 |
 |
Misleading of the Stiffness Degradation Curve from Monotonic Loading Test
Supot Teachavorasinskun Associate Professor
Department of Civil Engineering, Faculty of Engineering, Chuloangkorn University, Phayathai Rd., Pathumwan, Bangkok 10330, Thailand Pulpong Pongvithayapranu Department of Civil Engineering, Faculty of Engineering, Chuloangkorn University, Phayathai Rd., Pathumwan, Bangkok 10330, Thailand
| |
|
ABSTRACT |
The maximum shear modulus is generally defined from the stress-strain relationship obtained from laboratory tests. The monotonic loading test has recently gained popularity in this role due to its simplicity. Stiffness degradation curve; the semi-logarithmic plot between stiffness and strain level, is usually prepared in such a study. The present study points at the shortcoming of the stiffness degradation curve obtained from a monotonic loading test in determination of the maximum stiffness. A simple calculation based on errands of the semi-logarithmic plot is presented first. Next the results of the triaxial tests that have been conducted for this study are presented in order to demonstrate this discrepancy. It is observed that the degradation curve from a monotonic loading test can mislead the determination of the maximum stiffness. The explanation offered is that the initial or reference point (i.e., initial stress and strain) used for computing the secant stiffness plays a significant influence on the computed value of the maximum stiffness. Moreover, the conventional degradation curve defined from any point on the stress-strain relationship will always exhibit the elastic-like behavior. Namely, the secant stiffness gradually decreases from its maximum value. The present study calls for great caution in usage of the degradation curve obtained from a monotonic loading test.
Keywords: Secant stiffness, Stiffness degradation curve, Stress-strain relationship, Initial stiffness
Get the entire paper (pdf)
Go back to the TOC
