Serviceability (cracking, deformations, deflections), but not the strength requirements often are the governing design criterion of modern reinforced concrete bridges. Serviceability aspects of concrete structures due to complexities and inaccuracies surrounding this matter are not adequately taught at most European universities. Therefore, structural engineers both at large and small design companies lack confidence in dealing with serviceability problems and have vague understanding of various aspects of deformational analysis. It is a common design practice to calculate deformations of reinforced concrete structures in a simplified way which disregards or deals in a very approximate manner with concrete cracking, creep and shrinkage and other complex non-linear effects. Then errors in deflection estimates can be over 100 %.

The Fellow has recently developed an innovative statistically verified constitutive model (called the Integral Constitutive Model [1,2]) for deformational analysis of reinforced concrete members. The Integral Constitutive Model gives more accurate deflection predictions than other known constitutive models or design code methods such as ACI (American code), EC2 (Eurocode) and SNiP (Russian code).

In the project, the integral constitutive model is to be transferred to analysis and design of large reinforced concrete structures such as bridge structures. The following effects are to be introduced into both analytical and numerical methods: concrete cracking, creep and shrinkage, tension stiffening, stress relaxation in steel, temperature changes, size, dynamic effects, etc. Experimental data on deformations of models and real structures are to be collected. Comparison of the experimental deformations with the predicted ones by the analytical and numerical models is to be carried out. The comparison results are to be critically reviewed with possible modification of the proposed models. The Fellow is eager to transfer his knowledge on deformations, cracking and time effects of concrete structures to the host and other Danish and European institutions. Results achieved in the project are to be reported at conferences and seminars to be held this year in Denmark, the Netherlands, South Korea and Japan.

Description of the host institution

COWI is one of the world leading companies in bridge design. Since 1930 it has designed over 1500 bridges around the world since 1930. COWI is recognised world-wide for its state-of-the-art knowledge on cable stayed and suspension bridges. Some significant references in recent years are the Great Belt Link (Denmark), the Oresund Link (Denmark/Sweden), the Normandy Bridge (France), Yamuna Bridge (India), the Höga Kusten Bridge (Sweden) and Stonecutters Bridge (Hong Kong), the world's largest cable stayed bridge. Also in the field of smaller bridges COWI holds leading expertise. Within the last 5 years alone COWI has designed more than 100 concrete motorway bridges in Denmark. Further, COWI has more than 40 years of experience in maintenance and rehabilitation of bridges.

Potential benefit and impact of knowledge exchanged for both host and home research groups:

• Impacting the state-of-the-art on serviceability models of concrete bridge structures.
• Conveying the acquired knowledge and experience to academic, engineering and industrial institutions of Denmark, Lithuania and other European countries.
• Implementing the constitutive deformational models, methods and software to practical projects.
• Impacting the European codes for concrete structures (EC2) through the Fellow's participation in the activities of the Task Group 4.1 "Serviceability Models" of the international organisation FIB (Federation of Structural Concrete).
• Impacting economic, safety and environmental aspects of design.
• Acquiring by the Fellow high-tech industrial experience in bridge construction. This will impact not only further elaboration of the theoretical methods, but also personal career of the Fellow in terms of professional and management skills.
• Impacting further collaboration between host institution and the Fellow's research group.

• G. Kaklauskas and J. Ghaboussi. Stress-Strain Relations for Cracked Tensile Concrete from RC Beam Tests. ASCE (Amer. Soc. Civ. Eng.) Journal of Structural Engineering, January 2001, Vol. 127, Issue 1, p. 64-73.
• G. Kaklauskas. Integral Flexural Constitutive Model for Deformational Analysis of Concrete Structures. Vilnius, Technika, 2001, 139 p.