Contributions to structural mechanics and durability in structural engineering

van Zijl, Gideon Pieter Adriaan Greeff (2016-12)

Thesis (DEng)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Contributions to structural engineering have been made since 2001 from the basis of the Department of Civil Engineering of Stellenbosch University (SU). The inauguration of the Centre for Development of Sustained Infrastructure (CDSI) in 2002 has been instrumental in defining, directing and scoping the research and development in the categories Advanced cement-based construction materials, Crack formation and durability towards durability design, Renovation and retrofitting towards extended life span and Sustainable energy harvesting structures. The contributions are structured along these categories as chapters of this dissertation. Early career background in structural Engineering at the Institute for Structural Engineering (1987-1989) and Bureau for Mechanical Engineering (1989-1992) and higher education in computational and structural mechanics (PhD 1995-1999, Research Fellow 1999-2001, TU Delft), shaped the research interests in these fields. Continued affiliation with TU Delft (30%) and SU (70%) in the years 2001-2009 provided access to collegial expertise in related fields of experimental research, materials engineering, risk and reliability, and structural design at these institutions and beyond. In this way, national and international collaboration complemented structural and computational mechanics in well-rounded research programs in the mentioned categories. Clearly, the contributions are the result of collaboration in which the author to various degrees led, participated in and supervised research and development. Highlights of the contributions in the four categories are described at a relatively high level towards conveying the contributions in the national and international context. To a degree selective reporting is done, and the reader directed to detailed elaborations in roughly 200 dissertations, theses and technical papers supervised or co-supervised, authored and co-authored. Approach by the infrastructure pre-fabrication industry in South Africa towards development of accelerated and new product lines led to the development of advanced cement-based construction materials (ACM) with local ingredients, and appropriate adaption of the materials to industrial fabrication process of high-pressure extrusion. What started as fibre inclusion towards reduced traditional steel reinforcement in concrete pipes, led to development, characterisation, manufacturing and constitutive modelling of steel fibre concrete and strainhardening cement-based composites (SHCC). Roles of international leadership in co-chairing and chairing RILEM technical committees followed, as well as co-editing of books on the state-of-the-art of Durability of SHCC and a Framework of durability design with SHCC respectively. Particular contributions of significant potential towards the ability to design for durable, sustainable infrastructure, were made in chloride-induced corrosion and alkali silica reaction. In both cases crack formation and durability, i.e. structural durability in service conditions are the points of departure in order to assess actual structural performance in presence of such deteriorating processes. The work in ACM was extended to ultra-high strength concrete, and recently to lightweight aerated concrete (LWAC) and lightweight foam concrete (LWFC). The thermal, acoustic and potential mechanical advantages of LWAC and LWFC are subjects of a current significant research effort in the CDSI towards developing these lightweight materials for structural application in residential infrastructure. Constitutive models developed for traditional construction materials, as well as several of the ACM, enabled the iterative computationalexperimental development and validation of retrofitting strategies for both unreinforced load-bearing masonry and reinforced concrete structures for new functionality or extended structural life span. Finally, a role of leadership and collaboration was fulfilled in research of the solar chimney power plant concept with national and international partners, bringing the concept for harvesting of sustainable energy to a pre-feasibility level. The contributions have laid the link between construction material properties, structural behaviour and durability. Through the fundamental experimental research, structural mechanics and computational mechanics, it has been made possible to utilise the advanced properties of ACM to advance structural performance and durability. Human capital well-versed in the fundamental principles of this multi-level structural engineering approach has been developed in the process of research supervision by the author.

AFRIKAANSE OPSOMMING: Bydraes tot struktuuringenieurswese is gemaak sedert 2001 met die Department van Siviele Ingenieurswese van Universiteit Stellenbosch (US) as basis. Die stigting van die Sentrum vir Ontwikkeling van Volhoubare Infrastruktuur (CDSI) in 2002 was instrumenteel in die bepaling, afbakening en stuur van navorsing en ontwikkeling in die kategorië Gevorderde sementbasis konstruksiemateriale, Kraakvorming en duursaamheid met die oog op duursaamheidsontwerp, Renovering and versterking tot verlengde lewenspan en Strukture vir ontginning van volhoubare energie. Die bydraes word gestruktureer aan die hand van hierdie kategorië as hoofstukke van hierdie proefskrif. Vroë-loopbaan ervaring in struktuuringenieurswese by die Instituut vir Struktuuringenieurswese (1987-1989) en die Bureau vir Meganiese Ingenieurswese (1989-1992), en hoër opleiding in berekenings- en struktuurmeganika (PhD 1995-1999, Navorsingsgenoot 1999-2001, TU Delft), het die navorsingsbelang in hierdie velde gevorm. Voortgesette affiliasie met TU Delft (30%) en US (70%) in die jare 2001-2009 het toegang verleen tot kollegiale kundigheid in verwante velde in eksperimentele navorsing, materiaalingenieurswese, risiko en betroubaarheid, en struktuurontwerp by hierdie instansies en andere. Op hierdie manier het nasionale en internasionale samewerking struktuur- en berekeningsmeganika gekomplementeer in afgeronde navorsingsprogramme in die vermelde kategorië. Die bydraes is duidelik die gevolg van samewerking, waarin die outeur navorsing en ontwikkeling tot verskillende mate gelei het, aan deelgeneem het, en studieleiding verskaf het. Hoogtepunte van die bydraes in die vier kategorië word beskryf op ‘n relatief hoë vlak, met die doel om die bydraes in die nasionale en internasionale konteks te plaas. Die beskrywings is tot ‘n mate selektief, en die leser word verwys na gedetaileerde beskrywings in rofweg 200 proefskrifte, tesisse en tegniese artikels wat deur die outeur begelei, mede-begelei, of geskryf is as hoof- of mede-outeur. Toenadering deur die infrastruktuur voorafvervaardigingsindustrie in Suid-Afrika ter versnelde en nuwe produksielyne het gelei tot die ontwikkeling van gevorderde sement-basis konstruksiemateriale (ACM) met plaaslike ingrediente, en geskikte aanpassing van die materiale om met ‘n industriële vervaardigingsproses van ekstrusie onder hoë druk vervaardig te kan word. Wat begin het as insluiting van vesels om tradisionele staalbewapening in betonpype te verminder of te vervang, het gelei tot die ontwikkeling, karakterisering, vervaardiging en konstitutive modellering van staalvesel beton en vervormingsverhardende sementbasis saamgestelde materiale (SHCC). Dit is gevolg deur internasionale leierskap as mede-voorsitter en voorsitter van RILEM tegniese komitees, en mede-redakteurskap van boeke oor die huidige stand van Duursaamheid van SHCC en ‘n Raamwerk vir Duursaamheidsontwerp met SHCC onderskeidelik. Spesifieke bydraes van potensieel noemenswaardige belang is gelewer tot die vermoë om duursame, volhoubare infrastruktuur te ontwerp, met spesifieke verwysing na chloriede geïnduseerde korrosie en alkali silika reaksie. In beide gevalle is kraakvorming en duursaamheid, dit wil sê strukturele duursaamheid onder dienstoestande, die vertrekpunt om ware strukturele gedrag in die teenwoordigheid van hierdie degradasieprosesse te assesseer. Die werk in ACM is uitgebrei tot ultra-hoë sterkte beton, en onlangs ook tot liggewig belugte beton (LWAC) en liggewig skuimbeton (LWFC). Die termiese, akoestiese en potensiele meganiese voordele van LWAC en LWFC is die onderwerp van ‘n huidige intense navorsingsprogram in die CDSI ter ontwikkeling van hierdie liggewig materiale tot strukturele toepassing in residensiële infrastruktuur. Konstitutiewe modelle wat ontwikkel is vir tradisionele konstruksiemateriale, sowel as verskeie van die ACM, het die iteratiewe numerieseeksperimentele ontwikkeling en validasie van versterkingstrategië moontlik gemaak, vir beide ongewapende lasdraende messelwerk en gewapende betonstrukture vir nuwe funksionaliteit of verlengde lewenspan. Laastens, is ‘n rol van leierskap en samewerking vervul in navorsing oor die sontoring kragsentrale konsep, saam met nasionale en internasionale vennote, wat hierdie konsep vir ontginning van volhoubare energie gebring het tot die vlak kort voor lewensvatbaarheid. Die bydraes vorm ‘n skakel tussen konstruksiemateriaal eienskappe, struktuurgedrag en duursaamheid. Deur die fundamentele eksperimentele navorsing, struktuurmeganika en berekeningsmeganika, is dit moontlik gemaak om die gevorderde eienskappe van ACM te benut om struktuurgedrag en -duursaamheid te bevorder. Hoogsopgeleide menslike kapitaal, goed vertroud met die fundamentele beginsels van hierdie multi-vlak ingenieursbenadering is ontwikkel in die proses van navorsingsbegeleiding deur die outeur.

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