Concrete Shell Roofs Research Articles

R.C.C Shell Structure Design of Selected Head Cap Shape

Abstract: A shell structure is a thin structure composed of curved sheets of material, so that Shell structures are inspired from natural element named “SHELL”. A thin curved member or slab usually of reinforced concrete that function as tension member and shell. The waviness plays an important role in the structural behavior realizing a spatial form. Some of natural elements like eggshell, seashell, fruit shells (walnut) etc are showing shell structure properties. The present reinforced concrete shells as a very efficient structure, spanning wide, architectonically beautiful, relevant and valuable structural solution. Shell structures are very attractive lightweight structures, which are especially suited to Architectural building, industrial application, commercial projects etc.. The actual design of shells, involves theories of shells and the use of appropriate codes of practice. Types of curved shell like Parabolic, Hyperbolic or Cylindrical members are often said to act as tension rigidity hence called tensile members. For achieving the optimized load capability and flexural strength of such an element in form of shell covering structure is checked in for M30 grade concrete. Tensile shell members are structural edifice that caries only tension and without buckling or bending. Tensile structures are the most common type of thin-shell structures used worldwide from past decades. The profile and aspect of structure used are unlike for loading conditions, geographical locations and Architecture design differs as such as horizontal, sloping or curved member (dome and shell member). In this research work the tensile shell (plate) structure is designed in the form of beam and as grid shell slab element (plate). After then load has been applied for analysis via software tool i.e. STAAD Pro. The types of load assigned dead and live loads. The Design code specifications for curved shell member in IS: 2210–1994, IS 2204-1962 “Code of practice for construction of reinforced concrete shell roof” [CED 13: Building Construction Practices including Painting, Varnishing and Allied Finishing] and the load case criteria is to be as per IS: 875(2)–2000. RCC design specifications as per IS: 456–2000

Initial Parameters Affecting the Multilayer Doubly Curved Concrete Shell Roof

Doubly curved shell roof structures have been widely studied and applied in civil buildings, because of their compressive capacity. As a spatial structure, it should increase the space, reduce the thickness of the shell, and create the architecture for the building. In particular, reinforcement is needed to repair the shell surface, forming the multilayer curved shell roof structures. In this multilayer curved shell roof, it is necessary to investigate the influence of thickness of layers, the influence of the location of the steel fibres concrete layer, and the influence of steel fibres content contained in concrete on the state of stress and strain and build relationships, load-vertical displacement and stress in the x and y directions of the shell in the investigated cases. So, this paper presents an ANSYS numerical simulation study related to the state of stress and strain in double-layer doubly curved concrete shell roof with the initial parameters being changed such as the thickness of the layers, the location of the steel fibres concrete layer in the structure (the steel fibres concrete layer that is placed above and below the normal concrete layer), and the steel fibres content contained in concrete shell with the size of 3000 × 3000 mm, which is simulated by ANSYS after being experimentally conducted on this curved shell roof; the results of experimental and simulation study are verified by each other. Research results show that the thickness of the steel fibres concrete layer is placed below the normal concrete layer, the percentage of steel fibres contained in the concrete is 2%, and the bearing capacity of the curved shell is optimal.

Dual-purpose concrete domes: A strategy for the revival of thin concrete shell roofs

The use of thin concrete shells as long-span roofing solutions has declined over the past 60 years, largely as a result of the expensive nature of the formwork for curved surfaces, and the stiff competition from other more economical options such as steel space grids. The purpose of this contribution is to explore the simultaneous use of thin concrete shells for roofing and liquid-containment purposes. It is hoped the concept of dual-purpose concrete shells will provide enhanced justification for the higher costs associated with the construction of curved surfaces, thereby helping to revive the widespread use of elegant thin concrete shells once again. Specifically, the state of stress in various dual-purpose configurations is evaluated, and the effect of varying shell thickness in critical zones is investigated, allowing some preliminary insights to be gained. With appropriate thickness enhancement in the critical zones, the concept appears feasible, but before firm conclusions can be made, detailed buckling studies need to be undertaken.

Form Finding and Dimensioning of Reinfornced Concrete Shell Roof for Akrotiri (Santorini)

Shells are long-span and inherently light-weight structures used for both their aesthetic and structural benefits. This paper develops a robust methodology for the reinforced concrete (RC) roof shell design of Akrotiri, an archaeological site in Santorini island, Greece. The methodology uses Oasys GSA and finite element package Abaqus which allow both form finding analysis and dimensioning to be conducted. Through the step-by-step application of this method, a protective shell cover is designed and its applicability demonstrated.

Health monitoring and repair of a concrete shell roof structure

A Corrugated doubly curved sea shell form Concrete Structure of 70 mm thickness is functioning for the past 21 years, with good performance in an institutional building entrance hall of size 30m x 30m. The shell having only boundary beam; sloping to one diagonal corner at + 5 m level, the adjacent two opposite diagonal corners at +7 m level and the peak corner is at + 9 m level, supported by columns and footings are resting on rock. The designer has not taken care for thermal resistance performance and not checked for earth quake, and there was no maintenance except periodical cement based whitewash. But, it has performed well in an earthquake of Richter magnitude 4.0 and performing well for the climatic temperature variations ranging from 19◦C to 44◦C during the 21 years of life span. Vertical micro cracks were noticed in the boundary beams. Roof Shell is fixed with the boundary beams. The roof top surface is fixed with weathering ceramic tiles of size 25 mm x 25 mm bonded using tile bond branded chemical adhesive, has opened bonding in a period of five years in the higher deformation area. Hence, the observation was started by performance based health monitoring. Suitable smart materials were applied for surface skin coat to take care of the positive and negative stress-strains and deformations due to temperature variations. The static and dynamic stability against overturning, sliding and gravity forces is ensured adequate. The integral action of the system and the Elastic and Inelastic ductile behaviour of the shell are observed to be higher.

'Toys that save millions' – a history of using physical models in structural design

Small-scale physical models have been used to determine the most efficient form of pure compression and tensile structures since the 17th century – and to predict structural behaviour of some full-size structures since the mid-19th century. This paper traces the development of model testing in the design of building structures from its origins in the design of bridges and ship hulls in the 19th century, to the design of gravity and arch dams in the early 20th century, through the early days of designing concrete shell roofs in the 1920s and 1930s, to its most sophisticated use in the 1960s and (in conjunction with computer modelling) the 1970s. The great strength of model testing was, and is, to deal with new types of structures without design codes and even without precedent.

Evaluation of Distress in Supports of Hyperbolic Paraboloid Shell

A church building structure, composed of a saddle-type hyperbolic paraboloid concrete shell roof supported by buttresses and brick masonry walls, was constructed in 1963. At one corner of the structure, the perimeter of the roof shell projects beyond the exterior building walls to form a canopy over the main entrance. This canopy is partially supported by two brick masonry fin walls that project outward from the main building walls. At the time of original design, closed-form methods (equations) were the only practical way of analyzing this shell structure. However, the configuration of the roof shell was not consistent with detailing requirements of the closed-form methods. After 36years of service, the fin walls had bowed significantly, were exhibiting wide cracks, had slipped laterally with respect to the roof shell, and were in danger of collapse. The writer led an investigation team that developed a finite element model of the church structure, studied the behavior of the church structure when subjected to applied loads and temperature changes, and developed repairs to restore structural integrity and serviceability.

Buckling behaviour of model steel base shells of the Comshell roof system

Steel–concrete composite shell roofs (Comshell roofs) are formed by pouring concrete on a thin stiffened steel base shell which serves as both the permanent formwork and the tensile steel reinforcement. The thin steel base is constructed by bolting together open-topped modular units consisting of a base plate with surrounding edge plates, giving a shell with thin stiffeners in both directions. The new system retains all the benefits of thin concrete shells, but eliminates the need for temporary formwork and minimises the required falsework. A key issue in the design of such shell roofs is to ensure that the steel base shell can carry the wet concrete loading safely during construction. This paper presents the results of a series of buckling experiments on model steel base shells under simulated wet concrete loading. The test results show that both local buckling and overall buckling may occur in these steel base shells, but the latter generally controls the final collapse as the former has a stable postbuckling path. Local buckling may occur in the base plates or the edge plates or both, depending on the specific configurations of the modular units. The overall buckling mode is symmetric in the circumferential direction when the shell is shallow but becomes asymmetrical when the shell becomes deeper. The test results presented in this paper provide the first insight into the buckling behaviour of these shells as well as useful data for future verification of numerical models.

Nondestructive testing and repair of the concrete roof shell at the Seattle Kingdome

As part of major rehabilitation and repair of the 33,445 m 2 (360,000 ft 2) reinforced concrete shell roof of the Kingdome in Seattle, a comprehensive nondestructive testing program employing Infrared Thermographic and Impact Echo techniques was performed to evaluate various in-situ concrete conditions. Questions had developed regarding the extent and significance of areas that exhibited honeycomb or paste voiding near reinforcing steel on the underside of the roof shell following removal of acoustical ceiling tile. The objective of the nondestructive testing program was to identify locations of large, planar-type regions of deep voiding or delamination associated with the consolidation and reinforcement placement conditions. The combined use of Infrared Thermography and Impact Echo techniques allowed for effective scanning of the large roof shell structure entirely from the interior. Anomalous areas identified by the testing were verified by additional nondestructive testing, visual inspection, local exploratory openings and core samples. Based on results of the nondestructive testing, a broad-based repair program was implemented to correct conditions of near-surface voiding and through-thickness honeycomb. Repairs consisted of the application of structural shotcrete to restore integrity in thickened, key load transfer zones of the shell and the overall treatment of the entire underside of the shell with sprayed mortar. This paper presents an overview of why Infrared Thermographic and Impact Echo testing techniques were chosen for this unique project. In addition, their theories of operation and a discussion of this specific application, logistics, and results from testing of the concrete shell of the Seattle Kingdome will be included.

Shotcrete for structural and architectural restoration of concrete shell built in 1905

The Herbivora Building at the Cincinnati Zoo (Cincinnati is a city in southern Ohio, in the midwestern USA), presently housing elephants, giraffes and rhinos, was constructed in 1905. This unique building is one of the earliest examples of reinforced concrete shell roof construction in the United States. The building experienced severe structural and architectural deterioration over a long service life, and was restored in a series of phased projects after 75 years of service. The restoration of structural integrity and the replacement of architectural features and appearance was achieved through the use of shotcrete (also called gunite or pneumatically applied or sprayed concrete) applied to walls, teams, window openings and the dome roof structure.

CONCRETE SHELL ROOFS, 1945-1965.

In the period 1945-1965, considerable numbers of reinforced concrete shell roofs were designed and constructed for relatively routine jobs. This paper considers the commercial background to this activity, and describes the layout of typical structures. The detailing of the concrete structure and the reinforcement is explained and examples of typical completed structures are given.

大スパン球形シェル屋根の設計と施工

大スパン球形シェル屋根の設計と施工

Composite Suspended Shells on Cyclical Plan

The problems connected with the research of rational types of reinforced concrete shell roofs satisfying the demands of city-planning, functional, economic and technological requirements were under investigation during the last decades in TTU and MNIITEP. This paper suggests the use of composite suspended polygonal shells. The structures consist of the curvilinear plates and systems of radial two-level supporting elements. 5 and 12 angle structures were created for the investigations of stress-strain conditions of the complex roofs. The experiments were carried out on fiberglass plastic models and results assure the possibility to use such structures.

水平梁を有する鉄筋コンクリート造円筒シェル屋根の終局耐力 : 直交異方性円筒シェル屋根の解析と終局耐力評価式

This paper presents an evaluating procedure of ultimate strength of reinforced concrete cylindrical shell roofs with vertically supported edge beams. Differential equations of the roof with orthtropic materials are analyzed by applying the Galerkin's method. And, it is shown that stress resultants of the roof are few affected by a variation of Young's modulus of the shell. This let us evaluate the stress resultants after occuring concrete cracking on the shell. Then, an procedure that evaluates ultimate strength of three typical failure mechanism of the reinforced concrete cylindrical shell roof is shown and is examined by comparing with experimental study.

Geometrically and materially nonlinear analysis of reinforced concrete shells of revolution

Reinforced concrete dome shell roofs are often used to provide a light, efficient structure spanning over a large clear space. Examples include auditoria, gymnasia, water tanks, and storage structures. These domes generally have a conical, spherical or ellipsoidal meridian, but they may have a complex meridional profile and a continuously varying thickness. When the shell is thin and the radius of curvature is large, they are susceptible to axisymmetric snap-through buckling or collapse. The collapse of a shell in this manner instigated the work described in this paper. Existing solutions for snap-through buckling are often used in current design, but they are generally of limited value because they relate to elastic shells of uniform thickness. However, the non-uniformity of the shell thickness, and the cracking and yielding in reinforced concrete have strong influences on the snap-through collapse load. In this paper, a general finite element formulation is presented for the large deformation and collapse analysis of reinforced concrete doubly-curved axisymmetric shells. The nonlinear behaviour of concrete is modelled using a rigorous concrete plasticity model. It includes the effects of flexural, stretching, thermal and shrinkage cracking. The analysis is applied to an example dome roof which fails by snap-through buckling.

Buckling Analysis of Segmented Conical Concrete Shell Roof

A finite element nonlinear formulation for the stability analysis of a conical concrete shell roof for a cathedral in India is presented. The degenerated shell elements are used to idealize the shell and the buckling load is calculated based on eigenvalue approach as well as load deformation response using the nonlinear incremental structural analysis program and the conclusions are drawn.

Limit analysis of reinforced concrete cylindrical shell roofs

Two approximate yield criteria are proposed for reinforced concrete cylindrical shell element. Three lower bound solutions are developed for cylindrical shell roofs with free longitudinal edges. Two shells with different geometric parameters are analysed. Elastic analysis is also done at working load. Graphs are presented to show the variation of stress resultants at critical sections.

片持コノイドおよび筒形シェルの動的特性に関する研究 (その 1)

The main purpose of this study is to investigate the dynamic characteristics of cantilever-type concrete shell roofs. Three types of roofs are considered. They are conoidal shells, cylindrical shells and plane plates, which have the same plan and dimensions. Free vibrations and elastic dynamic responses of these shells and plates are analyzed by the finite element method and the behaviors of these shells are compared with one another. The effects of rises and thicknesses of shells are considered. The maximum displacements and stresses of shells in the dynamic response analysis are compared with those in the static analysis. As the results of this study, it is found that conoidal shells have some structural superiority to cylindrical shells and plane plates, as far as cantilever-type shells are concerned.

GIANT PRESTRESSED HP SHELL FOR PONCE COLISEUM

The recently completed hyperbolic paraboloid concrete shell roof for the Ponce Coliseum in Puerto Rico represents a significant thrust forward in the design of shell structures. The shell roof cantilevers 138 ft (measured along the edge beams) making it the world's longest cantilever shell of the HP type. Post-tensioning was used both in the shell membrane and also along the edge beams to control deflections and stresses. In addition, the piers on opposite sides of the shell were post-tensioned beneath the ground to resist the horizontal thrust. The finite element method was used to analyze the structural behavior and to calculate the moments, stresses, and deflections in the shell and edge beams. This article describes the design and construction techniques used in building this shell roof.

A new method of experimental buckling of circular cylindrical roof shell models with free edges subjected to external pressure

Non-linear snap-through behavior of a thin concrete shell roof characterized by free edges, or free edge members supported by several columns, is considerably influenced by the boundary conditions and the edge disturbances developed in the prebuckling state. This paper presents a method of realizing all four natural boundary conditions along a free edge of a roof shell model subjected to external pressure. The experimental method is shown to be useful for investigating non-linear behaviour of circular cylindrical roof shell models with free generator edge beams. The method has a wide applicability to a variety of roof shell models with free edge members lying on a horizontal plane.