A kind of external prestress strengthening method of prestressed concrete box-beam bridge
The present invention relates to the reinforcement means of the common disease of a kind of prestressed concrete beam bridge, the external prestressing strengthening that is particularly useful for common diseases such as the large-span prestressed concrete beam of box section, firm structure and T structure bridge, belong to the fixedly field of reinforcement of structure such as bridge, specifically relate to a kind of external prestress strengthening method at diseases such as downwarp in the prestressed concrete box tee section spanning, web crackings.
Has the favor of striding stressed approaching, advantage is subjected to world's bridge engineering circle such as system stiffness big, the driving steady, the later maintenance workload is little of footpath wide accommodation, construction state and operation state owing to prestressed concrete box-beam bridge, obtained extensive use in countries in the world since the sixties in 20th century, maximum span has reached 330m.Yet in this bridge type development, the long-term shrinkage and creep influence that causes owing to high-level compressive stress under the dead load, the construction quality of structure are uneven, overload effect, the effect of local temperature stress and the high-stress state concrete fatigue down of the loss of prestressing force effective stress, carload or the like reason, cause both at home and abroad the disease cases such as span centre downwarp, web cracking about the prestressed concrete continuous box girder bridge quite general; Stride greatly downwarp in the prestressed concrete continuous box girder spanning of footpath and web cracking the two be association, in case take place, then reciprocal causation forms vicious circle, has caused the linear influence driving even exist the accident potential of caving in to become unsafe bridge of having some setbacks of bridge.And these similar bridge defects are reinforced targetedly, can prolong the service life of bridge construction, produce direct economic results in society.
Have the reinforcing of comparative maturity to calculate and use different with the external prestressing strengthening of simply supported girder bridge, the external prestress strengthening method of bridge complex structures such as continuous beam is still immature.Way the most close with the present invention in existing external prestressing strengthening technology is for providing the external pre-stress bundle anchoring and turn to reinforcement means at inner concreting diaphragm of case beam and tooth plate, as the South Sea, Guangdong Jinsha bridge, the reinforcement means of engineerings such as the Yellow River, Sanmenxia Gorge highway bridge, be at the inner concreting tooth plate of case beam, external pre-stress bundle is anchoring and stretch-draw on tooth plate, all pass to case beam base plate or top board and tooth plate is stressed by the bar planting of shearing groove, turning to by build powerful concrete diaphragm in case beam inside of external pre-stress bundle realizes, diaphragm needs the turning point setting at external pre-stress bundle, by bar planting mode and case back plate, base plate is connected with web.The defective of this method is: 1. because the inconsistent of shrinkage and creep makes that new-old concrete co-operation effect is undesirable; 2. in order to satisfy local anchoring and to turn to the requirement of stress, the anchoring tooth plate is with to turn to diaphragm relative powerful, and case beam built-in function space is limited, the difficulty of construction of a large amount of concreting is big, increased burden, and the strengthening construction cycle is long, engineering quantity is big, need interruption of bridge deck traffic to original structure; 3. the present bundle mode of joining is striden this three of web shearing resistance with pier top hogging moment, span centre positive bending moment and 1/4 and is equal to and treats, and the cross section property minimum of spaning middle section, positive bending moment is little a lot of with respect to pier top hogging moment, shearing is zero substantially, its external bundle consumption is controlled by the spaning middle section compressive stress, far can not reach the requirement of balance pier top hogging moment; 4. because anchoring and turn to the restriction of factors such as constructing local stress and original structure concrete strength to make that the consumption of external bundle is also limited.Above factor makes external bundle not reach desirable consolidation effect, and therefore domestic many bridge blocks have to take the limit for tonnage measure.
Summary of the invention
The purpose of this invention is to provide a kind of external prestress strengthening method at the common disease of prestressed concrete box-beam bridge, be optimized by the layout of analytic method, adopt the Steel Space Truss be installed in the case beam as the anchoring of external pre-stress bundle with turn to structure external pre-stress bundle.External pre-stress bundle consideration structural damage situation on the basis of optimizing result of calculation is arranged, the cloth bundle mode that adopts the short bundle of elongated bundle and fulcrum top board to combine, the short bundle of top board can according under the web cracking situation curved to the anchoring of steel truss lower edge to provide web pre-shearing; Steel truss is arranged according to turning to the anchoring needs of external pre-stress bundle, the steel truss rod member adopts section steel manufacture, in the case beam, respectively arrange a truss structure near the web side, each internode is provided with sway bracing, so that turning to and anchoring structure of external pre-stress bundle to be provided, concrete box web rigidity and shear-carrying capacity have been strengthened simultaneously; Steel truss and case beam adopt the bar planting mode to be linked to be integral body.Owing to adopt steel truss as the anchoring of external pre-stress bundle with turn to structure, make external pre-stress bundle consumption and arrange more flexibly, specific aim is stronger, external pre-stress bundle layout efficient height.
Technical scheme of the present invention is achieved in that
Described external prestressing strengthening technology is optimized layout according to influencing the lineation opinion to external pre-stress bundle.Because external pre-stress bundle is only got in touch with original structure at anchor point and turning point, so can adopt the mode of nodal forces to analyze the effect of external pre-stress bundle to original structure.The variation that external pre-stress bundle is arranged can be simulated by nodal forces different active positions structurally, adopt influencing line numerical value and just can drawing the action effect of nodal forces to structure of structure, the external bundle layout of finding out maximum action effect correspondence is The optimum layout.Optimizing the result shows: 1. there is an optimal value in the layout of fulcrum top board bundle; 2. there is an optimal value in the layout of striding the base plate bundle in; 3. end bay base plate bundle is unfavorable to the main span span centre; 4. the web bundle is little to the mid-span deflection contribution, but favourable to the web shearing resistance in its coverage; 5. there is an optimal value in the layout of full UNICOM head's bundle.Therefore, the layout of external pre-stress bundle is wanted targetedly, and top board bundle, base plate bundle will be raised the efficiency to obtain maximum acting force arm away from the girder centre of form as far as possible, and the web bundle then will provide enough pre-shearings at the web fracture area.
Described external prestressing strengthening technology, the employing steel truss is as the external pre-stress bundle anchoring and turn to structure.Steel truss can make full use of the Materials with High Strength characteristic of steel work, and local anchorage stress is handled easily, reduces difficulty of construction in the case; The flexible arrangement that is set to external pre-stress bundle of steel truss is provided convenience, and makes the layout of external pre-stress bundle more to consider the structural damage situation and needn't be limited by the processing of local structure; The invar truss is in light weight, and only only need arrange usually in web cracking scope, and is little to the side effect of original structure; Sway bracing is set between longitudiual truss, strengthens the globality of truss, for the anchoring of external pre-stress bundle provides the space.Steel truss can adopt the trifle spacing with the joint face of increase with the case beam, guarantees the reliable delivery of external prestressing.
Described external prestressing strengthening technology can be according to the analysis result of above-mentioned optimization cloth bundle, the cloth bundle mode that adopts the short bundle of elongated bundle and fulcrum top board to combine.Elongated bundle can be regarded the combination of the short bundle of top board, the short bundle of web and the short bundle of base plate as, turns to by optimum turning point and can obtain best consolidation effect; In addition, introduced the compressive stress deposit in the elongated Shu Zailiang body, for short layout of restrainting provides condition, and long short bundle is for providing the compressive stress deposit than short short bundle.Be balance pier top hogging moment, need to adopt the short bundle of top board, the short bundle of top board should be arranged in the last turning point of elongated bundle, thereby utilize tensile stress behind the compressive stress deposit balance anchor of elongated bundle, the short bundle of top board can be in the top board anchoring, also curved under the needs that can reinforce in conjunction with web at web cracking place to base plate, in the anchoring of truss lower edge.The short bundle of elongated bundle and top board can disperse anchoring and turn to, and promptly the processing of steel truss and case beam joint construction is convenient in anchoring and turning on vertically different panel points successively.Adopt the cloth bundle mode of " many of tuftlets ", help eliminating tensile stress behind the anchor, and the moment of flexure that this dispersed placement external pre-stress bundle forms meets the shape that fulcrum hogging moment envelope diagram gradually changes, and also can better cover the web fracture area that needs reinforcement, and more helps the reinforcing of web.
Advantage of the present invention:
1. can adopt influences the lineation opinion various external pre-stress bundle arrangement forms is carried out analytical optimization, takes all factors into consideration to optimize the result and the structural damage situation is arranged external pre-stress bundle, the efficient height and the flexible arrangement of external pre-stress bundle.
2. adopt the steel truss be connected with the case beam as the anchoring of external pre-stress bundle with turn to structure, make external pre-stress bundle and to turn to according to the needs anchoring of structural calculation, by using Materials with High Strength and only need being arranged in the web cracking scope usually, alleviated side effect greatly, strengthened concrete box web rigidity and shear-carrying capacity simultaneously original structure.
3. the arrangement that adopts the short bundle of elongated bundle and top board to combine is reinforced targetedly, can arrange external pre-stress bundle according to the degree of impairment of structure, reinforces the restriction that consumption is not subjected to local structure.
4. all strengthening constructions all carry out in case beam inside, need not to dig the top board concrete perfusion, can uninterrupted traffic, or carry out the temporary transient traffic control of part, and the economic loss that causes is few, and social influence is little.
Description of drawings
Fig. 1 is that the vertical bridge of the embodiment of the invention is to the general arrangement schematic diagram;
Fig. 2 is that the steel truss structure is indulged bridge to arranging schematic diagram in the embodiment of the invention;
Fig. 3 is that external pre-stress bundle is indulged bridge to arranging schematic diagram in the embodiment of the invention;
Fig. 4 is the elongated bundle enlarged diagram of external pre-stress bundle in the embodiment of the invention;
Fig. 5 is the short bundle of an external pre-stress bundle top board enlarged diagram in the embodiment of the invention;
Fig. 6 be Fig. 1 external pre-stress bundle on steel truss A anchoring and turn to the layout enlarged diagram;
Fig. 7 is the fulcrum cross sectional representation in the embodiment of the invention;
Fig. 8 is the main span span centre cross sectional representation in the embodiment of the invention;
Fig. 9 is a steel truss layout place cross sectional representation in the embodiment of the invention.
The specific embodiment
The invention will be further described below in conjunction with embodiment and accompanying drawing, and this embodiment is the prestressed concrete continuous box girder bridge of a span for (65.425+126+65.425) m.
Fig. 1 is that the vertical bridge of the embodiment of the invention is to the general arrangement schematic diagram.Adopt plane leverage finite element program to calculate the nodal forces of being concerned about the cross section mechanics parameter at the concrete structure in the present embodiment and influence line, using this influences the The optimum layout that line is obtained elongated bundle of external prestressing and the short bundle of external prestressing top board, and the stressing conditions of consideration structure is determined the final arrangement form of external prestressing; Fig. 3 is that the vertical bridge of external pre-stress bundle is to arranging schematic diagram in the embodiment of the invention, and Fig. 4 is the elongated bundle enlarged diagram of external pre-stress bundle in the embodiment of the invention, and Fig. 5 is the short bundle of an external pre-stress bundle top board enlarged diagram in the embodiment of the invention.Stride the bearing capacity restriction of spaning middle section in the consumption basis of the elongated bundle of external prestressing wherein and determine, afterwards, the reinforcing amount that deducts the elongated bundle of external prestressing according to the definite total reinforcing amount of fulcrum top board hogging moment is determined the short consumption of restrainting of external prestressing top board.Fig. 2 is that the steel truss structure is indulged bridge to arranging schematic diagram in the embodiment of the invention.According to turning to and the anchoring needs of the The optimum layout form of external prestressing, consider the web degree of impairment of structure, determine the steel truss inner vertically arrangement form of original structure case beam in an embodiment, the internode of truss is got the active force of little internode distance with the dispersion external pre-stress bundle apart from according to the anchoring of external prestressing with turn to the needs that the joint construction of needs, truss and concrete box girder handles and the convenience of case beam case chamber interior construction to be provided with as far as possible when meeting above the requirement.
Fig. 6 be Fig. 1 external pre-stress bundle on steel truss anchoring and turn to the layout enlarged diagram, i.e. external prestressing turning on steel truss with anchoring and in vertical layout of original structure case beam case chamber interior.Steel truss upper chord 3 is connected by steel truss web 5 with steel truss lower chord 4, winding up by steel truss is connected steel truss upper chord 3 with case back plate joint construction 6 with case back plate 1, steel truss lower chord 4 is connected with case beam base plate 2 with case beam base plate joint construction 7 by the steel truss lower edge; When elongated bunchy top plate portion 8 was elongated bundle, it turned on steel truss upper chord 3; When elongated bunchy top plate portion 8 is the short bundle of top board, if the short bundle of external prestressing top board does not need to bend down then directly to be anchored on the steel truss upper chord 3, if it is curved down that the short bundle of top board needs, then by turning to back anchoring on steel truss lower chord 4 on the steel truss upper chord 3, the short corset plate portion 11 of top board has remedied common corset plate portion 10 disappearance herein, has improved the shear-carrying capacity of web; Elongated bundle different node on steel truss upper chord 3 and steel truss lower chord 4 disperses to turn to, the short bundle of top board different node on steel truss upper chord 3 and steel truss lower chord 4 disperses anchoring and turns to, and alleviated wind up intractability with case back plate joint construction 6 and steel truss lower edge and case beam base plate joint construction 7 of steel truss.
Fig. 7 is the fulcrum cross sectional representation in the embodiment of the invention.Elongated bundle 8 ' of external prestressing and external prestressing top board weak point bundle 8 " in the case beam, bore a hole on the pier diaphragm 12 and pass through; the position of perforation is as far as possible near case back plate 1 lower edge; the elongated bundle 8 ' of external prestressing restraints 8 with the external prestressing top board is short like this " and can obtain maximum acting force arm, improve the efficient of external pre-stress bundle.
Fig. 8 is the main span span centre cross sectional representation in the embodiment of the invention.The elongated bundle 9 ' of external prestressing is as far as possible near case beam base plate 2 upper limbs, and the elongated bundle of external prestressing can be obtained maximum acting force arm like this, improves the efficient of external bundle.
Fig. 9 is a steel truss layout place cross sectional representation in the embodiment of the invention, transverse truss 13 connects two Pin longitudiual truss 14, last integral node plate 15 connects transverse truss 13 and case back plates 1, on the last integral node plate 15 perforation for external pre-stress bundle pass through, anchoring; Following integral node plate 16 connects transverse truss 13 and case beam base plates 2, on the following integral node plate 16 perforation for external pre-stress bundle by, anchoring; Last integral node plate 15 laterally all is connected by the bar planting mode with the case beam in whole case beam camber with following integral node plate 16, and contact area is big, but the bar planting position is many, and being connected of reliable longitudiual truss 14 and concrete box girder is provided; Go up simultaneously integral node plate 15 and perforation on the following integral node plate 16 and can be used for locating external pre-stress bundle, handle with local anchoring structure processing by the structure of putting more energy into and also have for the external pre-stress bundle damping, turn to and the anchoring function.