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AB4STRACT Costa Rica is located at the boundary of four tectonic plates where the regularity of destructive earthquakes highlights the necessity of seismic hazard estimations. This study contains the most recent Probabilistic Seismic Hazard Assessment (PSHA) for Costa Rica, calculated with the largest and the most updated earthquake database from both—the Earthquake Engineering Laboratory and the National Seismological Network of the University of Costa Rica. For the PSHA, we updated the seismicity parameters for the upper plate, subduction interplate, and intraslab tectonic domains, characterized the upper-plate zones by percentages of fault types, and used weighted ground-motion models for each of the tectonic domains. The resulted maps of peak ground acceleration (PGA) at return periods of 475 yr (PGA-475) and 2475 yr, as well as the spectral accelerations, show geographic trends that allow for the division of the country in four seismic hazard levels: (1) extremely high for the Nicoya, Osa, and Burica peninsulas, situated directly above the subduction interplate, where the PGA-475 could be 0.55–1.20g; (2) very high for most of the Guanacaste Province, where the PGA-475 may be 0.55–0.70g; (3) high for most of the country (∼41%) with PGA-475 values of 0.40–0.55g, including Central Costa Rica and the capital city of San Jose; and (4) moderate for the Talamanca Cordillera and Northern Costa Rica, with PGA-475 up to 0.40g. These ground-motion values are 0.1–0.6g higher than the previous PSHA for the Pacific peninsulas, Guanacaste, and the southeastern Caribbean. Further, hazard curves, uniform hazard spectra, and a hazard disaggregation indicate that the seismic hazard is lower but more complex in San Jose than in Liberia—the largest city in Guanacaste.

Structural health monitoring (SHM) has been conducted by placing sensors on structures, so-called contact sensors, to measure displacements, strains, and accelerations of engineering structures. Contact sensing is accurate and effective, but suffers from some critical shortcomings, such as high cost, intensive labor, and traffic interruption. With the advancement and wide availability of digital video cameras, compounded with the development and enhancement of computer vision algorithms, vision-based sensing using a video camera as a sensor for SHM has become a viable alternative and a complementary method to remotely capture structural responses. Several computer vision algorithms are proposed, together with specific type of video camera, for capturing and processing the SHM video for the dynamic structural responses, e.g. displacements of selected targets. Up to date, there is a limited number of successful applications using video camera as a sensor in SHM practice. To facilitate the real-world applications of vision-based SHM, this paper presents the integrated methods, and a software tool for analyzing SHM videos using template matching algorithms along with a subpixel method that enhances the accuracy of the vision-based structural responses. The integrated approach is flexible and versatile for not only extracting displacements, strains, velocities, and accelerations, but also detecting damage of the desired multiple points or areas (templates) from videos. The methods and the software tool have been applied to a comprehensive analysis of the lab structural test, which was video-recorded by a third party without any involvement of the authors or any intension in using video camera as sensor. Good agreement for the lab test has been achieved for the structural responses (e.g. displacement and strain) and the damage detection recorded by the conventional sensors and extracted from the video by applying the integrated tool. The approach has been further validated on a highway bridge in the field, where a contact-based SHM system is permanently installed on the bridge and serves a good baseline reference for validating the proposed approach. The vision-based SHM results obtained for the highway bridge application show good correlation with the structural responses captured by conventional sensors and indicate that the developed analysis methods and software tool perform well for highway bridge test and structural health monitoring.

Bridge Weigh-In-Motion (BWIM) has been demonstrated to be reliable for obtaining critical information about the characteristics of trucks that travel over the highways. Continued improvements provides greater opportunity for increased use of BWIM. Traditional BWIM systems based on measuring the bending strain of the bridge have various challenges which has led to a class of BWIM methodologies that employ the use of shear strain in determining the gross vehicle weight (GVW) of crossing trucks. However, the known techniques of these shear-strain BWIM methods assume or measure the shear influence line for the calculation of the GVW. In this paper, an alternative shear-strain based BWIM technique is proposed. The method presented here is independent of the influence line, does not require a measurement of the speed of the truck, and is based on the difference in magnitude observed at the discontinuity of the shear strain record as a truck crosses over the sensor location on the bridge. A series of field tests is presented that demonstrate this shear-strain based BWIM method has error levels consistent with other more complex BWIM methods and as such has great potential to be used for determining the GVWs of trucks that travel on simple or multispan bridges in a consistent and reliable manner. Existe literatura que demuestra que el pesaje en movimiento con puentes, conocido por sus siglas en inglés como BWIM (Bridge Weigh-In-Motion) es confiable para obtener información acerca de las característicasde los camiones que transitan por las carreteras. El mejoramiento continuo de estos sistemas presenta oportunidades para incrementar su uso. Los métodos BWIM tradicionales basados en la flexión en vigasenfrentan distintos retos, los cuales han propiciado la aparición de otras metodologías que emplean deformaciones unitarias cortantes. Sin embargo, las técnicas conocidas que utilizan deformaciones unitariascortantes, asumen o miden líneas de influencia para el cálculo de los pesos brutos vehiculares. En este artículo, se propone una metodología BWIM alternativa, que es independiente de las líneas de influencia, norequiere mediciones de la velocidad de los camiones y se basa en la discontinuidad que se observa en el registro de deformaciones unitarias cortantes, la cual ocurre cuando un camión cruza sobre el lugar en donde se coloca el sensor. A partir de una serie de experimentos realizados en campo, se demuestra que los niveles de error obtenidos con el método propuesto son similares a los obtenidos con otros métodos BWIM más complejos, por lo que se considera que existe potencial para poder ser utilizado para obtener los pesos brutos vehiculares de camiones que transitan por puentes continuos o simplemente apoyados, en una forma consitente y confiable.

Los sistemas de pesaje en movimiento para puentes, en inglés Bridge-Weigh-In-Motion (BWIM), han sido utilizados con éxito para identificar algunas de las propiedades de los vehículos pesados que transitan sobre una vía. No obstante, las fuentes de incertidumbre no son siempre fáciles de controlar y por lo tanto podrían afectar la confiabilidad de los resultados. En esta investigación, se estudió la influencia de algunas de las dificultades experimentales que se presentan al utilizar el método BWIM basado en deformaciones unitarias. En particular, se analizaron tres efectos: el nivel de ruido presente en la señal, la ubicación de los sensores en el puente y la tasa de muestreo utilizada para la recolección de datos. Estos efectos se simularon numéricamente al añadir ruido generado sintéticamente a una onda de respuesta idealizada. En este trabajo se discuten los resultados con énfasis en posibles consecuencias sobre las estimaciones de velocidad y peso de vehículos pesados en pruebas de campo.

In May 2002 Timor Leste (East Timor) emerged as a new nation after centuries of foreign rule and decades of struggle for independence. Its birth was a painful one; a United Nations-brokered Popular Consultation in August 1999, in which an overwhelming majority of the people opted for independence, was followed by several weeks of vengeful violence, looting, and destruction by pro-Indonesia militias. It left the territory and all of its essential services devastated. In this context, the United Nations Transitional Administration in East Timor (UNTAET), with the country's leaders and people and many other partners, set about restoring order and services, building a government structure, and preparing for independence. This paper summarizes the rehabilitation and development of the health sector from early 2000 to the end of 2001.