Non-linear seismic analysis of RC structures with energy-dissipating devices

The poor performance of some reinforced concrete (RC) structures during strong earthquakes has alerted about the need of improving their seismic behavior, especially when they are designed according to obsolete codes and show low structural damping, important second-order effects and low ductility, among other defects. These characteristics allow proposing the use of energy-dissipating devices for improving their seismic behavior. In this work, the non-linear dynamic response of RC buildings with energy dissipators is studied using advanced computational techniques. A fully geometric and constitutive non-linear model for the description of the dynamic behavior of framed structures is developed. The model is based on the geometrically exact formulation for beams in finite deformation. Points on the cross section are composed of several simple materials. The mixing theory is used to treat the resulting composite. A specific type of element is proposed for modeling the dissipators including the corresponding constitutive relations. Special attention is paid to the development of local and global damage indices for describing the performance of the buildings. Finally, numerical tests are presented for validating the ability of the model for reproducing the non-linear seismic response of buildings with dissipators

Ineslatic analysis of geometrically exact rods

In this work, a formulation for rod structures, able to consider coupled geometric and constitutive sources of nonlinearity in both the static and the dynamic range, is developed. It is extended for allowing the inclusion of passive energy dissipating elements as a special rod element and geometric irregularities as a full three-dimensional body connected to the framed structure by means of a two-scale model. The proposed formulation is based on the Reissner-Simo geometrically exact formulation for rods considering an initially curved reference configuration and extended to include arbitrary distribution of composite materials in the cross sections. Each material point of the cross section is assumed to be composed of several simple materials with their own thermodynamically consistent constitutive laws. The simple mixing rule is used for treating the resulting composite. Cross sections are meshed into a grid of quadrilaterals, each of them corresponding to a fiber directed along the axis of the beam. A mesh independent response is obtained by means of the regularization of the energy dissipated at constitutive level considering the characteristic length of the mesh and the fracture energy of the materials. Local and global damage indices have been developed based on the ratio between the visco-elastic and nonlinear stresses. The consistent linearization of the weak form of the momentum balance equations is performed considering the effects of rate dependent inelasticity. Due to the fact that the deformation map belongs to a nonlinear manifold, an appropriated version of Newmark's scheme and of the iterative updating procedure of the involved variables is developed. The space discretization of the linearized problem is performed using the standard Galerkin finite element approach. A Newton-Raphson type of iterative scheme is used for the step-by-step solution of the discrete problem. A specific element for energy dissipating devices is developed, based on the rod model but releasing the rotational degrees of freedom. Appropriated constitutive relations are given for a wide variety of possible dissipative mechanisms. Several numerical examples have been included for the validation of the proposed formulation. The examples include elastic and inelastic finite deformation response of framed structures with initially straight and curved beams. Comparisons with existing literature is performed for the case of plasticity and new results are presented for degrading and composite materials. Those examples show how the present formulation is able to capture different complex mechanical phenomena such as the uncoupling of the dynamic response from resonance due to inelastic incursions and suppression of the high frequency content. The study of realistic flexible pre-cast and cast in place reinforced concrete framed structures subjected to static and dynamic actions is also carried out. Detailed studies regarding to the evolution of local damage indices, energy dissipation and ductility demands are presented. The studies include the seismic response of concrete structures with energy dissipating devices. Advantages of the use of passive control are verified

Geodetic, teleseismic, and strong motion constraints on slip from recent southern Peru subduction zone earthquakes

We use seismic and geodetic data both jointly and separately to constrain coseismic slip from the 12 November 1996 M_w 7.7 and 23 June 2001 M_w 8.5 southern Peru subduction zone earthquakes, as well as two large aftershocks following the 2001 earthquake on 26 June and 7 July 2001. We use all available data in our inversions: GPS, interferometric synthetic aperture radar (InSAR) from the ERS-1, ERS-2, JERS, and RADARSAT-1 satellites, and seismic data from teleseismic and strong motion stations. Our two-dimensional slip models derived from only teleseismic body waves from South American subduction zone earthquakes with M_w > 7.5 do not reliably predict available geodetic data. In particular, we find significant differences in the distribution of slip for the 2001 earthquake from models that use only seismic (teleseismic and two strong motion stations) or geodetic (InSAR and GPS) data. The differences might be related to postseismic deformation or, more likely, the different sensitivities of the teleseismic and geodetic data to coseismic rupture properties. The earthquakes studied here follow the pattern of earthquake directivity along the coast of western South America, north of 5°S, earthquakes rupture to the north; south of about 12°S, directivity is southerly; and in between, earthquakes are bilateral. The predicted deformation at the Arequipa GPS station from the seismic-only slip model for the 7 July 2001 aftershock is not consistent with significant preseismic motion

Continuous Structural Monitoring of Adobe Buildings: Summary of a Three Years Experience in Peru

The paper describes in detail the application of a vibration-based structural health monitoring system installed in the “San Pedro Apostol” church of Andahuaylillas located in Cusco (Peru), a 16th century adobe church considered a representative example of South America baroque architecture. The results of three years of long-term vibration and temperature and humidity monitoring program are reported in detail in the paper, with a focus on the long-term and short-term correlations between natural frequencies and environmental parameters. The results demonstrate that an accurate estimation of the first eight frequencies in the range 2-6 Hz is possible in the case of complex adobe structure and the existence of an annual cyclical behavior of the natural frequencies with a clear correspondence with the changes in environmental conditions due to seasonal influences. The performed correlations of ambient conditions and structural parameters confirmed the presence of different timescales and their not negligible influence in the case of a vibration-based structural health monitoring assessment of adobe systems with large thermal inertia large thermal inertia

Earthquake-Induced Structural and Nonstructural Damage in Hospitals

This article was published in the journal, Earthquake Spectra [© (2011) Earthquake Engineering Research Institute]. This article may be downloaded for personal use only. Any other use requires prior permission of the Earthquake Engineering Research Institute.The Sichuan (China) and L’Aquila (Italy) earthquakes have again highlighted the question of our preparedness for natural hazards. Within a few seconds, an earthquake can demolish many buildings, destroy infrastructure, and kill and injure thousands of people. In order to reduce the impact of earthquakes on human life and to prepare hospitals to cope with future disasters, this paper discusses earthquake-related damage to healthcare facilities. It investigates the damage to 34 healthcare facilities in seven countries caused by nine earthquakes between 1994 and 2004, in order to determine common and specific issues. The investigation shows that structural and architectural damage tended to be different and specific to the situation, while utility supplies and equipment damage were similar in most cases and some common trends emerged

The October 15, 1997 Punitaqui earthquake (Mw = 7.1) : a destructive event within the subducting Nazca plate in the Central Chile

Tectonophysics, v. 345, n. 1-4, p. 199-210, 2002. http://dx.doi.org/10.1016/S0040-1951(01)00213-XInternational audienc

The October 15, 1997 Punitaqui earthquake (Mw=7,1) : a destructive event within the subducting Nazca plate in Central Chile

Tectonophysics, v. 345, n. 1-4, p. 199-210, 2002. http://dx.doi.org/10.1016/S0040-1951(01)00213-XInternational audienc

An Evaluation of the Applicability of Current Ground-Motion Models to the South and Central American Subduction Zones

The applicability of existing ground‐motion prediction equations (GMPEs) for subduction‐zone earthquakes is an important issue to address in the assessment of the seismic hazard affecting the Peru–Chile and Central American regions. Few predictive equations exist that are derived from local data, and these do not generally meet the quality criteria required for use in modern seismic hazard analyses. This paper investigates the applicability of a set of global and regional subduction ground‐motion models to the Peru–Chile and Central American subduction zones, distinguishing between interface and intraslab events, in light of recently compiled ground‐motion data from these regions. Strong‐motion recordings and associated metadata compiled by Arango, Strasser, Bommer, Boroschek, et al. (2011) and Arango, Strasser, Bommer, Hernandez, et al. (2011) have been used to assess the performance of the candidate equations following the maximum‐likelihood approach of Scherbaum et al. (2004) and its extension to normalized intraevent and interevent residual distributions developed by Stafford et al. (2008). The results of this study are discussed in terms of the transportability of GMPEs for subduction‐zone environments from one region to another, with a view to providing guidance for developing ground‐motion logic trees for seismic hazard analysis in these regions

Vibration-based damage detection in historical adobe structures: laboratory and field applications

Structural Health Monitoring (SHM) has demonstrated to be a fundamental tool for detecting damage in early stages in existent civil engineering structures. This paper explores the accuracy of vibration-based SHM for identifying the existence of damage in adobe constructions, a widespread structural system but on which limited experimental and numerical applications of the technique are available. Two damage detection methodologies are investigated: (i) Autoregressive Models to predict the structural dynamic response taking into account the environmental parameters as input; and (ii) Principal Component Analysis to detect patterns and anomalies in this response without the need of information about environmental conditions. The results of the laboratory tests on a real scale adobe wall positively indicate the capabilities of these two methodologies to accurately identify damage. They also evidence the importance of monitoring several modes as their sensitivity to damage depends on damage location itself. Furthermore, the application of these two damage detection methodologies in a real case study related to the long-term monitoring of a 16(th) Century adobe church allowed confirming the building safe condition during almost two years of monitoring period, as well as the absence of damage after a 5.2Mw earthquake.The present work was carried out by the Engineering and Heritage research group of PUCP in collaboration with the Civil Engineering Departments of the University of Chile and the University of Minho. The work was developed thanks to the funding provided by the program Cienciactiva from CONCYTEC in the framework of the Contract N ° 222-2015and the funding received from the Pontificia Universidad Católica del Perú PUCP and its funding office DGI-PUCP (Project 349-2016). The second author gratefully acknowledges ELARCH program for the scholarship in support of his PhD studies (Project Reference number: 552129-EM-1-2014-1-IT-ERA MUNDUS-394 EMA21). The third author gratefully acknowledges CONCYTEC for the scholarship in support of his MSc studies (Contract N° 232-2015 FONDECYT)