scholarly journals Efficiency of Stress-Strain Models of Confined Concrete With and Without Steel Jacketing to Reproduce Experimental Results

2016 ◽  
Vol 10 (1) ◽  
pp. 65-86 ◽  
Author(s):  
G. Campione ◽  
L. Cavaleri ◽  
M.F. Ferrotto ◽  
G. Macaluso ◽  
M. Papia
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Constitutive Law ◽  
Confined Concrete ◽  
Good Prediction ◽  
Existing Buildings ◽  
Combined System ◽  
Concrete Members ◽  
External Reinforcement ◽  
Strength And Deformation

The improvement and the capacity assessment of existing buildings has become the main topic of the last years so that different studies can be found devoted to damaged structures or structures not having a capacity compatible with the safety levels of the actual codes. Reinforced concrete framed structure buildings represent a conspicuous rate of the existing constructions so many efforts are addressed to them. Referring to this type of buildings, a good prediction of strength and deformation capacity requests models able to interpret the constitutive law of concrete confined by internal reinforcement or by eventual external reinforcement applied to increase capacity of cross-sections. Considering that one of the techniques much diffused for the improvement of the capacity of reinforced concrete members is the steel jacketing by the combined system of angles and battens, models able to predict the real contribution of this kind of intervention are desirable. In this connection the paper discusses the different confined concrete models available in the literature, analyzing all the characteristics and comparing the σ-ε constitutive laws for different type of RC cross sections. Also, an experimental campaign aimed to the validation of the above models is presented. Through the paper, the results of tests on columns reinforced with steel jacketing are described and the reliability of some costitutive laws for concrete confined by steel jacketing is examined.

A Nonlinear Analysis for the Retrofitting of a RC Existing Building by Increasing the Cross Sections of the Columns and Accounting for the Influence of the Confined Concrete

2012 ◽  
Vol 204-208 ◽  
pp. 3604-3616 ◽  
Author(s):  
Donato Cancellara ◽  
Fabio de Angelis
Keyword(s):  
Nonlinear Analysis ◽  
Cross Sections ◽  
Constitutive Law ◽  
Confined Concrete ◽  
Inelastic Behavior ◽  
Nonlinear Capacity ◽  
Existing Building ◽  
Beneficial Effects ◽  
Displacement Demand ◽  
The Cross

In the present paper a nonlinear analysis is presented for the retrofitting of a Reinforced Concrete (RC) building by increasing the cross sections of some columns and by considering the effects of the confined concrete in the nonlinear model. The adopted design methodology is based on a displacement based approach in order to ensure the compatibility condition between the displacement capacity of the structure and the displacement demand according to the seismic codes. The displacement demand is achieved through the increase of the cross section of the RC columns with a consequent increase of the lateral stiffness of the existing structure. In the case of the retrofitted columns the disposition of the reinforcement makes realistic to consider the beneficial contribution of the confinement action of the transversal reinforcement with respect to the internal core. Consequently in the nonlinear analysis the influence of the confined concrete has been considered in the definition of the proper constitutive law for the retrofitted columns. An analysis of the beneficial effects of this confinement action on the nonlinear capacity curve of the structure is described and details are illustrated on the possible ways to take into account the confinement action in the verification of the inelastic behavior of the retrofitted structure.

scholarly journals ELASTIC-PLASTIC FRACTURE ANALYSIS OF STRUCTURAL COLUMNS

2006 ◽  
Vol 12 (2) ◽  
pp. 181-186 ◽  
Author(s):  
Abdesselam Zergua ◽  
Mohamed Naimi
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Correlation Study ◽  
Flow Rule ◽  
Elastic Plastic ◽  
Concrete Members ◽  
Proposed Model ◽  
Compression Region ◽  
Frame Work ◽  
Compressive Axial Load

This research is achieved in the general frame‐work of the study of the concrete behaviour. It has for objective the development of a numerical tool able to predict the behaviour of reinforced concrete columns with circular and square cross‐sections under an increasing compressive axial load. The concrete behaviour is assumed as elastic‐plastic model with an associated flow rule in compression region and as elastic with tension stiffening behaviour in the tension region. Two yield surfaces have been taken into account according to the Drucker‐Prager and Rankine failure criterions. However, the reinforcing steel is assumed as an elastic strain hardening model. A finite element method using solid cube elements for concrete, and bar elements for the reinforcement have been used. Correlation study between numerical and experimental results is conducted with the objective to establish the validity of the proposed model and identify the significance of the transverse reinforcement volumetric ratio effect on the response of reinforced concrete members. Good agreement has been observed in comparing these results.

Deflection of GFRP-reinforced concrete beams

2021 ◽  
pp. 002199832110029
Author(s):  
Katarína Gajdošová ◽  
Róbert Sonnenschein ◽  
Stanislav Blaho
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Bending Test ◽  
Fiber Reinforced Polymers ◽  
Concrete Members ◽  
Glass Fiber Reinforced ◽  
Gfrp Reinforcement

This paper presents an investigation of the performance of concrete beams reinforced with glass fiber-reinforced polymers (GFRP) under short-term loading. A total of six specimens with rectangular cross-sections (75 mm in height and 150 mm in width) were tested under a four-point bending test to failure. Each specimen was reinforced with two GFRP bars with diameters of 8 mm. The results of this study demonstrated the behavior of GFRP-reinforced concrete members and a validation of the available calculation methods for the deflection of these members and assumed possibilities of the use of a GFRP reinforcement over the long term. The results of the study presented show a very good agreement of an experimentally measured and theoretically calculated instantaneous deflection when using the approaches in the European and American standards. In calculations of long-term deflections, the results are highly inconsistent and seem to be quite overestimated in some cases. The study shows the necessity of real-time long-term measurements to demonstrate the real deformations to be assumed during design of structures reinforced with GFRP reinforcement.

scholarly journals Experimental Behavior of Concrete Columns Confined by Transverse Reinforcement with Different Details

2020 ◽  
Vol 14 (1) ◽  
pp. 250-265 ◽  
Author(s):  
Mariateresa Guadagnuolo ◽  
Alfonso Donadio ◽  
Anna Tafuro ◽  
Giuseppe Faella
Keyword(s):  
Reinforced Concrete ◽  
Concrete Strength ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Experimental Program ◽  
Transverse Reinforcement ◽  
Eurocode 8 ◽  
Strength Increase ◽  
Existing Buildings ◽  
Concrete Confinement

Introduction: Most of the existing reinforced concrete buildings often have columns with poor transverse reinforcement details. Models for computing the confined concrete strength were developed using experimental tests performed on specimens with transverse reinforcement typical of seismic design. The paper presents the results of an experimental program performed to investigate the effect of type, amount and pitch of transverse reinforcement on the behavior of confined concrete. Aim: The paper is also aimed at evaluating whether the current code models are suitable for estimating the confined strength of concrete in existing buildings. Methods: A total of 45 reinforced concrete columns with four volume ratios of transverse reinforcement were tested under axial loads. Type and pitch of transverse reinforcement typical of existing r/c buildings not designed according to seismic standards were considered. Therefore, columns reinforced by spiral and hoops with 135° or 90° hooks at the end are investigated for comparing their behavior. The confinement of spirals and hoops to core concrete is discussed as the amount of transverse and longitudinal reinforcement varies. Small increases in strength due to the concrete confinement were measured for hoop pitch of 150 mm (ranging between 2% and 7%), but also for hoops with 90° hook and pitch of 75 mm. Greater increments were obtained by spirals and hoops with 135° hook in the case of 75 mm pitch and when rhomboidal hoops or cross-ties were arranged in addition to the perimeter hoops. A comparison with some similar experimental results is also performed, achieving quite similar results. The mean experimental stress-strain curves are also analyzed. Results: The results show how the increase in concrete strength due to the confinement is more dependent on the transverse reinforcement pitch than the type and detail of transverse reinforcement or even less diameter of longitudinal bars. Finally, the experimental strength of confined concrete is then compared with the values provided by Eurocode 8 and the new Italian Building Code, showing that the higher the volumetric percentage of transverse reinforcement, the greater the overestimation of code models. Conclusion: An overestimation of codes up to 30% is assessed, systematically lower in the case of spirals, and higher in the case of hoops with 90° hooks at the end. The results highlight the need to develop specific equations to determine the strength increase due to the concrete confinement in the case of existing buildings with poor transverse reinforcement.

scholarly journals Effect of stirrup type on shear capacity of reinforced concrete members with circular cross section

2020 ◽  
Vol 156 ◽  
pp. 05022
Author(s):  
Sri Hartati Dewi ◽  
Rendy Thamrin ◽  
Zaidir ◽  
Taufik
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Circular Cross Section ◽  
Shear Capacity ◽  
Shear Behaviour ◽  
Test Results ◽  
Flexural Mode ◽  
Concrete Members ◽  
Monotonic Loads ◽  
Test Result

An experimental study of shear behaviour of reinforced concrete members with solid circular cross sections is presented. The test variables were ratio of longitudinal reinforcement and type of stirrups. The test was carried out on nine beams. Three beams were designed without stirrups, three with closed hoop stirrups, and the other with spiral stirrups. All tested beams were subjected to two-point monotonic loads. The test results showed that all beams without stirrups failed due to the shear force. Beams with hoop or spiral stirrups failed in flexural mode. The flexural capacity of beams with hoops and spiral stirrups was similar but the beams with spiral stirrups showed a slightly higher ductility. Analytical predictions showed that the chosen numerical model predicted the test result with good accuracy.

scholarly journals The use of FRP of increased thickness for strengthening structures

2021 ◽  
Vol 263 ◽  
pp. 02033
Author(s):  
Oleg Simakov
Keyword(s):  
Reinforced Concrete ◽  
Carbon Fiber ◽  
Cross Sections ◽  
Experimental Studies ◽  
Calculation Methods ◽  
Reinforcement System ◽  
External Reinforcement ◽  
Concrete Elements

The external reinforcement system based on carbon fiber has been used for decades to strengthen reinforced concrete elements. At the same time, it is impossible not to recognize that the existing calculation methods are largely based on empirical dependencies obtained from experimental studies. One of these issues is related to the application of the methodology for materials of heterogeneous origin-tapes and laminates. In general, the possibility of applying the calculation methods accepted in the norms for laminates of generally accepted thicknesses up to 1.6 mm is determined. The question related to the possibility of using laminates of greater thickness is not sufficiently studied. This article deals with the calculation of the reinforcement of the normal cross sections of the bent reinforced concrete elements with the reinforcement of laminates with a thickness of 5 mm.

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