Parametric studies on the ductility of axial loaded square reinforced concrete column made of normal-strength concrete (NSC) and high-strength steel confining rebar (HSSCR) with various ties configuration (original) (raw)
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In the limit state of collapse design approach for reinforced concrete (RC) columns, the conceptual design criteria is formulated based on the balanced limiting strains i.e. simultaneous crushing of concrete and yielding of steel occurs in extreme concrete fiber and steel, which is designated as 0.0035 and 0.002+(f y +1.15/E s) respectively. But the tensile strain in extreme layer of steel is permitted to reach any value more than the prescribed value under crucial scenarios of high seismic influence. Therefore the premature yielding of extreme steel layer over the crushing of concrete, i.e. the under reinforced design of RC columns is not authentified by the existing design approach. Adding to this whenever RC columns are subjected to seismic forces, reversal of stresses occurs i.e. the predominant compressive forces in column changes its behavior to tensile forces. Hence it is mandatory to determine the tensile capacity of column and its corresponding ductile behavior and the strain energy stored in it. The tensile capacity of the column and the range of tension failure under combined compressive axial load and bending is thus identified by determining the Balanced Axial load factor λ ,in which the computation involves the limiting strain states in concrete and steel. A numerical study is made over the Balanced Axial Load factor λ by, varying parameters such as Column section, Percentage of reinforcement excessive limiting strains in steel and with the orientation of the column. Hence a more accepted under reinforced design approach i.e. ductile design is proposed for columns subjected to seismic forces. Analysis of Tensile Capacity of Reinforced Concrete Columns and its Ductility Performance towards Seismic Behavior
Effect of Lateral Reinforcement on Strength and Ductility of Reinforced Concrete Columns
International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2023
: Concrete confined by stirrups has a greater ductility than unconfined concrete which is widely used in reinforced concrete (RC) structures and its behavior is a classic topic ofdiscussion. Non-linear behavior of reinforced concrete is complex due to involvement of various heterogenic material properties and cracking behavior of concrete. It is very important to understand the response and failures of columns subjected to lateral loadsin order to save lives and reduce the damage to the building components. ANSYS is widely used finite element analysis (FEA) software which has the tools to analyze structural elements and their non-linear behavior based on the finite element procedure The failure prediction of reinforced concrete elements is usually carried out using experimental testing, and the observations are recorded only at critical locations due to restriction at the cost of testing equipment and accessories. To avoid the destructive testing, cost-cutting of materials and labor, the behavior prediction of reinforcedconcrete elements is typically carried out using numerical methods like Finite Element Method which responds well to non-linear analysis as each component possesses different stress-strain behavior
Measurement, 2019
This paper presents an investigation based on tests results of high-strength concrete (HSC) columns externally confined with post-tensioned steel straps, subjected to monotonic axial load. The parameters of the tests were eccentricity ratio (e i /e s = 0, 1), load eccentricity (e = 25 mm, 50 mm), slenderness ratio (k = 16, 24, 32) and confining volumetric ratio (q v = 0.09, 0.25, 0.50). This paper is served as a continuation of a previous paper conducted by Ma et al. (2014b), which focuses on the ductility and stiffness analysis. The results show that the confinement of post-tensioned steel straps is beneficial to HSC columns but confining efficiency reduced drastically with the increase of column slenderness. Two ductility models were proposed to predict the ultimate ductility for slender confined HSC columns with the consideration of important parameters. The proposed models are simple and easy to apply but adequately accurate estimation is guaranteed. It is believed that the proposed ductility models can aid structural engineers in the designing a ductile structure especially in the seismic region. The confinement has no significant effect on the flexural stiffness of HSC columns.
Seismic Behavior of Under Confined Square Reinforced Concrete Columns
Structures, 2018
The role of confining reinforcement in dissipating a large amount of energy in reinforced concrete (RC) elements at the time of seismic events has been well demonstrated in previous studies. In India, this practice of providing special confinement in RC elements began to be followed after the ductile detailing code came into being in the year 1993. Hence, the structures built before 1990s in seismicaly active areas had no ductile detailing, as the design recommendation of pre 90s era do not consider adequate confinement requirements. The Present experimental study is a part of an ongoing project of upgrading these old reinforced concrete structures, which had no special confinement and are located in seismically active regions. Three full-scale columns with different amount of transverse reinforcement (volumetric ratio of 1.31, 0.33, and 0.22) were tested in a specially made testing setup. One specimen was designed as per the current Indian guidelines for ductile detailing (IS 13920:2016), while the other two specimens were designed as per the guidelines which existed before the Code on ductile detailing was implemented. The response of the columns under quasi-static reverse lateral cyclic loading (at constant axial load) was recorded in terms of lateral load v/s deflection, moment v/s curvature, energy dissipation, stiffness reduction and different ductility parameters. As expected, the results of the study show inferior seismic performance of under-confined columns as indicated by the key strength and ductility parameters. The results have though quantified the strength and ductility deficit of these under confined RC columns, which shall be of great help in designing suitable retrofit for the existing structures constructed with no ductile detailing features.
Shear Strength Model for Reinforced Concrete Columns with Low Transverse Reinforcement Ratios
Advances in Structural Engineering, 2014
This paper introduces an equation developed based on the strut-and-tie analogy to predict the shear strength of reinforced concrete columns with low transverse reinforcement ratios. The validity and applicability of the proposed equation are evaluated by comparison with available experimental data. The proposed equation includes the contributions from concrete and transverse reinforcement through the truss action, and axial load through the strut action. A reinforced concrete column with a low transverse reinforcement ratio, commonly found in existing structures in Singapore and other parts of the world was tested to validate the assumptions made during the development of the proposed equation. The column specimen was tested to failure under the combination of a constant axial load of 0.30 f'cAgand quasi-static cyclic loadings to simulate earthquake actions. The analytical results revealed that the proposed equation is capable of predicting the shear strength of reinforced concr...
Journal of Physics: Conference Series, 2018
Column is a pressed element that enabels to withstand the loads for its structure. The analysis was conducted at the round reinforced column and tied rather than the spherical round reinforced column. The proportion of this column structure was designed in accordance with the fuction of a building and the zone area of the same earthquake, as well as its loading and dimension of the same space.Furthermore, the researcheralso did comparing the ductility's score of reinforced concrete column of a building from wich a model of history building with its width of 20 m, length 30 m and height 40 m had been designed. Based on its proportion of inner force and column ductility and calculation result of ties spiral round space column it was obtained that the inner force of maximum axial (P) = 4356,6 kN, Shear2-2 (V2) = 132.3 kN, Moments 3-3 (M3) = 142.9 kNm and ductility = 4.59. Meanwhile, the ties rounded-space column was obtained that its axial maximum force was (P)=4169.8 kN, Shear2-2 (V2) = 131.3 kN, Moments 3-3 (M3) = 141.4 kNm and ductility 4, 11. Based on the analysis above, it was concluded which had ductility score greather than that of rounded-ties space with the same space (Ag).
Asian Journal of Civil Engineering
Columns with low transverse reinforcement, i.e., poor detail, small size, wide spacing are used commonly in the old buildings. It is often failed in shear with brittle mode that can lead to suddenly collapse entire building. Therefore, the exact determination of shear strength is significant for estimating the response of reinforced concrete (RC) columns under earthquake events. Based on four large full scale RC columns (8008003200)mm with low transverse reinforcement, the paper pointed out the factors that effect on shear strength, and proposed the revised shear strength equation, also the interaction diagram between bending moment (M)-shear force (V)-axial compression force (N) to design or check the shear ability of RC columns. Yet, the simple process to build the backbone curves and hysteretic loops was proposed and compared with tested results and test database.
Behavior of Reinforced Concrete Columns Subjected to Axial Load and Cyclic Lateral Load
2017
Columns subjected to pure axial load rarely exist in practice. Reinforced concrete columns are usually subjected to combination of axial and lateral actions and deformations, caused by spatially‐complex loading patterns as during earthquakes causes lateral deflection that in turn affects the horizontal stiffness. In this study, a numerical model was developed in threedimensional nonlinear finite element and then validated against experimental results reported in the literatures,to investigate the behavior of conventionally RC columns subjected to axial load and . lateral reversal cyclic loading. To achieve this goal, numerical analysis was conducted by using finite element program ABAQUS/Explicit. The variables considered in this study were axial load index, concrete compressive strength, column aspect ratio, longitudinal and transverse reinforcement ratios. According to numerical case studies, the results revealed that axial load index and longitudinal reinforcement ratio have t...
In zones of high seismicity, properly detailed reinforced concrete columns contain adequate transverse reinforcement to resist the large shear demand associated with the development of the column's full flexural strength. Unfortunately, this capacity design methodology was not fully adopted into building codes until the early 1970's; thus rendering older reinforced concrete building columns vulnerable to premature shear failure (shear-critical) and associated loss of lateral load capacity. The fact that shear-critical columns have the potential to sustain a shear failure prior to axial failure is well established and implemented in evaluation standards such as FEMA 356 and ASCE 41. However, if the concrete core is not adequately confined, shear and axial failure are likely to occur simultaneously. This paper discusses computer simulations of three shear-critical reinforced concrete columns subjected to lateral load reversals of increasing magnitude with the intent to investigate the principal mode of failure as well as any secondary modes of failure. Results from three-dimensional nonlinear finite element models developed using the computer program ABAQUS are compared with data from three similar column assemblies tested to study the collapse risk of older reinforced concrete structures. Two of the column assemblies exhibited simultaneous shear and axial failure. Simulating the response of this type of column is a very challenging computational task due to the brittle behavior of the concrete, which results from the small amount of transverse reinforcement. A reasonable match was found between experimental and analytical response up to the point of axial failure, with the finite element model providing an accurate representation of the changes in stiffness observed during the test.
2007
Designing of widely used concrete structures requires certain information on the load bearing capacity, ductility, failure mode, etc., which should be obtained by expensive and time consuming experiments. Hence, analytical investigation of nonlinear behavior of concrete structures need to be studied. Concrete is a relatively unknown material, although it is increasingly used, because of its brittle nature, which leads to sudden failure under compressive stresses. The amount of flexibility and energy absorption capacity in structures, especially under lateral load, are so important that new methods are needed to improve them. Strength and flexibility of concrete can be highly increased by controlling the lateral expansion by confining and enclosing. Using rectangular stirrups is one of the most common methods of confining the concrete members. In this paper, in order to investigate the function of stirrups in increasing the strength and ductility of reinforced concrete columns, the b...