Applied Mechanics and Materials Vols. 353-356

Abstract: The finite element method is used to compute the ultimate bearing capacity of a fictitious strip footing resting on the surface of c-φ weightless soils and a real strip footing buried in the c-φ soils with weight. In order to compare the numerical solutions with analytical solutions, the mainly existing analytical methods are briefly introduced and analyzed. To ensure the precision, most of analytical solutions are obtained by the corresponding formulas rather than table look-up. The first example shows that for c-φ weightless soil, the ABAQUS finite element solution is almost identical to the Prandtls closed solutions. Up to date, though no closed analytical solution is obtained for strip footings buried in c-φ soils with weight, the numerical approximate solutions obtained by the finite element method should be the closest to the real solutions. Apparently, the slip surface disclosed by the finite element method looks like Meyerhofs slip surface, but there are still some differences between the two. For example, the former having an upwarping curve may be another log spiral line, which begins from the water level of footing base to ground surface rather than a straight line like the latter. And the latter is more contractive than the former. Just because these reasons, Meyerhofs ultimate bearing capacity is lower than that of the numerical solution. Comparison between analytical and numerical solutions indicates that they have relatively large gaps. Therefore, finite element method can be a feasible and reliable method for computations of ultimate bearing capacity of practical strip footings.

Abstract: In this paper, the equivalent mechanical spring model of the three-dimensional continuum is studied. By using stiffness calculation formulas of three-dimensional continuum column under axial force and bending force, which are primary force states in the column, a mechanical equivalent trusses model with the same width and height is derived. The equivalent model is statically indeterminate trusses system of spring. The 3D spring calculation model can be used in the dynamic characteristic analysis. With the comparison of the first four order frequency values between the solid model and the equivalent spring model, it shows that the equivalent spring model not only have the equivalent stiffness in the static analysis but also have the equivalent dynamic characteristics in the dynamic analysis.

Abstract: Consider the simply connected spring-mass system with partial mass connected to the ground. The inverse mode problem of constructing the physical elements of the system from two eigenpairs, the grounding spring stiffness and total mass of the system is considered. The necessary and sufficient conditions for constructing a physical realizable system with positive mass and stiffness elements are established. If these conditions are satisfied, the grounding spring-mass system may be constructed uniquely. The numerical methods and examples are given finally.

Abstract: According to the actual structure of grouting sleeve, the ABAQUS finite element model of grouting-sleeve reinforcement-connection component under axial tension load was established, and the stress distribution at reinforcement, grouting material and sleeve were gotten. Numerical simulation shows that the compressive cones in grouting material are formed to transfer load between reinforcement and sleeve. Moreover, simulation indicates that mechanical property of grouting material is the most important factor for the physical reliability of reinforcement connection.

Abstract: This paper is examining the instabilities of reeled pipelines during spooling of initially straight or laying of initially bent pipe and sifting parametrically number of reel lay mechanisms. A combination of composite materials is studied and number of bending stability cases (i.e., ovalization and bifurcation buckling) is discussed. It is demonstrated that composite pipeline exhibit more stability than Steel pipes. The bending stability of spooled pipeline is examined in detail and, in particular, the case on the diameter drum of the reel lay system. Moreover, results on the strain energy release in the reel lay system are presented, extending the findings of previous works on controlling the spooling or laying mechanism.

Abstract: The R-function theory and variational method are employed to solve the torsion problem of the bar with a complicated cross-section. When the variational method is used to solve the elastic torsion problem alone, the stress function can be set to meet the boundary condition, only with the simple cross-section such as the rectangle and ellipse. For the complicated cross-section, it is hard to find a stress function to meet the boundary condition. The R-function theory can solve the problem, and it can be used to describe the complicated cross-section by implicit function form. Introducing the R-function theory can be easy to construct the stress function that satisfied the boundary of the complicated cross-section. A numerical example demonstrates the feasibility and efficiency of the present method.

Abstract: A new approach, namely the global residue harmonic balance, was developed to determine the accurately approximate periodic solution of a class of nonlinear Jerk equation containing velocity times acceleration-squared and velocity. Unlike other improved harmonic balance methods, all the forward harmonic residuals were considered in the present approximation to improve the accuracy. Comparison of the results obtained using this approach with the exact one and the existing results reveals that the high accuracy, simplicity and efficiency of the presented solution procedure. The method can be easily extended to other strongly nonlinear oscillators.

Abstract: Dynamic stress computation of long suspension bridges under both railway and wind loading is required for either strength or fatigue assessment. However, the effect of dynamic coupling among bridge, railway vehicle and wind on bridge stress response is not well understood. This paper presents a method for predicting bridge dynamic stress responses with coupling effects included. The bridge model (bridge subsystem) and vehicle model (vehicle subsystem) are established using the finite element method, and they are related to each other through wheel-rail contact conditions. The spatial distribution of both buffeting forces and self-excited forces over the bridge deck surface is considered to facilitate the computation of local stress responses. The Tsing Ma suspension bridge in Hong Kong and the data recorded by a Wind and Structural Health Monitoring System (WASHMS) installed in the bridge are utilized as a case study to verify the proposed method to some extent. The railway loading and wind speed measured by the WASHMS are taken as input for the computation simulation. The computed local stress responses are compared with the measured ones. The results from the case study demonstrate that the proposed method could effectively predict the local stress responses of the coupled traffic vehicles and suspension bridge system in cross winds.

Abstract: The structural optimization based on FE (Finite Element) software ANSYS is an emerging subject which is combines computational mechanics, mathematical programming, computer science and other engineering subject. Up to now, substantial research breakthroughs have been achieved in optimization theory. This essay is mainly about the theory analysis and internal stress optimization on the modal displayed on the contests of the Fifth National Structure Design Contest for College Student, including selection of basic components, size detail optimization of components. The optimization of structural stress is to find the optimal solutions while keep the variable within certain range. As for this paper, it is to find the optimal solution to mass while the internal stress, component size, load are under constrained. Finally, to ensure the safety of structure and component, analysis was made on the computation results.

Abstract: The power consumption is too large when the method saving energy by air injection is used on large ship because of the deep draft. The feasibility and some key matters of the implication of airfoil diversion technology on air lubrication ,such as the attack angle, the distance from the airfoil to the plate and the position of the air injection, was investigate by a numerical method. The result shows that the pressure of the air injection entrance is significantly decreased by setting an airfoil at the air injection entrance reasonably, the pressure of the plate surface declines when the distance from the plate to the airfoil is decreasing and the attack angle is increasing, however, the resistance became larger. For the airfoil 2032cjc we investigated in this paper, when d/C=0.3, the attack angle range from 6°~8°,the pressure reduces comparative large and the resistance increases small. The best position for air injection is determined by the position and attack angle of the airfoil.