The large lifting capacity of 10 tons and a maximum lifting height of 42 meters make it suitable for truss lifting operations. The crane is heavy, and its ground pressure when moving without load is 79012 Pa. The design load capacity of the floor in Room 1 is specified, so it's essential to use steel plates as a walking path for crawler cranes. Based on calculations, each basement section should be supported with a cross-section of 250 x 25 mm and wooden columns made of 2.5 x 2.51 m to form the main structural grid.
For the installation sequence of components, the stiff columns of the shaft and the ⑧ axis, along with components ①, ②, and ③, are constructed first to an elevation of 30.000 meters. These components form the structural system of the podium and the main building, combined with the beam and slab systems of each floor. At this stage, the concrete in the columns is poured. The stiff column also functions as part of the truss, forming the structure with cross braces and large joints. Component number 2 refers to the installation order. Due to their size and weight, the truss must be fabricated in sections in the factory. One challenge during the assembly process is that the No. ⑤ brace lacks a fulcrum.
The installation method for the No. 4 diagonal brace involves connecting the lower end to the bracket attached to the stiff column and leaving the upper end free, which can tend to move out of plane. To prevent instability during splicing, a No. 40 I-beam is installed between two 13-meter-long bars at a high elevation. Temporary support is provided by connecting the I-beam to the diagonal brace at the intersection. The connection sequence begins with attaching the lower end of the diagonal brace using a connecting plate and corbel. Then, the door is moved from the end to the structural column. Once the column has sufficient rigidity, a manual hoist is used to adjust the diagonal brace to the desired angle. Finally, 17 steel plates are used for hidden connections, ensuring the rod remains stable. The same method is applied to install the second diagonal brace, following the sequence to complete the assembly.
For correction and measurement, the principle is to ensure that each truss member lies within its own plane and that the axis deviation of the 1-axis column does not exceed 30 mm. All connections follow the standards for steel members, including weld seam width and verticality. However, these do not meet the overall steel truss inspection requirements. A jack is used for single-chip calibration, and measurements are taken until the acceptance standard is met. Only after inspection is the welding performed.
The truss welding is full penetration welding, with all welds rated as grade one. A reasonable welding sequence is necessary to minimize deformation. The principle includes welding inclined rods first, then straight rods; welding parts of the same rod before the other end; and starting with vertical welding before flat welding. Anti-deformation measures or intermittent welding are used during the process. During welding, the shrinkage and changes of the weld are monitored, and anti-deformation measures are implemented.
Ultrasonic flaw detection is used to inspect the weld seams. The first party conducts self-inspection, and any unqualified welds are cut using carbon arc gouging and re-welded and inspected again. Repairs are limited to two times.
Concrete is poured into the slant bar and large joint of the truss-pressed bar. This significantly improves load-bearing capacity, but construction is difficult due to internal stiffeners and partitions, making it hard to ensure compactness. Since the rods are sealed, it’s impossible to visually confirm the pouring condition. After research, the following measures were taken: improve concrete workability, pre-open a round hole in the appropriate position for initial pouring, and then pour from the top after closing. Using 10-meter-long, 5-meter-diameter tools, the Shenzhen World Trade Center Building Preparation Office, Zhang Jinglin, introduced a single-sided treatment technology for the friction surface of steel structures.
Steel structures require high-strength bolt friction-type connections. When the pre-tension is constant, increasing the friction coefficient on the contact surface is necessary to enhance the load capacity of the joint. Sandblasting is typically used for double-sided treatment, but factors such as large blasting areas and handling difficulties have affected construction quality and schedule. In the dry coal shed project at Wuhan Yangluo Power Plant, the friction coefficient did not meet the design requirement due to improper surface treatment.
Later, a single-sided treatment method using composite sandblasting was adopted to solve the problem. The steel structure of the dry coal shed hinged arch in Wuhan Yangluo Power Plant consists of 7 arch trusses, 84 auxiliary trusses, 2 connecting trusses, 14 ground schools, and 7 sets of natural hinges connected by 14,000 high-strength bolts. Each arch frame weighs about 30 tons and is divided into 16 sections, with connections using 2 or elbow 16 torsion shear type high-strength bolts.
In Luozun Village, the setting of juice in high-strength bolt connections requires sandblasting on the contact surface to achieve a friction coefficient of no less than 0.45. However, production personnel used grinding wheels, resulting in insufficient friction coefficients. To address this, pickling treatment was proposed for the friction surface. The method involved wiping rust from the surface using coarse sandcloth, avoiding a bright finish, followed by washing with 15% dilute sulfuric acid. The treated surface became grayish-black with a rough texture, similar to 0.4–0.6 emery cloth, and no bright spots were visible.
The sandblasting process was adjusted to use quartz sand instead of other materials. The process included heating components to 700°C, sandblasting, cooling, brushing off loose sand, and repeating the process at 600°C. Key areas around bolt holes were carefully handled to avoid leaks. The final surface had uniform spots and a rough feel, meeting the required friction coefficient.
Random sampling of 2 specifications and 6 groups showed average friction coefficients of 0.503 and 0.483, exceeding the design value of 0.450. The dry coal shed project was successfully completed, proving the effectiveness of the single-sided friction surface treatment. This approach saved 350,000 yuan in material costs and processing time.
Most splint connections in large steel structures are located on the main truss and often operate outdoors. The sandblasting process is affected by weather, leading to unstable quality and friction coefficients not meeting design requirements. The core plate part is mostly used in the webs of the brace bar and auxiliary truss, which are small in size, light in weight, and easy to transport, allowing them to be processed in a controlled blasting room.
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