Honorable Mention: Water Structures Category
Repair of Wisla-Czarne Dam Concrete Structures
The Wisla-Czarne Dam is a small earth dam built in 1973. Workmanship faults, poor concrete quality and exposure to severe environmental conditions caused deterioration of the concrete, which was unsuccessfully repaired several times over the years. This project allowed the evaluation of the structures to detect the damage that was causing the water infiltration. Test repairs were performed that enabled the selection of effective repair materials and sealing methods for underground tunnels being repaired 25 meters below water level. Six years of field testing were conducted to check durability and select the best material for protection of the concrete shield against wavy motion and ice aggression. Field corrosion monitoring was performed to determine the proper repair system for the carbonated walls of the overflow channel.
Once the research was completed, the project was awarded. Once the repairs began, different structural faults of the expansion joints were detected and repaired. Each of the renovated structures (service and monitoring tunnels, bottom outlet valves chamber, concrete shield on the upstream side of the dam, overflow channel, bridge over the overflow channel and discharge basin) demanded different, individually selected repairs and protection dedicated to local exposure conditions. All repairs were successfully completed and water infiltration was dramatically reduced.
Award of Merit: Transportation Category
Man Maurizio Viaduct Joint Repair
The San Maurizio Viaduct, located on Highway A22 in northern Italy, was built in the 1960s and underwent repairs from 2006 to 2009. The main reason for repair was the continual failure of mechanical expansion joints between adjacent multiple-span bridge decks. The new solution to the problem of leaking expansion joints was the development of continuous bridge decks. This continuity was achieved by removing the expansion joints and replacing a portion of two adjacent decks with sections of reinforced ductile concrete.
In the case of the San Maurizio Viaduct, the designers suggested substituting 80% of the mechanical joints using continuous low-stiffness ductile slabs. The adjacent bridge decks had been connected over four to six spans to a length of 590.5 ft (180 m). The link slabs needed the following properties: a high-deformation capacity under cyclic loading, a low Young’s Modulus, high strength, and high resistance to fatigue. Ductile cement-based materials are able to absorb big deformation-generating, well-distributed small cracks without crack localization. This large strain capacity is over 100 times that of normal concrete. The ductile high-fracture energy concrete was then poured directly from the concrete mixer truck.
Reinforced ductile high-fracture energy concrete met all of the requirements that were essential for the link-slab application, as it has high strain capacity under tension and compression regime while forming small, closely spaced microcracks. It also allowed for the deformation under thermal loads, along with the creation of a partially uninterrupted deck to protect the underlying superstructure and substructure. Finally, the advantages were not just related to the lower repair cost. When considering lifecycle costs, the link slabs became not only feasible, but also advantageous. This was the first time that ductile link slabs had been used in Europe.
Award of Excellence: Special Projects Category
Seismic Retrofitting of Floors with Low Thickness UHPFRCC Micro-Concrete
The Domenico Cotugno Hospital, constructed in 1930 in Bari, Italy, and located in Seismic Area Class 3, was recently renovated to be the new headquarters of the IRCCS Istituto Tumori Giovanni Paolo II. As a part of the analysis for design of the project, it was determined that the existing structure required seismic strengthening to bring the building into compliance with current codes.
One of the key elements of the seismic strengthening plan was membranic reinforcement of the floors using fiber-reinforced micro-concrete that was bonded to the existing concrete floors. This bond was needed to ensure that horizontal forces from an earthquake are transferred to the new partitions and existing walls.
The membranic reinforcement of the floors was achieved by using specially formulated ultra-high-performance fiber-reinforced cementitious composite (UHPFRCC) micro-concrete. The UHPFRCC material was formulated to be applied in a layer on reinforced floors.
UHPFRCC micro-concrete is a fiber-reinforced, self-consolidating mixture with very high mechanical strength and fracture energy. The three component product consists of a powder component, a liquid additive, and steel and polymer microfibers (0.6 in. [15 mm] long). The product sets in about 1 hour and develops high strength in the early stages so it can be opened to foot traffic after about 14 hours.
The main advantages of this system are minimal application thickness (0.6 to 0.8 in. [15 to 20 mm]), resulting in minimal increased load; adhesion to the substrate without necessity of connectors or resins; no reinforcement mesh required; very high ductility and resistance to cyclic load; increased bearing capacity in terms of bending moment and stiffness with reduced floor deflection; speed of application because of self-leveling material properties; and no construction or contractive joints.