The load steps were applied to the reference sample in the experiments are given in Fig. 13. There was variation in the number of load steps in other samples according to the shear wall position. Cracks and lateral displacements in the samples under the horizontal load effect were recorded. In the test experiment samples, the appearance of the developed cracks in case of the final load and displacement is reported for each sample. Crack development was observed during the load steps and noted. Crack development is important in terms of structure behavior. Element surfaces are defined as A, B, C and D surfaces in order to determine the level of crack development on column and shear wall. Accordingly, the level of crack development in each cycle was followed for push and pull. The cracks that occurred during pushing were drawn with a blue-colored pencil and the cracks that occurred during pulling were drawn with a red-colored pencil.
The first crack development in the columns, except Model 5, similar cracks developed at close forces in other models. Since Model 5 is more rigid than all the other models, crack development started in the 6th loading cycle. The first cracks that occurred in the column-beam junction area were in the 3rd loading cycle of Model 1, in the 7th loading cycle for both of Model 2, Model 3 and Model 4, and in the next loading cycle of Model 5 this area cracking started.
The first crack formation in the beam differed between the experimental models. While the Model 2 had the lowest load beam cracking, it was Model 5 with the highest beam cracking load. The first crack that occurred in the shear wall-beam junction area of the Model 2 and the Model 3 were close to each other, while the development of the first cracks in the Model 4 and the Model 5 was at the following loading cycles. While the first cracks in the shear walls were almost close to each other in Model 2, Model 3 and Model 4, but the shear wall first crack of Model 5 was at in the loading of 40kN at pushing direction. The first crack in the slab was not found in Model 1, Model 2 and Model 3 but there was slab cracking in Model 4 at 240kN and in Model 5 at 270kN. Cracks in the carrier systems at the end of the experiment are as seen in (Fig. 14).
In order to evaluate the behavior of three-dimensional reinforced concrete samples, evaluations were made by drawing the relationship curves between the applied lateral loads and the peak point displacement. Hysteresis curves are drawn depending on the measured peak displacements for each lateral loading step (Fig. 15).
As a result, according to the Table 3, when there is no shear wall in a reinforced concrete frame, since the lateral forces acting on the structure are shared equally by the columns, the horizontal displacement capacity of the structure is fully utilized. However, it causes an increase in the shear wall yield load in the other shear walled samples and a decrease in the deflection ability of the reinforced concrete frame. The reason for the increase in the yield load is that the shear wall bears the major part of the lateral load affecting the structure and reduces the load on the columns.
Table 3
Experiments Yield Loads and Displacements
Model | Yield Cycle No | Lateral Force | Yield Load (kN) | Displacement (mm) |
1 | 10 | Pull | 99,61 | 37,17 |
2 | 16 | Push | 157,92 | 25,63 |
3 | 17 | Push | 169,92 | 24,18 |
4 | 31 | Pull | 310,49 | 17,63 |
5 | 32 | Push | 320,29 | 16,96 |
The fact that the shear wall position is in the middle axis caused the yield load to increase by approximately 100% and the horizontal displacement to decrease approximately by 40% compared to the position of the shear wall on the outer axis. In addition, if the shear wall is located on the outer axis, it exceeds the bearing capacity of the columns on the opposite side to the shear wall at lower horizontal load values. The reason for this situation is the torsion moment and torsion cracks that occur as a result of the non-overlap of the centers of mass and rigidity in the system plan. Thus, it has been observed that the shear wall being on the middle axis is more effective in carrying lateral loads than being on the side axis. This is because, since the shear wall is not balanced with the counter rigidity, the presence of the shear wall on the outer axes causes significant torsion in the structure and creates additional cross-section effects against lateral loads, and loss of capacity is experienced.
If the reinforced concrete frame is without shear wall, it has more displacement and has a lower yield load, while the presence of the shear wall in the frame causes less displacement and increases the yield load. This situation has been explained as shear wall fulfilling their basic function. Another important result is that when the shear wall is close to the push direction of the frame, the yield load is higher and the displacement of the structure is less. When we look at the yield load, it seen that the shear walled Model 5 is as the largest lateral load bearing capacity model. It has been observed that the yield load of the experimental samples is not equal to the maximum lateral load acting on the carrier systems. In the cycle after the carrier systems yield cycle, the lateral force distribution also changed in the carrier elements (columns and shear wall). Therefore, due to the monolithic structure of the experiments, the amount of lateral load in the fibers that reached the power exhaustion limit was met by other nearby fibers and a higher load value could be read than the yield load.
The experiment samples are compared according to their maximum lateral load-carrying capacity, their values are given in Table 4. It is seen that the Model 2 and the Model 3 have 84% more lateral load carrying capacity than the Model 1. The lateral load carrying capacity of the Model 4 and the Model 5 has been calculated to be 310% more than the Model 1’s lateral load carrying capacity. It is seen that the lateral load carrying capacity of the Model 4 and the Model 5 is 68% higher than the Model 2 and the Model 3’s lateral load carrying capacity. This result revealed that the shear wall position will have an effect on the lateral load carrying capacity.
Table 4
Comparison of Lateral Load Bearing Capacities of Experiment Models
Experimental Model | Maximum Lateral Load / Displacement | Maximum Lateral Load Rate | Ductility |
Load (kN) | (δ/H) |
Model-1 | 103 | 0.030 | 1.00 | 1.83 |
Model-2 | 190 | 0.036 | 1.84 | 2.21 |
Model-3 | 190 | 0.026 | 1.84 | 2.32 |
Model-4 | 320 | 0.019 | 3.10 | 2.98 |
Model-5 | 320 | 0.011 | 3.10 | 3.70 |
The initial stiffness of the models is given in Table 5. When the stiffness changes are compared to Model 1, which is the reference experiment sample, it has been determined that Model 2 is 87%, Model 3 is 137%, Model 4 is 448% and the Model 5 is 467% from the reference Model (Model 1's) initial stiffness. When the stiffness changes in the maximum load case were compared, it was seen that the stiffness change compared to Model 1 was 33% higher for Model 2, 87% higher for Model 3, 436% for Model 4 and 478% for Model 5. It is seen that the average maximum load rate of Model 4 and Model 5 is 348% higher than Model 2 and Model 3. This result reveals that the shear wall position may also have an effect on the stiffness in behavior. Then, the ductility values of the models were calculated for both the push and pull cycles by using the formulation (µ = Δu/Δy) and then the average ductility values calculated (Dirikgil and Atas 2019). The average ductility values of the models are as shown in Table 4. It has been observed that model 5 has the biggest ductility value among all the models and therefore placing the shear wall as in Model 5 gives the model more ductility than the shear wall being in other places.
Table 5
Experimental Models Stiffness Comparison
Experimental Model | Stiffness Values (kN/mm) | (δ/H) Ratios | The Ratio of Initial Loop Stiffness | The Ratio of Max. Load Stiffness |
First Loop | Max. Load | Last Loop | Max. Load | Last Loop |
Model-1 | 12.58 | 2.20 | 1.19 | 0.030 | 0.050 | 1.00 | 1.00 |
Model-2 | 23.53 | 2.93 | 2.37 | 0.036 | 0.040 | 1.87 | 1.33 |
Model-3 | 29.85 | 4.12 | 3.03 | 0.030 | 0.037 | 2.37 | 1.87 |
Model-4 | 68.97 | 11.80 | 3.16 | 0.019 | 0.045 | 5.48 | 5.36 |
Model-5 | 71.43 | 12.73 | 2.23 | 0.011 | 0.050 | 5.67 | 5.78 |
Stiffness reduction graphs of experimental models are given in Fig. 16. The energy consumption rates of the experiment samples when they reach their maximum lateral load carrying capacity are given in Table 6.
When compared to the reference sample, the energy consumption rates were found to be 98% higher in Model 2, 60% higher in Model 3, 83% higher in Model 4, and 78% higher in Model 5. At the end of the test, when it reaches the lateral load carrying capacity, the energy consumption rates are calculated to be 43% higher in Model 2, 22% higher in Model 3, 114% in Model 4 and 87% higher in Model 5 compared to the reference sample. It is seen that Model 4 and Model 5 have 51% more energy consumption ratio capacity at the end of the experiment than Model 2 and Model 3. This result reveals that the shear wall position will also be important in terms of its efficiency in the energy consumption rate. Total consumed energy graphs of experimental models are given in Fig. 17.
Table 6
Experimental Models Energy Consumption Capacities Comparison
Experimental Model | Consumed Energy Values (kNmm) | Consumed Energy Ratios |
Max. Load | End of Experiment | Max. Load | End of Experiment |
Model_1 | 4455 | 6693 | 1.00 | 1.00 |
Model_2 | 8855 | 9585 | 1.98 | 1.43 |
Model_3 | 7168 | 8163 | 1.60 | 1.22 |
Model_4 | 8164 | 14341 | 1.83 | 2.14 |
Model_5 | 7933 | 12576 | 1.78 | 1.87 |
With the help of 7 strain gauges located to the longitudinal and transverse reinforcements in shear walls and columns, unit strain-Lateral load relationship and unit strain-time relationship graphs were drawn. The amount of elongation and shortening in the longitudinal reinforcement at the end of each cycle is determined. When the graphics are examined, it is seen that less deformation occurs in the case of shortening than elongation, as in the limit cases given in Table 7. In stirrups, due to the elongation at the end of each loading cycle, a more symmetrical formation draws attention in the graphics. On the graphs of the unit deformation-time relationship, a gradual increase in the unit deformation has been observed after each loading cycle due to the increase in the lateral force and displacement (Fig. 18 - Fig. 21).
Table 7
Unit Pressure Deformation and Relative Floor Drifts Limits According to TEC2007
Damage Boundary | Pressure Reduction for Concrete and Reinforcement Steel | Tensile Elongation for Reinforcement Steel | Relative Floor Drifts Ratio |
Minimum Damage Boundary | εcu = 0.0035 | εs = 0.01 | δ/h = 0.01 |
Security Bound | εcg = 0.0135 | εs = 0.04 | δ/h = 0.03 |
Collapse Bound | εcg = 0.0180 | εs = 0.06 | δ/h = 0.04 |
As can be seen in the graphics in Fig. 15, the results of strain gauge affixed to the lower stirrup of S3 column in Model 1 and to the lower part of the transverse horizontal body reinforcements of the shear wall in other models were examined. Since there is no pressure shortening in stirrups in general, the unit deformations of the reinforcement in the push and pull cycles have similar values. Maximum unit deformations occurred at the end of the experiment after taking the maximum value of the lateral load and the yield point occurring. In Model 1, tensile elongation occurred predominantly during the test in the lower stirrup in S3 column and the measured unit deformation range was between (-0.0175mm / mm and + 0.003mm / mm). While the unit deformation range of Model 2 is (-0.019mm / mm to + 0.00001 mm / mm), in Model 3 this range is (-0.0037 mm / mm to + 0.0001 mm / mm). Accordingly, when the unit deformations taken from the outer lower transverse horizontal body reinforcements of Ø4mm diameter reinforcement bars of the P1 shear wall are evaluated in the samples where the shear wall is on the outer axis, it was seen that the deformations when the reinforced concrete shear wall is away from the push force in the system are more than the deformations in the case of close proximity. Model 4 and Model 5 behaved similarly. While the unit deformation range of Model 4 is (-0.0037 mm / mm to + 0.0001 mm / mm), in Model 5 this range is (-0.0048 mm / mm to + 0.0001 mm / mm). Consequently, when the unit deformations taken from the outer lower transverse horizontal body reinforcements of Ø4mm diameter reinforcement bars of the P1 shear wall are evaluated in the samples where the shear wall is in the middle axis, it was seen that the deformations when the reinforced concrete shear wall is away from the push force in the system are less than the deformations in the case of close proximity.
As shown in the graphics in Fig. 19, the strain gauge results affixed to the lower part of the S3 column longitudinal reinforcement in Model 1 and to the lower part of the Ø6mm body longitudinal outer reinforcement of the shear wall in other models were examined. In general, the unit deformations that occur during the shortening in the longitudinal reinforcement have occurred less than the elongation. The reason for this situation can be explained as working with the reinforcement at the time of shortening due to the concrete being under compressive stresses, and also because the reinforcement alone withstands tensile stresses at the time of elongation. In Model 1, the unit deformations occurring in the lower longitudinal reinforcement in S3 column during the shortening is occur more than the elongations, being more pronounced throughout the test. The unit deformation range measured in Model 1 was (-0.0045mm / mm to + 0.0033mm / mm). While the unit deformation range of Model 2 is (-0.018mm / mm to + 0.00001mm / mm) and in Model 3 this range is (-0.0624mm / mm to + 0.003mm / mm) values. Accordingly, in the samples where the shear wall is on the outer axis and when the unit deformations taken from the outer lower part of the Ø6mm diameter body longitudinal reinforcement of P1 shear wall are evaluated, it has been observed that the deformations when the reinforced concrete shear wall is far from the pushing force in the system are less than when it is close. Model 4 and Model 5 showed opposite and similar behavior.
While the unit deformation range of Model 4 is (-0.03mm / mm to + 0.0023mm / mm) and in Model 5 this range is (-0.043 mm / mm to + 0.00001 mm / mm) values. Accordingly, in the samples where the shear wall is on the middle axis and when the unit deformations taken from the outer lower part of the Ø6mm diameter body longitudinal reinforcement of P1 shear wall are evaluated, it has been observed that the deformations when the reinforced concrete shear wall is far from the pushing force in the system are less than when it is close.