The construction organization design of simply supported hollow slab girder and the construction org

The main dimensions that need to be proposed for the design of reinforced concrete simply supported T beams are: beam width, beam height, web thickness, and flange plate thickness.

The diaphragm plays a role in ensuring that the main beams are connected to each other as a wholeThe greater its stiffness, the better the integrity of the bridge, and the better the main beams can work together under load. However, the diaphragm is arranged to make the girder template work slightly more complicated, and the welding joint of diaphragm is often carried out on the special working frame that is located under the bridge again, and the construction is more troublesome. Practice has proved that for simply supported girder bridges, generally in the middle of the span, the four points, and the fulcrum at each set up a diaphragm can meet the requirements.

Main size beam height: the common span of prefabricated reinforced concrete simply supported beams. China's standard design is 10, 13, 16, 20m and so on, the beam height is respectively, after analysis and comparison, it shows that the economic range of the high span ratio (the ratio of beam height to span) is about 1 11 1 18, and the large span is taken from the value of the small ear ant. If the height of the main beam is not limited by the height of the building, the height-span ratio should be larger. Increase the beam height, only increase the web height, the number of concrete pin buried increase is not much, but can save the amount of steel bar, often more economical.

The design steps are as follows:

1. Determine the cross-sectional size: according to the span, load and force of the beam, determine the cross-sectional size of the beam, including the height, width and cross-sectional shape of the beam.

2. Calculate the reinforcement ratio: according to the strength grade and stress state of the concrete, calculate the minimum reinforcement ratio of the beam, that is, the ratio of the reinforcement section in the beam cross-sectional area to the concrete cross-sectional area.

3. Determine the main reinforcement: according to the span, load and force of the beam, calculate the diameter and spacing of the main reinforcement, and determine the position and number of the main reinforcement.

4. Calculate the spacing of the abdominal reinforcement: according to the span, load and stress of the beam, calculate the spacing of the abdominal reinforcement to meet the force requirements of the abdominal reinforcement.

5. Determine the diameter of the abdominal tendon: according to the spacing of the abdominal tendon and the reinforcement ratio of the rubber base, calculate the diameter of the abdominal tendon, and meet the force requirements of the abdominal tendon.

6. Determine the stirrups: according to the cross-sectional size of the beam and the diameter of the main reinforcement, calculate the diameter and spacing of the stirrups, and determine the position and number of stirrups.

1) In order to avoid the transverse bending of the beam, the tendons should be symmetrically arranged on the cross-section.

2) The bending bundle should be arranged in the web and peduncle rib as much as possible, and the flat bending should be minimized or avoided to simplify the structure and reduce the prestress loss.

3) top and bottom plate tendons should be appropriately concentrated in the position that the concrete such as web and stem rib is thicker, and should not adopt uniform dispersed arrangement mode, can avoid longitudinal cracks.

4) If the number of tendons is large and have to be laid in the middle of the plate, should try to avoid the transverse positive moment of the larger area or use the small type of prestressed tendon instead.

5) when there are many tendons, they can be arranged in layers, and the tendons close to the middle of the web are anchored or bent first.

6) when the cantilever of cross-section is larger or box girder web spacing is larger, under load, cross-section transverse stress is larger, and transverse prestressed tendon is arranged in box girder roof. The function of vertical prestressed tendons is shear resistance, and coarse steel bars are often used, which are arranged in the web.