Slenderness Ratio and Influencing Parameters on the NL Behaviour of RC Shear Wall

Shear walls are very efficient structural elements to resist lateral seismic disturbance. Despite the aforementioned seismic performance, recent investigations report that they have suffered from significant structural damage after recent seismic activity, even for those complying with seismic provisions. These deficiencies in resistance and deformation capacities need to be explored. This study considers the influence of plastic length Lp , concrete compressive strength fc28 , longitudinal reinforcement ratio ρl, transverse reinforcement ratio ρsh, reduced axial load ν, confinement zone depth CS and focusing on the geometric slenderness λ. The parametric study has been conducted through NL pushover analysis using Peform3D software. The chosen coupled shear-flexure fiber macro model was calibrated with well-known cyclic experimental specimens. The paper points out the discrepancy between the two well-known codes EC8 and ASCE/SEI 41-13. In fact, the value of the slenderness ratio (λ) that trigger the beginning of a purely flexural behaviour recommended by EC8 (λ > 2) is very different from the value of the ASCE/SEI 41-13 (λ > 3) without accounting for the effect of the reduced axial force. Finally, it was found that RCW capacities are very sensitive to fc28, ν, ρl, Lp and less sensitive to ρsh and CS. However, (λ) is the most decisive factor affecting the NL wall response. A new limit of slenderness and appropriate deformations of rotations are recommended to provide an immediate help to designers and an assistance to those involved with drafting codes.


Introduction
Reinforced concrete (RCW) structural walls have commonly been used as building lateral force-resisting elements in regions of moderate-to-high seismic hazard, for providing an adequate stiffness and sufficient strength to ensure an elastic seismic response and an adequate ductility to dissipate energy. Structural RCW are defined as ductile, when they have the ability to deform inelastically corresponding to their displacement ductility μΔ. Despite the aforementioned seismic characteristics, technical investigations conducted after recent earthquakes in 2003 (Algeria) [1], 2010 (Chile) and 2011(Mexico), showed that the recorded structural damage (crushing, rebar buckling, and lateral instability) in concrete shear walls exceeded the level recommended by seismic regulations, even when there was compliance to design provisions [2]. Thus, questions have been raised about current design provisions and current understanding of the determinants of NL behaviour of RCW. This paper seeks to extend the understanding of the main parameters that influence NL behaviour of RCW and advocates that a performance-based approach, where performance goals rely on limit states based on damage levels, should be taken.
The study revealed, that the lateral capacities of the concrete shear walls are sensitive to the concrete resistance (fc28), the reduced normal force (ν), the longitudinal reinforcement ratio (ρl) and the extent of the plastic hinge (Lp); while they are less sensitive to the transverse steel ratio (ρsh) and confinement zone depth CS. The slenderness ratio (λ) was, however found, the most decisive factor affecting the seismic NL wall behaviour expressed in terms of the aspect ratio (height to length, hw/lw). We point out the existence of a discrepancy between the two well-known codes EC8 [5] and ASCE ASCE/SEI 41-13 [6] in the definition of the slender wall. In fact, the value of the slenderness ratio (λ) that trigger the beginning of a purely flexural behaviour recommended by EC8 (λ > 2), is very different from the value of the ASCE/SEI 41-13 (λ > 3), in addition, to being expressed as the ratio of (hw/lw) neglecting the reduced axial force ν effect. To understand this discrepancy, we had explored the range between the slenderness ratio (λ) values of the two well-known codes and a new limit of λ is proposed. Moreover, deformation limit state values (θIO, θLS, θNC) for a normally reinforced section are recommended, since the values given in the relevant literature treat the lightly and heavily reinforced cases. The chosen value 0.5Lw of plastic hinge given by the codes is also discussed The present paper is organised into five sections. The first section introduces the existing problem and outlines the research question and main objectives of this study. The second section presents the main modelling concepts commonly used by researchers. In Section 3, four commonly used experimental models, selected from the relevant scientific literature, have been used to calibrate the adopted numerical model. The fourth section deals with the parametric study by considering the main parameters that influence the NL behaviour of RCW while proposing some control tools that can be used to help the structural designer. The last section is devoted to the general conclusions and recommendations of the study.

Modeling
There are two main families of models used in the numerical simulation of the inelastic response of concrete shear walls structures [7].

Microscopic Models
The models are based on the finite element method and are particularly useful when studying the local behaviour of structures. The concrete wall is discretized by a set of finite elements. The use of this type of model provides local responses which faithfully reflect the observations and results of experimental tests [8][9][10][11]. However, for highly redundant systems, the computation time becomes prohibitive (convergence problems). Their use in modelling therefore becomes a choice to be discarded.

Macroscopic Models
Compared to microscopic models, macroscopic models are relatively simple and numerically efficient with a reduced computation time. Their accuracies and areas of use vary significantly from one model to another. Their implementation and their use in calculations must be done appropriately so that the results obtained will be representative and agree with those obtained from experiments [12][13][14][15]. The main macroscopic models widely implemented in numerical simulation are summarized [7]:

Modeling Aspect
It is recognized that distributed-plasticity beam-column models with fiber sections [20][21][22] provide a more accurate approach to simulate NL behaviour RC walls than lumped-plasticity models under both static and dynamic loads [18], because they can capture the variation of axial force in the axial-flexural interaction. This behaviour can be expressed by shear, bending, or combined shear-bending [7]. Since classic fiber model cannot capture the NL behaviour of squat walls mainly controlled by shear. Thus Fiber models must be modified to overcome this shortcoming. To better capture the shear effect (conventional and distortional), the macro-model used for the simulation is based on the fiberbased element with consideration of the strut effect; however, the shear induced by the normal force is neglected. An ultimate deformation for vertical steel is introduced to avoid an out of plane effect. The modelling work was carried out using the Perform3D software [23].

Modeling Data
The fiber behaviour laws are introduced through a uni-axial trilinear force-deformation curve (Inelastic 1D Concrete material, Inelastic Steel material Non-Buckling). These laws reflect the behaviour of the material starting from the elastic phase, passing to the elastoplastic to plastic stage until reaching failure or total loss of strength. The RCW is discretized on two main families of steel and concrete fibers (Figure 1b), where its Behavioural law is introduced:  Perform3D uses two methods of modelling wall elements. The first is called "Shear Wall, inelastic section, suitable for slender walls ", and the second is called "General Wall, inelastic section, used to introduce the effect shear through the strut effect ", suitable to model squat walls. The shear effect is introduced by a force-strain curve ( Figure 1f   The hardening stiffness is equal to the non-degraded value (Figure 2b), resulting on a maximum elastic range and a minimum strain hardening range.
 PERFORM allows to control the elastic range, using the Unloading Stiffness Factor. A factor of 1.0 gives a maximum unloading stiffness and minimum elastic range. A factor of -1.0 gives a minimum unloading stiffness and maximum elastic range. The default is midway between these extremes [23].

Model Calibration
Four experimental models ( Figure 3; and Table 2) selected from the relevant scientific literature, namely SW1-1, and SW1-2 [25], RW2 [26] and PW1 [27]; the most commonly used were taken as references for the calibration of the adopted numerical analysis model. It should be noted that the limits introduced in the macro-model are those taken from the references.    However, if the energy is considered as a control tool, an average deviation of 12.3% is registered. In this context, Kappos [28] reports that a difference of 11% is recorded between the numerical and experimental curves. It can be concluded that the chosen macro-model, guarantees a remarkable reliability and is therefore used in the following parametric investigation.

Parametric Study
The study takes into consideration the parameters influencing the sectional capacity, namely:  The longitudinal steel ratio ρl (0.5, 1, and 2%); weakly, moderately and heavily reinforced.
 The transverse steel ratio ρsh (0.5, 1 and 2%), weakly, moderately and heavily confined section.  The extent of the plastic hinge Lp and the geometric slenderness λ (1, 1.5, 2, 2.5, 3, and 3.5) which affect the behaviour of the structural member.
The presented results in this paper were selected from the obtained numerical ones in accordance with the requirements of the RPA99 [29] by considering the following limits:  The concrete strength fc28 (25,30 and 35 MPa), which are common values in Algeria;  The slenderness ratio λ (2.5 and 3.5) representing the combined bending-shear and purely flexural effects;  The reduced normal force ν (0.10 and 0.25) extreme values considered by the RPA99 [29];  The longitudinal reinforcement ratio ρl (0.5%, 1% and 2%);  The confining reinforcement ratio ρsh (lightly confined, moderately confined and highly confined); The length of the plastic hinge was taken as Lp = 0.5Lw.

Material Limit states
The parametric study is carried out by considering the behaviour laws of the materials used, namely: tw: thickness of the wall; l0 : buckling length of the wall, is taken generally equal to the extent of its plastic length; [29]and limited to 0.5Hw.
The parameter c ξ was originally proposed by Paulay and Priestley [30] as: Mechanical ratio of the resistance reinforcement in the confined area

Limit States for Bending Behaviour (Yielding and Ultimate)
To evaluate the ductility capacity of the elements it becomes necessary to determine the yielding and ultimate displacement. The first limit may not have a well-defined point due to the nonlinear behaviour of materials. Several definitions have been adopted by researchers in the field to evaluate the yielding displacement [31]. The yielding displacement of the equivalent elastoplastic system which has a reduced stiffness or secant stiffness is determined by reaching the first yielding of the steel or for a force = 0.75 . Nonlinear elastic behaviour is due to cracking of the concrete. The latter definition is considered by R. Park [31] as the most realistic one as it has been adopted in cyclic quasi-static loading tests by leading researchers in the field from different countries USA-New-Zealand-Japan-China. Nowadays, this approach continues to be adopted [31,32]. Therefore, it is retained for the rest of the study, i.e. the yielding displacement is assumed to be achieved if one of the two conditions is reached first:  The yielding of the longitudinal reinforcement.
 The intersection of the line Fmax and the line through the origin and the theoretical value Fy=0.75Fmax. The ultimate limit state is assumed to be reached for whichever of the two conditions comes first ; After a 20% drop in strength, for a force Fu=0.8 Fmax or if the transverse or longitudinal steel fails or if the longitudinal steel buckles.

Limit States for Shear Behaviour (Distortion)
The residual performance within an earthquake damaged structure can be assessed through the observed damage levels, in order to take a decision about its immediate occupation, repair or its safety against collapse. In this context, Teroaka et al. [27] conducted a research work on 33 specimens of interior joints and drew a map relating the level of seismic performance with distortion and structural damage (shear angle and crack width).
γA: is the limiting distortion (LD) for good serviceability (0.04%); γB: LD for easy repair (0.4%); γsl: LD for loss of serviceability (0.5%) and γc: LD for difficult repair (1.0%). The schematic relationship between distortion-damage and residual seismic performance (serviceability, repair and collapse safety), assumed to vary linearly respectively. The distortion of the panels is mainly caused by the extension of the diagonal due to crack propagation and not to the compression of the concrete in the other direction. This extension can be controlled by the transverse reinforcement and the resistance reinforcement; Teroaka et al propose the following limits [33]:  Distortion for easy repair 0.4%;  Distortion for difficult repair 1.0%.
In this context and to avoid difficult repair, Graham Powell's [4] limiting distortions are adopted for the rest of the study are taken as follows:  Du= 0.4%, Dx= 1.2%, DL= 0.75%, DR= 1.0% and no stiffness reserve is considered after yielding.

Extent of the Plastic Hinge
The plastic hinge is usually defined, as that section of the structural element, where plasticisation of concrete in compression and yielding of steel in tension zone has occurred, causing section rotation under constant ultimate effort. The shape of plastic hinges, changes from concentrated zone for linear element, to a spread area such as shear walls. It is found that plastic zone length is only slightly sensitive to boundary element reinforcement ratio, shear span ratio and axial load level (which reduces slightly the spread of plasticity along the wall); but it is significantly affected by the wall length and wall height [35]. The ultimate deformation capacity of a component depends on the ultimate curvature and plastic hinge length. Many researchers have proposed equations for the plastic hinge length LP of RC shear walls to simulate the ultimate displacement [29,34]. Theses equations formulated as a function of the length of the wall, the axial load υ, the moment-shear ratio M/V and the material characteristics. However, seismic code provisions recommend generally a value depending on the length of the wall (ex. Lp = 0.5Lw).The influence of the plastic hinge length Lp, on the seismic performance of RCSW was highlighted in a previous work [36] where the combined effect of shear-flexure was considered. The numerical investigation was conducted for a variable plastic length values. The obtained results show that Lp affects the behaviour of the structure, the member and the material. The main conclusions drawn from this work are summarised as follows:

Global Behaviour
The

Figure 6. Global behaviour
The curves show that the ductility is significantly influenced by the variation of the plastic hinge length. It goes from a medium class of ductility (Figure 6e) for Lp = 0.378Lw (α=6) to a high class of ductility for Lp = 0.5Lw ( Figure  6e). The recorded gain is about 18% for Lp = 0.63Lw compared to Lp = 0.25Lw.

Behaviour of the Element
The rotation of the element increases proportionally with the length of the plastic hinge Lp, until it reaches its maximum value for Lp=0.63Lw (Lp=10tw) (Figure 7a). This specific point illustrates the ultimate limit state, maximum rotation-minimum resistance. After this critical limit, the results become irrational, for the rotation decrease and the resistance increase (abnormal went back) (Figure 7b, 7c).

Effective Damping
In practical applications, the maximum inelastic displacement is the most sought-after parameter, which is directly related to ductility. The equivalent linearisation method evaluates this displacement as the maximum displacement of a linear elastic system with lower lateral stiffness and higher damping coefficient than those of the inelastic system [37]. Several analytical expressions relating effective period Teff, and effective damping βeff to ductility μ are nowadays evaluable within the relevant technic literature. Figure 6d shows the variation of βeff function of LP while using Iwan's relation [38],   In the same context and taking the specific point 0.63 Lw as a reference, appropriate values characterizing the limit state levels (IO, LS and NC) for bending-shear behaviour dominated by flexure and for a reduced normal force ν ≤ 0.25 (for an usual steel ratio) are proposed, in order to keep sufficient reserve of deformation capacity.

Sectional Behaviour
The length of the plastic hinge Lp also influences the behaviour of the materials making up the section. The variation in the length of the hinge Lp causes a shift of the neutral axis of the RC shear section, leading to two families of behaviour grouped and delimited by the normative value of 0.5Lw (Figure 8b). This shift of the neutral axis starts from 0.57Lw to 0.68Lw leading to an optimization of the materials (compressed confined concrete) reflecting the increase of the compressed concrete area and the improvement of the cross-section rotation. This phenomenon is also recorded for concrete and steel materials if the stress state is considered as a control parameter (Figure 8a).

Figure 8. Sectional behaviour
The summary of the results presented shows that the code limit of 0.5Lw is an optimum position, for which it is adopted to conduct the rest of the study.

Concrete Strength fc28
The obtained results are gathered (Figure 9) in shear-drift curves categorised according to slenderness λ and reduced force ν. It can be seen that slender walls λ = 3.5 exhibit a purely flexural behaviour. The moderately slender walls λ = 2.5 show a combined bending-shear behaviour if they are heavily loaded ν = 0.25 whatever the concrete strength. This same behaviour is observed if the walls are lightly loaded ν = 0.10, for low concrete strengths (25 MPa).  λ = 2.5 a small resistance gain is recorded fluctuating between 23 and 30% for v = 0.10 and between 30 and 50% for ν = 0.25, whatever the slenderness value (Table 4)

Impact on the deformation
In terms of deformation, fc28 influences the yielding point recording a gain fluctuating between 6% for ν = 0.1 and ν = 0.25 if λ = 3.5. For λ = 2.5, this gain varies between 32 and 44% for fc28 = 30 and 35MPa if ν = 0.1, and 82% and 147% for fc28 = 30 and 35MPa if ν = 0.25. It should be noted that no change in this gain is recorded for a concrete strength above 30Mpa ( Table 4). The concrete strength affects only the ultimate deformation of the wall having a slenderness of 2.5, where a gain of 11.7% is recorded for ν = 0.1. This gain is 29% and 72% respectively for 30 and 35 MPa of concrete strength and v = 0.25. The same observation is made for the overall ductility where it is the shortest wall that is affected.

Impact on ductility
For λ = 2.5, the overall ductility loss recorded increases with the increase of both of the concrete strength and axial force intensity (15% and 27% if ν =0.1 respectively for fc28= 30 and 35MPa and (30% if ν =0.25).

Longitudinal Steel Ratio ρl
The results obtained are grouped (Figure 10), in the form of families of shear-drift curves categorized according to the slenderness λ and the reduced force ν. Slender walls λ = 3.5 show a purely flexural behaviour unless the section is heavily reinforced ρl = 2%. Moderately slender walls λ = 2.5 show a combined flexural-shear behaviour if they are heavily loaded ν = 0.25 regardless of the reinforcement ratio ρl. This same behaviour is also observed if the walls are lightly loaded ν = 0.10, for reinforcement rates ρl =1-2% and it becomes flexural if the section is lightly reinforced (ρl = 0.5%).

Impact on the Strength
A gain in resistance is registered fluctuating between 27 and 63% for ν = 0.1 and 16 and 18% for ν = 0.25 respectively for λ = 2.5 and λ = 3.5.

Impact on Deformation
Longitudinal reinforcement ratio ρl significantly influences the yielding point and the ultimate limit.
 For λ = 3.5 and ρl = 1%, an increase at the yield point up to 50% for ν = 0.1 and 19% for ν =0.25 is registered. On the case of ρl=2% this gain is reduced to 40% for ν = 0.1 and a loss of 12% is registered for ν =0.25.However, the ultimate limit records a deficit of deformation from 3 to 16% for ν = 0.1 respectively for ρl = 1 -2%, and on the case of ν =0.25 a loss of deformation is from 16 to 25% respectively for ρl = 1 -2%.

The Reduced Normal Force ν
The results obtained are gathered (Figure11), in the form of families of shear force-drift curves categorised according to slenderness λ and reduced stress ν. Figure 11. Influence of axial load ratio

Impact on strength
For λ = 3.5 a considerable gain in resistance is registered (around 30%) when ν shifts from 0.1 to 0.25. However, this gain fluctuates between 14.7% and 28.2% respectively for fc28 = 30 MPa and fc28 = 35 MPa when ν shifts from 0.1 to 0.25 and λ = 2.5.

Impact on the deformation and ductility
The increase of ν significantly reduces the yielding rotation: 13 to 17% for λ = 3.5 and ν = 0.25 resulting in an increase in overall ductility 14 to 20%. If λ = 2.5 this reduction in yielding rotation passes from 44 and 21% respectively fc28 = 30 MPa and fc28 = 35 MPa for ν = 0.25, leading to an increase in ductility of 13 and 11.7%.

Transverse steel ratio ρsh
The results obtained are gathered (Figure 12), in the form of families of shear force-drift curves categorised according to slenderness λ and reduced stress ν.

Impact on strength
A small gain in resistance is recorded (3-8%) only for λ = 3.5.

Impact on the deformation and ductility
For λ = 2.5 ρsh has a small influence on the yielding limit (10 to 12%) if ν =0.1 and no effect for ν = 0.25. The ultimate limit is weakly affected (5 to 16%). A loss in the overall ductility is noticed (5 to 10%) for ν = 0.25. It can be concluded that the influence of the transverse reinforcement ratio is negligible. The results obtained are grouped (Figure 13), in the form of shear force-drift curves categorized according to slenderness λ and reduced axial force ν. It can be seen that the extent of the confined area has no effect on the strength and deformation capabilities of the wall regardless of its slenderness and the bearing axial force.

Slenderness Ratio λ
The increase in slenderness ratio λ enhances the element deformability and reduces its stiffness. It delays the onset of the yield point:  150% is recorded for λ =2.5 and 186% for λ =3.5 for ν = 0.1;  65% is registered for λ =2.5, and 175% if λ =3.5 for v = 0.25.
This results in a significant loss of stiffness; hence a drop in strength of 30% for ν = 0.1 and 7% for ν =0.25. Furthermore, the ultimate deformation is also delayed in an appreciable way (sup a 90%) increasing the energy dissipation capacity. For lightly loaded RCW (ν = 0.1) flexural behaviour is noticeable for λ = 2.5, however this behaviour starts for λ = 3 for heavily loaded ones (ν = 0.25) and be dominant after λ = 3.5.

Compression Strut Effect
The study of the influence of the compression strut on the behaviour of CRW was carried out using the PW1 model (already studied under cyclic effect) for a monotonic load case.it was conducted while varying the geometric slenderness (from the squat to slender wall) for two limit values of the reduced axial force = 0.1 and = 0.25 (from lightly to heavily loaded). This specimen was chosen because of its geometrical dimensions corresponding with commonly used RCSW (absence of the scaling effect) and the accessibility of the experimental details. Figure 15 shows that:  The compression strut effect for RCW with slenderness ≥ 2 is not significant (gains do not exceed 10%,

Figure 16. Registered gain due compression strut
The synthesis of the obtained results gives a clear answer on the limit slenderness beyond which the RCW will exhibit a purely flexural behaviour for both loading cases (v=0.1 and v=0.25). It can be concluded that the geometric slenderness of 3.5 can be considered as a threshold beyond which the RCW exhibits a purely flexural behaviour.
Contrary to EC8 and the ASCE/SEI 41-13 code which recommend a limit slenderness independently of the wall position (lightly or heavily loaded cases) and giving values of 2 and 3 respectively for a such behaviour.

Extent of the Plastic Hinge
The plastic length significantly affects the strength and deformation of wall structures for values 0.25Lw ≤ Lp ≤ 0.63Lw. The strength and deformation gain increases linearly until reaching LP = 0.63lw where it remains unchanged. This specific value characterises the ultimate limit state beyond which the obtained results become irrational. The normative value of LP =0.5Lw limits the incursion into the plastic domain providing an additional safety margin (20% in deformation). The variation of the plastic length causes a shift of the neutral axis of the web section forming two behaviour families ( − ) delimited by the normative value of 0.5Lw. This shift is more pronounced between 0.57Lw and 0.63Lw leading to an optimisation of materials (confined concrete in compression) resulting in a larger confined area increasing thus the rotation capacity. Rotation values consistent with Limit state deformations (I.O), (L.S), (N.C) for bending-shear behaviour are proposed for a conventional steel reinforcement: θIO = 0.0033 rd , θLS =0.0083 rd , θNC = 0.0128 rd .

Concrete Strength
The increase of fc28 improves the strength (up to 50% gain) of the heavily loaded slender walls (λ=2.5) and decreases the ductility (30% of loss is recorded). However, it has no significant effect for slender walls (λ=3.5).

Longitudinal Reinforcement Ratio
The increase in ρl leads to a significant gain in strength (up to a 50% gain) for lightly loaded slender walls (v=0.1 for λ = 2.5-3.5). Whereas a loss in ductility is noticed (25 and 40%) respectively for v = 0.25 and v=0.1 for (λ = 2.5 -3.5). The ultimate steel deformation εsu=0.30 is recommended in order to avoid the out-of-plane instability phenomenon.

The Reduced Axial Force
Reduced axial force ν improves slightly the strength of slender walls only for (λ=3.5). However, it reduces the yielding strength leading to a substantial increase in ductility for λ = 2.5.

Transverse Reinforcement Ratio
For λ = 3.5 ρsh has a small effect on the capacity of resistance for ν =0.1 and 0.25; for λ = 2.5 ρsh has a small effect on the capacity of resistance if ν = 0.1 and no effect if ν = 0.25; the transverse reinforcement ratio ρsh has a low effect on the deformation capacity. In order to achieve a rational confinement ratio, an effective limit of the transverse reinforcement ratio (ρsh =1%) is recommended.

Extent of the Confined Section CS
The extent of the confined area has no effect on the strength and deformation capabilities of the web (regardless of its slenderness and its bearing axial force).

Compression Strut and Slenderness Ratio Effect
The effect of the compression strut for RCW with slenderness ≥ 2 is negligible (gains do not exceed 10%), however, it will be significant for squat RCW where these gains can exceed 20%. The increase in slenderness ratio λ, favours the deformability of the wall, reducing its stiffness. It delays the onset of the yield point (ranging from 65% to 186%) which leading to a consequent loss of stiffness resulting in a drop in strength. The ultimate deformation is significantly delayed (over 90%) thus increasing the energy dissipation capacity.
It should be pointed out that for lightly loaded shear walls (ν = 0.1) the flexural behaviour is noticeable for a slenderness ratio of λ = 2.5 and is dominant for λ = 3.0. However, for those highly loaded (ν = 0.25) this behaviour takes effect for λ = 3 and becomes dominant after λ = 3.5. The slenderness ratio describing a purely flexural behaviour (introduced as the (Length/width)), omitting the effect of the reduced normal force ν is not realistic. A limit of this factor taking into account the effect of the position of the shear wall (light or heavy load case of ν) is proposed λmin ≥ 3.5 × (1-(0.25-ν)). We conclude that the slenderness of λ = 3.5 is a threshold beyond which the RCW exhibits a purely flexural behaviour. Finally, it was found that Reinforced Concrete Shear Walls (RCW) capacities are very sensitive to the concrete compressive strength fc28, the reduced axial load ν, the longitudinal reinforcement ratio ρl, the Plastic Length Lp; while being less sensitive to transverse the reinforcement ratio ρsh and the confinement zone depth CS. However, the geometric slenderness λ is the most decisive factor affecting the NL wall response. The purpose of this study, is to go towards a future study where the RCW is studied in the context of a whole building taking into account the percentage of short and slender walls composing it, in order to propose a global factor behavior function of the ductility, λ(ν), the existing percentage of squat and slender walls.