Simplified Modeling and Analysis of Pattern Loading Effects on Shoring Systems During Construction

Abstract

This paper examines the effect of concrete placement patterns on temporary structures. Specific consideration is given to scaffold shoring systems used in construction. A simplified two-dimensional portal frame model is developed to investigate the system stability for different load patterns corresponding to different concrete placement procedures. Then, a three-dimensional structural model is developed to identify the location and magnitude of the critical formwork load both during and after concrete placement. A second-order elastic analysis of the system is performed to determine the critical loads. For the sway case, there exists a unique critical (collapse) load which is independent of load pattern (placement paths) and partial loads. However, the amount of lateral deflection varies for different load patterns or paths. Thus, a single limiting lateral deflection of the temporary structure may not be suitable as an early-warning index signaling imminent collapse during construction. An analysis based on the concept of influence surfaces confirms that an equivalent uniform load may be used in design to account for pattern loading during construction.

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