Ethiotime1
We have made a site visit with my colleague Dawit W. Nega , Reinforced Concrete-III Lecturer, for our graduate students. We are so lucky to have a such grand project which can help us to show our students about pre-stressed concrete. There are two structural engineers by Joint consultants (Turkey and Ethiopia) side who explained the current phase of construction. As we heard, the support system of the whole bridge is going to change from a cantilever to a continuous one soon. The middle segment is underway. The construction system is as well changed from a balanced cantilever to Belly Beam. I’ll come up with details for the final stage. The bridge system is working by supporting 70% of the action with pre-stressed concrete. It consists of longitudinal post-tensioning and transversal post-tensioning, Vertical tension, and a Stay cable system. A 380m long prestressed concrete low-pylon cable-stayed bridge has 72 stay cables made of steel strands and each stay cable is made of a single layer of protective monofilament coated with epoxy steel strands. As we have seen from Stay Cable Installation Method Statement Document, the stay cable consists of an anchoring section + transition section + free section + anti-sliding section + saddle section in pylon column + anti-sliding anchoring section + free section + transition section + anchoring section. We have got illustrations of the longitudinal post-tensioning system. It consists of a corrugated duct, spiral reinforcements, Bearing plate, strands(Tensile capacity-1860MPa), anchor head, wedges, limiting plate, stressing jack and hydraulic pump, grip anchor head, and grip wedges. The duct shall sufficiently flexible to accept the required curvature without kinking. It is also supposed to resist corrosion as well. The stay cable is not fully tensioned for maintainability purposes. Each cable will support different loads as we go away from the piers. The contract period of the project has expired. Due to different inconveniences, the construction time has got additional days to finish with adjacent roads. I couldn’t forget such experiential learning with this iconic bridge. #sitevisit #graduate_students #structural #engineers #stay_cable_extradose_box_girder_bridge #experncial_learning Biruk Yenehun Lemlem , Tekletsion Yehulu , Mehrtash Soltani, Ph.D
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