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Unbonded post-tensioned rocking walls have demonstrated superior seismic performance with greatly reduced damage and excellent self-centering behavior. Current design guidelines (ACI 550.7) and representative research on rocking walls are summarized in this paper. Some inconsistencies and voids in the major design parameters for rocking walls are identified. A brief description is provided for two rocking-wall specimens tested under quasi-static cyclic loading. Force flow and failure mechanisms of rocking walls observed from the tests were studied, and it is discovered that they are very different from those of special structural walls. The test data showed that the concentration of compressive strain in concrete at the corners of rocking walls was a local behavior such that the need for confinement reinforcement higher above the toe region was diminished. Fiber grout weaker than concrete in rocking walls used as ductile bearing materials at the wall-foundation interface is a reasonable alternative to ACI 550.7. Design recommendations for height and volumetric ratio of confinement reinforcement are provided. A requirement for the aspect ratio of rocking walls stricter than that in ACI 550.7 is proposed to prevent shear sliding of the walls. [ABSTRACT FROM AUTHOR]

Each year a large number of concrete bridges are subjected to impact by overheight vehicles or vehicles carrying overheight objects. Most bridge owners in the United States are concerned with the increasing trend of bridges impacted by overheight vehicles, thereby increasing the urgency to evaluate the resistance of bridges to lateral impact loads. The present integrated numerical and experimental study investigates the behavior of a critical connection, between girders and floor beams, in a type of bridge that is considered to be particularly vulnerable, prestressed concrete through-girder (PCTG) pedestrian bridges. PCTG pedestrian bridges comprise precast, prestressed concrete girders connected by cast-in-place, reinforced concrete floor beams and a cast-in-place deck. The deck is connected to the floor beams only, and the floor beams are joined to the girders using embedded concrete anchors. The investigation combines three-dimensional finite-element analyses with physical testing to elucidate the load-deformation characteristics of the girder-floor beam connections. A series of six girder-floor beam connection subassemblage specimens were built and tested, three of which were subjected to vertical loading, while the other three specimens had a combination of vertical and horizontal load. Three types of anchors were investigated, including two types of loop inserts and one bolt insert. The study revealed that specimen response depends upon the characteristics of the embedded concrete anchors. Deterioration of specimen load capacity was found to be associated with concrete cracking, formation of a cone breakout surface, yielding of the anchors, and fracture of the inserts. The floor beam-girder subassemblages were able to resist large displacements after attaining peak load, even though postpeak load carrying capacity was undermined in most cases. DOI: 10.1061/(ASCE)0733-9445(2007) 133:11 (1670) CE Database subject headings: Bridges, girder; Beams: Connections; Concrete, precast; Bridges, pedestrian; Lateral loads; Deformation; Finite element method; Impact loads.

The viability of effective force testing (EFT), a real-time dynamic testing procedure for large-scale structures, has been validated by comparing results of tests on idealized structural models to analytical results. In this paper, the results of tests on a shake table are compared to those conducted using the EFT method. The test structure was a one-story steel structure consisting of typical structural components. The paper also presents an overview of critical issues required for conducting the EFT test, and highlights several problems and solutions that may affect the performance of EFT tests. The comparison of the test results indicates that with proper velocity feedback compensation, the EFT method can be used to apply real-time seismic simulation to structures undergoing nonlinear deformation. DOI: 10.1061/(ASCE)0733-9445(2006) 132:9(1473) CE Database subject headings: Dynamic tests; Earthquake engineering; Comparative studies; Shake table tests.

A large-scale structural assemblage was tested under quasi-static loading to investigate the seismic performance of a rocking-wall structure assembled by precast members. An innovative PreWEC (precast wall with end columns) system, which consisted of a precast non-bearing rocking wall, energy-dissipating O-connectors, and adjacent load-bearing end columns was used as the rocking-wall system. The structure surrounding the PreWEC included precast edge beam and columns and a floor system formed by untopped precast planks. Wall-floor connections were used to isolate the floor from vertical movements of the wall. Test results showed that the floor was successfully isolated from the uplift of the wall throughout the test. The surrounding structure barely increased the strength of the PreWEC system, as anticipated. The entire specimen was almost damage-free at 2% design drift and demonstrated excellent self-centering performance even after experiencing 5% lateral drift. Design recommendations are provided for the key components of this type of precast rocking-wall structure (wall-floor connections, end columns, and floor-beam connections). [ABSTRACT FROM AUTHOR]

This study examined the extent to which self-perceived work-related skills and barriers to employment are associated with current employment status among a sample of recipients of Temporary Aid to Needy Families (TANF). The degree to which these perceptions differed between chronic drug using and non-using women in the sample was then assessed. The probability of employment was significantly affected by conceptions of self-competencies and barriers faced. Chronic drug use independently further reduced the chances of employment. Policy implications for TANF's mandatory work requirements are discussed in light of these findings.