Steel Space frame Support Nodes

In the actual construction of space frame buildings, parts such as support nodes are relatively prone to quality problems in the construction process. The construction should be strictly in accordance with the quality specifications, so as to avoid various quality problems. During the construction of the space frame, what problems will occur in the support nodes?

1 question

In the construction of support joints such as H-shaped steel frames and space frames with large engineering volume, large area, and complex structures, it often occurs that the deviation of the embedded height of the embedded parts of the concrete frame column corbel is too large, the deviation of the positioning axis of the embedded parts exceeds the limit, The phenomenon of disengagement or lack of compactness between the anchor plate of the embedded part and the concrete directly affects the bearing capacity of the column corbel and the progress of future construction.

2 reasons

(1) The roof steel frame is a space structure, and one steel frame has multiple supports. The detailed drawing of the support of the design institute did not consider the overall deviation or relative deviation that may occur in the construction of embedded parts in civil engineering and the installation of steel frames. Embedded anchor bolts are used Connection; the contracting of the steel structure project lags behind the civil works, the construction technicians of the steel structure cannot cooperate with the construction of the embedded parts of the civil work, the owner is unable to determine the subcontractor of the steel structure project for a long time, the joint review of the drawings is not organized according to the regulations before the construction of the civil work, and the proposal cannot be made early Deviations or problems that may occur in the production and installation of steel structures; before the steel components are processed and manufactured, the steel structure subcontractor fails to carry out handover inspection on the pre-embedded position of the column corbel top embedded parts as required. As a result, the pre-embedded anchor bolts cannot be aligned with the anchor bolt holes of the steel frame support bottom plate, so subsequent construction and installation cannot be carried out.

(2) The engineering and technical personnel on the civil engineering site lack relevant work experience or insufficient experience in steel structures. Before the formwork installation of the column corbel support, they failed to provide technical disclosure to the formwork workers, or due to the rush of progress, the formwork installation adopted irregular methods: The steel structure project is not completed uniformly by one unit. The size of civil engineering is calculated in centimeters, and the size of steel structures is often calculated in millimeters. During separate construction, there will be inconsistencies in the overall installation of the structure; The main reinforcement of the structure is firmly welded, and various types of work are cross-operated. The anchor plate of the embedded part is trampled or squeezed by materials and tools and moves without repair and correction; the slump of the pumped concrete is large, and the slump of the concrete is not often measured. During the hardening process, voids or cracks are generated due to volume shrinkage, and the inner side of the anchor plate of the embedded part and the anchor bolt are corroded. The above-mentioned non-standard practices will inevitably lead to the deviation of the pre-embedded parts of the column corbel top beyond the limit and the subsequent process cannot be carried out, or the bearing capacity of the column corbel support is insufficient and damaged.

3 Prevention and treatment suggestions

(1) The owner should select the steel structure subcontractor about one month before the joint review of the drawings. During the joint review of the drawings, various structural problems that may arise during construction should be fully considered to improve the design of the drawings. Eliminate or reduce the modification and changes of design drawings during construction, especially in the later stage of construction. The installation of the steel structure should be carried out after the substructure axis and embedded parts have passed the acceptance inspection, and the installation unit and the design unit can determine the installation sequence. In order to ensure that the design of the H-shaped steel frame support joints is convenient for construction and that the anchor bolt holes of the support bottom plate will not be misaligned due to the position deviation of the embedded anchor bolts, an additional transitional steel plate connected with countersunk bolts, after installation and positioning, weld the two sides of the transitional steel plate to the anchor plate of the embedded part and connect the countersunk bolts on the transitional steel plate to the support bottom plate.

(2) In order to ensure the accurate positioning of the embedded parts, the subcontractor of the steel structure should cooperate with the civil engineering unit to do the embedding, calibration, and review of the embedded parts. Small-diameter short steel bars should be welded inside the anchor plate of the embedded part to strengthen the bond strength between the anchor plate and the concrete. The technical clarification of various types of work must be done well before the construction of the corbel bearing of the civil engineering column. During the construction, the technical review of the positioning of the main reinforcement of the structure and the formwork should be strengthened, so as not to rework. The embedded parts should be buried before the structural concrete is poured, and the anchor bolts should be welded firmly to the main reinforcement of the structure. Before pouring concrete, a scientific pouring and vibrating process should be formulated, including vibrating time, vibrating method, etc., to avoid over-vibration and missing vibration. The concrete slump should be frequently sampled and measured at the pouring site during the concrete pouring process, and the allowable error of the concrete slump is specified in the specification as +30mm. During the concrete pouring process, special personnel must be arranged to protect the embedded parts to prevent the construction from colliding with the anchor plate.