Progressive Collapse Analysis of Large-span Reticulated Domes

Qinghua Han,Mingjie Liu,Yan Lu,Chenxu Wang 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.2

The paper presents the progressive collapse analysis of large-span reticulated domes based on Alternate path (AP) method. Nonlinear buckling analysis is conducted on a large span roof with two different structural layouts. The results show that although large-span single-layer reticulated dome has a certain redundancy. When 10 key elements or 3 key nodes were removed, the single-layer reticulated dome under the service load would cause progressive collapse. Therefore the protection of key nodes of this structure should be strengthened. However, the redundancy of large-span double-layer reticulated dome is 7 to 13 times that of single-layer reticulated dome. When 10 key elements or 3 key nodes were removed, the double-layer reticulated dome under the service load would not cause progressive collapse. Hence, the resistance to progressive collapse of large-span double-layer reticulated dome is better than that of large-span single-layer reticulated dome.

Fatigue Behaviour of G20Mn5QT Cast Steel and Butt Welds with Q345B Steel

Qinghua Han,Qi Guo,Yue Yin,Ying Xing 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.1

A total number of 44 fatigue tests were conducted under total stain control, 26 for G20Mn5QT cast steel and 18 for butt welds between G20Mn5QT cast steel and Q345B steel. Based on the test results, cyclic stress response, plastic strain energy, strainlife curves and Coffin-Manson equations were presented. Comparing with hot rolled steels widely used in steel construction, the fatigue behaviour of G20Mn5QT cast steel is poor, the reason for which was imputed to the defects caused by the casting process. The welds between G20Mn5QT cast steel and Q345B steel exhibited similar fatigue performance as G20Mn5QT cast steel. Fatigue crack tends to initiate in the heat affected zone (HAZ) at the cast steel. Microstructure observations using optical and scanning electron microscope showed that casting defects are the common fatigue source for both G20Mn5QT cast steel and the butt welds between G20Mn5QT cast steel and Q345B steel.

Static push-out test on steel and recycled tire rubber-filled concrete composite beams

Qinghua Han,Ying Xing,Jie Xu,Zi-Lin Li 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.4

Recycled tire rubber-filled concrete (RRFC) is employed into the steel-concrete composite structures due to its good ductility and crack resistance. Push-out tests were conducted to investigate the static behavior of steel and rubber-filled concrete composite beam with different rubber mixed concrete and studs. The results of the experimental investigations show that large studs lead a higher ultimate strength but worse ductility in normal concrete. Rubber particles in RRFC were shown to have little effect on shear strength when the compressive strength was equal to that of normal concrete, but can have a better ductility for studs in rubber-filled concrete. This improvement is more obvious for the composite beam with large stud to make good use of the high strength. Besides that the uplift of concrete slabs can be increased and the quantity and width of cracks can be reduced by RRFC efficiently. Based on the test result, a modified empirical equation of ultimate slip was proposed to take not only the compressive strength, but also the ductility of the concrete into consideration.

Cyclic Response and Constitutive Model Study of G20Mn5QT Cast Steel

Qinghua Han,Qianwen Huang,Yan Lu 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.4

A series of cyclic loading tests of G20Mn5QT cast steel are carried out at the strain ratio of − 1. The results of tests show that the G20Mn5QT cast steel has the similar tendency in cyclic softening with diff erent constant strain amplitude. A slight strain softening is observed, and then the stress states keep steady during the remaining cycles. A new damage variable is proposed considering the eff ects of strength degeneration within two inner variables which are the maximum equivalent plastic strain and the equivalent plastic strain increment. The damage variable provides better insight into the multiaxial cyclic loading and gives a reasonable prediction of failure under the loading history of constant strain amplitude. The proposed damage variable is further introduced in the cyclic constitutive model by the user subroutine interfaces VUMAT by the software ABAQUS. The relationships between the equivalent plastic strain and the damage variable, Young’s modulus and yield strength are fi nally put forward as it is expedient to get the equivalent plastic strain in the numerical analysis.

Experimental research on load-bearing capacity of cast steel joints for beam-to-column

Qinghua Han,Mingjie Liu,Yan Lu 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.1

The load transfer mechanism and load-bearing capacity of cast steel joints for H-shaped beam to square tube column connection are studied based on the deformation compatibility theory. Then the monotonic tensile experiments are conducted for 12 specimens about the cast steel joints for H-shaped beam to square tube column connection. The findings are that the tensile bearing capacity of the cast steel joints for beam-column connection depends on the ring of cast steel stiffener. The tensile fracture happens at the ring of the cast steel stiffener when the joint fails. The thickness of square tube column has little influence on the bearing capacity of the joint. The square tube column buckles while the joint without concrete filled, but the strength failure happens for the joint with concrete filled column. And the length of welding connection between square tube column and cast steel stiffener has little influence on the load-bearing capacity of the cast steel joint. Finally it is shown that the load-bearing capacity of the joints for H-shaped beam to concrete filled square tube column connection is larger than that of the joints for H-shaped beam to square tube column connection by 10% to 15%.

Microstructure Evolution and Mechanical Performances of SiCf Reinforced (Al3Ti + Al3Ni)-Based Metallic–Intermetallic Laminate Composite

Yuqiang Han,Qinghua Que,Ran Cheng,Ran Cheng,Chunfa Lin,Wenqing Han,Enhao Wang,Junyi Zhu,Haoran Yan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10

In present work, a novel SiCfreinforced (Al3Ti + Al3Ni)-based metallic–intermetallic laminate (Ti–(Al3Ti + Al3Ni)/SiCf-MIL) composite without centerline defect was prepared using Ti, Al foils, NiTi wires and SiC fibers by vacuum hot pressingsintering method. Electron backscatter diffraction was employed to characterize the microstructure and phase constituents ofTi–(Al3Ti + Al3Ni)/SiCf-MIL composite during various stages of preparation process. The elimination mechanism of intermetalliccenterline was discussed. Besides, quasi-static compressive performance and fracture toughness of the synthesizedcomposite were investigated. The experimental results indicated that as reaction time increasing, the NiTi/Al interfacialreaction occurred prior to the Ti/Al interfacial reaction to form an Al3Ti/Al3Ni zone. Then, the oxides gathered at the frontof Ti/Al interfacial reaction layer were dispersed in the intermetallic layer rather than being pushed together to generate thecenterline due to the Al3Ti/Al3Ni zone. After reaction, there were no residual NiTi phases and intermetallic layers mainlyconsisting of Al3Tiand Al3Niphases were obtained in this composite. In addition, high angle grain boundaries in Al3Tigrains occupied a large proportion, conversely, low angle grain boundaries dominated in Al3Nigrains. Furthermore, stressconcentration appears at the interface between layers instead of along the middle plane of intermetallic layer. Moreover,both compressive strength and fracture toughness of the composite are superior in comparison with SiCfreinforced Ti–Al3Timetallic–intermetallic laminate composite (Ti–Al3Ti/SiCf-MIL) ascribed to the elimination of centerline.

Structural Behaviour of an Assembled Steel Joint Composed of CHS KK-Joint and Doubler Plate for Connection with Steel Tensile Rods

Bo Zhao,Han Zhu,Yue Yin,Zhuo Liu,Qinghua Han 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.2

Structural behavior of an assembled steel joint composed of CHS KK-joint and a doubler plate for connection with steel tensile rods was studied. A full-scale test was conducted for the assembled joint on a special made self-balanced reaction frame with three high strength steel strands to apply tensile loads on two ear plates and compressive load on the chord member of the joint. Ultimate load carrying capacity, failure mode and stress distribution of the joint under monotonic loads were obtained experimentally. The static behavior of the joint was also determined by nonlinear fi nite element analysis. The results of numerical analysis agreed very well with those of the test, which verifi ed the rationality of the fi nite element model. The hysteretic behavior of the joint was then studied by fi nite element analysis. Hysteretic curve was obtained, based on which ductile ratio and energy dissipation factor were calculated. Outcomes from both the test and the fi nite element analysis proved that the assembled joint has satisfactory load carrying capacity and acceptable seismic performance.

Fatigue behavior of stud shear connectors in steel and recycled tyre rubber-filled concrete composite beams

Jie Xu,Qinghua Han,Yi-Hong Wang,Ying Xing 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.2

This paper extends our recent work on the fatigue behavior of stud shear connectors in steel and recycled tyre rubber-filled concrete (RRFC) composite beams. A series of 16 fatigue push-out tests were conducted using a hydraulic servo testing machine. Three different recycled tyre rubber contents of concrete, 0%, 5% and 10%, were adopted as main variable parameters. Stress amplitudes and the diameters of studs were also taken into consideration in the tests. The results show that the fatigue lives of studs in 5% and 10% RRFC were 1.6 and 2.0 times greater of those in normal concrete, respectively. At the same time, the ultimate residual slips' values of stud increased in RRFC to highlight its better ductility. The average ultimate residual slip value of the studs was found to be equal to a quarter of studs' diameter. It had also been proved that stress amplitude was inversely proportional to the fatigue life of studs. Moreover, the fatigue lives of studs with large diameter were slightly shorter than those of smaller ones and using larger ones had the risk of tearing off the base metal. Finally, the comparison between test results and three national codes was discussed.

A numerical investigation of seismic performance of large span single-layer latticed domes with semi-rigid joints

Zhang, Huidong,Han, Qinghua Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.1

It is still inadequate for investigating the highly nonlinear and complex mechanical behaviors of single-layer latticed domes by only performing a force-based demand-capacity analysis. The energy-based balance method has been largely accepted for assessing the seismic performance of a structure in recent years. The various factors, such as span-to-rise ratio, joint rigidity and damping model, have a remarkable effect on the load-carrying capacity of a single-layer latticed dome. Therefore, it is necessary to determine the maximum load-carrying capacity of a dome under extreme loading conditions. In this paper, a mechanical model for members of the semi-rigidly jointed single-layer latticed domes, which combines fiber section model with semi-rigid connections, is proposed. The static load-carrying capacity and seismic performance on the single-layer latticed domes are evaluated by means of the mechanical model. In these analyses, different geometric parameters, joint rigidities and roof loads are discussed. The buckling behaviors of members and damage distribution of the structure are presented in detail. The sensitivity of dynamic demand parameters of the structures subjected to strong earthquakes to the damping is analyzed. The results are helpful to have a better understanding of the seismic performance of the single-layer latticed domes.

A numerical investigation of seismic performance of large span single-layer latticed domes with semi-rigid joints

Huidong Zhang,Qinghua Han 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.1

It is still inadequate for investigating the highly nonlinear and complex mechanical behaviors of single-layer latticed domes by only performing a force-based demand-capacity analysis. The energy-based balance method has been largely accepted for assessing the seismic performance of a structure in recent years. The various factors, such as span-to-rise ratio, joint rigidity and damping model, have a remarkable effect on the load-carrying capacity of a single-layer latticed dome. Therefore, it is necessary to determine the maximum load-carrying capacity of a dome under extreme loading conditions. In this paper, a mechanical model for members of the semi-rigidly jointed single-layer latticed domes, which combines fiber section model with semi-rigid connections, is proposed. The static load-carrying capacity and seismic performance on the single-layer latticed domes are evaluated by means of the mechanical model. In these analyses, different geometric parameters, joint rigidities and roof loads are discussed. The buckling behaviors of members and damage distribution of the structure are presented in detail. The sensitivity of dynamic demand parameters of the structures subjected to strong earthquakes to the damping is analyzed. The results are helpful to have a better understanding of the seismic performance of the single-layer latticed domes.