Stability of Steel Modules During Construction

Concrete-filled composite plate shear walls (CF-CPSW) are being considered for high-rise buildings because of their potential for modularity, construction speed, and structural efficiency. The system is composed of a concrete core sandwiched between two steel faceplates. The steel plates are connected to each other by tie bars, rods, or steel shapes, and composite interaction between steel faceplates and infill concrete is developed by these tie systems and headed stud anchors (if included). The empty steel modules-which are composed of steel faceplates, tie bars, and shear studs-are fabricated in a shop and shipped to the site for erection. The erected steel modules serve as formwork and falsework during construction and concrete casting. The stability of the steel modules during construction, while supporting construction loads, the weight of the surrounding steel frames, and the floor systems during concrete casting, is vital.

This paper presents the results of numerical and analytical studies conducted to evaluate the stiffness and stability of empty steel modules (of CF-SPSW) to resist gravity loads during construction. The stability of empty modules is governed by their effective shear stiffness (GAeff), which in turn depends on the relative flexural stiffness (EI/L) of the faceplates and the tie bars. The finite element method can be used to determine the effective shear stiffness (GAeff) and critical buckling stress (scr) of the steel module. Additionally, the effective shear stiffness and the critical buckling stress can also be estimated conservatively using simple equations developed using a mechanics-based approach and proposed in this paper for design purposes. When the ratio of the steel faceplate flexural stiffness (EIp/S, where s is the tie spacing) to the tie bar stiffness (EIt/d, where d is the tie diameter) is less than 25, the buckling of empty steel modules is somewhat independent of the load eccentricity, end conditions, and module height. For the design of steel modules, it is not recommended for this ratio of EIp/S to EIt/d to be greater than 25, because the empty modules become extremely flexile and the critical buckling stress becomes less than 1000 psi.

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