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A new concept of self-centering links using post-tensioned composite tendons consisting of shape memory alloy rods and steel rods is proposed. This new concept is applicable to both short and long links and is able to fully exploit the hysteresis capacity of the used shape memory alloy material. A general scheme for preliminary design of the proposed self-centering links is developed. A typical example is used to verify the proposed concept and its design scheme. A comparison between the example using composite tendons and the previously reported example using pure shape memory alloy tendons is carried out. It is found that the system using composite tendons needs less than half of the shape memory alloy material needed by the system using pure shape memory alloy tendons to possess comparable hysteresis properties meeting the given design demands. The new concept of self-centering links is applied to a typical eccentrically braced frame system to validate its feasibility and advantages in structural systems. [ABSTRACT FROM AUTHOR]

This article presents an improved approach for topology optimization of tensegrity structures. The ground structure method is used to model the topology optimization problem of tensegrity structures into a mixed integer linear programming formulation. To improve the controllability of the found tensegrity structure, the nodes, besides the members, of the ground structure are treated as optimization variables, and direct and customized controls on the must-be-used nodes and on the number of struts connecting to each node are realized. A multi-objective function combining the previously used single objectives and a new developed single objective by weight coefficients is proposed to consider the multi-requirement on different aspects of tensegrity structures. Numerical examples are carried out to verify the proposed approach. [ABSTRACT FROM AUTHOR]

With the aid of self-developed wireless sensors of structural stress and temperature, long-term measurement of stress and temperature was applied to steel structure of the National Stadium. Based on the measured data, this paper analyzes the distribution of the temperature field, and according to the non-uniformity of the temperature field, the actions of temperature field consists of two parts, uniform and non-uniform. Then this paper studies the performance of the structure under temperature action, during which a comparison was made between the actions of uniform and non-uniform temperature field. With the measured data throughout a whole year, it is indicated that: 1) there is obvious difference between different parts of the structure, and also, the temperature of the structure differs from the air temperature; 2) the stress variation was notable under uniform temperature field action, and the member stress is linear to its temperature ; 3) the non-uniform temperature field makes the stress variation grow larger. At some parts such as the top chords, stress variation caused by non-uniform temperature field is larger than that caused by uniform temperature field action. [ABSTRACT FROM AUTHOR]

The application of tensegrity structures has been extended to deployable structures, smart structures, and robots. In these applications, large displacement shape control is usually involved. The problem of finding a collision-free path for the shape control emerges. In this article, a preliminary study on the collision-free shape control of tensegrity structures is carried out based on a representative two-dimensional tensegrity system. An incremental procedure based on dynamic relaxation method is proposed to track the trajectory of the movement during shape control. For every increment along the trajectory, collision is checked by a method based on geometrical analysis. The effect of the size of the obstacle to the number of feasible paths is investigated. It is found that when the size of the obstacle reaches a critical value, the structure is no longer able to move to the target configuration by a single step. As a result, a relay point is added in the free space. Via the relay point, free paths connecting the initial configuration and the target configuration are found. [ABSTRACT FROM AUTHOR]

• The control system is designed based on the singular values of a sensitivity matrix. • The method to determine control strategy is robust to noise. • The pre-stress error is greatly reduced by adjusting a small number of members. The pre-stress errors caused by construction affect the structural performance of cable-strut structures. The pre-stress errors can be reduced by adjusting the lengths of the structural members. Previous studies did not consider the computational robustness and sparseness of adjusted elements. This paper proposes a robust approach for the pre-stress adjustment of cable-strut structures based on sparse regression. The sensitivity matrix relating the element elongations to the relative pre-stress variations is derived. The active and measured elements are selected based on the physical meaning of the singular values of the sensitivity matrix. Sparse regression is used to obtain the element elongations, and a modified orthogonal matching pursuit method is proposed to obtain the sparse solution. The effectiveness of the proposed approach is demonstrated using a typical numerical example. It shows that the proposed approach can significantly decrease the pre-stress errors by adjusting a small number of active elements and is robust to noise. [ABSTRACT FROM AUTHOR]

Advanced structural health monitoring systems have been widely applied to large-span structures for obtaining various structural responses and loads, which are the foundation of performing condition assessment. The structural deformation is continuously employed to estimate the structural condition because it directly provides information about the overall stiffness of the whole structure. Therefore, accurate prediction of structural deformation is essential for reliable assessment of structural conditions. The deformation variation of a large-span prestressed structure is characterized by typical geometric nonlinear effects. This work presents a robust Gaussian process regression (GPR) for building a deformation prediction model for large-span space structures. The proposed approach overcomes the problem of computational cost and employs optimal distribution for modeling noise in monitoring data. Specifically, the PCA method is utilized to reduce the dimension of the input datasets for GPR. The optimal input dataset and noise distribution are estimated via 4 indexes, which are introduced to estimate the prediction performance of deformation prediction models. Simulated structural deformation from Hangzhou Gymnasium is used for verifying the effectiveness of the GPR-based deformation prediction models. Then, the proposed method is employed to predict the vertical deformation of the National Speed Skating Oval (NSSO) during snowfall. Furthermore, the prediction performance of the prediction model is comprehensively investigated via residual analysis. The proposed prediction model could provide a data foundation for the condition assessment of prestressed large-span structures. • Proposed a data-driven prediction model for deformation of large-span prestressed structure based on GPR. • Determined optimal input dataset of prediction model and noise distribution to consider the outlier in monitoring data. • Reduced the computational complexity of GPR-based prediction model via PCA and a moving window strategy. • Revealed the distribution of snow load of the large-span structure by comparing predicted deformations at different points. [ABSTRACT FROM AUTHOR]

• Propose a form-finding approach with given cable forces and strut lengths. • Transform the form-finding problem to a stationary point problem. • Define an intermediate function to solve the stationary problem. This paper presents a form-finding method for cable-strut structures with given cable forces and strut lengths. The topology of the structure, the internal force distribution of cables and the rest length of struts are given in advance. A total potential energy function in terms of nodal coordinates is derived according to the initial conditions. The equilibrium configuration satisfying the given initial conditions is essentially a stationary point of the energy function. An intermediate function is proposed and used to solve the stationary point problem. A configuration expected by the designer can be obtained when proper initial nodal coordinates are used. The effectiveness and practicability of the proposed method are verified by two typical examples. [ABSTRACT FROM AUTHOR]

Passive dynamic control with integrated dampers is an efficient strategy for the vibration of a cable-strut system. Except the rigid components, the flexible components are also a triable direction as the integrated damper, especially for the continuous cable systems. This paper proposes a novel dynamic control method for pre-stressed cable systems by using frictional sliding cables. Firstly, a simplified dynamic simulation method is introduced. The friction of sliding cables can be considered in the dynamic analysis of a continuous cable system. Secondly, two numerical examples with sliding cables including the types of Levy and Geiger are established. The results show that frictional sliding cables can reduce the structural dynamic response. Thirdly, a dynamic experiment of a Geiger-type cable dome with sliding ridge cables is carried out. The acceleration of the structure during vibration is recorded and compared with the results of the conventional configuration. The dome with sliding cables exhibits higher damping ratios, indicating superior vibration reduction capabilities. The frictional energy dissipation of this study can be taken as a dynamic control strategy for continuous cable structures during the design and analysis process. • A novel dynamic control method for pre-stressed cable systems is proposed. • An improved method for the dynamic analysis of frictional continuous cables is developed. • A physical model experiment of a Geiger-type cable dome with sliding ridge cables is built. [ABSTRACT FROM AUTHOR]

Structural health monitoring obtains data reflecting the service status of grid structures through sensors. One of the issues to consider in optimal sensor placement is how to obtain as much information as possible with a limited number of sensors. In this paper, a sensor placement method is proposed based on damage sensitivity and correlation analysis, which is based on strain energy calculation and is suitable for grid structures. Specifically, with the sensor locations as optimization variables, a mathematical optimization model is established by considering the damage sensitivity and redundancy of the monitoring scheme, and a genetic algorithm is employed for computation. Two examples, including a lattice shell and a flat grid, are provided to illustrate the method, followed by a discussion of the sensitivity of parameters such as stiffness reduction degree and load form. The results indicate that the redundancy of the optimized schemes for the two examples decreased by approximately 80% and 30%, respectively. The proposed method ensures a certain degree of damage sensitivity while significantly reducing redundancy, demonstrating its applicability and robustness in sensor placement for grid structures. [ABSTRACT FROM AUTHOR]

Summary: Identification of earthquake ground motion from structural health monitoring (SHM) data provides a good means to reconstruct seismic loads that are essential for postearthquake safety assessments and disaster simulations of structures. Because the data measured by an SHM system are structural absolute response, they cannot be directly applied to the structural motion equation, which is established in relative coordinate system. As such, this paper originally derives the motion equation in absolute coordinate system and then expands the equation into modal space. In addition, the proposed method allows for identifying earthquake ground motion using incomplete modal information and limited measurements through the standard Kalman filter. Subsequently, a numerical two‐dimensional frame is used to validate the feasibility of the proposed method, and the influences of modal parameters and measurement noise on the identification accuracy are also fully investigated. The results show that the proposed method is sensitive to frequency and measurement noise but insensitive to modal shape and damping ratio. It is also found that the identified ground motion subjected to certain measure noise can still be reliably employed for postseismic response calculations of medium‐ and long‐period structures. Finally, a shaking table test performing on a five‐floor frame further demonstrates the effectiveness and accuracy of the proposed identification algorithm for practical application. [ABSTRACT FROM AUTHOR]

The main structure of the central detector at the Jiangmen Underground Neutrino Observatory (JUNO) is a spherical shell structure, which has a giant acrylic spherical shell connected to a stainless-steel (SS) reticulated shell with 590 SS rods. The acrylic spherical shell is submerged into water and filled with detection liquid and prone to rotation subjected to considerable buoyancy. The stability against rotation of this super-deep underground spherical shell structure needs to be fully investigated. In this study, an effective and practical method consisting of parametric analysis and optimization procedure is proposed to improve the stability against rotation. Specifically, two indicators, namely, the critical loading multiplier and the rotation angle, are proposed to evaluate the stability against rotation of the acrylic spherical shell in linear and nonlinear stability analyses, respectively. Then, parametric analysis is performed to assess the sensitivity of the stability against rotation to four parameters of interest (i.e., rod outer end constraints, liquid level difference, disc spring stiffness, and rod deviation). Based on the obtained parametric analysis results, the liquid level difference and disc spring stiffness are finally selected as design variables for the subsequent optimization process to further improve the stability against rotation. An efficient scheme combining design variable discretization and exhaustive method is adopted to identify the optimal variable values at which the acrylic spherical shell has good stability against rotation. The results indicate that the proposed method is efficient and effective for optimization of stability against rotation of such super-deep underground spherical shell structure. The proposed method is practical and easy to use for structural designers, and provides an efficient approach to the stability design of such rod-connected spherical shell structures. • An effective method is proposed to improve the stability against rotation of an underground spherical shell structure. • Two indicators are proposed to evaluate the stability against rotation of the spherical shell structure. • Influence of the parameters on the stability against rotation is fully investigated to choose the important parameters. • An efficient scheme combining design variable discretization and exhaustive method is adopted for optimization. [ABSTRACT FROM AUTHOR]

• A Lorentz force-based SH-typed EMAT was developed and systematic tested. • A specially design of the flexible circumferential printed circuit was presented. • The designed CPC-EMAT is easy to be assembled and fabricated in real application. • It can generate omnidirectional SH 0 waves with desirable central frequencies. Structural health monitoring (SHM) of in-service structures is becoming increasingly important. The fundamental shear horizontal (SH 0) guided wave mode in plate-like structures shows great potential in damage detection due to its non-dispersive and in-plane vibration properties. In order to generate SH 0 waves, a practical Lorentz force-based electromagnetic acoustic transducer (EMAT) was introduced in this study using the flexible circumferential printed circuit (CPC). The designed principle of CPC-EMAT was similar to that of the circumferential magnet array (CMA)-based EMAT. However, the structure of the CMA-EMAT is complex, and it is difficult to assemble for generating high frequency and uniformly distributed omnidirectional SH 0 waves. Firstly, the performance of the CMA-EMAT with different numbers of magnets was investigated by finite element simulations. Then, the CPC was proposed to replace the CMA with an optimized designed on its size. The CPC-EMAT is easier to fabricate compared to the CMA-EMAT. Finally, experimental tests were conducted for systematic validations on the transducer properties. Simulation and experimental results show that the CPC-EMAT can successfully generate the desirable and acceptable omnidirectional SH 0 waves. The proposed CPC-EMAT is anticipated to find widespread application in SH-typed guided wave-based SHM. [ABSTRACT FROM AUTHOR]

This study presents a general approach to the topology design of tensegrities with rigid bodies. To the best of the authors' knowledge, all existing topology design methods of tensegrities focus on tensegrities that only consist of members carrying axial forces, which are referred to herein as classic tensegrities. However, another category of tensegrities, referred to as general tensegrities, contains rigid bodies aside from axially loaded members. The equilibrium and stability conditions of general tensegrities are different from those of classic tensegrities because of the existence of rigid bodies, which makes the existing topology design methods invalid for general tensegrities. In this study, the equilibrium and stability conditions of general tensegrities are first derived. A topology design approach for general tensegrities is then proposed based on a mixed-integer linear programming optimization scheme. The topology (i.e., member connectivities) is treated as a binary variable, and the member forces are treated as continuous variables. Three essential attributes, namely self-equilibrium, unilateral member force, and class- k condition, of a general tensegrity, as well as some other practical requirements, are formulated as constraints. Different objective functions are employed to design different general tensegrities. Some well-known general tensegrities are reproduced, and various numerical examples are presented to verify the effectiveness and versatility of the proposed approach. The proposed topology design method is verified to be a truly general approach for the topology design of tensegrities with or without rigid bodies. [ABSTRACT FROM AUTHOR]

A novel type of reticulated shell structure composed of built-up plate members has been proposed based on its benefits in efficiency and precision of fabrication, as well as convenience of storage and transportation. This study aims to investigate the stability behavior of such structures by conducting numerical simulation analysis. The configuration of the structure is illustrated at first. Then, a validated numerical model is presented for parametric studies on two typical structural forms. Next, geometric nonlinear analysis is conducted, demonstrating the symmetrical characteristic of failure modes, and the results are utilized to develop practical prediction formulas for the elastic buckling load. Finally, material and geometric nonlinear analysis is performed to examine the impact of parameters on structural stability performance. The sensibilities of the material nonlinearity, geometric dimension, geometric imperfection, and joint stiffness on the structural stability are illustrated. This study provides insights into the instability mechanism of such structures and offers valuable guidance for their design and application. • A novel type of reticulated shell structure composed of built-up plate members. • Presented numerical models are validated by experimental data. • The structural stability behavior and influencing factors are revealed. • Practical prediction formulas for the elastic buckling load are developed. [ABSTRACT FROM AUTHOR]

Vibration data from physical systems, such as civil structures and machinery, often carries important information about the dynamic characteristics, but streaming acquisition of higher-frequency vibration often accrue large volumes of data, resulting in data transmission and storage challenges. Compressive sensing (CS) is a relatively newly-developed technique for efficient data representation, capable of reconstructing the target signal using only a few random measurements through sparse optimization. However, the real-world application of CS is hindered by the strong assumption of signal sparsity and a costly reconstruction process. In this work, we propose a novel deep learning method for vibration data reconstruction by using deep convolutional generative adversarial networks (DCGAN), which is composed of a generator G and a discriminator D. A modified 1D symmetric U-net architecture with shortcuts is presented for G to flexibly deal with different inputs, while a typical 1D classifier is used as D. A composite adversarial loss function is proposed considering errors in both time and frequency domains. The proposed DCGAN approach has several appealing properties. First, it directly learns the end-to-end mapping between the compressed and original signals without employing the sparsity assumption or random sampling, which fundamentally differs from existing sparsity-based CS methods. Second, the reconstruction process is highly computationally efficient as the network is fully feed-forward and no optimization is needed during data reconstruction. The proposed DCGAN approach is evaluated using the simulation data from a numerical 9-floor frame as well as experimental data collected from a large test steel grandstand. The results demonstrate the superiority of the proposed DCGAN in computational accuracy and efficiency compared to the tested sparsity-based algorithms. Furthermore, the influences of network configurations (network depth, down-sampling strategy, and shortcuts) are comprehensively explored. • A novel CS approach is proposed for vibration data reconstruction using DCGAN. • The DCGAN can reconstruct vibration data without employing sparsity assumption. • The proposed feed-forward network is highly computationally accurate and efficient. • The DCGAN is evaluated using simulated and experimental data, respectively. • The influences of network configurations are comprehensively explored. [ABSTRACT FROM AUTHOR]

• A generalized objective function is proposed for tensegrity topology-finding. • Different tensegrities can be found via adjusting the weight coefficients. • A circular computing strategy is proposed to efficiently obtain various tensegrities. • Novel tensegrity structures based on common Archimedes polyhedrons are given. This paper proposes a generalized objective function for the topology-finding of tensegrity structures to be able to assign selection priorities to different members and efficiently find multiple tensegrity structures through a single ground structure. The generalized objective function is constructed by the sum of the product of member internal forces and weight coefficients. The member weight coefficients can be defined and adjusted freely to change the selection priorities of different members in the topology-finding process. By adjusting the weight coefficients, different tensegrity structures can be generated. The weight coefficients can be determined by the designer according to the practical design requirements and preferences, e.g., member length limitations, member position requirements. In addition, a circular computing strategy is proposed for the weight coefficient adjustment to efficiently obtain a large number of tensegrity structures through a single ground structure. The topology design of typical regular tensegrity structures, as well as irregular ellipsoid tensegrity structures, are carried out to demonstrate the effectiveness of the proposed method. Furthermore, by using the proposed method, multiple novel tensegrity structures based on common Archimedes polyhedrons have been found; detailed information (e.g., member connectives, self-stress) are given as an open database for future investigation and applications. [ABSTRACT FROM AUTHOR]

• A general computational framework for active tensegrity topology design is proposed. • Structure member topology and actuator layout coupling relation is handled. • The proposed method can result in more lightweight active tensegrity with novel forms. • The proposed framework applies for optimum design of any type tensegrity structures. Existing studies on active tensegrity structure optimum design only focus on sizing and/or shape optimization i.e., the structural element topology does not change during the design process, which vastly limits the design space and further improvement of mass-saving performance. This study investigates the optimum design of active tensegrity structures through topology optimization, which has never been done to the best of the authors' knowledge. Structural member topology and actuator layout are considered as binary design variables and their coupling relation is handled by auxiliary constraints. Member cross-sectional areas are treated as discrete design variables considering practical availability. Member prestress, actuator length changes, and other necessary auxiliary parameters are defined as continuous variables and designed simultaneously. Equilibrium conditions, member yielding, cable slackness, strut buckling, and the limitations on the nodal displacements as well as other design requirements are formulated as constraints. Linearization algorithm is proposed to transform the bilinear expressions in the objective and constraint functions to allow the problem to be solved to global optimum. Typical benchmark examples indicate that the topology-optimized active designs obtained through the proposed approach can further decrease the material consumption compared with sizing-optimized active tensegrity designs hence leading to more lightweight structures. [ABSTRACT FROM AUTHOR]

Rubber bearings are crucial components in seismic isolation systems to mitigate the damaging effects of earthquakes on structures. Rubber bearings generally consist of alternate layers of steel and rubber bonded together. Simplified two-point spring models omit this layered construction and have limitations in adaptability and programmability, while refined multiple solid models lead to substantial computational costs. This study presents an effective and efficient approach to simulate rubber bearings by using multi-layered solid element based on the finite particle method (FPM). The traditional "Zigzag" shape function is extended into the 3D situation to reflect the serrated deformation within the layered construction. Based on the simplified assumption of stress continuity, an iterative approach is presented for the deformation gradient to achieve the force continuity between layers in dynamic nonlinear scenarios. The multi-layered solid models for both natural rubber bearings (NRBs) and lead rubber bearings (LRBs) are proposed based on this element. The errors of the hysteresis curves of rubber bearings are below 3.1 % between the numerical results obtained by using the multi-layered solid model and the experimental results. The computational speedup ratio of the proposed multi-layered solid model is verified to be 19 relative to the refined multiple solid model. The proposed method is applied to a base-isolated frame structure to demonstrate its effectiveness in structural seismic analysis. • A novel approach to model rubber bearings by using multi-layered solid element is proposed. • Zigzag shape function is adopted inside the element to keep stress continuity. • Multi-layered solid models for natural rubber bearings and lead rubber bearings are presented and validated. • The proposed method is applied to a base-isolated frame structure with lead rubber bearings. [ABSTRACT FROM AUTHOR]

This paper is concerned with the optimal design of double-level guyed towers against buckling with a given material volume. The double-level guyed tower is simplified as a lateral braced column considering the pre-tensioned cable stiffness. The buckling criterion for double-level guyed towers is then analytically derived based on a matrix stiffness method (MSM) that enables the use of one element per member for an exact solution. Optimal designs of double-level guyed towers under various base fixity factors are obtained through an optimization procedure involving two decision variables: the height ratio and the cross-sectional area ratio between the upper level and the lower level. Optimization results indicate that pinned-ended double-level guyed towers achieve their maximum buckling load at a height ratio of 1.19 and a cross-sectional area ratio of 1.19. In contrast, fixed-ended towers achieve their maximum buckling load with a height ratio of 0.70 and a cross-sectional area ratio of 1.13. Transitioning from pinned to fixed base conditions increases the maximum buckling load by approximately 1.52 times. Design recommendations for double-level guyed towers are further presented. • Optimal design of double-level guyed towers against buckling is investigated considering a given material usage. • Analytical buckling criterion for double-level guyed towers is derived. • An exact matrix stiffness method that enables the use of one element per member for the buckling solution is presented. • Design recommendations for pinned-ended and fixed-ended double-level guyed towers are presented. [ABSTRACT FROM AUTHOR]

• A GPU-accelerated approach combining FPM and CZM is proposed. • The internal forces of four-particle cohesive elements are derived. • An explicit GPU-based parallel computing framework is developed. • The parallel solver for cohesive elements is implemented. • The effectiveness and efficiency of the proposed approach are verified. The fracture analysis of structures typically involves strong discontinuity and nonlinear behaviors, and it requires fine meshing and small time steps, making it time-consuming. This study proposes an approach accelerated by graphics processing units (GPU) for two-dimensional (2D) fracture analysis of structures combining finite particle method (FPM) and cohesive zone model (CZM). Specifically, the equations of motion of particles are presented, and the internal forces of planar triangular elements are derived based on FPM. Subsequently, the internal forces of four-particle cohesive element are derived to describe the CZM, and the linear elastic stage, softening stage, and failure stage are depicted according to the traction-separation criteria. An explicit GPU-based FPM analysis strategy for structural fracture analysis is then developed, and the parallel solvers for particles, triangular elements, and cohesive elements are implemented. A quasi-static fracture analysis of a concrete beam and a dynamic fracture analysis of the Kalthoff problem is conducted to verify the effectiveness of the proposed approach. The obtained crack propagation path, load vs. displacement curves, and crack propagation speed are in good agreement with the experimental results and the results in the literature. The efficiency of the proposed approach is also investigated. The achieved maximum speedup ratio of the GPU-accelerated approach to the central processing unit (CPU)-based approach reaches around 24, and the achieved speedup ratio relative to the commercial finite element software Abaqus/Explicit reaches around 11.5, demonstrating the computational efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

• An improved CMT-BCS method is developed. • The CMT-BCS formulation is restructured to deal with the 'incomplete' CS problem. • The proposed CMT-BCS method has high computational efficiency. • The superiorities of proposed CMT-BCSmethod in accuracy and efficiency are demonstrated. • The influences of the relevant critical parameters are comprehensively explored. The long-term structural health monitoring (SHM) provides massive data, leading to a high demand for data transmission and storage. Compressive sensing (CS) has great potential in alleviating this problem by using less samples to recover the complete signals utilizing the sparsity. Vibration data collected by an SHM system is usually sparse in the frequency domain, and the peaks in their Fourier spectra most often correspond to the same frequencies. This underlying commonality among the signals can be utilized by multi-task learning technique to improve the computational efficiency and accuracy. While being real-valued originally, the data after discrete Fourier transformation are in general complex-valued. In this paper, an improved complex multi-task Bayesian CS (CMT-BCS) method is developed for compression and reconstruction of SHM data requiring a high sampling rate. The novelty of the proposed method is twofold: (i) it overcomes the invalidity of the conventional CMT-BCS approach in dealing with the 'incomplete' CS problem, and (ii) it improves the computational efficiency of conventional CMT-BCS approach. The former is achieved by restructuring the CMT-BCS formulation, and the latter is realized by sharing a common sampling matrix across all tasks of concern. The improved CMT-BCS is evaluated using the shaking table test data of a scale-down frame model and the real-world SHM data acquired from a supertall building. A comparison with several existing BCS methods that enable to deal with complex values is also provided to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

• A dictionary is proposed for CS of wind speed using correlation. • A new sliding window is used considering lag, and window size is suggested. • The performance is evaluated using two large-scale spatial structures. • The performance is compared with Fourier basis and linear interpolation. • The influences of relevant critical parameters are comprehensively explored. The real-time wind monitoring is widely used to evaluate the wind effect on the large-scale spatial structures. Wireless sensor network (WSN) is usually the first choice for the large-scale spatial structures to collect wind monitoring data because of its super-large size. Compressive sensing (CS) has great potential in solving the energy problem of WSN and reduces the difficulty in transmission of massive data based on sparsity. However, wind signals are often not naturally sparse on the traditional bases (e.g., Fourier basis). This paper proposes a new method of constructing a dedicated dictionary for wind speed signals using the time-shift strategy. With this proposed dictionary, the signals can be compressed by random sampling and recovered by ℓ 1 -norm sparse regularization. The performance of the improved CS methodology is evaluated using two large-scale spatial structures. The results show that the proposed CS methodology has better performance than the traditional CS algorithm with the Fourier basis and the linear interpolation method. Furthermore, the influences of the relevant critical parameters (regularization parameter, lag, sliding window size, and compression ratio) of the improved CS methodology are comprehensively explored. [ABSTRACT FROM AUTHOR]

Based on the finite particle method, this work presents a general numerical method to perform the nonlinear dynamic collapse analysis of space semi-rigid structures. A space connection element composed of two particles and six zero-length springs is proposed to simulate the space semi-rigid connection. Geometrical nonlinearity is addressed through fictitious motion, while material and connection behavior nonlinearities are captured by updating the element stiffness matrix and the connection stiffness matrix, respectively. Member and connection fracture models are convenient for simulating fracture behaviors during collapse processes. To verify the effectiveness of the proposed method, the numerical results are compared with those from previous studies, and energy conversion analyses are adopted. The analysis results indicate that only member fractures occur at beam ends in the rigid and linear semi-rigid frames, while only connection fractures occur at beam ends in the nonlinear semi-rigid frame. • A space connection element model was proposed based on the finite particle method. • Connection behavior nonlinearity was captured by updating the connection stiffness matrix. • The developed member and connection fracture models were convenient. • A general numerical method was proposed to perform the nonlinear dynamic collapse analyses of space semi-rigid frames. • The effectiveness of the proposed method was verified by energy conversion analyses. [ABSTRACT FROM AUTHOR]

• A general method for designing minimal mass active tensegrity structures is proposed. • The design of the structure parameters and actuator parameters are integrated. • The performance of different actuator layout modes on mass-efficiency is investigated. • The method is a unifying framework for designing minimal mass tensegrity structures. Tensegrity structures have been widely utilized as lightweight structures due to their high stiffness-to-mass and strength-to-mass ratios. Minimal mass design of tensegrity structures subject to external loads and specific constraints (e.g., member yielding and buckling) has been intensively studied. However, all the existing studies focus on passive tensegrity structures, i.e., the structural members cannot change their lengths actively and the structure has to passively resist external loads. An active tensegrity structure equipped with actuators can actively adapt its internal forces and nodal positions and thus can actively resist external loads. Therefore, it is expected that active tensegrity structures use less material compared to passive tensegrity structures thus leading to a smaller mass. Due to the integration of the active control system, the design of active tensegrity structures is different from passive tensegrity structures. This study proposes a general approach for the design of minimal mass active tensegrity structures based on a mixed integer programming scheme, in which the member cross-sectional areas, prestress, actuator layout and control strategies (i.e., actuator length changes) are designed simultaneously. The member cross-sectional areas, prestress level, and actuator control strategies are treated as continuous variables and the actuator layout is treated as a binary variable. The equilibrium condition, member yielding, cable slackness, strut buckling, and the limitations on the nodal displacements as well as other practical requirements are formulated as constraints. Three typical active tensegrity structures are designed through the proposed approach and the results are benchmarked with the equivalent minimal mass passive designs. It is illustrated that the active designs can significantly decrease the material consumption compared with the equivalent passive designs thus leading to more lightweight tensegrity structures. [ABSTRACT FROM AUTHOR]

• A unifying framework for form-finding and topology-finding of tensegrity structures. • The computational framework is based on rank-constrained linear matrix inequalities. • A Newton-like algorithm is employed to solve the rank-constrained LMIs efficiently. • Tensegrity structures with single and with multiple self-stress state(s) can be handled. • Symmetric/regular and non-symmetric/irregular tensegrity structures can be handled. This paper presents a unifying framework for the form-finding and topology-finding of tensegrity structures. The novel computational framework is based on rank-constrained linear matrix inequalities. For form-finding, given the topology (i.e., member connectivities), the determination of the member force densities is formulated into a linear matrix inequality (LMI) problem with a constraint on the rank of the force density matrix. The positive semi-definiteness and rank deficiency condition of the force density matrix are well managed by the rank-constrained LMI-based formulation. A Newton-like algorithm is employed to solve the rank-constrained LMI problem. Two methods, named direct method and indirect method , are proposed to determine the nodal coordinates once the force densities have been obtained. For topology-finding, given the geometry (i.e., nodal coordinates), the determination of the topology is also formulated into an LMI problem with a constraint on the rank of the tangent stiffness matrix. Numerical examples demonstrate that different types of form-finding problems (such as tensegrity structures with single and with multiple self-stress states, symmetric and irregular tensegrity structures) can be uniformly and efficiently solved by the proposed approach. Furthermore, three well-known tensegrity structures are reproduced to verify the effectiveness of the proposed formulation on the topology-finding of tensegrity structures. [ABSTRACT FROM AUTHOR]

Planar steel plates have many advantages, including high precision, flexible outline shape fabrication, and convenient transportation and storage, which make them suitable for various steel structures (e.g., reticulated shell structures). However, the steel plates are not commonly used as structural members, because they have a relatively low out-of-plane flexural stiffness. To improve the flexural buckling resistance, a novel type of built-up plate member comprising two longitudinal plates is proposed in this study. Additionally, the flexural buckling behavior of the novel built-up members is investigated. A series of compression tests on 42 specimens of built-up plate members is conducted to determine the elastic and ultimate critical loads. Flexural buckling about the minor axis is observed to be the failure mode of the specimens. The equivalent slenderness ratio method is used to determine the theoretical elastic critical loads of the specimens. With consideration of the measured material properties, geometric imperfections, and residual stresses of the specimens, a refined finite-element model is developed to simulate the flexural buckling behavior. Furthermore, the applicability of two representative specifications (American and European) to the novel built-up member is discussed. The results indicate that the design strengths calculated using these specifications are generally conservative for determining the ultimate loads of the built-up plate members. Design curve "c" in Eurocode 3 is found to be the most suitable among the specifications of interest for determining the design strength. This study provides valuable guidance for the design of built-up plate members. Unlabelled Image • Experiment on flexural buckling behavior of built-up plate member under compression • Validation of refined FE model considering imperfection, residual stress, contact • Verification of equivalent slenderness ratio method for elastic critical load • Applicability of American and European specifications for designing member strength [ABSTRACT FROM AUTHOR]

• A general computational framework for the form-finding of tensegrity is proposed. • The proposed formulation is based on rank minimization of force density matrix. • The proposed method bypasses the number of self-stress states in a tensegrity. • Tensegrity with a force density matrix with more than d + 1 rank deficiency can be handled. This study proposes a general computational framework for the form-finding of tensegrity structures. The procedure is divided into two stages in which the member force densities and nodal coordinates are obtained respectively. In the first stage, the determination of force densities is transformed into a rank minimization problem regarding the force density matrix and then formulated into a semi-definite programming. The unilaterality condition of member forces and the positive semi-definiteness condition of force density matrix are incorporated as constraints. In the second stage, the determination of nodal coordinates is formulated into a constrained nonlinear programming model. The nodal positions and member lengths are assigned as constraints and auxiliary variables are introduced to homogenize the member lengths. The proposed formulation bypasses the number of self-stress states in a tensegrity structure thus applies to both tensegrity structures with single and multiple self-stress states. Different from existing studies that are based on the minimum required rank deficiency condition of force density matrix, the proposed method can handle tensegrity structures that have a force density matrix with rank deficiency greater than the required minimum number. Several examples are presented to verify the effectiveness of the proposed method on different types of tensegrity structures. [ABSTRACT FROM AUTHOR]

Pile-supported wharves may be subjected to severe damage during major earthquakes. As such, efficient strategies for retrofitting wharf systems are needed. In this study, we investigate the seismic performance of a pile-supported wharf retrofitted by the following three conventional slope strengthening strategies: i) improving the ground with a soil-cement mixture, ii) driving pin piles near dike toe, and iii) creating an underwater bulkhead system using sheet piles. Effectiveness of the three retrofit schemes is assessed comprehensively. First, seismic response of the as-built and retrofitted pile-supported wharf is investigated. Subsequently, performance of the retrofit strategies in mitigating the seismic vulnerability is thoroughly investigated by comparing component- and system-level fragility curves. It was found that: (1) overall, the strategies are effective in mitigating the seismic response and in reducing the seismic fragilities of the wharf system; (2) the performance of the retrofit measures varies at the structural component level, as a retrofit measure may have an isolated local negative effect for a certain structural component. In this regard, an appropriate retrofit strategy should be identified based on specifically defined retrofit purposes; and (3) as implemented, the soil-cement mixture performed best (in lowering the system seismic fragility), followed by the pin pile, and lastly the sheet pile. • Three slope strengthening strategies (i.e., creating a soil-cement mixture, driving pin piles, and constructing a sheet pile) for improving the pile-supported wharf are designed. • Finite element modeling of the as-built and retrofitted pile-supported wharf is detailed. • A wide spectrum of seismic response of wharf-ground system before and after retrofit is fully explored under a representative seismic excitation scenario. • Both component-and system-level seismic fragility of the as-built and retrofitted pile-supported is systematically investigated. [ABSTRACT FROM AUTHOR]

The cable-strut structures have the features of low stiffness and weak damping, resulting in large vibration response under dynamic excitation. The vibration response of the cable-strut structures can be reduced by active control methods. However, many traditional active control methods need to build a state-space model (SSM) based on finite element model (FEM), and solving the active control force for the high-dimensional SSM is time-consuming. In this paper, the dynamic mode decomposition with control (DMDc) method is proposed to achieve a data-driven reduced-order SSM for active vibration control of cable-strut structures. This proposed method only uses the data of structural response and control force input to build reduced-order SSM and does not rely on the FEM. Linear quadratic regulator (LQR) design using the DMDc-based reduced-order SSM (DMDc-LQR) is more computationally efficient than that using the FEM-based SSM (FEM-LQR). The relationship between the design parameters of the DMDc-LQR controller and the FEM-LQR controller is established, which ensures that the control performance indexes of the DMDc-LQR controller and the FEM-LQR controller are equal. The effectiveness of the proposed DMDc-LQR method is validated using numerical Kiewitt cable dome and tensegrity grid under wind and seismic loads. The results show that the DMDc-LQR controller maintains similar control effect to that of the FEM-LQR controller and has advantage of high computing efficiency as well. In addition, the influence of critical parameters (i.e., data noise and model order) on vibration control effect is comprehensively explored. It is found that increasing the model order is effective to mitigate the noise influence on the DMDc-based reduced-order SSM and ensures the effectiveness of the DMDc-LQR controller. • A data-driven reduced-order state-space model (SSM) method is proposed. • The linear quadratic regulator (LQR) is designed based on reduced-order SSM. • The control effect and design efficiency of two LQR controllers are discussed. • The influence of noise and model order on the vibration control effect is explored. [ABSTRACT FROM AUTHOR]