Composite bridges in Sweden are commonly designed as a twin I-girder section. To stablizie the bridge during launching and concreting horizontal cross bracings are used. These are normally connected to a transverse web stiffener that is welded with a throat size of 5 mm regardless of the dimensions of the bridge. During an inspection of Vårby Bridge south of Stockholm in 2006 cracks were found in this weld between the transverse web stiffener and the top flange. After discovering of these problems the Swedish Transport Administration (Trafikverket) wants the designer to present calculations for this weld. The aim of this thesis was to investigate and compare the stresses in the weld between the top flange and the transverse stiffener for different cross bracings. A finite element model of a typical composite bridge, with five different types of cross bracings, was investigated using the FE program Brigade Plus. A selection of loads including temperature-, traffic- and fatigue loads were considered. The thesis clearly shows that the design of cross bracings will affect the stress levels in the weld.

A number of recent research studies have investigated the performance of panel zones in seismic-resistant steel Special Moment Resisting Frames (SMF). These recent studies investigated various options for attaching doubler plates to the column at beam-column joints in SMF for purpose of increasing the shear strength of the panel zone. This previous work was primarily focused on doubler plates that extend beyond the top and bottom of the attached beams, and considered cases both with and without continuity plates. As an extension to this previous research, this thesis explores the situation when a doubler plate is fitted between the continuity plates. The objective of this research was to evaluate various options for welding fitted doubler plates to the column and continuity plates through the use of finite element analysis, and to provide recommendations for design. The development and validation of the finite element model are described, along with the results of an extensive series of parametric studies on various panel zone configurations and attachment details for fitted doubler plates. Based on the results of these analyses, recommendations are provided for design of welds used for attaching fitted doubler plates in the panel zone of SMF systems. / text