To discuss the structure design and optimization of building curtain wall, the dynamic characteristics of point supported glass curtain wall system are analyzed by the finite element method. The various technologies are made use of, and according to the characteristics of the structure system, the finite element analysis model with steel structure glass plate beam element and shell element as the basic elements is established. Then, the dynamic characteristics are analyzed, and the modal parameters such as inherent frequency and vibration type are identified. The research results show that the node displacement response power spectrum under the load of wind is obtained, which provides the basis for rationally optimizing the structure. Based on the above findings, it is concluded that the optimization design based on finite element model has a wide significance, which is a useful attempt to reduce the blindness of design and has great engineering significance and application value.
The characteristics of point supported glass curtain wall in glass curtain wall is that it has high permeability, and the supporting structure is concise and lively, which shows the melody beauty of point connecting structure and modern sense of glass support structure system. With the progress of glass technology and a large number of public building construction, point supported glass curtain wall is more and more widely applied at home and abroad [
With the rapid development of modern engineering technology, higher requirements have been put forward for the modeling and applicability of buildings. The supporting structures in buildings are becoming more and more light, and the requirements for structural dynamic characteristics are increasing. As the building envelope structure, the structure of the curtain wall is becoming lighter and lighter, so the vibration of the structure is more prominent. Building curtain wall industry is an edge industry. Compared with the main structure of building, the analysis of its dynamic characteristics is still a blank [
The whole structure of the point supported glass curtain wall is composed of a glass faceplate, a supporting structure, a supporting structure connecting the glass and the supporting device. Glass curtain wall facade dimension is 62.7 meters in width, and 20.95 meters in height, and the entire building has been included. According to the characteristics of the project, in order to ensure transparent glass properties and buildings inside and outside space circulation and integration, two schemes are put forward. Scheme 1 is that the top of tapered I-beam and steel pipe span out is connected with tube type steel frame structure; and scheme 2 is that the top with variable cross section I-beam spanning out is connected with Fishbelly steel structure [
The glass of point supported glass curtain wall is connected to point supported glass curtain wall supporting structure through a series of floating connection systems, and the thickness of the glass relative to the area is less than 1%. As a result, the glass unit is established by using shell 63 housing unit, which is connected to the supporting structure at the four corners of the glass. In the support structure, tapered I-beam root is fixed connected with the building, and the end, with the ear plate and pin, is connected with tube type steel frame or lenticular steel truss hinge. Therefore, the beam 44 element is used to establish tapered I-beam unit, root fixed constraint, and the end of the tubular steel frame or Fishbelly steel truss is coupling for hinge. Tubular steel frame or Fishbelly steel truss uses pin shaft to connect with the ear plate, and the ear plate is fixed on a concrete foundation. In consequence, the beam element is adopted to build the tubular steel frame or lenticular steel truss element, and the upper part of tapered I-beam girder is hinged with the lower coupling, and the coupling is hinged with the base.
Considering the basic principle of finite element method, the finer the mesh division is, the closer it is to the actual structure, but the time of dynamic analysis and calculation will increase exponentially. The two factors influence each other and restrict each other, so we must consider it as a whole. Under the premise that the calculation accuracy is satisfied, the machine time is shortened as much as possible, and the operation efficiency is improved. As mentioned above, according to the characteristics of the point supported glass curtain wall structure system, finite element analysis model with steel structure glass plate beam element and shell element as the basic element is established, and the reasonable connection and boundary conditions between structures are rationally simulated [
Scheme 1 (tubular steel frame) structure description: Cross section of variable section I-beam is 300 *300 to 300 *700; steel plate thickness is 14 mm; pipe type steel frame riser is
span I-beam span is 7 m; vertical height and spacing of pipe type steel frame are 20.95 m and 5.9 m, respectively. 10 + 1.52 PVB + 8 mm transparent laminated glass is applied, the grid division size is 1.6 *1.9 m, and a series of 250 floating barge systems are used.
Scheme 2 (Fishbelly steel truss) structure description: Cross section of variable section I-beam is 300 *300 to 300 *700; steel plate thickness is 14 mm; Fishbelly steel truss front riser is
After the finite element analysis, the point supported glass curtain wall system is discretized into a system with n degrees of freedom. Dynamic equilibrium equation is:
In the above formula,
Without external forces, that is
In the free vibration, we set the nodes have simple harmonic vibration, and its displacement can be expressed as:
In (3),
The necessary and sufficient condition with not zero solution of (4) is:
Now that in the general finite element analysis, the degrees of freedom of the system are of variety, and in the study of the dynamic characteristics, we often only need to know a few lower order eigenvalues and corresponding eigenvectors, in finite element analysis, some effective solutions that adapt to the above features are developed [
Block Lanczos algorithm used in the study means to use a group of vectors to realize Lanczos recursive computation. This method, similar to the subspace method, is accurate, and the speed is faster and the solution efficiency is higher. No matter what kind of solution machine is used for the solution, Block Lanczos method can automatically apply sparse matrix equation to solve the problem, which is especially suitable for large eigenvalue problems.
Because only the lower natural frequencies and modes have great influence on the structural dynamics, the natural frequencies and modes of the point supported glass curtain wall system are calculated mainly in this paper.
The modal analysis of the structure is helpful to the further study of the structural vibration and provides a reliable basis for the structural design. For the general structure, the vibration of the structure can be discretely expressed as a linear combination of the order natural frequency. The dynamic effect of low order natural modes is stronger than that of the high order modes. As a result, the low order modes determine the dynamic characteristics of the structure.
Taking the study of modal structure of point supported glass curtain wall as the major work,
Compare scheme 1 and scheme 2, the steel structure weight of scheme 1 and scheme 2 is 34,806 kg and 38,399 kg, respectively. For the steel structure weight, scheme 2 is 1.1 times of scheme 1. The steel materials consumed has no great difference, while the dynamic characteristics of the two schemes are significantly different. The natural frequency in the first order of scheme 1 is only 0.75410 (HZ), no more than 35% of the natural frequency 2.2084 in the first order of
Order number | Natural frequencies (HZ) | Modes description |
---|---|---|
1 | 0.75410 | The left and right part with large size has greater vibration amplitude than the middle part. |
2 | 0.77060 | The left side―backward, the right side―forward, doing antisymmetric vibration. |
3 | 0.96608 | The left and right―forward, the middle part―backward. |
4 | 1.0888 | The left, right and middle parts, in their own range, do forward and backward antisymmetric vibration. |
5 | 1.3795 | The middle part―backward, the left and right parts― forward, and the external side vibrates backward. |
Order number | Natural frequencies (HZ) | Modes description |
---|---|---|
1 | 2.2084 | The left side―backward, the right side―forward. |
2 | 2.2084 | The left and right―forward, the middle part―backward, accompanied with torsional vibration of Fishbelly steel truss. |
3 | 2.4213 | The left, right and middle parts, in their own range, do forward and backward antisymmetric vibration. |
4 | 2.4218 | Middle part―backward, the left and right parts―forward, and the external side vibrates forward. |
5 | 2.8850 | Middle part of right side―backward and the two sides―forward; middle part of left side―forward and the two sides―backward. |
scheme 2, and its dynamic stiffness is worse.
The fluctuating wind is a stochastic process, and the most widely used one is Davenport spectrum. And the wind spectrum is expressed as:
With the use of the numerical analysis software, the spectrum diagram calculated in accordance with formula programming is shown in
According to Davenport spectrum, the fluctuating wind has the largest peak in the low frequency range of 0 - 1 (Circular frequency
This paper uses CAE technology to analyze the dynamic characteristics of finite element analysis of point supported glass curtain wall structure system, so as to have a comprehensive understanding of dynamic characteristics of point supported glass curtain wall structure. In addition, based on the dynamic characteristics research results, the pseudo excitation method is used for random vibration analysis. The results show that the CAE technology is a feasible and effective analysis method in modern architectural structure design, so it is necessary to study the technology of point supported glass curtain wall system. The finite element method can accurately and effectively determine the dynamic characteristics of complex structures, and has important engineering application value.
I would like to express my gratitude to all those who helped me during the writing of this thesis. I gratefully acknowledge the help of my supervisor who has offered me valuable suggestions in the academic studies. In the preparation of the thesis, she has spent much time reading through each draft and provided me with inspiring advice. Without her patient instruction, insightful criticism and expert guidance, the completion of this thesis would not have been possible. I also owe a special debt of gratitude to all the professors in Foreign Languages Institute, from whose devoted teaching and enlightening lectures I have benefited a lot and academically prepared for the thesis.
Gong, Z.W., Zeng, B., Han, W.C. and Xue, S.D. (2017) Discussion on Structure Design and Optimization of Building Curtain Wall. Open Journal of Civil Engineering, 7, 303-310. https://doi.org/10.4236/ojce.2017.72020