Span Diameter Research Articles

A Study on the Ultimate Span of a Concrete-Filled Steel Tube Arch Bridge

In order to study the ultimate span of a concrete-filled steel tube (CFST) arch bridge, taking the structural strength, stiffness, and stability as the limiting conditions, the finite element analysis method is adopted to carry out research on the influence law of a single parameter of the pipe diameter, wall thickness, and cross-section height on the ultimate span of the arch axial shape. The result is used as a sample point to determine the ultimate span of the CFST arch bridge under multifactor coupling based on the response surface method. The finite element method is used to check the strength, stiffness, stability, number of segments and maximum lifting weight, steel content rate, and steel pipe concrete constraint effect coefficient of the CFST arch bridge under the ultimate span diameter. The results show that, when analyzed using a single parameter, the ultimate span diameter of the CFST arch bridge increases with the increase in the steel pipe diameter and the cross-section height, and then decreases. Moreover, it increases with the increase in the wall thickness of the steel pipe, and the CFST arch bridge reaches the ultimate span with the increase in the steel pipe wall thickness. When the pipe diameter is 1.38 m, the CFST arch bridge reaches the ultimate span; according to a multi-parameter coupling analysis, when the pipe diameter is 1.49 m, wall thickness is 37 mm, and cross-section height is 17 m, the CFST arch bridge reaches the ultimate span of 821 m, which meets all of the limiting conditions, and, at this point, the arch axial coefficient is 1.2. The results of the finite element calculation show that the structural strength, prior to the stiffness, stability, and other limitations, just reaches the critical value of the limiting conditions.

Experimental study on stiffness deterioration of cracked RC hollow-core slab beams

To accurately assess the performance degradation of RC hollow-slab beam after service, in-situ static load tests were carried out on a RC hollow-slab beam bridge with a span diameter of 11.25 m, which is part of the Chongqing–Chengdu Highway Viaduct. Indoor single-girder static load tests were also carried out to study the deflection concrete strain and reinforcement strain at key locations on the hollow-slab beam. Crack development was recorded to investigate the stiffness degradation law of hollow-core slabs. Inverse secant stiffness–residual deflection and inverse secant stiffness–maximum crack width relationship models were established. Results show that the calibration coefficients obtained in the in-situ static load tests were greater than one, indicating potential for stiffness deterioration and insufficient structural safety reserves during service. The initial crack width was increased and extended upwards before the test beam yielded, with many new vertical cracks in the pure bending zone which extended continuously. The slope of deflection curve was larger before yielding and smaller after yielding, the secant stiffness of RC hollow-slab beam was exponentially decreased with load before yielding and changed linearly with load after yielding. The inverse secant stiffness–residual deflection and inverse secant stiffness–maximum crack width curves of the test beam were approximately bilinear, with a larger slope at the beginning of the test and a smaller slope in the plastic phase.

Engineering Mechanics Methods in Stability Studies of Bridge Structures and Innovations in Future Bridge Designs

Abstract With the development of science and technology and transportation, high pier and large-span bridges are rapidly rising. Due to the increase in span diameter and pier height, nonlinear and stability problems of bridges become more and more important. In this paper, the stability of large-span steel box-girder suspension bridges is investigated using engineering mechanics methods. Based on the finite element analysis method to solve the bridge structure of the first type of stability problems and the second type of stability problems, the use of the response spectrum method for bridge seismic response. Taking “Xiling Yangtze River Bridge” as the engineering background, the seismic response is analyzed by establishing a finite element model. The axial force of the bridge tower generated by the downstream earthquake is larger than that generated by the transverse earthquake. In the transverse direction, the bending moment MZ is larger than the bending moment MY in the transverse direction, and the bending moment of the pile foundation is larger than the bending moment of the pile foundation in the longitudinal direction. The Xiling Yangtze River Bridge plays a dominant role in transverse seismicity, and its downstream seismic excitation plays a dominant role in longitudinal seismicity. However, the energy-demand ratio corresponding to the transverse moment MY is only 1.83, and the strength of the pile section needs to be further improved. For the future innovation of bridge design, a high-performance bridge structure based on UHPC is an important direction for future development.

Oak decline alters leaves and fruit of Persian oak (Quercus brantii Lindl.)

Biotic and abiotic stressors are known to modify the morphology of forest trees. Nevertheless, there is little information on the effects of tree decline on leaf and fruit morphology of oaks. To understand morphological adaptations of Persian oak (Quercus brantii Lindl.) to oak decline, we compared leaves and fruit from healthy and declining Persian oaks from six populations in the Zagros Forest of Iran. Fruits and leaves were sampled from five healthy and five declining trees from each population (30 declining and 30 healthy trees total). Fifteen leaves and fruits were sampled from each tree, for a total of 900 leaves and 900 fruit. We measured fruit length and diameter, scar diameter, cupule length, cupule span diameter, and fruit cover length as well as leaf length, petiole length, maximum lamina width, width of the lamina base, and width of the lamina apex. The leaf area was estimated from the product of length, maximum width, and a shape coefficient. Leaf trichomes were examined with SEM and classified as either mostly stellate or non-stellate. Healthy Persian oaks from five of the six populations had larger leaves, with greater lamina area, when compared with declining individuals. Moreover, the trend was the same across all six populations. Leaves of declining oaks also had distorted trichomes. Moreover, declining Persian oaks had smaller (shorter) fruit. The impact of oak-decline on Persian oak morphology, however, varied greatly among the six populations, limiting leaf and fruit size as indices of oak-decline. Leaves and fruit are smaller in declining Persian oaks, and trichomes are degraded. Nevertheless, care must be taken in using these traits as reliable proxies for tree decline, simply because the effect varies among populations.

Numerical Study on Ballistic Resistance of Thin Aluminium Plate Subjected to Variable Diameter Projectile Impacts

The ballistic resistance of a thin aluminium plate was investigated against rigid hemispherical nosed projectile impact. The target span was varied as 68 mm, 100 mm, 150 mm and impacted normally by 19 mm diameter hemispherical nosed projectile. The residual velocity and ballistic limit velocity obtained from the numerical results using nonlinear finite element code LS-DYNA is compared with the experimental results available in the literature. Further, parametric study has been carried out for different projectile diameter with the same target span and validated with Recht and Ipson’s model. The ballistic limit has been decreasing with decrease in projectile diameter and it is also observed that ballistic limit of the target increases with increase in target span diameter.

Ballistic response of double layered 1100-H12 aluminium hemispherical shell structure

The ballistic resistance and energy absorption characteristics of the thin hemispherical shells were evaluated against ogive and blunt nosed projectile impact with varying span and configuration of the shell. The span diameter of the 1100-H12 aluminium shell was varied as 68, 100, 150 and 200 mm whereas the configuration of the shell was varied as monolithic and double layered (0.5/0.5, 0.33/0.67 and 0.67/0.33) which was hit at the crown by 19 mm diameter, 50.8 mm length and 52.5 g mass projectile. Three dimensional numerical simulations were carried out through commercially available finite element code ABAQUS. The accuracy of the numerical model was validated by comparing the numerical result of monolithic shell with experimental result conducted through the pressure gun. Numerical simulation result were further employed to extract the total energy absorption in plastic deformation by computing the strain energy in stretching in polar, radial, elevation and shear directions of the shell by using a user defined programme written in python. The influence of projectile nose shape, incidence velocity of the projectile and configuration of the hemispherical shell on the mechanics of failure, ballistic resistance, ballistic limit and energy dissipation characteristics were studied. The double layer hemispherical target showed better performance against ogive nosed projectile however opposite behaviour was observed against blunt nosed projectile.

Impact Response of Thin Aluminium Plate with Varying Projectile Obliquity and Span Diameter

This paper presents a three-dimensional (3-D) numerical investigation to know the effect of projectile obliquity and target span diameter on ballistic performance of 1-mm-thick target plate against ogive nosed projectile. The span diameter of 1100-H12 aluminium targets were varied as 68, 100, 150, 200 and 255 mm. Each span diameter of the target was impacted by ogive nosed projectile with varying angle of incidence as 0°, 10°, 20°, 30°, 40°,50° and 60° or till ricochet occurred. The numerical findings were validated through experiments for 0° projectile obliquity. Both the target span and angle of incidence of the projectile affected the mechanics of target deformation and its ballistic resistance significantly. The ballistic limit was found to be increased with increase in target span diameter as well as projectile obliquity. Moreover, the critical angle of ricochet also decreased with increase in target span diameter particularly at high incidence velocity.

Energy dissipation in plastic deformation of thin aluminum targets subjected to projectile impact

The present study explores the energy absorption in plastic deformation due to work done in radial, circumferential, axial and tangential directions in monolithic and layered aluminum 1100-H12 targets subjected to oblique impact by ogive nosed projectile. Circular targets of 255mm span diameter and 0.5mm thickness were modelled in ABAQUS as a deformable body in the configuration of two and three layers in contact. Also, to compare the ballistic performance of single and layered configurations, the monolithic targets of 0.5, 1.0 and 1.5mm were impacted at same incidence velocities and ballistic limit was obtained. The projectiles were modelled as a rigid body and impacted at normal as well as 30° and 45° oblique angles. ABAQUS/Explicit solver was used to simulate all the problems. The mode of failure was observed to be petal formation in all the targets. However, due to oblique impact, the number and shape of petals were changed. Both monolithic and layered targets showed enhanced ballistic limit when angle of incidence was increased. The ballistic resistance of 1mm thick monolithic target was found to be 9.1%, 10.4% and 5.7% higher than equivalent double layered in-contact target, at 0°, 30° and 45° angles of incidence, respectively. Further, the plastic work done in 1mm thick monolithic target was about 19%, 22% and 28% higher in comparison to the energy absorbed by equivalent in-contact layered configurations impacted at 0°, 30° and 45° oblique angles, respectively.

Energy absorption characteristics of thin aluminium plate against hemispherical nosed projectile impact

The energy absorption characteristics of monolithic and layered aluminium plates made of aluminium 1100-H12 were investigated against hemispherical nosed projectile impact both experimentally and numerically. The span diameter of 1mm thick monolithic plates were varied as 68, 100, 150, 200, 255, 350, 450, 550, 650 and 750mm whereas the effect of target configuration were studied for monolithic (1mm), layered in contact (0.5+0.5) and spaced target (0.5+0.5) of 150mm free span diameter. The spacing between thin layers was varied as 4.5, 10, 20, 30, 40, 50 and 60mm. Each target was impacted normally by 19mm diameter hemispherical nosed projectile. Some of numerical results were validated with experimental results with varying target span diameter (68, 100, 150, 200 and 255mm), layered in contact target and the target with 4.5mm spacing. Numerical results were found to be quite close with experimental results. A pressure gun was employed to carry out the experiments while the numerical simulations were performed on ABAQUS/Explicit finite element code. Further numerical simulation results were used to calculate the energy dissipation in plastic deformation. The energy was further disintegrated in stretching in radial, circumferential, axial and tangential directions. Both the ballistic performance and energy absorption characteristics were significantly influenced by target span and configuration. The ballistic limit has been found to be significantly increased with an increase in the span diameter of the target. The monolithic target was found to be superior followed by layered in contact and spaced target.

Energy Absorption in Metallic Targets Subjected to Oblique Impact

The present study investigates mode of failure and energy absorption in impact of 1 mm thick Al 1100 H12 monolithic and double layered targets of 0.5 mm thickness in-contact with each other. The 255 mm span diameter circular targets were impacted by EN-24 steel ogive nosed projectile of 19 mm diameter and 52.5 g mass at different angles of incidence viz., 0o, 30o, 45o. Three dimensional modelling of targets and projectiles were carried out in ABAQUS/CAE module. The targets were modelled as a deformable body whereas, rigid body behavior was assumed for the projectiles due to negligible deformation observed in impact. ABAQUS/Explicit solver was used to simulate all the problems and results were discussed in terms of ballistic resistance, failure mode of the target and energy absorption during the impact.

Influence of Target Span and Boundary Conditions on Ballistic Limit of Thin Aluminum Plate

A collective study was performed to probe the influence of projectile nose shape, target span and target boundary condition on ballistic limit of thin aluminium plates. 1 mm thick 1100-H12 aluminium target plates were normally impacted by ogive and blunt nosed projectiles of 19 mm diameter and 50.8 mm length. The target span was varied as 95, 190, 285, 380, 475, 570, 665 and 760 mm whereas the target boundary condition was studied by varying the fixity at the target circumference region as 100%, 75%, 50% and 25%. ABAQUS/Explicit finite element code using Johnson-Cook elasto-viscoplastic material model were employed to carry out the numerical simulation. To validity of numerical results are revealed by experiments performed on pressure gun in the sub-ordnance velocity regime.The numerical as well as experimental study revealed that the ballistic limit of thin target plate was significantly affected by target span as well as target circumference fixity. The ballistic limit increases with increase in target span diameter while opposite trend was observed with increase in the region of fixity.

Energy dissipation in thin metallic shells under projectile impact

Abstract The ballistic performance of hemispherical aluminium shells was studied and the energy absorption in different modes of deformation has been computed. The experiments were performed wherein blunt and ogive nosed steel projectiles of 19 mm diameter were fired on 0.7–1.5 mm thick 1100-H12 aluminum hemispherical shells of different effective spans. The mechanics of deformation and energy absorption capacity was found to be significantly influenced by the shell thickness and projectile nose shape. The ogive nosed projectile caused failure through perforation by petal formation. Against blunt nosed projectile, however, the shells underwent significant dishing and reverse bending and thus defeated the projectile by dissipating its energy in global plastic deformation. The experimental findings were reproduced numerically on ABAQUS/Explicit finite element code. The numerical results were further employed for the computation of plastic strain energy in stretching in polar, radial, elevation and shear directions of the shell in order to eventually extract the total energy absorbed in plastic deformation. For a given span diameter and thickness of shell, the energy dissipation was found maximum in shear stretching while it was minimum in polar stretching of the material.

Ballistic performance and energy absorption characteristics of thin aluminium plates

The paper presents an experimental and finite element investigation to explore the influence of target to projectile diameter ratio (D/d) on the ballistic performance and failure mechanism of thin aluminium plates. 1100-H12 aluminium target plates of 1 mm thickness were impacted by 19 mm diameter ogive and blunt nosed projectiles. The D/d ratio was varied by varying the span diameter of the target keeping the projectile diameter constant, 19 mm. The finite element simulations were carried out at D/d ratios 3.6, 5, 7.9, 10, 15, 20, 25, 30, 35 and 40. The validation of the simulation results was carried out by performing experiments at D/d ratio 3.6, 5, 7.9, 10 and 15.The total work done in plastic deformation of the target was disintegrated into circumferential, radial, axial and tangential stretching. An initial increment in D/d ratio from 3.6 to 10 has been found to have prominent effect on the ballistic limit particularly against blunt nosed projectile. Subsequent increase in the D/d ratio however, could not influence the ballistic resistance significantly. The energy absorption inplastic deformation was found maximum for D/d ratio 10. The maximum energy dissipation occurred in circumferential stretching against bunt and in tangential stretching against ogive nosed projectile. The minimum energy dissipated in axial stretching against both the projectile.

Effect of Periphery Fixity on Ballistic Limit of Thin Aluminum Plate Subjected to Blunt and Ogival Projectile Impact

Three-dimensional numerical simulations were carried out with the ABAQUS/explicit finite element code to study the influence of target boundary conditions on its ballistic limit. 1mm thick 1100-H12 aluminum target of 255 mm span diameter was hit by 19 mm diameter and 50.8 mm length blunt nosed projectile. The mass of the projectile was kept as 52.5 gm. The boundary condition effects on the ballistic limit were investigated by varying the target periphery boundary condition as fully clamped and partially clamped target (75%, 50% and 25%) subjected to projectile impact. The energy absorption and ballistic limit of the target was found to be significantly affected by the boundary conditions. Some of the finite element analysis results were compared with experimental and numerical results reported in international literature and a good agreement between the two was found.

The ballistic resistance of thin aluminium plates with varying degrees of fixity along the circumference

The ballistic performance of thin aluminium targets and influence thereon of different circumferential fixity conditions were studied both experimentally and by finite element simulations. A pressure gun was employed to carry out the experiments while the numerical simulations were performed on ABAQUS/Explicit finite element code using Johnson–Cook elasto-viscoplastic material model. 1 mm thick 1100-H12 aluminium plates of free span diameter 255 mm were normally impacted by 19 mm diameter ogive and blunt nosed projectiles. The boundary conditions of the plate were varied by varying the region of fixity along its circumference as 100%, 75%, 50% and 25% in experiments and the numerical simulations. Further, simulations were carried out to compare the response of the plates with 50% and 75% continuous fixity with those with two and three symmetrical intermittent regions of 25% fixity respectively.The variation in the boundary condition has been found to have insignificant influence on the failure mode of the target however; it significantly affected the mechanics of target deformation and its energy absorption capacity. The ballistic limit increased with decrease in the region of fixity. It decreased for intermittent fixity in comparison with equivalent continuous fixity. And, it has been found to be higher for the impact with projectile having blunt nose in comparison with the one having ogive nose.

Effect of Configuration and Target Span on the Ballistic Resistance

Numerical simulations were carried out wherein 20 mm diameter conical nosed projectiles were hit on Weldox 460 E steel targets of varying span and configuration in order to study the influence on the ballistic limit. The effect of configuration was studied with 12 mm thick monolithic and double layered in contact target (2 × 6 mm) of 500 mm span diameter whereas the influence of target span was investigated by varying the diameter of 12 mm thick monolithic target as 100, 200, 300, 400 and 500 mm. The monolithic targets were found to offer higher ballistic limit than that of the layered in-contact target. The ballistic limit was also found to be affected by the variation in span diameter; its value was found to be 199.5, 213.9, 220.7, 226.08 and 230 m/s for 100, 200, 300, 400 and 500 mm span diameter respectively.

Response of 1100-H12 Aluminum Targets to Varying Span and Configuration

The influence of target span as well as configuration was studied with 1 mm thick 1100H12 aluminum target subjected to19 mm diameter ogive nosed projectile impact. The effective span of 1 mm thick monolithic target was varied as 95, 190, 285, 380 and 475 mm. The configuration of 255 mm span diameter target was varied as 1 mm thick monolithic, double layered in-contact (2 x 0.5 mm) and double layered spaced. The spacing between the layers was also varied as 2, 5, 10 and 20 mm. The target was impacted normally by ogive nosed projectile to obtain the ballistic limit, failure mode and deformation. The ballistic limit was found to increase with an increase in span diameter. The monolithic target offered highest ballistic limit followed by layered in-contact and spaced targets respectively. The variation of spacing between the layers did not have significant influence on the ballistic limit.

Multi-hit ballistic impact on S-2 glass/SC15 thick-section composites: experiments

Multi-hit ballistic impact and damage behavior of thick-section composites are of interest to many military and aerospace applications. The effect of support spans on single-hit penetration resistance and the effect of relative distance between multiple impacts on the penetration resistance are the subject matter of the present investigation. In order to study the effect of support spans on penetration resistance, single-hit ballistic experiments are conducted on two plain-weave (PW) S-2 glass/SC15 composite laminates of thickness, 13.5 mm (22 layers, 22L) and 20.4 mm (33 layers, 33L), respectively at two different support span diameters, i.e. 102 mm and 203 mm. On the other hand, the effect of multiple impacts on penetration resistance has been investigated by impacting both the laminates (22L and 33L) at four additional radial shot locations (90 degrees apart) with a support span diameter of 203 mm. In both the impact scenarios, 0.50cal fragment simulating projectiles (0.50cal FSP) were used while the composite laminates were clamped between a cover and a support plate. In addition, the maximum dynamic deflection of the composite laminates were recorded using a thin aluminum witness plate at the rear end of the laminate, and the through-thickness ballistic damage of the composite laminates was investigated by sectioning through the impact centers, dying with an ink-alcohol solution, and taking optical photographs of the cross-sections. Results show that the single-hit ballistic limit velocity increases marginally with support span diameter investigated. The curvatures of the dynamic deflection profiles at the support edge suggest that the dynamic deflection was constrained by the smaller support span while the dynamic deflection was not constrained by the larger support span. There was no noticeable difference in the single-hit maximum dynamic deflection between the two laminate thicknesses as a function of impact velocity to ballistic limit velocity ratios. Single-hit through-thickness damage extended toward the edges of the larger support spans such that the subsequent multiple impacts were on partially damaged laminates; however, the pre-existing ballistic damage showed about 4.5% and 9.0% decrease in site specific multi-hit ballistic limit and energy, respectively.

Effect of target span and configuration on the ballistic limit

Three-dimensional numerical simulations were carried out with ABAQUS/Explicit finite element code to study the influence of target span and configuration on its ballistic limit. 1 mm thick 1100-H12 aluminum targets of varying span diameter and configuration were impacted by blunt and ogive nosed projectiles of 19 mm diameter and 52.5 g mass. The effect of target span was studied by varying the span diameter of 1 mm thick monolithic target as 50 mm, 100 mm, 204 mm, 255 mm and 500 mm. The effect of configuration was studied by taking the monolithic, double layered in-contact and double layered spaced targets of 1 mm equivalent thickness and 255 mm span diameter. The spacing between the layers was varied as 2 mm, 5 mm, 10 mm, 20 mm and 30 mm. In each case the target was impacted normally by blunt and ogive nosed projectile to obtain the ballistic limit. The highest ballistic limit was observed for monolithic target followed by layered in-contact and spaced targets respectively. The variation of spacing between the layers did not have significant influence on the ballistic limit in the case of ogive projectile but some effect was seen in the case of blunt projectile. The ballistic limit was found to increase with increase in target span diameter for both the projectiles and it was found to be higher for blunt nosed projectile as compared to that of ogive nosed projectile for all the spans considered excepting in the case of 50 mm span for which it was higher for ogive nosed projectile.

Greenfield caval filters: long-term radiographic follow-up study.

Sixty-nine patients with a Greenfield inferior vena cava (IVC) filter in place for 1-9 years were evaluated with supine abdominal radiographs. In 22 patients (32%) the filter span diameter had increased by 3-11 mm, and in six patients (9%) it had decreased by 3-18 mm. Twenty patients (29%) had caudad migration of 3-18 mm, and four (6%) had cephalad migration. In five patients (7%) the filter was at an angle of more than 16 degrees from the vertical. A decrease in filter span of 7 mm or more may result in IVC occlusion, whereas an increase of 6 mm or more may result in caval wall penetration. Caudad migration may be caused by a fibrous reaction around the struts which slowly draws the filter caudally. A change in filter angle may result from displacement of a strut into the right renal vein as well as from physiologic changes. The abdominal radiograph is a valuable method for follow-up study of patients with Greenfield filters if the filter position, span, migration, and angle are noted in the report.