scholarly journals Efficient construction of concrete shells by Pneumatic Forming of Hardened Concrete: Construction of a concrete shell bridge in Austria by inflation

2019 ◽  
Vol 21 (1) ◽  
pp. 4-14
Author(s):  
Benjamin Kromoser ◽  
Johann Kollegger
Keyword(s):  
Hardened Concrete ◽  
Concrete Construction ◽  
Efficient Construction ◽  
Concrete Shell ◽  
Concrete Shells

scholarly journals Shell-supported footbridges

2020 ◽  
Vol 7 (1) ◽  
pp. 199-214
Author(s):  
Luigi Fenu ◽  
Eleonora Congiu ◽  
Giuseppe Carlo Marano ◽  
Bruno Briseghella
Keyword(s):  
Topology Optimization ◽  
High Efficiency ◽  
Shell Structures ◽  
Form Finding ◽  
Fundamental Research ◽  
Spring System ◽  
Earthquake Action ◽  
Concrete Shell ◽  
Concrete Shells ◽  
Thrust Network Analysis

AbstractArchitects and engineers have been always attracted by concrete shell structures due to their high efficiency and plastic shapes. In this paper the possibility to use concrete shells to support footbridges is explored. Starting from Musmeci’s fundamental research and work in shell bridge design, the use of numerical form-finding methods is analysed. The form-finding of a shell-supported footbridge shaped following Musmeci’s work is first introduced. Coupling Musmeci’s and Nervi’s experiences, an easy construction method using a stay-in-place ferrocement formwork is proposed. Moreover, the advantage of inserting holes in the shell through topology optimization to remove less exploited concrete has been considered. Curved shell-supported footbridges have been also studied, and the possibility of supporting the deck with the shell top edge, that is along a single curve only, has been investigated. The form-finding of curved shell-supported footbridges has been performed using a Particle-Spring System and Thrust Network Analysis. Finally, the form-finding of curved shell-supported footbridges subjected to both vertical and horizontal forces (i.e. earthquake action) has been implemented.

An experimental study of the stresses in a shell of revolution with geometrical imperfections and cracks

1981 ◽  
Vol 16 (1) ◽  
pp. 59-65 ◽  
Author(s):  
L A Godoy ◽  
J G A Croll ◽  
K O Kemp ◽  
J F Jackson
Keyword(s):  
Reinforced Concrete ◽  
Complete Loss ◽  
Geometric Imperfections ◽  
Shell Models ◽  
Wide Range ◽  
Geometrical Imperfections ◽  
Concrete Shell ◽  
Concrete Shells ◽  
Doubly Curved ◽  
Hoop Stresses

Interest in the effects of geometrical imperfections and cracks on the stresses in reinforced concrete shells has been stimulated by the failure of the Ardeer cooling tower. Due to the extreme difficulties of testing doubly curved, reinforced concrete shell models, a programme of experiments on an axially loaded aluminium cylinder containing controlled axisymmetric geometric imperfections has been carried out to show the nature of the stress distributions that occur when meridional cracking passes across the imperfection. Results over a wide range of crack configurations, for which the discrete cracks have both partial and complete loss of stiffness in the circumferential direction, are found to be in close agreement with predictions from an appropriate finite element numerical modelling. It is shown how the concentration of membrane hoop stresses associated with the imperfections are redistributed to cause substantial changes in meridional bending and membrane stresses only when a complete loss of stiffness occurs at the cracks. With the thin reinforced concrete shells used in cooling towers having only limited flexural capacity, the combination of geometric imperfections and cracks could, as a consequence, readily lead to failure once yield or fracture of the hoop reinforcement occurs.

scholarly journals Form Finding of Shell Bridges Using the Pneumatic Forming of Hardened Concrete Construction Principle

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Benjamin Kromoser ◽  
Thomas Pachner ◽  
Chengcheng Tang ◽  
Johann Kollegger ◽  
Helmut Pottmann
Keyword(s):  
Fundamental Problem ◽  
Construction Method ◽  
Hardened Concrete ◽  
Membrane Action ◽  
Form Finding ◽  
Construction Principle ◽  
New Construction ◽  
Spring System ◽  
Concrete Shells ◽  
Curved Panels

Concrete shells are fascinating structures. Even thin shells can span over large areas without requiring any columns. If a form-defining load case exists, the shape of the shell can be designed to ensure that the forces in the structure are transferred primarily by the membrane action, which leads to an even distribution of the stresses across the shell surface. Concrete as a material, characterized by high compressive strength and low tensile strength, can be used with a very high degree of utilization. A fundamental problem with building concrete shells is the high effort required for the production of the complicated formwork. A new construction principle called Pneumatic Forming of Hardened Concrete (PFHC) was invented at TU Wien and requires no traditional formwork or falsework during the construction process. An air cushion is used to lift a flat hardened concrete plate, and at the same time, additional post-tensioning cables are tightened to support the transformation of the flat plate into a double-curved shell. One possible application of PFHC is the construction of shell bridges. Here, the shape of the shell has to be designed according to the acting loads and the boundary conditions of the construction method. This paper describes the partly conflicting factors involved in the form-finding process for practical application and the semiautomated workflow for optimizing the geometry of shell bridges. In the first optimization step, the final bridge shape is determined using a particle-spring system or alternatively a thrust-network approach. In the second optimization step, the shell is completed to form a full dome—this is called the reference geometry and is required for the new construction method. Finally, the reference geometry is discretized into single-curved panels by using a mesh-based optimization framework. To frame the presented work, an overview of different experimental and computer-aided form-finding methods is given.

scholarly journals Pneumatic Formwork Systems in Structural Engineering

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Benjamin Kromoser ◽  
Patrick Huber
Keyword(s):  
Structural Engineering ◽  
Construction Material ◽  
Hardened Concrete ◽  
Hollow Structures ◽  
Curved Structures ◽  
Building Components ◽  
The Many ◽  
The Individual ◽  
Concrete Shells ◽  
Doubly Curved

Concrete as a construction material is characterized by high compressive strength, low tensile strength, and good casting ability. In order to fully utilize the potential of this material, the form of load-carrying structures has to be designed according to the stress distribution in the structure. Partially hollow structures, such as hollow beams, or doubly curved structures, such as shells, have favorable characteristics. In hollow structures, material savings are achieved in the individual building components by locally reducing dimensions. Concrete shells, if designed properly, are able to span over large areas by transferring the loads mainly by membrane stresses. The main problem with these structures, however, is the high effort required for producing the complicated formwork. One possibility of reducing this effort is to use a pneumatic formwork. This paper describes different pneumatic formwork systems invented in the past 100 years and presents the latest developments in this area. The many types of possible applications are divided into three categories in order to obtain a clearer overview. Finally, a new construction method, called “Pneumatic Forming of Hardened Concrete (PFHC),” is presented. This method was invented at the TU Vienna and uses the pneumatic formwork in a novel way.

scholarly journals Concrete shells - towards efficient structures: construction of an ellipsoidal concrete shell in Switzerland

2013 ◽  
Vol 14 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Aurelio Muttoni ◽  
Franco Lurati ◽  
Miguel Fernández Ruiz
Keyword(s):  
Concrete Shell ◽  
Concrete Shells

The Influence of Concrete Class on Vibrations of Thin-Walled Cylindrical Reinforced Concrete Shells

2019 ◽  
Vol 945 ◽  
pp. 299-304 ◽  
Author(s):  
K.Q. Qahorov ◽  
Y.O. Sysoev ◽  
A.Y. Dobryshkin
Keyword(s):  
Reinforced Concrete ◽  
Theoretical Calculation ◽  
Nuclear Power ◽  
Power Plants ◽  
Forced Oscillations ◽  
Emergency Situations ◽  
Thin Walled ◽  
Concrete Shell ◽  
Concrete Shells ◽  
External Loads

The article deals with the theoretical calculation of the cylindrical thin-walled shell of concrete of different classes with different modules of elasticity. Constructions in the form of a cylindrical shell are widely used in the construction of hydraulic facilities, nuclear power plants, stadiums and other large-span structures. During the operation of such facilities, they are affected by wind and snow loads, including the operation of equipment from the action of which there are forced oscillations. The imposition of own fluctuations of thin shells and forced vibration from external loads, which have not been taken into account by the designer or improper work in the course of construction that result in emergency situations. In addition to the theoretical calculation of the cylindrical closed thin-walled reinforced concrete shell, the article considers the results of the study as a practical part where it is shown how the forced oscillation occurs in different concrete classes and how the concrete class affects the Frequency spectrum of forced oscillations.

scholarly journals Formwork with Variable Geometry for Concrete Shells Production Technology

2015 ◽  
Vol 2 ◽  
pp. 63
Author(s):  
Vitalijs Lusis
Keyword(s):  
Thin Shell ◽  
Precast Concrete ◽  
Variable Geometry ◽  
Concrete Technology ◽  
Thin Walls ◽  
Fiber Concrete ◽  
Development Technology ◽  
Concrete Shell ◽  
Concrete Shells ◽  
Shell Production

One of the main constructive materials in the building sphere is a precast concrete and fiber concrete. It is well influenced by scientific research basis, development and implementation of progressive technologies. The fiber concrete it is an ideal material with practically unlimited number of shapes. A nomenclature of concrete articles increases, it is working on different shape formation and processing. While preparation for this document started with the concept fabrication, it is necessary to understand the methods of construction variable geometry formwork of concrete thin-shell surfaces, both past and present as a point of departure. An understanding of this background helps provide an essential foundation for the exploration of new potential advances in the field of thin-shell construction. Obviously that is the reason for fiber concrete to be the most widespread constructive building material all over the world. In the article are considered shell development technology features and is evaluated technical and economical effectiveness of concrete shells with thin walls. Now variable geometry systems from flexible materials are developing and improving, there is a great potential followed by modern events in concrete technology. The results of laboratory experiments have proved that the technology can be used for fibro concrete shell production and construction.

scholarly journals An algorithm for the automatic design of concrete shell reinforcement

2014 ◽  
Vol 7 (1) ◽  
pp. 53-67
Author(s):  
A. B. Colombo ◽  
J. C. Della Bella ◽  
T. N. Bittencourt
Keyword(s):  
Numerical Stability ◽  
Large Scale ◽  
Design Method ◽  
Material Model ◽  
Single Element ◽  
Shell Elements ◽  
Large Scale Structures ◽  
Scale Structures ◽  
Concrete Shell ◽  
Concrete Shells

An algorithm developed for the design of reinforcement in concrete shells is presented in this text. The formulation and theory behind the development is shown, as well as results showing its robustness and capability of application on fairly large-scale structures. The design method is based on the three-layer model for reinforced concrete shell elements. A material model is also proposed in order to improve the numerical stability of the algorithm. Comparisons of single element design show that the modifications made to the material model don't effect significantly the final results while making for better numerical stability.

scholarly journals Cracked reinforced concrete walls of chimneys, silos and cooling towers as result of using formworks

2018 ◽  
Vol 146 ◽  
pp. 02002 ◽  
Author(s):  
Marek Maj ◽  
Andrzej Ubysz
Keyword(s):  
Reinforced Concrete ◽  
Concrete Cover ◽  
Cooling Towers ◽  
Concrete Walls ◽  
Reinforced Concrete Walls ◽  
Steel Bars ◽  
Live Loads ◽  
Moisture Influence ◽  
Concrete Shell ◽  
Concrete Shells

There are presented in this paper some problems connected with reinforced concrete shell objects operation in the aggressive environment and built in method of formworks. Reinforced concrete chimneys, cooling towers, silos and other shells were built for decades. Durability of cracked shells are one of the most important parameters during process of designing, construction and exploitation of shells. Some reasons of appearance of horizontal and vertical cracks as temperature, pressure of stored material, live loads e.g. dynamic character of wind, moisture, influence of construction joints, thermal insulation, chemistry active environmental etc. reduce the carrying capacity of the walls. Formworks, as is occurred recently, are the reason for technological joints with leaking connection, imperfections of flexible formworks slabs and as result can initiate cracks. Cracked surface of this constructions causes decreasing capacity and lower the state of reliability. Horizontal, vertical cracks can caused corrosion of concrete and steel bars, decreasing stiffness of contraction, increasing of deflection and carbonation of concrete cover. Local and global imperfactions of concrete shells are increasing according to greater number of cracks...

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