Finite element analysis of single-storey unreinforced alternative masonry walls

The most commonly cited obstacles to the uptake of alternative masonry units on a meaningful scale, despite significant research investment, are a lack of standards and understanding of their structural behaviour. This paper contributes to the body of knowledge on finite element analysis of alternative masonry structures, towards improved understanding of their structural behaviour. Two critical masonry wall configurations, in the context of South African low-income, government-subsidised housing, are analysed using the simplified micro-modelling approach, under ultimate limit state wind and seismic actions. Three alternative masonry materials are characterised and employed in the numerical analyses, geopolymer, compressed-stabilised earth and adobe blocks, as well as conventional concrete blocks as benchmark. Despite the wide spectrum in masonry materials analysed, the chosen modelling approach captured the major failure mechanisms well. The four materials performed as expected relative to one another, but most wall/material configurations failed to resist the required design load, including the conventional concrete masonry material.http://ase.sagepub.comhj2022Civil Engineerin

Die invloed van die swart gewoontereg op boedelbeplanning, boedelbereddering en erfopvolging in Suid-Afrika

Thesis (LL.M.)--Potchefstroom University for Christian Higher Education, 2000During the last few years tremendous changes took place in South Africa. Apartheid and all other statutes based on discrimination were abolished and a new Black middle class was established. The customary law is also recognised in the 1996 Constitution and a big section of the community abide by, and respect customary law Black people also have a choice between a marriage in terms of the common law, or in terms of the customary law. Before 2 December 1988 all Black common law marriages were out of community of property, unless otherwise determined by an ante-nuptial contract. Since the inception of the Marriage and Matrimonial Property Law Amendment Act 3 of 1988 all the differences between black and western civil marriages disappeared and all civil marriages were put on the same footing. The legislator also Save recognition to customary law marriages through the Recognition of Customary Marriages Act 120 of 1998. All these marriage systems also have a profound effect on estate planning, especially the customary law as it created new possibilities for inter alia the reduction of an estate through donations to and by spouses. Immovable property in tribal areas posed a problem as it is difficult to sell the land without the permission of the tribal authority, or minister. Black women also experienced trouble in obtaining rights in land. This situation is to be remedied. Succession in the customary law can lead to unfair results, especially as far as women are concerned, the need for a valid will therefor can't be stressed enough. The will is the most important estate planning instrument and must be utilised to ensure that assets are distributed as soon as possible after the death of the testator. The will is also an important instrument to ensure that the male successors are not prejudiced by the inception of the Amendment of the Customary law of Succession Bill 8109 of 1998 as culture determines that the male successor is also responsible for the payment of debts and the maintenance of the family, Through estate planning the estate planner must therefore give effect to the values of the 1996 Constitution and ensure that social order is maintained.Master

Alternative wall‑to‑slab connection systems in reinforced concrete structures

CITATION: Gerber, J. D. & Van Zijl, G. P. A. 2017. Alternative wall‑to‑slab connection systems in reinforced concrete structures. Journal of the South African Institution of Civil Engineering, 59(3):36-47, doi:10.17159/2309-8775/2017/v59n3a5.The original publication is available at http://www.scielo.org.zaENGLISH ABSTRACT: In many reinforced concrete structures the walls precede the construction of the connecting floors. A system is, therefore, required to connect the floors to the already cast walls. There are many different floor-to-wall connection systems available in South Africa, but their behaviour and capacity are not always fully understood, especially when the moment capacity of the joint is to be utilised. This study focuses on four systems: continuous starter-bars, pre-bent site-installed starter-bars, preassembled starter-bars and cast-in anchors with mechanical couplers. The design procedure for the continuous starter-bar system is well understood and documented in design codes, but not enough information is available on the design procedure for the other systems. Certain practical aspects of the installation process are also not fully understood. Cold-bending and straightening of the starterbars are inevitable in both bend-out systems. Previous research shows that this cold-working of the reinforcement can reduce the yield stress and E-modulus of the steel. In order to investigate these findings, a series of tensile tests are conducted. The results indicate that a significant reduction can be expected in both the yield stress and modulus of elasticity of the steel. Low-cycle fatigue tests further suggest that cold-bent steel also has a reduced ductility. The tensile tests are followed by the construction and testing of the systems in full-scale wall-to-slab connections. The effect of the coldbending on the starter-bars is clearly visible, as both the responses of the bend-out systems are less satisfying than the results from the continuous starter-bar system. The experimental phase is followed by numerical analysis of the connection systems. The finite element analyses show that the structural performance is significantly more sensitive to a reduction in the yield stress of the starter-bars, than to the use of a lower concrete grade. It is concluded that all the alternative connection systems can be implemented successfully in a moment-fixed wall-to-slab connection, but that the site-installed bendout system is the preferred method. However, in order to ensure that the system performs on the same level as conventional systems, it is recommended that the design should be conducted with a set of modified steel properties to allow for the negative effect of the cold-working on the starter-bars.http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192017000300005Publisher's versio

Steel fibre-reinforced concrete: Multi-scale characterisation towards numerical modelling

The Mode I and II fracture response of steel fibre-reinforced concrete is investigated experimentally at the single fibre and composite scale. A constitutive material model is developed and is implemented in a numerical procedure via a user material (UMAT) in the commercial finite element package ABAQUS. An empirical model reconciles the single fibre and composite scale for Mode II fracture

Contributions to structural mechanics and durability in structural engineering

Thesis (DEng)--Stellenbosch University, 2016.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

Mechanical and Durability Properties of Recycled Concrete Aggregate for Normal Strength Structural Concrete

The purpose of this study was to determine the suitability of using Recycled Concrete Aggregate (RCA) in structural concrete based on a better understanding of its strength, stiffness and durability. RCA was collected from three different sources: a local landfill site, a local aggregate supplier and from the demolition of two old cooling towers in Cape Town, South Africa (RSA). All RCA was prepared by crushing the demolished concrete in a laboratory crusher at University of Stellenbosch. Their physical properties were determined for comparison of different sources of RCA. RCA replacement percentages of 0%, 30% and 100% to partially replace natural aggregate (NA) in concrete were tested at different ages. Cube strength classes 30-40 MPa concrete were made to investigate the mechanical properties of RCA. Creep, shrinkage and durability properties were also tested for concrete with 0% and 30% RCA replacement of NA. It was found that RCA replacement by 30% (RCA30%) of NA does not lead to any significant difference in strength and stiffness compared to concrete containing 100% NA in concrete. RCA100% replacement does show reduced strength and stiffness, but this is not significant and can be compensated for in standard ways. Durability index tests indicated similar durability performance of concrete with reasonable quality RCA30% compared with NA100%. Increased creep was however observed for RCA30% which must be considered in structural design. Little information is available about both the mechanical and durability properties of local RCA in RSA, where this research has been performed. The authors believe this report will assist to increase the confidence of engineers to consider using RCA in structural concrete in RSA as well as abroad

Chloride-induced corrosion modelling of cracked reinforced SHCC

Corrosion of steel bars in concrete is usually a slow electrochemical process which may need a long time before damage becomes visible in the reinforced concrete (RC). However, cracks provide quick access to chloride, oxygen and water into concrete and accelerate the corrosion process. Corrosion modelling is essential for structural design for a particular life span, or to inform decisions on repair of RC structures to reach or extend their service life. This paper reports experimental research results of accelerated chloride exposure of cracked reinforced strain hardening cement-based composite (R/SHCC) specimens for a period of one year. Based on these novel results, a corrosion model is proposed which incorporates crack width, crack spacing, free chloride content and cover depth. The model is shown to capture the corrosion results of cracked R/SHCC reported in this paper.Accepted versio

Retrofit and Renovation of Concrete Bridges with Fibre Reinforced Polymer (FRP): The Third Alternative

This paper presents Fibre Reinforced Polymer (FRP) as a third alternative construction material worth considering when retrofitting a bridge structure. FRP offers the following advantages: lighter than steel and concrete, non-corrosive, low in maintenance, stronger than structural steel and fatigue resistant. FRP has been used in Europe and more specifically in the Netherlands for almost 20 years in the retrofitting of road bridges, in new pedestrian bridges, road bridges and lock doors for sluices. The Netherlands has recently developed the updated Dutch Design Code CUR Recommendation 96, which was published in December 2017. The CUR Recommendation 96 will form the basis for developing the Eurocode FRP which is expected to be published between 2020 and 2025. The use of FRP in retrofitting of bridges is presented using examples which demonstrate how existing concrete decks, and steel and concrete substructures could be retained by the use of FRP in the retrofitting solution. Due to FRP being a relatively unknown material within the South African bridge design field, the authors have embarked on an awareness campaign targeting academics, government bodies, suppliers, manufacturers and contractors, with the aim of presenting FRP as a third alternative construction material in the South African bridge fraternity

Retrofit and Renovation of Concrete Bridges with Fibre Reinforced Polymer (FRP): The Third Alternative

This paper presents Fibre Reinforced Polymer (FRP) as a third alternative construction material worth considering when retrofitting a bridge structure. FRP offers the following advantages: lighter than steel and concrete, non-corrosive, low in maintenance, stronger than structural steel and fatigue resistant. FRP has been used in Europe and more specifically in the Netherlands for almost 20 years in the retrofitting of road bridges, in new pedestrian bridges, road bridges and lock doors for sluices. The Netherlands has recently developed the updated Dutch Design Code CUR Recommendation 96, which was published in December 2017. The CUR Recommendation 96 will form the basis for developing the Eurocode FRP which is expected to be published between 2020 and 2025. The use of FRP in retrofitting of bridges is presented using examples which demonstrate how existing concrete decks, and steel and concrete substructures could be retained by the use of FRP in the retrofitting solution. Due to FRP being a relatively unknown material within the South African bridge design field, the authors have embarked on an awareness campaign targeting academics, government bodies, suppliers, manufacturers and contractors, with the aim of presenting FRP as a third alternative construction material in the South African bridge fraternity