Dynamic analysis of a bridge repaired by CFRP: Experimental and numerical modelling M. Abdessemed a,c , S. Kenai b,⇑ , A. Bali c , A. Kibboua d a Public Works Ministry, Algiers, Algeria b Civil Engineering Department, Geomaterials Laboratory, University of Blida, Algeria c Construction & Environment Laboratory, Polytechnic National School of Algiers, Algeria d National Earthquake Engineering Centre (CGS), Algiers, Algeria article info Article history: Received 8 May 2009 Received in revised form 27 July 2010 Accepted 2 September 2010 Available online 28 September 2010 Keywords: Bridge Reinforced concrete Strengthening Carbon fibres Ambient vibrations Modelling Finite element abstract A significant number of existing reinforced-concrete bridges all over the world require maintenance and repair. Hence, the need for a rapid evaluation procedure for the diagnosis of existing bridges. This paper presents the application of a dynamic analysis methodology for structural evaluation of reinforced-con- crete bridges. The methodology is based on the application of ambient vibrations non-destructive testing method and the identification of the structure total response using finite element method. A case study of a three span reinforced concrete bridge in a strong seismic activity area in the north of Algeria is analysed. The ambient vibration testing was carried out on the bridge, before and after its repair by the application of carbon fibre composites. The tests were conducted using an acquisition system made up of four accel- erometers with three components placed at specific locations on the bridge. The finite element model gave comparable results to the experimental ambient vibrations tests. The modal parameters of the bridge before and after repair were identified by this in situ testing. The application of composite material to strengthen the structure increases the transverse rigidity of the structure and thus its modal frequency. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction A significant number of existing reinforced-concrete bridges require maintenance and repair. In Algeria there are more than 4850 road bridges of which more than 40% require repair. Many of these structures have suffered cracking and various damages during their life span [1]. The causes of these damages are either due to errors in design, detailing, calculation or construction and also due to ageing and fatigue. In addition, Algeria is located in a high activity earthquake zone and its infrastructure is often dam- aged by seismic actions. Therefore, there is a need to evaluate and diagnosis these structures in order to repair and strengthen them when necessary. Bridge inspection is currently conducted mainly based on visual inspection and hence there is a need to im- prove bridge assessment techniques. The evaluation procedure should be a quick method that could detect any damage at its early stage and propose repair and/or strengthening method to reinstate the initial transverse rigidity of the structure and improve its per- formance and durability. The non-destructive testing methods (NDT) that permit the evaluation of the materials properties and the performance of the structure without interfering with its use and without affecting its carrying capacity are the most recom- mended for this kind of evaluation. The mostly used NDT tech- niques are optical fibres, ambient excitation or forced vibrations [2]. Vibrations testing on bridges are not recent and several studies are reported by various researchers and testing laboratories [3]. This technique has gained recently a widespread use for structural evaluation. This technique could be divided into two main catego- ries: the category of testing by measurement of inputs generally called ‘‘measured-input testing’’ intended for large structures such as stayed-girder bridges, suspension bridges or structures with large lattice road surface, and a second category known as ‘‘ambi- ent testing’’ intended for medium and small scale structures, such as reinforced concrete or steel beam bridges with reinforced con- crete slab deck [4]. Ambient vibration testing could be applied using excitation by vehicles. For bridges with heavy traffic that cannot be interrupted, another form of ambient vibration testing is applied which is that of the excitation of the circulating traffic itself on the structure in use that could be associated with other sources of ambient excita- tion such as wind. This type of excitations was applied on 57 large bridges in California in 1982. Ambient excitation by wind and waves as well as pedestrians was also applied on the Oakland 0950-0618/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2010.09.025 ⇑ Corresponding author. Tel.: +213 25 433939; fax: +213 21404921. E-mail address: sdkenai@yahoo.com (S. Kenai). Construction and Building Materials 25 (2011) 1270–1276 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat