Reinforced Concrete Shells Research Articles

Capturing Out-of-Plane Shear Failures in the Analysis of Reinforced Concrete Shells

AbstractA procedure for nonlinear analysis of RC slabs and shell structures is presented. Cracked RC is treated as an orthotropic material governed by a smeared rotating crack procedure and the constitutive formulations of the disturbed stress field model. The analysis procedure is implemented within the framework of a finite-element program employing layered thick-shell elements that consider out-of-plane (through-thickness) shear deformations. A simple modification method employing an effective shear strain concept is introduced to improve the out-of-plane performance of the layered shell element for RC applications. The adequacy of the procedure is verified using test data of RC members controlled by out-of-plane shear failure mechanisms and elements under combined in-plane and out-of-plane loading scenarios. The nonlinear finite-element program is shown to be suitable for elements exhibiting ductile or brittle responses, and the shear modification method introduced is found to be capable of capturing ...

Flexural behaviour of reinforced concrete jacketed columns under reversed cyclic loading

The objective of the present study is the development of an analytical model for predicting the response under reversed cyclic loading of structural members with ‘old-type’ detailing, strengthened with reinforced concrete (RC) jacketing. The analytical model introduces one additional degree of freedom between the existing member (core of the retrofitted member) and its outer RC shell, thus allowing slip to take place at the interface between the existing member and the jacket. Shear resistance mechanisms, such as aggregate interlock, friction, and dowel action, are mobilized to resist slip. Existing constitutive models are further improved to describe the mechanisms that resist sliding under cyclic shear reversals and implemented for the first time in an analytical model for deriving the response of RC jacketed members. A calculation algorithm is developed to estimate the flexural response under cyclic loading taking into account slip at the interfaces. The sensitivity of the proposed analytical model to the shear transfer mechanisms degradation rules, as well as to the crack spacing estimation, was evaluated. The validity of the proposed analytical model is assessed against experimental results.

Numerical modeling of reinforced concrete structures: static and dynamic analysis

A numerical model using the Finite Element Method (FEM) for the nonlinear static and dynamic analysis of reinforced concrete (RC) beams, plates and shells is presented in this work. For this purpose, computer programs based on plasticity theory and with crack monitoring capabilities are developed. The static analysis of RC shells up to failure load is carried out using 9-node degenerated shell finite elements while 20-node brick finite elements are used for dynamic applications. The elasto-plastic constitutive law for concrete is coupled with a strain-rate sensitive model in order to take into account high loading rate effect when transient loading is intended. The implicit Newmark scheme with predictor and corrector phases is used for time integration of the nonlinear system of equations. In both cases, the steel reinforcement is considered to be smeared and represented by membrane finite elements. Various benchmark examples are solved with the present numerical model and comparisons with other published data are performed. For all examples, the path failure, collapse loads and failure mechanism is reproduced with great accuracy.

Repairing and Strengthening of Elliptical Paraboloid Reinforced Concrete Shells with Openings

Abstract This investigation is carried out to evaluate the repair and strengthening the techniques of elliptical paraboloid reinforced concrete shells with openings. An experimental program of several different techniques in repair and strengthening is executed. The materials, which are considered for strengthening, are; Glass fiber reinforced polymers GFRP at different position of the shell bottom surface, steel strip and external tie. They loaded by four concentrated loads affected on the corners of the opening. The initial and failure loads as well as the crack propagation for the tested shells at different loading stages, deflections and failure load for repaired and shells are recorded. A non-linear computer program based on finite element techniques is used to study the behavior of these types of shells. Geometric and materials nonlinearities are considered in the analysis. The efficiency and accuracy of computer program are verified by comparing the program results with those obtained experimentally for the control shell with opening and strengthened shells.

Influence of wind on seepage of gases through the shell of smoke stacks

The effect of wind on the distribution of static pressure at the outer surface of thermal power station smoke stacks is considered. It is shown that the wind velocity and direction are the main factors influencing on the seepage of gases through the shell of smoke stacks when no excess static pressure is exerted from the side of flue gases. A procedure for determining the wind influence zone on the seepage processes in smoke stacks is proposed. This procedure supplements the previously adopted approach for estimating the operating modes of smoke stacks taking the influence of wind into account. The proposed procedure is used for determining if seepage of flue gases is possible and for finding the wind influence lower boundary for different operating conditions. The described procedure can be used in designing new smoke stacks and in repairing and retrofitting existing ones, and also in developing new techniques for revealing through flaws in smoke stack shells during their examination by means of an infrared imager. As an example, the results from infrared flaw detection of a smoke stack are presented, which testify that a change occur in the direction of seepage processes taking place in a reinforced-concrete shell when a change occurs in the wind effect pattern.

A Practical Method for Calculation of the Membrane Efforts of Elliptic Reinforced Concrete Shells

The paper analyses the problem of elliptic reinforced concrete shells calculation, while only taking into account membrane efforts. Normal and shear forces of such shells are usually determined using stress function. This paper discusses the estimation of the coefficients of the chosen stress function.

Collapse analysis of real RC spatial structures using known failure schemes of ferro-cement shell models

Large-span reinforced concrete (RC) shells collapses that occurred in the last decade caused many death toll as well as significant losses to national economies. The most famous cases were the collapse of the aqua park cover in Moscow on February 2004 and the 2E terminal roof destruction at Charles de Gaulle Airport near Paris on May 2004. Following the publications of the appropriate commissions that have studied the reasons of these events, the influence of concrete creep and changes in the shell geometry on buckling of RC thin-walled shells was not properly considered in the design. This study is focused on buckling of such shells, taking into account geometrical and physical nonlinear behaviour of compressed concrete. Other important reasons of concrete shells collapse are also analysed. The study is based on available experimental and theoretical investigations of ferro-cement shells' models previously performed by the first author. The results of these investigations, obtained for small-scale ferro-cement models of thin-walled shallow RC shells, are discussed. Behaviour of the tested models is compared with that of the above-mentioned real shells and similar structures, which also collapsed. The critical buckling loads for the shells are obtained. It is shown that these loads are lower than the actual ones; thus, the shells buckling was unavoidable. To prevent brittle shell failure, they should be designed using other dominant failure modes that appear before the buckling. Possible failure schemes of real RC shells can be predicted using dominant failure modes obtained by laboratory testing of scaled models. Copyright © 2012 John Wiley & Sons, Ltd.

Nonlinear analysis of RC shell structures using multilevel modelling techniques

PurposeThe purpose of this paper is to present integrated methodologies based on multilevel modelling concepts for finite element analysis (FEA) of reinforced concrete (RC) shell structures, with specific reference to account for the nonlinear behaviour of cracked concrete and the other associated features.Design/methodology/approachGeometric representation of the shell is enabled through multiple concrete layers. Composite characteristic of concrete is accounted by assigning different material properties to the layers. Steel reinforcement is smeared into selected concrete layers according to its position in the RC shell. The integrated model concurrently accounts for nonlinear effects due to tensile cracking, bond slip and nonlinear stress‐strain relation of concrete in compression. Smeared crack model having crack rotation capability is used to include the influence of tensile cracking of concrete. Propagation and change in direction of crack along thickness of shell with increase in load and deformation are traced using the layered geometry model. Relative movement between reinforcing steel and adjacent concrete is modelled using a compatible bond‐slip model validated earlier by the authors. Nonlinear iterative solution technique with imposed displacement in incremental form is adopted so that structures with local instabilities or strain softening can also be analysed.FindingsProposed methodologies are validated by evaluating ultimate strength of two RC shell structures. Nonlinear response of McNeice slab is found to compare well with that of experiment available in literature. Then, a RC cooling tower is analysed for factored wind loads to study its behaviour near ultimate load. Numerical validation demonstrates efficacy and usefullness of the proposed methodologies for nonlinear FEA of RC shell structures.Originality/valueThe present paper integrates critical methodologies used for behaviour modelling of concrete and reinforcement with the physical interaction among them. The study is unique by considering interaction of tensile cracking and bond‐slip which are the main contributors to nonlinearity in the nonlinear response of RC shell structures. Further, industrial application of the proposed modelling strategy is demonstrated by analysing a RC cooling tower shell for its nonlinear response. It is observed that the proposed methodologies in the integrated manner are unique and provide stability in nonlinear analysis of RC shell structures.

Numerical Evaluation of the Effects of Edge Beams Attached to the Cylindrical R/C Shell Structures

In Reinforced concrete (R/C) shell structures, the free edges of them are not usually continuous depending on the design and the supporting purposes. To strengthen these edges, edge beams are placed on such cutting edges. To obtain the sufficient strength of such shell structures, an appropriate size of edge beams must be applieed. In this paper, the numerical analysis of the R/C cylindrical shell with edge beams by using the nonlinear finite element method. In numerical analysis, the degenerate shell elements with layered approach are adopted. Both shells and beams are modeled by these elements. To represents the nonlinear behavior of R/C shell elements, combineed material and geometric nonlinearities are taken into account. From the numerical analyses, the stiffness of the edge beams plays an important role to show the deformation characteristics annd the ultimate strength of R/C shell structures. Considering the effects of edge beams on these phenomena, the minimum size of the edge beam to represent the maximum ultimate strength of cylindrical R/C shell is represented under several conditions.

Analysis of Reinforced Concrete Shells with Transverse Shear Forces

This research investigates the simultaneous effect of in-plane and transverse loads in reinforced concrete shells. The infinitesimal shell element is divided into layers (with triaxial behavior) that are analyzed according to the smeared rotating crack approach. The set of internal forces includes the derivatives of the in-plane components. The corresponding generalized strains are determined using an extension of the equivalent section method valid for shells. The formulation yields through-the-thickness distributions of stresses and strains and the spatial orientation of the concrete struts. Although some simplifications are necessary to establish a practical first-order approximation, higher-order solutions could be developed. Despite the fact that constitutive matrices are not symmetric because of the tension-softening formulation, the equilibrium and compatibility conditions are satisfied, the stiffness derivatives are explicitly calculated, and the algorithms show good convergence. The formulation p...

Shield-assisted thermal and moisture protection of the reinforced-concrete shell of the cooling tower at OAO Mosenergo’s TETs-23 cogeneration station

Shield-assisted thermal and moisture protection for cooling towers is considered. The results from an analysis of the factors of a negative climatic effect and methods for reducing this effect are presented, as well as data from tests of cooling tower No. 3 at the TETs-23 cogeneration station after it was equipped with a modern thermal and moisture protection shield for its reinforced-concrete shell.

Nonlinear Analysis of Reinforced Concrete Shells using Layered Elements with Drilling Degree of Freedom

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Adaptive FE Analysis of RC Shells. I: Theory

This paper contains the description of an adaptive calculation scheme for nonlinear (elastoplastic) finite element (FE) analysis. The underlying error estimator accounts for the error in the elastic regime as well as for the one arising from plastic loading. It is based on the stress recovery scheme proposed by Zienkiewicz and Zhu in 1992. The adaptation of the FE mesh is performed by means of the h-version of mesh refinement. The advancing front method is employed for remeshing. Before restart of the analysis after mesh refinement, the transfer of variables from the old to the new mesh must be performed. Unlike as for commonly used transfer schemes, the presented mode of transfer employs stresses and displacements for the evaluation of the state variables for the new mesh. All ingredients of the adaptive calculation scheme (i.e., error estimation, mesh generation, and the transfer of variables) are extended for application to the layer concept and to curved surfaces. Both extensions are necessary for adaptive analyses of reinforced concrete (RC) shells (see companion paper).

Analysis of Reinforced Concrete Shells for Transverse Shear and Torsion

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Thermal Analysis of Reinforced-Concrete Shells

A finite-element formulation that can be used for the analysis of reinforced-concrete shells subjected to thermal and mechanical loads is presented. It incorporates the nonlinear material model for concrete, which takes into account cracking of concrete, tension stiffening, softening of concrete in compression, and yielding of reinforcement. The finite elements used are the degenerate, isoparametric shell elements. The resulting finite-element procedure was checked by comparison of the theoretical and experimental results. A parametric study was undertaken, in which several special considerations associated with the thermal analysis of reinforced concrete were addressed and discussed.

Modeling of Collapse Mechanisms of Thin Reinforced Concrete Shells

A numerical model based on an elasto-plastic–fracturing formulation is presented to predict the ultimate strength as well as the related mode of failure of thin reinforced concrete (RC) shells. The model defines a safe domain within which the shell would not collapse under the applied load. It predicts two possible modes of failure, which may be broadly classified into bending-type failure and buckling-type failure. Important issues are considered in the model: the effects of holes, reinforcing members, and concentrated loads; and shape deviations due to construction or modeling imperfections. By comparison with analytical solutions as well as experimental observations, the model is shown to lead to reasonably accurate predictions of the main events leading to the failure of RC shells, including the loading path relating the downward vertical displacement to the applied load. From detailed investigations, the relations between the actual mode of failure and the level of the bending force are explained. To provide a shell with the maximum ultimate strength can be dangerous if an inadequately safe domain results.

Structural Analysis and Rehabilitation of Reinforced Concrete Shells

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Reinforced Concrete Shell Elements Subjected to Bending and Membrane Loads

Reinforced Concrete Shell Elements Subjected to Bending and Membrane Loads

Progress in analysis and design of RC shells

A historical overview of progress in reinforced concrete (RC) thin shells from early to modern times is presented. As this paper is prepared for a special issue of Engineering Structures in honour of Professor Alexander C. Scordelis, his notable contributions to the analysis of reinforced concrete shells and folded plates receive special attention.

Design and Capacity Evaluation of Reinforced Concrete Shell Membranes

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