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In a masonry veneer wall system, tie strengths and stiffnesses vary randomly and so are not consistent for all ties throughout the wall. To ensure an economical and safe design, this paper uses tie calibration experimental approach in accordance with the standard AS2699.1 to investigate the tie failure load under compression and tension loading. Probabilistic wall tie characterisations are accomplished by estimating the mean, coefficient of variation and characteristic axial compressive and tensile strength from 50 specimens. The displacement across the cavity is recorded, which resulted the complete load versus displacement response. Using the maximum likelihood method, a range of probability distributions are fitted to tie strengths at different displacement histogram data sets, and a best-fitted probability distribution is selected for each case. The inverse cumulative distribution function plots are also used along with the Anderson-Darling test to infer a goodness-of-fit for the probabilistic models. An extensive statistical correlation analysis is also conducted to check the correlation between different tie strengths and associated displacement for both compression and tension loading. Based on the findings, a wall tie constitutive law is proposed to define probabilistic tie behaviour in numerical modelling.

openaire: EC/H2020/814753/EU//FLARE The structural damage of ships in navigational accidents is influenced by the hydrodynamic properties of surrounding water. Fluid structure interactions (FSI) in way of grounding contact can be idealized by combining commercial FEA tools and specialized hydrodynamic solvers. Despite the efficacy of these simulations, the source codes idealizing FSI are not openly available, computationally expensive and subject to limitations in terms of physical assumptions. This paper presents a unified FSI model for the assessment of ship crashworthiness following ship hard grounding. The method uses spring elements for the idealization of hydrostatic restoring forces in 3 DoF (heave, pitch, roll) and distributes the added masses in 6 DoF on the nodal points in way of contact. Comparison of results against the method of Kim et al. (2021) for the case of a barge and a Ro–Ro passenger ship demonstrate excellent idealization of ship dynamics. It is concluded that the method could be useful for rapid assessment of ship grounding scenarios and associated regulatory developments.

Fabric anisotropy and fines content (fc) in sands modify significantly their mechanical behaviour, particularly as related to static liquefaction under undrained conditions. The fabric anisotropy aspect, expressed by means of an evolving fabric tensor F, has been addressed in the recently developed Anisotropic Critical State Theory (ACST) that enhances the two critical state conditions on stress ratio (η) and void ratio (e) of the classical Critical State Theory by an additional condition on the critical state value of F in relation to loading direction; based on this concept it introduces the dependence of dilatancy on fabric anisotropy. Various models have been successfully developed within this framework for clean sands. The fc aspect has been addressed within the Equivalent Granular State Theory (EGST) that substitutes a properly defined equivalent granular void ratio (e*) for e in any model for clean sand in order to obtain the response of sand with fines without any other change of the model structure and constants. Along these lines, a constitutive model is constructed in this work in order to address the effect of both F and fc simultaneously, by a combination of these two powerful propositions. The idea is very simple: one takes a constitutive model developed within ACST for clean sands, hence it accounts for fabric anisotropy, and substitutes the e* for e, as well as the derivative quantities of such substitution, hence it accounts for fc. The result yields a model that can simulate data on the undrained response for a range of fc, with emphasis on static liquefaction. It is shown that the inclusion of fabric anisotropy improves previous similar simulations made within the EGST but without the framework of ACST. Refereed/Peer-reviewed

This state-of-the-art review provides an overview of the evolution of self-centering structures from early historical structures that inherently exhibited a recentering response to modern systems engineered for enhanced seismic resilience. From the early research investigations that were conducted since the 1960s, to the sharp increase of interest in this topic over the last two decades, self-centering seismic-resistant structures that can mitigate both damage and residual drifts following major earthquakes have seen significant advances. These systems achieve the intended self-centering response by either allowing for the rocking of primary structural elements in a controlled manner, commonly coupled with mechanical restraints and energy dissipation devices, or by including self-centering devices as main structural or supplemental structural members. To better explain the concepts and the underlying mechanics governing their seismic response, detailed schematic illustrations were developed in this article, highlighting the fundamentals behind each of these systems. This article covers a historical overview, presents the state of the research and of the art, discusses general design challenges and practical considerations, and concludes with future research needs to advance the development and broader application of self-centering systems in real structures.

Numerous studies in the literature are concerned with proposing new constitutive models for sands to simulate cyclic loading. Despite considerable progress in this area, there are various limitations on their simulation capabilities that are either overlooked or not communicated clearly by the developers. A number of these limitations are rather crucial for the end users, and therefore, providing discussion and analysis of them would be of great value for both applications and future developments. The present work is devoted to discussing seven characteristic limitations, which are frequently observed in cyclic loading simulations. Four advanced constitutive models are considered in this study: two bounding surface elastoplasticity and two hypoplasticity models—with the models in each category following a hierarchical order of complexity. Relevant cyclic loading experimental test data on Toyoura and Karlsruhe fine sands support the analysis. The key issues discussed include stress overshooting, one-way ratcheting in cyclic strain accumulation, liquefaction strength curves, stress attractor in strain-controlled shearing, hypoelasticity, cyclic oedometer stiffness, and effect of drained preloading. The presented results elaborate on the specific limitations and capabilities of these rather advanced models in simulating several essential aspects of cyclic loading of sands.

Canada experiences a relatively large number of tornadoes, which can cause a significant amount of damage and fatalities. In this study, a preferred prediction model for the spatially varying tornado occurrence rate is developed for Canada. The development takes into account the most commonly used spatial stochastic models and the underreporting that is due to low population density. It incorporates the annual average cloud-to-ground lightning flash (ACGLF) density and annual average thunderstorm days (ATD) as covariates in the prediction model. The model parameters estimation is carried out by using both the maximum likelihood method and the Bayesian inference. The analysis results indicate that the negative binomial model is preferable to the zero-inflated Poisson model and the Poisson model. The results show that tornado occurrence in Canada is associated with large overdispersion. Also, the statistical analysis indicates that the prediction model for the tornado occurrence rate developed on the basis of Bayesian inference is relatively insensitive to the assumed “noninformative” prior distributions. A prediction model is suggested for the spatially varying tornado occurrence rate based on the negative binomial model with the ACGLF density and ATD as covariates.

The stringent early-age strength requirements for production of prestressed hollowcore (HC) slabs have restricted the use of alternative cementitious materials, such as ground granulated blast furnace slag (GGBS). In the present paper, an experimental study conducted in a precast factory is described in which GGBS-concrete HC slabs with 30 and 50% GGBS are compared with concrete slabs made from control samples (using 100% CEM II A-L cement, as used in summer mixes). The use of a novel admixture, thermal curing and a new early-age strength determination technique enables confirmation of the development of the required very early strength, such that cutting and lifting of the HC slabs can occur within 20 h of pouring. The HC slabs are instrumented to study the internal temperatures in the different slabs, leading to early-age strength development whereby these slabs are tested for immediate transportability and ultimate capacity. Further, the control and 30% GGBS slabs are tested for early-age creep under a flexural test in the factory. At later ages, using the new technique for making cube specimens, cubes and cores cut from the actual HC slabs are shown to have similar 28-day strengths and density.

Failure of unreinforced masonry following the 2011 Christchurch earthquake demonstrated that many masonry strengthening solutions were inadequate for the peak ground accelerations that were experienced, and also that many of the failures were associated with underperformance of masonry anchors. Recent in-situ pull-out tests of anchors in vintage masonry structures has identified that in these tests, the failure is predominantly via splitting of the masonry units. This finding is in contrast to current design approaches that only consider failure via the formation of a cone or wedge, or masonry unit extraction. To further examine the potential for unit splitting prior to the failure modes identified in current design approaches, a laboratory campaign investigating masonry unit properties and anchor pull-out capacities, covering quasi-static, cyclic and impact loading of anchors and also incorporating the influence of quality of installation is reported here. The results of this campaign confirm that the unit splitting is an important failure mode, which may explain the observed anchorage underperformance. It is further observed that whilst cyclic and impact loading, as well as poor quality of installation have a detrimental effect on anchor performance, performance nonetheless exceeds published characteristic strengths. Additionally, as part of the laboratory campaign, a simple method for supporting masonry test units has been developed which has demonstrated good replication of the in-situ test results.

The use of natural hemp fabric for strengthening existing concrete columns was investigated in this work. The results presented in this paper were based on an experimental setup analysing the efficiency of natural hemp fibres for the confinement of existing concrete columns. The variables considered were the number of hemp fabric layers, the column length/diameter ratio and the presence of transverse reinforcement. Uniaxial compression tests were performed on 36 specimens. The axial stress–strain curves ductility, and failure modes were analysed. The test results indicate that the three variables considered had significant effects on the confined columns’ strength and post-peak behaviour.

Biomineralisation is a process of formation of calcite from supersaturated solution due to the presence of bacterial cells and biochemical activities. In this article, a biological approach towards the development of sustainable construction materials is studied. Evidence of bacterial precipitation of calcite has led several research groups to explore the possibility of adopting this process in the area of construction materials. The goal of this review paper is to highlight the application of biomineralisation in concrete. The effect of a bio-based agent and bacterial solution on various properties of concrete is discussed. Additionally, the factors in the choice of bacteria for the biomineralisation process are also elaborated. This green biotechnology concept is a promising, environmentally safe substitute for conventional and current remediation methods to mitigate environmental problems in multidisciplinary fields.

Replacement of Portland cement (PC) by fly ash (FA) is currently limited to 15–30% by mass, mainly due to low early age strength development of concrete. This research uses calcium formate (Ca(HCO2)2; CF) as an admixture to high-volume FA (HVFA) composites to improve its strength properties. HVFA represents 60–70% of cement replaced by FA and dosage of CF varies from 0.5% up to high dosage of 9% of cement content. Compressive strength, isothermal calorimetry, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy were conducted to investigate the effects of CF on hydration and microstructural aspects. The results show that both HVFA pastes with 60% and 70% FA achieved the highest strength at the CF dosage of 3%. At the age of 28 days, adding 3% CF to HVFA mixes led to higher consumption of FA as well as higher formation of calcium hydroxide (Ca(OH)2), calcium silicate hydrates, calcium carbonate (CaCO3) and ettringite, which contribute to the increase of strength. The addition of very high dosages of CF at 9% increased the hydration of tricalcium aluminate but could hinder the hydration of tricalcium silicate in both PC and HVFA pastes with 60% and 70% FA.

This paper presents a procedure for the estimation of propeller effective wakes in oblique flows. It shows how a recently developed method for controlling coupling errors can be applied to analyze propellers operating in off-design conditions. The approach allows the use of fast potential flow methods for the representation of the propeller in the context of viscous flow solvers and works accurately for a wide range of advance numbers and incidence angles with a minimum computational cost. The new method makes it possible to disclose flow phenomena on the effective wake that were hidden in conventional approaches of effective wake simulation. Different application cases are analyzed, such as a propeller-shaft configuration in inclined flow, a pod propulsor in an oblique inflow, and a ship hull advancing at a yaw angle. A dipole-like distortion on the effective wake is unmasked for a uniform flow incident to a propeller mounted on an inclined shaft. The flow component perpendicular to the axis is found to be responsible for the distortion. The effect of the direction of propeller rotation on the effective wake is illustrated for a single-shaft ship moving at a yaw angle. In particular, keel vortices are either attracted to or repelled from the propeller disk depending on the sign of the yaw angle or alternatively on that of the propeller rotation.

This study presents an analytical model for the load-moment (P-M) interaction diagrams of circular geopolymer concrete (GPC) columns reinforced with glass fiber-reinforced polymer (GFRP) bars and GFRP helices. The analytical P-M interaction diagrams of GPC columns were developed using the layer-by-layer numerical integration method. The analytical predictions of GFRP reinforced GPC columns were then validated against the experimental results on the behaviour of GFRP reinforced GPC columns under different loading conditions. It was found that the developed analytical model predicted the load and moment capacities of GFRP reinforced GPC columns with good accuracy. Further, a parametric study showed that the influence of increasing the compressive strength of GPC was more pronounced on P-M interaction diagrams of GPC columns under concentric and low levels of eccentric axial loadings. Also, the increase in longitudinal and transverse reinforcement ratios resulted in significant improvements in the load and moment capacities of GPC columns reinforced with GFRP bars and GFRP helices.

This paper utilises non-linear finite-element analysis with three-dimensional (3D) solid elements to gain insight into the role of shear reinforcement in increasing punching shear resistance at internal columns of flat slabs. The solid element analysis correctly captures the experimentally observed gradual decrease in concrete contribution to shear resistance with increasing slab rotation and the failure mode but is very computationally demanding. As an alternative, the paper presents a novel approach, in which 3D joint elements are combined with non-linear shell elements. Punching failure is modelled with joint elements positioned around a control perimeter located at 0.5d from the column face (where d is the slab effective depth). The joint elements connect the nodes of shell elements located to either side of the punching control perimeter. The punching resistance of the joints is related to the slab rotation using the failure criterion of the critical shear crack theory. The joint-shell punching model (JSPM) considers punching failure both within the shear-reinforced region and due to crushing of concrete struts near the support region. The JSPM is shown to accurately predict punching resistance while requiring significantly less computation time than 3D solid element modelling.

This paper proposes a methodology for managing complex sewerage networks based on the concomitant use of two performance evaluation methods, namely, the failure modes, effects, and criticality analysis (FMECA) and the analytical hierarchy process (AHP). The FMECA is used to determine the risks of structural failures making it possible to establish a methodology for managing these failures. The AHP is used to check the relationship consistency between the performance indicators allowing the determination of the overall performance (OP). This proposed methodology was utilized for the urban sewerage network of Oued-Kniss in the city of Algiers, Algeria, as part of the efforts engaged in for sustainable and efficient management.

In this experimental study, Glass Fiber Reinforced Polymer (GFRP) plates were used to retrofit timber I-joists having a top flange-notch or a web-hole. Three types of GFRP reinforcing plates were used to retrofit and test 27 flange-notched and 27 web-holed I-joists for 3.65 m and 6.1 m span lengths. Another 200 I-joists were also tested to compare the performance improvement of the GFRP retrofitted I-joists. These I-joists had two different sizes of flange notch (100 mm × 100 mm and 100 mm × 150 mm) and two different diameters (150 mm and 200 mm) of web-hole located at different locations from the support. Although North American codes do not allow any form of a notch in the flange of I-joist, the current study shows that full capacity restoration can be achieved with proper retrofitting. From the four-point bending test of the I-joists, it is observed that GFRP plates can improve the structural capacity of retrofitted flange-notched or web-holed I-joists up to 605% and 106%, respectively, compared to the capacity of I-joists with a flange notch or a web hole, respectively. Two prediction models proposed here can predict the structural capacity of the retrofitted flange-notched and web-holed I-joists with different GFRP reinforcements with reasonable accuracy.

Seismic response of masonry towers has been widely studied, whereas research on their behavior under other dynamic forces is not common. The aim was to study the dynamic effects of bell swinging on a masonry tower, evaluating the response through different approaches. For this purpose, the south tower of the National Palace of Mafra was adopted due to its slenderness and its four swinging bells located at 49 m height. Dynamic identification tests allowed to determine the tower’s dynamic properties aimed at calibrating a numerical model. Frequency analyses assessed possible resonance effects by comparing the frequencies of the excitations with those of the tower. Nonlinear dynamic analyses evaluated the response in terms of displacements and cracking, while nonlinear static analyses determined damage patterns assuming different load combinations. Variations of structural stiffness and intensity of the forces were also studied. The results demonstrated that the tower, subjected to bells action, remains within the elastic range with a high safety level. Moreover, crack patterns correspond to local damage, which do not compromise the stability of the structure. Finally, parametric analysis allowed to obtain equivalent static load factors for bells of the Spanish system., This work was performed in the University of Minho with the funding from the ELARCH Program (Euro-Latin America partnership in natural Risk mitigation and protection of the Cultural Heritage), an Erasmus Mundus Action 2 Partnership (552129-EM-1-2014-1-IT-ERA MUNDUS-EMA21) by the European Commission and coordinated by the University of Basilicata, Italy.

To facilitate construction and on-site quality testing, a new type of panel joint using cast-in-place connecting beams was developed and studied. The proposed connecting beams consist of overlapping vertical U-shaped steel bars stretching out of the wall and the footing, longitudinal prestressed steel strands, L-shaped steels and infilled high-strength grout. One monolithic shear wall specimen and five precast specimens were tested under simulated seismic loads. The test parameters studied included the presence or absence of L-shaped steel, sectional depths and the locations of connecting beams and locally non-bonded U-shaped steel bars. The effects of these parameters on the failure modes, hysteresis curves, stiffness, ductility and energy dissipation capacity were evaluated. The test results showed that the precast shear walls with the proposed panel joint achieved desirable seismic behaviour – comparable to or better than that of monolithic specimens – and can thus be safely applied in buildings in seismic zones. The use of L-shaped steel, prestressed steel strands and high-strength grout effectively delayed concrete crushing at the wall toes and thus improved the loading capacity, deformation capacity, initial stiffness, ductility and energy dissipation capacity of the precast shear walls.

This investigation evaluated the feasibility of combining lightweight concrete (LWC) and engineered cementitious composite (ECC) in specific configurations to develop a lightweight hybrid composite with improved impact resistance. In this study, three mixtures were investigated: one LWC mixture fully produced with lightweight fine and coarse expanded slate aggregates; one ECC mixture developed with polyvinyl alcohol fibers (ECCP); and one ECC mixture developed with steel fibers (ECCS). For testing, cylindrical specimens and small-scale beams were constructed in a two-layer composite system having different configurations (i.e., different arrangements and depths). Additional specimens fully cast with LWC, ECCP, and ECCS were tested for comparison. The interface bond strength between LWC and either ECCP or ECCS was also evaluated. The performance of the developed composites was assessed under static flexural loading and drop-weight impact. The results showed that both ECCP and ECCS could achieve a good bonding with LWC substrate, i.e., above 90% of that measured for the monolithic LWC specimens, even with no surface preparations (i.e., roughening or using shear keys). Combining LWC with either ECCP or ECCS generated novel lightweight hybrid composites that can offer superior performance for different structural lightweight members exposed to high impact loading. For given arrangement and depth, the LWC-ECCS composite exhibited higher mechanical and impact performance whereas the LWC-ECCP was distinguished by achieving an excellent impact resistance at a lighter self-weight.

Evolutionary node shifting is an effective approach to the shape optimization of spatial structures for excellent mechanical performance. In this paper, a novel shape optimization algorithm is proposed, which is applicable to complex gridshell structures of irregular geometries and non-uniform grids. With the objective of maximizing the structural stiffness, the nodal coordinates are iteratively updated according to the sensitivity information. The perturbation displacements referring to the inverse hanging method are applied to the initial flat model. By analysis, we found that the irregular grids give rise to non-smooth gradient fields, which results in jagged surfaces. To normalize the non-smooth gradient fields and to prevent the optimization process from falling into local optima, a double filter scheme is introduced in the process of optimization. A variety of examples are presented to demonstrate that the proposed algorithm can effectively solve shape optimization problems of general gridshell structures.

This paper investigates and compares the effect of steel fibres obtained through recycling waste tyres (known as RTSF), and a commercially available hooked steel fibre (HSF), on plastic shrinkage cracking in self-compacting concrete. The volumetric deformations of the specimens, bleeding, and the mass loss have been quantified. Mixtures containing 2.5, 5, 7.5 and 10 kg/m3 of RTSF, and 5 and 7.5 kg/m3 of HSF have been tested. The results show that an almost similar reduction of the crack area can be attained if HSF is replaced by a slightly higher amount of RTSF. However, the former seems to be more effective in restraining plastic shrinkage. Both fibres decreased the volumetric shrinkage and the bleeding capacity of the specimens.

There is a global drive to promote and optimize the design of high performance buildings at low cost and minimum environmental impact. Although reinforced masonry construction is known for its better fire protection, structural durability, and construction cost reduction, its use is hindered by a lack of understanding of its resistance to earthquake loads. This research aims to quantify the effect of influential parameters on the seismic performance of Reinforced Masonry Shear Walls (RMSW) with masonry boundary elements (MBEs). A new system/configuration for RMSW with C-shaped masonry units has been proposed. A new experimental test setup was designed and built to capture the response of the lower panel of RMSW in a 12-storey building subjected to quasi-static loading protocol. Test results showed that the proposed system could provide the lateral strength and ductility required to resist earthquake events and that the average measured compressive strain was almost four times the limit specified in CSA S304-14. The results also showed that single out-of-plane support at the loading beam level was inadequate, leading to out-of-plane failure. When additional out-of-supports were provided, the failure mode changed to web crushing and buckling of vertical web reinforcement.

Structural damage in offshore wind jacket support structures are relatively unlikely due to the precautions taken in design but it could imply dramatic consequences if undetected. This work explores the possibilities of damage detection when using low resolution data, which are available with lower costs compared to dedicated high-resolution structural health monitoring. Machine learning approaches showed to be generally feasible for detecting a structural damage based on SCADA data collected in a simulation environment. Focus is here given to investigate model uncertainties, to assess the applicability of machine learning approaches for reality. Two jacket models are utilised representing the as-designed and the as-installed system, respectively. Extensive semi-coupled simulations representing different operating load cases are conducted to generate a database of low-resolution signals serving the machine learning training and testing. The analysis shows the challenges of classification approaches, i.e. supervised learning aiming to separate healthy and damage status, in coping with the uncertainty in system dynamics. Contrarily, an unsupervised novelty detection approach shows promising results when trained with data from both, the as-designed and the as-installed system. The findings highlight the importance of investigating model uncertainties and careful selection of training data.

Recent numerical and experimental studies on reinforced concrete shear walls and coupled walls have shown shear forces greater than expected when the walls are subjected to earthquakes at an intensity level that does not exceed the design values. This amplification of shear forces is attributable to the effects of higher modes after the walls develop a plastic hinge at the base. These effects have been recently recognized in North American design codes for cantilever walls and is currently neglected in the design of ductile coupled walls. As part of the research program described in this article, a parametric study was carried out on coupled wall systems to identify the geometric and physical parameters having the greatest influence on the seismic shear amplification. Using the results of this parametric study, an extensive numerical study was conducted on classes of ductile coupled walls subjected to seismic excitation representative of Western and Eastern Canada. This extensive study led to the establishment of shear amplification prediction equations for use in building codes.

In the research of ship collision avoidance and automatic collision avoidance decision-making system, collision risk level is especially important. To evaluate the risk of ship collision, the nature of the risk level of ship collision is analyzed. Based on the fuzzy comprehensive evaluation model based on improved AHP, the concepts of space collision risk and time collision risk are proposed, and the models for space collision risk, time collision risk and collision risk level are established at the same time. The model developed and perfected the concept of ship collision risk, and are more logical, laid a solid foundation for subsequent comprehensive evaluation.

In the initial stage of emergency rescue for major railway emergencies, there may be insufficient emergency resources. In order to ensure that all the emergency demand points can be effectively and fairly rescued, considering the fuzzy properties of the parameters, such as the resource demand quantity, the dispatching time and the satisfaction degree, the railway emergency resources dispatching optimization model is studied, with multi- demand point, multi-depot, and multi-resource. Based on railway rescue features, it was proposed that the couple number of relief point - emergency point is the key to affect railway rescue cost and efficiency. Under the premise of the maximum satisfaction degree of quantity demanded at all emergency points, a multi-objective programming model is established by maximizing the satisfaction degree of dispatching time and the satisfaction degree of the couple number of relief point - emergency point. Combined with the ideal point method, a restrictive parameter interval method for optimal solution was designed, which can realize the quick seek of Pareto optimal solution. Furthermore, an example is given to verify the feasibility and effectiveness of the method.

The effects of different variables of closed conduit transient partially pressurized flows on the maximum air pressure are investigated from an energy exchange perspective. It was found that when t...

In order to solve the problem of false terrains caused by environmental interferences and tunneling effect in the conventional multi-beam seafloor terrain detection, this paper proposed a seafloor topography detection method based on fast two-dimensional (2D) Censored Mean Level Detector-statistics Constant False Alarm Rate (CMLD-CFAR) method. The proposed method uses s cross-sliding window. The target occlusion phenomenon that occurs in multi-target environments can be eliminated by censoring some of the large cells of the reference cells, while the remaining reference cells are used to calculate the local threshold. The conventional 2D CMLD-CFAR methods need to estimate the background clutter power level for every pixel, thus increasing the computational burden significantly. In order to overcome this limitation, the proposed method uses a fast algorithm to select the Regions of Interest (ROI) based on a global threshold, while the rest pixels are distinguished as clutter directly. The proposed method is verified by experiments with real multi-beam data. The results show that the proposed method can effectively solve the problem of false terrain in a multi-beam terrain survey and achieve a high detection accuracy.

Bugholes are usually considered an aesthetic problem rather than a durability problem. Surface bugholes often appear on the sidewalls of a tunnel's lining concrete, which can be mitigated but never eliminated. However, the impact of surface bugholes on concrete durability is still unidentified. In cold regions, the lining concrete of a road tunnel is exposed to de-icer solutions splashed by traffic, and it is additionally exposed to freeze–thaw (F–T) cycles. This study focuses on the durability to F–T cycles of tunnel lining concrete with surface bugholes. For the objectives, the study was carried out on a laboratory-scale F–T test using large concrete blocks. An image analysis based on the RGB values of each pixel in the coloured photographic image was performed to detect and quantify deterioration of the concrete surface throughout the F–T cycles. Although severe scaling never occurred during the 300 F–T cycles, the concrete with bugholes indicated a significant local scaling at the edges of the bugholes. Some bugholes enlarged and some merged with existing bugholes, in accordance with such local scaling. The paper presents synergetic and negative effects of bugholes on the local scaling of tunnel lining concrete exposed to F–T cycles.

The appropriate radiation conditions of ship motion problem with advancing speed in frequency domain are investigated from a theoretical and practical point of view. From extensive numerical experiments that have been conducted for evaluation of the relevant radiation conditions, a hybrid radiation technique is proposed in which the Sommerfeld radiation condition and the free surface damping are mixed. Based on the comparison with the results of the translating and pulsating Green function method, the optimal damping factor of the hybrid radiation technique is selected, and the observed limitations of the proposed hybrid radiation technique are discussed, along with its accuracy obtained from the numerical solutions. Comparative studies of the forward-speed seakeeping prediction methods available confirm that the results of applying the hybrid radiation technique are relatively similar to those obtained from the translating and pulsating Green function method. This confirmation is made in comparisons with the results of solely applying either the free surface damping, or the Sommerfeld radiation condition. By applying the proposed hybrid radiation technique, the wave patterns, hydrodynamic coefficients, and motion responses of the Wigley III hull are finally calculated, and compared with those of model tests. It is found that, in comparison with the model test results, the three-dimensional Rankine source method adopting the proposed hybrid radiation technique is more robust in terms of accuracy and numerical stability, as well as in obtaining the forward speed seakeeping solution.

The broadband noise can be dominant or important for total characteristics for marine propeller noise representing the minimum base of self-noise. Accurate prediction of such noise is crucial for survivability of underwater military vessels. While the FW-H Formulation 1B can be used to predict broadband trailing edge noise, the method required experiment measurements of surface pressure correlations, showing its limitations in generality. Therefore, in this study, the methods are developed to utilize wall pressure spectrum models to overcome those limitations. Chase model is adopted to represent surface pressure along with the developed formulations to reproduce pressure statistics. Newly developed method is validated with the experiments of airfoils at different velocities. Thereafter, with its feasibility and generality, the procedure incorporating computational fluid dynamics is established and performed for a propeller behind submarine hull. The results are compared with the experiments conducted at Large Cavitation Tunnel, thus showing its usability and robustness.

In the field of civil engineering, the meteorological data available usually do not have the detailed information of the wind near a certain site. However, the detailed information of the wind field during typhoon is important for the wind-resistant design of civil structures. Furthermore, the resolution of the meteorological data available by the civil engineers is too coarse to be applicable. Therefore it is meaningful to obtain the detailed information of the wind fields based on the meteorological data provided by the meteorological department. Therefore, in the present study, a one-way coupling method between WRF and CFD is adopted and a method to keep the mass conservation during the simulation in CFD is proposed. It is found that using the proposed one-way coupling method, the predicted wind speed is closer to the measurement. And the curvature of the wind streamline during typhoon is successfully reproduced.

Steel reinforcement corrosion due to chloride penetration into concrete is one of the main causes of the degradation of marine structures and has been the subject of much research. Among the various factors that influence chloride penetration into concrete are environmental factors such as temperature and exposure conditions. In this context, the present study evaluated chloride penetration for three different exposure conditions (atmospheric, tidal variation and submerged) at temperatures of 15°C, 20°C, 25°C and 30°C over 18 months; samples were collected every 6 months, at depths of 1–5 mm. The environmental conditions were simulated in the laboratory. The results showed a higher concentration of chlorides in the submerged specimens. Moreover, the chloride concentration increased more intensively from 6 to 12 months and temperature was more influential above 20°C. The temperature effects were also found to be higher at advanced ages.

Several bond–slip models considering corrosion effects are available in the literature to describe the change in bond due to corrosion of longitudinal reinforcement. However, these models do not consider either the beneficial effect of stirrups or corrosion of the stirrups. This is very important because stirrups provide a confinement effect that enhances the bond strength of reinforcement, but the effect deteriorates with corrosion impacts. To address this limitation, a new bond–slip model was developed that includes the influence of corrosion of both the reinforcement and stirrups. More significantly, the model also provides a correlation between the corrosion in stirrups and longitudinal reinforcement. This means that the model can be applied with knowledge of the corrosion of either the longitudinal reinforcement or the stirrups. This is beneficial for the prediction of the corrosion level of longitudinal bars and, to take a step further, for the prediction of the mechanical behaviour of structures as it is relatively easy to measure the corrosion level of stirrups physically. The new model is presented in this paper along with a parametric study based on the developed model.

With the transition on planning and construction of offshore wind turbine (OWT) from North Europe to other regions like America and East Asia, challenges are proposed for the direct application of international OWT experience to these territories due to disparate natural condition like cyclones. This article is intended to evaluate the impact of cyclone on the long-term performance of an OWT to be installed in cyclone-prone regions. To have a comprehensive consideration on the aero-hydro-structural-soil interaction, an improved decoupled method is proposed and validated for an onshore wind turbine before its application to an OWT. Two cyclone models combined with two wave theories are considered in the fatigue evaluation of an OWT under different working status, and their implications on the final estimation of fatigue damage are compared and discussed. The results obtained from this study indicate that the fatigue life reduction which is caused by cyclone, for an OWT can be conspicuous for a reasonable cyclone strength and average recurrence interval. This implies that potential premature failure of an OWT tower and relevant economic losses can be encountered during its service life if the cyclone contribution to fatigue damage is ignored in the initial conceptual design.

A special ceramic roller bearing press (SCRBP) is developed to press two bearings efficiently and precisely at the same time. A speed control mathematical model of the bearing press is built to obtain stability bearing pressing speed. The fuzzy adaptive PID controller of the bearing pressing speed of SCRBP is designed. The simulation model is also built. Fuzzy adaptive PID control is compared with conventional PID control. By simulation analysis, the simulation results show that adjusting time of fuzzy adaptive PID control is short, and its overshoot is very small, almost coincides with the set pressing speed. Moreover, fuzzy adaptive PID is suitable for the pressing speed control of the bearing pressing speed system with step interference signal. The pressing stability speed is obtained by fuzzy adaptive PID control.

The wave power extraction by multiple Wave Energy Converters (WECs) deployed in a Y-shaped Water Channel Resonator (WCR) has been investigated. A WCR consists of a long water channel, and a V-shaped wave guider installed at the entrance of a water channel. If the period of the incident waves coincides with the natural periods of the fluid in a WCR, resonance occurs, as a result, the internal fluid in a WCR is greatly amplified. To estimate the wave power by multiple WECs placed at the antinodal points in a WCR, the heave motion response, time-averaged power, and capture width ratio were calculated for several design parameters. Also, the systematic model tests were conducted in a 2D wave tank. The numerical results are in good agreement with the experimental data. It was verified that a WCR helps the WECs to produce electricity more effectively by amplifying the wave energy in a WCR.

Simulation-based hull form optimization is a typical HEB (high-dimensional, expensive computationally, black-box) problem. Conventional optimization algorithms easily fall into the “curse of dimensionality” when dealing with HEB problems. A recently proposed Cross-Entropy (CE) optimization algorithm is an advanced stochastic optimization algorithm based on a probability model, which has the potential to deal with high-dimensional optimization problems. Currently, the CE algorithm is still in the theoretical research stage and rarely applied to actual engineering optimization. One reason is that the Monte Carlo (MC) method is used to estimate the high-dimensional integrals in parameter update, leading to a large sample size. This paper proposes an improved CE algorithm based on quasi-Monte Carlo (QMC) estimation using high-dimensional truncated Sobol subsequence, referred to as the QMC-CE algorithm. The optimization performance of the proposed algorithm is better than that of the original CE algorithm. With a set of identical control parameters, the tests on six standard test functions and a hull form optimization problem show that the proposed algorithm not only has faster convergence but can also apply to complex simulation optimization problems.

This paper studies the method of determining the fracture parameters of pre-notched concrete beams with horizontal pre-set cracks and the influence of fracture intersection on fracture characteristics of concrete based on the three-point bending test. Pre-notched concrete beams with horizontal pre-set cracks were designed as 13 groups according to the different positions, lengths and widths of horizontal pre-set cracks. The fracture toughness was calculated on the basis of the cohesive force model of concrete, and the crack opening displacement obtained by using the digital image correlation technique. The study's results indicate that the distance between the pre-set crack and the notch tip as well as the pre-set crack length and width have various influences on the fracture propagation of edge mode I crack, the bearing capacity and unstable fracture toughness of concrete beams owing to varying degrees of loss of cohesion in the fracture process zone (FPZ). The study also finds that a large lack of cohesion in the FPZ indicates a high possibility of a reduction in the bearing capacity and unstable fracture toughness of concrete beams.

The behaviour of concrete reinforced with steel fibres at elevated temperatures was investigated in terms of shear deterioration. Using three different steel fibre contents (0, 40 and 80 kg/m3), 45 push-off specimens were tested at five maximum temperatures (20, 150, 300, 500 and 700°C). The main objective of the research was to investigate the effect of steel fibres on the behaviour of concrete at different maximum temperatures in terms of shear failure. The results revealed enhanced ductility and shear strength at elevated temperatures. In addition, the crack widths and crack slips were measured using linear variable differential transducers. It was found that the use of steel fibres increased the shear strength of the concrete at ambient temperature by 103% and 102% for steel fibre contents of 40 and 80 kg/m3, respectively. Although this enhancement was reduced at the high temperatures (500 and 700°C), the mixes containing fibres still had higher residual shear strengths than the plain concrete mix. The steel fibre content also affected the ductility at both ambient and high temperatures.

Maneuvering motions of a ship in calm water are studied through the concept of MMG model. Governing forces are defined by the use of available empirical formulae that require only main ship particulars as input variables. In order to validate the calculation tool, a full-scale sea experiment was carried out in Osaka Bay using a 17-m twin-screw passenger ferry. Test execution and data measurement were performed through the utilization of an autopilot control unit and satellite compass. The result of a straight running test confirms the acceptable accuracy in addressing the surge motion problem. Reasonable agreement between simulation and experiment is also confirmed for 5 ∘ / 5 ∘ and 10 ∘ / 10 ∘ zig-zag tests despite the strong environmental disturbance. The current model can generally represent the subject ship maneuvering motions and is promising for the application to other ship hulls.

Wave energy is one of the most available sources of renewable energy in the world. It has been previously proven that the flapping foil can generate thrust forces using energy from the surface waves and an empirical formula was proposed to predict the thrust forces generated by a flapping foil consist of NACA0015 section (Kumar and Shin, 2019a). However, the proposed empirical formula was restricted to the head waves i.e. 0° azimuth angle which was not useful for the flapping foils encountering with oblique and following waves. Therefore, in this study, the thrust empirical formula was modified to include the effects of azimuth angles based on the experimentally obtained data. And the modified empirical equations were validated by the combination of foils experimentally.

The punching and post-punching shear behaviours of reinforced concrete (RC) flat plate structures are often studied by using a representative slab–column connection isolated from the parent structure. In this study, a set of numerical modelling techniques is established to create a competent three-dimensional non-linear model to simulate punching and post-punching shear behaviours of RC slab–column connections without shear reinforcement, through the use of which the punching shear failure featuring a critical punching shear surface and an abrupt drop of the applied force in the load–displacement response is able to be accurately reproduced. The post-punching shear behaviour, taking the form of an increased load-carrying capacity which is ceased by rebar fracture in the suspension stage, is also well captured. Using the proposed numerical model, typical punching and post-punching shear failure mechanisms are studied in some detail.

Biofouling represents an important problem in the shipping industry since it causes the increase in surface roughness. The most of ships in the current world fleet do not have good coating condition which represents an important problem due to strict rules regarding ship energy efficiency. Therefore, the importance of the control and management of the hull and propeller fouling is highlighted by the International Maritime Organization and the maintenance schedule optimization became valuable energy saving measure. For adequate implementation of this measure, the accurate prediction of the effects of biofouling on the hydrodynamic characteristics is required. Although computational fluid dynamics approach, based on the modified wall function approach, has imposed itself as one of the most promising tools for this prediction, it requires significant computational time. However, during the maintenance schedule optimization, it is important to rapidly predict the effect of biofouling on the ship hydrodynamic performance. In this paper, the effect of biofilm on the ship hydrodynamic performance is studied using the proposed performance prediction method for three merchant ships. The applicability of this method in the assessment of the effect of biofilm on the ship hydrodynamic performance is demonstrated by comparison of the obtained results using the proposed performance prediction method and computational fluid dynamics approach. The comparison has shown that the highest relative deviation is lower than 4.2% for all propulsion characteristics, lower than 1.5% for propeller rotation rate and lower than 5.2% for delivered power. Thus, a practical tool for the estimation of the effect of biofouling with lower fouling severity on the ship hydrodynamic performance is developed.

Floor systems constructed from slabs and beams are critical structural elements of reinforced concrete (RC) frame structures, allowing them to resist progressive collapse. To elucidate the complex effects of the slab and its thickness on the progressive-collapse resistance of RC spatial frame structures, three 1/3-scale 2 × 2 span substructure specimens, including one three-dimensional (3D) skeletal frame substructure and two 3D frame–slab substructures with different slab thicknesses, were tested in a middle-column-removal scenario. The test results indicated that the frame–slab substructure exhibited two resisting progressive-collapse stages: a primary mechanism stage, with small deformations, and a secondary mechanism stage, with large deformations. The slab contributions were separated from the floor system and quantified by comparing the results for the skeletal frame substructure and frame–slab substructure. Although there were no in-plane confinements, the slab also significantly improved the resistance against progressive collapse, owing to the compressive and tensile membrane action in the primary and secondary mechanism stages, respectively. Increasing the slab thickness increased the compressive membrane action of the slab, which significantly enhanced the progressive-collapse resistance under small deformations. However, under large deformations, the beam and slab did not work synergistically, which limited the development of secondary mechanisms against progressive collapse.

As part of this study a series of columns built with high-strength concrete and Grade 690 MPa high-strength reinforcement are tested under blast loads using a shock-tube. The performance of the columns is compared to a control set of specimens built with Grade 400 MPa reinforcement. In addition to the effects of concrete and steel type, the effects of longitudinal steel ratio and seismic detailing are also investigated. The results show that concrete strength has limited effects on blast behavior. Conversely, use of high-strength bars significantly enhances column blast performance by reducing displacements and increasing blast resistance, with an ability to reduce the required amount of steel reinforcement. The results further demonstrate that increasing the longitudinal steel ratio and seismic detailing improve the blast behavior of columns built with conventional and high-strength bars. As part of the analytical study the blast response of the columns is predicted using nonlinear single degree of freedom analysis and finite element modelling.

This paper examines the effect of heating rate on the microstructure of cement-based systems exposed to sustained elevated temperatures. Besides a conventional mortar designed to attain a compressive strength of 30 MPa at 28 d, a high-strength mortar was also designed to achieve a corresponding strength of 90 MPa. Samples were extracted for testing under three different heating rates, ranging from 1°C/min to 10°C/min, to a sustained elevated temperature up to 400°C. This study finds that the microstructure of high-strength mortar is more sensitive to the heating rate in comparison with that of the normal-strength mortar. The porosity of the mortar mixtures uniformly increases with an increase in the temperature of exposure. However, there was a decrease in the porosity, at any sustained elevated temperature, with an increase in the heating rate. It is seen that the fractal dimension of the pores increases with an increase in the sustained temperature. Additionally, this fractal dimension was seen to increase with an increase in the heating rate. However, this trend was more pronounced at lower temperatures of exposure, so that the rate of heating appears to become less conspicuous at higher temperatures of soaking.