Catamaran gantry crane for engineering–procurement–construction–installation contract

The objective of this article is to introduce a new piece of multi-purpose and cost-effective offshore installation equipment suitable for onshore fabrication work, shallow water oil and gas field development and wind turbine installation. Shallow water shall mean less than 100 m in this context. The equipment can also be used in the disused platform removal market, which will become a multi-billion dollars offshore business in the near future. The equipment has a special feature: it can be used to loadout a deck from the fabrication yard onto a material barge for towing to site, install the deck, then remove a disused deck and offload it from a material barge back to the yard for rework. With a simple modification, it can install wind turbine and minimal platform. Creating a sustainable business for the equipment is a key consideration.     

A multidirectional p–y model for lateral sand–pile interactions

The lateral loads applied to pile foundations, as induced by winds or earthquakes, are usually multidirectional. Experimental studies have indicated that the lateral resistance of the pile under multidirectional paths is generally lower than that under a unidirectional path and the degree of reduction depends on the characteristics of the loading paths. On the other hand, most currently used p–y models can take the soil–pile interaction under unidirectional lateral loading into account, but it cannot be applied directly to analyze the response of piles under multidirectional lateral loading. A multidirectional p–y model is proposed in this study, which is formulated within the framework of the bounding-surface elastoplastic theory and consists of two loading mechanisms: the parallel loading and the orthogonal loading. The model has five parameters, which are readily available or calibrated. To demonstrate its ability to model soil–pile interactions under both unidirectional and multidirectional lateral loadings, the proposed model is incorporated into a finite-element program to analyze laterally loaded piles. The responses of piles with different embedment lengths subject to various loading paths are investigated. The non-coaxial relationship between the force increment and the displacement increment vectors at the pile head under the multidirectional loading, and the impact of the multidirectional loading on the lateral resistance are well captured in the analyses.     

Design-oriented stress–strain model for FRP-confined concrete

External confinement by the wrapping of FRP sheets (or FRP jacketing) provides a very effective method for the retrofit of reinforced concrete (RC) columns subject to either static or seismic loads. For the reliable and cost-effective design of FRP jackets, an accurate stress–strain model is required for FRP-confined concrete. In this paper, a new design-oriented stress–strain model is proposed for concrete confined by FRP wraps with fibres only or predominantly in the hoop direction based on a careful interpretation of existing test data and observations. This model is simple, so it is suitable for direct use in design, but in the meantime, it captures all the main characteristics of the stress–strain behavior of concrete confined by different types of FRP. In addition, for unconfined concrete, this model reduces directly to idealized stress–strain curves in existing design codes. In the development of this model, a number of important issues including the actual hoop strains in FRP jackets at rupture, the sufficiency of FRP confinement for a significant strength enhancement, and the effect of jacket stiffness on the ultimate axial strain, were all carefully examined and appropriately resolved. The predictions of the model are shown to agree well with test data.     

Seismic analysis incorporating detailed structure–abutment–foundation interaction for quasi-isolated highway bridges

The Illinois Department of Transportation has adopted an economical and pragmatic methodology for designing earthquake-resistant highway bridges in the Midwestern United States. These so-called quasi-isolated bridges employ low-cost non-seismically designed bearing components as sacrificial structural fuses. During seismic events, fusing actions of these components and subsequent sliding of superstructures on substructures are intended to achieve response characteristics similar to those of conventionally isolated bridges that employ specially designed isolators. This study explores seismic structure-abutment-foundation interaction for quasi-isolated bridges in Illinois, employing a detailed yet efficient non-linear finite-element model for seat-type bridge abutments. The abutment model incorporates many structural components and geotechnical mechanisms that are critical to seismic response of the structure-abutment-foundation (SAF) system. Through non-linear static analyses performed on a complete bridge model, the force-transfer mechanisms, component fusing performance, and potential failure modes of the SAF system were explored. Using earthquake ground motions, non-linear dynamic analyses were conducted to evaluate seismic characteristics of the quasi-isolated bridge, sequences of critical limit state occurrences, and effects of abutment attributes on bridge seismic performance. The influence of abutment model sophistication on simulated bridge response was also highlighted by direct comparison of simulation results obtained from different models.     

Development of cork–gypsum composites for building applications

This paper presents an experimental analysis on a new composite material, cork–gypsum composite. It is shown that cork and plaster are mutually compatible and that a lot of new building materials can be made by mixing those materials in different volume fractions. Mechanical properties of the cork–gypsum composite have been measured. The acoustic absorption coefficient and thermal conductivity of this new composite have also been experimentally obtained and those values are reported for design purposes. Concerning the acoustical insulation characteristics, this composite is not a sound-absorbing material but a reflecting one, and it needs some kind of perforations to behave as an absorbing construction material for sound and noise. The thermal insulation properties are quite good as a result of the thermal conductivity tests. This new composite material is suggested for use in building applications as partitions.     

A combined Bayesian–wavelet–data fusion approach for borehole enlargement identification in carbonates

Petrophysical logs are usually acquired in most of the drilled wells and some of them have good correlations with mechanical properties of the rock. In this paper, a new multi-variable workflow is proposed in order to identify the location of borehole enlargements along the wellbore in correlation with some of the petrophysical logs acquired using wireline or logging while drilling tools in addition to mud weight and in-situ vertical stress data. This approach employs number of data processing techniques including Bayesian classification, wavelet de-noising, and data fusion to determine borehole intervals with maximum likelihood of enlargement. The application of the proposed method is to identify enlargement zones and does not provide information about stresses orientations and magnitudes. This paper explains the methodology and presents its results in five study wells in a carbonate field. The study confirms the applicability and the generalization capability of the method in carbonate formations with a significant accuracy.     

Concession period for PPPs: A win–win model for a fair risk sharing

Public Private Partnership (PPP) is adopted throughout the world for delivering public infrastructure. Despite the worldwide experience has shown that PPP can provide a variety of benefits to the government, to fully gain them several critical aspects related to a PPP project need to be managed, among these the determination of the concession period.     

Value for Money and Risk in Public–Private Partnerships

Problem, research strategy, and findings: Delivering improved public services at lower cost, also known formally as value for money (VfM), is often the main rationale for procuring large infrastructure projects through public–private partnerships (PPPs). However, it is unclear whether the ex ante assessments of PPPs account for key planning concerns, including limitations on community consultation, contractual lock-ins that curtail public flexibility to make future plans, and a political preference for PPPs that may influence the way that projects are structured and evaluated. This set of questions is examined for 28 infrastructure PPPs delivered in Ontario, Canada, and interviews with18 senior political, government, and private-sector participants in the province's PPP industry. We find that transferring of construction risks from government to the private-sector partners drives VfM results, and may overvalue the extent to which planning related risks can be transferred.

Takeaway for practice: PPP contract structures should permit more transparency during the project planning process and preserve the flexibility of governments to control key planning tasks such as user fees, service coordination and facility expansion. Strategies might include: the unbundling of construction and operation phases of the PPP in all but the most unique situations, the use of competitive dialogue tendering to deepen public–private collaboration earlier in the planning process, and the inclusion of contract rebalancing terms to better share rather than transfer project risks.

Research support: This research was funded through a Standard Research Grant from the Social Sciences and Humanities Research Council of Canada (Application Number: 110998).     

Visual–auditory learning network for construction equipment action detection

Action detection of construction equipment is critical for tracking project performance, facilitating construction automation, and fostering construction efficiency in terms of construction site monitoring. Particularly, the auditory signal can provide additional information on computer vision-based action detection of various types of construction equipment. Therefore, this study aims to develop a visual–auditory learning network model for the action detection of construction equipment based on two modalities (i.e., vision and audition). To this end, both visual and auditory features are extracted from the multi-modal feature extractor. In addition, the multi-head attention and detection module is designed to conduct the localization and classification tasks in separate heads in which different attention mechanisms for each task are applied. Particularly, the content-based attention mechanism and the dot-product attention mechanism are, respectively, adopted for spatial attention in the localization head and channel attention in the classification head. The evaluation results show that the precision and recall of the proposed model can reach 86.92% and 84.00% with the adoption of the multi-head attention and detection module, which has proven to improve overall detection performance by utilizing different correlations of visual and auditory features for localization and classification, respectively.     

Near–surface sensors for condition monitoring of cover-zone concrete

With more demands being made on reinforced concrete, 100-year guarantees of durability will become a necessity. Lifetime calculations, and prediction of the residual service-life of structures, require quantitative information on cover-zone properties and threshold values for corrosion initiation. It is clear that there exists a need to determine quantitatively those near-surface characteristics of concrete which promote the ingress of gases and/or liquids containing dissolved contaminants. In addition, in-situ monitoring of the temporal change in such properties could assist in making realistic predictions as to the in-service performance of the structure; likely deterioration rates for a particular exposure condition or compliance with the specified design life. This paper details covercrete sensor arrangements; format of data presentation and information that can be obtained from embedded sensors. Such sensors could, ultimately, form part of a high-level monitoring strategy and should be considered at the design stage.     

Experimental investigation on pressure–leakage relation for high-density polyethylene pipe

ABSTRACT

Leakage control decision-making analysis needs a deep recognition of the pressure–leakage relationship. In this study, leakage behavior in High-Density Polyethylene (HDPE) pipes is investigated by a semi-industrial pilot-scale. Accordingly, some experiments were conducted on circular, longitudinal and circumferential slits for studying the effect of diameter, thickness, and material of pipes, forms, and dimensions of the leak opening, the surrounding environment, and temperature. New equations are presented to estimate the discharge coefficient for orifices and longitudinal slits in HDPE pipes. Leakage value from a longitudinal slit depends on elastic or plastic behavior of the leak area, to distinguish this, a new criterion has been introduced between elastic and plastic behaviours of the longitudinal slit. Results show that, for same leakagel area and pressure, the leakage rate of circumferential slits is generally more than orifices and less than longitudinal slits. Results of this study can be utilized for estimating the leakage rate.     

Stress–strain model for FRP-confined concrete under cyclic axial compression

One important application of fibre-reinforced polymer (FRP) composites in construction is as FRP jackets to confine concrete in the seismic retrofit of reinforced concrete (RC) structures, because FRP confinement can enhance both the compressive strength and ultimate strain of concrete. For the safe and economic design of FRP jackets, the stress–strain behaviour of FRP-confined concrete under cyclic compression needs to be properly understood and modelled. This paper presents a stress–strain model for FRP-confined concrete under cyclic axial compression. The model consists of the following major components: (a) a monotonic stress–strain model for FRP-confined concrete developed by the authors in a previous study for predicting the envelope curve; (b) new algebraic expressions for predicting unloading and reloading paths; and (c) predictive equations for determining the permanent strain and stress deterioration, with the effect of loading history duly accounted for. The capability and accuracy of the proposed model in predicting the complete stress–strain history of FRP-confined concrete under cyclic axial compression are demonstrated through comparisons between predictions of the proposed model and test results.     

Development of a baseline for structural health monitoring for a curved post-tensioned concrete box–girder bridge

The establishment of a baseline is essential for long-term structural health monitoring and performance evaluation. Usually, field testing data and finite element (FE) model are two critical tools used to develop the baseline. In this paper, the establishment of the baseline field database for a curved post-tensioned concrete bridge with expansion bearings is first introduced to include the effect of varying temperature conditions on the field testing data. This database uses data collected from a full year and is based on an undamaged status. The development of a baseline FE model for the bridge is then discussed. Model updating for the FE model are detailed in this paper which includes calibration of material properties, utilization of spring bearing elements, and replacement of Mindlin plate elements (MP4) on box–girder by recently developed cracked Mindlin plate elements (MP4C) to represent the bridge service conditions. A good agreement in modal results has been observed between the baseline FE model and the baseline field data. The proposed structural health baseline can be used for near real-time damage detection, development of monitoring techniques, and condition assessment. Finally, as an application of the baseline, this FE model is used for an earthquake simulation with a selected ground motion on the bridge. The seismic analysis demonstrates the beneficial effect of the guided expansion bearings on the bridge deck in the longitudinal direction.     

Energy-based cyclic force–displacement relationship for reinforced concrete short coupling beams

For use in the inelastic analysis of coupled walls, the cyclic force–displacement relationship and energy dissipation of short coupling beams with various reinforcement layouts were studied. First, a nonlinear truss model analysis was performed to investigate the cyclic behavior of short coupling beams. The results of this numerical analysis showed that the hysteretic energy of the short coupling beams was dissipated mainly by the diagonal reinforcing bars rather than by the concrete and conventional longitudinal and transverse reinforcing bars. Based on this result, simplified methods for predicting the energy dissipation and force–displacement relationship of short coupling beams with various reinforcement layouts were developed. The hysteretic energy dissipation was calculated as the sum of the plastic energies dissipated by the diagonal reinforcing bars. The cyclic force–displacement relationship was defined in a manner such that the area enclosed by the cyclic curve was the same as the predicted hysteretic energy dissipation. For verification, the proposed method was applied to existing test specimens.     

An approach for optimizing pavement design–redesign parameters in PPP projects

Modeling the elasticity modulus of unbound granular pavement materials has attracted significant research interest because of its importance in pavement design particularly in PPP/BOT projects. These efforts have been hampered by three factors: (i) inability to capture the correlations between the asphalt and granular layers and the subgrade, (ii) inadequate modeling of the effects of external factors on the elasticity modulus of unbound materials, and (iii) widespread use of linear statistical relationships to model a complex and non-linear phenomenon. In this paper genetically optimized neural networks and falling weight deflectometer (FWD) back-analysis results from a newly constructed BOT project in Athens, Greece, are employed in order to evaluate pavement section design parameters. It is shown that parameter values adopted during design do not co-inside with those observed from the back-analysis studies. Further, the results indicate that the relative estimation error for the modulus of elasticity of the unbound material does not exceed 25%, while the correlation between actual and predicted values is 86%, both suggesting that the proposed approach models the physical phenomenon adequately, a finding with important practical implications particularly in PPP projects.     

Derivation of the bond–slip characteristics for FRP plated steel members

In order to understand the behaviour of steel members retrofitted using adhesively bonded fibre reinforced polymer (FRP) plates, the bond–slip characteristics of the adhesive joint between the FRP and steel must first be established. This is important so that debonding does not occur whilst the members are in service. Previously, purely empirical research on establishing the bond–slip characteristics involved strain gauging the length of the FRP plate, which can lead to a major scatter of results as well as underestimating the peak shear stress. The subject of this paper is to describe a technique for quantifying the bond–slip characteristics based on a structural mechanics approach and which does not require strain gauging the plate. Two types of pull tests and a partial-interaction numerical model are used to quantify the major characteristics of the bond–slip and two types of adhesive are used to illustrate the approach.     

Palygorskite–TiO2 nanocatalysts for photocatalytic degradation of tebuconazole in water

Palygorskite–TiO₂ nanoparticles are frequently used as nanocatalysts. In the present study, two different nanocatalysts were developed based on the use of different palygorskite–TiO₂ ratios: 40–60 and 10–90. The nanocomposites were investigated for the photocatalytic degradation of the common fungicide tebuconazole (TEB), under aquatic conditions. The samples were extensively characterized by X-ray powder diffraction, attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy and N₂ specific surface area (SSA) by Brunauer–Emmett–Teller (BET) analytical techniques. The TiO₂ nanoparticles were successfully dispersed on the mineral's surfaces and the photocatalytic activity reached 88.4% for the palygorskite–TiO₂ ratio of 40:60, where the dispersion was better as proved by the total pore volume and BET parameters (0.49 cm³/g and 258 m²/g compared to 0.33 cm³/g and 220 m²/g of the 10:90 ratio). The photocatalytic efficiency of the proposed materials was significantly higher than Degussa P25 (33.2%), and that makes the palygorskite–TiO₂ nanocomposites very promising for advanced application in fungicides' degradation in aquatic environments.     

Encoder–decoder with pyramid region attention for pixel-level pavement crack recognition

Timely and accurate extraction of pavement crack information is crucial to maintain service conditions and structural safety for infrastructures and reduce further road maintenance costs. Currently, deep learning techniques for automated pavement crack detection are far superior to traditional manual approaches in both speed and accuracy. However, existing deep learning models may easily lose crack details when processing images containing complex background textures or other noises. Although many studies have alleviated this challenge by introducing attention mechanisms, especially the non-local (NL) block, which has the ability to efficiently capture long-range dependencies to facilitate crack pixel capture, the huge computational cost of NL makes the inference time of the model too long, which is not conducive to practical implementation. In this study, a new module, namely, the pyramid region attention module (PRAM), was developed by combining the pyramid pooling module in the pyramid scene parsing network and optimized NL, which can achieve global multi-scale context integration and long-range dependencies capture at a relatively lower computational cost. By applying PRAM to deep skip connections in the modified U-Net, an effective crack segmentation model called CrackResU-Net was developed. The test results on the existing CrackForest dataset showed that CrackResU-Net not only achieved an F1 score of 0.9580 but also took only 25.89 ms to process an image with a resolution of 480 × 320, which had advantages in accuracy and speed, compared with several other state-of-the-art crack segmentation approaches. It was fully demonstrated that this approach could realize automatic fast and high-precision recognition of pavement cracks for engineering purposes.     

Cost–benefit analysis for optimal distributed generation placement in distribution systems

This paper presents an optimisation method to determine optimal allocations of distributed generation (DGs) and capacitors based on maximisation of a profit/worth analysis approach. The optimal locations and sizes of DGs and capacitors have been determined by minimising the power distribution loss. This method considers various technical and economic factors such as line losses, sizes of DGs and capacitors at optimal locations, investment costs, operating costs and maintenance costs of DG and capacitor to achieve the objective for a predetermined number. The electricity market price of grid power has been considered to recover initial investment in a specified time period. The improvement in the voltage profile of the system has also been considered in this work. The particle swarm optimisation technique has been used to solve the optimal placement of DGs and capacitors to maximise the profit. The proposed technique is tested on 33-bus and 69-bus test systems.