FINITE ELEMENT ANALYSIS OF MOMENT CONNECTIONS WITH STEEL SHEAR DAMPERS OF DIFFERENT GEOMETRY

Abstract

Since late 90s, extensive researcheshave been conducted on the use ofvarious materials and systems that will absorb seismic energy within the structure itself in order to improve thebehavior of the steel structures under seismic effects. In order to address the issue, an innovative structural system withsteel shear damper was developed, which could not only provide good seismic performance butalso could easily be repaired after a major earthquake. Numerous studies are being carried out with different types of shear dampers around the world.However, interchangeability in the use of such various forms of dampers is yet to be established. Besides, steel shear dampersare not still widely used and its provisionsare not included in the codes. Further regularization of existing dampers are also needed. Hencemore researchesare required regarding steel shear dampers.

In the present study, three-dimensional finite element modelsare developed considering both material and geometric nonlinearity for investigating the behavior of seismic moment connection system with steel shear dampers of different geometry.The developed finite element models have been used to simulate experimental studies done by past researchers for static cyclic loading and it has been found that good agreements exist between present analysis and past experimental results, which established the acceptability and validity of the present finite element models to carry out further investigation.

Study is then carried on shear dampers made of mild steel and having different geometry such as elliptical steel slit damper, butterfly-shaped steel strut damper and pintle damper to find out equivalency of these with oblong steel slit damper having similar plastic strength. Study shows that the existing formulas for predicting plastic strength of these dampers may not be accurate and further refinement is warranted. Some parametric studies have been performed to observe the effects of different parameters such as strut width, strut height, thickness etc. Based on the pattern of parametric study results, closed-form semi-empirical algebraic expression of damper plastic strength is developed for these shear dampers which shows realistic compliance with analysis results. The results of the parametric studies have been compared with energy quantities and presented graphically to better understand the effects of different parameters on the system. It has been shown that the plastic strength predicted by these closed-form semi-empirical analytical expressions are reasonably accurate as found from numerical finite element simulation of experimental results. The proposed expressions of plastic strength of various types of dampers shall enable us to use any one type alternately in a building for earthquake protection of structures