. Official proceedings . ed that this crude assumptionwas reasonably close to the truth. In the model, and in theprototype also, the impact was measured by recording the mo-tion of weighted springs carrying a stylus, which left a recordof its movement on smoked glass. Proportions of the main supporting pier, the rollway, andthe obelisk were fixed so that the base, or the end nearest thesupporting pier, would strike the river bottom a fraction of asecond before the outer end; that is, the obelisk had not rotateda full 90 deg. before it touched bottom. The plans were madein this way- because it
. Official proceedings . ed that this crude assumptionwas reasonably close to the truth. In the model, and in theprototype also, the impact was measured by recording the mo-tion of weighted springs carrying a stylus, which left a recordof its movement on smoked glass. Proportions of the main supporting pier, the rollway, andthe obelisk were fixed so that the base, or the end nearest thesupporting pier, would strike the river bottom a fraction of asecond before the outer end; that is, the obelisk had not rotateda full 90 deg. before it touched bottom. The plans were madein this way- because it was believed that there would be lessprobability of the mass being shattered if the lower end touchedfirst. As it later developed, this precaution, combined with theother preparations, was ample to ensure the safe dropping ofthe huge mass. During the progress of the design, the idea persisted thatthe huge mass of concrete, falling on the rock of the river bot-tom, would be considerably shattered. It was considered neces-. FIG. 5—WINTER CONSTRUCTION ON OBELISKNote Forms, Housing for Heating, and Ice Formed by Condensed Steam Studies for Reinforcing 181 sary to heavily reinforce the entire mass, so that the wholewould be held together after this occurred. For reinforcement,old steel cables were largely used. They were preferred toreinforcing steel because of their greater flexibility. In additionto the longitudinal cables grouped in fours, diagonal strandswere placed throughout the mass so that no matter what direc-tion might be taken by a line of fracture, it would be crossedby cables nearly perpendicular to it, which would hold the frag-ments in place. For example, in the upper two-thirds of theobelisk, enough diagonals were inserted to insure that at least60 per cent of them would cross any horizontal plane. Much to everyones surprise—and probably because of theamazingly accurate fit of the obelisk to the river bottom andthe effectiveness of the water as a cushion—there
Size: 1960px × 1275px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidofficialproc, bookyear1901
