This paper treats the use of horizontal trusses between the bottom flanges of new I-girder bridges, to create a box-like behaviour. In contrast to the general vertical cross frames of an I-girder bridge, the horizontal trusses bring along substantial torsional stiffness of the cross section of a bridge. The concept gives large advantages when it comes to fatigue caused by eccentric loading, since the I- girders will share the load more equally. The concept is exemplified by bridges in Finland, Guatemala and France, and some design aspects as well as practical aspects are discussed.

The overall traffic density and the allowed vehicle weights have been increasing over the last decades. As a response, new roads and railway lines are continuously planned and built. On the other hand, the existing bridges must also be capable of dealing with the increasing traffic volume and the increasing vehicle weights. Many existing bridges were not originally designed for the high traffic loads and todays traffic volume. To cope with the increased loads and load frequencies, the aged structures need repair and strengthening. To avoid the replacement of existing structures, the overall objective is to improve the structural performance of existing steel and steel-concrete bridges by providing innovative and well documented repair and strengthening solutions to bridge designers and road/railway-administrations in Europe. In this paper the use of UHPFRC as a solution for bridge and viaduct repair and strengthening has been presented.

Today, steel girder bridges with concrete deck slabs are generally constructed as steel-concrete composite structures, to utilize the material and the structural parts in an efficient way. However, many existing bridges constructed before the early 1980´s were designed without shear connectors at the steel-concrete interface. With increasing traffics loads and higher amount of load cycles, there is sometimes a need to strengthen these bridges. One way to increase the bending moment capacity is to create composite action by post-installation of shear connectors. The authors have studied the concept of strengthening by post-installed shear connectors, with a focus on a connector called coiled spring pin. This paper presents the results from the first beam tests performed with this kind of shear connector. In line with the previous push-out tests, the test results indicate a very ductile shear connection, with a potential to be a material- and cost-efficient strengthening alternative.

Traffic density and vehicle weight have been increasing over time, which implies that many existing road bridges were not designed for the high service loads and the increased number of load cycles that they are exposed to today. One way to increase the traffic load capacity of non-composite steel- concrete bridges is to use post-install shear connectors and one type of shear connector is the coiled spring pin. This type of connector has advantages for strengthening of existing bridges, since it enables an installation from below while the bridge is still in service and does not bring along removal of concrete and pavement, nor welding to the top flange.This paper describes one ~50 years old Norwegian single span steel-concrete bridge that was strengthened with post-installed coiled spring pins. The strengthening method and the design procedure are presented, along with the results from a field monitoring on Sagstu bridge, performed to evaluate the behaviour of the strengthened structure. The results show that the coiled spring pins counteract the slip and bring along a very good degree of composite action.

A requirement for heavier vehicular transport on the Norwegian road network has resulted in a demand for increased bearing capacity for many of the older bridges in the country. Many of the bridges that have been found to have insufficient capacity against present-day demands are steel girder bridges with concrete slabs without a shear connection between steel and concrete. There is a large number of bridges of this type in Norway and the paper presents strengthening of two of those, in Aust-Agder county in the south of the country. These bridges are approximately 30 m long, single span. The bearing capacity has been upgraded by installing composite action between the steel girders and the concrete slab using coiled pins, in conjunction with thickening of the bottom flange of the steel girders. To obtain composite action, the pins are fitted to tightly drilled holes through the top flange of girders up into the concrete slab. Coiled pins have not been used much for bridge applications. In the work presented, the method has been found to have advantages in terms of cost and workability. Furthermore, the method has benefits when viewed from an environmental standpoint, since it allows strengthening of existing non-composite bridges using relatively little new material, and minimizes traffic disruptions.

Many existing bridge structures experience much more significant loads and load cycles than were anticipated when the bridges were originally designed. An effective way to increase the load capacit ...

The structural analysis of existing bridges is not widely covered by the various codes and standards, resulting in the insecure and, in some cases, critical condition of this type of structure. Regarding national regulation, few states include compulsory codes that define the methods and procedures of inspection, assessment, maintenance and retrofitting of bridges. Although an accurate retrofitting procedure can prolong the life of an existing bridge, the more accurate management of national infrastructure assets can result in financial savings in the long term. This article deals with: (a) the assessment step-level procedure, (b) suggestions for bridge load tests and bridge categories, (c) bridge material analysis, (d) structural testing analysis, and (e) the main retrofitting interventions to prolong the life of existing steel and steel composite bridges. Furthermore, a representative case study is analysed and discussed, including examples of the retrofitting solutions implemented to prolong the service life of the bridge.

Many existing bridges were not originally designed for the traffic loads and the number of load cycles which they now experience. In order to increase the load capacity of non-composite steel- concrete bridges, post installed shear connectors can be used. This paper describes a field monitoring of a steel-concrete bridge which have been strengthened with post-installed coiled spring pins as shear connectors. During the monitoring, the bridge was loaded with a 31 tonnes truck placed in specific positions while strains were measured in the steel main girders, together with the horizontal slip at the steel-concrete interface. The results indicate that the coiled spring pins prevent the slip and that they can be used for strengthening purpose. It is also observed that the friction in the steel-concrete interface can contribute quite a lot to the composite action, even though that effect cannot be accounted for in the design.

Prolonging the life of existing steel trusses all over the world is a incoming necessity for all managing authorities wherever these structures have reached a particular state of use. The unsatisfactory behavior of these structures under the current type and increasing number of loads make clearer that innovative solutions are needed. For this purpose, the realization of different techniques are presented, in order to retrofit the actual load onto a structure conceived with historical codes, characterized by lower design live loads. The possibilities of retrofitting bridges with different solution studied in a recent research program are presented and compared in this study.

The number of heavy vehicles and their weight have been increasing over time, implying that many bridges are experiencing traffic loads with higher magnitude and frequency than they were originally designed for. In some cases, it will be necessary to either replace or strengthen the structures to keep the bridges in service. For existing non-composite steel girder bridges, post-installation of shear connectors can often be used to increase the traffic load capacity significantly. One type of shear connector that is suitable for post-installation, even though not commonly used, is the Coiled Spring Pin. These interference fit connectors can be installed from below the bridge deck during traffic, in order to minimize the impact on road users. This paper describes an experimental study on the fatigue strength of Coiled Spring Pins and a compilation of previously performed fatigue tests on this type of connector. The new test series, with nine specimens, are evaluated statistically and a fatigue strength design equation is proposed. The results show that there are large variations between different test series, while tests within the same series show good agreement. The reasons for this are discussed in the paper along with recommendations for future testing.

Prolonging the life of existing steel trusses allover the world is a incoming necessity for all managing authorities wherever these structures have reached a particular state of use. The unsatisfactory behavior of these structures under the current type and increasing number of loads make clearer that innovative solutions are needed. For this purpose, the realization of different techniques are presented, in order to retrofit the actual load onto a structure conceived with historical codes, characterized by lower design live loads. The possibilities of retrofitting bridges with different solution studied in a recent research program are presented and compared in this study.

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.

Many existing bridges were not originally designed for the traffic loads and the number of load cycles which they now experience. In order to increase the load capacity of steel-concrete bridges, post installed shear connectors can be used. This paper presents a state-of the art study of post- installed shear connectors in general and coiled spring connectors in particular.

The old Årsta Bridge, a double track railway bridge with a main span carried by a truss arch, was opened in 1929. Due to high fatigue loading and the low ductility of the rail girders and the cross girders, it was decided to replace the bridge deck in year 2015. This paper describes the project from the design stage to the reopening of the upgraded bridge.

This paper describes the large‐scale tests on a composite bridge with prefabricated deck elements and dry joints between the elements. The work is part of the European R

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.

Determining the most efficient and economical way to build a new or replacement bridge is not as straightforward a process as it once was. The total cost of a bridge project is not limited to the amount spent on concrete, steel, and labor. Construction activities disrupt the typical flow of traffic around the project and results in additional costs to the public in the form of longer wait times, additional mileage traveled to get around the work zone, or business lost attributable to customers avoiding the construction. The risk of injury to workers because of traffic interactions or construction activities increase with each hour spent at the construction site. Finding a way to shorten the time spent on the jobsite is beneficial to the contractor, the owner, and the traveling public. Prefabricating certain bridge elements reduces the time spent at the construction site and reduces the effects on the road users and the surrounding community. For example, steel beams with composite concrete decks reduce the construction time over cast-in-place concrete superstructures. In some instances, entire structures have been fabricated off-site under strict environmental and quality controls and then shipped to the site and erected in a matter of days instead of months. The total cost of using prefabricated bridge elements (PBE) depends greatly on the scale of the prefabrication. The more that prefabrication is used, the lower the costs. Even under limited use, however, prefabrication is usually comparable to traditional construction techniques. However, when durability and user costs are taken into account, the overall cost may be significantly less than traditional piece-by-piece construction. To improve the competitiveness of prefabricated composite bridges, a European research and development project, ELEM RFSR-CT-2008-00039, was started in 2008. The overall objective of the project is to make prefabricated bridges more competitive through development of new cost-effective, time-efficient, and sustainable bridge structures. The project has started with a knowledge extension, in the form of the workshop on "Composite Bridges with Prefabricated Deck Elements." This workshop was held in Stockholm, Sweden, in March 2009 to share the knowledge and experience gained by agencies around the globe. During the workshop, experiences from Europe and the United States were presented in an effort to promote the use of accelerated bridge construction (ABC) and prefabricated bridge elements. (C) 2012 American Society of Civil Engineers.

The new railway bridge project over Södertälje Canal comprises the replacement of the 80 year old bridge, which has reached the end of its useful life. The new bridge consists of a main lifting span section spanning 57 m over the canal and two 70 m approach spans, one on each side of the main bridge. In total, the bridge is 229·5 m long. The main lifting section is a steel truss bridge structure and is capable of opening when large ships pass under. Normal elevation free height is 26·7 m and the top elevation is approximately 40·5 m. The approach spans are composite bridges with a main steel box girder and an in situ cast concrete top plate.

A prefabricated concrete deck with dry joints between deck elements has been developed to make prefabricated bridges even more competitive. This type of bridge deck has been used on single span bri ...

The savings in construction time is one reason why composite bridges have become a popular solution in many countries. Further time savings can be achieved by prefabricating not only the steel but also the concrete deck and the substructure. Taking these savings into account also from a road user perspective makes this concept even more interesting. In this paper different solutions, presented at an international workshop in Stockholm, are discussed. This includes a prefabricated deck solution with dry joints, used for three one span bridges in northern Sweden. Finally a European R&D project, aiming at developing the concept for multi span bridges, is presented.