Origami‐based designs refer to the application of the ancient art of origami to solve engineering problems of different nature. Despite being implemented at dimensions that range from the nano to the meter scale, origami‐based designs are always defined by the laws that govern their geometrical properties at any scale. It is thus not surprising to notice that the study of their applications has become of cross‐disciplinary interest. This article aims to review recent origami‐based applications in engineering, design methods and tools, with a focus on research outcomes from 2015 to 2020. First, an introduction to origami history, mathematical background and terminology is given. Origami‐based applications in engineering are reviewed largely in the following fields: biomedical engineering, architecture, robotics, space structures, biomimetic engineering, fold‐cores, and metamaterials. Second, design methods, design tools, and related manufacturing constraints are discussed. Finally, the article concludes with open questions and future challenges.

The objective of this paper was to investigate the evolution of air voids (AV) and deformation and the failure mechanism of porous asphalt (PA) mixtures under high temperatures. An advanced repeated loading permanent deformation (ARLPD) test was used to investigate the high-temperature permanent deformation of PA mixtures. A staged ARLPD test (first stage test, secondary stage test, and third stage test) and a staged X-ray computed tomography (CT) scanning test were designed to evaluate the three-stage evolution of the AV and deformation in the ARLPD test. Total AV content ($A{V}_{\mathrm{total}}$ ) and interconnected AV content ($A{V}_{\mathrm{interconnected}}$ ) decrease in the first stage, and $A{V}_{\mathrm{total}}$ , $A{V}_{\mathrm{interconnected}}$ , and the number of AV ($A{V}_{\mathrm{num}}$ ) increase in the secondary stage. $A{V}_{\mathrm{total}}$ and $A{V}_{\mathrm{interconnected}}$ decrease and $A{V}_{\mathrm{num}}$ increases in the tertiary stage. Based on the changes of AV and intuitive image analysis, the failure mechanism of PA mixtures was discussed. The first stage is a densification stage, during which radial deformation develops faster than vertical deformation. Densification failure was observed in the tertiary stage, which shows that vertical deformation develops faster than radial deformation.

Bifurcation behavior analysis is the key part of mobility in the application of origami-inspired deployable structures because it opens up more allosteric possibilities but leads to control difficulties. A novel tracking method for bifurcation paths is proposed based on the Jacobian matrix equations of the constraint system and its Taylor expansion equations. A Jacobian matrix equation is built based on the length, boundary, rigid plate conditions, and rotational symmetry conditions of the origami plate structures to determine the degrees-of-freedom and bifurcation points of structural motion. The high-order expansion form of the length constraint conditions is introduced to calculate the bifurcation directions. The two kinds of single-vertex four-crease patterns are adopted to verify the proposed method first. And then, the motion bifurcations of three wrapping folds are investigated and compared. The results demonstrate the rich kinematic properties of the wrap folding pattern, corresponding to different assignments of mountain and valley creases. The findings provide a numerical discrimination approach for the singularity of rigid origami structure motion trajectories, which may be used for a wide range of complicated origami plate structures.

This paper presents an experimental investigation of the seismic performance of interior beam–column joints with beams reinforced with Grade 600MPa longitudinal steel bars. Six full-scale reinforcement concrete (RC) interior joints are designed with different axial compression ratios and longitudinal reinforcement ratios, which are tested under reversed cyclic loading. Failure modes, hysteretic curves, skeleton curves, energy dissipation capacity, and the ductility of joints are investigated systematically. Moreover, the effect of the different axial compression ratios and longitudinal reinforcement ratios on the seismic behavior of the joints are deeply studied. Comparisons performed between specimens demonstrate that among the beam–column joints with 600 MPa high strength steel bars, specimens with high reinforcement ratios have better energy dissipation capacity, slower stiffness degradation, and lower ductility. Moreover, with the increase of the axial compression ratios, the energy dissipation capacity and ductility become weaker. The test results show the favorable seismic properties of beam–column joints equipped with 600 MPa high strength steel bars, which can be regarded as the research basis of the popularization and application of 600 MPa high strength steel bars in reinforcement concrete frame structures.

The compliant mechanism can effectively reduce friction and eliminate the joint gap during the motion. The performances of compliant joints directly determine the overall behavior of mechanisms. In this paper, a new type of compliant joint is designed based on weakened creases and elastic–plastic materials. Parametric analysis is carried out to investigate the influence of compliant joint details on its structural performances by combining finite element methods and experiments. The compliant joints are evaluated and optimized regarding the rotational stiffness and plastic strain magnitude of the slot region. In addition, the optimized compliant joint is introduced to the Miura unit. The configuration analysis is performed for the folding, unfolding, and releasing processes, which are further extended to the discussion on the cyclic performance of the compliant joint. It can be found that the origami-inspired structures can maintain a high residual stiffness after the release process. Finally, the methodology is applied to the Miura origami array embedded with the designed compliant joint. The results of dimensional errors and stress distributions can show that the design of the compliant joints can effectively control the configuration of the Miura origami array. The principle in this paper can open a new avenue to design and utilize the compliant in the deployable or morphing structures.