Monolithic Shells Research Articles

Systematical structural analysis of monolithic domes

Monolithic dome structures were built in the 1970s in Europe and America. These dome structures share common benefits of being cost efficient, earth-friendly, extremely durable, and easily maintained. Monolithic shells are easily constructed and are extremely cost-effective. Monolithic domes respond efficiently to any climate, even to extremely cold or hot temperatures. In terms of utility savings, monolithic domes can cut electricity consumption by up to one-third, thereby saving 60–70% of total energy costs. Moreover, monolithic structures provide the highest survivability rates from destructions. The interior of monolithic domes have perfect, concave shapes to ensure that sound travels through the dome and perfectly collected at different vocal points. These dome structures are utilized for domestic use because the scale allows the focal points to be positioned across daily life activities, thereby affecting the sonic comfort of the internal space. This study examines the various acoustic treatments and parametric configurations of monolithic dome sizes. A geometric relationship of acoustic treatment and dome radius is established to provide architects guidelines on the correct selection of absorption needed to maintain the acoustic comfort of these special spaces. In this study we cannot take the particular research paper for comparison of results. The location of structure for terrain category I calculated and so the wind speed varies according to terrain and this results in different value of load calculation for different terrain category.

Cost-effective design of long cylindrical shells of high-strength sand concrete

The use of high strength sand concrete (HSSC) is an alternative to high-strength crushed stone concrete. Its use is economically viable for those regions of Russia in which crushed stone belongs to imported building materials. So, crushed stone is supplied to the Republic of Tatarstan (RT) from the Ural, and local sand reserves are significant.Authors give the information on the cost-effectiveness of designing prefabricated and monolithic long cylindrical shells from HSSC of B60 and B80 classes compared to heavy concrete of B20-B80 classes.The determination of the forces in the shell elements was performed by using the LIRA-CAD software package (SP). The calculation of the elements of prefabricated shells was carried out in the stages of operation, manufacture, transportation and installation. It was carried out by an engineering method according to the methodology of current standards. Calculation of monolithic shells was performed using an SP. The density of heavy concrete, its strength and deformation characteristics were accepted according to the standards. The same characteristics for HSSC were based on the results of the experiments of the department “Technology of building materials, products and structures” (TBMPS) of Kazan State University of Architecture and Engineering (KSUAE).The performed calculations showed that the use of HSSC of B60 and B80 classes compared with the heavy ones makes it possible to obtain a significant economic effect in the Republic of Tatarstan (RT). Namely: to reduce the consumption of steel (up to 30.6 % in prefabricated shells and up to 23.7 % in monolithic), concrete (up to 15.9 % in prefabricated shells and up to 14.0 % in monolithic) and the total cost of materials (up to 18.9 % in prefabricated shells and up to 20.3 % in monolithic).

Lynx x-ray optics based on thin monolithic shells: design and development

Lynx is the future x-ray observatory with superb imaging capabilities (<1 arc sec half-energy width) and large throughput (2 m2 effective area @ 1 keV), which is being considered in the U.S. to take over Chandra. The implementation of the x-ray mirror module represents a very challenging aspect, and different approaches are being considered. Thin and low-weight substrates, working in grazing incidence configuration, are necessary to meet the severe mass constraints, but they have to also preserve the requirement of an excellent angular resolution. The use of monolithic glass (fused silica) shells is an attractive solution, provided that their thickness is kept very small [<4 mm for mirror shells up of 3-m diameter]. We present the optomechanical design of the Lynx mirror assembly based on this approach, together with the ongoing technological development process. In particular, we discuss the figuring process, which is based on direct polishing followed by an ion-beam figuring correction. A temporary structure is specifically devoted to support the shell during the figuring and polishing operations and to manage the handling of the shell through all phases up to integration into the final telescope supporting spoke wheel. The results achieved so far on a prototype shell will be discussed.

Full-shell x-ray optics development at NASA Marshall Space Flight Center.

NASA's Marshall Space Flight Center (MSFC) maintains an active research program toward the development of high-resolution, lightweight, grazing-incidence x-ray optics to serve the needs of future x-ray astronomy missions such as Lynx. MSFC development efforts include both direct fabrication (diamond turning and deterministic computer-controlled polishing) of mirror shells and replication of mirror shells (from figured, polished mandrels). Both techniques produce full-circumference monolithic (primary + secondary) shells that share the advantages of inherent stability, ease of assembly, and low production cost. However, to achieve high-angular resolution, MSFC is exploring significant technology advances needed to control sources of figure error including fabrication- and coating-induced stresses and mounting-induced distortions.

Axial compressive collapse of ultralight corrugated sandwich cylindrical shells

Ultralight all-metallic sandwich cylindrical shells with corrugated cores are designed and fabricated using a method involving tamping and shape correction. Quasi-static axial compressive behaviors of the sandwich shells are investigated using a combined experimental, theoretical and numerical approach. Based on the analytical model and numerical approach, systematic parametric study is carried out to explore the effects of key geometrical parameters on the failure load and energy absorption capacity. Minimum weight design as a function of the failure load is subsequently carried out for the proposed sandwich shell. As an attempt for further performance enhancement, the foam-filled corrugated-core sandwich cylindrical shell is proposed and a preliminary experimental study is carried out. The superiority of sandwich shells over monolithic shells in terms of initial failure load and energy absorption is clearly demonstrated, potentially important for applications demanding simultaneous ultra-lightweight, load-bearing and energy absorption.

Acoustic of monolithic dome structures

Monolithic dome structures were built in the 1970s in Europe and America. These dome structures share common benefits of being cost-efficient, earth-friendly, extremely durable, and easily maintained. Monolithic shells are easily constructed and are extremely cost-effective. Monolithic domes respond efficiently to any climate, even to extremely cold or hot temperatures. In terms of utility savings, monolithic domes can cut electricity consumption by up to one-third, thereby saving 60–70% of total energy costs. Moreover, monolithic structures provide the highest survivability rates from destructions.The interior of monolithic domes have perfect, concave shapes to ensure that sound travels through the dome and perfectly collected at different vocal points. These dome structures are utilized for domestic use because the scale allows the focal points to be positioned across daily life activities, thereby affecting the sonic comfort of the internal space. This study examines the various acoustic treatments and parametric configurations of monolithic dome sizes. A geometric relationship of acoustic treatment and dome radius is established to provide architects guidelines on the correct selection of absorption needed to maintain the acoustic comfort of these special spaces.

Stretching and bending deformations due to normal and shear tractions of doubly curved shells using third-order shear and normal deformable theory

ABSTRACTWe analyze static infinitesimal deformations of doubly curved shells using a third-order shear and normal deformable theory (TSNDT) and delineate effects of the curvilinear length/thickness ratio, a/h, radius of curvature/curvilinear length, R/a, and the ratio of the two principal radii on through-the-thickness stresses, strain energies of the in-plane and the transverse shear and normal deformations, and strain energies of stretching and bending deformations for loads that include uniform normal tractions on a major surface and equal and opposite tangential tractions on the two major surfaces. In the TSNDT the three displacement components at a point are represented as complete polynomials of degree three in the thickness coordinate. Advantages of the TSNDT include not needing a shear correction factor, allowing stresses for monolithic shells to be computed from the constitutive relation and the shell theory displacements, and considering general tractions on bounding surfaces. For laminated shells we use an equivalent single layer TSNDT and find the in-plane stresses from the constitutive relations and the transverse stresses with a one-step stress recovery scheme. The in-house developed finite element software is first verified by comparing displacements and stresses in the shell computed from it with those from either analytical or numerical solutions of the corresponding 3D problems. The strain energy of a spherical shell is found to approach that of a plate when R/a exceeds 10. For a thick clamped shell of aspect ratio 5 subjected to uniform normal traction on the outer surface, the in-plane and the transverse deformations contribute equally to the total strain energy for R/a greater than 5. However, for a cantilever shell of aspect ratio 5 subjected to equal and opposite uniform tangential tractions on the two major surfaces, the strain energy of in-plane deformations equals 95–98% of the total strain energy. Numerical results presented herein for several problems provide insights into different deformation modes, help designers decide when to consider effects of transverse deformations, and use the TSNDT for optimizing doubly curved shells.

A new, unified, theoretical framework for the formulation of general, nonlinear, single-scale shell theories

A new, general theoretical framework for the generation of single-scale shell theories is presented. The framework is developed for application to the analysis of the general laminated and monolithic shells. The proposed framework is intended to allow the accurate prediction of the effects of material nonlinearity and wave propagation effects through the thickness of a shell.The starting point for the framework is a general, single-scale description of the displacement field expressed in terms of arbitrary expansion functions through the thickness of the shell. The functional forms and orders for the expansion functions in the displacement field representation are arbitrary. The development of the governing equations for the theory is carried out using the general nonlinear equations of continuum mechanics referenced to the initial configuration within the context of general coordinate systems. The equations of motion and the lateral surface boundary conditions for the theory are derived using the method of moments over the domain of the expansion functions. The (arbitrary) top and bottom surface boundary conditions (BCs) are satisfied exactly. The interfacial constraints (continuity of tractions and (dis) continuity of displacements) are also satisfied exactly. Delamination effects are incorporated into the theory through the use of arbitrary functions relating the displacement jumps to appropriate state variables. These functions can be changed without the need for reformulation of the governing equations. The theory is formulated in a sufficiently general fashion that any type of history-dependent material model can be used to describe the history-dependent behavior of the material composing a layer without the need to reformulate the theory.The theoretical framework is unified in the sense that any type of desired single scale shell (smear/equivalent single layer (ESL), discrete layer, or zig-zag) theory can be obtained through suitable specialization of the framework. In the case of a smeared or ESL representation the domain of the displacement representation applies across the entire thickness of the shell. To generate a zig-zag theory within the context of the proposed framework is simply a matter of carrying out the interfacial analysis appropriate to the zig-zag assumptions and substituting the resulting displacement representation into the framework and then proceeding as with a smeared/ESL theory. In the case of a discrete layer analysis the displacement representations applies across each of the individual domains. The domains may correspond to several layers, a lamina, or a sublamina. Thus, the framework represents a comprehensive approach to modeling shells.The predictions of the theory are compared with the results obtained from an exact elastic solution for the static response of a sphere and the exact elastic solution for the dynamic response of monolithic sphere. Both exact solutions are based on the assumptions of spherically symmetric boundary conditions. It is shown that the theory is capable of providing accurate predictions for the pointwise (displacement, strain, and stress) fields distributions in laminated and monolithic shells. Furthermore, it is shown that the behavior of the theory is self-convergent and thus increasing the order of the analysis always converges the predictions to the correct answer.

Evaluation of the strength of a new type of detachable joint in a compound glass shell

1. Compound shells with a detachable joint directly connecting the glass elements showed a satisfactory breaking strength under the effect of a single external hydrostatic pressure and can be recommended for working under such conditions up to loads amounting to no more than 0.3 of the calculated value characteristic for monolithic shells similar to them. 2. For the successful realization of direct joining of the glass elements and for eliminating their premature damage and destruction in the joint zone, it is necessary to polish their contact surface with respect to the third class of precision and to provide an arithmetic mean deviation of the profile of the contact surfaces of not more than 0.32 μm. 3. The strength of the assembled shells with a detachable butt joint is determined by the value of the contact strength of the material under conditions of the interaction of glass with glass in the joint in the presence of large specific compressive forces and technological imperfections of the contact surfaces of the joint. The most dangerous type of such imperfections is the presence of chips and gas bubbles on the contact surfaces. Misalignment of the contact surfaces in the plane of the joint, causing the occurrence of inside overhanging edges, also substantially reduces the strength of the compound shells. 4. The direct contact between glass elements on the surface of detachment does not provide a high level of operational capability of the joint in the case of repeated static loading by an external pressure and can be recommended only for one-time (1–10 cycles) use. 5. The cyclic strength of the detachable butt joint of compound shells is entirely determined by the aforementioned factors and its level of stress under conditions of frictional interaction of the contact surfaces. 6. Strengthening of the contact surfaces of glass elements by chemical etching does not improve the joint; the bearing capacity of the compound spherical shell remains at the former level.