Hysteretic Behavior of Specimens of Circular Concrete-Filled CFRP-Steel Tubular Beam-Column

To study the difference in hysteretic behavior of specimens of circular concrete-filled CFRP-steel tube under different influencing factors, 12 specimens were designed, and their failure modes and P-Δ curves were studied. ABAQUS was used to simulate the specimens’ P-Δ curves and deformation mode. Based upon the simulation results, the stress distribution of all of the specimens’ component materials and the interaction between the steel tube and concrete was analyzed throughout the entire loading process, and the trilinear model, the restoring force model of circular concrete-filled CFRP-steel tube, was proposed. All of the specimens’ P-Δ curves were full and demonstrated excellent hysteretic behavior. The specimens’ P-Δ curves, the skeleton curves, and deformation mode were simulated by the ABAQUS, and the simulation results agreed well with the experimental results. Further, the results of the restoring force model built based upon the trilinear model agreed well with the finite element simulation results.

Understanding the thermal durability of wood-based composites (WBCs) using crack propagation fracture toughness

Wood-based composites (WBCs) are engineered wood products that are commonly used in the building and furniture industries. Most research on their durability has relied on internal bond testing, bending strength properties, or damage observations. An alternative property with potentially more information is fracture toughness. Here, fracture toughness was continuously measured during crack propagation for three different composites—oriented strand board (OSB), medium density fiberboard (MDF), and particleboard (PB). The resulting plots for fracture toughness as a function of crack growth are known as the material’s R curve. To assess the role of temperature on WBC durability, R curve experiments were repeated at 10 different temperatures from 20 to 200 °C. Trends in experimental results could be described by a trilinear model. OSB and MDF toughness initially increased with temperature and then decreased above 80 °C. The toughness of PB, which was made with a different resin, remained constant or decreased slightly until decreasing faster above 140 °C. Both the resin type and composite structure affected the results.

Experimental study of moment carrying behavior of typical Tibetan timber beam-column joints

This study aimed to investigate the moment carrying behavior of typical Tibetan timber beam-column joints under monotonic vertical static load and also evaluate the influence of length ratio of Gongmu to beam (LRGB) and dowels layout on the structural performance of the joint. Six full-scale specimens were fabricated with same construction but different Gongmu length and dowels position. The moment carrying performance of beam-column joints in terms of failure mode, moment resistance, and rotational stiffness of joints were obtained via monotonic loading tests. Test results indicated that all joints are characterized by compressive failure perpendicular to grain of Ludou. Additionally, it was found that greater LRGB leads to greater initial rotational stiffness and maximum moment of the joint by an increase of restraint length for beam end; however, offsetting dowels toward column resulted smaller stiffness and ultimate bending moment of joints, particularly, offsetting Beam-Gongmu dowels toward column changed the moment-rotation curve pattern of the beam-column joint, accompanied by a hardening stiffness at last phase. Furthermore, a simplified trilinear model was proposed to represent the moment-rotation relationship of the typical Tibetan timber beam-column joint.

Probabilistic Characteristics of Moment Capacity and Rotational Stiffness of Wedge Joints Used in Support Systems Reflecting Reused Members

The moment capacity and rotational stiffness of wedge joints, which connect vertical and horizontal members of assembled support systems, were evaluated experimentally considering the characteristics of reused members. Since temporary structures, such as supports, tend to be reused, experiments were conducted with reused members, and the normality of the measured data was assessed. The lower and upper limits of the 95% confidence intervals of the moment capacity and rotational stiffness of wedge joints with reused members were determined. Experiments were also conducted on a joint system with new members to analyze the influence of reused members. In integrating both new and reused members, the maximum moments of wedge joints were observed to be normally distributed. The lower limit of the 95% confidence interval of the maximum moment of joints was 0.997 kNm, and the upper limit was 1.074 kNm. The rotational stiffness of the wedge joint was evaluated using a trilinear model. The initial rotational stiffness decreased with continued use of the joint. The average rotational stiffness of the joint, analyzed by combining the results for new and reused members, was found to be 22.475 kNm/rad for the first interval, 4.705 kNm/rad for the second interval, and 1.577 kNm/rad for the third interval. The lower limit of the 95% confidence interval of the initial rotational stiffness was 20.688 kNm/rad, and the upper limit was 24.262 kNm/rad.

Load Transfer of Offshore Open-Ended Pipe Piles Considering the Effect of Soil Plugging

Open-ended pipe piles have been increasingly used as the foundations for offshore structures. Considering the soil plugging effect, a novel analytical model is proposed in this paper to study the load transfer mechanism of open-ended pipe piles. A trilinear model for the external shaft friction was introduced, while a rigid plastic model was adopted to describe the load transfer at the pile-plug interface. Furthermore, an equilibrium equation of the soil plug was proposed, based on the hypothesis of a trilinear distribution of lateral earth pressure. The pile end resistance was analyzed by dividing it into two parts, i.e., the soil plug and pile annulus, the behaviors of which were described by the double broken line model. A calculation example was carried out to analyze the load transfer properties of the open-ended pipe piles. As a validation, similar load transfer processes of the open-ended pile were also captured in a newly built discrete element method model, mimicking the 100g centrifuge testing conditions.

An Improved Trilinear Model-Based Angle Estimation Method for Co-Prime Planar Arrays

Angle estimation methods in two-dimensional co-prime planar arrays have been discussed mainly based on peak searching and sparse recovery. Peak searching methods suffer from heavy computational complexity and sparse recovery methods face some problems in selecting the regularization parameters. In this paper, we propose an improved trilinear model-based method for angle estimation for co-prime planar arrays in the view of trilinear decomposition, namely parallel factor analysis. Due to the principle of trilinear decomposition, our method does not require peak searching and can conduct auto-pairing easily, which can reduce the computational loads and avoid parameter selection problems. Furthermore, we exploit the virtual array concept of the whole co-prime planar array through the cross-correlation matrix obtained from the received signal data and present a matrix reconstruction method using the Khatri–Rao product to tackle the matrix rank deficiency problem in the virtual array condition. The simulation results show that our proposed method can not only achieve high estimation accuracy with low complexity compared to other similar approaches, but also utilize limited sensor number to implement the angle estimation tasks.

An Expanded Trilinear Model-Based Angle Estimation Algorithm for MIMO Radar with Small Number of Transmit/Receive Antennas

In this paper, we address the problem of angle estimation in a bistatic multiple-input multiple-output (MIMO) radar which exploits nonuniform linear array at both the transmitter and the receiver with small number of antennas. It is demonstrated that the conventional trilinear decomposition-based angle estimation algorithm can identify only a comparatively small number of targets under this condition. In order to increase the number of identifiable targets, we derive an expanded trilinear decomposition-based angle estimation algorithm for MIMO radar, which can expand the size of the trilinear model. The proposed algorithm not only has the advantages of not requiring spectral peak searching, nor additional pair matching and being suitable for nonuniform arrays, but also identifies more targets than the conventional trilinear decomposition-based angle estimation algorithm under the same conditions. Moreover, the angle estimation performance of the proposed algorithm is better than that of the conventional trilinear decomposition-based angle estimation algorithm and the estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm. Simulation results illustrate the effectiveness and improvement of the proposed algorithm.

Two-Dimensional Direction of Arrival (DOA) Estimation for Rectangular Array via Compressive Sensing Trilinear Model

We investigate the topic of two-dimensional direction of arrival (2D-DOA) estimation for rectangular array. This paper links angle estimation problem to compressive sensing trilinear model and derives a compressive sensing trilinear model-based angle estimation algorithm which can obtain the paired 2D-DOA estimation. The proposed algorithm not only requires no spectral peak searching but also has better angle estimation performance than estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm. Furthermore, the proposed algorithm has close angle estimation performance to trilinear decomposition. The proposed algorithm can be regarded as a combination of trilinear model and compressive sensing theory, and it brings much lower computational complexity and much smaller demand for storage capacity. Numerical simulations present the effectiveness of our approach.

Study on Moment-Curvature Hysteretic Model of Steel-Concrete Composite Box Beam

In this paper, by the finite element analysis software-ABAQUS, nonlinear analysis models of steel concrete composite beams under vertical low-cycle repeated load were simulated. The influence of seismic performance parameters, such as degree of shear connection, the ratio of height to thickness of the web were studied, and these parameters’ appropriate range were advised. According to the finite element analysis and test results, formulas of positive and reverse stiffness degradation, a trilinear model for moment-curvature hysteretic performance of simply-supported steel concrete composite beam were proposed.