Abstracts Engineering

Analysis of Negative Sequence Current Control for MMC HVDC Transmission Systems:

by I Shalom

Advanced Cementitious Materials (ACM’s) are products with materials found in conventional concrete (cement, silica fume, sand, superplasticizer, and water) plus distinctive materials like fibers (steel, carbon) and quartz. The superiority of ACM’s in terms of strength, ductility, and durability marks it as high potential replacement of traditional concrete. The growing expansion of ACM applications and technical experience gained in the last two decades in counties including Japan, Germany, Austria, Australia, USA, Denmark, Canada, France, and the Netherlands results in new frontier of cement materials used in infrastructure. The economic feasibility of ACM’s has been demonstrated in footbridges, outstanding bridges, and large pre-cast series. Furthermore safety and durability of ACM’s, especially of Ultra-high performance concrete (UHPC) has been proven encouraging further research efforts. This research is one part of an ongoing research under the supervision of Professor D.A. Hordijk at the Technical University of Delft on the application of ACM’s in infrastructure. The biggest potential for new infrastructure with ACM’s is in precast girders and thin plates. Throughout utilizing the excellent properties of ACM’s like UHPC, a new lighter- weight, durable, efficient, and adaptable superstructure has been developed in this study to replace the existing traditional design of bridges in the nearby future. One example of the approach taken in this thesis is the benefit of long life-cycle. Due to dense matrix, which prevents the ingress of detrimental substances apply UHPC selectively in the superstructure where it required to sustain high level of durability. Another example of the mindset of this thesis is lightweight design, means material distribution follows the forces distribution. In this thesis the outcome of an extensive material study was an overview of the ACM’s properties, time depended behavior, non-linear behavior, design standards, and field of application. Based on the material study different parameters are analyzed to enhance the understanding of the behavior of structure with ACM. It has been found that structural elements from UHPC are far more efficient then their corresponded traditional concrete structures. The maximum crack size is significantly lower, the slenderness is much higher which result in higher efficiency and reduction of the dead loads. Also the shrinkage and creep of ACM’s is studied. The time-depended imposed deformation of UHPC elements (plate, flange, truss member) with different sizes cause stresses in the model ends up as transverse cracks when the deformation is restrained. Based on the drawn conclusion of the parametric study, the design stage of the new ACM superstructure was initiated complying with requirements & boundaries according to the NEN norms and SETRA (French recommendation for UHPC). The new superstructure is 35% lighter than traditional solution, with efficient material distribution, built only from concrete, with elegant simple solutions. The low reliability… Advisors/Committee Members: Hordijk, D.A., Van der Veen, C., Kolstein, M.H., Reitsema, A.D., De Waardt, H..