Impact Stiffness of the Contact-Element Models for the Pounding Analysis of Highway Bridges: Experimental Evaluation

For the requirement of pounding analysis of highway bridges, how to properly choose the impact stiffness has become a primary issue for an achieving accurate result. This article presents an evaluation test of the impact stiffness of four types of contact-element models based on the shaking table test results of a steel highway bridge model. The analytical results indicate that the theoretical impact parameters are significantly larger than the identified values because the assumptions for deriving those models cannot match the actual impact conditions. The possible reasons causing those differences are discussed at the end of this study.     

Point-to-Surface Pounding of Highway Bridges with Deck Rotation Subjected to Bi-Directional Earthquake Excitations

Post-earthquake survey of several strong earthquakes demonstrated that pounding between the neighboring civil infrastructures, such as building and highway bridge, would induce significant structural damage, even collapse, of the structures. This article presents a pounding experiment of highway bridge, especially focused on the point-to-surface pounding of bridge decks due to torsional rotation, when subjected to extreme bi-directional earthquake excitations. To experimentally investigate the point-to-surface pounding between the neighboring bridge segments, a base-isolated highway bridge model, in which the mass centers of the bridge decks do not strictly coincide with the corresponding stiffness centers, is manufactured. A series of shaking table tests of the highway bridge model are carried out for the structural model with large and small separations of the expansion joint to investigate the dynamic responses of the bridge model with and without including the pounding effects, respectively. An analytical model of the highway bridge, in which the point-to-surface pounding is represented by using a modified contact-friction element, is also established based on the lump mass model with three degrees of freedom for each segment. Based on the test results, the model parameters of the modified contact-friction element are identified, and the analytical responses of the highway bridge model with pounding effects are compared with the experimental data. The results show that the highway bridge is vulnerable to the deck rotation, and point-to-surface pounding should be considered in the structural design to lighten the pounding damage of the highway bridge under strong earthquake excitations.     

Snow-tracking and GIS: using multiple species-environment models to determine optimal wildlife crossing sites and evaluate highway mitigation plans on the Trans-Canada Highway

Snow-tracking data were collected for cougars (  Felis concolor ), lynx (  Lynx canadensis ), martens ( Martes americana ) and wolves ( Canis lupus ) and combined with remotely sensed imagery in a geographic information system (GIS) to identify wildlife crossing sites on the Trans-Canada Highway in Banff National Park, Alberta. We used logistic regression to assess the dependent (species presence/absence) relative to measures of topography and vegetation. The exponent form of each logistic regression equation was used to predict crossing sites in a GIS, which were then contrasted with mitigation sites proposed by Parks Canada. We found that: (1) cougars were influenced positively by normalized difference vegetation index (NDVI); negatively by northness and distance to ruggedness, (2) lynx were influenced positively by wetness, greenness, rugged terrain, eastness and distance to rugged terrain; negatively by slope, (3) martens were related positively to wetness, elevation, eastness, and distance to rugged terrain; negatively to northness, (4) wolves were influenced positively by distance to ruggedness; negatively by brightness, elevation, eastness and terrain ruggedness. There were few sympatric crossing sites for all species, supporting the use of species-specific mitigation or wide structures that capture multiple species needs. Inconsistencies were observed between the crossing sites predicted in this study and the Parks Canada proposal. The usefulness of GIS and track data to enhance mitigation projects is illustrated.     

Politicians, Parishes and Police: The Failure of the 1812 Night Watch Bill

The public outcry heard in the wake of the Ratcliffe Highway murders of December 1811 was muted by May 1812 when the 1812 Night Watch Bill died in the house of commons. Responding to the moral panic following the murder of two East End families, the home office gathered considerable information and input from the professional police magistrates and local authorities before proposing the reform of parochial night watch in much of metropolitan London. Nevertheless the bill ran into concerted opposition on grounds of practicality as well as of ideology. A close study of its trajectory through parliament illuminates the role of parliament as a broker for conflicting demands emanating from differing concepts of the public good. The failure of the Night Watch Bill adds significantly to our understanding of the genesis of legislative initiatives, calling into question whether it is possible to distinguish accurately whether particular bills originated from back- or front-bench activity as well as to our knowledge of the relationship between parliamentary activity, ministerial objectives and public opinion.