The beam layout in reinforced concrete (RC) shear wall residential buildings shall fulfill both the structural requirements of efficiently transferring vertical loads to the lateral structural members and the architectural requirements of aesthetics and more spatial flexibility. The traditional beam layout design is labor intensive and time-consuming; while the existing intelligent methods do not adequately consider the above requirements. Therefore, this study proposes a multi-objective design method for beam layouts based on mathematical programming (MP), whereby the beam layout is formulated as a 0-1 integer programming problem. A grid generation mechanism for potential beam layout scenarios is provided, and a multi-objective mathematical model is proposed for generating beam layouts compatible with the architectural layout. The efficacy of the proposed method is demonstrated by 12 test cases, which indicate its ability to rapidly generate beam layouts closely resembling those designed by experienced engineers.

This study proposes a novel steel-encased beam-end (SEBE) K-shaped joint for connecting prefabricated prestressed reinforced concrete (PPRC) braces to concrete-filled steel tube (CFST) columns in a latticed double-column pier system. Focusing on the critical tensile behavior of this joint, an experimental program involving ten half-joint specimens was conducted. The tests investigated the effects of key parameters, including loading protocol, reinforcement ratio, joint configuration, the number of post-tensioned (PT) strands, prestressing level, grouting material, and connection type between the cover plate and the flange plate. Two distinct failure modes were identified: pull-out failure (PF) at the SEBE joint and tensile failure (TF) of the PPRC brace. Experimental results demonstrate that specimens achieving TF exhibited excellent hysteretic performance, stable energy dissipation, and minimal residual displacements throughout the tests. In contrast, PF led to severe strength and stiffness degradation in the later loading stage. The use of steel fiber-reinforced grout (SFRG) and enhanced confinement through plug welding between cover plates and flange plates were found to be effective in preventing PF. The force transfer mechanism within the joint was analyzed and discussed in detail, and a theoretical model for predicting the tensile capacities of the specimens was established, showing good agreement with experimental results. The findings confirm the feasibility and effectiveness of the proposed SEBE joint system for CFST double column-PPRC brace hybrid structures.

To advance the application of midply shear walls in wood-frame construction, monotonic and cyclic tests were conducted on nine groups of double-shear sheathing-to-framing (DSSF) connection specimens. The effects of framing materials, including spruce-pine-fir (SPF) and laminated veneer lumber (LVL), sheathing materials, such as oriented strand board (OSB) and plywood, sheathing thickness, fastener types (common nails, spiral nails, and self-tapping screws), loading direction, and loading protocol on the lateral performance of DSSF connections were systematically investigated. The experimental results indicate that framing materials and fastener types significantly influence the lateral performance of DSSF connections, whereas sheathing materials, thickness, and loading direction have a relatively minor effect. In contrast to the monotonic-loaded DSSF connection specimens, which failed due to fastener bending or sheathing edge tear-out, the cyclic-loaded specimens failed due to premature low-cycle fatigue fracture of the fasteners. As a result, compared to their corresponding monotonic-loaded connections, all cyclic-loaded DSSF connections exhibited reductions in lateral load-carrying capacity and corresponding displacement of 5.0%-28.8% and 16.8%-54.2%, respectively. Finally, the Q-pinch model was calibrated using the experimental data, and the simulated results indicate that the model can effectively capture both the monotonic and hysteretic behavior of DSSF connections. This study provides valuable data and reference for simulating the sheathing-to-framing connections in the finite-element model of midply shear walls.

Large-eddy simulation (LES) of flow problems subjected to turbulent inflow requires the specification of time-varying velocity fields and other relevant flow variables at the inlet. Precursor simulations are widely used to provide such unsteady inflow data. This study proposes a consistent mapping method (CPSM) for transferring turbulence data from precursor simulations to successor LES on collocated finite-volume grids. The method reconstructs the discretized system coefficients at a virtual interface between the precursor and successor domains, thereby improving the consistency of turbulence propagation. The proposed method was validated using two representative cases: fully developed channel flow and atmospheric boundary layer (ABL) wind-field simulations. The results showed that CPSM preserved turbulence statistics and coherent flow structures more accurately than the traditional direct mapping approach. In the ABL case, the longitudinal turbulence-intensity error associate with the traditional method increased from approximately 23% near the inlet to 38% at x = 0.8L, whereas the error obtained using CPSM remained negligible. In the channel-flow case, the maximum relative errors of fluctuating pressure and vorticity were reduced from approximately 30% and 60% to below 1% and approximately 1.2%, respectively. These results demonstrate that CPSM provides a more consistent and quantitatively accurate turbulence-transfer strategy for successor LES simulations.

Large-size concrete filled steel tubular (CFST) columns are increasing adopted in long-span and heavy-loaded structures. An extensive review of the existing test database has revealed that square CFST columns showed the size effect of the shear strength. Given the sudden and destructive nature of earthquakes, the study on the size effect of square CFST columns under cyclic-shear loading is vital. However, the previous relevant studies mainly focused on small-size square CFST members (i.e., B = 100–200 mm) under cyclic-shear loading or on size effect of CFST members under cyclic-bending. To fill this research gap, in this work, a total of 6 square CFST columns with varying sizes and shear span-to-depth ratios were tested under cyclic-shear loading. The failure modes and load-deformation curves were analyzed detailed. The results indicated that the cyclic-shear behavior, including the peak strength, ductility, strength degradation, energy dissipation capacity and stress of the steel tube, showed the size effect to varying degrees. Finally, the tested peak strengths were compared with current design provisions and the design recommendations were given.

In composite beams, shear connectors are essential to transfer the interfacial forces between concrete slabs and steel beams to guarantee these two components work integrally. The latest research trend is to develop simple on-site assembly of composite beams using demountable shear connectors so that both the steel beams and the concrete slabs are prefabricated in a factory, and then delivered to site for assembly. In general, this construction method will significantly reduce manpower demand, and construction time and costs. A pair of high-strength large-diameter bolts together with a steel block welded onto a steel beam, i.e. Connection RBN, together with precast concrete slabs is proposed by the authors for simple on-site assembly of composite beams, and this paper presents a systematic numerical investigation into structural behaviour of the proposed shear connections. Based on an extensive experimental investigation into a total of 16 shear connections with the proposed connections, advanced finite element models were developed and calibrated against test data. Comprehensive parametric studies with 48 models of the proposed shear connections were then performed with various dimensions and grades of bolts, steel blocks, concrete blocks and precast concrete slabs to examine their effects onto the structural behaviour of these shear connections. In addition, the numerical results were thoroughly analyzed to provide essential understanding for development of load transfer mechanisms within these shear connections. should be noted that the proposed shear connections behave as twin shear connections according to their possible failure modes taken place in the steel bolts, the concrete blocks and also in the concrete slabs. Moreover, a complementary design method is developed for accurate prediction on the shear resistances of the proposed shear connections.

To accurately determine the stress concentration factors (SCFs) and multiplanar influence factors (MIFs) of concrete-filled steel tubular (CFST) KK-joints with internal ring stiffeners under axial force, this study developed a refined finite element (FE) model that explicitly incorporates the weld geometry. A comprehensive parametric study was conducted to investigate the effects of key geometric parameters, including beta, gamma, tau, and theta, on the SCFs and MIFs distributions along the weld toe. The analysis revealed that the presence of the internal concrete and ring stiffeners results in a highly complex SCFs and MIFs distribution patterns, where the fluctuation trends, extreme values, and their locations are interactively influenced by both the loading direction and the geometric parameters. Based on the parametric findings, a series of parametric equations were proposed for predicting the SCFs and MIFs distribution curves on the chord side of CFST KK-joints with internal ring stiffeners under axial force. The accuracy and reliability of these proposed equations were further corroborated through verification with additional FE models, demonstrating their excellent potential for practical engineering application.

The rapid expansion of wind turbine installations in seismically active regions necessitates enhanced seismic performance. To address this issue, this study proposes a novel partial self-centring wind turbine (PSCWT), which incorporates a reduced tower section (RTS) with partial self-centring dampers (PSCDs). During an earthquake, energy dissipation is achieved through the PSCDs and RTS, while the PSCDs also provide self-centring capacity. First, the PSCWT concept and working mechanism are introduced. Subsequently, finite element models are developed for an onshore wind turbine (OWT) prototype structure and PSCWT prototype structures with varied hysteretic behaviour. The seismic dynamic responses of all structures are examined. Finally, seismic fragility analyses are performed using design-spectrum-compliant ground motions. The results show that the PSCWT exhibits improved seismic performance, with a collapse capacity 120.1 % higher than that of conventional OWT. The structural response is appreciably influenced by the hysteretic behaviour parameters of PSCD, namely postyield stiffness and energy dissipation ratio. In addition, the configuration of the RTS, which can be quantified by the diameter-to-thickness ratio, also affects the seismic response of the structure. Increasing post-yield stiffness or diameter-to-thickness ratio enhances energy dissipation while maintaining self-centring capacity. However, a higher energy dissipation ratio improves collapse resistance, but the residual deformation is increased.

Recently, prestressing has been incorporated into concrete-filled steel tubular lattice towers, leading to a novel structural solution for onshore wind turbines in low-wind-speed regions. The adoption of unbonded posttensioned strands provides the tower with enhanced seismic resilience and post-earthquake reparability. To elucidate the load-resisting mechanisms and the role of prestressing under combined compression-bending-torsion loading, a novel four-chord prestressed concrete-filled steel tubular rocking lattice tower was developed by intentionally leaving the bottom flange bolts untightened to permit uplift-induced rocking, while prestressed strands served as key structural components resisting lateral loads. Quasi-static scaled experiments were conducted to compare the proposed rocking tower with a conventional fixed-base tower in terms of load-displacement curves, energy dissipation, stiffness degradation, prestress evolution, and steel strains. Results showed that the conventional fixed-base tower was governed by extensive batten failure, whereas the proposed rocking tower reached its ultimate state through fracture of prestressed strands. The degradation patterns of lateral stiffness before and after cyclic rocking remained generally consistent, with variations in flexural and torsional capacities limited to approximately 5%. However, the flexural and torsional ductility coefficients decreased by 39.22% and 22.76%, respectively, indicating that the rocking behavior effectively mitigated plastic damage while reducing global structural ductility. Prestress loss was closely associated with structural plastic deformation. Based on the validated finite element model, a systematic parametric investigation was conducted to evaluate the effects of key design parameters on the rocking behavior of the tower, and corresponding design limits for the axial load ratio, batten-to-chord wall-thickness ratio, and diameter ratio were proposed for design applications.

Given the substantial dimensions and weight of precast concrete components in wind turbine hybrid towers, traditional lifting anchors prove inadequate to meet the hoisting requirement, driving the adoption of a special lifting anchor system recently. This lifting anchor system, composed of a specialized steel anchor and supplementary reinforcement, is recommended by existing design codes to prevent anchorage failure. However, the shear design method remains undefined, particularly regarding the effect of supplementary reinforcement configuration. To address this, the shear behaviour of this lifting anchor system for precast concrete components is investigated in this study, considering actual dimensions and reinforcement configurations. A cyclic shear test programme including four lifting anchor specimens was conducted, while the typical failure mode and shear capacity were discussed. Numerical models were developed and validated utilizing test data, and then adopted to analyze shear behaviour and identify key parameters, including configurations of supplementary reinforcement and structural reinforcement, embedment depth, edge distance, and lifting anchor type. Besides, the mechanism of supplementary reinforcement and structural stirrup was revealed. Subsequently, the applicability of calculation methods in existing design codes was evaluated against test results. Building on quantitative assessment of shear contributions of reinforcements, a calculation method was developed, exhibiting higher accuracy than existing design codes for the objects in this study. Lastly, recommendations for lifting anchor and supplementary reinforcement layout were provided. The combination of the proposed calculation method and layout recommendations can provide guidance for the hoisting design of precast concrete components of wind turbine hybrid towers

Inerter-based Vibration Absorbers (IVAs) have gained extensive attention in research in vibration control due to their high performance and light weight. In practice, the optimal tuning parameters of IVAs are determined by structural dynamic properties of the primary structure for an optimal control performance. However, the structural dynamic properties (such as natural frequency) may deviate from the design values, which leads to mistuning of IVAs, thus weakening the control performance. In order to address this issue, an in-situ adjustable IVA with a rhombus amplification mechanism (R-IVA) is proposed to compensate for the mistuning in practice. Firstly, the theoretical model of the proposed R-IVA was established. Subsequently, based on H∞ optimization, closed-form solutions for the optimal parameters of the proposed R-IVA are derived. Parametric studies are performed to explore the influence of essential parameters of the R-IVAs. Finally, the applicability of R-IVA and the theoretical optimization solution is illustrated by numerical analysis on prototype structures under seismic excitations. Conclusively, with the rhombus amplification mechanism, in-situ adjustable inertance can be achieved by tuning the assembly angle. The mistuning problem in practice can be effectively rectified by the proposed R-IVA device and optimization method.

This paper proposes a novel cold-formed steel (CFS) composite truss system and investigates its flexural behavior through testing and numerical simulation. Three composite trusses with different spans and shear connection degrees were designed and tested under four-point bending. A detailed finite element modeling method was developed, and extensive parameter studies were conducted to examine the effects of concrete slab width and thickness, CFS member thickness, shear connection degree, and joint behavior. Finally, the theoretical calculation method was proposed to predict the failure mode and bearing capacity for practical applications. The results indicated that: (1) The composite action effectively prevented the compressive buckling of the top chord. The failure modes of CFS composite trusses included shear failure of the joint and tensile yielding of the bottom chord. (2) Joint behavior was the most important factor influencing the failure modes, bending strength, and stiffness. When the shear strength and stiffness of screw connections doubled, the failure mode shifted from shear failure of the joint to tensile yielding of the bottom chord. The capacity under the serviceability limit state (SLS) increased by 26%-48%, while the capacity under the ultimate limit state (ULS) increased by 81%-138%. (3) The bearing capacity of composite trusses was generally governed by the deflection limit (SLS), which corresponded to 75%-82% of that at failure (ULS). The proposed calculation method can accurately predict the failure mode and capacity under ULS and provide conservative predictions for capacity under SLS.

Prestressed concrete-filled steel tubular lattice towers combined high load-bearing capacity with substantial lateral stiffness. The incorporation of prestressed steel strands effectively mitigated issues related to excessive tower dimensions and fatigue. During service, wind turbine towers are subjected to combined compressionbending-torsion loads, with compression-bending dominating. To investigate their mechanical behavior under such complex loads, quasi-static tests were conducted on three scaled models to examine failure modes, hysteretic behavior, prestress variation, and steel strain. Results showed that under compression-bending, failure was primarily governed by tearing and bending of outer steel tubes at the chord base. Under compressionbending-torsion, non-prestressed specimens first experienced battens rupture followed by corner chord failure, whereas prestressed specimens exhibited effectively suppressed corner chord damage and markedly reduced concrete cracking in the tensile zone. Compared with non-prestressed specimens, prestressed specimens achieved increases of 18.36%, 31.74%, and 67.46% in initial elastic stiffness, structural ductility, and energy dissipation capacity, respectively. Prestress had little effect on yield and ultimate load, whereas loading type significantly influenced combined bearing capacity. Inclined battens strength strongly affected overall stiffness, and prestress loss closely correlated with prestress strand shrinkage and plastic deformation of chords. Based on experimentally validated finite element models, parametric analyses were performed to assess effects of axial load ratio, material strength, dimensions, and prestress on the tower load-displacement performance, providing guidance for rational tower design.

To address the issues such as poor cementitious properties, insufficient water resistance, and brittle fracture behavior encountered when using phosphogypsum in building materials, as well as to fill the gap concerning the interaction mechanism between polypropylene fibers and the phosphogypsum-slag system, this study prepared polypropylene fiber-reinforced phosphogypsum slag concrete (PF-PSC) in an alkaline environment. The performance and hydration mechanism of PF-PSC were then evaluated through macroscopic property tests and microscopic characterization. The results indicated that when GBFS content was 40% and PF content ranged from 0.1% to 0.3%, the cubic compressive strength at 28 d reached 78.9 MPa, meeting the C60 strength grade. Compared with the reference group, the splitting tensile strength and flexural strength increased by 27.1% and 66.7%, respectively. The softening coefficient rose to 0.93, the gas permeability coefficient decreased to as low as 1.53 & times; 10(-18 )m(2) (close to UHPC), and the chloride migration coefficient significantly decreased. The established chloride diffusion model showed good accuracy. Microscopically, the C-S-H and ettringite formed by the hydration reaction of GBFS, combined with the bridging effect of PF, a dense 'gel bonding-fiber crack resistance' microstructure was formed. The proportion of harmless pores (<10 nm) reached 19.1%, and the total porosity decreased to 6.06%. Environmental-economic assessments demonstrated that the carbon emission per cubic meter of PF-PSC was reduced by over 31% compared with traditional C60 OPC concrete, while the cost was lowered by 42%. This study could provide theoretical support for the high-value utilization of phosphogypsum and the development of green concrete.

This research reported the development of self-centring connections equipped with thin-walled shape memory alloy plates (SMA-plate connections) for seismic retrofitting of steel frame structures, where the SMA plates primarily undergo ‘tension-release’ responses to provide moment resistance, self-centring driving force, and energy dissipation for the connection. An experimental study was conducted on four SMA-plate connection specimens to examine their hysteretic behaviour under different loading protocols. In addition, given the limited thickness of the SMA plates commercially available, the feasibility of using double layers of thin-walled SMA plates in the connection was examined in the tests. A hybrid modelling technique for SMA plates was used to conduct numerical simulations of the test results. Design equations were derived to predict the skeleton responses of the specimens. The experimental results demonstrated that the SMA-plate connection specimens exhibited flag-shaped self-centring hysteretic responses within a certain range of deformation. The SMA plates played a key role in achieving satisfactory self-centring performance and stable hysteretic responses, while the configuration of the web connector also affected the residual deformations and energy dissipation capacities. The viability of the double-layer configuration was evidenced by the enhanced strength, stiffness, and energy dissipation. The developed numerical models were capable of reproducing the deformed shapes and hysteresis curves of the specimens. The rationality of the design equations was validated by the good agreement between the predicted skeleton curves and those measured in the tests.

This study presents a novel, reinforcement-free prefabricated composite beam system integrating 3D-printed concrete (3DPC) slabs and glued laminated timber (GLT) beams. The system employs an ultra-high-performance concrete (UHPC)-filled notch-screw shear connector to address the interfacial bonding challenge between the two materials. Push-out tests on the connector demonstrated that its load-bearing capacity and slip stiffness increased with notch depth and length, while the shear length ahead of the notch had a minor influence. For the critical 3DPC-UHPC interface, three failure modes were identified, with performance governed by matrix interlayer properties and interface morphology. The X-interface with an original 3DPC surface was optimal, and adding polyoxymethylene fiber further enhanced performance. Connectors with a vertical printing path showed superior performance, with approximately 8% higher load capacity than those with a horizontal path. Bending tests on composite beams clarified the influence of cross-sectional mesh configuration and printing material. Beams with a transverse mesh exhibited 28.8% greater initial stiffness than those with a top-surface mesh. Crucially, the system achieved satisfactory structural performance without traditional steel reinforcement, validating the feasibility of the proposed reinforcement-free, prefabricated approach. Finally, predictions for bending stiffness and interface shear capacity based on the gamma method showed good agreement with experimental values.

Floating offshore platforms are increasingly deployed for deep-water renewable energy yet are highly susceptible to ultra-low-frequency wave excitation, demanding effective vibration isolation. Quasi-zero-stiffness (QZS) technology, which provides high-static-low-dynamic stiffness, offers a promising solution. This study investigates larch timber—a renewable biomass material—as a sustainable material for QZS isolators. A cross-shaped configuration combining double-buckling beams (negative stiffness) and Z-shaped members (positive stiffness) is proposed. Quasi-static tests confirm a distinct low-stiffness plateau of approximately 10 mm at a load capacity of 145 N. A refined finite element model incorporating timber anisotropy and brittle damage is validated and used for parametric analysis. A machine-learning-based inverse optimization then integrates a high-precision XGBoost surrogate with the NSGA-II multi-objective algorithm and entropy-weighted TOPSIS, yielding optimized structural parameters. Dynamic simulations of a spar-type floating platform under JONSWAP wave excitation show that the optimized multi-layer isolator reduces maximum displacement by over 50% and maximum acceleration by more than 73%. These results establish biomass-derived timber as a mechanically tunable, eco-friendly alternative to conventional steel or elastomer-based marine vibration isolators.

The prestressed concrete wind towers have applications potential in lower wind velocity region. The calculation of the ultimate limit states of thin-walled concrete structures under combined loads has attracted widespread attention. In this paper, a series of works have been conducted on its combined compressive-flexural-shear-torsional behaviour. A test system was designed using a combined loading method and considering various types of damage. The results show that the composite failure modes can involve multiple failure phenomena occurring simultaneously. Increasing the reinforcement ratio can enhance the post-yield bearing capacity of the specimens but has little effect on their stiffness. Finally, based on the unified formula for the ultimate bearing capacity of reinforced concrete, two assumptions of the eccentric compression formula for circular ring sections were derived using the strut-and-tie model and compared with the test results. The results indicate that the method recommended by the code is generally conservative for many conditions but has higher coefficient of variability. In contrast, the improved method reduces computational variability by 28.8 % while maintaining safety, providing more consistent and reliable predictions. This indicates that the improved method exhibits higher applicability across various loading conditions. The improved method addresses the gaps in current codes for design under combined loading conditions, integrating the verification of individual loading states into a more effective verification approach.