Ramiro Vargas - Academia.edu (original) (raw)

Papers by Ramiro Vargas

En Panama la instrumentacion sismica de edificios comenzo en el ano 1999 con la Resolucion No.365... more En Panama la instrumentacion sismica de edificios comenzo en el ano 1999 con la Resolucion No.365 del 9 de Diciembre de 1998, de la Junta Tecnica de Ingenieria y Arquitectura, mediante la cual se adopto la Norma de Instrumentacion Sismica, promulgada por el Reglamento para el Diseno Estructural en la Republica de Panama (REP-94). De esta manera, Panama se sumaba a paises de la region como Mexico, Colombia, Venezuela, Chile, Costa Rica, y otros, que cuentan con normativas para el monitoreo de vibraciones sismicas en edificios.

Passive energy dissipation (PED) devices have been implemented to enhance structural performance ... more Passive energy dissipation (PED) devices have been implemented to enhance structural performance by reducing seismically induced structural damage. In this paper metallic dampers are defined to be structural fuses (SF) when they are designed such that all damage is concentrated on the PED devices, allowing the primary structure to remain elastic. Following a damaging earthquake, only the dampers would need to be replaced, making repair works easier and more expedient. Furthermore, SF introduce self-centering capabilities to the structure in that, once the ductile fuse devices have been removed, the elastic structure would return to its original position. A comprehensive parametric study is conducted leading to the formulation of the SF concept, and allowing to identify the possible combinations of key parameters essential to ensure adequate seismic performance for SF systems. Nonlinear time history analyses are conducted for several combinations of parameters, in order to cover the range of feasible designs. The structural fuse concept can be implemented in new or existing structures using various kinds of metallic passive energy dissipating (PED) elements. This paper describes how to use metallic dampers to implement the SF concept and improve the structural behavior of systems under seismic loads. Detailed design process is presented, as well as the modifications necessary to the process for retrofitting applications.

2019 7th International Engineering, Sciences and Technology Conference (IESTEC), 2019

The first formal regulations for assessment and seismic rehabilitation of structures started in 1... more The first formal regulations for assessment and seismic rehabilitation of structures started in 1980's, with the implementation of the results of developed research, and efforts conducted by organizations such as the Applied Technology Council (ATC), Federal Emergency Management Agency (FEMA), American Society of Civil Engineers (ASCE), among others; which have compiled different methodologies for evaluation and rational design of structures subjected to seismic loads. In our country, the Structural Design Code for the Republic of Panama, in its last version (REP-2014) incorporates for the first time design methodologies based on performance, as an alternative lateral force method; and refers to the document An Alternative Procedure for Seismic Analysis and Design of Tall Buildings located in the Los Angeles region. This article specifically presents the nonlinear static procedures for structural performance evaluation of buildings. Nonlinear modelling to generate the seismic ca...

En esta Edicion Especial de la Revista Mente & Materia, se realiza en conmemoracion del Aniversar... more En esta Edicion Especial de la Revista Mente & Materia, se realiza en conmemoracion del Aniversario 55 del Centro Experimental de Ingenieria (CEI). Durante mas de medio siglo de funcionamiento interrumpido, el CEI se ha convertido en un referente nacional en el ambito de la ingenieria, con alta calidad demostrada en los servicios tecnicos, consultorias e investigaciones cientificas que dia a dia desarrollamos.

The floor demands of Single-Degree-of-Freedom (SDOF) systems designed or retrofitted with metalli... more The floor demands of Single-Degree-of-Freedom (SDOF) systems designed or retrofitted with metallic structural fuses are studied in this article. Floor velocity and acceleration are obtained and comparisons are made between the floor response of bare frames and the floor response of systems with metallic fuses. Furthermore, velocity and acceleration spectra are developed from the floor time history responses to assess how the behavior of nonstructural components may be influenced by the use of metallic fuses.

Nathan M. Newmark was an internationally renowned educator and engineer. He was widely recognized... more Nathan M. Newmark was an internationally renowned educator and engineer. He was widely recognized for his research in structural engineering and structural dynamics at the University of Illinois at Urbana-Champaign (UIUC), and for his contributions to the design of earthquake-resistant structures, including the Latin American Tower in Mexico City and for his work on the design of the trans-Alaska pipeline. His important contributions to earthquake resistant design of structures have led him to be regarded as the founding father of earthquake engineering.

Seismic design relies on inelastic deformations through hysteretic behavior. However, this transl... more Seismic design relies on inelastic deformations through hysteretic behavior. However, this translates into damage on structural elements, permanent system deformations following an earthquake, and possibly high cost for repairs. An alternative design approach is to concentrate damage on disposable and easy to repair structural elements, while the main structure is designed to remain elastic or with minor inelastic deformations. The implementation of the structural fuse concept into actual buildings would benefit from a systematic and simple design procedure. Such a general procedure is proposed in this paper for designing new or retrofitted structures. The proposed structural fuse design procedure for MDOF structures relies on results of a parametric study, considering the behavior of nonlinear SDOF systems subjected to synthetic ground motions. This procedure is illustrated as an example of application using Buckling-restrained braces (BRBs) as metallic structural fuses. To verify and validate the developed design procedure, an experimental project was conducted on the shaking table at University at Buffalo, which consists of a three-story frame designed with BRBs working as metallic structural fuses. This experimental project also assesses the replaceability of BRBs designed as sacrificeable and easy-to-repair members.

Summary Passive energy dissipation (PED) devices have been implemented to enhance structural perf... more Summary Passive energy dissipation (PED) devices have been implemented to enhance structural performance by reducing seismically induced structural damage. In this article, metallic dampers are defined to be structural fuses (SF) when they are designed such that all damage is concentrated on the PED devices, allowing the primary structure to remain elastic. Following a damaging earthquake, only the dampers would need to be replaced, making repair works easier and more expedient. Furthermore, SF introduce self-centering capabilities to the structure in that, once the ductile fuse devices have been removed, the elastic structure would return to its original position. A comprehensive parametric study is conducted, leading to the formulation of the SF concept, and allowing the identification of the possible combinations of key parameters essential to ensure adequate seismic performance for SF systems. Nonlinear time history analyses are conducted for several combinations of parameters, ...

Summary Metallic dampers can enhance structural performance by reducing seismically induced later... more Summary Metallic dampers can enhance structural performance by reducing seismically induced lateral displacements, and by reducing inelastic behavior of beams and columns. Limiting story drift also indirectly allows for mitigation of damage to nonstructural components that are sensitive to lateral deformations. However, many nonstructural elements and components are vulnerable to excessive accelerations. Therefore, in order to protect these components, floor accelerations in buildings should be kept below certain limits. In this perspective, this paper investigates the seismic performance of single-degree-of-freedom (SDOF) systems with metallic and viscous dampers installed in parallel, to determine the effectiveness or appropriateness of using metallic dampers to mitigate lateral displacements, simultaneously with viscous dampers to reduce acceleration demands. Parametric analyses investigate the effectiveness of adding various levels of viscous damping on the equivalent hysteretic...

Journal of Structural Engineering, 2009

Seismic design relies on inelastic deformations through hysteretic behavior. However, this transl... more Seismic design relies on inelastic deformations through hysteretic behavior. However, this translates into damage on structural elements, permanent system deformations following an earthquake, and possibly high cost for repairs. An alternative design approach, proposed in the past, is to concentrate damage on disposable and easy to repair structural elements ͑i.e., "structural fuses"͒, whereas the main structure is designed to remain elastic or with minor inelastic deformations. The implementation of the structural fuse concept into actual buildings would benefit from a systematic and simple design procedure. Such a general procedure is proposed here for designing new or retrofitted structures. The proposed structural fuse design procedure for multi-degree-of-freedom structures relies on results of a parametric study ͑presented in the paper͒, considering the behavior of nonlinear single degree of freedom systems subjected to synthetic ground motions. Nonlinear dynamic response is presented in dimensionless charts normalized with respect to key parameters. The proposed design procedure is illustrated as an example of application using Buckling-restrained braces as metallic structural fuses. This example is used in an experimental project ͑which is described in a companion paper͒ as a proof of concept to the developed design procedure.

Journal of Structural Engineering, 2007

Metallic dampers can enhance structural performance by reducing seismically induced lateral displ... more Metallic dampers can enhance structural performance by reducing seismically induced lateral displacements, and by reducing inelastic behavior of beams and columns. Limiting story drift also indirectly allows us to mitigate damage of nonstructural components that are sensitive to lateral deformations. However, many nonstructural elements and components are vulnerable to excessive accelerations. Therefore, in order to protect these components, floor accelerations in buildings should be kept below certain limits. In this perspective, this paper investigates the seismic performance of single-degree-of-freedom ͑SDOF͒ systems with metallic and viscous dampers installed in parallel, to determine the effectiveness or appropriateness of using metallic dampers to mitigate lateral displacements, simultaneously with viscous dampers to reduce acceleration demands, knowing that their behavior is fundamentally different ͑i.e., metallic dampers are displacement dependent, whereas velocity dampers are velocity dependent͒. The effect of a combination of these damping systems is, therefore, studied for SDOF structures as a contribution to the state-of-the-art of seismic protection of nonstructural components. Parametric analyses investigate the effectiveness of adding various levels of viscous damping on the equivalent hysteretic damping and on the spectral floor acceleration for short, intermediate, and long period structures. Argand diagrams are used to explain why in some instances it is observed that adding viscous dampers to strongly inelastic systems can result in increases in floor acceleration ͑rather than the intended decreases͒. Results from this study are also applicable to buildings that have been retrofitted with viscous dampers and whose original frame still behaves inelastically after the retrofit.

Journal of Structural Engineering, 2009

Seismic design relies on inelastic deformations through hysteretic behavior. However, this transl... more Seismic design relies on inelastic deformations through hysteretic behavior. However, this translates into damage on structural elements, permanent system deformations following an earthquake, and possibly high cost for repairs. An alternative design approach, proposed in the past, is to concentrate damage on disposable and easy to repair structural elements ͑i.e., "structural fuses"͒, whereas the main structure is designed to remain elastic or with minor inelastic deformations. The implementation of the structural fuse concept into actual buildings would benefit from a systematic and simple design procedure. Such a general procedure is proposed here for designing new or retrofitted structures. The proposed structural fuse design procedure for multi-degree-of-freedom structures relies on results of a parametric study ͑presented in the paper͒, considering the behavior of nonlinear single degree of freedom systems subjected to synthetic ground motions. Nonlinear dynamic response is presented in dimensionless charts normalized with respect to key parameters. The proposed design procedure is illustrated as an example of application using Buckling-restrained braces as metallic structural fuses. This example is used in an experimental project ͑which is described in a companion paper͒ as a proof of concept to the developed design procedure.

Journal of Structural Engineering, 2009

II. [Journal of Structural Engineering 135, 394 (2009)]. Ramiro Vargas, Michel Bruneau. Abstract.... more II. [Journal of Structural Engineering 135, 394 (2009)]. Ramiro Vargas, Michel Bruneau. Abstract. ... The seismic isolation device consists of a bearing with a spherical ball rolling in conical steel plates, also called a ball-in-cone system. ...

2019 7th International Engineering, Sciences and Technology Conference (IESTEC), 2019

Journal of Structural Engineering, 2009

Seismic design relies on inelastic deformations through hysteretic behavior. However, this transl... more Seismic design relies on inelastic deformations through hysteretic behavior. However, this translates into damage on structural elements, permanent system deformations following an earthquake, and possibly high cost for repairs. An alternative design approach, proposed in the past, is to concentrate damage on disposable and easy to repair structural elements ͑i.e., "structural fuses"͒, whereas the main structure is designed to remain elastic or with minor inelastic deformations. The implementation of the structural fuse concept into actual buildings would benefit from a systematic and simple design procedure. Such a general procedure is proposed here for designing new or retrofitted structures. The proposed structural fuse design procedure for multi-degree-of-freedom structures relies on results of a parametric study ͑presented in the paper͒, considering the behavior of nonlinear single degree of freedom systems subjected to synthetic ground motions. Nonlinear dynamic response is presented in dimensionless charts normalized with respect to key parameters. The proposed design procedure is illustrated as an example of application using Buckling-restrained braces as metallic structural fuses. This example is used in an experimental project ͑which is described in a companion paper͒ as a proof of concept to the developed design procedure.

Journal of Structural Engineering, 2007

Journal of Structural Engineering, 2009

Seismic design relies on inelastic deformations through hysteretic behavior. However, this transl... more Seismic design relies on inelastic deformations through hysteretic behavior. However, this translates into damage on structural elements, permanent system deformations following an earthquake, and possibly high cost for repairs. An alternative design approach, proposed in the past, is to concentrate damage on disposable and easy to repair structural elements ͑i.e., "structural fuses"͒, whereas the main structure is designed to remain elastic or with minor inelastic deformations. The implementation of the structural fuse concept into actual buildings would benefit from a systematic and simple design procedure. Such a general procedure is proposed here for designing new or retrofitted structures. The proposed structural fuse design procedure for multi-degree-of-freedom structures relies on results of a parametric study ͑presented in the paper͒, considering the behavior of nonlinear single degree of freedom systems subjected to synthetic ground motions. Nonlinear dynamic response is presented in dimensionless charts normalized with respect to key parameters. The proposed design procedure is illustrated as an example of application using Buckling-restrained braces as metallic structural fuses. This example is used in an experimental project ͑which is described in a companion paper͒ as a proof of concept to the developed design procedure.

Journal of Structural Engineering, 2009