国家体育场桁架柱外柱节点设计研究

国家体育场桁架柱外柱节点的几何关系复杂,存在T型、K型及KT型等多种腹杆形式,腹杆侧壁与外柱壁板斜交,还存在与立面次结构相交的情况。焊接薄壁箱形构件相贯节点的刚度差,承载力低。本文通过在外柱内设置横向加劲肋与局部纵肋等构造做法,可以有效提高节点刚度与承载力。对于有次结构的外柱节点,次结构的上、下壁板不能全部贯通,在保证腹杆与外柱传力可靠的前提下,在外柱节点区设置传力三角区。对于K型腹杆节点,翼缘较厚的腹杆贯通;对于KT型腹杆节点,中间腹杆贯通。通过合理设计拼接焊缝位置、采用整板切割等方式,可以有效减少焊缝数量,避免焊缝重叠。采用有限元法分析外柱节点的受力形态,并根据“最大平均应力”的原则确定节点域板件的厚度,实现“强节点”的设计理念,保证节点的可靠性与经济性。

Design and research of outer-column connections of trussed columns for the National Stadium

The geometrical configuration of the connections of the outer columns for the National Stadium is complicated,as there are many forms of diagonals such as T-shaped,K-shaped and KT-shaped ones.The wall of the diagonals is oblique to neighboring wall plate of the outer column,and the diagonals also intersect with the secondary structure of the facade.The conventional welding connections for the welded thin-wall box member have poor stiffness and low bearing capacity.A design method for connections of the outer trussed columns with welded box section is presented in this paper.By adopting the construction methods such as setting transverse stiffeners and local vertical stiffeners within outer columns,the stiffness and bearing capacity of the connections can be effectively improved.As for the connections of the outer column with secondary structure,the upper and lower wall plate of the secondary structure cannot be straight-through,therefore a triangle area for load transfer is set in the connection area of the outer column on the premise of ensuring reliable load transfer of the diagonals and outer columns.As for connections of K-shaped diagonals,the diagonals with thick flange are straight through;as for connections of KT-shaped diagonals,mid-diagonals are straight through.The number of welding seams is effectively reduced and the welding seams are moved outwards through reasonable design of the splice-welding seam positions and by means of full-plate cutting.The loading case of the connections is analyzed with finite element method.The thickness of the plate element in the connection area is determined according to the principle of "the maximum average stress".As a result,the concept of "strong connection" is realized and the reliability and economical efficiency are ensured in the project.