IDEALIZE LOAD-DISPLACEMENT CURVES

•  This software uses the energy equivalence method to idealize the load-displacement curves obtained from monotonic loading tests.

• Experimentally obtained load-displacement and moment-curvatures curves are idealized by the methods described in Figure 1 (please see guideline).  In Figure 1, the area under the bilinear curve is equated to the actual “experimental” curve, and the area of the hatched region A1+A2 is equal to the area of the hatched region A3”.  

 Once the load-displacement curves are idealized, the test results are summarized for:

• Yield strength: Yield strength is determined by using energy equivalence method and shown as fy.

• · Displacement at yield strength: Displacement at yield strength is obtained from corresponding yield strength and shown as  ∆y. 

• Ultimate strength: Ultimate strength is determined by using energy equivalence method and shown as fu. 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 and shown as ∆u.

• Initial stiffness: Initial stiffness is determined dividing the yield strength by the displacement at yield strength and shown as k1. 

• Secondary stiffness: Secondary stiffness is determined by dividing the difference between the ultimate load and the yield load by the corresponding displacement differences and shown as k2.

• Displacement ductility ratio: Displacement ductility ratio is determined by dividing the ultimate displacement to yielding displacement and shown as μD=∆u/(∆y).

• Ductility index: The energy-based ductility index is determined as the ratio of the cumulative energy dissipation to the cumulative dissipated energy at the yield strength and shown as μE=Eu/Ey.

• Cumulative energy dissipation capacity: Dissipated energy capacities are determined by integrating the area under the load–displacement curves and shown as E.