Precast Pearl-Chain concrete arch bridges

• Pearl-Chain Bridges consist of prefabricated concrete elements assembled by post-tensioning.
• The concept is flexible and competitive to other similar closed-spandrel arch bridge concepts.
• The elements are Super-Light Decks consisting of both normal and light aggregate concrete.
• Different Pearl-Chain Bridge geometries are studied with load at the ¼ point of the span.
• The bending moment capacity depends on the level of pre-stressing, post-tensioning, and filling.

A Pearl-Chain Bridge is a closed-spandrel arch bridge consisting of a number of straight pre-fabricated so called Super-Light Deck elements put together in an arch shape by post-tensioning cables. Several Pearl-Chain arches can be positioned adjacent to each other by a crane to achieve a bridge of a desired width. On top of the arch is a filling material to level out the surface of the above road. The filling only transfers vertical loads to the arch.The geometry and material properties of Super-Light Decks are presented, and we refer to several full-scale tests of Pearl-Chain arches where the technology was used. We also study other important components and details in the Pearl-Chain Bridge concept and review the effects of different types of loads.A theoretical case study of a circular 30 m span Pearl-Chain Bridge is presented showing the influence of a number of parameters: The number of post-tensioning cables, the rise to span ratio, the height of the filling, and the height of the Super-Light Decks. We find that Pearl-Chain Bridges can be adjusted to resist specific moment loads by changing the normal force in the arch cross section by altering the above parameters. It is also found that the negative bending moment capacity starts decreasing before the positive bending moment capacity does, when the normal force in the cross section is increased. This is because of the cross section of the Super-Light Decks include a combination of normal concrete and light aggregate concrete with light aggregate concrete blocks in the bottom of the cross section.The positive bending moment capacity is therefore often larger than the negative, and that corresponds well with the required capacities when a concentrated load close to the quarter point of the span is applied. Such load is critical for arches, and gives a large positive bending moment below the load and a smaller negative bending moment in the unloaded side.When the Pearl-Chain Bridge concept is compared to other pre-fabricated arch bridge solutions we find a number of advantages when using Pearl-Chain Bridges: Straight elements, combination of normal concrete and light aggregate concrete, flexible design control, and joint details.