Zhaohui Huang

Brunel University London · Department of Civil and Environmental Engineering

This paper investigated the effect of the vertical deflection of the edge beam on the post-fire residual behaviour of the beam-slab specimens, including three fire-damaged specimens and two reference specimens. The mechanical properties of these specimens were investigated, including the load–deflection curves, concrete and reinforcement strains, c...

In this study, four RC specimens representing as many two-bay slab-beam assemblies were tested under two fire scenarios (extended fire and travelling fire) to investigate the interaction between the rectangular slab and the supporting beam positioned along the short median of the slab (interior beam). The primary focus was on the effects that the f...

This paper proposed one new method to determine the residual ultimate loads of the fire-damaged beam-slab specimens. Based on the conventional yield line method, the stiffness and deflection of the edge beam was considered to establish the theoretical method, and the residual ultimate loads of several beam-slab specimens in the literature were anal...

This paper presents a newly developed method for determining the influence of tensile membrane action on the ultimate loading capacity of a two-way RC concrete slab. In this method, more realistic membrane action and two failure criteria of a slab panel are established. The developed method has been validated against the test results and good agree...

This study investigated the effect of travelling fire scenarios, span–thickness ratios, and recurring ages on the post-fire residual behaviour of small-scale continuous reinforced concrete slabs. The mechanical performance of five fire-damaged continuous slabs and one reference slab were investigated, including load–deflection curves, concrete and...

This paper presents the experimental results of six small-scale continuous reinforced concrete slabs with three compartments subjected to various compartment fire scenarios. The study investigates the influence of several key factors, including concrete age, thickness (span-thickness ratio), applied loads, and fire scenarios, on the fire behaviour...

This paper presents a numerical investigation of the fire performance of eight reinforced concrete two-way slabs subjected to different in-plane restraints. A comparison of the experimental results with results predicted by a numerical model showed generally satisfactory agreement. The effects of geometric nonlinearity, or linearity, and concrete t...

An experimental investigation of the performance of reinforced concrete continuous slabs is presented in this paper, following the exposure of the slabs to different compartment fires. The influence that several factors, including compartment fire scenarios, reinforcement ratio, and bar arrangement, have on the deflections, strains, crack patterns,...

This paper presents an experimental study on the post-fire residual behavior of continuous reinforced concrete (RC) slabs. The mechanical performance of five post-fire continuous RC slabs is investigated, including load-deflection curves, concrete and reinforcement strains, cracking patterns, and failure modes. The results indicate that the residua...

This paper experimentally investigates the effect of number and position of heated compartments on the fire behaviour of continuous reinforced concrete slabs. A total of five continuous three-span slabs are tested under single compartment fire, two-compartment fires and three-compartment fires. The measurements involve furnace temperatures, slabs’...

This paper presents the experimental results of four continuous reinforced concrete slabs with three compartments under different compartment fire scenarios. The research focuses on the quantitative relationships of the compartment fire temperatures, the temperature distribution along the thickness of the slabs, the vertical and horizontal deflecti...

This paper presents a comprehensive experimental study to investigate the bond behaviour between early age concrete and steel bar subjected to cyclic loading after fire. In this research, three temperatures of 150 °C, 350 °C, 550 °C and four curing ages of 3, 7, 14, 28 days were used. The effect of cooling methods on the bond behaviour has been eva...

In the current context of displacement-based design, the yield displacement is a key parameter for predicting the target displacement and ductility displacement demand of the bridge system for direct-displacement based design approach. The main objective of this paper is to develop a new model to calculate the yield displacement of reinforced concr...

This paper firstly presents the experimental results of two simply supported full-scale reinforced-concrete (RC) slabs (unheated and fire-damaged). Thereafter, an analytical model for predicting the load–deflection curves of post-fire RC slabs is described in detail. The model can predict ultimate loads and displacements in both post-fire RC slabs...

This paper presents the results of four fire tests on full‐scale cast‐in‐situ, hollow core concrete slabs, constructed using filler boxes and an assembly box system. Experimental data include the furnace temperature, temperature distribution in the slab, and vertical and horizontal deflections during the heating and cooling phases, as well as obser...

A numerical procedure for the thermal analysis of RC slabs at elevated temperatures is the subject of this study, where the moisture increase due to the so-called moisture clog occurring in the cooler parts of reinforced concrete (RC) slabs is introduced as well. Starting from a systematic investigation on the existing concrete constitutive laws av...

This paper presents the results of eight seismic performance tests on end-perforated reinforced concrete beams strengthened with carbon-fibre-reinforced polymer sheets. The beams had different sizes of perforations and strengthening arrangements and were subjected to hybrid load-displacement control loading conditions. The ultimate load resistance,...

Due to the fast developments of large-space multi-functional architectures, large-span steel structures have been widely used in recent years. Therefore, the fire-resistance design of this kind of structures has attracted more attentions. Since traditional ISO834 standard fire curve is not suitable for large space structures, performance-based fire...

In this paper a comprehensive experimental investigation on the residual bond strength between the early aged fly ash concrete and steel ribbed bar after exposed to high temperature has been presented. The research focused on the influences of different temperatures, curing ages, cooling methods and standing times of the specimens after high temper...

This paper implements hydrophobic modified clay layers with ammonia salts (Organoclay) using ultra-sonication and water as a solvent to develop functional clay/Poly vinyl alcohol (PVA) aerogel composites through an environmentally friendly freeze drying process. Various compositions have been designed aiming at the high effectiveness of reducing mo...

In this paper a comprehensive experimental investigation on the residual compressive strength of cement-based grouting materials after exposed to high temperature is presented. The research focused on the influences of different temperatures, curing ages before and after heating and water mixing ratios on the residual compressive strength of the ma...

In this paper four large scale fire tests on the reinforced concrete slabs, under combined uni-axial in-plane and out-of-plane loading conditions with vertical restraint at four corners of the slabs, are presented. The research focuses on the quantitative relationship between horizontal restrained force and deformations, cracking patterns and spall...

In this paper a robust model has been developed to predict the average bond stress-slip relationship between the strands and concrete of prestressed concrete structural members. Two bond-slip curves have been proposed to represent the bond-slip characteristics for the three-wire and seven-wire strands. This model considers the variation of concrete...

In this paper, two half-scaled test tower models for a typical 110 kV single-circuit power transmission tower were designed and fabricated. The scaled test tower models were tested under the horizontal support’s stretching (tensile) and compressive movements with the normal working loading conditions. The deformations of the tested tower models and...

This paper presents a robust finite-element procedure for simulating the localised fracture of reinforced concrete members. In this new model, the concrete member is modelled as an assembly of plain concrete, reinforcing steel bar and bond-link elements. The four-node quadrilateral elements are used for two-dimensional modelling of plain concrete e...

This paper presents the results of an extensive experimental investigation of the thermal and mechanical properties of Q345 steel pipe at elevated temperatures using both the steady-state and transient-state test methods. Under these two test conditions, the thermal expansion coefficient, yield strength and elastic modulus of the specimens at diffe...

This paper presents a robust hybrid finite element procedure for predicting the large individual cracks within reinforced concrete floor slabs at elevated temperatures. For modelling the cracks formations and propagations within the floor slabs, the smeared crack model is used for modelling early stages of crack evolution, and then the ‘delayed ext...

In this paper, the performances of a generic three dimensional 45m x 45m composite floor subjected to ISO834 Fire and Natural Fire are investigated. The influences of reinforcing steel mesh and vertical support conditions on the tensile membrane action of floor slabs are investigated in details. Two robust 2-node connection element models developed...

This paper presents a robust model for predicting the bond-slip between the concrete and steel reinforced bar at elevated temperatures. The model is established based on a partly cracked thick-wall cylinder theory and the smeared cracking approach is adopted to consider the softening behaviour of concrete in tension. The model is able to consider a...

According to full-scale fire tests, it is noticed that tensile membrane action within the concrete floor slabs plays an important role in affecting the fire resistance of composite buildings. It is well known that the development of tensile membrane actions relies on the vertical support along the edges of the slab panel. However, there is at prese...

A robust finite element procedure for modelling the localised fracture of reinforced concrete beams at elevated temperatures is developed. In this model a reinforced concrete beam is represented as an assembly of 4-node quadrilateral plain concrete, 3-node main reinforcing steel bar, and 2-node bond-link elements. The concrete element is subdivided...

A numerical procedure has been developed to model the sequences of failure which can occur within steel beam-to-column connections under fire conditions. In this procedure two recent developments, a static–dynamic solution process and a general component-based connection element, have been combined within the software Vulcan in order to track the s...

This paper presents a simplified robust 2-noded connection element for modelling the behaviour of partial end-plate connections under fire conditions. In this new model the partial end-plate connection is modelled as a 2-noded nonlinear spring element. The characteristics of the spring – such as stiffness, tension, compression, shear strengths and...

A static/dynamic version of the software Vulcan has recently been developed, in which the numerical singularity of a static analysis, induced by a local instability of a structure, for instance the buckling of a column, can be covered by switching to the explicit dynamic procedure. This version of Vulcan allows the post-buckling behaviour of a memb...

In this paper a robust 2-noded connection element has been developed for modelling the bolted end-plate connection between steel beam and column at elevated temperatures. The numerical procedure described is based on the model proposed by Huang (2011), incorporating additional developments to more precisely determinate the tension, compression and...

In this paper a robust 2-noded connection element has been developed for modelling the bolted end-plate connection between steel beam and column at elevated temperatures. The numerical procedure described is based on the model proposed by Huang, incorporating additional developments to more precisely determinate the tension, compression and bending...

This paper presents a robust numerical model for dealing with temporary instabilities which occur in the numerical analysis of steel structures under fire conditions. The model adopts the combined static-dynamic solution procedure to model 'snap-through' behaviour of industrial steel portal frame in fire. This new method allows solution procedure a...

Progressive collapse mechanisms of braced two-dimensional steel-framed structures, subjected to fire heating, are investigated using a robust static–dynamic procedure developed by the authors. 20 cases have been analysed to provide a comprehensive view of the mechanisms of progressive collapse for these frames, with different bracing systems under...

In this paper a robust static-dynamic procedure has been developed. The development extends the capability of the Vulcan software to model the dynamic and static behaviour of steel buildings during both local and global progressive collapse of the structures under fire conditions. The explicit integration method was adopted in the dynamic procedure...

In this paper a robust 2-noded connection element has been presented for modelling the bolted end-plate connections between steel beam and column at elevated temperatures. The connection element allows the element nodes to be placed at the reference plane with offset and the non-uniform temperature distributions within the connection. In this model...

The eight-node 3D solid element is one of the most extensively used elements in computational mechanics. This is due to its simple shape and easy of discretization. However, due to the parasitic shear locking, it should not be used to simulate the behaviour of structural members in bending dominant conditions. Previous researches have indicated tha...

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...

In this paper a robust 2-noded connection element has been developed for modelling the bolted end-plate connection between a steel beam and column at elevated temperatures. The connection element allows the element nodes to be placed at the reference plane with offset and the non-uniform temperature distributions within the connection. In this mode...

A non-linear procedure is presented for modelling the bond characteristic between concrete and reinforcing steel for reinforced concrete structures in a fire. The accuracy and reliability of the model are demonstrated by the analysis of one pull-out test and one beam test at ambient temperature and four full-scale beams tested under two fire condit...

In this paper a robust model is presented based on the previous layer procedure developed by the author to also take into account the effects of concrete spalling on the behaviour of concrete slabs under fire conditions. In this study, a detailed analysis of a uniformly loaded reinforced concrete slab subject to different degrees of concrete spalli...

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...

In this paper a robust finite-element procedure is presented for three-dimensional modelling of reinforced concrete structures under fire conditions. In this non-linear procedure a reinforced concrete building is modelled as an assembly of finite plain beam-column and slab elements, reinforcing steel bar elements and bond-link elements. Both materi...

In this paper a recently developed static/dynamic procedure, which extends the capability of the Vulcan software to progressive collapse analysis, is described. This can also be utilized to allow a basically static analysis to continue beyond temporary instabilities, due for example to major concrete cracking or to failure of an individual bolt in...

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...

For single-storey steel portal frames in fire, especially when they are situated close to a site perimeter, it is imperative that the boundary walls stay close to vertical, so that fires which occur are not allowed to spread to adjacent properties. A current UK fire design guide requires either that the whole frame be protected as a single element,...

It is evident from a series of tests on simply supported reinforced concrete slabs that the failure of the slabs at large deflections is due to the formation of individual large cracks. This failure mode was also observed in the Cardington full-scale fire tests. Previous research indicates that the global behaviour of concrete slabs subject to larg...

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...

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.

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...

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...

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...

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...

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...

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...

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...

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...

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...

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 nonlinear finite element procedure for predicting the structural behavior of planar-reinforced concrete members subjected to fire is described. The proposed procedure is based on an iterative, secant stiffness formulation. The complex features of structural behavior in fire conditions, such as thermal expansion, shrinkage, creep, cracking, or cru...

A non-linear finite element procedure is proposed to predict the temperature distribution history of cross-sections of structural members, such as beams composed of reinforced concrete, in fire conditions. In this model the effect of moisture in concrete has been taken into account, and the thermal properties of concrete have been considered as tem...

Pre-compressed concrete has been observed to acquire a large amount of irreversible strain (called Transient Thermal Strain or Load-Induced Thermal Strain) when it is heated. This effect appears not to occur when heating precedes the application of compressive stress. The objective of the research reported in this paper is to assess how this phenom...

A large generic composite flooring system with a footprint of 36m x 36m has been designed. A series of analyses has been performed, based on different patterns of fire protection to the downstand steel beams. It is evident that the presence or absence of tensile membrane action in the concrete slabs is a major influence on the ultimate integrity of...

Large-scale fire tests in the UK appear to confirm that, in real buildings, unprotected composite beams have a significantly greater fire resistance than when furnace-tested as isolated members. This is due to interactions between the heated structure within the fire compartment and adjacent cool structure. The computer program Vulcan has been deve...

This research is aimed at analysing the performance in fire of Bi-Steel panels used predominantly as compressive structures, such as building cores. In this paper, thermal behaviour of the Bi-Steel panel is analyzed, and a series of parametric studies are carried out. A further object of this research is to develop a non-linear procedure for modell...

In this study a large generic composite flooring system with a footprint of 36m x 36m has been designed. The frame is 4 bays wide and 4 bays deep, each bay having dimensions 9m x 9m. A series of analyses has been performed, based on different patterns of fire protection to the downstand steel beams. The influence of the steel reinforcement on the s...

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...

Thesis (Ph. D.)--University of Central Lancashire, 1995.