With the increasing complexity of civil engineering and the increasing requirements of engineering practice for civil engineering analysis and calculation, the application of finite element technology in civil engineering is becoming more and more extensive. This paper mainly introduces the application of the international large-scale general finite element software abaqus in civil engineering, mainly including the application in construction engineering, bridge engineering and geotechnical engineering, in order to provide some references for relevant engineering designers.
With the increasing complexity of civil engineering, engineering practice has higher and higher requirements for civil engineering analysis and calculation, and the continuous development of computer technology, the application and research of finite element technology in civil engineering have also been well developed. At present, large-scale general-purpose finite element software widely used in the civil engineering industry includes ANSYS, MARC, and ABAQUS. Based on the engineering background, this paper introduces the analysis examples of the large-scale general finite element software abaqus in construction engineering, bridge engineering, geotechnical engineering, etc., the purpose of this paper is not to describe the analysis process of finite element in detail, but to introduce some analysis examples, hoping to provide reference for relevant designers.
Abaqus is a powerful finite element software for engineering simulations that solves problems ranging from relatively simple linear analyses to many complex nonlinear problems. abaqus includes a rich library of elements that can be used to model arbitrary geometries. It has a library of various types of material models that can simulate the performance of typical engineering materials, including metals, rubbers, polymers, composites, reinforced concrete, compressible hyperelastic foams, and geological materials such as soil and rock. As a versatile simulation tool, abaqus can solve a large number of structural (stress-displacement) problems, as well as many problems in other engineering fields, such as heat conduction, mass diffusion, thermoelectric coupling analysis, acoustic analysis, geotechnical analysis (fluid permeability stress coupling analysis), and piezoelectric media analysis.
Abaqus offers a wide range of features to the user and is very simple to use. A large number of complex problems can be easily simulated with different combinations of option blocks. For example, the simulation of a complex multi-component problem is done by combining an option block that defines the dimensions of each component with the corresponding material properties option block. In most simulations, even for highly nonlinear problems, the user only needs to provide some engineering data, such as the shape of the structure, material properties, boundary conditions, and load cases. In a nonlinear analysis, Abaqus automatically selects the corresponding load increment and convergence limit. Not only is he able to select the appropriate parameters, but he is also able to continuously adjust the parameters to ensure that the exact solution is obtained efficiently during the analysis. By precisely defining the parameters, the user has good control over the numerical calculation results. Due to its excellent analytical capabilities and reliability in simulating complex systems, Abaqus is widely used in industry and research in various countries.
With the continuous complexity of building structures, the continuous emergence of complex building structure nodes and column bases, and the dynamic elastoplastic analysis of structures under rare conditions, finite element software is required.
The author has used abaqus software to analyze and study reinforced concrete components, concrete-filled steel tubular components, steel-concrete-filled steel tube components, rectangular steel tube bending and torsional components, prismatic steel pipe compression-bending components, hollow box-shaped steel-reinforced concrete components, section steel concrete components and concrete-filled steel tube superimposed columns, etc., which provides a good reference for the practice of related projects. On this basis, the finite element analysis of the concrete-filled steel tube column-reinforced concrete ring beam joints, rectangular concrete-filled steel tube T-joints, steel structure cast steel joints, and concrete-filled steel filled columns and column bases used in building structures was carried out by using ABAQUS software, which provided a reference for improving the construction drawing design of related projects. Due to space limitations, some typical application examples are introduced.
Due to the interaction between steel pipe and concrete, concrete filled steel tubular has the advantages of high bearing capacity, good plasticity and toughness, convenient construction, good fire resistance and good economic effect. The key problem in simulating concrete-filled steel tubular components is to determine the reasonable constitutive relationship of the materials and to deal with the interfacial contact between the steel tube and the concrete. Fig. 1 shows the comparison of the calculation curves and experimental curves of a typical concrete-filled steel tube under axial stress, and Fig. 2 shows the cross-sectional shear stress distribution of a typical round concrete-filled steel tube member under pure torsional stress.
Fig.2 Section shear stress distribution of round concrete-filled steel tube under pure torsional stress.
The authors have used abaqus software to conduct in-depth research on the working mechanism of concrete-filled steel tubular components under complex stress conditions, and achieved good results, and the relevant research results have been approved by the Fujian Provincial Engineering Construction Standard "Technical Regulations for Concrete-filled Steel Filled Steel Tube Structures" DBJ13-51-2010, Jiangxi Provincial Engineering Construction Standard "Technical Regulations for Concrete-filled Steel Filled Steel Tube Structures" DB36 J001-2007, and Gansu Provincial Engineering Construction Standard Technical Regulations for Concrete-filled Steel Tube Structures》 J11395-2009 adopted. Reinforced concrete has the advantages of high strength, good fire resistance and seismic performance better than that of concrete structures, and is widely used in practical engineering. In the finite element analysis model of reinforced concrete components, it is necessary to consider the bond-slip relationship between the reinforcement and the concrete. The spring element Spring2 provided by ABAQUS software was used to simulate the contact behavior between steel and concrete. The rebar and concrete nodes are connected with three Spring2 spring elements to simulate the contact behavior of the rebar and concrete nodes in three directions in 3D space. Two spring elements perpendicular to the direction of the rebar are used to simulate the gripping force of the surrounding concrete on the rebar, and the spring rate can be taken as a large number. Fig. 3 shows the finite element model of a typical reinforced concrete beam and the distribution of stress and strain during failure.
Fig. 3 Model of typical reinforced concrete beam and distribution of stress and strain.
For long-span space structures, the upper roof is a steel structure, and the lower part is usually a concrete structural system. In order to safely transfer the superstructure loads into the concrete structure (concrete columns and shear walls), reliable nodal supports should be used in the design. Due to the large load of the column base joint and the key part with complex stress, its reliable design is directly related to the safety of the whole structure. However, there is no clear basis for the mechanical property analysis and bearing capacity check of the cast steel joint and the concrete cap of the complex structure below, in order to ensure the safety and reliability of the structure, the finite element analysis of the column base is carried out by abaqus. For this kind of complex three-dimensional solid model, the direct use of abaqus software to model, the efficiency is low, usually civil engineering technicians use aut0cad software for solid modeling, aut0cad software is also the software that most civil engineers are familiar with. Fig. 4 shows the analysis results of a complex column base, which plays a good role in guiding and improving the structural design.
In the analysis of bridge structures, there are generally two types of plane rod system analysis software and space finite element software, mainly including G**S, **X, BRIDGE DOCTOR, MIDAS, ABAQUS, ANSYS, SAP2000, ALGOR, etc. At present, the development of plane analysis software is relatively perfect, which solves a large number of practical engineering problems, but can not well simulate the spatial action, local stress and contact simulation of the structure.
With the continuous development of social economy and the continuous improvement of transportation infrastructure, the bridge structure that plays an important role in the transportation hub has put forward the requirements of "lightweight, high strength, long span, environmental protection and beauty". At present, it is difficult to analyze and calculate this kind of bridge with the commonly used bridge-specific software, and the finite element software abaqus is used to model and analyze this new type of bridge, and the mode shape modes of the first two orders of the typical example are shown in Fig. 6.
Fig.6. An example of a typical steel web-concrete composite bridge.
Corrugated steel web PC composite box girder bridge is a new type of bridge structure that was applied in France in the 80s of the 20th century. This structure replaces the concrete with the corrugated copper plate as the web of the box girder, and adopts the external prestressing technology to realize the lightness of the main girder, increase the spanning capacity of the bridge, and conform to the development trend of today's bridge. Because the theoretical research results of the structure can not fully meet the needs of engineering design, it is unsafe to design the structure by the general planar rod system analysis software, and we can better meet our design requirements by using abaqus software. Fig. 7 shows the renderings and abaqus finite element model of the Shenzhen Nanshan Bridge (using corrugated steel web PC composite box girder) designed by Shenzhen Municipal Design and Research Institute.
Because the abaqus software provides a constitutive model that truly reflects the soil properties, such as the yield characteristics and dilatancy characteristics of the soil, and the abaqus software has a powerful contact surface processing function, it can well deal with the interaction between soil and structure. In addition, ABAQUS provides an infinite element element, which can simulate the boundary conditions at infinity of the foundation, so the ABAQUS software has good adaptability in rock engineering. The following is a typical example of an analysis.
Slope stability analysis is one of the topics that has not been satisfactorily solved in the earliest test of classical mechanics, and the finite element method is used to analyze the slope stability problem to overcome the shortcomings of the traditional limit equilibrium method to assume the soil strip as a rigid body, and can consider the elastic-plastic constitutive relationship of the soil, as well as to simulate the instability process of the slope and the shape of the slip surface, which has been more and more widely used. The strength reduction elastoplastic finite element method is a numerical analysis method that is widely used in slope stability analysis and has a good prospect, which combines the strength reduction technology with the elastoplastic finite element method, and analyzes the slope stability by adjusting the reduction coefficient under the given evaluation index, so as to obtain the minimum stability safety factor of the slope. The author uses abaqus software and strength reduction technology to analyze the stability of a subgrade slope, and obtains good analysis results, and the analysis results are also verified by the professional geotechnical analysis software plaxs, and the correlation type and analysis results are shown in Figure 8.
Fig.8. Finite element analysis of subgrade slope.
Pile-soil interaction is a rather complex engineering problem, in order to determine the complete load-settlement relationship of a single pile, that is, the p-s curve, the traditional method is to do the destructive load test of the pile, but for the large diameter pile to carry out this kind of test, both from the loading conditions and from the test technology has great difficulty, so it can be through the means of finite element analysis. As mentioned above, abaqus provides a relatively complete soil constitutive model and a good function to consider pile-soil contact, so it is more convenient to carry out pile-soil interaction analysis. The initial in-situ stress and lateral force coefficient are set in *initialconditions, and the equilibrium can be achieved in geostatic. Fig. 12 shows the soil stress analysis of a typical pile subjected to vertical loads. In order to eliminate the influence of the analysis boundary on the analysis results, the pile end was extended downward by 1 times the pile length, and the horizontal direction was taken as 20 times the pile diameter.
Fig.9 Pile ** same work analysis.
This paper mainly introduces the application of the international large-scale general finite element software abaqus in civil engineering, mainly including typical application examples in construction engineering, bridge engineering, and geotechnical engineering, in order to provide some reference for relevant engineering designers, hoping to play a role in "throwing bricks and attracting jade".