Academic literature on the topic 'Concrete bridges – South Africa – Design and construction'

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.

The Olifants River Bridge B3611 carries the N11 over the Olifants River, just North of the Loskop Dam. This structure was originally built in 1979 and was recently widened as part of the South African Roads Agency Limited (SANRAL)’s upgrade to the N11. At the time of design, very little was known about the bridge as no ‘As Built' drawings were available. Due to the remote locality of the structure, exploratory investigations were reserved until the construction phase. The final design solution was therefore amended during the construction phase in order to account for the reinforcement found within the structure. In addition to the heavier dead weight of the new widened deck, the bridge would be required to carry higher loads under modern loading codes. Widening works included new widened cantilevers with new reinforced concrete balustrades, tying into existing reinforcement. Strengthening for bending was provided to the main deck beams by means of longitudinal FRP plates epoxied to the soffit. Transverse pierhead strengthening using DYWIDAG bars was installed to counter increased moments, and pier strengthening using a reinforced concrete jacket was implemented to strengthen the piers. Durability concrete was specified in accordance with current SANRAL regulations and the durability performance of the concrete, even in this remote location was excellent. This paper summarises the work that was completed as part of this project.

Bridge engineers are continually faced with the challenge of providing efficient and cost-effective structures. In particular, the Florida Department of Transportation has recognized the need to develop economical bridge configurations in the medium-span range of 200- to 400-ft (60.96-to 121.92-m) spans and authorized a research project at the University of South Florida to identify and develop innovative design concepts within this span range. The study identified the concept of a steel bridge with double-composite action as an innovative bridge concept with the potential for significant cost savings compared with conventional modes of construction. This bridge type has been used with good success in Europe, but to the authors’ knowledge it has not been used in the United States. In addition to a composite concrete top slab, the double-composite bridge concept utilizes a composite concrete bottom slab in the negative moment regions. The result is provision of a design meeting compact requirements throughout, increased stiffness with corresponding decrease in fatigue stress range and deflections, savings in cross frames, and savings in flange material. The design implications of this system are examined, including redistribution effects due to creep and shrinkage, implications of different construction sequences, and strength and serviceability issues. Trial designs are presented, including both plate and box girder type structures, and design considerations are discussed. A prototype structure is identified for further development of the double-composite concept.

The Central Artery/Third Harbor Tunnel Project in Boston, Massachusetts, is one of the largest highway projects over undertaken in the country. It requires the replacement of the existing elevated artery, I-93, with an underground tunnel extending through downtown Boston and an extension of the Massachusetts Turnpike Authority (MTA) I-90 from its existing termination at the I-93 interchange to Boston's Logan International Airport. The I-90 extension tunnels east under the existing South Station intercity and commuter railroad tracks, under historic Fort Point Channel while crossing above the 1915 twin subway tunnels, and continues through industrial South Boston with ramps surfacing in a new South Boston interchange, the heart of tremendous growth in Boston. From there the tunnel connects to the recently completed Ted Williams Tunnel harbor crossing to East Boston and Logan International Airport. The unique design challenges and solutions relating to the Fort Point Channel crossing, particularly the use of in-the-wet construction with concrete immersed-tube tunnels and the design interface to the ventilation structures, are presented. Structures required for the I-90 extension are concrete immersed tubes and jacked tunnels, as well as more conventional cut-and-cover tunnels, bridges, surface roads, and ancillary buildings. The geometric and physical restraints of the alignment initially required the placement of the ventilation building, which serves the tunnels, on a cut-and-cover tunnel transition section between the jacked tunnels and the concrete immersed tubes. Ultimately, placement of the ventilation building on the immersed tubes created a substantial cost and schedule benefit.

Cracking in concrete can occur due to temperature changes at early ages and exposure to ambient temperature changes in the long term. Design codes and standards allow engineers to design for cracking by quantifying the effects of thermal variations into outputs such as limiting crack widths and reinforcement configurations. Design values given in these codes are however not fully understood by many users, may not be representative of recent developments in concrete materials technology and can potentially result in over-conservative designs. In this paper, concrete hydration temperatures were measured on site using a Thermocouple Data Logger and compared to values used in the project-specific design with the intention of providing a basis on which a database of temperatures representative of mixes commonly used in the South African industry may be compiled. Findings revealed that measured temperature values were around 30 – 50% lower than those given in design codes. Among the reasons identified for this is the fact that readily used design codes for crack-width design of water-retaining concrete structures in South Africa were compiled with data obtained from the use of 42.5 N cements, which may well have been quite different from the now more modern and readily available 52.5 N cements. Furthermore, design codes focus extensively on factors like binder content, binder type and formwork type, while the effects of other factors such as coarse aggregate type, coarse aggregate nominal size and construction sequence (which also play a significant role) are not quantified in the selection process of temperature values. Recommendations for further studies are made which aim to incorporate a wider variety of factors that affect development of thermal properties of concrete. This can allow members of the project team (engineer, contractor) to act during the relevant stages of design/construction of a project to mitigate thermal effects that can incur unwanted cracking.

Over recent decades there has been rapid increase in the industrial waste materials and by-products yields due to the progressive growth rate of population, development of industry and technology and the growth of consumerism. With the growing environmental pressures to reduce waste and pollution, Intensive research studies have been conducted to explore all suitable reuse methods. Wastes such as construction waste, blast furnace, steel slag, coal fly ash and bottom ash have been approved in many places as alternative materials in bridges, roads, pavements, foundations and building construction. The use of industrial solid waste as a partial replacement of raw materials in construction activities not only saves landfill space but also reduces the demand for extraction of natural raw materials. Ferrochrome slag is a by-product from the production of chrome. There are environmental and economic advantages in seeing slags as a potentially useful resource rather than as waste products. Slag management at ferrochrome producing companies has been influenced by the limited space available and financial cost implications of the slag dumps. Internationally, e.g. South Africa, India, Norway, Turkey, East Europe, China, Sweden and USA, ferrochrome slag is used commercially in the road and construction Industries. This material is being used for road construction, as aggregates in concrete industry, brick manufacturing, and in pavement construction as engineering fill and has recently been tried in cement. This paper presents an overview of the recent advances of the use of ferrochrome slag in various civil engineering applications such as road construction, and cement and concrete industries.

In 2009, the National Route 1 Section 1 between km 56.1 and km 61.5, located North East of Paarl in the Western Cape Province of South Africa, was rehabilitated and widened. As part of the rehabilitation and widening contract the downhill truck crawler lane was constructed as an experimental pavement section. This experimental pavement section was constructed with a 50 mm thick Ultra-Thin Continuously Reinforced Concrete Pavement (UTCRCP). Early in 2010 sections of the experimental UTCRCP started to fail and consequently necessitated repair. In October 2014 a service provider was appointed for the special maintenance of the truck crawler lane on the National Route 1 Section 1. The project called for the reinstatement of the failed experimental UTCRCP with a re-engineered UTCRCP and a Enrobé à Module Élevé (EME) asphalt base layer with an Ultra-Thin Friction Course (UTFC), at various locations along the southbound (downhill) truck crawler lane. The project objective was specifically formulated to enable a long term performance comparison of both the re-engineered UTCRCP and the EME with UTFC under repeated traffic loading. The focus of this paper is the documentation and assessment of the initial pavement (structural analysis) and material design process, the construction of the UTCRCP, with cognizance of the challenges experienced during construction as well as the initial performance comparison. EME will not be discussed in this paper.

Concrete technology has continued to advance throughout the years to meet the demands of designers and innovative structural systems. With the advent of high-performance concrete (HPC), which contains large amounts of cementitious materials, the investigation of the impact of concrete temperature development during hydration on concrete performance is of keen interest. Match-curing technology was used to investigate the influence of concrete temperature development during hydration on the mechanical and material property performance of prestressed and precast HPC beams. These members were fabricated for use in two recently constructed HPC bridges in Texas. The investigation was conducted in conjunction with the design, instrumentation, and construction of the Louetta Road Overpass in Houston, Texas, and the North Concho River US-87 and South Orient Railroad Overpass in San Angelo, Texas. FHWA and the Texas Department of Transportation cosponsored these projects as part of the Strategic Highway Research Program to stimulate the use of HPC and to demonstrate the suitability of HPC in highway structures. The results of the study indicated that for HPCs that contain large amounts of cementitious materials, the concrete temperature during hydration can have a dramatic impact on both the mechanical and the material (durability) performance of the concrete. Temperature recommendations are provided to avoid less than optimal concrete performance on the basis of the member shapes and mix designs investigated in the study.

The construction of ‘hard’ impermeable surfaces in urban areas results in the increased flow of stormwater runoff and its associated pollutants into downstream receiving waters. Permeable Pavement Systems (PPS) can help mitigate this. The most common type of PPS in South Africa is permeable interlocking concrete pavement (PICP), but there is currently insufficient information available on the relative treatment performance of different PICP designs. This paper describes an investigation into the performance of ten different PICP systems constructed in the Civil Engineering Laboratory at the University of Cape Town for the treatment of various nutrients commonly found in stormwater runoff. It was found that removal efficiencies ranged from 27.5% to 78.7% for ammonia-nitrogen and from −37% to 11% for orthophosphate-phosphorus; whilst 4% to 20.2% more nitrite-nitrogen and 160% to 2580% more nitrate-nitrogen were simultaneously added. The presence of a geotextile resulted in higher ammonia-nitrogen removal efficiencies but also higher nitrate-nitrogen addition than those cells without—with small differences between various types. The cell with a permanently wet ‘sump’ had the highest nitrate-nitrogen addition of all. Lower pH results in higher nitrate-nitrogen concentrations, whilst the electrical conductivity strongly depends on the length of the periods between rainfall ‘seasons’, decreasing rapidly during wet periods but increasing during dry periods. Paver type also had a minor impact on nutrient removal.

In many parts of the world, high-level engineering solutions are inappropriate for rural areas where expertise, skills, and equipment are unavailable. Often these areas suffer from difficult terrain that also makes accessibility a problem. At the 1999 International Conference on Low-Volume Roads, a design catalogue was presented for a flexible portland cement concrete pavement using geocells, which was suitable for labor-intensive construction. However, the catalogue required layer works, which meant that construction equipment, although minimal, was required. This was seen as a major constraint, particularly when communities become involved in the construction of these local access roads. In addition, in difficult terrain the handling of drainage becomes a major engineering undertaking for which expertise may not be locally available. The aim of this study was to develop a structural design catalogue that caters for the range of traffic and material conditions typically encountered in these remote rural areas. Additionally, standard solutions were developed for dealing with steep gradients and surface drainage that are coupled to the structural design. The fundamental engineering principles were used to derive the structural design catalogue and in the management of surface drainage. Case studies were conducted in the successful application of the design catalogue to demonstrate the approach and design procedures. This approach has made a significant contribution in improving the quality of life of rural communities, particularly in remote and often poor regions of South Africa.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Precast concrete has been used for decades in the construction industry, locally as well as internationally. Rapid urban development and the need for shorter construction periods for building and infrastructure projects have however encouraged more use of precast concrete construction. The improved speed of construction, high quality and less labour requirements that precast offers makes it an effective type of construction method for modern development. The utilization of various precast concrete systems has been frequently used in the international construction industry, making it a very popular construction method. It was however found that one of the major drawbacks or concerns with the use of precast concrete is the connections between the precast elements. In-situ construction does not have this problem, because it is designed to a monolithic structure or building. It was identified that if the connections in precast buildings or structures are designed or constructed in an insufficient way, it can lead to severe structural problems and even failure. This highlights the importance the design and construction of precast concrete connections have on the overall stability, strength and robustness of the structure. Precast concrete buildings are not merely separate precast elements, connected together to eventually form the same principals of in-situ construction. Precast concrete and connection design is considered to be a specialist field and requires the sufficient expertise and knowledge to understand the structural system and all its different aspects. The precast connection’s function is not merely to transfer loads, but also to develop continuity and ensure monolithic behaviour of the entire precast concrete structure (Englekirk 2003). The most important or desirable structural functions of precast connections are; (i) direct transfer of loads (load paths and flow or forces), (ii) develop structural continuity and integrity, (iii) distribution of concentrated loads, (iv) allow for movements and unintended restraints and lastly to (v) ensure efficient rigidity and robustness for the connection. It can be seen that there is many factors that contribute to the overall design and construction phases of precast concrete connections. The aim of this study is to identify and investigate aspects that influence the design and construction of precast concrete connections. This study will mainly focus on precast concrete and precast connection preferences of participants in the South African construction industry. During this study, industry participants (contractors and consultants) were asked to identify certain aspects and concerns associated with precast concrete and precast connection construction. These answers were used to develop guidelines and preferences that can be used by industry participants to improvise and effectively manage the precast construction, mainly focussing on the connections between the precast elements.
AFRIKAANSE OPSOMMING: Voorafvervaardigde beton word al vir dekades gebruik in die konstruksiebedryf, plaaslik sowel as internasionaal. Vinnige stedelike ontwikkeling en die behoefte vir korter konstruksie tydperke vir die struktuur en infrastruktuur projekte het egter die gebruik en implementasie van voorafvervaardigde beton konstruksie laat toeneem. Die verbeterde spoed van die konstruksie proses, 'n hoë gehalte produk en minder arbeid vereistes wat voorafvervaardiging bied maak dit dus 'n effektiewe tipe konstruksie metode vir moderne ontwikkelings. Die benutting van verskeie voorafvervaardigde beton sisteme en elemente word reeds herhaaldelik gebruik in die internasionale konstruksiebedryf, wat dit vervolglik ʼn baie populêre en effektiewe sisteem maak. Dit is egter bevind dat een van die groot struikelblokke of probleme met die gebruik van voorafvervaardigde beton is die verbindings tussen die voorafvervaardigde elemente. In-situ beton konstruksie het dus nie hierdie probleem nie, want dit word ontwerp om 'n monolitiese beton struktuur of gebou te vorm. Dit was immers geïdentifiseer dat as die verbindings in ʼn voorafvervaardigde gebou of struktuur, ontwerp word deur ʼn ontoereikende manier, dit kan lei tot ernstige strukturele probleme en selfs strukturele faling. Dit beklemtoon dus die belangrikheid wat die ontwerp en konstruksie proses van voorafvervaardigde beton verbindings het op die algehele stabiliteit, sterkte en robuustheid van die struktuur. Voorafvervaardigde beton geboue en strukture kan nie slegs beskou word as aparte voorafvervaardigde elemente wat met mekaar verbind word om eventueel dieselfde beginsels van insitu konstruksie te vorm nie. Voorafvervaardigde beton en verbinding ontwerp word beskou as 'n spesialis veld en vereis dat die ontwerper die nodige kundigheid en kennis van die strukturele stelsel en al sy verskillende aspekte verstaan. Voorafvervaardigde beton verbindings se funksie is nie net om toegepaste kragte oor te dra nie, maar ook om strukturele kontinuïteit te ontwikkel en te verseker dat monolitiese gedrag gehandhaaf word vir die hele voorafvervaardigde beton struktuur (Englekirk 2003). Die mees belangrike strukturele funksies van voorafvervaardigde beton verbindings sluit die volgende in; (i) verseker direkte oordrag van toegepaste kragte (vloei van kragte), (ii) ontwikkeling van strukturele kontinuïteit en integriteit, (iii) die verspreiding van puntbelastings, (iv) moet voorsiening maak vir die bewegings in die voorafvervaardigde element en konneksie self en laastens (v) verskaf doeltreffende rigiditeit en robuustheid vir die konneksie sone. Dus kan daar afgelei word dat daar baie faktore is wat bydra tot die algehele ontwerp en konstruksie fases van voorafvervaardigde beton verbindings. Die doel van hierdie studie is om aspekte te identifiseer en te ondersoek wat die ontwerp en konstruksie van aspekte beton verbindings wel beïnvloed. Die studie sal hoofsaaklik fokus op voorafvervaardigde beton en verbindings voorkeure van persone in die Suid-Afrikaanse konstruksiebedryf. Tydens die studie was persone in die industrie (kontrakteurs en konsultante) ook gevra om sekere aspekte en kwellings wat verband hou met voorafvervaardigde beton asook die verbindings te identifiseer. Die antwoorde wat verkry was uit die industrie deelnemers kan toepaslik gebruik om word riglyne en voorkeure op te stel wat vervolglik gebruik en toegepas kan word in die konstruksie bedryf van Suid Afrika. Die riglyne kan effektief gebruik word om voorafvervaardigde beton asook die verbindings te verbeter en persone in die konstruksie bedryf in te lig oor voorkeure en toepassings van hierdie metode.

Plastic shrinkage cracks, although not inherently structurally debilitating, expose the reinforcement in low-volume reinforced concrete roads to deleterious substances, which may reduce its effectiveness leading ultimately to structural failure. In un-reinforced low-volume concrete road these cracks appear unsightly and cause the road user an unpleasant riding experience. Many researchers believe that plastic shrinkage crack development remains a concern to the concrete industry, occurring in particularly large–area pours such as low-volume concrete roads, and therefore requires further research to understand their formation and minimization. This study reports findings on the effectiveness of oxyfluorinated polypropylene fibres to control plastic shrinkage cracks, and the effect the addition of ultra-fine material has on the formation and/or propagation of these cracks. Findings indicate that low volume dosages (2 kg/m³), of oxyfluorinated polypropylene fibre significantly reduced the formation of plastic shrinkage cracks under test conditions. Furthermore, that the addition of ultra-fine material in excess of 63 kg/m³ increased the formation and/or development of plastic shrinkage cracks.

Damage to reinforced concrete bridges due to carbonation and chloride induced corrosion is widespread in South Africa and prone in environments where carbon dioxide is at high levels as well as in marine environments where chlorides are present. Performance specifications are therefore essential in order that structural concrete can be designed and constructed to the required standards ensuring that the long term durability can be maintained. This dissertation includes a review of SANRAL‘s current durability specifications. The specifications are critiqued in terms of the testing methodology followed as well as strength and environmental exposure considerations, and recommendations are made for improving the specifications. The literature review, outlines the background to both carbonation and chloride induced corrosion to reinforced concrete bridges , considering the fundamental causes of deterioration of concrete caused by carbonation and chloride ingress and repair costs during their service life. The South African Durability Index tests are presented and reviewed, in particular the laboratory testing apparatus and procedures. In addition, the index tests are compared with durability test methods currently being used internationally. The background and previous durability specifications used in South Africa on road bridges as well as details of research into specifications to ensure durable concrete with specific emphasis on curing of concrete is summarised. The indications are that performance based specifications for concrete on bridge structures internationally follow similar criteria to the specifications currently being adopted by SANRAL. Both performance and prescriptive specifications used usually depend on the risk that a constructor needs to carry. Importantly both cement extenders to ensure long term durability and penalties are applied in performance based durability. SANRAL‘s current durability specifications are reviewed and both the negatives and positives are presented for the various sections. Amendments to the Committee of Land Transport Officials (COLTO) standard specifications are recommended address shortcomings. The latest project specifications used on SANRAL contracts incorporating target requirements for cover and oxygen permeability are evaluated. These impose penalties if targets are not achieved, while limits are placed on chloride conductivity values for various blended binders. Data is also included for the sorptivity index values on the five projects which may analysed and target values can be set and implemented in future. Descriptions of the five projects with regard to durability specifications, their environmental exposure condition and concrete mix designs are presented. Five projects in KwaZulu-Natal, are used as case studies for durability tests and specifications. The only distinct difference in the specifications is that the three projects commencing in 2006 and early in 2007 had the target values for water sorptivity whereas for the project, sorptivity values are only reported on. Durability index testing results at each of the sites from the trial panels, additional test cubes (cast for coring and testing of durability indexes) as well as coring and testing from the bridge structures are presented. A major change is coring and testing of samples from trial panels and additional test cubes on the site instead of coring of the structure. The information is drawn together and relationships are determined between the various durability indexes as well as to strength. It is evident that the quality of concrete as constructed in the structure which is reflected by the durability index results is different to that produced in the test cubes and trial panels. It is deduced that while more care is being taken to produce quality concrete on the sites, certain aspects of the specifications need revision in order to remove confusion as well as to ensure that the concrete in the structure meets the target requirements. Finally it is noted that climate change is having an impact on design of bridge infrastructure, and while the surveys undertaken at Ethekwini and Msunduzi Municipalities shows that carbon dioxide levels being recorded are still average levels, worldwide there has been an increase in CO2 levels and further modifications to specifications in future may be required.
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

<p>The new Erasmusrand Pedestrian bridge replaced the previously severely damaged pedestrian bridge spanning across the National Route N1 highway in Pretoria, South Africa, for the South African National Roads Agency SOC Ltd (SANRAL). The structure consists of a steel arch supporting a composite steel/concrete deck with inclined square hollow steel struts. The bridge spans 73m across a 10-lane dual carriageway freeway providing access to a local school from the suburbs. Several challenges were presented in the project with procurement, design and construction.</p>