Camber in prestressed concrete

[maddog67]

I am trying to find out the predicted camber of a prestressed hollowcore unit . Rule of thumb is usually length/300 . However some publications say this is to determine the maximum allowable camber , whereas others say it is the predicted camber and subsequently has a 50% margin of error plus or minus .
Could anyone help me find documentaion to settle this matter , especially for the UK . Any help would be most welcome .

 

[Dinosaur]

If you are using straight strands, it should be a simple matter to compute M/EI and determine the radius of curvature from that. Then subtract the dead load deflection due to selfweight and you have the camber. However, "E", Youngs Modulas, will not be precise and there will be P/S loses that give variation to the result. Good Luck.

 

[civilperson]

One method to deal with differing camber in adjacent hollowcore units is to hang a weight from below the high unit to produce equal top elevations prior to placing topping. After the topping has strength the "grout key" at the edge of adjoining units will hold relative location in place. This method has the advantage of producing uniform topping thickness.