Te c h n i c a l s u b m i s s i o n SETTING: BT Project Number of Civil Construction Part of Wuhan Urban Rail Transit Airport Line of China Railway Eleventh Bureau Group: Main sending unit Bridge nine teams T h e n u m b e r o f p a g e s Engineering name Constructio n of cast-inplace beams Engineering location The first 1 pag e com mon 3 Bracket preloading pag e Interpretation: Overview of the project: The 86-97The deadweight of 25m box girder is 378.6t and that of 30m box girder is 443.5t. Bracket preloading 1Laying bottom formwork The elevation is adjusted by the top bracket, and a special bottom die is laid on the top of the woodwork beam.When the floor is laid, foam double sided adhesive is used to fill the gap between the boards.Place the support before laying the bottom die, and open the hole on the bottom die when the support seat is placed. 2Preloading load In order to check the bearing capacity of the support, reduce and remove the inelastic deformation of the support and the settlement of the foundation.After the bottom formwork of the box girder is laid, the bracket and formwork of the bridge are preloaded, and the preloading load is considered as 1.2 times the dead weight of the beam. 3Preloading method: Precast concrete blocks are used for preloading, and cranes are used for loading step by step. Each block is calculated at 2.5T.The preloading weight is loaded step by step three times, that is, 0%-40%, 40%-80%, 80%-120%; that is, laying the first layer, then laying the second layer, and finally laying the third layer.After each stage of loading is completed, the settlement of the support should be monitored every 12 hours. When the average value of the settlement difference between two consecutive times of measuring points of the support is less than 2 mm, the loading can be continued.Unloading is also carried out in three stages, in the reverse order of loading. H Schematic Chart of Surcharge (Side Mould Not Installed Just for Indication) Organization : To review: Sign for: Specific date Note: "Technical submission statement" in duplicate, one to the person in charge of the receiving unit as the basis for construction, one to be kept for reference and handed over formalities. Te c h n i c a l s u b m i s s i o n SETTING: BT Project Number of Civil Construction Part of Wuhan Urban Rail Transit Airport Line of China Railway Eleventh Bureau Group: Main sending unit Bridge nine teams T h e n u m b e r o f p a g e s Engineering name Constructio n of cast-inplace beams Engineering location The first 2 pag e com mon 3 pag e Bracket preloading Interpretation: 4Pre-pressure observation When preloading, there are 5 sections in each span, i.e. 0/4, 1/4, 1/2, 3/4 and 4/4. There are 5 observation points in each section, including 3 on the bottom template and 2 on the wing plate. The observation points are monitored once every 24 hours. If the average settlement of each monitoring point for 24 hours is less than 1 mm or the average settlement of each monitoring point for 72 hours is less than 5 mm.The settlement can be considered stable and the total settlement can be calculated.The observation method is measured by leveling instrument. The elevation before loading is Delta 1, after loading is Delta 2, after unloading is Delta 3, then Delta 1-Delta 3 is irrecoverable deformation and Delta 3-Delta 2 is elastic deformation.The settlement curve is drawn according to the observation results.Before, after and during preloading, the deformations of 1/4 beam spans are observed with instruments at any time, and the stress of each fastener of the bracket is checked. 5Uninstall The observation points are monitored once every 24 hours. If the average settlement of each monitoring point in the first 24 hours is less than 1 mm or the average settlement of each monitoring point in the first 72 hours is less than 5 mm.No more observations start unloading.Cranes are also used to unload prefabricated blocks one by one.After unloading, the settlement and elastic deformation of the support were observed. 6Bracket adjustment After the preloading of the support is completed, the central axis of the bridge is re-calibrated and the plane position of the bottom formwork of the box girder is lofted.After preloading, the base formwork elevation and the preset camber can be adjusted accurately by adjusting the top bracket. Quality assurance measures 1Before laying the bottom and side formwork, we should s