Study of the residual axial capacities of shear-damaged reinforced concrete columns: Part 2—experimental verification of an evaluation model

2018 ◽  
Vol 22 (2) ◽  
pp. 459-472
Author(s):  
Yong Yang ◽  
Kazuto Matsukawa ◽  
Ho Choi ◽  
Yoshiaki Nakano

This article presents an experimental program to further verify the arch resistance model, which was proposed for evaluating the residual axial capacities of shear-damaged reinforced concrete columns in part 1 of the companion papers. Three reinforced concrete columns with different transverse reinforcement ratios are designed and tested up to axial collapse under different axial force levels. Based on the experimental results, the transverse reinforcement within the shear-damaged region of the designed specimens is confirmed to be able to fully develop their strength at axial collapse. With regard to the evaluation of residual axial capacities, when the damage pattern of the concrete core is consistent with that described in the proposed model, the residual axial capacity of the column along with the included two contributions of the concrete core and longitudinal bars are estimated with a high level of accuracy. When the damage pattern of the concrete core is not completely consistent with that described in the proposed model, although the contribution of the concrete core is not accurately estimated, the contribution of the longitudinal bars is still accurately evaluated. Furthermore, because of the low percentage of the contribution of the concrete core, the damage pattern of the concrete core has little effect on the evaluation accuracy of the residual axial capacity of the column. Thus, using the proposed model, the residual axial capacities of the columns with slightly different damage patterns of the concrete core are still estimated with a high accuracy in this experimental program.

2018 ◽  
Vol 22 (2) ◽  
pp. 311-322
Author(s):  
Yong Yang ◽  
Kazuto Matsukawa ◽  
Ho Choi ◽  
Yoshiaki Nakano

This is the first of two companion papers addressing the residual axial capacities of shear-damaged reinforced concrete columns. To evaluate the residual axial capacity, this article presents an arch resistance model that is based on the theory of mechanics and can reasonably explain the collapse mechanism of shear-damaged reinforced concrete columns. In the proposed model, the residual axial capacity of the column is evaluated by considering the interaction between the contributions of the longitudinal bars and the concrete core rather than by simply adding the two contributions together. The proposed model is also verified using an experimental database of shear-damaged reinforced concrete column specimens compiled from previous studies. The result shows that the proposed arch resistance model has an improved level of accuracy for evaluating the residual axial capacities of most column specimens. However, because the available information about column specimens in the compiled experimental database is limited, it is difficult to further verify the proposed model, and a new experimental program will be presented in Part 2.


Author(s):  
Hazem Elbakry ◽  
Tarek Ebeido ◽  
El-Tony M. El-Tony ◽  
Momen Ali

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.


Author(s):  
Ю. Г. Москалькова ◽  
С. В. Данилов ◽  
В. А. Ржевуцкая

Постановка задачи. Исследуется метод усиления железобетонных колонн устройством стальной обоймы с обетонированием, который позволяет восстанавливать эксплуатационные показатели колонн, имеющих значительные дефекты и повреждения. Предпосылкой настоящих исследований явилось предположение о том, что усиление стальной обоймой с обетонированием является эффективным способом повышения несущей способности железобетонных колонн, причем вариант приложения нагрузки - только на бетонное ядро или ко всему сечению - существенно на эффективность усиления не влияет. В связи с этим целью исследования является определение необходимости устройства стального оголовка и включения в работу ветвей стальной обоймы при условии обетонирования стержня колонны по всей высоте. Результаты и выводы. Рациональным признан способ передачи нагрузки только на бетонное ядро усиленных колонн, поскольку устройство оголовка стальной обоймы требует применения сложных конструктивно-технологических решений, но при этом дополнительно увеличивает несущую способность незначительно (согласно проведенным исследованиям менее чем на 10 %). Ввиду отсутствия необходимости устройства конструкций стального оголовка снижаются трудоемкость и сроки производства работ по усилению колонн. Statement of the problem. The method of strengthening reinforced concrete columns with a steel clipping and the concrete surfacing is investigated. This method allows one to repair the columns with significant defects and damage. The prerequisite for this study was the assumption of strengthening with a steel clipping and the concrete surfacing is an effective way to increase the ultimate limit state of reinforced concrete columns, furthermore, the option of applying the load (only to the concrete core or to the entire section) does not significantly affect the strengthening effectiveness. In this regard, the purpose of the investigation was to identify the need to include the steel jacketing in the work, on the condition the column is coated with concrete along with the entire height. Results and conclusions. The load transfer method only to the concrete core of the strengthened columns is recognized as rational since the device of the steel clipping head requires the use of complex structural and technological solutions, but at the same time additionally increases the ultimate limit state insignificantly (according to the studies by less than 10 %). Due to the absence of the need to establish structures of the steel jacketing head, the labor intensiveness and terms of work production on strengthening the columns are reduced.


Author(s):  
Hesham A. Haggag ◽  
Nagy F. Hanna ◽  
Ghada G. Ahmed

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.


2013 ◽  
Vol 8 (2) ◽  
pp. 41-50
Author(s):  
Štefan Gramblička ◽  
Peter Veróny

Abstract In the article we are dealing with the influence of transverse reinforcement to the resistance of a cross-section of the reinforced concrete columns and also with the effective detailing of the column reinforcement. We are verifying the correctness of design guides for detailing of transverse reinforcement. We are also taking into account the diameter of stirrups and its influence over transverse deformation of column.


Author(s):  
F. A. Zahn ◽  
R. Park ◽  
M. J. N. Priestley

The results of recent experimental and analytical studies of the stress-strain behaviour of concrete confined by New Zealand manufactured Grade 275 or Grade 380 reinforcing steel are presented. First, the behaviour of three pairs of concentrically loaded reinforced concrete columns containing spirals from either Grade
275 or Grade 380 steel are compared, including the stage at which spiral fracture occurred. Second, the results of tests on four reinforced concrete columns containing Grade 380 spiral or rectangular hoop reinforcement and subjected to combined axial
load and cyclic lateral loading are reported. An analytical
study which was conducted to determine the available curvature ductility factor at the stage of fracture of the transverse reinforcement is described. The results are used to give a guideline for the safe use of Grade 380 steel as transverse confining reinforcement.


Author(s):  
Matheus Wanglon Ferreira ◽  
Luiz Carlos Pinto da Silva Filho ◽  
Mauro de Vasconcellos Real

ABSTRACT: A three-dimensional (3D) transient numerical model for thermomechanical analysis developed with Finite Element Method (FEM) using the software ANSYS 19.1 is exposed in this paper. The proposed model aims to predict the structural behavior of reinforced concrete columns in a fire situation since it is known that high temperatures significantly reduce their mechanical resistance. For this, the main factors that govern their structural behavior should be considered. Analyses obtained by the proposed model were validated with results from experimental data, evidencing a good correlation between numerical and experimental fields.


2014 ◽  
Vol 17 (10) ◽  
pp. 1373-1385 ◽  
Author(s):  
Cao Thanh Ngoc Tran ◽  
Bing Li

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' c A g and 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 concrete columns with low transverse reinforcement ratios subjected to reversed cyclic loadings to a satisfactory level of accuracy


Sign in / Sign up

Export Citation Format

Share Document