Fillet-welded Connections Research Articles

Fatigue Tests and Numerical Analyses of a Connection of Steel Sandwich Plates

In shipbuilding, steel sandwich plates are applied in several areas. Particularly the connections between the sandwich plates may be prone to fatigue in the case of cyclic loads. Therefore, the fatigue strength of a fillet-welded connection of a steel sandwich plate under in-plane loading has been investigated experimentally and numerically. Numerical calculations are performed using the crack propagation and the effective notch stress approach. In the notch stress approach, the modelling of the weld root may create problems as the relatively thin face plates are affected by the notch rounding of 1 mm. Two different shapes are considered. Furthermore, the small size notch approach with a reference radius of 0.05 mm is applied. From the comparison of the results with the fatigue strength found in the tests, conclusions are drawn for appropriate modelling.

Evaluation of Fatigue Strength of Fillet Welded Connections with Respect to Different Post-Weld Treatment Methods

In the study herein, the fatigue test was conducted on the fillet welds of the load carrying cruciform joint, which is frequently used in the steel structures such as bridges, ships, etc. In addition, the fatigue stress was analyzed with respect to the different post-weld treatment. The treatment methods used include Toe Grinding, TIG Dressing, and Weld Profiling. The fatigue test was under constant amplitude with repeated load for these test specimens. In the load carrying full penetration fillet welded joints, regardless the conduction of the post-weld treatment or not, they all secured the fatigue strength of category "F", which exceeds the fatigue design specifications of BS Code. In the comparison of the fatigue strength upon the post-weld treatment, the fatigue strength tends to increase according to the order: Toe Grinding, TIG Dressing, and Weld Profiling.

Evaluation of a finite element modelling approach for welded aluminium structures

Experimental and numerical studies were carried out to investigate the behaviour of quasi-statically loaded fillet-welded connections in aluminium alloy EN AW 6082. The components were designed so that fracture should occur in the heat-affected-zone (HAZ), which was also the case in the experiments. In the numerical study, the components were modelled in LS-DYNA using shell elements. A user-defined material model comprising the Barlat and Lian anisotropic yield criterion and a ductile fracture criterion was adopted. The strength and hardening data for the HAZ, weld and base material were taken from existing experimental data in the literature. The constants for the yield criterion were identified from uniaxial tensile tests by various methods, and the set of constants that best represents the measurements was adopted in the numerical analysis. Reasonable estimates on ductility were obtained by the simulations when a refined mesh was used, while the strength was somewhat over-predicted.

Design basis of Lithuanian steel and aluminium structure codes and their relations to Eurocode

The background in the development of national building technical regulations for the design of steel and aluminium structures is discussed. National Design Standards are under consideration in comparison with the main concepts of EC3 and EC9. Standard features of design parameters of materials, partial safety factors and metallic cross-sections are considered in this article. The resistance criterion of members in combined compression and bending is analysed. The effect of member slenderness and fillet weld connections on design results given by National technical regulations and Eurocodes is illustrated.

Low cycle fatigue strength assessment of butt and fillet weld connections

The paper presents the analysis of the low cycle fatigue strength of axially tensioned welded connections between I- or H-profile and gusset plate, in which butt and fillet welds cooperate in transmitting the load. The presented approach is based on the local strain state at the notch directly. The method of stress analysis was presented, which was divided into global finite element analysis at the geometrical stress level, coupled with a local finite analysis of the notch area. Local elastic–plastic stress–strain behaviour at the notch root was evaluated from Neuber’s rule and load–life curves were established for such connections from equation based on Langer’s formula. Although in steel structures the applied nominal load does not vary in fully cyclic type, material anisotropy developed during first plastic strain in notch area can lead after unloading to fully reversed plastic stress. In some cases, the first crack can occur after a small number of load cycles.

The static strength of end and T fillet weld connections

The ultimate strength of fillet welded joints is of vital importance when analysing the collapse behaviour of a welded structure. However, both the small size and difficulties in determining accurately, for the different regions of the weld, relevant material properties to input in a finite element analysis complicates modelling. Hence the strength of fillet welds forming lap (cover plate) and cruciform (T) joints has been analysed by reviewing the various empirical relationships, based on both experimental and theoretical treatments, proposed in the literature. These results are compared with the strength of fillet welds predicted by different design codes, and are used to establish the correct materials parameters for input to a finite element model of a welded T joint analysed by the finite element program DYNA 3D.

Factored resistance of welded connections subject to shear and moment

The ultimate capacity of eccentrically loaded fillet-welded connections was experimentally determined by Dawe and Kulak. They proposed an analysis technique for such connections based on an assumption of rigid body rotation of the connection plate about the instantaneous center and the use of weld group load–deformation curves. The Canadian Institute of Steel Construction (CISC) published factored resistance tables for such connections based on this theory. Unfortunately, the theory and design tables can be subjected to the following criticisms : (1) the theory is complex and cannot be easily used for design purposes unless design tables are available; (2) the results from a modified theory were apparently used for comparison with the eight laboratory test results; and (3) the CISC design tables were obtained by using an analysis procedure that does not appear to satisfy all of the design code limitations given by CSA-S16.1-1974.In this paper the author examines the statical behavior of such connections. This study indicates that the overall effect of the last two points is not too serious. The author presents explicit equations approximating the factored load resistance. The use of these equations obviates the first criticism.The design equation developed in this study is very simple; it may be applied with ease in any system of units since it is essentially nondimensional; and it satisfies the specifications of the design code.

Welded Connections under Combined Shear and Moment

An analytical method is developed for predicting the ultimate strength of eccentrically loaded fillet weld connections not free to deform in the compression zone. The method uses the true load-deformation response of the welds rather than some idealized one. The validity of the approach has been verified by a testing program using 16 full-size specimens. Comparison of the ultimate strength obtained by this method with allowable loads calculated assuming elastic behavior shows that the resulting factor of safety is both high and inconsistent.