Abstract

Despite the multitude of benefits tilt-up construction has to offer in low rise commercial buildings, there is still room for improvements in the performance of tilt-up buildings. One opportunity for improvement is to minimize a particular, undesirable cracking pattern often seen in concrete tilt-up panels (See Figure 1), which in some cases requires significant cosmetic patching (See Figure 2). This concrete cracking can first appear as non-problematic and non-structural, but even small cracks can become weathered and lead to water intrusion and rebar corrosion. At the very least, these cracks are cosmetic concerns for the owner or tenant potentially resulting in significant paint/patch costs.

As part of an undergraduate research project, the authors sought to determine the cause of this cracking pattern in the panel’s lower half and to have a convincing argument for where the problem originates. Work was conducted at the California Polytechnic State University in San Luis Obispo (Cal Poly) within the Architectural Engineering Department.

Historically, there have been many suggested causes for this cracking pattern; including, setting panels too hard, excessive out-of-plane bending stress, in-plane shear stress, poor bond-breaker performance and lifting stresses, or other construction-related issues. However, to an engineer, a handful of indicators such as the cracking location, direction, amplitude, and cracking entirely through the panel, suggest that these cracks are due to the shrinkage restraint at the base of the panel. Despite the regularly spaced panel joints in tilt-up, natural concrete shrinkage can still be restrained by ties to adjacent panels, to the adjacent floor slab, and to the foundation, preventing free movement.

Disciplines

Architectural Engineering

Number of Pages

7

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URL: https://digitalcommons.calpoly.edu/aen_fac/175