RESISTANCE OF STEEL FRAMES WITH RIGID AND HINGED JOINTS TO PROGRESSIVE COLLAPSE

A tri-state prismatic modular robotic system

The farming of black-lip pearl oyster Pinctada margaritifera (Linnaeus, 1758) has been a viable industry for small and large-scale farmers in the South Pacific, but not in the Philippines, where it is monopolized by large-scale farms primarily based on the gold-lip pearl oyster Pinctada maxima. To promote the industry among small-scale players, we simplified the culture method by using bamboo slats as frame materials and compared them to the common material used in pearl oyster culture, metal rods. A total of 400 individuals seven-month-old hatchery-produced P. margaritifera were used as experimental animals, distributed in the following treatments with five replications: T1 (metal-framed pocket net basket with monthly cleaning), T2 (metal-framed pocket net basket without monthly cleaning), T3 (bamboo-framed pocket net basket with monthly cleaning), and T4 (bamboo-framed pocket net basket without monthly cleaning). Growth was fast in the first four months and slowed down after that. Two-way analysis of variance found no significant differences between the average anteroposterior shell (APS) length increments of pearl oysters between two types of frame, and between two cleaning conditions. Survival rates did not significantly differ between types of basket frame, and between cleaning conditions. Parameters of the “Typical” von Bertalanffy growth model (L∞ = 118.41 mm, K = 1.03 year-1, and t0 = 0.12) suggested that oyster would take about 23.16 months to reach 100 mm APS length, a size suitable for nucleus implantation. The life span of bamboo slats as basket frame was half of the metal frame, and the absence of cleaning has reduced the operational cost by up to 82.08%.

AimsThe timing of when to remove a circular frame is crucial; early removal results in refracture or deformity, while late removal increases the patient morbidity and delay in return to work. This study was designed to assess the effectiveness of a staged reloading protocol. We report the incidence of mechanical failure following both single-stage and two stage reloading protocols and analyze the associated risk factors.MethodsWe identified consecutive patients from our departmental database. Both trauma and elective cases were included, of all ages, frame types, and pathologies who underwent circular frame treatment. Our protocol is either a single-stage or two-stage process implemented by defunctioning the frame, in order to progressively increase the weightbearing load through the bone, and promote full loading prior to frame removal. Before progression, through the process we monitor patients for any increase in pain and assess radiographs for deformity or refracture.ResultsThere were 244 frames (230 patients) included in the analyses, of which 90 were Ilizarov type frames and 154 were hexapods. There were 149 frames which underwent single-stage reloading and 95 frames which underwent a two-stage reloading protocol. Mechanical failure occurred after frame removal in 13 frames (5%), which suffered refracture. There were no cases of change in alignment. There was no difference between refracture patients who underwent single-stage or two-stage reloading protocols (p = 0.772). In all, 14 patients had failure prevented through identification with the reloading protocol.ConclusionOur reloading protocol is a simple and effective way to confirm the timing of frame removal and minimize the rate of mechanical failure. Similar failure rates occurred between patients undergoing single-stage and two-stage reloading protocols. If the surgeon is confident with clinical and radiological assessment, it may be possible to progress directly to stage two and decrease frame time and patient morbidity.Cite this article: Bone Jt Open 2022;3(5):359–366.

Response during energy absorption of a tube system is the key for its application in structures under dynamic loading. An ideal energy absorber should behave with a low peak force, high mean crushing force and with a smooth force displacement curve while under dynamic loading. In this particular study, a bunch of metallic 3-step stepped-tubes with ascending number of stepped-tubes in different configurations are placed inside a metallic thin-walled tube and are numerically investigated for its energy absorption characteristics under dynamic axial loads. Stepped-tubes can absorb energy with progressive failure as per specific need of the design but their geometry parameters influence their performance. One of the initial proposed configurations with five stepped-tubes arrangement is further investigated for changing geometry of stepped-tube and sensitivity of energy absorption characteristics with changed geometry are studied. Deformation modes and different energy absorption parameters such as peak value of crushing force, specific energy absorption, mean crushing force and crush force efficiency are plotted for all of the configurations. Results are compared with published numerical and experimental results for the impact of the proposed configurations on energy absorption capability.

Dear Editor, Recently, Gogate et al. reported a poor compliance (300 out of 1018 [30%]) of spectacle wear amongst rural secondary school children.[1] About 17.4% of children in the same study reported "broken spectacles" as the cause of non-wear. In a fresh report, Mohan[2] stated that about 22% of spherocylinders in adults have optically and clinically significant errors in dispensing. We feel the issue of dispensing spectacle frames and lenses need further evaluation especially in young children. Incorrect frame fitting may have far-reaching consequences on the compliance to spectacle wear and inappropriate lenses would have an additional negative impact on the vision of the patient. We evaluated the spectacles (frames and lenses) of 54 consecutive children based on predefined criteria [Table 1]. The mean age of the children was 8.4 years (standard deviation [SD] ±2.7, range: 5-15 years) of which 31 were males and the average duration of spectacle wear was 9.4 (±6.2, 0.5-24 months).Table 1: Criteria used for spectacle frame and spectacle lens evaluationWe required a sample size[3] of 51 patients for group comparison and performed Chi-square test to derive the P value. (n = 2 [Z1− α/2 − Z1 − B] 2Xp[1 − p]/d2, 80% power, 5% significance, 10% effect size). About 61.1% children used plastic frames, 14.1% used metal frames and 24.1% used combination frames (hybrids). Evaluation of frame fitting revealed good four point touch in 55.6%, fair in 18.5% and poor in 26%. The eye wire was optimal in 62.9% and suboptimal in 38.1%. The nose bridge was graded as not good in 66.7%. The temple parallelism was good in 27.7% and poor in 72.3%. The temple pressure was ideal in only 53.7%. The temple length was adequate in 48% and inadequate in 51.8%. The spectacle lens evaluation revealed a mean decentration of 3.5 mm (SD ± 1.4, range: 1-6). Plastic lenses were used in 94.4% and glass lenses in 5.6%. The lens surface was graded good in 16.6%, fair in 37% and poor in 46.3%. The mean error in the lens power was 0.02D (SD ± 0.5D range: −4.0D to + 1.0D). The mean error in cylinder axis was 4.4° (SD ± 11.0, range: 0-90). Overall, quality of spectacle fitting was 1.25 on a scale of 0-3 (0 = worst, 3 best) and quality-of-lens was 1.67 on a scale of 1-3 (1 = poor, 2 = fair, 3 = good). No statistically significant differences [Table 2] were found in the overall quality of frame fitting or quality of lenses between the age group (less than or more than 7 years [P = 0.7,1.0]), gender (male or female [P = 0.3,0.2]), type of frame (metal or plastic [P = 1.0]) and type of lenses (plastic or glass [P = 0.9]) and duration of wear (less than 6 months or more than 6 months [P = 0.5,0.2]).Table 2: Criteria for ideal spectacle frame and spectacle lens in childrenWe concluded that the optical dispensing (frames as well as lenses in its entirety) in children was poor irrespective of the gender, age, type/material of the frame or duration of wear [Fig. 1]. More patient (parent) education and responsiveness of the opticians is needed to improve the quality of spectacle dispensing. Both, the frame evaluation and lens evaluation are necessary.Figure 1: Examples of poor spectacle frames and lenses in children. (a) Temple non -parallelism, (b) Loss of four-point touch, (c) Short temple length, (d) Lens scratches, (e) Lens pits and scratches, (f) Lens chipping, (g) Poor overall fit, (h) Not good nose bridge and (i) Poor mastoid bendIt may be advisable that the patient come back with the newly dispensed spectacle for a quality check to the ophthalmologist soon after they are dispensed. The ophthalmologists must refer to ideal fitting and quality criteria [Table 2] to ensure an optimum lens and frame dispensing. Further studies are needed to assess the impact of improved spectacle fitting and quality of lenses on the compliance of spectacle wear in children, which in turn may translate in the better and faster visual rehabilitation.

Gas foil bearings (GFBs) have clear advantages over oil-lubricated and rolling element bearings, by virtue of low power loss, oil-free operation in compact units, and rotordynamic stability at high speeds. However, because of the inherent low gas viscosity, GFBs have lower load capacity than the other bearings. In particular, accurate measurement of load capacity and dynamic characteristics of gas foil thrust bearings (GFTBs) is utmost important to widening their applications to high performance turbomachinery. In this study, a series of excitation tests were performed on a small oil-free turbomachinery with base excitations in the rotor axial direction to measure the dynamic load characteristics of a pair of six-pad, bump-type GFTBs, which support the thrust collar. An electromagnetic shaker provided dynamic sine sweep loads to the test bench (shaking table), which held rigidly the turbomachinery test rig for increasing excitation frequency from 10 Hz to 200 Hz. The magnitude of the shaker dynamic load, represented as an acceleration measured on the test rig, was increased up to 9 G (gravity). An eddy current sensor installed on the test rig housing measured the axial displacement (or vibrational amplitude) of the rotor thrust collar during the excitation tests. The axial acceleration of the rotor relative to the test rig was calculated using the measured displacement. A single degree-of-freedom base excitation model identified the frequency-dependent dynamic load capacity, stiffness, damping, and loss factor of the test GFTB for increasing shaker dynamic loads and increasing bearing clearances. The test results show that, for a constant shaker force and the test GFTB with a clearance of 155 μm, an increasing excitation frequency increases the dynamic load carried by the test GFTB, i.e., bearing reaction force, until a certain value of the frequency where it jumps down suddenly because of the influence from Duffing’s vibrations of the rotor. The bearing stiffness increases and the damping decreases dramatically as the excitation frequency increases. Generally, the bearing loss factor ranges from 0.5 to 1.5 independent of the frequency. As the shaker force increases, the bearing dynamic load, stiffness, damping, and loss factor increase depending on the excitation frequency. Interestingly, the agreements between the measured GFTB dynamic load versus the thrust runner displacement, the measured GFTB static load versus the structural deflection, and the predicted static load versus the thrust runner displacement are remarkable. Further tests with increasing GFTB clearances of 155, 180, 205, and 225 μm revealed that the vibrational amplitude increases and the jump-down frequency decreases with increasing clearances. The bearing load increases, but the bearing stiffness, damping, and loss factor decrease slightly as the clearance increases. The test results after a modification of the GFTB by rotating one side bearing plate by 30° relative to the other side bearing plate revealed insignificant changes in the dynamic characteristics. The present dynamic performance measurements provide a useful database of GFTBs for use in microturbomachinery.

This paper responds to the discussion [1] by Dr. K. Giannakos over our technical note [2].[...]

The problem connected with the mine support with metal frames in unstable rock mass subjected to stoping is analyzed. In terms of the complicated geological conditions of the Orlov mine (East Kazakhstan), the application of Blok-Fil phenol resin in filling voids and domes after rock falls in the gap between the metal frames and roof is tested at the laboratory and pilot scale. It is found that owing to complete filling of voids with resin, no dynamic loads on the support due to rock falls and self-heating of ore and mine air are observed.

3D micromechanical progressive failure simulation for fiber-reinforced composites

The optimal treatment of high energy tibial fractures remains controversial and a challenging orthopaedic problem. The role of external fixators for all these tibial fractures has been shown to be crucial. A five-year consecutive series was reviewed retrospectively, identifying two treatment groups: Ilizarov and Taylor Spatial Frame (TSF; Smith & Nephew, Memphis, TN, US). Fracture healing time was the primary outcome measure. A total of 112 patients (85 Ilizarov, 37 TSF) were identified for the review with a mean age of 45 years. This was higher in women (57 years) than in men (41 years). There was no significant difference between frame types (p=0.83). The median healing time was 163 days in both groups. There was no significant difference in healing time between smokers and non-smokers (180 vs 165 days respectively, p=0.07), open or closed fractures (p=0.13) or age and healing time (Spearman's r=0.12, p=0.18). There was no incidence of non-union or re-fracture following frame removal in either group. Despite the assumption of the rigid construct of the TSF, the median time to union was similar to that of the Ilizarov frame and the TSF therefore can play a significant role in complex tibial fractures.

Recent trends towards constructing taller and increasingly slender buildings imply that these structures are more sensitive to wind excitation. This paper presents a technique for the wind‐resistant optimal design of supertall buildings with a complex structural system including concrete‐filled steel tube columns, shear walls, and various types of beams and columns. In each optimal design cycle, the dynamic wind load acting on a building is transformed into a set of multiple‐oriented equivalent static wind loads, which converts the optimal design for a building acted by dynamic loads into a simpler optimal design problem that considers only static loads. The objective function and constraint functions are explicitly formulated for various types of frame and area members, and consequently, the optimal design problem is mathematically modeled. The optimality criteria method is employed to seek a solution to the optimal design problem. A 68‐story actual supertall building with a height of 303 m is considered for a case study. The obtained results show that the presented technique is capable of giving a good numerical optimal solution for practical use. The technique and results obtained from this study are valuable for academic and professional engineers involved in wind engineering and structural design.

ABSTRACT: Over its 30-year history, the design of ground support schemes at the LaRonde mine has evolved significantly to meet the demands of the rock mass while mining from surface to the current depth of over 3000 m. Over the past decade, seismicity and dynamic loading on ground support systems have become a focus of ground control management and one of the major challenges at LaRonde mine. In some rare occurrences, dynamic loading from seismic events have exceeded the capacity of ground support schemes. Furthermore, the ground control practices implemented to safely manage seismic conditions in development drives have been largely successful despite the operational challenges of a deep mine. Thus, as the mine progresses ever deeper, there is a continuous need to implement ground support schemes that are not only tougher but also more efficient to install considering the mine configuration and available equipment. As part of this endeavor, a dynamic testing program was developed at Geobrugg's testing facility, in association with Geobrugg and the Kittilä mine. The test program involved various elements of ground support schemes from LaRonde and Kittilä mines. This paper presents the testing program, instrumentation set up and results analysis process as well as testing results for three of the LaRonde tests. The testing program is intended to guide improvements in ground support schemes designs for deep mining environments. 1. INTRODUCTION Deep underground mining environments present unique challenges for the design of ground support schemes, particularly in zones susceptible to stress-induced rock failure and rockbursting. Traditional ground support schemes, designed primarily to control gravity-induced rockfalls in blocky rock masses, have been found to be unsuitable for such environments. For the sake of consistency, the authors have adopted the terminology proposed by Windsor and Thompson (1992) as presented in Villaescusa et al (2023). A Ground Support Scheme is therefore defined as a combination of a surface support system, composed of plates, mesh, liner or shotcrete, with an internal reinforcement system consisting of rockbolts and cable bolts. In blocky ground, under static conditions, the design of a ground support scheme aims primarily at meeting the load demand and minimizing deformation to maximize the reinforcement function. In weak and highly deforming ground, ground support schemes require increased ductility to meet the deformation demand while retaining load capacity. Under dynamic conditions, the ground support schemes must also satisfy energy dissipation, rapid rock mass deformation demands and ensure load transfer from the rock mass to the reinforcement, and to the surface support. The ground support elements' load and deformation characteristics must be matched to enable this load transfer.

The article discusses environmental issues as well as two design options of a condominium: a design scheme with a 6000x6000 m grid of columns and a design scheme with a 6000x12,000 m grid of columns. The calculation results for Naberezhnye Chelny are given, excluding dynamic loads with an elastic foundation and considering wind pulsations on a rigidly restrained foundation. The analysis of the calculation of the load-bearing systems of a multistorey building with a monolithic frame is presented, aimed at the maximum possible reduction in the cross-section of the frame elements transmitting the load, as well as their number, respectively, and at reducing costs. Considering all the requirements and norms, the structural scheme of the monolithic frame of the building, designed on an elasticfoundation, which was optimal in all parameters, was developed, subject to the given soil options. Wind and snow loads were calculated. Loads of the dead weight of structures, roof and floor were also considered. The calculation for the impact of dynamic loads, namely the pulsations of the wind, given along the axes of coordinates X and Y [2; 3]. Loads were determined with an elastic foundation and a grid of 6x6 m and 6x12 m columns excluding wind pulsations and loadings, considering the dynamic load of wind pulsations with rigid support of the foundation. The strength test was performed for three combinations. Calculations were made for maximum and minimum efforts and stresses. The selection of reinforcement with an elastic foundation and with dynamic loads of wind pulsations has been performed. Calculation and selection of supporting structures and required reinforcement were performed using SCAD software. The calculation results were also verified here. The structure of a multi-storey condominium with a 6 by 6 column grid is designed in such a way that it can withstand the acting forces and loads, i.e. mobilize reaction forces that guarantee the balance of the frame with an elastic foundation. As a result of the above calculations, a positive assessment was given of the possibility of designing a building with a calculation scheme with a 6000x6000 m grid of columns.

A ballistic method for impacting spectacle lenses mounted in safety frames is presented. Industrial thickness polycarbonate lenses were found to resist fracture at high levels of impact energy, and were displaced from plastic and metal safety frames with and without accompanying frame fractures. Group comparisons revealed no significant difference between two types of plastic frames; a highly significant difference was revealed between either type of plastic frame and the metal frame. It is concluded that metal safety frames are not as effective as plastic frames in retaining plastic lenses against ballistic impacts. Furthermore, polycarbonate plastic lenses offer great promise for truly effective eye protection against missiles if scratch resistance of the lenses and retention performance of frames can be improved.

The effect of (1) initial imperfections and (2) material degradation of reinforced concrete columns on their safety in emergency situations was investigated. The research was limited to low- and medium-flexibility columns. Numerical modeling and proven regulatory methods of analysis were applied to determine the ultimate bearing capacity, taking into account supplementary dynamic loading by a longitudinal force and a bending moment in case of emergency. The numerical model, describing the column structure, has 3D elements simulating concrete, and rebars simulating reinforcement frames (cages). Imperfections are simulated by (1) the physical loss of elements, (2) unzip of nodal elements, and (3) unzip and further zip using nonlinear elements simulating gaps and cohesion between concrete and reinforcement. Implicit dynamics and an incremental method were employed to make computations. Within the framework of this computational scheme, a nonlinear problem was solved using the Newton–Raphson method with nodal forces convergence. The effect of imperfections, such as geometrical deviations and deterioration of mechanical characteristics, on the bearing capacity of compressed bending elements was identified under emergency actions. Risks of mechanical safety loss were analyzed to find that columns in the frame structures of highly hazardous, technically complex, and unique buildings and structures, subjected to supplementary loading, need an additional safety margin in the range of 3–21%. Rectangular cross-sections of columns are the most effective in terms of the safety criterion.