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Fiber Reinforced Elastomeric Isolators (FREIs) have been proposed as an alternative to Steel Reinforced Elastomeric Isolators (SREIs) and several studies have highlighted the advantages of this technology over conventional devices. When FREIs are unbonded to the top and bottom substructure, the bearings exhibit softening under imposed lateral deformations with or without instability depending on the aspect ratio of the device. Research studies available in literature have focused on the response of rectangular bearings when loaded in shear along their base. Very little is known on the lateral response of these devices under bidirectional shear loading. This study aims to assess the response of rectangular FREIs under combined axial and bidirectional shear loads and to show the effects of (i) the secondary shape factor of the bearing, of (ii) the axial pressure, of (iii) the horizontal loading direction on the stability of these devices. As result of a large set of analyses, stability domains have been derived which take into account all of the variables listed above. Based on the results of this work, simple to use design considerations can be derived. Results of this study contribute towards the real implementation of this technology particularly in developing regions of the world.

The use of elastomeric bearings for base isolation is well established through several studies. This paper is mainly focused on an innovative Fiber-Reinforced Bearing (FRB) developed using recycled...

Since (Aronoff, Mark. 1994. Morphology by itself. Cambridge, MA: The MIT Press), the disparate morphosyntactic roles that past participle forms have in Latin (and Italian) morphology have played a central role in arguing for morphomic approaches. In this article, I will propose an alternative analysis of the special behavior of these participle forms in Distributed Morphology (DM, Halle Morris, & Alec Marantz. 1993. Distributed morphology and the pieces of inflection. In Kenneth Hale & Samuel Jay Keyser (eds.), The view from building 20: Essays in linguistics in honor of Sylvain Bromberger, 111–176. Cambridge, MA: MIT Press.). In particular, I will propose that morphological spell-out, as a first stage of the PF derivation, includes morphological repairs triggered by abstract “morphomic” constraints. These repairs can insert “ornamental” pieces – structures that are not motivated syntactically or semantically but only morphologically – to mediate the interface between abstract syntactico-semantic structures and surface PF construction. I will demonstrate the role that these repairs play in accounting for the surface convergence between perfect and passive participle forms, and adjectival stative ones, and for the appearance of past participles in nominalizations. The article ends with an analysis of Latin past participle morphology focusing on its historical development. The first part of this analysis deals with the development of Latin verbal structure from Proto-Indo-European (PIE) and in particular with the development of “ornamental” thematic vowels. It then turns to a brief investigation of the historical development of the Latin past participle exponent /-t-/ from PIE adjectival suffix *-tó-, and of the PIE agentive and action/result nominal suffixes *-tér/tor, *-ti-, *-tu, *-men-(to)-. This will lead to a discussion of Latin nominalizations, the supine and the future participle and a possible explanation of why they contain participial morphology.

A phonological process can be accounted for not only in terms of a rule that simultaneously identifies a configuration to be changed and prescribes what to do to it, but also by means of a negative constraint that states that a certain configuration is illicit but does not prescribe how to fix or remove it. A further operation—a repair—is used to do that. The second approach is inherently more complex since other possible repairs need to be excluded. Starting from the mid-1980s there was a general feeling among phonologists that such complexity was needed in phonological analysis, if not always, at least in the account of certain processes. I will investigate the theoretical and empirical motivations that led to the development of constraint-and-repair approaches in the works of Singh, Paradis, and Calabrese, and their collaborators, and also discuss the differences and commonalities these approaches have with Optimality Theory.

Fiber-reinforced elastomeric isolators (FREIs) are generally installed in unbonded configurations. Because of the simultaneous application of axial loads and large lateral deformations, instability of these bearings is a major concern. This paper shows the results of a large series of 3D finite element analyses (FEAs) on square-shaped FREIs. The analyses aimed at obtaining easy to use design charts where the stability limits of these devices can be rapidly determined. The output of the analyses is compared to analytical results available in literature and the limitations of well-known closed form solutions are discussed.

Over the last decade, significant efforts have been dedicated to develop novel low-cost seismic protection systems that could be used on a large scale in developing regions of the world. In the attempt of reducing the cost of conventional base isolation devices, the feasibility of using flexible reinforcements to replace the steel sheets of traditional steel-reinforced elastomeric isolators (SREIs) has been validated. It has also been verified that these bearings can be installed in unbonded configurations. Previous research has verified the performance of fiber-reinforced elastomeric isolators in unbounded configuration (U-FREIs) using recycled elastomers. The use of recycled rubber to manufacture U-FREIs is very appealing because of its low-cost and its limited environmental impact. In this paper a thorough comparison of the performance of natural-rubber unbounded fiber-reinforced elastomeric isolators (NU-FREIs) and that of recycled rubber bearings (RU-FREIs) is proposed. To this end, the paper discusses the manufacturing and the main features of the two different technologies, as well as the results of experimental tests on the devices and small-scale structures tested on a shaking-table. Overall, the performance of NU-FREIs was found to be better than that of RU-FREIs. Nevertheless, recycled rubber devices are very promising when it comes to protecting non-engineered constructions from moderate to high seismic inputs at a fraction of the cost of conventional technologies.

Nowadays, the structural health monitoring through the identification of nonlinear dynamic systems is frequently applied in the field of civil engineering. An unscented Kalman filter (UKF) is proposed in this paper, to estimate the coefficient of friction of friction-based isolators (Curved Surface Sliders), using the measured accelerations of the isolated superstructure as measurement input in the UKF. The results of a numerical simulation of a two degree of freedom system, isolated with Curved Surface Sliders, are used in order to evaluate the UKF estimation results and to prove its reliability. Simulation results prove an excellent state estimation accuracy obtainable through this approach and the ability of the UKF to identify the coefficient of friction. The methodology can be used for the determination of the friction coefficient of sliding isolators in real applications to identify their state of wear.

© 2020 The study of Fiber Reinforced Elastomeric Isolators (FREIs) has gained momentum over the last decade for their potential to be adopted directly under the foundation of masonry buildings with no need for costly rigid diaphragms and transfer structures, which are required for the application of conventional base isolation (BI) devices. While the possibility of base isolating masonry structures with no diaphragms at the isolation level is fascinating, this requires FREIs with a tunable response in all 3 directions (i.e., devices that can be engineered to perform in a specific way in each direction of loading). It is known that unbonded FREIs exhibit softening and instability under large displacements. While softening of the bearings is beneficial because it reduces the force demand on structural elements, instability is not. This is particularly true as the unstable branch of FREIs is followed by a sharp hardening response. With the aim of contributing (i) towards the development of tunable FREIs and (ii) towards the development of FREIs with tunable hardening under large lateral deformations, this manuscript describes the findings of a wide set of Finite Element Analyses (FEAs) performed to assess the effectiveness of modifying the stiffness and the lateral response of FREIs through lateral holes. Results of the analyses show that, a simple to implement strategy can be used to tune the lateral response of FREIs to a desired hardening and lateral displacement capacity. The findings of this work constitute a step towards the development of scalable technologies for the isolation of non-engineered buildings in developing regions of the world., Engineering Structures, 222, ISSN:0141-0296

This paper describes the results of bidirectional shaking-table tests performed on novel, low-cost, and eco-friendly recycled-rubber fiber-reinforced bearings (RR-FRBs). The research aims to demonstrate the adequacy of square bearings made of recycled rubber when it comes to performing a base isolators in low-rise residential buildings in developing regions of the world. The results of shear tests on RR-FRBs are described in this paper as well as the response of a base-isolated prototype building under bidirectional ground-motion excitation. Compared with the results of a fixed-base structure, the peak drift ratio, peak base shear, and peak acceleration on the different floors are significantly reduced for the base-isolation system of the RR-FRBs. The results of this work confirm the option of adopting RR-FRBs as base isolators in real structures, with the stability of the devices under major bidirectional excitation requiring further investigation.

The dynamic motion of liquid sloshing in a container due to an external excitation can cause pressure pulses that severely damage the structure. In this study, a 2D rectangular tank was used to numerically model the hydrodynamic characteristics of sloshing and the pressure response in a typical industrial container. Harmonic and ground motion excitations were considered, and seven recorded ground motions were used to simulate the pressures at specified monitoring points. The contributions of the filling depth, ground motion components, and damping baffle to the pressure response history under impulsive and convective mode were examined. Based on the analysis of the dynamic response, a suitable damping baffle system was developed for all seismic excitations. The results of this work contribute toward improving tank design in earthquake-prone regions of the world.

The lack of validated physical models concerning the degradation of the coefficient of friction of sliding isolators induced from the heating of the sliding surfaces during the seismic motion hampers the interpretation of experimental data and the formulation of accurate numerical models. An estimator based on a Constrained Unscented Kalman Filter (CUKF), suitable for real-time monitoring, combined with a Random Walk Model approach (RWM) which identifies the friction degradation function without the a priori knowledge of a physical model and ensuing analytical law has been developed in the study. Both numerical analyses and experimental tests of a 2 DOF shear-type physical model are employed to demonstrate the validity of the technique. The proposed estimator is able to provide an accurate estimation of the state of the system, by predicting the structural displacement histories, and to identify the hysteretic degradation function in different friction conditions, from low to high friction.

Fiber Reinforced Bearings (FRBs) have proven to be a valuable rubber-based base isolation technology in which flexible fiber reinforcements are used to replace the steel layers commonly adopted for the manufacturing of Laminated Rubber Bearings (LRBs). Thanks to the low weight and cost of FRBs, these devices could prove to be instrumental for the promotion of base isolation applications to houses and residential buildings of developing countries of the world in seismic regions. This study is based on the results of a large set of Finite Element Analyses (FEAs) aimed to assessing the performance of FRBs under combined axial and shear loads. The aim of this work is that of filling a lack of knowledge regarding the lateral displacement capacity of FRBs: research studies available in literature do not consider the effects of axial pressure, material properties, primary and secondary shape factors on the response of these devices under combined axial and lateral loads. Conclusions of this study underline that the simple design formula commonly adopted for the design of FRBs underestimate the effect of the axial pressure in limiting the lateral displacement capacity of the bearings. Moreover, available simplified formula, do not offer an accurate estimate of the force response of these bearings under combined loads. Additional FEAs are needed to extend the results of this study to bearings of other shapes, including circular and square isolators.

Rubber based devices for seismic isolation have been adopted worldwide to protect buildings and bridges from seismic events. Very recently, a significant research effort has been dedicated to the study of Fiber Reinforced Bearings (FRBs), a low cost rubber based device for seismic hazard mitigation. In some applications, FRBs could be preferred over traditional steel reinforced isolators as: (i) they are lighter than conventional devices, (ii) FRBs can be produced with an easy manufacturing process where each bearing is cut to size and shape from a pad of large dimensions, (iii) FRBs require materials with low mechanical properties and cost. This is because FRBs are generally adopted in unbounded configurations and they are free to roll off from the supports. While these devices have shown to be an effective passive protection strategy in many applications, the effects of aging and other environmental conditions on the mechanical properties of these bearings are still to be addressed. With this consideration in mind, the aims of this work are those of: (i) studying the long-term performance and durability of FRBs through experimental testing, (ii) verifying the effects of aging on the response of FRBs both in compression and shear, (iii) determining the effects of aging of the bearings on the seismic response of a benchmark base isolated building, while (iv) comparing the as new and aged response of neoprene FRBs against that of conventional steel reinforced bearings. This work contributes toward determining the viability of FRBs as base isolation devices for residential buildings and toward determining the effects of their aging on the seismic response of a typical residential building.

The aim of this study is to assess the applicability of two well-known hysteresis models for the prediction of the response of a Recycled Rubber – Fiber Reinforced Bearings (RR-FRBs) base isolated building under ground motion excitation. Results of experimental tests on low-cost rubber bearings are used to determine their response under cyclic loading, and to derive the parameters of the Bilinear and the Bouc–Wen hysteresis models using consolidated procedures. Response History Analyses (RHAs) are then performed to assess the behavior of a prototype building when base isolated with the low-cost devices. The outputs of RHAs are then compared to shaking table test results to validate the capability of the hysteresis models of predicting the peak structural responses under ground motion excitations. Findings of this research confirm the advantages of using low-cost rubber devices for earthquake hazard mitigation. The potentials and limitations of adopting simple models of hysteresis when assessing the seismic response of a RR-FRBs base isolated structure are discussed in this study.

This paper presents the results of a numerical and experimental study aiming to define the vertical and horizontal stiffness of Fiber-Reinforced Elastomeric Isolators (FREIs). In FREIs, the conventional steel shims of laminated rubber bearings are replaced by flexible fiber reinforcements. The axial and lateral response of these bearings is influenced by the flexibility of these layers. This study describes results of an analytical model capable of providing an accurate estimation of the vertical and horizontal stiffness of the bearings under static and dynamic loads. Results of this analytical model are compared to output of finite element analysis (FEM) available in literature. The influence of the geometry of the isolator (i.e., strip and circular shape), its shape factor and type of reinforcement on the vertical and horizontal stiffness are discussed. Considerations are also given on the effects of the compressibility of the rubber on the axial and lateral response of the devices.

The aftermath of the Mw 7.1 Central Mexico earthquake struck at 13:14 CDT on 19 September 2017 confirmed, once again, the need of introducing seismic mitigation technologies that can effectively be implemented on a wide scale to reduce the seismic risk in developing regions of the world. With this in mind, the aim of this paper is the validation of Recycled Rubber-Fiber Reinforced Bearings (RR-FRBs) as base isolation devices for low-cost houses in developing counties. Results of Response History Analyses (RHAs) of a RR-FRBs base isolated residential building are discussed in this work, together with the design, Finite Element Analyses (FEAs), manufacturing and testing of full-scale prototype bearings for the building under investigation. In addition, the seismic performance of the RR-FRBs base isolated structure is compared to the response of the same building when isolated at the base with conventional devices, namely Laminated Rubber Bearings (LRBs) and Friction Pendulum Systems (FPSs). Results of this work underline the high potential of these low-cost bearings as base isolation devices for residential buildings, confirming the possibility of achieving a significant improvement of the seismic performance of ordinary structures by using the low-cost and easy to manufacture RR-FRBs.

The dynamic performances of a new typology of rubber isolators are discussed in this paper. The devices are denominated recycled rubber-fiber reinforced bearings (RR-FRBs). RR-FRBs are made by replacing natural rubber, commonly used for the production of structural bearings, with a recycled rubber-like material obtained by the reuse of exhausted tires and/or industrial leftovers. In RR-FRBs, steel transversal reinforcements are replaced by fiber sheets and vulcanization is avoided by using a polyurethane adhesive for bonding of the different layers. Thanks to the aforementioned characteristics, devices are extremely low-cost and lightweight if compared to traditional bearings for structural control. This paper presents an overview of theoretical models for the analysis of the compressive and shear behavior of the isolators. Moreover, the paper describes the findings of an experimental campaign conducted to assess the behavior of RR-FRBs both in compression and shear. Different reinforcement materials, geometries and configurations were tested. The study constitutes a deep assessment of the technology’s potentiality. The work underlines the possibility of using RR-FRBs for seismic risk mitigation of low-cost housing in seismic prone regions of the world.

An experimental study on unbounded square carbon Recycled Rubber–Fiber Reinforced Bearings (RR-FRBs) was conducted to investigate their lateral and vertical behavior, under seismic loading. These low-cost rubber bearings are innovative elastomeric bearings that employ recycled rubber and fiber as reinforcement material. They have significant advantages compared to those bearings made up of natural rubber reinforced by steel layers or fiber sheets: higher dissipation capacity, lower manufacturing cost, light weight. RR-FRBs are intended for seismic isolation of ordinary low-rise buildings located in high seismic risk regions, and are designed to be mounted with no need of bonding to the upper and lower structures. This feature allows them to deform freely, reducing, and possibly eliminating, the tensile stresses generated by shear deformations. In this work, the seismic performance of the proposed bearings is investigated by means of both experimental tests and Finite Element Analyses (FEAs). The study provides useful information on both horizontal and vertical stiffness, and on the damping properties of the isolators. Moreover, a description of the instability of the bearings is discussed. The sensitivity of RR-FRBs to lateral displacement history and vertical pressure applied on the bearings is pointed out. Moreover, the validity of easy to apply design criteria is discussed.