Abstract

The use of pozzolana to improve the characteristics of concrete has been  one of the main innovations in concrete technology. This art was known 2000 years ago during the Romans Era, but it was lost during de Middle Age, and it was not rediscovered until the middle of the twentieth century. Besides the technological advantages that it provides as a mineral addition that allows partial substitution of the cement in concrete, it is of great importance within the sustainability vision. During the last years, the Popocatepetl volcano has thrown significant amounts of ashes, forming deposits in the surrounding of the crater. In this paper, the chemical and physical characteristics of this ash are evaluated, and tests are performed to verify its influence in the concrete when used as an addition in its natural condition

Abstract

This paper describes the development of the project designared as Line 4 of the Santiago's subway, which includes the construction of a new railway fine with 32.4 kilometers of longitvde, consisting of underground, surface and elevared tracks in the city of Santiago, Chile. The design of the viaduct has been based on the intensive use of interlocking prefabricared structures (segmenta/ bridges), with the purpose of minimizing the impact- regarding time and space - that this type of project usual/y generares on che roadways surrounding its layout. In addition, this project has achieved an architectural design of slender forms and soft and rounded fines, in harmony with che surroundings. The design of che viaduct ís characterized by a "U" type superstructure, which is built with interlocking prefabricated segments (segmental bridges). This method is quite usual in developed countries but is applied for the first time on a viaduct in Chile. Another important issue addressed in this project has been the seismic analysis of the area. To perform this study, a design spectrum was created based on four seismic movements that affected Santiago in the past.

Abstract

The paper presents a description of the technology of concrete pavement rehabilitation and demolition applying the rubblizing construction technique. Thistechnique basically consists of fracturing concrete pavement in angular and interlocked pieces using a "resonant vibration" machine. As soon as the rubblizingprocess is done, it is possible to build an overlay over the surface or to remove the material in the case of pavement demolition. The international experienceof applying rubblizing shows that this technology presents advantages from technical (better performance of the pavement), economical (cost is reducedcompared with a reconstruction) and environmental (reduces air pollution, noise, and debris) points of view. An economic assesment proved that therubblizing technique reduces costs from 20% to 43% compared with traditional rehabilitation methods for concrete pavement used in Chile.

Abstract

A mathematical model to identify the dynamic matrices of rigidity and flexibility of reticular structures starting from data of forced vibration measurementis presented. In the proposition it is considered that the behavior of the structural system is lineal, elastic and not buffered. The definition of the dynamicmatrices of rigidity and flexibility is possible when identifying by means of vibration measurement: the modal matrix, the natural frequencies of vibrationand the driving force frequency. It is necessary to propose the system’s masses matrix due to the fact that has not been possible to deduce it experimentallyin this stage of the investigation. The application of the developed methodology to a simple structural model is shown and the obtained results are commented.

Abstract

The construction industry is one of the most important economic activities in most of the countries. Nowadays, society demands civil engineering works tobe carried out under quality criteria, with respect for the environment and assuring the safety and health of construction workers. All of this should be donewithin a sustainable development framework. Construction’s labor accident indexes are very high and produce important social and economic costs. Theintegration of labor risk prevention into construction procedures may contribute to reduce work accidents and to improve the work conditions at constructionsites This paper examines the importance of an adequate labor risk prevention in civil engineering construction projects, which must start at the planningstage of the project and continue during the execution of the work and during the maintenance and conservation of the infrastructure.