Discussion on the application of long-span operation method in hotel engineering?

A hotel project is located at the intersection of century avenue in Jinjiang City, Fujian Province and the planned 13 road. Designed and built according to the five-star standard of domestic hotels. With a total construction area of 65 199m2, there is a basement, an overground 16 floor, with a total building height of 64.8m The top floor of the podium is a grand banquet hall that can accommodate about 600 people. In order to achieve good dining and banquet effects, no structural columns are designed in this area. The four main beams of roof concrete are post-tensioned bonded prestressed structures with a main span of 30.8 m, a section size of 750 mm× (2000 ~ 2430) mm and a concrete strength grade of C35. The prestressed beam WYKL 1 is 5-9 φ s 15.2, and WYKL2 is 4-9 φ s 15.2, as shown in figure 1 and figure 2.

2 prestressed concrete beam construction technology

2. 1 Materials and equipment used in prestressed construction

(1) prestressed reinforcement. Prestressed concrete structures must use steel with high strength and certain plasticity [1]. In this project, φs 15.2 high-strength steel strand with low relaxation is used for prestress, and the standard value of tensile strength FPTK = 1860 MPa. There must be no cracks and oil stains on the surface of the material, and there must be no pull marks and mechanical damage that affect the use [2].

(2) Corrugated pipes and grouting materials. Φ 75 metal corrugated pipe is used for 9 holes of prestressed beam, corrugated pipe with corresponding large size is used for joint pipe, and ordinary silicate 42.5 cement is used for grouting.

(3) Anchorage. This project is bonded, and it is all tensioned at one end. The tensioning end adopts 9-hole anchor group, and the fixed end adopts extrusion anchor. When the anchorage comes into play, the product quality certificate shall be checked in the engineering part according to the three provisions of appearance inspection, hardness inspection and static load anchorage performance test [3].

(4) Tension equipment. YDC2500 is selected as the tensioning jack according to the anchorage model, and the supporting oil pump is ZB4-500 electric pressure pump. Before tensioning, the Project Department shall inspect and calibrate the machines, tools, equipment and oil meters, and the tensioning equipment shall be used within the validity period specified in the calibration.

2.2 Prestressed concrete beam construction technology

Pre-stressed steel bar blanking-site leveling-erection of full steel pipe scaffold-laying beam bottom formwork, arching to find the correct bottom elevation-binding non-prestressed steel bar of beam-determining the curvilinear coordinate position of pre-stressed steel bar, welding positioning steel bar-inserting corrugated pipe into beam and fixing it-leaving vent hole to support side formwork-binding non-prestressed steel bar (bottom reinforcement) of floor slab-installing tensioning end of pre-stressed steel bar-installing professional pipe for hydropower, etc. -Binding non-prestressed reinforcement of floor slab (second floor reinforcement)

2.3 Embedding of Bonded Prestressed Grouting Pipe

Grouting with bonded prestressed tendons requires embedded grouting pipes, which can be buried after the prestressed tendons are laid (Figure 5). Grouting holes should be left at the high points of prestressed beams. Tie grouting pipe's pressure plate with metal bellows, and then tie it with adhesive tape. The length of grouting pipe should be 20 ~ 30 mm higher than the concrete surface, and then the grouting nozzle should be bent to death to prevent slurry leakage. In order to prevent the grouting pipe from breaking due to collision in the process of pouring concrete, steel bars can be inserted into the grouting pipe, and then the grouting pipe and the steel bars of the beam can be firmly bound. The fixed end can be a long grouting pipe, one end is inserted into the corrugated pipe end, and the other end leads to the concrete surface, and then the gap at the corrugated pipe end is blocked with cement to prevent slurry leakage and pipe plugging. At the same time, be careful not to leave the pipe outlet in the template or wall template.

2.4 concrete pouring

The beam with a main span of 30.8 m in this project has a section size of 750 mm× (2000 ~ 2430) mm, and the structural steel bars are very dense. Besides high fluidity, it is also required to extend the initial setting time as much as possible, so the slump of concrete must be strictly controlled. The technical points of this project include: ① Optimize the concrete mixture ratio, reduce the cement dosage, strengthen vibrating curing, and ensure the concrete curing time to reduce the prestress loss caused by shrinkage and creep. (2) In the process of concrete pouring, the beam concrete is continuously poured in layers, each layer is about 400mm thick, and no construction joints are left, at the same time, the load balance during formwork support construction is ensured. (3) During pouring, attention should be paid to protecting the embedded parts such as corrugated pipes to prevent accidents such as displacement and slurry leakage.

3 Conclusion

Since 1928, the French adopted prestressed concrete beams made of high-strength steel bars, prestressed concrete has been applied to various buildings with its unique properties, and the prestressed technology has been rapidly popularized. Super-long-span prestressed concrete beam is the key part of large-scale public building structure, and its construction technology is difficult, which has great influence on construction period, quality, safety and cost [10-1]. In the process of construction, the formwork and its supporting system are required to be highly stable, with many processes and complicated construction, and tensioning equipment, anchorage and other facilities are needed. At the same time, in order to establish correct and effective prestress of post-tensioned super-long-span prestressed concrete beams, the prestress loss can be reduced by over-tensioning, and the elongation value should be controlled at 6%. With the rapid development of China's construction industry and the continuous improvement of construction technology and the quality of construction team, prestressed concrete will surely usher in a better application prospect.

I believe that after the above introduction, everyone has a certain understanding of the application of long-span operation method in hotel engineering. Welcome to Zhong Da for more information.

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