Residual Vertical Displacement Research Articles

Centrifuge bearing behaviors of batter-piled wharf under lateral cyclic loading

This article investigates bearing behaviors of a batter-piled wharf subjected to cyclic episodes of lateral loading with varying amplitude through two-way displacement-controlled centrifuge modeling. Results show that the lateral load vibrated around residual values and deviated toward waterside. Lateral stiffness exhibited degradation with increasing cycles in each constant magnitude sequence. The residual vertical displacement kept decreasing and tended to become constant over time. The residual pore pressure was positive in the seabed soil and around piles over time; the soil around double-plumb piles registered larger residual pore pressure and magnitudes than other areas. The increase or decrease of soil pressure depends on the balance of pore pressure redistribution and soil reconsolidation in the upper soil, and the lower soil registered decreasing soil pressures owing to poor drainage condition induced soil softening. Plumb piles exhibited waterside curvature in the upper part, and the bending moment around the front double-plumb pile head was larger than other plumb piles. The whole forward batter pile exhibited waterside curvature induced by the soil settlement, while the backward batter pile bore the largest bending moment around the pile head, and its landside curvature tended to relieve affected by the soil settlement.

Estimation of Seismic and Aseismic Deformation in Mexicali Valley, Baja California, Mexico, in the 2006–2009 Period, Using Precise Leveling, DInSAR, Geotechnical Instruments Data, and Modeling

Ground deformation and seismicity in Mexicali Valley, Baja California, Mexico, the southern part of the Mexicali-Imperial valley, are influenced by active tectonics and human activity. In this study, data from two successive leveling surveys in 2006 and 2009/2010 are used to estimate the total deformation occurred in Mexicali Valley during 2006–2009. The leveling data span more than 3.5 years and include deformation from several natural and anthropogenic sources that acted at different temporal and spatial scales during the analyzed period. Because of its large magnitude, the aseismic anthropogenic deformation caused by fluid extraction in the Cerro Prieto geothermal field obscures the deformation caused by other mechanisms and sources. The method of differential interferograms stacking was used to estimate the aseismic (interseismic tectonic and anthropogenic) components of the observed displacement, using SAR images, taken in 2007 during a period when no significant seismicity occurred in the study area. After removing the estimated aseismic signal from the leveling data, residual vertical displacement remained, and to identify possible sources and mechanisms of this displacement, a detailed analysis of records from tiltmeters and creepmeters was performed. The results of this analysis suggest that the residual displacement is mainly caused by moderate-sized seismicity in the area of study. Modeling of the vertical ground deformation caused by the coseismic slip on source fault (primary mechanism) of the two most important earthquakes, May 24, 2006 (Mw = 5.4) and December 30, 2009 (Mw = 5.8), was performed. The modeling results, together with the analysis of geotechnical instruments data, suggests that this moderate-sized seismicity influences the deformation in the study area by coseismic slip on the source fault, triggered slip on secondary faults, and soft sediments deformation.

Steel Strap으로 횡구속된 무철근 바닥판의 정적 및 피로거동 특성 연구

Jo, Byung Wan Kim, Cheol HwanAbstractIn the steel-free bridge concrete deck, steel straps are genera lly used instead of conventional steel rebar while laterally restrained in the perpendicular direction to the traf fic in order fir the arching effect of concrete deck. In this paper, the minimum amount of FRP bar is to be suggested based o n the structural strength, crack propagation, stress level and others in order to control cracks. As a result of lab oratory tests, the structural strength of deck with 0.15 percentage of steel strap showed improved structural strength i ncluding ductility. The long-term serviceability of steel strap deck with FRP bar proved to satisfy the requirements and to be structurally stable while showing the amount of crack and residual vertical displacement within the allowable l imits after two million cyclic loadings. The structural failure of RC bridge deck is generally caused from the punching shear r ather than moment. Therefore, the ultimate load at failure could be estimated using the shear strength formula in the two-way slab based on ACI and AASHTO criteria. However the design criteria tend to underestimate the shear str ength since they don’t consider the arching effects and nonlinear fracture in bridge deck with lateral confinement. In this paper, an equation to estimate the punching shear strength of steel strap deck is to be developed considering the actual failure geometries and effect of lateral confinement by strap while the results are verified in accordance with labo ratory tests.Keywords: Concrete bridge slab, Steel free, Steel strap, FRP bar, Punchin g shear

Deciphering vertical deformation and poroelastic parameters in a tectonically active fault-bound aquifer using InSAR and well level data, San Bernardino basin, California

SUMMARY Using InSAR and hydrogeologic time-series spanning 1995 to 2000, we characterize the elastic storage and surface deformation in the vicinity of the San Bernardino basin, California. The region encompasses a complex major aquifer located at the junction of the San Andreas and San Jacinto faults that supplies groundwater to over 600,000 people. We remove the elastic vertical surface displacement associated with changes in groundwater levels from the InSAR time-series by a least squares inversion. Our method estimates a poroelastic ratio at 60 well sites, which we normalize by basin depth, allowing for comparison of the elastic response of the aquifer skeleton from site to site. Our method also estimates residual vertical displacement rates at each well site, surface displacement not explained by observed trends in groundwater levels. Residual vertical displacement rates reveal patterns of subsidence and uplift across the basin over the 5-yr period from 1995 to 2000. In a narrow zone of observed residual subsidence near the San Jacinto fault, where many normalized poroelastic ratios trend higher than expected, we find permanent compaction of clay-rich strata to be the most likely explanation for 0.5–2.0 mm yr –1 of residual subsidence. This permanent compaction is likely a result of delayed compaction due to previous overdraft conditions and/or a result of the installation of deep production wells during the span of the InSAR time-series. Observations of localized subsidence within stepovers of the San Jacinto fault zone and relative uplift at the range fronts are consistent with current basin development models; however, interseismic strain modelling of the regional faults does not reproduce the surface displacement pattern or magnitude of these observations.

Unstable fractures of the pelvis treated by Ilizarov external fixation device

We reviewed seven patients with an unstable fracture of the pelvic ring who had been treated with a Ilizarov external fixation device after a mean follow-up of 5.5 years. There were four "open-book" injuries (type B according to Tile) and three rotationally and vertically unstable injuries (type C according to Tile). In all patients union of fracture site had been achieved after a mean period of 65 days in patients with type B injuries and 98 days in patients with type C injuries. In the four patients with an "open-book" injury the symphyseal diastasis was partially reduced from 46 mm to 13 24mm to 13mm. The radiological result was excellent in one patient, good in one and poor in two patients. The functional outcome was rated as excellent in three patients and good in one patient. In patients with type C injury vertical displacement was partially reduced from 21mm to 12mm. The patients in this group had excellent, good and poor radiological result, respectively. The functional outcome was excellent in two cases and good in one case. General surgical complications were not seen. Infection at the pin sites was seen in six patients. In our study unsatisfactory or poor functional result was not registrated due to construction characteristics of Ilizarov device. Because of this characteristics there were no residual vertical displacement more then 8 mm.

Failure of reduction with an external fixator in the management of pelvic ring injuries

We reviewed 110 patients with an unstable fracture of the pelvic ring who had been treated with a trapezoidal external fixator after a mean follow-up of 4.1 years. There were eight open-book (type B1, B3-1) injuries, 62 lateral compression (type B2, B3-2) and 40 rotationally and vertically unstable (type C1-C3) injuries. The rate of complications was high with loss of reduction in 57%, malunion in 58%, nonunion in 5%, infection at the pin site in 24%, loosening of the pins in 2%, injury to the lateral femoral cutaneous nerve in 2%, and pressure sores in 3%. The external fixator failed to give and maintain a proper reduction in six of the eight open-book injuries, in 20 of the 62 lateral compression injuries, and in 38 of the 40 type-C injuries. Poor functional results were usually associated with failure of reduction and an unsatisfactory radiological appearance. In type-C injuries more than 10 mm of residual vertical displacement of the injury to the posterior pelvic ring was significantly related to poor outcome. In 14 patients in this unsatisfactory group poor functional results were also affected by associated nerve injuries. In lateral compression injuries the degree of displacement of fractures of the pubic rami caused by internal rotation of the hemipelvis was an important prognostic factor. External fixation may be useful in the acute phase of resuscitation but it is of limited value in the definitive treatment of an unstable type-C injury and in type-B open-book injuries. It is usually unnecessary in minimally displaced lateral compression injuries.

Failure of reduction with an external fixator in the management of injuries of the pelvic ring. Long-term evaluation of 110 patients.

We reviewed 110 patients with an unstable fracture of the pelvic ring who had been treated with a trapezoidal external fixator after a mean follow-up of 4.1 years. There were eight open-book (type B1, B3-1) injuries, 62 lateral compression (type B2, B3-2) and 40 rotationally and vertically unstable (type C1-C3) injuries. The rate of complications was high with loss of reduction in 57%, malunion in 58%, nonunion in 5%, infection at the pin site in 24%, loosening of the pins in 2%, injury to the lateral femoral cutaneous nerve in 2%, and pressure sores in 3%. The external fixator failed to give and maintain a proper reduction in six of the eight open-book injuries, in 20 of the 62 lateral compression injuries, and in 38 of the 40 type-C injuries. Poor functional results were usually associated with failure of reduction and an unsatisfactory radiological appearance. In type-C injuries more than 10 mm of residual vertical displacement of the injury to the posterior pelvic ring was significantly related to poor outcome. In 14 patients in this unsatisfactory group poor functional results were also affected by associated nerve injuries. In lateral compression injuries the degree of displacement of fractures of the pubic rami caused by internal rotation of the hemipelvis was an important prognostic factor. External fixation may be useful in the acute phase of resuscitation but it is of limited value in the definitive treatment of an unstable type-C injury and in type-B open-book injuries. It is usually unnecessary in minimally displaced lateral compression injuries.

Vertical shear injuries: is there a relationship between residual displacement and functional outcome?

Residual vertical displacement is often cited as being related to poor outcome in patients with pelvic injuries. This study attempts to clarify the relationship between residual vertical displacement and functional outcome. From 1982 to 1989, over 500 patients with pelvic ring injuries were treated at two Level I trauma centers. Thirty-three patients with vertical shear (Tile C) fractures and residual displacement (2-52 mm) were evaluated. Outcomes were quantified by using SF-36 Short-Form Health Survey (SF-36) and the Iowa Pelvic Score (IPS). There was no correlation between IPS or SF-36 scales and residual vertical displacement. The IPS correlated (p<0.05) with seven of eight SF-36 categories, excluding mental health. Patients reporting limp and leg length discrepancy also correlated with the IPS and select SF-36. Pelvic injuries showed no correlation between functional outcome and residual vertical displacement suggesting other factors. The degree of residual vertical displacement does not affect functional outcome.

The Long-Term Results of Nonoperatively Treated Major Pelvic Disruptions

Twenty-six patients with major anterior-posterior pelvic disruptions not involving the acetabulum were reevaluated an average of 8 years (minimum 5 years) after injury. All pelvic injuries were treated nonoperatively. Subjective complaints at the time of follow-up included frequent or daily low back discomfort (50%), localized distal dysesthesias (46%), and some degree of work disability (38%). Objective neurologic deficit (42%) and a limp (32%) were often detected on examination. The amount of residual vertical displacement was measured on plain AP radiographs and graded as none, displaced less than 1 cm, or displaced greater than 1 cm. The long-term outcome correlated exceptionally well with both the amount of residual vertical displacement and the stability of the fracture.