Segmented Shells Research Articles

Making the Hypar Up pavilion: (in)efficiencies of upcycling surplus timber products

This paper illustrates the design and fabrication processes of the Hypar Up pavilion, which served as a proof-of-concept to demonstrate the viability of a design-to-fabrication workflow for complex yet modular architectural geometries that utilise small and planar timber offcuts geometries discretised as Planar Quadrilateral (PQ) meshes. By integrating computational design and optimisation with efficient manufacturing processes, this research highlights the technical challenges of repurposing materials with unknown characteristics, notably detailing solutions, and evaluates the efficiency of design-to-manufacturing workflows with surplus timber products, using a quantitative cost analysis of the fabrication and assembly phases. While exploring the potential of repurposing scrap wood into hypar-shaped modular construction components, this work expands on existing research on segmented shells and investigates methods and means to move beyond the use of shell structures as monolithic and static artefacts. The pavilion is intended as a 1:1 modular prototype that can be resized to accommodate different dimensions of the timber panel offcuts and potential applications to be tested in future applications, such as load-bearing walls and facade retrofitting.

Practical finite element modelling of segmented vaulted structures with assessment of imperfect dry-joints

The response of vaulted structures with dry-joints such as arches and shells can be predicted using graphical methods, limit state analysis, and rigid block analysis. However, these approaches assume material deformations are negligible. While acceptable for conventional masonry structures, there is a growing body of work investigating segmented vaulted structures where the segments comprise a large portion of the overall span. In such cases, material deformations and non-linearities can play a significant role. Typical analysis tools available are usually difficult to use and are not widely used by industry practitioners. In this paper, a modelling approach using a widely used finite element analysis package (LS-DYNA) is presented, using an ‘out-of-the-box’ approach for parameter tuning and modelling. This was then benchmarked against five experimental tests of dry-joint arches undergoing support displacements and a segmented concrete shell with large segments tested under a central point load. Crucially, the segmented shell exhibited imperfect dry-joints, with gaps occurring throughout various locations. A method of modelling and assessing such imperfections in a simple and practical manner is investigated through the use of a positive penetration allowance in the contact surfaces. The results show that the modelling approach is able to predict the collapse mechanism and failure support displacement for arches well, with further experimental tests required for 3D systems. It is envisioned that this work will add to the number of tools designers will have for analysing segmented vaulted structures with dry-joints.

Effects and Cost-Benefit of Low and High Protein Levels in Snail Diets with Constant Levels of Energy and Calcium

Snails are invertebrates with soft segmented shells. Snail farming is still at the infant stage compared to other farming enterprises because of limited information on the nutrient requirement of the animal. Therefore, a 12-week study was conducted to determine the effect of snails’ diets containing low and high Crude protein (CP) levels with constant level of energy and calcium on the growth performance of African giant land snail Archachatina marginata. In a completely randomized design, a total of 120 snails of the same weight and breed were randomly allotted to five (5) different dietary treatments: PR1 (20% CP), PR2 (22% CP), PR3 (24% CP), PR4 (26% CP) and PR5 (28% CP) with constant energy (2.6 Mcal/kg Metabolizable Energy) and calcium level. The snails were placed in 12 experimental compartments each measuring 0.5x 0.5m2. Results revealed that the body weight gain, feed intake, cost of feed per kg weight gain and dressing percentage yield was significantly (p < 0.05) higher at the 28% CP. Furthermore, results showed significant (P< 0.05) interactions between protein across the treatments performance indices, shell length, shell width, feed cost per kg weight gain and dressing percentage yield. Feed intake decreased significantly (p < 0.05) at 20% CP level while the FCR values decreased (p < 0.05) at 28% CP level. Shell length, width and thickness was enhanced (p < 0.05) at 20% CP level. Also, the Feed cost per kg weight gain was observed to be significantly (p < 0.05) reduced at the 24% CP. The results obtained in the present study showed that the dietary protein of 24% CP, with constant energy of 2.6Mcal/kg ME is optimally suitable for the growth of African giant land snails Archachatina marginata at reduced cost.

Calculation of VAT and assessment of the strength of a segmented cylindrical shell made of composite materials with metal inserts

The paper considers a cylindrical segmented shell - a pressure cylinder made by winding from unidirectional roving. The shell has a different thickness and reinforcement scheme for segments, and metal embedded elements on the front and rear ends of the shell for fixing the covers. The problem of calculating the stress-strain state and estimating the strength of the shell under loading by internal pressure is posed. To solve the problem, a two-level numerical mathematical model of the shell is developed. At the first level, the shell is modeled using the effective characteristics of the composite material by segments. At the second level, the deformation of individual segments of the shell is modeled - the front and rear joint nodes with metal embedded elements and a pin-pin connection with an explicit description of the segment reinforcement scheme. The boundary conditions for the segment deformation problem are determined as a result of calculating the shell VAT using the first-level model. The developed model is compared with the results of bench tests of the shell for the effect of internal pressure. Based on the results of solving the problem for the shell segments, the analysis of interlayer stresses in the contact zone of the composite shell - metal embedded was performed and estimates of the structural strength were obtained.

Математична модель для визначення проєктних параметрів космічної надувної платформи з корисним навантаженням

The development and application of inflatable space structures is of considerable interest in modern space science and technology. Today, these structures enjoy wide application from aerodynamic inflatable deorbit means to inflatable residential sections for the International Space Station. This is because the masses of inflatable structures are smaller in comparison with others, which in turn minimizes the cost of their orbital injection. In view of the considerable interest in orbital constellations, the authors of this article propose the use of an inflatable space aerodynamic system as a platform for a payload. In doing so, we obtain a distributed satellite system on an inflatable space platform. The advantage of this technology is that it assures the maintenance of the relative position of the elements (payload) of a distributed satellite system of this type with minimal energy consumption. In its turn, to analyze the features of the operation of a particular space technology, its mathematical model is required. Because if this, the aim of the article is to develop a mathematical model for estimating the design parameters of an inflatable payload-bearing space platform. The mathematical model of the operation of an inflatable payload-bearing space platform developed in this work consists of three modules: a module of orbital motion, a module of calculation of the thermodynamic parameters of the inflatable platform, and a module of calculation of its variable inertia tensor. The article also identifies four gas modes of operation of the inflatable segment of the space platform and gives the inertia tensor as a function of the ambient temperature, which is necessary for further research. It should be noted that the application of the mathematical model allows a priori analysis of a wide range of inflatable space platform design parameters. On this basis, a design parameter analysis method that uses this model was developed. The application of this method may greatly simplify further research into the synthesis of an angular motion controller for an inflatable payload-bearing space platform, the choice of the design parameters of inflatable segment shell materials, and the study of the platform operation in different gas modes.

Shell Side Single-Phase Experimental Heat Transfer Analysis of a Vertically Oriented Single Segmental Baffle Bundle With Dimpled Tubes

Abstract This paper presents single-phase shell side heat transfer performance of a vertically oriented shell and tube bundle. Steady-state single-phase experiments were conducted to determine the shell side Nusselt number with water and water/glycol solution as working fluids for both counter and parallel flow configurations. Experiments were carried out for Reynolds number varying from 3000 to 15,000 with Prandtl number ranging from 10 to 20. Counter flow configuration showed slightly better performance. Nusselt number correlations are presented for both configurations using a modified Wilson plot method. Comparison of results with previous studies and commercial software are presented. Thermal performance for all flow rate conditions showed close comparison to the results from a reputable commercial software. The correlation was further validated by comparing results for 30 different cases to calculations from 2 widely used commercial softwares. Comparison showed that the correlation can be used for the design of single-phase single segmental shell and tube heat exchangers.

Dynamic analysis of composite laminated doubly-curved revolution shell based on higher order shear deformation theory

The main content of this paper is to establish an analysis model for dynamic analysis of composite laminated doubly-curved revolution shell based on the Higher order Shear Deformation Theory (HSDT). Firstly, the energy functional of shell is established based on higher order shear theory. Then, the multi-segment partitioning technique is introduced to segment the shell along the generatrix direction, which is mainly to relax the boundary conditions of shell, and then reduce requirements for the displacement function. At the boundary position, the boundary spring parameters are used to obtain the corresponding boundary conditions. Similarly, the connecting spring parameters are introduced to simulate the continuity conditions between the segmented shells. The parameters of boundary spring and connecting spring can be regarded as the weight parameter. Thirdly, all displacement components of the composite laminated doubly-curved revolution shell are expressed by Jacobi orthogonal polynomials. Finally, the whole dynamic characteristics are obtained by Rayleigh-Ritz method with respect to unknown Jacobian expansion coefficient. The convergence, validity and dynamic characteristics of the analytical model established in this paper are given by a series of numerical examples.

Parametric Creative Design of Building Free-Forms Roofed with Transformed Shells Introducing Architect’s and Civil Engineer’s Responsible Artistic Concepts

The article concerns a parametric description of unconventional building forms roofed with folded sheeting transformed elastically into shells. The description supports the designer in the search for attractive forms and a rational use of materials. The adoption of strictly defined sets of initial parameters determines the diversification of the designed architectural free-forms. An impact of selected proportions between these parameters on these forms is illustrated by an example of a single structure. Folded elevations and a segmented shell roof make each such structure internally coherent and externally sensitive. The mutual position and proportions of the shape of all elements, such as the roof, eaves, and façades, along with regular patterns in the same structure, determine this consistency of its form and sensitivity to harmonious incorporation into the natural or built environments. The study is a new insight into shaping free-forms of buildings in which the modern and ecological materials determine the important shape and mechanical limitations of these forms. With a skillful approach, the materials allow their extensive use in buildings. However, various interdisciplinary problems related to architectural shaping of free-forms and static and strength work thin-walled shell sheeting roofs must be solved. For effective design it is necessary to use relevant software applications, where spatial reasoning is crucial for ordering the three-dimensional space by means of simplified engineering models.

Natural Fibre-Reinforced Polymer Composites (NFRP) Fabricated from Lignocellulosic Fibres for Future Sustainable Architectural Applications, Case Studies: Segmented-Shell Construction, Acoustic Panels, and Furniture.

Due to the high amounts of waste generated from the building industry field, it has become essential to search for renewable building materials to be applied in wider and more innovative methods in architecture. One of the materials with the highest potential in this area is natural fibre-reinforced polymers (NFRP), which are also called biocomposites, and are filled or reinforced with annually renewable lignocellulosic fibres. This would permit variable closed material cycles’ scenarios and should decrease the amounts of waste generated in the building industry. Throughout this paper, this discussion will be illustrated through a number of developments and 1:1 mockups fabricated from newly developed lignocellulosic-based biocomposites from both bio-based and non-bio-based thermoplastic and thermoset polymers. Recyclability, closed materials cycles, and design variations with diverse digital fabrication technologies will be discussed in each case. The mock-ups’ concepts, materials’ compositions, and fabrication methods are illustrated. In the first case study, a structural segmented shell construction is developed and constructed. In the second case study, acoustic panels were developed. The final case studies are two types of furniture, where each is developed from a different lignocellulosic-based biocomposite. All of the presented case studies show diverse architectural design possibilities, structural abilities, and physical building characteristics.

Ambient occlusion – A powerful algorithm to segment shell and skeletal intrapores in computed tomography data

During the last decades, X-ray (micro-)computed tomography has gained increasing attention for the description of porous skeletal and shell structures of various organism groups. However, their quantitative analysis is often hampered by the difficulty to discriminate cavities and pores within the object from the surrounding region.Herein, we test the ambient occlusion (AO) algorithm and newly implemented optimisations for the segmentation of cavities (implemented in the software Amira). The segmentation accuracy is evaluated as a function of (i) changes in the ray length input variable, and (ii) the usage of AO (scalar) field and other AO-derived (scalar) fields. The results clearly indicate that the AO field itself outperforms all other AO-derived fields in terms of segmentation accuracy and robustness against variations in the ray length input variable. The newly implemented optimisations improved the AO field-based segmentation only slightly, while the segmentations based on the AO-derived fields improved considerably.Additionally, we evaluated the potential of the AO field and AO-derived fields for the separation and classification of cavities as well as skeletal structures by comparing them with commonly used distance-map-based segmentations. For this, we tested the zooid separation within a bryozoan colony, the stereom classification of an ophiuroid tooth, the separation of bioerosion traces within a marble block and the calice (central cavity)-pore separation within a dendrophyllid coral. The obtained results clearly indicate that the ideal input field depends on the three-dimensional morphology of the object of interest. The segmentations based on the AO-derived fields often provided cavity separations and skeleton classifications that were superior to or impossible to obtain with commonly used distance-map-based segmentations. The combined usage of various AO-derived fields by supervised or unsupervised segmentation algorithms might provide a promising target for future research to further improve the results for this kind of high-end data segmentation and classification. Furthermore, the application of the developed segmentation algorithm is not restricted to X-ray (micro-)computed tomographic data but may potentially be useful for the segmentation of 3D volume data from other sources.

Biomimetic timber shells made of bending-active segments

In the research field of segmented timber shells, two construction systems have lately received much attention, which both expose interesting structural and constructional characteristics: planar plate structures made of thin plywood and actively bent plywood structures. The research presented in this article combines elements of both approaches, resulting in a construction system for segmented shell structures with elastically bent elements. The increasing complexity of this approach requires a sophisticated design process, which integrates fabrication constraints as well as structural feedback. As a consequence, form-finding strategies of bending-active timber shells are discussed, with a special focus on the programming of the stiffness distribution in order to fulfil geometrical requirements. The authors also reflect on the specific structural challenges of joining thin sheets of plywood by transferring traditional textile connection methods to timber construction. Investigations of biological role models such as the sand dollar led to transfers of constructional principles on different levels. The resulting construction system was validated through the design and construction of a full-scale architectural prototype.

Optimal Segmentation of Glass Shell Structures

Monolithic glass shells can be constructed in limited sizes. Segmented shells allow coverage of larger spans. Three shell systems - spherical dome, cylindrical roof and hyperbolic paraboloid were segmented using four different curved glass segment shapes – square, diamond (or pie for dome), hexagon and hexalock. Three joint materials were analysed- glass (resulting in a monolithic glass shell), silicone (soft adhesive) and epoxy (hard adhesive). A Reissner-Mindlin finite element was used in ANSYS to discretize the modelled geometry. The boundary conditions were setup keeping in mind the favourable membrane behaviour of shell structures. It was found out that glass segment shape and joint stiffness has an influence on the shell behaviour. Optimal shapes show similar behaviour in comparison to monolithic glass shell. Others show a significant increase in the deflection and bending moment values which is unwanted. The in-plane membrane forces remain unaffected and thus are found to be independent of glass segment shape and joint stiffness.

Fatigue analysis of bolted flange joints of a rotary dryer

Abstract This paper describes the fatigue failure of a rotary dryer in a chemical plant. The process conditions required the dryer to be rotated continuously at a speed of about two and half revolutions per minute. The shell structure of this large drum is formed by combining segmented shell parts using bolted ring flange joints. Because of the gross weight of the dryer in operation time, each joint was subjected to bending moment. In the first two years in service, micro cracks were occurred by fatigue. The failure was analyzed using the fatigue curves given in ASME Boiler and Pressure Vessel Code Section VIII Division 2 and EN 13445 Unfired Pressure Vessels Part 3 Codes. Finally, flange joints were removed from the drum and new cylindrical parts adapted to the drum using butt welding after reaching better results in FEM and fatigue calculation.

A way of geometrical shaping effective shell forms

The main content of the paper is a presentation of a way of arranging individual light gauge steel shells in the three-dimensional space to obtain a structure whose general shape corresponds to a regular surface called a base surface characterized by any sign of the Gaussian curvature. The way enables us to achieve: a) an integration of the shape and locations of any number of elements of a shaped building object including walls, windows, roof shell stripes by a diversification of their inclination to the vertical direction and a horizontal plane, b) an effective structural work of the shell folds of the deformed sheets producing individual shells, c) an effective arrangement of the stripes passing crosswise the whole structure by means of the base surface, d) an effective cover of the shell strips with the shell sheets. These aims were achieved by means of auxiliary polyhedral compositions whose side and edges are close to planes and straight lines normal to the base surface as accurate as possible at the point chosen initially. In the next stage, the directrices of the stripes are determined on the planes of this controlling structure composed of the above auxiliary compositions. The models of the stripes are fixed on the base of these directrices so that each model would be contained in one controlling composition. The proposed way can be easily extended over more complicated shell structures, including segment shell structure, characterized by a great integration of any number of elements of a building object.

28Does a greater contact force create more scar? A quantification of the relationship between late gadolinium enhancement on cardiac MR imaging and catheter contact on af ablation

Introduction: Catheter-myocardium contact force (CF) is an important determinant of radiofrequency (RF) lesion generation. Novel RF-catheters enable real-time monitoring of CF, but evidence that CF is the primary determinant of lesion quality is lacking in humans. We used late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) to assess the relationship between applied contact force and chronic scar formation. Method: Twelve patients underwent pulmonary vein isolation using a CF-sensing catheter (SmartTouch Thermocool, Biosense-Webster, CA, USA). Ablation position was recorded using the CARTO-3 electroanatomical mapping system. LGE CMR was performed at a median of 7.2 (range 3-11) months post- ablation using an Achieva 3.0T MRI scanner (Philips, Amsterdam, The Netherlands) with a 3D ECG triggered, free-breathing inversion recovery turbo field echo scan sequence. The LGE-CMR images were segmented using Seg3D by an experienced observer. Signal intensities (SI) were projected onto the segmented shell, using a maximum intensity projection and fused to the CARTO-3 shell using an Iterative Closest Point (ICP) algorithm. The two shells (Contact Force and LGE signal) were then compared using custom built software. The shells were thresholded to blind the observer to local variations in LGE SI and CF before paired paths along the ablation lines were manually drawn on the surface of each shell. Results: For 1710 ablation points across 12 patients, there is a small but significant relationship between applied CF and chronic scar formation as indicated by CMR LGE SI (p<0.0001, R2=0.02) and between grouped CF and mean LGE SI (one- ANOVA, p=0.02). For every ablation line, regions are identifiable in which there is a relationship between CF and SI (see figure). Conversely, other regions of the same ablation lines do not show a close correlation between applied CF and resulting scar formation. Conclusions: Post-ablation scar, as assessed by MRI LGE signal intensity, is qualitatively related to CF, and quantitative analysis shows a weak but significant correlation. However, the majority of variation in scar formation is not explained purely by contact force, and may be related to other ablation parameters such as local cardiac anatomy, regional cooling effects and catheter stability. ![Graphic][1] [1]: /embed/inline-graphic-1.gif

Defect Detection of the Segmental Spherical Shell Based on Ultrasonic Transducer Array

It is of great significance to monitor and quantify the defects in the thin segmental spherical shell components. In the paper the guided wave’s inspiring method has been obtained from the wave-mode conversion based on the theory of the guided wave propagating in the thin spherical shell. Using the wavelet to process the testing signal, and the ellipse localization imaging algorithm, the defect’s localization and orientation can be detected accurately. Experimental results show the defect’s direction and location can be detected effectively and clearly.

A comparison of late gadolinium enhancement magnetic resonance imaging and left atrial endocardial voltage

Background Following catheter ablation for atrial fibrillation (AF), late gadolinium enhancement magnetic resonance imaging (LGE MRI) may be able to visualise areas of fibrosis and therefore reduced endocardial voltage. Unlike previous studies describing qualitative visual comparisons, we have developed a new quantitative technique for comparison of left atrial (LA) endocardial voltage with 3D LGE MRI signal intensity and have applied it in patients undergoing repeat left atrial ablation. Methods Ten patients who had undergone previous catheter ablation for AF, and who represented with either paroxysmal AF (n=4) or atrial tachycardia (AT) (n=6) underwent pre-ablation LGE MRI. A 3D LA reconstruction was created by projecting the LGE data on to a segmented LA shell (signal intensities were displayed as the number of standard deviations (SD) from the mean signal intensity of the atrial blood pool). During the ablation procedure, high density (mean number of points: 368 ± 127) LA endocardial voltage maps were acquired in either sinus rhythm or AT using CARTO 3 (Biosense Webster). The 3D LGE MRI reconstructions and endocardial voltage maps were manually segmented into LA regions (left and right WACA, roof, mitral line, anterior, posterior, inferior, septum and lateral) using custom-written software to derive the mean signal intensity and endocardial voltage for each segment. Results

Tube bundle replacement for segmental and helical shell and tube heat exchangers: Performance comparison and fouling investigation on the shell side

Conventional segmental baffles in shell and tube heat exchangers, while having an excellent record of acceptance and functionality, represent some limitations and shortcomings. In particular, shell-side flow path is wasteful which causes excessive pressure loss while recovering less heat transfer. This particular arrangement of baffles also limits maximum thermal effectiveness and encourages dead zones where fouling occurs. This paper describes the results of tube bundle replacement of a segmental shell and tube heat exchanger with a helical heat exchanger, which was conducted in Tabriz Petroleum Company. The aim of the project was to reduce fouling and pressure drop of the critical heat exchanger and; as a result, reduce operation and maintenance costs. Present paper consists of 3 phases. First, tube bundle replacement in industrial field and also the advantages of helical baffles over conventional segmental baffles are going to be discussed. Then, due to limits on the access to the heat exchangers in production lines, comparison of shell-side flow behavior in both cases is going to be presented by CFD means. Finally, computational code is going to be introduced to investigate on heat transfer and pressure drop for both segmental and helical shell and tube heat exchangers.

ChemInform Abstract: Shell‐Based Support Structures for Nb3Sn Accelerator Quadrupole Magnets

AbstractReview: 19 refs.

Test Results of LARP 3.6 m ${\rm Nb}_{3}{\rm Sn}$ Racetrack Coils Supported by Full-Length and Segmented Shell Structures

As part of the LHC Accelerator Research Program (LARP) to build a high performance quadrupole magnet with Nb3Sn conductor, a pair of 3.6 m-long Nb3Sn racetrack coils has been made at Brookhaven National Laboratory (BNL) and installed in two shell-type support structures built by Lawrence Berkeley National Laboratory (LBL). These magnet assemblies have been tested at 4.5 K at BNL to gauge the effect of extended length and prestress on the mechanical performance of the long structure compared to earlier short models. This paper presents the results of quench testing and compares the overall performance of the two versions of the support structure. We also summarize the shell strain measurements and discuss the variation of quench current with ramp rate.