Design Support Research Articles

Blast-Resistant Design of Reinforced Concrete Slabs with Auxetic-Shaped Reinforcement Layout

This paper presents a numerical study of a blast-resistant design of reinforced concrete panels with a novel auxetic reinforcement layout inspired by auxetic materials, which have a negative Poisson’s ratio, i.e., shrink under compression and expand under tension. A series of two-way supported panels reinforced with re-entrant auxetic-shaped rebars were numerically tested under a TNT explosion. The high-fidelity multi-physics explicit solver of LS-DYNA was utilized to analyze the efficiency of the proposed design. Firstly, the incident pressure of a TNT explosion data and the structural response of a conventional reinforced concrete panel under a TNT explosion were successfully validated by comparing with the experimental and empirical results. Secondly, the blast-resistant capacity of the proposed model was evaluated in comparison to two different conventional designs. Moreover, a parametric study was carried out to reveal the driving parameters of the newly proposed auxetic-shaped reinforcement design. It has been proved that the proposed auxetic reinforcement layout significantly reduces the spalling radius and increases the energy absorption capacity of panels. As a result of the parametric study, the increased reinforcement volume ratio was ineffective on the spalling radius, although the cell size of auxetic reinforcement was found to be quite effective for the blast-resistant design of concrete panels. Overall, the proposed re-entrant auxetic reinforced panel performed far better than conventional designs under blast load. With the recent developments in 3D printing technology, the proposed auxetic reinforcement layout is a strong candidate to deal with blast-resistant designs of concrete panels.

A Numerical Analysis of the Role of Pile Foundations in Shaft Sinking Using the Vertical Shaft Sinking Machine (VSM)

The use of the Vertical Shaft Sinking Machine (VSM) for shaft construction marks a significant advancement in modern technology and is recognized as one of the leading techniques in the field. However, much of the existing research focuses on mechanical and technical challenges, often overlooking the effects on surrounding soil and the structural integrity of shafts. This study demonstrates that increasing pile diameter by 20% improves load-bearing capacity by 15% and reduces soil settlement by 12%, though these improvements come with higher construction costs. Additionally, larger diameters improve lateral stability, but excessively long piles lead to diminishing returns. To address the limited research on reinforcement design in soft soils, a series of numerical models were employed to investigate the effects of pile spacing, length, and diameter on surrounding soil behavior. This in-depth analysis aims to provide a scientific foundation for optimizing VSM technology in caisson pile foundations, particularly in soft-soil conditions.

Analysis of Wind Turbine Towers subjected to Blast Loading

The research work in this paper mainly focuses on the dynamic simulation of a High strength steel wind turbine tower subjected to blast loading in increasing order, conducted by using ABAQUS. The analysis of the wind turbine tower evaluates the response and performance of the structure when subjected to blast load levels in the form of TNT charges ranging from 500 kgs to 2000 kgs applied at the base and at the top of the tower respectively. The study focuses mainly on the key parameters such as Von Mises stress, displacement, and reaction forces in which the results indicate that the High strength steel wind turbine tower passes the Von Mises stress limit up to a blast load of 1500 kgs at the base but fails under higher loads of 1750 kgs and 2000 kgs respectively where stresses of the wind turbine tower exceeds the tensile strength of the material. Moreover, at the top of the tower, the structure fails at a low charge of 500 kgs demonstrating its vulnerability to the blast load. Displacement of the wind turbine tower surpasses its recommended limit for TNT charges beyond 1500 kgs at the base with a maximum displacement of 129.49 mm at 2000 kgs. The maximum reaction force recorded was 2890 KN at a TNT charge of 1750 kgs. The study concludes by revealing the findings of the limitations of High-strength steel wind turbine towers under extreme blast conditions and throws spotlight on the need for structural reinforcement or alternative designs and hybrid towers for the wind turbine for improved performance and use in high-risk environmental zones.

Degradation law of bond strength of reinforced concrete with corrosion-induced cracks and machine learning prediction model

During long term operation service, reinforced concrete (RC) structures are subjected to corrosive media such as chloride salts, which results in the degradation of interface bond performance, subsequently reducing the load bearing capacity and service life of the structures. To accurately assess the durability of RC structures in environments such as oceans and salt lakes, this study combines experimental methods with machine learning (ML) techniques to explore the degradation patterns and predictive models of bond performance under chloride salt corrosion. Accordingly, a series of central pull-out tests were conducted based on an electrochemical accelerated-dry-wet cycle corrosion regime to investigate the degradation patterns of bond performance between corroded steel bars and concrete under different corrosion degree and corrosion-induced crack widths. By comparatively analyzing the evolution patterns of cracks and the morphology of the steel bars in reinforced concrete specimens and their failure modes, and integrating the mechanical degradation mechanism with chemical and microscopic corrosion mechanisms, an in-depth analysis of the corrosion-induced degradation patterns at the bond interface was performed. The internal relationships between corrosion degree, corrosion-induced crack width and bond strength were discussed, and the variation patterns of bond strength with corrosion-induced crack width and corrosion degree were explored. Moreover, the bond strength patterns were analyzed from an energy perspective. The results indicate that bond strength and bond energy decrease with an increase in the corrosion-induced crack width of the concrete. Additionally, based on the experimental data from this study, ML predictive models for bond strength were established using corrosion-induced crack width as the control variable. The results show that the ML-based bond strength predictive models fit well with the experimental data, offering higher accuracy and reliability compared to traditional bond strength models. The research findings provide significant theoretical basis and practical guidance for safety assessment, maintenance, reinforcement, and full-life design of corroded RC structures.

Study on the structural behavior and reinforcement design of openings in subway station floor slabs

This paper investigates the structural behavior of openings in subway station floor slabs through model experiments and finite element simulation. The study analyzes the effects of the opening's aspect ratio, dimensions, and position on the stress characteristics of various structural components. Based on the stress levels and failure characteristics at different locations in the station structure, three reinforcement schemes are proposed: adding corner fillets, installing buttress columns, and adding ring beams. Comparative analysis with the original structure's internal forces and displacement patterns reveals the effectiveness of each reinforcement scheme. The results show that openings reduce the moment of inertia of the floor slab cross-section, weakening the slab's stiffness and making the area around the openings and slab-column joints prone to local damage. Increasing the aspect ratio of the opening, enlarging its dimensions, or closely arranging multiple openings diagonally reduces the local load-bearing capacity of the structure. Adding corner fillets can reduce the maximum equivalent stress in the slab by more than 15 %, alleviating stress concentration caused by the openings. Buttress columns and ring beams increase the stiffness of the side walls, distribute the lateral forces causing wall bending moments, and enhance the structure's resistance to lateral displacement.

Reinforcement topology optimization considering the dynamic instability

AbstractThe present study develops a new topology optimization scheme considering the dynamic instability caused by the unsymmetrical properties of system. From a mathematical point of view, the left and right eigenvectors of asymmetric system are observed with the complex eigenvalues. With the dynamic instability, the magnitudes of structural responses are increasing with respect to time and this phenomenon causes many engineering issues. As the dynamic instability is one of the serious problems, the suppression is desired from an engineering point of view. To systematically reduce this dynamic instability, the present study develops a new topology optimization scheme for the reinforcement design. To overcome the numerical difficulties of the mode conversion and the highly nonlinear behavior, this research proposes the summation of the first several complex eigenvalues. To show the issues of the dynamic instability and the validity of the present approach, several topological reinforcement problems are solved.

Research and Application Status of Soft Steel Dampers

Soft steel dampers have stable hysteresis characteristics and can effectively dissipate energy under repeated loads, providing good shock absorption effects for structures. It can be used for both seismic design of new buildings and seismic reinforcement of existing buildings. Suitable for various structural forms of buildings, including concrete structures, steel structures, and heavy-duty wooden structures. It is also applied in bridge structures, which can effectively reduce the vibration response of bridges under earthquake, wind vibration, etc., and improve the seismic performance and safety of bridges. Countries with rapid development in the application of structural control technology, such as the United States, Japan, Canada, New Zealand, and Mexico, are the main ones. Italy, France, Russia, Singapore, and other countries are also actively applying it in practical engineering. More than a hundred buildings abroad have adopted soft steel dampers.

Computational modeling of three-dimensional slope reinforcement by anchor cable micropile group considering coordinated deformation

The application of anchor cable micropile group (ACMPG) in small and medium-sized slope support is gradually widespread. However, the coordination deformation of the structure and the resistance of the soil in front of the piles are less considered in the existing calculation models. Therefore, based on the load transfer approach and according to the structural characteristics of the ACMPG, the calculation method was provided for the resistance of the soil in front of the pile and the tension of the anchor after deformation. And the equations for calculating the resistance of the ACMPG were established. Based on the method of upper bound limit analysis, the display equation had been established for the safety factor of reinforcing the 3D slope of the structure. And finite element models were developed to validate the theoretical model. Finally, a parametric study was conducted to investigate the influence of slope angle, soil friction angles, location, 3D effects, on the slope safety factor and the support effect of piles and anchor cables supporting the structure. The results showed that the theory proposed in this paper can accurately calculate the safety factor of slopes, which is helpful for the design and construction of slope reinforcement.

Parametric analysis on mechanical performance and additional reinforcement design method of reinforced concrete chimneys with openings

Parametric analysis on mechanical performance and additional reinforcement design method of reinforced concrete chimneys with openings

Overcoming the brittleness of sustainable compression-cast recycled aggregate concrete through steel spiral confinement

The loose and porous adhered mortar of recycled aggregates produces concrete with low strength and poor durability. The newly developed compression casting technology applies pressure to fresh concrete to squeeze out excess water and air in the recycled aggregate concrete (RAC) and force the cement paste into the old adhered mortar to strengthen it, thereby effectively solving the aforementioned problems. However, the significant increase in the compactness and compressive strength of the RAC is accompanied by a pronounced increase in compression brittleness. Hence, this study attempts to overcome the brittleness of sustainable compression-cast RAC through proper design of transverse reinforcement. To achieve this objective, the axial compression behaviour of steel spiral-confined RAC specimens was experimentally investigated. It is found that the compression casting approach almost doubled the compressive strength of the unconfined RAC and improved the ultimate axial stress of the steel spiral-confined RAC by up to 69.9 %. The steel spiral-confined normal-cast RAC exhibited typical compression failure accompanied by a stress–strain curve characterised by strain hardening, whereas the steel spiral-confined compression-cast RAC exhibited localised shear failure accompanied by a stress–strain curve characterised by strain softening. The strain-softening behaviour of steel spiral-confined compression-cast RAC can be significantly improved by reducing the spiral pitch. Based on the test results obtained in this study and in the literature, stress–strain models were proposed separately for the steel spiral-confined compression-cast RAC and normal-cast RAC. The stress–strain models exhibited a significantly higher prediction accuracy than the selected models in the literature.

Reinforcement of Insufficient Transverse Connectivity in Prestressed Concrete Box Girder Bridges Using Concrete-Filled Steel Tube Trusses and Diaphragms: A Comparative Study

To address the issue of insufficient transverse connectivity in prestressed concrete box girder (PCB) bridges, this study investigates two transverse strengthening methods—installing diaphragms and utilizing concrete-filled steel tube trusses (CFSTTs). A finite element model was developed for a typical 30 m PCB bridge and was validated by on-site load test results for reliability. Based on the deflection and load distribution of PCB bridges before and after reinforcement, as well as the maximum stress and strain of the diaphragms and the CFSTTs, comparative analyses were conducted on diaphragms of different thicknesses and materials, as well as on CFSTTs of various strength grades. The results show that the addition of a transverse partition and CFSTTs can effectively improve the load distribution of the PCB bridge and reduce the maximum deflection of the girder, especially when using the CFSTT reinforcement method. The unique structural design improves the reinforcement effect of the material in the post-elastic stage. When using CFSTTs, increasing the steel tube wall strength significantly reduces the maximum deflection of the main girder. For example, using steel tubes with yield strengths of 235 MPa and 420 MPa filled with concrete of 50 MPa compressive strength reduced the maximum deflections by 15.32% and 24.55%, respectively, and improved the load distribution coefficients by up to 7.31% and 11.57%. Additionally, steel diaphragms demonstrated better reinforcement effects compared with concrete diaphragms. The load transverse distribution coefficients for the CFSTT-reinforced PCB bridge were calculated using the hinge plate (beam) and the rigid plate (beam) methods, showing minimal differences between the two approaches. The findings of this study provide valuable insights into the design of diaphragm and CFSTT reinforcement in PCB bridges, aiding in the selection of optimal reinforcement strategies.

Physical model case study: treatment effect of soft ground by vacuum preloading combined with liquid bag pressurization method

Vacuum preloading and composite ground reinforcement are commonly used methods for reinforcing soft soil, but there is a lack of integrated design method for vacuum preloading combined with composite ground. This case study introduces an innovative approach that combines vacuum preloading with liquid bag pressurization to achieve the integrated design of consolidation drainage method and composite ground reinforcement, which is different from the reported air bag pressurization. To illustrate the effectiveness of this method. Model tests were carried out to analyze the variation of water discharge, pore water pressure, ground settlement, and average consolidation degree in the process of vacuum consolidation. The study investigated the water content, undrained shear strength, and ground bearing capacity of composite ground after ground treatment. A correlation between average undrained shear strength and characteristic value of ground-bearing capacity was established to evaluate and predict the treatment effect of composite ground. Research shows that compared with traditional vacuum preloading, the undrained shear strength can be increased by 13.78%–65.08%, and the characteristic value of bearing capacity for the composite ground can be enlarged by 2.3–4 times. These results indicate that the vacuum preloading combined with liquid bag pressurization can significantly improve reinforcement effect on soft ground.

Research on the Water Inrush Mechanism and Grouting Reinforcement of a Weathered Trough in a Submarine Tunnel

Based on the structural and geological characteristics of the F1 weathering trough of a submarine tunnel and its spatial relationship with the cavern, a simplified calculation model of the weathering trough water inrush was established, and the formation, development process and influencing factors of the water inrush channel in the water-resistant rock layer were carried out by a numerical simulation of particle flow. It shows that the integrity and stability of the critical water-resistant rock mass is the key to preventing water inrush, and the identification and positioning of the water inrush channel is the basis for the grouting reinforcement design of the weathering groove of the submarine tunnel. Based on above research results, the F1 weathering trough was blocked and reinforced by the composite grouting method, and the engineering reinforcement effect was good.

Seismic response investigation of prestressed anchor cable supporting rock slope with weak interlayer in Qinghai-Tibet Plateau, China

Earthquake-induced rock landslides in the eastern mountains of the Tibetan Plateau, especially landslides with weak interlayers pose a significant threat to major construction projects. Prestressed anchor cable is one of the main reinforcement methods of rock slopes. This paper combines shaking table model tests and numerical simulation to study the reinforcement effect and dynamic response characteristics of prestressed anchor cables applied to rock slopes with weak interlayers under strong earthquakes. The research results show that prestressed anchor cables can effectively reinforce slopes with weak interlayers. A small cable inclination, a small spacing and a high prestress are recommended in the seismic reinforcement design of prestressed anchor cable. In addition, the characteristics of slope progressive damage and prestress loss under the earthquake are found by the shaking table test. The results have been applied in hazard prevention and control of rock slopes on the Chengdu-Lanzhou Railway at the eastern Qinghai-Tibet Plateau.

A Numerical Study of Reinforcement Structure in Shaft Construction Using Vertical Shaft Sinking Machine (VSM)

Using the Vertical Shaft Sinking Machine (VSM) for shaft construction is an emerging modern technology, which is also currently one of the most advanced techniques in the field of shaft sinking. Current research on VSM technology primarily focuses on mechanical and technical issues, neglecting the impact of the construction on the surrounding soil and the structure itself. This oversight leaves structural design lacking a reliable foundation. Additionally, there is insufficient information on the role of reinforcement design during construction in soft soils. These engineering challenges have hindered the widespread implementation of this new technology. Therefore, a series of numerical models were used to analyse the mechanical behaviour of shaft and soil during or after the sinking process, with the aim of addressing these gaps by investigating the influence of shafts constructed using VSM technology, and providing a scientific basis for reinforcement design in soft soil. The case study shows that increasing the soil-cement strength does not have a significant effect on the overall deformation of the soil surrounding the shaft, but leads to a notable reduction in the plastic zone volume, subsequently enhancing the overall stability of the neighbouring soil. The ring bottom beam design effectively reduces convergence deformation by about 50%, while also improving the horizontal internal force distribution near the cutting edge. However, this approach significantly escalates local vertical bending moments, necessitating thorough consideration in the design stage.

Achieving isotropic thermal properties in graphite flake/Cu composites through the radial structural design of reinforcement

Conventional graphite flakes (GFs)/Cu composites suffer from severe anisotropy in terms of their thermal conductivity (TC) and coefficient of thermal expansion (CTE) between the in-plane and through-plane directions, which as thermal management materials (TMMs) play crucial roles in the overall heat dissipation performance of electronic components. To address this issue, a radial structural design for the reinforcement phase of GFs was developed. In this study, conventional stacked structured GFs/Cu composites and newly designed radial structured GFs/Cu composites were prepared by electroless plating of Cu on the surface of GFs followed by fast hot-pressing technology. The GFs content was varied from 30 to 70 vol%. The spatial orientation of the GFs was determined via X-ray computed tomography. For the radial structured GFs/Cu composites, the CTE were 11.52 and 14.42 ppm K−1 in the in-plane direction through-plane direction when the GFs content was 50 vol%, and the TC reached maximum values of 681 and 590 W m−1 K−1 in the in-plane direction and through-plane direction when the GFs content was 50 vol%. The TC in the through-plane direction was nine times greater than that of the stacked structured GFs/Cu composites (65 W m−1 K−1) at the same GFs content, demonstrating overall isotropy. Although radial structured GFs/Cu composites have more defects that can affect their thermal properties due to process factors, they have better heat dissipation abilities in practical applications; this indicates their great potential as a new generation of TMMs.

Preparation, mechanical properties and anti-oxidation behavior of lightweight porosity-controlled SiC(rGO, xZrB2) composite PDCs for thermal protection

Achieving well-balanced light weight with simultaneous improvement in mechanical and antioxidant properties of SiC-based composite polymer-derived ceramics (PDCs) for hypersonic vehicle components is still a huge challenge. Herein, lightweight SiC(rGO, xZrB2) composite PDCs were prepared via re-pyrolyzing ball-milling-induced ZrB2-SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene (PCS-VTES-GO, PVG) blends. Main reinforcements consist of ZrB2, ZrO2(ZrC), ZrOSi and SiO2/β-SiC phases, among which favorable compatibility enables enhanced bear loading performances and high-temperature oxidation resistance. Rigid SiC(rGO)p tightly links with flexible PVG pyrolysis products, and co-assembles into robust SiOxCy/Cfree(rGO) matrix in framework owing to plentiful Si-dangling bonds at their interfaces. More interestingly, interfacial ZrOSi/ZrC transition zone can augment structural disorder of ceramic network, give bridging effects, strengthen interfacial compatibility, and even hinder further crack propagation for self-densification. Particularly, SiC(rGO, 30%ZrB2) composite PDCs possess optimal hardness (6.49 GPa) and outstanding fracture toughness (5.77 MPa⋅m1/2). Porous SiC(rGO, 30%ZrB2) composite PDCs own stable structure integrity within 60-min testing under butane torch flame at 1300 °C. Self-healing protective SiO2-ZrO2 glass layer avoids destructive structure and timely covers defects, thus retains good mechanical performances. Such good synergistic reinforcement and multiscale design of porosity-controlled composite, realizes integration of lightweight/good load-bearing characteristics with improved oxidation resistance for thermal protection system (TPS) of hypersonic vehicles.

Stability Analysis of MSE Walls with Stepped Reinforcement Design

Stability Analysis of MSE Walls with Stepped Reinforcement Design

CFRP-strengthened shear walls: Combined effects of CFRP and reinforcement ratio

This study presents a three-dimensional numerical model based on the Hashin damage criteria to assess the seismic performance of Carbon Fiber Reinforced Polymer (CFRP)-strengthened Reinforced Concrete (RC) shear walls, accurately capturing the rupture of CFRP strips. The effectiveness of various CFRP-concrete interface modeling methods in capturing CFRP debonding was initially discussed. A series of numerical simulations were then conducted to investigate the combined effects of the CFRP ratio and the horizontal reinforcement ratio on the seismic behavior of CFRP-strengthened shear walls. The results indicate that an increase in the CFRP ratio reduces the failure degree of shear walls, as the shear damage shifts progressively from the concrete and horizontal reinforcement to the CFRP strips. However, an increase in the horizontal reinforcement ratio counterproductively weakens the shear-strengthening effect provided by the CFRP strips. To specifically evaluate the shear contribution of the CFRP strips, a novel coefficient was proposed and validated, capturing the combined effect of the CFRP ratio and the horizontal reinforcement ratio on the shear contribution of the CFRP strips. This coefficient provides a quantitative measure to optimize the reinforcement design of RC shear walls.

Enhanced strength–ductility synergy of SiC particles reinforced aluminum matrix composite via dual configuration design of reinforcement and matrix

To overcome the strength-ductility conflict in particle reinforced aluminum matrix composites (PRAMCs), a novel dual configuration strategy of microstructure was proposed in this work. The dual configuration including both heterogeneous grain structure and hybrid reinforcements was obtained by powder metallurgy, which was designed as submicron-sized SiC particles (SiCsm)/Al and micron-sized SiC particles (SiCm)/2024Al components. Representative alternating coarse grain (CG) bands containing SiCm and ultra fine grain (UFG) bands with dispersed SiCsm were revealed in microstructural characterizations. Compared to corresponding homogeneous composites with the same fraction particles, the dual configuration composite achieved simultaneous enhancement in strength and ductility and remained a comparable Young’s modulus of 98GPa, which represented 442 MPa in yield strength, 590 MPa in ultimate strength and 8.7 % in fracture elongation. The extra strength provided by hetero-deformation induced (HDI) strengthening is a potential dominant strengthening mechanism. The intrinsic toughening mechanisms primarily contribute to HDI strain hardening and enhanced dislocation accumulation capacity, while the extrinsic toughening mechanisms presumably attribute to more uniform microcrack distribution and blunting effect of CG zones on cracks. Our work provides a feasible route including ball milling and powder assembly to preparate high-modulus aluminum matrix composites for strength-ductility balance design.