Behavior of Circular Fiber-Reinforced Polymer-Steel-Confined Concrete Columns Subjected to Reversed Cyclic Loads: Experimental Studies and Finite-Element Analysis

This paper studied experimentally the behavior of circular fiber-reinforced polymer (FRP)-steel-confined concrete columns subjected to reversed cyclic loads. The influence of main structural factors on the cyclic behavior of the columns is discussed. Test results showed the outstanding seismic performance of FRP-steel-confined RC and steel-reinforced concrete (SRC) columns. The lateral confinement effectiveness of glass fiber-reinforced polymer (GFRP) tubes and GFRP-steel tubes was verified and a simplified OpenSees-based finite-element method (FEM) model was developed to simulate the experimental results of the test columns. Based on the proposed FEM model, a parametric analysis was conducted to investigate the effects of main factors on the reversed cyclic behavior of GFRP-steel-confined RC columns. Based on the test and numerical analyses, the study discussed the influence of variables such as the lateral confinement on the plastic hinge region (PHR) height and peak drift ratio of the columns under reversed cyclic loads. Results indicate that lateral confinement significantly affects the PHR height of circular confined RC columns. Based on the analyses of the data from this study and literature, a simple model was suggested to predict the peak drift ratio of confined RC columns

Monotonic axial compressive behaviour and confinement mechanism of square CFRP-steel tube confined concrete

Steel tube confined concrete (STCC) is widely used in the vertical members of high-rise buildings such as columns. The axial load is not directly resisted by the steel tube in STCC, but is resisted via the interfacial frictional stress between steel tube and concrete core, which is different with that of concrete filled steel tube (CFT) members and would effectively suppress the outward local buckling of steel tube at early stage. Recently, fibre-reinforced polymer (FRP) confined STCC presents a potential to enhance the ductility and durability of such vertical elements. This paper presents an experimental study on monotonic axial compressive behaviour of carbon FRP (CFRP) confined STCC (CFRP-STCC) stub column and an analytical study on the confinement mechanism of and the ultimate axial bearing capacity of the elements. A three-stage confinement mechanism involving the different contributions of the steel tube and the CFRP wrap in CFRP-STCC elements was proposed based on the test results. A prediction model of the ultimate axial bearing capacity of CFRP-STCC stub columns was developed subsequently. Results show that the presence of CFRP wrap enhances effectively the load-bearing capacity and the ductility of steel tube confined plain concrete and reinforced concrete elements, and significantly prevents the local buckling of the steel tubes in the elements. The proposed prediction model of ultimate axial bearing capacity assesses test results with a great agreement

Occupant behaviour: a major issue for building energy performance

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Assessment of the effects of temperature and moisture content on the hygrothermal transport and storage properties of porous building materials

International audienc

New hybrid cement-based composite material externally bonded to control RC beam cracking

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Occupant presence and behavior: A major issue for building energy performance simulation and assessment

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Damage control of the masonry infills in RC frames under cyclic loads: a full-scale test study and numerical analyses

This study investigates the effect of damage control methods on the seismic performance of masonry infilled walls in reinforced concrete (RC) frames, by experimentally investigating three full-scale infilled RC frames with different treatment details and finite element method (FEM) analysis. The control methods included full-length connecting steel rebars, styrene butadiene styrene (SBS) sliding layers, and two gaps between the wall and frame columns. The results indicated that the ductility, wall damage, and residual deformation of the frame with gaps or SBS layers were significantly improved. However, the initial stiffness, energy dissipation capacity, and lateral load-carrying capacity of the frames with SBS sliding layers all were reduced. The fully infilled frames exhibited a better lateral load-carrying capacity, stiffness, and energy dissipation capacity, but presented larger lateral residual deformation and lower ductility. The damage of the infilled walls in RC frames can be controlled by using longer connecting rebars. The gaps and sliding layers can both significantly reduce the in-plane damage of the walls. A simplified FEM model was proposed and applied to conduct a parametric analysis for an in-depth study of fully infilled RC frames with and without sliding layers. The results show that SBS is the optimal sliding layer material, and its optimal spacing in RC frames is recommended as 1000 mm

Numerical study of composite material (FRP/TRC)-reinforced masonry walls under in-plane loading

International audienceFibre-reinforced polymers (FRPs) and textile-reinforced concretes (TRCs) are becoming increasingly common solutions for strengthening masonry walls. This study focuses on different approaches for modelling the behaviour of hollow concrete block masonry walls strengthened with FRPs and a TRC subjected to in-plane loading. Specifically, the masonry is modelled using the heterogeneous approach, wherein the damage post-peak softening behaviours of both bricks and mortar are considered, as this approach is appropriate for material and structure scales. To model the FRP/TRC-reinforced masonry walls, the reinforcements (FRPs/TRC) are perfectly connected to the substrate. Although the homogeneous approach is proposed to model the FRPs with linear elastic behaviour and is shown to be appropriate for modelling the FRP-reinforced masonry walls, the TRC is modelled using the heterogeneous approach, allowing for the real contribution of the filaments to be expressed through an ‘efficiency factor’. The numerical results show that this factor has a significant influence on the behaviour of the TRC and therefore, on the overall behaviour of the TRC-reinforced walls. However, the ‘efficiency factor’ of the TRC sample is significantly higher than that of the TRC in the strengthened wall. This result confirms that the choice of the heterogeneous approach to model the TRC in our case is appropriate. Moreover, it verifies that it is impossible to transpose this global factor from the material scale (uniaxial tensile stress) to the structure scale when the application target is a masonry wall (multi-axiality, and therefore, complexity of the stress). Consequently, the constitutive laws of the TRC composite obtained through only direct uniaxial tensile characterization procedures are insufficient to enable a suitable restitution of the overall behaviour of the masonry reinforced with the TRC. In addition, regardless of the nature of the reinforcement, the overall behaviours of the masonry walls reinforced with the FRPs/TRC are governed by both the axial stiffness of the reinforcement and the compressive strength of the masonry substrate