In the case of beam launching, the only load acted on the beam is the selfweight. The issue may not be critical in the case of prestressed member since the beam is stressed at upon attainable required concrete strength. The issue is becoming critical in the case of precast RC member where we need to know the strength of concrete upon launching. Contractor should seek the advice from the designer on what age of concrete can the launching be done. Alternatively, guide stipulated in JKR concrete specification on removal of forms period can be resorted to as the basis.
Lifting hook shall be positioned at the point of contraflexure so that minimum stresses exert onto the beam under the selfweight and this is typically one-fifth of the beam length.