International Concrete Abstracts Portal

Performance evaluation of sacrificial exterior shear keys under simulated seismic loading is presented in this paper. The performance evaluation was conducted in terms of damage levels observed during testing. The experimental program consisted of six experiments, and the variables investigated during testing were; (1) inclusion and exclusion of back and wing walls to determine influence of these walls in the seismic response of the shear keys, (2) adoption of different design details such as the use of sacrificial flexural keys, and (3) prestressing of the abutments with the main objective of decreasing damage propagation into the abutment walls. These experiments provided results that were used to make realistic assumptions of the load-deformation response of sacrificial exterior shear keys as well as their post-peak performance under cyclic loads. Experimental and analytical results were also used to develop a hysteretic model for exterior sacrificial shear keys at the abutments. The development of this hysteretic model is also discussed in the paper.

Corrosion of reinforcing steel in concrete usually initiates from chloride ingress. The temperiiture of thd service environment and cementitious material blends influence chloride ingress. This paper presents data from a multi-year experiment designed to illustrate the effects of temperature and supplementary cementing materials on chloride diffusion in concrete. This experiment consists of six concrete mixtures, five of which contained different supplementary cementing materials. Test specimens were submerged in 6% sodium chloride solution, and stored at a temperature of 10, 23, and 32 C for approximately three and one-half years. The chloride ingress data are presented, and the impact of temperature on chloride diffusion coefficients along with its implications for corrosion service life modeling am discussed presently, most service life prediction models adjust for the service temperature of a structure by using the Arrhenius Equation. The time-to-cormsion data obtained in this study suggests that the net result of temperature related effects does not match the predictions based on the Arrhenius Equation.

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.