How to build public rental housing?

1. First of all, we distinguish between traditional structural design and assembled structural design. In most cases, the traditional structure is relatively mature, and the construction unit entrusts the design unit to design, and then entrusts the construction enterprise to construct according to the drawings. However, at present, most design units in China are relatively backward, and only a few qualified and experienced design units can be appointed. The construction unit can only adopt the integration of design and construction to bid, which brings the importance of design time to the total construction period of the whole project.

2. Judging from the design time of XXX Phase II public rental housing, although the contract time is only 45 days, it has actually extended to the end of the structure, because the whole process is divided into preliminary design-functional decomposition-process decomposition-expert demonstration-design modification-drawing review-final drawing. Among them, functional design and process decomposition diagram are particularly important. ① Functional design often needs to involve local laws and regulations, water, electricity, gas, solar energy and other aspects, and can be completed at one time! Factory production cannot be changed after molding, and it cannot be as flexible as the traditional structure. (2) The process split diagram is completely made by the factory according to this diagram, and most nodes are only clear to the factory technicians. After the factory mass production is finalized, it is pulled into the site for hoisting, and construction is started one by one according to the site sequence diagram, which shows the importance of functional decomposition and process decomposition diagram.

3. Another difficulty in design is how to truly integrate design and construction. As mentioned above, the integration of design and construction can only be used in the bidding stage. However, from the reality of XXX public rental housing, it is found that the real integration of design and construction cannot be realized. Although there is a connection between the person in charge of design and the person in charge of construction, the actual tracking of the construction process has not been realized. In the actual process of model house, many joints, such as column and beam joints; Nodes between wallboard and concealed column; There is something wrong with the anti-windowsill joint in the bathroom. It often takes 2 to 3 people to tie a stirrup with an embedded column, which takes half a day to complete. The efficiency is extremely low, and designers can't meet the operability of actual construction. In this process, it is found that the construction is difficult because of the modification from scratch or even the partial replacement of cast-in-place and steel bars. On the other hand, the design process and construction process are too complicated, and a node often needs to be discussed for one month. The final implementation, the design can not be decided in writing at the first time, which has a great impact on the whole total construction period. In addition, there are some details that I won't repeat. How to truly achieve the integration of design and construction remains to be studied.

02

Second, the construction process

Key points: sleeve grouting, grouting, floor flatness, joint control and outer frame protection.

(1) Sleeve grouting: XXX public rental housing phase II 1-3 floors are cast-in-place structures, and floors 4-25 are integral assembled structures. The most important and difficult thing is the four-story transfer floor, which is an important floor connecting the upper part, and the most important thing is the bearing wall connected with 18 casing. The accuracy of reserved steel bars and precast wallboard should reach 100%. After the installation is completed, sleeve grouting shall be carried out for a period of time, and high-pressure grouting shall be carried out with grouting machine, focusing on whether the sleeve is full or not, and follow-up inspection shall be carried out.

(2) Ground flatness and slurry sitting: They complement each other, and flatness is the basis of slurry sitting. If the flatness can't be effectively controlled, the mortar setting can't effectively meet the requirements of specifications and quality, and it will increase the loss of materials. Therefore, it is necessary to increase the control of floor flatness in the process, which will play a good role in the later mortar setting.

(3) Control of slab joints: Because prefabricated structures are spliced independently one by one, vertical joints and horizontal joints will inevitably appear, so the splicing quality of slabs should be strengthened in the construction process. In most cases, the size of the seam cannot be completely controlled, and it can only be reduced as much as possible. The reasons, the extrusion between plates in the assembly process, the avoidance of hidden columns and the limitation of lifting level. Therefore, the selection of materials, elastic modulus and professional team must be controlled to meet the quality requirements.

(4) Outer frame protection: Safety is always the most important. The frame selection of the second phase of XXX public rental housing is far from the original idea. The biggest problems are: ① it can't be synchronized with the construction; ② it can't effectively use the corner pendant; ③ the rotation is too deformed. Therefore, the above points should be fully considered in the later selection, otherwise the safety cannot be effectively ruled out. From many surveys, the traditional framework is the most effective, but there are too many holes in the external wall and more treatment points. Secondly, tripod-type two-layer synchronous protection can also be considered, but the disadvantage is that the external wall is artificially perforated and fixed with bolts, which is easy to interrupt the steel bar and difficult to control the later waterproofing; Most importantly, because there are many bolts, it is necessary to check whether each fixing point is screwed in place, otherwise the consequences will be unimaginable. In a word, the outer frame protection needs people and experts from all sides to study and gradually improve.