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Research on Lateral Stiffness of Embedded Wall Board Steel Frame Structure
Yiling Chen, Jinliang Jiang, Jingzhong Tong
2023, 38(11): 1-9.   doi: 10.13206/j.gjgS22110501
Abstract(0) PDF (14106KB)(0)
Steel structure buildings have the characteristics of factory production, good seismic performance, recyclability, environmental protection and other characteristics. They are widely used in prefabricated buildings. In prefabricated steel structure buildings, embedded wallboards are often used as filling walls for steel frame structures. However, in the existing structural design theory, the period reduction factor is generally used to consider the influence of embedded wallboards on the lateral stiffness of steel frame structures. Sometimes, this causes a large difference between the simulated lateral stiffness of the frame and the actual stiffness, which is not conducive to refined engineering design. It is necessary to further study the influence of embedded wallboards on the lateral stiffness of steel frames. Therefore, in this context, in order to further study the changes of the lateral stiffness of steel frames caused by different influencing factors in the discrete connection between embedded wallboard and steel frame, ABAQUS finite element software was used to establish a structural model of steel frame with embedded autoclaved lightweight concrete(ALC) wallboard. The influence of the number of connection nodes and the stiffness ratio of the wallboard to the embedded wallboard steel frame structure(referred to as EWSF structure) was considered when connecting the ALC wallboard to the frame beam, the frame column, and the frame beam column together.
The results show that the lateral stiffness of EWSF structure is greatly improved compared with the steel frame structure without wallboard. According to different connection conditions, the improvement degree can reach 4 to 6 times. The results of multi parameter analysis show that the change of connection conditions has a greater impact on the overall lateral stiffness of EWSF structure. With the increase of the number of connection nodes, the initial lateral stiffness of EWSF structure when the ALC wallboard is connected to the frame beam increases more significantly than when it is connected to the frame column. Compared with the case when the ALC wallboard and the frame beam column are connected separately, the effect of the joint connection of the ALC wallboard and the frame beam column on improving the lateral stiffness of EWSF structure is more significant. When the structure has fewer connection nodes, the change of beam column connection has little effect on the lateral stiffness of EWSF structure. The lateral stiffness of EWSF structure increases with the decrease of the stiffness ratio of the embedded wallboard to the steel frame. Based on the model analysis and theoretical derivation of the influence of factors such as the number of connection nodes and the stiffness ratio on the initial lateral stiffness of the structure, the influence coefficient β of the initial lateral stiffness of the structure when the embedded wallboard is fully rigid connected to the steel frame and the influence coefficient α of the initial lateral stiffness of the structure when the embedded wallboard is discrete connected are introduced respectively. And the formula for calculating the initial lateral stiffness of the structure is proposed. The calculation result is consistent with the finite element analysis result, which can provide a certain reference for engineering design.
Coupled Vibration Analysis of Vehicle and Bridge of Simple Rigid Suspension Bridge in Mountainous Area
Ziwan Wang, Rui Li, Debiao Ning, Xiaozhang Li, Shuhao Liu
2023, 38(11): 10-19.   doi: 10.13206/j.gjgs22053002
Abstract(0) PDF (5111KB)(0)
Simple rigid suspension bridges, characterized by large spans, fast construction and low environmental requirements, are one of the bridge types often considered in the southwestern part of China. However, with the rapid development of transportation infrastructure, people are more concerned about the comfort and safety of bridges during operation. The requirements of the bridge are getting higher and higher, and the bridge will have a certain impact on the driving experience of vehicle under the combined action of factors such as the vehicle and the unevenness of the road. This paper uses the finite element software ANSYS to simulate and analyze a simple rigid suspension bridge in the mountainous area, and extract the natural frequency and mode shape of the structure. Referring to the power spectrum statistics method, the road surface unevenness is simulated on the MATLAB software by using the harmonic superposition method, and the influence of road surface unevenness on the coupled vibration response of the axle is analyzed. At the same time, with reference to the traffic load characteristics of low-grade highways in Yunnan, appropriate vehicle parameters such as vehicle speed and vehicle weight are selected, and a coupled model of vehicle and bridge is established through the displacement coupling method, and a single parameter of the vehicle is changed by the control variable method to analyze the vibration response of the bridge under the action of different vehicle characteristics. The time course curves of the vertical displacement and acceleration of the main nodes of the suspension bridge under different parameters are used to analyze the influence of road surface unevenness, vehicle weight and speed on the vibration response of the suspension bridge. The results show that:the increase of vehicle speed, the increase of vehicle weight and the increase of road surface roughness will increase the vibration response of the bridge, in which the vehicle speed is the main factor affecting the vertical acceleration vibration response of the bridge, the vehicle weight is the main factor affecting the vertical displacement response of the bridge, and the unevenness of the road surface has an effect on the vertical acceleration vibration response and the vertical displacement response of the bridge. Moreover, with the increase of vehicle speed, the road surface unevenness increases the vibration response of the structure. Based on this, it can provide a theoretical basis for analyzing the comfort and safety of pedestrians walking on bridges affected by vehicle-induced vibration, so as to select appropriate loading conditions to calculate the vibration response of the structure, and then evaluate the comfort of the bridge.
Construction Technology
Research and Analysis Simulation on the Installation Plans of an Irregular Steel Structure
Shanjiang He, Weimin Xu, Chunchun Yu, Bin Liu
2023, 38(11): 20-27.   doi: 10.13206/j.gjgs23052301
Abstract(0) PDF (13363KB)(0)
The irregular steel structures or steel-concrete composite structures of super high-rise buildings are not only subjected to very complex forces during the structural use stage, but also have particularly complex deformation and stress during the construction process. This project is a steel frame-core tube structure of special architectural form, with many oblique truss structures, whose top is strongly connected with the giant truss or core tube on the opposite side through horizontal members to be a "Mega-structure". There are significant differences in the stress forms of the main components of the steel truss before and after the overall structure synthesis. Therefore, it is considered that the vertical components and corresponding floors should be constructed layer by layer in the conventional sequence, while the diagonal steel truss should be assembled in place first, and the temporary support should be removed after the overall structure is formed, with the gravity load being applied at the same time. Besides, as the vertical stiffness of the core tube and truss varies greatly, the vertical deformation difference between them causes a large internal force on the member connected with the core tube. Because of this, in order to reduce the effect of vertical deformation difference, "release" is adopted in the design, which means the components next to the core tube adopt a method of subsequent fixation and installation to reduce the adverse impact of vertical deformation difference. In order to reduce the initial deformation and internal force of the structure in the process of construction, as well as achieve the above "release" requirements, two construction assembly plans, precise simulation and simplified simulation, were designed and formulated with considering the force requirement and the feasibility and economy of construction, and finite element program SAP2000 was used for calculation and comparison. The precise simulation plan refers to strictly following the construction sequence, fully considering the deformation and stress during the component assembly process, and accumulating them into the final internal force calculation and deformation control. Simplified simulation refers to forming most components in a computation model at once, with a focus on the impact of post installation and post consolidation of some components on the overall structure and related components. The main difference between the two schemes is that Scheme A considers that the newly assembled steel truss will be in a cantilever state for a period of time before the construction is completed, while Scheme B does not consider the impact of this part.
Taking a typical steel truss as an example, this article specifically analyzes and compares the calculation results of the internal forces of the members and node displacements of the two schemes. Due to particularity of the construction plan for this project, the calculation model and parameters are specially processed to achieve accurate simulation of some steps in the construction plan.
The results show that there is no significant difference in the internal force and deformation of the final state between the two simulation schemes, and the deformation modality and internal force distribution are similar. The variance of internal force in the final state of most components is less than 3%. According to the analysis results, the simplified simulation is selected to improve the analysis efficiency on the premise of ensuring the accuracy of calculation.
Research and Implementation of Construction Plan for Long-Span Steel Corridor in Egyptian CBD Project
Hao Yuan, Wenming Hu, Changbiao Huang, Junjie Ma, Ting Pan, Ciwen Heng, Xuelin Bi
2023, 38(11): 28-34.   doi: 10.13206/j.gjgS23021201
Abstract(0) PDF (18528KB)(0)
In recent years, long-span high-altitude conjoined steel structures have been widely used in various complex large-scale public buildings, such as the new headquarters building of CCTV in Beijing, Raffles City in Chongqing, and the Marina Bay Sands Hotel in Singapore, of which the construction methods are very complex and difficult. For the design of the hotel in the Central Business District(CBD) project in the new administrative capital of Egypt, the form of a high-altitude long-span steel structure corridor was also adopted. The steel structure corridor plane is arc type, a total of 2 layers, the height of the first layer is 9.0 m, the height of the second layer is 6.5 m, the maximum span of the outer arc is 43.0 m, the width is 24.0 m. The total weight of the steel structure corridor is about 600 t. According to the characteristic of steel structure corridor, and combined with domestic and foreign long-span high-altitude conjoined steel structures construction methods, two construction hoisting schemes were proposed according to the characteristics of the steel structure corridor. Scheme 1 adopts the method of "segmented hoisting and high-altitude connection". After installation completed on the ground, the fragments are hoisted in a reasonable order and the overall connection is completed in the air. Scheme 2 adopts the method of "high-altitude cantilever bulk installation". The steel truss members are hoisted one by one at the end support position, and are butted together at the mid-span position to form a space truss. Comprehensively considering factors such as construction period requirements, cost requirements, quality requirements, safety requirements, and the ability of local workers, the construction method of Scheme 1 was proposed.
The construction process simulation method was used to calculate and analyze Scheme 1. The results show that the vertical displacement of the main truss and the component stress ratio are small during the installation of the steel structure, the hoisting sequence is reasonable, and the lateral support is effective, which can meet the requirements of steel component stability and construction precision control during the construction process. The feasibility of the scheme has been verified. At the same time, in order to ensure the safety and quality of the construction process, a number of key control measures have been adopted. Super crawler crane was used to ensure the safety of the hoisting process; temporary supports were set to ensure the stability of components during the construction process; and adjustable tie rods were set to control the levelness of components; it set strict control the daily work time to avoid temperature differences from affecting the installation accuracy, etc.
Monitoring and Analysis of Lifting Process of High-Altitude Conversion Steel Truss Structure
Chaoqun Zhao, Mingming Dong, Xiaofei Gao, Lei Zhang, Zan Zhang, Guojun Sun
2023, 38(11): 35-42.   doi: 10.13206/j.gjgs23050502
Abstract(0) PDF (10537KB)(0)
As a lightweight and high-strength structural system, steel truss has excellent seismic performance. The application of steel trusses to the conversion layer of residential buildings can greatly improve the seismic capacity of the entire residential structure and provide a safer living environment. Compared with the traditional concrete structure, it is more lightweight, less self-weight, has faster construction speed and can achieve large-span column-free design, provide more flexible spatial layout, and improve space utilization. Therefore, steel trusses are widely used in modern residential structures. However, due to the huge volume of steel trusses and the high precision requirements for lifting, the lifting operation is facing great challenges. At present, there are relatively few systematic and normative studies in the field of high-rise steel truss lifting. Therefore, it is necessary to study the stress and deformation of key parts of steel truss in the lifting process, so as to provide scientific basis and guidance for the lifting process, improve work efficiency and safety.
Based on the steel truss transfer floor project of Qinhuangdao Jinmeng Bay Phase II residential building, this paper establishes an accurate three-dimensional finite element model through the finite element software ABAQUS. The lifting points are set at both ends of the steel truss, and the constraint mode is hinged. The lifting scheme of the project is simulated and analyzed. Through the finite element simulation, the stress and deformation of the steel truss in the lifting process can be simulated, which provides a basis for the selection of measuring points in the key parts of the construction process. The stress and strain of the key components in the lifting process are monitored in real time, and the simulation results are compared with the actual monitoring data. The results show that the maximum stress obtained by simulation is located near the left hanging point of the second truss. The stress level of the whole truss component is much lower than the yield stress of the component, and the steel truss has sufficient strength to resist the load. The maximum vertical deformation is located in the middle of the truss span and meets the requirements of the engineering code. The deformation of the steel truss is controlled within a reasonable range. In the process of lifting, different lifting points are subjected to different lifting reactions. The lifting points with large lifting reactions will cause the hydraulic cylinder in the hydraulic system to respond differently when subjected to pressure, resulting in asynchronous lifting stress, causing stress concentration at the lifting point, but its stress is still within the safe range; real-time monitoring of the truss lifting process can accurately obtain the stress and deformation of the key parts, which is convenient for fine-tuning during the lifting process and ensures the safety and accuracy of the lifting. The monitoring value is slightly smaller than the simulation value, and the actual lifting of the project is safer than the simulation analysis. The accuracy of the finite element analysis and the lifting scheme is verified, which provides useful experience for improving the safety and stability of the project and provides reference for subsequent similar projects.
Design Discussion
Why Requiring Frame Capable of Resisting at Least 25% of Prescribed Seismic Forces in Dual Systems
Genshu Tong
2023, 38(11): 43-45.   doi: 10.13206/j.gjgS23022720
Abstract(0) PDF (3338KB)(0)
Static behavior of resisting lateral-force of steel frame, compressive and tensile braces is reviewed, emphasis is put on the deteriorating of compressive capacity of the brace as the lateral drift increases. Two series of dual structural systems are analyzed to reveal their lateral force-drift behavior, the lateral capacity ratio of frame and braces is 1:1 and 1:3 respectively. It is found that, although the contribution of the compressive brace decreases continually, the curve of the series with 1:1 ratio does not deteriorate as the lateral drift increases, due to coming into play of the frame's capacity; while the series with 1:3 ratio has a 20% decrease in the total lateral capacity due to weaker compensating capacity of the frame. As the 20% decrease is almost the maximum amount that is acceptable by a system with good aseismic behavior, it implies that if the frame cannot resist at least 25% of the seismic force, the aseismic behavior will be short of expectations.
Hot Spot Analysis of Steel Structures
2023, 38(11): 46-46.  
Abstract(0) PDF (390KB)(0)