CN108374324B - large truss arch bridge - Google Patents
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- CN108374324B CN108374324B CN201810312184.3A CN201810312184A CN108374324B CN 108374324 B CN108374324 B CN 108374324B CN 201810312184 A CN201810312184 A CN 201810312184A CN 108374324 B CN108374324 B CN 108374324B
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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
- E01D12/00—Bridges characterised by a combination of structures not covered as a whole by a single one of groups E01D2/00 - E01D11/00
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
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Abstract
The invention discloses a large truss arch bridge, which mainly comprises arch ribs, main beams, vertical web members, inclined web members, flexible suspenders and transverse struts; the vertical web members are vertically arranged near 1/4, 1/2 and 3/4 of the arch ribs respectively; two ends of the inclined web member are respectively connected with the bottom of the middle vertical web member and the tops of the two vertical web members; the arch rib, the main beam, the vertical web member and the inclined web member form a large truss structure which takes the arch rib as an upper chord member and the main beam as a lower chord member and is provided with a flexible suspender. The large truss arch bridge has the characteristics of not damaging the stress characteristics of the arch structure, but also having the characteristics of trusses, and can greatly improve the rigidity, the stability and the dynamic characteristics of the structure. The sagittal ratio can be made smaller, so that sagittal height can be effectively reduced, and construction difficulty is reduced. The invention has good mechanical properties, can be used for building bridges with high requirements on rigidity and dynamic properties, and has great engineering application value.
Description
Technical Field
The invention belongs to an arch bridge system, and particularly relates to a large truss arch bridge.
Background
The arch-type structural system is used as an old bridge type, and is a bridge structural system which has the longest construction history, stronger competitiveness, and is always abundant and continuously developed by the special technical advantages of large spanning capacity, available place materials, low manufacturing cost, low maintenance cost, attractive appearance and the like. Even in modern times, arch bridges are the main bridge types of established or under construction bridges in China, and have many forms and wide construction areas, and are called the world's most. Therefore, the research on the arch structure system has great practical significance.
Arches are one of the most basic structural forms of bridges, the arch-type structure is mainly pressed, and the main bearing structure is an arch ring or an arch rib. Under the action of vertical load, horizontal thrust is generated at two ends. It is the horizontal thrust force, so that axial pressure is generated in the arch, and the section bending moment of the arch ring is greatly reduced, so that the arch ring becomes an eccentric pressed component, and the stress distribution on the section is even compared with that of the bent beam. The main arch section material strength can be fully utilized to increase the spanning capability.
The arch bridge is the most varied structure in all bridge systems, and can be divided into a circular arch, a parabolic arch, a catenary arch, a broken line arch and the like according to the arch axis; the bridge deck and the arch rib are divided into an upper bearing type arch, a middle bearing type arch and a lower bearing type arch according to the relative positions of the bridge deck and the arch rib; the arch section form can be divided into a plate arch, a rib arch, a box arch, a truss arch and a rigid frame arch; the system arch bridge with thrust and without thrust, the simple system arch bridge, the combined system arch bridge and the like can be classified according to stress.
The arch bridge has extremely wide application in China, and the achievement of magnificence is achieved, the arch bridge can be traced back to Zhao Zhouqiao built in 595-605 years of the ancient dynasty, and the history of more than 1400 years exists so far, so that the arch bridge is the second earliest and most complete ancient single-hole open shoulder stone arch bridge in the current world. Today, a plurality of world records of arch bridges are also kept by China, for example, the arch bridge with the largest main span in the world is a Chongqing dynasty bridge, the steel pipe arch bridge with the largest main span in the world is a Shanghai Lu Puda bridge, the Changjiang bridge in Chongqing ten is a reinforced concrete arch bridge with the largest span and standard in the world at that time, and the Changjiang bridge of a Chongqing vegetable garden dam is the first of three worlds: the span of the steel box arched girder is 420 meters, which is the first length of the world; is a first road and light rail two-purpose urban bridge in the world; and is also a bridge installed by adopting a cable crane on the first seat of the world.
Many researches have been conducted on structural improvement of the arch bridge; the utility model discloses a steel pipe truss arch bridge like chinese patent application number is CN201310613938.6, including two hollow round steel pipe arched ribs, hollow round steel pipe tie beam and stull, the stull welds between two hollow round steel pipe arched ribs, the welding has the crossbeam on the hollow round steel pipe tie beam, still includes arch foot connecting device, the rigid knot is formed through the arch foot connecting plate at the both ends of hollow round steel pipe arched rib and the both ends of hollow round steel pipe tie beam, be connected with truss web member between the belly of hollow round steel pipe arched rib and the hollow round steel pipe tie beam. The steel pipe is manufactured into a finished steel pipe by adopting a factory, the steel pipe sections are welded on a construction site, the sections are fewer, the welding quality is easy to ensure, the construction is convenient, and the construction period is short. As another example, chinese patent application No. cn201710067044.X discloses a method for constructing a tension-formed composite-structure arch bridge, the arch bridge comprising at least two straight lower chords parallel to each other, at least two upper chords parallel to each other, a set of crossbars transversely connected between two adjacent upper chords, a set of web members connected between the same-side upper chords and the lower chords, and a set of beams connected between two adjacent lower chords; the lower chord and the cross beam together form a planar bridge deck system; the lower strings are formed by splicing a group of lower string pipes sequentially penetrating through the lower string steel cables, and the adjacent lower string pipes are connected through flange bolts; the upper chord is formed by sequentially welding upper chord tubes, and bottoms of two ends of the spliced upper chord tubes are respectively welded at two ends of the spliced lower chord tubes; and micro-expansion mortar or concrete is poured into the spliced lower chord pipe and upper chord pipe. The invention can integrate construction into form and operation load state in arch bridge construction, and has the advantages of rapid construction, simplicity and economy. The two schemes are that the rigid web members are arranged in the whole span, the whole structure has the characteristics of a truss, the stress characteristics of an arch are weakened, and the structural stress level is high; the number of statically indeterminate times of the whole structure is increased, and the stress level of the arch rib of the structure is obviously increased under the action of temperature.
That is, although the existing arch bridge has many advantages, many problems due to the characteristics of the structure and the stress of the existing arch bridge are still to be solved, and in the aspect of designing and building the large-span arch bridge, the exposed problems are more and more important due to the wide use of new materials and new technologies. Firstly, with the continued breakthrough of arch bridge span, rib stability becomes a critical issue in arch bridge design. Secondly, the construction of the high-speed railway brings strict requirements to the rigidity of the railway arch bridge, and how to enable the arch bridge to obtain higher rigidity is an important subject for improving the running speed and the running comfort of the train. Third, the lateral and vertical fundamental frequencies of the arch bridge are most affected by the span, and the larger the span, the lower the fundamental frequency, especially the undermount flexible boom arch. To continue to maintain advantages and to gain substantial development, new approaches must be sought to break through the above bottlenecks.
Disclosure of Invention
The invention aims to solve the outstanding problems of the existing arch bridge and provides a novel arch bridge, namely a large truss arch bridge. The large truss arch bridge is characterized in that web members are arranged in 1/4-3/4 areas of arch ribs, so that a large truss structure with the arch ribs as upper chords, main beams as lower chords and flexible suspenders is formed. The large truss arch bridge has the characteristics of not damaging the stress characteristics of the arch structure, but also truss, and can greatly improve the rigidity, stability and dynamic characteristics of the structure. The sagittal ratio can be made smaller, so that sagittal height can be effectively reduced, and construction difficulty is reduced. The invention has good mechanical properties, can be used for building bridges with high requirements on rigidity and dynamic properties, and has great engineering application value.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a large truss arch bridge mainly comprises arch ribs, main beams, vertical web members, inclined web members, flexible suspenders and transverse struts; the vertical web members are provided with three pairs and are respectively and vertically arranged near 1/4, 1/2 and 3/4 of the arch ribs, the upper ends of the vertical web members are connected with the arch ribs, and the lower ends of the vertical web members are connected with the main beams; the upper ends of the pair of diagonal web members are connected with the upper ends of the vertical web members arranged near 1/4 of the arch rib, and the lower ends of the pair of diagonal web members are connected with the lower ends of the vertical web members arranged at 1/2 of the arch rib; the upper ends of the other pair of diagonal web members are connected with the upper ends of the vertical web members arranged near 3/4 of the arch ribs, and the lower ends of the diagonal web members are connected with the lower ends of the vertical web members arranged at 1/2 of the arch ribs; the arch rib, the main girder, the vertical web members and the inclined web members form a large truss structure with the arch rib as an upper chord, the main girder as a lower chord and the flexible suspender.
The large truss arch bridge not only maintains the stress characteristic of the arch structure, but also has the characteristics of trusses, and can greatly improve the rigidity, stability and dynamic characteristic of the structure. In the present invention, the load acting on the main beam follows the following force transmission path: main girder, flexible suspender/web member, arch rib, foundation.
As a further illustration of the present invention, the flexible boom described above may be diagonally symmetrical or vertically disposed between the rib and the main beam.
As a further explanation of the present invention, the ribs described above are of steel construction or steel-concrete composite construction; the vertical web member and the inclined web member are both in steel structures. The sections and materials of the main beam, the cross brace and the flexible hanging rod are the same as the traditional ones.
As a further explanation of the present invention, the arch rib described above is a normal arch when it is not inclined; when the arch rib is inclined inwards, the arch rib is a basket arch.
As a further illustration of the invention, the ribs described above may be concrete-encased at the arch springing depending on the load-bearing capacity requirements.
The invention has the advantages that:
the invention is characterized in that vertical web members are arranged only near 1/4, near 3/4 and at the arch crown (1/2) of the arch rib, two ends of the diagonal web members are respectively connected with the bottom of the middle vertical web member and the tops of the two vertical web members, so that a large truss structure with the arch rib as an upper chord member, the main beam as a lower chord member and flexible suspenders is formed. The large truss arch bridge has the advantages of both arch and truss structures, and can greatly improve various mechanical properties of the structure:
1. the action of the flexible suspender and the web members enables the main beam to be a continuous beam with multipoint elastic support, so that the vertical rigidity of the main beam is greatly improved, the in-plane rigidity of the structure can be greatly improved after the web members rigidly connect the arch rib with high vertical rigidity with the main beam, and the vertical web members strengthen the weak parts of the arch rib. Compared with the common flexible suspender arch bridge, the deflection of the main beam of the bridge is greatly reduced under the action of moving load, namely the rigidity is very high.
2. The in-plane stability and out-of-plane stability of the girder arch bridge are improved, and in-plane stability is particularly improved.
3. Because the bridge has higher rigidity, the dynamic characteristic of the bridge is greatly improved, and the comfort level of driving is ensured.
4. The sagittal ratio of the large truss arch bridge can be made as small as possible, so that sagittal height is greatly reduced, construction difficulty is reduced, and the large truss arch bridge is favorable for structural earthquake resistance.
5. The large truss arch bridge can also reduce part of horizontal thrust, so that the construction of a foundation is simplified, and the manufacturing cost is reduced.
Drawings
Fig. 1 and 2 show two arrangements of the girder arch bridge according to the present invention.
Fig. 3 is a schematic plan view of fig. 1 and 2.
Fig. 4 is a schematic diagram of the relationship of the arch axis to the pressure line.
Fig. 5 is a schematic illustration of the offset of the arch axis.
Figure 6 is a schematic illustration of the force applied to the rib under constant load.
Fig. 7 is a deformation diagram of the rib under constant load.
Fig. 8 is a graph of the displacement envelope of the rib under a moving load.
Fig. 9 is a schematic illustration of the effect of a non-steering force system on arch stabilization.
Fig. 10 is a schematic view of a rib transverse deformation.
Fig. 11 is a schematic view of the transverse deformation of the main beam.
Reference numerals: 1-arch rib, 2-girder, 3-vertical web members, 4-diagonal web members, 5-flexible suspenders and 6-transverse struts.
Detailed Description
The mechanics principle and the structure of the invention will now be described with reference to fig. 1-11:
1. bridge formation description of large truss arch bridge
After the arch bridge is formed according to the common flexible suspender, the web member is installed, so the construction difficulty is not increased by the structure.
2. Arrangement of web members
2.1 analysis of arch rib bending moment diagram
The arch bridge has the main advantages that the arch axis is adopted to reduce bending moment, so that the arch bridge is in a small eccentric pressed structure. The stress is characterized in that: the arch crown is acted by positive bending moment, the arch foot is acted by negative bending moment, 1/4 and 3/4 of the arch foot are reverse bending points, and in general, when the arch axis adopts a catenary, the relationship between the arch axis and the dead weight pressure line of the three-hinged arch structure is shown as figure 4. The m value can be determined according to the five-point overlapping method, and the dome only has the structure self-weight thrust H passing through the center of gravity of the section as known by the symmetrical condition that the bending moment of the dome is zero and the structure self weight g Corresponding bending moment M d =0, shear force Q d =0. In FIG. 4, the sum M A =0, get
By sigma M B =0, get
H g y 1/4 -∑M 1/4 ＝0
H of formula (1-1) g Substituted into the above formula to obtain
Wherein: sigma M j -bending moment of self weight of the half arch structure to the arch foot section;
∑M l/4 -bending moment of the structural dead weight of the arch to the area of the arch span l/4 against the l/4 section.
Moment M of dead weight pair l/4 of arch center ring structure of equal cross section catenary arch and arch foot cross section l/4 、M j Can be found from the tables (III) -19 of arch bridge. ObtainingThereafter, m can be found back from the following formula, namely:
the m value of the open web arch bridge is still determined by a successive approximation method. Firstly, assuming an M value, defining an arch axis, drawing and arranging an arch building, and then calculating the moment sigma M of the dead weight of the arch ring and the arch building to l/4 and the arch foot section l/4 Sum sigma M j Y is obtained according to the formula (1-2) l/4 And/f, calculating the m value by using the formula (1-3), if the m value does not match the assumed m value, calculating again by taking the calculated m value as a new assumed value until the two values are close. It should be noted that the arch axis of the free arch is determined by the method, and only the five points of the arch axis are coincided with the dead weight pressure line of the three-hinged arch structure, and other sections, the arch axis and the dead weight pressure line of the three-hinged arch structure deviate to different degrees. Calculations prove that from dome to point l/4, the pressure is in generalThe line is above the arch axis; from point l/4 to the arch springing, the pressure line is mostly below the arch axis. The deviation of the arch axis from the dead weight pressure line of the corresponding three-hinged arch structure is similar to a sine wave (fig. 5).
From mechanical knowledge, the deviation of the pressure line from the arch axis creates additional internal forces in the arch. For a statically determinate three-hinged arch, the deflection bending moment value M of each section p Can be expressed by the deviation delta y of the three-hinge arch pressure line from the arch axis in the section (M p ＝H g X Δy); for a hingeless arch, the magnitude of the deflection bending moment cannot be expressed by the deflection value of the three-hinged arch pressure line and the arch axis, but is calculated by the deflection value M p As a load, a deflection bending moment value of the free arch is calculated. From structural mechanics, the redundant force of the elastic center caused by the load acting on the basic structure is that
Wherein:
M p bending moment generated by deviation of dead weight pressure line of three-hinged arch structure from arch axis line, M p ＝H g ×Δy；
Δy—the deviation value of the dead weight pressure line of the three-hinged arch structure from the arch axis [ as shown in figure (5) ].
As can be seen from FIG. 5, Δy is positive and negative, integrating along the full archThe value of DeltaX is not large, as shown in the formula (1-4) 1 The value is smaller. If->Δx is then 1 =0. From the calculation, deltaX determined by the formula (1-5) 2 Constant positive value (pressure). The deflection bending moment (FIG. 5) of any section is
ΔM＝ΔX 1 -ΔX 2 ×y+M p (1-6)
Wherein: y-the ordinate of the arch axis with the elastic center as the origin (positive upwards).
For arch crown and arch foot section, M p =0, offset bending moment of
Wherein: y is s -the distance from the elastic center to the dome.
The hollow type arch-free bridge adopts an arch axis determined by a five-point overlapping method, and is overlapped with the structural dead weight pressure lines of the corresponding three-hinged arch at five points of the arch crown, the two l/4 arch legs and the two arch legs, but the relationship of the five-point overlapping is not existed with the structural dead weight pressure lines of the non-hinged arch (the structural dead weight pressure lines for short). As can be seen from (1-7), the deflection bending moment is generated in the arch crown and the arch foot due to the deflection of the arch axis and the structure dead weight pressure line. Research proves that the deflection bending moment delta M of the vault d Negative, and the deflection bending moment DeltaM of the arch springing j Positive, the sign of the control bending moment is exactly opposite to that of the two sections. This fact demonstrates that in a hollow arch bridge, the arch axis defined by the "five-point overlap method" is advantageous for both the arch and the footing from bending moments. Thus, the hollow arch axis without hinged arch is more reasonable than the structure dead weight pressure line.
From the above analysis, it is known that the arch axis can be drawn toward the pressure line due to the bending moment at A, C, and that the elastic constraint is set outside the A, B, C three points, which can adversely affect the rib stress.
2.2 analysis of arch rib deformation
The stress schematic diagram and the deformation diagram of the arch rib under the action of constant load are respectively shown in fig. 6 and 7, and the maximum deformation position of the arch rib occurs at A; the displacement envelope of the rib under the moving load is shown in fig. 8, with the maximum deformation occurring at B. It follows that under constant load, the weak position of the arch rib is at the arch top, and under moving load, the weak position is at 1/4 and 3/4.
2.3 selection of constraint points
By combining the stress and deformation characteristics of the arch rib, A, B is selected as an elastic constraint point for the half arch rib, so that the arch rib deformation can be reduced, and the arch rib is basically the same as the stress state of a common flexible suspender arch bridge in a constant load state, and the arch axis is not damaged.
According to the invention, the flexible suspenders at 1/4, 1/2 and 3/4 are replaced by the vertical web members with larger rigidity, and two ends of the inclined web members are respectively connected to the bottom of the middle web member and the top of the side web member. Thereby forming three hoops between the vertical web member and the transverse bridge deck in the transverse plane; a large truss structure with a flexible suspender is formed in the longitudinal surface, wherein an arch rib is used as an upper chord, a main beam is used as a lower chord. Because three rigid connection is carried out between the upper part and the lower part, and the inclined web member is additionally arranged, the integrity of the invention is enhanced, and the bending moment deformation and the shearing deformation of the structure are effectively reduced.
In summary, the elastic constraint is only arranged near three A, B, C positions, so that the stress characteristics of the arch rib in the constant load state are maintained, and the truss-like structure is also provided.
3. Positive effect analysis of non-directional force of newly added component
From the analysis, the web members of the novel arch bridge are beneficial to reducing the deformation of the arch ribs and have the effect of improving the stability of the arch ribs. The improvement in-plane stability is evident, and the effect of out-of-plane stability is analyzed as follows:
similar to conventional flexible boom arch bridges, the effect of web members and boom operating conditions on the stability of the arch bridge herein is not negligible. For the present invention, when the rib is laterally unstable (fig. 9), the web member and the diagonal boom are laterally inclined due to the horizontal constraint applied by the main beam, and the generated horizontal component force has a tendency to slow down the lateral instability of the rib, and the non-directional force effect is positive. After the arch rib is tilted, the suspender and the web member incline, as shown in fig. 10 and 11, the tension T of the suspender and the web member generates an outward horizontal component force to the main beam to cause the main beam to bend and deform laterally b (x) While an inward horizontal component H (x) is generated for the rib:
wherein,
taking into account the main beam out-of-plane stiffness (EI by ) Far larger than the arch rib, so the EI is approximately taken by = infinity, u b Approaching 0, formula (2-2) can be simplified to:
the arch bridge is additionally provided with five pairs of web members, so that the non-directional force effect is more obvious, and the lateral stability is also improved.
4. Novel arch bridge integral cooperation principle
The arch rib is used as a small eccentric compression member, has higher vertical rigidity relative to a beam with the same span, and for the main beam of the novel arch bridge, the main beam is a continuous beam constrained by multipoint elasticity due to the actions of the suspenders and the rigid web members, the vertical rigidity of the main beam is increased to be capable of cooperating with the arch rib, and the main beam and the arch rib are connected together through the rigid member, so that a structure with high rigidity is formed, and the structure has better integrity.
5. Arch abutment thrust analysis
The arched bridge is provided with inclined suspenders and inclined web members, horizontal component forces generated on the main beams are balanced with each other, and the horizontal component forces generated on the arched ribs can balance part of arch abutment thrust, so that bending moment and shearing force of the inclined web members are omitted for simplifying calculation, and the arched bridge is obtained by a mechanical balance principle:
wherein H is arch abutment thrust, q is equal uniformly distributed load of arch ribs, l is span, f is sagittal height, S i Alpha is the tension of the ith boom i The included angle between the ith suspender and the horizontal direction is T is the axial force of the diagonal web member, and beta is the axial force of the diagonal web member and waterIncluded angle in the flat direction.
6. Stress state analysis
The bridge forming explanation shows that the web members can not bring great concentrated force to the arch ribs under the constant load state, thereby ensuring the uniform stress of the arch ribs. The web members participate in working under the action of moving load, and because the section rigidity is very high, the vertical displacement of the structure can be greatly reduced, but the internal force is concentrated, so that the arch rib is concentrated to a certain extent. Under the action of temperature, the invention increases some statically indeterminate times, and the temperature effect is obvious compared with the common flexible suspender arch bridge. In general, after load combination, the maximum stress usually occurs at the arch springing, and the stress value can be reduced (such as concrete is wrapped outside a steel box) by increasing the section of the arch springing section according to actual conditions, so that the economical efficiency is ensured.
7. Comparative analysis with existing CN201310613938.6, cn201710067044.X technology
The technical solutions disclosed in the prior CN201310613938.6 and the prior CN201710067044.X are all provided with rigid web members in a full span, and have the following main disadvantages: the rigid web members are arranged in the whole span, the whole structure has the characteristics of a truss, the stress characteristics of an arch are weakened, and the structural stress level is high; the number of statically indeterminate times of the whole structure is increased, and the stress level of the arch rib of the structure is obviously increased under the action of temperature; compared with the invention, the steel consumption is increased, the economy is poor, the structural constant load is large, and the stress level is also large; when the span is increased, the structural stability is obviously reduced, and the steel consumption is also increased sharply; in addition, the construction difficulty is high, and the bridge is not easy to form. Under comprehensive consideration, the economic span is only about 300 m.
The invention skillfully utilizes the relation between the arch axis and the pressure line, and only sets vertical web members near 1/4, 3/4 and vault of the arch rib, and two ends of the diagonal web member are respectively connected with the bottom of the middle web member and the top of the side web member, thereby forming a large truss structure with the arch rib as an upper chord member, the main beam as a lower chord member and flexible suspenders. Therefore, the invention not only maintains the stress characteristic of the arch, but also has the characteristics of the truss structure, various mechanical indexes are improved to a certain extent, and particularly the in-plane rigidity of the structure is greatly improved. The economy of the structure is still better as only 5 pairs of web members are added, and the structure also retains the flexible suspenders, so that the bridge is easier to form.
In conclusion, the technical scheme disclosed by the invention is obviously different from the technical scheme disclosed by the prior CN201310613938.6, CN201710067044.X in terms of mechanical principle, bridging mechanism, structural form and the like, and has better economy and stronger spanning capability. The structural design of the present invention will be further described in detail with reference to the accompanying drawings and examples.
Examples:
the span arrangement of the girder arch bridge of this embodiment is the same as that of the Lu Puda bridge (total investment of 25 gigabytes). The method comprises the following steps: a large truss arch bridge is provided, which is additionally provided with 5 pairs of web members on the basis of the traditional flexible suspender arch bridge. Namely, mainly comprises arch ribs 1, main beams 2, vertical web members 3, diagonal web members 4, flexible suspenders 5 and transverse struts 6; the vertical web members 3 are provided with three pairs and are respectively and vertically arranged at 1/4, 1/2 and 3/4 of the arch ribs 1, the upper ends of the vertical web members 3 are connected with the arch ribs 1, and the lower ends of the vertical web members 3 are connected with the main beams 2; the inclined web members 4 are provided with two pairs, wherein the upper ends of one pair of inclined web members are connected with the upper ends of the vertical web members arranged at 1/4 of the arch rib, and the lower ends of the two pairs of inclined web members are connected with the lower ends of the vertical web members arranged at 1/2 of the arch rib; the upper ends of the other pair of diagonal web members are connected with the upper ends of the vertical web members arranged at 3/4 of the arch rib, and the lower ends of the diagonal web members are connected with the lower ends of the vertical web members arranged at 1/2 of the arch rib; concrete is covered around the arch feet of the arch ribs, and flexible suspenders 5 are uniformly arranged at the rest positions of the main beams 2; the arch rib 1, the main girder 2, the vertical web members 3 and the inclined web members 4 form a large truss structure with the arch rib 1 as an upper chord, the main girder 2 as a lower chord and the flexible suspender 5. The web members increase the vertical and transverse rigidity of the structure and reduce the deformation of the arch ribs, so that the structure has better stability, dynamic performance and larger rigidity. According to the different arrangement modes of the flexible suspenders, the following two schemes exist:
the first scheme adopts a first structural form (the flexible suspenders 5 are obliquely and symmetrically arranged between the arch rib 1 and the main girder 2), as shown in fig. 1, and adopts the above structural form, the main arch sagittal span ratio is 1/5.5, and 5 pairs of web members are arranged. Compared with the Lu Puda bridge: the arch rib of the scheme has basically the same stress, so the arch rib area is basically unchanged; the consumption of the cross brace material is reduced by 20%, the flexible suspender is only increased by 5%, and the cost is comprehensively reduced to be 0.01 hundred million yuan; the added web member cost is 0.0047 billion yuan; thus, the girder arch bridge has a total cost saving of 0.2% compared to the Lu Puda bridge. But the arch rib rigidity and the overall rigidity of the large truss arch bridge are respectively improved by 75 percent and 67 percent; the first-order in-plane stability is improved by 155%, and the out-of-plane stability is improved by 23%; the frequency of the first occurrence of the in-plane vibration is increased by 165%.
The second scheme adopts a second structural form (the flexible suspender 5 is vertically arranged between the arch rib 1 and the main girder 2), as shown in fig. 2, and adopts the structural form, the main arch sagittal ratio is 1/4.1325, and five pairs of web members are arranged. Compared with a skyhook bridge: the arch rib of the scheme has basically the same stress, so the arch rib area is basically unchanged; the consumption of the cross brace material is reduced by 30%, the flexible suspender is reduced by 10%, and the cost is saved by 0.03 hundred million yuan; the added web member cost is 0.0047 billion yuan; thus, the girder arch bridge has a total cost saving of 0.3% compared to the skyscraper bridge. But the arch rib rigidity and the overall rigidity of the large truss arch bridge are respectively improved by 68 percent and 60 percent; the first-order in-plane stability is improved by 147%, and the out-of-plane stability is improved by 20%; the frequency of the first occurrence of the in-plane vibration is improved by 158%.
Example technical parameter comparison table
| Cost saving (%) | Rigidity improvement (%) | Stability enhancement (%) | Fundamental frequency increases (%) | |
| Scheme one | 0.2 | 75% and 67% | 155％ | 165％ |
| Scheme II | 0.3 | 68% and 60% | 147％ | 158％ |
Claims (3)
1. A large truss arch bridge, characterized by: the device mainly comprises arch ribs (1), main beams (2), vertical web members (3), inclined web members (4), flexible suspenders (5) and transverse struts (6); the vertical web members (3) are provided with three pairs and are vertically arranged near 1/4 of the arch ribs (1) and near 1/2 and 3/4 of the arch ribs respectively, the upper ends of the vertical web members (3) are connected with the arch ribs (1), and the lower ends of the vertical web members are connected with the main beams (2); the inclined web members (4) are provided with two pairs, wherein the upper ends of one pair of inclined web members are connected with the upper ends of the vertical web members arranged near the arch ribs 1/4, and the lower ends of the inclined web members are connected with the lower ends of the vertical web members arranged at the arch ribs 1/2; the upper ends of the other pair of diagonal web members are connected with the upper ends of the vertical web members arranged near 3/4 of the arch ribs, and the lower ends of the diagonal web members are connected with the lower ends of the vertical web members arranged at 1/2 of the arch ribs; the arch rib (1), the main beam (2), the vertical web member (3) and the inclined web member (4) form a large truss structure which takes the arch rib (1) as an upper chord member, the main beam (2) as a lower chord member and is provided with a flexible suspender (5);
the flexible suspenders (5) are obliquely and symmetrically arranged or vertically arranged between the arch rib (1) and the main beam (2);
the arch rib adopts a steel structure or a steel-concrete combined structure; the vertical web member (3) and the inclined web member (4) are both in steel structures.
2. A girder arch bridge as claimed in claim 1, wherein: when the arch rib (1) is not inclined, the arch is a common arch; when the arch rib (1) inclines inwards, the arch is a basket arch.
3. A girder arch bridge as claimed in claim 1, wherein: the arch rib (1) can wrap concrete at the arch springing according to the bearing capacity requirement.
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| CN108677682A (en) * | 2018-08-09 | 2018-10-19 | 广西大学 | Novel Deck Arch Bridges |
| CN112411743A (en) * | 2020-11-26 | 2021-02-26 | 湖南鸿阳钢结构有限公司 | Novel assembled pipe truss structure |
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