Suspended floor
Flexural Strengthening of Old Timber Floors with Laminated Carbon Fiber Reinforced Polymers,
Biscaia, Hugo, Chastre Carlos, Cruz David, and Franco Noel
, Journal of Composites for Construction, p.04016073, (2016)
AbstractA set of three old suspended timber floors were flexurally-strengthened with Carbon Fiber Reinforced Polymers (CFRP) strips in order to investigate the effectiveness of externally bonding FRP to their soffits. The specimens were from an old building and 740 mm-wide bands were transferred to the laboratory in order to be tested in a 4-point bending test. One specimen was tested with no strengthening system and the results obtained were used as reference values for comparison with the specimens those were externally bonded and reinforced (EBR) with CFRP strips. Two similar EBR systems were studied: (i) keeping both ends of the CFRP strips free of any restriction (traditional technique); and (ii) embedding both ends of the CFRP strips into the timber, thus providing a bonding anchorage of the strips (new technique). The installation of the new strengthening system comprises the opening of holes in the timber and the creation of a transition curve between the holes and the timber surface. This transition curve allows a smooth transition of the CFRP laminate between the hole and the timber surface, thus avoiding stress concentrations in this area. After the opening of the holes, the resin is applied inside the hole and on the beam surface, and then the CFRP laminate is mounted. The load-carrying capacity of the specimens, the rupture modes, the strains and bond stress distributions within the CFRP-to-timber interface are presented. A nonlinear numerical simulation of the specimens based on the mid-span cross-sectional equilibrium is also presented. The results showed that the use of the new strengthening system enhances the performance of the specimens when compared with the traditional strengthening system.
Flexural strengthening of columns with CFRP composites and stainless steel: Cyclic behavior,
Faustino, Pedro, and Chastre Carlos
, Journal of Structural Engineering, 21 September 201, Volume 142, Number 2, p.04015136, (2016)
AbstractThis study presents the testing, completion, and analysis of different external strengthening systems applied to rectangular reinforced concrete columns with rounded corners. The experimental study included confinement strengthening with carbon-fiberreinforcedpolymer (CFRP) sheets, longitudinal strengthening with CFRP laminates and confining CFRP jacket, longitudinal strengtheningwith stainless steel bars and confining CFRP jacket, tested column until reinforcing steel failure, repair and CFRP confining jacket,and longitudinal strengthening with stainless steel bars. The analysis of the experimental results included lateral load-displacement relationship, energy dissipation, ductility, and curvature damage assessment classifications. It was concluded that the use of externallongitudinal strengthening combined with CFRP confinement is effective for enhancing performance and is viable in terms of execution. The load capacity increase due to strengthening reached 36–46% with good ductile behavior (failure was reached at 4.4% drift ratio). Despite some differences between CFRP laminates and stainless steel, all columns presented moderate degrees of damage between 1 and 2% drift ratio and minor damage degree until 1% drift ratio.
