LIGHTWEIGHT REINFORCED CONCRETE--VERIFICATION OF THE DESIGN ASSUMPTIONS

In parallel with the erection of a road bridge of precast lightweight reinforced concrete, structural elements similar to those used in the actual structure were tested in the laboratory. Test loads to the point of collapse were applied to two test beams to verify the design assumptions for lightweight concrete. Measurement of deformation included deflections as well as steel and concrete strains. The deflections and concrete strains agreed well with calculated values and thus provided experimental verification of the design assumptions. The measured steel strains were however much less than expected, which is attributed to defective bond. In the fracture zone early splitting of the concrete was observed with the associated low bond stresses. The correctness of applying the conventional theory of reinforced concrete for design and calculation of deformations for lightweight concrete is thus confirmed. Calculated and observed deformations agree very well at working load; at ultimate load account must be taken of the greater variation in bond strength. The slip of the reinforcing bars can be prevented by suitable detailing. As in normal density reinforced concrete care should be taken not to stop off reinforcing bars in areas of high tensile stresses. /TRRL/