دانلود رایگان مقاله انگلیسی رفتار ستون های فولادی FRP پر شده از فولاد فیبر تقویت شده: یک مدل عنصر محدود - الزویر 2018

ABSTRACT

This paper presents the results of an experimental study together with the first finite element (FE) model for the compressive behavior of fiber-reinforced polymer (FRP)-confined steel fiber-reinforced concrete (SFRC). 73 existing experimental test results of FRP-confined and actively confined SFRC specimens tested under axial compression were initially assembled. Additional axial compression tests were conducted on 16 actively confined SFRC specimens to address the gaps in the existing test database to compile a reliable database for the FE modeling of FRP-confined SFRCs. The analysis of experimental test results revealed that the compressive behavior of FRP-confined SFRCs is influenced by the steel fiber volume fraction and aspect ratio. New expressions were developed for the hoop rupture strain of the FRP jacket, axial strain-lateral strain relationship of FRPconfined and actively confined SFRC, and relationship between the confining pressure and the compressive strength of actively confined SFRC by considering the influences of the volume fraction and aspect ratio of internal steel fibers. A recently developed concrete damage-plasticity model, which was shown to be the most accurate currently available model for confined plain concrete, was adopted for the prediction of the compressive behavior of FRP-confined SFRC. The failure surface and flow rule of the model were modified based on the results from actively and FRP-confined SFRC. The results show that model predictions of the axial stress-axial strain, lateral strain-axial strain, axial stress-volumetric strain, plastic volumetric strain-axial plastic strain, and plastic dilation angle-axial plastic strain relationships are in good agreement with the experimental results of FRP-confined SFRC. The new model provides improved accuracy over the best performing existing models of FRP-confined plain concrete in predicting the behavior of FRP-confined SFRC.

6. Summary and conclusions

This paper has presented the first FE model to predict the compressive behavior of FRP-confined SFRCs in circular sections. A test database containing 73 datasets from axial compression tests of FRPconfined and actively confined SFRC was assembled based on the results available in the literature. Additional axial compression tests were conducted on 16 actively confined SFRC specimens to address the gaps in the existing test database. The analysis of the experimental test results indicated that the compressive behavior of FRP-confined SFRC is influenced by the steel fiber volume fraction and aspect ratio. Therefore, the model by Lim and Ozbakkaloglu, which was proposed for FRP-confined plain concretes, was extended to predict the compressive behavior of FRP-confined SFRCs by considering the influences of steel fiber volume fraction and aspect ratio. In the proposed model, the hoop rupture strain of the FRP jacket, dilation relationship between axial strain and lateral strain of actively confined and FRP-confined SFRC, and relationship between the confining pressure and the compressive strength of actively confined SFRC were established by modifying the previously proposed models for confined plain concrete. The improved failure surface and flow rule of the concrete damage-plasticity model were achieved by incorporating the effects of steel fiber volume fraction and aspect ratio into the accurate failure surface and flow rule models given for plain concrete in Refs. [31,34]. The comparison of model predictions with the experimental results shows that the new models closely predict the axial stress-axial strain, lateral strain-axial strain, axial stress-volumetric strain, plastic volumetric strain-axial plastic strain, and plastic dilation angle-axial plastic strain relationships of FRP-confined SFRC. The analysis results also indicate that the new FE model provides improved accuracy in predicting the compressive behavior of FRP-confined SFRCs compared to the predictions of the model given by Lim and Ozbakkaloglu for conventional concrete. The availability of such an accurate model is of vital importance for practical applications of FRP-confined SFRC columns.

Because of the influence of the steel fiber parameters on the mechanical behavior of FRP-confined SFRC, the application of the models of FRP-confined plain concrete to predict the behavior of FRP-confined SFRC is not recommended. Therefore, additional targeted studies are recommended on the FRP-confined and actively confined SFRC columns to expand the existing test database to enable the development of additional models for FRP-confined SFRCs with a broader range of applicability, such as those for square and rectangular columns.