Structural details to accommodate seismic movements of highway bridges and retaining walls

This report describes datailing for structural movements for bridges and retaining walls for new construction in the western and eastern U.S. Bridge retaining devices such as longitudinal joint restrainers, vertical motion restrainers, shear keys, and integral superstructure ti substructure connections are described. Many of these details are traditional methods that have been used in new bridge construction to limit displacements for seismic events. Sacrificial elements, which include abutments and joints, are also described. These types of details have been used in new seismic designs within the last two decades. An introduction to passive energy dissipating devices and isolation bearing systems is provided as well as recommendations for detailing. Both devices are relatively new as a method to limit displacements in bridges within the U.S. In fact, isolation bearing systems have just emerged for new bridge construction within the last few years. The minimun support length requirements are reviewed. The current practice for designing earth retaining systems for seismic displacements is reviewed and some recommendations for detailing are provided. The effects of substructure flexibility on the isolation system is documented. An example study and comparison is given to illustrate the impact of substructure flexibility.(AU)

Toxicologic evaluation of a high-selenium hay diet in captive pronghorn antelope (Antilocapra americana).

Five captive-raised pronghorn antelope (Antilocapra americana) were fed an alfalfa-grass hay diet containing 15 ppm total dietary selenium (Se) for 164 days. Four additional captive-raised pronghorns fed a similar diet containing approximately 0.3 ppm total dietary Se served as controls. None of the pronghorns had clinical signs attributable to the high Se hay. Plasma Se increased more rapidly than blood Se concentrations, from baseline concentrations (< 0.15 g/ml) to > 0.40 g/ml within the first 50 days on the high selenium diet, but thereafter declined to approximately 0.30 microgram/ml. Mean primary antibody response to hen egg albumin was less in pronghorn on Se hay. No significant gross or histological lesions attributable to selenosis were found, nor was there any evidence of dystrophic hoof growth. The greatest Se tissue concentrations were found in liver and kidney (5.67 to 10.4 micrograms/g and 2.36 to 3.14 micrograms/g, respectively) from experimental animals; liver and kidney from the controls contained considerably less (< or = 0.52 microgram/g and < or = 0.61 microgram/g, respectively). Exposure of pronghorns for more than 5 mo to a diet containing 15 ppm Se caused significant increases in plasma, liver and kidney Se concentrations, in the absence of clinical disease or pathologic lesions due to selenosis. Based on these results, we propose that pronghorns are less susceptible to selenosis than previously reported and that diagnostic criteria for the disease should be modified.