Large-span Spatial Structures Research Articles

Influence of Prestress on Vibration Frequency of Beam String Structures Based on Exact Matrix Stiffness Method

Beam string structures (BSS) are frequently employed in large-span spatial structures due to their high load-carrying efficiency and elegant appearance. Owing to the neglect of the influence of prestress, the natural frequency of the BSS is often overestimated which could be crucial to the dynamic behavior of BSS. This paper presents an exact matrix stiffness analysis method (MSM) for investigating the relationship between prestress and the natural frequency of the planar BSS. A novel dynamic stiffness matrix of beam–columns considering the natural frequency and axial force is used to develop the MSM. The dynamic analysis of the structural vibration stability of BSS is performed by using the global structural stiffness matrix which is assembled from the element stiffness matrices in the global coordinate system. The proposed MSM with the exact dynamic element stiffness matrix for the dynamic analysis of the BSS is verified by comparing with previous results based on the finite element method. The illustrative examples demonstrate that the prestress in the cable has a negative effect on the natural frequency of the BSS and should be considered in the dynamic analysis. As the axial force increases from zero to the buckling load [Formula: see text], the natural frequency of the BSS decreases from the maximum vibration frequency to zero. The influence of prestress on the vibration frequencies of BSS is particularly significant when the prestress to balance the loads is large, especially in the case of large dead and live loads (e.g. floor slabs).

Seismic Assessment of Large-Span Spatial Structures Considering Soil–Structure Interaction (SSI): A State-of-the-Art Review

Soil–structure interaction (SSI), which characterizes the dynamic interaction between a structure and its surrounding soil, is of great significance to the seismic assessment of structures. Past research endeavors have undertaken analytical, numerical, and experimental studies to gain a thorough understanding of the influences of SSI on the seismic responses of a wide array of structures, including but not limited to nuclear power plants, frame structures, bridges, and spatial structures. Thereinto, large-span spatial structures generally have much more complex configurations, and the influences of SSI may be more pronounced. To this end, this paper aims to provide a state-of-the-art review of the SSI in the seismic assessment of large-span spatial structures. It begins with the modelling of soil medium, followed by the research progress of SSI in terms of numerical simulations and experiments. Subsequently, the focus shifts towards high-lighting advancements in understanding the seismic responses of large-span spatial structures considering SSI. Finally, some discussions are made on the unresolved problems and the possible topics for future studies.

Research on damage identification of large-span spatial structures based on deep learning

Research on damage identification of large-span spatial structures based on deep learning

Seismic Resistance of Non-Linearly Deformable Large-Span Spatial Structures of Unique Buildings

Analytical, computer and experimental modeling methods are applied in the study of seismic resistance and changing dynamic parameters of long-term loaded non-linearly deformed large-span spatial shell structures. Physically and geometrically nonlinear deformation models and computational algorithms for solving dynamic problems are proposed for estimating the stress-strain state of smooth and ribbed spatial systems with variable stiffness caused by damage accumulation and orthotropic structure reinforced by ribs. The possibility of using the proposed method of taking into account variable dynamic stiffness in calculations for solving problems of dynamic strength and stability of spatial large-span shells of unique buildings of complex geometry is shown.

Nondestructive Testing and Health Monitoring Techniques for Structural Effective Prestress

Prestressed structures are widely employed in bridges and large-span spatial structures, and the accurate evaluation of prestress state is of great importance for structural maintenance. This paper reviews the nondestructive testing (NDT) and health monitoring techniques for structural effective prestress. Specifically, the fiber Bragg grating (FBG) sensor-based, magnetic-elastic (ME) sensor-based, dynamic response-based, ultrasonic guided wave (UGW)-based, electromechanical impedance (EMI)-based, and electrical resistance-based methods are reviewed in this paper. Firstly, the principle, application range, and measuring accuracy of each technique are introduced and analyzed, and the benefits and limitations of each technique are summarized: The FBG sensor and ME sensor take on high measuring accuracy and have been applied in practical engineering, but they are required to be preinstalled during structural construction; the dynamic response-based method is greatly effective in cable force assessment but not suitable for prestress evaluation of prestressed concrete (PSC) structures; the UGW-based, EMI-based, and electrical resistance-based methods have shown favorable potential for prestress assessment in laboratory experiments, but their feasibility and accuracy in practical engineering need to be verified. Secondly, the challenges and discussion of each method are discussed in the following four aspects: measuring range, reliability of measuring results, stability and durability considering long-term monitoring, and cost-efficiency. Finally, a decision tree is proposed to choose the most appropriate prestress evaluation method in a specific application scenario.

Experimental study on thermo-mechanical behaviour of beam string structures

Beam string structures (BSS) have been widely employed in large-span spatial structures, while the experimental study on BSS in fire conditions is limited. This paper presents experimental investigation on thermo-mechanical behaviour of BSS with different load ratio. ISO834 standard fire and large space fire are adopted as fire conditions, respectively. The strain of BSS at high temperatures is measured by advanced strain gauges. The test results show that the prestressed string is the most vulnerable component of BSS in fire. The temperature distribution is non-uniform, and the temperature difference between the top flag and string can be up to 396.3 °C. The critical string temperature is in a range of approximate 350 °C–450 °C. Load ratio has little effect on the critical string temperature, and fire conditions with higher heating rate can increase the critical string temperature. Furthermore, the drop of residual prestress causes the rapid increase of mid-span vertical displacement and horizontal displacement. The direction of horizontal displacement of BSS without external load is outward, due to the thermal expansion. The strain distribution along the cross section indicates the additional bending moment induced by temperature. In addition, three behaviour modes of BSS at elevated temperatures are proposed according to the contribution of prestress. The behaviour modes illustrate the working mechanism of BSS as the temperature increases. Finally, a thermo-mechanical finite element model of BSS in fire conditions is established by assembly load method. The numerically predicted temperature distribution, displacement and residual prestress have a good agreement with the experimental results.

Theoretical and Numerical Studies of Elastic Buckling and Load Resistance of a Shuttle-Shaped Double-Restrained Buckling-Restrained Brace

A new type of shuttle-shaped double-restrained buckling-restrained brace (SDR-BRB) is proposed, which adopts the form of a shuttle-shaped deformation section similar to its bending moment distribution as the external restraining system. The SDR-BRB has the advantages of superlong size, high load-carrying capacity, and lightweight components, and is suitable for use in large-span spatial structures and bridge structures with an exposed BRB. First, the calculation formula of the elastic buckling load of a pin-ended SDR-BRB is derived based on the equilibrium method, which is verified through the eigenvalue buckling analysis method, and the effects of the main geometric parameters on its elastic buckling behavior are evaluated. The effects of multiple key factors on the load-carrying capacity of the SDR-BRB are then studied by parametric analysis. The results show that the restraining ratio, initial imperfection, and gap have significant effects on the ultimate load-carrying capacity and overall stability of the SDR-BRB, while the effect of the diameter–thickness ratio is relatively small. On this basis, the fitting formula of the critical restraining ratio of the SDR-BRB considering the influences of initial imperfection and gap is proposed and verified by finite element analysis. The research lays a foundation for further research into the elastic–plastic hysteretic behavior and design method of an SDR-BRB.

Exploration of Damage Identification Method for a Large-Span Timber Lattice Shell Structure in Taiyuan Botanical Garden based on Structural Health Monitoring.

Large-span spatial lattice structures generally have characteristics such as incomplete modal information, high modal density, and high degrees of freedom. To address the problem of misjudgment in the damage detection of large-span spatial structures caused by these characteristics, this paper proposed a damage identification method based on time series models. Firstly, the order of the autoregressive moving average (ARMA) model was selected based on the Akaike information criterion (AIC). Then, the long autoregressive method was used to estimate the parameters of the ARMA model and extract the residual sequence of the autocorrelation part of the model. Furthermore, principal component analysis (PCA) was introduced to reduce the dimensionality of the model while retaining the characteristic values. Finally, the Mahalanobis distance (MD) was used to construct the damage sensitive feature (DSF). The dome of Taiyuan Botanical Garden in China is one of the largest non-triangular timber lattice shells worldwide. Relying on the structural health monitoring (SHM) project of this structure, this paper verified the effectiveness of the damage identification model through numerical simulation and determined the damage degree of the dome structure through SHM measurement data. The results demonstrated that the proposed damage identification method can effectively identify the damage of large-span timber lattice structures, locate the damage position, and estimate the degree of damage. The constructed DSF had relatively strong robustness to small damage and environmental noise and has practical application value for SHM in engineering.

Seismic response of a single-layer reticulated dome: Fault-to-structure simulation

Seismic response of large-span spatial structures is particularly susceptible to soil-structure interaction and spatial variability of ground motions. Yet existing seismic analysis fail to properly account for the foundation soil, and the ground motions are commonly determined based on empirical formulas. Physics-based 3D seismic simulation has recently been developed to provide site-specific ground motions, and the fault-to-structure simulation facilitates the incorporation of seismic wave field and soil-structure interaction into the analysis of engineering structures. This article innovatively implements the fault-to-structure simulation on a single-layer reticulated dome. Structural response of fault-to-structure model and two commonly used models is compared and discussed. Results show that the damping of soil reduces the stress and horizontal acceleration of the reticulated dome, while the soil movement leads to an increase in displacement. Noticeably, the seismic propagation characteristics increase vertical acceleration of the inner rings. Compared with fault-to-structure model, the multi-support excitation model and uniform excitation model reduce the vertical displacement of 29.1% and 50.1%, respectively, and reduce the vertical acceleration of the inner rings of 59.9% and 69.0%, respectively.

Axial Compression Behaviour and Modelling of Pultruded Basalt-Fibre-Reinforced Polymer (BFRP) Tubes

Laminated fibre-reinforced polymer (FRP) tubes are increasingly used as compression members in large-span spatial structures due to their high bearing capacity, corrosion resistance, and superior stability compared to high-strength steel pipes. In this study, axial compression tests were conducted on slender BFRP tubes to evaluate their compression characteristics as compression members. The results indicated that BFRP tubes exhibited three distinct failure modes, namely local failure, critical failure, and buckling failure. Overall, buckling was identified as the primary mode of failure under compression. The stress–strain curves of BFRP tubes were characterized by three stages, including elastic, elastic-plastic, and plastic stages. To enable design-oriented approaches, two three-stage theoretical models for BFRP tubes were developed through experimental data analysis. The models predicted the stress–strain curves and the load-lateral deflection curves, taking into account the post-peak softening behaviour of the stress–strain curves. Comparisons between the test results and the predictions calculated using the proposed models indicated that they were in good agreement.

Influence of welding residual stress on bending resistance of hollow spherical joints

Welded hollow spherical joints are widely used in large-span spatial structures because of their simple organization and convenient construction. However, in the sphere-pipe connection welds of the joints, welding residual stress is generated, which will adversely affect the mechanical properties of the joints and the overall structure. In this paper, the parametric model of welded hollow spherical joints was established by employing the geometric configuration dimensions of those joints frequently used in engineering. Through the combination of experimental research and numerical simulation, the welding residual stress of welded hollow spherical joints and its impact on joints' bending resistance were studied. First of all, based on the distribution pattern of the stress, bending test of the joints was carried out and revealed the influence of welding residual stress on the bending stiffness and ultimate bending capacity of the joints; Then, through the results of experimental analysis and finite element calculation, and with parametric analysis, the impact of welding residual stress on joints' bending resistance was clarified with the variation of parameters such as the hollow sphere diameter D, wall thickness t and the connecting steel pipe diameter d. It is shown that welding residual stress has a great impact on joints' bending stiffness, with a reduction more than 10%, while it doesn't affect their ultimate bending capacity much, with an influence no more than 5%. In addition, as D increases, t, and d decrease, its impact on the bending resistance rises.

Deformation prediction of large-span spatial structure considering adverse weather conditions

For exposed large-span spatial structures affected by solar radiation, the temperature field of the structure is time-varying and non-uniform. Currently, the research on the transient temperature field of the structure is based on the ideal sunny day, and the impact of adverse weather is usually not considered. Such simplification leads to inaccurate prediction results of temperature deformation of steel structures, especially during the construction process of the steel structure, when the structural deformation prediction needs to be employed to control the structural spatial configuration after completion. In this paper, a new method is proposed to predict the time-varying and non-uniform temperature field of large-span spatial structures using the limited information of weather forecasts. A large-span steel truss structure with inclined leg is employed to illustrate and discuss the parameters of the daily temperature model, and the temperature field of the structure under different weather conditions is calculated using a simulation program based on MATLAB and ANSYS. Finally, the accuracy of the simulation results is verified by the monitored data. The results show that the optimized daily temperature model is well predicted for the actual temperature change under different weather conditions. The structure temperature field and effect of different weather conditions have observable differences and the weather factors cannot be ignored. When the structural member reaches the highest temperature afternoon, all the temperature difference of the member exceeds 20% under different weather conditions.

Experimental and numerical investigation on the temperature field and effects of a large-span gymnasium under solar radiation

The temperature distribution of large-span spatial structures with different roofing materials shows non-uniform under solar radiation. However, in the structural design specifications, it is generally assumed that the temperature change is a slow and uniform process. In this paper, the temperature distribution of the roof and steel structure of an 82 m-span gymnasium under solar radiation is experimentally investigated using infrared thermometry. A simplified simulation method for the temperature field of the steel structure is proposed and verified by experimental data, which can effectively consider the effects of transparent and non-transparent roofing materials. The results show that the temperature distribution of the roof is more non-uniform than steel structure, and the impact of roofing materials should not be ignored, with a roof temperature difference of 19.4 °C in the initial analysis. The feasibility of the numerical method is verified by the experimental results, with temperature errors ranging from 3.8 % to 23.1 % for the steel structure. In addition, a parametric analysis of the steel structure is performed, and its thermal behavior is calculated under uniform and non-uniform temperature loads. The research method and conclusions can provide valuable references for further research on the temperature field of large-span spatial structures.

Mesh Division Method of Large Span Spatial Structure based on Free-Form Surface

All Free-form architecture has novel and unique shapes, complex and diverse changes, and has become the trend of modern architectural development with its rich shape changes and soft lines. The traditional grid layout method is not applicable to the grid division of free-form surfaces, and how to divide a smooth and beautiful grid is a hot research problem for large-span spatial structures. In response to the above problems, after investigating the current scientific research results at home and abroad, our team proposes a meshing method using the 3D software Rhino platform to solve the problems of uneven meshing of free-form surfaces and low intelligence, and to divide a smooth and beautiful mesh.

Hysteretic behaviour and structural control performance of a piezoelectric friction damper

This study proposes a novel piezoelectric friction damper (PFD). Experiments and numerical simulations are carried out to investigate the mechanical model of the PFD, and the effects of loading speed, displacement amplitude, voltage, friction plate material, piezoelectric stack actuator dimensions, and spring parameters on the hysteretic characteristics of the PFD. Results show that the PFD attains a stable mechanical performance within the design loading speed and displacement amplitude. The piezoelectric stack actuator functioning as a friction control device, can increase friction by 54% at 120 V. In damper design, an appropriate increase of the constraint stiffness of the damper and a piezoelectric stack actuator with the same stiffness as the damper constraint can achieve greater output force, and the preload of the spring should be greater than the friction to prevent residual displacement. The PFD has better seismic performance for large-span cable dome structures than the traditional friction damper. The vertical peak displacement and acceleration reduction ratio reached 45.1% and 67.7% with PFDs, respectively. The PFD with semi-active control is suitable for large-span spatial structures.

Wind Velocity Field Simulation of the Large-Span Spatial Structure Based on the Wavelet Decomposition Method

In this study, the wavelet decomposition method is combined with the vector AR model of the linear filter method to present a new method for simulating the fluctuating wind field of a large-span spatial structure. This method performs wavelet expansion on the autoregressive coefficients of the vector AR model in adequate space and adopts the least square method to estimate the autoregressive coefficients of the AR model. The implementation steps of this method are to simulate the wind field of large-span structures are given. The method is applied to the wind velocity field simulation of a large-span spatial structure, and the comparison between the simulation result and the target value and the comparison with the simulation result of the vector AR model are given. The results prove that the proposed method can reduce the information loss of wind velocity time-series analysis in the frequency domain, can accurately simulate the wind velocity time series of large-span spatial structures, and has high computational efficiency.

Experimental and numerical study on the axial compression performance of the prestressed sleeved members

The progressive collapse of large-span spatial structures can be triggered by the buckling of compression members. To further improve the stable load capacity of compression members, this study proposes a prestressed sleeved member by combining a prestressed stayed column system with a sleeved member. The experimental results show that the prestressed sleeved members possess a high load capacity, large secondary stiffness and moderate recovery performance, with the buckling modes of the members including first-order and second-order buckling. A nonlinear finite element (FE) model for the prestressed sleeved members is developed based on the experimental model. In addition, a series of parametric analyses are conducted to investigate the effects of the initial imperfection amplitude ratio, inner tube length to slenderness ratio, strand cross-sectional area ratio, inner and outer tube cross-sectional stiffness ratio and central support plate equivalent height ratio on the axial compression performance of the specimens. Furthermore, a simplified calculation model of the prestressed sleeved members is proposed for the case of second-order buckling, and theoretical calculation formulas are presented for three key points of the axial force–displacement curves of specimens. In contrast to the theoretical and FE results, the maximum errors of axial displacement and axial force do not exceed 15%. In addition, the steel strand tension, the contact force, and the lateral deflection of the middle section of the inner half-tube are highly consistent, which verifies the proposed relevant assumptions and theoretical calculation formulae.

Experimental study on the impact resistance of single-layer spherical reticulated shell roof panels

As a landmark of the city, the impact damage of long-span spatial structures caused by terrorist attacks will cause great social panic. Therefore, the dynamic response and failure modes of large-span spatial structures under impact are significant. In previous research, the effect of roof panels on the impact response was considered less. In this study, to investigate the effect of the roof panel on the impact response of a single-layer spherical reticulated shell structure, a drop hammer impact test of a two-scaled single-layer spherical reticulated shell was conducted. The test is divided into elastic impact test and destructive impact test. In the two scaled models, Model-2 arranged the roof panels. By comparing the experiment and parallel finite element simulation, the accuracy of the simulation method is verified, and it is found that the laying of the roof panels has a great effect on the dynamic response of the reticulated shell structure. In addition, the effects of roof panels on overall displacement, main rod displacement, and strain of the structure were compared and analyzed. Subsequently, the effect of the roof panel on the failure mode of the reticulated shell structure under impact was proved by the destructive impact test and corresponding finite element simulation.

Experimental study on the mechanical properties of a multi-dimensional vibration control damper

The load and structural response of large-span spatial structures have obvious multi-dimensional characteristics. In contrast to double-layer structures, single-layer reticulated large-span spatial structures are usually subjected to a combination of the multi-dimensional internal force. In this study, a multi-dimensional vibration control damper (MD-damper) for single-layer reticulated large-span spatial structures was developed. The MD-damper provided multi-dimensional carrying capacity and achieved vibration control. The theoretical analysis of the mechanical properties of the damper was performed. The vibration reduction mechanics model and the theoretical formula of the restoring force calculation of the damper were derived from the geometric decoupling and mechanical analysis. A calculation program was developed for solving the theoretical formula. An experimental study on the mechanical properties of MD-damper was performed to verify the theoretical results, and the finite element software ABAQUS was used for simulation analysis. The theoretical and simulation results were compared with that of the experimental results to verify the accuracy of the theoretical formula and the applicability of the simulation analysis method. The energy consumption mechanism of the MD-damper and the effect of vibration reduction were revealed. The results exhibited that the hysteresis curves of the experimental results were in good agreement with that of the simulated data. The deviation between the theoretical and simulation results of peak restoring force was in the range of 0.34–5.00% compared with that of the experimental results. The MD-damper exhibited optimum energy consumption performance and provided effective multi-dimensional vibration reduction. Hence, MD-Damper is an effective vibration control damper that can be used for single-layer reticulated large-span spatial structures.

Substructure hybrid test examining the seismic response of point-supported glass façades attached to large-span spatial steel structures

Point-supported glass façade (PSGF) is one of the most widely used types of non-structural components. Its earthquake damage may not only cause economic loss, but also interruption of building use and even casualties. This paper aims at investigating the seismic response of the large-span spatial structure and PSGF coupling system through the substructure hybrid test. The substructure pseudo-dynamic (PSD) test method is used, that is, the loading rate of the test is slow as that of the quasi-static tests. The finding is that when the glass panel begins to fail, the cracks occur and instantly spread to the whole glass panel along the diagonal direction due to the stress concentration at a bolt hole of double-layer laminated glass, accompanied by looseness of several point-fixed fitting screws. The drift angle of one glass panel is about 50.0%–81.9% of that of glass façade δ in the critical and failure state, indicating that the supporting system can reduce the in-plane deformation of the glass panel. And the glass façade can reduce the acceleration responses of the mid-span upper chord nodes of the large-span spatial structure by 4.74%–13.98%. Finally, the seismic performance evaluation indexes of PSGF are determined based on the drift angle δ and percentage of damaged glass panels for the slight, moderate, and extensive limit states. It will provide an example and reference for the seismic performance evaluation of the PSGF.