MUD-CONCRETE SLAB SYSTEM FOR SUSTAINABLE CONSTRUCTION

The urgency of global climate emergency has drawn significant attention to the building industry over the last few years. Today, the building sector is responsible for 38% of the world’s greenhouse gas emissions, according to UNEP. 60% -70% of embodied carbon in a conventional column-beam reinforced concrete building is in its floor system. This paper discusses the possibility of constructing an earthen slab system using mud-concrete. It investigates a doubly curved shell structure, working predominantly in compression, to fulfil both environmental and economical demands in the construction industry; reducing the cost and labour expenses nearly 50% compared with that of traditional reinforced concrete slab systems. A 1 m x 1 m prototype mud-concrete slab was constructed to check the potential for modular construction with a square footprint. Poured mud-concrete shell of 50 mm thickness is the primary structural component, while a non-structural mud-concrete filling to a horizontal level 50 mm from apex was used to create a usable floor surface. Masonry mould method was used as the formwork system for the construction considering its cost effectiveness and ease of construction.

Inverted Umbrella-type Hyperbolic Paraboloid Reinforced Concrete Shell Structures (Inverted Umbrella HP RC Shells)

The inverted umbrella HP RC shells became a predominant type of single column structure during the 1950s and 1960s. The paper provides a historical overview of architecturally most attractive inverted umbrella HP structures made out of reinforced concrete. It starts in the second quarter of the 20th century with the world’s oldest umbrella structures, designed by three pioneers: F. Aimond, A. Williams and K. Hruban. The most notable master in designing was F. Candela, as he constructed a number of this structures in Mexico between 1953-68. During the 1960s this form became widely used all over the Western world but suddenly disappear after 1975. The results of the paper are presented in three figures where the inverted umbrella HP RC shells are analysed according to several criteria (number of built elements, roof dimensions with shapes, use of the structures in relationship to year of completion). The similarities and differences between elements of the analysed buildings are compared and discussed. In the conclusion, the advantages and disadvantages are briefly exposed.

Prefabrication of a Thin Concrete Shell: The Case of St Kevin's Church in Dee Why, Australia

Location of Project: Dee Why, NSW, Australia<br/> Structural Type: Prefabricated thin concrete shell <br/> Project Scale: Length 30 m, width 15.5 m, height 12 m <br/> Owner/Client: Warringah Catholic Parish <br/> Architect: Gibbons & Gibbons Architects <br/> Structural Engineer: Concrete Industries Australia (Monier) Engineers Pty. Ltd.<br/> Construction: Concrete Industries Australia (Monier) Pty. Ltd. <br/> Construction year: 1961<br/>

PHOTOGRAMMETRY, HBIM, AND DAMAGE ANALYSIS OF COSMIC RAYS PAVILION FOR RAISING AWARENESS TO ITS CULTURAL HERITAGE

This paper presents a comparative approach between a digital documentation workflow using contemporary tools versus a traditional documentation technique for Felix Candela's hyperbolic paraboloid (hypar) modern heritage building: Cosmic Rays Pavilion. This documentation was undertaken to better understand the building’s structure, its evolution, and to assess the performance of this concrete structure for future seismic and damage analysis. Furthermore, the paper discusses the challenges related to producing a Heritage Building Information Model (HBIM) of this building using point cloud data in Autodesk’s Revit BIM-authoring software. This project states the importance of a parallel study between the traditional and the contemporary documentation methods; which led to discoveries about the current state of the extrados in the hypar after several earthquakes. Upon analyzing the HBIM and comparing it to the historical drawings, a gap was discovered between the moisture barrier membrane and the concrete shell. Visualizing the building in 3D provides a deeper and more accurate understanding of the current state of this pavilion and is one of many advantages of using digital technologies. The insights provided by digital documentation techniques and analyzing the historical images of the pavilion showed that the curvature of the pavilion has been modified over time. The results imply two hypotheses. First, the curvature profile has been altered due to earthquakes. Second, the modification is due to improper maintenance of the pavilion, namely, multiple additions of the membrane layers. This could not have been detected by solely relying on traditional documentation techniques.

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.

Experimental study on seismic performance of partially precast steel fiber high-strength concrete columns with high-strength steel bars

To study the cyclic behavior of partially precast steel fiber high-strength concrete columns with high-strength steel bars, four full-sized square column specimens were fabricated and tested under constant axial load and horizontal cyclic load. The effects of the strength of precast concrete shell and the diameter of cast-in-place column core were analyzed in detail. The results show that partially precast steel fiber high-strength concrete columns have good seismic performance and deformation ability. Compared to the concrete column with lower strength of precast concrete shell, the concrete column with higher strength of precast concrete shell showed higher bearing capacity and energy dissipation capacity while lower ductility. Moreover, with the increase of the diameter of cast-in-place column core, the bearing capacity and the deformation ability of the specimen decreased. Finally, based on the experimental research and theoretical analysis, a calculation model for predicting the maximum bearing capacity was proposed, and the results obtained from the formulas were in good agreement with those from the experiments.

Loss of stability of thin-walled structures

The stability of a flat reinforced concrete shell is considered. A variational method is used to solve a nonlinear problem. The values of the upper and lower critical loads are given depending on the design features and dimensions of the coating shell.

Parametric Analysis of the Dome of the Sports Palace of Mexico City

The Sports Palace of Mexico City was built in 1968 and became a turning point in the design and construction of laminar shells, leading the transition from reinforced concrete to metallic grid structures. Felix Candela observed that the use of concrete in designing laminar structures was limited to achieve great spans for sport spaces; he thus changed his first proposal for using a concrete laminar shell to a metallic structure. However, in the first architectural conception of the metallic structure, a lighter cable structure was proposed respecting the built geometry, with the intent of using high-strength wires in the upper and lower chords of the arches. In this paper, three different proposals are modeled. The first uses a 3D modelled concrete shell for understanding the geometry. The others use the final geometry and are analyzed using advanced NURBS (Non-uniform rational Bspline) modeling techniques with Rhinoceros and a parametric design with Grasshopper, where the parameters and results obtained in previous tests are compared with the results obtained in the simulations. Paneling plugins, forces simulation add-ons, finite elements analysis and environmental design simulation tools in Grasshopper are used to compare the results under normal design conditions.

Feasibility study of the construction of foundations with a convex upward curved shape of the contact surface

In the article the comparison of the two technologies of foundations: the traditional technology of cast-in-situ solid slab Foundation and the alternative technology foundations with the upward-convex curved shape of the contact surface. The foundation with an upward curved contact surface is a geometrically complex structure consisting of monolithic belts (support contours), united by flat cylindrical shells convex upwards with respect to the ground, made along the curved surface of the soil mass with an undisturbed natural structure. Due to the joint work of monolithic belts and a reinforced concrete shell located in the span of the foundation, made along the curved contact surface of the ground mass, this foundation structure is an alternative to a solid slab foundation. When the support contours are drained under load, the reinforcement of the shell is tensioned, the soil under the shell is compressed and thus the soil is involved in the work, which allows increasing the strength characteristics of the foundation and reducing the overall draft of the building. The author of the article describes the structural and technological features of this type of foundation. Due to the complex geometric shape of the foundation under study, the total labor costs and the duration of the work increase in the construction practice. As part of the study, two types of foundations were compared according to technological and economic indicators, using the example with the specified geometric parameters. As a result of the obtained data, an increase in labor costs for performing manual molding of the soil mass and the device of a monolithic convex up shell of the foundation in comparison with the traditional technology of the device of a solid slab foundation was revealed. But at the same time, a reduction in direct costs by 30 % was revealed in the construction of a band-shell foundation, due to a reduction in the consumption of steel and concrete, which determines the effectiveness of this type of foundation and expands its scope in the construction of buildings and structures.

Design and verification of reinforced concrete shell elements

abstract: Reinforced concrete shell elements are relevant in several civil and industrial structures. It is important to know the methods for designing and verifying such elements. In this context, the present paper aims at describing the iterative three-layer method proposed by Colombo et al. This method is based on the Model Code/1990, and it can be applied in the design of shell elements. An additional method for verifying reinforced concrete shell elements is also proposed and discussed. This one is based on the multilayer method proposed by Kollegger et al. Formulations as well as numerical examples are presented for both methods. The design proposed by Colombo et al. is verified by using the methodology based on the multilayer method. Although both methods lead to the equilibrium between applied and resistance loads using approximately the same amount of reinforcement, especially for small neutral axes in relation to the element thickness, one may conclude that the three-layer design method has limitations due to not considering strain compatibility along the thickness of the element and due to the impossibility to calculate the compression reinforcement. Although the multilayer method overcomes such limitations, it is a verification method, and more studies about its use in the design of reinforced concrete shell elements are necessary.