Rural Masonry Isolating Structure and LRB Experiment: Seismic Resistance Properties and Statistical Data Curve Analyses

The low masonry structure is the most commonly applied building type in rural China. It is possible to install small-diameter, low cost, and easily constructed laminated rubber bearing (LRB) components. Isolation technology has broad application prospects in rural buildings. We developed a small-diameter LRB in this study wherein the isolation layer is set above the floor for easy installation and replacement. We built and tested 4 walls to observe the effects of different LRB thicknesses; we assessed test respective phenomena and seismic parameters accordingly. We ran another test on five small-diameter LRB components with varying horizontal stiffness, different forms of shear strain-equivalent horizontal stiffness, and postyield stiffness while changing the fitting formula for the second shape coefficient to give small-diameter LRB design providing gist.

Multihazard Response Control of Base-Isolated Buildings under Bidirectional Dynamic Excitation

The issues of safety and posthazard functionality of structures under multihazard scenarios are some of the significant challenges in the current dynamic and rapidly growing urban environment. In this paper, multistory base-isolated buildings are investigated under the independent multihazard scenario of earthquake and blast-induced ground motion (BIGM). Multistory building models equipped with five different types of isolation systems, namely, the laminated rubber bearing (LRB), lead-rubber bearing (N-Z system), pure friction (PF) system, friction pendulum system (FPS), and resilient-friction base isolator (R-FBI) are assessed under bidirectional multihazard excitations. The suitability of the isolation systems and their key parameters in protecting multistory buildings is evaluated. Furthermore, the influence of the superstructure characteristics, such as the superstructure damping and the number of stories, is also assessed. The effect of bidirectional hazards on fixed-base buildings is also presented for comparison. The key response quantities of base-isolated buildings are presented and compared for different isolation systems. Parametric investigations are also conducted, and the trends of the response quantities are presented to study the influence of important parameters of isolation systems in protecting the buildings under the multihazard scenario of earthquake and BIGM. The results of the investigation show that the behaviors of the buildings equipped with various isolation systems are different for the two hazards. Moreover, the influences of the key parameters of the isolation systems are found to be different for various hazards. Therefore, the selection of design parameters of isolation systems shall be made with due consideration of the influence of multiple hazards. Additionally, the influence of the properties of the superstructure, such as the number of stories and the damping of the superstructure, on the behavior of the base-isolated buildings under the multihazard loading, is presented.

Evaluation of Seismic Performance Focusing on Increasing Response of Lead Rubber Bearing (LRB) and Over Strength of RC Pier During Earthquake

The characteristics of the seismic bearing change depending on various factors. When an earthquake occurs, the behavior of the bridge may differ from the values expected in the structural design. The shear deformation of the seismic bearing may increase, but it is difficult to reach the fracturede formation. This paper studied the effect of the stiffness due to various dependency and durability on Lead Rubber Bearings (LRB) and the over strength of bridge piers on the bearing behavior when an earthquake occurred. As a result, if the stiffness of LRB reduces within the criteria, seismic performance can be expected safety even if the shear strain designed in the current design is greater than the allowable shear strain. The reason is that the hardening phenomenon in the high strain region of the laminated rubber bearing suppresses the displacement. Also, since the seismic bridges with over strength of the piers have come near elastic behavior when an earthquake occurs, shear strain is easy to be large.

Effects of Shape Memory Alloys on Response of Steel Structural Buildings within Near Field Earthquakes Zone

Base isolation is one of the effective ways for controlling civil engineering structures in seismic zone which can reduce seismic demand. Also is an efficient passive control mechanism that protects its superstructure during an earthquake. However, residual displacement of base-isolation systems, resulting from strong ground motions, remain as the main obstacle in such system’s serviceability after the earthquake. Shape Memory Alloys (SMA) is amongst the newly introduced smart materials that can undergo large nonlinear deformations with considerable dissipation of energy without having any permanent displacement afterward. This property of SMA may be utilized for designing of base isolation system to increase the structure’s serviceability. Here, a proposed semi-active isolation system combines laminated rubber bearing system with shape memory alloy, to take advantage of SMAs high elastic strain range, in order to reduce residual displacements of the laminated rubber bearing. Merits of the system are demonstrated by comparing it to common laminated rubber bearing isolation systems. It is found that the optimal application of SMAs in base-isolation systems can significantly reduce bearings’ residual displacements. In this study, OpenSees program for a three dimensional six-storey steel frame building has been used by locating the isolators under the columns for investigating the feasibility of smart base isolation systems, i.e., the combination of traditional Laminated Rubber Bearing (LRB) with the SMA, in reducing the structure’s isolated-base response to near field earthquake records are examined. Also, a new configuration of SMAs in conjunction with LRB is considered which make the system easier to operate and maintain.

Development of Small-Sized Lead Inserted Laminated Rubber Bearing for Nuclear Component Seismic Isolation

This paper presents a design specification of the small-sized lead inserted laminated rubber bearing (LRB) for application to nuclear component seismic isolation and describes the results of test verification on design performance parameters such as effective horizontal stiffness, equivalent viscous damping ratio, design seismic isolation frequency, and ultimate shear deformation. To do this, two types of LRB, having the same vertical design load of 10 kN but with different shape factors, are designed, fabricated, and tested by the quasi-static procedures. To determine the effective horizontal stiffness and the equivalent damping value from the test results, the new method is proposed and compared with the methods of the ASCE and ISO standards in case that the tangential stiffness curve is not linear in tests. From the comparison between tests and design specifications in the performance parameters, it was found that the design specifications developed in this paper are in a good agreement with the test results. Furthermore, the target design shear deformation limits are confirmed to have sufficient design margins in ultimate shear deformation tests.

Rayleigh Damping Coefficients of Laminated Rubber Bearing

In isolating the ground structure and the above ground structure from seismic loads, a significant device called laminated rubber bearing is usually found in structure. The complexity of the material which is made up from a combination of rubber and steel shim plates in alternate layer, has made it difficult to measure damping value. Damping is a dissipation of energy or energy losses in the vibration of the structure. Measuring the accurate amount of damping is fundamental as damping plays a crucial role in fixing the borderline between stability and instability in structural systems. Therefore, to determine the damping value including dynamic properties in any materials, modal analysis can be used. Hence, the main objective of this research is to determine the Rayleigh’s damping coefficients α and β and to evaluate the performance of the laminated rubber bearing using finite element and experimental modal analysis. Finding shows that, the finite element modal analysis with the addition of Rayleigh’s damping coefficients α and β, shows a good agreement with the experimental modal analysis in term of natural frequencies and mode shapes. Findings show that, the values of natural frequencies reduced when precise Rayleigh’s damping coefficient added in the finite element modal analysis. It can be concluded that both finite element and experimental modal analysis method can be used to estimate the accurate values of damping ratio and to determine the Rayleigh’s damping coefficients α and β as well.