A Possibility to Build Isolated Masonry Housing in High Seismic Zones Using Rubber Seismic Isolators

New residential buildings in developing countries often have inadequate seismic protection, particularly for masonry. Such material is widely preferred because the cost and application are relatively cheap. To decrease the vulnerability, an interesting option is represented by seismic isolation, but the cost should remain relatively low, and this is the reason why rubber isolation with few pads remains the most suitable technical solution to adopt. In this study, we deal with a newly conceived low-cost seismic isolation system for masonry buildings relying on elastomeric bearings. The elastomeric isolator here proposed consists of few layers of rubber pads and fiber lamina, making it cheaper comparing to the conventional isolators. A detailed 3D finite element (FE) analysis to predict the behavior of the low-cost rubber isolator undergoing moderate deformations is carried out. A Yeoh hyperelasticity model with coefficients estimated through available experimental data is assumed for rubber pads. Having so derived the shear behavior, such isolation system is implemented at a structural level into a two stories masonry house prototype, identifying the 3D model with a damped nonlinear spring model, so making the FE analysis computationally inexpensive. For masonry, a concrete damage plasticity (CDP) model available in the commercial FE code Abaqus is adopted. A nonlinear static-pushover analysis is conducted to assess the performance of the isolated building. To simulate a realistic condition under seismic event, a ground motion data is applied to observe the dynamic behavior of the building by monitoring the damage level of masonry. Through a-posterior estimation, it is also possible to monitor the deformation of the isolators during the seismic excitation, to determine whether the isolator is capable of resisting shear deformations in different angles. According to the results obtained, quite good isolation is obtained with the system proposed, with immediate applicability at a structural level

Vulcanization degree influence on the mechanical properties of Fiber Reinforced Elastomeric Isolators made with reactivated EPDM

Rubber is well known as the basic material for some structural devices, such as seaport fenders and seismic isolators. In practice, to seismically isolate a structure it is necessary to interpose between the foundation and the superstructure a rubber device that increases the period of the superstructure, a feature that allows the structure to be “transparent” to the seismic excitation. A seismic isolator is constituted typically by a package of several rubber pads 1–2 cm thick vertically interspersed with either steel laminas or FRP dry textiles suitably treated. In this latter case the isolator is called FREI (Fiber Reinforced Elastomeric Isolator). FREIs exhibit light weight, easy installation and low cost. In this study, recycled rubber in the form of reactivated EPDM has been used to produce very low cost FREIs, combined with glass fiber reinforcement. To be ready for structural application, the rubber used must be vulcanized correctly to properly create the polymer crosslinking. However, all rubber mechanical properties are strongly affected by curing temperature and curing time. Here, the mechanical properties of a typology of FREI conceived and produced by the authors in prototypes are evaluated through a series of experimental tests and numerical computations, taking into account the different levels of vulcanization degree. Shore A hardness test, uniaxial tensile test, and relaxation test have been conducted and verified through Finite Element (FE) modeling. All collected data allow to precisely determine the curing time and temperature to use in the industrial production to obtain optimal output mechanical properties for FREIs

Seismic Retrofitting of Indonesian Masonry Using Bamboo Strips: An Experimental Study

Unreinforced masonry (UM) is well known as a vulnerable structure against earthquakes. However, it remains a popular structural system for low-rise residential housing in many high-seismicity areas, particularly in developing regions due to its low cost and easy construction. In the present study, a retrofitting strategy using locally available material, bamboo strips, was proposed. In addition to its fast-growing rate, the tensile strength of bamboo is considered high, nearly comparable to its steel counterpart. A series of experimental tests were performed in this study, including the bamboo tensile test, the mortar flexural test, the diagonal compressive shear test on the masonry assemblages, and the in-plane pushover test on masonry wall specimens without and with bamboo reinforcement. The retrofitted specimens with different volumes of bamboo reinforcement were also considered. The results show that the application of bamboo reinforcement, at a proper volume, significantly increases the ultimate strength and the ductility of the masonry wall. Such results indicate that the brittle failure of UM structures can be avoided by means of bamboo retrofitting

Rubber compounds made of reactivated EPDM for fiber-reinforced elastomeric isolators: an experimental study

Rubber recycling technology is a popular issue in many research fields, considering the huge amount of rubber waste in the environment. This paper discusses an application of regenerated ethylene propylene diene monomer (EPDM) to produce vulcanized items such as fiber-reinforced elastomeric isolators (FREIs), which are nowadays considered efficient low-cost seismic protection devices for low rise buildings (e.g., made by masonry) in developing countries. Two types of regenerated EPDM are studies and blended with two different virgin rubbers, Vistalon 3666 and Dutral 4038. The first virgin rubber is used to produce a compound with a hardness of around 30 Shore A, while the latter exhibits 60 Shore A. The present study, which is part of a wider research project aimed at the production of low cost un-bonded seismic isolation devices, focuses exclusively on the determination of both crosslinking degree through rheometer tests and elasticity/mechanical properties of the rubber pads, before and after ageing (hardness, tensile strength, elongation-at-break, stretch-stress behavior before and after ageing). The results show that the compounds with the second reactivated EPDM (type B) exhibit the most satisfactory performance, before and after ageing. This paper discusses also the method of fabrication of FREIs, obtained by the interposition of pads made by the selected recycled rubber and dry glass fiber-reinforced polymer (GFRP) textiles. The hardness tests performed on the sliced FREI specimen indicate that the vulcanization temperature used in the production is roughly suitable to obtain the expected rubber properties

Seismic protection of masonry buildings by means of a reactivated epdm-fiber reinforced elastomeric isolation system

Masonry is widely known as a structure with high vulnerability to horizontal loads. This study investigates the possibility of improving the seismic performance of existing masonry churches using reactivated EPDM (ethylene propylene diene terpolymer) rubber formed as an unbonded fibre reinforced elastomeric isolator (UFREI) type application. Such recycled material can reduce the production cost of the isolation system. Experimental tests are performed to characterize the mechanical properties of the reactivated EPDM. In series, detailed three-dimensional (3D) finite element (FE) models are used to characterize the behaviour of UFREIs. An Abaqus User Element (UEL) is developed to simulate the 3D behaviour of UFREIs for large scale seismic analyses of complex isolated structures. The results of cyclic shear analyses show that the proposed UEL model can accurately predict the UFREI’s behaviour. A series of non-linear dynamic analyses are performed to investigate the seismic response of an historical masonry church in the original and base-isolated configurations employing UFREIs. Numerical results show that the fixed-base model of the church experiences severe and widespread damage, while UFREI is found to be effective in significantly reducing the damage level of the church when subjected to moderate-to-high seismic actions. Moreover, it can be observed that the isolator satisfies the maximum lateral displacement requirements

Design of isolated masonry housing using re-cycled rubber materials

Unreinforced and nonengineered confined masonry are widely used in developing regions for economic reasons. This study investigates the possibility of improving the seismic performance of masonry housing by means of elastomeric isolation reactivated EPDM. Experimental tests are performed to characterize the mechanical properties of the reactivated EPDM. In parallel, detailed three-dimensional (3D) finite element (FE) models are used to characterize the behaviour of unbonded fibre reinforced elastomeric isolators (UFREIs) using reactivated EPDM rubber. An Abaqus User Element (UEL) is developed to simulate the 3D behaviour of UFREIs for scale seismic analyses of isolated structures. The results of cyclic shear analyses show that the proposed UEL model can accurately predict the UFREIs behaviour. A series of non-linear dynamic analyses are performed to investigate the seismic response of a masonry housing prototype in the original and base-isolated configurations employing UFREIs. Numerical results show that the fixed-base model of the housing prototype experiences severe and widespread damage, while UFREI is found to be effective in significantly reducing the damage level of the housing when subjected to moderate-to-high seismic actions. Moreover, it can be observed that the isolator satisfies the maximum lateral displacement requirements

Seismic performance of a masonry house prototype retrofitted using FRP

Masomy is widely employed in the construction of residential buildings due to its relatively cheap cost. particularly in developing countries. However, unenforced masonry structures present inadequate seismic resistance and are highly vulnerable to horizontal loads. This paper, which is based on the results of an experimental campaign, presents the main outcomes of FE analyses conducted to assess the performance of a masonry house prototype retrofitted using fiber reinforced polymer (FRP). The results obtained from nonlinear time history analyses show that the proposed retrofitting strategy using FRP reinforcement can significantly mitigate the damage of the masonry house

Estimation of the functions of some iron-based ternary systems within Miedema model and comparison with experiment

© 2020 The Authors The Miedema model is used to estimate the enthalpy of intermetallic compounds and the solid solution of ternary systems. The results showed that the chemical enthalpy values of the binary systems (Fe-Al, Fe-B, Fe-V, Fe-Ga, Al-V, and Al-Mn) are negative. Whereas, the chemical enthalpy values of the binary systems (Fe-Mn and Al-Ga) are positive. The most negative enthalpy is observed for Fe-Al-Ga, Fe-Al-B, and Fe-Al-Sn systems with a mole fraction of 50% of Fe. For ternary systems, the enthalpy varies with the mole fractions of the components. Studies of the products of mechanosynthesis - binary alloy and Fe-Al-based ternary systems: Fe65Al35, Fe65Al35-xMx (Mx = Ga, B, Sn; 5 and 10 at. %) and Fe65-yAl35My (My = Mn, V; 3, 5 and 10 at. %) were confirmed. It concluded that the applicability of the Miedema model for prognostic purposes for estimating the enthalpies and the possibility of obtaining multicomponent systems

Effectiveness of different base isolation systems for seismic protection: Numerical insights into an existing masonry bell tower

Recent earthquakes in Italy have emphasized the high seismic vulnerability of historical masonry constructions and the need of effective retrofitting interventions. This paper investigates the possibility of improving the seismic performance of a historical masonry bell tower using different types of commercial isolators: High Damping Rubber Bearing (HDRB), Lead Rubber Bearing (LRB) and Friction Pendulum System (FPS) Isolator. Detailed three-dimensional (3D) finite element (FE) models are created to characterize the behavior of the three types of isolators. Then, an Abaqus User Element (UEL) is used to represent the 3D behavior of the isolators for global seismic analyses of isolated structures. The results of cyclic shear analyses show that the proposed UEL model can accurately predict the behavior obtained through detailed 3D FE models. Non-linear dynamic analyses are performed to investigate the seismic response of the historical masonry bell tower in the original and base-isolated configurations subjected to moderate-to-high seismic actions: moreover, the effects of near fault earthquakes are analyzed. The results obtained from the numerical simulations show that the HDRBs do not ensure an adequate seismic protection of the masonry bell tower in terms of damage patterns and top displacements. On the other hand, the LRBs and FPS isolators are very effective in reducing the earthquake effects on the masonry tower: residual displacements are negligible and the isolator displacements are limited. In case of near fault earthquakes, an isolation system with higher damping and larger dimension is required to reduce the drifts of the tower and to accommodate the large displacements of the isolators

Seismic performance of Unbonded Fiber-Reinforced Elastomeric Isolators (UFREI) made by recycled rubber. Influence of suboptimal crosslinking

Seismic base isolation is considered effective to reduce the vulnerability of structures and it represents an optimal retrofitting solution in terms of reliability and effectiveness. Nowadays, one of the most promising devices is the Unbonded Fiber Reinforced Elastomeric Isolator (UFREI), which is considered a low-cost device, thanks to its lightweight, easy installation, and the total absence of steel. The rubber used to assemble the devices must be vulcanized correctly to create the polymer crosslinking to be ready for structural application. All rubber mechanical properties are strongly affected by curing temperature and curing time. In this paper, a series of experimental tests and numerical analyses have been performed to investigate the influence of crosslinking on the seismic performance of UFREIs made of regenerated Ethylene Propylene Diene Monomer (EPDM) combined with glass fiber reinforcement. Two prototypes have been considered, one vulcanized correctly at 150 °C for 40 min and the other at 130 °C for 40 min. Results obtained from Finite Element (FE) cyclic shear tests analysis and nonlinear time history analyses of a preliminary structural application have shown that the devices vulcanized at 130 °C for 40 min, although having suboptimal crosslinking density, are suitable to isolate low-rise masonry buildings properly