CN108374324A - Big truss arched bridge - Google Patents
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- CN108374324A CN108374324A CN201810312184.3A CN201810312184A CN108374324A CN 108374324 A CN108374324 A CN 108374324A CN 201810312184 A CN201810312184 A CN 201810312184A CN 108374324 A CN108374324 A CN 108374324A
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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
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Abstract
The invention discloses a kind of big truss arched bridges, are mainly made of arch rib, girder, perpendicular web member, diagonal web member, flexible suspension rod and stull；The perpendicular web member is vertically arranged in 1/4 neighbouring, 1/2,3/4 vicinity of arch rib respectively；Diagonal web member both ends are connected to intermediate perpendicular web member bottom and both sides are erected at the top of web member；Big truss structure of the arch rib, girder, perpendicular web member, diagonal web member composition one using arch rib as top boom, girder as lower boom and with flexible suspension rod.The big truss arched bridge of the present invention neither destroys the stress characteristic of arch structure, and has the characteristics of truss, and the rigidity, stability, dynamic characteristics of structure can be made to be greatly improved.Because its ratio of rise to span be can be made smaller, rise can be effectively reduced, to reduce difficulty of construction again.The present invention has good mechanical property, can be used for building and requires rigidity, power performance high bridge, there is 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 structure system is an ancient bridge structure system, and becomes a bridge structure system which has the longest building history, stronger competitiveness, and is always prosperous and continuously developed by using the unique technical advantages of large spanning capacity, available local materials, economic manufacturing cost, less maintenance and repair cost, beautiful appearance and the like. Even in modern times, the arch bridge is still the main bridge type of the bridge built in China or under construction, and the arch bridge has many forms and wide construction regions, which is the most important in the world. Therefore, the research on the arch structure system has great practical significance.
The arch is one of the most basic structural forms of the bridge, the arch structure is mainly pressed, and the main load-bearing structure is an arch ring or an arch rib. Under the action of vertical load, horizontal thrust is generated at two ends. The horizontal thrust can generate axial pressure in the arch, so that the section bending moment of the arch ring is greatly reduced to form an eccentric compression component, and the stress distribution on the section is more uniform than that of a bending beam. The strength of the main arch section material can be fully utilized to increase the spanning capability.
The arch bridge is a structure which changes most in all bridge systems and can be divided into an arc arch, a parabolic arch, a catenary arch, a broken line arch and the like according to an arch axis; the arch can be divided into a top-bearing type arch, a middle-bearing type arch and a bottom-bearing type arch according to the relative position of the bridge deck and the arch rib; according to the form of the arch section, the arch can be divided into a plate arch, a rib arch, a box arch, a truss arch and a rigid frame arch; the arch bridge can be divided into a thrust system arch bridge and a non-thrust system arch bridge, a simple system arch bridge, a combined system arch bridge and the like according to stress.
The arch bridge has extremely wide application in China, also has splendid achievements, can trace back to the Zhao state bridge built between the inertial dynasty in 595-605 b.c. and 595 years, has more than 1400 years history today, and is the second earliest and most complete ancient single-hole open-shoulder stone arch bridge in the world today. At present, a plurality of world records of the arch bridge are kept by China, for example, the arch bridge with the largest main span and span in the world is a Chongqing Tianmen bridge, the steel pipe arch bridge with the largest main span and span in the world is a Shanghai Lupu bridge, the Chongqing Wanzhou Changjiang bridge is a reinforced concrete arch bridge with the largest span and scale in the world at that time, and the Chongqing vegetable garden dam Changjiang bridge creates the first three world: the span of the steel box arched girder is 420 meters, which is the first length in the world; is a dual-purpose city bridge of a first highway and a light rail in the world; and is also the first bridge in the world installed by adopting a cable crane.
Many studies have been made on the structural improvement of arch bridges; for CN201310613938.6 discloses a steel pipe truss arched bridge, including two hollow circular steel tube arched ribs, hollow circular steel tube tie beam and stull, the stull welding is between two hollow circular steel tube arched ribs, the welding has the crossbeam on the hollow circular steel tube tie beam, still includes hunch foot connecting device, the both ends of hollow circular steel tube arched rib and the both ends of hollow circular steel tube tie beam form the rigid knot through the hunch foot connecting plate, be connected with truss-like web member between the belly of hollow circular steel tube arched rib and the hollow circular steel tube tie beam. The steel pipe is manufactured by a factory to be a finished steel pipe, the steel pipe sections are welded on a construction site, the number of the sections is small, the welding quality is easy to guarantee, the construction is convenient, and the construction period is short. Also, for example, chinese patent application No. cn201710067044.x discloses a method for constructing a stretch-formed arch bridge of a combined structure, which includes at least two straight lower chords parallel to each other, at least two upper chords parallel to each other of the upper arches, a set of wales transversely connected between the two adjacent upper chords, a set of web members connected between the upper chords and the lower chords on the same side, and a set of cross members connected between the two adjacent lower chords; the lower chord and the cross beam jointly form a plane bridge deck system; the lower chord is formed by splicing a group of lower chord pipes sequentially penetrating through the lower chord steel cable, and the adjacent lower chord pipes are connected through flange bolts; the upper chord is formed by sequentially welding upper chord pipes, and the bottoms of the two ends of the spliced upper chord pipes are respectively welded to the two ends of the spliced lower chord pipes; micro-expansion mortar or concrete is poured into the spliced lower chord tube and the spliced upper chord tube. The invention can integrate the construction form and the operation load state into a whole in the construction of the arch bridge, and has the advantages of quick construction, simplicity and economy. In the two schemes, the rigid web members are arranged in the full span, so that the whole structure has the characteristics of a truss, the stress characteristic of an arch is weakened, and the structural stress level is higher; the hyperstatic times of the whole structure are increased, and the stress level of the structural arch rib is obviously increased under the action of temperature.
That is to say, although there are many advantages of the existing arch bridge, many problems due to the characteristics of its structure and stress are still to be solved, and in the aspect of designing and building the large-span arch bridge, the problems that are exposed due to the wide use of new materials and new technologies are more and more regarded by people. First, with the continuous breakthrough of arch bridge span, arch rib stability becomes a key issue in arch bridge design. Secondly, the construction of the high-speed railway puts a strict requirement on the rigidity of the railway arch bridge, and how to obtain higher rigidity of the arch bridge is an important subject for improving the running speed and the running comfort of the train. Thirdly, the transverse and vertical fundamental frequencies of the arch bridge are influenced most by the span, the larger the span is, the lower the fundamental frequency is, and particularly, the arch is made of the through flexible suspender. To continue to maintain advantages and gain a great deal of growth in arch bridges, new ways must be found to break through the above bottlenecks.
Disclosure of Invention
The invention aims to provide a novel arch bridge, namely a truss arch bridge, aiming at the outstanding problems of the existing arch bridge. The large truss arch bridge is provided with the web members only in the areas of the arch ribs 1/4-3/4 to form a large truss structure which takes the arch ribs as upper chords and the main beam as lower chords and is provided with flexible suspension rods. The large truss arch bridge does not destroy the stress characteristic of the arch structure, has the characteristics of a truss, and can greatly improve the rigidity, stability and dynamic characteristics of the structure. The rise ratio can be made smaller, so that the rise can be effectively reduced, and the construction difficulty is reduced. The invention has good mechanical property, can be used for building bridges with high requirements on rigidity and dynamic property, and has great engineering application value.
In order to achieve the purpose, the invention adopts the following technical scheme:
a large truss arch bridge mainly comprises arch ribs, a main beam, vertical web members, diagonal web members, flexible suspension rods and cross braces; the vertical web members are provided with three pairs and are respectively vertically arranged near 1/4, 1/2 and 3/4 of the arch rib, the upper end of each vertical web member is connected with the arch rib, and the lower end of each vertical web member is connected with the main beam; the two pairs of the diagonal web members are arranged, wherein the upper ends of one pair of the diagonal 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 diagonal 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 the arch rib 3/4, and the lower ends of the other pair of diagonal web members are connected with the lower ends of the vertical web members arranged at the arch rib 1/2; 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 and the main beam as a lower chord and is provided with a flexible suspender.
The large truss arch bridge not only keeps the stress characteristic of an arch structure, but also has the characteristics of a truss, so that the rigidity, the stability and the dynamic characteristic of the structure can be greatly improved. In the present invention, the load acting on the main beam follows the following force transmission path: girder → flexible boom/web → arch rib → foundation.
As a further illustration of the invention, the flexible hanger bars described above may be diagonally symmetrically arranged or vertically arranged between the ribs and the main beam.
As a further explanation of the present invention, the arch rib described above adopts a steel structure or a steel-concrete composite structure; the vertical web members and the inclined web members are all made of steel structures. The sections and materials of the main beam, the cross brace and the flexible hanging rod are all consistent with the traditional method.
As a further explanation of the present invention, the arch rib described above is a normal arch when not inclined; when the arch rib is inclined inwards, the arch rib is an arch of the basket.
As a further illustration of the invention, the ribs described above may be concrete-encased at the arch springing depending on the load bearing requirements.
The invention has the advantages that:
the invention is characterized in that vertical web members are arranged only near 1/4, 3/4 and a vault (1/2) of the arch rib, two ends of each diagonal web member are respectively connected with the bottom of the middle vertical web member and the tops of the two side vertical web members, thereby forming a large truss structure which takes the arch rib as an upper chord member, takes the main beam as a lower chord member and is provided with a flexible suspender. The big purlin arch bridge has the advantage of encircleing and purlin formula structure concurrently, can make each item mechanical properties of structure all obtain very big improvement:
1. the flexible suspender and the web member are used for enabling the main beam to be a continuous beam with multi-point elastic support, so that the vertical rigidity of the main beam is greatly improved, after the arch rib with high vertical rigidity is rigidly connected with the main beam through the web member, the in-plane rigidity of the structure can be greatly improved, and the weak part of the arch rib is reinforced by the vertical web member. Compared with the common flexible suspender arch bridge, the flexibility of the main girder of the bridge is greatly reduced under the action of moving load, namely the rigidity is very high.
2. The large truss arch bridge of the invention has improved in-plane and out-of-plane stability, especially in-plane stability.
3. Because the bridge has higher rigidity, the dynamic characteristic of the bridge is greatly improved, and the comfort level of driving is further ensured.
4. The rise-span ratio of the large truss arch bridge can be reduced as much as possible, so that the rise height is greatly reduced, the construction difficulty is reduced, and meanwhile, the structure earthquake resistance is facilitated.
5. The large truss arch bridge of the invention can also reduce partial horizontal thrust, so that the construction of the foundation can be simplified, thereby reducing the manufacturing cost.
Drawings
Fig. 1 and 2 show two arrangements of the truss arch bridge of the invention.
Fig. 3 is a schematic top view of fig. 1 and 2.
FIG. 4 is a schematic representation of the relationship of the arch axis to the pressure line.
Fig. 5 is a schematic view of the offset of the arch axis.
Fig. 6 is a schematic view 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-orientation preserving force system on arch stabilization.
Fig. 10 is a schematic view of transverse rib deformation.
FIG. 11 is a schematic view of a transverse deformation of the main beam.
Reference numerals: 1-arch rib, 2-main beam, 3-vertical web member, 4-oblique web member, 5-flexible suspender, 6-cross brace.
Detailed Description
The mechanical principle and structure of the present invention will now be described with reference to fig. 1-11:
1. bridge formation description of truss arch bridge
After the arch bridge is built according to the common flexible suspender, the web members are installed, so the structure does not increase the construction difficulty.
2. Setting of web members
2.1 Arch Rib moment diagram analysis
The main advantage of the arch bridge is that the arch axis is adopted to reduce the bending moment, so that the arch bridge becomes a structure with small eccentric compression. The stress characteristic is as follows: the arch crown is acted by positive bending moment, the arch foot is acted by negative bending moment, the 1/4 and 3/4 positions are reverse bending points, and generally, when the arch axis adopts a catenary, the relationship between the stress line and the dead weight pressure line of the three-hinged arch structure is shown in figure 4. The value of m can be determined according to the 'five-point coincidence method', and the vault only has the structure dead weight thrust H passing through the section gravity center according to the symmetric conditions that the vault bending moment is zero and the structure dead weightgCorresponding bending moment Md0, shear force Qd0. In FIG. 4, the signal is represented by ∑ MA0, get
By sigma MB0, get
Hgy1/4-∑M1/4＝0
H of the formula (1-1)gSubstituted into the above formula to obtain
In the formula: sigma MjThe bending moment of the dead weight of the semi-arch structure on the cross section of the arch springing;
∑Ml/4the dead weight of the structure from the vault to the arch span l/4 point area is opposite to the bending moment of the l/4 section.
Constant section catenary arch main arch ring structure dead weight pair l/4 and bending moment M of arch springing sectionl/4、MjCan be found from the arch bridge table (III) -19. To obtainThen, m can be solved back by the following formula:
the m value of the open arch bridge is still determined according to a successive approximation method. Firstly, assuming a value M, defining an arch axis, drawing and arranging the arch building, and then calculating the self-weight of the arch ring and the arch building to l/4 and the moment sigma M of the arch foot sectionl/4Sum sigma MjThen, y is obtained from the formula (1-2)l/4Then, the m value is calculated by the formula (1-3), and if the m value does not match the assumed m value, the m value is recalculated as a new assumed value,until the two approach. It should be noted that the arch axis of the hollow arch is determined by the above method, and only five points of coincidence with the pressure line of the self weight of the three-hinged arch structure are kept, and other cross sections have different deviations from the pressure line of the self weight of the three-hinged arch structure. The calculation proves that from the arch to the point l/4, the general pressure line is above the arch axis; from the l/4 point to the arch springing, the pressure line is mostly below the arch axis. The deviation of the arch axis from the pressure line of the corresponding three-hinged arch structure's own weight is similar to a sine wave (fig. 5).
From mechanics knowledge, deviations of the pressure lines from the arch axis will generate additional internal forces in the arch. For static three-hinged arch, the deviation bending moment value M of each sectionpCan be expressed by the deviation value delta y of the pressure line of the three-hinged arch and the arch axis in the section (M)p＝HgX Δ y); for a non-hinged arch, the magnitude of the bending moment cannot be represented by the deviation value of the pressure line of the three-hinged arch from the arch axis, but should be represented by the deviation value MpAs the load, the bending moment of deflection without a hinge arch was calculated. From the structural mechanics, the redundant force of the load acting on the basic structure to cause the elastic center is
In the formula:
Mp-bending moment, M, generated by the deviation of the dead weight pressure line of the three-hinged arch structure from the arch axisp＝Hg×Δy；
Deltay is the deviation value of the pressure line of the self weight of the three-hinged arch structure from the arch axis [ as shown in figure 5 ].
As can be seen from FIG. 5, Δ y has positive or negative values, and is integrated over the full archIs not large, as is known from the formula (1-4) < delta > X1The numerical value is small. If it isThen Δ X10. From the calculation, Δ X determined by the formula (1-5)2Constant positive values (pressure). The bending moment of deviation of arbitrary cross section (FIG. 5) is
ΔM＝ΔX1-ΔX2×y+Mp(1-6)
In the formula: y-arch ordinate with elastic center as origin (positive upward).
For arch crown, arch foot sections, Mp0, bending moment of deflection
In the formula: y issThe distance from the elastic center to the dome.
The hollow non-hinged arch bridge has arch axis determined by five-point overlapping method and superposed with the pressure line of the dead weight of the corresponding three-hinged arch at five points of arch crown, two/4 and two arch feet, and has no pressure line of the dead weight of the non-hinged arch structure. As can be seen from the formulas (1-7), due to the deviation of the arch axis and the pressure line of the self weight of the structure, the deviation bending moment is generated at the arch crown and the arch foot. Research proves that the deviation bending moment delta M of the vaultdIs negative, and the bending moment Δ M of deflection of the arch footjBeing positive, the sign of the bending moment is exactly opposite to that of the two sections. This fact shows that in the hollow arch bridge, the arch axis arch shaft determined by the five-point coincidence method is beneficial to the arch crown and the arch foot by deviating the bending moment. Therefore, the arch axis of the hollow non-hinged arch is more reasonable than the pressure line of the dead weight of the structure.
From the above analysis, it can be seen that the action of the bending moment at A, C can make the arch axis close to the pressure line, and if elastic constraint is set beyond the three points A, B, C, the stress on the arch rib is adversely affected.
2.2 Arch Rib deformation analysis
The stress schematic diagram and the deformation diagram of the arch rib under the constant load are respectively shown in fig. 6 and 7, and the maximum deformation position of the arch rib occurs at a position A; the displacement envelope of the rib under moving load is shown in figure 8, with the maximum deformation occurring at B. It can be seen that under constant load the weak point of the rib is at the dome and under moving load the weak point is at 1/4, 3/4.
2.3 selection of constraint points
By combining the stress and deformation characteristics of the arch ribs, A, B is selected as an elastic constraint point for half arch ribs, so that the deformation of the arch ribs can be reduced, and the stress state of the arch ribs is basically the same as that of a common flexible suspender arch bridge under a constant load state, and the arch axis is not damaged.
The invention changes the flexible suspension rods at 1/4, 1/2 and 3/4 into vertical web members with larger rigidity, and connects the two ends of the diagonal web member to the bottom of the middle web member and the top of the side web member respectively. Thereby forming three hoops by the vertical web members, the transverse links and the bridge deck in the transverse plane; and an arch rib is formed in the longitudinal plane and serves as an upper chord, the main beam serves as a lower chord, and the large truss structure is provided with a flexible suspender. Because three rigid connections are carried out between the upper part and the lower part and the diagonal web members are 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 conclusion, the invention only arranges elastic restraint at A, B, C, which not only keeps the stress characteristic of the arch rib under the constant load condition, but also has the characteristic of the truss structure.
3. Analysis of positive effect of non-orientation-preserving force of newly added component
From the above analysis, the web members of the new arch bridge are beneficial to reducing the deformation of the arch rib and improving the stability of the arch rib. The improvement in-plane stability is evident, and the effect on out-of-plane stability is analyzed as follows:
similar to the traditional flexible boom arch bridge, the influence of the working state of the web members and the booms on the stability of the arch bridge is not negligible. For the present invention, when the transverse instability of the arch rib occurs (fig. 9), the web member and the oblique suspension rod are restrained by the main beam to become inclined laterally, the generated horizontal component force has the tendency of alleviating the transverse instability of the arch rib, and the non-direction-maintaining force effect is positive. When the ribs are tilted, the hanger bar and web members tilt, and the tension T exerts an outward horizontal component on the main beam, causing lateral bending deformation u as shown in fig. 10 and 11b(x) And 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 greater than the arch rib, so approximate EIbyInfinity then ubClose to 0, equation (2-2) can be simplified to:
and five pairs of web members are additionally arranged on the arch bridge, so that the non-direction-retaining action is more obvious, and the lateral stability is also improved.
4. Novel arch bridge integral cooperation principle
The arch rib is as little eccentric compression component, for the roof beam with the span, has higher vertical rigidity, and to the girder of novel arched bridge, because jib and rigid web member's effect become the continuous beam that receives the multiple spot elastic constraint, its vertical rigidity grow and can with the cooperation of arch rib, link together through rigid member to form a structure that rigidity is big, and then make the structure have better wholeness.
5. Arch thrust analysis
The arch bridge is provided with the oblique suspender and the oblique web member, the horizontal component force generated on the main beam is balanced with each other, the horizontal component force generated on the arch rib can balance partial arch abutment thrust, the bending moment and the shearing force of the oblique web member are ignored for simplifying calculation, and the arch bridge can be obtained by a mechanical balance principle:
h is the abutment thrust, q is the equivalent uniform load of the arch rib, l is the span, f is the rise, SiTension of the ith boom, αiIs the included angle between the ith suspension rod and the horizontal direction, T is the axial force of the diagonal web member, and β is the included angle between the diagonal web member and the horizontal direction.
6. Stress state analysis
It can be known from the description of bridging that the web members do not bring a great concentrated force to the arch rib under the constant load state, thereby ensuring the uniform stress of the arch rib. Under the action of moving load, the web member participates in work, and because the rigidity of the section of the web member is very high, the vertical displacement of the structure can be greatly reduced, but the internal force is concentrated, so that the arch rib has stress concentration to a certain degree. Under the action of temperature, the present invention has several hyperstatic times, so that its temperature effect is obvious. Generally, after load combination, the maximum stress usually appears at the arch springing, and the stress value can be reduced by increasing the section of the arch springing section according to actual conditions (such as concrete is wrapped outside a steel box), so that the economy 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 all arrange rigid web members in a full span, and mainly have the following disadvantages: the rigid web members are arranged in the full span, so that the whole structure has the characteristics of a truss, the stress characteristics of an arch are weakened, and the structural stress level is higher; the hyperstatic times of the whole structure are increased, and the stress level of the structural arch rib is obviously increased under the action of temperature; compared with the invention, the steel consumption is increased, the economy is poorer, the structure constant load is larger, and the stress level is larger; when the span is increased, the structural stability is obviously reduced, and the steel consumption is also sharply increased; in addition, the construction difficulty is high, and the bridge is not easy to form. In general terms, the economic span is only about 300 m.
The invention skillfully utilizes the relation between the arch axis and the pressure line, the vertical web members are only arranged near 1/4, 3/4 and the arch crown of the arch rib, and the 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 which takes the arch rib as an upper chord member, the main beam as a lower chord member and is provided with a flexible suspender. Therefore, the invention not only keeps the stress characteristic of the arch, but also has the characteristics of a truss structure, and all mechanical indexes are improved to a certain degree, particularly the in-plane rigidity of the structure is greatly improved. Because only 5 pairs of web members are added, the economy of the structure is still better, and the flexible suspender is reserved in the structure, so that the bridge is easier to form.
In conclusion, the invention is obviously different from the technical schemes disclosed by the prior CN201310613938.6 and the prior CN201710067044.X in the aspects of mechanical principle, bridging mechanism, structural form and the like, and has better economical efficiency and stronger spanning capability. The structural design of the present invention is further explained in detail below with reference to the drawings and the embodiments.
Example (b):
the span arrangement of the truss arch bridge of the embodiment is the same as that of the rupu bridge (25 hundred million yuan of total investment). The method specifically comprises the following steps: a large truss arch bridge is characterized in that 5 pairs of web members are additionally arranged on the basis of a traditional flexible suspender arch bridge. The main structure mainly comprises arch ribs 1, a main beam 2, vertical web members 3, oblique web members 4, flexible suspension rods 5 and cross braces 6; the vertical web members 3 are provided with three pairs and are respectively vertically arranged at 1/4, 1/2 and 3/4 of the arch rib 1, the upper ends of the vertical web members 3 are connected with the arch rib 1, and the lower ends are connected with the main beam 2; the two pairs of the diagonal web members 4 are arranged, wherein the upper ends of one pair of the diagonal 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 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 at 3/4 of the arch rib, and the lower ends of the other pair of diagonal web members are connected with the lower ends of the vertical web members arranged at 1/2 of the arch rib; concrete is coated near the arch springing of the arch rib, and flexible suspenders 5 are uniformly arranged at the rest positions of the main beam 2; the arch rib 1, the main beam 2, the vertical web members 3 and the inclined web members 4 form a large truss structure which takes the arch rib 1 as an upper chord and the main beam 2 as a lower chord and is provided with a flexible suspender 5. The web members increase the vertical and horizontal rigidity of the structure and reduce the deformation of the arch ribs, so that the structure has better stability and dynamic performance and higher rigidity. According to different arrangement modes of the flexible suspender, the following two schemes are adopted:
the first scheme adopts a structural form I (flexible suspenders 5 are obliquely and symmetrically arranged between the arch rib 1 and the main beam 2) as shown in figure 1, and adopts the structural form, the main arch-span ratio is 1/5.5, and 5 pairs of web members are arranged. Compared with the Lupu bridge: the stress of the arch rib is basically the same, so the area of the arch rib is basically unchanged; the consumption of the cross brace material is reduced by 20 percent, the flexible suspender is only increased by 5 percent, and the cost is comprehensively saved by 0.01 hundred million yuan; the added cost of the web member is 0.0047 billion yuan; therefore, compared with the Lupu bridge, the large truss arch bridge saves the cost by 0.2 percent altogether. But the arch rib rigidity and the integral 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 percent, and the out-of-plane stability is improved by 23 percent; the frequency of the first in-plane vibration was 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 beam 2), as shown in figure 2, and adopts the structural form, the main arch-span ratio is 1/4.1325, and five pairs of web members are arranged. Compared with the overpass towards the overhead door: the stress of the arch rib is basically the same, so the area of the arch rib is basically unchanged; the consumption of the cross brace material is reduced by 30 percent, the consumption of the flexible suspender is reduced by 10 percent, and the cost is saved by 0.03 hundred million yuan; the added cost of the web member is 0.0047 billion yuan; thus, a large truss arch bridge saves a total of 0.3% of the cost compared to a bridge facing the skyway. But the arch rib rigidity and the integral 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 percent, and the out-of-plane stability is improved by 20 percent; the frequency of the first in-plane vibration was increased by 158%.
Comparison table of technical parameters of examples
| Cost savings (%) | Stiffness increase (%) | Stability enhancement (%) | Fundamental frequency increase (%) | |
| Scheme one | 0.2 | 75% and 67% | 155％ | 165％ |
| Scheme two | 0.3 | 68 percent and 60 percent | 147％ | 158％ |
Claims (5)
1. A big purlin arch bridge which characterized in that: mainly comprises arch ribs (1), a main beam (2), vertical web members (3), oblique web members (4), flexible suspension rods (5) and cross braces (6); the vertical web members (3) are provided with three pairs and are respectively vertically arranged near 1/4, 1/2 and 3/4 of the arch rib (1), the upper end of each vertical web member (3) is connected with the arch rib (1), and the lower end of each vertical web member is connected with the main beam (2); the two pairs of the diagonal web members (4) are arranged, wherein the upper ends of one pair of the diagonal 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 diagonal 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 the arch rib 3/4, and the lower ends of the other pair of diagonal web members are connected with the lower ends of the vertical web members arranged at the arch rib 1/2; the truss structure is characterized in that 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 and the main beam (2) as a lower chord member and is provided with a flexible suspender (5).
2. The macrocornal arch bridge of claim 1, wherein: the flexible suspension rods (5) are obliquely and symmetrically arranged or vertically arranged between the arch rib (1) and the main beam (2).
3. The macrocornal arch bridge of claim 1, wherein: the arch rib adopts a steel structure or a steel-concrete composite structure; the vertical web members (3) and the inclined web members (4) are both made of steel structures.
4. The macrocornal arch bridge of claim 1, wherein: when the arch rib (1) is not inclined, the arch rib is a common arch; when the arch rib (1) inclines inwards, the arch rib is a basket arch.
5. The macrocornal arch bridge of claim 1, wherein: the arch rib (1) can be wrapped with concrete at the arch springing according to the bearing capacity requirement.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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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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