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Showing 3 results for Residual Displacement

A.r. Khaloo, I. Eshghi, P. Piran Aghl,
Volume 8, Issue 3 (9-2010)

In this paper the response of cantilevered reinforced concrete (RC) beams with smart rebars under static lateral loading has been numerically studied, using Finite Element Method. The material used in this study is SuperelasticShape Memory Alloys (SE SMAs) which contains nickel and titanium elements. The SE SMA is a unique alloy that has the ability to undergo large deformations and return to their undeformed shape by removal of stresses. In this study, different quantities of steel and smart rebars have been used for reinforcement andthe behavior of these models under lateral loading, including their load-displacement curves, residual displacements, and stiffness, were discussed. During lateral loading, rebars yield or concrete crushes in compression zone in some parts of the beams and also residual deflections are created in the structure. It is found that by using SMA rebars in RC beams, these materials tend to return to the previous state (zero strain), so they reduce the permanent deformations and also in turn create forces known as recovery forces in the structure which lead into closing of concrete cracks in tensile zone. This ability makes special structures to maintain their serviceability even after a strong earthquake

H. Liu, M. He, J. Guo, Zh. Hou, Y. Shi,
Volume 13, Issue 2 (6-2015)

Self-centering pier (SCP) has been viewed as a remarkable accomplishment which is able to sustain major lateral loading with reduced structure damage in seismic engineering. Stiffness deterioration observed in experiment is vital for the seismic performance of self-centering concrete pier. In this contribution, the associated stiffness deterioration with respect to the structural damage is modeled in a modified analytical model for SCP comprehensively. In the proposed modified theoretical model, the lateral force-displacement relation associated with the stiffness reducing is analyzed. Three damage factors are introduced in the stiffness deterioration analysis to illustrate the damage evolution caused by gradually increasing lateral displacement. The proposed modified quasic-static model with damage evolution or stiffness deterioration has been validated against an experiment we conducted, where a good agreement is clearly evident. Subsequently, a parametric investigation focusing on aspect ratio, initial pre-tension, and ratio of ED (Energy Dissipator) was conducted to evaluate the hysteretic behavior of SCP under quasi-statically cyclic loading.

Volume 15, Issue 4 (6-2017)

Bridges normally undergo nonlinear deformations during a near field strong ground motion resulting in a critical deviation of their columns from the plumb state due to considerable residual deformations. These excessive residual deformations make a bridge, which has not collapsed, ‘irreparable’ and in turn ‘not operable.’ Therefore, reasonable prediction of these types of bridge piers deformations is of great importance in order to evaluate the serviceability of bridges subjected to a seismic scenario. Conventional hysteresis models formulated for typical concrete columns are normally used for this purpose which most of times fail to correctly predict the residual deformations occurred as a result of a one-sided or directivity pulse excitation. The present research aims at development of a peak oriented hysteresis model being able to regenerate residual deformations more reasonable compared to the conventional hysteresis models. This multi linear peak oriented model considers strength deterioration in each half cycle in addition to stiffness degradations in unloading cycles. Yielding points differ in both positive and negative sides of the hysteresis model that enables us to define a different elastic stiffness of both sides in asymmetric concrete sections. Another remarkable property of this model is breaking points and strength deterioration in unloading and reloading stages. This work also compares the obtained results to the conventional hysteresis models, namely bilinear, Clough, Q-Hyst, Takeda and Bouc-Wen in terms of prediction of residual nonlinear deformations in cyclic or dynamic analysis of reinforced concrete single-column bridge piers. The obtained results prove higher relative accuracy of the proposed model.

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