Search results for "confined concrete"
showing 10 items of 12 documents
Experimental investigation on the compressive behavior of short-term preloaded carbon fiber reinforced polymer-confined concrete columns
2017
Strengthening of concrete columns with fiber reinforced polymer sheets provides a good improvement to the existing structural members in terms of load and strain capacity due to the properties of the composite jacket. A proper knowledge of the load–strain response of the composite members is necessary to design retrofitting intervention of existing structures; however, so far the available design methods do not allow to take into account the effect of the possible presence of service loads on the compressive behavior of the reinforced columns. An experimental investigation on the compressive behavior of preloaded circular concrete columns reinforced with carbon fiber reinforced polymer was …
Compressive response of substandard steel-jacketed RC columns strengthened under sustained service loads: From the local to the global behavior
2018
Abstract This paper presents an experimental investigation on substandard partially steel jacketed RC columns strengthened under sustained loads and loaded until failure. The aim of the study is to compare the compressive response of preloaded columns with respect to the tests without preload to obtain a more realistic prediction of load-carrying capacity of structural columns after retrofitting under serviceability loads. The influence of the preload level, the delayed contribution of the confining device during the loading process and the time dependent effects are highlighted for the tested specimens. Based on the experimental observations, an analysis-oriented model is proposed for the …
Stress-Strain Law for Confined Concrete with Hardening or Softening Behavior
2013
This paper provides a new general stress-strain law for concrete confined by steel, fiber reinforced polymer (FRP), or fiber reinforced cementitious matrix (FRCM), obtained by a suitable modification of the well-known Sargin’s curve for steel confined concrete. The proposed law is able to reproduce stress-strain curve of any shape, having both hardening or softening behavior, by using a single closed-form simple algebraic expression with constant coefficients. The coefficients are defined on the basis of the stress and the tangent modulus of the confined concrete in three characteristic points of the curve, thus being related to physical meaningful parameters. It will be shown that if the v…
Behavior of fiber-reinforced concrete columns under axially and eccentrically compressive loads
2010
An experimental investigation into the behavior of 16 short, confined, reinforced concrete columns with and without steel fibers was carried out. The columns with square sections had a concrete core 165 x 165 mm (6.49 x 6.49 in.) at the midsection and were hunched at the ends to apply eccentric loading and prevent boundary effects. The specimens were tested to failure at different strain rates under two loading schemes: concentric compression and eccentric compression with a constant eccentricity. The axial load and axial strains were obtained to evaluate the effects of the presence of steel fibers, the thickness of the cover concrete, and the eccentricity of the applied axial load. The com…
A strategy for the finite element modeling of FRP-confined concrete columns subjected to preload
2018
Abstract Compressive behavior of columns strengthened by means of an outer elastic confinement provided e.g. by fiber-reinforced polymer (FRP) jackets has become a main topic in the field of structural retrofitting. In details, the problem of the response assessment of strengthened columns is still under study. Many analytical formulations have been proposed to describe the compressive behavior of confined concrete under both monotonic and cyclic loads. However, the effect of a stress/strain level in the columns already present prior to apply the confinement has been generally neglected until now, also because of the lack of well defined strategies of modeling. In this frame, here, (1) a FE…
Analysis-oriented stress–strain model of CRFP-confined circular concrete columns with applied preload
2018
The compressive behavior of FRP-confined concrete is a current issue in the field of structural retrofitting. The available models well predict the stress–strain behavior under monotonic and cyclic loads. However, in the practical applications, columns that need an increasing of bearing capacity are often strengthened under serviceability load conditions, with a stress and strain state that could change the response of the reinforced systems with respect to the case of the unloaded state. In this paper, the compressive behavior of circular FRP-confined concrete columns with preload is analyzed with the introduction of a modified analysis-oriented model. Differently from the classical formul…
Stress-strain models for normal and high strength confined concrete: Test and comparison of literature models reliability in reproducing experimental…
2017
SUMMARY: The adoption of proper constitutive laws for confined concrete is basic for seismic assessment of new and existing reinforced concrete civil structures. The deformation capacity of reinforced concrete (RC) columns subjected to axially centred and eccentric loads depends on the effectiveness confinement action. A proper assignment of the stressstrainlaws for concrete allows obtaining an adequate definition of the ductility of the crosssections and correctly identifying mechanical nonlinearities in computational models.Several studies concerning the behaviour of confined concrete have been carried out, highlighting the role of different geometrical and mechanical parameters to the ov…
Strength and ductility of confined concrete columns under axial load and biaxial bending
2012
The behaviour of prismatic reinforced concrete columns under increasing eccentric compression load was experimentally investigated and analytically modelled. Columns with distributed longitudinal reinforcement and closely spaced transverse reinforcement were tested up to failure, considering different values and directions of eccentricity. Preliminary tests were carried out under concentric compression in order to validate the choice of the stress-strain laws adopted for the confined concrete and the longitudinal steel bars in compression. In the paper, closed form expressions able to approximate the experimental results in the case of uniaxial bending are presented. Finally, a fibre numeri…
COMPRESSIVE BEHAVIOR OF CONCRETE COLUMNS AXIALLYLOADED BEFORE CFRP-WRAPPING. REMARKS BY EXPERIMENTALNUMERICAL INVESTIGATION
2018
Strengthening of existing concrete columns with Fiber Reinforced Polymers (FRP) results generally in a satisfactory structural member improvement in terms of load and strain capacity. A reliable prediction of the capacity obtained by these reinforcement strategies requests a proper knowledge of the load-strain response of the confined concrete elements. However, so far, the available design methods and technical codes do not consider the effect of the possible presence of service loads at the moment of application of the reinforcement, and therefore, the compressive behavior of the concrete confined under preload is still unclear. In this paper, the effect of sustained loads on the compress…
Assessment of the load carrying capacity of reinforced concrete columns strengthened by steel cages Specificità nella valutazione della capacità port…
2018
In the present paper, a selected review of the most relevant analytical models provided for the evaluation of the con-finement properties of Steel Jacketed RC columns is discussed. The reliability of the models is tested by comparing the analytical predictions of the load capacity with experimental results available in the literature depending on the type of mechanical end-connections. Moreover, new considerations regarding the application of the steel jacketing on columns while loaded are faced by experimental investigation