Computer based estimation of backbone curves for hysteretic Response of reinforced concrete columns under static cyclic lateral loads (original) (raw)
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International Journal of Concrete Structures and Materials
In older reinforced concrete (RC) buildings, columns are fragile elements that can induce collapse of entire buildings during earthquakes. An accurate assessment of the seismic vulnerability of RC buildings using nonlinear response history analyses requires an accurate numerical model. The peak-oriented hysteretic rule is often used in existing numerical models to simulate the hysteretic behavior of RC members, with predefined backbone curves and cyclic deterioration. A monotonic backbone curve is commonly constructed from a cyclic envelope. Because cyclic envelope varies according to loading protocols, particularly in a softening branch, it is difficult to obtain a unique backbone curve irrespective of loading protocols. In addition, cyclic deterioration parameters irrespective of loading protocols cannot be found because these parameters are estimated with respect to the backbone curves. Modeling parameters of existing numerical models can also vary with respect to loading protoco...
Analytical Load Displacement Curves of RC Columns under Constant Axial and Cyclic Lateral Loads
The cyclic tests of the columns are of practical relevance to the performance of compression members during earthquake loading. The strength, ductility and energy absorption capabilities of RC columns, subjected to cyclic loading, have been estimated by many researchers. These characteristics are not normally inherent in plain concrete but can be achieved by effectively confining columns through transverse reinforcement. An extensive experimental program, in which performance of four RC columns detailed according to provisions of ACI-318-08, was studied in comparison with that of four columns confined by a new proposed technique. Out of total eight, this paper presents performance of three columns which were detailed according to provision of ACI-318-08 and cast with 25 and 32 MPa concrete. The experimentally achieved load-displacement hysteresis and backbone curves of the three columns are presented. Two approaches, which utilize moment-curvature and shear-shear strain relationship of RC columns achieved through Response-2000, have been suggested to draw analytical load-displacement curves of the columns. The experimental and analytical load-displacement curves are found in good agreement. The suggested analytical technique is simple and easy to implement. The technique will be available to the engineers involved in design to estimate capacity of RC columns.
Flexural and shear hysteretic behaviour of reinforced concrete columns with variable axial load
Engineering Structures, 2003
The importance of non-linear biaxial models that are applicable to the analysis of reinforced concrete members under cyclic and dynamic loads has been recognized. Variations in the axially applied force can influence strength, stiffness and deformation capacity of such members. In this study, an inelastic biaxial model based on plasticity theory, is proposed. This quadri-linear degrading model takes into account the effect of axial load variation on lateral deformation. The model predictions are examined against available experimental results. Using the developed model, the effect of various axial loading patterns on the lateral deformation of reinforced concrete columns is investigated.
Hysteretic cyclic response of concrete columns reinforced with smooth bars
Bulletin of Earthquake Engineering, 2013
The application of smooth (plain) bars in reinforced concrete (RC) construction has been abandoned since the 1970s; however, there are many old reinforced concrete buildings in the world whose construction is based on this old style that are now in need of structural seismic rehabilitation according to the requirements of present day seismic rehabilitation codes. The focus of this study concerns the investigation of the hysteretic cyclic response of RC columns with smooth bars. The results of six column specimens having a variety of details for overlapping splices of longitudinal bars while experiencing two different levels of axial loads under cyclic loading reversals are presented. Through analysis of test observations and the obtained experimental results, it is attempted to clarify major aspects of hysteretic response for RC columns with smooth bars, from a seismic assessment point of view. The hysteretic force-drift responses of columns are deeply investigated and a new concept explaining the flag shape form of the hysteretic response is presented. Furthermore, the rocking response of columns is predicted with a new formulation that assumes an internal compression strut inside the column body as a consequence of rocking that originated from high base rotations. Finally, a simple hysteresis rule is proposed which is the result of considering the combination of two springs in parallel to provide the total hysteretic response as the summation of rocking hysteretic and bottom anchor (smooth bar) hysteretic responses.
2017
It has been observed in the past that, reinforced concrete (RC) bridge columns are, very often, subjected to torsional moment in addition to flexure and shear during seismic vibration. However, the torsional moment is generally ignored in typical design pr actices. Previous studies have show n that, ignoring torsional moment may lead to brittle shear failure of the columns triggering collapse of the entire or part of the bridge structure. Therefore, rational models n e ed to be developed to consider the effect of torsion in the design of RC bridge columns. Performance based seis mic design is an emerging design concept which calls for accurate prediction of the hysteresis behavior of structural elements to ensure safe and sustainable design under earthquake loadi ng. However, very few investigations in the past focused on the development of analytical model to accurately predict the response of RC members under cyclic torsion. Though quite a good number of models are available for p...
Hysteresis modelling of reinforced concrete columns under pure cyclic torsional loading
Structural Engineering and Mechanics, 2017
It has been observed in the past that, the reinforced concrete (RC) bridge columns are very often subjected to torsional moment in addition to flexure and shear during seismic vibration. Ignoring torsion in the design can trigger unexpected shear failure of the columns (Farhey et al. 1993). Performance based seismic design is a popular design philosophy which calls for accurate prediction of the hysteresis behavior of structural elements to ensure safe and economical design under earthquake loading. However, very few investigations in the past focused on the development of analytical models to accurately predict the response of RC members under cyclic torsion. Previously developed hysteresis models are not readily applicable for torsional loading owing to significant pinching and stiffness degradation associated with torsion (Wang et al. 2014). The present study proposes an improved polygonal hysteresis model which can accurately predict the hysteretic behavior of RC circular and square columns under torsion. The primary curve is obtained from mechanics based softened truss model for torsion. The proposed model is validated with test data of two circular and two square columns. A good correlation is observed between the predicted and measured torque-twist behavior and dissipated energy.
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...
Behavior of High-Strength Concrete Columns under Cyclic Flexure and Constant Axial Load
ACI Structural Journal, 2000
In recent decades, high strength concrete (HSC) has been widely accepted by designers and contractors to be used in concrete structures, especially in high compressive stress elements. The research aims to study the behavior of high strength concrete columns under eccentric compression using experimental and analytical programs. The research is divided into two main parts; the first part is an experimental investigation for ten square columns tested at the Cairo University Concrete Research Laboratory. The main studied parameters were eccentricity of the applied load, column slenderness ratio; and ratios of longitudinal and transverse reinforcement. The second part is analytical analysis using nonlinear finite element program ANSYS11 on nineteen columns (ten tested square columns and nine rectangular section columns) to study the effect of the previous parameters on the column ultimate load, mid-height displacement, and column cracking patterns. The analyzed columns revealed a good agreement with the experimental results with an average difference of 16% and 17% for column ultimate load and mid-height displacement respectively. Results showed an excellent agreement for cracking patterns. Predictions of columns capacities using the interaction diagrams based on ACI 318-08 stress block parameters indicated a safe design procedure of HSC columns under eccentric compression, with ACI 318-08 being more conservative for moderate reinforced HSC columns.
Title Seismic Performance Assessment of L-Shaped Reinforced Concrete Columns
This paper presents an experimental investigation carried out on 10 reinforced concrete (RC) columns with L-shaped sections subjected to simulated seismic loadings. The primary objective of the study was to assess the suitability of using L-shaped RC columns in regions of low-to-moderate seismic risk. The variables of interest included the axial load, loading direction, and aspect ratio. The specimen performances were analyzed and discussed in terms of crack patterns, hysteretic response, curvature distribution, displacement decomposition, strain profile, and energy dissipation capacity. Results highlighted that the L-shaped columns possessed good seismic resistance, that failure mechanism of L-shaped columns was mainly governed by vertical splitting cracks, and that shear strength of L-shaped columns was not significantly affected by the level of applied axial force and the direction of horizontal force while initial stiffness was considerably affected by aspect ratio. Further analysis showed that ignoring the contribution of flanges, the shear equation (special provisions for walls) in ACI 318-11 yields good estimations of shear strength for the cases of L-shaped columns.
Seismic Performance Assessment of L-Shaped Reinforced Concrete Columns
ACI Structural Journal, 2015
This paper presents an experimental investigation carried out on ten reinforced concrete (RC) columns with L-shaped sections subjected to simulated seismic loadings. The primary objective of the study was to assess the suitability of using Lshaped RC columns in regions of low-to-moderate seismic risk. The variables of interest included the axial load, loading direction and aspect ratio. The specimen performances were analyzed and discussed in terms of crack patterns, hysteretic response. Results highlighted that the L-shaped columns possess good seismic resistance; Failure mechanism of L-shaped columns was mainly governed by vertical splitting cracks; Shear strength of L-shaped columns were not significantly affected by the level of applied axial force and the direction of horizontal force while initial stiffness was considerably affected by aspect ratio. Further analysis showed that ignoring the contribution of flanges, the shear equation (special provisions for walls) in ACI 318-11 yields good estimations of shear strength for the cases of L-shaped columns.