Ultimate Load-bearing Capacity Research Articles

Study on ultimate capacity and design method of cold-formed steel equal lipped angle components under axial compression

This study focuses on evaluating the load-bearing capacity of cold-formed steel (CFS) equal lipped angle components. It delves into the structural behavior and design methods, taking into account various edge conditions and buckling modes. By considering the key parameters, which are component length, component thickness, total lip length, and lip bending angle, a total of 555 numerical models are developed for a systematic analysis on the components with two types of cross-sectional shapes. Since the coefficients within the direct strength method (DSM) inadequately capture the ultimate load-bearing capacity of lipped angle components, we introduce a design methodology rooted in the DSM framework to address global and global-local coupling buckling modes while imposing constraints to prevent local-distortion coupling buckling modes. The machine learning models (XGBoost, BPNN, and 1D-CNN) are adopted to predict the structural behavior of the two types of lipped angle components. These models can integrate the analysis of the components with two types of cross-section shapes in predictions of ultimate load capacity, axial deformation, and buckling modes. Meanwhile, the prediction accuracy of the machine learning models surpasses that of the analytical design methodology, offering more accurate prediction for ultimate load capacity, axial deformation and buckling modes.

Comparative Performance Analysis of Small Concrete Beams Reinforced with Steel Bars and Non-Metallic Reinforcements

This research investigates the performance of small concrete beams that are reinforced with glass fiber-reinforced polymer (GFRP) bars, basalt fiber-reinforced polymer (BFRP) bars, and traditional steel bars. It addresses the limitations of traditional steel reinforcement, emphasizing the need for alternative strategies. Fiber-reinforced polymer (FRP) materials, including GFRP and BFRP, are examined for their mechanical characteristics compared to steel. The experimental program focuses on ultimate load-bearing capacity, deflection, deformation at different load levels, and failure modes. The concrete specimens, prepared according to Eurocode, consist of six small concrete beams measuring 80 × 120 × 1100 mm with varied reinforcements. The study reveals that GFRP-reinforced beams outperform BFRP and steel reinforcements in ultimate load-bearing capacity, showcasing enhanced structural performance. The GFRP-reinforced beams exhibit capacity and resilience characteristics surpassing those of both BFRP and steel, whereas the deflection observed was higher on both fiber-reinforced beams than on the steel-reinforced beams. The examination of failure modes reveals that the concrete beams that were reinforced with FRP bars showed a bending property before failure, while those reinforced with steel broke easily without bending much. This comprehensive research contributes to advancing our understanding of FRP materials’ application in concrete structures, paving the way for further optimization and overcoming limitations in reinforcement materials.

Performance Analysis of the Structures Using Glass-Fiber-Reinforced-Polymer-Produced Hollow Internal Molds

Hollow structures reduce weight without compromising load-bearing capacity and are widely used. The new Glass-Fiber-Reinforced Polymer high-strength thin-walled inner mold simplifies internal cavity construction and boosts structural performance. This study first investigates the influence of a GFRP high-strength thin-walled circular tube on the cross-sectional load-carrying capacity of hollow slabs. Then, a formula for the bending load-carrying capacity of the section under the action of the tube is derived. The results indicate that when the height of the concrete compression zone meets certain conditions, GFRP high-strength thin-walled circular tubes can improve the ultimate load-carrying capacity of the hollow floor slabs. In order to achieve a more economical design, the bending moment modification of a GFRP high-strength thin-walled circular tube of a continuous slab was studied. Research has found that the bending moment modulation limit for a continuous slab is 35.65% when it is subjected to a load of Pu=24 kN. Experimental analysis has shown that the results are generally consistent with the calculations. In practical engineering, the application of a GFRP high-strength thin-walled circular tube of continuous slabs has limitations. Therefore, this study investigated a GFRP high-strength thin-walled honeycomb core slab and found that its ultimate load-bearing capacity is greater compared to waffle slabs. In addition, the stress performance of the GFRP high-strength thin-walled honeycomb core internal mold is superior, making it more promising for practical applications.

Biomechanical mechanisms of anterior cruciate ligament injury in the jerk dip phase of clean and jerk: A case study of an injury event captured on-site

BackgroundWeightlifting exposes athletes to significant loads, potentially placing the knee joint in an abnormal mechanical environment and leading to anterior cruciate ligament (ACL) injuries. Once an ACL injury occurs, it can affect athletes’ competitive ability to varying degrees and even prematurely end their career. Understanding the biomechanical mechanisms of ACL injuries in weightlifters helps in comprehensively understanding the stress patterns and degrees on ACL during human movement, and identifying potential injury-causing factors, thereby enabling the implementation of appropriate preventive measures to reduce the occurrence of injuries. This study aimed to explore the biomechanical mechanisms of ACL injuries during the jerk dip phase of clean and jerk in weightlifters, providing a theoretical basis for the prevention of ACL injuries in weightlifting sports. MethodsThis study utilized the German SIMI Motion 10.2 movement analysis system and the AnyBody simulation system to analyze the kinematic and dynamic parameters of a 109 kg + class weightlifter (height: 191 cm, age: 22 years, weight: 148 kg, athletic level: elite) performing a 205 kg clean and jerk (non-injured) and a 210 kg clean and jerk (ACL injury occurred). The differences in kinematic and dynamic indicators of lower limb joints under injured and non-injured jerk dip conditions were investigated. ResultsKnee joint torque during non-injured clean and jerk was consistently positive (i.e., external rotation) but turned from positive to negative (i.e., from external rotation to internal rotation) during injured clean and jerk and reached a maximum internal rotation torque of 21.34 Nm at the moment of injury. At every moment, the muscle activation and simulated muscle force of the quadriceps and gastrocnemius during the injured clean and jerk were higher than those during the non-injured clean and jerk. By contrast, the muscle activation and simulated muscle force of the semitendinosus, semimembranosus, biceps femoris, and soleus during non-injured clean and jerk were higher than those during injured clean and jerk. The knee joint internal rotation angle during injured clean and jerk first increased and then declined, reaching a peak at 46.93° at the moment of injury, whereas it gradually increased during non-injured clean and jerk. The proximal tibia on the left side during the injured clean and jerk moved forward faster by 0.76 m/s compared with that during the non-injured clean and jerk. ConclusionsThe small muscle activation and simulated muscle force of the hamstring and soleus could not resist timely and effectively the large muscle activation and simulated muscle force of the quadriceps (especially the medial quad) and gastrocnemius. As such, the force applied to the ACL could exceed its ultimate load-bearing capacity. Kinematic indicators in the athlete's injured lift demonstrated certain disparities from those in their non-injured lift. Knee internal rotation and tibial anterior translation during the jerk dip phase of weightlifting might be the kinematic characteristics of ACL injuries.

Experimental and numerical studies on the behavior of corrugated steel-sprayed ECC composite arches with full-shear-connection

This paper proposes a novel corrugated steel-sprayed ECC (CSSECC) composite arch, which possesses high load-bearing capacity and fast construction speed. To investigate the ultimate load-bearing capacity, composite effect, and key mechanical indices, five 6 m-span arch specimens were tested. A finite element model was developed, and parametric analysis was conducted. The results indicate that the ultimate load-bearing capacity and damping ratio of the CSSECC composite arch specimens can reach 3.4 and 6.5 times that of the corrugated steel (CS) arch, respectively, and increasing the ECC thickness significantly enhances the damping ratio. Both studs and epoxy resin contribute to the composite effect, but studs are more reliable than epoxy resin even though their design shear connection degree is the same at 1.2. Finally, a design method for the stability bearing capacity under axial compressive was proposed.

Using Machine Learning to Predict Axial Pile Capacity

Accurate estimation of the ultimate axial load bearing capacity of piles is necessary to ensure the safety of the supported structures and to prevent cost overruns. Traditional mechanics-based design methods do not always predict pile capacity accurately, or precisely, leaving room for improvement. This study focuses on the potential of machine learning (ML) in estimating pile capacity. A dataset of 546 load tests was compiled from three databases. The baseline performance of traditional design methods was first established by comparing the capacities computed using four traditional approaches, against the capacities interpreted from load tests using Davisson’s criterion. Sixteen different ML techniques were explored. First, the optimal feature selection technique for model training was investigated. Second, hyperparameters of each technique were optimized. The process involved the training of 32,000 different models and tuning their hyperparameters. Next the dataset was randomly split into training (70%) and testing (30%) for comparing the 16 different ML regression models. Each of the optimized models was then trained using six feature sets. The performance of each of the 16 ML models with the best performing feature subset was compared with the baseline performance from traditional methods. Evaluation criteria included measured versus predicted capacities, influence of soil type on accuracy, as well as the absence of pile diameter, or length effects on accuracy and precision. In general, the ML methods performed significantly better than the best traditional method. The current research demonstrated that ML may offer advantages in geotechnical design when large datasets are available.

Cyclic loading behavior of novel internally stiffened double steel plate shear wall

In this paper, a novel Internally Stiffened Double Steel Plate Shear Wall (ISD-SPSW) is proposed based on the concept of improving the buckling mode of steel plates and enhancing the lateral resistance of steel plate shear wall (SPSW). The ISD-SPSW consists of double outer steel plates on both sides, inner stiffened rib plates, and boundary members. The seismic behavior of ISD-SPSW was investigated through tests and numerical simulations. Five ISD-SPSW specimens with different heights of the wall, thickness of the outer steel plate and boundary member, and different numbers of internally stiffened steel plates were investigated in cyclic loading tests. The performance indexes such as hysteresis curves, strain curves, and skeleton curves of ISD-SPSW were obtained. The finite element model of ISD-SPSW was established and verified by the test results. The test results reveal two distinct failure modes for the ISD-SPSW. The first mode involves the failure of diagonal tension bands, which is a result of local buckling in the outer steel plates. The second mode is characterized by the overall instability of the shear wall, resulting from the out-of-plane deformation of the boundary members. Lowering the height of the wall can markedly improve the load-bearing capacity and out-of-plane stability of ISD-SPSW. Increasing the thickness of the outer steel plate can improve the ultimate load-bearing capacity, but has adverse effect on the boundary members. Reducing the thickness of the boundary member can significantly reduce the load-bearing capacity and seismic performance. Reducing the number of inner stiffened rib plates decreases the shear load-bearing capacity and energy dissipation capacity. The ductility coefficient of most specimens is greater than 3.0, indicating that the ISD-SPSW has good ductility. In addition, the results of the established finite element model are in good agreement with the test results, which verifies the accuracy of the model.

Ultimate bearing behavior in the post-buckling stage of composite pressure hulls based on new detection methods

This study employs novel testing methods and analysis techniques to investigate the ultimate load-bearing characteristics and failure mechanisms of composite thin-walled pressure hulls. An analytical model based on the classical laminated plate theory, incorporating the Hashin damage failure criterion, is developed to determine their ultimate bearing capacity. Five carbon fiber cylindrical shells are manufactured to validate the failure mechanism and evaluate the model's predictions. Deep-sea pressure testing and ultrasonic testing are conducted on these shells. The resulting data is analyzed using both macroscopic and microscopic approaches to gain insights into their load-bearing behavior and failure mechanisms. The study demonstrates the significant influence of the thickness (t) to radius (R) ratio on the ultimate load-bearing capacity of these composite thin-walled pressure hulls. Failure primarily arises from compression failure in both the matrix and fibers. The load-bearing process encompasses uniform shrinkage, critical buckling, and post-buckling states. Material failure primarily occurs during the post-buckling stage, while no damage occurs during the initial buckling. On a microscale, failure at the interface between the fibers and matrix is identified as the primary contributor to overall structural failure. Enhancing the fracture energy of the interface is recommended to enhance the ultimate load-bearing capacity of the hulls.

Effect of Horizontal Distance of Web Opening on the Ultimate Load Carrying Capacity of Castellated Steel Beams by an Analytical Approach

Objectives: The primary objective of this current research is to determine the ideal horizontal spacing for hexagonal web openings and their maximum load-bearing capacity through Finite Element Analysis (FEA). Methods: The ISMB150 was implemented as a cross-sectional profile to fabricate distinct models of castellated beams with heights of 225 mm. The height of the web openings remained constant at 150 mm for the castellated beam model. The entire analysis is being done on ANSYS 19.2. Findings: The analysis has revealed that, for castellated beams with shallower depths, an optimal horizontal spacing of 44.9 mm for the web openings yields an ultimate load-bearing capacity of 144.26 KN. The results of castellated beams are measured in terms of ultimate load-carrying capacity, span-to-deflection ratio, load density, failure location, span-to-beam depth ratio, and the ratio of horizontal distance of opening-to-opening depth. Novelty: This research contributes analytical findings for the ideal horizontal distance of hexagonal web opening through maximum load-bearing capacity. Castellated beams have gained immense popularity within the structural engineering community today due to their visually appealing design featuring a variety of web-opening shapes. The primary objective of this current research is to determine the ideal horizontal spacing for hexagonal web openings and their maximum load-bearing capacity through Finite Element Analysis (FEA). The ISMB150 was implemented as a cross-sectional profile to fabricate distinct models of castellated beams with heights of 225 mm. The height of the web openings remained constant at 150 mm for the castellated beam model. The analysis has revealed that, for castellated beams with shallower depths, an optimal horizontal spacing of 44.9 mm for the web openings yields an ultimate load-bearing capacity of 144.26 KN. The results of castellated beams are measured in terms of ultimate load-carrying capacity, span-to-deflection ratio, load density, failure location, span-to-beam depth ratio, and the ratio of horizontal distance of opening-to-opening depth. This research contributes valuable insights into optimizing the design of castellated beams for enhanced structural performance. Further exploration and validation could provide additional refinements and applications in structural engineering. Keywords: Horizontal distance of web opening, Number of openings, Ultimate load carrying capacity, Failure modes, ANSYS, Castellated beams

Force Performance Analysis and Numerical Simulation of Assembled Ribbed-Slab Abutments

This study investigates the structural performance of assembled rib-plate bridge abutments (ARBAs) with two different connection methods: bull leg bolt and flange connections. In addition, we explored the bending and shear performance of the connection parts and related areas to assess the damage characteristics and modes of these ARBAs. Utilizing model testing, a numerical analysis was conducted to define the force performance of the ARBA, with reference to a cast-in-place rib-plate abutment. The research results indicate that the bearing capacity and deformation capacity of the cap part of the assembled ribbed slab abutment model with cow leg connections are lower than those of the cast-in-place structure. When the structure fails, a 45° diagonal crack develops from the cross-section at the mid-span joint to the connection between the rib slab and the cap, until the concrete protective layer at the joint is crushed, exhibiting a shear failure mode. The bearing capacity of the assembly rib plate type abutment cap connected by the flange plate is basically the same as that of the cast-in-place structure, and the deformation capacity is weaker than that of the cast-in-place rib plate type abutment. The expansion of structural cracks is consistent with that of the rib plate type abutment connected by the cow leg. When the flange plate at the mid span is damaged, the contact surface between the flange plate and the concrete is pried off, resulting in the inability of the structure to continue bearing, exhibiting a shear failure mode. Through numerical simulation, taking the stress performance of the integral cast-in-place ribbed slab abutment as a reference, the assembled ribbed slab abutment connected by the flange plate is basically consistent with the integral cast-in-place ribbed slab abutment in terms of ultimate load, concrete damage, and steel reinforcement skeleton stress, and the connection device has not yet reached the yield state. The ultimate displacement is slightly weaker than that of the integral cast-in-place ribbed slab abutment. By comparison, it can be seen that the ultimate bearing capacity of the assembled ribbed slab abutment connected by the flange is basically the same as that of the cast-in-place ribbed slab abutment, and the stress performance can reach an “equivalent cast-in-place”, making it the preferred solution for the assembled abutment structure. The finite element parameter analysis of the flanged ARBA revealed that the thickness of the stiffening ribs, the number of bolts, and length of the flange plate anchoring steel plate were proportional to the ultimate load-bearing capacity of the prefabricated ARBA. In the case of no change in the structural damage mode, considering the economic benefits and load-bearing capacity of the structure, the following parameter combinations of the flanged ARBA are recommended: a thickness of 30 mm of the stiffening ribs, the number of bolts is 12, and a length of 50 cm of the length of flange plate anchoring steel plate.

Experiment investigation and theoretical analysis of an improved aluminum alloy gusset joint

This study presents enhancements made to traditional aluminum alloy gusset (AAG) joints, including the integration of a central stiffening (CS) system, an inter-panel stiffening (IS) system, and a peripheral stiffening (PS) system. Three sets of tests on a full-scale specimen are conducted to investigate the improved AAG joint's axial stiffness, in-plane and out-of-plane bending stiffness, as well as ultimate load-bearing capacity. Nonlinear refined finite element models (FEMs) are established and validated through experimental results. Theoretical mechanical models are developed by integrating experiments and FEMs. These models elucidate the contribution of the stiffening systems to the joint's mechanical performance. The CS system is proven to significantly assist in load transfer, particularly in out-of-plane bending conditions. The IS system enhances overall inter-panel integrity, especially during the plastic deformation phase under out-of-plane bending moments. The PS system improves joint stiffness by participating in load transmission under both axial load and in-plane bending moments. Compared to traditional AAG joints, the combined effects of the three stiffening systems enhance overall structural integrity, stiffness, and load-bearing capacity. This enables the full utilization of component material properties and provides excellent ductility before failure occurs.

Study on load-bearing behaviors of prestressed post-grouting tubular piles in the karst region of northern Fujian Province, China

The karst that is dominated by medium-weathered limestone and caves with various spatial features is widely distributed in the northern Fujian Province. This paper discusses the load-bearing behaviors of post-grouting tubular piles in karst region of north Fujian Province with reference to the prestressed tubular piles adopted in the residential buildings of Haixi Comprehensive Trade City Phase II Project in Sanming City. The load-settlement curve, pile side friction resistance, and pile end resistance of tubular piles are analyzed by finite element numerical simulations and field static load tests. The load-bearing behaviors of prestressed tubular piles under karst geological conditions with two different spatial features are comparatively investigated, and the effectiveness of tubular pile reinforcement is verified by field settlement observation. The results reveal that the finite element numerical model can effectively simulate the tubular pile-soil interaction. The use of pile end post-grouting of prestressed tubular piles in the karst region can significantly increase their load-bearing capacities. The top settlements of grouted tubular piles under the maximum test load can be reduced by 16.8%–22.3% compared with these of ungrouted test piles, and the theoretical simulated ultimate load-bearing capacity can be increased by 27.3%. The adoption of pile end post-grouting technique can reduce the pile end displacement of tubular piles and improve the proportion of pile end resistance. Plastic-hard plastic breccia silty clay can be used as a bearing stratum for post-grouting to achieve excellent grouting performance. The bead-shaped karst caves are more unfavorable to the exertion of load-bearing capacity of the tubular piles than the karst caves filled with plastic-hard plastic breccia silty clay to which the piles have direct access. The field monitored average settlements of the 19# and 17# buildings under karst geological conditions with two different spatial features are −12.88 mm and −8.98 mm, respectively, both of which do not exceed the warning value, indicating that it is feasible for the project to adopt the pile end post-grouting technique of the tubular piles. The achievements of this study help to further reveal the load-bearing mechanism of this type of pile, which can provide a basis for its engineering design and construction optimization.

Study on the Tensile and Shear Performances of Fully Precast Partially Composite Floor Slab Joints

This study explored the tensile and shear characteristics of fully prefabricated partially composite floor slab joints through the design and testing of two tensile specimens, three steel–concrete specimens, and three concrete–concrete shear specimens. These tests aimed to evaluate how various connection designs influence the joints’ load-bearing capabilities and failure patterns. The findings revealed that the tensile specimens predominantly showed bond failures at the interface of the precast and cast-in-place layers, accompanied by rebar pull-out. Incorporating reinforcing bars or sleeves was found to potentially increase their ultimate load-bearing capacity by about 20%. The shear failures in the steel–concrete specimens were primarily due to interactions between the steel beam and adjacent composite slab, whereas the concrete–concrete specimens mostly underwent local crushing at the load application point and failure at the bonding interface. These observations affirmed the accuracy of the existing methods for calculating tensile and shear strengths, offering vital insights for the architectural design and construction of such floor joints.

Investigation on the flexural–tensile behaviour of CFRP tendon composite anchorage system

The cable at the anchorage end is in a bending–tension condition in service due to the variable loads. A new composite anchorage system was proposed to study the flexural–tensile behaviour of the anchorage system with CFRP tendon. Four groups of single-tendon composite anchorage and three groups of five-tendon composite anchorage with bend restrictor were tested. Besides, one group of five-tendon composite anchorage without bend restrictor was tested as a control group. The effects of the bending angle, inner cone angle of the steel barrel and pre-tension force on the flexural–tensile behaviour of the anchorage system were investigated. The internal force state of the tendon inducing different failure modes was analysed. A finite element method was used to analyse the failure mechanism of the anchorage system under the bending–tension condition. Moreover, the flexural–tensile behaviours of the anchorage systems with different elastic moduli of the bonding medium were compared. Results showed that the efficiency coefficients of the composite anchorage with multi-tendon exceeded 0.9 when the end bending angle was less than 4.2°. The setting of the bending restrictor improves the flexural–tensile bearing capacity of the anchorage system and increases the maximum allowable bending angle. A larger bending angle will lead to a faster increase in the transverse shear stress at the loading end. Furthermore, increasing the pre-tension force can prompt the cooperation ability of the tendons and reduce the ultimate slips, thus improving the ultimate load-bearing capacity of the anchorage. The increase in the elastic modulus remarkably reduces the slip of the tendon, but increases the shear stress at the loading end under the bending–tension condition.

Effect of Textile Layers and Hydroxypropyl Methylcellulose on Flexural Behavior of TRLC Thin Plates

To examine the flexural toughness characteristics of textile-reinforced lightweight aggregate concrete (TRLC), a four-point bending test was conducted to assess the impact of varying numbers of textile layers and the inclusion of hydroxypropyl methylcellulose on the ultimate load-bearing capacity and deformation capacity of TRLC thin plates. Six groups of specimens were prepared for the experiment, and the bending capacity of the thin plates in each group was evaluated. The flexural toughness index was utilized to quantify the bending performance of TRLC thin plates. The findings revealed that increasing the number of textile layers improved the initial cracking load, initial cracking deflection, ultimate load, ductility, and flexural toughness of the thin plates. For the specimens without HPMC, the initial cracking load was increased by up to 36.1%, the ultimate load by up to 40.9%, and the flexural toughness index by up to 292% as the number of textile layers was increased. For specimens doped with HPMC, the initial cracking load was increased by up to 61.7%, the ultimate load by up to 246.7%, and the flexural toughness index by up to 65%. The TRLC thin plate containing hydroxypropyl methylcellulose exhibited a reduced initial cracking load yet displayed a stronger matrix consistency and good flexural toughness. Moreover, the enhancement in the ultimate load of TRLC thin plates with hydroxypropyl methylcellulose was more pronounced with an increased number of textile layers, resulting in a significantly higher number of cracks compared to TRLC without hydroxypropyl methylcellulose and an 11.40-fold increase in the flexural toughness index.

Theoretical and Numerical Simulation Study on the Ultimate Load Capacity of Triangular and Quadrilateral Truss Structures

Spatial truss structures (STSs), serving as the bottom support structure of a cooling tower, effectively harness the superior load-bearing capacity offered by lattice-type truss structures. STSs are composed of main bars, diagonal bars, and horizontal bars, with horizontal bars serving as vital components of the truss structure. They play a pivotal role in maintaining the overall integrity and stability of the structure. The proportional relationship between the stiffness of each bar in STSs has a profound impact on the mechanical characteristics of the overall structure. This relationship directly influences the ultimate load-bearing capacity of the structure. Therefore, conducting research on the influence patterns of this relationship is of utmost importance. This paper explores the study of triangular truss structures (TTSs) and quadrilateral truss structures (QTSs). Firstly, through theoretical analysis, considering structural elements such as the stiffness of the horizontal bars, the number of layers in the truss, and the angle between the diagonal bars and the horizontal bars, theoretical expressions for the calculation of the ultimate load capacity of TTSs and QTSs are derived. Furthermore, a parametric finite element (FE) model was established for the TTSs and QTSs. Through numerical simulations, the validity of the theoretical calculation expressions was verified. Finally, this paper discusses the influence of factors such as the stiffness of the horizontal bars, the number of layers in the truss, and the angle between the diagonal and horizontal bars on the TTSs and QTSs. It analyzes the patterns and trends of these influences. The research results indicate that the theoretical and numerical simulation results for the TTSs have an error ranging from 0.40% to 4.93%, while the relative error for the QTSs ranges from 1.59% to 4.88%. These errors are within an acceptable range for engineering calculations. As the stiffness of the horizontal bars increases, the proportionality coefficient of the truss’s ultimate load capacity shows an initial increase followed by a stable trend. It reaches an equilibrium state when the stiffness of the horizontal bars reaches a certain threshold. As the number of layers in the truss and the angle between the diagonal and horizontal bars increase, the proportionality coefficient of the load capacity gradually decreases. The research findings provide a theoretical basis for the application of TTSs and QTSs in cooling towers.

Experimental study on CFRP reinforcement and static performance of CHS KT-joints

Owing to the engineering application demands for the reinforcement of complex joints in multiplanar circular hollow section (CHS) trusses, this study investigated the reinforcement methods and static performance of KT-joints strengthened with carbon fibre-reinforced polymer (CFRP) sheets. First, CFRP reinforcement strategies for KT-joints were studied. Experimental comparisons in static performances were then conducted between bare and CFRP-strengthened CHS KT-joints. Meanwhile, CFRP reinforcement mechanisms were analysed. Finally, CFRP effective strain index η was proposed for quantitative assessment of CFRP strength utilisation. The results indicated that CFRP effectively restrained chord depression and expansion deformation, prevented local buckling of the compressive brace, and reduced strain concentration near the intersection lines. Compared with the bare joint, the ultimate load-bearing capacity and ductility of the joint reinforced with 4 layers of CFRP sheets on the chord and 3 layers on the braces increased by 24% and 25%, respectively. The initial stiffness of the joint at compressive and tensile brace locations increased by 48% and 375%, respectively. The η varied at different regions of the joint, with the maximum η found near the K-shaped gap and the intersection line of compressive brace. Based on the distribution of η, strategies for improving CFRP strength utilisation were proposed.

Study on the Ultimate Load-Bearing Capacity of Disc Buckle Tall Formwork Support Considering Uncertain Factors

Disc buckle steel pipe brackets are widely used in building construction due to the advantages of its simple structure, large-bearing capacity, rapid assembling and disassembling, and strong versatility. In complex construction projects, the uncertainties affecting the stability of disc buckle steel pipe support need to be considered to ensure the safety of disc buckle steel pipe supports. A surrogate model based on a deep neural network is built and trained to predict the ultimate load-carrying capacity of a stent. The results of the finite element model calculations are used to form the sample set of the surrogate model. Then, we combined the computationally efficient DNN surrogate model with the Monte Carlo method to consider the distribution of the ultimate load capacity of the disc buckle bracket under the uncertainties of the bracket node pin wedge tightness, the wall thickness of the steel pipe, and the connection of the connecting wall member. At the same time, based on the DNN model, the SHapley Additive exPlanations (SHAP) interpretability analysis method was used to study the degree of influence of various uncertainty factors on the ultimate bearing capacity of the stent. In practical engineering, the stability analysis of a disc buckle tall formwork support has shown that a surrogate model based on a deep neural network is efficient in predicting the buckling characteristic value of the support. The error rate of the prediction is less than 2%. The buckling characteristic values of the bracket vary in the range of 17–25. Among the various factors that influence the buckling characteristic value of the bracket, the joint wedge tightness has the greatest impact, followed by the bottom and top wall-connecting parts.

Mechanical Behavior of Precast Circular Semi-Continuous CFST Columns under a Uniaxial Eccentric Load

For this study, we conducted a detailed examination and comprehensive comparative analysis of the structural responses and mechanical behavior of bolted sleeve connections in precast circular semi-continuous steel tubular concrete (PCSCFST) columns. The research involved fourteen specimens, and we considered the impacts of various parameters, including eccentricity, external steel sleeve thickness, bolt diameter, and slenderness ratio. The findings revealed that the external steel sleeve significantly enhances the protection of the connection area, enabling the bolts to effectively withstand eccentric loads. However, sleeves that are too thick may lead to premature bolt failure, reducing their ultimate load-bearing capacity. Using bolts to transfer loads to the concrete significantly strengthens the restraining effect of the steel sleeve. Nonetheless, increasing the bolt diameter beyond a certain threshold may diminish this beneficial impact, potentially leading to connection failure and a decrease in ultimate load-bearing capacity. A new ‘cooperative value q’ measures component collaboration at ultimate capacity, showing that shorter columns offer less effective coordination than longer ones. Through regression analysis, we formulated a prediction for axial ultimate bearing capacity, closely aligning with the experimental data (Npre-a/Nu average value of 1.003, variance 0.00248). Three N–M curves, including the Eurocode 4 method, offered conservative predictions, with Eurocode 4 closely matching the experimental results. A refined prediction method following Eurocode 4 was developed, yielding an average Ppre-U/Pu value of 0.971 and a variance of 0.0107.

Global stability design of double corrugated steel plate shear walls under combined shear and compression loads

As a novel structural component, the Double Corrugated Steel Plate Shear Wall (DCSPSW) is formed by interlocking two corrugated steel plates using high-strength bolts. This paper investigates the global stability design methods for DCSPSWs under combined shear and compression loads. Firstly, this paper examines the elastic buckling performance of DCSPSWs under horizontal shear loads and vertical compression loads separately. A bolt spacing factor (η) is introduced to reflect the influence of bolt spacing on the elastic buckling stress of DCSPSWs. Then, based on extensive finite element analysis (FEA), this paper investigates the elastoplastic buckling behavior of DCSPSWs under shear loads and compression loads and establishes the corresponding stability curves to predict ultimate load-bearing capacity. It is found that the stability coefficients (φs and φc) are closely related to the normalized slenderness ratios (λns and λnc). A smaller bolt spacing allows the DCSPSWs to exhibit improved elastic and elastoplastic stability. Finally, this study investigates the load-bearing performance of DCSPSWs under combined shear and compression loads and proposes the design formulas. The results show that the correlation curve of N/Nu-V/Vu can provide a conservative and accurate design. The research findings of this paper are advantageous for promoting the application of the innovative DCSPSWs.