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）.doc

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）Talk about simply supported continuous bridge structure construction technology of RSS 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 points of construction technology, discusses using simple technology in the construction 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 development of bridge construction, home to the emergence of a new type bridge structure 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 gradually to the simply supported continuous beam bridge structure 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 continuous beam bridge and bridge two bridge, overcome their shortcomings, so the discussion on the simply supported continuous bridge construction technology has important 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 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 prestressed concrete T beam (box) in the form of the long span prestressed concrete continuous girder bridge construction, the main methods of using balanced cantilever casting method or assembly method. But because the construction of cast-in-place continuous beam is complicated and time-consuming, 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 construction of the continuous beam is often said we simply supported continuous construction method.(two) the advantages 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 structure, the advantages are as follows: (1) with high stiffness, small deformation, expansion joints and the advantages 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 prestressed steel beam caused by ground obstacles; (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 continuous bridge structure after simply supported(1) the general process of the construction of simply supported and continuous bridges1. precast girder, 100% to meet the design strength of concrete strength, the prestressed steel beam lazheng bending zone, grouting and timely cleaning girder (prestressed concrete simply supported continuous box girder bottom hole).2. set temporary support and install the permanent support, install the main beam by hole, put it on the temporary support for the simple support state, and connect the bridge bar and the crossbeam steel bar in time.3. connect joint section steel bar, set up joint steel 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 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 removing 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 construction.(two) characteristics of simple continuous construction after simply supported;1. precast T 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 construction, the friction coefficient of steel and 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. In order to meet the full combination of cast-in-place 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.3. design and selection of temporary support. Design of temporary bearings must meet the bearing beam and construction convenient disassembly requirements. The commonly used method can be made of sulfur mortar temporary support, embedded in the sulfur mortar electric heating wire, in the system conversion, the use of electrothermal method to remove temporary bearings. Also can use steel and hard logs or precast reinforced concrete circular block made of sand box type temporary support, in erecting beam plate through the test to determine the settlement of temporary support for a sand box, and according to the difference between 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-in-place concrete construction. Buried steel in cast-in-place continuous pre connection can be used to tie a welding or welding, cast section of concrete and concrete by Liang Bantong, in order to prevent the occurrence of cast-in-place continuous concrete in the hardening process of curing contraction cracks in the 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 box made of bamboo plywood, so as to prevent leakage.5. negative bending moment, two times tension. Two times tension of negative bending moment is the tension of prestressed steel beam on the top of beam and beam, which is the essential difference between simply supported continuous bridge and simple supported beam bridge. The prestressed steel beam is made of high strength and low relaxation steel strand, and the steel beam is tensioned with both sides at the same time. The tension sequence is from the outside to the inside, and each time a steel strand is stretched until the end of tension. Grouting work shall be carried out in time after completion of tensioning.Three 、 quality control of continuous bridge construction after simply supportedCombining with the construction process of prestressed concrete simply supported to continuous T beam and prestressed concrete simply supported to continuous box girder, the author puts forward quality control during construction to ensure construction 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 disassemble 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, the permanent support is tightly jointed with the pier head and the bottom of the beam. Combined with the current construction technology, temporary support has a variety of methods of installation, in order to unload sand box support construction methods as an example. When sand box support is adopted, the settlement of the sand box and the weight of the bridge crane should be taken into full consideration, and the gap between the bottom of the beam and the support of the basin should be left T. In the construction of sand box will appear every settlement will not be exactly the same situation, 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 installation of temporary support, control of T beam the installation elevation and the design 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 support, which is directly poured onto the steel plate to form the concrete beam boots.(two) setting requirements 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 design 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 installation to be strictly controlled, the error is not more than 2mm.(three) quality control of continuous cast-in-place concrete constructionThe 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 continuous 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 adding 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-in-place joint 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, f