Discussiononconstructiontechnologyofcontinuousbridgewithsimplysupportedstructure谈先简支

1、Discussion on construction technology of continuous bridge with simply supported structure （谈先简支后结构连 续桥梁施工技术）Discussion on construetion technology of continuous bridgewith simply supported structure （谈先简支后结构连续桥梁施工技术）Talk about simply supported continuous bridge strueture construction technology of R

2、SS print copy the link and release time： 2010-06-09 12:26:08 Abstract: built in recent years Chinas high-grade highways the big bridge, almost all of the simply supported continuous system. This paper expounds the simply supported continuous system in practical engineering, the advantages and main p

3、oints of construction technology, discusses using simple technology in the construetion process, finally put forward the simply supported continuous bridge construction quality control.Key words: simply supported first; continuous bridge construction; bridge designIn recent years, with the rapid dev

4、elopment of bridge construction, home to the emergence of a new type bridge strueture of simply supported continuous girder bridge structure, it has advantages of simply supported girder bridges and continuous girder bridge, the provinces of the country especially in the highway bridge design gradua

5、lly to the simply supported continuous beam bridge stmeture instead of the original single beam bridge or continuous girder bridge. The practical engineering shows that the simply supported continuous beam bridge has the advantages of continuoils beam bridge and bridge two bridge, overcome their sho

6、rtcomings，so the discussion on the simply supported continuous bridge construction technology has importsnt significance.First, simply supported continuous bridge outline(1) the introduction of a continuous bridge with a simple support;With the rapid development of high-grade highways in China, the

7、quality requirements of bridges connected with highways are correspondingly improved, and the construction technology of bridges is also very criticaL The present situation is: for the small span highway bridge with reinforced concrete slab prefabricated beam, bridge middle span with prefabricated p

8、res tressed concre te T beam (box) in the form of the long span prestressed concrete continuous girder bridge construetion, the main met hods of using balanced can ti lever casting met hod or assembly method. But because the construetion of cast-in-place continuous beam is complicated and time-consu

9、ming, people always want the superior performance of beam prefabricated production batch and continuous beam combined with precast beam or plate mass production way to accelerate the constmetion of the continuous beam is often said we simply supported continuous construction method.(two) the advanta

10、ges of simply supported and continuous bridgesSimply supported continuous prestressed concrete beam bridge structure is two and two span above by cast-in-place concrete form a continuous strueture, the advantages are as follows: (1) with high stiffness, small deformation, expansion joints and the ad

11、vantages of comfortable driving; (2) simply supported prestressed steel beam in the factory Zhang pull, and the arrangement of prestressed tendons in the negative moment area and Zhang Lajun in girder, only the lifting equipment lifting beam, reduce construction equipment, and can avoid the prestres

12、sed steel beam caused by ground obstaeles;(3) the precast beam standard component factory unified production and management, have for the technical operation, save construction time and shorten the construction period, improve economic efficiency;Two. The main points of the construction of the conti

13、nuous bridge structure after simply supported(1) the general process of the construction of simply supported and continuous bridgesL precas t girder, 100% to meet the design st reng th of concre te strength, the prestressed steel beam lazheng bending zone, grouting and timely cleaning girder (prestr

14、essed concrete simply supported continuous box girder bottom hole).2. set temporary support and install the permanent support, ins tall the main beam by hole, put it on the t emporary suppor t for the simple support state, and connect the bridge bar and the crossbeam st eel bar in ti me.3. connec t

15、joi nt section steel bar, set up joi nt st eel bellows, and through the beam. At the lowest temperature of day (not higher than +15 degrees), the continuous joint, middle beam and both sides of the middle span of the steel beam are integrated into the whole deck. At the design strength of 100%, the

16、tensioning roof steel beam and grouting.4. after the completion of the joint, from the middle to the fulcrum of the remaining part of the bridge deck integrated concrete, after the completion of the casting，the demolition of a temporary bearing in the union, to complete the system conversion.When re

17、moving temporary support, special attention should be paid to prevent the impact of high temperature on rubber bearing quality.5. spray waterproof layer, install telescopic device, bridge deck constmction.(two) charac teris tics of simple continu ous cons true tion after simply supported;L precast T

18、 beam concrete strength of 100% of the design strength can be tensioned prestressed steel beam. The tensioning sequences are 1, 4, 2, and 3. The 1 beams should be tensioned at the same time so as to avoid transverse bending of the main beam. During construetion, the friction coefficient of steel and

19、 channel, the deviation coefficient K of the duct and the loss of anchor mouth m k shall be measured, and the actual tensile stress of sigma km can be calculated by adding the measured sigma m and the design tension control stress sigma.The end shape at the cast-in-place section of the 2. box girder

20、. In order to meet the full combination of cast-inplace section and box girder and force transmission and construction requirements， continuous box girder end is made of stepped horseshoe shape, and according to the operation requirements, reserve size and style of the steps of cast-in-place section

21、.3. design and selection of temporary support Design oftemporary bearings must meet the bearing beam and construction convenien t disassembly requireme nts. The commonly used met hod can be made of sulfur mortar temporary support, embedded in the sulfur mortar electric heating wire, in the system co

22、nversion, the use of electrothermal method to remove t emporary bearings. Also can use st eel and hard logs or precas t reinforced concrete circular block made of sand box type t emporary suppor t, in erec ting beam pla te t hrough the test to det ermine the settl ement of temporary support for a sa

23、nd box, and according to the difference bet ween the beam and the corresponding installation elevation of pier cap pad stone elevation is filled with sand and add high cover adjustment in order to better control the accuracy of beam height after erection.4. continuous section cast-inplace concrete c

24、onstruetion. Buried steel in cast-in-place continuous pre connection can be used to tie a welding or welding, cast section of concrete and concre te by Liang Ban to ng, in order to preve nt the occurrence of cast-in-place continuous concrete in the hardening process of curing contraction cracks in t

25、he concrete influence the whole two time tension in the process of bearing capacity and the bridge performance of Cast-in-situ Continuous joint concrete adding micro expansion agent. The gap between the permanent rubber support and the bottom mold is sealed with a rust treated steel plate or a sand

26、box made of bamboo plywood, so as to prevent leakage.5. nega tive bending momen t, two ti mes t ens ion. Two ti mes tension of negative bending moment is the tension of pres tressed steel beam on the top of beam and beam, which is the essential difference between simply supported continuous bridge a

27、nd simple supported beam bridge. The prestressed steel beam is made of high st reng th and low relaxation steel st rand, and the steel beam is tensioned with both sides at the same ti me. The tension sequence is from the out side to the inside, and each time a steel strand is stretched until the end

28、 of tension. Grouting work shall be carried out in time after completion of tensioningThree quality control of continuous bridge construction after simply supportedCombining with the construction process of prestressed concre te simply suppor ted to conti nuous T beam and pres tressed concrete simpl

29、y supported to continuous box girder, the author puts forward quality control during construetion to ensure construetion quality.(1) quality control of temporary support setting;It should be guaranteed that the temporary support should be of sufficient strength and rigidity, easy to assemble and dis

30、assemble and uniform beam falling. When the prestressing force is completed, the temporary support can be removed until the strength of the grout is greater than 35MPa Removal of temporary support should be symmetrical, uniform, synchronous and smooth by hole. When the temporary bearing is removed,

31、the permanent support is tightly jointed with the pier head and the bottom of the beam. Combined with the curren t cons true tion technology, temporary support has a variety of methods of installation，in order to unload sand box support constmetion met hods as an example. When sand box suppor t is a

32、dop ted, the settlement of the sand box and the weight of the bridge crane should be taken into full considerstion, and the gap between the bottom of the beam and the support of the basin should be left T. In the construetion of sand box will appear every settlement will not be exactly the same situ

33、ation, resulting in part of the T beam Diaokong, have quality problems, there are two solutions: (1) the average settlement preloading test made in force after the sand box, which is used to guide the on-site instaliation of temporary support, control of T beam the installation elevation and the des

34、ign elevation; (2) appropriate to reduce the bearing pad stone elevation, set aside about 3cm concrete beam height boots.When pouring the wet joint, a steel plate is placed on the basin suppor t, which is direc tly poured onto the st eel pla te to form the concrete beam boots.(two) setting requireme

35、nts of tension prefabricated base;The tension prefabricated base shall be firm and free from subsidence, which is good for drainage and prevents the foundation from sinking due to poor drainage. The inverse camber of the base shall be determined by reference to the camber value provided by the desig

36、n document and the tensioning of the actual construction and production trial beams. The camber should be made into a parabola. In addition, to ensure the accuracy of bridge ins talla tion to be stric tly cont rolled, the error is not more than 2mm.(three) quality control of continuous cast-in-place

37、 concrete construetionThe construction found that the connection between the new and old concrete is the main problem of cast-in-place continuous concrete. Therefore, the end of the precast beam slab must be strictly handled by the chisel. In order to prevent the occurrence of cast-in-place continuo

38、us concrete in the hardening process of curing contraction cracks in the concrete influence the overall two times in the process of stretching capacity and bridge stress performance of cast-in-place continuous joint concrete adding micro expansion agent, 0. 5% to the general control in the cement ad

39、ding dose of 1%. The temperature of the cast-in-place continuous joints shall be basically the same at first, then the temperature shall be controlled within 5 degrees, and shall be arranged as far as possible in the day when the air temperature is lowest.(four) quality control of cast一in-place join

40、t and wet joint of main beamThe concrete pouring sequence shall be carried out strictly according to the requirements of the design documents, and the time from the main beam prefabrication to the pouring of the transverse wet joints shall not exceed 3 months. The construction of wet joint concrete can be carried out by lifting formwork The formwork shall be made of steel formwork with sufficient rigidity and strength. When the formwork is firmly installed, flush