Search Results (100)

High-performance waterproof and breathable nanofiber membranes (WBNMs) are in great demand for various advanced applications. However, the fabrication of such membranes often relies on fluorinated materials or involves complex preparation processes, limiting their practical use. In this study, we present an innovative approach by utilizing silicon-containing polyurethane (SiPU) as a single-component, fluorine-free raw material to prepare high-performance WBNMs via a simple one-step electrospinning process. The electrospinning technique enables the formation of SiPU nanofibrous membranes with a small maximum pore size (d_max) and high porosity, while the intrinsic hydrophobicity of SiPU imparts excellent water-repellent characteristics to the membranes. As a result, the single-component SiPU WBNM exhibits superior waterproofness and breathability, with a hydrostatic pressure of 52 kPa and a water vapor transmission rate (WVTR) of 5798 g m⁻² d⁻¹. Moreover, the optimized SiPU-14 WBNM demonstrates outstanding mechanical properties, including a tensile strength of 6.15 MPa and an elongation at break of 98.80%. These findings indicate that the single-component SiPU-14 WBNMs not only achieve excellent waterproof and breathable performance but also possess robust mechanical strength, thereby enhancing the comfort and expanding the potential applications of protective textiles, such as outdoor apparel and car seats. Full article

Cylindrical retaining structures are widely adopted in intercity railway tunnel engineering due to their exceptional load-bearing performance, no need for internal support, and efficient utilization of concrete compressive strength. Measured deformation data not only comprehensively reflect the influence of construction and hydrogeological conditions but also directly and clearly indicate the safety and stability status of structure. Therefore, based on two geometrically similar cylindrical shield tunnel shafts in Shenzhen, the surface deformation, structure deformation, and changes in groundwater outside the shafts during excavation were analyzed, and the deformation characteristics under the soil–rock composite stratum were summarized. Results indicate that the uneven distribution of surface surcharge and groundwater level are key factors causing differential deformations. The maximum horizontal deformation of the shafts wall is less than 0.05% of the current excavation depth (H), occurring primarily in two zones: from H − 20 m to H + 20 m and in the shallow 0–10 m range. Vertical deformations at the wall top are mostly within ±0.2% H. Localized groundwater leakage in joints may lead to groundwater redistribution and seepage-induced fine particle migration, exacerbating uneven deformations. Timely grouting when leakage occurs and selecting joints with superior waterproof sealing performance are essential measures to ensure effective sealing. Compared with general polygonal foundation pits, cylindrical retaining structures can achieve low environmental disturbances while possessing high structural stability. Full article

Underground structures are subject to deterioration conditions in which water leakage occurs through cracks due to the long-term influence of soil and groundwater. Therefore, composite waterproofing sheets can play an important role in securing the leakage stability of structures by combining them with concrete structures. In this study, a total of eight composite waterproofing sheets were used according to the thickness of the compound and the properties of the material attached to the concrete, and the deformation characteristics at the bonding surface were identified through repeated tensile tests. Types A, B, and C, with a compound thickness of 1.35 to 1.85 mm and a single layer, had strong bonding performance, with a deformation rate of 0.5 to 2 × 10⁻⁴ and a DE/RE ratio of 0.3 to 1.3; tensile deformation progressed while maintaining integrity with the concrete at the bonding surface. Types D and E were viscoelastic and non-hardening compounds with a compound thickness of 1.35 to 3.5 mm, where the strain rate due to tensile deformation was the lowest, at 0.1 × 10⁻⁴ or less, and the DE/RE ratio was −5 to 3; therefore, when internal stress occurs, the high-viscosity compound absorbs it, and the material is judged to have low deformation characteristics. Types F, G, and H, which were 2 to 2.9 mm thick and had two layers using a core material, were found to have characteristics corresponding to tensile deformation, as the strain rate increased continuously from 0.2 to 0.5 × 10⁻⁴, and the DE/RE ratio increased up to 8 mm of tensile deformation. Full article

Rubber seals have been widely applied in mechanical sealing structures in various fields such as automobiles, aerospace, and deep-sea hydraulic systems. The current analysis methods for O-ring sealing performance mainly include experiments and simulations. This study takes the motor sealing structure as the research object and proposes a multi-objective optimization method for designing sealing structures. Based on the finite element analysis model, the main indicators related to sealing performance were obtained. These indicators transfer to multi-objective optimization analysis to determine the influence of different groove depths on sealing performance. The analysis results show that when the bolt preload is 50 N, a groove depth of 0.9 mm is the optimal design scheme. The optimal relationship between the O-ring diameter D and the sealing structure groove depth is H = 0.6 D. Moreover, a prototype test under the condition of IPX7 requirement verifies the optimal design scheme’s waterproof performance. The proposed method provides multiple design schemes for comprehensive evaluation considering different sealing structures. It reveals that the sealing performance is not only determined by rubber material characteristics but also by seal structure dimension. Full article

The present work addresses the critical challenge of assessing building facade watertightness against wind-driven rain, a major threat to structural integrity and durability. The current evaluation methods rely heavily on standardized test outcomes, neglecting a disconnect between test conditions and real-world exposure, leading to subjective judgments. To bridge this gap, this paper developed a quantitative method linking key inspection parameters (pump pressure, water spray distance) to wind-driven rain characteristics (wind speed, rainfall intensity) in the Shanghai area using statistical return periods. The calculation process encompasses regression models that correlate extreme rainfall and wind velocity values over sub-daily intervals, as well as a method for extrapolating maximum wind velocities using wind data coinciding with rainfall events. This approach enables specification-compliant performance assessment and tailored inspection protocols, such as JGJ/T 299, EN 12155, and ASTM E547. Applied to two Shanghai buildings, the method demonstrated a robust framework for translating environmental data into actionable inspection criteria. The results show a direct correlation between test parameters and extreme weather statistics. For instance, the watertightness performance of an old building is quantitively assessed as a return period of 1.02 years, while a new office building aiming for 50-year waterproofing could be inspected at a pump pressure of 900 kPa and a spraying distance of 0.15 m using the proposed method. This paper offers a data-driven alternative to empirical assessments, enhancing reliability in facade design and regulatory compliance, and provides a scientific basis for decision-making in building maintenance and renovation. Full article

In order to exploit the deep underground space, the construction of ultra-deep excavation in Shanghai is growing rapidly. In multi-aquifer strata, deep excavations typically require dewatering of confined aquifers to ensure engineering safety. However, existing studies have seldom conducted in-depth analysis on the influence of the soil parameters and construction measures on the deformation of retaining structures. In this study, a three-dimensional hydro-mechanical numerical model was developed to evaluate the performances of excavation and dewatering of the foundation pit. The model was validated by comparing the calculated and measured wall deflections and groundwater drawdowns of a 45 m ultra-deep double-wall excavation in Shanghai. According to the characteristics of soil stratification and construction activities, three parameters were selected for subsequent analysis, including the hydraulic conductivity of aquitard below the bottom of the pit, the pumping rate in the second confined aquifer and the construction of TRD wall. The stress distributions on both sides of the diaphragm wall were examined to elucidate the deformation mechanism. The results indicate that the aquitard hydraulic conductivity directly affects the effective stress of the overlying aquifer, which plays a crucial role in resisting wall deflection. An increase in the hydraulic conductivity leads to smaller effective stress, greater wall deflection and larger ground settlement. While an appropriately increased pumping rate enhances effective stress, over-pumping may induce excessive wall deflection at depth and disproportionate ground settlement. The TRD wall is quite useful in terms of waterproofing but the effect on deformation control is limited. The findings of this study provide valuable insights for engineering practices and the optimization of deep excavation construction measures in multi-aquifer strata. Full article

Superhydrophobic surfaces with arrayed pillar structures have huge application prospects in various industrial fields, such as self-cleaning, waterproofing, anti-corrosion, and anti-icing. The knowledge gap regarding the liquid–solid interaction between impacting droplets and microstructured surfaces must be addressed to guide the practical engineering applications more effectively. In this study, the effects of the stationary and horizontally moving superhydrophobic micro-pillar surfaces on the droplet impact dynamic behavioral characteristics are investigated numerically, focusing on the droplet morphology, spreading diameter, contact time, and energy conversion. Based on the numerical simulation results, new prediction correlations of the dimensionless maximum spreading diameter for droplets impacting stationary and horizontally moving micro-pillar surfaces are proposed. Moreover, significant rolling phenomena occur when droplets impact horizontally moving micro-pillar surfaces, which leads to an increase in viscous dissipation and forms a competitive mechanism with the asymmetric spreading–retraction process of the droplets. Two different stages are recognized according to the analysis of the contact time and velocity restitution coefficient. This study may provide new insights into understanding the dynamic behavior of droplets on microstructured surfaces. Full article

A survey and assessment of the technical condition of basement and semi-basement structures in public buildings aged 60 to 130 years were conducted to evaluate their suitability for use as basic shelters. Based on the survey results, the most adverse impacts were identified, including changes in groundwater levels, improper building operation, and the characteristic damages to underground structural elements. Structural solutions were proposed to eliminate the consequences of these damages. The reviewed cases indicate that the vertical and horizontal waterproofing systems used during construction cannot perform their function throughout the building’s entire life cycle. When designing new buildings, waterproof materials should be used for the enclosing structures of underground premises. While this may have a higher initial cost than membrane or coating waterproofing, considering life-cycle costs, it can provide a positive economic effect and improve the quality and comfort of the indoor environment. Full article

The principles of the circular economy and the effective utilization of construction and demolition waste are becoming increasingly important, as evidenced by a growing body of research in this field. However, studies focusing on the waterproofing properties and setting times of recycled concrete derived from various construction and demolition waste sources remain scarce. This research investigates the characteristics of recycled aggregates from different origins and explores how these characteristics influence the properties of concrete. The study examines the effects of pre-soaking aggregates to saturation, the incorporation of water absorption-reducing additives, and the ratio of recycled aggregates to natural aggregates on the properties of both fresh and hardened concrete. Laboratory tests were conducted on crushed recycled concrete aggregates (RCA), confirming that concrete produced with recycled aggregates can meet standard requirements for compressive strength and water resistance exposure classes despite the recycled aggregates themselves not meeting the required standards. The results were used to calculate an effective water–cement ratio and establish a correlation between this ratio and compressive strength. The findings indicated that the compressive strength of mixtures approached, and in most instances exceeded, that of the reference concrete utilizing natural aggregates. Specifically, the reference concrete (REF-1) achieved a compressive strength value of 51.4 MPa after 28 days, whereas the 30% recycled mixture (REC-10), made from pure concrete demolition waste, produced a compressive strength of 62.7 MPa. The maximum water penetration depth of the REC-10 mixture was measured at 11 mm, in comparison to 15 mm for the reference mixture (REF-1). Additionally, the initial setting time of the mixtures incorporating special additives reached the 80 min threshold. The practical aspects of this research examined potential industrial applications that do not necessitate special aggregate treatments, thus maintaining the water–cement ratio within acceptable limits. This study evaluates the feasibility of utilizing recycled concrete aggregates (RCA) from construction waste to produce concrete that satisfies the standard requirements for compressive strength and water resistance. It assesses the impact of RCA on performance, provides industrial insights, and suggests potential regulatory revisions. Full article

Connecting diaphragm walls as permanent components of underground spaces in relation to basement sidewalls is an effective method for enhancing structural stability, reducing structural footprint, and improving waterproofing performance. To investigate the influence of connection methods between diaphragm walls and sidewalls on the mechanical performance of combined walls and to determine the differences in mechanical behavior between combined and composite walls, four–point bending experiments were conducted based on static loading systems and digital imaging technology. The cracking characteristics, strain response, load–bearing capacity, displacement ductility, and interface mechanical behavior of a combined wall with interface roughening and rebar anchoring, a combined wall with shear grooves, and a composite wall with a high–density polyethylene waterproof layer were comparatively analyzed. The results showed that for the combined walls with interface roughening and rebar anchoring or with shear grooves, through–thickness cracks extended across the interface, with no interfacial slipping failure observed. The combined wall with shear grooves exhibited noticeable through–thickness cracks. For the composite wall, cracks were staggered on both sides of the interface, with significant interface slipping failure. Compared to the composite wall, the combined walls demonstrated superior overall performance with fewer cracks. Additionally, the load–bearing capacity and displacement ductility of the combined wall with interface roughening and rebar anchoring were significantly higher than those of the combined wall with shear grooves and the composite wall. The composite wall exhibited the lowest load–bearing capacity, while the combined wall with shear grooves demonstrated the least displacement ductility. Full article

Functional membranes with waterproof, breathable, and thermal regulation capabilities are increasingly sought after across various industries. However, developing such functional membranes commonly involves complex multi-step preparation processes. Herein, we introduced perfluorodecyltriethoxysilane (FAS) into the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) solution for one-step electrospinning, successfully fabricating membranes that combine these properties. The hydrophobicity of the PVDF-HFP/FAS membrane was greatly improved with the water contact angle increased from 120.6° to 142.9° and the solar reflectance rising from 72% to 92% due to the presence of fluorocarbon segments. The synergistic effect of enhanced hydrophobicity, small pore size, and elevated solar reflectivity resulted in robust water resistance (62 kPa), excellent water vapor transmission rate (12.4 kg m⁻² d⁻¹), and superior cooling performance (6.4 °C lower than commercial cotton fabrics). These findings suggest that the proposed PVDF-HFP/FAS membranes, characterized by desired multifunction characteristics and scalable production, hold great potential for application in diverse strategic fields. Full article

This study investigates the optimal design and operation of an underwater ultrasonic system for algae removal, focusing on the electromechanical load of Langevin-type piezoelectric transducers. These piezoelectric transducers, which operate in underwater environments, exhibit variations in electrical–mechanical impedance due to practical environmental factors, such as waterproof molding structures or variations in pressure and flow rates depending on the water depth. To address these challenges, we modeled the underwater load conditions using the finite element method and analyzed the impedance characteristics of the piezoelectric transducer under realistic environmental conditions. Based on this analysis, we developed an ultrasound-driven system capable of efficient output control by incorporating the impedance characteristics of the transducer under load variations and subaquatic conditions. This study proposes analytical and experimental methods for modeling and analyzing practical ultrasound-driven systems for algae removal. Full article

The Sustainable Development Center of the University of Brasilia is one of the modernist buildings that make up the Darcy Ribeiro campus. The architectural project contains several recommendations for the execution of a flat roof waterproofing system, as well as details for rainwater runoff and drainage, which reveals the architect’s concern with watertightness. This research seeks to identify the relationship between the pathological manifestations recognized on the roof and the details of the semicircular shape of the building, assessing the state of conservation using damage maps as an auxiliary analysis tool. This study is based on a field survey using aerophotogrammetry with a drone, the application of vector drawing software for graphic representation and discussion of the possible causes, and the agents and mechanisms of degradation at work. The results show the importance of mechanical protection for the good performance of the waterproofing system, as well as the need for correct sizing of expansion joints to absorb and relieve the stresses caused by hygrothermal variations. The incorporated methodology proved to be effective and economical in diagnosing and monitoring pathological manifestations, making it possible to plan maintenance actions that extend the useful life and preserve the intrinsic characteristics of building systems. Full article

Cementitious Capillary Crystallization Waterproofing Material (CCCW), as an efficient self-healing agent, can effectively repair damage in concrete structures, thereby extending their service life. To address the various types of damage encountered in practical engineering applications, this study investigates the impact of different mixing methods for CCCW (including internal mixing, curing, and post-crack repair) on the multi-dimensional self-healing performance of concrete. The self-healing capacity of concrete was evaluated through water pressure damage self-healing tests, freeze–thaw damage self-healing tests, mechanical load damage self-healing tests, and crack damage self-healing tests. The results show that the curing-type CCCW mixing method exhibited the best self-healing effect in repairing water pressure, freeze–thaw, and load damages, with corresponding healing rates of 88.9%, 92.7%, and 90.5%, respectively. The internally mixed CCCW method was also effective for repairing load damage in concrete, while the repair-type CCCW mixing method demonstrated the weakest repair effect on these types of damage. For concrete with induced pre-existing cracks, the internally mixed CCCW method, after 28 days of water-immersion curing, exhibited a significantly higher crack self-healing ability, with a self-healing ratio of 333.8%. Optical microscopy observations revealed that the crack surfaces were almost fully sealed, with a substantial deposition of white crystalline material at the crack sites. Further analysis using scanning electron microscopy (SEM) and X-ray Diffraction (XRD) provided insights into the surface morphology and phase characteristics of the self-healed cracks, indicating that calcium carbonate (CaCO₃) and calcium silicate hydrate (C-S-H) were the main products responsible for crack healing. Full article

Quadruped robots, with their biomimetic structure, are capable of stable locomotion in complex terrains and are vital in rescue, exploration, and military applications. However, developing multi-modal robots that feature simple motion control while adapting to diverse amphibious environments remains a significant challenge. These robots need to excel at obstacle-crossing, waterproofing, and maintaining stability across various locomotion modes. To address these challenges, this paper introduces a novel leg–fin integrated propulsion mechanism for a bionic quadruped robot, utilizing rapidly advancing soft materials and integrated molding technologies. The robot’s motion is modeled and decomposed using an improved central pattern generator (CPG) control network. By leveraging the control characteristics of the CPG model, global control of the single-degree-of-freedom drive mechanism is achieved, allowing smooth transitions between different motion modes. The design is verified through simulations conducted in the Webots environment. Finally, a physical prototype of the quadruped compliant robot is constructed, and experiments are carried out to test its walking, turning, and obstacle-crossing abilities in various environments. The experimental results demonstrate that the robot shows a significant speed advantage in regions where land and water meet, reaching a maximum speed of 1.03 body lengths per second (bl/s). Full article