Composite bridge design for small and medium spans

(1) The research project was undertaken to develop and test new composite bridge concepts that are easily buildable by the best possible application of construction materials and a high grade of prefabrication. (2) One ofthe problems was the use of hybrid girders which lead to significant material cost savings and to a reduction of girder heights. Therefore the fatigue rules given in ENV3 Part 2 have been validated experimentally and by numerical studies with a special regard to the local yielding of the web. (3) A further investigation were the use of dismountable shear connectors and headed studs with a diameter of 25 mm which are not considered in the codes until now. Studs with a diameter of 25 mm are favourable for bridges due to their higher shear resistance. This test series has included static and dynamic Push-Out tests. (4) Studies on the behaviour of joints of composite bridges took the special behaviour of partial-and full prefabricated slabs into account. Reference bridges have been used to design the test set-up and cycle loadings were applied to simulate moving traffic loads. The investigations were performed in order to verify the opening of the joints, the fatigue behaviour of the shear studs and to study the transfer of vertical shear forces between the elements. (5) The works on the fatigue tests on special joints of beams comprised connections in span and on support. Due to the fact that welding activities are expensive bolted connections and fillet welds instead of full penetration welds have been investigated. The best alternatives for an easy erection, stabilising of the steel beams during assembly and concreting as well as achieving a durable structure have been found. (6) Particular experimental and numerical studies on steel and composite beams with stocky and slender webs reveal that the resistance to vertical shear for S460 according to the ENV3 Part 1-1- and 1-5 and the influence of the concrete slab on the plate buckling behaviour under sagging and hogging moments have to be verified and improved. (7) The effects from the interaction with the concrete slab of the bridge have been evaluated. Comparisons between calculation methods and test results have shown that the simplified rules in ENV4 Part 2 are in a good accordance to more precise research approaches. A sophisticated software, called CASE, has been developed to determine the effects from creep and shrinkage on partial prefabricated slabs. (8) An additional working item about the vibration behaviour of composite bridges has been performed. Measurements on several composite bridges have shown that usually no adverse comments of pedestrians crossing the bridge simultaneously with traffic occurred. Slender constructions out of HSS and HSC seem to result in vibration problems due to strong perceptions of vibration. (9) The Design Guide include economic and durable concepts for composite bridges including detailed alternative technologies with background information and complete tender documents for reference bridges. A sophisticated software provide the practical engineer with a very fast and user-friendly tool by considering all possible variants for different designs. (10) The results of the research project can be transferred directly into new and improved design rules for steel and composite structures by implementing them in ENV 1993 (Design of Steel Structures) and ENV 1994 (Design of Steel and Concrete Composite Structures).