When strengthening existing I-girder composite bridges one idea is to make the cross section act like a box section, by adding a horizontal truss between the bottom flanges. This means that eccentric loads produce a torque that is transferred by shear forces around the section. The magnitude of the effects coming from introducing such a framework between girders is addressed in this article. The fatigue resistance will be improved by the reduced stress ranges and increased amount of tolerated load cycles and extend the lifetime of the details, and by so the lifetime for the bridge. The work described in the paper is part of the European R&D project Prolonging Life Time of Old Steel and Steel-Concrete Bridges (ProLife), RFCS 2015-00025.

A few decades ago, steel-concrete composite bridges were quite rare structures, whereas steel girder bridges with non-composite concrete decks were rather common. For the latter type of structure, composite action can be obtained long after the bridges were constructed by post installation of shear connectors. Most installation procedures involve reconstruction of pavement and concrete deck, which will result in traffic disturbance. There are however some types of shear connectors that can be installed from underneath, connecting the top flanges to the concrete deck, without affecting the upper surface. This means that the bridge can be strengthened during traffic. One type of such a shear connector is the coiled spring pin, which is an interference fit connector. This paper presents the results from push-out tests conducted in order to find the static capacity and the load-slip behaviour of coiled spring pins used as shear connectors.

As part of a project within the Swedish nuclear industry with the objective to investigate the performance of different constitutive models in ratchet simulation, an extensive experimental program has been conducted on pressurized tube specimens. In total 30 test specimens made of two different materials, 316L and P235, have been manufactured and tested. In order to determine material properties, monotonic tensile load and internal pressure experiments have been performed. The remaining test specimens have been used for ratcheting experiments. The experimental results show ratcheting in the hoop direction when the tube is subjected to certain combinations of internal pressure and cyclic axial strains. The higher the pressure is and the larger the strain ranges are, the higher the ratcheting response becomes. Measured ratcheting strains are compared to numerical simulations using different constitutive models. In this paper the interrelated models of Prager, Armstrong-Frederick and Chaboche are investigated. In addition to these, the Besseling model is investigated. Based on the result from this investigation, recommendations on how to conduct ratcheting simulation of pressurized equipment subjected to cyclic secondary loading are presented.

The primary stress pipe equations in the ASME code, subsection III, Ref. [1], and similar codes add stress contributions from pressure and bending and impose a limit on this sum, while a limit on the pressure hoop stress is imposed separately. The equations constitute interaction formulae for the resistance of the pipe cross-section to the combined action of pressure and bending, similar to the limits on primary membrane and primary membrane plus primary bending stress for a rectangular section. For the latter, an analytical limit load solution is found e.g. in Ref. [2]. In this paper, closed-form limit analysis collapse interaction formulas are derived by means of limit analysis for thin-walled as well as moderately thick-walled straight pipes subjected to internal pressure and pipe bending. The analytical solutions are confirmed by means of non-linear finite element analysis. Moreover, the resistance to combined loading as predicted from the derived interaction formulas is compared to the resistance according to the ASME code primary stress pipe equations and the deviations are elaborated.

Clamped abutment piles for integral abutment bridges experience both a compressive normal force and bending load cycles stemming from daily and yearly temperature variations. This paper describes experiments using full-scale models of clamped piles to demonstrate that a steel pipe pile can accommodate large inelastic deformations under strains six times greater than the yield strain for several hundred load cycles. This indicates that by permitting pile strains in excess of the yield strain (which is not permissible under most current design codes), integral abutment bridges could be erected with spans of up to 500 m and a projected service life of 120 years. The tests were carried out as a step towards the development of design rules for determining the capacity of piles for integral abutment bridges.

This paper describes the monitoring of a one-span composite bridge in northern Sweden. The bridge was built in 2000, with prefabricated deck elements connected to steel girders, and the back walls as well as the piers were also prefabricated. The monitoring was required to clarify the doubts regarding whether a bridge with dry deck joints can be expected to perform as a conventional composite bridge, with in situ cast deck and sections with sagging moments. To get a better understanding of the long-term structural behaviour, the bridge was monitored both during 2001 and 2011, instrumented with equipment measuring the deflections and strains in the steel cross section. The bridge was loaded with a truck in midspan having a total weight of 25 t. When the truck was centred between the girders, the results showed a symmetric behaviour, with respect to deflections and stresses. For the case with the truck stationed right above one of the steel girders, anti-symmetric behaviour was observed and studied by means of finite element calculations, taking into account the stiffness of the composite section as well as the end screens and the earth pressure below them.

In very large steel bridge girders, the web often must be composed of more than one plate strip. As an alternative to longitudinal stiffeners of a slender web of uniform thickness, the bottom web plate strip my be designed as a vertical extension of the bottom flange – thicker than the upper web strip. A thicker bottom web strip enhances both the shear buckling resistance of the web and the bending moment resistance of the cross-section. The magnitude of these beneficial effects are adressed in this article. Moreover, the effect on the shear-bending resistance interaction is investigated. Non- linear finite element simulation is conducted and comparison to the predictions of the EC 3 is made.

The competitiveness of composite bridges depends on several circumstances such as site conditions, local costs of material and staff and the contractor's experience. One major advantage compared to concrete bridges is that the steel girders can carry the weight of the formwork and the wet concrete. Another advantage is the savings in construction time, which saves some money for the contractor but even more so for the road users, a fact that usually is neglected when evaluating alternative bridge designs. A further step to improve the competitiveness of composite bridges is to prefabricate not only the steel girders, but also the concrete deck. In this paper a new concept with dry joints between the elements is described.