CN112942059B - Overall design method of unequal-height double-tower cable-stayed bridge - Google Patents
Overall design method of unequal-height double-tower cable-stayed bridge Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
- E01D11/00—Suspension or cable-stayed bridges
- E01D11/04—Cable-stayed bridges
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
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Abstract
The invention discloses a general design method of an unequal-height double-tower cable-stayed bridge, which is based on a structural mechanics method, deduces and obtains the relation between the midspan span and the bridge tower height of the unequal-height double-tower cable-stayed bridge, and simultaneously determines the bridge tower height and the side span by using empirical parameters to realize the rapid determination of the unequal-height double-tower cable-stayed bridge comprising the midspan spanLHeight of high and low tower bridgeh a、h bMid-spanL a/2、L b/2 and edge spanL as、L bsAnd the value of the overall design parameter is equal. Compared with the traditional design method, the relational expression between the key parameters is deduced based on the structural mechanics method, the concept is clear, the theoretical support is sufficient, and the problems that the value of the key parameters depends on experience and the subjective randomness is large can be solved; the method has the advantages that a finite element model of the structure is not required to be established, a complicated procedure of determining the overall design parameter value through repeated trial calculation is omitted, the overall design of the unequal-height double-tower cable-stayed bridge can be completed only by manual calculation, and the method has the advantages of clear mechanical concept and strong practicability.
Description
Technical Field
The invention relates to a bridge engineering technology, in particular to a general design method of an unequal-height double-tower cable-stayed bridge.
Background
The cable-stayed bridge is a bridge consisting of three components, namely a cable, a tower and a beam, and is more and more widely applied to modern bridges, particularly river-crossing and river-crossing bridges due to a series of advantages of high crossing capacity, high bearing efficiency and the like.
According to the number of the cable towers, the cable-stayed bridge can be divided into a single-tower cable-stayed bridge, a double-tower cable-stayed bridge and a multi-tower cable-stayed bridge, wherein the number of the double-tower cable-stayed bridge is the largest. In a double-pylon cable-stayed bridge, when the heights of two bridge pylons are different, the bridge is called a high-low pylon cable-stayed bridge or a sister pylon cable-stayed bridge, and is also called a sub-pylon cable-stayed bridge.
Compared with an equal-height pylon cable-stayed bridge, the unequal-height double-pylon cable-stayed bridge can better adapt to different hydrological, geological and topographic conditions, is different from the traditional cable-stayed bridge in symmetrical arrangement, and gives a novel and well-defined unique impression.
The unequal-height double-tower cable-stayed bridge is not the current mainstream cable-stayed bridge type, and the unequal-height double-tower cable-stayed bridge constructed at home at present has only 20 seats, so that the unique advantages of the unequal-height double-tower cable-stayed bridge in adaptability and aesthetic feeling are more and more recognized.
The conventional equal-height double-tower cable-stayed bridge is mature in design, but the research on the unequal-height double-tower cable-stayed bridge is less, so that the structural characteristics of the unequal-height double-tower cable-stayed bridge are not sufficiently known. At present, no design specification and design guide for the unequal-height double-tower cable-stayed bridge exist, the overall parameter value of the unequal-height double-tower cable-stayed bridge is mainly determined by experience during engineering design, and then the matched parameter combination is determined by repeated trial calculation and continuous correction, and the overall parameter design of the structure is finally completed. The design is not only tedious and highly subjective, but also has the risk of unreasonable selection of the total design value due to insufficient experience of designers.
Disclosure of Invention
The invention aims to provide a total design method of an unequal-height double-tower cable-stayed bridge aiming at the defect of irregularity in the existing design, so that the design is more scientific and efficient.
In order to achieve the purpose, the invention can adopt the following technical scheme:
the overall design method of the unequal-height double-tower cable-stayed bridge comprises the step of determining the midspan span of the unequal-height double-tower cable-stayed bridgeLHeight of high and low tower bridge towerh a、h bHalf-midspan span of high and low towersL a/2、L b/2 and edge spanL as、L bsThe parameter value of (2) specifically comprises the following steps:
firstly, determining the midspan span according to the requirements of the river spanned by the bridge on the navigation under the bridgeL；
Secondly, preliminarily drawing up the height of the high tower and the low tower according to the following formulah a、h b：
Wherein eta is1Taking 0.3-0.35, eta2Taking 0.18-0.24;
thirdly, calculating the half-midspan span of the high tower and the half-midspan span of the low tower respectively according to the following formulaL a/2、L b/2：
Fourthly, preliminarily drawing up the side span and span of the high tower and the low tower according to the following formulaL as、L bs：
Wherein the content of the first and second substances,ξ 1andξ 2taking values according to the structural form of the main beam: taking 0.3-0.4 of a steel main beam structure, 0.4-0.5 of a combined beam structure, 0.3-0.45 of a mixed beam structure and 0.4-0.45 of a concrete main beam structure;
fifthly, arranging stay cables on the main beam and the bridge tower respectively;
sixthly, fine adjustment is carried out according to the arrangement of the stay cables on the main beam and the bridge towerL a/2、L b/2、L asAndL bsand determining a final value according to the four parameters.
And fifthly, arranging the stay cables on the main beam and the bridge tower at equal cable spacing.
The method is based on a structural mechanics method, derives and obtains the relation between the mid-span and the bridge tower height of the unequal-height double-tower cable-stayed bridge, and simultaneously determines the bridge tower height and the side-span by using empirical parameters to realize the rapid determination of the unequal-height double-tower cable-stayed bridge comprising the mid-span and the side-spanLHeight of high and low tower bridgeh a、h bMid-spanL a/2、L b/2 and edge spanL as、L bsAnd the value of the overall design parameter is equal.
Compared with the traditional design method which depends on experience and needs to establish a finite element model for trial and error, the method has the advantages that:
1. the relational expression between the key parameters is deduced based on a structural mechanics method, the concept is clear, the theoretical support is sufficient, and the problems that the value of the key parameters depends on experience and the subjective randomness is large can be solved;
2. a finite element model of the structure is not required to be established, a complicated program for determining the overall design parameter value through repeated trial calculation is omitted, and the overall design of the unequal-height double-tower cable-stayed bridge can be completed only by manual calculation;
in conclusion, the design method of the invention can overcome the defects that the value of the key design parameter depends on experience during engineering design, so that the subjective randomness is large, and the design parameter needs to be trial-calculated repeatedly, and has the advantages of clear mechanical concept and strong practicability.
Drawings
Fig. 1a and fig. 1b are respectively a structural overall structure and a load schematic diagram of an unequal-height double-pylon cable-stayed bridge.
Fig. 2a and 2b are schematic diagrams of the tower side calculations.
Fig. 3a and 3b are schematic diagrams of low tower side calculations.
Fig. 4 is a design flow chart of the unequal-height double-pylon cable-stayed bridge.
Fig. 5 is a general layout of the unequal-height twin-tower cable-stayed bridge of embodiment 2.
Detailed Description
The design method of the present invention is further described in detail below with reference to the drawings and specific embodiments to facilitate understanding for those skilled in the art. It should be noted that the present invention is not limited to the following examples.
Example 1 principle derivation of the design method of the present invention
Taking the unequal-height double-tower cable-stayed bridge shown in fig. 1a as an example, the structure of the unequal-height double-tower cable-stayed bridge is analyzed, wherein the upper tower is A, the lower tower is B, the stay cable is X, the main beam is Z, and the ground line is D.
The stay cable is approximately regarded as a cable membrane in a vertical plane, and is analyzed as a continuum, and the following basic assumptions are made:
1) compared with the bridge span, the lengths of the main beam ropeless areas at the cable tower, the side span and the span are small and can be ignored;
2) the stay cables are arranged on the main beam and the bridge tower at equal cable spacing;
3) neglecting the dead weight of the stay cable, the dead load on the main beam is uniformly distributed, as shown in fig. 1 b;
4) the axial force at the ends of the main beams and at the mid-span position is zero.
One side of the column was taken for analysis as shown in FIG. 2 a:
wherein the parametersh a 、h a2、h a1Respectively the effective height of the bridge tower, the length of the stay cable anchoring area and the height of the lower edge of the anchoring area;L as 、L a /2are the edge span and the 1/2 mid-span;λ s 、λ c respectively the average cable distance on the side span and the middle span;λ h the cable distance of the stay cable on the bridge tower is adopted;q 1 、q 2 respectively the evenly distributed load concentration of the mid-span and the two side spans.
Taking the infinitesimal W of the position of the stay cable in the figure 2a for stress analysis (figure 2b is a stress great sample diagram at the infinitesimal position), the cable force at any point isT(x) Axial force ofN(x) From the force balance conditions, one can derive:
according to the basic assumption: the stay cable is arranged with the same cable distance on the girder and the bridge tower, and has:
the layout form equation of the inhaul cable obtained from the geometrical relationship satisfies the following conditions:
according to the basic assumption: the axial force at the end part of the main beam and the mid-span position is zero, and the above formula is substituted into the formula
And (3) integrating to obtain the axial force of the main beam at any position:
the stayed-cable is anchored more intensively on the bridge tower and arranged in a radial way, namely
Then, the above formula can be simplified as follows:
order tox=0, maximum pressure of main beam at cable tower available N aComprises the following steps:
taking one side of the lower tower for analysis, as shown in fig. 3a and fig. 3b, and obtaining the following steps by the same reasoning as the high tower analysis:
the sections of the main beams are not greatly different at the high and low tower positions, so that the main beams are made full use of materials and meet the requirement
The following can be obtained:
again, according to the basic assumptions: the lengths of the cable-free areas of the main beams at the cable towers, the side spans and the midspan are smaller, the lengths of the cable-free areas on the main beams are ignored, and the midspan spanLSatisfies the following conditions:
the height of the bridge tower has a great influence on the stress of the cable-stayed bridge, and generally has a positive correlation with the main span of the cable-stayed bridge. Setting the height of the high tower and the low towerh a、h bAnd satisfies the following conditions:
the determination of the height of the bridge tower is mainly based on engineering experience and existing engineering cases, and is suggested according to the statistical data of 21 built unequal-height double-tower cable-stayed bridges (see table 1 below) with limited quantity at home and abroadη 1Taking the mixture of 0.3 to 0.35,η 2taking 0.18-0.24.
Table 121 seat unequal-height double-tower cable-stayed bridge case and main design parameters
The combined type (1) and the formula (2) can obtain:
determining the side span according to empirical parameters provided in the current Specification "Fine design rules for Cable-stayed Highway bridges" (JTG/T D65-01-2007)L as、L bsSatisfies the following conditions:
wherein, for the steel main beam structureξ 1Andξ 2taking 0.3-0.4; for composite beam structureξ 1Andξ 2taking 0.4-0.5; for hybrid beam constructionξ 1Andξ 2taking 0.3-0.45; for concrete main beam structureξ 1Andξ 2taking 0.4-0.45.
To this end, the midspan span of the unequal-height double-pylon cable-stayed bridgeLHeight of high and low tower bridgeh aAndh bheight and two-side spanL as、L bsEtc. are determined.
Example 2 the process of the present invention is described in detail below with reference to specific examples
The overall parameter design is carried out on the double-tower unequal-height cable-stayed bridge spanning a certain navigation river, the main beam of the cable-stayed bridge adopts a steel-concrete composite beam, and the mid-span diameterLThe design is controlled by the navigation requirement under the bridge, and the side span and the span are not limited.
The specific design method is performed according to the flow chart shown in fig. 4.
Firstly, determining the midspan span of the cable-stayed bridge according to the demand of under-bridge navigation at the bridge positionL=425m, tower height below bridge floorh 0=35m。
Secondly, taking the statistical data of the existing 21 unequal-height double-tower cable-stayed bridges at home and abroadη 1=0.33，η 2= 0.21. According to the formula
Determining the height of high and low towersh a、h bAnd calculating:
thirdly, the height h of the high tower and the low tower is measureda、hbThe substitution into a formula is carried out,
is calculated by
Therefore, it can be preliminarily drawn up
。
Fourthly, referring to the specification of Highway cable-stayed bridge design rules (JTG/T D65-01-2007), and aiming at the cable-stayed bridge structure adopting the composite beamξ 1Andξ 2the value range is 0.4-0.5. This example is to getξ 1=0.5，ξ 2Equation of 0.4
Fifthly, respectively arranging stay cables on the main beam and the bridge tower, comprehensively considering anchoring and stress, wherein the basic arrangement distances of the stay cables on the main beam and the bridge tower are respectively 12m and 2.5 m.
Sixthly, fine adjustment is carried out according to the arrangement of the stay cables on the main beam and the bridge towerL a/2、L b/2、L asAndL bsthe four parameters are numerical values, so that the arrangement of the stay cables is uniform and reasonable. The final four values are
The overall detailed layout of the cable-stayed bridge is shown in fig. 5, and all the key design parameter values of the double-tower unequal-height cable-stayed bridge are determined up to this point.
It can be seen from the above embodiments that the overall design of the double-tower unequal-height cable-stayed bridge can be efficiently completed by adopting the design method of the invention, the whole process can be completed only by manual calculation, a structural calculation model established by finite element software is not needed, repeated parameter adjustment and trial calculation are not needed, and the invention has the advantages of clear mechanical concept, strong practicability and the like.
Claims (2)
1. The overall design method of the unequal-height double-pylon cable-stayed bridge comprises the step of determining the midspan span of the unequal-height double-pylon cable-stayed bridgeLHeight of high and low tower bridge towerh a、h bHalf-midspan span of high and low towerL a/2、L b/2 and edge spanL as、L bsThe parameter value of (2), which is characterized in that: the method specifically comprises the following steps:
firstly, determining the midspan span according to the requirements of the river spanned by the bridge on the navigation under the bridgeL；
Secondly, preliminarily drawing up the height of the high tower and the low tower according to the following formulah a、h b：
thirdly, calculating the half-midspan span of the high tower and the low tower respectively according to the following formulaL a/2、L b/2：
Fourthly, preliminarily drawing up the side span of the high tower and the low tower according to the following formulaL as、L bs：
Wherein the content of the first and second substances,ξ 1andξ 2taking values according to the structural form of the main beam: taking 0.3-0.4 of a steel main beam structure, 0.4-0.5 of a combined beam structure, 0.3-0.45 of a mixed beam structure and 0.4-0.45 of a concrete main beam structure;
fifthly, arranging stay cables on the main beam and the bridge tower respectively;
sixthly, fine adjustment is carried out according to the arrangement of the stay cables on the main beam and the bridge towerL a/2、L b/2、L asAndL bsand determining a final value according to the four parameters.
2. The overall design method of the unequal-height double-pylon cable-stayed bridge according to claim 1, characterized in that: and fifthly, arranging the stay cables on the main beam and the bridge tower at equal cable spacing.
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