Performance of a natural fibre reinforced polymer-concrete bridge pier in earthquakes

Glass or carbon fibre reinforced polymers are extensively used in the automobile and the aerospace industries. However, in civil infrastructure their usage is mainly limited to retrofitting, because synthetic fibres are expensive. Steel is heavy, expensive and subject to corrosion. Instead of steel reinforcement in civil structures the usage of natural materials will reduce the total mass and cost of the structures and circumvent the long-term problem of corrosion. In this paper flax fibre reinforced polymer (FFRP) and coconut fibre reinforced concrete (CFRC) are investigated. Because of the usage of less mass the corrosion-free composite structures will experience less effect of dynamic loads and require less running maintenance. The seismic performance of a simple bridge pier made of FFRP-CFRC composite is presented. The earthquake loading is simulated by a shake table. The results indicate that the new composite has a potential for becoming resilient construction materials for future structures

Ductility of RC Columns due to Strong Near Source Earthquakes

Near source earthquakes can produce strong vertical ground motions with large amplitude and high frequency content. In this paper the axial ductility behavior of RC columns due to near source earthquakes is investigated. The column is simplified to a SDOF system that only describes vertical vibrations of a structural column. The gravity load effect is represented by a pre-load. An elasto-plastic model accounting for different stiffness and strength in tension and compression is used in the analysis. The ductility demand as well as pseudo acceleration spectra are evaluated. The investigation shows that strong vertical ground motions should be considered in seismic design. From the results of this investigation suggestions for a seismic design in case of near source earthquakes can be derived

Bumpers for reducing the effect of pounding between bridge decks

The study addresses the influence of bumpers as reduction measures at the bridge decks. The considered devices are steel spring, steel spring with additional viscous damper or steel spring with additional friction element. Gap between bridge decks remains. The reduction measure is placed at one end of the neighbouring girders. The considered earthquakes are the 1994 Northridge earthquake and the 1995 Kobe earthquake. For the nonlinear analysis a finite element method is used. The investigation shows that compared to the other measures the best reduction of the pounding force can be achieved with a friction device

Resilient Civil Infrastructure under Dynamic Loadings

A resilient infrastructural system is an important component of a modern city. The main principles are safety, sustainability, functionality, maintainability, and fast recoverability following natural and/or man-made hazards. This special issue addresses new research developments in resilient infrastructural systems under dynamic loadings, for example, wind, traffic, tsunamis, and earthquakes

Modal testing of an unreinforced masonry house

There are a significant number of uncertainties in finite element models of unreinforced masonry structures related to the modelling assumptions and the properties of local materials. Therefore, it is necessary to implement calibration techniques for these models. Modal testing is a good option for assessing the dynamic properties of the structure. The experimental data is used to verify and improve the predicted response obtained by finite element model. The study presents the modal testing of a full-scale physical model of an unreinforced masonry house. The structure is tested under three different excitations: an impact by a calibrated hammer, a random excitation induced by a calibrated hammer, and a steppedsine excitation induced by a shaker. In addition, an operational modal test has been performed using ambient and random excitations. Two different methods are used for system identification: peak picking and stochastic subspace identification. The results of this research will be used in future studies for updating the model

Shake Table Study on the Effect of Mainshock-Aftershock Sequences on Structures with SFSI

Observations from recent earthquakes have emphasised the need for a better understanding of the effects of structure-footing-soil interaction on the response of structures. In order to incorporate the influences of soil, a laminar box can be used to contain the soil during experiments. The laminar box simulates field boundary conditions by allowing the soil to shear during shake table tests. A holistic response of a structure and supporting soil can thus be obtained by placing a model structure on the surface of the soil in the laminar box. This work reveals the response of structure with SFSI under mainshock and aftershock earthquake sequences. A large (2 m by 2 m) laminar box, capable of simulating the behaviour of both dry and saturated soils, was constructed. A model structure was placed on dry sand in the laminar box. The setup was excited by a sequence of earthquake excitations. The first excitation was used to obtain the response of the model on sand under the mainshock of an earthquake. The second and third excitations represented the first and second aftershocks, respectively

PERFORMANCE OF A NATURAL FIBRE REINFORCED POLYMER-CONCRETE BRIDGE PIER IN EARTHQUAKES

ABSTRACT Glass or carbon fibre reinforced polymers are extensively used in the automobile and the aerospace industries. However, in civil infrastructure their usage is mainly limited to retrofitting, because synthetic fibres are expensive. Steel is heavy, expensive and subject to corrosion. Instead of steel reinforcement in civil structures the usage of natural materials will reduce the total mass and cost of the structures and circumvent the long-term problem of corrosion. In this paper flax fibre reinforced polymer (FFRP) and coconut fibre reinforced concrete (CFRC) are investigated. Because of the usage of less mass the corrosion-free composite structures will experience less effect of dynamic loads and require less running maintenance. The seismic performance of a simple bridge pier made of FFRP-CFRC composite is presented. The earthquake loading is simulated by a shake table. The results indicate that the new composite has a potential for becoming resilient construction materials for future structures

Damage Identification of Unreinforced Masonry Panels Using Vibration-Based Techniques

Several damage indicators based on changes in modal properties validated for homogeneous materials were applied to detect damage in an unreinforced masonry cantilever panel. Damage was created by a “clean diagonal cut” at the center of the specimen which length was progressively extended towards the specimen’s corners. Numerical simulations were employed to determine the modal response at several damage states and this data was used to calculate the damage indicators. Those indicators presenting a good performance were then applied to identify damage on a physical specimen tested in the laboratory. The outcomes of this study demonstrated that vibration-based damage detection in unreinforced masonry structures can be satisfactorily performed. However, the identification of the damage spatial distribution using vibration-based methods in unreinforced masonry structures is still difficult. To improve the prediction of damage distribution, a large number of measurement points need to be considered to obtain an acceptable level of resolution