Temporal Acoustic Emission Index for Damage Monitoring of RC Structures Subjected to Bidirectional Seismic Loadings

This paper shows the acoustic emission (AE) analysis recorded during the loading process of reinforced concrete (RC) structures subjected to bidirectional seismic loadings. Two waffle plates (bidirectional) supported by isolated square columns were tested on a shaking table with a progressive and increasing ground acceleration until the final collapse. Each specimen was subjected to a different loading history. A relevant delay in the beginning of the significant AE energy is observed as the peak value of the ground acceleration increases. Based on this result, a new AE temporal damage index (TDI), defined as the time difference between the onset of the significant AE activity and the onset of the loading that causes this AE activity, is proposed and validated by comparing it with the plastic strain energy released by the concrete, typically used as a reliable damage level indicator. Good agreement was observed for both specimens and seismic inputs.This research was supported by the regional government of Andalucía, Consejería de Innovación, Ciencia y Tecnología, Project TEP-02429, by the Spanish Ministry of Economy and Competitivity, research project reference MEC BIA2017 88814 R and received funds from the European Union (Fonds Européen de Dévelopment Régional)

Seismic assessment of a heavy-timber frame structure with ring-doweled moment-resisting connections

The performance of heavy-timber structures in earthquakes depends strongly on the inelastic behavior of the mechanical connections. Nevertheless, the nonlinear behavior of timber structures is only considered in the design phase indirectly through the use of an R-factor or a q-factor, which reduces the seismic elastic response spectrum. To improve the estimation of this, the seismic performance of a three-story building designed with ring-doweled moment resisting connections is analyzed here. Connections and members were designed to fulfill the seismic detailing requirements present in Eurocode 5 and Eurocode 8 for high ductility class structures. The performance of the structure is evaluated through a probabilistic approach, which accounts for uncertainties in mechanical properties of members and connections. Nonlinear static analyses and multi-record incremental dynamic analyses were performed to characterize the q-factor and develop fragility curves for different damage levels. The results indicate that the detailing requirements of Eurocode 5 and Eurocode 8 are sufficient to achieve the required performance, even though they also indicate that these requirements may be optimized to achieve more cost-effective connections and members. From the obtained fragility curves, it was verified that neglecting modeling uncertainties may lead to overestimation of the collapse capacity

Numeric validation of the cyclic behaviour of interior connections in waffle-flat-plate structures

Several approaches are investigated to model interior reinforced concrete waffle-flat-plate-column connections. A model is proposed that provides very good results with reasonable low computational cost. The proposed model is validated with the experimental results obtained on a 3/5 scale specimen, subjected to quasi-static in cyclic loads up to collapse. To this end, the non-linear advanced theory of reinforced concrete is applied on a three-dimensional finite element model and non-linear analysis are conducted. Both fiber and layer elements are used for the one-dimensional and bi-dimensional components respectively. The main results of the simulation were: (i) the capacity curve obtained through out a push-over analysis with displacement control, (ii) the hysteretic curves of the slab, and (iii) the crack patterns. A very good agreement is found between numerical and experimental results

Energy-based seismic design methodology: a preliminary approach

By using energy-based methods to design earthquake-resistant structures, the effect of seismic action in terms both of force and displacement demands is taken into account, as well as the cumulative effect of damage produced by cyclic loading. Energy-based methods are effective tools for seismic design, especially when control techniques such as base isolation or energy dissipation systems are used to protect the structure. Although they were established in the 1950’s, design methods based on the energy balance equation require further investigation and development for use in the framework of a Performance Based Earthquake Engineering (PBEE) design approach. In particular, research efforts should address the characterization of uncertainties of the energy-based parameters involved in the design process. This paper proposes an energy-based general methodology to design seismic-resistant structures according to a PBEE approach. Ground motion prediction equations and optimal intensity measures to be applied within the proposed methodology are discussed, as well as ongoing research on key parameters used in energy-based methods such as the equivalent number of cycles and the shear strength coefficient

The relationship between bicycle commuting and perceived stress: a cross-sectional study

INTRODUCTION: Active commuting - walking and bicycling for travel to and/or from work or educational addresses - may facilitate daily, routine physical activity. Several studies have investigated the relationship between active commuting and commuting stress; however, there are no studies examining the relationship between solely bicycle commuting and perceived stress, or studies that account for environmental determinants of bicycle commuting and stress. The current study evaluated the relationship between bicycle commuting, among working or studying adults in a dense urban setting, and perceived stress. METHODS: A cross-sectional study was performed with 788 adults who regularly travelled to work or study locations (excluding those who only commuted on foot) in Barcelona, Spain. Participants responded to a comprehensive telephone survey concerning their travel behaviour from June 2011 through to May 2012. Participants were categorised as either bicycle commuters or non-bicycle commuters, and (based on the Perceived Stress Scale, PSS-4) as either stressed or non-stressed. Multivariate Poisson regression with robust variance models of stress status based on exposures with bicycle commuting were estimated and adjusted for potential confounders. RESULTS: Bicycle commuters had significantly lower risk of being stressed than non-bicycle commuters (Relative Risk; RR (95% CI)=0.73 (0.60 to 0.89), p=0.001). Bicycle commuters who bicycled 4 days per week (RR (95% CI)=0.42 (0.24 to 0.73), p=0.002) and those who bicycled 5 or more days per week (RR (95% CI)=0.57 (0.42 to 0.77), p<0.001) had lower risk of being stressed than those who bicycled less than 4 days. This relationship remained statistically significant after adjusting for individual and environmental confounders and when using different cut-offs of perceived stress. CONCLUSIONS: Stress reduction may be an important consequence of routine bicycle use and should be considered by decision makers as another potential benefit of its promotion

Avaliação do desempenho ambiental de uma instituição pública de ensino técnico e superior Environmental performance assessment of a public institution of technical and undergraduate education

O objetivo deste artigo foi relatar um estudo de caso baseado em indicadores ambientais categóricos no qual foi avaliado o desempenho ambiental de uma instituição pública de ensino técnico e superior. A revisão incluiu a série de normas ISO 14000, o Prêmio Nacional de Qualidade em Saneamento (PNQS) e o Ecoblock. O método usado foi adaptado do SBP, um conjunto de procedimentos para a mensuração do desempenho ambiental de uma atividade antrópica, que se vale de construtos latentes e indicadores categóricos que expliquem o desempenho. Os indicadores foram organizados em sete construtos. Segundo os avaliadores e o modelo, a instituição faz 56,7% do máximo possível em gestão ambiental. Os construtos mais carentes foram gestão de resíduos sólidos e poluição sonora. O resultado da avaliação pode ser usado para reformulação da política ambiental da instituição.<br>This article reports a case study in which the environmental performance of a public institution of higher and technical education was evaluated, based on environmental indicators in spades. The following standards series were reviewed: ISO 14000, National Quality Award in Sanitation (PNQS) and Ecoblock. The method was adapted from SBP, a set of procedures for measuring the environmental performance of an anthropic activity, composed by latent constructs and categorical indicators that explain the performance. The indicators were organized in seven constructs. According to the assessed respondents and the model, the institution reached 56.7% of the maximum possible in environmental management. Lower constructs were management of solid waste and noise pollution. The evaluation can be used for reshaping the environmental policy of the institution