Restoration Of Displacement Research Articles

Study on the Cyclic Behavior of an UPPC Beam with an Energy Dissipator and a Conventional UPPC Beam

In this study, low reversed cyclic loading experiments were performed on an Unbonded Partially Prestressed Concrete (UPPC) beam with an energy dissipator and a conventional UPPC beam to investigate the seismic performance of the beams, including displacement restoration, energy dissipation capacity, ductility, and failure patterns. Studies have shown that UPPC beams with energy dissipators are superior to conventional UPPC beams in terms of displacement restoration, energy dissipation capacity, and ductility and are inferior to conventional UPPC beams in terms of failure patterns. The results of this investigation can help us to improve the poor energy dissipation capacity and lack of displacement restoration in UPPC beams. The contact relationship between the unbonded prestressed tendon and the concrete was simulated using the coupling interaction method, The hysteresis curve based on the calculations was close to the hysteresis curve obtained experimentally. The ultimate bearing capacity and ultimate displacement are highly similar.

Deformation history of the northwestern Selwyn Basin, Yukon, Canada: Implications for orogen evolution and mid-Cretaceous magmatism

Neoproterozoic to Paleozoic slope-to-basin facies continental margin strata underlie area 700 x 200 km across central Yukon Territory, Canada, and collectively define the Selwyn Basin. In a Cordilleran framework, Selwyn Basin strata form a strongly deformed and thrust-faulted package located between the Mackenzie foreland fold-and-thrust belt, and accreted terranes and displaced elements of the ancient North American continental margin. Orogeny commenced in the Jurassic as exotic elements of the composite Yukon-Tanana terrane overrode the ancient continental margin. Collision-related deformation had ceased by ca. 100 Ma, and was followed by a Late Cretaceous (post–85 Ma) dextral transcurrent regime, which laterally displaced elements of the newly assembled continental margin along the orogen-parallel Tintina fault. In western Selwyn Basin, more than 100 km of structural overlap was accommodated on two main detachments, the Robert Service and underlying Tombstone thrust faults. Internal deformation within the thrust sheets is intense, characterized by shear-related folds and fabrics. Metamorphic grade reaches lower to middle greenschist facies at the deepest structural levels exposed, and is characterized by chlorite-muscovite schists. The onset of deformation is constrained by the Late Jurassic age of the youngest units deformed during orogeny. The end of ductile deformation is constrained by new 40Ar/39Ar ages for metamorphic muscovite that range from 104 to 100 Ma. Due to the low metamorphic grade, these ages are interpreted to closely follow the waning of deformation. At ca. 93 ± 3 Ma, isolated granitic intrusions of the Tombstone-Tungsten magmatic belt were emplaced across the western Selwyn Basin in a tensional, postcollisional regime. Restoration of displacement on the Tintina fault places the western Selwyn Basin adjacent to the Yukon-Tanana terrane uplands of east-central Alaska in the Early to mid-Cretaceous. Despite their adjacent positioning in cross-orogen section during orogenesis, the two elements feature some significant differences in Jurassic-Cretaceous deformation. Most notably, the Yukon-Tanana terrane uplands record a significant extensional event at 120–105 Ma, which resulted in NW-SE–oriented extension, exhumation of deep structural levels, and voluminous felsic plutonism. In contrast, western Selwyn Basin did not undergo equivalent uplift and extension, and features temporally and spatially restricted plutonism. Within an orogenic framework, the Yukon-Tanana terrane uplands can therefore be considered to represent an exhumed core characterized by high heat flow, whereas the western Selwyn Basin represents an immediate northeastern salient to the exhumed core. These differences have important implications for the geodynamic setting of mid-Cretaceous plutonism across these two major lithologic-tectonic entities of the northern Cordillera.

Restoring thrusting in the East Greenland Caledonides

Three principal lithostructural domains are recognized within the southern part (70°–76°N) of the East Greenland Caledonides. At the deepest structural levels, within foreland windows, a thin Neoproterozoic–lower Paleozoic succession unconformably overlies older basement. The foreland is overridden by two major thrust sheets, a lower and an upper thrust sheet. Each of these comprise Paleoproterozoic or older crystalline basement rocks and their metasedimentary cover, and preserve evidence of both a pre-Caledonian (ca. 930 Ma) thermal event and the superimposed Caledonian orogenesis. Transport directions on major thrusts are top-to-the-west-northwest, and restoration of displacements with respect to the foreland windows permits reconstruction of a 500–700-km-wide sector of the pre-Caledonian Laurentian margin. One implication of the reconstruction is that the 18.5-km-thick Neoproterozoic–lower Paleozoic succession preserved in the upper thrust sheet accumulated in a basin that was at least 200 km east of the foreland where the equivalent succession totals only 250–400 m. Scandian (ca. 430 Ma) thrusting resulted in 40%–60% shortening to produce the present ∼300-km-wide orogenic belt in East Greenland.