Live-Load Test and Finite-Element Model Analysis of an Integral Abutment Concrete Girder Bridge

As part of the Long Term Bridge Performance (LTBP) Program, a single-span, prestressed, integral abutment concrete girder pilot bridge near Perry, Utah was instrumented with different sensors at various locations onto the bridge for long-term monitoring and periodic testing. One of the periodic tests conducted on this bridge was a live-load test. The live-load test included driving trucks across the bridge, as well as parking trucks along different lanes of the bridge, and measuring the deflection and strain. The data collected from these tests was used to create and calibrate a computer model of the bridge. The model was afforded the same dimensions and characteristics as the actual bridge, and then the boundary conditions (how the bridge is being supported) were altered until the model data and the live-load data matched. Live-load distribution factors and load ratings were then obtained using this calibrated model and compared to the AASHTO LRFD Bridge Design Specifications. The results indicated that in all cases, the AASHTO LRFD Specification distribution factors were conservative by between 55% to 78% due to neglecting to take the bridge fixity (bridge supports) into account in the distribution factor equations. The actual fixity of the bridge was determined to be 94%.Subsequently, a variable study was conducted by creating new models based on the original bridge for changes in span length, deck thickness, edge distance, skew (angle of distortion of the bridge), and fixity to see how each variable would affect the bridge. Distribution factors were then calculated for each case and compared with the distribution factors obtained from the AASHTO LRFD Specifications for each case. The results showed that the variables with the largest influence on the bridge were the change in fixity and the change in skew. Both parameters provided ranges between 10% non- conservative and 56% conservative. The parameter with the least amount of influence was the deck thickness providing a range between 4% non-conservative and 19% non- conservative. Depending on which variable was increased, both increases and decreases in conservatism were exhibited in the study

A CENTER OF A POLYTOPE: AN EXPOSITORY REVIEW AND A PARALLEL IMPLEMENTATION

ABSTRACT. The solution space of the rectangular linear system Az b, subject to x> 0, is called a polytope. An attempt is made to provide a deeper geometric insight, with numerical examples, into the condensed paper by Lord, et al. [1], that presents an algorithm to compute a center of a polytope. The algorithm is readily adopted for either sequential or parallel computer implementation. The computed center provides an initial feasible solution (interior point) of a linear programming problem. KEY WORDS AND PHRASES. Center of a polytope, consistency check, Euclidean distance, initial feasible solution, linear programming, Moore-Penrose inverse, nonnegative solution

Live-Load Testing Application Using a Wireless Sensor System and Finite-Element Model Analysis of an Integral Abutment Concrete Girder Bridge

As part of an investigation on the performance of integral abutment bridges, a single-span, integral abutment, prestressed concrete girder bridge near Perry, Utah was instrumented for live-load testing. The live-load test included driving trucks at 2.24 m/s (5 mph) along predetermined load paths and measuring the corresponding strain and deflection. The measured data was used to validate a finite-element model (FEM) of the bridge. The model showed that the integral abutments were behaving as 94% of a fixed-fixed support. Live-load distribution factors were obtained using this validated model and compared to those calculated in accordance to recommended procedures provided in the AASHTO LRFD Bridge Design Specifications (2010). The results indicated that if the bridge was considered simply supported, the AASHTO LRFD Specification distribution factors were conservative (in comparison to the FEM results). These conservative distribution factors, along with the initial simply supported design assumption resulted in a very conservative bridge design. In addition, a parametric study was conducted by modifying various bridge properties of the validated bridge model, one at a time, in order to investigate the influence that individual changes in span length, deck thickness, edge distance, skew, and fixity had on live-load distribution. The results showed that the bridge properties with the largest influence on bridge live-load distribution were fixity, skew, and changes in edge distance

Notch and Wnt Signaling Mediated Rod Photoreceptor Regeneration by Müller Cells in Adult Mammalian Retina

Background: Evidence emerging from a variety of approaches used in different species suggests that Müller cell function may extend beyond its role of maintaining retinal homeostasis to that of progenitors in the adult retina. Enriched Müller cells in vitro or those that re-enter cell cycle in response to neurotoxin-damage to retina in vivo display multipotential and self-renewing capacities, the cardinal features of stem cells. Methodology/Principal Findings: We demonstrate that Notch and Wnt signaling activate Müller cells through their canonical pathways and that a rare subset of activated Müller cells differentiates along rod photoreceptor lineage in the outer nuclear layer. The differentiation of activated Müller cells along photoreceptor lineage is confirmed by multiple approaches that included Hoechst dye efflux analysis, genetic analysis using retina from Nrl-GFP mice, and lineage tracing using GS-GFP lentivirus in wild type and rd mice in vitro and S334ter rats in vivo. Examination of S334ter rats for head-neck tracking of visual stimuli, a behavioral measure of light perception, demonstrates a significant improvement in light perception in animals treated to activate Müller cells. The number of activated Müller cells with rod photoreceptor phenotype in treated animals correlates with the improvement in their light perception. Conclusion/Significance: In summary, our results provide a proof of principle for non-neurotoxin-mediated activation o

Genetics of photoreceptor degeneration and regeneration in zebrafish

Zebrafish are unique in that they provide a useful model system for studying two critically important problems in retinal neurobiology, the mechanisms responsible for triggering photoreceptor cell death and the innate stem cell–mediated regenerative response elicited by this death. In this review we highlight recent seminal findings in these two fields. We first focus on zebrafish as a model for studying photoreceptor degeneration. We summarize the genes currently known to cause photoreceptor degeneration, and we describe the phenotype of a few zebrafish mutants in detail, highlighting the usefulness of this model for studying this process. In the second section, we discuss the several different experimental paradigms that are available to study regeneration in the teleost retina. A model outlining the sequence of gene expression starting from the dedifferentiation of Müller glia to the formation of rod and cone precursors is presented

Physiotherapy Treatment and Rehabilitation Following Anterior Cruciate Ligament Injury in New Zealand: Are We Doing Enough?

Physiotherapists are lead providers of rehabilitation following anterior cruciate ligament (ACL) injury in New Zealand. Rehabilitation is considered an essential component following ACL injuries, but there is considerable variability regarding pre- and post-operative management. This study used data from the Accident Compensation Corporation (ACC) for the years 2013/14 to 2015/16 (the year being 1 July to 31 June) to gain insight into the physiotherapy management of ACL injuries in New Zealand. Data were extracted from 647 claims from people with a completed ACL reconstruction and 221 claims from people with a confirmed ACL injury who did not undergo surgery. In the 12 months following either ACL injury or surgery, 81% of claimants had fewer than 15 ACC-funded physiotherapy treatments, and 13% of claimants had no ACC-funded physiotherapy treatments. Nine percent of claimants had a previous or subsequent claim for an ACL injury. Compared to best practice literature, the results indicate a significant number of people in New Zealand received fewer than the recommended number of physiotherapy treatments following ACL injury. Possible reasons may include the cost of private physiotherapy services, a lack of endorsement from the respective orthopaedic surgeons, decreased patient adherence/motivation and decreased patient understanding of the importance of rehabilitation