Lopez Almansa, F.; Segues, E.; Rodriguez Cantalapiedra, I. Earthquake engineering and structural dynamics Vol. 44, num. 8, p. 1181-1202 DOI: 10.1002/eqe.2507 Data de publicació: 2015-07-10 Article en revista
This paper describes a new seismic protection system for timber platform frame buildings, either for new construction or retrofit. The system consists in connecting the timber frame to a steel structure that includes hysteretic energy dissipators designed to absorb most of the seismic input energy thus protecting the timber frame and the other steel members; alternatively, the system might use other types of dissipative devices. The steel structure consists of four steel stacks (located at each of the four facades) and steel collectors embracing each slab; the stacks and the collectors are connected, at each floor level, through the energy dissipators. The steel structure is self-supporting, that is, the timber frame is not affected by horizontal actions and can be designed without accounting for any seismic provision; in turn, the steel members do not participate in the main load-carrying system. The timber-steel interface is designed to avoid any stress concentration in the transfer of horizontal forces and to guarantee that the yielding of the dissipators occurs prior to any timber failure. The energy dissipation capacity of the suggested system is discussed, and an application example on a six-story timber building is presented; this case corresponds to highly demanding conditions because of the relatively large building height and weight, the high local seismicity, and the soft soil condition. This research belongs to a wider project aiming to promote the structural use of timber by improving the seismic capacity of wooden buildings; this research includes experiments and advanced numerical simulation. Copyright (c) 2014 John Wiley & Sons, Ltd.
The ability of a recently proposed seismic isolation system, with inherent self-stopping mechanism, to mitigate or even eliminate seismic pounding of adjacent structures is investigated under severe near-fault earthquakes. The isolation system is referred to as roll-in-cage (RNC) isolator. It is a rolling-based isolator that provides in one unit the necessary functions of vertical rigid support, horizontal flexibility with enhanced stability, hysteretic energy dissipation, and resistance to minor vibration loads. In addition, the RNC isolator is distinguished by a self-stopping (buffer) mechanism to limit the bearing displacement under excitations stronger than a design earthquake or at limited seismic gaps, and a linear gravity-based self-recentering mechanism to prevent permanent bearing displacement without causing vertical fluctuation of the isolated structure. A previously developed multifeature SAP2000 model of the RNC isolator is improved in this paper to account for the inherent buffer mechanism's damping. Then, the effectiveness of the isolator's buffer mechanism in limiting peak bearing displacements is studied together with its possibly arising negative influence on the isolation efficiency. After that, the study investigates how to alleviate or even eliminate those possibly arising drawbacks, due to the developed RNC isolator's inner pounding as a result of its buffer activation, to achieve efficient seismic isolation with no direct structure-to-structure pounding, considering limited seismic gaps with adjacent structures and near-fault earthquakes. The results show that the RNC isolator could be an efficient solution for aseismic design in near-fault zones considering limited seismic gaps. Earthquake Engineering and Structural Dynamics. Copyright (c) 2014 John Wiley & Sons, Ltd.
Rubió-Massegú, J.; Palacios-Quiñonero, F.; Rossell, Josep M. Earthquake engineering and structural dynamics Vol. 41, num. 7, p. 1199-1205 DOI: 10.1002/eqe.1167 Data de publicació: 2012-06 Article en revista
Molins, C.; Roca, P.; Barbat, A. H. Earthquake engineering and structural dynamics Vol. 27, num. 7, p. 731-747 DOI: 10.1002/(SICI)1096-9845(199807)27:7<731::AID-EQE754>3.0.CO;2-1 Data de publicació: 1998-07 Article en revista
A flexibility-based formulation of a new mass matrix for the dynamic analysis of spatial frames consisting of curved elements with variable cross-sections is presented. The main characteristic of such formulations is the exact equilibrium of forces at any interior point, with no additional hypotheses about the distribution of displacements, strains or stresses. Accordingly, the derived element mass matrix takes into account the exact stiffness and mass distribution throughout each element.
In validation tests, results obtained with this method are compared with those obtained by other numerical or analytical formulations, showing the accuracy of the proposed method. The comparison of experimental results for a multispan arch bridge subjected to a dynamic load with those achieved by means of the proposed method are finally included to illustrate its efficiency in the treatment of complex structures.
Luo, N.; Rodellar, J.; Sen, D. Earthquake engineering and structural dynamics Vol. 27, num. 3, p. 301-311 DOI: 10.1002/(SICI)1096-9845(199803)27:3<301::AID-EQE734>3.0.CO;2-Y Data de publicació: 1998-03 Article en revista
In this paper, composite robust active control schemes are proposed for a class of non-linear base isolated structures in the presence of unknown seismic excitation, parametrical uncertainties and actuator dynamics. Only the information on state variables of the structural base and the first floor of the main structure has been used in the control design. A numerical simulation example is given for a ten-storeyed base isolated structure under the El Centro earthquake to show the effectiveness of the proposed control scheme
Accelerations and displacements due to dynamic excitation by simulated traffic consisting of two trucks, were measured on the deck and tower of the Alamillo cable-stayed bridge. Also the dynamic testing program included the measurement with accelerometers of the free-damped vibration of the 26 cables achieved by means of quick-releasing force. From these measurements it was possible to obtain the dynamic parameters of the bridge (natural frequencies and damping ratios) and the real forces in the cables. In the paper, only the tests, results and conclusions related to dynamic parameters of the bridge are presented. The objective of the dynamic tests herein described was to validate the mathematical modelling and the wind-tunnel models used in the dynamic analysis of the bridge in front of traffic and wind-forces. As the agreement between dynamic parameters of the real bridge and theoretical and scaled models was very satisfactory, the correct dynamic behaviour of the bridge in response to traffic and wind (vortex shedding, flutter, etc.) can be deduced jointly with the correct alignment and expected internal forces in the permanent state in tower and deck.
Inaudi, J.; Lopez Almansa, F.; Kelly, J.; Rodellar, J. Earthquake engineering and structural dynamics Vol. 21, num. 6, p. 471-482 DOI: 10.1002/eqe.4290210602 Data de publicació: 1992-05 Article en revista
A control design for absolute motion reduction of base-isolated structures subjected to earthquake excitation is presented herein. The control objective is to provide a vibration-free environment for sensitive equipment protection. Predictive control theory is used for the control design. This theory allows the designer to handle time delays generated by the dynamics of actuators. The study reported herein demonstrates, by numerical simulation, the efficacy of this controller in reducing acceleration response in the superstructure in the presence of delays. Stability analysis, frequency response and response to ground motion excitation are developed to assess the characteristics of the controller.
In this paper a theoretical and numerical analysis on the robustness and the practical feasibility of a control system of an experimental model of a building structure is performed. This model has a mechanical actuator employing active cables and the control algorithm is based on a predictive strategy. In order to test the robustness one simulates numerically different control experiments under two kinds of non-ideal conditions: (i) discrepancies between the parameters of the system (mass, natural frequencies and the time delay in the actuator) and those assumed in the formulation of the control algorithm; (ii) operation of the active cables out of the operation range caused by excitations stronger than expected. In order to assess the feasibility, in every control experiment one obtains the values of four performance indices which provide full information about the features of the control action. The numerical results show that predictive control by active cables is robust and feasible.