In this research, an innovative damper with Austenite Nitinol wire was designed and constructed. This damper has the ability to withstand tensile and compressive stresses and when exposed to external forces half the wires are in tension. The shape memory alloy wires have been anchored in a modern and simple manner, so as the amount of dissipated energy is increased, the thermodynamic properties of the will not change. With the construction of this device, using a simple and accessible material, a damper with axial force mechanism has been created. The aforementioned damper is also easy to use in different parts of the structure. After the training of shape memory alloys, the damper was subjected to a quasi-static loading test according to a selected protocol with different strain rates. The test displacement range is 5 mm and the variable loading frequency is from 0.001 to 5 Hz. The results show that increasing loading frequency, leads to an increase in the temperature of the memory alloy; thus both the high and low stress levels of the transformation plateau increase and approach each other. Therefore, the inner region of the curve decreases, resulting in a decrease in the amount of dissipated energy. The device has a steady behavior in various load cycles because of the presence of a memory alloy after training it, and there is no sign of reduced hardness and resistance. The cyclic behavior is also spotted completely stable and considerably ductile. Because of its return to its original state, it can be used repeatedly. In order to increase the dissipated energy, steel wires have been used in different ratios including four different types of steel and memory alloy in parallel with Nitinol. The results show that increasing the ratio of the area of the memory alloy to the steel in the device reduces the residual deformation and the viscous damping of the device. The temperature of the memory wire was investigated in a super-elastic structural regime during loading at different rates. In the next step, it was checked how the device operates after generating a secondary yielding in the alloy during cyclic loading up to the maximum feasible displacement in the machine. In the numerical study, the constructed damper are modeled with OpenSees software and the results of numerical analyzes are the verified using the results of laboratory analyzes. Employing nonlinear time history analysis and the nonlinear incremental dynamic analysis, the seismic performances of structures 3, 7 and 12,have been eva‎luated. The damper is eva‎luated for four types, according to principles of the memorizing damper, in which the maximum strain experienced should be less than the strain of the end of the transformation. The first type of the damper has a steel wire, in the second type uses shape memory alloy that the amount of SMA choose based on the hardness of the steel, the third type of the damper has memory alloy with a memory material based on the steel yielding force and the fourth type damper has a memory alloy, the amount of material is considered to be the average yield point and hardness of the steel. During numerical studies, as expected, the frame with a shape memory alloy, even in the third type, displays less residual relative displacement ratios than the first one. The main purpose of the use of memory alloy dampers is to reduce the proportional displacement of the floor, which is well suited to all frames. Therefore, in this part of the study, according to the results of four design types for frames, a new criterion for comparing steel dampers with dampers with a memory alloy is presented. Accordingly, the design basis for comparing should be a proportion of yielding point to hardening point, rather than hardening of the two materials.

پيام اسدي

حسين تاجمير رياحي، محمود كدخدايي

حسين عموشاهي، فرهاد بهنام فر