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| Adaptable scaffolding system accelerates bridge refurbishment  Built in 1940, a reinforced concrete arched bridge which crosses the Rio Tua in the Portuguese province of Trás-os-Montes, is currently being extensively renovated. Access facilities and working platforms for the repair and maintenance work are being provided by a scaffold construction on the basis of the PERI UP Rosett Flex scaffolding system. The modular construction method of the scaffold allows optimal adjustment to bridge geometry and, at the same time, assembly is both fast and safe. The high level of safety during working operations during the use and the easy accessibility is accelerating the renovation work, so much that construction time will fall below the originally scheduled seven months.The bridge has a total length of 120 metres and is 8 metres wide. An 80 metres wide and 20 metres high concrete arch spans the river valley with the superstructure being supported on a number of piers along the two side extension sections. At present, various restoration measures are being undertaken: strengthening of the roadway surfacing and the T beam construction, repairing the concrete and corroded reinforcement, use of epoxy injection to fill the cracks as well as reconditioning the walkways and guardrails. The entire bridge deck will subsequently be re coated. The challenge was to create access to all structural elements which are to be renovated as well as sufficiently large and load-bearing working areas - also for the required equipment. A scaffold comprising of system components taken from the PERI UP Rosett Flex system could fulfil all requirements in spite of the very complicated geometry of the bridge construction and difficult accessibility in some areas. The PERI UP scaffold combines the assembly advantages of system scaffolding with the flexibility of the tube and coupler scaffold which is far more time-consuming to erect. The 25 cm grid dimension allows easy and simple adjustments to an extremely wide range of component geometries. Ledgers and decking can be optimally matched to each other and all scaffold bays can be completely covered with system decking. This means no dangerous gaps and the working safety level for site personnel is considerably increased. The erected scaffold has a maximum height of 20 metres with the contact area on the ground extending to around 7 metres whilst, at the highest point, the scaffold is 11.75 metres wide. The lateral cantilevers along with the bridging between the outer bridge piers were realized with PERI UP system diagonals without the need of any additional auxiliary components. For the construction of the bridging, the standards were connected with the node braces which had already been attached, and simply swivelled outwards via the ledgers with the scaffolders always in a safe and secure position. In spite of the special form of the concrete arch as well as the different dimensions of the piers, the scaffold has been constructed with a minimum of distance around each building component of the bridge. The advantage of the adaptability of the system has also been demonstrated especially during the assembly of the scaffolding: although a number of deviations between the original execution plan and the actual dimensions were determined, access means and platforms could be erected without requiring any time-consuming and expensive improvisation. Scaffold assembly with PERI UP standards, ledgers and steel decking is safe and fast. When fitting the ledgers, the wedge falls through its own force of gravity into the rosett opening and locks automatically. Thanks to this so-called gravity lock, the ledger can be always be installed from a safe position. The PERI logic simplifies and accelerates the assembly of PERI UP scaffolding. The low weight of the individual system components and the fact that each system part can be handled by only one person, facilitates fast and energy-saving work operations. The high rigidity of the PERI UP standard connections reduces the number of both bracing levels and required diagonals. A high level of safety during working operations is guaranteed by all-round guardrails and toe boards installed on each level of the scaffold construction. Construction crews have the feeling of complete safety which has promoted fast construction progress with the result that the planned schedule has been reduced. In addition, PERI UP provides a high load-bearing capacity, sufficient also for all the equipment required for the bridge renovation. All PERI UP system components are compatible with each other. As a result, working platforms, stairs and guardrails are easy and simple to install. As the main point of access, a stair tower comprising of system parts and a few auxiliary components for the tower is used - in this way, a 19 metres height difference has been cost-effectively bridged. The 75 cm flight width, along with the comfortable rise-to-tread ratio, ensures safe and quick access for site personnel. Between the bridge piers, ladders have been integrated which directly connect the working levels with each other. write your comments about the article :: © 2010 Construction News :: home page |