Effect of transverse reinforcement on short structural wall behaviour (original) (raw)
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Proceedings of the Vienna Congress on Recent Advances in Earthquake Engineering and Structural Dynamics, VEESD 2013, 2013
It is expected that walls which were designed either with increased ductility requirements according to the Greek Concrete Code 2000 or were designed to be in a high ductility category according to EC8: 2004, NZS 3101: 2006 and other modern international codes, present extensive tensile deformations, especially in the plastic hinge region of their base. Depending on the geometric characteristics and the level of ductility design of walls, large tensile deformations are expected. These tensile deformations can cause their lateral instability depending on their size. Large width cracks, which are created as result of deep entry in the plastic region, are required to close, so that the in-plane flexural mode of wall can be completely developed at the reversal of loading sign. It is obvious that there should be a sufficient wall thickness, so that it is ensured that the compressive force can be developed in the compression zone of the wall cross-section without the event of out-of-plane buckling. A critical situation arises when at the reversal of the sign of moment, the cracks that emanate from tension (at the previous semi-cycle of loading) cannot close and thus, traverse buckling takes place, which leads the wall end section to lateral instability. The current work investigates one of the most basic parameters affecting the stability of structural walls, which is (apart from the wall thickness) the degree of elongation of the longitudinal reinforcement of the boundary edges of load-bearing walls. The present work is experimental. It has to be noted that in order to examine experimentally the influence of elongation, 5 test specimens of scale 1:3 simulating the boundary edges of structural walls were used. These specimens were reinforced with high longitudinal reinforcement ratio (3.68%) and they all had the same reinforcement ratio. The degree of elongation which was applied was different for each specimen and it took values equal to 0‰, 10‰, 20‰, 30‰ and 50‰. The present paper tries to investigate the influence of the degree of elongation to the ultimate strength and to the modes of failure of test specimens.
DEVELOPMENT OF REINFORCEMENT DETAILS TO IMPROVE THE CYCLIC RESPONSE OF SLENDER STRUCTURAL WALLS
SUMMARY A series of four reinforced concrete walls were tested to failure to evaluate the influence of diagonal web reinforcement on the hysteretic response. Two walls contained conventional horizontal and vertical web reinforcement and two walls contained inclined reinforcement. Reinforcement details were representative of construction practice in regions of low to moderate seismic risk. A single layer of web reinforcement was used and the transverse reinforcement in the boundary elements did not confine the concrete core. Both walls with conventional web reinforcement failed due to web crushing. Pinched shapes characterized the hysteresis curves for top displacement and shear distortion near the base. In contrast, the walls with diagonal reinforcement displayed rounded hysteresis curves, and failed due to crushing of the boundary elements. The choice of web reinforcement did not have a significant influence on the maximum lateral load resisted by the walls, but measured crack widths were less, and more energy was dissipated by the walls with diagonal reinforcement during loading cycles to comparable levels of displacement.
ACI Structural Journal, 2000
The present study addresses the problem of cyclic shear in squat reinforced concrete walls and attempts to assess the validity of current design provisions, both in Europe (Eurocode 8) and in the U.S. (ACI 318). The paper describes a comprehensive experimental program involving 11 wall specimens, six with shear span ratios of 1.5 and five with 1.0, detailed to the provisions of EC8; problems in applying these provisions are pointed out and comparisons with the corresponding ACI 318 provisions are also made. The wall specimens are reinforced against shear, either conventionally (orthogonal grids of web reinforcement), or with cross-inclined bars; the effects of web and edge reinforcement ratio, of axial load level, and of the quality of construction joints are also investigated. The reported test results clearly show that properly designed and reinforced walls can reach their flexural capacities, even when their aspect ratio is as low as 1.0, that sliding shear in this category of walls is not a major problem, and that cross-inclined (bidiagonal) web reinforcement can effectively and economically control sliding and the subsequent pinching of the hysteresis loops, particularly when these bars intersect close to the critical section.
Proceedings of the Engineering a Concrete Future: Technology, Modeling and Construction, fib Symposium 2013, 2013
It is expected that walls which were designed to be in a high ductility category according to modern international codes, present extensive tensile deformations, especially in the plastic hinge region of their base. Depending on the geometric characteristics and the level of ductility design of walls, large tensile deformations are expected. These tensile deformations, depending on their size, can cause lateral instability to R/C walls. The current work is experimental and investigates one of the most basic parameters affecting the stability of structural walls, which is (apart from the wall thickness) the degree of elongation of the longitudinal reinforcement of the boundary edges of load-bearing R/C walls. Five test specimens of scale 1:3 simulating the boundary edges of structural walls were used. These specimens were reinforced with medium longitudinal reinforcement ratio (2.68%) and they all had the same reinforcement ratio. The degree of elongation which was applied was different for each specimen and it took values equal to 0‰, 10‰, 20‰, 30‰ and 50‰. The present article tries to investigate the influence of the degree of tension strain to the horizontal displacements and the modes of failure of test specimens.
Proceedings of the 15th World Conference on Earthquake Engineering, 15th WCEE 2012, 2012
One important aspect of seismic design of buildings with a dual reinforced concrete structural system is the lateral stability of structural walls, when they face this danger basically due to flexural overstrain. The deep excursion in the yield region of the boundary parts of bearing walls increases dramatically their flexibility and since at the same time they are liable, because of the earthquake vibration, to a reversing axial loading (tension-compression), their lateral stability is at stake. The possibility of failure because of lateral instability is limited significantly with the proper choice of an adequate thickness, which is specified by (most) modern seismic codes as a percentage of the height of the bottom storey. The current work investigates one of the most basic parameters affecting the stability of structural walls, which is (apart from the wall thickness) the degree of tension strain of the longitudinal reinforcements of the boundary edges of load-bearing walls. The present work is experimental. It has to be noted that in order to examine experimentally the influence of tension strain, 5 test specimens of scale 1:3 simulating the boundary edges of structural walls were used. These specimens were reinforced with low longitudinal reinforcement ratio (2,68%) and they all had the same reinforcement ratio. The degree of tension strain which was applied was different for each specimen and it took values equal to 0‰, 10‰, 20‰, 30‰ and 50‰. The present article tries to investigate the influence of the degree of tension strain to the ultimate bearing capacity of test specimens.
Proceedings of the 2013 International Van Earthquake Symposium, 2013
It is expected that walls which were designed either with increased ductility requirements according to the Greek Concrete Code 2000 or were designed to be in a high ductility category according to EC8: 2004, NZS 3101: 2006 and other modern international codes, present extensive tensile deformations, especially in the plastic hinge region of their base. Depending on the geometric characteristics and the level of ductility design of walls, large tensile deformations are expected. These tensile deformations, due to the cycling nature of loading, can cause lateral instability of seismic walls depending on the tensile deformations' size. The current work is experimental and investigates one of the most basic parameters affecting the stability of structural walls, which is the degree of tension strain of the longitudinal reinforcement of the boundary edges of load-bearing walls. The present paper tries to investigate the influence of the degree of tension strain to the ultimate strength and the modes of failure of test specimens using 5 test specimens with the same longitudinal reinforcement ratio (4.02%) but strained to different degrees of elongation.
Ductile Design of Slender Reinforced Concrete Structural Walls
2014
Slender reinforced concrete structural walls are commonly used in mid- to high-rise buildings as a main lateral load resisting element in earthquake regions. Past research has shown these walls to be efficient and effective in limiting the building lateral drifts due to their large in-plane stiffness. However, the damage sustained by concrete walls in recent earthquakes have demonstrated that current design requirements of these walls may need modifications, which is further supported by a NEES experimental study completed on slender concrete walls. To further understand the behavior of concrete walls and address the shortcomings of the current design requirements, an analytical study was conducted on slender rectangular concrete walls designed according to ACI 318-11. First, a simplified computational method to estimate force-displacement response of a structural wall, utilizing the moment-curvature relationship, was developed and validated using experimental data. Next, the influe...
Analysis of Confinement Effect on Strength and Ductility in Reinforced Concrete Structures
2014
The lateral confinement in reinforced concrete structural components is an essential parameter to allow designer to use a sufficient percentage of transverse reinforcement in order to ensure the required strength and ductility for the structure. This paper deals mainly with the influence of lateral confinement on strength and ductility in reinforced concrete structures designed according to Algerian standards. An overview of the non-linear static analysis method is described below to better understand this analysis. Two different representative structures designed according to Algerian code for the design of earthquake resistant buildings (RPA99/v2003) are identified for the purpose of this study. This analysis provides the capacity curves for each structure with regard to the compressive strength and the volume percentage of the transverse reinforcement. The results obtained show that the lateral confinement improves widely the strength and the local ductility of the structure elem...
The Open Construction & Building Technology Journal
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 ...
Transverse Reinforcement Effects on the Loading Behaviour of High Performances Concrete Beams
This work reports on an experimental investigation dealing with the effects of transverse reinforcement, in the form of stirrups, on the behaviour under load of high performances concrete (HPC) beams. The crack patterns and crack widths, the failure modes, the shear strengths and the ductility of HPC beams containing transverse stirrups were assessed and compared to those in ordinary concrete beams. The test results show that the use of transverse reinforcement in the form of stirrups restrains efficiently the inclined cracking and enhances the aggregate interlocking, known to be weaker in HPC without transverse reinforcement, and thus improves the shear strength of HPC beams. They also improve the contribution of the main longitudinal reinforcement to the shear strength through the dowel action. Finally, the transverse reinforcement improves appreciably the ductility of HPC beams at the ultimate state. In some cases, they changed the failure mode from a brittle shear to a markedly ductile flexure with an increased ultimate carrying capacity. The test results concerning the transverse reinforcement contribution to the shear strength are compared with those predicted by Eurocode 2. The comparison reveals a considerable overestimation of the contribution of the transverse reinforcement to the shear strength of HPC beams by the Eurocode 2. This reduces the safety margin required against shear failure, often catastrophic, and may even lead to unsafe shear design for high performances concrete.