•From the previous slide, the Clegg Hammer Modulus
(CHM) for the 4.5
kg Clegg Hammer (output: CIV) and 20 kg Heavy Clegg Hammer (output: CIV/H) at their set
drop-heights are calculated, in MPa and based on certain assumptions, as:
•
•Standard
CHM (CHM/S)
•4.5 kg
Clegg Hammer:- CHM/S (in MPa) = 0.088 [(CIV)(CIV)]
•5 cm Φ Hammer, 0.45 m
Drop-Height
•
•Heavy
CHM (CHM/H)
•20 kg
Clegg Hammer:- CHM/H (in MPa) = 0.23 [(CIV/H)(CIV/H)]
•13 cm Φ Hammer, 0.3 m
Drop-Height
•
•Qualifying remarks:- the coefficients in these
equations have been derived using double integration of time vs. deceleration to
determine the deflection and using this in elastic plate bearing theory to arrive at an elastic
modulus. They depend to some extent on the technique used for the integration and the theoretical
assumptions. The use of Clegg Hammer Modulus (CHM) as a “seed” modulus for iterative analysis
comparing calculated deflections with field observations should enable the coefficients to be
refined from time to time.