Ultra-large outfitting ships are especially vulnerable during extreme weather due to their shallow draft, large wind-exposed area, and absence of self-propulsion. This study investigates the mooring performance of a 15,000 TEU outfitting container ship through a validated numerical model, benchmarked against a 1:62 scale physical model test. Time and frequency domain analyses were applied to assess ship motions, mooring line tensions, and wharf structural responses under extreme conditions. Transverse motions were found to dominate, with resonance amplification and sway-roll coupling occurring when the wave period approaches the ship's natural roll period, greatly increasing mooring tensions and impact forces. Structural analysis indicated that transverse beams were most critical, and that long-period waves could cause longitudinal displacements exceeding design limits. To improve system stability, three mooring optimization strategies were evaluated: increasing the number, diameter, and pretension of mooring lines. Among them, increasing the number of mooring lines was most effective in reducing ship motions, alleviating peak line tensions, and constraining longitudinal displacement. Based on the project-specific operational control limit of 75% of the minimum breaking load and the validation-bias correction, the allowable environmental combinations were identified for outfitting ships under extreme conditions. These findings provide a reference for mooring arrangement selection, pre-event reinforcement, and operational safety assessment of similar outfitting ships under forecasted extreme conditions.

This study develops a conductive mortar incorporating conductive steel slag aggregate (CSSA) to enhance the electrical conductivity and sustainability of cementitious materials. CSSA was prepared by impregnating steel slag aggregate with modified agar gel containing carbon black and alkaline electrolyte. With carbon fibers, the mortar achieved an electrical resistivity of 1.94 Ω·m. For mortars containing only CSSA, the conductivity evolution with increasing CSSA content followed the General Effective Media approach. Compressive and flexural strengths increased by 18.4% and 25.9%, respectively, compared with the control mortar, demonstrating the multifunctional potential of CSSA in cementitious materials.

To explore compressive performance of high-strength coral aggregate seawater concrete columns (CASCC) with additional anti-corrosion technology, tests and numerical simulation analysis were carried out considering various rebars and eccentricities. Failure mechanisms, deformation characteristics and ultimate bearing capacity (Nu) of CASCC were studied. Furthermore, load-dependent displacement and strain relationships were formulated, and a numerical predictive model for CASCC's Nu was developed. Analysis indicates stress behavior and failure in CASCC columns are comparable to conventional concrete columns. Considering complex stress state changes of tension-compression-shear during loading, a numerical model suitable for describing the compression properties of CASCC was proposed based on concrete damage plasticity (CDP) theory. The average error between model predictions and experimental data remaining below 6.85 %, which can effectively display full process failure mode of CASCC and variation laws of displacement and strain. In addition, the accuracy of Nu calculated by numerical model is 17.0 % and 18.4 % higher than that of the current specification GB/T 50010-2010 and JGJ/T 12-2019, respectively. Addressing the poor applicability of the current specifications and incorporating the impact of rebar corrosion and interfacial bond-slip degradation on Nu of CASCC, the Nu optimization calculation formula is proposed and verified, and its accuracy is similar to numerical model.

Corroded reinforced concrete (RC) columns usually require retrofitting to ensure the seismic safety of engineering structures. This study employs an innovative combined strengthening system, comprising textile-reinforced ultra-high toughness cementitious composite (UHTCC) jackets and near-surface-mounted (NSM) BFRP (basalt fiber reinforced polymer) reinforcement, referred to as the TRU-NSM system. In this study, the seismic behavior of six corroded RC columns strengthened with the TRU-NSM system was investigated through cyclic lateral loading tests. The test variables included corrosion ratios, stirrup ratios, and axial load ratios. The experimental results indicated that the TRU jacket can effectively restrain shear deformation and concrete cracking in the plastic hinge zone, and all the strengthened specimens showed ductile flexural failure. When the corrosion ratio was below 13.59%, the seismic resistance of corroded columns can be effectively restored. Despite severe corrosion damage to the stirrups, the TRU jacket can still provide sufficient transverse confinement. With an increase in axial load ratio from 0.25 to 0.4, the ultimate load-bearing capacity of the strengthened columns increased by 1.12 times, but their deformation capacity was reduced to a great extent. Although the NSM reinforcement could enhance the peak load to some extent, early failure of the BFRP bars at a drift ratio of 3–5% resulted in a limited effect on their deformation and ductility. Furthermore, a numerical model that accounts for the slip effects of corroded reinforcement and BFRP bars was proposed to predict the hysteretic curves of TRU-NSM-strengthened corroded RC columns.

To reduce the carbon emission of island and reef engineering, the low carbon preparation and mechanical properties of coral aggregate seawater concrete (CASC) based on coral powder (CP) were studied. The effects of different CP calcination temperature, dosage, fineness and multiple composite cementitious materials on the strength of coral mortar were investigated. The mix proportion and mechanical properties (cubic compressive strength (fcu), axial compressive strength (fc), flexural strength (ff) and splitting tensile strength (fsp)) of low carbon CASC (LCCASC) with different strength grades were proposed. The carbon emissions in the manufacturing stage of CASC and LCCASC with different strength grades were analyzed. The results indicate that the optimum calcination temperature, dosage and fineness of CP are 900 degrees C, 10 % and D50 = 4.61 mu m, and the effect of 10 % CP and 20 % slag is the best. The ff of LCCASC is greatly improved compared with that of CASC without CP, which can be increased by 49.1 % at most. The conversion model between fcuand each of fc, ff and fsp of LCCASC is proposed. According to the conversion model, the prediction models of fc, ff and fsp are proposed. The low carbonization evaluation of CASC in the manufacturing stage was carried out, and it was verified that CP had better carbon reduction benefits as an alternative cementitious material.

A fully nonlinear potential flow (FNPF) solver has been developed using the Finite Element Method (FEM) to simulate time-domain interactions between free-surface waves and marine structures. The ALE framework is implemented alongside a segment spring analogy-based moving mesh strategy to accurately track evolving free surfaces and moving boundaries of floating bodies. The solver employs a preconditioned conjugate gradient method to efficiently resolve the resulting sparse, symmetric linear system at each time step. Temporal evolution is managed through a standard fourth-order Runge-Kutta scheme, while Chebyshev 5-point smoothing suppresses non-physical saw-tooth instabilities. The solver’s performance and reliability are verified through comprehensive benchmark tests, including free-surface sloshing, nonlinear wave propagation, and wave-structure interactions with submerged or floating bodies. Furthermore, the study explores a modified potential flow model incorporating a quadratic damping term to address viscous effects in gap/moonpool resonance problems.

This study aims at investigating the mechanism through which limestone calcium carbonate (CC) powder particle size and replacement level regulate cement paste rheology, systematically probing the hydration process, water state migration, particle flocculation, and pore solution ion evolution. Results demonstrated that a 10 wt% cement substitution by CC particles coarser than cement reduced the paste's initial static yield stress, dynamic yield stress, and plastic viscosity by weakening interparticle interactions and ionic strength, improving flowability. Conversely, CC particles finer than cement increased these parameters due to enhanced flocculation and agglomeration. Coarser CC also hindered static yield stress development over time by retarding hydration and increasing double-layer repulsion, while finer CC accelerated static yield stress growth at higher replacement levels via promoted hydration and flocculation. These findings offer valuable insights for CC-based rheological control in cementitious materials.

This study investigates the post-impact residual capacity and damage assessment of hybrid fibre-reinforced polymer (FRP)-concrete-steel double-skin tubular columns (DSTCs) through an integrated numerical simulation and explainable machine learning (ML) approach. Numerical models were established and validated against experimental results to simulate the lateral impact and residual compressive behaviours of DSTCs. The validated numerical models were subsequently employed to examine the impact force, global deflection, energy absorption, and local indentation characteristics of large-scale DSTCs with varying void ratios. Based on the numerical observations, damage indexes incorporating both global deflection and local indentation effects were proposed to quantify the impact-induced damage of DSTCs. Moreover, two types of damage predictive models were developed, and their predictive performances across different damage levels were assessed through regression and classification analyses, supported by confusion-matrix evaluation and Shapley additive explanations (SHAP). The proposed numerical-ML framework enables accurate and physically interpretable damage assessment of impacted DSTCs, and offers a reliable basis for the impact-resistant design and rapid damage assessment of DSTCs.

Although the material-scale degradation may be mitigated under combined chloride and sulfate attack, compared to single chloride or sulfate attack. It remains unclear whether bond degradation will be alleviated under combined attack, since bond is relied the interaction between the two degraded materials. In this study, the degradation and bond performance of reinforced concrete with plain and ribbed bars were studied. The samples were immersed in chloride solution and composite chloride-sulfate solution with an external electric field, respectively. The visual appearance, corrosion level, mechanical properties of concrete, failure mode, bondslip curve, and key bond parameters were analyzed. The sulfate attack was found to substantially alter the visual appearance of the concrete cover, decrease the corrosion level, and delay the time to cover cracking. For plain bars, sulfate attack enhanced the bond performance, but the positive effect was limited by the crack width. While for ribbed bars, sulfate attack weakened the bond, and the negative effect was independent of the crack width. The intrinsic relationship between bond parameters was highly dependent on the bar type, cover cracking, regardless of exposure conditions. The correlation between bond strength and crack width can be well described by an exponential function. These findings improve the understanding on the bond performance of steel bars in reinforced structures serving in saline soils, salt lakes, and marine environments.

High strength coral concrete (CASC) in tropical reef environments requires a large amount of cementitious materials, which can easily cause temperature difference cracks and shrinkage cracks, leading to rapid deterioration of CASC performance. This paper conducted research on the preparation and mechanical properties of two types of low shrinkage CASCs (LCC, LSC) with different strength grades. The experiment revealed the degradation law of mechanical properties of LCC and LSC, and constructed a CASC mechanical performance prediction model based on non-destructive testing technology. The results indicate that sulfate erosion has a promoting and early strengthening effect on the hydration of CASC. The brittleness of CASC is reduced through the addition of coral micro powder or an “expansion agent + superabsorbent polymers”. Meanwhile, the mechanical performance of LCC and LSC, including dynamic elastic modulus, cubic compressive strength (fcu), flexural strength (fcf), and splitting tensile strength (fst), tends to first increase and then decrease. At both below and above 28 dry-wet cycles, sulfate attack has a greater effect (enhancement or degradation) on fcu than chloride salt attack. This study fully considers the influence of coral powder, expansion agents, and the service environment on the mechanical properties of concrete, and incorporates experimental data from 90 to 720 days reported in the literature. Based on non-destructive testing technology, the fcu, fcf, and fst prediction models of CASC are proposed and validated. It is found that their accuracy improved by 62%, 28%, and 24% respectively compared to models that do not consider the above factors.

Both reinforcement corrosion and loading rate significantly influence the bond performance between reinforcement and concrete. However, most existing degradation models for bond strength between corroded reinforcement and concrete are based on concentric pull-out specimens and do not fully consider the constraint state of reinforcement in actual structures. This limitation hinders the accurate evaluation of bond performance between corroded reinforcement and concrete under dynamic loading. To investigate the effects of longitudinal reinforcement corrosion and loading rate on bond performance, electrically accelerated corrosion tests and eccentric pull-out tests were conducted on 100 reinforced concrete cubic specimens. In addition, the influence of key parameters, including longitudinal reinforcement corrosion rate, concrete strength, reinforcement diameter, and loading rate, was considered. After the two tests mentioned above, the dynamic bonding performance between corroded longitudinal reinforcement and concrete was evaluated, including post-corrosion state, failure modes, and bond strength. Subsequently, on the basis of the experimental data obtained from the present study and existing literature, both the bond strength model and peak slip model considering each influencing factor were developed. Building upon these models, a simplified bond stress-slip model was suggested and validated against the results of the present study and prior research findings.

To investigate the shear behavior of coral aggregate concrete beams (CACB), a combined approach of experimental and numerical simulation was employed. A numerical model to analyze the shear behavior of CACB was developed, uncovering the impact of diverse concrete strength grades on the shear behavior of CACB. The results indicated that balanced failure in the shear-critical section occurs in CACB with diverse concrete strength grades, which was fundamentally similar to that observed in OACB. Given the complex stress states, including tensile, shear, and compressive stresses, present in CACB during loading, a numerical simulation model based on Karagozian & Case (K&C) theory was proposed, which incorporates the corrosion effects and the brittle mechanical properties. It has been validated that this model effectively captures the entire process of diagonal cross-section damage for C25-C60 CACB, and key performance indicators such as shear capacity (Vcs) and mid-span deflection. Furthermore, it outperformed previous calculation formulas by an improvement margin of 5.7 %.

To realize the service life quantitative design of marine aggregate concrete (MAC) structures, the influence of exposed area, concrete strength grade/type/protective layer thickness and additional anti-corrosion measures on the service life of MAC structures were studied, the durability improvement technology and service life design methodology (40 similar to 100 a) of MAC structure were suggested. The results show that the increase of concrete strength grade/protective layer thickness, the service life of MAC structures gradually prolonged. Notably, at the same strength grade, ordinary aggregate concrete (OAC) structures demonstrate a longer service life relative to seawater seasand concrete (SSC) and coral aggregate concrete (CAC) structures. Considering factors such as engineering cost and structural durability, SSC/OAC structure is recommended for offshore engineering. When the concrete strength grade is C60 and protective layer thickness is 14 cm of OAC structure, after being coated with SP105 high-permeability epoxy protective material (SP), is capable of fulfilling the 100 a service life requirement. The CAC structure is recommended for far sea engineering. When the concrete protective layer thickness is 12 cm, strength grade is C65, and combined anti-corrosion measures of composite active mineral admixture (MA) inter-mixing and SP coating are adopted, the service life of CAC structure can reach 60 a.

Textile-reinforced ultra-high toughness cementitious composite (UHTCC) jackets, referred to as TRU jackets, are a type of high-performance strengthening system. TRU has the excellent tension ductility and crack control capacity of UHTCC, as well as the high tensile strength of textile. In this paper, axial compression tests of TRUconfined square concrete prisms were carried out. The effects of cross-section sizes and textile layer numbers on failure modes and mechanical properties were investigated. The experimental results showed that TRU jacket confinement effectively improved the compressive strength and deformation capacity of concrete. The effect of textile layer numbers was correlated with the sizes of cross-section. With an increase in the cross-section size of specimens, the enhancement of the axial compression performance of confined specimens decreased due to a decrease in the effective confinement stress of jackets. Based on the experimental results, a compressive stressstrain relationship model of TRU-confined concrete is proposed which includes an ascending branch, a plateau branch, and a descending branch. The predicted stress-strain curves are in good agreement with the experimental results, providing an analytical model for the design of TRU-confined concrete structures.

In the context of the national strategy for "Maritime power" and the construction of the "Belt and Road", marine engineering infrastructure construction of China has accelerated. The on-site use of raw materials such as coral and seawater to prepare marine concrete (MC) significantly reduces project costs, ensures the construction period, and reduces carbon emissions due to transportation. However, complex and harsh marine environments have a strong corrosive and destructive effect on structures, seriously affecting the use and safety of marine engineering structures. Therefore, it is of great significance to apply additional anticorrosion measures to MC structures and conduct research on service life prediction and durability design. In marine environments, the corrosion of steel bars inside concrete structures caused by chloride ions in seawater is a main reason for the deterioration in the durability of these structures. In this study, to effectively improve the durability of concrete structures in marine engineering, it was treated with two anti-corrosion measures: internal addition of composite active mineral admixtures (MA) and external application of high-permeability epoxy protective materials (SP). By investigating the diffusion law of Cl-in concrete, the effects of thicknesses of concrete protective layers, concrete types, strength grades, exposed areas, and additional anti-corrosion measures on the service life of coral aggregate concrete (CAC) and ordinary aggregate concrete (OAC) structures were studied. Design suggestions for improving the service life of MC structures were proposed based on the ChaDuraLife life prediction method, which combines the characteristics of the exposed environment of concrete structures in marine engineering. Theoretical and data support are provided for the application of MC in practical engineering. The results showed that under the same marine exposure zone, with an increase in the concrete strength grade and protective layer thickness, the service life of the CAC and OAC structures gradually increased. The service life of the OAC structures exhibited the trend of underwater zone > atmospheric zone > tidal zone in different ocean exposure areas. When the concrete strength grade, protective layer thickness, and exposure zone were the same, the service life of CAC structures was shorter than that of OAC and followed the pattern of atmospheric zone > underwater zone > tidal zone. The use of internally mixed composite mineral admixture MA, externally coated high-permeability epoxy protective material SP, and "internally mixed + externally coated" anti-corrosion measures increased the service life of OAC structures by 1.8/1.7, 2.4/2.4, and 3.4/3.2 times, respectively, compared with no measures. In underwater zone of the ocean, for CAC/OAC structures with a conventional protective layer thickness of 6 cm, even if the concrete strength grade reached C50, the service life remained relatively low. Additional anticorrosion measures, such as internal mixing and external coating, were required to improve the durability of the structure. Considering factors such as engineering costs and structural durability, the adoption of OAC structures for nearshore engineering is recommended. When the concrete strength grade is C50 or higher, the protective layer thickness is greater than 14 cm, and when the high-permeability epoxy protective material SP is applied externally, the service life of the underwater structure can reach up to 100 years. It is recommended that CAC structures be used in offshore engineering applications. When the concrete strength is greater than C65 and the thickness of the protective layer is 10 cm, the combined anti-corrosion measure of mixing MA and coating SP can significantly improve the service life of the engineering structure.

To promote the quality and utilization efficiency of coral aggregates, an innovative composite modification technique combining mild acid-washing with fast-setting pre-coating is proposed. Utilizing dilute acetic acid as the acid solution, the concentration and immersion duration were optimized by assessing alterations in the physical properties of the coral aggregates pre- and posttreatment. This approach effectively eliminates impurities from the surface layer and interior voids, thereby enhancing the interfacial adhesion between the aggregates and cementitious materials. Additionally, the application of an optimally proportioned sulphoaluminate cement (SAC) slurry as a coating markedly enhanced the strength and reduced the water absorption of the coral aggregates. In comparison to concrete composed of untreated coral aggregates, the composite-modified treatment significantly enhanced the workability and mechanical properties of coral aggregate concrete (CAC). Notably, the slump increased by 38.10 %, while the flexural and compressive strengths improved by 24.77 % and 30.40 %, respectively. These enhancements are ascribed to the gradient filling of pores within the internal weak zones, which elevated the modulus and hardness while markedly reducing the thickness of the interfacial transition zone (ITZ). This study provides a novel strategy for producing high-performance CAC, particularly suitable for marine engineering applications.

Ultra-high toughness cementitious composite (UHTCC) is known for its superior tensile strain-hardening behavior and crack control capability. However, in chloride-rich marine environments, reinforcement corrosion remains a critical issue, potentially affecting the bond performance between steel bars and UHTCC. This study experimentally investigated the bond behavior between corroded reinforcement and UHTCC using beam-type specimens. The influences of reinforcement corrosion ratio and cover-thickness to rebar-diameter ratio (c/d) on bond strength were analyzed. The experimental results showed that all specimens exhibited pull-out failure accompanied by diagonal and splitting cracks. Bond strength initially increased with rising corrosion ratio due to improved confinement of corrosion product filled cover, and then declined beyond a critical corrosion threshold due to severe rib degradation and loss of mechanical interlocking. The critical corrosion ratio, at which bond strength became lower than the initial strength, increased from 12 % at c/d of 1.5 to 22.5 % at c/d of 2.5, demonstrating UHTCC's superior confinement against bond degradation. Based on experimental data, an empirical bond strength model accounting for both corrosion ratio, c/d, and bond length to rebar diameter ratio (l/d) was developed, showing a good agreement between predicted and tested results (mean of 1.01, COV of 0.11). It provides a basic bond model for mechanical analysis and assessment of reinforced UHTCC members in chloride-corrosion environments.

This research experimentally and numerically investigates the dynamic response of hybrid fiber reinforced polymer (FRP)-concrete-steel double-skin tubular member (DSTM) under close-range blast load. Three DSTMs, 2500 mm in length and 200 mm in diameter, were designed and tested under close-range blast load at a scaled distance of 0.251 m/kg1/3. The blast pressure-time histories, damage modes and deflection characteristics of blasted DSTMs were acquired and analyzed. The test results demonstrate that the DSTMs exhibit highly localized damage mode (FRP tube ruptures and concrete fragmentations) under close-range blast load. Partial concrete filling into steel tube and adding steel ribs can both improve the blast resistant capacity of DSTM, with the effect of steel ribs more pronounced. Afterwards, refined numerical models were established, and the models' accuracies were validated using the current test data. The validated models were used to reveal the blast resistant mechanism of DSTM, including the damage evolution, energy absorption mechanism, and confinement/protective effect from FRP tube. Furthermore, parametric analyses were conducted to study the effects of blast scaled distance, void ratio, and steel rib configurations on the close-range blast behavior of DSTM.

The adsorption film of corrosion inhibitors on the steel surface can exert a steric hindrance effect on the permeation and diffusion of chloride ions, which delays the corrosion process of steel bars and reduces the risk of durability decline in reinforced concrete structures. In our study, the concrete specimens and reinforced concrete members incorporated with triethanolamine derivatives, namely triethanolamine phosphate (TP) and triethanolamine dodecylbenzene sulfonate (TDS), were subjected to chloride-induced accelerated corrosion by an electric field. The concrete properties, including compressive strength, ultrasonic pulse velocity, and concrete resistivity, before and after electric field treatment were compared. Meanwhile, the corrosion characteristics and bond-slip behavior of reinforced concrete members were studied. Results showed that electrification causes the deterioration of concrete material, among which the rapid decline in resistivity than strength of TDS concrete is related to the significant influence of TDS on concrete pore solution than interface transition zone. Due to the air-entraining effect, which provides more space to accommodate the expansive products in concrete, the duration of the electric field incurs no discernible effect on the bond strength of reinforced concrete members with TDS. Conversely, members with TP exhibited actual corrosion rates of the main reinforcements far less than the target corrosion rate, and bond strength was enhanced with the duration of the electric field. Finally, a bond-slip model for reinforced concrete pull-out members with TP and TDS was established according to the relationship between the ratio of main reinforcement corrosion rate.

Against the backdrop of the Belt and Road Initiative,engineering development and construction in tropical island areas along its routes have been accelerated,requiring a large amount of building materials.However,local traditional building material resources are lacking,while local coral,seawater,and other resources are abundant.Therefore,in the construction of island and reef projects,such as port terminals and roads,it is of great importance to prepare coral aggregate concrete beams(CACBs)on-site using coral,coral sand,and seawater.However,in the tropical marine environment with high wind,humidity,temperature,and radiation,the reinforcing bars inside CACBs are highly prone to rust,threatening the safety of structures.The shear failure of reinforced concrete beams is a typical brittle failure,and its failure risk is much greater than that of the same type of bending failure.Recently,numerical simulation technology has been widely used in the engineering field.Compared with traditional testing methods,it has the advantages of repeatability,strong controllability,low cost,and high time efficiency.Therefore,conducting research on the shear performance of different types of reinforcing bar CACBs by combining experiments and numerical analyses is of great scientific and engineering importance for the engineering construction and restoration of tropical islands and reefs.This study conducts experimental research on the shear performance of CACBs with different types of reinforcing bars through a combination of experiments and numerical simulations.Based on the experimental results,the constitutive model parameters of CACBs were determined,and a numerical analysis model of the shear performance of CACBs based on the Karagozian&Case(K&C)theory was established to analyze its crack development,failure deformation,and shear bearing capacity.Relationships such as the load-deflection curve and load-reinforcement strain were established,and the influence laws of different factors on the shear performance of CACBs were clarified.The results show that the type of steel bar has a significant influence on the shear performance of CACBs because ordinary steel bars rust easily,while stainless and coated steel bars can effectively inhibit corrosion.When the shear failure of CACBs occurred,the strain of ordinary steel bars was higher than that of newly coated organic steel bars.In addition,based on the K&C theory,a numerical analysis model for describing the shear resistance of CACBs was proposed.The applicability of the numerical model in CACBs ranging from C30 to C60 was verified.This model could better describe the oblique section failure morphology throughout the entire CACB process.The errors between the simulated and measured values of Vcr and Vcs,respectively,and the midspan deflection were all less than 18%.The shear bearing capacity calculated using the proposed numerical model improved by 63%and 31%compared with JGJ/T 12-2019 and GB50010-2010,respectively,and by 4%compared with the calculation formula proposed by the research group in the early stage.This indicates that the numerical model can effectively characterize the variation law of the shear performance of CACBs.