Experimental Study on Residual Mechanical Properties of Bolt-Sphere Joints After a Fire

Hongbo Liu,Zhilun Tan,Zhihua Chen,Zhansheng Liu,Dongyu Liu 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.3

Through tensile testing of 15 steel bolt-sphere joints and 15 aluminum alloy bolt-sphere joints, infl uencing rules of material type, high temperature and cooling mode on tensile properties of post-fi re bolt-sphere joints were studied, and then failure modes of the joints were determined. According to experimental data, the calculation formula of residual tension capacity of post-fi re bolt-sphere joints was presented. Experimental data indicated that (1) decreased extension on the mechanical properties of aluminum alloy bolt-sphere joints after high temperature in the fi re was signifi cantly higher than that of the steel bolt-sphere joints; (2) when fi re temperature was lower than 800 °C, the tension capacity of steel bolt-sphere joints could be restored by more than 90% after cooling; (3) when fi re temperature was lower than 500 °C, the tension capacity of aluminum alloy bolt-sphere joints could be restored by more than 50% after cooling; (4) bolt-sphere joints could still satisfy the requirement of “strong node and weak member” after a fi re; and (5) material type and fi re temperature were the main factors that infl uenced post-fi re mechanical properties of bolt-sphere joints.

Structural Behavior of Steel Tube and Coupler Scaffolds with Stability Strengthening Details

Hongbo Liu,Yi Meng,Li Jia,Zhihua Chen,Qun Liu,Suilin Wen 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.1

The multi-span steel tube and coupler scaffold is one of the main temporary structural forms in building and bridge construction. Given the insufficient research on their bearing capacity and design method, steel tube and coupler scaffolds have frequently collapsed in recent years and have caused serious casualties and economic losses. Through six prototype tests and a numerical analysis, this study investigated the effect of stability strengthening measures, such as vertical X-bracing, horizontal X-bracing, surrounding non-loading area, and lateral wall-tied constraints, on the ultimate bearing capacity and failure mode of multi-span steel tube and coupler scaffolds under a uniformly distributed line load of upper horizontal tubes. Using the finite element numerical analysis verified by the test data, the influence of height-width ratio, structure height, story height, spacing of vertical tubes, X-bracing layout, lateral wall-tied constraints, and surrounding non-loading area on the ultimate bearing capacity of multi-span steel tube and coupler scaffolds was analyzed. Design methods for multi-span steel tube and coupler scaffolds under a uniformly distributed line load of upper horizontal tubes were proposed based on the results of the prototype test and finite element numerical analysis. The reasonability of the design method was verified by the test data and finite element analysis results.

Structural behavior of aluminum reticulated shell structures considering semi-rigid and skin effect

Liu, Hongbo,Chen, Zhihua,Xu, Shuai,Bu, Yidu Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.1

The aluminum dome has been widely used in natatorium, oil storage tank, power plant, coal, as well as other industrial buildings and structures. However, few research has focused on the structural behavior and design method of this dome. At present, most designs of aluminum alloy domes have referred to theories and methods of steel spatial structures. However, aluminum domes and steel domes have many differences, such as elasticity moduli, roof structures, and joint rigidities, which make the design and analysis method of steel spatial structures not fully suitable for aluminum alloy dome structures. In this study, a stability analysis method, which can consider structural imperfection, member initial curvature, semi-rigid joint, and skin effect, was presented and used to study the stability behavior of aluminum dome structures. In addition, some meaningful conclusions were obtained, which could be used in future designs and analyses of aluminum domes.

Numerical and experimental investigation on the temperature distribution of steel tubes under solar radiation

Hongbo Liu,Zhihua Chen,Ting Zhou 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.6

The temperature on steel structures is larger than the ambient air temperature under solar radiation and the temperature distribution on the affected structure is non-uniform and complicated. The steel tube, as a main structural member, has been investigated through experiment and numerical analysis. In this study, the temperature distribution on a properly designed steel tube under solar radiation is measured. A finite element transient thermal analysis method is presented and verified by the experimental results and a series of parametric studies are carried out to investigate the influence of various geometric properties and orientation on the temperature distribution. Furthermore, a simplified approach is proposed to predict the temperature distribution of steel tube. Based on both the experimental and the numerical results, it is concluded that the solar radiation has a significant effect on the temperature distribution of steel tubes. Under the solar radiation, the temperature of steel tubes is about 20.6oC higher than the ambient air temperature. The temperature distribution of steel tubes is sensitive to the steel solar radiation absorption, steel tube diameter and orientation, but insensitive to the solar radiation reflectance and thickness of steel tube.

Structural behavior of the suspen-dome structures and the cable dome structures with sliding cable joints

Liu, Hongbo,Chen, Zhihua Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.1

Sliding cable joints have been developed for the cable dome structures and the suspen-dome structures to reduce the cable pre-stressing loss and obtain a uniform inner force in each hoop cable. However, the relevant investigation is less addressed on the structural behavior of the cable dome structures and the suspen-dome structures with sliding cable joints due to the lack of analysis techniques. In this paper, a closed sliding polygonal cable element was established to analyze the structural behavior of the cable dome structures and the suspen-dome structures with sliding cable joints. The structural behaviors with sliding cable joints were obtained.

Reinforcement of Circular Steel Tubes Using Welded Casings Under Axial Compression Loading

Hongbo Liu,Jie Hu,Zhi-Hua Chen,Longxuan Wang,W. A. H. Mashrah 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.3

To explore the mechanical behavior of circular steel tube components strengthened with welded casings, two groups of six specimens are designed, and two working conditions of zero-load reinforcement and load reinforcement are defi ned. Typical failure modes, ultimate bearing capacity, defl ection curves, and strain data of measuring points are obtained. The FE modeling method considering the thermal eff ect of the welding process is proposed and verifi ed. A total of 446 fi nite element models are established to explore the eff ects of the initial defects, the slenderness ratio, the boundary conditions, and the area ratio of the welded casing to the circular steel tube on the ultimate bearing capacity of the strengthened components. In addition, the ultimate bearing capacity equations for zero-load strengthened components is proposed using regression fi tting and considering the adverse eff ects of the residual stresses due to the rolling and welding processes. Moreover, equations for calculating the deformation and the ultimate bearing capacity of the load-strengthened components considering the eff ect of the welding heat are also derived. Finally, the experimental, numerical, and theoretical analyses results were consistent in high calculation validity and effi ciency.

Structural behavior of the suspen-dome structures and the cable dome structures with sliding cable joints

Hongbo Liu,Zhihua Chen 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.1

Sliding cable joints have been developed for the cable dome structures and the suspen-dome structures to reduce the cable pre-stressing loss and obtain a uniform inner force in each hoop cable. However, the relevant investigation is less addressed on the structural behavior of the cable dome structures and the suspen-dome structures with sliding cable joints due to the lack of analysis techniques. In this paper, a closed sliding polygonal cable element was established to analyze the structural behavior of the cable dome structures and the suspen-dome structures with sliding cable joints. The structural behaviors with sliding cable joints were obtained.

Experimental Analysis of the Mechanical Properties of Austenitic S30408 Stainless Steel Welded Joints at Low Temperatures

Hongbo Liu,Longxuan Wang,Yixin Yang,Ting Zhou,Jing Li 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.5

Austenitic S30408 stainless steel exhibits good low-temperature resistance and good welding performance. This steel is often used in liquefied natural gas stainless steel storage tanks. During the construction process, the tank wall is primarily connected by butt weld joints. Because welded joints are easily affected by temperature, low-temperature weld cracking can reduce the safety of structures. To study the cryogenic mechanical properties of austenitic S30408 stainless steel welded joints at low temperatures, the low-temperature mechanical properties of austenitic S30408 stainless steel base metal and welded joint components were studied by tensile tests from − 60 to 20 °C and scanning electron microscopy analysis of fractures at various temperatures. The results show that when the temperature decreases, the stress–strain curve of base metal components changes from a power function type to an inverted "s" type; in addition, secondary hardening occurs. The yield strength and tensile strength of the welded joint and base metal increased with decreasing temperature, and the elongation and reduction of area decreased. The plastic deformation capacity of the welded joint was significantly lower than that of the base metal, and there were obvious inclusions in the microstructure.

Numerical and experimental investigation on the temperature distribution of steel tubes under solar radiation

Liu, Hongbo,Chen, Zhihua,Zhou, Ting Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.6

The temperature on steel structures is larger than the ambient air temperature under solar radiation and the temperature distribution on the affected structure is non-uniform and complicated. The steel tube, as a main structural member, has been investigated through experiment and numerical analysis. In this study, the temperature distribution on a properly designed steel tube under solar radiation is measured. A finite element transient thermal analysis method is presented and verified by the experimental results and a series of parametric studies are carried out to investigate the influence of various geometric properties and orientation on the temperature distribution. Furthermore, a simplified approach is proposed to predict the temperature distribution of steel tube. Based on both the experimental and the numerical results, it is concluded that the solar radiation has a significant effect on the temperature distribution of steel tubes. Under the solar radiation, the temperature of steel tubes is about $20.6^{\circ}C$ higher than the ambient air temperature. The temperature distribution of steel tubes is sensitive to the steel solar radiation absorption, steel tube diameter and orientation, but insensitive to the solar radiation reflectance and thickness of steel tube.

Structural behavior of aluminum reticulated shell structures considering semi-rigid and skin effect

Hongbo Liu,Zhihua Chen,Shuai Xu,Yidu Bu 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.1

The aluminum dome has been widely used in natatorium, oil storage tank, power plant, coal, as well as other industrial buildings and structures. However, few research has focused on the structural behavior and design method of this dome. At present, most designs of aluminum alloy domes have referred to theories and methods of steel spatial structures. However, aluminum domes and steel domes have many differences, such as elasticity moduli, roof structures, and joint rigidities, which make the design and analysis method of steel spatial structures not fully suitable for aluminum alloy dome structures. In this study, a stability analysis method, which can consider structural imperfection, member initial curvature, semi-rigid joint, and skin effect, was presented and used to study the stability behavior of aluminum dome structures. In addition, some meaningful conclusions were obtained, which could be used in future designs and analyses of aluminum domes.