The report provides specific formulas to calculate the maximum lateral pressure ( Pmaxcap P sub m a x end-sub
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Pmax=ρ⋅g⋅Hcap P sub m a x end-sub equals rho center dot g center dot cap H (Where is density, is gravity, and is the pour height).
provides a standardized method for calculating this pressure, allowing designers to avoid excessively conservative (and costly) designs while maintaining safety. The report emphasizes that the pressure is not purely hydrostatic and depends heavily on the rate of placement and the stiffening of the concrete. 2. Key Parameters Influencing Concrete Pressure ciria report 108 concrete pressure on formwork
Pmax=D⋅[C1⋅R+C2⋅K⋅H−C1⋅R]cap P sub m a x end-sub equals cap D center dot open bracket cap C sub 1 center dot the square root of cap R end-root plus cap C sub 2 center dot cap K center dot the square root of cap H minus cap C sub 1 center dot the square root of cap R end-root end-root close bracket
In the late 1970s and early 1980s, CIRIA undertook a massive research project, observing real-world pours in walls, columns, and slipforms. The result, published in , provided empirical evidence that concrete stiffens (develops "shear strength") as it hydrates, thereby reducing peak pressure significantly below the hydrostatic maximum.
): The vertical speed at which the concrete level rises in the formwork (measured in meters per hour). Faster pours increase lateral pressure. Concrete Temperature ( The report provides specific formulas to calculate the
Encourages the use of established models like DIN or CIRIA, adapting them for modern construction techniques.
Hydrostatic check: D × H = 24 × 8 = 192 kN/m². Since 115.2 < 192, the CIRIA value controls. You can design formwork for 115 kN/m², not 192. That is a in required tie strength.
) at the bottom of the form would be strictly hydrostatic, calculated using the standard fluid equation: Can’t copy the link right now
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Before the release of CIRIA Report 108, formwork design often relied on simplified hydrostatic assumptions or outdated empirical formulas. These older methods frequently overestimated pressure, leading to over-designed, expensive formwork, or underestimated it, resulting in dangerous blowouts.