Correspondence. Distribution of Tensile Stress in Beams

WHILE many advantages of pre-stressed concrete beams over the ordinary reinforced concrete beam, such as reduction of deflections, lighter construction, greater safety against cracks, and possibilities for precast work, have been recognised, there is a widespread fear among engineers that these advantages may be lost due to a considerable loss of prestress in course of time. Uncertainty is also felt about the exact effects of pre-stressing on a normal reinforced concrete beam. Dr. K.L. Rao

Action of the plane polariscope-Behaviour of stressed material in polariscope -Isochromatic and isoclinic lines-The determination of the separate principal stresses- Optical system of a typical polariscope. A.W. Hendry

This month's letters include additional references for the June issue's Regent Street disease article and discussions about seismic design and minimum qualifications for carrying out structural engineering services.