Current Issue

2022, Volume 37,  Issue 3

Research
Research on Calculated Method of Initial Lateral Stiffness of Corrugated Steel Plate Shear Walls with Openings
Enfeng Deng, Liang Zong, Yang Ding
2022, 37(3): 1-9. doi: 10.13206/j.gjgS21100101
Abstract:
Corrugated steel plate is widely used as lateral-force resisting component for modular steel construction(MSC). Meanwhile, openings served as windows or doors are commonplace for the corrugated steel plate shear walls(CSPSWs) in MSC for the realization of the building function. However, there is a lack of research on the lateral performance and design method on CSPSWs with openings, which hinders the promotion and application of MSC to some extent.
Elaborate finite element model(FEM) was developed for CSPSWs with openings by general finite element software ABAQUS based on the previous cyclic tests on CSPSWs with openings, considering geometric nonlinearity, material nonlinearity and geometrical imperfection. The reliability of the FEM was verified against the test results and the failure mechanism of the specimens was revealed. It is indicated that the developed FEM can well predict the initial lateral stiffness, shear capacity and failure modes of CSPSWs with openings under low cyclic loading. Stress concentration exists in the corner regions of the opening under earthquake. It is recommended that the opening should be located off the end of the diagonal tension field to guarantee the deformation capacity and ductility of the specimen.
The theoretical calculating model of CSPSWs with openings was established. CSPSWs with openings was equivalent as some series-parallel connected springs. The theoretical formulas for predicting the initial lateral stiffness of CSPSWs with openings were deduced and validated against the related test and numerical results. It is indicated that the proposed formulas can predict the lateral stiffness of CSPSWs with openings with well precision. Parametric analysis was conducted to reveal the influence of the thickness of the infill panel, the height of the crest of the infill corrugated steel plate and the location of the opening on the initial lateral stiffness of CSPSWs with openings. The results indicate that the location of the opening location affects the initial lateral stiffness of CSPSWs with openings significantly. The opening is suggested to be located near the outer frame to obtain higher lateral stiffness. The present study provides calculating method for initial lateral stiffness of CSPSWs with openings and the location of the openings is recommended.
Mechanical Performance Analysis of Concrete Filled Steel Tubular K-joints Subjected to Random Local Corrosion
Wenjie Zhao, Jingyi Zhang, Chao Hou
2022, 37(3): 10-19. doi: 10.13206/j.gjgS21100801
Abstract:
Concrete filled steel tube(CFST) composite truss structures have superior structural performance and economic advantages due to the clear force transmission and excellent integrity. These structures have been widely used in large-scale infrastructures that serve in corrosive environments, such as cross-sea bridges, coastal towers, and offshore platforms. In such structures, the main bearing members and key connecting joints are affected by corrosion and sustained loads, which is a severe challenge to the safety and reliability of the structure. In practice, randomly distributed local corrosion normally occurs on the surface of steel. Due to the limitations of test facilities and numerical simulation technology, the research on CFST K-joints with random local corrosion is still limited, which restricts the understanding of the life-cycle performance and the establishment of scientific design methods for those structures. Thus, this paper aims to study the full-range performance of CFST K-joints subjected to random local corrosion and sustained load.
A detailed finite element analysis(FEA) modelling was presented to study the performance of CFST K-joints under random local corrosion and sustained load, which could take the random local corrosion of the outer steel tube and the complex time-dependent effects of the nonlinear material confinement into consideration. Based on the distribution trend of random local corrosion for steel structure in actual ocean environment, the simulation of random local corrosion on the surface of chord and brace was realized by combining Python and ABAQUS simulations, which can generate random pit distribution, identify corrosion elements and automatically mesh on the pitting corrosion area. In addition, the long-term characteristics of the core concrete and the time-dependent deterioration of nonlinear steel-concrete composite action are considered in the model. The established model was validated against reported test data and then used for further analysis, including the possible failure modes, the full-range load-deformation relationships, the residual ultimate strength, and the influence law of important parameters such as corrosion type(uniform distribution or random local distribution), volume loss rate, etc. The key parameters affecting the performance of CFST K-joints with random local corrosion were systematically evaluated, including the volume loss rate, the material properties, the diameter-ratio between chord and brace, the chord member diameter-thickness ratio, etc. Finally, simplified calculation methods for the residual strength of CFST K-joints were proposed based on parametric analysis. The accuracy of the formula was verified by the finite element results.
The results show that the failure mode of CFST K-joints with random local corrosion is mainly the local buckling of the compression brace, while the stress concentration tends to occur in the pitting corrosion concentrated area that leads to the local buckling failure. Due to the concrete infill in the chord, the mechanical performance of the joints is improved. Compared with uniform corrosion, local corrosion has a more significant effect on the performance of CFST K-joints while the random distribution of local corrosion further reduces the bearing capacity of CFST K-joints. When the volume loss rate remains constant, the ultimate joint capacity with random local corrosion is found about 13.2% lower than that with uniform corrosion; the volume loss rate of brace controls the ultimate strength of CFST K-joints.
Numerical Study on Cold-formed Steel Built-up Stiffened Cruciform Specimen Subjected to Axial Load
Qiliang Miao, Zhensen Song, Zhongxiang ZHANG
2022, 37(3): 20-27. doi: 10.13206/j.gjgS21103101
Abstract:
Either flexural and torsional buckling may occur when a cold-formed steel built-up stiffened cruciform column subjected to axial compression. A numerical investigation was performed to study the failure modes and ultimate resistances of cold-formed steel thin-walled columns made from built-up stiffened cruciform sections. In the finite element simulations, built-up columns with three different cross-sectional sizes were designed and specimens with various slenderness ratios and bolt spacing were investigated. The range of the slenderness ratios of the specimens was from 20 to 140 at an interval of 20. Three bolt spacings of 150, 300, 450 mm were employed to study the built-up effect on compressive resistance of the specimens.
The results show that the failure modes of such columns were dominated by their slenderness ratios. Overall torsional buckling occurred for specimens with λx<λω, while overall flexural buckling took place for specimens outside this range. The ultimate resistances were affected by the slenderness ratio, and the ultimate resistance of columns with the same cross-section size decreased as the slenderness ratio increased. The stiffness and ultimate bearing capacity of the column decreased when the bolt spacing increased, but such an effect was found insignificant within common bolt spacing ranges and the failure modes were not affected by the bolt spacing. The axial bearing performance of the built-up section columns was found to be inferior to their integral section column counterparts with same cross-sectional sizes, and this was more obvious for the columns failed by torsional buckling.
Design
Structural Analysis and Design of Guangzhou Show Theatre Roof
Lin Huang, Longgui Pu
2022, 37(3): 28-34. doi: 10.13206/j.gjgS21052501
Abstract:
Guangzhou Show Theatre is located in Huadu District of Guangzhou, which is a specific theme Theatre with a total building area of about 50 200 m2. The main structure adopted the frame core tube structure system, and the steel roof adopted single layer grid structure of free surface, with diameter of 105 m and height of 29.1 m. In order to meet the needs of the curtain, the steel roof structure was meshed into approximately 4 000 grids of triangle and quadrilateral with 3 m length of side.
It will make the load-transfered path unclear and increase construction difficulty when all numbers were designed to main forced components. The primary-secondary and the primary grid scheme were analyzed comparatively in order to select the better structure scheme. Comparative analysis of different boundaries models were carried out in order to confirm the most efficient boundary conditions. The whole model and independent model were analyzed comparatively in order to defining the scale of influence between the steel roof and the concrete structure. The static analysis and dynamic analysis was carried out in order to ensure mode, period of vibration and deformation was in a reasonable range. Buckling analysis was used to calculate the critical force and back calculate the calculation length of the element, so as to accurately check the strength of the element.
The following conclusions can be drawn from the result of analysis. 1) The primary-secondary grid structure scheme was adopted by comparative analysis, which not only had better mechanical performance, but also could reduce material consumption and construction difficulty. 2) The checking calculation results showed that maximum stress ratio of main member, secondary member and roof bracing member was respectively 0.78,0.85 and 0.72. 3) The overall stability of the structure was analyzed considering material nonlinearity and geometrical nonlinearity by ANSYS.The load-displacement curve showed that the structure was elastic under 1.8 times nominal load and the ultimate load was 4.6 time as the nominal load. Connections were specifically design in order to mechanical property of connections meet the calculation assumptions. 4) Hinged connection joint was set up between the roof members and the first, third and fifth concrete floor. 5) The structure static response analysis and dynamic response existed difference among the whole model and independent model, so the whole model was adopted to calculate the steel roof structure.
Construction Technology
Simulation Analysis of High-altitude Scattered Assembly Construction Process of a Long-span V-shaped Column
Zhiyuan Jiang
2022, 37(3): 35-42. doi: 10.13206/j.gjgS21101603
Abstract:
Spatial steel structure has various forms and beautiful shapes. It is a structure with three-dimensional shape and three-dimensional stress characteristics. However, with the improvement of construction technology, there are many steel structures with great difficulty in installation and construction, such as special-shaped columns, variable elevation space trusses and long-span trusses, showing the characteristics of long span and complex stress. Taking a long-span unequal height truss roof of Nanyang South Railway Station as the carrier, the construction technology of unequal high-span space truss is complex, and there is a large cantilever span, which produces large deformation and high stress on its lower V-shaped column. From the perspective of the project itself, the project is a spatial inverted triangular steel truss structure with a cantilever part of 25 m, which belongs to a long-span cantilever structure. According to the analysis of structural stress, the stress of long-span cantilever structure is unfavourable. Firstly, under the action of vertical force and horizontal force, the bending moment and shear force at the root of the cantilever are large, and the stress of the node at the root is complex, which is easy to become a weak point. Once it is damaged due to large stress, the whole structure will form a mechanism, resulting in the collapse or overturning of the whole structure. Secondly, the cantilever structure is very sensitive to vertical earthquake resistance. If the cantilever length is large and the cantilever part is self significant, this effect will be very obvious. Third, the overall stability of the cantilever structure is poor, so it is necessary to check the overturning resistance of the structure and take some targeted balance measures.
Considering the scheme suitable for the project, the conventional sectional hoisting method should be adopted, which has the advantages of strong operability and high safety factor. The high-altitude welding quality can also be controlled through targeted measures to ensure the project quality, as well as the simulation analysis of finite element software in the construction process, the simulation of three-dimensional dynamic model used in the hoisting process, real-time interference detection, so as to ensure that the components are installed in place, and the construction scheme can be optimized in time to ensure construction safety and construction efficiency. Therefore, the main research contents of this paper:use MIDAS analysis software to simulate the construction process of V-shaped column with high-altitude scattered assembly, so as to ensure the safety and efficiency of subsequent construction; ANSYS analysis software is used to calculate and analyze the key connection points of V-shaped column, and then corresponding reinforcement measures are taken to ensure the safety and quality of the project.
The results show that:1) the structural stress changes gradually from 8.65 MPa to 31.9 MPa during column assembly, which is located at the bottom of column foot and in elastic working state. 2) In the column assembly process, the maximum structural deformation is located in the cantilever area, and its value is 9.54 mm, which is less than the specified limit of deflection, and the stress is 31.9 MPa, which meets the requirements. 3) In the process of column splicing, the maximum deformation value and maximum stress are generated in the assembly process of column cantilever area. After structural strengthening, the joint stress and deformation can better meet the design criterion of "strong joint and weak member".
Construction Technology of Mid-span Jacking Closure of Long-span Hybrid Beam Cable-stayed Bridge
Guifeng Lin
2022, 37(3): 43-49. doi: 10.13206/j.gjgS21052502
Abstract:
The actual line type of the Shishou Yangtze River Highway cable-stayed bridge structure tends to the theoretical line while meeting the force requirements of the cable, main tower, and main girder. At the same time, it can ensure the safety of the bridge structure closure construction. It established a geometric control method closure scheme of the Shishou Yangtze River Highway Bridge based on theoretical analysis based on many factors such as the characteristics of the bridge structure, mechanical characteristics, estimated closing time and process implementation risks.
First, after comprehensively analyzing the advantages and disadvantages of the geometric control method and the temperature-matching cutting method, the geometric control method was used for closing construction. Secondly, it studied the mid-span push-closure scheme. First the special conditions related to the mid-span closure was found, and then the implementation control conditions of the push-closing process were found out, such as:arrange of the closing time, calculation of the length of the closure section and the pushing displacement, etc., and then analysis on the top reasoning. Once again, the mid-span was closed according to the steps. Finally, the key technology of mid-span closing was analyzed. 1) Before closing the dragon, the longitudinal jacking device of the South Tower was installed. The jacking device must not only be equipped with a forward jack, but also a reverse jack. 2) When the dragon was closed, it needed to be adjusted within the allowable range through the previous control process in advance, and the body deviation would not be adjusted when the dragon was closed. 3) The locking device of the closure must have good vertical and lateral flexural rigidity to ensure that the axis of the main beam was offset and the shape of the closure could maintain the adjusted state after the push was completed. After adjusting the shape of the closure, a tie rod was installed to complete the locking of the closure section, restricted the horizontal and vertical freedom of the closure section, and bore part of the weight of the closure section at the same time, so as to meet the requirements of the circular seam welding of the closure section.
By applying jacking force to the closure, the closure section of the one-sided lifting was embedded in the closure, eliminating the difference between the length of the closure section and the width of the closure due to the influence of temperature, and the lack of space for closure operations. It was safe, fast, and accurately realized the construction of the whole bridge closure.
Hot Spot Analysis of Steel Structures
2022, 37(3): 50-50.
Abstract: