Fiber-reinforced polymer (FRP) jacketing/wrapping has become an attractive strengthening technique for concrete columns. Wrapping an existing concrete column with continuous FRP jackets with the fiber in the jacket being oriented in the hoop direction is referred to as FRP full wrapping strengthening technique. In practice, however, strengthening concrete columns with vertically discontinuous FRP strips is also favored and this technique is referred to as FRP partial wrapping strengthening technique. Existing research has demonstrated that FRP partial wrapping strengthening technique is a promising and economical alternative to the FRP full wrapping strengthening technique. Although extensive experimental investigations have hitherto been conducted on partially FRP-confined concrete columns, the confinement mechanics of confined concrete in partially FRP-confined circular columns remains unclear. In this paper, an experimental program consisting of fifteen column specimens was conducted and the test results were presented. A reliable three-dimensional (3D) finite element (FE) approach for modeling of partially FRP-confined circular columns was established. In the proposed FE approach, an accurate plastic-damage model for concrete under multiaxial compression is employed. The accuracy of the proposed FE approach was verified by comparisons between the numerical results and the test results. Numerical results from the verified FE approach were then presented to gain an improved understanding of the behavior of confined concrete in partially FRP-confined concrete columns.

Behavior and Three-Dimensional Finite Element Modeling of Circular Concrete Columns Partially Wrapped with FRP Strips.

Experimental study on mechanical properties of fiber reinforced concrete: Effect of cellulose fiber, polyvinyl alcohol fiber and polyolefin fiber

Performance of axially loaded square RC columns with single/double confinement layer(s) and strengthened with C-FRP wrapping under close-in blast

Recently, CaCO3 whiskers (CW) are used as new-type micro-fibers for achieving reinforcing and toughening of cement-based materials due to their cracking resistance ability at micro-scale. In this paper, the combination of steel-polyvinyl alcohol (PVA) fibers are added into CW reinforced cement mortar (CWRCM) to further enhance the reinforcing and toughening effects at meso- and macro-scales. In addition, four analytical models of fiber reinforced cementitious composites (FRCC) were developed to describe the compressive stress-strain response. The cylindrical specimens are tested under uniaxial compressive loading to investigate the effect of different volume fractions of steel-PVA hybrid fibers in CWRCM. The test results indicated that the incorporation of steel-PVA hybrid fibers could significantly improve the stress-strain behavior of CWRCM, as compared to that of the CWRCM. The highest ultimate compressive strength (fc), elasticity modulus (Ec) and total compressive strain energy (ED) were observed in SF1.8PF0.2, but SF1.5PF0.5 showed a greater peak strain (eu). Moreover, the prediction models of compressive parameters were proposed by simultaneously considering the reinforcing index (RI) of steel and PVA fibers. The obtained parameters in four models were evaluated according to their essential requirements. It was found that only Model III met its essential requirements and parameters were closely associated with RI values of steel and PVA fibers.

Effect of steel-PVA hybrid fibers on compressive behavior of CaCO3 whiskers reinforced cement mortar

Seismic performance of rectangular ultra-high performance concrete filled steel tube (UHPCFST) columns

Stress strain behavior of hybrid steel-PVA fiber reinforced cementitious composites under uniaxial compression

Reinforced concrete column confined using two layers of stirrups is a new kind of column form recently proposed by the authors. The concrete of the column is under three different levels of confine...

Axial compressive behavior of square reinforced concrete columns confined using two layers of stirrups

RC columns with two layers of hoops is a new kind of column recently proposed. The concrete of the column is under three different degrees of confinement, namely unconfined concrete cover, singly-confined concrete between the two layers of hoops and doubly-confined concrete inside the inner layer of hoops. The strength and ductility of the column can be greatly enhanced due to better confinement. In this study, the behaviour of circular RC columns confined using two layers of spirals were investigated through axial compression test on scaled-down column models. The responses and failure modes of the columns were examined. The average stress-strain curves of the singly-confined and doubly-confined concrete were derived, taking advantage of the concept of average effective confinement pressure. The performance of a stress-strain model previously proposed for square RC columns with two layers of hoops was also investigated.

Behavior of circular RC columns with two layers of spirals

During the last decades, great progress has been made in the research and application of high strength concrete (HSC). Due to its high strength, low dilation and brittle nature, substantial more transverse reinforcement is needed for HSC columns to obtain ductile behavior, especially for columns with large axial load ratio and/or located in seismic zones. In this paper, a novel HSC concrete column with double high-strength stirrups is proposed, which features two concentric transverse stirrups. The concrete in the cross section are divided into three parts under different confinement level, namely unconfined concrete, singly and doubly confined concrete. This structural form possesses many advantages over traditional HSC with single stirrup and steel-concrete composite columns, including enhanced strength and ductility, easy to construction and easy to connection with RC beams. Three demonstrative circular HSC columns with double spirals were prepared and tested under concentric axial compression. A curre...

Behavior of a Novel Circular HSC Column with Double High Strength Spirals

Special-shaped columns are extensively used in residential and official buildings as they increase the efficiency of indoor space. However, many studies on normal special-shaped concrete columns ha...

Fang Yang

Papers

Stress strain behavior of hybrid steel-PVA fiber reinforced cementitious composites under uniaxial compression

Axial compressive behavior of square reinforced concrete columns confined using two layers of stirrups

Behavior of circular RC columns with two layers of spirals

Behavior of a Novel Circular HSC Column with Double High Strength Spirals

Axial compressive behaviour of special-shaped steel-fibre-reinforced concrete columns