Sustainable bridge construction through innovative advances

Sustainability is now recognised as a key issue that must be addressed in the design, construction and lifelong maintenance of civil engineering structures. This paper briefly discusses the generic aspects of sustainability, but the main focus is its application to bridges. Motorway bridges built in the 1960s and 1970s had design lives of 120 years; many, however, were showing signs of deterioration after only 20–40 years. This led to much (ongoing) debate on the issue of initial versus full life-cycle costing. In order to address the highly complex issue of the sustainability of bridges, this paper considers the following specific areas that impinge on this important subject: the impact on sustainability of different forms of bridge construction and maintenance/repair/replacement strategies; the utilisation of innovative in situ testing equipment for assessing the long-term durability of concrete; the development of innovative structural designs for bridges that inherently have greatly extended lives at minimal, if any, additional cost.

Estimating propeller scour at quays alongside a berthing ship.

This paper presents the findings from a experimental investigation in to the nature and extent of the scouring that occurs when a ship berths alongside a quay wall within the confines of a harbour. It examines the interaction between the relative position of the quay wall to the central axis of the ship and the influence that angle of the vessel’s rudder on the magnitude of the scouring produced. The experimental programme covered a range of sediment sizes and methods for calculating the depth of expected scour are presented both in terms semi empirical equations and through the use of trained artificial neural networks. This paper has been selected by the ICE publishing as one of their Best in Research and Practice papers. ICE Martime Engineering is the forefront UK publication for Civil Engineers working in this area.

Pre-treatment with Depo-Provera modifies the pharmacokinetics of CMPD167 in rhesus macaques following vaginal ring administration

BACKGROUND: Vaginal ring devices are being developed to provide sustained release of HIV microbicides. To date, only limited pharmacokinetic data is available from animal or human studies. Here we report the effect of Depo-Provera (DP) pre- treatment, commonly used to thin the vaginal epithelium in challenge experiments, on the pharmacokinetic profile of CMPD167 (a small molecule CCR5 co-receptor antagonist) in rhesus macaques following vaginal ring administration.

METHODS: A single 400mg CMPD167 silicone elastomer vaginal ring was inserted into each of twelve female rhesus macaques. Six macaques were treated with (DP) 30 days before ring placement; the other six macaques were untreated. Blood, vaginal fluid and vaginal biopsies were collected prior to and at various times during 28 days of ring placement and assayed for CMPD167 levels by HPLC. Rings were assayed for residual CMPD167 at the end of the study and the calculated amount of CMPD167 released in vivo compared with in vitro release data.

RESULTS: Vaginal fluid, plasma and tissue levels of CMPD167 were detectable throughout ring placement. Significant differences were observed in mean daily vaginal fluid levels between the DP-treated (16–56 mcg/mL) and untreated groups (48–181 mcg/mL). Plasma CMPD167 levels were significantly higher peaking at 4 ng/mL and maintaining levels of 1–2 nM throughout the 14 days of testing in animals pre-treated with DP compared to non DP-treated macaques (<1 ng/mL maintained). Tissue levels were varied between 2–10 g/mL CMPD167 with no significant difference between the DP-treated and untreated macaques.

CONCLUSIONS: The study demonstrates that clinically relevant, and possibly protective doses of CMPD167 are released in the vaginal vault of rhesus macaques from vaginal rings through 28 days duration. DP is known to induce vaginal epithelial thinning and lower vaginal fluid levels, which accounts for the increased plasma levels of CMPD167. In contrast, macaques not treated with DP had minimal absorption into plasma compartments and significantly higher levels of CMPD167 in the vagina, similar to those previously shown to be protective against vaginal challenge.

Experimental observations of the stress regime in unsaturated compacted clay when laterally confined

Construction processes often involve reformation of the landscape, which will inevitably encompass compaction of artificially placed soils. A common application of fill materials is their use as backfill in many engineering applications, for example behind a retaining wall. The post-construction behaviour of clay fills is complex with respect to stresses and deformation when the fills become saturated over time. Heavily compacted fills swells significantly more than the lightly compacted fills. This will produce enhanced lateral stresses if the fill is laterally restrained. The work presented in this paper examines how the stress regime in unsaturated clay fills changes with wetting under laterally restrained conditions. Specimens of compacted kaolin, with different initial conditions, were wetted to various values of suction under zero lateral strain at constant net overburden pressure which allowed the concept of K _{0 (the ratio between the net horizontal stress and the net vertical stress) to be examined. Tests were also carried out to examine the traditional concept of the earth pressure coefficient ‘at rest' under loading and unloading and its likely effects on the stress–strain properties. The results have shown that the stress regime (i.e. the lateral stress) changes significantly during wetting under laterally restrained conditions. The magnitude of the change is affected by the initial condition of the soil. The results have also indicated that the earth pressure coefficient ‘at rest' during loading (under the normally consolidated condition) is unaffected by suction and such loading conditions inevitably lead to the development of anisotropic stress–strain properties}

The settlement performance of stone column foundations

Vibrated stone columns are frequently used as a method of reinforcing soft ground as they provide increased bearing capacity and reduce foundation settlements. Their performance in relation to bearing capacity is well documented, but there is also a need for enhanced understanding of their settlement characteristics, particularly in relation to small-group configurations. This paper presents results obtained from physical model tests on triaxial specimens 300 mm in diameter and 400 mm high. Parameters investigated include column length to diameter ratio, area replacement ratio and single/group configuration. The findings of the work are as follows. The design is flexible: settlement can equally be controlled using short columns at relatively high area replacement ratios, or longer columns at smaller area replacement ratios. An optimum area replacement ratio of 30-40% exists for the control of settlement. The settlement performance of a small column group is highly influenced by inter-column and footing interaction effects.

Track displacement and energy loss in a railway embankment

The mainline railway track between Dublin and Belfast was constructed during the 1850s, with substantial lengths of railway embankment constructed over soft, peaty soils. In recent years Northern Ireland Railways (NIR) has noticed that the sections of the railway track constructed on these peaty soils have been deteriorating at an increasing rate. Train speeds have been reduced in response to concerns that cyclic track displacements appear to be increasing over time in response to train loading. Track maintenance has also increased significantly. The research described in this paper was undertaken to quantify the response to cyclic train loading of two portions of this track founded on peaty soils. Track displacements were recorded using a sensor system specifically created for this project. The sensor consisted of a photosensitive array, mounted on the sleepers, and a laser, which was targeted onto the photosensitive array from a location outside the area of influence of train loading. Track deflections from 5 to 20 mm were measured under train speeds from near zero to over 120 km/h. The temporal variation in track displacement was used to calibrate an analytical (Winkler) model. This analysis suggests that the deformation of the embankment under train loading was not due to dynamic excitation but rather to static deformation of the poor-quality fill and soft foundation materials. As a consequence, the analytical model highlighted that train speed has limited effect on the magnitude of the deflection of the embankment within NIR operating speeds, but has the potential to significantly reduce the power lost to the damping within the embankment and subgrade.

The pressure distribution along stone columns in soft clay under consolidation and foundation loading

The mechanism whereby foundation loading is transmitted through the column has received little attention from researchers. This paper reports on some interesting findings obtained from a laboratory-based model study in respect of this issue. The model tests were carried out on samples of soft clay, 300 mm in diameter and 400 mm high. The samples were reinforced with fully penetrating stone columns, of three different diameters, made of crushed basalt. Four pressure cells were located along each stone column. The 60 mm diameter footing used in the model was supported on a clay bed reinforced with a stone column and subjected to foundation loading under drained conditions. The results show that the dissipation of excess pore water pressure developed during the initial application of total stresses, when the foundation was subjected to no loading, generated considerable stresses within the column, and that this was directly attributable to the development of negative skin friction. The pressure distributions in the column during foundation loading showed some complex behaviour.

Rapid construction of arch bridges using the innovative FlexiArch

Masonry arches are strong, durable, aesthetically pleasing and largely maintenance free, yet since 1900 there has been a dramatic decline in their use. However, designers, contractors and clients now have access to a new method of constructing arches incorporating precast concrete voussoirs interconnected via polymeric reinforcement and a concrete screed. No centring is necessary, as the FlexiArch, when it is lifted, transforms under the forces of gravity into the desired arch shape. After discussing general aspects of innovation, the basic concept of the arch bridge system is presented along with technological advances since it was patented. Experiences gained from building over 40 FlexiArch bridges in the UK and Ireland and from model and full-scale tests carried out to validate the system during installation and in service are described. Thus under load the system behaves like a traditional masonry arch and existing analysis methods can be used for design and assessment.

Effect of Bauxol on properties of cement pastes

This paper presents the results of an experimental investigation carried out to evaluate the influence of Bauxsol, an artificially neutralised bauxite refinery residue (NBRR), on various properties of cement pastes. It was found that the NBRR does not have any pozzolanic properties and hence cannot be used as a supplementary cementitious material in concrete. In order to evaluate the effect of adding the product to Portland cement (PC) pastes, fresh properties (i.e. standard consistency and slump), setting time and heat of hydration were measured. In addition, its influence on chemical changes and compressive strength was investigated. It was found that the addition of this NBRR resulted in a decrease in compressive strength beyond 7 days. The setting time decreased with an increase in NBRR content in PC pastes. The rate of heat evolution for NBRR pastes was greater than that of the PC pastes, but a corresponding increase in the quantity of calcium hydroxide was not found. Therefore, it was concluded that unidentified hydration products when Bauxsol was used in PC pastes might have been the reason for the decrease in setting times.

Development and clinical validation of multiplex TaqMan® assays for rapid diagnosis of viral gastroenteritis.

There is a need to provide rapid, sensitive, and often high throughput detection of pathogens in diagnostic virology. Viral gastroenteritis is a serious health issue often leading to hospitalization in the young, the immunocompromised and the elderly. The common causes of viral gastroenteritis include rotavirus, norovirus (genogroups I and II), astrovirus, and group F adenoviruses (serotypes 40 and 41). This article describes the work-up of two internally controlled multiplex, probe-based PCR assays and reports on the clinical validation over a 3-year period, March 2007 to February 2010. Multiplex assays were developed using a combination of TaqMan™ and minor groove binder (MGB™) hydrolysis probes. The assays were validated using a panel of 137 specimens, previously positive via a nested gel-based assay. The assays had improved sensitivity for adenovirus, rotavirus, and norovirus (97.3% vs. 86.1%, 100% vs. 87.8%, and 95.1% vs. 79.5%, respectively) and also more specific for targets adenovirus, rotavirus, and norovirus (99% vs. 95.2%, 100% vs. 93.6%, and 97.9% vs. 92.3%, respectively). For the specimens tested, both assays had equal sensitivity and specificity for astrovirus (100%). Overall the probe-based assays detected 16 more positive specimens than the nested gel-based assay. Post-introduction to the routine diagnostic service, a total of 9,846 specimens were processed with multiplex 1 and 2 (7,053 pediatric, 2,793 adult) over the 3-year study period. This clinically validated, probe-based multiplex testing algorithm allows highly sensitive and timely diagnosis of the four most prominent causes of viral gastroenteritis.

Monitoring and repair of an impact damaged prestressed bridge

This paper details the monitoring and repair of an impact damaged prestressed concrete bridge. The repair was required following an impact from a low-loader carrying an excavator while passing underneath the bridge. The repair was carried out by preloading the bridge in the vicinity of the damage to relieve some prestressing. This preload was removed following the hardening and considerable strength gain of the repair material. The true behaviour of damaged prestressed concrete bridges during repair is difficult to estimate theoretically due to lack of benchmarking and inadequacy of assumed damage models. A network of strain gauges at locations of interest was thus installed during the entire period of repair. Effects of various activities were qualitatively and quantitatively observed. The interaction and rapid, model-free calibration of damaged and undamaged beams, including identification of damaged gauges were also probed. This full scale experiment is expected to be of interest and benefit to the practising engineer and the researcher alike.

Screening and Quantitative Confirmatory Method for the Analysis of Glucocorticoids in Bovine Milk Using Liquid Chromatography-Tandem Mass Spectrometry

An LC/MS/MS method was developed and validated for the simultaneous identification, confirmation, and quantification of 12 glucocorticoids in bovine milk. The method was validated in accordance with the criteria defined in Commission Decision 2002/657/EC. The developed method can detect and confirm the presence of dexamethasone, betamethasone, prednisolone, flumethasone, 6 alpha-methylprednisolone, fluorometholone, triamcinolone acetonide, prednisone, cortisone, hydrocortisone, clobetasol propionate, and clobetasol butyrate in bovine milk. Milk samples are extracted with acetonitrile; sodium chloride is subsequently added to aid partition of the milk and acetonitrile mixture. The acetonitrile extract is then subjected to liquid-liquid purification by the addition of hexane. The purified extract is evaporated to dryness and reconstituted in a water acetonitrile mixture, and determination is carried out by LC/MS/MS. The method permits analysis of up to 30 samples in 1 day.

Retrofit versus new-build house using life-cycle assessment

This paper reports the findings of research on the environmental performance of two case-study houses, a retrofit and new build. The retrofit was completed to a Passivhaus standard while the new build was completed to current Irish building regulations. Environmental performance of the retrofit and new build was measured using life-cycle assessments, examining the assembly, operational and end-of-life stage over life spans of 50 and 80 years. Using primary information, life-cycle assessment software and life-cycle assessment databases the environmental impacts of each stage were modelled. The operational stage of both case studies was found to be the source of the most significant environmental damage, followed by the assembly and the end-of-life stage respectively. The relative importance of the assembly and end-of-life stage decreased as the life span increased. It was found that the retrofit house studied outperformed the new build in the assembly and operational stage, whereas the new build performed better in the end-of-life stage; however, this is highly sensitive, depending on the standards to which both are completed. Operational energy savings pre- and post-retrofit were significant, indicating the future potential for adoption of high-quality retrofitting practices.

Non-linear finite-element analysis of punching capacities of steel-concrete bridge deck slabs

Punching failure is the common failure mode in concrete bridge deck slabs when these structural components are subjected to local patch loads, such as tyre loads. Past research has shown that reinforced concrete slabs in girder–slab type bridges have a load-carrying capacity far greater than the ultimate static loads predicted by traditional design methods, because of the presence of compressive membrane action. However, due to the instability problems from punching failure, it is difficult to predict ultimate capacities accurately in numerical analyses. In order to overcome the instability problems, this paper establishes an efficient non-linear finite-element analysis using the commercial finite-element package Abaqus. In the non-linear finite-element analysis, stabilisation methods were adopted and failure criteria were established to predict the ultimate punching behaviour of deck slabs in composite steel–concrete bridges. The proposed non-linear finite-element analysis predictions showed a good correlation on punching capacities with experimental tests.