org . americanscience jof http://www. ) 5 ( 9 2013; Journal of American Science 417 Application of a New Water-Structure Interaction Support System for Existing Bridges Medhat K. Abdullah Department of Civil Engineering, Faculty of Engineering, Helwan University, Cairo, Egypt. infra@infraconsultants.org Abstract: A new temporary supporting system, which has been developed by the author, is applied to temporarily support Al-Tabia existing bridge over a canal located at the route required for the transportation of the abnormal heavy packages to Abu Quir power station, Egypt. This new system depends mainly on water-structure interaction and it is approved by the Egyptian general authority of roads, bridges and land transportation (GARBLT) to be used for the transportation of heavy loads over existing bridges after it was developed and proven to be very successful- both analytically and experimentally by the author. The assessment, strengthening and health monitoring of the bridge is presented. The dynamic test results have been used as a monitoring tool to prove that the bridge have not been damaged by the additional imposed abnormal loads. [Medhat K. Abdullah. Application of a New Water-Structure Interaction Support System for Existing Bridges. J Am Sci 2013;9(5):417-424]. (ISSN: 1545-1003). http://www.jofamericanscience.org . 54 Keywords: Bridges, Heavy loads, Temporary support, Water-Structure interaction, Monitoring, Dynamic load test. 1. Introduction Al-Tabia Bridge is an existing bridge located in Abu Quir, Alexandria, Egypt where a new power station is decided to be built. This bridge has been designed for a load of 70 Ton which is extremely small compared to the abnormal heavy weights of equipments -that exceed 500 tons- required for this station. The bridge passes over a canal that makes the conventional temporary supporting techniques are very difficult due to the inaccessibility to the structural components. Moreover, it is very difficult to accurately assess the strength of the different structural elements of the bridge due to the lack of design drawings. As a result, a new technique that mainly depends on water-structure interaction is decided to be used as a temporary supporting system. This main concept of this technique which has been developed and verified by the author, [1], is to depend on the uplift force of the water to impose reversal forces on the bridge to counteract most of the loads expected from the abnormal heavy loads. Moreover, the process of temporarily coupling the bridge deck with a barrage supported by the water uplift, if accurately designed, results in a combined structure that has an effective combined rigidity which is highly above the bridge deck rigidity decreasing the deformations imposed by the loads. In the following parts, the details of applying this system to Al-Tabia Bridge are summarized. Details of the abnormal load The main features of the loading system are illustrated in figure 1 and may be summarized as follows:  Transportation on 1trailer x 3files x 16 axles, Each File contains 4 wheels  Weight of load is 404 Ton, Total Load is 510Ton  Block ground load is 4.56 Ton/m2. Description of the bridge: The bridge was inspected in the site to check its overall conditions. It is composed of 3main spans, 9.6m long each. The deck is slab-girder type. No design drawings are available and the general layout of the bridge is illustrated schematically in figure 2. The bridge was visually inspected and it was concluded that its general condition is very poor as illustrated in pictures 1 to 3. As a result of the visual inspection, and due to the lack of design information, it was decided to use the water-structure interaction technique described above, as a temporary support for this bridge. Analytical study: The bridge deck was analyzed under the effect of total load of the package including the weight of the trailer as shown before. The concrete Young’s modulus was assumed 250 ton/cm 2 and the analysis was performed by the computer software SAP90. The grillage method was used in the analysis of this bridge, [2]. The longitudinal main girders were modeled with the properties of a T-section and the slab was modeled as lumped transversal beams every 1.0-meter. The water uplift was modeled as spring forces distributed all over the area of the barrage. Steel beams are used to distribute the loads on the barrage and they were modeled with their actual stiffness. Figure 3 shows the analytical model for the bridge deck, the steel beams, the props, the barrage and the water uplift.