Foundations for auto shredders

Unbalanced forces developed by hammer wear and impact must be resisted by auto shredder foundations. Methods for estimating the impact forces are described. Because of different soil conditions, a concrete mat, a concrete block, and a pile-supported foundation system were adopted at three different construction sites. The design procedures involved in determining the dynamic response for each type of foundation are illustrated by examples. Vibration measurements made on the pile-supported foundation after construction permitted comparisons of prototype motions with design predictions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25356/1/0000803.pd

Seismic response analysis of multiple-frame bridges with unseating restrainers considering ground motion spatial variation and SSI

Unseating damages of bridge decks have been observed in many previous major earthquakes due to large relative displacement exceeding the available seat length. Steel cable restrainers are often used to limit such relative displacements. Present restrainer design methods are based on the relative displacements caused by the different dynamic characteristics of adjacent bridge structures. However, the relative displacements in bridge structures are not only caused by different dynamic characteristics of adjacent bridge segments. Recent studies indicated that differential ground motions at supports of bridge piers and Soil Structure Interaction (SSI) could have a significant influence on the relative displacement of adjacent bridge components. Thus the present design methods could significantly underestimate the relative displacement responses of the adjacent bridge components and the stiffness of the restrainers required to limit these displacements. None of the previous investigations considered the effects of spatially varying ground motions in evaluating the adequacy of the restrainers design methods. Moreover, the code recommendation of adjusting the fundamental frequencies of adjacent bridge structures close to each other to mitigate relative displacement induced damages is developed based on the uniform ground motion assumption. Investigations on its effectiveness to mitigate the relative displacement induced damages on the bridge structures subjected to spatially varying ground motion and SSI are made. This paper discusses the effects of spatially varying ground motions and SSI on the responses of the multiple-frame bridges with unseating restrainers through inelastic bridge response analysis

Influence of fluctuations in stress amplitude on fatigue of metals part 1

The purpose of this study was to investigate the fatigue life of unnotched and notched specimens of SAE 4340 steel and of 17S-T aluminum alloy when subjected to repeated stresses that fluctuated between two different predetermined amplitudes (one less and the other greater than the fitigue limit). Small high speed rotating cantilever beam fatigue testing machines applied to the specimens the two general types of loading cycles studied, which: (1) the amplitude of stress for each test was varied gradually between two predetermined limits, and (2) the stress amplitude was alternated abruptly at regular intervals between two predetermined values.N6 ORI 71 TO 4 48/07 PR