The pressure of concrete on vertical formwork in wide sections.

摘要

A theory is presented which describes the mechanismsudinvolved in concrete pressures on formwork in wide sections. Theudmain value of the theory is in providing a framework for analysingudsite data and indicating areas in which potential economies inuddesign might be made.udThe horizontal pressure of concrete on formwork comprisesudtwo components whose magnitude depends -on the proportion of theudvertical load taken by the particle structure and the pore waterudpressure. In normal formwork, the pore water pressure provides theudmajor contribution to the maximum horizontal pressure and thereforeudany factor which increases the rate of load transfer from the poreudwater pressure onto the particle structure, will decrease theudmaximum pressure. For example, porous formwork will give lowerudhorizontal pressures than impermeable formwork and the re-analysis ofudexisting site data supports this prediction.udNormal internal vibration does not have such a significant'udaffect on the maximum horizontal pressure as previously reported,udbut it can fluidify concrete to the depth of poker immersion.udThe elements of the theory are supported by an experimentaludprogramme, re-analysis of existing site data and new site measurements.udThese site measurements have shown that during underwater concretinguda rapidly falling tide can cause the horizontal pressure to exceedudthe vertical pressure.