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Objective: To explore the association between green space, multiple ambient air pollutants and depressive/anxiety symptoms and the mediating role of physical activity (PA) in Chinese adolescents. Method: A school-based health survey was conducted in eight provinces in China in 2021. 22,868 students aged 14.64 (±1.77) years completed standard questionnaires to record details of depressive, anxiety symptoms and PA. We calculated the average normalized difference vegetation index (NDVI) in circular buffers of 200 m, 500 m and 1000 m and estimated the concentrations of PM10, PM2.5, CO, NO2, O3, SO2 around the adolescents’ school addresses. Results: The exposure–response curves showed that the lower the NDVI value, the higher the risk of depressive and anxiety symptoms. CO, PM2.5 and SO2 and air pollution score were associated with increased risk of depressive and anxiety symptoms. NDVI in all circular buffers decreased the risk of depressive and anxiety symptoms at low levels of PA, but the associations were not significant at high levels of PA. In the subgroup analysis, PM10, PM2.5, CO, NO2, SO2, AQI and air pollution score increased the risk of depressive and anxiety symptoms at low PA levels, but the associations were not significant at high levels of PA. Mediation analysis indicated that the mediating effect of PA on the association between NDVI, NDVI-200 m NDVI-500 m, CO, PM10, PM2.5, SO2, AQI and depressive/anxiety symptoms was statistically significant（p

Submerged floating tunnel (SFT) may be subjected to sudden impact loads such as submarine and shipwreck. Besides the local damage caused by impact, the overall transient dynamic response may also affect its driving safety. Based on the dynamic impact finite element software, the full-length model and the locally truncated accurate model with solid element of the SFT are established respectively. By applying different spring stiffness constraints on the boundary of the truncated model, its first three modes are consistent with the full-length model, thus their dynamic characteristics are basically the same. The truncated model is further used to simulate the impact of a massive object on the SFT under different impact velocities, impact mass, impact angles and impact positions. The velocity and mass of the impact object have positive influences on the peak contact force, the displacement amplitude of the tube and the length of the damaged area. When the impact angle is perpendicular to the SFT tube, the contact force, displacement amplitude and the damaged area are the largest. The change of the impact position has little effect on the contact force and the damage area, but it will affect the distribution of displacement amplitude.

Due to the assumption of acceleration variation in traditional step-by-step integration methods such as Newmark, sufficiently small time steps are required to ensure numerical stability and accuracy in dynamic systems. In contrast, the state-space approach, based on piecewise interpolation of discrete load functions, does not rely on predetermined acceleration assumptions and has demonstrated high efficiency in terms of stability and accuracy. The original state-space method requires the calculation of the inverse of the structural mass in the transition matrix. However, when a lumped mass matrix is used, this computation renders the entire mass matrix singular, resulting in an invalid solution expression. To address this issue, this study proposes an improved state-space approach for the transient analysis of large-scale structural systems with local nonlinearities. In this approach, a nonlinear force corrector is introduced as an external force term applied to the linear elastic system to account for the nonlinear behavior of locally yielding components. Consequently, the original nonlinear dynamic system can be transformed into an equivalent linear elastic transient system. Furthermore, based on the lumped mass matrix, a first-order ordinary differential state-space equation for such an equivalent linear elastic transient system is derived. Simulation results from three transient system examples show that the state-space approach outperforms the Newmark method in terms of accuracy and stability for dynamic systems characterized by high frequency and low damping. The prediction results show that the state-space approach appears to be insignificantly affected by the choice of the consistent or lumped mass matrix. The numerical results show that the root-mean-square errors between the consistent and lumped matrices in the top displacement time histories of a 15-storey plane frame under various seismic intensities are all less than 1%, and in the base reaction time histories responses the discrepancies are only about 0.5%, indicating that the use of lumped mass matrices is quite reliable. When many nodes or degrees of freedom have no assigned mass, the dimensionality of the state-space equation can be significantly reduced using the lumped mass approach. Therefore, the simulation of large-scale systems can be simplified by employing the improved state-space approach with lumped mass matrices, yielding results nearly identical to those obtained using traditional methods. In conclusion, the improved state-space approach has great potential for the simulation of transient behavior in large-scale systems with local nonlinearities.

ABSTRACTAs the main load bearing component, the steel strand has a significant impact on the safety of civil infrastructure. Real-time monitoring of steel strand stress distribution throughout the damage process is an important aspect of civil infrastructure health assessment. Hence, this study proposes an optical-electrical co-sensing (OECS) smart steel strand with the DOFS and CCFPI embedded in. It can simultaneously measure small strains in the initial damage phase with high accuracy and obtain information in the large deformation phase with relatively low precision. Several experiments were carried out to test its sensing performance. It shows both DOFS and CCFPI have good linearity, repeatability and hysteresis. In comparison to DOFS, CCFPI has a relatively lower accuracy and resolution, but a large enough measurement range to tolerate the large strain in the event of a steel strand failure. To verify the reliability of the proposed smart steel strand in real structures, the strand strain distribution in the full damage process of bonded prestressed beams under four-point bending loading was monitored using the smart steel strand as a prestressing tendon. The strain measured by the OECS steel strand is shown to reflect the deformation and stiffness variation of prestressed beams under different load.

ABSTRACTCarbon fiber reinforced polymer (CFRP) can be applied for bridge cables due to its excellent properties. As the important load-bearing structural component, real-time force monitoring of the CFRP cable is required. This paper presents a new smart CFRP cable that combines the self-sensing rods with embedded sensors and the anchorage system using extrusion technology. By embedding optical fiber (OF) and coaxial cable Fabry-Perot interferometer (CCFPI) into CFRP rods respectively, two types of self-sensing rods (CFRP-OF rod and CFRP-CCFPI rod) were fabricated. A new anchorage unit using an extrusion process was proposed as a basic component of smart CFRP cables. Anchorage units holding a CFRP-OF rod and a CFRP-CCFPI rod were tested to obtain their sensing and mechanical properties. Three anchorage units were assembled to form a smart CFRP cable with self-sensing functionality. A verification test was carried out to confirm the capability of monitoring the cable force. The test results demonstrate that the smart CFRP cable composed of multiple anchorage units has good potential in bridge engineering.

As a widely used taut-wire mooring system for deepwater platforms, the Vertically Loaded Anchor (VLA) has better performance in bearing capacity, angle adaptability, and deepwater installation than other systems. However, the installation process of the VLA and its motion characteristics are significantly impacted by multi-layered seabed soil. In this paper, the coupled Eulerian‒Lagrangian (CEL) large deformation finite element analysis method has been applied to analyse the continuous penetration of a VLA in nonuniform clay with an interbedded stiff layer. A detailed parametric study has been carried out to explore the trajectory, drag angle, movement direction and drag force of the VLA in layered clay with different embedded depths, thicknesses and undrained shear strength of the stiff layer. The CEL numerical analysis results have been validated by comparison with the analytical solutions from the inverse catenary equation. Excellent agreement has been obtained between the results from the CEL analyses and the analytical solutions. The stiff layer leads to concave and convex shapes on the trend lines of the movement direction angle and drag forces, respectively. The embedded depth of the stiff layer determines where the concave and convex shapes appear on the trend lines, while the thickness affects the sizes of the openings of the shapes. The most decisive parameter, an abrupt variation in the undrained shear strength, causes predominant rotation at the interface of layered clay. It diminishes the final embedment depth and ultimate stable drag force, meaning that the bearing capacity of the VLA severely declined in layered clay.

Replacing micro-reinforcing fibers with carbon nanotubes (CNTs) is beneficial for improving the impact properties of ultra-high performance concrete (UHPC); however, the weak wettability and dispersibility of CNTs and the weakly bonded interface between CNTs and UHPC limit their effectiveness as composites. Therefore, this study aims to enhance the reinforcement effect of CNTs on the impact properties of UHPC via functionalization. Unlike ordinary CNTs, functionalized CNTs with carboxyl or hydroxyl groups can break the Si–O–Ca–O–Si coordination bond in the C–S–H gel and form a new network in the UHPC matrix, effectively inhibiting the dislocation slip inside UHPC matrix. Furthermore, functionalized CNTs, particularly carboxyl-functionalized CNTs, control the crystallization process and microscopic morphology of the hydration products, significantly decreasing and even eliminating the width of the aggregate–matrix interface transition zone of the UHPC. Moreover, the functionalized CNTs further decrease the attraction of the negatively charged silicate tetrahedron to Ca2+ in the C–S–H gel, while modifying the pore structure (particularly the nanoscale pore structure) of UHPC, leading to the expansion of the intermediate C–S–H layer. The changes in the microstructures of UHPC brought about by the functionalized CNTs significantly enhance its dynamic compressive strength, peak strain, impact toughness, and impact dissipation energy at strain rates of 200–800 s−1. Impact performance of UHPC containing a small amount of carboxyl-functionalized CNTs (especially the short ones) is generally better than that of UHPC containing hydroxyl-functionalized and ordinary CNTs; it is even superior to that of UHPC with a high steel fiber content.

This study investigates the effects of nanofillers on the interfacial transition zone (ITZ) between aggregate and cement paste by using nanoindentation and statistical nanoindentation techniques. Moreover, the underlying mechanisms are revealed through micromechanical modeling. The nanoindentation results indicate that incorporating nanofillers increases the degree of hydration in the ITZ, reduces the content of micropores and low-density calcium silicate hydrate (LD C–S–H), and increases the content of high-density C–S–H (HD C–S–H) and ultrahigh-density C–S–H (UHD C–S–H). In particular, a new phase, namely nano-core-induced low-density C–S–H (NCILD C–S–H), with a superior hardness of 2.50 GPa and an indentation modulus similar to those of HD C–S–H or UHD C–S–H was identified in this study. The modeling results revealed that the presence of nanofillers increased the packing density of LD C–S–H and significantly enhanced the interaction (adhesion and friction) among the basic building blocks of C–S–H gels owing to the formation of nano-core–shell elements, thereby facilitating the formation of NCILD C–S–H and further improving the performance of the ITZ. This study provides insight into the effects of nanofillers on the ITZ in concrete at the nanoscale.

Structural health monitoring (SHM) is critical to maintaining safe and reliable civil infrastructure, but the optimal design of an SHM sensing system, i.e., optimal sensor placement (OSP), remains a complex challenge. Based on the existing literature, this paper presents a comprehensive review of OSP strategies for SHM. It covers the key steps in OSP, from evaluation criteria to efficient optimization algorithms. The evaluation criteria are classified into six groups, while the optimization algorithms are roughly categorized into three classes. The advantages and disadvantages of each group of methods have been summarized, aiming to benefit the OSP strategy selection in future projects. Then, the real-world implementation of OSP on bridges, high-rise buildings, and other engineering structures, is presented. Based on the current progress, the challenges of OSP are recognized; its future development directions are recommended. This study equips researchers/practitioners with an integrated perspective on state-of-the-art OSP. By highlighting key developments, persistent challenges, and prospects, it is expected to bridge the gap between theory and practice.

Due to the difference of industrialization degree and meteorological conditions, there are obvious differences in the composition of air pollution between islands and inland areas. With Zhoushan (ZS) and Nanjing (NJ) representing islands and inland cities in the Yangtze River Delta, the differences in vertical distribution of atmospheric components were investigated. A combination of multi-axial differential optical absorption spectroscopy (MAX-DOAS), weather research and forecasting (WRF), and potential source contribution function (PSCF) models were used to obtain vertical distribution data for aerosols, nitrogen dioxide (NO2) and formaldehyde (HCHO), meteorological factors, and pollution sources in summer 2019. The findings indicate that, except for the aerosol extinction coefficient (AE), the atmospheric composition at the ZS site was not significantly stratified. However, the AE, NO2, and HCHO at NJ all displayed a decreasing trend with altitude. Here is the interesting finding that the ZS site has a higher AE value than the NJ site, while NJ displays higher NO2 and HCHO columns than the ZS site. This discrepancy was primarily attributable to Zhoushan City’s extremely low traffic emissions when compared to inland cities. In addition, HCHO in the YRD region was significantly affected by human activities. Analysis of potential pollution sources found that regional transport contributed to differences in atmospheric composition at different altitudes in different regions. Aerosols, NO2, and HCHO in Nanjing were significantly affected by transport in inland areas. Aerosols in Zhoushan were easily affected by transport in the Yellow Sea and East China Sea, and NO2 and HCHO were significantly affected by transport contributions from surrounding areas in inland areas. The study strongly suggests that land and sea breezes play an important role in the vertical distribution of aerosols over island regions.

Urban air pollution has become a regional environmental problem. In order to explore whether island areas were affected by the urban development of surrounding areas, in this paper, we systematically study the vertical distribution characteristics of atmospheric components, meteorological drivers, potential pollution sources, and the population health risks of fine particulate matter in island cities in China. The vertical profiles of three atmospheric pollutants (aerosols, NO2, and HCHO) in the lower troposphere of Huaniao Island in the East China Sea (ECS) were obtained using ground-based multi-axial differential optical absorption spectroscopy (MAX-DOAS). The results show that the aerosol extinction coefficients, NO2, and HCHO were primarily distributed at altitudes below 1 km, and the atmospheric pollutants in Zhoushan were obviously affected by high-altitude transfer. The main meteorological driving factors of aerosols, NO2, and HCHO were different at different altitudes. The key factor contributing to the high column concentrations of NO2 and HCHO in the upper air (greater than 400 m) was the transport of pollutants brought about by changes in wind speed. By exploring the main potential sources of atmospheric pollutants, it was found that the main sources of aerosols, NO2, and HCHO are coastal cities in the Yangtze River Delta, including southeast Zhejiang Province, southeast Fujian Province, Shanghai, ECS, and the Yellow Sea. Compared with aerosols and HCHO, local primary emissions are an important source of NO2, which are mainly related to industrial activities in Zhoushan Port. In addition, using the expose-response function model, the number of attributable cases of PM2.5 air pollution in Zhoushan City in 2019 accounted for 6.58% of the total population. This study enriches our understanding of the vertical distribution characteristics of atmospheric composition and health risk assessment on Chinese islands.

To investigate the long-term performance of the packaged fiber Bragg grating (FBG) sensors embedded in civil infrastructure for strain monitoring, in this paper, the influence of host matrix’s creep effect on the behavior of the FBG sensors was systematically studied through theoretical, numerical, and experimental analysis. A theoretical strain transfer analysis between the optic fiber, packaging layer, and host matrix to consider the creep effect of the host matrix was performed accordingly for long-term strain monitoring. Parametric studies were carried out using numerical analysis for FBG sensors packaged with glass fiber reinforced plastic (GFRP), also known as FBG-GFRP sensors in concrete, as an example. The results show that embedded in a creep medium, an acceptable long-term performance of packaged FBG sensors requires the packaging layer to have a minimum length and maximum thickness. Laboratory long-term creep tests using epoxy resin and concrete as host matrix for FBG-GFRP sensors also clearly demonstrated that the influence of creep effect cannot be ignored for strain measurements if the host matrix has a creep potential and the developed correction model performed well to reduce measurement errors of such sensors in creep medium.

BackgroundMucosa-associated lymphoid tissue (MALT) lymphoma is an extranodal lymphoma with an indolent natural course. The thyroid gland is an uncommon site of involvement. We aimed to investigate serial ultrasound features and the disease progression during the clinical course of thyroid MALT lymphoma.MethodsWe searched our hospital’s pathology database (5,418 patients with thyroid malignancy) between January 2000 and July 2022. The medical records and serial ultrasounds of 11 patients with 12 thyroid MALT lymphoma foci were analyzed retrospectively.ResultsAn enlarging neck mass, dyspnea, B symptoms, and neck lymphadenopathy were seen at diagnosis in 9 (9/11, 81.8%), 3 (3/11, 27.3%), 2 (2/11, 18.2%), and 9 (9/11, 81.8%) cases, respectively. Eleven cases were concomitant Hashimoto thyroiditis. Common ultrasound features included bilateral or unilateral asymmetric goiter or large, solid, and very hypoechoic nodules (11/12, 91.7%) interspersed with linear, reticular hyperechoic, and enhanced posterior echoes (11/12, 91.7%), and neck lymph node involvement (10/11, 90.9%). The Thyroid Imaging and Reporting Data System (TIRADS) categories showed higher diagnostic accuracy (11/12, 91.7%) than real-time ultrasound (2/12, 16.7%) in evaluating thyroid lesions for recommendation of fine-needle aspiration (FNA). Serial ultrasound showed self-limiting changes in three cases, relapse in three cases after subtotal thyroidectomy and chemotherapy, large cell transformation (LCT) in one case after left lobectomy, partial remission in one case, and complete remission after chemo/radiation in four cases; progression to enlarged thyroid nodules occurred in three cases without treatment, with no obvious change observed after diagnosis. Three patients died during follow-up.ConclusionOn sonograms, solid large thyroid nodules or goiter with very hypoechoic and enhanced posterior echoes in the setting of Hashimoto thyroiditis should raise suspicion for MALT lymphoma. TIRADS categories can improve the ultrasound diagnostic efficacy for malignancy. Serial ultrasound examinations demonstrated self-limiting and indolent natures of thyroid MALT lymphoma.

Carbon-fiber-reinforced polymer (CFRP) is a type of composite material with many superior performances, such as high tensile strength, light weight, corrosion resistance, good fatigue, and creep performance. As a result, CFRP cables have great potential to replace steel cables in prestressed concrete structures. However, the technology to monitor the stress state in real-time throughout the entire life cycle is very important in the application of CFRP cables. Therefore, an optical–electrical co-sensing CFRP cable (OECSCFRP cable) was designed and manufactured in this paper. Firstly, a brief description is outlined for the production technology of the CFRP-DOFS bar, CFRP-CCFPI bar, and CFRP cable anchorage technology. Subsequently, the sensing and mechanical properties of the OECS-CFRP cable were characterized by serious experiments. Finally, the OECS-CFRP cable was used for the prestress monitoring of an unbonded prestressed RC beam to verify the feasibility of the actual structure. The results show that the main static performance indexes of DOFS and CCFPI meet the requirements of civil engineering. In the loading test of the prestressed beam, the OECS-CFRP cable can effectively monitor the cable force and the midspan defection of the beam so as to obtain the stiffness degradation of the prestressed beam under different loads.

Abstract Background Multiple myeloma causes different types of renal injury. C3 glomerulonephritis (C3GN) is characterised by an abnormal deposition of complement C3 in the glomeruli due to abnormal activation of the alternative pathway of the complement system. While the association between C3GN and multiple myeloma has been well established, mild renal injury by C3GN in multiple myeloma patients with high levels of light chain has not been reported. Case presentation A 55-year-old Chinese man presented with proteinuria. Combined with immunofixation electrophoresis, bone marrow biopsy, and renal biopsy, he was diagnosed with IgA-type multiple myeloma accompanied by C3GN and light chain proximal tubulopathy without crystal deposits. Although he had a higher level of lambda serum-free light chain, the renal injury in this patient was mild. After treatment with four courses of BD, one course of PAD, and autologous stem cell transplantation, he achieved a very good partial hematologic response with stable renal function. Conclusions In multiple myeloma, the light chain reaches a certain level and persists, resulting in C3GN renal impairment. Early diagnosis and early intensive treatment are critical for the prognosis of such patients.

Abstract Background Universal gene targets are in persistent demand by real‐time quantitative polymerase chain reaction (RT‐qPCR)‐based methods in acute leukemia (AL) diagnosis and monitoring. Human Krüppel‐like factor 3 (hKLF3), a newly cloned human transcription factor, has proved to be a regulator of hematopoiesis. Methods Sanger sequencing was performed in bone marrow (BM) samples from 17 AL patients for mutations in hKLF3 coding exons. hKLF3 expression in peripheral blood (PB) and BM samples from 45 AL patients was dynamically detected by RT‐qPCR. PB samples from 31 healthy donors were tested as normal controls. Results No mutation was sequenced in hKLF3 coding exons. hKLF3 expression in PB of AL was significantly lower than that in healthy donors [0.30 (0.02‐1.07) vs 1.18 (0.62‐3.37), P

Clinical data of patients with severe aplastic anemia (SAA) were retrospectively analyzed to evaluate the outcomes of haploidentical hematopoietic stem cell transplantation (HID-HSCT) with matched related sibling hematopoietic stem cell transplantation (MSD-HSCT) in complications and survivals. Thirty consecutive patients were enrolled in the study with a median follow-up of 50 months (range 4, 141), and the median age of the patients was 21 years (range 3, 49). All the patients achieved myeloid engraftment in the two cohorts. The cumulative incidences of platelet engraftment were 95.5 and 100% in HID cohort and MSD cohort, respectively. The median time for neutrophil and platelet recovery was 11 (range 9, 19) and 15 (range 10, 25) days in HID cohort, and 12 (range 10, 19) and 14 (range 8, 25) days in MSD cohort. The cumulative incidences of grade II–IV and grade III–IV acute graft vs. host disease (aGvHD) in HID cohort and in MSD cohort were 18.9 vs. 14.3% (p = 0.77) and 10.5 vs. 0% (p = 0.42), respectively. The cumulative incidences of chronic graft vs. host disease (cGvHD) was 22.7% in HID cohort and 25.5% in MSD cohort (p = 0.868). The 5-year overall survival (OS) rates and 5-year failure-free survival (FFS) rates in HID cohort and MSD cohort were 85.1 vs. 87.5% (p = 0.858), 80.3 vs. 87.5% (p = 0.635), respectively. The median time to achieve engraftment, cumulative incidence of aGvHD and cGvHD, and the 5-year OS and FFS rates were not significantly different between the two cohorts. We suggest that HID-HSCT might be a safety and effective option for SAA patients without a matched donor.

Buckling-restrained brace (BRB) is a dual-function device that improves the seismic resistance and energy-dissipation capacity of structures in earthquake engineering. To achieve the expected performance under severe ground motions, BRB is usually designed to remain elastic under mild earthquakes, leading to the increased seismic forces and insignificant vibration-reduction effect on the structures at this stage. This study extends the concept of adaptive passive-control of structures by proposing a novel frictional-yielding compounded BRB (FBRB). FBRB is fabricated by connecting the BRB steel casing and end plates with the friction dampers (FDs) in such a way that the BRB steel core and FDs undergo compatible deformation. In this way, FD dissipates seismic energy under mild earthquakes, while FD together with the BRB core dissipates energy under severe ground motions, resulting in an efficient self-adaptive vibration-reduction mechanism. The proposed FBRB construction was experimentally validated by carrying out the reversed-cyclic test, and the result indicated reliable connection with stable hysteretic behavior. Subsequently, the FBRB-equipped frame was proposed and studied which adopted FBRB as the energy-dissipative devices. A parametric design method was developed to determine the FBRB parameters with which the maximum elastic drift of the system could be reduced to the code-allowable value. The approach was implemented on a 48-story mega FBRB-equipped steel frame as the case study. The seismic behavior of the FBRB-equipped case structure was compared with that of the BRB-equipped system, and critically evaluated by carrying out the nonlinear time-history analyses. Results revealed that FBRB compensated for the conventional BRB in terms of inadequate energy dissipation under mild earthquakes and, meanwhile, was more efficient than the conventional BRB in reducing the lateral drifts under severe ground motions. The analysis indicated potential application prospect of FBRB in practical engineering.

Studying the characteristics of new particle formation (NPF) is conducive to exploring the impact of atmospheric particulate matter on the climate, environment, and human health. The particle number size distributions (5.6–560 nm) of aerosols were measured using a fast mobility particle sizer (FMPS) from 1 to 11 May 2019. The clean atmosphere was one of the basic conditions for the occurrence of this continuous new particle formation events. It started between 9:00 and 12:00, and it mainly ended after 20:00. The growth rate (GR) and condensation sink (CS) values in Hefei were 2.98 ± 0.97 nm·h−1 and (3.0 ± 0.4) × 10−2 s−1, respectively. Back trajectory clustering analysis revealed that the mass concentration of the air masses from the southeastern part of Henan Province and the southern part of Anhui Province surrounding the study area were relatively high. The analysis results of the potential source contribution function (PSCF) and the concentration weighted trajectory (CWT) methods show that in addition to local pollution, the long-distance transport of pollutants in the Yangtze River Delta (YRD) greatly contributed to the accumulation modal particulate concentration in Hefei. Moreover, the population affected by PM2.5 during the observation period reached 8.19 × 104, accounting for 1.08% to the total population in Hefei. The premature death cases associated with PM2.5 reached 8.35 × 102. This study is helpful to understand the main influencing factors of consecutive NPF events and the health risks of fine particles.

For both the expansion of important islands/reefs and the development of marine resources in South China Sea, a modular integrated floating structure (MIFS) system with tidal self-adaptation dolphin-fender mooring (DFM) has been proposed. The DFM, coupled with wave energy converters (WEC), can serve as an anti-motion system. Considering both the modules’ hydrodynamic interaction effect and the connectors’ mechanical coupling effect, both dynamic responses of the MIFS system and the WEC’s output power characteristics were investigated under typical sea conditions. Based on the comprehensive consideration of key factors (safety, economy, and comfort), the effects of both the DFM and module connectors were systematically studied for the MIFS system. Preliminarily optimal design parameters of corresponding connectors and WECs were suggested. The security of the MIFS system under extreme sea conditions was checked, and a promising survival strategy has been proposed. In addition, the modular expansion scheme of the MIFS system was further discussed, and the results indicated that the proposed MIFS system shows good expansibility. The WEC can not only improve both dynamic responses and the comfort of inner modules, but also make considerable wave energy contributions.

Abstract Ozone pollution adversely affects human health. In recent years, ozone pollution has become an important research topic and a challenge. By combining differential absorption lidar (DIAL), meteorological gradient tower data, the Weather Research and Forecasting (WRF) model, and the backward trajectories model, changes in vertical ozone concentration, the influencing factors on ozone vertical distribution, and ozone sources were analyzed in Shenzhen from September 20 to 30, 2019. Results indicated that from September 25 to 30, there was obvious residual ozone and transport at night. The analysis of ozone concentration and meteorological factors shows that the temperatures of 291.3–301.8 K and the humidity of 19.4%–71.6% were conducive to ozone formation. As height increased from less than 0.1–0.3 km, the average ozone concentration increased, and the average NO2 concentration decreased. The analysis of potential ozone sources showed that ozone was mainly transported from the northeast of China and that the highest concentration of ozone mainly comes from southeast of Jiangxi province in southeastern China.

A buckling-restrained brace (BRB) serves as a typical load-bearing and energy-dissipative device for the passive control of structures under seismic loading. A BRB is generally designed to not yield under frequently occurring earthquake (FOE) and wind loads, resulting in it having less effectiveness in vibration reduction compared with post-yielding performance. To address this dilemma, this study proposed the concept and technique details of the viscoelastic-yielding compounded BRB (VBRB). Different from a conventional BRB, a VBRB is fabricated by attaching the viscoelastic damper (VED) to the surface of a BRB’s steel casing, ensuring a compatible deformation pattern between the VED and the BRB’s steel core. A dynamic loading test of VBRB specimens was carried out in which 0.2 Hz~0.6 Hz in loading rate and a maximum of 550 kN in load-bearing capacity had been applied, verifying the feasibility and performance of the VBRB. Subsequently, a parametric design procedure was developed to determine the required VBRB parameters so that the maximum elastic drift response of the structure could be reduced to the code-prescriptive value. The wind-resistance and seismic performances of the VBRB were critically evaluated through dynamic time-history analyses on a 48-story mega VBRB-equipped frame designed according to the Chinese seismic design code (GB50011-2010), and the effectiveness of the approach was also verified. Results indicate that the VBRB has advantages over a conventional BRB by providing a multi-stage passive energy dissipation capacity, resulting in a better vibration-control effect than conventional BRBs for structures subjected to wind load and seismic excitations.

A novel modular floating structure (MFS) system moored by tension legs was proposed, which is composed of hexagonal floating modules, floating artificial reefs and wave energy converters (WECs). The integration of floating artificial reefs and WECs into the MFS can improve the marine environment and produce considerable electricity. The effects of both wave characteristics and the module quantity on the hydrodynamic responses of the MFS system were studied in depth, based on a time-domain numerical model. Both the modules’ hydrodynamic interaction effect and the connectors’ mechanical coupling effect were considered. The results indicate that floating artificial reefs combined with WECs can effectively reduce wave loads and convert wave energy into electricity for the MFS system. More modules involved in the MFS system could significantly reduce motion response and produced more wave energy output, which indicates that the MFS system is suitable for large-scale expansion. The effect of different power take-off (PTO) damping coefficients on the WECs’ performance was further investigated, and the optimal damping coefficient was recommended for the MFS system. Finally, the main extreme responses of the MFS system were further investigated, and its safety was checked thoroughly. One survival strategy was proposed, which could efficiently reduce extreme connector loads by more than 50%.

An explicit inverse model of a magnetorheological (MR) damper is established to track the desired force in real time through experimental analysis and mathematical modeling. An algebraic hyperbolic tangent model is used to present the nonlinear behavior of MR dampers to avoid dynamic evolution due to effortless invertibility. A characteristic method is utilized to obtain the initial parameters of this algebraic hyperbolic tangent model; subsequently, the main parameters of the algebraic model are selected as quadratic functions of the applied current such that the closed-form expressions of the inverse model can be obtained. Then, the response time including communication and electromagnetic interactions in the experiment is investigated and modeled. By combining the force-current and electromagnetic models, an inverse model-based force tracking scheme is proposed. A series of validated tests are performed to study the force tracking performance. The proposed model exhibits high fidelity for tracking variable desired forces in experiments. Further analysis on force tracking errors demonstrates the mitigation of errors in various current fluctuating methods.

To analyze the long-term monitoring reliability and life expectancy of FBG-based steel strands, accelerated corrosion and tensile tests were carried out and a life-prediction model was constructed. The validation test results indicated that the monitoring strain sensitivity of FBG-based steel strands decreases with an increase in solution concentration and time in a corrosive acidic environment. When the sensitivity dropped to about 80% of its initial value, the FBG sensor suddenly failed. The life-prediction model indicates that the predicted monitoring life of an FBG sensor is about 56 years in an unstressed condition but about 27 years under the stressful conditions that FBG-based steel strands are subjected to in their working environment. So, to improve their monitoring reliability and monitoring life, it is suggested that FBG-based steel strands might be prepared by “pre-loading.”

The wind energy resource is considerably rich in the deep water of China South Sea, where wind farms have to face the challenge of extreme typhoon events. In this work, the typhoon effect on the aerodynamic performance of the 5MW OC3-Hywind floating offshore wind turbine (FOWT) system has been investigated, based on the Aero-Hydro-Servo-Elastic FAST code. First, considering the full field observation data of typhoon “Damrey” is a long duration process with significant turbulence and high wind speed, so one 3-h representative truncated typhoon wind speed time history has been selected. Second, the effects of both the (variable-speed and collective-pitch) control system of NREL 5 MW wind turbine and the motion of the floating platform on the blade aerodynamic performance of the FOWT system during the representative typhoon time history has been investigated, based on blade element momentum (BEM) theory (coupled with potential theory for the calculation of the hydrodynamic loads of the Spar platform). Finally, the effects of different wind turbine control strategies, control parameter (KP–KI) combinations, wave heights and parked modes on the rotor aerodynamic responses of the FOWT system have been clarified. The extreme typhoon event can result in considerably large extreme responses of the rotor thrust and the generated power due to the possible blade pitch angle error phenomenon. One active-parked strategy has been proposed for reducing the maximum aerodynamic responses of the FOWT system during extreme typhoon events.

Under cyclic load, local fatigue damage will occur in the metal damper widely used in the shear wall. This will deteriorate the stiffness of damper and weaken the hysteresis behaviour. The present paper proposed a new and easy method to manufacture kinds of coupling beam dampers. A thermography-based experiment was used to study the energy dissipation and damage accumulation during fatigue process of the metal damper. Based on the temperature variation related to fatigue damage process, the relationship between the plastic deformation and thermal energy dissipation was quantitatively established. Besides, the relationships between the temperature increase to damage accumulation and mechanical load were analyzed systematically.

Addition of fibers can give brittle material extrinsic toughness, mainly because of the bridging effects. However, such behavior is highly dependent on the interfacial interaction between fiber and brittle matrix. In order to optimize both the strength and ductility of cement, which is the most extensively used brittle material on this planet, here we propose a new strategy to control the interfacial property in the fiber-cement matrix. Silica-coated polyvinylalcohol fibers were successfully synthesized by a sol-gel method with controlled silica thickness, and then incorporated into cement paste. The interaction between fibers and cement matrix was significantly enhanced due to the greatly increased hydrophilicity and roughness of silica-coated fibers, as well as the pozzolanic reactivity of silica nanoparticles. Therefore, the interfacial region between fiber and cement becomes much more compact, promoting the fiber-cement interaction both physically and chemically. As such, the crack propagation would be severely constrained, resulting in the strength and ductility of cement significantly increased. We showed that the ultimate flexural strength and ultimate deflection of the cement composites reinforced by silica-coated polyvinylalcohol fibers increase by 187% and 980% with respect to pristine cement, and increase by 28% and 74% compared to cement reinforced by polyvinylalcohol fibers without silica, at the fiber content of 1 wt.%. This study illustrates the potential and effectiveness of interfacial design to overcome the mechanical dilemma of strength and ductility increase simultaneously, and open a new dimension to further improve the mechanical properties of cement.

This work presents a modular floating structure, which consists of five inner tension-leg platforms and two outermost wave energy converters (denoted as MTLPW). The hydrodynamic interaction effect and the mechanical coupling effect between the five inner tension-leg platforms (TLP) and the two outermost wave energy converters (WEC) are taken into consideration. The effects of the connection modes and power take-off (PTO) parameters of the WECs on the hydrodynamic performance of the MTLPW system are investigated under both operational and extreme sea conditions. The results indicate that the hydrodynamic responses of the MTLPW system are sensitive to the connection type of the outermost WECs. The extreme responses of the bending moment of connectors depend on the number of continuously fixed modules. By properly utilizing hinge-type connectors to optimize the connection mode for the MTLPW system, the effect of more inner TLP modules on the hydrodynamic responses of the MTLPW system can be limited to be acceptable. Therefore, the MTLPW system can be potentially expanded to a large degree.

Isolation technology has been successfully applied in seismic migration. With increasing of seismic demand, seismic performance of isolation structures subjected to very-rare earthquakes need further improvement. However, the isolation layer generally lacks sufficient deformation ability under very-rare earthquakes due to the deformation limit of classical isolation bearing. In order to circumvent the difficulty, this paper develops two new isolation bearings, namely super-large displacement rotation friction pendulum bearing (SLDRFPB) and super-large displacement translation friction pendulum bearing (SLDTFPB). By setting spherical shells with large span and large radius, large horizontal displacement and small horizontal stiffness can be achieved. Safety of the isolation layer and the isolation effect of the superstructure can be greatly improved. SLDTFPB differs from SLDRFPB in the motion state of the superstructure and space utilization of the isolation layer, thus SLDRFPB and SLDTFPB are suitable for structures with different requirements. Due to rotation of the superstructure with SLDRFPB or sliding frames in SLDTFPB, the traditional design method of friction pendulum bearing is no longer suitable. We present a new procedure to accurately and conveniently evaluate seismic performance of two developed bearings. Numerical simulation shows that the seismic response of both the superstructure and isolation layer is small. Developed SLDRFPB and SLDTFPB have sufficient emergency capacity and isolation resilience when subjected to very-rare earthquakes.

Coherent structures in the turbulent boundary layer were investigated under different stability conditions. Qualitative analyses of the flow field, spatial correlation coefficient field and pre-multiplied wind velocity spectrum showed that the dominant turbulent eddy structure changed from small-scale motions to large- and very-large-scale motions and then to thermal plumes as the stability changed from strong stable to neutral and then to strong unstable. A quantitative analysis of the size characteristics of the three-dimensional turbulent eddy structure based on the spatial correlation coefficient field showed that under near-neutral stability, the streamwise, wall-normal and spanwise extents remained constant at approximately 0.3 δ , 0.1 δ and 0.2 δ ( δ , boundary layer height), respectively, while for other conditions, the extent in each direction varied in a log-linear manner with stability; only the spanwise extent under stable conditions was also independent of stability. The peak wavenumber of the pre-multiplied wind velocity spectrum moves towards small values from stable conditions to neutral condition and then to unstable conditions; thus, for the wind velocity spectrum, another form is needed that takes account the effects of the stability condition.

The present wind tunnel study focuses on the effects of the steady-suction-based flow control method on the flutter performance of a 2DOF bridge deck section model. The suction applied to the bridge model was released from slots located at the girder bottom. The suction rates of all slots along the span were equal and constant. A series of test cases with different combinations of suction slot positions, suction intervals, and suction rates were studied in detail for the bridge deck model. The experimental results showed that the steady-suction-based flow control method could improve the flutter characteristics of the bridge deck with a maximal increase in the critical flutter speed of up to 10.5%. In addition, the flutter derivatives (FDs) of the bridge deck with or without control were compared to investigate the fundamental mechanisms of the steady-suction-based control method. According to the results, installing a suction control device helps to strengthen aerodynamic damping, which is the primary cause for enhanced flutter performance of bridge decks.

Combining the advantages of basalt fiber-reinforced polymer (BFRP) material and steel material, a novel BFRP-steel composite plate (BSP) is proposed, where a steel plate is sandwiched between two outer BFRP laminates. The main purpose of this research is to investigate the mechanical behavior of the proposed BSP under uniaxial tension and cyclic tension. Four groups of BSP specimens with four different BFRP layers and one control group of steel plate specimens were prepared. A uniaxial tensile test and a cyclic tensile test were conducted to determine the initial elastic modulus, postyield stiffness, yield strength, ultimate bearing capacity and residual deformation. Test results indicated that the stress-strain curve of the BSP specimen was bilinear prior to the fracture of the outer BFRP, and the BSP specimen had stable postyield stiffness and small residual deformation after the yielding of the inner steel plate. The postyield modulus of BSP specimens increased almost linearly with the increasing number of outer BFRP layers, as well as the ultimate bearing capacity. Moreover, the predicted results from the selected models under both monotonic tension and cyclic tension were in good agreement with the experimental data.

Fatigue, a hot scientific research topic for centuries, can trigger sudden failure of critical structures such as aircraft and railway systems, resulting in enormous casualties as well as economic losses. The fatigue life of certain structures is intrinsically random and few monitoring techniques are capable of tracking the full life-cycle fatigue damage. In this paper, a novel in-situ wireless real-time fatigue monitoring system using a bio-inspired tree ring data tracking technique is proposed. The general framework, methodology, and verification of this intelligent system are discussed in details. The rain-flow counting (RFC) method is adopted as the core algorithm which quantifies fatigue damages, and Digital Signal Processing (DSP) is introduced as the core module for data collection and analysis. Laboratory test results based on strain gauges and polyvinylidene fluoride (PVDF) sensors have shown that the developed intelligent system can provide a reliable quick feedback and early warning of fatigue failure. With the merits of low cost, high accuracy and great reliability, the developed wireless fatigue sensing system can be further applied to mechanical engineering, civil infrastructures, transportation systems, aerospace engineering, etc.

Fiber-reinforced polymer (FRP) composites have been widely employed to design advanced structural columns such as the hybrid FRP−concrete−steel double-skin tubular column (hybrid DSTC) with potential benefits. To date, the safety and self-monitoring of the hybrid DSTCs are still a challenge to overcome due to the complex damage scenarios. This paper investigates the self-sensing performance of a newly developed smart double-skin tubular confined concrete column (smart BFST-DSTC) made of basalt FRP−steel composite with built-in optical fiber Bragg grating sensors (OFBGs). The design of the smart BFST-DSTC and sensing principle are firstly addressed, followed by an experimental investigation on the basic mechanical properties and strain-based sensing performance of ten scaled specimens under axial compression. The outcomes reveal the enhancement of the proposed column in terms of load-carrying capacity, confinement ratio, and axial stress-axial strain behavior, as well as failure and damage modes when compared with the hybrid DSTC. The self-sensing investigation demonstrates that the measurement range satisfies the requirement to monitor and evaluate the hoop strains of the FRP jackets and the health state of the inner tube. The smart BFST-DSTC can replace the hybrid DSTC with the ability to provide early failure warning and life cycle health monitoring.

The communications in the quake-hit area are always cut off from the outside after the earthquake, and the traditional seismic field investigation method calls for immense time to accomplish house-to-house investigation, which goes against timeliness of the emergency rescue. In this paper, an emergency communication and quick seismic damage investigation method based on smartphone is proposed. Towards this, an application, E-Explorer, on iOS platform is initially developed. First, in the emergency communication module, the communication is available by using the Multipeer Connectivity Framework technology even without external network. A series of validation experiments are simulated without external network, and the results prove convincing. This module enhances the possibility of communication and increases the chances for rescue. Second, in the damage investigation module, E-Explorer integrates the functions of questionnaire and picture collection for damage phenomenon recording and image acquisition, following an intensity evaluation method according to seismic index. Last, a website, which provides guidance for rescue workers and collects damage information for quick intensity evaluation, is being built.

In the recent years, with the development and popularization of smartphone, the utilization of smartphone in the Structural Health Monitoring (SHM) has attracted increasing attention owing to its unique feature. Since bridges are of great importance to society and economy, bridge health monitoring has very practical significance during its service life. Furthermore, rapid damage assessment of bridge after an extreme event such as earthquake is very important in the recovery work. Smartphone-based bridge health monitoring and postevent damage evaluation have advantages over the conventional monitoring techniques, such as low cost, ease of installation, and convenience. Therefore, this study investigates the implementation feasibility of the quick bridge health monitoring technique using smartphone. A novel vision-based cable force measurement method using smartphone camera is proposed, and, then, its feasibility and practicality is initially validated through cable model test. An experiment regarding multiple parameters monitoring of one bridge scale model is carried out. Parameters, such as acceleration, displacement, and angle, are monitored using smartphone. The experiment results show that there is a good agreement between the reference sensor and smartphone measurements in both time and frequency domains.

In this study, two types of floating offshore wind turbine (FOWT) systems were proposed: a traditional tension leg platform (TLP) type and a new TLP type with additional mooring chains. They were both based on the National Renewable Energy Laboratory 5 MW offshore wind turbine model. Taking the coupled effect of dynamic response of the top wind turbine, tower support structure and lower mooring system into consideration, not only were the 1/60 scale model tests for the two floating wind turbine systems done in HIT’s wind-wave tunnel according to the typical design conditions in IEC61400-3 code, but also the numerical simulations corresponding to the scaled model tests were performed by advanced numerical tools. As a result, the numerical results displayed good agreement with the test data. Moreover, the additional mooring chains could play an active role in reducing the surge displacement, surge acceleration and typical tension leg force responses of the FOWT system, which is very beneficial for ensuring the good operational performance and the safety of the FOWT system.

For the safety of prestressed structures, prestress loss is a critical issue that will increase with structural damage, so it is necessary to investigate prestress loss of prestressed structures under different damage scenarios. Unfortunately, to date, no qualified techniques are available due to difficulty for sensors to survive in harsh construction environments of long service life and large span. In this paper, a novel smart steel strand based on the Brillouin optical time domain analysis (BOTDA) sensing technique was designed and manufactured, and then series of tests were used to characterize properties of the smart steel strands. Based on prestress loss principle analysis of damaged structures, laboratory tests of two similar beams with different damages were used to verify the concept of full-scale prestress loss monitoring of damaged reinforced concrete (RC) beams by using the smart steel strands. The prestress losses obtained from the Brillouin sensors are compared with that from conventional sensors, which provided the evolution law of prestress losses of damaged RC beams. The monitoring results from the proposed smart strand can reveal both spatial distribution and time history of prestress losses of damaged RC beams.

Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE) technology is adopted to monitor the fatigue damage evolution process. First, the relationship between stress and strain is determined through a tensile test for corroded and non-corroded steel wires. Results show that the mechanical performance of corroded cables is changed considerably. The AE characteristic parameters for fatigue damage are then established. AE energy cumulative parameters can accurately describe the fatigue damage evolution of corroded cables. The failure modes in each phase as well as the type of acoustic emission source are determined based on the results of scanning electron microscopy. The waveform characteristics, damage types, and frequency distribution of the corroded cable at different damage phases are collected. Finally, the number of broken wires and breakage time of the cables are determined according to the variation in the margin index.

In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring.

This paper presents a concept of a Self-sensing Carbon Fiber Reinforced Polymer (SCFRP) system, which integrates the piezoceramic transducers with the common concrete strengthening materials, CFRP fabric. This integration provides the SCFRP fabric with the ability to monitor the structural health condition when the SCFRP fabric is applied on reinforced concrete structures. In order to validate the feasibility of this system, several three-point bending beam (3PBB) specimens were fabricated and tested before and after the specimens were reinforced with the proposed SCFRP fabric. In addition, the specimens with the low (C25) and high (C40) concrete grades were also experimentally investigated to evaluate the reinforced effectiveness of the SCFRP fabric. Finally, the experimental results demonstrate that the proposed SCFRP fabric can significantly improve the bearing capacity of the concrete structures, and provided the reinforced concrete structures with an ability of self-sensing their health condition.

In the present work, a crashworthy device for a monopile offshore wind turbine has been proposed, which consists of the inner two-layer rubber torus and the outer thin steel shell. The performance of the crashworthy device against ship impact has been investigated experimentally. Based on the prototype of a 4 MW monopile wind turbine in the East China Sea, the scale ratio of the test model has been designed to be 1/50. The test ship model has been simplified as a “rigid car„ equipped with a high-frequency force sensor in the front, which is available for changing the ship mass with different weights. The ship-impact velocity can be accurately controlled by a motion platform driven by a direct current machine. The effect of the key design parameters of the crashworthy device on its anti-impact performance has been tested and compared under typical ship impact cases. The results indicate that the crashworthy device can effectively reduce both the ship impact force and the top nacelle acceleration, and the physical mechanism that has been clarified. The outer thin steel shell can significantly use its structural deformation to absorb the ship impact energy, which is beneficial for reducing the structural damage of the offshore wind turbine (OWT)’s tower. The inner rubber torus can effectively prolong the ship impact duration, which is available for smoothing the impact force. Finally, the porous design for the outer steel shell of the crashworthy device has been proposed and tested.

Concrete compressive strength is an important parameter of material properties for assessing seismic performance of reinforced concrete (RC) structures, which has a certain level of uncertainty due to its inherent variability. In this paper, the method of concrete strength validation of finite element model using smart aggregate (SA)-based stress monitoring is proposed. The FE model was established using Open System for Earthquake Engineering Simulation (OpenSEES) platform. The concrete strengths obtained from the material test, peak stress of SA, and estimated concrete strength based on SA stress were employed in FE models. The lateral displacement monitored by Liner variable differential transformer and vertical axial load monitored by load cell in the experiment are applied in the model. By comparing the global response (i.e., lateral reaction force and hysteretic loop), local response (i.e., concrete stress, rebar strain, and cross-section moment) and corresponding root-mean-square error obtained from experiment and numerical analysis, the capabilities of validation of FE model using SA-based stress monitoring method were demonstrated.

The structural health monitoring system has made great development nowadays, especially on bridge structures. Meanwhile, most SHM systems reported were designed, integrated, and installed into large-scale infrastructures by professionals and equipped with expensive sensors, data acquisition devices, data transfer systems, and so forth. And it is impossible to install SHM system for every civilian building. For this status, a kind of new idea for structural health monitoring using smartphone is introduced in this paper. A smartphone, with embedded responding SHM software and inner sensors or external sensors, can be used not only as a single wireless sensor node but also as a mini-SHM system. The method is described in detail, and then the swing test, cable force test in laboratory, and cable force test on an actual bridge based on the iPhone were conducted to validate the proposed method. The experimental results show that Mobile-SHM using smartphone is feasible. The realization of Mobile-SHM method using smartphones may be considered as a milestone in making SHM popular in the lives of people.

The coupling beam damper is a fundamental energy dissipation component in coupling shear wall structures that directly influences the performance of the shear wall. Here, we proposed a two-fold design method that can give better energy dissipation performance and hysteretic behavior to coupling beam dampers. First, we devised four in-plane yielding coupling beam dampers that have different opening types but the same amount of total materials. Then the geometry parameters of each opening type were optimized to yield the maximum hysteretic energy. The search for the optimal parameter set was realized by implementing the Kriging surrogate model which iterates randomly selected input shape parameters and the corresponding hysteretic energy calculated by the infinite element method. By comparing the maximum hysteretic energy in all four opening types, one type that had the highest hysteresis energy was selected as the optimized design. This optimized damper has the advantages of having a simple geometry and a high dissipation energy performance. The proposed method also provided a new framework for the design of in-plane coupling beam dampers.

The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

This work presents an offshore pipeline scour monitoring sensor network system based on active thermometry. The system consists of thermal cables, data acquisition unit, and data processing unit. As the thermal cables emit heats, the distributed DS18B20 digital temperature sensors record temperature information over time. The scour-induced exposure and free spanning can be identified by analyzing the temperature curves. Pipeline exposure and free-spanning experiments were carried out in laboratory, whose results show that the system is able to give overall information about the development of pipeline scour. Difference values analysis reveals the changing patterns of heat transfer behavior for line heat source in sediment and water scenarios. Two features, magnitude and temporal instability, are extracted from temperature curves to better differentiate sediment and water scenarios. Based on these two features, K -means clustering algorithm is adopted for pattern classification of the system, which was implemented in MATLAB and facilitated the automatic detection of the scour monitoring sensor network system. The proposed sensor network has the advantages of low cost, high precision and construction flexiblility, providing a promising approach for offshore pipeline scour monitoring, especially suitable for nearshore environment.

Structural health monitoring (SHM) has been regarded as a significant tool for the safety of civil infrastructures. Local fiber Bragg grating (FBG) sensor and distributed Brillouin optical fiber sensor have been successfully applied in civil engineering fields. Unfortunately, neither single FBG nor single Brillouin sensing technique can satisfy the requirements of simultaneously positioning full-scale structural damages and accurate local damage details. So it still matters to establish balance between localized high-precision measurement and large-scale distributed measurement with lower accuracy. This paper introduces an integration system by combining distributed Brillouin and local FBG sensors on one single-mode optical fiber. The temperature self-compensation and the data processing method of the integration system have been investigated. The integrated FBG/Brillouin sensor has been further packaged by glass fiber-reinforced polymer to be used as a robust and smart structural component. Finally the proposed integrated sensing system has been applied in three case studies, including investigation of reinforced concrete beam, smart cable, and smart steel strand to verify the feasibility. The test results illustrate that the integrated system can simultaneously provide accurate strain measurement at critical points by FBGs and the rough distributed strain measurement by Brillouin sensor, which can be further applied to various applications.

A novel tuned heave plate energy-harvesting system (THPEH) is presented for the motion suppressing and energy harvesting of a semi-submersible platform. This THPEH system is designed based on the principle of a tuned mass damper (TMD) and is composed of spring supports, a power take-off system (PTO) and four movable heave plates. The permanent magnet linear generators (PMLG) are used as the PTO system in this design. A semi-submersible platform operating in the South China Sea is selected as the research subject for investigating the effects of the THPEH system on motion reduction and harvesting energy through numerical simulations. The numerical model of the platform and the THPEH system, which was established based on hydrodynamic analysis, is modified and validated by the results of the flume test of a 1:70 scale model. The effects of the parameters, including the size, the frequency ratio and the damping ratio of the THPEH system, are systematically investigated. The results show that this THPEH system, with proper parameters, could significantly reduce the motions of the semi-submersible platform and generate considerable power under different wave conditions.