Roger Plank

The University of Sheffield | Sheffield · Department of Civil and Structural Engineering

Experimental evidence demonstrates the complexity of beam-to-column connections at elevated temperatures and its performance has been identified in association with instability of steel members or steel-framed structures. This paper presents a research work on the inelastic behavior of a sub-framed structure at high temperatures, adopting a compone...

Traditional beam connections to the minor axis of a column have relatively low strength and stiffness. A modified detail, using a plate welded between the toes of the column flange - referred to as a toe plate connection - is examined in this paper. The results of an experimental investigation for both flush and extended end-plate connections conne...

A number of simplified design methods have been developed to predict composite slab capacities in fire. Most of these extend ambient-temperature large-deflection slab behavior to the elevated-temperature phase by reducing the strengths of fire-exposed concrete and reinforcement while neglecting the effects of thermal expansion and thermal bowing of...

A previous paper covered the principles of practical modelling of common steel beam-to-column connections in frameworks at elevated temperatures, using a component-based approach to represent the main structural actions generally grouped at bolt rows. This is needed for the structural modelling which is a necessary part of performance-based structu...

Public-domain software currently allows designers to incorporate the enhancement of fire resistance due to tensile membrane action of composite slabs into their analysis of building behaviour in fire. Based on the Bailey–BRE Method, it enhances slab capacity by optimising reinforcement size in order to carry its fire limit state loading at the requ...

In this paper an approach is developed for practical modelling of the in-plane behaviour of connections between steel structural elements in global 3-dimensional frame analysis when structures are subject to heating by accidental fires. Because of the interactions between high deflections, thermal expansion and material weakening at high temperatur...

This paper presents a study of the mechanics of inelastic buckling using a Shanley-like simplified column model. The model is an extension of the original Shanley model with multiple springs and two dampers. The inclusion of damping enables the dynamic response of the model under constant loading to be captured. The model has been evaluated against...

Roger Plank, President of The Institution of Structural Engineers suggests that there are opportunities for structural engineers to take a leading role in exciting new areas. There are growing opportunities for structural engineers to provide expertise beyond their traditional core activities. These include two areas of special interest, namely fir...

This paper reports on a set of test results on flush end plate connections at ambient and elevated temperatures. The experiments aimed to investigate the behavior of connections at the ends of unprotected beams in fire situations, when they may be subjected to significant tying forces and large rotations at elevated temperatures, as a consequence o...

Universities of Sheffield and Manchester carried out research on structural steel I-section beam/column connections for fire safety, based on a program of research on robustness of different types of steel beam/column connections. The research project included two series of structural tests, one on isolated connections at elevated temperatures and...

A simplified analytical model for composite cellular floor beam, based on currently available design methods, has been completed. This has been used in an initial study of loaded composite cellular floor beams at normal and elevated temperatures. The approach predicts the capacity and failure type of a composite member by applying design criteria f...

The growing popularity of the use of Cellular steel beams in composite floors comes at the same time as an increasing attention to the fire safety engineering design. The recommendation for their design in fire limit states remains very primitive and this is due to the lack of general research in this area. In fire, the temperature distribution acr...

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 ana...

Conducting experimental tests is an attractive and straightforward 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 anal...

A three-dimensional (3D) eight-noded brick element, which is capable of representing the performance of composite structures subjected to 3D stress conditions at ambient and high temperatures, has been developed and incorporated into a finite-element analysis program Vulcan. In the formulation of this element, geometric nonlinearity, material nonli...

A finite element investigation into the behaviour, including local instabilities, of cellular composite members subjected to elevated temperatures has been conducted, considering material and geometrical non-linearities. Close correlation has been observed between the finite element results and data from a full scale fire test. The study has been e...

This paper summarises the findings of a recently-completed large series of experiments to investigate the resistance of simple connections to combinations of shear, bending and tension forces at temperatures up to 650°C. A total of 64 isothermal tests was conducted on double-angle web cleat, fin plate, partial depth endplate and flush endplate conn...

In this paper a robust nonlinear finite-element procedure is developed for three-dimensional modeling of reinforced concrete beam-column structures in fire conditions. Because of the changes in material properties and the large deflections experienced in fire, both geometric and material nonlinearities are taken into account in this formulation. Th...

A new dynamic model and a quasi-static solution procedure has been developed and incorporated into the finite element software Vulcan [1-3]. This new numerical model is tested in this paper on benchmark problems which relate to the behaviour of steel portal frames under fire conditions. The capabilities and the accuracy of this numerical model have...

Connection designs at ambient temperature generally consider only the initial stiffness and the plastic resistance, whereas ductility and failure modes are more important for connections in fire, as large deformations are generally experienced. This paper describes the development of a T-stub model to capture the behaviour of endplate connections a...

Accidental fires and full-scale structural tests have indicated that steel connections can be subjected to large deformations and fracture in fire. This is not currently considered in fire engineering design approaches because the connections are assumed to heat up more slowly than the structural frame members and therefore retain a greater proport...

The tying capacity of connections between beams and columns is very important in maintaining structural integrity when beam deflections are high due to accidental loads such as fire, but has not so far been thoroughly studied. The project which is the subject of this paper has investigated the robustness of common types of steel connection when sub...

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 behavio...

The companion paper has reported the results from a test programme in which web cleat connections were subjected to various combinations of shear, tying and moment actions at elevated temperatures. These tests showed that web cleat connections have very good tying resistance and rotational capacity, mainly due to the large deformation of which the...

The behaviour of composite cellular floor beams is becoming important as such members are increasingly used in multistorey buildings. In the event of fire, this issue becomes increasingly critical, particularly for exposed steelwork. In a fire situation, a composite beam has a much higher perimeter area exposed to fire in its lower web-flange secti...

This article outlines the importance of immediate action to ensure sustainable development and explains why construction has such a major role to play. The broader issues are introduced but the focus is on those actions which the construction industry can take to make the biggest improvements, namely reducing energy use associated with both the bui...

Fire resistance of steel framed structures has traditionally been ensured by attaching insulating materials around the steelwork. These include concrete, masonry, and plaster but lightweight specialist systems are now largely used including sprays, boards, blankets, and intumescent coatings. These can be expensive and evidence from real fires sugge...

The increasing use of performance-based approaches in structural fire engineering design of multi-storey composite buildings has prompted the development of various tools to help quantify the influence of tensile membrane action in composite slabs at elevated temperatures. One simplified method which has emerged is the Bailey-BRE membrane action me...

Behaviour of steel connections in fire is a multi-dimensional problem involving parameters such as temperature, tying forces and large deformations. Investigation of this behaviour will remain one of the main subjects for fire engineering research in the coming years. Finite element simulation plays an important role in the study of connections bec...

A numerical investigation of the structural behaviour of long-span composite truss systems, typically used in multi-storey floor construction, under fire conditions is presented. The non-linear finite element program, Vulcan, which has been specifically developed at the University of Sheffield for the analysis of structures at elevated temperatures...

In this study an orthotropic slab finite element is developed to model orthotropic slabs in fire, using a layered 9-noded isoparametric slab element and a 3-noded beam element. The element is assembled from a solid slab element which represents the continuous upper portion of the profile, and a special beam element which represents the ribbed lower...

It has been observed from a series of tests on simply supported reinforced concrete slabs that the main failure mode of the slabs at large deflections is due to the formation of large discrete tension cracks. This localised failure was also previously observed in the Cardington full-scale fire tests. Smeared cracking models can be used successfully...

This paper describes the development of a component-based element for endplate connections in fire. The reported research is part of an ongoing project aimed at understanding joint behaviour in fire. The paper summarises the derivation of the stiffness matrix of this new element, based on a spring model, and the incorporation of the element into th...

Recent structural collapses caused by fire have focused attention on research concerning fire safety in building design. Steel connections are an important component of any structural steel building, as they provide links between the principal structural members. The evaluation of the performance of steel connections at elevated temperatures has be...

On September 11th 2001, the twin towers of the World Trade Center in New York City were struck by two hijacked airplanes. Despite severe local damage induced by the impact, the towers were able to sustain 102 and 56 minutes of the subsequent multi-storey fires before collapsing. The purpose of this study is to contribute to the understanding of the...

This paper presents a numerical investigation of the thermal and structural results from a compartment fire test, conducted in January 2003 on the full-scale multi-storey composite building constructed at Cardington, United Kingdom, in 1994 for an original series of six tests during 1995–1996. The fire compartment's overall dimensions were 11 m×7 m...

Fire hazards and full-scale structural tests have indicated that steel connections could be subjected to large deformations and fracture in fire. This is not currently considered in design approaches because the connections are assumed to heat up more slowly than the structural frame members, and therefore retain more relative strength. A project a...

Despite the importance of steel joints in fire, little work has been undertaken on their failure. This paper describes the development of a simplified model for an end plate connection, with particular emphasis on the effects of axial load on the column web. Because of the large number of variables, a component based approach is the only practicabl...

In this paper the failure mechanisms in fire of single-storey haunched portal frames, subject to different support conditions at their column bases, are investigated using a simplified dynamic solution procedure which has been developed. These studies are used to evaluate a current design method.

Tensile membrane action can have a major influence on the performance of composite floor structures, and a number of design tools have been developed to take account of this. These represent a major advance on previous design methods and generally compare well with available test data. However, uncertainties remain about suitable failure criteria a...

In this paper a numerical analysis procedure which employs a sub-structuring technique together with selective node re-numbering, is described as a way of efficiently modelling the response of buildings to fires which are restricted to internal compartments. In this procedure user-defined cool regions of the building model are sub-structured and co...

In the past two decades, a significant amount of research has been conducted into the performance of composite steel-framed structures in fire. However, the same level of development has not taken place for other forms of construction. In terms of reinforced concrete construction, design is still based on simplistic methods which have been develope...

When an orthotropic composite slab cast on steel decking is subjected to fire attack, there is a decreasing temperature gradient from the bottom surface to the top surface. In addition, the temperature within the continuous upper portion of the slab varies in the horizontal sense due to the presence of the ribs. This makes it different from a flat...

This paper presents the results from a series of numerical studies conducted on unrestrained reinforced slabs, of relatively high span/depth ratio, at large displacements. Previous experimental work involved a series of tests carried out on thin model-scale slabs at ambient and elevated temperatures. The purpose of the studies reported here was to...

This paper describes the comparison of a series of high-temperature experiments on column webs under transverse compression at different axial load ratios and temperatures with a simplified design approach. The study forms a part of an ongoing project aimed at developing high-temperature models for the behaviour of the main components of steel end-...

In this paper an appropriate procedure, which employs a sub-structuring technique together with selective node re-numbering, for the numerical modelling of building response to fires which are restricted to compartments within the building, is described. In this procedure user-defined cool regions of the building model are sub-structured and conden...

Full-scale fire tests in the multi-storey steel framed building at Cardington have shown that the composite floor system, even with unprotected steel downstand beams, does not collapse, even at very large deformations. This enhanced resistance is attributed to tensile membrane forces which assist in maintaining the structural integrity through diap...

This paper describes a spring-stiffness model developed to predict the behaviour of flexible end-plate bare-steel joints at elevated temperature. The joint components are considered as springs with predefined mechanical properties (i.e. stiffness and strength). They are also assumed to follow a trilinear force–displacement relationship. The elevate...

This paper outlines the principal issues of sustainable construction as it relates to conditions in the UK, reviews some of the progress which has been achieved, and suggests ways in which this can be further improved.

Although connections are known to have a very significant effect on the behaviour of steel and composite framed buildings in the event of fire, the cost of high temperature tests on the broad range of connections used in practice means that their influence is not well detailed in current design codes. The paucity of data also limits the effective u...

This study involves the development of a computer program to analyze the local buckling stresses for theflange and the web of I-beams under compression at elevated temperatures, and the optimization algorithm to analyze the optimum ratios which does not occur their local buckling prior to yield failure. The high-temperature stress-strain relationsh...

This paper presents the results from 15 small-scale tests conducted on horizontally unrestrained slabs which were subjected to large vertical displacements. All the tested slabs showed a load-carrying capacity far greater than the design capacity using the well-established yield-line theory. The purpose of these tests was to investigate the influen...

At ambient temperature, researchers [Comput. Struct. 2 (1972) 253; AISC Engng J. (1984) 161; J. Construct. Steel Res. 45 (1998) 1] have focused on producing simplified models in order to predict the ultimate capacity of a column web subjected to transverse compressive forces and thereby assist engineers to design steel joints efficiently. Another r...

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-to-column 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 w...

Large-scale fire tests in the multi-storey steel framed building at Cardington have shown large reserves of fire resistance in unprotected composite floor systems. These tests showed that the floor system does not collapse, even at very large deformations. The enhanced resistance is attributed to membrane forces which assist in maintaining the stru...

A non-linear finite element, developed for three-dimensional modelling of beam-column elements of general cross-sections in fire conditions, is described. The procedure is based on general formulations proposed by Bathe, with further development to make it suitable for the analysis of steel, reinforced concrete and composite framed structures under...

This paper describes a simple procedure developed to predict the moment–rotation response of connections at elevated temperatures. It is based on the actual degradation of connection rotational stiffness and strength based on results obtained from the experimental tests. These tests were conducted on a range of connection sizes and types. The rate...

On the basis of test evidence a new design method has been developed recently by one of the authors, for calculating the performance of composite flooring systems subject to fire. The method models simply the influence of tensile membrane action in the composite floor slabs. The objective of this paper is to show some detailed comparisons between t...

This paper reports on experimental furnace testing and development of simple analytical models intended to initiate the development of a Component Method for modelling of steel beam-to-column connections in fire conditions. The basic theme of the Component Method is to consider any joint as an assembly of individual simple components. Each of these...

A series of analyses, accounting for the effects of tensile membrane action in the concrete slabs, has been performed on a large generic composite floor under fire conditions, using different patterns of fire protection for the steel beams. These demonstrate that it may often be possible to leave a significant proportion of the beams unprotected. T...

A computer program VULCAN has been progressively developed for some years at the University of Sheffield, with the objective of enabling three-dimensional modelling of the behaviour of composite buildings in fire. In this paper the theoretical basis of the non-linear layered procedure used to model the reinforced concrete floor slabs, which include...

A nonlinear layered finite element procedure for predicting the structural response of reinforced concrete slabs subjected to fire is described. The proposed procedure is based on Mindlin/Reissner (thick plate) theory, and both geometric and material nonlinearities are taken into account. The complications of structural behavior in fire conditions,...

A companion paper has documented a geometrically nonlinear layered procedure for modeling of the membrane actions in concrete slabs subject to very high deflections and in fire. The model is based on a layered procedure developed previously by the writers in which only material nonlinearities were taken into account. In this paper two solid reinfor...

A generalised beam-column element is presented for three-dimensional composite structures at ambient and high temperatures. The element can model reinforced concrete and steel sections of different shapes. The element has been implemented in the software VULCAN, and has then been validated by comparing with existing theoretical and experimental res...

Roger Plank, Chairman of the IStructE's sustainable construction panel, explains its aims and achievements. The aim is to enable members to become familiar with the issues and share their experience. Sustainable construction encompasses a wide range of environmental issues such as minimising energy, resources, waste and pollution.

The objective of this paper is to summarise the results of numerical modelling of six full-scale fire tests carried out in 1995-1996 on the composite frame constructed at the BRE laboratory at Cardington, representing cases in which different degrees of in-plane restraint to heated steel members were provided by the adjacent structure. The computer...

This paper describes a general approach for modelling the three-dimensional behaviour of asymmetric steel beam-columns under fire conditions using two-noded one-dimensional beam elements. It is based on a development of the program VULCAN which has been shown to compare well with test data for symmetric beams and columns. A method for refining the...

Steel is seriously affected by fire, losing strength and stiffness leading to large deformations and often collapse. Using applied fire protection remains the most common way of satisfying structural fire resistance requirements, despite its cost. Parametric studies are conducted to investigate the effect of connection characteristics on beam respo...

A computer code VULCAN was developed for the structural analysis of steel framed and composite buildings in fire. Emphasis was given to the layered procedure for the modeling of concrete floor slabs. A number of studies were performed to show the influence of floor slab details on the structural behaviour in fire conditions. These studies provided...

A computer program VULCAN has been progressively developed for some years at the University of Sheffield, with the objective of enabling three-dimensional modelling of the behaviour of composite buildings in fire. In this paper the theoretical basis of the non-linear layered procedure used to model the reinforced concrete floor slabs, which include...

In this paper a modified layered slab element is developed based on the layered procedure previously developed for the modelling of composite slabs in fire. In the development reported here, the ribs forming the lower part of any slab cast onto metal decking are included in the slab modelling. The basic idea is to use the nominal thickness of the c...

This paper outlines the behaviour of steel and composite structures in fire, and reviews recent research developments in this field, and describes the practical implications for designers. The initial focus is on isolated beams, columns and slabs. The effect of structural continuity afforded by skeletal frame construction is considered, and the imp...

A three-dimensional, nonlinear finite-element procedure for modeling composite and steel-framed building behavior in fire is presented. In this approach, composite steel-framed buildings are modeled as an assembly of finite beam-column, spring, and slab elements. The beam-columns are represented by two-noded line elements. The cross section of the...

This paper summarises current developments in the behaviour of bare-steel and composite connections at elevated temperature. This includes both experimental and analytical work. The paper also reviews the progress occurred in the numerical modelling of connections at elevated temperature. The paper highlights the influence of the structural continu...

A computer program VULCAN has been progressively developed for some years at the University of Sheffield, with the objective of enabling three-dimensional modelling of the behaviour of composite buildings in fire. In this paper the current theoretical basis of the program is very briefly outlined. Three of the fire tests carried out in 1995-96 on t...

In structural behaviour observed from real large-scale fire tests it has been seen that adjacent cool structure can be an important influence on the structural behaviour within the fire compartment, and should be investigated in more detail. In this paper a large generic composite steel framed building is designed, and a series of analyses are carr...

A three-dimensional non-linear procedure is presented for modelling partial shear connection in composite steel-framed buildings in fire. The model has been incorporated within the computer program VULCAN which has been developed to model such structures. The accuracy and reliability of the model are demonstrated by analyses of four previously test...

A series of analytical studies are presented on the behaviour of an unprotected `rugby post' frame exposed to fire. The main purpose is to assess the effects of interactive structural behaviour on predicting the critical temperature for individual members. The influence of certain key parameters is considered, including the axial load applied to th...

Because of the high cost of fire testing it is becoming increasingly important to have analytical methods that can predict the behaviour of structures when subjected to fire conditions. In recent years a computer program, VULCAN, has been developed at the University of Sheffield for the three-dimensional structural analysis of composite and steel-f...

A nonlinear layered finite element procedure for predicting the structural response of reinforced concrete slabs subjected to fire is described. The proposed procedure is based on the Mindlin/Reissner (thick plate) theory and an iterative, tangent stiffness formulation is employed. The complex features of structural behavior in fire conditions, suc...

A series of alternative designs of steel-frame floor construction subject to fire are used to demonstrate the significant benefits that can be generated from a close working relationship between the designer and the researcher. The structural fire design strategy, the modeling and detailed analysis that support the chosen designs for a recent prest...

A finite element code has been developed to simulate the structural response of steel and composite framed buildings subjected to fire. A series of numerical simulations was carried out on the fire tests on the full-scale, eight-storey composite frame at the BRE laboratory at Cardington in 1995 and 1996. The floor slab within the three-dimensional...

The degradation of steel and composite connection characteristics at elevated temperatures is investigated. Five series of tests are carried out in a portable connection furnace at the Building Research Establishment. The test series includes two full end-plate and one flexible end-plate bare steel connections, and two flexible end-plate composite...

The transformation of ESDEP, a conventionally produced set of teaching material for structural steelwork design to engineering students, into a multi-media system accessible by a much wider range of users is presented. The project has developed a means of translating the existing material efficiently into a computer-based system. This has involved...

Buildings consume energy in a number of ways, the energy implicit in the production of the building materials and the construction process, incidental energy such as that used by occupants or users travelling to and from the building, and operational energy associated with lighting, heating, cooling and ventilation. There are ways in which designer...

Although steel beams are often designed as simply supported, practical connection details generally afford significant rotational stiffness. When exposed to fire, this can have the effect of improving the survival of the beam. The analytical approach described provides a means of studying this. Indicative studies using this method are included to i...

The paper presents the derivation of a two-dimensional non-linear inelastic finite element model for the structural analysis of steel-concrete composite beams with flexible shear connection. The effects of slip between the steel beam and concrete slab and the non-linear nature of the force-slip characteristics of the shear connectors are included....

This paper summarizes the results from the first phase of a collaborative project to investigate the moment-rotation behaviour of commonly used connections at elevated temperatures. The results from a single test at ambient temperature and five tests at elevated temperature of a bare steel flush endplate beam-to-column connection are presented and...