CN1100770A

CN1100770A - Long span post-tensioned steel/concrete truss and method of making same

Info

Publication number: CN1100770A
Application number: CN 93118105
Authority: CN
Inventors: 阿尔弗莱德·A·伊
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-09-25
Filing date: 1993-09-25
Publication date: 1995-03-29

Abstract

There is provided a large span truss, its upper and lower edges both have reinforced concrete shell, the shell of lower edge or upper edge, if necessary, has posttensioning prestressed reinforcing steel, the fabrication method involves firstly mounting a steel truss of light structure and a temporary scaffold to support the mould plates, placing the steel bars and prestressed reinforcing steel in the mould and pouring concrete to wrap the upper and lower edges of the truss, owing to posttensioning of the prestressed reinforcing steel, it has most high loading capacity.

Description

Long span post-tensioned steel/concrete truss and method of making same

The present invention relates generally to traditional steel work large-span truss, and the concrete involucrum is arranged on its upper limb and the lower edge, is added with reinforcing bar in the concrete involucrum, at lower edge with also can be chosen in the reinforcing bar that posttension is arranged in the concrete involucrum of upper limb.The invention still further relates to a kind of method of making above-mentioned truss, in this method, at first set up the light structure steel truss, and interim steel scaffold and strut are set, with supporting template.Reinforcing bar and tendon place template, and placing of concrete, with the upper and lower edge of parcel truss.Reinforcing bar is posttension, makes it to have maximum load-carrying capacity.Truss of the present invention is used in and acts under the situation that heavy duty is arranged on the large span, as bridge, the colosseum that grandstand is arranged, convention hall etc., particularly advantageous is to cross over the busy main line of communication or water route when truss, and truss comprises single span or uses two of one or more intermediate supports to stride or two stride above continuous trusse.

The truss that adopts structurally has multiple pattern and configuration, upper limb and lower edge are arranged usually, be rigidly connected with some vertical or oblique struts between the upper and lower edge, the end that links together on truss is supported, thereby in lower edge, produce pulling force, and in upper limb, produce pressure, in another case, continuous trusse is except that two ends, also be bearing in mid point, therefore except lower edge, upper limb also produces pulling force, and this depends on the relation between truss and fulcrum.As everyone knows, in concrete, be in order to increase the intensity of truss with trussmember parcel or cladding, insulation, fire-resistant and reach other purpose.Trussed construction in the past, behind erection of truss, do not wrap up upper limb and this way of lower edge with concrete again, at this moment, it is low weight steel truss that truss can be designed to, support the concrete template that pouring is used for wrapping up the upper and lower edge of truss with it, be provided with prestressed reinforcement in lower edge and also optional upper limb, these reinforcing bars are posttension, make truss have maximum load-carrying capacity.

An object of the present invention is, a kind of large-span truss of steel work is provided, upper limb and lower edge have the steel concrete outer envelope, and lower edge and also optional upper limb and lower edge have prestressed reinforcement, and this reinforcing bar is posttension, makes truss that best supporting capacity be arranged.

Another object of the present invention is to propose a kind of method of making large-span truss, in this method, at first set up lighter steel truss, come supporting template, so that can water the concrete that surrounds the upper and lower edge of truss with it, reinforcing bar and fixture are positioned in the template before placing of concrete together, to strengthen truss, reinforcing bar is arranged in the steel concrete, adopt traditional post-tensioned technology, make the reinforcing bar posttension, significantly improve the strength and stiffness of truss thus.

Further aim of the present invention provides achieve the above object truss and method, and wherein, when truss during only at its two supports, but only lower edge has the reinforcing bar of posttension; When truss is continuous and establishes intermediate support except that two supports, but lower edge and upper limb all have the prestressed reinforcement of posttension.

A further object of the invention provides a kind of large-span truss and its manufacture method, wherein truss is a steel work, upper limb and lower edge wrap up with concrete, but lower edge and also can comprise the reinforcing bar that is provided with posttension in the upper limb, they can be made truss that maximum load-carrying capacity be arranged by posttension, this truss is particularly useful for doing large-span truss, as be used in bridge, have in the structures such as colosseum, convention hall and other buildings of grandstand, in these occasions, large-span truss is more favourable.

Some purposes of these and other and advantage can be referring to accompanying drawings with from hereinafter content and claim, find out in the more complete explanation that structure and construction are done, in the accompanying drawing with a kind of part with identical numbering.

Fig. 1 vertical section schematic diagram is represented basic lightweight steel structure truss, and it has curve-like lower edge and straight upper limb, connects with vertical or oblique strut between the two;

Fig. 2 is similar to the view of Fig. 1, and concrete upper limb and lower edge have been wrapped up in expression;

The cross-sectional view of a plurality of truss of Fig. 3, expression is contained in template on the relevant truss by scaffold, and scaffold is fixed on the truss with strut;

The 4-4 drawing in side sectional elevation of Fig. 2 that Fig. 4 ratio is amplified, expression has steel concrete to superscribe the trussed construction of lower edge, is added with reinforcing bar in the upper limb concrete, and lower edge has the tendon of reinforcement, and stiffener is posttension, makes truss that maximum supporting capacity be arranged;

Fig. 5 is similar to the longitudinal plan of Fig. 2, but represent a kind of structure, continuous trusse wherein has a fulcrum at least at the center, and expression is because continuous trusse has one or more intermediate supports, can in upper limb, produce pulling force, so upper limb wherein also has the prestressed reinforcement of posttension.

Fig. 1 represents traditional truss 10, and has described the first step in the reinforced concrete truss method of making large span posttension of the present invention.Truss 10 is traditional form of structure, and it comprises upper limb 12, lower edge 14, and it is rigidly connected in the termination of label 16 places and upper limb 12, plumb post 18 and hound 20.The member of truss 10 is low weight i iron or other shape that is suitable for, and adopts various fixing meanss to be rigidly connected mutually between the member, as with bolt or welding.The length of truss 10 and concrete shape can change.For example, upper limb 12 and lower edge 14 can be straight, curved or oblique, and this will depend on the requirement of facility.

Fig. 2 represents to have the truss 22 of structure of the present invention, and is basic identical with truss 10, and not existing together is that upper limb 12 is wrapped up by concrete 24 now, and lower edge is equally also wrapped up by concrete 26, and the bearing support 28 that schematically illustrates is positioned at the truss outer end.

Fig. 3 represents the truss cross section that several separate each other parallel.The scaffold 30 that is fixed on the truss 10 is separated by a distance with it under upper limb 12, scaffold 32 is a distance below lower edge 14, scaffold supports with strut 34, strut 34 is connected on the

strut

18 and 20 of truss 10, or is fixed on the truss with the suitable mode of any effectively support foot supporting 30 and 32.Scaffold 30 is supporting the template 36 of upper limb 12, the template 38 of scaffold 32 supporting lower edges 14, and

template

36 and 38 can schematically illustrate " U " shape mould into the upward opening symmetry, but placing of

concrete

24 and 26 in the template makes concrete parcel upper limb 12 and lower edge 14.

Truss 22 after Fig. 4 represents to finish, at this moment, upper limb 12 is wrapped up by concrete 24, does not have reinforcing bar 40 in the concrete 24.Lower edge 14 is by concrete 26 parcels that add reinforcing bar 42 and tendon 44, and tendon 44 carries out posttension with traditional post-tensioning technology after concrete 26 sclerosis.

The truss 46 that Fig. 5 represents is similar to truss 22, and its difference just in truss 46, has only the part of upper limb 48 to wrap up with concrete 50, and lower edge 52 is whole in concrete 54 parcels.In this structure, the concrete 50 of parcel upper limb 48 parts is also stretched below tiltedly at label 56 places, wraps hound 58.In addition, as shown in Figure 5, be provided with an intermediate support 62, it and overhang bracket 62 together support truss, one or more intermediate supports 60 can produce pulling force in upper limb.Therefore, tendon is wrapped up with same mode shown in Figure 4 in the concrete of upper limb 48 and strut 58, tendon connects the total length of

concrete involucrum

50 and 56, this tendon also extends to the end of external wrapping concrete 54, so the tendon in upper limb and the lower edge external wrapping concrete adopts a traditional posttension in the truss termination.Another kind of scheme is, only in the part of upper limb, and not on any strut, external wrapping concrete, in this case, when in large-span truss, adopting one or more intermediate support, can be to be wrapped in the independent posttension of the tendon that does not extend to the upper limb termination in the concrete always, to increase the tensile strength of upper limb.

As mentioned above, at first set up the steel truss 10 of light structure, be used for supporting template, template is used in splendid attire and supporting pouring eight templates with the concrete involucrum of parcel upper limb and lower edge.The tendon that adds reinforcing bar and adding posttension in the concrete involucrum, when reinforcing bar is in stress, the intensity of truss is obviously increased, for example the ultimate strength of reinforcing bar is 270000psi, compare with common structural iron, the limit yield strength of general structural steel is in 36000 to 50000psi scopes.The posttension of reinforcing bar has also reduced the amount of deflection that produces when large-span truss is subjected to heavy load.Wrap up the concrete of lower edge and upper limb, increased the rigidity of structure of member, upper limb also plays the main compression member of truss.This trussed construction is under situation about significantly reducing cost, maximum and best load ability to bear is provided, and this is owing to having utilized the lightweight advantage of structure to reach, and it is easy to set up, thereby an overhead falsework is provided easily, has been used to water the steel concrete of upper limb and lower edge.By the lightweight steel truss supporting template that uses, no longer need temporary transient or permanent pillar, thereby exempted expensive technical equipment, this facility also has the obstruction and the shortcoming of obstructing the view, and this point is being built sledge beam, graded crossing and related in other similar facilities of traffic particularly important.

In addition, adopt the steel truss supporting template, the concrete that pumps is put in place along the upper limb and the lower edge of steel truss, thereby can exempt the huge spending of setting up big weight large-span truss.Though in lower edge or also the expense of the reinforcing bar of embedding posttension approximately is the twice of structural iron expense in upper limb, it will provide about five times intensity.Concrete provides required rigidity of the upper and lower edge of truss and fire-resistant shell, owing to compare with structural iron, concrete is a kind of cheap material, so can reduce expense.Yet concrete in static is great, make it to be difficult to for large-span truss prefabricated and set up, the situation in overhead ceiling, land communications or water transportation for example.

As shown in Figure 4, truss can be used to shell of doing on support, concrete floor system 64 and ceiling structure 66, metal etc.

Interim scaffold

30,34 and 32 can be stayed the original place as framework, the ceiling structure made from suspension, and a support of table and operating personnel's passage is provided, so that carry out the work such as installation, maintenance, replacing, repairing of circuit, pipe-line system, lighting apparatus.As shown in Figure 5, between the termination, have two to stride or the continuous trusse of multispan, can effectively utilize the concrete involucrum and the posttension of fold shape as shown in Figure 5 or microscler supporting region, in microscler, the concrete involucrum does not extend along hound, but concrete involucrum district the same manner posttension of a upper limb part.Therefore, the concrete involucrum of truss upper limb can extend to the end from the end of truss, or terminates in before the end, or extends to the lower edge strut, and carry out at the position that posttension only needs in upper limb.In addition, the shape of steel truss can be different from planform represented among the figure, and same principle can be applicable in 3, the 4 or 5 multispan degree of striding, and the requirement of related facility is depended in these changes.

Above only for example understand principle of the present invention.In addition, because the technology skilful person is easy to expect various modifications and variations,, therefore, can makes various suitable modifications within the scope of the present invention and adopt equivalent so the invention is not restricted to represented and concrete structure that introduced.

Claims

1, large-span truss comprises elongated lower edge, with lower edge the elongated upper limb of spacing, many vertical and oblique struts is arranged, strut connection upper limb and lower edge are to constitute rigid truss, upper and lower edge and strut are steel, the concrete involucrum is wrapped in this upper limb and lower edge, the reinforcing bar that the concrete involucrum is wrapped in whole upper limb, lower edge and contains, tendon is wrapped in the concrete involucrum of lower edge, and tendon is by posttension, to improve the intensity of lower edge and truss.

2, according to the described truss of claim 1, it is characterized by: tendon comprises many spaced-apart reinforcing bars, and embedded steel is in the concrete involucrum, and by posttension.

3, according to the described truss of claim 1, also be included in the tendon in the concrete involucrum of parcel truss upper limb, when truss support during at its end and an intermediate point, tendon is by posttension, to improve the intensity of upper limb.

4, according to the described truss of claim 3, it is characterized by: the expanded range of upper limb concrete involucrum is less than the total length of upper limb, to improve the intensity of passing through the zone of intermediate support defined in the upper limb.

5, according to the described truss of claim 3, it is characterized by: the expanded range of upper limb concrete involucrum is less than the total length of upper limb, and extend along hound, converge and be connected with the involucrum of parcel lower edge, the tendon of posttension, extend along the concrete involucrum of parcel upper limb and the concrete involucrum of parcel hound, to improve truss intensity.

6, the method for making large-span truss may further comprise the steps: set up the lightweight steel truss; Scaffold and strut are fixed on the steel truss; The concrete blinding relevant with the upper and lower edge of truss is contained on the scaffold; Reinforcing bar is placed template; Tendon is inserted, and they longitudinally connect the length of truss lower edge; Placing of concrete in template with the upper and lower edge of parcel truss, allows hardening of concrete, and the posttension reinforcing bar.

7, the step according to the described method of claim 6 also comprises, concrete casting is poured into go in the template relevant with upper limb before, tendon is placed in the template relevant with upper limb, and the parcel upper limb hardening of concrete after, the tendon of posttension in upper limb.

8, the step according to the described method of claim 7 also comprises, stripping, and when carrying out the various work relevant, utilize scaffold and strut to go to support roof, ceiling or personnel with truss.