occurring of interface plastic softening and crack slipping in the top of bolt. The result indicates that the continuous change of axis force with bolt depth reflects that the bolt interface bond strength changes with the increase of pulling load.

Abstract: The end effects of symplectic direct solution to Stokes flow in a rectangular cavity are considered. Based on establishing the dual equations for Stokes flow in Hamilton system, the non-zero eigenvalues and their eigensolutions for an anti-symmetric problem were obtained. Expanding the solutions of dual equations by non-zero eigensolutions and determining the expansion coefficients by the end boundary conditions, the decay tendency and interaction mechanism of end effects were discussed and the end boundary errors were investigated. The resultant velocity caused by tangentially driving lid is gradually decayed along the longitudinal direction of cavity. The more number of the expansion items are superposed, the more accurate the solutions are. The smaller the depth-to-width ratios are, the stronger the interference between the end velocities is. The error of ends moving in the same directions is bigger than that in opposite directions.

Abstract: We use the nonstandard finite difference (NSFD) method to construct discrete models of the reaction diffusion equation. A nonstandard finite difference scheme for the reaction-diffusion equation is given. We demonstrated that the space denominator function can be based on the use of a transformation from the simple expression (Δx)²to an 4C(sin[(1/C)^1/2((Δx)/2)])².which is clearly valid for sufficiently small Δx. Another important class for which this method keeps the equation solutions are positivity and can be applied is those PDE's without advection term.

Abstract: In order to meet the necessity of the code for seismic design of buildings: Principle for strong connections and feebleness member. The exernal steel tube of column and steel beam are joining with three kinds of style. Containing two strengthen styles T-style stiffening plate and appending haunch. The result reveals that the two strengthen connections ultimate load are much bigger, good ductility, better seismic behavior. The deformation of the column and the region of the connection is smaller when it was broken, Indicating the connections’s globality is better and the stiffness is bigger. It avoids brittleness for breaking styles when they are given more load.

Abstract: According to existing experimental results, a systematic analysis of stress–strain relation of concrete under uniaxial dynamic loading is carried out. Research shows that the dynamic loading rate has a direct effect on concrete strength and elastic parameters. Finally, a constitutive law is proposed in this paper.

Abstract: Abstract. Connection joint with penetrated diaphragm, which is better for the stressing state of the welding connection, is a new type joint for the beam and column connection. Static test and pseudo-static test are put to 17 crossing joints. The stress distribution of the steel beam and the penetrated diaphragm are discussed. The experiment shows that the penetrated diaphragm transfer most tension force of the steel beam’s upper flange to the core region of the joint, which could effectively decrease the stress and strain gradient within the connection area of the steel beam’s upper flange and steel tube column. As the result, the shear force of the core region is decreased. The front weld is avoided being surfing great tension. The ductility of the joint and the energy dissipation capacity of the structure are then increased. The type and the size of the penetrated diaphragm show great affection to the stress distribution of steel beam and penetrated diaphragm. The study achievement enriches the joint connection type of the composite structure with concrete- filled steel tube.

Abstract: The ill-posedness of nonlinear identification equation in time domain of structural dynamics system is studied and a new calculating method to weaken the influence of ill-posedness is proposed. Damped least squares method is an algorithm of Jacobian matrix positive-definable, which can obtain the solution of ill-posed nonlinear identification equation. But the solution is sensitive to the test noise of response in time domain of the structure. To solve the problem of instability of the solution, a new calculating method is proposed which combines damped least squares method with Tikhonov regularization method. First, the estimate of structural parameters is introduced to Tikhonov regularization function, and a more stable identification equation in time domain can be obtained. Second, the identification equation is solved with damped least squares method, and the iterative result is an approximate solution of the former ill-posed problem. The numerical example shows that the new method in this paper is efficient to solve the ill-posed nonlinear identification equation in time domain.

Abstract: Some calculated methods of shear capacity of RC beams strengthened with FRP (fiber reinforced polymer) are reviewed based on the experimental data on shear capacity of RC beams strengthened with FRP. Therefore, according to the destruction forms of steel and concrete composite beams strengthened with FRP, the formula for calculating the shear capacity of the beams are given. The formula is expressed clearly, simple and easy to use.

Abstract: Abstract: Tensioning for Concrete cramp iron usually is controlled by two rule: controlling tensioning stress is main, measuring elongation is auxiliary. The rate of elongation value is only for checking data. In this article, the author describes that if applying mathematics theory in forecasting the tensile value of prestressing cramp iron, the estimation for the tensile value will be more accurate. By more accurate value, the elongation measuring method can become a un-auxiliary method for tensile controlling method.