Compressive Ring Research Articles

Enhanced rational horizontal tying force method for practical robustness design of building structures

Under the backdrop of the rational horizontal tying force method recently developed at Imperial College London, which focuses on the tying resistance of floor systems based on constant tying forces and its planar interaction with the surrounding structure alone, this paper presents relevant enhancements to the original method. These enhancements involve simplified mechanics-based models quantifying i) the residual flexural resistance arising from the curtailed reinforcement in tying via beams, ii) the additional flexural resistance from transverse beam in one-way tying via floor systems and iii) the planar restraint stiffness from the surrounding structure, including the influence of the compressive ring mobilised within the affected floor system under tensile membrane action. Following a detailed exposition of the formulation of the models, the paper presents several studies which demonstrate the effectiveness of the enhanced tying force method. Importantly, the method addresses resistance and stiffness mechanisms not covered in the current prescriptive tying requirements within a practical application framework that is still comparable in simplicity to such requirements, thereby further promoting the rational horizontal tying force method as a potential replacement for the prescriptive tying requirements in the next generation of robustness design codes.

A compressive vascular ring: A case report and review of literature

A compressive vascular ring: A case report and review of literature

Numerical simulation and experimental study on the interaction between a convex ring PDC bit and rock

To address the problems of low rock-breaking efficiency and high energy consumption of polycrystalline diamond compact (PDC) bits in hard formations of deep well sections, a convex ring PDC bit is proposed that alters the stress distribution law of the smooth bottom hole of a conventional PDC bit and forms a double-order stress state of the bottom-hole rock. The interaction law between the convex ring PDC bit and rock is explored by combining numerical simulation and experiment. The numerical simulation of conventional PDC bit and convex ring PDC bits is conducted using the discrete element method. The simulation results show that the stress concentration occurs at the convex ring of the new drill bit, resulting in multiple main cracks and facilitating volume crushing. The surrounding compressive stress ring formed by the new drill bit exhibits obvious pressure differences, which can effectively induce the penetration of cracks. The location and size of the convex hull structure have an important influence on the rock's damage law. The experimental results show that the potholes in the bottom hole morphology of the new bit are significantly larger than those of the conventional bit, and the formed cuttings are a factor of 1–2.5 larger than those of the conventional bit. The new PDC bit has a critical WOB, when the WOB exceeds the critical value, the mechanical specific energy of the new bit is lower than that of the conventional bit, and the ROP is higher than that of the conventional bit, it has better rock-breaking efficiency. These research results should provide a theoretical basis for the application and promotion of the new convex ring PDC bit.

Experimental study on the collapse response of flat slab structures with drop panels under gravity loading condition

This paper presents the results of an experimental study on the collapse behavior of two reinforced concrete flat slab assemblies with drop panel connections subjected to uniformly distributed loads applied through 24 loading points. The two tests, named MC and PC, simulated local failures at mid-span columns and penultimate columns, respectively. Both assemblies exhibited elastic behavior until cracking values were reached, followed by degradation of stiffness due to crack development beyond the elastic zone and a long plateau near collapse. The main differences between the assemblies were the higher collapse load of the MC assembly, attributed to slab additional slab extension surrounding two test panels, and the load redistribution pattern. Both assemblies showed ductile behavior in the inelastic region, with large deformation capacity allowing tensile membrane action to mobilize. The collapse modes observed were the failure of the outer compressive ring and the tearing out of tension slab reinforcement from the concrete. The traditional yield-line method may not be suitable for quantifying the collapse resistance of this type of structure, and numerical simulations are suggested for this purpose. The experimental data from these tests, as well as previous tests, could be valuable for validating simulation models.

Management of prenatally detected vascular rings: a United Kingdom national survey.

To investigate UK variability in prenatal and postnatal management strategy of right aortic arch and double aortic arch (RAA/DAA). Online surveys were sent to senior physicians (consultants) of the National Fetal Cardiology Working Group regarding prenatal diagnosis, counselling, and perinatal management of antenatally diagnosed RAA/DAA and to the British Congenital Cardiovascular Association regarding postnatal management strategies. There were 28 prenatal and 90 postnatal surveys completed. Prenatally, there was consensus for potential associated chromosomal/genetic anomalies, but there was variation in the risk quoted. Confidence in defining aortic arch morphology was reported by 43% (12/28) of fetal cardiologists. There was variation in what was felt to be possible symptoms/signs of a compressive vascular ring, postnatal investigation, postnatal management, follow-up duration of asymptomatic patients, and indications for surgical intervention. This study has highlighted important areas for future research: improving accuracy of prenatal diagnosis, clarification of potential symptoms, optimal investigation strategies, and indications for surgery.

Steel-concrete composite floor systems with different structural and loading configurations under a corner column removal scenario: Experimental tests

In this study, quasi-static tests were performed on three 3D steel–concrete composite floor systems under a column removal scenario with two variables, i.e., secondary beam connection type and pre-existing axial loads on columns. The work focused on the behavior of the three composite floor systems, including the load–deflection response, failure mode, load-resisting mechanism, e.g., flexure, catenary action and tensile membrane action (TMA), and load redistribution. It was found that secondary beam connection had a pronounced effect on the load–deflection response. Pre-existing axial loads on columns significantly influenced the load redistribution process and intensified the stresses in adjacent columns connected by the secondary beam to the removed column. For all the three specimens, a peripheral compressive ring with TMA was not observed in the composite slab due to a lack of rotational restraint from the perimeter beams and the main girder. However, at large deformation stage, when the composite slab deformed into an approximate hyperbolic-parabolic surface, the entire reinforcing mesh in the slab was in tension. It was observed that, at the early stage, the applied load was mainly resisted by flexure in the slab and the main composite girder and the secondary composite beam connecting to the removed column. But at large deformation stage, part of the applied load was resisted by flexure in the partially damaged slab and the main girder, and the intact secondary beam. Other load-carrying contributions came from catenary action in the main girder and TMA in the slab. In the end, most of the applied loads were redistributed to the columns adjacent to the removed column.

Analysis of sealing performance of a kind of profiled rubber gasket used in the radial contact seal structure

Sealing performance of standard rubber gaskets in the radial contact seal structure are observed through the experiment. A kind of profiled rubber gasket is proposed to replace the standard gasket. Leakage experiment and numerical simulation are carried out to study the sealing performance and failure mode of the profiled gasket. Several equations are presented to help analyze the failure reason. Results show that sealing performance of the profiled rubber gasket is more reliable than that of the standard rubber gasket. The failure reason of the profiled rubber gasket is that the friction force between the gasket external face and tube wall cannot balance the tube internal pressure. Dimension precision of the metal compressive ring has a great effect on the failure pressure.

Engineering characteristics of soils prone to rainfall-induced slope failure in Viti Levu, Fiji

Fiji's infrastructure is regularly affected by rainfall-induced slope failures, but the engineering properties of failed soils are rarely described. We report mineralogical, geotechnical and index properties of soils from headscarp exposures of 18 slope failures from tropical residual soils of differing parent rocks in Viti Levu, Fiji. Scanning electron microscopy and X-ray diffraction revealed that kaolinite and smectite are the dominant clay minerals in the soils. Index properties included in situ moisture content (28–114%), dry bulk density (0.7–1.5 g cm −3 ), Atterberg limits (25–56% plastic limit; 38–79% liquid limit), effective particle size (0.4–12.6 μm) and clay fraction (0.6–19%). Geotechnical measurements included field compressive strength (127–461 kPa), hydraulic conductivity ( c. 10 −7 m s −1 ), shear vane (16–128 kPa), ring shear (9.3–17.4°) and Emerson dispersion. Collectively, results indicated that most of the soils were cohesive, stiff, sensitive and in a plastic state in the field. Soils plotted below the A-line on the plasticity chart as fine silts of intermediate to high plasticity, and can theoretically sustain >50° slopes. Failure of these soils following high rainfall events is influenced by low permeability and the presence of expanding clays (e.g. smectite), causing temporary porewater pressure increases. No explicit relationships between soil properties and parent lithology were evident.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ УСЛОВИЙ РАЗРУШЕНИЯ ТОНКОСТЕННЫХ ЦИЛИНДРИЧЕСКИХ ОБОЛОЧЕК ПРИ ВНЕШНЕМ ДАВЛЕНИИ И ОСЕВОМ РАСТЯЖЕНИИ

The stability loss conditions under plastic deformation of a thin-walled cylindrical shell, including large-diameter pipes, under tensile (positive) axial stresses and compressive (negative) ring stresses are considered . The purpose of the article is to specify the dependences of critical deformations, stresses, pressures, and axis loads on the shell on the parameters and loading conditions. The research method is based on the application of Swift–Marciniak criterion on the loss in stability of the plastic deformation process. The material of the shell is assumed to be isotropic with exponential-power deformation diagram. Explicit analytical expressions for the target values were obtained. Considering the given parameters of the shell and loading conditions, the results allow to determine critical pressures, critical axial loads and wall thickness at a given working pressure.

Analytical model for predicting membrane actions in RC beam-slab structures subjected to penultimate-internal column loss scenarios

The potential for progressive collapse of RC buildings can be estimated by column loss scenarios. The loss of either internal or external penultimate columns is among the most critical scenarios since the beam-slab substructures associated with the removed column becomes laterally unrestrained with two discontinuous edges. At large deformations, membrane behaviour of the associated slabs, consisting of a compressive ring of concrete around its perimeter and tensile membrane action in the central region, represents an important line of defence against progressive collapse. The reserve capacity can be used to sustain amplified gravity loads and to mitigate the progressive collapse of building structures. In this paper, based on experimental observation of 1/4 scaled tests together with investigation of previous research works, an analytical model is proposed to predict the load-carrying capacity of beam-slab structures at large deformations. Comparison with the test results shows that the analytical model gives a good estimation of the overall load-carrying capacity of the RC slabs by membrane actions.
 Article history: Received 15 March 2018, Revised 28 March 2018, Accepted 27 April 2018

A study of severe flange wrinkling in first-pass conventional spinning of hemispherical part

Flange wrinkling is one of the most common defects in conventional spinning. Slight wrinkles can be eliminated by a reasonable design of the spinning process parameters or assisted process, while severe wrinkles lead to low forming quality or even defective products. A lot of work has been done to find the reason for flange wrinkling and the way to avoid it, while limited research has been done to study the severe flange wrinkling phenomenon in conventional spinning process. In this paper, the severe flange wrinkling phenomenon in first-pass conventional spinning of the hemispherical part has been studied through FE (finite element) simulations and experiments. A double curved surface buckling prediction model based on the energy method is proposed in order to predict severe flange wrinkling. Experiments are designed to verify the theoretical severe flange wrinkling prediction method. It turns out that the wrinkling of the inner compressive stress ring leads to the severe fluctuations of the spinning force, and it can be taken as a sign of severe flange wrinkling in the conventional spinning process. Furthermore, the effects of flange wrinkling on the spinning qualities of the final formed hemispherical parts are researched. It is concluded that slight flange wrinkles in the first-pass have little effects on thickness distribution and geometry accuracy of the final formed part, while severe flange wrinkles lead to failed products. Severe flange wrinkling prediction is significant for the conventional spinning of the hemispherical part.

Effect of GGBFS and lime binders on the engineering properties of clay

Although lime is one of the most suitable binders in soil improvement projects, the associated environmental impact and some accompanying mechanical deficiencies should not be ignored. Partial substitution of lime with other binders is one of the ways of reducing the associated harm and improving the engineering properties of lime. This study investigated the effect of the partial substitution of lime with ground granulated blast furnace slag (GGBFS) on the strength and mechanical properties of lime stabilised clay by performing a total of 246 volumetric shrinkage strain (VSS), unconfined compressive strength (UCS) and ring shear (RS) tests. The VSS results demonstrated that the addition of GGBFS to lime is very effective in reducing the volumetric shrinkage of lime stabilised clay, and that the reduction in volumetric shrinkage behaviour is linearly related to curing period. The UCS results revealed that the partial replacement of lime with GGBFS led to significantly higher compressive strength for all ageing periods. The ring shear results also demonstrated that the partial replacement of lime with GGBFS led to a greater shear strength. Moreover, microstructural studies were performed to better understand the reactions of the mixtures. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) carried on selected specimens revealed that the addition of GGBFS in a lime stabilised clay results in production of the cementitious products in a faster rate. X-ray powder diffraction (XRD) test results revealed that the main hydration products are cementitious products such as calcium silicate hydrates (CSH), calcium aluminates (CAH).

Experimental and numerical evaluation of composite floor systems under fire conditions

This paper presents novel experimental results and observations from three one-quarter scale tests on two-way concrete slabs supported by protected steel edge beams under fire conditions. The sizes of the protected secondary edge beams were varied to study the effect of beam stiffness on the fire behaviour of the assemblies. Test results showed that as the stiffness of the protected secondary edge beams increased, the slab central deflection decreased and failure of the slab occurred later. However, composite action between the edge beams and the concrete slab plays a key role in mobilising this beneficial effect. Once the composite slab-beam action is weakened by cracks in the slab over the main or secondary edge beams, the benefit associated with a greater stiffness of the edge beams is lost. Tensile membrane action was mobilised at a deflection equal to 0.9 to 1.0 of the slab thickness irrespective of the bending stiffness of the edge beams. The commencement of tensile membrane stage was marked by one of three indicators: (a) concrete cracks which formed a peripheral compressive ring in the slab; (b) horizontal in-plane displacements along the slab edges; and (c) horizontal and vertical displacements of four corner protected steel columns. The test results were used to validate a finite element model developed using Abaqus/Explicit. Good correlation between the predicted and experimental results was obtained.

Experimental Response of Beam-Slab Substructures Subject to Penultimate-External Column Removal

AbstractThis paper presents an experimental program to investigate the progressive collapse resistance of reinforced-concrete (RC) building structures subjected to a loss of a penultimate-external (PE) column that is the exterior one nearest to the building corner. Under this accidental scenario, any mobilization of catenary action in beams and slabs bridging over the column, as an alternative load path, should rely solely on the strength of a half perimeter compressive ring forming within the deflected slab area. Three one-third scaled beam-slab substructures were designed, built, and tested by a static loading scheme to examine the overall load capacity and displacement ductility that are two aspects of the progressive collapse resistance of RC building structures. The test variables are (1) additional amounts of beam stirrups, (2) additional beam longitudinal reinforcement, and (3) the aspect ratio of the slab panel. The boundary condition of the specimens is rotationally and vertically restrained, but...

Thermal Effect Test of Outer Compressive Ring of the Roof of Bao'an Stadium

Based on the project of construction monitoring for cable structure of the roof of Shenzhen Baoan stadium, the displacement and stress of outer compressive ring caused by temperature change were monitored before the radial cable was tensioned, analyzed and compared the monitoring results. Comparing the measured results and simulation results shows the temperature change characteristics of outer compressive ring and the temperature change characteristics are valuable for delicacy construction of other similar projects.

Experimental study of beam–slab substructures subjected to a penultimate-internal column loss

Progressive collapse resistance of reinforced concrete building structures can be evaluated by using column loss scenarios. The loss of a penultimate column is among the most critical scenarios since it leave the associated structures with the least lateral restraint. At large deformations, any mobilization of catenary action, as an alternative load path, should rely solely on the strength of a perimeter compressive ring forming within the deflected slabs. This paper presents an experimental study to investigate the static response of double-span beam–slab substructures bridging over a penultimate-internal (PI) column. Three ¼ scaled beam–slab substructures were designed, built and tested by a static loading scheme. The boundary condition of specimens was rotationally and vertically restrained, but laterally unrestrained. A 12-point loading system was used to simulate uniformly distributed loads. The static response of the test structures was identified with negative bending moments that were greatly affected by T-beam effect, and catenary action replacing positive bending moment in the central region at very early stage. At large deformations, the overall load-carrying capacity of test structures although benefit from the continuous development of catenary action, was adversely affected by accompanying partial failures such as fracture of beam bottom bars and compressive failure of beam-to-column connections. Based on failure modes of test structures, the typical collapse mode of actual buildings was further discussed.

Membrane actions of RC slabs in mitigating progressive collapse of building structures

Potential for progressive collapse of RC buildings can be studied using sudden column loss scenarios. The loss of either a penultimate-internal (PI) column or a penultimate-external (PE) column is among the most critical scenarios since it leaves the associated beam-and-slab substructures laterally unrestrained. At large deformations, the membrane behaviour of the affected slabs, consisting of a peripheral compressive ring of concrete supporting tensile membrane action in the central region, represents an important line of defence against progressive collapse. In this paper, an advanced finite element model (FEM), which has been validated by available test data, is used to investigate the membrane behaviour in laterally unrestrained slabs associated with PI column loss in the presence of interior double-span beams, rotational restraints along the perimeter edges, and the slab top reinforcement. It has been shown that in the central region, greater tensile membrane forces are mobilised due to the participation of beam reinforcement and slab top reinforcement. In the outer region, the compressive ring of concrete is also strengthened by slab hogging moment. Hence, the overall load-carrying capacity of the affected structures can be enhanced significantly to sustain the gravity applied loads which are severely amplified by both double-span effect and dynamic effect.

Biomechanical analysis of penile erections: penile buckling behaviour under axial loading and radial compression

To characterize the biomechanics of erectile function, as contrary reports have modelled the penis as an isotropic material and state that only axial buckling tests can effectively predict penile rigidity; that assumption is questioned and an alternative structure proposed and validated. Three experimental physical cylindrical models of diameters 1.9, 2.54 and 3.81 cm were fabricated and the relationship between axial loading and radial compression was measured for cylindrical pressures of 8-20 kPa. A finite element analysis (FEA) computer model of the penis was constructed to simulate the response of the corpora cavernosa to axial and radial loading for differing diameters and lengths of the penile shaft. The stresses developed in the tunica albuginea of the corporal bodies of the penis during buckling were assessed using a mathematical analysis. From the analysis of surface stresses under variable axial loading, as the angle of an applied load changes on an isotropic shaft, the magnitude of surface stresses varies up to 50 kPa, and for a pressure vessel the magnitude of surface stresses varies up to 100 kPa. The FEA model showed that nodal displacements were greatest around a ring under radial compression, and for the axially loaded model displacements were greatest at the vessel tip under the force gauge. All displacements were 0.1-1.0 mm. There was an exponential relationship between internal pressure and the axial force required to cause buckling in a thin-walled pressure vessel. There was a nearly constant relationship between circumferential displacement and internal pressure under uniform radial compression. The displacement values on the FEA analysis were approximately equal outside of the areas of high stress which were under the load of the external device (compressive ring or force gauge) in both cases. Physical modelling shows that when a pressurized vessel is under either axial or radial load the internal pressure increases. Vessels at high internal pressure require more force to cause buckling than vessels at lower internal pressure. The circumferential displacement of a vessel under radial compression is higher in vessels of lower internal pressure and less in vessels of high internal pressure. The size of a vessel also contributes to its ability to be buckled. Smaller vessels buckle under smaller load, but the ratio of force required to buckle vs. diameter of the cylinder remained constant. The computer simulations show that with slight deviations from perfectly aligned axial loading the stresses felt on the walls of cylindrical columns vary considerably, whether they are isotropic beams or pressurized vessels. The material properties of the tissues within the corpora cause it to behave as a thin-walled pressurized vessel, in which the hoop stress and axial stress have a constant relationship independent of the length to diameter ratio rather than as an isotropic beam where this relationship varies. Patient discomfort and high operator dependency further contribute to the inconsistencies of axial loading methods to determine penile buckling. Based on the constant relationship between hoop stress and axial stress in thin-walled pressurized vessels this study confirms the validity and desirability of using radial compression methods to assess penile rigidity in lieu of axial loading methods.

Diagnostic microstructures for the measurement of intrinsic strain in thin films

Freestanding flexible microstructures fabricated from deposited thin films become mechanically unstable when internal stresses exceed critical values. A series of structures with varying geometries is used to determine the critical geometry at which buckling occurs. Observation with an optical microscope quickly reveals qualitative and quantitative information about the internal strain in the film. Strain values between +or-1.5% can be measured for a 2.0 mu m thick film using doubly-supported beams for compressive strain fields, and ring and beam structures for tensile strain fields. Parametric formulae are developed for diagnostic structure response with selected verification by finite element computations.