CN1644826A - Lattice loading method for treating random distributed load on curved surface - Google Patents

Abstract

A grid load method for processing distributed loads on arbitrary spatial surfaces in the technical field of civil and architectural engineering, which expands the concept of surface loads as grid loads for processing distributed forces on spatially closed grids. The processing steps are as follows: (1) Using a three-dimensional view Revolving Unwrap converts a spatial surface into a 2D viewing plane. (2) Use the view projection surface to form a closed grid that composes the curved surface. (3) Establish grid load data: sequentially record the serial numbers of the cells that make up each side of the closed grid to form a description of the grid shape; the grid load unit is an independent graphic with corresponding grid serial numbers, coordinates, and applied load parameters and other attributes. (4) The distributed load in the closed grid area is derived to the surrounding units. The method of the present invention is simple and fast in processing, can process distributed loads on complex spatial grid surfaces in one operation, and can be used to process wind pressure, water pressure and other types of loads, and at the same time, the grid load unit is used as an independent figure with more advantages Great adaptability and flexibility.

Description

Mesh Loading Method for Dealing with Distributed Loads on Surfaces in Arbitrary Space

technical field

The invention relates to a method for processing distributed loads on arbitrary spatial curved surfaces, in particular to a grid load method for processing distributed loads on arbitrary spatial curved surfaces. It belongs to the technical field of civil engineering.

Background technique

The loads acting on civil and architectural engineering can be divided into two types according to the action form: one is the load directly acting on the beams, columns and walls of the main structural components, such as the gravity load of the filling wall on the beam; the other is acting on the structural maintenance Or distributed loads on non-mainly stressed components, such as building roof loads and wind pressure loads on the outer surface of structures. The latter type of load does not directly act on the main components of the structure. Since in structural calculations, non-main load-bearing components such as floors and walls generally do not participate in structural calculations, these distributed loads need to be derived to beams, columns, walls, etc. on the main components. At the same time, since the floor slab and other maintenance components are supported by beams and walls, even if the floor slab participates in the overall calculation of the structure, it is necessary to guide the distributed load of the floor slab to the main structural components such as beams and walls. Only for the distributed load on the roof of the horizontal building, the prior art has relatively complete processing methods.

There is no perfect method to deal with the distributed load of space sloping roof and arbitrary curved surface. On the one hand, the operation is relatively cumbersome, and boundary nodes need to be selected separately for a single grid. On the other hand, the function is relatively single, and it can only handle the gravity load of the building roof. The problem of distributed load processing of arbitrary surface is different from the problem of surface meshing in general finite element. Because in the problem of surface meshing, there is a complete geometric description of the surface itself. However, the surface in distributed load processing is a grid composed of the edges of linear components such as space beams and columns, and planar components such as walls, and there is no real surface. And in the actual structure, there are not only components inside the grid surface, but also components outside the grid surface, and these components are criss-crossed in space. Effectively separating the surface where the distributed load is located and forming a geometric description of the surface is the key to deal with the distributed load on the surface.

After searching the literature of the prior art, it was found that Wang Lixin's paper "Skills of Building Structure Analysis Program Guided Load" published in the 2nd issue of "Building Structure" in 1996, involved the processing of the distributed load on the roof of the horizontal building. However, it cannot be applied to the distributed load processing of arbitrary curved surfaces.

Contents of the invention

The purpose of the present invention is to address the deficiencies of the existing methods for processing distributed loads on roofs and spatial curved surfaces, and propose a grid load method for processing distributed loads on arbitrary spatial curved surfaces. The roof and space surface can be processed at one time; second, the surface load processing function is expanded, so that it can not only be used for the processing of the gravity load of the building roof, but also for the processing of surface wind pressure, surface earth pressure, and water pressure. .

The present invention is achieved through the following technical solutions. The present invention expands the concept of surface load as a problem of distributed force on a closed space grid in a broad sense, and calls it grid load, so it is called grid load method. The steps to process mesh loads are as follows:

(1) Use the view projection surface to expand the spatial grid surface

Although the spatial grid surface has great arbitrariness and uncertainty, as a computer geometric model, it can always be transformed into a non-overlapping surface in the view plane through 3D view transformation. In this way, in the 2D viewing plane, the spatial surface is transformed into a 2D plane.

(2) Use the view projection surface to form a closed grid that composes the curved surface

According to the two-dimensional coordinates of the view plane of the grid surface, find each closed grid in the surface. The processing steps are as follows:

1) Process mesh edges, remove overlapping edges, and remove independent cantilever edges.

2) According to the two-dimensional coordinates of the view projection, start from point A, find the edge connected to this point in the counterclockwise direction, and return to point A again to form a closed grid.

3) Each side is divided into forward and reverse, and each side is allowed to be found once for forward and reverse. During an edge finding process, if an edge has been found in the same direction, the edge finding process will be terminated.

4). Repeat steps 2) and 3) above for all points on the grid surface to find all closed grids.

5) The found grid will contain the grid composed of the peripheral boundary, and the grid will be deleted according to the grid area. To judge the connectivity of the surface, for the multi-region surface, delete the peripheral grids of each region respectively.

(3) Establish grid load data

The data of the grid load includes two parts that are independent and related to each other:

1) Description of grid shape. The shape of the grid can be described by sequentially recording the unit numbers (or surface unit sides) that make up each side of the closed grid. Although the formation of the grid is based on the two-dimensional coordinates of the view projection, after the grid is formed, the load grid obtained according to the actual spatial position of the grid points and edges will be a three-dimensional grid. At the same time, the method of the present invention directly refers to the unit as the grid edge, which saves resources on the one hand, and on the other hand, when the unit is deleted and changed, it can be reflected on the grid in time.

2), grid load unit. The method of the present invention applies the grid load to a special graphic unit, and the unit has the following attributes:

a) The corresponding grid number;

b) Its own coordinate parameters, generally the area center of the corresponding grid;

c) Load parameters such as the value, direction, working condition, and derived load mode of the applied surface load.

(4) Deriving the load to the surrounding cells of the grid

According to the space enclosed area determined by the load grid (which can be approximately regarded as a plane in a small area), and the load parameters recorded on the grid load unit, according to the set mode, the surface load in the grid area is finally derived to On the surrounding elements, it acts as a line load directly acting on beams, columns, and walls.

The invention utilizes the view projection surface to form a load grid of any curved surface in space, and for a complicated spatial grid surface, all curved surface units can be selected at one time to form the geometric data of the grid, which significantly improves the operation efficiency.

The invention describes the grid load and the grid geometric parameters separately, which are not only interrelated but also independent of each other. When the mesh edges are changed and incomplete, the original mesh is deleted, but the load elements still exist. If the changed grid shape does not change, as long as the grid is formed again, the new grid is connected to the load unit without additional input of load parameters, which simplifies the operation. If multiple grids have the same shape and parameters, the existing load unit can be copied, and the operation of inputting load parameters can also be omitted.

The invention uses the grid load as a graphic unit with its own coordinate parameters, so that the grid load can be deleted, copied, and moved like ordinary graphics, and the operation is more convenient. Moreover, the grid load is regarded as an independent graphic unit, which can not only handle the general gravity surface load, but also apply wind pressure load, water pressure, and soil pressure on the grid load, which greatly expands the scope of use of the grid load. . As long as the grid load unit is formed, various loads can be added directly, which greatly facilitates the operation process of these special distributed loads.

Using the geometric description of the spatial position of the grid corresponding to the grid load unit, the normal vector and tangent vector of the spatially closed grid can be determined, so that the load related to the shape of the surface can be applied. For example, the load perpendicular to the surface and the load tangent to the surface also greatly expand the function of the grid load.

Description of drawings

Figure 1(a), a complex sloping roof project

Figure 1(b), a complex sloping roof project, the projected surface of the sloping roof view is unfolded

Fig. 1 (c), a complex sloping roof project, the grid load unit (small square among the figure) that the grid load method of the present invention forms

Fig. 1(d), a complex slope roof project, the line load on the beam obtained by the grid load method derivation of the present invention

Figure 2(a), a steel truss dome project

Figure 2(b), a steel truss dome project, the view projection surface of the applied load surface is expanded

Fig. 2 (c), a steel truss dome project, the grid load unit (small square among the figure) that the grid load method of the present invention forms

Fig. 2 (d), a steel truss dome project, the line load on the beam obtained by the grid load method derivation calculation of the present invention

Figure 3(a), an open circular pool

Figure 3(b), an open circular pool, the projected surface of the side wall and the curved surface of the bottom plate is expanded

Fig. 3 (c), an open circular pool, the grid load unit that the grid load method of the present invention forms

Fig. 3 (d), an open circular pool, the grid load method of the present invention deduces the vertical water pressure on the surface of the curved surface as the beam grid line load

Fig. 4, the method of the present invention forms a load grid diagram on the view projection plane

Detailed ways

In order to better understand the technical solution of the present invention, further description will be made below in conjunction with the accompanying drawings and embodiments.

With reference to FIG. 4 , the specific process of forming a curved surface closed grid by using the view projection surface in the method of the present invention can be well understood.

This figure is a part of a space grid surface, which has been transformed into a fully expanded and non-overlapping projection plane in a two-dimensional view plane through a three-dimensional view transformation.

According to the two-dimensional coordinates of the view projection, starting from point A, find the edge counterclockwise until returning to point A again to form a closed grid ABCD, as shown in Figure 4.

For edge AB, connect to two closed grids ABCD and AFEB respectively. Let point A to B be the positive direction of the side. For the process of forming an ABCD closed grid, the AB edge is the reverse edge finding process. For the process of forming AFEB closed grid, the AB edge is the forward edge finding process.

Each side is allowed to be found once in forward direction and reverse direction. During an edge finding process, if the found edge has already been found in this direction, the edge finding process will be terminated.

All the edges of the grid surface are searched counterclockwise in the positive direction and the reverse direction respectively, and all closed grids in the space grid surface will be formed.

Example 1

As shown in Figure 1(a), the complex slope roof project has 3 floors and 4 floors, and the slope roofs are not connected to each other. The sloping roof is a cast-in-place concrete slab. The self-weight of the slab, the self-weight of other roof materials, the load of people on the roof, and the snow load are used as surface loads, which need to be derived to the roof beams.

Close the beams and columns of each layer below the slope roof, keep only the beams and columns of the slope roof, and perform a three-dimensional view conversion, so that the slope roof is unfolded on the view projection plane, as shown in Figure 1(b). Use the software to select all the beams and columns of the sloping roof at one time. Columns are rejected as cantilevered edges connected at only one end.

Utilizing the method of the invention, according to the two-dimensional plane figure on the view projection plane, a three-dimensional load grid in space and corresponding grid load units are formed. For spatially disconnected domains, the method of the invention can automatically detect and eliminate the outermost grids of each connected domain. Add the corresponding roof load value, direction, derived load mode and other parameters to the grid load unit. As shown in Fig. 1(c), the small square in the figure is the diagram of the grid load unit.

The final line load on the beam obtained in this embodiment is shown in Fig. 1(d).

Example 2

The dome structure shown in Figure 2(a) is an observatory building with a circular arc truss structure. Surface distributed loads such as the self-weight of the panels, the maintenance load of the superior, and the wind load acting on the surface of the dome need to be derived to the upper chords of the arc trusses and the horizontal tie rods between the trusses as line loads.

Close the lower chord and web of the arc truss, and perform a three-dimensional view conversion (vertical upper view), so that the outer surface of the dome is unfolded on the view projection plane, as shown in Figure 2(b).

Using the method of the invention, all dome surface components are selected at one time, and a three-dimensional load grid in space and corresponding grid load units are formed according to the two-dimensional plane graphics on the view projection plane. And add the corresponding surface load value, direction, derived load mode and other parameters to the grid load unit. As shown in Figure 2(c).

The upper line load of the dome surface member finally obtained in this embodiment is shown in Fig. 2(d).

Example 3

As shown in Figure 3(a), the open circular pool adopts the structure type with plates in the beams. It is necessary to derive the surface vertical water pressure inside the pool to the beams that make up the pool structure.

For 3D view transformation, the inner surface of the pool is unfolded on the view projection plane, as shown in Fig. 3(b). By using the method of the invention, all components are selected at one time, and a three-dimensional load grid in space and corresponding grid load units are formed according to the two-dimensional plane graphics on the view projection surface. Use the software to apply the surface water pressure that varies along the height and is perpendicular to the grid plane to all the grid load elements at one time. As shown in Figure 3(c).

The line load on the beam grid of the pool finally obtained in this embodiment is shown in Fig. 3(d) (partially).

As can be seen from the situation of the above embodiments, the inventive method has achieved the purpose of the invention: 1, for complex sloping roofs, space curved surfaces, and complex combined curved surfaces, the requirement that one operation can be fully loaded has been reached; 2, the expanded The function of the grid load is not only used for the derivation of the distributed gravity load of the building roof, but also for the derivation of the special load of the vertical pressure on the surface.

Claims (2)

1, a kind of grid loading method of handling any space curved surface distributed load is characterized in that, with the Concept Extension of area load, as the problem of the distributed force on the space sealing grid of broad sense, and is called the grid load, and the step of handling the grid load is as follows:

(1) utilize the view plane of projection to launch the space lattice curved surface: the space lattice curved surface launches space curved surface by the 3-D view conversion in view plane, in the two dimension view plane, space curved surface is converted into two dimensional surface;

(2) utilize the view plane of projection form to form the sealing grid of curved surface:, to look for and respectively seal grid in the curved surface according to the view plane two-dimensional coordinate;

(3) set up the data of grid load:

1. the description of mesh shape: the unit number or the face element sides on each limit of sealing grid formed in journal, can describe the shape of grid;

2. grid load cell: as a kind of independently graphic element, this unit has following attribute with the grid load: A) pairing grid sequence number; B) coordinate parameters of self is the centre of area of corresponding grid; C) numerical value of the area load that applies, direction, affiliated operating mode, lead the pattern of calculating load;

(4) load is led calculate the grid peripheral unit: according to closed area, the determined space of load grid, with the load parameter that writes down on the grid load cell, by the pattern of setting, area load in the net region finally led calculate on the peripheral unit, as the line load that directly acts on beam, post, the wall.

2, the grid loading method of any space curved surface distributed load of processing according to claim 1 is characterized in that, described step (2), and treatment step is as follows:

1. handle the grid limit, reject overlapping limit, reject independent cantilever limit;

2. according to view projection two-dimensional coordinate,, look for the limit that is connected with this point in the counterclockwise direction, finish, form a sealing grid up to getting back to the A point once more since 1 A;

3. every limit is divided forward and reverse, and forward is allowed on every limit, oppositely each is looked for the limit once, and in once looking for the limit process, if any the equidirectional limit of having been looked for, a limit, then this time looks for the limit process to end;

4. above the institute of grid surface being repeated a little 2., 3. step, find all sealing grids;

5. in the grid that finds, will comprise the grid that peripheral boundary is formed, judge this grid deletion,, delete each regional peripheral meshes respectively the multizone curved surface according to the grid area.

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