Robert Hällmark

Prefabricated Bridge Construction across Europe and America

AbstractDetermining 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 r...

Innovative Prefabricated Composite Bridges

The competitiveness of composite bridges depends on different circumstances such as site conditions, local costs of material and staff, and the experience of the contractor. Two major advantages of composite bridges compared to concrete bridges are the ability of the steel girders to carry the weight of the formwork and the fresh concrete, and the shorter construction time which not only saves money for the contractor but even more for the road users. A further step is to prefabricate not only the steel girders, but also the concrete deck. In this paper, a new concept for composite bridges is described, with dry joints between the prefabricated concrete elements. The principal of the technique is presented, as well as some laboratory test simulating the load situation at an internal support in a multi-span bridge. Also, some experiences from an already built single span composite bridge with dry joints are presented.

The behaviour of a prefabricated composite bridge with dry deck joints

Abstract 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.

Prefabricated Composite Bridges

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.

Simulation of Low-cycle Fatigue in Integral Abutment Piles

Integral abutment bridges are bridges without any expansion joints, and their largest benefits are the lower construction- and maintenance costs. In order to build longer integral bridges it might be necessary to allow plastic hinges to be developed in the piles. Lateral thermal movements are the major reason to plastic deformations, and since temperature variations are cyclic it has to be proved that low-cycle fatigue will not occur. A simulation of the pile strain spectra should be able to take into account the strains caused by temperature variations and traffic loads. Such a model has been created from real temperature data and traffic loads measured by Bridge-Weigh-In-Motion technology. Monte Carlo simulations have been performed in order to simulate daily and annual temperature changes as well as the varying traffic loads. Piles strains have been calculated, and their fatigue effect has been evaluated.