CHARACTERIZATION OF ENERGY DISSIPATIVE CUSHIONS MADE OF Ni-Ti SHAPE MEMORY ALLOY

Earthquake-resistant design of structures requires dissipating seismic energy by deformations of structural members or additional fuse elements. Owing to its easy-to-produce, plug-and-play, high equivalent damping ratio, and large displacement capacity characteristics, energy dissipative steel cushions were found to be an efficient candidate for this purpose. However, similar to other conventional metallic dampers, residual displacement after a strong shaking is the most notable drawback of the steel cushions. In this work, cushions produced from Ni-Ti shape memory alloy are evaluated numerically by experimentally verified finite element models to assess their impact on the performance of earthquake-resistant structures. Furthermore, a reinforced concrete testing frame is retrofitted with energy dissipative steel and Ni-Ti cushions. Performance of the frames (e.g. dissipated energy by the cushions, hysteretic energy to input energy ratio, maximum drift, and residual drift) with different types of cushions are evaluated by nonlinear response history analyses. The numerical results showed that the steel cushions are effective to reduce peak responses, while Ni-Ti cushions are more favorable to reduce residual drifts and deformations. Hence, a hybrid system, employing the steel and shape memory alloy cushions together, is proposed to reach optimal seismic performance.

Probability Distribution of ADAS Metal Dampers in R.C. Buildings Using Nonlinear Analysis: التوزيع الاحتمالي لمخمدات معدنية من نوع ADAS في المباني البيتونية المسلحة باستخدام التحليل اللاخطي

This study discusses the effect of metallic yielding dampers (ADAS) on the behavior of reinforcement concrete buildings when exposed to seismic shocks. The objective of the study is to reduce the negative impacts on the main structural elements (plastic, fall) by using the technique of metallic dampers. The method of metallic dampers is one of the modern ways based on the principle of dissipating the resulting energy from the seismic shock and reducing the needed energy in the main structural elements of the building to keep it in a flexible state. This technique also provides a controlling mechanism for story displacement, the handling of the soft story mechanic and the torsion mechanic of the buildings. In this study, the effect of the addition of ADAS dampers on the construction behavior was observed in terms of (building period, base shear, roof displacement, roof acceleration, story displacement, dissipative energy). Based on the preceding, this study will give the possibility of predicting the behavior of the building when using ADAS metal dampers in the reinforced concrete structures with their distribution methods.

Optimum Strength Distribution for Structures with Metallic Dampers Subjected to Seismic Loading

A key aspect of the seismic design of structures is the distribution of the lateral strength, because it governs the distribution of the cumulative plastic strain energy (i.e., the damage) among the stories. The lateral shear strength of a story i is commonly normalized by the upward weight of the building and expressed by a shear force coefficient αi. The cumulative plastic strain energy in a given story i can be normalized by the product of its lateral strength and yield displacement, and expressed by a plastic deformation ratio ηi. The distribution αi/α1 that makes ηi equal in all stories is called the optimum yield-shear force distribution. It constitutes a major aim of design; a second aim is to achieve similar ductility demand in all stories. This paper proposes a new approach for deriving the optimum yield-shear force coefficient distribution of structures without underground stories and equipped with metallic dampers. It is shown, both numerically and experimentally, that structures designed with the proposed distribution fulfil the expected response in terms of both damage distribution and inter-story drift demand. Moreover, a comparison with other distributions described in the literature serves to underscore the advantages of the proposed approach.