International Concrete Abstracts Portal

Imaging and non-imaging sensors that collect spectral data of surface materials are rapidly becoming available to engineers due to advances in electrooptics and sensor technology. Applications of remote sensing for the identification of surface materials and determination of some of their characteristics have been developed in the geological sciences. Transportation research systems are moving aggressively towards using these types of technologies for materials such as soil subgrades, concrete, asphalt, and, to a lesser extent, steel. A series of experiments were identified to analyze the spectral response of laboratory prepared surfaces, primarily of materials with a mineralogical origin, including soil, aggregate, and concrete. This paper presents the experimental procedure and results of a series of tests performed on a mortar mixture. Temperature, strength, and spectral reflectance were measured for a period of time during curing of the mortar. Results revealed apparent correlations between temperature, water content (curing rate), and spectral response.

Under seismic loading, floor and roof systems in reinforced concrete (RC) buildings act as diaphragms to transfer lateral earthquake loads to the vertical lateral force resisting system (LFRS). In current practice, horizontal diaphragms are typically assumed to be rigid, thus neglecting the effect of the in-plane movement of the diaphragms relative to the vertical LFRS. This study focuses on evaluating the impact of diaphragm flexibility on the structural response of typical RC rectangular building structures using a performance-based approach. Three-story and five-story RC buildings with end shear walls and two aspect ratios (approximately 2: 1 and 3: 1) were developed and designed according to current code procedures assuming rigid diaphragm behavior. The performance-based design criteria outlined in the NEHRF' Guidelines for Seismic Rehabilitation of Buildings (FEMA 273) (4) were used to assess the adequacy of the four case study buildings when diaphragm flexibility was included in the structural response. It was found that the use of a flexible diaphragm model had the largest impact on the 3-story, 3: 1 aspect ratio building and the various analysis procedures gave differing assessments of the adequacy of this case study building. The remaining three case study buildings generally satisfy the FEMA 273 acceptance criteria for three performance levels based on an evaluation of critical structural elements.

Test results of four composite RCS beam-column-slab subassemblies under cyclic loading are presented in this paper. The specimens were designed for beam plastic hinging and controlled joint deformations through the use of a deformation-based design model for RCS connections. Tho types of simple connection details were used in the specimens, one with overlapping U-shaped stirrups passing through the steel beam web, and the other with steel band plates wrapping around the column just above and below the steel bem flanges. The performance of the test specimens was evaluated in terms of load-displacement response, beam rotations, joint deformations and energy dissipation capacity. The accuracy of the deformation-based joint model was also evaluated. Excellent response was observed for all specimens, with large beam rotations, minor to moderate joint damage, and significant energy dissipation capacity, indicating that RCS frame construction is adequate for use in zones of high seismicity. Good agreement was also found between predicted and experimental shear force vs. shear deformation response in RCS connections.

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 optical fiber monitoring system was designed and built into a three-span high performance concrete highway bridge. The Rio Puerco Bridge, locgted 15 miles west of Albuquerque, is the first bridge to be built using HPC in New Mexico. The bridge has 3 spans with length of 29 to 30 m. It is designed to be simply supported for dead load and continuous for live load. HPC was used for the cast-in-place concrete deck and the prestressed concrete beams. A total of 40 long-gage (2-m long) deformation sensors, along with thermocouples were installed in parallel pairs at the top and bottom flange of the girders. The embedded seams measured temperature and deformations at the supports, at quarter spans and at mid-span. Measurements were collected during: Beam Fabrication (Casting of the beams, Steam curing, Strand release, Storage), Bridge Constructio~ and Service. The data collected was analyzed to calculate the prestress losses in the girders, compare the losses to the predicted losses using available code methods, and get a better understanding of the properties and behavior of high performance concrete. The project is funded by the Federal Highway Administration, the New Mexico State Highway and Transportation Department, and the National Science Foundation.