THE CHILDREN’S THEATRE, ENDELL STREET, W.C.2. W. Braxton Sinclair, F.R.I.B.A., Architect.
The entrance to the Children’s Theatre, room for which had to be found in a narrow street frontage, is particularly well designed. The arched doorway, although of modest dimensions, by being deeply recessed is. given a formal emphasis which the function of the hall behind it deserves. Additional publicity for the theatre is obtained by two octagonal sign-boards and also an illuminated sign, while a small arched window shows an attractive poster devoted to the purpose of advertising the plays. Balancing this, on the right of the entrance is a charming little shop window;
thus the frontage is not only elegant in itself, but has been put to its fullest economic use.
Plastic Yield, Shrinkage and other Problems of Concrete Design
Being an abstract from a paper by Dr. Oscar Faber,
O.B.E., D.Sc., M.Inst.C.E., before the Institution
of Civil Engineers on Tuesday last, November 15.
Steel is a simple elastic material, changing in length (within the elastic limit) under two influences only—change of stress and change of temperature. The effect, either singly or combined, of these changes are determinable; and, moreover, the deflection of such a structure due to loading (within the elastic limit), disappears when the load is removed. The application of the same factors to structures of concrete and reinforced concrete was the result of imperfect understanding of these materials. The author put forward a thesis that structures of reinforced concrete, taking stresses within those allowed in good practice, continue to deflect without change of load or tempera-, ture, a result due partly to shrinkage and partly to plastic yield. It followed, therefore, that the absence of permanent set or deflection must not he insisted upon as a necessary criterion of safety where the test involves an appreciable time limit. The effect of tlr s plastic yield and shrinkage is to produce a grac.ual redistribution of stress between the steel and the cor mete in reinforced concrete structures of such a n.A’U’e, generally, as to relieve the stress on the conci ate and add to that of the steel. Such structures were not dangerous by reason of these phenomena, if these were taken into account in designing; but. special care is necessary, in binding compression steel, whether in beams or columns. The deflection of rein
forced concrete beams, while only about six-tenths of the calculated deflection when the load is first applied, may amount to about six-tenths more than the calculated deflection after six months, the final deflection being about two and two-thirds times the original. When the load is removed, only the initial elastic deflection disappears, the balance, attributable to shrinkage and plastic yield, remaining as a permanent set. Present regulations take no account of these factors and leave much to be desired.
In support of his thesis, the author first adduced the results of observations in recent years by American and German engineers, bearing on continuing deformation under normal stresses at the end of various periods of time, ranging from 60 to 950 days. The main part of his paper, however, dealt in great detail with the results of special researches undertaken by him with the assistance of Mr. R. H. H. Stanger, Assoc. M.Inst.C.E., who conducted the actual tests, the object being to ascertain how yield varies with stress. Constant conditions as to temperature, humidity, etc., were aimed at and, for this reason, the tests were carried out in Mr. Stanger’s laboratory on four small reinforced concrete beams, of 15 feet span. One of the beams, used as a control, carried its own weight; the other three had central loads of 30 lbs., 60 lbs. and 90 lbs. respectively. The results of observations on the behaviour of these beams are set out in numerous tables and graphs. The readings of deflection commenced four
The entrance to the Children’s Theatre, room for which had to be found in a narrow street frontage, is particularly well designed. The arched doorway, although of modest dimensions, by being deeply recessed is. given a formal emphasis which the function of the hall behind it deserves. Additional publicity for the theatre is obtained by two octagonal sign-boards and also an illuminated sign, while a small arched window shows an attractive poster devoted to the purpose of advertising the plays. Balancing this, on the right of the entrance is a charming little shop window;
thus the frontage is not only elegant in itself, but has been put to its fullest economic use.
Plastic Yield, Shrinkage and other Problems of Concrete Design
Being an abstract from a paper by Dr. Oscar Faber,
O.B.E., D.Sc., M.Inst.C.E., before the Institution
of Civil Engineers on Tuesday last, November 15.
Steel is a simple elastic material, changing in length (within the elastic limit) under two influences only—change of stress and change of temperature. The effect, either singly or combined, of these changes are determinable; and, moreover, the deflection of such a structure due to loading (within the elastic limit), disappears when the load is removed. The application of the same factors to structures of concrete and reinforced concrete was the result of imperfect understanding of these materials. The author put forward a thesis that structures of reinforced concrete, taking stresses within those allowed in good practice, continue to deflect without change of load or tempera-, ture, a result due partly to shrinkage and partly to plastic yield. It followed, therefore, that the absence of permanent set or deflection must not he insisted upon as a necessary criterion of safety where the test involves an appreciable time limit. The effect of tlr s plastic yield and shrinkage is to produce a grac.ual redistribution of stress between the steel and the cor mete in reinforced concrete structures of such a n.A’U’e, generally, as to relieve the stress on the conci ate and add to that of the steel. Such structures were not dangerous by reason of these phenomena, if these were taken into account in designing; but. special care is necessary, in binding compression steel, whether in beams or columns. The deflection of rein
forced concrete beams, while only about six-tenths of the calculated deflection when the load is first applied, may amount to about six-tenths more than the calculated deflection after six months, the final deflection being about two and two-thirds times the original. When the load is removed, only the initial elastic deflection disappears, the balance, attributable to shrinkage and plastic yield, remaining as a permanent set. Present regulations take no account of these factors and leave much to be desired.
In support of his thesis, the author first adduced the results of observations in recent years by American and German engineers, bearing on continuing deformation under normal stresses at the end of various periods of time, ranging from 60 to 950 days. The main part of his paper, however, dealt in great detail with the results of special researches undertaken by him with the assistance of Mr. R. H. H. Stanger, Assoc. M.Inst.C.E., who conducted the actual tests, the object being to ascertain how yield varies with stress. Constant conditions as to temperature, humidity, etc., were aimed at and, for this reason, the tests were carried out in Mr. Stanger’s laboratory on four small reinforced concrete beams, of 15 feet span. One of the beams, used as a control, carried its own weight; the other three had central loads of 30 lbs., 60 lbs. and 90 lbs. respectively. The results of observations on the behaviour of these beams are set out in numerous tables and graphs. The readings of deflection commenced four