Precast Concrete Structures in Earthquake Regions

In earthquake regions the requirements to ductility of precast concrete structures are often considerably higher than in other regions. Therefore often the concepts developed in Denmark have to be modified when they are applied in earthquake regions.
The purpose of the project is to find new and better design models for structural elements and joints applicable in such situations.
Primarily the efforts are concentrated on developing reliable models for monotonic loads because the behavior predicted for monotonic loads usually envelopes the behavior for cyclic loads. This part of the project has been finished by the publication of a ph.d. dissertation (Jens Christoffersen).
Concrete strength is partly determined by cracking. Cracks may be microcracks already present before loading. Loading may enhance microcracking and further introduce macrocracks. Emphasis has been put on the role of cracking by developing new models for the behavior of structural elements super-sensitive to crack development, e.g. non shear reinforced beams and slabs. Further the particularly important problem related to the microcracking due to stressed reinforcement passing a macrocrack has been treated. Finally, a new micromechanical model for concrete considered as a two-phase material is developed. This part of the project has been terminated by the publication of a ph.d. dissertation (Jin-Ping Zhang).
Complicated structural elements may preferably nowadays be calculated using finite element methods. A new finite-element program has been developed. The program takes into account the development of macrocracks and changes in crack direction and yielding of reinforcement. The strength reduction due to cracking as described above is handled according to the Jin-Ping Zhang model. Project finished by ph.d. dissertation (Lars Jagd).