Buick Davison

Steel designers' manual

Single-storey buildings - Range of building types Loading Design of common structural forms Worked example Multi-storey buildings- Introduction Factors influencing choice of form Anatomy of structure Worked example Industrial steelwork - Range of structures and scale of construction Anatomy of construction Loading Structure in its wider context Bridges - Introduction Selection of span Selection of type Codes of practice Traffic loading Other actions Steel grades Overall stability and articulation Initial design Worked example Other structural applications of steel - Towers and masts Space frames Cable structures Steel in residential construction Atria Applied metallurgy of steel - Introduction Chemical composition Heat treatment Manufacture and effect on properties Engineering properties and mechanical tests Fabrication effects and service performance Summary Fracture and fatigue - Fracture Linear elastic fracture mechanics Elastic-plastic fracture mechanics Materials testing for fracture properties Fracture-safe design Fatigue Sustainability and steel construction - Introduction Environmental impacts Embodied energy Operational energy Summary Bolt and weld groups Other elements - Sheet pile sections Floor plate design tables Construction - Fire information sheets, Section factors Minimum thickness of spray protection Basic data on corrosion Codes and standards

Component modelling of flexible end-plate connections in fire

This paper describes a component-based model for simulating the behaviour of flexible end-plate connections between beams and columns in steel framed structures in fire conditions. In this method, a simple steel connection was split into a number of active components for which mechanical properties are represented by non-linear springs. The behaviour of a steel connection is then determined by assembling the individual behaviour for each active component into a spring model. The component model presented in this paper is capable of predicting the behaviour of steel connections under varied loading conditions. It is also capable of predicting the tying resistance and critical components of failure for steel connections in fire. Compared with experimental test data, a good correlation with the simplified model has been achieved and this method, combined with finite element modelling, may be used to examine the performance of simple steel connections in fire conditions.

A Study of Progressive Collapse in Multi-Storey Steel Frames

Although progressive collapse is not a new topic in the structural field, recent collapses have brought this issue to the fore. Following the partial collapse of the Ronan Point residential tower block in London, the UK building regulations provided recommendations to guard against disproportionate collapse. These UK guidelines aimed to prevent progressive collapse by ensuring adequate tying of a structure (in concrete or steel) so that catenary action could develop, and this approach has often been cited as good practice. It is noteworthy that little research has been conducted into these recommendations, particularly whether they are adequate to protect a damaged structure from progressive collapse. This paper reports an analytical study of the forces generated in steel framed structures during a progressive collapse. The analyses were conducted using LS-DYNA [Hallquist, 1998], a non-linear, explicit finite element code. A hybrid design method that can improve structural performance during progressive collapse is proposed.

A Component Approach to Modelling Steelwork Connections in Fire: Behaviour of Column Webs in Compression

This paper outlines some of the main results in an ongoing project aimed at developing high temperature models for the behaviour of the main components of steel end -plate beam-tocolumn connections in fire. In this particular phase of the work the emphasis is on the compression zone in the column web, when transverse compression acts concurrently with axial compression due to superstructure loading. The ultimate objective is to be able to construct component-based models of end-plate connections within global numerical modelling of steel and composite building structures in fire conditions. This is the only feasible analytical approach to connection modelling under the simultaneous effects of loading, thermal degradation of materials and forces due to restraint to thermal expansion. A simplified semi-empirical model has been validated against ANSYS modelling and isothermal high-temperature experiments.

Multi-Scale Modelling of Flexible End Plate Connections under Fire Conditions

Conducting experimental tests is an attractive and straight-forward research approach but is time-consuming and expensive in comparison with finite element modelling. A numerical approach has been developed in this project to investigate the performance of simple steel connections in fire conditions. This paper presents a quasi-static numerical analysis with cohesive elements to investigate the resistance and ductility (rotation capacity) of simple steel connections (flexible end plates) in fire conditions. In comparison with experimental test data, a good correlation with the finite ele- ment analysis is achieved and the method is suitable to study the tying resistance and ductility for simple steel connections with various dimensions at different temperatures. This numerical approach was also compared with component-based connection models, which have been developed in the previous research work. The analytical results produced demonstrated that the component-based approach is capable of as an alternative method to analyse the connection performance under fire and non-fire conditions, and this approach is sim- ple but without loss of accuracy.

DEVELOPMENT OF A GENERAL COMPONENT-BASED CONNECTION ELEMENT FOR STRUCTURAL FIRE ENGINEERING ANALYSIS

This paper reports on the development of a general-purpose Eurocode-compliant component-based connection finite element for steel-to-steel joints in fire. The development begins by utilising the temperature-dependent connection component characteristics previously developed at the University of Sheffield to create a component-based connection finite element to model flush endplate connections. Subsequently the element was extended to a new connection type with high ductility, the reverse channel. The component models have been developed for the reverse channel under tension and compression. The element has been incorporated into the nonlinear global structural analysis program Vulcan, in which it has been used along with a static-dynamic formulation. The use of the element is illustrated by modelling a fire test at the University of Manchester in which reverse channel connections were used.

Structural Integrity of Steel Connections Subjected to Rapid Rates of Loading

A series of analyses were conducted on some of the most common steel connections used in the UK such as flexible end plates, web cleats, flush and extended endplates, using LS-DYNA (Hallquist 1998), an explicit finite element analysis code, to assess their ability to resist rapidly applied tensile loads. Characteristics such as strength, energy absorption and response to different strain rates were studied. The effect of material strain rate sensitivity was accounted for using the Cowper and Symonds formulation. This paper reports this work and comments on the applicability of the British Standard recommendations for the avoidance of progressive collapse to situations in which tying forces are applied dynamically.

Tensile Behaviour of Galvanised Grade 8.8 Bolt Assemblies in Fire

In structural fire engineering, the importance of bolt assemblies is often overlooked. Connection design uses the temperature-dependent bolt strength-reduction factors prescribed in Eurocode 3, despite the existence of two distinct failure modes under tension; necking of the bolt shank, and thread-stripping. While literature exists to predict failure modes at ambient temperature, there is no method for failure mode prediction for elevated temperatures where ductility is critical to avoid collapse. Galvanised M20 structural bolt assemblies and bolt material from a single batch have been tested under tension at a range of temperatures and strain-rates typical of those experienced in fire. Turned-down bolt test data produced stress-strain curves characteristic of different microstructures at ambient temperature, despite a tempered-martensitic microstructure being specified in the standards. The failure modes of bolt assemblies were found to be dependent on the as-received microstructure at ambient temperature. At elevated temperatures, however, only thread-stripping was observed.

Minimizing the Environmental Impact of Steel Structures

Within the construction industry there is an increasing awareness of the importance of sustainable design. When considering the structure, the main focus will often be on minimising the carbon embodied within it. This paper discusses a strategy, design for deconstruction, aimed at minimising the embodied carbon of steel structures. This design tactic facilitates steel elements being reused after their first life. Following a PAS2050 methodology, the environmental impact of the element is spread out between the numbers of potential lives. This not only reduces embodied carbon but also lessens the exploitation of natural resources. The potential energy and carbon savings that can be accrued are estimated and the web-based tool, Sakura, used for these calculations is presented. This work culminates with an overview of projects that are already pioneering this approach in steel.

A structural fire engineering prediction for the Veselí fire tests, 2011

Fire hazards and full-scale structural tests have provided evidence that the beam-column connections of building frames are the weakest structural elements, which are vulnerable to fracture in fire. Connection fractures may lead to extensive damage or even progressive collapse. However, current design methods for connections are solely based on ambient-temperature behaviour, the additional forces and rotations generated in fire are not taken into account. The Structural Fire Engineering Research Group of the University of Sheffield is involved in a European-collaborative project which concerns the behaviour and robustness in fire of practical connections to composite columns. This includes two natural fire tests in a full-scale composite structure in Veseli, the Czech Republic. The Sheffield team was responsible for predicting the structural behaviour in the tests before they were conducted. This assessment was conducted using the specialist structural fire engineering FEA program Vulcan. This paper reports the results of this predictive analysis.