It is said that so-called shear friction is one of the important mechanisms for shear resistance on the construction joint and also important for the joint between members of precast concrete structure, which has connecting bars arranged perpendicularly against joint. When numerical estimation about shear resistance about construction joint and precast joint may be considered, the thought of "coefficient of shear force" is often introduced.
By the past studies it was said that coefficient of shear friction depended on only the way of roughing the construction joint: for example what tool was used for roughening. This way to consider only the roughening way is qualitative. But the author thought that the coefficient of shear friction depends not only on the way of roughing the surface of construction joint but also on the estimated value of surface roughness defined mathematically, not only qualitative but also quantitative.
So the author performed two experiments to make clear whether my thought was correct or not.
First experiment was to measure of surface roughness of construction joint and to estimate that roughness numerically. 36 specimens were made and roughened on these face by using several kinds of tools, and those roughness were measured by using laser beam transducer. All specimens had bars which were arranged perpendicularly against those roughened face, and those bars were regarded as connecting bars in the following next experiment. After measuring, roughness measuring data were calculated by numerical way and transformed to one numerical estimate value.
Second experiment was to suffer shear force to those roughened joint; those roughened joint was regarded as construction joint and precast joint. To modify condition of joint as correct as possible, some unique improvement had been made in shear loading setup.
By results of the first measurement and the second loading test the following facts were concluded:
1. The shear force could be predicted by using the numerical estimate value of surface roughness of construction joint if slip dislocation is limited within 1mm.
2. Coefficient of shear force about construction joint and precast joint could be expressed by using those numerical estimate values.
3. The behavior of joint bars and the coefficient of shear friction can be predicted by using the estimate values of surface roughness.