Pieces of Iowa’s Past, January 16, 2013

Pieces of Iowa’s Past, published by the Iowa State Capitol Tour Guides weekly during the legislative session, features historical facts about Iowa, the Capitol, and the early workings of state government. All historical publications are reproduced here with the actual spelling, punctuation, and grammar retained. January 16, 2013 THIS WEEK: Iowa Senator James Harlan Becomes U.S. Senator BACKGROUND: Fifth Iowa General Assembly The Fifth Iowa General Assembly convened December 4, 1854, and adjourned January 26, 1855, a 54-day session. The Democrats numbered 17 members in the Senate and 31 members in the House. The Whigs held 14 seats in the Senate and 40 seats in the House—a total of 102 members. Iowa’s population at the 1850 census was 192,214. Iowa’s President of the Senate was Maturin Fisher and the Speaker of the House of Representatives was Rueben Noble. During the Fifth General Assembly, Stephen P. Hempstead finished his term as Governor and James W. Grimes was sworn in as Iowa’s third governor.

Investigation of the Loss of Prestress in Prestressed Concrete Beams due to Steam Curing, HR-62, 1961

Mass production of prestressed concrete beams is facilitated by the accelerated curing of the concrete. The ·method most commonly used for this purpose is steam curing at atmospheric pressure. This requires concrete temperatures as high as 150°F. during the curing period. Prestressing facilities in Iowa are located out of doors. This means that during the winter season the forms are set and the steel cables are stressed at temperatures as low as 0°F. The thermal expansion of the prestressing cables should result in a reduction of the stress which was placed in them at the lower temperature. If the stress is reduced in the cables, then the amount of prestress ultimately transferred to the concrete may be less than the amount for which the beam was designed. Research project HR-62 was undertaken to measure and explain the difference between the initial stress placed in the cables and the actual stress which is eventually transferred to the concrete. The project was assigned to the Materials Department Laboratory under the general supervision of the Testing Engineer, Mr. James W. Johnson. A small stress bed complete with steam curing facilities was set up in the laboratory, and prestressed concrete beams were fabricated under closely controlled conditions. Measurements were made to determine the initial stress in the steel and the final stress in the concrete. The results of these tests indicate that there is a general loss of prestressing force in excess of that caused by elastic shortening of the concrete. The exact amount of the loss and the identification of the factors involved could not be determined from this limited investigation.