New Trends in Advanced Construction Technology, Sustainable Construction Materials and High-Performance Building Structures

The external bonding (EB) of fiber-reinforced polymer (FRP) is a usual flexural reinforcement method. When using the technique, premature debonding failure still remains a factor of concern. The effect of incorporating multi-wall carbon nanotubes (MWCNTs) in epoxy resin on the flexural behavior of reinforced concrete (RC) beams strengthened with basalt fiber-reinforced polymer (BFRP) sheets was investigated through four-point bending beam tests. Experimental results indicated that the flexural behavior was significantly improved by the MWCNT-modified epoxy. The BFRP sheets bonded by the MWCNT-modified epoxy more effectively mitigated the debonding failure of BFRP sheets and constrained crack development as well as enhanced the ductility and flexural stiffness of strengthened beams. When the beam was reinforced with two-layer BFRP sheets, the yielding load, ultimate load, ultimate deflection, post-yielded flexural stiffness, energy absorption capacity and deflection ductility of beams strengthened using MWCNT-modified epoxy increased by 7.4%, 8.3%, 18.2%, 22.6%, 29.1% and 14.3%, respectively, in comparison to the beam strengthened using pure epoxy. It could be seen in scanning electron microscopy (SEM) images that the MWCNTs could penetrate into concrete and their pull-out and crack bridging consumed more energy, which remarkably enhanced the flexural behavior of the strengthened beams. Finally, an analytical model was proposed for calculating characteristic loads and characteristic deflections of RC beams strengthened with FRP sheets, which indicated a reasonably good correlation with the experimental results. Full article

In recent years, the prefabricated subway station structure (PSSS) has become a hot spot of underground structure research. In this paper, the numerical model of a soil–subway station structure in a slowly inclined liquefiable site at the surface is established by using FLAC3D finite difference software. And the applicability of the PSSS under the gently inclined liquefiable site is investigated through the foundation pore water pressure, lateral movement of liquefied soil, and dynamic response and uplift characteristics of the subway station structure. It is found that under the gently inclined liquefiable site conditions, the PSSS exhibits tilting and floating behaviors and has an anti-liquefaction effect within a certain range of surrounding soil layers. Compared with the same type of cast-in-place subway station structure (CIPSSS), it has better resistance to overturning and uplift, and the structure has less stress. Under the premise of ensuring static waterproofing, the PSSS can be applied to surface inclined liquefiable sites. Full article

Set-back modification represents a dependable method to reducing the wind effects on high-rise buildings, but the flow mechanism and aerodynamic responses of set-back tall buildings have not been explored systematically. Using the square building as the benchmark model, six set-back building models with varying steps and sizes were chosen for numerical simulation in this study. The results of mean wind pressure and local wind force distribution, power spectral densities of base moment, flow field, and structural response of the proposed building models are compared and analysed using the Large Eddy Simulation (LES) technique. The results demonstrate that the aerodynamic performance of set-back tall buildings dramatically improved, with the actual optimization in the cross-wind direction being more significant. Generally, a single set-back measure can enhance the aerodynamic performance of high-rise buildings more effectively than a double set-back measure. The outcome of this study provides an aerodynamic design guide for set-back tall buildings. Full article

Cross-sea cable-stayed bridges encounter challenges associated with cable corrosion and cable-force relaxation during their service life, which significantly affects their structural performance and seismic response. This study focuses on a cross-sea cable-stayed bridge located in Hainan Province. Utilizing an LSTM deep learning model, this study aims to fill in the gaps in short-term cable-monitoring data from the past year using the available cable-force-monitoring data from the same period. The authors of this study interpolated the cable-force data in the absence of sensors and employed a SARIMA machine learning time-series-prediction model to predict the future trends of all cable forces. A finite-element model was constructed, and a dynamic time-history analysis of the seismic response of the cross-sea cable-stayed bridge was conducted, considering the influence of cable-force relaxation and cable corrosion in the future. The findings indicate that the LSTM-SARIMA model predicted an average decrease of 11.81% in the cable force of the cable-stayed bridge after 20 years. During the lifecycle of the cables, cable corrosion exerts a significant impact on the variation in cable stress within the bridge structure during earthquakes, while cable-force relaxation has a more pronounced effect on the vertical displacement of the main beam of the bridge structure during seismic events. Compared to when using the traditional model that only considers cable corrosion, the maximum negative vertical displacement of the main beam increases by 29.7% when using the proposed model if the earthquake intensity is 0.35 g after 20 years, which indicates that the proposed machine learning model can exactly determine the seismic behavior of the lifecycle cross-sea cable-stayed bridge, considering the impacts of both cable-force relaxation and cable corrosion. Full article

The work presented in this paper includes the construction methods and lessons learned from the placement of a non-proprietary ultra-high performance concrete (UHPC) overlay through the rehabilitation of a concrete bridge deck located in Socorro, New Mexico, USA. The selected bridge is a multi-cell, box girder bridge with four spans and a total length of 91.4 m and a width of 16.5 m with two traffic lanes. Rehabilitation of the bridge involved removing the top surface of the existing deck (deteriorated concrete), installing a high-performance deck (HPD) leveling course, and placing a 25 mm UHPC overlay. Sensors were installed in the bridge superstructure (multi-cell box girders, HPD, and overlay) for long-term monitoring. Overlay assessment included physical testing to evaluate the condition of the overlay–substrate bond by chain dragging and direct tension pull-off testing. Conclusions and lessons learned from this investigation serve as a fundamental list of best practices and recommendations for field construction of a non-proprietary UHPC overlay. Recommendations for preparatory tasks including material selection, substrate surface preparation, placement preparation, handling of materials, and UHPC mixing are provided. The recommendations also list best practices concerning the placement of the overlay, curing procedures, and quality assurance testing. Lastly, suggestions are presented for contracts pertaining to UHPC overlay projects. Full article

This study explores the potential of using basalt reinforced UHPC by incorporating simultaneously self-cleaning and self-luminescent features, paving the way for sustainable advancements in civil engineering. New green formulations of UHPC were developed by integrating supplementary cementitious materials and optimizing water to the binder ratio, followed by using basalt fibers to enhance strength and ductility. The fabricated samples with high particle-packing density exhibit sufficient workability and compressive strength up to 136 MPa, and, when incorporating basalt fibers, a notable reduction in brittleness. The inner microstructure of basalt fibers was observed to be smooth, homogeneously distributed, and well adhered to the UHPC matrix. To ensure the desired long-lasting visual appearance of decorative UHPC and reduce future maintenance costs, a time-effective strategy for creating a light-emitting biomimetic surface design was introduced. The samples exhibit high surface roughness, characterized by micro to nano-scale voids, displaying superhydrophobicity with contact angles reaching up to 155.45°. This is accompanied by roll-off angles decreasing to 7.1°, highlighting their self-cleaning features. The self-luminescence feature showcased intense initial light emission, offering a potential energy-efficient nighttime lighting solution. Full article

The TOD mode with rail transit stations as the center has become an important direction of future central city construction. However, at present, there is still a lack of simplified calculation methods for the seismic design of a subway station complex structure of TOD mode. Based on the load-structure model of the classic response displacement method and the seismic deformation characteristics of the underground complex structure, an improved response displacement method for seismic calculation of the subway station complex structure considering the influence of the upper frame structure was proposed in this paper. Then, based on the actual engineering case, the applicability of the improved reaction displacement method was verified through investigating the influencing factors such as seismic wave type, ground motion intensity, building position, structure form, structure stiffness, and stratum stiffness. Furthermore, a series of numerical simulation experiments were conducted to verify the simplified method and further evaluate its computational accuracy. The result shows that the error in calculating the internal force and deformation response of a station complex structure by using the improved reaction displacement method can be controlled at about 10%. The improved response deformation method is proved to be a highly practical pseudo-static method. Full article

The double-story isolation structure is a novel development based on the mid-story isolation structure. To accurately reflect the seismic response of the double-story isolation structure, this study considers a dynamic elastoplastic analysis model that incorporates soil–structure interaction (SSI). Comparative models of a base-fixed structure and a mid-story isolation structure are also established. The results indicate that the double-story isolation structure has a longer structural period compared to the mid-story isolation structure. Furthermore, the structural period increases as the soil softens and the structure becomes more flexible. When considering SSI on hard soil versus not considering SSI, the double-story isolation structure exhibits smaller base shear, story force, inter-story displacement, maximum acceleration of the top floor, and displacement of the upper isolation layer, indicating the significant shock-absorbing effect of the double-story isolation structure. However, when SSI is considered on soft soil, the shock-absorbing effect of the isolation structure diminishes, and the effectiveness of the double-story isolation structure may not necessarily surpass that of the mid-story isolation structure. In all three soil conditions, the compressive stresses of the isolation bearings in the upper isolation layer of the double-story isolation structure were lower than those in the isolation bearings of the base isolation layer. Additionally, the double-story isolation structure demonstrates reduced compressive stress in the isolation bearings, fewer plastic hinges in the frame, and less stress damage compared to the mid-story isolation structure. Consequently, the risk of overturning damage in the double-story isolation structure is significantly reduced compared to the mid-story isolation structure. The effect of soft ground on structures can be highly detrimental, which should be paid more attention to during the design process. This study offers valuable insights for future research on double-story isolation systems and serves as a reference for the development of high-performance building structures in the future. Full article

Recycled aggregate concrete (RAC) technology has received a lot of attention as a green environmental protection technology. However, the unsatisfactory mechanical behavior of RAC restricts its application in engineering practice. The structure of basalt fiber-recycled aggregate concrete-filled circular steel tubes (C-BFRACFST) can dually improve the mechanical behavior of RAC. To observe the axial compression behavior of the C-BFRACFST column, seven specimens were designed with recycled aggregate replacement ratio (0%, 50%, 100%), basalt fiber (BF) content (0 kg/m³, 2 kg/m³, 4 kg/m³) and length–diameter (L/D, 5, 8, 11) as variable parameters for axial compression tests. The failure mode, load–displacement/strain curve, axial compression deformation, ultimate bearing capacity, energy dissipation, and ductility of specimens have been analyzed. The derived constitutive relation of core basalt fiber-reinforced recycled aggregate concrete (BFRAC) constrained by the circular steel tube and the 3D finite element model of C-BFRACFST column have been established to simulate the whole process of compression. It is observed that instability or shear failure occurs in specimens under axial compression load. When the recycled aggregate replacement ratio was increased from 50% to 100%, the change in the energy-dissipation capacity of the specimens was not significant but the ultimate bearing capacity and displacement ductility coefficient decreased by 3.45% and 8.91%, respectively. When the BF content was increased from 2 kg/m³ to 4kg/m³, the change in the ultimate bearing capacity of specimens was not significant; the energy-dissipation capacity at the later stage of bearing increased, and the displacement ductility coefficient was noted to increase by 13.34%. When the L/D was increased from 8 to 11, the energy-dissipation capacity of specimens was decreased, and the ultimate bearing capacity and displacement ductility coefficient declined by 1.37% and 43.52%, respectively. The finite element simulation results are in agreement with the test results. Full article

This study presents a detailed numerical investigation into the web buckling behaviour exhibited by high-strength aluminium alloy channels, namely 7075-T6 and AA-6086, when subjected to concentrated loading. A nonlinear finite element (FE) model was established and verified using the experimental data reported by other researchers, and the material properties of 7075-T6 and AA-6086 high-strength aluminium alloy were obtained through the literature. A parametric study comprising 1024 models was performed using the validated FE models. Variables examined in this work included web slenderness ratio, internal corner radii, bearing lengths, and aluminium alloy grades. The numerical results generated by the parametric investigation were used to evaluate the applicability and reliability of the most recent design specifications given in the Australian and New Zealand Standards (AS/NZ S4600) (2018) and Australian Standards (AS/NZS 1664.1) (1997). The comparison indicated that the calculated design strength using AS/NZ S4600 was over-conservative by 41% and 43% for 7075-T6 and AA-6086 aluminium alloy, correspondingly, while the design strength computed using AS/NZS 1664.1 was marginally unconservative, compared to numerical results. Finally, using bivariate linear regression analysis, new design formulas with new coefficients for determining the web buckling behaviour of 7075-T6 and AA-6086 high-strength aluminium alloy channels were proposed. A reliability analysis was then undertaken, indicating that the proposed design equations possess the capability of accurately predicting the web buckling behaviour of these members. Full article

Damage to nonstructural components, such as air ducts, in buildings during earthquakes, which are more fragile than single-layer reticulated domes, has a significant impact on the sustainability of the building’s functionality. To study the coupling effect and failure mode of a single-layer reticulated dome with an air duct system, then, simplified finite element models of air ducts and flange bolt joints were established and validated against the solid element model. Moreover, the simplified finite element models of support hangers were also built and validated against the existing experiment. Three kinds of support hanger layout schemes were studied to analyze the dynamic characteristics and seismic responses of a single-layer reticulated dome with an air duct system from earthquakes at different intensities. The results showed that the simplified finite element model can effectively simulate the coupling effect and failure mode of the single-layer reticulated dome with an air duct system. The coupling effect of the air duct system reduces the natural vibration frequency in the dome and increases the number of damaged members in the dome by strong earthquakes. The rate of falling air ducts with all the seismic support hangers is the highest compared to the two other support hanger layout schemes. Full article

Recently, new types of C-shaped members made from AA-6086 and 7075-T6 high-strength aluminium alloy have become more popular due to their high yield strength and lower cost. These members are often manufactured with pre-punched web perforations to simplify the installation of services, but this can reduce their strength. Also, such aluminium C-shaped members that contain perforated webs are vulnerable to web buckling failure, as aluminium alloy has a lower elastic modulus compared to steel. However, this influence has not been investigated for high-strength aluminium alloy sections to date. An extensive numerical investigation was undertaken to examine the effect of web perforations on the web buckling resistance of high-strength aluminium alloy C-shaped members under an end-two-flange (ETF) loading case, and this study focused on two types of aluminium alloys, namely 7075-T6 and AA-6086. To achieve this, a nonlinear finite element (FE) model was developed and validated using the test data in the literature. The material properties used in the FE models were obtained from the relevant literature. A parametric investigation was carried out, consisting of a total of 1458 models. In this investigation, a number of variables were examined, including the web hole size, web hole location, bearing length, fillet radius and aluminium alloy grades. The results showed that increasing the a/h ratio from 0.1 to 0.5 resulted in a decrease of 9.7% and 9.3% in the web buckling resistance for the 7075-T6 aluminium and AA-6086 aluminium, respectively. When the length of the bearing plates (N) varied from 100 mm to 200 mm, the web buckling resistance experienced an average increase of 61.7% for the 7075-T6 aluminium and 54.1% for the AA-6086 aluminium. Also, the web buckling resistance increased by 6.2% for the 7075-T6 aluminium alloy, while the strength increased by 4.0% for the AA-6086 aluminium alloy when the x/h ratio increased from 0.1 to 0.5. The numerical data generated from the parametric study were used to assess the accuracy and suitability of the latest design recommendations, and it was found that the design rules presented in the previous literature cannot provide reliable and safe predictions for estimating the web buckling resistance of aluminium C-shaped members that contain perforated webs under an ETF loading case. Finally, new design formulas were proposed in the form of strength reduction factors. A reliability assessment was then undertaken, and the results of this analysis indicated that the proposed design formulas can accurately predict the web buckling resistance of such members with perforated webs. Full article

Two types of high-strength aluminium alloy (HA)—namely, AA-6086 and 7075-T6—have been developed and extensively used in recent years. These high-strength aluminium alloys offer advantages such as lower prices and higher yield strength than traditional alloys. The webs of aluminium channel members under concentrated loads are susceptible to web buckling failure, which restricts their applications. However, no research work has been reported that has evaluated the web buckling performance of high-strength aluminium alloy channel sections subjected to end-two-flange (ETF) loading, and the material characteristics of these high-strength aluminium alloys differ significantly from those of conventional aluminium alloys. This work addresses this gap by conducting a detailed numerical investigation. A parametric investigation consisting of 1024 models was performed using the finite element (FE) models previously developed for traditional aluminium alloys. A wide range of high-strength aluminium alloy sections covering varying web slenderness ratios, internal corner radii, bearing lengths, and aluminium alloy grades were considered in this investigation. It was shown that the latest design recommendations in the Australian and New Zealand Standards (AS/NZ S4600) and (AS/NZS 1664.1) were over-conservative when estimating the web buckling strength of such channel sections. Finally, new web buckling design equations for high-strength aluminium alloy channel sections were proposed through reliability analysis in this investigation. Full article

Aiming to investigate the mechanical performance of UHPC T-section beams, five specimens are fabricated and tested, considering the variable steel fiber volume fraction (SFVF). The code of the Association Francaise de Génie Civil (AFGC) is evaluated by test data. Additionally, based on Abaqus (2020), refined finite element analysis (FEA) models of specimens are established and validated by experimental data. Moreover, the parametric sensitivity analysis is carried out, which aims to further investigate the effect of shear span ratio, longitude reinforcement ratio, and stirrup ratio on the bending-shear behavior of T-section beams. The test results indicated that the ultimate load of the specimen improves with the increase of SFVF, and the use of steel fibers can greatly improve the shear capacity instead of the bending capacity. Furthermore, SFVF can change the failure mode; the specimens fail in shear failure when SFVF < 2%, while they fail in bending failure when SFVF ≥ 2%. From the evaluation of codes, the AFGC code is conservative in the prediction of ultimate capacity, which can guide the design of UHPC structures well. Additionally, from the parametric analysis of FEM, the failure mode transformed from shear failure to bending failure as the shear span ratio increased, particularly in specimens with SFVF ≥ 2.5%. Moreover, the stirrup ratio ρ_sv has a significant effect on the shear performance of structures with SFVF ≤ 1%, while it has less effect with SFVF ≥ 2%. Full article

This paper presents the experimental and numerical studies in the investigation of the concentrated compressive behaviors of cold-formed steel-foam concrete composite wall. The failure modes, load–displacement curves, and load–strain curves of the specimens were obtained from the experiments. The infilled specimen failed due to distortional buckling of the end stud and cracking of the concrete near the corner of the wall. The strength of the high strength cold-formed steel was not being fully utilized. A finite element model was established by ABAQUS software and validated by the test results to investigate the effect of the concrete strength, steel strength, the spacing between stud openings, and the thickness of the concrete protective layer on the behaviors of the composite wall. The results indicate that the improvement of concrete strength has the most obvious effect on the bearing capacity of the composite wall, while the changes in steel strength, concrete cover thickness, and hole spacing have limited effects. Full article

In this paper, the thermal-related stress–strain behavior of alkali-activated slag (AAS) concretes, with different alkali concentrations and moduli, was studied under compression. After exposure to high temperatures (200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C), a compression test was carried out on the specimens. The stress–strain relationship, axial compressive strength, and elastic modulus were expressed using both a displacement extensometer and the digital image correlation (DIC) technique. It was mainly determined that: (1) With the increase in temperature, the stress–strain curves of the AAS concretes tended to be flattened, indicating reductions in both axial compressive strength and elastic modulus. After 1000 °C, only 2.5–3.7% axial compressive strength and 1.4–3.9% elastic modulus remained, respectively. (2) The DIC technique was used for thermal strain measurements of the AAS concrete. Compared to the traditional extensometer, DIC yielded a small error of 4.5% and 7.2% for axial compressive strength and elastic modulus measurements, respectively. The strain cloud chart obtained from DIC was helpful for monitoring the damage process of the specimens. The findings of this paper refined scientific systems of AAS concrete under thermal action, and also provided a newly non-contact approach for thermal strain measurements of AAS concrete under compression. Full article

The all around construction and development of rural areas not only promotes the economic promotion of rural areas and the optimization and adjustment of various industrial structures, but also leads to the deterioration of rural living environments. There is a close relationship between the planning and design of residential buildings and the living environment, which can integrate human life and architecture into a whole. Virtualization technology is a new technology developed in recent years, which integrates computer graphics, multimedia, digital image processing, and other technologies. In this paper, a virtual building model of a rural residential environment based on a convolutional neural network (CNN) is constructed, and the virtual reconstruction of the residential environment is realized by extracting the bottom features of images. The experimental results show that, compared with the support vector machine (SVM) algorithm, the accuracy of the proposed human settlements modeling method is improved by 27.85%. This model can effectively solve the problem of unclear and not stereo images, and at the same time keep the clarity of the virtual reconstruction images of buildings, which can provide theoretical support for the improvement of the rural living environment under the background of a rural revitalization strategy. Full article

In order to reduce the impact of the environment on the accuracy and sensitivity of detection, and to meet the requirements of concealment from detection and being lightweight, a technology for detecting flying metal objects based on photoelectric composite sensors is proposed. The method first analyzes the target’s characteristics and detection environment, and then compares and analyzes the methods for detecting typical flying metal objects. On the basis of the traditional eddy current model, the photoelectric composite detection model that meets the requirements of detecting flying metal objects was studied and designed. For the problems of the short detection distance and the long response time of the traditional eddy current model, the performance of the eddy current sensor was improved to meet the requirements of detection through optimizing the detection circuit and coil parameter model. Meanwhile, to meet the goal of being lightweight, an infrared detection array model applicable to flying metal bodies was designed, and simulation experiments of composite detection based on the model were conducted. The results show that the flying metal body detection model based on photoelectric composite sensors met the requirements of distance and response time for detecting flying metal bodies and may provide an avenue for exploring the composite detection of flying metal bodies. Full article

The production of Portland cement is energy-intensive and polluting. As a result, the search for ecological and economical alternatives has become a global priority. Geopolymers are among the most promising ecological alternatives to Portland cement. Their properties depend on the nature and concentration of the activators. This study investigates the effect of Na₂SiO₃/NaOH ratio and NaOH molarity on the alkaline activation of natural volcanic pozzolan. The physico-mechanical and microstructural properties of the investigated geopolymer were evaluated using compressive strength, density, porosity, water absorption, X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. The results indicate that the optimal parameters for activation are a NaOH molarity of 8 mol/L and Na₂SiO₃/NaOH ratio of 1.2. These parameters enhance the dissolution of the volcanic pozzolan and the formation of a N-A-S-H geopolymer gel, resulting in a dense, less porous matrix with good resistance. Full article

In this research, the feasibility of using Acanthocardia tuberculata shell waste from the canning industry in the manufacturing of self-compacting mortar (SCM) was tested. The seashells were finely ground to be used as filler instead of the limestone filler normally used in this type of SCM. First, a physicochemical and microstructural characterisation of all raw materials was carried out, including the particle size distribution of both fillers. Subsequently, the self-compactability properties in the fresh state of SCM were evaluated using a total substitution by volume of limestone filler for seashell powder, using different self-compactiblity parameters. The mineralogical phases of all the SCM tested were identified once hardened by means of X-ray diffraction technique, thermogravimetric and differential thermal analysis. In addition, the mechanical properties, water absorption capacity, dry bulk density and accessible porosity of water of hardened mortars at 28 days of curing were analysed. The effect of replacing limestone filler by Acanthocardia tuberculata filler resulted in a decrease in compressive strength of 29.43, 16.84 and 2.29%, respectively. The results indicate that it is possible to completely replace natural limestone filler with Acanthocardia tuberculata shell filler without significantly affecting the mechanical properties of SCM. Full article

The out-of-plane compression behaviour of 6061-T6 aluminum alloy super-stub honeycomb cellular structures without and with friction stir welding (FSW) facesheets are presented in this paper. A total of twelve axially compressed experiments on large-scale specimens, six with square hollow section (SHS) cores and six with hexagonal hollow section (HHS) cores, were conducted, with failure modes, ultimate resistances and axial load-end shortening curves analysed. The accuracy of finite element (FE) models was validated in accordance with test results. The numerical data obtained from extensive parametric analyses combined with test data were subsequently used to evaluate the applicability of existing design rules in Chinese, European and American aluminium alloy specifications. The results showed that the three specifications generally yielded very conservative predictions for the out-of-plane compression resistances of SHS and HHS super-stub honeycomb cores without and with FSW facesheets by about 30–37%. Design recommendations on the cross-section effective thickness are finally proposed and shown to provide much more accurate and consistent predictions than current design methods. The research results are beneficial to the application and development of large-scale super-stub honeycomb structures in structural engineering, such as the helicopter landing platforms, the base of fluid and gas tanks and ship decks. Full article

Torque-shear high strength bolts were developed and widely used recently, and such high-tensile bolts may fracture in practical engineering due to the frequent complex loads, resulting in economic losses and even casualties. However, the fatigue performance of M20 torque shear high-strength bolts under constant-amplitude loading has not been investigated yet, and there are no specific design provisions for determining the constant-amplitude fatigue performance of such bolts. Hence, a total of 10 constant-amplitude fatigue tests were conducted using an MTS fatigue testing machine. For comparison, five different stress amplitudes were investigated. The fatigue performance, stress concentration and fracture analysis were analyzed. The scanning electron microscope images of fatigue failure were obtained to analyze the fatigue fracture characteristics of high-tensile bolts. A finite element model was established to analyze the stress distribution and the hot-spot stress of the bolts. The results suggested that the allowable nominal stress amplitude of M20 torque-shear type high-strength bolts was 96.371 MPa, while the allowable hot-spot stress amplitude was 283.296 MPa. Finally, the test results were compared against the existing design provisions. Upon comparison, the existing design formulas in GB 50017(2017), ANSI/AISC 360-16 (2010) and Eurocode 3 (2003) were found to be generally conservative. The S-N curve of torque-shear high strength bolts under constant-amplitude loading was proposed using the hot-spot stress amplitudes. Full article

In this paper, the flexural strength and buckling of the partially concrete-filled steel tubes (PCFST) under laterally repeated loads was investigated through three-point bending test configuration. Three-dimensional Finite Element (FE) models of the bending tests of the PCFST were developed, in which the concrete filling was modelled using elastic-plastic-fracture model capturing crack development and the tube steel was modelled using elastic-plasticity model. The bond between concrete and tube was considered as frictional touching contact. The validation showed the FE results including the ultimate flexural load and buckling failure mode of the steel tube were in excellent agreement with the experimental ones. A parametric study was then conducted using the verified FE models to investigate the effects of the tube diameter-to-thickness ratio, the concrete filling length ratio, the compressive strength of concrete, and the tube steel’s yield and tensile strengths on the PCFST’s ultimate flexural strength. Based on this study, buckling modes, the optimal concrete filling lengths, and the confined compressive strengths of concrete were determined considering the effects of all these parameters. The confined compressive stresses and strains in concrete predicted by the FE models were evaluated against those determined by theoretical models. The results revealed that the effects of concrete compressive strength to the PCFST’s flexural capacity was insignificant while increasing the tube diameter-to-thickness ratio or the tube steel’s yield and tensile strengths could significantly increase the PCFST’s flexural capacity and the confined compressive strength of concrete; and there was an optimal length of concrete filling at about 66% of the tube length. It demonstrated that the Finite Element analysis can therefore be used as a powerful method to the analysis and design the PCFST columns under lateral loads. Full article

In engineering practice, longitudinal brace systems for column-braced systems are designed to resist both horizontal and vertical loads. In previous experimental research on horizontal brace forces for column-braced systems of intermediate height, only vertical loads were considered. Hence, this paper presents a numerical simulation of numerous column-braced systems subjected to horizontal and vertical loads. In the numerical simulation, second-order analysis was adopted, and the Monte Carlo method was used to incorporate the randomness of initial imperfections in the horizontal brace and column. From the finite element (FE) analyses and probability model statistics, the normal probability density equation for intermediate-height horizontal brace forces under horizontal and vertical loads was obtained, and the corresponding design intermediate-height horizontal brace forces were determined and compared with those under vertical loads only. The results indicate that the design intermediate-height horizontal brace forces under horizontal and vertical loads are significantly greater than those under only vertical loads, and that the design intermediate-height horizontal brace forces under horizontal and vertical loads are also greater than the simple superposition results of horizontal loads and intermediate-height horizontal brace forces under only vertical loads. Full article

The influence of hydric state on the elasto-viscoplastic behaviour of a unstabilised rammed earth (URE) wall has yet to be studied in the literature. This paper presents an experimental campaign on a rammed earth wall. The aim is to evaluate the link between the mechanical properties (including viscosity) and the varying hydric state inside the drying wall after manufacture. Cyclic axial compression and stress relaxation tests were carried out for this purpose. A compression test was conducted up to 0.1 MPa, followed by a stress relaxation test. These tests were periodically performed over 32 weeks. In addition, the hydric state inside the wall was monitored by humidity sensors. The results show that both the elastic modulus and the dynamic viscosity coefficient increase as the structure dries. A dependence of the mechanical behaviour on time is therefore found in these samples in the transient state. This can occur when the sample is in the drying or wetting phase. As rammed earth is a material particularly sensitive to water, this result is crucial for the durability of earthen constructions. Full article

To probe into the performance of concrete-filled double-skin elliptical steel tubular (CFDEST) members, this paper designs and conducts an experiment on CFDEST short columns imposed with axial pressure, and finite element (FE) models of the axially compressed CFDEST stub columns are established and verified by the test outcomes, taking the influences of elliptical cross-section and hollow ratio into account. The impressions of various parameters, such as hollow ratio, diameter-to-thickness ratio, aspect ratio and so on, on the load-bearing capacity, initial rigidity and ductility property were investigated systematically. Moreover, the typical failure modes, contact pressure and concrete longitudinal stress of the axially compressed CFDEST short column are revealed. In light of the findings acquired by the laboratory tests and numerical analyses, the calculation formulae for evaluating the axial compress capacity of the CFDEST short column are proposed by taking the impact of the sectional aspect ratio and hollow ratio into account. The results indicate that the failure morphologies of axially compressed CFDEST short columns mainly include outward local bulges of the outside EST, the inward bulges of the inside EST and the crushing of core concrete. The axial compress capacity of the CFDEST short column would increase with the decrease in the sectional hollow ratio and aspect ratio. The calculation method is proved to be an accurate and reliable approach to evaluate the axial compress capacity of the CFDEST short column. Full article

Studying the seismic performance of assembled beam–column joints is essential for the development of assembled frame structures. In this paper, a novel dry connection beam–column joint with a high degree of modularity and a simple structure is proposed and tested using a pseudostatic test. The joint is composed of a precast concrete beam with a steel axillary plate at the end and a precast concrete column connected by long bolts. By analyzing the characteristics of the hysteresis curve, skeleton curve, and stiffness degradation curve, we were able to investigate the seismic performance of this novel new joint under low circumferential reciprocating load as well as the impact of bolts of various strength grades on the joint’s seismic performance. The results illustrated the robust overall bearing performance of the newly assembled beam–column joint. However, when connected with common bolts, the joint deforms more, exhibits good ductility, clearly displays semi-rigid characteristics, and performs better in terms of energy dissipation. This contrasts with connecting with low-strength bolts, which cause the joint to deform little and have poor energy dissipation capacity. The prefabricated columns and beams remain undamaged, making it possible to quickly repair the assembled building structure after an earthquake; however, the joints are harmed due to the bending and fracture of the connection bolts. It has been suggested that researchers add damping energy dissipation devices to the new joint to increase its energy dissipation capacity and control the joint’s overall deformation because the joint’s energy dissipation capacity is insufficient under the low circumferential reciprocating load. Full article

Cement emulsified asphalt mortar (CA) is widely used as the cushion of two types of ballastless track (CRTS I and CRTS II) in high-speed railways. Nowadays, the lack of durability of CA mortar has severely affected the quality of high-speed railways, failing to meet the requirements of sustainability. Since CA mortar is a kind of porous material, its performance can be significantly affected by its microstructures, which means that revealing the evolution law of its microstructures can provide the basis for improving its durability. Therefore, CA mortar species with different asphalt-cement ratio under different curing ages were prepared based on the requirements of CRTS II in this research and the pore structures were determined based on SEM and NMR methods. Then, a fractal model of CA mortar pore volume was proposed based on the concept of box fractal dimension, and the fractal dimension of pore volume was calculated. The relationship between fractal dimensions and mechanical property was analyzed based on Pearson correlation coefficient and regression analysis. The results suggested that the overall microstructure of CA mortar shows a loose porous space structure with cement hydration products being the continuous phase and asphalt being the dispersed phase. With the increase in A/C ratio, the hydration products produced by cement hydration decrease, and the total porosity and average porosity of CA mortar gradually increase due to the increase of asphalt hindering the hydration process of the cement. With the increase in curing age, the pore structure of CA mortar becomes more compact. However, the evolution law of CA mortar pore structure with age is not consistent under different A/C ratios due to the influence of asphalt. The pore structure of CA mortar was proved to have obvious fractal characteristics based on the concept of box fractal dimension and the experimental data of NMR. In addition, the correlation analysis proves that the fractal dimension of pore structure has an obvious positive correlation with the compressive and flexural strength, which suggests that the fractal dimension of pore volume can be a bridge for connecting the macro-property and micro-structures of CA mortar. Full article

A new S600E sorbite stainless steel (SS), which performs outstanding mechanical properties, was introduced in a plate girder to enhance the resistant performance and durability. The resistance from the flange for S600E sorbite SS plate girders developing post-buckling capacity was investigated through numerical analyses, which included the material and geometrical nonlinearity. The value of distance between plastic hinges performed significant effects on resistance from flange. There was a certain distribution range of the flange plastic hinge. Hence, it was difficult to determine the value of distance between plastic hinges accurately based merely on the failure behavior. Considering the theoretical basis of EN 1993-1-4: 2006+A1, the new methods to obtain resistance from the flange and determine the value of distance between the plastic hinges were proposed to avoid the aforementioned error. The parametric study was conducted to investigate the effect of key parameters on the resistance from the flange. To take the above effect into account, a correction factor was proposed for the design equation in EN 1993-1-4: 2006+A1 to predict the distance between flange plastic hinges accurately. The comparison was conducted to validate the accuracy of the proposed equations. The results indicated that the new modified equation could be used to predict the resistance from the flange of the S600E sorbite SS plate girder more accurately. Full article

The cold-formed steel (CFS) double-lipped equal-leg angle is widely used in modular container houses and cold-formed steel buildings. To study the buckling behavior and bearing capacity design method of the cold-formed steel (CFS) double-lipped equal-leg angle under axial compression, 24 CFS double-lipped equal-leg angles with different sections and slenderness ratios the axial compression were conducted. The test results showed that the distortional buckling occurs for specimens with a small width-to-thickness ratio and small slenderness ratio. The buckling interactive with distortional and global flexural buckling was observed for the specimens with small width-to-thickness ratios and large slenderness ratios. The specimens with large width-to-thickness ratios and small slenderness ratios showed interactive buckling with local and distortion buckling. The specimens with large width-to-thickness ratios and large slenderness ratio developed interactive buckling with local, distortional, and global flexural buckling. The finite element model established by ABAQUS software was used to simulate and analyze the test. The buckling modes and the load-carrying capacities analyzed by the finite element model agreed with the test results, which showed that the developed finite element model was feasible to analyze the buckling and bearing capacity of the CFS double-lipped equal-leg angles. The experimental results were compared with those calculated by the direct strength method in the North American standard and the effective width method in the Chinese standard. The comparisons indicated that the calculated results are very conservative with maximum value 36% and 51% for direct strength method and effective width method, respectively. The coefficient of variation was 0.276 and 0.397, respectively. Finally, the modified direct strength method and the modified effective width method were proposed based on the experimental results. The comparison on the ultimate strength between test results and calculated results by using the modified method showed a good agreement. The modified method can be as a proposed desigh method for the ultimate strength of the CFS double-lipped equal-leg angles under axial compression. Full article

Automated construction progress monitoring using as-planned building information modeling (BIM) and as-built point cloud data integration has substantial potential and could lead to the fast-tracking of construction work and identifying discrepancies. Laser scanning is becoming mainstream for conducting construction surveys due to the accuracy of the data obtained and the speed of the process; however, construction progress monitoring techniques are still limited because of the complexity of the methods, incompleteness of the scanned areas, or the obstructions by temporary objects in construction sites. The novel method proposed within this study enables the extracting of BIM data, calculating the plane equation of the faces, and performing a point-to-plane distance estimation, which successfully overcomes some limitations reported in previous studies, including automated object detection in an occluded environment. Six datasets consisting of point clouds collected by static and mobile laser scanning techniques including the corresponding BIM models were analyzed. In all the analyzed cases, the proposed method automatically detected whether the construction of an object was completed or not in the as-built point cloud compared to the provided as-planned BIM model. Full article