Editorial overview
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Editorial overview Timber construction I Smith University of New Brunswick, Canada Timber construction can be aesthetically pleasing; economic to build, operate and maintain; environmentally friendly; and have good fire and acoustical performances. The papers in Volume 1 dealt with performance of buildings subject to extreme events such as hurricanes and earthquakes, methods for making reliable joints in heavy timber construction, and recent developments in medium- rise light frame timber construction. Papers in this issue concern advanced structural jointing technology, fire performance of timber buildings, and initiatives in the USA aimed at improving timber bridge technology. It can be argued that the most onerous challenges faced by designers of timber structures relate to making connections which are capable of developing capacities similar to those of members being joined together. As anybody who has hammered nails into timber members knows, wood’s tendency to split is not a helpful characteristic from the point of view of making joints. It is desirable that connections exhibit considerable ductility and energy absorption capabilities, and do not allow slip to occur prior to carrying load. The paper ‘Influence of semi-rigidity of joints on the behaviour of timber structures’ by Hans J. Larsen and J. L. Jensen draws heavily on work performed between 1991 and 1999 under the concerted European action ‘Semi-rigid behaviour of civil engineering structural connections’. The authors discuss various novel techniques for making joints that eliminate initial slip and have high levels of ductility. Not surprisingly, the theme running through the various new jointing techniques is reinforcement of timber members so that there is bearing failure of wood beneath fasteners rather than brittle fracturing (splitting). I understand that several of the new joint techniques have already successfully been applied in the field. The authors give guidance on when and how a designer should account for semi-rigid behaviour of timber joints. A very common misconception is that timber construction inherently has poor fire performance. On the contrary, timber buildings have excellent fire performance if properly designed and properly constructed. Large dimension timbers have excellent and highly predictable behaviour during fires and only significantly lose load carrying capability after a long burning period. Small dimension timbers and metal parts, e.g. steel parts and fasteners should not be exposed to fire hazards. Alternatively there needs to be a smoke detection and sprinkler system for fire suppression. The paper ‘Fire performance of timber construction’ by Andy H. Buchanan deals with the background concept of the nature of fires and how they effect different types of timber construction. Approaches to fire design in different parts of the world are highlighted. There are examples of traditional timber bridges in many parts of the world. On a largely historical note, the town of Hartland in my own province of New Brunswick has a covered timber highway bridge built in 1921 which is 390.8 m long. It is claimed to be the longest covered bridge in the world. Recently interest in timber highway bridges has increased. Largely this reflects demonstrated good performance of modern stress laminated bridges and bridge decks. Currently there is an ambitious research and technology transfer programme being undertaken in the USA. The paper ‘Timber bridge initiatives in the United States’ by Mike A. Ritter describes that initiative. He gives an overview of work on various aspects of bridge technology, ranging from new construction forms to preservative treatment, inspection and rehabilitation of timber bridges. Much reference material is available on the world wide web and addresses of relevant sites are given in the paper. I hope that readers find the papers as interesting as I did and offer my thanks to the authors for all their effort. Please contact me with any comments and suggestions for future topics. Ian Smith PhD PEng FIWSc Professor of Timber Engineering, Faculty of Forestry and Environmental Management, University of New Brunswick, P.O. Box 44555, Fredericton, NB, Canada E3B 6C2 E-mail: ismith@unb.ca 263 Copyright ^ 2000 John Wiley & Sons, Ltd. Prog. Struct. Engng Mater. 2000; 2:263}266
Transcript of Editorial overview
Editorial overview
Timber constructionI SmithUniversity of New Brunswick, Canada
Timber construction can be aesthetically pleasing;economic to build, operate and maintain;environmentally friendly; and have good fire andacoustical performances. The papers in Volume 1 dealtwith performance of buildings subject to extremeevents such as hurricanes and earthquakes, methodsfor making reliable joints in heavy timberconstruction, and recent developments in medium-rise light frame timber construction. Papers in thisissue concern advanced structural jointing technology,fire performance of timber buildings, and initiatives inthe USA aimed at improving timber bridgetechnology.
It can be argued that the most onerous challengesfaced by designers of timber structures relate tomaking connections which are capable of developingcapacities similar to those of members being joinedtogether. As anybody who has hammered nails intotimber members knows, wood’s tendency to split isnot a helpful characteristic from the point of view ofmaking joints. It is desirable that connections exhibitconsiderable ductility and energy absorptioncapabilities, and do not allow slip to occur prior tocarrying load. The paper ‘Influence of semi-rigidityof joints on the behaviour of timber structures’by Hans J. Larsen and J. L. Jensen draws heavily onwork performed between 1991 and 1999 under theconcerted European action ‘Semi-rigid behaviour ofcivil engineering structural connections’. The authorsdiscuss various novel techniques for making jointsthat eliminate initial slip and have high levels ofductility. Not surprisingly, the theme running throughthe various new jointing techniques is reinforcementof timber members so that there is bearing failure ofwood beneath fasteners rather than brittle fracturing(splitting). I understand that several of the new jointtechniques have already successfully been applied inthe field. The authors give guidance on when and howa designer should account for semi-rigid behaviour oftimber joints.
A very common misconception is that timberconstruction inherently has poor fire performance. Onthe contrary, timber buildings have excellent fireperformance if properly designed and properlyconstructed. Large dimension timbers have excellent
and highly predictable behaviour during fires andonly significantly lose load carrying capability aftera long burning period. Small dimension timbers andmetal parts, e.g. steel parts and fasteners should not beexposed to fire hazards. Alternatively there needs tobe a smoke detection and sprinkler system for firesuppression. The paper ‘Fire performance of timberconstruction’ by Andy H. Buchanan deals with thebackground concept of the nature of fires and howthey effect different types of timber construction.Approaches to fire design in different parts of theworld are highlighted.
There are examples of traditional timber bridges inmany parts of the world. On a largely historical note,the town of Hartland in my own province of NewBrunswick has a covered timber highway bridge builtin 1921 which is 390.8 m long. It is claimed to be thelongest covered bridge in the world. Recently interestin timber highway bridges has increased. Largely thisreflects demonstrated good performance of modernstress laminated bridges and bridge decks. Currentlythere is an ambitious research and technology transferprogramme being undertaken in the USA. The paper‘Timber bridge initiatives in the United States’by Mike A. Ritter describes that initiative. He gives anoverview of work on various aspects of bridgetechnology, ranging from new construction forms topreservative treatment, inspection and rehabilitationof timber bridges. Much reference material is availableon the world wide web and addresses of relevant sitesare given in the paper.
I hope that readers find the papers as interesting asI did and offer my thanks to the authors for all theireffort. Please contact me with any comments andsuggestions for future topics.
Ian Smith PhD PEng FIWScProfessor of Timber Engineering,Faculty of Forestry and Environmental Management,University of New Brunswick, P.O. Box 44555,Fredericton, NB, Canada E3B 6C2E-mail: [email protected]
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Copyright ^ 2000 John Wiley & Sons, Ltd. Prog. Struct. Engng Mater. 2000; 2:263}266
Structural masonryS C AnandClemson University, USA
The two articles in the area of structural masonry,‘Developments in insitu and prefabricated masonryfor the 21st century’ by J Caine of CURTINSConsulting Engineers, London, and ‘Rehabilitationand reuse of historic masonry buildings in Europe’ byL Binda and A Anzani of Politecnico di Milano, Italy,that appeared in Volume 1, Issue 3 of this journal inApril 1998, have set an excellent stage for reviewingnew developments in other important topics in thisfield of structural engineering. This editor has selectedthree areas and has invited experts in these areas topresent the current state of the art in masonry researchand construction in the form of four papers in thisissue of the journal.
The first of these papers, ‘New masonry productsand materials,’ is authored by Christine Beall. Ms Beallis a practising architect in Texas. She is an activemember of The Masonry Society, and is currently theChair of the technical committee that deals with thedevelopment of new masonry materials. As is evidentfrom the title, her paper reviews the current state ofthe art as well as the future developments that areexpected in masonry products and materials. Thesedevelopments include new masonry units andmaterials, new masonry systems, new mortaradditives, as well as new masonry ties andreinforcement.
The next two papers, entitled ‘Prestressed masonry,’by M E Phipps, University of Manchester, UK, and‘Post-tensioned masonry: state of the art,’ by Dora Fotiand Pietro Monaco, University of Bari, Italy, both dealwith the effects of prestressing masonry to obtainadditional load bearing capabilities of masonryconstruction for cases where a masonry structurecould be subjected to possible tension stresses due tolateral loads. The paper by Phipps, who is a worldrenowned investigator in this area, not only dealswith the past research in prestressed masonry butpresents the current design procedures which havebeen adopted by various codes. The emphasis inthe second paper is on the loss of prestress due tocreep, shrinkage and variation in humidity. Thesetwo papers complement each other quite well sothat the reader is able to appreciate the challengesthat one may encounter during prestressing totake advantage of this new and unique form ofmasonry construction. Both papers provide quitea large dossier of references about the past and currentresearch as well as construction practices onprestressed masonry.
Although a large amount of research on masonryconstruction subjected to seismic loads has beencarried out during the past 15 or 20 years, especially inthe United States and Japan that has been supportedby a joint program funded by the US and Japanesegovernment and research agencies, the availableliterature in this field in too fragmented for anyengineer to use in practice. Carlos Casabonne isa practising structural engineer in Lima, Peru whodeals with the practical seismic issues in his designoffice on a regular basis and is very familiar with theseismic masonry design codes and their applicabilityto an appropriate country, especially in the Americas.In his paper, he reviews the current practices ofbearing wall construction and wall reinforcing inSouth America, as well as the current issues of seismicinterest in North America. Additional topics includethe use of partially grouted masonry, general wallbehavior, prestressed masonry, use of analytical andengineering models, materials, masonry properties,reinforced masonry, and confined masonry for use inthe seismic areas of the developed and developingworld. The paper ends with damage control,retrofitting, and codes and standards.
As is evident from the topics covered in this issue,masonry construction has come a long way from thepractices that have been used in the past, and to somedegree are still being used today. Of course the pasthas served us well but structural engineers areconstantly making progress to make the futurestructures more safe and economical, and aestheticallymore attractive. It is in this spirit that all past and newresearch in structural engineering must be consideredirrespective of the material under consideration. Thereare many more important topics in masonry designand construction, such as evaluation of existingmasonry buildings, restoration and repair with groutinjection, construction quality control, fire resistancein masonry construction, stress-strain behavior andbond strength, stability analysis and numericalanalysis of masonry structures, etc., that need to bereviewed in the future. It is the earnest hope of thiseditor to have the opportunity to tap on the expertiseof individuals for future issues of this journal who aredesirous of making structural engineering communitymore knowledgeable and all structures moreeconomical, safe as well as worthy of building.
Subhash C Anand PhD PEProfessor, Department of Civil Engineering,Lowry Hall, Box 340911,Clemson University, Clemson, SC 29634-0911, USAE-mail: [email protected]
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Smart structuresT FujitaUniversity of Tokyo
The area of ‘smart structures’ is interpreted in a widersense in this journal, and covers the followingtechnical fields:
f seismic isolation,f passive damping,f active control, andf structural health monitoring.
I have planned that the ‘Smart structures’ section inthe first two or three volumes should outline thepresent state of applications in the four fields givenabove; after that, reviews of various topics concerningresearch, development and applications in these fieldsshould follow.
In this volume, the section consists of three articles:the first concerns seismic isolation, the second, passivedamping, and third, structural health monitoring,although no article is concerned with active control.The first article, ‘Seismic isolation of civil buildings inNew Zealand’ describes seismic isolation systemsdeveloped and used in New Zealand, recent projectsfor retrofit of seismic isolation to existing buildings ofhistoric significance in New Zealand, and futuredirections for seismic isolation in which standardizingisolation systems to improve qualities and to reducecosts is asserted.
The second article, ‘Passive damping technology forbuildings in Japan’ reviews the concept of the damage-controlled structure which is a sort of passivedamping technology, dynamic analysis methods forbuildings using various passive dampers includinghysteretic dampers, viscous dampers and viscoelasticdampers, dynamic tests for steel frames withhysteretic dampers, and a number of applications ofpassive damping technology to buildings in Japanwhich shows progress of the application of thetechnology after the Hanshin-Awaji earthquake of17 January 1995.
The third article, ‘Application of civil structuralmonitoring in Europe using fiber optic sensors’reviews various fiber optic sensors used for civilstructural monitoring in Europe, which include SOFOdisplacement sensors, Microbend displacementsensors, Bragg grating strain sensors, Fabry–Perotstrain sensors, Raman-distributed temperaturesensors, Brillouin-distributed temperature sensors,and Hydrogell-distributed humidity sensors. Thearticle is concluded with a look at future progress ofthe applications of fiber optic sensors.
Takafumi Fujita Dr EngProfessor, Institute of Industrial Science,University of Tokyo7-22-1, Roppongi, Minato-ku, Tokyo 106-8558, JapanE-mail: [email protected]
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Structural analysis and CADY K Cheung and S H LoUniversity of Hong Kong
Development in structural analysis and CAD alwaysremains an interesting subject for academics andpractising engineers. However, advances in structuralanalysis can go in various directions, in areas such asnumerical computations, methodology, generalengineering structures and particular structural types,etc., and the results would have quite differentimpacts on professionals in various sectors. Thearticles in this issue reflect the diverse spectrum ofinteresting topics in structural analysis. With theadvent of computer equipment and graphicstechniques, emphasis could be placed on numericalcomputational aspects making use of computers forimproved engineering solutions. The paper ‘Bucklinganalysis of thin-walled structures: numericaldevelopments and application’ by Kim Rasmussenand Gregory Hancock demonstrates how numericaltechniques can help in predicting the instability modesof thin-walled structures. The method has reachedsuch a mature stage that it is ready to be incorporatedinto the design code.
The finite strip method remains as a general tool ofstructural analysis, and is especially efficient for thin-walled structures. The research of this technique hasnever been slowed down since its inception more thanthirty years ago. The main ideas of the newdevelopments are rather scattered in publications innumerous journals and conferences. Included in thisissue is an article, ‘A review of the finite strip method’
by Y K Cheung and L G Tham, which summarizes thedevelopment and areas of applications of the methodover recent years.
Design of bridges is always a challenging job both inits construction phase and upon completion to carrythe intended load under natural gravitational anddynamic forces. The paper ‘Recent developments oncomputer bridge analysis and design’ describes thestructural behaviour and design considerations ofmodern bridges. In the paper ‘Flat slab–columnconnections’, W H Dilger investigates the possibility ofdirectly connecting columns to slab without usingbeam elements. This would create more head room forbuilding structures. The basic idea will be introduced,and the corresponding analysis and design will bediscussed for practical engineering construction.
Y K Cheung PhD DSc DE FEngProfessor, Department of Civil andStructural Engineering,University of Hong Kong,Pokfulam Road, Hong KongE-mail: [email protected]
S H Lo BSc(Eng) MPh Doc-IngSenior Lecturer,Department of Civil andStructural Engineering, University of Hong Kong,Pokfulam Road, Hong KongE-mail: [email protected]
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