1. Introduction
Reticulated shell structures form the basis for numerous practical engineering applications and novel, reasonable architectural structures. Additionally, they are widely exploited for their beautiful shape and the ability to distribute forces in a uniform manner, which refers to the even spread of stresses primarily under vertical loads. These structures are also designed to resist horizontal loads effectively, and special considerations are considered to manage local effects and stress concentrations around openings. Reticulated shells are often the structures of local landmark buildings. However, frequent terrorist attacks and military activities have brought attention to the impact resistance of architectural structures; large-span space buildings are mostly national and regional landmark buildings, which can easily become targets of terrorist and military attacks and suffer from external impact, resulting in immeasurable losses. In this context, studying the impact resistance of long-span space structures is of great political and economic significance.
Before studying the dynamic response of structures under an impact load, the mechanical properties of materials under high-speed impact should be defined. Cowper and Symonds [
1] proposed the C-S constitutive model, which provides the relationship between material stress and strain rate. This piecewise-linear plasticity model can effectively characterise the dynamic mechanical behaviour of metal materials; thus, it is widely used in the field of structural impact resistance. Johnson and Cook [
2] proposed the J-C constitutive model, which comprehensively considers the influence of large strain, large stress, and high temperature on metal materials under high-speed impact. Paul [
3] proposed an elastoplastic constitutive model that is suitable for wide strain rates and temperature ranges. This model was adapted to characterise the dynamic mechanical behaviour of steel and has been successfully applied to low-carbon steel ES, DP600, and TRIP700. However, the parameters of this model are coupled with each other and difficult to calibrate. This bottleneck restricts the application of this model to a wide range of materials. Based on the above research analysis, the current research on the dynamic mechanical properties of materials is relatively mature, among which the Cowper-Symonds constitutive model and the Johnson-Cook constitutive model are widely used in the field of structural impact resistance.
The dynamic response of structural components to impact loads is a critical area of research in structural engineering. In the realm of metallic components, Al-Thairy et al. [
4], Liang et al. [
5,
6], Li et al. [
7], and Xiang et al. [
8] have contributed significantly. Their research spans from the numerical simulation of steel columns under impact to the assessment of energy absorption in dimpled steel sheets and the analysis of impact resistance in steel parking structure columns. For non-metallic components, Bambach et al. [
9], Wang et al. [
10], Goswami et al. [
11], Lee et al. [
12], Li et al. [
13], and Li et al. [
14] have provided valuable insights. Their work includes the exploration of concrete-filled steel beams, ULCC-filled pipe-in-pipe composites, concrete slab shear failure, steel plate-concrete composite walls, and the dynamic performance of concrete beams, among others. The dynamic analysis of light weight structures is also being studied; Slimane et al. [
15] suggested using a bilayer ceramic/aluminum honeycomb sandwich panel (HSP) for spacecraft shielding against orbital debris, showing improved resistance compared to monolayer concepts through modelling and experiments; Sun et al. [
16] studied the impact response of a composite structure consisting of a metal-packaged ceramic interlayer and an ultra-high molecular weight polyethylene (UHMWPE) laminate through a ballistic test and numerical simulation. Additionally, the influence of impact angles is a crucial aspect; Yang et al. [
17] simulated the circular steel tube response to lateral impact. It analysed factors such as impact angle, energy, and failure modes, finding that impact forces depended on angle and velocity, while failure modes were energy-driven. This research has illuminated how impact angles affect the forces and failure modes in structural components, which is vital for the design and safety of structures.
Recent years have witnessed a significant focus on the dynamic response of large-span space structures under various impact loads. Gupta et al. [
18,
19,
20,
21] conducted in-depth studies on thin-walled spherical aluminium shells, examining deformation modes under axial compression and impact loads, thereby laying a foundation for understanding the collapse behaviour of metallic shells. Fan et al. [
22,
23,
24] contributed by proposing an efficient method for solving impact problems using finite element analysis, identifying four distinct failure modes in reticulated domes. Zhi et al. [
25,
26] expanded this research to the safety and protective measures of single-layer reticulated domes under various loads, including impact and seismic forces. Their work was complemented by Zhai et al. [
27], who focused on blast resistance strategies for dome structures. Wang et al. [
28,
29], Ma et al. [
30,
31], and Hu et al. [
32] furthered the understanding of dynamic responses, failure modes, and energy mechanisms in reticulated shell structures and hemispherical shell systems under impact loads. This line of inquiry was continued by Su et al. [
33], who studied the dynamic response of long-span reticulated shells under external explosion loads. The research scope was broadened by Zhi et al. [
34], Ma et al. [
35], and Nazari et al. [
36], who investigated the dynamic behaviour of reticulated domes and double-layer domes under various impact scenarios. Wu et al. [
37], Deepshikha et al. [
38], and Pilarska et al. [
39] contributed by examining multi-point impacts, roof-substructure interactions, and seismic effects on dome structures. Xu et al. [
40,
41] focused on the impact response of spherical reticulated shell structures and plane cable-membrane structures, respectively, exploring the effects of various factors on dynamic response and failure modes. Rossot et al. [
42] conducted studies on geodesic domes and composite materials under impact, enhancing the understanding of structural behaviour under different loading conditions. Gou et al. [
43] and Shen et al. [
44] explored the dynamic behaviour of welded spherical joints and mesh shells and the impact resistance of large-span net shell structures, respectively, using advanced numerical methods and experimental techniques to assess the effects of combined loads and material properties on structural response. This body of work collectively enhances our understanding of the dynamic behaviour of these critical structures, guiding future designs towards greater resilience against impact loads.
In the current landscape of research, studies on the performance of steel structures under oblique impact loads predominantly focus on individual components [
17]. Notably, the mass, velocity, initial kinetic energy, and impact angle of the impactor play a crucial role in influencing the dynamic response of reticulated shell structures [
44]. However, most existing research on these structures’ centres around vertical and horizontal impacts, with limited exploration into the effects of oblique impacts. This study investigated the dynamic response and failure modes of reticulated shell structures under oblique impact loads. Utilizing a numerically simulated method, which was validated through experimental data, we examined the dynamic responses of these structures under different oblique impact loads on a plumb surface and assessed the influence of the impactor parameters on their dynamic behaviour. Our investigation first identified and analysed two distinct failure modes—unpenetrated and penetrative—and their energy dissipation capacity. Further, we delved into the intricacies of node displacements and internal member stresses, particularly noting their correlation with proximity to the impact point. A pivotal aspect of our research was the assessment of how variations in the oblique impact angle affected the structure’s response. Finally, our findings provided insights for optimising the design and reinforcement of reticulated shell structures.