Behavior of Thin-walled Circular Hollow Section Stub Columns Under Axial Compression

Lanhui Guo,Yong Liu,Hui Jiao,Shilong An 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.3

Thin-walled steel circular hollow section (CHS) is widely used in wind turbine towers, where the tube is subjected to axial load combined with bending moment. Understanding the behavior of axially loaded thin-walled tubes with large diameter-tothickness (D/t) ratios is crucial for the design of such structures. To investigate the behavior of axially loaded thin-walled circular hollow section steel tubes, 16 stub columns were tested with the D/t ratio ranging from 75 to 300. The experimental results showed that the compressive strength decreased sharply with the increase of the D/t ratio. The experimental result indicated that the tubes with smaller D/t ratios failed with outward deformation without visible local buckling. With the increase of the D/t ratio, local buckling appeared at the peak load. The finite element method was used to model the behavior of axially loaded stub columns. The experimental results were used to validate the accuracy of the finite element results. Based on the finite element model, the influences of the D/t ratio, the initial geometric deformation and the initial residual stress were analyzed. Design guidelines in Eurocode3, AISC-LRFD, AS4100 and S16-9 on thin-walled steel members were used to compare with the experimental and calculated results. Among them, the results based on AS4100 were the closest to the experimental results.

Hysteretic Analysis and a Simplifi ed Model of Buckling Restrained Steel Plate Shear Walls

Lanhui Guo,Jian Hou,Zhiguo Li,Sumei Zhang 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1

As a kind of new lateral resistance member, buckling restrained steel plate shear walls (BRSPSWs) possess good ductility and energy dissipation ability, which begin to be used in buildings. In the use of BRSPSWs, it is hard to simulate BRSPSWs in high-rise buildings using shell elements due to convergence problems. Hence, a simplifi ed analysis model for BRSPSWs is needed by engineers. In this paper, the fi nite element analysis of BRSPSWs under cyclic loads was done. The available experimental results are applied to validate the accuracy of fi nite element analysis results. Then the behavior of typical BRSPSW under cyclic loads is analyzed. Also, the infl uence of bolt distance, reinforced concrete (RC) panels’ thickness, height-to-thickness ratio and span-to-height ratio of steel plate on the hysteretic behavior of BRSPSWs is studied. The analytical results show that the bolt distance and RC panel thickness have obvious infl uence on the energy dissipation ability. At last, a simplifi ed model is proposed, which can be used to simulate the hysteretic behavior of BRSPSWs instead of shell element in high-rise buildings.

Behavior of Steel Plate Shear Wall Connected to Frame Beams Only

Lanhui Guo,Qin Rong,Xinbo Ma,Sumei Zhang 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.4

This paper presents the study of steel plate shear walls which are connected to frame beams only. As the shear walls are not connected to frame columns, the premature failure overall buckling or local buckling of frame columns can be prevented. In fact, most of both structural design engineers and architects prefer this kind of steel plate shear walls because the dimension of their opening space is relatively flexible by using several steel plates with small span-to-height ratio placed parallel to each other. In this paper, two steel plate shear walls were fabricated and tested. The influence of stiffeners on the hysteretic behavior of this kind of member was studied. The experimental results showed that this kind of specimen had good ductility and energy dissipation capacity. The energy dissipation capacity of specimen with stiffeners was larger than that of the specimens without stiffeners. Meanwhile, the finite element method was applied to analyze the behavior of steel plate shear walls, whose results were validated by comparing with the corresponding experimental results. Analytical results showed that the free edges deformed with evident out-of-plane deformation and should be constrained by stiffeners to meet the design requirements. The energy dissipation capacity is much better for steel plate shear walls with lower height-to-thickness ratio and larger span-toheight ratio. At last, the skeleton curve of steel plate shear wall was proposed for calculating the elastic rigidity and loadcarrying capacity.

Hysteretic Analysis of Thin Steel Plate Shear Walls

Lanhui Guo,Mingming Jia,Ran Li,Sumei Zhang 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.1

Thin steel plate shear walls (TSPSWs) are especially concerned due to the economic factor and excellent energy dissipation capacity. TSPSWs commonly define as steel plate with height-to-thickness ratio over 300. The post-buckling capacity,deformability and energy dissipation capacity of TSPSWs are now accepted by structural engineers. This brings about evident economic benefit. This paper presents a finite element analysis of TSPSWs under cyclic loading. The calculated results are compared with experimental results to validate its accuracy. Then based on the finite element model, the influence of heightto-thickness ratio and span-to-height ratio on the hysteretic behavior of TSPSWs is analyzed. Also, the influence of column moment rigidity on the development of tension field is studied. At last, a new simplified Combined Strip Model is introduced which is suitable for the hysteretic analysis of TSPSWs. Based on the Combined Strip Model, a formula for calculating shear strength is proposed, which considers the compression effects of TSPSWs.

Study on the Infl uence of Connection Confi guration on Composite Joints

Shan Gao,Lanhui Guo 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.3

Steel–concrete composite joints possess higher bearing capacity, initial stiff ness and redundancy than bare steel joints. The confi guration of beam-column connection would infl uence the behavior of composite joints, such as rigidity, rotation capacity and so on. In this paper, the test of two fully welded rigid composite joints and two fl ush endplate semi-rigid composite joints was introduced. The loading conditions in the tests involved sagging moment and hogging moment. The mechanical behavior of composite joints under bending moment was studied in detail, especially on the infl uence of connection confi guration. The test results indicated that the experimental phenomena and failure mode of fully welded composite joint and fl ush endplate composite joint under hogging moment were similar to each other. The buckling of bottom fl ange of steel beam determined the behavior of composite joint under hogging moment, such as initial stiff ness and bending strength. It indicated that using fl ush endplate connection instead of fully welded connection in composite joints had little infl uence on the behavior of the joint under service loads if the failure mode of joints is governed by the same component. Four models for moment-rotation relation of composite joints are compared with experimental results. Based on the comparison, a new combination model of power function expression and linear expression is developed. With proper optimum shape parameter and descending stiff ness, the new model could present the moment-rotation relation of composite joints, regardless of connection confi guration or loading condition.

Performance Testing and Comparison of Buckling-restrained Braces with H and Crisscross Cross Section Unrestrained Segments

Mingming Jia,Lanhui Guo,Dagang Lu 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.4

Buckling-restrained braces (BRBs) deliver ductile, stable, and repeatable hysteretic behavior. The plastic deformationcapacity of the BRBs indicates the good indexes both in terms of ultimate deformation and in terms of energy dissipationcapacity. In this paper, the load-carrying elements of BRBs were fabricated with steel (Chinese Q235), and four layers of plasticfilm (0.2 mm in thickness) were used as unbounded materials to prevent the buckling of inner cores in higher modes andprovide spaces to facilitate its lateral expansion in case of compression. The differences of ultimate compression and tensionloads were controlled in a small range. The transformation of the unrestrained segment’s section from crisscross shape to Hshape can significantly improve the moment-resistance capacity of the unrestrained segment, avoiding buckling instabilityeffectively due to evident moment stiffness enhancement. The experimental results of pseudo-static tests (PSTs) under cyclicload indicate: BRB with H cross section unrestrained segments can undergo fully-reversed axial yield cycles without loss ofstiffness or strength, which have large ductility and superior seismic energy dissipation ability. There is obvious strainintensification in tension and compression phases. But there is evident decreasing of stiffness and strength on BRB withcrisscross section unrestrained segments due to the buckling of unrestrained segment under compression, the ductility andenergy dissipation ability decline distinctly.

Progressive Collapse Analysis of 20-storey Building Considering Composite Action of Floor Slab

Shan Gao,Lanhui Guo 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.2

Until now, the prototypes for finite element modeling are usually practice buildings or designed by researchers themselves which means there is no uniform standard for evaluation and comparison of progressive collapse analysis results. In this paper, using software Abaqus, a 3-D model of 20-storey building considering composite action of floor slab is developed to simulate and evaluate the behavior of high-rise composite building under sudden column failure. The methodology for the modeling techniques which could improve the computational efficiency is validated by the results from a progressive collapse test. The 20-storey benchmark building considering composite action of floor slab designed to meet American seismic code has adequate load paths and redundancy to resist the spread of local collapse due to sudden column removal. The column failure in where the column size changes does not influence the behavior of structures too much. The results of progressive collapse analysis adopting 20-storey benchmark model provide important information for standardization design to prevent progressive collapse.

Studies on CFST column to steel beam joints using endplates and long bolts under central column removal

Shan Gao,Bo Yang,Lanhui Guo,Man Xu,Feng Fu 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.2

In this paper, four specimens of CFST column joints with endplates and long bolts are tested in the scenario of progressive collapse. Flush endplate and extended endplate are both adopted in this study. The experimental results show that increasing the thickness of the endplate could improve the behavior of the joint, but delay the mobilization of catenary action. The thickness of the endplate should not be relatively thick in comparison to the diameter of the bolts, otherwise catenary action would not be mobilized or work effectively. Effective bending deformation of the endplate could help the formation and development of catenary action in the joints. The performance of flexural action in the joint would affect the formation of catenary action in the joint. Extra middle-row bolts set at the endplates and structural components set below the bottom beam flange should be used to enhance the robustness of joints. A special weld access hole between beam and endplate should be adopted to mitigate the chain damage potential of welds. It is suggested that the structural components of joints should be independent of each other to enhance the robustness of joints. Based on the component method, a formula calculating the stiffness coefficient of preloaded long bolts was proposed whose results matched well with the experimental results.