Precast concrete sandwich panel is an effective solution for integrating thermal resistance and load bearing, while the adoption of green materials and lightweight design remains limited. This study has developed a precast geopolymer concrete sandwich panel (PGCSP), which features geopolymer concrete, ribbed wythes, and hexagonal tube glass fiber-reinforced polymer (GFRP) connectors, and aims to investigate its structural performance under eccentric loading. A total of seven PGCSPs were tested, focusing on the effects of load eccentricity, connector spacing, and the type of reinforced concrete (RC) wythe. Meanwhile, a 2D finite element (FE) model was established, and a parametric investigation was conducted. Finally, an empirical equation based on regression analysis was developed to estimate the eccentric load-carrying capacity. The findings of this study demonstrated that: the ribbed RC wythes can reduce the self-weight of the panel by 20 % while retaining the ductile failure and eccentric load-carrying capacity of the specimens; the eccentric load-carrying capacity is significantly reduced with increasing load eccentricity and height-to-thickness ratio; the proposed FE model can accurately reproduce the performance of the specimens; and the empirical equation can reliably predict the eccentric load carrying capacity of the PGCSP.

A large amount of waste glass fiber reinforced polymer (GFRP) is generated during manufacturing and decommissioning stages of wind turbine blades, while high-value utilization technologies for such GFRP waste remain insufficient. In this study, this recycled GFRP was used to manufacture GFRP connectors in precast concrete sandwich panel (PCSP), and the anchorage performance of the connector was investigated. Dovetail groove and I‐shaped anchorages were proposed. The influences of dovetail groove angle, embedded length, connector width, and concrete type [i.e., ordinary Portland cement concrete (OPCC), high‐performance geopolymer concrete (HPGC), ultra‐high‐performance geopolymer concrete (UHPGC), and ultra‐high‐performance concrete (UHPC)] were investigated by 55 pull-out specimens. Furthermore, 3D finite element (FE) analysis considering GFRP damage and GFRP-concrete interaction was conducted to reproduce the test. A parametric study was then conducted to confirm the pull-out capacity of the connector in OPCC with different strength grades. The results indicated that reducing the dovetail groove angle, adopting the I‐shaped anchorage or ultra‐high‐performance concrete would transfer the failure manner from concrete splitting to GFRP shear; the dovetail groove with a 79° angle and 35 mm embedded length was recommended for engineering practice; the FE model well predicted the connector pull‐out performance and verified the considerable pull‐out capacity of recommended connector in different strength grade OPCC.

This paper presents a seismic resilient column base joint incorporating disc spring bolts (DSBs) and buckling-restrained flange cover plates (BFCPs) as self-centering and energy dissipation components, respectively. A theoretical hysteretic model is developed for the joint. Quasi-static tests are conducted on seven joints, followed by replacement tests under a controlled or uncontrolled displacement to evaluate the seismic and post-earthquake replacement performance of the proposed joint, respectively. The post-earthquake replacement tests analyze replacement duration and difficulty, variations in the load and displacement. A finite element model (FEM) considering test boundaries is established and validated with test data, further analyzing the hysteretic performance of the joint with ideal boundaries. The results indicate the proposed joint offers expected self-centering capability and energy dissipation, with DSBs effectively reducing residual displacement and BFCPs enhancing energy dissipation and load resistance. Controlled displacement replacement is faster than uncontrolled displacement replacement, with core plate removal being the most time-consuming step in both cases. The joint functionality is quickly restored after replacing the core plates. The FEM captures the test boundaries of column-top friction and column-bottom deformation, accurately predicting the hysteretic behavior of the test joints. The theoretical hysteretic model closely matches the numerical hysteretic curves of the ideal boundary joint.

Precast concrete sandwich panels (PCSPs) integrated structural load-bearing and thermal insulation functions, traditional PCSPs used concrete block or fiber-reinforced polymer (FRP) connectors exhibited thermal bridge or a low degree of composite action. To overcome these shortcomings, the authors proposed a novel precast three-RC-wythe geopolymer concrete sandwich panel reinforced with basalt fiber-reinforced polymer (BFRP) grids was developed. The adjacent wythes were connected by staggered geopolymer concrete block connectors, which effectively reduced thermal bridge and improved the composite behavior of the panel. This study primarily investigated the direct shear performance of high performance geopolymer concrete (HPGC) block connectors applicable to the proposed wall system through experimental test and finite element (FE) analysis, considering key parameters including connector shape, thickness, size, and steel fiber ratio. The results showed that: due to the bridging effect of steel fiber, the inclusion of steel fibers significantly enhanced the shear capacity and ductility of the connectors, but reduced their secant stiffness. In addition, both shear capacity and stiffness increased approximately linearly with the increase of section area, were slightly influenced by shape, and decreased with the increase of thickness. The proposed 3D FE model could accurately predicted the shear capacity of the HPGC block connector. A simplified calculation formula for the shear capacity of HPGC block connectors was proposed.

Recycled waste glass (RWG) is rarely used as fine aggregate in geopolymer mortar due to its susceptibility to alkali-silica reaction under high alkalinity. Therefore, this study employs low-alkalinity Na2CO3-activated geopolymer mortar, which allows for the use of RWG as a replacement for river sand as fine aggregate. Eight geopolymer mortar mixtures were prepared to investigate the effects of RWG replacement ratios (0

Wind turbine blade production and disposal produce large glass fiber reinforced polymer (GFRP) waste, while reuse research remains scarce. In this study, perforated waste GFRP sheets from blade production were used as the reinforcement, and fiber-reinforced geopolymer mortar with recycled waste glass aggregate (RWGA) was used as the matrix to fabricate one-way thin panels. Four-point loading tests were conducted on seven panel specimens, with investigated parameters including GFRP sheet perforation ratio, hole spacing, reinforcement ratio, and matrix type. Current codes of practice were used for accessing the shear resistance. Furthermore, 3D finite element (FE) model was developed to reproduce the test. The results showed all specimens failed in shear; reducing the GFRP perforation ratio from 19% to 5% lowered shear resistance by 25.04%, while increasing hole diameter from 30 mm to 60 mm reduced shear resistance by 36.43%; existing codes underestimate panel shear resistance, as the predicted-to-measured ratio was 0.88 for both ACI 440.1R-15 and GB 50608-2020; the developed FE model well reproduces the shear behavior of the specimens and could be used for further study.

In this study, red mud was adopted as a partial replacement for the precursor, and recycled waste glass aggregate (RWGA) was employed as a substitute for natural river sand in slag-fly ash based alkali-activated mortar. Five mix proportions were designed (with red mud replacement ratios of 10% and 20%, and RWGA replacement ratios of 50% and 100%) to explore the effects of these replacements on the workability, mechanical strength, interfacial transition zone (ITZ), and reaction products of the mortar. Tests conducted included flowability measurement, setting time determination, compressive and flexural strength tests, along with microstructural characterisation using Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectrometer (EDS), X-ray diffraction (XRD), and Fourier Transform Infra-red spectroscopy (FTIR). The results indicated that although increasing the replacement ratios of red mud and RWGA led to a reduction in workability and mechanical properties, the developed alkali-activated mortar still exhibited satisfactory workability (minimum flow diameter of 212.5 mm) and mechanical strength (28-day compressive strength up to 62 MPa). The reduction in strength was primarily attributed to the dilution effect and inert filler role of red mud, and the formation of the loose gel structure.

The developed ultra-high performance concrete (UHPC) sandwich panel represents an innovative building envelope element, integrating thin, high-strength UHPC wythes reinforced with basalt fiber-reinforced polymer (BFRP) grids, a thermally efficient insulation core, and BFRP grid shear connectors that ensure composite action. This study systematically investigated the mechanical performance of BFRP grid connectors and UHPC sandwich panels through an integrated experimental and numerical approach. Direct shear tests were initially performed to characterize the shear-slip behavior of two different BFRP connector sizes, confirming their structural suitability for UHPC sandwich panel applications. Subsequently, four full-scale panel specimens with varying design parameters (including BFRP grid reinforcement ratios and connector dimensions) were subjected to flexural testing to evaluate their out-of-plane load-bearing capacity, deformation characteristics, and failure mechanisms. The experimental program also revealed the correlations between these design parameters and the panels' structural performance. Based on the physical tests, a finite element modeling methodology was developed and validated against experimental results from flexural tests, demonstrating good agreement in predicting load-displacement responses and failure modes. The findings of this research provide experimental evidence and practical references for the application of this innovative UHPC sandwich panel system.

The steel mesh-reinforced engineered cementitious composite (ECC) overlay with anchoring steel bolts has been experimentally proven to effectively compensate for the strength deficiency in reinforced concrete (RC) beams due to the inadequate lap splice length. This study investigates the failure mechanism and flexural performance of the strengthened RC beams using a two-dimensional finite element (FE) model, which accounts for the bond-slip behavior between concrete and steel rebars, the cohesive interaction between the overlay and the RC beam, and the anchorage effect of the steel bolts. The load-deflection curves and interfacial slip distributions between the overlay and the RC beam were predicted using the FE model, which was validated through comparisons with existing experimental data. Parametric analyses were conducted on 81 specimens to assess the effects of thickness and length of overlay, as well as spacing and layout of steel bolts, on the structural behavior of the strengthened specimens. The results indicated that the failure mode and the load-carrying capacity are governed by the distributions of interfacial slips, which are strongly influenced by the designs of the overlay and anchor layout. In addition, thicker ECC overlays and a greater number of anchoring steel bolts contribute to lower interfacial slips and higher load-carrying capacities.

The surface roughness of precast elements significantly impacts the shear performance of the bonding surface (BS). To enhance roughness while minimizing environmental impact, this study introduces a frustum multikey block rough surface created via a mold. To assess the shear performance of this key block BS, push-off tests were conducted on 48 specimens. The study focused on key factors such as the types of BS, key block sizes, defect rates, confining stress levels, and concrete strength classes. The results revealed that the key block BS exhibited the highest shear capacity (Vu) among all BS types. Vu increased with increasing key block size and confining stress and concrete strength but decreased as the defect rate increased. Additionally, finite element simulations and prediction formulas for Vu were developed, and the results closely aligned with the test data.

Energy-based seismic design, which integrates both the accumulated hysteretic energy and plastic deformation of the structure, provides a more comprehensive evaluation of structural seismic performance compared to other performance-based seismic design methods. In damping control structures, the distribution of hysteretic energy is clearly defined, with the expected positions for energy dissipation and damage concentrated in the dampers. This facilitates the application of an energy-based design method in such structures. This research presented a novel direct energy-based design (DEBD) method for damping control reinforced concrete (RC) structures, following the principle that the energy dissipation capacity of the structural members and dampers exceeds the hysteretic energy dissipation demand. With this principle, an energy-based damage index, which is directly correlated with structural damage state, was introduced. Subsequently, a detailed energy-based design process was provided. To achieve the desired seismic performance, the required energy dissipation capacity of dampers was determined using a pre-select damage index, and thereby, identifying the design parameters of the dampers. Finally, to validate the feasibility of the proposed design method, an 8-story RC frame with friction dampers was chosen as an example. The energy dissipation capacity and damage state of the designed structure were evaluated through nonlinear time-history analyses, and the results demonstrate the successfully achievement of the predefined seismic performance.

Precast concrete sandwich panels (PCSPs) have been widely adopted for constructing exterior walls in prefabricated residential buildings, but they face threats from impact loads such as natural disasters, terrorist attacks, and runaway vehicles. Their impact performance directly affects the overall safety and durability of the structure. However, research on the impact performance of such exterior walls remains limited. In this study, LS-DYNA R11 software is employed to establish a numerical model of PCSPs. The proposed numerical simulation method is validated by comparing the results with existing experimental data. On the basis of this numerical method and adopting an actual prefabricated residential building project as the background, the damage behavior of three distinct types of PCSPs in a bedroom is numerically investigated under varying impact location and energy conditions. The results demonstrate that the interior wythe of the PCSPs studied in this work exhibit excellent stability under external impact loading, with the most of damage absorbed by the exterior wythe, which provides effective protection to the interior wythe. Compared with windowed PCSPs subjected to impact, loads at the same energy level exhibit concrete spalling and a more pronounced dynamic response. Additionally, the windowed surface of L-shaped PCSPs is more susceptible to generating significant dynamic responses, with the non-windowed side exhibiting at least 13.2% lower maximum displacement under impact compared to the windowed side.

Through introducing disc springs into the bolt box, a novel shear wall structure with disc spring-bolt (DS-B) subassembly connections was proposed in this study. This design utilizes disc springs to provide self-centering capability and employs steel bolt box to assist in compressing the concrete, resulting in excellent resilience. A traditional bolt-connected shear wall specimen (S-1) and a DS-B subassembly connected specimen (S-2) were designed and fabricated. The seismic performance of the two specimens was evaluated through pseudo-static testing, and the impact of disc spring type and axial compression ratio on the seismic behavior of S-2 was examined. The results show that the novel shear wall structure demonstrated satisfying resilience even after a maximum considered earthquake. The hysteresis curve of S-2 exhibited flag-shape pattern characterized by its nearly rectangular loops with sharp transitions between loading and unloading paths and minor residual displacement, resulting in a small enclosed area and indicating limited energy dissipation capacity. Subsequently, a numerical simulation methodology was developed for this structural system, and a parametric study was conducted to evaluate the influence of frictional forces in the loading device, pre-tension force, and the number of DS-B subassemblies. Finally, a lateral force-displacement constitutive model for this structure and the calculation method for the loads according to the three key points of the constitutive model were proposed. The proposed method demonstrates a margin of error between calculated and experimental values ranging from 1.33 % to 18.05 %, thereby validating the reliability of the developed analytical approach.

This study investigated the out-of-plane shear performance of the textile reinforced concrete (TRC) sandwich panel through a comprehensive numerical analysis. A two-dimensional (2D) finite element (FE) model was conducted which considered the brittle nature of the core foam insulation, the bond effect between fiber and mortar, and between the TRC wythe and insulation. The FE model was validated by the existing test, and the interfacial slip distribution between the wythe and insulation was studied. Thereafter, a parametric analysis based on 126 specimens was conducted to evaluate the effect of the TRC wythe thickness, reinforcement ratio of the TRC, and the thickness of the foam board on the load carrying capacity and degree of composite action of the specimens. The results indicated that the FE model could accurately reproduce the failure process and the load-deflection relationship of the specimens; the slip distribution curve of the specimen would be influenced by the cracking behavior of the wythe and insulation; the load carrying capacity would be improved with the increase of the reinforcement ratio, insulation and TRC wythes thicknesses; while the degree of composite action would be decreased with the insulation and TRC wythes thicknesses.

The tensile behavior represent a fundamental mechanical property of fiber-reinforced ultra-high performance concrete (UHPC). Consequently, developing accurate tensile constitutive models is essential for finite element analysis and design of UHPC elements. Existing investigations have demonstrated that the tensile response of UHPC exhibits strong dependency on steel fiber volume fraction and orientation. In this study, an integrated experimental-numerical approach was employed to establish quantitative relationships between fiber volume fraction, orientation distribution, and the direct tensile behavior of UHPC, with the ultimate objective of developing uniaxial tensile constitutive models. The research methodology comprised four key phases: experimental characterization through direct tensile testing of UHPC specimens; quantitative analysis of fiber orientation distributions using image processing techniques; three-dimensional mesoscale numerical simulation incorporating fracture modeling and fiber-matrix interactions simulation via cohesive interface elements; and constitutive model development through combination of numerical simulation results, theoretical analysis, and empirical data fitting. The proposed constitutive models were validated through comprehensive comparisons between theoretical predictions and experimental tensile stress-strain curves, incorporating both the test results in this study and relevant data from published literature. The results demonstrated that the proposed constitutive models accurately capture the diverse tensile behavior of UHPC.

Rectangular concrete-filled hot-rolled-steel tubular flat columns (RCSTFCs) exhibit excellent load-carrying capacity and deformation performance due to the confinement effects of the steel tube on the concrete. This paper first studied the influence of the thickness of the internal steel plate (ti) and external angle steel (te) on the seismic performance of RCSTFCs. The RCSTFCs with different ti and te values exhibited similar failure modes. The damage was concentrated on the bottom of the steel tube. The concrete experienced only minor damage. Furthermore, finite element models, including the solid element model (SEM) and fiber element model (FEM) of RCSTFCs, were built in ABAQUS and OpenSees software, respectively. The test results validated the SEM and FEM. The average errors of the lateral load-carrying capacity between the FEM results to SEM and the test results were 6.9 % and 7.5 %, respectively. The influence of the axial force ratio on the seismic performance of RCSTFCs was investigated using FEM. Finally, a simplified skeleton model of RCSTFCs was proposed. The calculation method for the key parameters in the skeleton curves, such as the elastic stiffness, yielding point, and ultimate point, was deduced. The test and simulation results validated the theoretical skeleton curves of the RCSTFCs. The average errors in elastic stiffness, yielding, and ultimate load-carrying capacity were 5 %, 30 %, and 10.5 %, respectively.

A common steel frame is installed at the bottom of a prefabricated equipment cabin (PEC) in modular cabin-type substations to create ample space for equipment routing and maintenance. This paper proposes an earthquakeresilient steel frame instead of the common one, which uses replaceable buckling-restrained cover plates (BRCPs) to dissipate energy and disc spring bolts (DSBs) to provide restoring force. Two PECs with the common frame and the resilient frame were designed and produced, called the seismic model and baseline resilient model respectively. Two natural ground motions were selected, and the two models were tested at three earthquake levels. Then, one replacement resilient model and three parametric resilient models were loaded under maximum considered earthquakes. The test results showed that the acceleration amplification factor of the top of the two frames ranged between 1.17 and 2.09, indicating that the bottom frames amplified the acceleration of the PECs. The resilient frame proposed in this paper significantly reduced the acceleration amplification factor of the cabin roof relative to the cabin bottom. It should be noted that the equipment acceleration was greater than that of the prefabricated cabin, and the equipment acceleration in the resilient models was slightly greater than that in the seismic model, implying that further research is needed to control the response of equipment inside the prefabricated cabin. The resilient frame can guide structural damage to the replaceable core plate, without residual deformation after earthquakes, and has good rapid recovery after earthquakes. Reducing the preload of DSBs can effectively enhance the acceleration control effect of the structure while removing the core plate of the beamcolumn joint or column foot joint has less impact.

By adopting the segmental precast post-tensioning method in foundations, the efficiency of constructing precast concrete structures can be significantly enhanced. To study the shear behavior of precast concrete segmental foundation (PCSF) joints, 13 double shear specimens were tested. The failure mode and shear carrying capacity ( Vu) of the specimens were investigated. The parameters which were studied included the type of shear key, the confining stress, the type of bond for the internal post-tensioned bars and the application of epoxy resin. The results showed that design parameters changed the crack extensions of the joints. The Vu of the key unreinforced specimens was 29.14% lower than that of the reinforced specimens. After grouting of the post-tensioned ducts, the average Vu increased by 112.87% than that before grouting. With the increased in confining stress and the application of epoxy resin, the average Vu of the specimens increased by 21.9% and 48.45%, respectively. Finally, the test results were compared with the predicted results for the Vu of the joints. In predicting Vu for PCSF joints, the dowel action of the bonded post-tensioned reinforcement and the action of the reinforcement in the key must be considered on the basis of the existing prediction expressions.

In this study, the out-of-plane performance of ultra-high performance concrete (UHPC) thin panels reinforced with basalt fiber reinforced polymer (BFRP) bars was investigated. Eight panels were tested under four-point load, with the investigating parameters including panel thickness, reinforcement ratio, and the presence of steel fibers. The failure mode, crack pattern, load vs. mid-span displacement, and reinforcement strain relationships were studied. Test results revealed that panels with a higher thickness (70 mm) exhibited 178.6% higher initial stiffness, 34.5% higher cracking loads, and 88.7% higher peak loads compared to those with a lower thickness (50 mm). The effects of a larger reinforcement ratio and the presence of steel fibers became more pronounced after concrete cracking, leading to 21.2% and 22.1% higher post-cracking stiffness, respectively. Adding steel fibers helped control the development of diagonal cracks and shifted the panel failure mode from shear to flexural failure. Based on the comparison of test results with design codes, the expressions in CAN/CSA-S806-12 were recommended for predicting the load-carrying capacity of the specimens. Furthermore, a two-dimensional finite element (FE) model was developed to reproduce the test results, which validates the adopted CDP model for UHPC and the bond-slip behaviors between UHPC and BFRP bars.

Ultra-high performance concrete (UHPC) curtain wall is a new type of non-structural building envelope component. Given its large size and high cost, rational connecting systems should be employed to prevent potential seismic damage and economic losses. In this study, two novel connecting systems, including an isostatic connecting system and a frictional energy dissipating connecting system, were proposed for reinforced concrete (RC) frame with UHPC curtain walls. The design methods for these two connecting system were provided first. Then, to evaluate the feasibility of the proposed connecting systems and the corresponding design methods, three 1/2-scale RC frame structures (i.e., one bare frame without curtain walls, one with isostatic curtain wall connecting system, and one with frictional energy dissipating curtain wall connecting system) were designed and fabricated for pseudo-static tests. The damage evolution, failure mode, strength, stiffness, and energy dissipation capacity of the three test substructures were assessed. The test results demonstrated that through reasonable design, independent rocking deformation of the curtain walls was achieved in both the isostatic and frictional energy dissipating connecting systems, allowing the curtain walls to remain free from damage even under an inter-story drift of 1/36, thus validating the reliability of the proposed connecting systems and design methods. Further, compared to the bare frame, curtain walls employing the isostatic connecting system exhibited a negligible effect on the seismic performance of the frame. On the contrary, curtain walls employing frictional energy dissipating connecting system effectively enhanced the strength and energy dissipation capacity of the frame, allowing dual damage control for both walls and frame. Consequently, the frictional energy dissipating connecting system is considered to be a more rational method for enhancing the seismic performance of buildings.