Paul Shepherd

The effect of axial restraint on the fire resistance of steel columns

The paper represents the outcomes of a joint research between the University of Ulster and the University of Sheffield into the performance of axially restrained steel columns during fire. The Ulster experimental program incorporates 37 high temperature tests that investigate three parameters: slenderness ratio (λ=49,75,98), degree of axial restraint (αk=0, 0.1,0.2,0.3) and loading ratio (αL=0,0.2,0.4,0.6). A unique test rig which allows the application of both axial restraint and loads, either separately or at the same time has been especially designed for the experimental program. Typical results from the fire tests are presented, which illustrates characteristic response of the columns to the imposition of axial restraint, coupled with the temperature increase. In addition, trend graphs charting generic response are discussed. An associated computational study by Sheffield provides satisfactory accurate computer simulations of fire tests, using standard materiel property input data. The computer modelling exercises has been extended to parametric studies, to include the effects of many more levels of axial restrain. The linked experimental and computational study has thus validated a computational model, which can be used to provide the basis design guidance of the behaviour of restrained columns in fire situations.

Thinking Topologically at Early Stage Parametric Design

Parametric modelling tools have allowed architects and engineers to explore complex geometries with relative ease at the early stage of the design process. Building designs are commonly created by authoring an abstract graph representation that generates building geometry in model space. Once the graph is constructed, design exploration can occur by adjusting metric sliders either manually or automatically using optimization algorithms in combination with multi-objective performance criteria. In addition, subjective aspects such as visual and social concerns may be included in the search process. The authors propose that whilst this way of working has many benefits if the building type is already known, the inflexibility of the graph representation and its top-down method of generation are not well suited to the conceptual design stage where the search space is large and constraints and objectives are often poorly defined. In response, this paper suggests possible ways of liberating parametric modelling tools by allowing changes in the graph topology to occur as well as the metric parameters during a building design and optimisation.

Aviva Stadium: a parametric success

The Aviva Stadium, Dublin, is the first stadium to be designed from start to finish using commercially available parametric modelling software. A single model in Bentleys Generative Components was shared between architects and engineers, which allowed the optimised design of form, structure and façade. The parametric software was extended where necessary to integrate with structural analysis and to automate fabrication. By reducing the overhead associated with design iterations, this approach allowed detailed exploration of options and early identification and resolution of potential problems. In this paper, the authors add to the body of scientific knowledge by describing in detail the methods which led to the construction of the Aviva Stadium. This paper is written in light of the completed building and provides information on the generation and control of the envelope geometry, development and analysis of structure and documentation for construction. Whilst these components have been discussed independently previously [1–4], here these aspects are drawn together for the first time and are presented alongside thoughts on the manufacturing and construction processes from the project architect.

Aviva Stadium: A Case Study in Integrated Parametric Design

The nature of large complex buildings requires specialized skills across a multi-disciplinary team and high levels of collaboration and communication. By taking a parametric approach to design and construction, high quality results can be delivered on budget on time. This type of approach facilitates the opportunity for design teams to work in an iterative manner. A parametric model reduces the time associated with complex design changes while providing a centralized method for coordinating communication. In this paper the recently completed Aviva Stadium is used to illustrate the ways in which these benefits manifest themselves on built work. The authors identify the moments in the design and construction process that truly justify the effort in implementing a parametric approach. By approaching design in this way a “design conversation” can take place between parties involved, resulting in a better building.

Performance Based Interactive Analysis

This paper re-approaches structural engineering through an interactive perspective by introducing a series of tools that combine parametric design with structural analysis, thus achieving a synergy between the architectural shape and its structural performance. Furthermore, this paper demonstrates how the design can be realised into an efficient structural form by applying novel techniques of form-finding through the exploitation of the generated analytical output. The combination of these tools and their parametric control contributes to a new design approach that outrides the generation of single solutions and enables a deeper exploration of the design parameters leading to multiple performance- based outcomes. This paper describes the integration between a Parametric Design software, McNeal’s Grasshopper 3D and a Finite Element Analysis software, Autodesk’s Robot Structural Analysis. The generated synergy between form and structure is demonstrated through a series of case studies through which the interactive control of the parameters the enables the designer to iterate between a range of form-found solutions.

Fabric formed concrete: physical modelling for assessment of digital form finding methods

© 2016, A.A. Balkema Publishers. All rights reserved. Fabric formwork is a novel concrete construction method which replaces conventional prismatic moulds with lightweight, high strength sheets of fabric. The geometry of fabric formed structures is therefore dictated by the behaviour of fabric under hydrostatic loading. While there are numerous examples of digital and physical modelling of this problem, there have only been limited efforts to link the two through measurement. In this investigation, a number of small scale fabric formed beams were manufactured using both ‘free hanging’ and ‘keel mould’ methods, and the resulting forms were accurately measured with a digital 3D scanner. Computational form finding tools were also developed, enabling a comparison to be made between the predicted and build geometries. This allowed assessment of both the accuracy of the construction methods and the limitations of the form finding techniques used. The data collected provides a useful assessment of existing form finding techniques and will be used as a reference data set as these are developed further.

Applying dynamic relaxation techniques to form-find and manufacture curve-crease folded panels

The research incorporated in the paper stems from the design and fabrication of a self-supporting, multi-panel installation for the Venice Biennale 2012 and operates against the backdrop of the exciting potentials that the field of curved-crease folding offers in the development of curved surfaces that can be manufactured from sheet material. The two main challenges were developing an intuitive design strategy and production of information adhering to manufacturing constraints. The essential contribution of the paper is a proposed interactive form-finding method for curve-crease geometries that could negotiate the multiple objectives of ease of use in exploratory design, and manufacturing constraints of their architectural-scale assemblies.

Research data supporting 'An analytical failure envelope for the design of textile reinforced concrete shells'

Numerical data from specimen tests. This includes load, extension and strain data captured from data logging equipment.

Prototyping and load testing of thin-shell concrete floors

Buildings are being constructed at ever faster rates, fuelled by population growth and urbanisation. The total worldwide floor area of buildings is expected to almost double over the next 40 years, the equivalent of constructing Paris every five days. The majority of the mass and embodied energy (60% to 70%) in a typical multi-storey building structure exists within the floors, making these a primary target for sustainable structural design. In a typical reinforced concrete slab, much of the concrete is assumed to be cracked and therefore not structurally utilised, but nevertheless adds significant weight. This project proposes a radical re-design of concrete floors, using precast textile-reinforced concrete shells with an in-situ foamed concrete fill. By harnessing membrane action, self-weight savings of 62% have been demonstrated for typical spans (compared to traditional flat slabs). This paper discusses the design, optimisation, construction, measurement, analysis and structural testing of two prototype shells, one with and one without foamed concrete fill. The construction accuracy was quantified using digital scanner measurements which were then used as a geometry input for the analysis model. Each shell was loaded both uniformly and asymmetrically to beyond the design loading before failure. The foamed concrete was found to provide only a small increase in strength and stiffness. A design methodology for full-scale, practical application is currently under development.

Developing an innovative lightweight concrete flooring system for sustainable buildings

This project brings together modern developments in computational design, materials and construction methods to propose a novel thin-shell concrete flooring system for multi-storey buildings, aiming to create a low embodied energy and lightweight alternative to traditional reinforced concrete flat slabs.