Mr. Mensch says of rectangular water tanks that they are not held (presumably at the corners) by any such devices, and that there is no doubt that they must carry the stress when filled with water.  A water tank,[V] designed by the writer in 1905, was held by just such devices.  In a tank[W] not held by any such devices, the corner broke, and it is now held by reinforcing devices not shown in the original plans.

Mr. Mensch states that he “does not quite understand the author’s reference to shear rods.  Possibly he means the longitudinal reinforcement, which it seems is sometimes calculated to carry 10,000 lb. per sq. in. in shear;” and that he “never heard of such a practice.”  His next paragraph gives the most pointed out-and-out statement regarding shear in shear rods which this voluminous discussion contains.  He says that stirrups “are best compared with the dowel pins and bolts of a compound wooden beam.”  This is the kernel of the whole matter in the design of stirrups, and is just how the ordinary designer considers stirrups, though the books and reports dodge the matter by saying “stress” and attempting no analysis.  Put this stirrup in shear at 10,000 lb. per sq. in., and we have a shearing unit only equalled in the cheapest structural work on tight-fitting rivets through steel.  In the light of this confession, the force of the writer’s comparison, between a U-stirrup, 3/4-in. in diameter, and two 3/4-in. rivets tightly driven into holes in a steel angle, is made more evident, Bolts in a wooden beam built up of horizontal boards would be tightly drawn up, and the friction would play an important part in taking up the horizontal shear.  Dowels without head or nut would be much less efficient; they would be more like the stirrups in a reinforced concrete beam.  Furthermore, wood is much stronger in bearing than concrete, and it is tough, so that it would admit of shifting to a firm bearing against the bolt.  Separate slabs of concrete with bolts or dowels through them would not make a reliable beam.  The bolts or dowels would be good for only a part of the safe shearing strength of the steel, because the bearing on the concrete would be too great for its compressive strength.

Mr. Mensch states that at least 99% of all reinforced structures are calculated with a reduction of 25% of the bending moment in the center.  He also says “there may be some engineers who calculate a reduction of 33 per cent.”  These are broad statements in view of the fact that the report of the Joint Committee recommends a reduction of 33% both in slabs and beams.

Mr. Mensch’s remarks regarding the width of beams omit from consideration the element of span and the length needed to develop the grip of a rod.  There is no need of making a rod any less in diameter than one-two-hundredth of the span.  If this rule is observed, the beam with three 7/8-in. round rods will be of longer span than the one with the six 5/8-in. rods.  The horizontal shear of the two beams will be equal to the total amount of that shear, but the shorter beam will have to develop that shear in a shorter distance, hence the need of a wider beam where the smaller rods are used.