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Idealized load-displacement curves
Idealize your own monotonic or cyclic load-displacement curves for RC Beams and Columns.
Moment-displacement or load-displacement curves can be idealized.
Example excel file
Once the related load-displacement curves are idealized, the test results can be summarized for
- Yield strength: Yield strength is obtained by using energy equivalence method.
- Displacement at yield strength: Displacement at yield strength is obtained from corresponding yield strength.
- Ultimate strength: Ultimate strength is obtained by using energy equivalence method. It should be noted that ultimate load is defined as 85% of the maximum load.
- Displacement at ultimate strength: Displacement at ultimate strength is obtained from corresponding ultimate strength.
- Initial stiffness: Initial stiffness is determined dividing the yield strength by the displacement at yield strength.
- Secondary stiffness: Secondary stiffness is obtained by dividing the difference between the ultimate load and the yield load by the corresponding displacement differences.
- Displacement ductility ratios: Displacement ductility ratio is determined by dividing the ultimate displacement to yielding displacement.
An example of an idealized curve.
Idealized load-displacement curves for RC columns and summarized test results
Once the related load-displacement curves are idealized, the test results can be summarized for the selected specimens.
- Yield strength: Yield strength is obtained from idealized curved.
- Displacement at yield strength: Displacement at yield stregth is obtained from corresponding yield strength.
- Ultimate strength: Ultimate strength is obtained by defining the 85% of the maximum load.
- Displacement at ultimate strength: Displacement at ultimate stregth is obtained from corresponding ultimate strength.
- Stiffness degradation: The stiffness of each RC column is calculated according to procedure described by Sun et al. (2008)."Sun, Z.; Si, B.; Wang, D.; and Guo, X., 2008, "Experimental Research and Finite Element Analysis of Bridge Piers Failed in Flexure-Shear Modes," Earthquake Engineering and Engineering Vibration, V. 7, No. 4, pp. 403-414".
Displacement ductility ratios: The displacement ductility ratio ( ) of each RC column is calculated by dividing the ultimate displacement by the yield displacement.
Cumalative energy dissipation capacity at yield "ΣEy" and ultimate "ΣEu"strength: The cumulative energy dissipation capacity of all RC columns is calculated.
1000 US dolars to idealize 4 test results.
Important notes for uploaded data!!: Following items are needed to be considered to be able to idealize the cyclic load displacement curves for RC columns.
Under normal conditions, in an experimental study, when the load is fully unloaded in pushing or pulling directions, load value should reach to zero value in case of complete unloading.
However, during data collection, the exact zero value cannot be obtained when this value changes from pushing or pulling or from pulling to pushing. There are two reasons can be counted for this situation. The first reason is the sensitivities of the data collection devices, and the second reason is that it cannot reach the exact zero value when the load is unloaded as a result of permanent deformations.
Therefore, for the experimental data received from the data collection device, each cycle must start from zero load and end at zero load. In order to perform the idealization, the raw data from the data collection must be modified for zero.
Modification example from an experimental data is shown as below:
As shown in figure below, when a cycle is completed a recorded load value from data logger is equal to 0.033626856 and not exactly equal to ZERO. The value "0.033626856"should be either converted into ZERO or keep it as same and add additional load value for that displacement "-0.000885651" which is "-0.000885651; 0".
Option a) Covert the -0.000885651; 0.033626856 to -0.000885651; 0
or
Option b) -0.000885651; 0.033626856 keep it as same but add additional data as shown as below:
-0.000885651; 0.033626856
-0.000885651; 0
"This modification is needed to be applied for each following completed cycle to be able to idealize your cyclic load-displacement curves". Note that such modifications do not affect the overall structural behavior test results.
