Improvment of a locking mechanism for the seismic isolation system made of spring tube braces

In the scope of the this M.Sc. thesis, a locking mechanism that is on the new seismic isolation system made of spring tube braces has been invented and studied in order to get a relatively high initial stiffness on the system to satisfy the comfort requirements for low intensity earthquake and wind effects. Experimental and theoretical investigations was carried out during the term of the study at the Structural and Earthquake Laboratory of Istanbul Technical University, (ITU). In the first phase, various alternatives was evaluated as locking system on the spring tube braces. When effective and low cost system is considered proper hole is opened to get through suitable material to supply high initial stiffness on the spring tubes. In the second phase, material experiments are performed to find suitable material for locking system. At the beginning of the study, a experimental setup which has double shear effects is prepared to make material experiments. The experiments conducted show that HSS (High Speed Steel) type steel sticks which conclude carbon, chrome, vanadium, tungsten and molibden is suitable to use as the locking material. Experiments are also realized to have stiffness and ultimate load values at different diameters of the HSS type steel sticks. Therefore, according to low intensity ground motions, suitable diameter of material can be select for locking system. In the third phase, high speed steel sticks which are suitable for use in respect to diameter are implemented (attached) to spring tube and experiments are realized under the vertical MTS. After having concluded experiments, the results show forcedisplacement values of spring tube. Owing to these values we deduced ultimate force and stiffness values of the spring tube that has locking mechanism. In the fourth phase, spring tube braces which has the locking mechanism are attached to ¼ scaled isolation story. Then, the isolation story which consists of hinge-ended steel columns subjected to varying horizontal load levels is assessed in the quasistatic tests. The quasi-static tests carried out on the modified spring tubes prove that there is a relatively high stiffness between the analytical and experimental studies. Next, representative 2 story loads which are used in Karayel et. Al, 2016 research paper take on load to isolation story and quasi-static experiments are carried out to understand behaviour of the new system. Thus, analytical and experimental results are compared to prove locking system's efficiency. Finally, studies has been carried out regarding effect on people of low intensity ground motion and some acceleration values which has some effect on people are derived.