Ultra-low cycle fatigue tests of Class 1 H-shaped steel beams under cyclic pure bending

Xianzhong Zhao,Yafeng Tian,Liang-Jiu Jia,Tao Zhang 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.4

This paper presents experimental and numerical study on buckling behaviors and hysteretic performance of Class 1 H-shaped steel beam subjected to cyclic pure bending within the scope of ultra-low cycle fatigue (ULCF). A loading device was designed to achieve the pure bending loading condition and 4 H-shaped specimens with a small width-to-thickness ratio were tested under 4 different loading histories. The emphasis of this work is on the impacts induced by local buckling and subsequent ductile fracture. The experimental and numerical results indicate that the specimen failure is mainly induced by elasto-plastic local buckling, and is closely correlated with the plastic straining history. Compared with monotonic loading, the elasto-plastic local buckling can occur at a much smaller displacement amplitude due to a number of preceding plastic reversals with relative small strain amplitudes, which is mainly correlated with decreasing tangent modulus of the material under cyclic straining. Ductile fracture is found to be a secondary factor leading to deterioration of the load-carrying capacity. In addition, a new ULCF life evaluation method is proposed for the specimens using the concept of energy decomposition, where the cumulative plastic energy is classified into two categories as isotropic hardening and kinematic hardening correlated. A linear correlation between the two energies is found and formulated, which compares well with the experimental results.

Flexural behavior of steel storage rack base-plate upright connections with concentric anchor bolts

Xianzhong Zhao,Zhaoqi Huang,Yue Wang,Ken S. Sivakumaran 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.3

Steel storage racks are slender structures whose overall behavior and the capacity depend largely on the flexural behavior of the base-plate to upright connections and on the behavior of beam-to-column connections. The base-plate upright connection assembly details, anchor bolt position in particular, associated with the high-rise steel storage racks differ from those of normal height steel storage racks. Since flexural behavior of high-rise rack base connection is hitherto unavailable, this investigation experimentally establishes the flexural behavior of base-plate upright connections of high-rise steel storage racks. This investigation used an enhanced test setup and considered nine groups of three identical tests to investigate the influence of factors such as axial load, base plate thickness, anchor bolt size, bracket length, and upright thickness. The test observations show that the base-plate assembly may significantly influence the overall behavior of such connections. A rigid plate analytical model and an elastic plate analytical model for the overall rotations stiffness of base-plate upright connections with concentric anchor bolts were constructed, and were found to give better predictions of the initial stiffness of such connections. Analytical model based parametric studies highlight and quantify the interplay of components and provide a means for efficient maximization of overall rotational stiffness of concentrically anchor bolted high-rise rack base-plate upright connections.

The Influence of Epoxy Functionalized Acrylate Particles on the Properties of Plasticized PLA Blown Films

Ye Zhang,Yan Zhao,Hongwei Pan,Xianzhong Lang,Huili Yang,Huiliang Zhang,Huixuan Zhang,Lisong Dong 한국고분자학회 2016 폴리머 Vol.40 No.3

Polylactide (PLA) was plasticized with poly(diethylene glycol adipate) (PDEGA). The plasticized PLA was further blended with core-shell structured particles of glycidyl methacrylate-functionalized methyl methacrylate-butyl acrylate copolymer (GACR) using a twin-screw extruder, and the extruded samples were blown using the blown thin film technique. Both PDEGA and GACR significantly influenced the physical properties of the films. Compared to neat PLA, the elongation at break and tear strength of the films were significantly improved. The shear yielding induced by cavitation of GACR particles was the major tearing mechanism. GACR could act as a tear resistance modifier for PLA blown films. The spherulite size of the PLA/PDEGA/GACR films decreased with the addition of GACR. The biodegradability of the PLA/PDEGA/GACR films decreased slightly. These findings contributed new knowledge to the additive area and gave important implications for designing and manufacturing polymer packaging materials.

Test and Numerical Simulation of Partially Encased Composite Columns Subject to Axial and Cyclic Horizontal Loads

Yiyi Chen,Tuo Wang,Jing Yang,Xianzhong Zhao 한국강구조학회 2010 International Journal of Steel Structures Vol.10 No.4

Partial encased composite (PEC) members with thin steel plates and three types of constructional detailing are studied. Six pieces of PEC column specimens were tested under constant vertical load and cyclic horizontal loads. A numerical FE model is established. In the model, the in-filled concrete is decomposed as transverse and longitudinal springs, considering the functions and the properties of the concrete in two directions. This model simplifies the numerical computation with high efficiency, and acquires a satisfied agreement with test results in both capacity and deformability of the PEC member. The parametrical study by the FE model is performed. By tests and numerical analysis, it is found that though local buckling of thin plate of H steel is a crucial factor, when the compressively axial load does not surpass the encased steel capacity, the PEC could behave quite well under cyclic horizontal loads. No distinguished difference in three kind details was observed, so that PEC member could be built in a simple way.

Rotational capacity of H-shaped steel beams under cyclic pure bending

Liang-Jiu Jia,Yafeng Tian,Xianzhong Zhao,Siyuan Tian 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.2

This paper presents experimental study on effects of width-to-thickness ratio and loading history on cyclic rotational capacity of H-shaped steel beams subjected to pure bending. Eight Class 3 and 4 H-shaped beams with large width-to-thickness ratios were tested under four different loading histories. The coupling effect of local buckling and cracking on cyclic rotational capacity of the specimens was investigated. It was found that loss of the load-carrying capacity was mainly induced by local buckling, and ductile cracking was a secondary factor. The width-to-thickness ratio plays a dominant effect on the cyclic rotational capacity, and the loading history also plays an important role. The cyclic rotational capacity can decrease significantly due to premature elasto-plastic local buckling induced by a number of preceding plastic reversals with relative small strain amplitudes. This result is mainly correlated with the decreasing tangent modulus of the structural steel under cyclic plastic loading. In addition, a theoretical approach to evaluate the cyclic rotational capacity of H-shaped beams with different width-to-thickness ratios was also proposed, which compares well with the experimental results.

Improved mechanical properties, barrier properties and degradation behavior of poly(butylenes adipate-co-terephthalate)/poly(propylene carbonate) films

Hongwei Pan,Yanping Hao,Yan Zhao,Xianzhong Lang,Ye Zhang,Zhe Wang,Huiliang Zhang,Lisong Dong 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.5

Poly(butylene adipate-co-terephthalate) (PBAT) was blended with poly(propylene carbonate) (PPC) by a twin screw extruder and then the blends were made onto films via the blown film technique. PPC dispersed uniformly in the PBAT matrix, and the glass transition temperature (Tg) of PBAT were decreased with the increasing content of PPC. Wide angle X-ray diffraction confirmed that the crystallite dimension of PBAT was decreased after blending PBAT with the amorphous PPC. The results of mechanical tests indicated that the PBAT/PPC films showed high tensile strength and tear strength. In addition, the PBAT/PPC films showed high carbon dioxide permeability and moderate oxygen and nitrogen permeability. After embedding in soil, the weight loss and mechanical properties analysis demonstrated that the films were remarkably biodegraded. These findings contributed to application of the biodegradable materials, such as design and manufacture polymer packaging.