The Influence of the Friction-Sliding Coefficient of Support Structures and Parameters of Seismic Actions on Reactions and Reliability of Structures with Seismic Protection

The study is focused on a structure represented by a multimass elastic cantilever rod with dry friction seismic isolation elements in the support part under a horizontal random impact of a seismic type. The paper aims at investigating the seismic reaction and selecting optimal parameters of the seismic isolation system involving random impact characteristics, limit parameters of the structure, and the seismic isolation system. The researches are based on dynamic computations; the impacts and fluctuations of the system are random processes. The dynamic model of the structure with the considered seismic isolation is presented in the form of a cantilever rod with concentrated masses; a system of differential equations describing the displacement of the structure with the seismic-isolating sliding elements at the level of the top of the foundations is compiled; and a seismic impact is modeled in the form of a nonstationary random process. An algorithm is developed to integrate the system of differential equations of motion and to determine the statistical characteristics of the seismic reaction and reliability indicators of the structures with the seismic isolation. A method aimed at evaluating effectiveness of the seismic isolation system and selecting its rational parameters is suggested. We developed the computational dynamic model of the structure with the seismic-isolating sliding elements installed at the top level of the foundations, and elastic and rigid limiters for the movement of the sliding supports. This model is made in the form of a multimass cantilever rod that takes into account the relative movements of the masses and the stops of the system on the movement limiters. The structure’s movement under a seismic impact is described by a system of differential equations that takes into account the conditions of transitions of the structure from the state of sticking to the state of sliding and vice versa. The statistical characteristics of the seismic reaction and the reliability indicators of the structure in the process of vibrations are determined for different values of the maximum acceleration of the ground vibration, the prevailing period of impact, the number of masses in the calculated model and the coefficient of friction-sliding of the support elements. The influence of the impact parameters and the system on the efficiency of the seismic isolation of the structures with sliding elements is estimated. The proposed approach to selecting the optimal parameters of the seismic isolation system can be used as a research method aimed at improving efficiency of systems with different design options for seismic isolation of structures.

PERANCANGAN ALAT UJI DEFLEKSI BATANG KANTILEVER FLEKSIBEL

Deflection is the change in shape experienced by the beam in the y direction due to the vertical loading applied to the beam or bar. Cantilever rods are if one end of the beam/rod is clamped and the other end is free. In this study, a flexible cantilever rod deflection test device was designed. This tool is used to determine the deflection/deflection that occurs in the beam/strip plate after being given a load. The method used is library research, a data collection method that is carried out by reading, studying, and researching the relevant literature with the title of this thesis which aims to collect data and analyze a theoretical understanding. This research will focus on designing and testing flexible cantilever rod deflection test equipment and utilizing beam/ strip plate as a test specimen for flexible cantilever rods. This tool has a height of 100 cm and a width of 90 cm and this tool is equipped with an HC-SR04 sensor which is directly connected to a digital number. The results of testing the strip plate with a load of 1 kg and 1.5 kg using the HC-SR04 sensor showed that the deflection at the smallest end was 20 mm, and the largest value was 30 mm. the theoretical calculation with equation (2-9) obtained the smallest result of 1.06 mm and the largest value of 3.5 mm.Defleksi adalah perubahan bentuk yang dialami balok pada arah y akibat adanya pembebanan vertikal yang diberikan terhadap balok atau batang. Batang kantilever yaitu jika salah satu ujung balok/batang dijepit dan yang ujung lain bebas. Pada penelitian ini dirancang sebuah alat uji defleksi batang kantilever fleksibel alat ini difungsikan untuk menentukan lendutan/defleksi yang terjadi pada beam/plat strip setelah diberi beban. Metode yang digunakan yaitu dengan penelitian kepustakaan suatu metode pengumpulan data yang dilakukan secara membaca, mempelajari, dan meneliti literature-literature yang relevan dengan judul skripsi ini yang bertujuan untuk mengumpulkan data dan menganalisa suatu pengertian yang bersifat teoritis. Pada penelitian ini akan berfokus pada perancangan dan uji coba alat uji defleksi batang kantilever fleksibel dan memanfaatkan beam/plat strip sebagai bahan spesimen uji batang kantilever fleksibel. Alat ini mempunyai tinggi 100 cm dan lebar 90 cm dan alat ini dilengkapi dengan sensor HC-SR04 yang langsung terhubung dengan digital number. Hasil pengujian plat strip beban 1 kg, dan 1.5 kg menggunakan sensor HC-SR04 didapatkan hasil defleksi pada ujung yang terkecil yaitu 20 mm, dan pada nilai yang terbesar 30 mm. pada perhitungan secara teoritis dengan persamaan (2-9) didapatkan hasil terkecil 1.06 mm dan nilai yang terbesar 3.5 mm.

OFF-CENTER COMPRESSION OF THE ROD BY POTENTIAL AND NONCONSERVATIVE FORCES

The paper studies the stability of the rectilinear form of equilibrium with the construction of the boundaries of the stability region for a rod with uniformly distributed mass. The stability of the cantilever rod is considered for the off-center application of potential and tracking forces. In case of non-conservative loads, when it is possible to lose the stability of the equilibrium position, a dynamic method of research is used. it is shown that the influence of the eccentric application of loads does not affect the location of the flutter boundary, but in contrast to the classical problem, the rod oscillations do not occur in the vicinity of the rectilinear form of equilibrium, but in the vicinity of the curved shape determined by the eccentricity value.

Transient Dynamic Analysis of a Cantilever Rod with Axial Impulse Loading Using Finite Element Method

The behavior of bodies subjected to impulse loading is of prime importance in the study of forces that occur in impulse facilities. Before performing the actual tests, theoretical and numerical simulations are carried out to obtain the response of bodies subjected to impulse loading. The simplest model for this study can be considered as a rod of circular cross section fixed at one end and free at other end. When a transient impulse load is applied on a body, vibrations occur in the body for the brief period of time. In this paper, the effect of a half sine impulse force applied on a cantilever rod in the axial direction has been discussed. The displacements at the tip of the rod were obtained based on two theories, the basic vibration formulae and FEM analysis. Simulations were performed using ANSYS and compared with the displacements obtained from the two theoretical methods.

A new measurement method for operation mode dependent dynamic behavior of magnetorheological fluid

This paper presents a new measurement method to investigate the operational mode dependent dynamic behavior of magnetorheological fluid. The proposed measurement system is designed using an electromagnetically actuating cylindrical rod coupled with the magnetorheological fluid squeezing setup. The cylindrical rod is clamped to base at one end and the other end is free to move in the z- and y-axis. A disc-type permanent magnet is attached to the free end of the cantilever rod and an electromagnetic actuator is placed nearer to the permanent magnet. The magnetorheological fluid squeezing setup is mounted nearer to the fixed end. The magnetorheological squeezing setup is designed using two electromagnetic coils placed face to face in z-axis with the gap of “ d”. The magnetorheological fluid is placed between the gap “ d” to form the squeezing effect. The direction of vibration of the cantilever rod to bottom surface is determined by the angular position of electromagnetic actuator. The actuator position is fixed to the desired angle with the help of stepper motor setup. The horizontal direction of vibration of cantilever rod produces the shear mode operation of the magnetorheological fluid in the magnetorheological fluid squeezing setup. Similarly, the vertical and intermediate direction of vibration of rod produces the squeeze and coupled mode operation of the magnetorheological fluid, respectively. The analytical and experiment analyses to determine the dynamic damping behavior of the magnetorheological particles for various directions of actuation angle is undertaken using the proposed measurement system. The analytical model of the proposed measurement system is firstly derived and the experimental setup is then developed in real-time laboratory environment. The analytical and experimental results show that the dynamic damping behavior of squeeze mode operation of the magnetorheological fluid is superior to the shear and coupled mode operation of the magnetorheological fluid. The effectiveness and novelty of the proposed measurement system is demonstrated by presenting dynamic force variation and vibration amplitude reduction at different modes like squeeze, shear, and intermediate mode operation of the magnetorheological fluid.