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The paper deals with the seismic behaviour of column bases and beam-to-column joints made with high strength steel tubular columns subject to seismic loading. A test programme was carried out at the University of Trento with the aim of evaluating the seismic performance of these joints under monotonic, cyclic and random loads. With these load protocols, it was possible to assess the activation and location of plastic hinges and the stiffness and resistance of beam-to-column joints and column bases, as well as to quantify the ductility behaviour of some joint components. The cyclic tests were performed by employing a standard loading protocol and the random tests utilised displacements provided by Finite Element based simulations of a five-storey steel-concrete composite building subject to seismic loading. The paper reports and describes experimental tests on both beam-to-column joint and column bases. [ABSTRACT FROM AUTHOR]

The developments of steel structures aim at light and slender constructions. Therefore, high-strength steels with good welding characteristics and a high ductility, aside from higher strength, have been developed by the steel industry. With increasing strength of the steel, the loads which have to be transferred in the welded connections are also growing. In building constructions, fillet and partial penetration connections are commonly used. When using high-strength steels, it is very important to ensure strength, as well as sufficient ductility and toughness of these welded connections, in order to allow for the necessary redistribution of stresses and internal forces. The use of high-strength steels can bring significant savings in terms of material consumption, weight, transportation and fabrication costs. Beside the savings due to the reduced material consumption, advantages result from the smaller construction weight and a faster fabrication by reduction of the weld thickness. However, especially for high-strength steel grades S460 and S690, the benefit of saving of material cannot be used, due to the present restrictive design rules. Therefore, the aim of this research project, realized by four partners, was the development of appropriate and modern construction and design rules, as well as manufacturing principles, in order to achieve an economical use of high-strength fine grained steels. This paper presents the results of a research project, investigating the strength and ductility of fillet welded connections of high-strength steels S460 and S690, by means of experimental and numerical analyses. Experimental and numerical investigations of the load bearing capacity and safety against brittle fracture at lap joints with longitudinal fillet welds, cruciform joints with transverse fillet welds and butt joints with partial penetration double-V-groove welds of high-strength steels S460M/ML and S690Q/QL have been carried out. Numerical investigations in terms of welding simulation and measurements of residual stresses have been performed, in order to identify the local microstructure, hardness, residual stresses and strength in the weld profile. These results support the assessment of strength and ductility of welded connections. Based on the investigations, recommendations for the design of welded connections of high-strength steels, in terms of load bearing capacity and safety against brittle fracture, as well as manufacturing principles, were derived. The results of the research project thus contribute significantly to an optimized use of high-strength steel in welded constructions. [ABSTRACT FROM AUTHOR]

In this paper for the evaluation of the fatigue strength of welded structures a simplified numerical analysis has been proposed. The approach considers the use of FE code for the estimations of the equivalent stress defined by the implicit gradient approach. Then, the equivalent stress can be used for the prediction of the fatigue life of the welded components. [ABSTRACT FROM AUTHOR]

This paper will present the experimental and numerical investigation on the fatigue crack failure at the root of the enhanced partial joint penetration welds in the circular hollow section X-joint specimens subjected to constant - amplitude brace in-plane bending actions. The enhanced partial joint penetration welds, which include a portion of the brace wall as the inherent "back-plate" for the welds, reduce the workmanship requirement on the welding procedure and improve the quality control of the welded joint. This study compares the fatigue crack developments observed at both the weld toe and the weld root in three large-scale X-joint specimens with different post-weld surface treatments. Root cracking does not take place in as-welded tubular X-joint specimens, of which the fatigue life depends on the weld toe failure. In specimens with post-weld grinding treatments to enhance fatigue resistance of the material near the weld toe, however, the finite-length root face triggers the initiation and propagation of fatigue cracks with an applied number of cycles more than that required to initiate a toe crack in the same tubular X-joint. Ultimate strength testing of specimens with large fatigue cracks, and post-test sectioning, reveals that fatigue failure weld-toe fatigue cracks remain more critical than the root cracks. [ABSTRACT FROM AUTHOR]

Following the first part, which was about the ultimate resistance check of the welded connections, the present paper focuses on the fatigue design criteria. After an introduction about the general problem of the fatigue, the article presents the standard design criteria based on the simplified Wöhler curves and with respect to the load history and structural detailing available. The final part handles with the Hot Spot Method, increasingly used and well-linked to the FEM. [ABSTRACT FROM AUTHOR]

The paper is going to discuss the basic topics about distortions and geometrical tolerance in steel structures manufacturing and erection. The theoretical aspects about the residual strain of welded joints are shortly presented and the practical consequences of the distortions on welded panels or slender structures are discussed. Finally the European Standard recommendations are taken into account and the methods to restrain the welded joint or to reduce the distortion as flame straightening are discussed. [ABSTRACT FROM AUTHOR]

The opening of the new Panama Canal is planned in 2014. Cimolai started in October 2010 the construction of the sliding gates for the opening and closing of the locks. The work consists of 16 gates of significant size, for a total weight of about 55,000 tons, and it will require a commitment of about 4 years for the manufacture, the installation and the commissioning. This paper presents the main characteristics of the "lock gates" and an overview of the most critical steps of the construction activities. [ABSTRACT FROM AUTHOR]