Abstract: Nantong International Convention and Exhibition Center is located in Chongchuan District of Nantong City, on the northeast shore of Purple Lang Lake, with a total building area of about 80 000 square meters. Along the long direction of the building plan, the multi-function hall and the banquet hall and the conference hall were respectively arranged into two major functional divisions, which were connected by the entrance hall in the middle. The total length of the building is 280 meters, the width is 84 meters, and the maximum height of the functional structure roof is 23 meters. 1 underground floor used concrete structure for the garage and civil air defense function. The floors above the ground are 1 to 3, and the height is 9 meters, 6 meters and 4.5 meters respectively from bottom to top. The main body adopted the steel frame structure system, and the long-span space roof adopted the steel truss structure, with the maximum span of 54 meters. The top molding roof was free-form surface with a maximum height of about 30 meters and adopted cross pipe truss structure.
Combined with the architectural function, the main structure of the conference center adopted steel frame and long-span steel truss structure system, spatial grid structure was used to form the skeleton of the roof. The overall structure has the characteristics of multi-high-rise structure and spatial structure. Due to the super length of the structure and two structural units with different functional distinction, the overall structure was connected by the entrance hall roof and local roof. The structural design has many design difficulties, such as weak linkage, obvious torsion effect, and the design of peripheral supporting columns. In order to solve the above difficulties, the analysis and research were carried out from the aspects of conceptual design, computational analysis and construction measures. Buckling restrained braces were introduced to avoid overload of the supporting frame due to absorbing too much seismic actions, while maintained sufficient torsion resistance of the entire structure. Considering the unfavourable integration of over length plane and weak connective of the roof, an envelope bearing capacity design was conducted to cover difference from structural components designed as single structures to structural components designed as one connected structure. The weak connective position was locally strengthened. In order to realize the architectural effect of ultra-thin columns along the perimeter, the constraint conditions of the perimeter columns and the corresponding roof structural arrangement were optimized based on the seismic design concept. The column was designed to not participate in system of horizontal lateral swing column. The bottom of the pillars and columns released the bending constraints and only provided vertical and not participate in the overall lateral. At this point, the supporting column did not belong to frame column and construction measures slenderness ratio could be greatly reduced. The transformation joints of box-shape to I-shape of truss chord were analyzed from the aspects of force transmission mechanism and manufacturing difficulty, and finally a new joint form with simple structure and reliable force transmission was adopted, which reduced the difficulty of processing, manufacturing and field construction. Combined with the functional characteristics of the building, the local use of the latest research and development of high strength refractory corrosion resistant steel has played a good demonstration role.