scholarly journals Near-field explosion effects on reinforced concrete columns: an experimental investigation

2018 ◽  
Vol 45 (4) ◽  
pp. 289-303 ◽  
Author(s):  
Abass Braimah ◽  
Farouk Siba
Keyword(s):  
Reinforced Concrete ◽  
Experimental Testing ◽  
Near Field ◽  
Axial Loading ◽  
Concrete Columns ◽  
Load Level ◽  
Experimental Program ◽  
Rc Columns ◽  
Reinforced Concrete Columns ◽  
Scaled Distance

Explosion effects on structures have been an area of active research over the past decades. This is due to the increasing number of terrorists’ action against infrastructures. Although significant amount of work is continuing on the effects of explosions on infrastructures, experimental work involving live explosion testing is limited. Moreover, experimental testing of reinforced concrete (RC) columns subjected to near-field explosions is scant. This paper presents results of an experimental program designed to investigate the effects of near-field explosions on RC columns with different tie spacing and at different scaled distances. The results show that the response of columns is strongly dependent on scaled distance. As the scaled distance increased the severity of damage reduced; seismic columns showed better response. The effect of axial loading was also observed to increase the level of damage on reinforced concrete columns at the axial load level and blast loads considered in the test program.

scholarly journals Behavior of Square RC Short Columns with New Arrangement of Ties Subjected to Axial Load: Experimental and Numerical Studies

2022 ◽  
Author(s):  
Hazem Elbakry ◽  
Tarek Ebeido ◽  
El-Tony M. El-Tony ◽  
Momen Ali
Keyword(s):  
Reinforced Concrete ◽  
Axial Load ◽  
Concrete Columns ◽  
Experimental Program ◽  
Transverse Reinforcement ◽  
Reinforcing Bars ◽  
Rc Columns ◽  
Reinforced Concrete Columns ◽  
Short Columns ◽  
Numerical Studies

Reinforced concrete columns consume large quantities of ties, especially inner cross-ties in columns with large dimensions. In some cases, nesting of the pillars occurs as a result of the presence of cross-ties. The main objective of this paper is to develop new methods for transverse reinforcement in RC columns and investigate their effect on the behavior of the columns. The proposed V-ties as transverse reinforcement replacing the ordinary and cross-ties details are economically feasible. They facilitate shorter construction periods and decrease materials and labor costs. For this purpose, experimental and numerical studies are carried out. In the experimental program, nine reinforced concrete columns with identical concrete dimensions and longitudinal reinforcing bars were prepared and tested under concentric axial load with different tie configurations. The main parameters were the tie configurations and the length (lv) of V-tie legs. As part of the numerical study, the finite element model using the ABAQUS software program obtained good agreement with the experimental results of specimens. A numerical parametric study was carried out to study the influence of concrete compressive strength and longitudinal reinforcement ratio on the behavior of RC columns with the considered tie configurations. Based on the experimental and numerical results, it was found that using V-tie techniques instead of traditional ties could increase the axial load capacity of columns, restrain early local buckling of the longitudinal reinforcing bars and improve the concrete core confinement of reinforced concrete columns.

Numerical Simulation of Air Shock Wave Propagation Effects in Reinforced Concrete Columns

2020 ◽  
Vol 12 (1) ◽  
pp. 12-22
Author(s):  
Ebrahim Akhlaghi
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Reinforced Concrete ◽  
Low Cost ◽  
Near Field ◽  
Research Work ◽  
Concrete Columns ◽  
Rc Columns ◽  
Reinforced Concrete Columns ◽  
Finite Element Package

Reinforced concrete has been shown to be a desirable material of choice in blast resistant structures due to its availability, relatively low cost, and its inherent ability to absorb energy produced by explosions. Most research work investigating the behaviour of reinforced concrete columns to blast loading have concentrated on their response to planar loading from far-field explosions. Limited amount of work is available on the effects of near-field explosion on the behaviour of reinforced concrete columns. This study is aimed to investigate effects of explosive loads on RC column by using ALE method. Commercial finite element package, LS-DYNA is used to simulate the behavior of blast wave on RC columns. Numerical simulation is validated against experimental work done in literature. The experience gained from this research provides valuable information for the development of the finite element modeling of real blast load effects on RC columns.

scholarly journals Experimental study of the strengthening effect of reinforced concrete columns jacketed under service load level

2018 ◽  
Vol 183 ◽  
pp. 02008 ◽  
Author(s):  
Pavlo Krainskyi ◽  
Yaroslav Blikharskyy ◽  
Roman Khmil ◽  
Zinoviy Blikharskyy
Keyword(s):  
Experimental Study ◽  
Reinforced Concrete ◽  
Concrete Columns ◽  
Load Level ◽  
Strengthening Effect ◽  
Engineering Structures ◽  
Reinforced Concrete Columns ◽  
Technical Modification ◽  
Service Load

The need of structural retrofitting and strengthening of different buildings, engineering structures or their elements is always present. Among the main reasons are demages and material deterioration due to aging, improper maintenance or physical damages; planed repairs; reconstruction or extension of the building; technical modification or complete change of operations inside the building or the structure, etc. In some cases operation of the building during retrofitting or strengthening of its structures has to be partially or fully stopped. In other cases the strengthening process takes place while the building is still operational which means that structures are strengthened under service loads. The main goal of this research is to determine the strengthening effect of reinforced concrete jacketing applied to columns under service load level. For that the experimental study of six reinforced concrete columns were carried out: four reference columns, both strengthened by jacketing and unstrengthened and two strengthened under service load. The main results of the research are presented.

scholarly journals Behavior of Columns Confined With FRP Fabrics under Repeated Lateral Loads

2019 ◽  
pp. 1-19
Author(s):  
Hesham A. Haggag ◽  
Nagy F. Hanna ◽  
Ghada G. Ahmed
Keyword(s):  
Reinforced Concrete ◽  
Carbon Fiber ◽  
Axial Load ◽  
Axial Loading ◽  
Concrete Columns ◽  
Fiber Reinforced Polymers ◽  
Lateral Loads ◽  
Reinforced Concrete Columns ◽  
Reinforced Polymers ◽  
Axial Capacity

The axial strength of reinforced concrete columns is enhanced by wrapping them with Fiber Reinforced Polymers, FRP, fabrics.  The efficiency of such enhancement is investigated for columns when they are subjected to repeated lateral loads accompanied with their axial loading.  The current research presents that investigation for Glass and Carbon Fiber Reinforced Polymers (GFRP and CFRP) strengthening as well.  The reduction of axial loading capacity due to repeated loads is evaluated. The number of applied FRP plies with different types (GFRP or CFRP) are considered as parameters in our study. The study is evaluated experimentally and numerically.  The numerical investigation is done using ANSYS software. The experimental testing are done on five half scale reinforced concrete columns.  The loads are applied into three stages. Axial load are applied on specimen in stage 1 with a value of 30% of the ultimate column capacity. In stage 2, the lateral loads are applied in repeated manner in the existence of the vertical loads.  In the last stage the axial load is continued till the failure of the columns. The final axial capacities after applying the lateral action, mode of failure, crack patterns and lateral displacements are recorded.   Analytical comparisons for the analyzed specimens with the experimental findings are done.  It is found that the repeated lateral loads decrease the axial capacity of the columns with a ratio of about (38%-50%).  The carbon fiber achieved less reduction in the column axial capacity than the glass fiber.  The column confinement increases the ductility of the columns under the lateral loads.

SEISMIC PERFORMANCE OF GFRP-RC RECTANGULAR COLUMNS: NUMERICAL STUDY

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Ehab El-Salakawy ◽  
Fangxin Ye ◽  
Yasser Mostafa Selmy
Keyword(s):  
Reinforced Concrete ◽  
Cyclic Loading ◽  
Axial Load ◽  
Numerical Study ◽  
Concrete Strength ◽  
Weight Ratio ◽  
Concrete Columns ◽  
Load Level ◽  
Reinforced Concrete Columns ◽  
Rectangular Columns

Composite materials like glass fiber-reinforced polymer (GFRP) is becoming widely acceptable to be used as a reinforcing material due to its high ultimate tensile strength-to-weight ratio and excellent resistance to corrosion. However, the seismic behavior of GFRP-reinforced concrete columns has not been fully investigated yet. This paper presents the results of a numerical analysis of full-size GFRP-RC rectangular columns under cyclic loading. The simulated column depicts the lower part of a building column between the foundation and the point of contra-flexure at the mid-height of the column. GFRP reinforcement properties and concrete modeling based on fracture energy have been incorporated in the numerical model. Experimental validation has been used to examine the accuracy of the constructed finite element models (FEMs) using a commercially available software. The validated FEM was used to perform a parametric study, considering several concrete strength values and axial load levels, to study its influence on the performance of the GFRP-reinforced concrete columns under cyclic loading. It was concluded that the hysteretic dissipation capacity deteriorates under high axial load level due to severe softening of the concrete. The FE results showed a substantial improvement of the lateral load-carrying capacities by increasing concrete compressive strength.

scholarly journals Gravity Load Collapse Behavior of Nonengineered Reinforced Concrete Columns

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Chichaya Boonmee ◽  
Kittipoom Rodsin ◽  
Krissachai Sriboonma
Keyword(s):  
Reinforced Concrete ◽  
Cyclic Loading ◽  
Axial Load ◽  
Concrete Columns ◽  
Poor Quality ◽  
Load Level ◽  
Longitudinal Reinforcement ◽  
Reinforced Concrete Columns ◽  
Gravity Load ◽  
Collapse Behavior

This paper aims at investigating gravity load collapse behavior of extremely poor quality reinforced concrete columns under cyclic loading. Such columns were usually constructed by local people and may not be designed to meet any of the standards. It was found that their concrete strength may be as low as 5 MPa and the amount of longitudinal reinforcement may be lower than 1%. This type of column is deliberately defined as “nonengineered reinforced concrete column,” or NRCC. During earthquake, the gravity load collapse of the NRCC columns caused a large number of death tolls around the world. In this study, four columns as representative of existing NRCC were tested under cyclic loading. The compressive strength of concrete in order of 5 MPa was used to be representative of columns with poor quality concrete. Two axial load levels of 6 and 18 tons were used to study the influence of axial load level on maximum drift at gravity load collapse. To investigate the effect of bar types on drift capacity, 9 mm round bars were used in two specimens and 12 mm deformed bars were used for the rest of the specimens. The maximum drift before gravity load collapse was very dependent on the axial load level. The maximum drift of the specimens subjected to high axial load (18 tons) was extremely low at approximately 1.75% drifts. The use of deformed bars (associated with larger amount of longitudinal reinforcement) caused the damage to severely dissipate all over the height of the columns. Such damage caused columns to collapse at a lower drift compared to those using round bars. Finally, the plastic hinge model was used to predict the maximum drift of the low strength columns. It was found that the model overly underestimates the drift at gravity load collapse.

scholarly journals Investigation of Parameters Affecting the Equivalent Yield Curvature of Reinforced Concrete Columns

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1594
Author(s):  
Umut Hasgul
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Axial Load ◽  
Concrete Columns ◽  
Load Level ◽  
Combined Effects ◽  
Reinforced Concrete Columns ◽  
Independent Effects ◽  
Equivalent Yield ◽  
Section Dimension

In this study, the response quantities affecting the equivalent yield curvature, which is important in the deformation-based seismic design and assessment of structural systems, are investigated for reinforced concrete columns with a square cross-section. In this context, the equivalent yield curvatures were determined by conducting moment–curvature analyses on various column models, in which the axial load level, cross-section dimension, longitudinal reinforcement ratio, and concrete compression strength were changed parametrically, and the independent and/or combined effects of the relevant parameters were discussed. Depending on the axial load levels of P/Agfc′ < 0.3, P/Agfc′ = 0.3, and P/Agfc′ > 0.3 for the considered columns, the yielding of reinforcement, yielding of reinforcement and/or concrete crushing, and concrete crushing governed the yield conditions, respectively. It can be noted that the cross-section dimension and axial load level became the primary parameters. Even though the independent effects with regard to particular parameters remained at minimal levels, the combined effects of them with the axial load became important in terms of the equivalent yield curvature.

Optimum Design of Reinforced Concrete Columns

2020 ◽  
pp. 92-115
Keyword(s):  
Reinforced Concrete ◽  
Optimum Design ◽  
Axial Loading ◽  
Concrete Columns ◽  
Computer Code ◽  
Shear Forces ◽  
Structural Concrete ◽  
Rc Columns ◽  
Compressive Stresses ◽  
Loaded Column

In the design of reinforced concrete (RC) columns, ductility is provided by allowing yielding of steel in the part of section under tensile stresses. This situation cannot be provided for RC columns since sections of columns are generally under compressive stresses resulting from axial loading including weight of all upper stories, flexural moments, and shear forces. To practically provide ductility, axial force is limited, and stirrups are densely designed. These rules are given in design regulations and must be checked during optimization. In this chapter, an optimum design methodology for biaxial loaded column is presented. Uniaxial loaded column methodology is given with the computer code. Finally, the slenderness effects are presented via ACI 318: Building code requirements for structural concrete and optimum results are given for several numerical cases using various metaheuristic algorithms.

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