1. Requirements for pad stone and bearing
(1) Check the pad stone and support before erecting the beam; The concrete strength of the bearing pad stone shall meet the design requirements, and the top elevation shall be accurate and flat; The pad stone shall not be leveled with mortar to avoid deflection, uneven stress or void between the support and the beam bottom after installation; After the beams and slabs are placed, they should be checked again to ensure that the beams and slabs are in place accurately and closely attached to the support; When the positioning is inaccurate or the support is not closely attached to the beam slab, the beam shall be lifted and measures shall be taken to make the beam in place accurately and the support stressed evenly.
(2) If there are steel plates in the bearing pad stone or at the bottom of the beam, the model and surface elevation of the steel plates shall be ensured; The concrete at the bottom of the steel plate shall be vibrated and compacted, and the steel plate shall not be suspended.
(3) All self-made bearing embedded steel plates and their reinforcement shall be hot-dip galvanized after welding; For bearings purchased by the manufacturer in sets, the manufacturer shall be required to hot dip galvanize the upper and lower steel plates and protect them during transportation; The steel and iron parts of the basin support shall also be hot-dip galvanized; Bolts, nuts and washers shall be galvanized, and the threads shall be cleaned or centrifuged.
(4) The upper and lower steel plate positioning bolts of the support shall be cut flush, and shall not prevent the free displacement of the support. The dust cover of the support shall be laid in time.
(5) All performance indexes of the bearing shall be comprehensively checked, including the length, width, thickness, hardness, allowable load, allowable temperature difference and appearance inspection of the bearing. If it does not meet the design requirements, it shall not be used.
(6) After the bridge deck pavement and crash barrier are completed, attention should be paid to checking the bearing pressure of the side beam, and measures should be taken to ensure that the bearing is evenly stressed.
(7) After the installation of the support, the sundries shall be cleaned up in time, and the temporary support or other temporary fixed facilities shall be removed. The movable support shall be filled with lubricating materials as required.
2. Requirements for transportation and erection of precast beams
(1) When the beam is lifted off the pedestal, the concrete quality at the bottom of the beam should be checked (mainly cavities, exposed reinforcement, reinforcement protective layer, etc.); In order to ensure the installation accuracy of the beam body, the precast beam shall meet the quality requirements before installation, and the qualification certificates shall be attached before delivery to the site.
(2) Before the erection of the beam, the size, elevation, plane position of the support structure and the pier and abutment support and size shall be checked, and the rust, mortar and other sundries of the support steel plate shall be removed.
(3) When the beam is initially hoisted, the trial hoisting shall be carried out first. During the trial lifting, the beam shall be suspended after being lifted about 20mm to 30mm away from the bearing surface. The function of the main stressed parts shall be carefully checked. After confirming that the stress is good, the support pad can be removed and the lifting can continue.
(4) The transportation and erection of bridge segments shall meet the requirements of specifications and standards to ensure the safe and smooth erection of beam segments.
(5) During the installation of the beam, attention should be paid to the temporary fixation (support) of the beam when it is moving and after it is in place to prevent sideways. The installation sequence of the beam body shall be determined according to the performance of the bridge erecting machine. Generally, the installation shall be carried out from side to middle and then to side.
(6) The hoisting, longitudinal movement, bottom dropping, horizontal movement and positioning of precast beams shall be under unified command, coordinated and properly carried out according to the predetermined construction sequence. The lifting of the beam shall be carried out smoothly and at a uniform speed, and the height difference at both ends shall not be greater than 300mm. When the beam is lowered, one end shall be dropped first, and then the other end. The lifting appliance can be removed only after confirming that the side braces at both ends of the beam have been fixed well. At the corner contact between the binding steel wire rope and the bottom and side of the beam, the beam protection iron tile or rubber pad shall be placed.
(7) When loading the beam, the deviation between the center of gravity line of the beam and the longitudinal center line of the vehicle shall not exceed 10mm. The beam shall be placed according to the design fulcrum, and the beam shall not be lifted or placed sideways. When placing the beam, it shall be supported before loosening the hook; When transporting beams by cars and tractors, the traveling speed shall not exceed 5km / h. There should be special personnel in charge of commanding before and after the beam delivery vehicle.
(8) After the beam is installed in place, it should be measured and corrected. Only when it meets the design requirements can it be allowed to weld or pour joint concrete. After welding, it must be rechecked and recorded.
3. Construction requirements for negative moment prestress
(1) Before the construction of negative moment prestress, the duct sealing protection and the anti rust treatment of anchor base plate should be done well.
(2) It is not allowed to penetrate the tendon before pouring the concrete of the continuous section at the beam end. The concrete strength of the continuous section at the beam end must meet the design requirements before penetrating the tendon for negative moment prestressed construction.
(3) Before tensioning, the reserved holes should be checked with a through-hole device or other reliable methods.
(4) The tensioning sequence of prestressed reinforcement shall meet the design requirements. If there are no regulations in the design, the short beam shall be first followed by the long beam, and the long beam can be tensioned only when the strength of the short beam sealing concrete reaches more than 80%.
(5) The welding slag, burr, concrete residue, etc. at the contact between the end embedded plate and the anchorage and the base plate shall be removed, and the concrete can be poured only after the end sealing concrete notch is cleared and qualified.
(6) Comb shaped plate shall be used at the end of the reserved hole to avoid bleeding and loosening.
4. Wet joint construction requirements
(1) After the beam and slab are in place, the wet joint shall be poured in time, and the gap between adjacent beams and slabs shall be filled tightly.
(2) The beam joint concrete shall be poured according to the regulations. The welding of reinforcement at the joint or the weld of metal parts shall be subject to the acceptance of concealed works before pouring joint concrete.
5. Quality control requirements
(1) After installation, the beam ends shall be neat and uniform, the beam end joints shall be straight, and the width shall meet the requirements. The components shall be free of defects such as hard damage, corner dropping and cracks.
(2) The contact of the support shall be tight without gap, and the position shall meet the design requirements.
