In 1999 research was started at Luleå University of Technology with the purpose to collect experiences from USA and UK on bridges with integral abutments and transfer the experience to Swedish conditions. Since then at least 20 integral bridges with one row of piles under each abutment have been built in Sweden and the European research project INTAB has been completed. Most of the bridges are short and it seems to be difficult to design integral bridges that are longer than 40 m. The reason for this being that piles in integral abutment bridges can experience severe strain during service due to soil restraint and annual fluctuations in bridge temperature, which displace and rotate the end of the pile that is clamped to the superstructure. Most design codes do not allow strains exceeding the yield point at the serviceability limit state (e.g. EN 1993-2). This will limit the possibility to build longer integral abutment bridges founded on steel piles. Since bridges are designed to be used 100 years or more, the strains caused by the annual temperature variations can be considered as a low cycle fatigue problem.The aim of this thesis is to improve the method to design steel piles in integral abutment bridges. This means that the designer with less effort should be able to make a safer or equally safe design as before by using the methods described in this thesis. The thesis describes how the analysis of piles of integral abutment bridges can be done. In order to study how steel piles in integral abutments are used and how they behave an international workshop was arranged in Stockholm (Collin et. al. 2006), a literature study was conducted, a bridge was designed, built and monitored and laboratory tests were made. With the results from the research activities as base a design method is suggested.

Under 1999 startades ett forskningsprojekt vid Luleå tekniska universitet med syfte att samla in erfarenheter, vad gäller broar med integrerade landfästen, från USA och Storbritannien och överföra dessa till svenska förhållanden. Sedan dess har minst 20 broar med integrerade landfästen (med en rad av pålar under varje landfäste) byggts i Sverige och det europeiska forskningsprojektet INTAB har slutförts. De flesta av broarna är korta och det verkar vara svårt att utforma broar med integrerade landfästen som är längre än 40 meter. Anledningen till detta är att pålar i broar med integrerade landfästen kan utsättas för höga töjningar under drift på grund av omgivande jords styvhet och temperaturvariationer, vilket förskjuter och roterar påltoppen som är fastspänd i överbyggnaden. De flesta normer tillåter inte att töjningar i stål överskrider sträckgränsen i bruksgränstillstånd (t.ex. EN 1993-2). Detta begränsar möjligheten att bygga längre broar med integrerade landfästen på stålpålar. Syftet med denna avhandling är att förbättra metoden för att dimensionera stålpålar i broar med integrerade landfästen. Det innebär att konstruktören med mindre ansträngning ska kunna göra en säkrare eller lika säker konstruktion som tidigare med hjälp av de metoder som beskrivs i denna avhandling. Avhandlingen beskriver hur analysen av pålar i broar med integrerade landfästen kan göras. För att studera hur stålpålar i integrerade landfästen fungerar gjordes en litteraturstudie, långtids- och korttids-mätningar på en bro med integrerade landfästen och laboratorietester har utförts. Med resultaten från forskningen som utgångspunkt föreslås en dimensioneringsmetod.

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.

Field tests of two jointless bridges are presented, focusing on the magnitude and significance of earth pressure behind the abutments. The Haavistonjoki Bridge is a 56 m long, continuous three span bridge. Instrumentation was used to measure the horizontal displacement of an abutment, abutment rotation, abutment pile strains, earth pressures behind the abutments, superstructure displacements, frost depth and air temperature. The measured earth pressures were compared with pressures that had been calculated on the basis of Nordic codes of practice and the Eurocodes pertaining to bridges. The bridge over the Leduån is a single span composite bridge with a cast‐in‐place concrete deck on top of two steel beams. This bridge, spanning 40 m, is slender, with a 1.7 m high superstructure. The bridge was fitted with strain and displacement gauges and short term measurements were made using a loaded truck. The field test results for this bridge were verified with calculations based on an abutment rotation stiffness calculation model developed during the research presented in this paper.

One of the most commonly discussed problems regarding bridges with integral abutments is the influence of longitudinal elongation of the superstructure as a result of seasonal temperature variations. A bridge built with integral abutments is often supported by a row of piles made of steel or concrete. The longitudinal elongation of the superstructure induces a displacement and a rotation at the top of the pile, which in turn may cause strains that exceeds the yield strain. Such seasonal variations may lead to low-cyclic fatigue failure in the pile. Therefore, it is of great interest to investigate the amplitude of these strains, as well as the general behaviour of the bridge. In 2005, the European R&D project, INTAB (RFSR-CT-2005-00041, "Economic and Durable Design of Bridges with Integral Abutments, 2005-2008") was started. Within the INTAB project a composite bridge was built and monitored in Northern Sweden.

In the design and construction of bridges, questions of sustainability, maintenance and durability are becoming more and more important for European road administrations, in addition to safety and serviceability issues. Therefore integral abutment bridges are becoming highly attractive to designers, constructors and road administrations, as they tend to be less expensive to build, easier to maintain and more economical to own over their life time. Bearings and joints are main sources of maintenance costs during a lifetime. These costs vanish because the bridges are joint- and bearing-free. However, this very advantage complicates the design compared to conventional bridges in some crucial respects. Combined with the fact that most European countries have only limited experience with integral bridges to date, this leads to a reluctance of road administrations to use this bridge type. Thus the main objective of the project is to experimentally and theoretically investigate the behaviour of critical points of integral abutment bridges. Regarding the soil-structure interaction, recommendations are elaborated based on monitoring results as well as previous research and monitoring campaigns. Conventional HP piles and sheet piles are investigated as a foundation. Furthermore a hinged HP connection is developed to decrease the stresses in the pile system. An investigation of the design and construction of the slab to pavement approach is also carried out to avoid major damages to the structure. Finally the most important information is condensed into the essential features in form of a 'Design guide for composite bridges with integral abutments'

Integral abutment bridges are becoming more popular in Europe, but the traditions differ from country to country. This leads to different technical solutions for the same problem in each country. A European survey was conducted in early 2007 to illustrate the design criteria used by each different country for integral abutment bridges. The survey requested information useful to a designer comparing the design requirements and restrictions of various European countries. As an added measure of comparison, these results were compared to some recently conducted surveys of state agencies within the United States. When looking at the results of the European survey responses and past surveys of U.S. transportation agencies, it is clear that there are many similarities in design assumptions and construction practices. Yet, there are also significant differences.

The study deals with the development of long jointless bridges with a focus on soil- structure interaction. The instrumentation of Haavistonjoki Bridge was completed in the autumn of 2003. The data were collected by monitoring altogether 191 gauges installed in the bridge structures during construction. The instrumentation was used to measure, for instance, the abutment's horizontal displacement, abutment rotation, abutment pile strains, earth pressures behind abutments, superstructure displacements, frost depth, and air temperature. Haavistonjoki Bridge is a 56 m long continuous 3-span slab bridge. The measured earth pressures were compared with calculated pressures. The bridge over Leduan is a single span composite bridge. The cast-in-place concrete deck acts together with two steel beams. The 40 m span bridge is very slender with the height of superstructure 1.7 m. Totally 34 measurements were constantly recorded and stored in a period of at least 18 months. The bridge over Edslan has a 19.8 m span and a 7.65 m wide concrete slab. The test results are verified with calculations.--------------------------------------------------------------------------------

In integral abutment bridges clamped abutment piles are in addition to a compressive normal force subjected to bending load cycles from daily and yearly temperature variations. Through experiments with full-scale specimens representing a clamped pile it is shown that a steel pipe pile loaded in bending can withstand several hundred load cycles at strain ranges greater than 6 times the yield strain with almost full load bearing capacity. By means of an example it is shown that by permitting pile strains greater than the yield strain, in contrast to most present design codes, integral abutment bridges can be erected with a span length up to 500m and a prospected service life of 120 years.

Preliminary results obtained from short term test-loading are used to illustrate possibilities of FEM used to calibrate complex interaction characteristics between a pile and soil in a bridge with integral abutments. The measurements are obtained during the winter season on the bridge over Ledån, Northern Sweden. The bridge is built in 2006 and used for long term monitoring within the international project supported by RFCS. The main objective of the on-going research project is to proposed recommendations for rational analysis and design of bridges with integral abutments.

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.