Peak Pressure Data Research Articles

Numerical simulation of reinforced concrete slab subjected to blast loading and the structural damage assessment

The structural dynamic response and failure behavior of reinforced concrete slab subjected to TNT blasts under different conditions are studied numerically. Three-dimensional finite element model with TNT, air and reinforced concrete slab was established, in which the reinforced concrete structure adopts the solid hexahedral separation common node modeling. Fluid-structure coupling algorithm combined with appropriate constitutive model and failure algorithm were used to analyze different explosion conditions. Intensive numerical simulations are carried out on different combinations of working conditions for TNT mass from 0.1 kg to 3.5 kg, blast distance from 100 mm to 800 mm, reinforced concrete slab thickness from 40 mm to 120 mm. Then, the relationship between the different explosion conditions and different damage levels (Low damage, Medium damage and Severe damage) of the reinforced concrete structure is established in this paper. In order to verify the numerical modeling and materials parameters, numerical simulation model validation is given, the results presents well the fracture and collapse of the reinforced concrete structure subjected to TNT blasts. Shock Wave's Peak Pressure data obtained by the numerical simulation is in good agreement with the prediction results of Henry's Formula. The results of reinforced concrete structural damage, including collapse radius and deflection, are in good agreement with the experimental phenomenon and data obtained by Wang et al. (2012).

Uncertainties in prediction of local peak wind pressures on mid- and high-rise buildings by considering gumbel distributed pressure coefficients

Design wind pressures for components and cladding (C&C) are key design parameters. For mid- and high-rise buildings, design pressures for C&C are often evaluated from wind tunnel tests, especially when building geometries are irregular or surrounding environments are complex. Wind tunnel data acquisition and analysis approaches both contribute to uncertainties of predicted design wind pressure coefficients. Although there is still debate on the most appropriate probability distribution to fit the peak pressure data and the best method to obtain the design pressures, Gumbel distribution and the generalized least square method (also known as BLUE) are widely considered and adopted in engineering practices. Wind tunnel test durations and number of peaks used in the extreme value analysis also influence peak pressure predictions. Some recent studies investigated the effect of these factors for predicting design wind pressures on low-rise buildings, which typically have a model scale of about 1:30 to 1:100. It is not clear whether observations in these studies are directly applicable to mid- and high-rise buildings or stadiums, which typically have a much smaller model scale (~1:400). For this purpose, a long duration wind tunnel test was conducted by employing a model with a generic high-rise building geometry. The desired design percentile of extreme pressures is briefly discussed. The effect of test durations and number of peaks involved in the extreme value analysis was investigated. Lastly, this study investigated the influence of inconsistency between the averaging time of design wind speeds and the target reference periods, in which the design pressure coefficients were expected to occur, on the prediction of design wind pressures. The results suggest that an adequate combination of test durations and number of peaks used in the extreme value analysis reduces uncertainties significantly and results in appropriate design wind pressures for engineering applications.

Local pressures for ships in ice: Probabilistic analysis of full-scale line-load data

Ships operating in ice might be exposed to significant ice loading. Using a probabilistic semi-empirical method known as the event-maximum method, the long-term maximum level of ice loading on a ship can be estimated based on parent distributions of short-term full-scale ice load measurements. The event-maximum method is used to model the relationship between extreme local ice pressures and impact area by estimating parameters corresponding to the inverse slope (α) and intercept (x0) for the line of best fit for the tail of ranked peak pressure data versus the natural logarithm of the Weibull plotting position. These best-fit lines are assumed to follow an exponential distribution and associated α and x0 values are produced for different local design areas. This allows for the determination of α-area curves, which reflects the relationship between ice pressure and the local design area. Previous studies have determined α-area curves for different geographical areas such as the Beaufort Sea and South Bering Sea, representing different ice types including both first-year and multi-year ice. In this study, two separate sets of full-scale ice load measurements having been considered, namely measurements from the Kara Sea and the Barents Sea, as well as measurements from the Antarctic Ocean. Using these two datasets, two new α-area curves have been generated that represent among other operating areas (the Kara Sea and the Barents Sea), operating modes (icebreaker assisted operation) and impact areas (aft shoulder) not covered by other curves. Earlier formulations of the event-maximum method are based on local design areas in which the width and height of areas are defined by the size of instrumented rectangular panel areas (or combinations of those areas) on the bow of the vessel from which the data were collected. In that approach, ice thickness is not directly considered since the height of individual panels is based on the dimensions of instrumented areas and moreover, detailed ice thickness records were not available for those data sets. In the present study, an alternative approach has been developed to extend the event maximum method for use with ship line-load data. In this approach ice pressures are calculated by dividing the ice force measured on frames by the corresponding line-load area (ALL), which is the product of the width (W) that is based on frame spacing and an assumed line-load height (H) corresponding to 30% of the maximum prevailing ice thickness, as per best design practice, along the lines of the Finnish-Swedish ice class rules. Data already presented as line-loads (in units of force per unit width), are converted to pressures by dividing line-loads by height H. The event definition used in the present approach is defined as the maximum pressure corresponding to 10- or 20-min intervals, as opposed to the impact event definition used in earlier works. In applying this extended method to develop new α-area curves, valuable insights into the relationship between local peak ice pressure and prevailing ice thickness have been gained for the above-mentioned full-scale measurements. The determined curves indicate a negative correlation between prevailing ice thickness and maximum local nominal ice pressure. Finally, it has been demonstrated that it is feasible to apply such curves in combination with the principle of the event-maximum method to estimate the maximum nominal ice pressure expected for a ship given a specified transit distance in sea ice with different prevailing thicknesses.

The effects of vibro-medical insole on sensation and plantar pressure distribution in diabetic patients with mild-to-moderate peripheral neuropathy

BackgroundThe first aim of this study was to determine the effect of a vibro-medical insole on pressure sensation and the second was to measure the effects of a vibro-medical insole with and without random noise on plantar pressure distribution in diabetic patients with mild-to-moderate peripheral neuropathy. MethodsTwenty patients with mild-to-moderate diabetic neuropathy were recruited in the clinical trial pre-test, post-test study. A medical insole was made for each participant and a vibratory system was inserted into it. Pressure sensation was evaluated before and after the 30-min walk using the vibro-medical insole with added random noise by Semmes-Weinstein Monofilaments. Peak pressure data was measured before and after 30-min walking with a vibro-medical insole with and without random noise by the Pedar-x system. FindingsPressure sensations showed improvement after 30-min walking with the vibro-medical insole with added random noise at the heel, metatarsophalangeal heads and hallux of both feet in all participants (p < 0.05). Peak pressure decreased significantly in the heel, MTP2,3, MTP4,5 and hallux (p < 0.05) and increased in midfoot (p < 0.05) using the vibro-medical insole with and without random noise compared to the shoe only condition. Only the peak pressure of the heel region decreased using the vibro-medical insole with random noise compared to without random noise (p = 0.006). InterpretationThirty minute walking with a vibro-medical insole seems to improve pressure sensation and alter peak pressure in diabetic patients with mild-to-moderate peripheral neuropathy. This work suggests that vibro-medical insoles can be used for daily living activities and possibly decreases the risk of ulceration in diabetic neuropathy patients.

The effects of vibro-medical insole on sensation and plantar pressure distribution in diabetic patients with mild-to-moderate peripheral neuropathy

The first aim of this study was to determine the effect of vibro-medical insole on pressure sensation and the second was to measure the effects of vibro-medical insole with and without random noise on plantar pressure distribution in diabetic patients with mild-to-moderate peripheral neuropathy. Twenty patients with mild-to-moderate diabetic neuropathy were recruited in the clinical trial pre-test, post-test study. Medical insole was made for each participants and vibratory system was inserted it. Pressure sensation was evaluated before and after the 30-minute walks using the vibro-medical insole with Semmes-Weinstein Monofilaments. Peak pressure data was measured using the vibro-medical insole with and without random noise by Pedar-x system. Pressure sensation is shown improvement using the vibro-medical insole with added random noise at heel, metatarsophalangeal heads and hallux of both feet in all participants ( P < 0.05). Peak pressure decreased significantly in heel, MTP 2,3 , MTP 4,5 and hallux ( P < 0.05) and increased in midfoot ( P < 0.05) using the vibro-medical insole with and without random noise compared to shoe only condition. Only the peak pressure of the heel region decreased using the vibro-medical insole with random noise compared to without random noise ( P = 0.006). Vibro-medical insole seems to improve pressure sensation and alter peak pressure in the diabetic patients with mild-to-moderate peripheral neuropathy. This work suggests that vibro-medical insole with added random noise can be used for daily living activities to overcome sensory loss and probably decrease the risk of ulceration in diabetic neuropathy patients.

Peak pressure data and pressure-time integral in the contralateral limb in patients with diabetes and a trans-tibial prosthesis

BackgroundClinicians currently rely on observational clinical data pertaining to the biomechanics of the diabetic foot. However, advances in technology can objectively describe this. A thorough understanding of the functional and mechanical consequences following trans-tibial amputations is lacking. Research questionDoes a trans-tibial prostheses significantly increase peak plantar pressures and pressure time integrals in the intact foot of patients with type-2 diabetes and neuropathy? MethodsA prospective quantitative matched-subject design was employed. Twenty participants living with diabetes and peripheral sensory neuropathy were recruited. Ten participants presented with a trans-tibial amputation and 10 had intact feet. Participants were matched for gender, age, foot type and BMI. Peak plantar pressure and pressure time integral data were recorded using the Tekscan HR™ pressure mat system, using the two-step gait protocol. The Shapiro-Wilk test was used to determine normality of data. The Independent Samples t-test and the Mann Whitney U test were carried out to reject the null hypothesis. ResultsAlthough no significant differences (p < 0.05) in mean peak plantar pressures were observed in all the foot masks analysed between the amputee and the control group, a significant difference (p = 0.002) in mean pressure time integrals was recorded with highest pressure time integral (PTI) values under the 2nd–4th metatarsophalangeal joint (MTP joint) for the trans-tibial amputee group. SignificanceCumulative exposure of both pressure and time can lead to tissue damage. PTI could be considered as an important contributory factor in determining ulcer formation. Elevated PTI under the 2nd–4th MTP joints sustained in the intact contralateral limb in patients using below knee prosthesis could possibly be due to gait alterations in this population. The preservation of the contralateral limb is of great concern and importance as this might impact patient’s mobility and quality of life.

Plantar Pressure Distribution During Level Walking, and Stair Ascent and Descent in Asymptomatic Flexible Flatfoot

The first purpose was to identify the plantar pressure distributions (peak pressure, pressure integral time, and contact area) during level walking, and stair ascent and descent in asymptomatic flexible flatfoot (AFF). The second purpose was to investigate whether peak pressure data during level walking could be used to predict peak pressure during stair walking by identifying correlations between the peak pressures of level walking and stair walking. Twenty young adult subjects (8 males and 12 females, age years) with AFF were recruited. A distance greater than 10 mm in a navicular drop test was defined as flexible flatfoot. Each subject performed at least 10 steps during level walking, and stair ascent and descent. The plantar pressure distribution was measured in nine foot regions using a pressure measurement system. A two-way repeated analysis of variance was conducted to examine the differences in the three dependent variables with two within-subject factors (activity type and foot region). Linear regression analysis was conducted to predict peak pressure during stair walking using the peak pressure in the metatarsal regions during level walking. Significant interaction effects were observed between activity type and foot region for peak pressure (F=9.508, p

The impact of ulnar collateral ligament tear and reconstruction on contact pressures in the lateral compartment of the elbow

Complete ulnar collateral ligament (UCL) injury increases articular pressure and reduces contact area compared with the normal intact UCL. UCL reconstruction restores the contact area and contact pressure observed in the native joint. Six male cadaveric elbows were mounted on a custom jig capable of simulating the 2 critical phases of the throwing motion during pitching. A contact sensor was placed through an anterior arthrotomy into the radiocapitellar joint. Each specimen then underwent valgus loading at 1.75 and 5.25 Nm of torque with the biceps, brachialis, and triceps under axial load in each testing condition. The average valgus laxity in the intact elbow at 90° was 3.7° ± 0.6° at the 5.25 Nm level of torque, which doubled after transection. The reconstruction group demonstrated less laxity (2.4° ± 0.4°) and reduced valgus angulation of the ulna at 5.25 Nm of torque. The transected UCL condition showed peak contact pressure 67% higher compared with the native ligament group at 5.25 Nm of torque. The reconstructed group increased peak articular cartilage pressures by 33% from the native ligament. At 5.25 Nm of torque for the 90° flexion phase, the transected UCL condition showed an average contact pressure of 84% greater than that of the native ligament group. Reconstruction of the UCL restored average articular pressures to within 20% of intact values at 90°. UCL injury increases radiocapitellar contact pressures and reduces resistance of the elbow to valgus loading. Contact pressures and valgus laxity can be improved with UCL reconstruction. Taken as a whole, the peak pressure data indicate that the reconstruction restores valgus stability and lateral contact pressures to nearly normal levels under the conditions tested. Because the 90 position is the clinically significant position, these laboratory data support the clinical success of the docking procedure.

Explosion Phenomena and Effects of Explosions on Structures. III: Methods of Analysis (Explosion Damage to Structures) and Example Cases

This is Part III of a three-part paper on the phenomena of explosions and effects of explosions on structures. The overall paper is intended to provide the reader with a practical overview of the various types of explosions and methods available to predict explosion effects, with emphasis on air blast. The response of structures to air blast is discussed and methods of analysis are presented. Since the subject area is broad, reference sources for more in-depth information on many of the topics presented are provided. In this paper, Part III, methods are presented for predicting the response of structures to explosion effects. The methods that are discussed include peak pressure as a criterion, lumped mass, pressure-impulse as criteria, and finite-element analysis. Some example cases are given. A comprehensive tabulation of damage produced by different peak pressure levels is provided in Appendices I and II. A discussion of the appropriate use of such peak pressure data in predicting structural response is...

In vivo visco-elastic properties of the heel fat pad during gait: Is the heel pad at its physiological maximum during walking?

The fat pad of the human heel is a highly specialised adipose tissue, which is widely regarded to function as a shock absorber during the impact phase of gait. Although altered mechanical properties of the heel pad have been implicated in the development of several overuse injuries, in vivo measurement of the visco-elastic properties of the heel pad during dynamic activities, such as walking, remain largely unexplored. This study used cine-radiography synchronised with a pressure platform to obtain stress-strain data for the heel pad of nine healthy subjects (age, 46 ± 12 years; height, 1.67 ± 0.11 m; weight, 80.1 ± 10.4 kg) while walking at their preferred pace. The initial thickness and compressive strain of the fat pad were estimated from dynamic lateral radiographs, while the compressive stress was derived from peak pressure data. Principle visco-elastic parameters of the heel pad, including peak strain, secant modulii, hysteresis and time constants were estimated from the stress-strain curves. Real in vivo transient loading profiles associated with walking induce rapidly changing strain rates in the heel pad and create irregular stress-strain curves that differ notably from those previously reported for standard materials tests. Moreover, in vivo viscous properties of the heel pad at physiologically relevant strain rates fall between those commonly cited by studies using conventional quasi-static and ballistic loading methods, despite similar absolute deformations. Given that deformation of the fat pad (11 ± 2 mm) in the current study is similar to that previously reported for barefoot running, it would appear that the heel pad operates near its physiological maximum, even during walking.

The effect of seating velocity on pressure within impressions

Oral mucosa can distort under impressions. To reduce or control mucosal distortion, modern impression techniques aim to reduce or control the impression pressure. If changing seating velocity significantly changes pressure, then this effect should be considered for clinical impressions of mucosa. The purpose of this study was to investigate the relationship between seating velocity and pressure generation during simulated impressions. Vinyl polysiloxane impression material (Express) was placed between 2 approximating discs in a universal testing machine. The velocity at which the discs approximated was varied. The 7 selected seating velocities were 0.75 mm/s, 1 mm/s, 1.25 mm/s, 1.5 mm/s, 2 mm/s, 2.5 mm/s, and 3 mm/s. The pressure generated at the center of the disk was recorded. Five separate recordings were made for each velocity. One-way ANOVA and post hoc tests (Tukey B and Dunnett T3) (alpha=.05) were used to evaluate peak pressure data at each velocity. The mean (SD) of the recorded pressures for each velocity were 239 (6.67) KPa, 273 (14.89) KPa, 347 (11.97) KPa, 425 (19.73) KPa, 487 (17.84) KPa, 547 (21.25) KPa, and 624 (32.60) KPa, respectively. As the velocity increased, there was a significant (P<.001) concurrent increase in peak pressure. In this in vitro experiment, changing the velocity of seating had a significant effect on the peak pressure produced during simulated impressions.

Permeability Determination from On-the-Fly Piezocone Sounding

Solutions are developed for the steady, partially drained, fluid pressure field that develops around a moving penetrometer. These include rigorous solution for a point volumetric dislocation moving in a saturated elastic soil and an approximate solution for a pseudostatic, finite-volume, penetrometer moving in a nondilatant soil. These solutions provide a consistent framework for viewing the penetration process, and enable the nondimensional sounding indices of normalized tip resistance Qt, friction factor Fr, and pore pressure ratio Bq, to be straightforwardly linked to important material properties of the soil, most notably that of permeability, via a nondimensional permeability KD. This factor KD is inversely proportional to penetration rate, and is directly proportional to both permeability and vertical in situ effective stress. Simple relationships are developed to link these nondimensional sounding metrics, via KD. Most notably, the resulting simple relationship KD =1/ BqQt enables soil permeability to be determined from peak fluid pressures recorded on-the-fly. Importantly, these parameterizations enable plots of Bq˛ Qt, Fr ˛ Qt, and Bq˛ Fr to be contoured for KD, and hence for permeability. These plots define the relative superiority of using Bq˛ Qt data pairs over those for Fr ˛ Qt and Bq˛ Fr, in defining permeability. Similarly, the feasible range of permeabilities that may be recovered from peak pressure data are defined; permeabilities must be sufficiently high that penetration is not undrained, and sufficiently low that the resulting pressure response is not null ~fully drained!. These limits are a natural product of the analysis and represent permeabilities in the range 10 ˛4 -1 0 ˛7 m / s. The utility of these characterizations is confirmed with data from two locations where cone soundings are correlated with independently estimated permeabilities. DOI: 10.1061/~ASCE!1090-0241~2005!131:5~643! CE Database subject headings: Soil permeability; Penetrometers; Saturated soils .