On June 15, 1999, a magnitude Mw = 7.0 earthquake occurred with epicenter located southwest from the city of Tehuacan, Puebla, and on September 30, 1999, a Mw = 7.5 magnitude earthquake occurred with epicenter located northeast from the city of Puerto Escondido, Oaxaca, Mexico. The earthquakes affected a wide geographical area, including seven states. Few casualties were recorded. In Puebla, 15 percent in the State of Oaxaca and only the remaining ten percent in the States of Morelos, Mexico, Tlaxcala, Veracruz and Guerrero; the second earthquake only affected the State of Oaxaca. Historical buildings, dwellings, hospitals, schools and roads were mostly impacted. Some damages were also experienced in bridges and lifelines. The economic activities were not severely impaired. This paper summarizes the seismological characteristics of the event, its economic impact and the Emergency measures adopted by the authorities. Observation made during several visits to the affected regions of Puebla and Oaxaca on the behavior of soils and foundations, lifeline, schools, dwellings, historical monuments and commercial buildings are described. Recommendations for the development o fvulnerability reduction programs are presented.

Recycled aggregates used in combination with high-volume fly ash is an example of sustainable construction material because it represents a judicious use of resources by recycling by-products, that results in a lower environmental impact through reduced carbon dioxide emissions and reduced natural aggregate extraction from quarries. Furthermore, the related concrete mixtuns yield satisfactory mechanical performance. The goal of the experimental work reported here was to investigate the effect of recycled aggregate andor fly ash on carbonation and chloride penetration depth, as well as the effect on corrosion behavior of either bare or galvanized steel in cracked reinforced concrete. The concrete mixture contained equal amounts of fly ash and cement. The results show that the introduction of the sustainability concept in concre&e trechnology by using recycled aggregate andor fly ash did not cause any deleterious effects on durability of reinforced concrete specimens in terms of both chloride and carbon dioxide penetration, and reinforcement corrosion in cracked concrete.

This paper presents a rational approach used for the evaluation of inplace concrete pavement with flexural strength requirements. During the construction of a concrete paving project at McCarran International Airport in Las Vegas, Nevada, data was developed from the testing of over 450 specimens of concrete beams, cylinders, and cores representing samples from nearly 170 locations. Hexural, compressive, and splitting tensile strength testing was performed on these samples obtained from locations where comparison between the different types of strength tests was possible. Relationships between this data were evaluated and a rational approach to the evaluation of in-place concrete for compliance with flexural strength requirements was developed. This approach that begins with trial batch data and includes cast and cored specimen, could be applied to other concrete paving projects with similar concerns.

An extensive laboratory program was initiated in the early 1980's to develop high-strength lightweight concrete for use in offshore oil and gas structures in severe marine environments. From the results of that development program, four mixtures were chosen to be evaluated under field conditions. Large prisms (305 by 305 by 914mm) of each mixture were placed in the tidal zone at the U.S. Army Corps of Engineers Severe Weather Exposure Station on the border between Canada and the United States. The mixtures used an expanded slate aggregate from the USA and a pelletized clay aggregate from Japan. All mixtures contained silica fume and had total binder content from 494 to 556 kg/cu m with water-binder ratios of 0.28 by mass. The concrete density varied from 1800 to 1990 kg/cu m, with 90-day strength from 60 to 73 MPa depending on the mixture. The prisms under-went annual visual and non-destructive evaluations. After 10-years exposure in the tidal zone, the prisms were removed to the laboratory where they were examined for strength, robustness and chloride ion penetration. This paper reports the results of the test program. In general, the overall performance looks very good.

The behavior of liquid containing structures (LCS) subjected to seismic excitations is reviewed. The major parameters affecting the response of concrete circular tanks for LCS are discussed. Existing codes aud standards related to seismic design of LCS are reviewed. With the aid of a design example, results of the various design standards are compared. The effects of earthquake load on the behavior of reinforced concrete (RC) tanks are also investigated through a detailed example.