Structures最新文献

To address the inferior performance of precast reinforced concrete beam-column joints compared to cast-in-place joints during earthquakes, this study designed a precast concrete frame beam-column interior joint incorporating disc springs. The disc springs, installed based on grouted sleeve connections, aimed to enhance structural ductility and mitigate seismic forces on the joints. Five joints, including one cast-in-place joint, two ordinary precast joints, and two precast joints with disc springs, were tested quasi-statically and monitored using acoustic emission technology. The precast joints had axial compression ratios of 0.2 and 0.4. Parameters such as energy, count, and b-value from acoustic emission monitoring were analyzed. The Gaussian mixture model was employed for the clustering analysis of RA-AF parameters, and a damage model was developed to evaluate performance differences among the joints in the quasi-static tests. The results indicate that precast joints with the same axial compression ratio can achieve performance similar to cast-in-place joints, with more rapid damage development at higher axial compression ratios. Installing disc springs decelerates damage progression in the later stages of loading, maintaining joint integrity for a certain period even after reaching maximum load, thereby demonstrating improved ductility. At higher axial compression ratios, the b-value curve of joints with disc springs more closely resembles that of ordinary joints. Disc springs' positive effect is more pronounced in clustering analysis and damage models, such as their lower proportion of shear fractures.

Point-supported glass façades (PSGFs) have a wide application in gymnasia, airport terminals, and commercial buildings to achieve excellent balance between aesthetics and functionality. As the crucial components of PSGFs, the mechanical behavior of metallic connecting pieces directly impacts the security and stability of facades. This paper concentrates on the axial mechanical behavior of non-linear metallic connecting pieces used in PSGFs based on static and quasi-static tests. The effects of spider dimension, spider arm shape, and routel type on the mechanical behavior of connecting pieces are considered. Then, the refined finite element numerical models are established to perform parametric analyses. Results indicate that the spiders with cylindrical arms possess the most excellent load-bearing capacity, but the routel type has no effect on the bearing capacity of metallic connecting pieces. The deformation of test specimens under axial tensile load can be characterized by three stages, while just two stages under axial compressive load. There is no stiffness degradation of metallic connecting pieces under cyclic load, and their poor energy dissipation capacity in earthquakes can be inferred from the shape of load-deformation curves. Then, the stress distribution on the spider arm surface is obtained through theoretical calculation, so as to determine the most unfavorable section position of the spider arm under axial load. Finally, the simplified mechanical models of metallic connecting pieces under axial load are established according to their deformation features, which can be used for the numerical analysis of the point-supported glass facades.

Deployable structures have demonstrated significant potential in various applications, such as space solar power stations and deep space communication due to their intuitive design, high folding efficiency, and compact launch volume. As their use becomes more prevalent, understanding the deployment mechanisms of these structures is increasingly essential. This study focuses on a specific type of deployable structures, known as inflatable membrane beams. We introduce a novel cross section hypothesis, proposing a triangular shape instead of the conventional elliptical shape to represent the cross section of an inflatable membrane beam undergoing bending deformation. This new hypothesis is then integrated into the theoretical framework. Based on this enhanced theoretical formulation, we develop two beam models, i.e., one with full enclosure and one with partial enclosure. These models allow us to analyze the effects of various parameters, including the beam deployment angle, the length and radius of the membrane beam, and the internal pressure of the beam, on its deployment moment. Extensive experimental analysis is conducted to deepen our understanding of the intrinsic relationships between these parameters and the deployment moment. The experimental results indicate that the new theoretical analysis offers superior prediction accuracy compared to the original theoretical model. The findings of this research provide theoretical support for the efficient and orderly folding, shape formation, and maintenance of large-scale deployable structures in orbit, contributing significantly to the future space missions and technologies.

This paper introduces a sliding-type rapid joint and investigates the joint's failure modes under compression-shear loading with a combination of numerical and experimental methods. The study analyzes the influence of axial force, arrangement methods, and segment thickness on the joint's shear resistance. Additionally, a detailed examination of stress distribution within the joints provides a deeper understanding of their mechanical behavior. The results reveal that four-stage exists in the shear-dislocation curve of joints, including static frictional stage, partial sliding stage, overall sliding stage, and descending stage. Increasing axial force enhances the joint's shear resistance, but excessively high axial forces raise the risk of shear failure in T-shaped components. Under the trans-arrangement, the sliding-type rapid segmental joint exhibits superior shear resistance, especially under high axial loads. The material strength of C-shaped components impacts the joint's shear resistance, and increasing segment thickness enhances the joint's shear resistance. Under reverse-radial shear conditions, the structure's shear capacity is not solely determined by the joint strength. Tangential shear occurs during the assembly process, emphasizing the need to avoid excessive assembly forces. The junction between the T-shaped structure and the joint panel is a vulnerable point for T-shaped components, and reinforcement by increasing size and thickness can prevent shear failure at this location.

In previous seismic analyses of cast-in-place stations, the importance of the construction process was typically not emphasized. Unlike cast-in-place stations, prefabricated subway stations feature innovative construction methods. The effect of ignoring the complete construction process on the seismic performance of prefabricated subway stations remains unclear, and this study aims to address this issue. In this research, a three-dimensional nonlinear numerical model considering soil-structure interaction (SSI) was established. First, the complete construction process of the station, including excavation of the foundation pit and structural assembly, was replicated. The initial state before dynamic loading was clearly defined. Subsequently, the seismic response mechanisms of the station, including deformation, SSI, acceleration, and internal forces, were thoroughly investigated, revealing the impact of structural type and construction method on seismic performance. The results indicate that neglecting the complete construction process leads to differences in the initial state before dynamic loading, resulting in variations in seismic response. Specifically, ignoring the assembly process causes an average bending moment error of 59 % and an axial force error of 35 % for each component. By comprehensively analyzing these findings, a deeper understanding of the intricate interplay between assembly techniques, structural behavior, and construction processes in seismic contexts can be attained, thereby informing more robust engineering practices.

When an earthquake occurs, a substantial amount of elastic strain energy is released, and its intensity is typically measured by Peak Ground Acceleration (PGA). Installing dampers in buildings is a recognized method for dissipating this energy. Passive energy dissipation devices perform effectively under both high and low PGA conditions. Hybrid dampers combine two or more devices into a single unit and are designed to overcome individual weaknesses and enhance overall strength. This study provides a comprehensive review of hybrid passive energy-dissipating devices, emphasizing their crucial role in enhancing the seismic performance of structures. Hybrid dampers are instrumental in reducing roof displacement, drift, inter-story movement, floor acceleration, and base shear, thus significantly improving seismic resilience. The review also outlines various types of devices that are combined to create hybrid dampers, highlighting their importance in ongoing research. Despite numerous numerical analyses and experimental tests, research into implementing hybrid dampers in concrete structures remains limited. Consequently, there is a significant opportunity for improvement, design, development, and implementation of hybrid damping devices in buildings. These devices offer superior vibration control characteristics, making them an attractive option for enhancing the overall structural stability of structures.

Deflection is a crucial indicator in structural health monitoring, directly impacting the service life, safety, and economic viability of structures. However, current indirect methods for measuring deflection, such as multi-element FBG sensors or accelerometers, often have limitations. While they may be suitable for flexure-dominated reinforced concrete (RC) specimens in the elastic stage, they neglect the significant influence of nonlinearity and shear deformation. This paper introduces a new approach for estimating the deflection of reinforced concrete (RC) beams using distributed long-gauge optic sensors. The method tackles the limitations of current methods by incorporating the crucial factors of shear deformation, neutral axis position variation and shear stiffness degradation. Experimental studies are first conducted to validate the accuracy and stability of long-gauge optic sensors in small-scale RC members. Algorithms are then utilized the measurement data to estimate the deflection. The results demonstrate the excellent performance of long-gauge optic sensors in measuring shear deformation and vertical deflection of RC beams, as evidenced by comparisons with LVDT measurements. Additionally, a method for decoupling flexural and shear deformation is proposed. This method offers a preliminary assessment of the reinforced concrete (RC) beam type by quantifying the relative significance of shear deformation.

Concrete-filled steel tube (CFST) is a combination of materials, in which the interfacial bond-slip behavior is the prerequisite to reflect the synergistic loading of external steel tube and core concrete. The inorganic polymer concrete within the concrete-filled steel tube (IPCFST) compensates for the drying shrinkage of the concrete and enhances the adhesion at the interface between the steel tube and the concrete. However, the current code is too simple for the bond strength of CFSTs, and the existing theoretical calculation methods are not universally applicable. This paper aims to develop a practical artificial neural network tool for predicting the interfacial bond strength of ordinary CFSTs and IPCFSTs. An efficient prediction model for the bond strength of CFST interfaces was developed using a radial basis function network (RBFNN), with concrete strength, steel tube size, bond length and other factors as the main parameters. Bond performance test data was collected for a sample database of 322 circular CFST columns, including 56 ordinary CFSTs and 263 IPCFSTs. The results show that the Artificial Neural Network (ANN) algorithm can effectively address the bond strength problem of CFST structures and improve the accuracy and density of prediction in the comparative analyses with the measured values and the results of the semi-theoretical formulations. Based on the prediction results of ANN model, a sensitivity analysis of the parameters using Garson's algorithm shows that the diameter-to-thickness ratio and concrete strength significantly affect bond strength for both ordinary CFSTs and IPCFSTs. This study provides a more reliable prediction method and technical support for the engineering design of CFST structures.

Buckling is a common failure mode of laminated shell structures during service, and isogeometric analysis methods are highly suitable for the buckling analysis due to their accurate geometric modeling capability and high-order continuity. However, the isogeometric buckling analysis for a multi-patch structure and its optimal design still face challenges in computational efficiency. To address this issue, this paper proposes an integrated framework for the buckling optimization of multi-patch laminated shells, which leverages 3D solid elements, lamination parameters, and the penalty coupling method. Solid-shell elements have advantages in shell analysis due to their simplicity, absence of rotational degrees of freedom, and adaptive layering in the thickness direction. Lamination parameters simplify the optimization of fiber orientations in laminated shells by condensing the design variable space and improving the convexity of the optimization problem. The penalty method can handle the coupling in multiple patches at a relatively low cost. Nevertheless, lamination parameters are rarely applied to the case of solid-shell elements. In addition, despite using lamination parameters, the number of design variables for multi-patch structures remains significantly large. To tackle these issues, this study derives the solid-shell formulation in lamination parameters and the sensitivity analysis formulae in the reverse mode. Experiment validation is conducted to assess the accuracy of the proposed method based on lamination parameters with solid elements, the feasibility of the multi-patch optimization model, and the computational efficiency of optimization sensitivity based on the reverse mode compared to the forward counterpart common in the literature.

In this paper, the strength, serviceability and failure modes of eleven reinforced concrete (RC) deep beams were evaluated. The small, medium and large-size specimens with heights ranging from 300 to 1250 mm and effective spans from 600 to 2500 mm were tested up to failure under the three-point bending test. The length of loading and bearing plates varied from 100 to 400 mm, and the percentage of horizontal web reinforcement varied between 0.00 % and 0.45 %. Test results revealed that distributed web reinforcement and proportionate loading and supporting plates mitigate the size effect. Further, when the percentage of horizontal shear reinforcement increased, the mode of failure changed from diagonal tension to shear compression. From the test results, it has been concluded that the optimum horizontal web reinforcement was 0.25 % for achieving the highest ultimate and service load. The strength reduction factor of maximum shear force expression of ACI 318–19 [25] code adequate even in the case of deep beams failing in shear compression mode is experimentally validated.