High Damping Rubber Model for Energy Dissipating Devices

This work presents the results of a study carried out to characterize the mechanical response of a high damping rubber to be used in designing and constructing energy dissipating devices and base isolators for controling strong vibrations in civil engineering structures. A new parametric model of the elastomer is proposed to be employed in the design procedure and structural analysis of passive controlled structures. The parameters of the model are calibrated using experimental data obtained from tests on rubber specimens under different loading paths. The main dissipating energy mechanisms of the rubber are identified. The proposed model is able to reproduce those main mechanisms as well as geometric second order effects such as tension stiffening due to the effect of axial strains in the response. The response predicted by the proposed model is compared with that obtained from experimental tests and from the Kelvin and plasticity models

Study of the environmental influence on the dynamic behavior of adobe walls: preliminary test in laboratory specimens

The shift of modal parameters induced by temperature and humidity effects may mask the changes of vibration properties caused by structural damage because the dynamic properties are often sensitive to changing environmental conditions. Furthermore, temperature and humidity are generally non-uniform and time-dependent variables, and therefore, their simple record in air or at a specific surface cannot be sufficient to obtain useful models to understand the relationship between the dynamic properties and environmental effects.The present paper aims at presenting preliminary findings in the task of quantifying the effects of environmental conditions (variations in temperature and humidity) on the dynamic properties of earthen constructions with a laboratory test campaign. The first stage of the research consisted on the analysis of a real structural system and for this three 1:1 scale adobe walls were built in the laboratory. This stage considered the performance of a long-term monitoring program recording environmental conditions, the surface and inner walls variation of temperature and humidity and the dynamic behaviour of the walls. The second stage consisted on the understanding the correlation between dynamic properties and environmental parameters. In particular, linear auto-regressive models with exogenous variables (ARX) and multiple linear regression models (MLRM) were built and compared. The paper presents the results of the measurements and shows that is possible to distinguish the changes of dynamic properties due to environmental effects in adobe walls.The present work was developed thanks to the funding provided by the program Cienciactiva from CONCYTEC in the framework of the Contract No. 222-2015. The first author acknowledge FONDECYT for the scholarship in support of graduate studies (Contract No. 027-2015-FONDECYT). The second author gratefully acknowledge ELARCH program for the scholarship in support of his PhD studies (Project Reference number: 552129-EM-1-2014-1-IT-ERA MUNDUS-EMA21)

Experimental analysis of the thermohygrometric effects on the dynamic behavior of adobe systems

Through long-term monitoring, modal parameters identified in-situ can provide important information about the safety state of civil buildings and infrastructures. Unfortunately, structures are subjected to changing environmental conditions that can mask variations in the dynamic properties caused by damage and, therefore, lead to an incorrect condition assessment. The quantification of the influence of environmental conditions on modal parameters is a crucial step to eliminate their interference in a safety evaluation. Under current state-of-the-art considerations, this step is still an open challenge because environmental variables are time-dependent non-uniform quantities that have different influences on structural systems depending on the predominant material. In this paper, the effects of ambient temperature and humidity on the dynamic properties of earthen constructions are investigated using laboratory tests. A dynamic monitoring system was successfully implemented on adobe walls of different thicknesses to examine the influence of seasonal and daily variations of temperature and humidity. Three 1:1 scale adobe masonry walls were built and exposed to ambient conditions for 240 days. Temperature and humidity variations on the exterior, as well as in the inner walls, were continuously recorded together with the dynamic behavior using ambient vibration. The results provide useful insights on the influence of thermohygrometric parameters on the dynamic properties of adobe systems. The seasonal results indicate unclear correlations of ambient parameters and environmental variables. On the other hand, at a daily scale, the results indicate the existence of a clear relationship between inner measurements and dynamic properties. Moreover, the results indicate the existence of a delayed effect of external ambient parameters in the dynamic behavior of earthen systems.This research was performed by the Engineering & Heritage research group at PUCP with collaboration from the Department of Structural Engineering of the University of Minho in Portugal, and the Department of Civil Engineering at the University of Chile. The authors would like to acknowledge the Directorate of Research Management at PUCP (project No 349-2016) for funding this research. Complementary funding was also received from the program Cienciactiva from CONCYTEC in the framework of the Contract No 222-2015. The first 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-EMA21). The authors acknowledge the contribution of the MEng Rick Delgadillo to the indispensable laboratory work presented in this paper

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