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AbstractThis article reviews research on cold-formed steel structures published in 2013 and 2014 in three leading journals: the Journal ofStructural Engineering, ASCE, Thin-Walled Structures and the Journal of Constructional Steel Research. It also reviews papers published in thethree main conferences in the area over the same period. These are Eurosteel 2014 (Naples, Italy), the 7th International Conferenceon Thin-Walled Structures (Busan, Korea) and the 22nd International Specialty Conference on Cold-Formed Steel Structures (StLouis, MO, USA). Three research areas which have recently been incorporated in the North American Specification NAS S100:2012or are being incorporated in the Australian/New Zealand Standard AS/NZS 4600 have been highlighted. These are the works on thesemi-analytical finite strip method for sections in shear by the author and his colleagues at the University of Sydney, net section rup-ture by Associate Professor Lip Teh at the University of Wollongong and fire design by Professor Mahendran at QueenslandUniversity of Technology.
Keywordscold-formed connections, cold-formed steel, cold-formed structures, research review
Introduction
Cold-formed steel (CFS) structures are structures com-posed of structural sections formed by folding at ambi-ent temperature without any heat treatment. They arenormally thin-walled but sections up to 25-mm thickare now being cold-formed from plate and strip. Theusual manufacturing process is by roll forming wherecoil steel passes through a series of rollers which pro-gressively form the desired shape. Traditionally, simplechannels (Cs), zeds (Zs), hat sections and decking havebeen used mainly in roof and wall systems, steel stor-age racks, steel-framed houses (residential) and manyother similar secondary applications. However, thesections are now being used more commonly in pri-mary structures such as portal frames and floor sys-tems. Furthermore, as the sections become thinner inhigher strength steel, more complex shapes are beingcreated with the inclusion of more complex stiffenersboth in the flat elements and at the section lips.
Research into CFS structures has increased consid-erably in recent years. In 2003, the author of this arti-cle published a similar review in the Journal ofConstructional Steel Research (Hancock, 2003) whichcontained 60 publications. This review cites over 200papers over a similar 2-year period 2013–2014 indicat-ing a more than threefold increase in research in thearea. Since the publication of the 2003 paper, there
have been significant developments in CFS designspecifications and standards. The 2007 and 2012 edi-tions of the North American Specification NAS:S100and the 2005 edition of the Australian/New ZealandStandard AS/NZS 4600 included the direct strengthmethod (DSM) of design in addition to the effectivewidth method (EWM). In the same period, EuropeanCommittee for Standardisation published Eurocode 3Part 1.3 for cold-formed members and sheeting. It issubstantially based on the EWM. A recent textexplaining this code with examples has been preparedby Dubina et al. (2013b). The Chinese Technical Codeof Cold-Formed Thin-Walled Steel Structures GB50018 was published in 2002 based on the EWM.
Since 2003, there has been a considerable shift inthe areas of research. Some areas such as section buck-ling including generalised beam theory (GBT), thefinite strip method (FSM) and the constrained finitestrip method (cFSM), the DSM of design, shear walls,fire design, and seismic design have increased
School of Civil Engineering, The University of Sydney, Sydney, NSW,
Australia
Corresponding author:
GJ Hancock, School of Civil Engineering, The University of Sydney,
considerably. On the other hand, areas such as corru-gated and curved panels, torsion and distortion(excluding distortional buckling) and enhancedmechanical properties have seen a reduction inresearch. A review of cold-formed stainless steel hasnot been included in this review.
Section buckling and design includingGBT, FSM and DSM
With the advent of the DSM of design based on thebuckling signature curve concept, there has been a sub-stantial increase in research into the different methodsof buckling analysis of thin-walled sections. The twoprincipal methods used are the GBT and the FSM.The finite element method (FEM) can be used, but it isless useful in isolating the separate local, distortionaland overall (flexural/torsional) modes at this time andthe interaction between them. In preparing this review,it has become difficult to separate buckling analysesfrom design. However, papers where investigation ofthe elastic buckling modes are the primary aim of thepaper are classified as buckling, whereas papers wherethe theory or test results are used in design such as theDSM have been classified as design.
Elastic buckling including interaction
The major work in elastic buckling has concentratedon GBT mainly from Professor Camotim and his col-leagues at the Universidade de Lisbon (TUL), thecFSM both from Professor Schafer and his colleagues
at Johns Hopkins University and Professor Adany andhis colleagues at Budapest University of Technologyand Economics and the FSM for shear buckling at theUniversity of Sydney (Pham and Hancock). Otherresearchers in the area are also cited.
Papers published using GBT (Basaglia et al., 2013,2014b; Bebiano et al., 2014; De Miranda et al., 2013;Taig et al., 2014) cover the areas of continuous purlins,distortional postbuckling, inclusion of extension andshear modes and the new GBTUL-2.0 software. Paperspublished using the cFSM (Adany, 2013, 2014; Adanyand Schafer, 2014a, 2014b, 2014c; Li et al., 2014e)include generalisation to arbitrary cross-sections andextension to the FEM. Alternative methods (Becqueand Li, 2014; Karakonstantis and Becque, 2014) formodal decomposition have recently been developedbased on polarisation. Further work on including per-forations in the FSM has been performed by Smithand Moen (2014).
Recent developments in the FSM include shear andlocalised loading (Hancock and Pham, 2013, 2014a,2014b; Pham and Hancock, 2013b). A new develop-ment in these latter papers is the ‘shear signature curve’as shown in Figure 1(b) for sections in pure shear asshown in Figure 1(a).
The curve semi-analytical finite strip method(SAFSM; program bfinst7.cpp) is the buckling stressversus half-wavelength ‘signature curve’ of a lippedchannel in pure shear with unrestrained end sections,and the curve labelled reSAFSM (program bfinst8.cpp)is the elastic buckling curve versus length for a sectionrestrained with simply supported ends so that it is
Figure 1. Lipped channel section in shear: (a) shear flow distribution and (b) shear buckling curves (Hancock and Pham, 2013).
prevented from cross-sectional deformation at its ends.A shear buckling mode at a half-wavelength of200 mm from the SAFSM is shown in Figure 2(a) andat with simply supported ends at a fixed length of200 mm from reSAFSM is shown in Figure 2(b).When the reSAFSM model length is increased to1000 mm, then the buckling mode shown in Figure 3with multiple half-wavelengths results. In this case, theend conditions become less important so that the buck-ling stress is close to the value for the unrestrained sin-gle half-wavelength in Figure 2(a) as can be observedfrom the stresses in Figure 1(b) by comparing thereSAFSM curve at 1000 mm with the SAFSM at200 mm.
Considerable research has been undertaken in thearea of mode interaction between local, distortionaland/or flexural/flexural–torsional or combinations ofthese (Dinis et al., 2014a; Dubina et al., 2013a;
Loughlan and Yidris, 2014; Martins et al., 2014a,2014b; Rizzi et al., 2013; Santos et al., 2014;Ungermann et al., 2014). Based on this research, thereis a need to review some of the design rules in existingstandards and specifications to further account for theinteractions.
DSM and other design methods
The DSM has been further investigated in detail forcompression members, flexural members, combinedbending and compression, members in shear and theinteraction between the modes. The references are forcolumn design (De Miranda et al., 2014; He et al.,2014; He and Zhou, 2014; Landesmann and Camotim,2013; Young et al., 2013), for beam/purlin design(Basaglia and Camotim, 2013; Basaglia et al., 2014a;Gao and Moen, 2014; Keerthan and Mahendran,2014a; Kumar and Kalyanaraman, 2014; Pham andHancock, 2013a), for shear design (Pham et al., 2014a,2014b, 2014d; Pham and Hancock, 2014) and forstructural systems (Camotim and Basaglia, 2014). Asfor buckling, there is a need to review some of thedesign rules in existing standards and specifications tofurther account for interaction. A rig for measuringand classifying global, distortional and local imperfec-tions in cold-formed members is described by Zhaoand Schafer (2014).
Compression members including wallstuds
Considerable work has taken place in the area of com-pression members including angles, sections with per-forations and holes, sections built-up from single
Figure 2. Lipped channel buckling modes in pure shear (200 mm) (Hancock and Pham, 2013): (a) unrestrained buckling mode(SAFSM) and (b) restrained buckling mode (reSAFSM).
Figure 3. Simply supported lipped channel shear bucklingmode at L = 1000 mm (reSAFSM) (Hancock and Pham, 2013).
members, wall stud member with sheathing attachedand eccentric loading (beam–columns). The referencesare for angles (Shifferaw and Schafer, 2014; Silvestreet al., 2013), members with dimples and other indenta-tions, perforations and holes (Ekmekyapar et al., 2014;Kubde and Sangle, 2014; Kulatunga et al., 2014;Kulatunga and Macdonald, 2013, 2014; Macdonaldand Kulatunga, 2014; Nguyen et al., 2014; Xu et al.,2014), Carbon Fiber Reinforced Plastic (CFRP)strengthening (Kalavagunta et al., 2013), for membersbuilt-up from channel sections (Crisan et al., 2014a;Dabaon et al., 2014; Fratamico and Schafer, 2014; Liet al., 2014b; Piyawat et al., 2013; Selvaraj andMadhavan, 2014; Ting and Lau, 2014a, 2014b), forfixed-ended columns (Dinis et al., 2014c; Gunalan andMahendran, 2013b), for sheathed members (Petermanand Schafer, 2014) and for members in combinedbending and compression (Li et al., 2014a; Torabianet al., 2014). Clearly, the most recent research isdirected away from unperforated and single membersto more complex arrangements including perforatedmembers.
Flexural members including purlins,sheeting and decking
Research into flexural members is wide ranging frompurlins with sleeves and different types of sheetingrestraint, novel shapes and sections including corru-gated and stiffened webs, shear including shear withholes, flexure with holes, web crippling, compositefloors including Oriented Strand Board (OSB), andsheeting and decking. The references are for purlinsand beams (Gelji et al., 2014; Georgescu andUngureanu, 2014; Gutierrez et al., 2013; Kujawa andSzymczak, 2014; Loureiro and Calvo, 2014; Moenet al., 2013; Pham et al., 2014c; Seek, 2014; Uzzamanet al., 2014; Ye et al., 2013), novel shapes includingstiffened and corrugated webs (Dubina et al., 2014;Dubina and Ungureanu, 2014; Laım et al., 2013,2014a; qukowicz and Urbanska-Galewska, 2014;Paczos, 2014; Siahaan et al., 2014a, 2014b; Tondiniand Morbioli, 2014; Wang et al., 2014c; Wang andYoung, 2014a, 2014b, 2014c), combined bending andcompression (Cheng et al., 2013), shear including com-bined bending and shear (Acharya et al., 2013;Bruneau et al., 2014; Keerthan et al., 2014a; Keerthanand Mahendran, 2013a, 2013b, 2013c, 2014b, 2014c),web crippling (Gunalan and Mahendran, 2014c;Keerthan et al., 2014b; Keerthan and Mahendran,2014a, 2014d; Natario et al., 2014a, 2014b; Uzzamanet al., 2013), composite floors including OSB board(Chatterjee et al., 2014b; Zhou et al., 2014) and sheet-ing and decking (Adany et al., 2013; Casariego et al.,
2014; Danilov and Tusnina, 2014; Guo et al., 2014;Lawson and Popo-Ola, 2013). The influence of sheet-ing, decking, sandwich panels and OSB board on flex-ural member behaviour including both purlins andfloors is being further investigated in detail to improvereliability and performance.
Connections and fasteners
Research into connections has focussed on five areas.These are bolted connections which include the major-ity of the papers, clinching, screwed connections, fas-tener reliability and moment connections. Thereferences are for bolted connections including sectionrupture and bearing failure (Bolandim et al., 2013;Clements and Teh, 2013; Liu et al., 2014; Teh andGilbert, 2013a, 2013b, 2014a, 2014b; Yu andPanyanouvong, 2013; Yu and Xu, 2013), clinching andpinned connections (Di Ilio, 2014; Lambiase and DiIlio, 2014; Mathieson et al., 2014; Mucha andWitkowski, 2014), screwed connections (Moen et al.,2014; Sivapathasundaram and Mahendran, 2014), fas-tener reliability (Chatterjee et al., 2014a) and momentconnections (Bucmys et al., 2014; Lim et al., 2014;Sabbagh et al., 2013). The design of bolted connectionsin net section rupture has had the most investigationand is being incorporated in the NAS S100 and AS/NZS 4600 standards. However, less research on con-nections seems to be being undertaken than in thepast.
Net section tension rupture is probably the mostfamiliar failure mode of bolted connections to bothengineers and non-engineers. Examples of this failuremode in a flat sheet and in a channel section, both ofwhich are composed of cold-reduced sheet steel, areshown in Figure 4. The net section tension capacity ofsuch a bolted connection may be reduced by the exis-tence of shear lag, relative to bolted connections inmore ductile steel members.
Figure 4. Net section tension rupture in a flat sheet and achannel section.
Attempts to account for the shear lag effect in flatmembers by the major CFS design specificationsworldwide have led to anomalies (Teh and Gilbert,2014a), which persisted despite various amendmentsover the past several decades. For a bolted connectionwhere the bolt spacing is at least twice the bolt dia-meter, all the prevailing code equations predict the netsection tension capacity to increase with decreasing netsection area. This anomaly was recently resolved viathe use of calculus, and a new equation (Teh andGilbert, 2014a) that avoids the known anomalies hasbeen adopted into the 2016 edition of the NorthAmerican Specification for the Design of Cold-FormedSteel Structural Members.
Comparisons between the in-plane shear lag factorsgiven by the prevailing design standards and the newequation for a bolted connection in a flat brace can bemade in Figure 5. The variable d denotes the bolt dia-meter, and W is the bolt spacing in the direction per-pendicular to loading, or, for a single boltedconnection, the connected member width.
Bolandim et al. (2013) found that the net sectiontension rupture provisions in NAS S100:2012 forbolted connections in angle and channel braces led toreliability indices much lower than the target index of3.5. Based on reliability analyses, they calculated therequired resistance factors to be as low as 0.30 for thespecification’s design equations.
Teh and Gilbert (2013b) considered the three fac-tors affecting the net section efficiency of a channelbrace bolted at the web, namely the in-plane shear lag,the out-of-plane shear lag and the interaction betweenthe detrimental moment due to connection eccentricityand the counteracting moment provided by the boltedconnection. They proposed a design equation that hassince been shown to provide reasonable estimates forchannel braces composed of G450 and SSC400 sheetsteels having various aspect ratios and bolting config-urations (Teh and Gilbert, 2014a). This equation willbe adopted into the 2016 edition of the NorthAmerican Specification for the Design of Cold-Formed Steel Structural Members NAS S100.
Comparisons between the net section efficiencies oftypical channel braces bolted at the web given by theunderlying equation in NAS S100:2012 and the newequation to be used in NAS S100:2016 can be seen inTable 1. The results of a regression analysis equationderived by the Center for Cold-Formed SteelStructures (CCFSS) at the University of Missouri arealso shown in the table. The variable Ww is the overallweb depth, Wf is the clear flange width, t is the wallsheet thickness, �x is the connection eccentricity and Lis the connection length.
For angle braces bolted at one leg, Teh and Gilbert(2014b) proposed a design equation which will beadopted into the 2016 edition of the North AmericanSpecification for the Design of Cold-Formed SteelStructural Members NAS S100. It has a similar formto that proposed by Teh and Gilbert (2013b) for chan-nel braces bolted at the web.
Figure 5. Shear lag factors for bolted connections in flatsheets.
Table 1. Net section efficiencies of channel braces bolted at the web.
There has been a significant increase in research intosteel-framed clad walls, both in shear and compres-sion. Investigations of both seismic and dynamic beha-viour have become prominent. The references are forclad shear walls in compression (Vieira and Schafer,2013), blast load (Bondok et al., 2013), static shear(Baldassino et al., 2014; Hernandez-Castillo et al.,2014; Shakibanasab et al., 2014; Tian et al., 2013;Yanagi and Yu, 2014) and seismic/dynamic shear(Baldassino et al., 2014; Balh et al., 2014; Bian et al.,2014; Buonopane et al., 2014; Iuorio et al., 2014a,2014b; Javaheri-Tafti et al., 2014; Lin et al., 2014;Macillo et al., 2014; Shahi et al., 2014; Shamim andRogers, 2013; Shimizu et al., 2013; Vigh et al., 2013;Yu et al., 2014). It is clear that clad and braced shearwalls are useful for resisting seismic shear loads onCFS frames.
Storage racks
The vast majority of storage racks are constructedfrom CFS so that much of the research in the area ofthe stability of steel framing is covered by storageracks. The references are for rack uprights includingbuckling (Bernuzzi and Maxenti, 2014; Casafont et al.,2014; Crisan et al., 2014b; Dinis et al., 2014b; Nedelcuet al., 2014; Ren and Zhao, 2014; Trouncer andRasmussen, 2014), analysis of frames (Gilbert et al.,2014; Rasmussen and Gilbert, 2013) and connections(Wang et al., 2014d; Zhao et al., 2014). Interactionbuckling in the uprights of storage rack frames isclearly an active area of investigation.
Fire design
Fire design research has become more prominent inrecent years especially as more CFS is used in residen-tial construction. Fire design rules in EC3 Part 1.2(EN 1993-1-2, 2005) are considered to be applicable toCFS members within the scope of EC3 Part 1.3 (EN1993-1-3, 2006). However, they were specifically devel-oped for hot-rolled steel structures, and despite somespecial provisions given in Annex E of EC3 Part 1.2for thin-walled sections, past studies have demon-strated the need for specific research on CFS membersexposed to fire conditions in order to develop suitablefire design rules. CFS members are not always sub-jected to a uniform temperature exposure. For exam-ple, CFS wall and floor systems are often protected byfire-resistant gypsum plasterboards (Figure 6), andhence, their lipped channel members (studs and joists)will be subjected to a non-uniform temperature distri-bution when exposed to fire on one side (Figure 7).
The simplified method in EC3 Part 1.2 (EN 1993-1-2, 2005) requires that the design action effects in adesign fire is less than or equal to the correspondingdesign capacity of the steel members at any given timeduring the design fire, that is, subject to a particularnon-uniform or uniform elevated temperature expo-sure. This design approach requires thermal perfor-mance evaluation of members to determine theirtemperature at any given time during the design fire(Figure 7), a good understanding of the behaviour andreduced capacities of CFS steel members (columns andbeams) subject to various buckling modes such aslocal, distortional and flexural and flexural–torsionalat elevated temperatures (Figure 8) as well as thereduced mechanical properties of CFSs at elevatedtemperatures (Figure 9). Fire research on CFS mem-bers has been addressing the above issues so thatimproved fire design rules can be developed. Mostresearch was aimed at using the ambient temperaturedesign rules with appropriately modified elevated tem-perature mechanical properties of CFSs.
During 2013–2014, Gunalan et al. (2013) andGunalan and Mahendran (2013a) extended the fireresearch on CFS members at the QueenslandUniversity of Technology to CFS wall systems usingboth full-scale fire tests and finite element analyses topredict their structural and thermal performances instandard fire conditions and developed suitable fire
Figure 6. CFS wall system.
Figure 7. Non-uniform temperature distribution in wall studs.
design rules within the Australian, North Americanand European CFS design provisions. These designrules can be used to predict the capacity of wall studsin fire and the associated fire resistance ratings of wallsystems. Ariyanayagam and Mahendran (2014)expanded this research to include CFS wall systemsexposed to more realistic fire time–temperature curvesincluding those based on parametric fires given in EC3Part 1.2. Professor Y.C. Wang from the University ofManchester continued his work on CFS wall systemsto develop a simple method to determine the non-uniform temperature distributions in the wall stud sec-tions exposed to fire on one side without the need touse finite element simulations (Shahbazian and Wang,2013). Shahbazian and Wang (2014) then proposed afire design method for CFS walls exposed to para-metric fires. In this design method, their simple tem-perature distribution prediction method is first used todetermine the wall stud temperatures in a given para-metric fire, and their DSM-based design rules are then
used to calculate the capacity of wall studs subject tolocal, distortional or global buckling effects, whichprovide the required ultimate load of wall studs versustime in such parametric fires.
Chen et al. (2013) and Chen and Ye (2014) con-ducted full-scale fire tests of CFS walls made of differ-
ent configurations and confirmed Gunalan et al.’s
(2013) findings that the use of external insulation
instead of cavity insulation improved the fire perfor-
mance of walls. Chen et al. (2013) investigated the
effects of using different fire protection boards, based
on which suitable recommendations were made to
improve the fire performance.Research on individual CFS columns and beams
was also continued during 2013–2014. Craveiro et al.
(2014) conducted fire tests of lipped channel and built-
up channel columns with restrained thermal elongation
to investigate the effects of cross-section, end support
conditions, surrounding structure stiffness and applied
load level. Their results identified the critical para-
meters that reduced the critical temperature signifi-
cantly. Laım et al. (2014b) conducted a similar study
for CFS lipped channel and built-up channel beams to
investigate the effects of four different profiles, axial
restraint to thermal elongation and rotational stiffness
of beam supports on the failure modes, temperatures
and times. Their tests showed that any axial restraint
to thermal elongation was detrimental to fire perfor-
mance while the use of closed built-up profiles
improved the fire performance. Cheng et al. (2014)
investigated the fire performance of CFS members
under axial and transverse loading while Gunalan
et al. (2014) investigated the flexural–torsional buck-
ling behaviour of CFS columns using uniform elevated
temperature tests and finite element analyses to
develop suitable fire design rules, which showed their
adequacy when appropriately reduced mechanical
properties were used.Local buckling effects of CFS members at elevated
temperatures are currently accounted for using the
conventional EWM with elevated temperature yield
strength based on 0.2% proof strength. Couto et al.
(2014) used a numerical study to investigate the accu-
racy of this approach and proposed modified effective
width expressions for internal and outstand elements
of CFS profiles exposed to uniform elevated tempera-
tures. Many research studies mentioned above used
nonlinear 3D finite element analyses to study the fire
performance of CFS members and to investigate the
accuracy of elevated temperature design rules.
Ellobody (2013) presents more details of this approach
and the main parameters to be considered for the heat
transfer and structural analyses of CFS columns in fire
conditions.
Figure 8. CFS member and wall failures in fire.
Figure 9. Elevated temperature mechanical properties of CFS(Dolamune Kankanamge and Mahendran, 2011).
Limited work has been undertaken on CFS connec-tions in fire. Yan and Young (2013) address this issuethrough a detailed experimental study of double shearbolted connections of thin steels exposed to uniformelevated temperatures. They showed that the use ofambient temperature design equations for connectionstrengths provided conservative predictions when ele-vated temperature mechanical properties were used.
Assessing the residual strength of CFS structuresfollowing a fire event is important and thus Gunalanand Mahendran (2014a, 2014b) investigated the post-fire mechanical properties of CFSs and proposed suit-able predictive equations for this purpose.
Fire research on CFS members, connections andstructural systems is continuing, which will lead toaccurate design methods to predict their structural fireperformance for inclusion in future design standards.
Seismic design
As CFS structures are used in more active seismicareas, there is an increasing need to carry out researchon cold-formed members and structural systems sub-ject to cyclic loading. Shear walls under cyclic load arealready covered in section ‘Shear walls’. The referencesare for moment frames (Bai and Lin, 2013; Li et al.,2014d), strap-braced frames (Dao and Van de Lindt,2013; Pali et al., 2014; Terracciano et al., 2014), mid-rise construction (Ozaki et al., 2013; Yuan and Xu,2014) and framing members (Padilla-Llano et al.,2014a, 2014b, 2014c). It is interesting to see increasingresearch on mid-rise and moment-resisting frames.
Frames
Portal frames composed entirely of cold-formed mem-bers are being used frequently and so more researchon their structural behaviour is being undertaken. Thereferences are for residential and framed buildings (Liet al., 2013, 2014c; Peterman et al., 2014), moment andportal frames (Hanna, 2014; Zhang and Rasmussen,2014) and stressed skin action (Phan et al., 2014a,2014b; Wrzesien et al., 2014). A significant new area ofresearch is clad framed and residential buildings andthe effect of the cladding on the frame behaviour espe-cially during seismic action.
Optimisation
Research into section shape optimisation has been car-ried out for a long time and continues as new algo-rithms are developed. The references are Ostwald andRodak (2013), Moharrami et al. (2014), Franco et al.
(2014), Leng et al. (2014) and Wang et al. (2014a,2014b).
Conclusion
This article provides a bibliographical review of paperspublished in the area of CFS structures in the Journalof Structural Engineering, ASCE; Thin-WalledStructures; Journal of Constructional Steel Research;Eurosteel 2014 Conference, Naples; 7th InternationalConference in Thin-Walled Structures, Busan, Korea,2014; and the 22nd International Specialty Conferenceon Cold-Formed Steel Design and Construction, StLouis, MO, USA, 2014. The notable feature of thisarticle is the threefold increase in the number of papersbetween a similar review in 2003 and this review from60 to over 200. The highlight in the period has beenthe inclusion of the DSM of design in the NorthAmerican Specification NAS:S100 and the Australian/New Zealand Standard AS/NZS 4600. This has led toa significant increase in stability research using theGBT and the FSM including mode interaction. Twoother areas with a major increase in research are firedesign and shear walls particularly under seismic load.There is an increased need to incorporate much of thisresearch into new design specifications and standards.At the time of writing, new editions of NAS:S100 andAS/NZS 4600 are under preparation using much ofthis research.
The author has noted several areas that need furtherresearch during this review. These are the inclusion oflocalised loading/web crippling in the DSM of designso that all modes of failure are covered, more studieson structural systems and system effects including thenewly developing method of modular construction,more research on the use of advanced analysis methodsfor frames and further investigation of seismic designof systems as opposed to simply shear walls.
Acknowledgements
The author is grateful for the material provided byProfessor Mahendran (QUT) and Associate Professor LipTeh (UOW).
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest withrespect to the research, authorship and/or publication of thisarticle.
Funding
The author(s) received no financial support for the research,authorship and/or publication of this article.
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