China Dalian Plaza 66 project is located in the former People’s Stadium in Xigang District, Dalian City. The project covers an area of about 63,400 m2, with 4 floors underground and 7 floors above ground. The building height is 60 m, and the total construction area is about 371,900 m2. The plane shape is like a combination of two fish. . It is invested and constructed by Hong Kong Hang Lung Real Estate. After completion, it will be the largest single commercial building integrating shopping, catering and entertainment in Northeast China.
The structure type of the project is a cast-in-place reinforced concrete frame-shear wall structure (part of the beams and columns are steel-concrete components), with an arc-shaped axis design and a truss roof at the top. The curtain wall is composed of 11 curtain wall systems such as fish scale feature wall and roof vertical seam panel curtain wall.
The interior adopts high-grade marble and imported artificial stone for ground paving, and alumina board and aluminum square pass for large-space ceiling construction.
Overview of skirt-type hyperbolic streamlined stone staircase
The skirt-type hyperbolic streamlined stone staircase is located in the atrium, connecting the public areas of the L1 and L2 floors. It is usually used by customers for shopping. When holding large-scale events, it can also be used as an event venue or a catwalk. It is the most decorated part of the Plaza 66. One of the characteristic parts. The stairs are designed as skirts, and the skirts on both sides swing naturally to form the outline of the stairs.
In order to pursue its natural swing effect, the bending radius of the contours on both sides of the stairs ranges from a minimum of 1280 mm to a maximum of 7050 mm, with a total of 48 arcs.
The length of the middle steps can be freely changed with the skirt, and the three steps at the bottom are arranged in a fan shape. The finish of the stairs is beige natural marble, and the top of the handrail and the anti-skid strip of the stairs are provided with stainless steel strips.
Due to the complex shape and no specific construction drawings for the characteristic staircase, the only basis for construction is to provide a 3D rhinoceros model (Figure 1).
Figure 1 Schematic diagram of the effect of skirt-type hyperbolic streamlined stone staircase
No design construction drawing The BIM technology is used to carry out the detailed design of the construction drawing of the skirt-type hyperbolic streamlined stone staircase. The structural staircase completes the stair skirt shape with broken lines, and the curved stone cannot be closely attached to the structural edge. In order to ensure the firm installation of the facade stone, the facade curved stone adopts the dry hanging stone technology.
The architectural effect of the characteristic staircase is high, and the curved surface is not allowed to be replaced by a short polyline, and to ensure the natural swing of the skirt, a single piece of stone is also a hyperbolic shape whose four corners are not on the same plane, so the stone processing effect is that the characteristic staircase finally meets the architectural requirements. the premise of the effect. In order to ensure the stone processing accuracy, the GL3 type nine-interpolation axis high-yield automatic cutting machine produced by GMM Company is used to cut the curved stone.
The method of measuring and laying out the line is the second key factor affecting the effect of the characteristic staircase after stone processing. The 1:1 wooden stair model will be made first, and the stone steel skeleton will be measured and installed on site according to the outer contour of the wooden model, and then the processed stone will be accurately positioned and installed on the steel skeleton to complete the positioning and installation.
4.1 BIM detailed design
The detailed design is based on the only 3D model of the rhinoceros. The outer surface of the stairs is hyperbolic and special-shaped, and it is impossible to deepen the steel skeleton of each supporting stone, and the size of the steel skeleton is set out with the wooden model.
The main work of the deepening design is the deepening of stone blocks. Take the outer corner of the curved surface as the horizontal dividing line, and the vertical adjustment width is about 800 mm. Try to use the angle mutation line as the dividing line to ensure that the corners of the same stone are as close to the same plane as possible, which can reduce the thickness of the stone blocks.
The whole staircase is made up of 48 arcs with different diameters and different radians. Therefore, the positioning of the curved stone cannot rely on the axis, but must be accurately positioned with the help of three-dimensional coordinates. Establish a stair own coordinate system for precise positioning of each part of the stair.
4.2 Inverse 3D printing
The hyperbolic special-shaped stone in the stone processing space is inspired by the idea of 3D printing. Since 3D printing cannot use natural stone as the printing material, the inverse 3D printing method in which large blocks are used to cut off the irrelevant parts of the stone shape is used for three-dimensional multi-angle surface processing.
By investigating the processing of special-shaped stone in the industry, it was decided to use the GL3 type nine-interpolation axis high-yield automatic cutting machine produced by GMM Company to process the special-shaped stone in this project.
Edit the 3D model into a stone CNC machining program, import the cutting equipment, and reverse the 3D printing principle. The cutting group on the equipment performs 3D precise positioning and cutting of the stone, and removes the unnecessary stone that forms a hyperbola in units.
According to the uploaded cutting program, the stone is cut in parallel, orthogonal, diagonal, polygonal, arc and circle. After the cutting is completed, it is polished and polished to finally meet the requirements of use.
The thickness of stone blocks ranges from 150 to 450 mm. Each block of stone blocks is determined according to the three-dimensional model processing program. After the cutting is completed, ensure that the overall thickness of the stone blocks is uniform, and the thinnest part is not less than 30 mm. Each piece of stone is numbered before and after processing according to the requirements of the detailing drawing.
4.3 Entity Simulation Spatial Positioning
The stone is dry-hanging and steel keel, the stone is arranged in different shapes, and the precise positioning of the steel keel cannot be carried out. The reverse method is used to give priority to the construction of a 1:1 wooden solid model with general accuracy, and then the curved surface of the wooden model is pushed inward. The position of the steel keel is finally adjusted. The hyperbolic special-shaped stone is three-dimensionally positioned one by one to complete the dry hanging installation.
The wooden model is only used to provide a rough outline of the outer edge of the decorative surface for the steel frame, and the construction accuracy of the wooden model is controlled within 20 mm. Using the good flexibility of the wood plank, the wood formwork is bent to form the outer contour of the stairs. The panels on the outer surface of the wooden stairs are the same as those of the stone. Based on the y-axis of the stair’s own coordinate system established above, the distance, angle and ±0.000 height difference between each plate and the x, y-axis are measured in the three-dimensional model.
The coordinate axis is ejected on the stair structure surface by the ink fountain, and the measuring tape is used to measure horizontally and the height is measured for panel positioning and installation. The curve control line near the inner side of the stair handrail is drawn with the aid of a total station.
4.4 Steel skeleton reverse construction
After the construction of the wooden stair model is completed, the construction personnel enter the inner side of the stair model from the gap between the wooden panel surface and the structural stair to carry out the reverse construction of the main keel of the steel frame.
The main keel is set out according to the size of the outer surface of the main keel from the inside of the wooden panel to the inside of 100 mm. The steel frame is connected with the base layer by expansion bolts, the nuts must be tightened, and spring washers are used to prevent loosening. The steel frame is connected with the embedded parts of the base, and the welding length and thickness of the electric welding must be carried out according to the design requirements. After the steel frame is installed, it must be derusted with special anti-rust paint.
4.5 Spatial positioning and installation of stair stone
The installation precision of the hyperbolic special-shaped stone is high, and there is no gap between the stone and the stone in principle. Each stone is positioned independently to avoid the accumulation of errors.
According to the 4-corner coordinates of each stone obtained from the own coordinate system in the 3D model, a BTS-901 laser intelligent total station is set up on both sides respectively, and the automatic suspension measurement function of the total station is used to locate the stone in the air.
The first installation stone is positioned at 3 corners, 1 corner is reviewed, the second and third stones are aligned with the first stone on one side, and the total station automatically measures the coordinates of 2 points on one side for positioning. Stone installation adopts the installation sequence from the middle to both sides, which can reduce the accumulation of positioning errors.
The single-row stones are installed from the middle to both sides, and the overall order of the single-sided stones is also installed from the middle to the top. Since the stone is a special-shaped stone, after the main keel of the steel frame is installed, the secondary keel cannot be installed temporarily, and it is necessary to give priority to the pre-positioning of the first installation stone.
Use the total station for positioning, and determine the position of the stone by assisting manual lifting. Determine the position of the secondary keel according to the position of the upper and lower edges of the stone to the 1/4 position of the side length of the center of the stone, and mark the position of the secondary keel on the main keel. Mark the adapter location on the stone.
Remove the stone, weld the secondary keel and the stone opening. Plate area larger than 1 m2 set 8 holes (4 pairs); 0.6~1 m2 set 6 holes (3 pairs), less than 0.6 m2 set 4 holes (2 pairs), special small size slate shall not be less than 2 holes.
The slot hole is located on the center line of the plate thickness, the hole diameter is not less than 20 mm, and the hole depth is not less than 20 mm. The four corners of the stone are pasted with a special reflector for the total station to locate the stone.
When the coordinates of one corner are accurately positioned, temporarily fix it, and position the remaining triangles of the stone in turn until all the four corners are positioned accurately.
Install the connector, the angle is not suitable, and the steel keel is simmered and bent for fine adjustment. After the connector is installed, tighten the nut, and apply superglue to the tightened bolt for reinforcement.
The installation of the second stone is horizontally adjacent to the first stone. Before the installation of the second stone, the position of the second stone’s sub-keel can be determined according to the arrangement position of the second stone’s sub-keel and the direction of the stone’s arrangement, and the secondary keel can be installed first. Pre-assemble the second piece of stone, leaving no gap in theory, so that the second piece and the first piece of installed stone are tightly pressed on one side, and then use the total station to check the two corners of the other side of the second piece of stone until the positioning is accurate, The height difference between adjacent stones shall not exceed 3 mm.
4.6 Cutting, repairing, grinding, crystallization
Use a dust-free slitting machine and a 2 mm thick slit sheet for slitting treatment, cut the stone spacing to a uniform 2 mm, and use a vacuum cleaner to absorb the dust in the joints. Meet the cleanliness requirements before refilling. To color the high-quality marble glue, the color is required to be close to the color of the plate, slightly lighter than the plate (to prevent aging and the amount of color change in the later stage of maintenance) The curing agent is prepared according to the designed amount, and the glue seam is required when filling the glue. It must be higher than the surface of the stone, (to avoid the phenomenon of collapse after grinding) for the glue seam that cannot be filled at one time, it must be filled in time.
Grinding is done in order of 50 mesh, 150 mesh, 300 mesh, 500 mesh, 800 mesh, 1 000 mesh, 2 000 mesh, and 3 000 mesh from coarse to fine.
50 mesh, 150 mesh and 300 mesh are the rough grinding stage. In the rough grinding stage, a small electric grinder is used for dry grinding, mainly grinding the notch and marble glue. Edges, no waves.
500~1 000 mesh is the fine grinding stage, which is mainly used to repair the scratches left by the coarse grinding disc, and 2 000~3 000 mesh is the fine grinding stage, which is used to polish the fineness and restore the luster of the stone.
In the fine grinding stage, spray can be used to solve the water required for grinding, or water-based protective agent can be used to replace clean water. After grinding, the overall stone is smooth, and there is no obvious bulge, and the luster of the stone application appears.
Polish the polished stone with crystalline powder, wait for the stone to be completely dried, and then carry out protective agent penetration and brushing treatment. The drying time in general environment is 5~7 d, and the surface of the crystallized stone has better gloss and fineness. Has a hardening effect.
Through the successful practice of the construction technology of the skirt-type hyperbolic streamlined stone staircase in this project, the key points of each stage from the scheme planning to the on-site implementation of the complex modeling, full-body stone and streamlined stone components are systematically displayed, which provides the construction of similar projects in the future. A complete set of technical reference and planning guidance.