Renovation of olive-shaped steel structure space frame dome

The steel space frame dome on the roof of the swimming pool presents a half olive-shaped spatial three-dimensional structure as a whole. Below the middle part is a swimming pool of 50mx21m. The height from the swimming pool plane to the highest point of the dome is 29m. According to the calculation, the area of the entire dome is about 5,000 square meters. The length of the steel space frame in the north-south direction is 86m, and the space frame can be divided into 32 spans according to the lower chord of the space frame in the east-west direction; the widest point in the east-west direction is 49.7m. Due to the long service life of the swimming pool, the curved ceiling on the original roof grid has a large area of yellow watermarks, the original paint of the maintenance ladder has partially yellowed and peeled off, and there is a lot of ash floating on the steel space frame and maintenance ladder, which makes the dome look obsolete. One of the construction contents of the renovation of the swimming pool is the renovation of the steel space frame dome paint, the dust removal of the steel space frame, and the paint renovation of the maintenance ladder.

Scheme selection of space frame dome renovation

The surface layer of the inner wall of the swimming pool is an exposed plastic waterproof surface layer, and no damage is allowed during this renovation. Before the construction, the initial plan used Mantanghong scaffolding, but considering that the plastic waterproof surface layer in the swimming pool adopts Mantanghong steel pipe scaffolding, it will be more difficult to protect. The swimming pool on the first floor is surrounded by a two-story stepped stand (the ground and seats on the second floor do not move). so it is difficult to set up full of scaffolding. In addition, due to the long period and high cost of using red scaffolding, and due to the tight construction period of this project and the limitation of special funds, Party A hopes to reduce the cost of dome renovation. In view of the above difficulties, the project department began to study the remaining alternative construction schemes. The overall composition of the dome observed on site is as follows: from the highest point to the lowest point of the dome, the lower chords of the north-south space frame can be divided into 8 spans. In the vertical direction, there is a vertical inspection staircase at each of the 6 spans from the north and south ends to the skylight at the highest point. In the horizontal direction, there is a horizontal maintenance staircase at the third and sixth spans, which is connected to the vertical maintenance ladder. After repeated research on the structure of the space frame nodes, it can be found that some of the space frame nodes in the middle and lower parts of the dome have some internal struts that are close to the horizontal state, which can be used to lay the foot plate to form the operation platform, and the top of the dome can take other auxiliary measures to achieve the operation platform.  At the same time, the safety protection problem is solved by hanging a safety net below and outside the operation layer.   

3 Construction process and measures

3.1 Construction division and construction process of space frame dome

According to the analysis of the shape of the space frame dome, the construction progress plan and the turnover of protective materials, the renovation plan of the dome is divided into 6 areas for construction, and the protective materials in 2 areas are also used for turnover.

During the construction, first set up the platform and protective net in area 1. After the protection and platform erection and acceptance are completed, the oiling worker in area 1 shall spray and roll paint from the dome downwards, and at the same time, area 2 on the south side began to build a platform and protective net. After the paint and paint refurbishment and acceptance in Zone 1 are completed, the access platform in Zone 2 has been erected, and construction can be entered into Zone 2. At the same time, the access platform and protective net in Zone 1 will be dismantled from top to bottom and moved to Zone 3 for erection. While removing the protection and platform, the scaffolder completed the dedusting of the grid in the area. After the paint and paint renovation in Zone 2 is completed, the platform for people in Zone 3 has also been set up, and people can enter Zone 2 for construction. At the same time, the upper platform and protective net in area 1 are removed from top to bottom and moved to area 3 for setting up. While removing the protection and platform, the framers will complete the dust removal of the space frame in the area.  After the renovation and acceptance of paint and paint in Area 2, the upper platform in area 3 has been set up and can be entered into area 3 for construction.  At the same time, the upper platform and protective net in area 2 will be removed and moved to area 4 for installation, and so on, and finally complete the renovation of all the dome.  Repainting of the access ladder in each area should be completed before the protection is removed.  The construction sequence of dome coating and dust removal in each zone is from high to low construction to prevent the pollution of the lower finished product when the coating and dust fall.  Construction personnel and materials (including protective materials, paint and paint) transportation are to use the existing maintenance ladder into each zone.  

3.2 Dome coating renovation and space frame dust removal

The refurbishment of the space frame dome coating must first remove the dust and clean the original base layer, and then carry out the coating operation, spray the bottom coating and finish the paint twice. The construction sequence should be sprayed from top to bottom. In order to ensure that the paint does not pollute the roof purlins and space frame rods, the method of wrapping with waste newspapers and plastic sheets can be used for protection. The space frame dust removal is the last process, which is constructed by professional frame workers. The space frame dust removal is to carry out dust removal construction while removing the protection of the area after the paint acceptance is completed. When removing the dusting, first stand on the scaffolding board and use a rag to remove the upper space frame member, then remove the scaffolding, finally remove the safety net, and clean the lower rod after the last safety net.