The following are summaries of papers published in other parts of ICE Proceedings during 2006 that readers of Structures and Buildings may find of interest. Summaries of all papers in ICE journals are freely available and fully searchable at the ‘journals on-line’ section of the ICE website. See www.ice.org.uk/journals for details.
The replacement of Heath Town footbridge
A. G. Mordey
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 1, March, 3–7
Heath Town footbridge was constructed in 1999–2000 to replace an existing concrete bridge that was in poor condition and had failed its assessment. The existing bridge had performed two functions, one as a footbridge over an urban dual carriageway and service road between high-level walkways in Heath Town, Wolverhampton, the other being to carry district heating pipes from the boiler house on one side of the road to flats and other premises on the other side of the road. The new bridge is a parabolic arch in steel, on piled foundations. It was originally designed to carry the district heating pipes in the same way as the previous one, but permission was given to bury these permanently beneath the dual carriageway, which prompted a redesign of the deck, making it simpler in detail.
A fuzzy optimum model to assess bridge design options
H.-L. Wang, Z. Zhang, C.-L. Huang and L. Shi
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 1, March, 9–15
In the process of bridge design, it is necessary to select the best from a number of feasible alternatives by comparison and selection or elimination. The set of criteria used to evaluate and select the satisfactory alternative consists of many qualitative and quantitative factors. Therefore, the selection is a problem of multi-criteria and semi-structural decision making. A new framework and methodology for evaluation of bridge alternatives, which differs from the traditional methods used in semi-structural decision making, is presented in this paper. First the set of criteria for the evaluation of alternatives is established. Next, the method of construction of the relative membership degree matrix, in which both qualitative and quantitative factors are consistent with the uniform calculating standard, is studied. A new weight-assessing method is then developed for calculation of the weightings, based on the relative membership degree matrix and finally a fuzzy optimum model is adopted to select the various alternative bridge designs that satisfy the criteria. A case study is then presented, to show the efficiency and robustness of the new framework and methodology.
Development of in situ joints for pre-cast bridge deck units
S. R. Gordon and I. M. May
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 1, March, 17–30
This paper, which extends research described in a previous paper, describes and discusses tests carried out to develop in situ joints suitable for pre-cast reinforced concrete deck units, for the decks of steel concrete composite bridges, in negative moment areas. The results of 18 tests of symmetric and non-symmetric arrangements of straight and looped bars are given together with comparisons to the theoretical strengths. The behaviour of the joints at serviceability and ultimate loads and beyond, are discussed. The tests show that the failure loads of joints containing looped bars can be accurately predicted based on the ultimate strength of the reinforcement provided there are adequate transverse lacer bars. Crack widths were measured in a number of specimens and it was concluded that they would be unlikely to impose a limitation at the serviceability limit state.
Calculating an influence line from direct measurements
E. J. O'Brien, M. J. Quilligan and R. Karoumi
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 1, March, 31–34
The response of a bridge to a pre-weighed truck can be measured on site. This paper describes a mathematical method for converting the measured response of a load effect into an influence line for that effect. One influence ordinate is calculated for each scan of the data acquisition system. The vector of ordinates is found by solving a large set of simultaneous equations expressed in matrix form. The general form of the matrices is described, and the particular matrices for a three-axle truck are given. The technique is demonstrated using measured strain on two bridges using pre-weighed trucks with different numbers of axles.
Heat-straightening repairs to a steel road bridge
S. K. Clubley, S. N. Winter and K. W. Turner
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 1, March, 35–42
On 16 July 2002 a low-loader lorry carrying heavy machinery travelling eastbound on the A27 struck the underside of Brockhampton Road new bridge. The bridge suffered structural damage to the main beams and bracing. From an initial emergency inspection, the damage was found to be located close to the point of contraflexure in an area where the bottom flange was in tension. It was not considered necessary to impose immediate closures or traffic restrictions. A heat-straightening repair of the damaged beams was proposed. Detailed analysis using both hand calculations and the finite-element method confirmed the structural adequacy of the bridge to undergo the heat-straightening process. These checks encompassed the temporary conditions prior to, during and after the heating. The major heat-straightening process was successfully completed on site in ten days. Impact damage to the beams was repaired within acceptable tolerances and the straightened steel was subjected to hardness and magnetic particle investigation testing. The repairs to Brockhampton Road new bridge were concluded without undue disruption to the travelling public or local residents.
Engineering, architecture and the River Po footbridge, Turin
D. Mairs and M. Whitby
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 2, June, 47–52
This paper traces the changes in the roles of both engineers and architects in bridge design. It argues that, with footbridges, because of the particular challenges these pose, both roles have come together. To illustrate this point, the paper then looks in detail at the River Po Footbridge in Turin, Italy, which was designed by a bridge team that includes both architects and engineers.
Reducing damage to concrete stitches in bridge decks
A. K. H. Kwan and P. L. Ng
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 2, June, 53–62
In bridge widening projects, it is a common practice to provide a monolithic connection between the existing and new decks by casting an in situ concrete stitching slab. Due to the difficulties associated with complete closure of the bridge, traffic flow has to be maintained on the existing deck. As a result, the existing deck will deflect under traffic load and the concrete stitching slab will be subjected to differential deflection, which is cyclic in nature. Such cyclic differential deflection hinders strength development of the concrete and may affect the structural integrity of the stitching slab. Some possible methods of reducing the differential deflection so as to mitigate damage to the curing concrete stitches have been proposed, but no systematic comparative studies have been carried out. These methods include traffic restriction, provision of temporary shear connections, provision of temporary propping and segmental concrete stitching. This paper evaluates the relative effectiveness of these mitigation measures as well as their different combinations by conducting grillage analysis of the widening bridge deck at various stages of construction. Based on the results, it is advocated that among these, the combination of temporary shear connection and segmental concrete stitching should be the most practicable and effective.
Eight footbridges in the Rembrandt Park in Amsterdam
J. Smits
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 2, June, 63–67
Eight footbridges were erected in the Rembrandt Park in Amsterdam, the Netherlands in 2001. The decks are in weathering steel and the parapets in structural glass and stainless steel. The project involved the design of eight bike and pedestrian bridges to replace their worn out wooden predecessors. Elegant and light, these are a modern interpretation of the typical nineteenth century park bridge. A CorTen steel bridge deck is embraced by balustrades made from steel and strengthened glass. The balustrades are made from curved and laminated glass panels, which hang from the bridge by stainless steel supports. The stainless steel handrails frame the glass panels above the deck, whilst underneath the bridge the glass hangs free, allowing the free-flow of rainwater.
A Bayesian belief network model of bridge deterioration
N. O. Attoh-Okine and S. Bowers
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 2, June, 69–76
Bridge deterioration is a major component in making bridge management decisions. It is obvious that the deterioration of one bridge element may accelerate the overall deterioration of a bridge. Current studies, although very promising, fail to address interaction among bridge elements in an effective manner. Fault tree modelling has been advocated as one of the methods that effectively handle the issue of bridge element interaction. Fault tree analysis, however, is well suited for catastrophic failure, which is uncommon in bridge deterioration. As an alternative to fault trees, belief networks are more appropriate for modelling the long-term deterioration that is typically characteristic of bridges. This paper develops a new deterioration modelling procedure based on belief networks. Belief networks effectively capture and illustrate the hierarchical, interaction, and uncertainty factors present in the bridge deterioration process. An example belief network deterioration model is presented and used to address ‘what if ‘ issues that are characteristic of any bridge maintenance and management process.
St Paul's Footbridge, Ebbw Vale, Wales—landmark structure
D. E. Williams
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 2, June, 77–81
The paper outlines the design processes involved in the creation of St Paul's Footbridge, a new landmark footbridge at Ebbw Vale, South Wales. The provision of a landmark footbridge forms part of the council's broader strategy to stimulate recovery and regeneration of this area through delivery of quality urban infrastructure design. Regular effective communication throughout the team, drawing on the creative flair of an artist and practical expertise of contractor and fabricator, resulted in a striking structure being delivered for the Ebbw Valley. The team and framework set up to deliver the footbridge and the constraints affecting the design and construction of the bridge are described. The parameters that affected the design of the deck and its foundations together with the fabrication/erection issues that were encountered are also presented. Finally, some factors to be considered when designing infrastructure projects for disabled access are reported.
Long-term maintenance strategies for highway bridges
P. R. Vassie and C. Arya
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 2, June, 83–90
The need for cost-effective maintenance strategies for highway bridges is becoming increasingly important as these structures age and the demands for funding expand. Shortfalls in the annual budget to complete all the identified work also requires that rational procedures be formulated regarding when maintenance work on different structures within a stock should take place. Two main types of maintenance are considered: steady state and essential. The concept of an optimal maintenance programme is introduced. In most cases this is the ideal situation since it minimises long-term costs and disruption to users of the structures. In practice, optimal maintenance strategies may not be affordable when first introduced if there is a backlog of work resulting in a need to prioritise parts of the work. Prioritisation is discussed in terms of quantifying the consequences of deferring maintenance work, and ranking the bridges in the stock by their value of cost: benefit ratio of deferring the work. The use of a long-term plan to eliminate maintenance backlogs that arise from long-term underfunding is explained and the ‘long-term plan formula’ is introduced. A flow chart is provided to prioritise the maintenance on bridges included in a long-term plan.
Briefing: Restoration of Bersted Crossing footbridge, Bognor Regis, UK
A. Macfarlane
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 3, September, 93–95
Bersted Crossing footbridge is a good example of a wrought iron, lattice girder railway structure from the end of the Victorian era. The poor aesthetic condition of the bridge led to public perception that it required replacement. A sympathetic restoration scheme taking into account the unmodified nature of the wrought iron was shown to be economical and was carried with no disruption to train services. The work received a commendation as part of the 2005 Historic Bridge and Infrastructure awards. This briefing article describes the background to the structure and the work that took place to restore it.
Load-carrying capacity of flooded masonry arch bridges
K. M. Hulet, C. C. Smith and M. Gilbert
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 3, September, 97–101
Many existing codes of practice for masonry arch bridge assessment fail to provide engineers with adequate guidance on the adverse effects that saturated environmental or flood conditions are likely to have on load-carrying capacity. Analysis indicates that the load-carrying capacity of a fully flooded arch bridge backfilled with cohesionless fill could typically be reduced by a factor of 1$6–1$8, or even more in specific circumstances. The significant influence of flooding on load-carrying capacity has now been verified using small-scale experiments which are described in the paper. The effects of flooding on waterproofed and unwaterproofed bridges are also analysed numerically and the circumstances under which capacity reductions are likely to be highest are identified. This paper should be useful to engineers dealing with bridges which are at risk of flooding.
Analytical fatigue assessment of riveted rail bridges
B. Imam, T. D. Righiniotis, M. K. Chryssanthopoulos and B. Bell
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 3, September, 105–116
As some of the older riveted railway bridges are close to or have even exceeded their theoretical fatigue lives, it is desirable to develop a comprehensive fatigue assessment methodology for fatigue-critical details. The aim of this study was to present damage and fatigue life estimates for the riveted connections of a typical riveted UK railway bridge through finite-element analyses. In particular, the effect of connection fixity and assumed fatigue detail classification, the effect of the simultaneous passage of two trains over the bridge, the effect of a reduced Young's modulus for the bridge material and the effect of dynamic amplification are studied under different loading scenarios. A historical load model was developed in order to represent bridge rail traffic between 1900 and 1970. The BS 5400 medium traffic trains were used to represent the bridge traffic from 1970 onwards. It was found that the connection damage is axle-dominated and is affected by the parameters mentioned above. The fully-fixed stringer-to-cross-girder connections were found to be the most fatigue-critical details. The damage accumulation rate was found to be small in the pre-1970 period under the historical load model but showed a considerable increase with the introduction of the BS 5400 trains (post-1970).
Developments in the use of GPS for bridge monitoring
C. J. Brown, G. W. Roberts and X. Meng
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 3, September, 117–119
This paper informs engineers about the role and potential use of the global positioning system (GPS) in monitoring large structures, particularly bridges. It gives the briefest introduction to GPS and its different applications. GPS technology for the investigation of structures is described, along with some of the trials that have recently been completed. Outstanding issues for future research are identified.
Innovations in concrete arch bridge design
J. Radić, Z. Šavor and A. Kindij
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 3, September, 121–126
Innovation in the design and construction of large-span arch bridges was investigated by considering buildability, maintainability and durability factors and their interaction at the design stage in terms of their effects on quality of construction and whole-life costs. In this study the utilisation of innovative composite arch ribs was examined and comparisons were made with concrete and steel arch ribs. A parametric study of a new composite arch rib was performed for a two-hinged arch in the span range 300–1000 m. The arch cross-section comprised three steel trusses interconnected by concrete slabs in composite action with the top and bottom truss chords. The results appeared promising for the span range 300–600 m in comparison with the steel arch and therefore the composite arch rib was tested in a new Croatian arch bridge carrying the highway over the Krka river. The fixed arch has a 204 m span and a rise of 52·0 m with a rise-to-span ratio of f/l = 0·25.
Structural repair of elevated Harrow Road (westbound), UK
D. Yeoell, T. Parasram and B. Hodgkinson
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 3, September, 127–135
This paper provides a review of the structural problems regarding repair and refurbishment of the Elevated Harrow Road (westbound). The step-by-step approach taken to investigate the causes of the defects and for the development of the successful repair strategy is examined. The problems faced by the city council, consultant and contractor leading to the adopted solutions, culminated in the successful delivery of a complex repair to a concrete structure which supports one of the key highway routes out of central London.
Design and construction of two launched bridges
N. Beavor and J. Cai
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 3, September, 137–145
The 194 m long A500 railway bridge and the 63 m long New Relley bridge are both steel concrete composite bridges constructed using longitudinal launching with the concrete deck slab cast prior to the launch. This paper describes the design and construction of the two bridges and contrasts the different launching techniques used. The reasons for launching as opposed to conventional crane erection are explained, as are the design and fabrication details required. Information is given on the contract and planning framework for both schemes. The A500 railway bridge, passing over a total of 14 overhead electrified tracks, is believed to be the first example in the UK of a major steel–concrete composite bridge launched with the concrete deck in place. Both launches were successfully completed within tight railway possession periods. The safety advantages of having the permanent vehicle parapets in place directly after the deck installation are emphasised. This form of construction has proved itself to be effective for road-over-rail bridges where only short track possession periods are available and also where headroom constraints hinder normal crane operations.
Briefing: Eurocodes implementation for highway bridges in the UK
S. Chakrabarti and S. Garden
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 4, December, 149–151
The implementation of structural Eurocodes is the biggest ever change to codified structural design in the UK. The new standards will replace British Standards for structural design, and will be implemented by the Highways Agency (‘the Agency’) for bridge design over the next four years. The Agency is committed to using Eurocodes for the design of all highway structures and will introduce the Eurocodes for all new procurement at an appropriate time after the respective UK National Annexes are published. This briefing note discusses the implementation aspects in more detail, outlining the Agency's Eurocodes strategy. This includes the effects on the Design Manual for Roads and Bridges and the design studies that have been carried out to ensure highway bridges continue to be designed safely and economically following implementation of the Eurocodes.
GPS measurements on the London Millennium Bridge
G. W. Roberts, X. Meng, C. J. Brown and P. Dallard
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 4, December, 153–161
Trials conducted on the London Millennium Footbridge in 2000 monitored movements using three GPS receivers. After initial processing, the results gave plausible vertical and lateral (sideways) displacements, but also described implausible longitudinal movements along the axis of the bridge. Digital signal processing techniques applied to the data are reported. Due to the satellite constellation in the UK, a large void exists from the zenith to the horizon in a northerly direction. This lack of GPS satellites results in poor satellite geometry in the north-south direction, and hence poor north-south precision, explaining the unsatisfactory element of the Millennium Bridge results. More importantly a technique to overcome the issues is described. Notwithstanding this, the lateral vibration frequencies obtained from the GPS data agree extremely well with those found in the modal surveys carried out by Arup, even when displacement amplitudes are small.
An environmental comparison of bridge forms
D. Collings
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 4, December, 163–168
The embodied energy and carbon dioxide emissions from the use of construction materials are among the concerns engineers must consider when planning, designing and constructing a bridge. Previous studies have been carried out on building structures to assess both the energy consumed and the CO2 emissions in their construction and use but less information is available to bridge designers. This paper outlines the range of embodied energy and CO2 emissions for materials commonly used in bridges and the variability of these values is discussed. A study is carried out for a moderate length river bridge of energy use and CO2 emission during construction. A number of different bridge forms and materials are considered. The primary forms are girder, tied arch and cable stayed. Three broad material groups were investigated, namely concrete, steel and steel–concrete composite. The study also estimates the continuing CO2 emission throughout the life of the structure from maintenance and repairs. From the study a number of broad trends are discussed and some design guidance offered for those wishing to provide more environmentally responsible bridges
Recent concrete, self-anchored suspension bridges in China
Z. Zhang, Q.-J. Teng and W.-L. Qiu
Proceedings of the Institution of Civil Engineers, Bridge Engineering, 159, No. 4, December, 169–177
The self-anchored suspension bridge provides a competitive solution for bridges with short or moderate spans. This paper introduces some key techniques used in three concrete, self-anchored suspension bridges in China: GoldenBay Bridge, LanQi Bridge and WanXin Bridge. GoldenBay Bridge was the first concrete selfanchored suspension bridge in China. WanXin Bridge has a main span of 160 m. The appropriate structural forms were designed to take account of their different geographic positions, surrounding environments and functions. In the WanXin Bridge, two sliding saddles and one fixed saddle are set at each end of the main girder. The cables are made of a continuous galvanised steel rope passing over all saddles, and the two main cables form a closed loop. It was the first time that the practice of using a looped main cable had been utilised in China. Currently, the WanXin Bridge has the longest span of all concrete, self-anchored suspension bridges in the world. The final part of the paper describes the model investigation, developed to understand the basic structural behaviour of the WanXin Bridge.
Briefing: Steel buildings remain cheaper than concrete
S. Rawlinson
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 1, February, 5
Steel-framed buildings are still cheaper than concrete-framed equivalents despite recent hikes in steel costs—and substantially cheaper than two decades ago. Simon Rawlinson of Davis Langdon reports on the results of a recent comparative design project.
Briefing: Design change: new software makes it easy
J. Strongitharm
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 1, February, 6
Civil engineering design is usually a slow and iterative process, often involving extensive changes to suit many stakeholders. Parametric three-dimensional model-based software could make things lot quicker, according to Jack Strongitharm of Autodesk.
The Deep, Hull: urban regeneration with attitude
Martin Finlay
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 1, February, 16–23
Success of Lottery-funded visitor attractions on derelict UK sites is also a bit of a lottery. However, if you combine stunning architectural design with outstanding engineering and then fill the whole thing with sharks, you have a winning ticket. The Deep oceanic experience centre was built on a former shipyard site at the point where the Hull and Humber rivers meet in northeast England. Since the £53 million attraction first opened in 2002, visitor numbers are running at more than double the amount anticipated. As this paper reports, designing and building its main 10 m deep, 3000 t aquarium tank were just some of the many engineering challenges on what is now widely regarded as a benchmark regeneration project.
On the ropes: civil engineers get closer to rail bridges
Chris James
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 1, February, 24–31
Bridges and viaducts are an essential part of transport infrastructure, particularly on railway networks where the variety of structural type, size and age usually exceeds that of the highway network. Inspection and examination form a large part of the management of these structures, which are often high and in remote locations. This paper details how rope access techniques are being increasingly used for the inspection of such structures in the UK and argues the benefits for more civil engineers to be trained in rope-access work.
Lessons learned from tsunami damage in Sri Lanka
P. Dias, R. Dissanayake and R. Chandratilake
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 2, May, 74–81
Around 300 000 people were killed by the tsunami that followed the Sumatra–Andaman earthquake on Boxing Day 2004, making it one of the worst disasters in modern history. Up to 40 000 died in Sri Lanka alone, where around 80 000 houses were also destroyed when waves up to 15 m high swept ashore. This paper reports on how coastal buildings and infrastructure in Sri Lanka behaved under various tsunami wave heights and the many lessons learned for reducing vulnerability to future events. In particular, newly published national guidelines for reconstruction emphasise the importance of tying down structures against upward and lateral loads as well as the need to anticipate and reduce soil scour around foundations, especially of backfilled earth.
Union Chain Bridge: linking engineering
G. Miller
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 2, May, 88–95
Civil and marine engineering have long been linked, but perhaps no more symbolically than by the Union Chain Bridge between Scotland and England over the River Tweed. It was built 186 years ago by Sir Samuel Brown, who made the transition from Royal Navy captain to designer of the world's longest iron suspension bridge in one single leap. This paper reports on his remarkable eight-year journey, from leaving the Royal Navy in 1812 to start an anchor-chain business to building the record-breaking Union Chain Bridge in 1820. He went on to design the Brighton Chain Pier and supply Isambard Kingdom Brunel with chains for his Great Eastern steamship, while his company remained the navy's sole chain supplier for over a century. Union Chain Bridge, which still carries road traffic today, thus serves as an inspiration to all engineers of the benefits of cross-disciplinary thinking.
Briefing: Three quarters of Eurocodes now published
H. Gulvanessian
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 3, August, 99
Eurocodes are now 75% completed and well on their way to becoming the world's new structural design standards. Haig Gulvanessian, chairman of the UK's pan-industry Eurocodes Expert advisory group, provides an update.
How Athens' Olympic stadium was finally pulled together
F. Siriani and M. Di Silverio
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 3, August, 114–119
Completing the dramatic 18 500 t main stadium roof for the 2004 Athens Olympics was tension engineering in every sense. The 304 m long, 80 m high cable-stayed steel and polycarbonate roof designed by Santiago Calatrava was literally pulled together at the last minute, just as it was on the verge of being abandoned. This paper describes how the two sinuous halves of the roof were built 70 m away from each side of the existing 20-year-old stadium, using a series of strand-jack towers, and then how they were drawn together using a strand-free pulling system devised at the eleventh hour. The final pull was completed on 6 June, just four days before the first test events. It is a timely reminder of the huge challenges that engineers invariably have to overcome in delivering monumental sporting arenas on time.
Jane Coston Cycle bridge: a model for managing vibration
M. Black and G. Webster
Proceedings of the Institution of Civil Engineers, Civil Engineering, 159, No. 3, August, 120–125
The growing popularity of long-span slender footbridges, as key elements in schemes to encourage greater walking and cycling, has required design engineers to look much more closely at dynamic behaviour. Following high-profile problems with the London Millennium Bridge and Passerelle Solferino in Paris, designers of the 77 m span Jane Coston bridge in Cambridge studied dynamic effects of pedestrians particularly carefully. The study established the specific requirements for the structure and also a new general approach for future footbridge design. It suggests that slender footbridges can be designed for static loading, and that dynamic effects can be cost-effectively accommodated by making provision for possible damper installation after completion.
Briefing: Stress-lamination: utilising low-grade timber in construction
G. Freedman and A. Kermani
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 1, February, 7–10
Stress lamination of timber, as an engineering concept, has a useful future in construction, and should provide many opportunities to utilise UK timber—a readily available lightweight material, excellent in compression yet good in bending. That combination will particularly encourage its use.
Joining timber with glass fibre and epoxy
P. Claisse and B. Masse
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 1, February, 11–17
Wood–glass–epoxy joints are made by wetting glass fibre cloth with epoxy resin and bonding it to the sides of the timbers. They represent an economic alternative to punched metal plates or bolts in a variety of applications, including those where high durability, waterproofing or an attractive appearance are required. They may also be used to enhance the properties of the timber members themselves. Previously published work has shown that these joints perform well in fatigue. This paper presents test results for strength and stiffness for various different joint configurations with the timbers parallel and at 308, 608 and 908 to each other. The results indicated that uniaxial glass cloth performs better than biaxial glass cloth in all joints. Misaligning the glass with the direction of loading has a significant detrimental effect on performance. For the non-parallel joints the unavoidable effect of loading at an angle to the grain reduced both the failure loads and the stiffness.
A fracture-based model for the compressive strength of masonry
T. M. Roberts and T. G. Hughes
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 1, February, 19–22
A mechanical model for explaining and quantifying the uniaxial compressive strength of masonry has been developed. The mechanical model is based on the development of tensile cracks from shear plane flaws in the units and the stress intensity factor resulting from the applied loading and tensile stresses induced by lateral straining of the mortar. Calibration of the model requires knowledge of only the compressive strength of the units, and the corresponding compressive strength of the masonry for a single mortar compressive strength. Theoretical predictions are compared and show close correlation with characteristic compressive strengths given in codes of practice.
Development of bitumen-bound waste aggregate building blocks
J.-P. Forth, S. E. Zoorob and I. N. A. Thanaya
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 1, February, 23–32
The paper describes the optimisation of several mixes for the development of a new range of construction units (Bitublock) composed entirely of recycled and waste aggregates. The development of this new range of building units is driven by the issue of sustainability, both nationally and globally, and this complete replacement of traditional aggregates is possible because Bitublock uses bitumen as the binder. Five main waste materials are considered in this optimisation: crushed glass, pulverised fuel ash (PFA), incinerated bottom ash (IBA), incinerated sewage sludge ash (ISSA) and steel slag. In addition two types of bitumen were also considered: 50 penetration bitumen and harder H 80/90 bitumen. Several properties of the Bitublock were measured to assess their performance in relation to concrete block masonry products found in the UK. These were: shape, density, water absorption, compressive strength, elastic modulus and time-dependent properties. It is shown that all these properties are dependent onthe types of aggregate and the binder used, as well as on the compaction pressure and the curing regime. It is clear that Bitublock can be produced with properties that are at least equivalent to those of current concrete block masonry units. The long-term stability of Bitublock is significant in terms of construction, because its use could negate the need for—or at least reduce the frequency of—required movement joints in masonry.
Estimating concrete strength using a modified maturity model
Y. A. Abdel-Jawad
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 1, February, 33–37
The maturity concept has been widely used for decades as a proper approach for estimating the in situ strength of concrete at different ages and at different curing temperatures. Various maturity models and equations have been developed and proposed in the last three decades to be used in estimating the strength of concrete cured at different temperatures. Most of the developed models estimate the strength of concrete at early ages reasonably well, but fail to estimate the strength at later ages with the same accuracy. In this paper a general review of the development of the maturity concept is presented, showing the drawbacks of the present models. A modified maturity model is presented and validated using collected experimental data available in the literature. The model shows that a better estimation of concrete strength at later ages is achievable.
Briefing: Aircrete
C. A. Fudge and M. C. Limbachiya
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 2, May, 49–51
Aircrete, also known as autoclaved aerated concrete (AAC), was first produced in the UK in the 1950s. It is one of the lightest forms of concrete, and one of the most technically advanced materials used for the manufacture of mass-produced concrete blocks. It is manufactured in a range of densities from 400 to 800 kg/m3, making it considerably lighter than conventional aggregate concrete. Approximately 3 000 000 m3 of aircrete masonry units are now produced in the UK annually, representing about a third of all concrete masonry. The main benefit is that acoustic, energy conservation, fire resistance and structural properties are provided in one product. This briefing note explains the manufacture, design and application of aircrete masonry units. Innovative methods of construction have also been made possible as a result of modern manufacturing techniques, such as thin-layer mortar jointing and blocks with handholds in the block perpends.
Performance of helically shaped metal fasteners in timber
G. Coste, A. Kermani and A. Porteous
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 2, May, 53–60
This paper presents an experimental investigation into the withdrawal resistance of a new connector type for use in structural timber. The structural performance of several helically shaped metal fasteners, which for some years have been used as wall ties and in masonry repairs, are investigated for use in a variety of timber connection systems. This paper describes part of a research programme investigating the withdrawal resistance and behaviour of these fasteners compared with conventional nails. It also details the effects of predrilling, density of timber, depth of penetration and timber grain orientation on the withdrawal resistance of these fasteners. The results show that helically shaped metal connectors achieve greater withdrawal resistance and exhibit a more ductile behaviour than common nails. A semi-empirical model is developed to predict the withdrawal performance of the fasteners.
Composite model for basic creep of high-strength concrete
S. Setunge and J. Anaton
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 2, May, 77–84
Most of the reported work on creep of high-strength concrete (HSC) covers measurements of total creep on standard specimens kept in a standard environment of 50% relative humidity and 23°C. The results of these studies are used to establish the basic creep factor of high-strength concrete, assuming that the environmental effect on creep of HSC is similar to that for normal strength concrete (NSC). However, some recent work has shown that the effect of the environment on creep of HSC is different from that observed for NSC, which indicates that a realistic creep model for HSC needs to be developed based on more fundamental material behaviour. This paper reports a theoretical study of a composite model for predicting basic creep of concrete, considering it as a composite material of coarse aggregate, fine aggregate and cement paste. The model is based on the age-adjusted effective modulus method proposed by Bazant, and can take into account the composition of the concrete, the degree of compaction and the hydration of cement paste. The model is shown to predict basic creep measurements reported in the literature with reasonable accuracy.
Behaviour of interlocking mortarless block masonry
M. S. Jaafar, A. H. Alwathaf, W. A. M. Thanoon, J. Noorzaei and M. R. Abdulkadir
Proceedings of the Institution of Civil Engineers, Construction Materials, 159, No. 3, August, 111–117
Various types of interlocking mortarless (dry-stacked) block masonry system have been developed worldwide. However, the characteristics of dry joints under compressive load, and their effect on the overall behaviour of the interlocking mortarless system, are still not well understood. This paper presents an experimental investigation into the dry-joint contact behaviour of masonry and the behaviour of interlocking mortarless hollow blocks for grouted and ungrouted prisms under compression. Two experimental test set-ups are proposed to evaluate the contact behaviour of dry joints, considering the geometric imperfections in the contacting faces. The results show that the contact behaviour of a dry joint is highly affected by geometric imperfections in the block bed. Different patterns of deformation are distinguished in mortarless hollow (ungrouted) and grouted prisms. Dry joints predominantly affected the hollow prism deformation until the compressive load reaches 0$57 of the maximum load. However, this behaviour is not common in grouted prisms, because noticeable deformation commences after 0.38 of the maximum load. Furthermore, the variations of strength and deformation in grouted specimens are diminished compared with those in ungrouted specimens.
Foundation design for a large arch bridge on alluvial soils
J. Monnet, D. Allagnat, J. Teston, P. Billet and F. Baguelin
Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, 159, No. 1, January, 19–28
The Crozet bridge is located on the Grenoble–Col du Fau motorway, on the Grenoble–Sisteron route, 15 km south of Grenoble, France. It crosses a 350 m wide valley and the RN75 national road. The adaptation of the bridge into the landscape has involved an arch design with three bays (in the Grenoble–Sisteron direction) and one bay (in the Sisteron–Grenoble direction). The supports of the structure were difficult to build because of the huge horizontal force and the low displacement tolerance. The low stiffness and strength characteristics foreseen led to a geotechnical investigation by cyclic pressuremeter tests with a friction angle and cohesion interpretation. The foundation calculations were carried out by a finite element calculation using the CESAR-LCPC program to determine the support rigidity. The complete computation of the bridge was done with the calculated support rigidity, which showed that displacements of the arches were lower than the tolerance. The bridge is located in a low seismic area of France, and the design takes into account the maximum foreseeable magnitude, and analysis of the soil liquefaction risk. Monitoring carried out for completion of the bridge in 1999 and along the surveying shows displacements lower than tolerance values. Since 1999, the bridge has withstood huge service weights without any difficulty.
Eurocode design of underground metro structures
D. R. Beadman
Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, 159, No. 1, January, 29–33
Eurocodes were used for the design of a new metro, for which the contractor's design was undertaken largely between 1996 and 1999, when the Eurocodes were in their infancy. This paper discusses the experience, the difficulties encountered and the benefits gained by the project, with particular reference to the geotechnical design of the underground stations. Eurocodes 1, 2 and 7 were used for the design of the retaining walls for the deep stations. Two design parameters created challenges for the structural design of the reinforced concrete embedded retaining walls: a restriction on the maximum allowable crack width, and a large cover to the reinforcement, required by the construction method. Benefits were gained by using the observational method.
Design of braced excavations to limit ground movements
A. S. Osman and M. D. Bolton
Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, 159, No. 3, July, 167–175
The authors have developed a new approach to the estimation of ground movements around braced excavations retaining thick deposits of soft clay, incorporating actual stress–strain data and the undrained shear strength profile of the soil on site. The method is based on the assumption of a plastic deformation mechanism local to a braced excavation, and which avoids any slippage on shear surfaces. Mobilised shear stresses beneath and around the face are found from an equilibrium calculation derived from the deformation mechanism by virtual work. The strains required to mobilise these stresses are finally entered into the deformation mechanism to predict boundary displacements. The outcome is a prediction based on simple calculations that otherwise would have called for elaborate constitutive modelling and finite element analysis. The capability of this mobilisable strength design (MSD) method in calculating the magnitude of wall displacements is demonstrated through the back analysis of a previously published case history of a braced excavation at a soft clay site in Singapore. The relative effectiveness of heave-reducing piles in controlling ground movements is then demonstrated using the MSD method.
Piled foundations for Eureka Tower, Melbourne, Australia
M. C. Ervin and J. E. Finlayson
Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, 159, No. 3, July, 187–194
The Eureka Tower project in Melbourne is a 92 level (300 m high) residential development. The geology of the site is complex. Bored piled foundations were recommended, requiring socketing into very-high strength basalt or high-strength siltstone. For the piles proposed to be socketed into the basalt, the successful piling contractor proposed the alternative of continuous flight auger (CFA) piles bearing directly on to the basalt rock. The design bearing stresses for both these CFA piles and the bored piles in siltstone exceeded previously adopted values in Melbourne. Statnamic and dynamic testing was performed on the CFA piles. For the bored piles an extensive investigation programme provided confidence in the socket design, with the assumed conditions verified during construction. This paper was first published in the BGA International Conference on Foundations, University of Dundee, 2003. It has been revised and expanded slightly to cover construction aspects of the project.
Building a deep isolating wall by an existing rail tunnel
C. Molins and A. Ledesma
Proceedings of the Institution of Civil Engineers, Geotechnical Engineering, 159, No. 3, July, 219–226
This paper describes the design, construction and early performance of a retaining structure close to a subway tunnel in Barcelona. The excavation, about 16 m deep, was carried out in 2001 during the construction of a new hospital, and involved a rectangular area with the longer side (170 m) almost parallel to the tunnel. The design had to fulfil two requirements: first, the influence of the excavation on the existing tunnel had to be minimised; and, second, the new hospital had to be isolated from vibrations from the subway owing to the high sensitivity of the medical instruments. In order to achieve this, the retaining wall was designed to be independent of the main building, and movements during the excavation stages had to be controlled. In addition, the use of subhorizontal anchors was not allowed by the metro administration, and therefore the wall comprised a line of T-shaped panels linked to shorter intermediate panels excavated using a hydromill. The stability of the wall and bending resistance were provided by the buttressing effect of the forward-facing T and the compression in the panels and anchoring force provided by post-tensioning anchors drilled into the underlying bedrock through ducts installed in the rear section of the T panels. The wall was designed using a beam–spring model with ground parameters derived from in situ tests, and the interaction between the excavation and the tunnel was modelled using a plane-strain finite element analysis imposing the wall displacements on the section. Monitoring of the wall and the tunnel confirmed that the influence of the work on the neighbouring tunnel was negligible.
Rehabilitation of a sea wall in Mandal, Norway
A. E. Lothe and T. Birkeland
Proceedings of the Institution of Civil Engineers, Maritime Engineering, 159, No. 3, September, 113–120
Gismerøy is a small island close to the city of Mandal on the south coast of Norway. The site has been selected for industrial development. An industrial estate was developed close to the sea with no particular attention to protection. The landfill and a factory building were nearly completely destroyed by two consecutive storms in May and October 2000. After the second storm, detailed studies and model tests were carried out to specify a reliable and safe design. The new design was based on a berm breakwater principle, but with some important local adaptations. It was also discovered that the wave runup due to a rock formation was so great that the rock would have to be removed. This work was especially challenging because there was a strong wish to preserve the infrastructure and investments that had already been laid down, and because the areas adjacent to the site are designated as natural recreational areas.
Specifying seawall crest levels using a probabilistic method
M. T. Reis, T. S. Hedges, A. Williams and K. Keating
Proceedings of the Institution of Civil Engineers, Maritime Engineering, 159, No. 4, December, 137–145
Probabilistic methods provide a powerful framework for the design of coastal defences. However, present knowledge of the behaviour of these structures is insufficient to permit a full assessment of their safety. It is possible to assess their safety against specific types of failure, such as excessive overtopping by wave action. However, the choice of overtopping model used to describe the failure is crucial to the outcome of the assessment. The paper illustrates the different results obtained from two models used to describe wave overtopping. The models are implemented in a software package known as PARASODE-BALI which employs the Level II First Order Reliability Method (FORM) for the design and safety assessment of coastal structures. For large overtopping discharges relevant to structural safety, the two overtopping models provide similar results. However, the differences are much greater for the small discharges commonly required to ensure the safety of people and property in urban areas.
