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This paper presents the instability mechanism of an innovative Rhombic Grid Hyperboloid-Latticed Shell (RGHLS) under vertical load through experimental and numerical investigations. The RGHLS is only composed of bidirectional inclined primary and secondary columns without any circumferential members or lateral braces in its radial direction along its height. Therefore it would likely fail by out-of-plane multi-column interaction instability and the corresponding load-carrying capacity should be predicted. The experimental investigation of a reduced-scale test model of RGHLS was firstly performed to study its vertical load-carrying capacity and the multi-column interaction instability. A special spatial beam-string device for vertical multi-point loading of the test model has been initially designed and fabricated to precisely distribute the concentrated load to the top of the columns according to proportional distribution of loads required by designers. The experimental results revealed that the inclined columns indeed exhibited strong mutual restraining actions, and the ratio of the actual ultimate load-carrying capacity of the test model to its design load was 3.37, indicating a reasonable safety margin. In addition, FE numerical results of the test model corresponded well with the experimental results. Ultimately, additional FE numerical analyses have been conducted on the test model. Accordingly the effects of the ratio of stiffness between the secondary and primary columns, overall initial geometric imperfection, in-plane stiffness of top ring beam, and dimensions of portal columns on the load-carrying capacity and failure mode of RGHLS have been investigated extensively. As a result, the ratio of stiffness between the secondary and primary columns has been particularly recommended within a range of 0.46–0.70, so as to eliminate premature failure of X-joints prior to the instability of columns in the prototype of RGHLS.

The rhombic grid hyperboloid-latticed shells (RGHLSs) in the China Comic and Animation Museum (CCAM) are located on the ground floor, and they sustain enormous vertical and horizontal loads induced from upper building structures on top of them. Each RGHLS consists of numerous bidirectional inclined major and secondary columns that intertwine with one another to form a rhombic grid with X-shaped joints. Without both horizontal circumferential members and horizontal lateral braces in the radial direction of the RGHLS, as well as the existence of significant difference of compressive stiffness between major and secondary columns, the RGHLS would ultimately fail in a complicated form of in-plane and out-of-plane multi-column interaction instability in addition to its overall twist deformation under relatively low vertical loads. Currently, no design method for estimating its design strength and safety is available. Therefore, the load-carrying capacity of the RGHLS must be examined experimentally. This paper selects the RGHLS denoted by Y4 in the structure of the CCAM as the prototype, and presents an experimental investigation of its reduced scale (1:1/4) test model. A loading protocol consisting of six loading phases has been devised in order to predict the static vertical and horizontal load resistance, and horizontal hysteretic response of the RGHLS by keeping the amplitudes of the vertical load constantly as 1.0, 1.4 and 1.6 times the vertical design load of the reduced-scale test model, respectively. The experimental results obtained indicate that the test model remains elastic under 1.8 times its design loads, which is commonly adopted as static structural strength limit in practical design in China. In addition, horizontal cyclic load test indicated that the reduced-scale test model demonstrated sufficiently large horizontal load-carrying capacity as well as exhibited stable and ample hysteretic curves even under 1.6 times vertical load actions without any obvious stiffness reductions. This study comprehensively introduces the experimental test schemes and deeply analyzes the experimental results, thus forming an important basis for designing the load-carrying capacity of such RGHLSs. Ultimately, according to the experimental loading protocol, numerical simulations and analyses of the test model have been conducted by adopting ANSYS 12.1. The interaction strength design curve of the test model under a combination of vertical and horizontal loads is also proposed by carrying out additional numerical simulations of the model. The FE and experimental results have been compared, and they correspond well to one another, indicating that the results of the reduced-scale test model are accurate enough and reliable.

A new type of core-separated buckling-restrained braces, namely a core-separated battened buckling-restrained brace (B-BRB) has been proposed. Its load-carrying capacity and hysteretic response are investigated theoretically and experimentally in this paper. The B-BRB has a remarkable advantage over a common buckling-restrained brace (BRB), in which the newly formed cross-section of the B-BRB is spread outwards by spacing two cores, hence resulting in higher material utilization efficiency in its structural design. In addition, the two independent all-steel BRBs, each having a single plate core simply in-filled in a narrow hollow section, are connected by longitudinally distributed battens rather than continuous plates. Based on the elastic-plastic FE analysis of a B-BRB under monotonic compressive load, its ultimate resistance and failure modes are investigated numerically, considering the effect of its overall initial geometric imperfection. An interaction formula between normalized slenderness ratio and buckling factor of the B-BRB is proposed for predicting its ultimate load-carrying capacity. Consequently, the hysteretic response of the B-BRB is explored through elastic-plastic FE analysis. The maximum normalized slenderness ratios of the B-BRBs required for a load-bearing type and an energy-dissipation type are proposed in their strength designs, respectively. Ultimately, hysteretic responses of five B-BRB specimens have been experimentally investigated. The experimental results are compared with the FE numerical analysis, which considers plate local buckling of all components of the B-BRBs. The comparison has verified the rationality of the proposed design method.

Grid Cylindrical-Lattice Shells (GCLSs) have found their wide application in high-rise buildings and TV towers as the outer cylindrical frame of tube-in-tube structures subjected mainly to axial compression. This paper presents the elastic buckling behaviour of Grid Cylindrical-Lattice Shells (GCLSs) under axial compression. Because of a lack of lateral braces in the radial direction of the GCLS along its height, the GCLS tends to fail by two buckling modes under axial compression, namely global flexural buckling and circumferential multi-wave buckling. First, the fundamental three-story GCLS is investigated by using the energy method. The restraining action of the ring beam on the columns in the two buckling modes is explored separately, and this exploration leads to the radial rotational restraint stiffness, tangential rotational restraint stiffness and translational restraint stiffness of the ring beams, denoted by βr, βt and α, respectively; in addition, the corresponding elastic buckling loads of the three-story GCLS in the two buckling modes are separately derived. Then, based on the three key parameters, simple fitting formulas are developed to separately predict the elastic buckling loads of the multi-story GCLS in the two buckling modes. This outcome provides fundamentals for further establishing load-carrying capacity design of GCLSs under axial compression.

Surface icing and delamination damage have been tough problems of outdoor devices and equipment in many fields including aerospace, new energy and electronics. Herein, one new thermally resistant tri-layered composites with superhydrophobic surface and great self-healing after complete fracture were fabricated based on self-healable epoxy resin (hEP), multiwalled carbon nanotubes (CNTs) and superhydrophobic copper powders (nCu). Integrated properties of composites are greatly associated with the loading of CNTs. The composite with 10 wt% CNTs (nCu-CNT3/hEP-hEP) shows excellent superhydrophobicity, and its glass transition temperatures of bottom layer (hEP) and interlayer (CNT3/hEP) are as high as 110–113 °C, guaranteeing the dimensional stability during Joule heating. Under a voltage of 10 V, ice blocks on nCu-CNT3/hEP-hEP melt within 26 s and rolled off from the superhydrophobic surface with a 5° horizontal tilt. Besides, two pieces obtained by cutting a whole block of nCu-CNT3/hEP-hEP composite were replanted to produce a perfect block of the composite after staying at 160 °C for 1 h; moreover, the healed composite also exhibits excellent superhydrophobicity, proving good abilities to ensure lifespan of related products. The mechanism behind these remarkable properties of nCu-CNT3/hEP-hEP properties was elucidated.