Modeling and Calculating of Residual Stress and Strain of Butt Welded Joint

The non-uniform thermal expansion and contraction resulting from welding processes cause residual stresses and strains. Experimental studies on measuring welding residual stresses and strains of structure are costly and sometimes they are not possible. Previously, analytical methods with idealized models were developed to determine the welding residual stresses and strain. Recently, numerical methods are constructed to analyze the stresses and the strains in welded structures. This paper presents the calculation results of residual stress and welding strain in butt welded joint of S355J2G3 carbon steel of 5 mm thickness made by MAG welding process with a single pass. The calculation is performed by two methods: the imaginary force method and the finite element method. In the finite element method, the SYSWELD software is used to simulate and to determine residual stresses and strain of this welded joint. The results of finite element method are compared with those of imaginary force method to show the rationality and the advantages of finite element method. The study results have shown that in this welded joint, only the longitudinal and transverse stress components are important and the other stress components are negligible.

Shape and force control of cable structures with minimal actuators and actuation

Shape adjustment and stress control can be considered as one of the effective parameters in prestressed cable structures since such structures are widely constructed nowadays due to their characteristics. The assembly errors and applied loads hugely affect the cables’ nodal positions and stress due to their delicacy. The former could disturb the shape, which affects the appearance and the function of the structure. In contrast, the latter may increase the stress in some cables above the upper limit or induce slack in some others. Accordingly, a technique has been proposed that combined fmincon optimization that relies on four different algorithms with a controlling approach based on the force method. The presented method aims to minimize the total amount of actuation and miniaturize the number of actuators. The targets of previously confirmed techniques can be obtained with less actuation and fewer actuators by using the current technique. Based on the verified examples, the advantage of the current approach over the quoted methods is up to 55% and 37% in terms of the number of actuators and the total amount of actuation, respectively.

RIGIDITY DIAPHRAGM OF HIGH-RISE BUILDINGS WITH ASYMMETRICALLY POSITIONED DOORWAYS

To increase the strength of the stiffness diaphragm, the doorways are not arranged symmetrically in height, i.e. in staggered order. Thus, excessive flexibility of the diaphragm is partially eliminated. To perform the calculation of such an irregular system relative to the openings causes a certain difficulty and from that we have implemented an elementary calculation. The design scheme was considered as a multi-story frame, for the action of horizontal wind load and floor-by-floor two-span beams with variable cross-sections on hinged supports for the action of vertical loads. The tasks were solved by the force method and graphoanalytically. Methods for determining the bending stiffness of the diaphragm from various loads are considered.

Numerical Simulation of Ship Maneuvers through Self-Propulsion

The typical maneuvering of a ship can reflect its maneuvering characteristics, which are closely related to the safety and economy of its navigation. The accurate prediction of a ship’s maneuvering characteristics is essential for its preliminary design. This paper adopts the overset grid method to deal with multibody motion and the body-force method to describe the thrust distribution of the propeller at the model scale, as well as to obtain the changes in the hydrodynamic load and the characteristic parameters in a computational fluid dynamics (CFD) maneuver simulation. Then, the paper compares the results with those of a self-propulsion experiment conducted at the China Ship Scientific Research Center. The numerical results show that the maneuverability characteristics obtained from the CFD simulation are in satisfactory agreement with the experimental values, which demonstrates the applicability and reliability of the combination of the overset grid with the body-force method in the numerical prediction of the typical maneuvering of a ship. This provides an effective pre-evaluation method for the prediction of a ship’s maneuvering through self-propulsion.