Time-dependent Deformation of Non-composite and Composite Sand-lightweight Prestressed Concrete Structures

Download or read book Time-dependent Deformation of Non-composite and Composite Sand-lightweight Prestressed Concrete Structures written by Dan E. Branson and published by . This book was released on 1969 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented in this report is an investigation of the use of "sand-lightweight" concrete in prestressed concrete structures. The sand-lightweight concrete consists of 100% sand substitution for fines, along with Idealite coarse and medium lightweight aggregate and Type I Portland Cement. The study is divided into three parts: a materials study of the concrete itself, a laboratory study of the behavior of both non-composite (5 beams) and composite (4 beams) prestressed beams, and the field measurement of camber of prestressed bridge girders (5 girders). The test period for the laboratory beams was 5 months, although the data collection is continuing for 3 of the beams. The test period included in this report for the bridge girders was 4 months. The laboratory beams were designed in three groups (3 beams in each group) to investigate the loss of prestress, initial and time-dependent camber, load-deflection behavior, and effect of different slab casting schedules. Of principal interest in this Phase I study is the time-dependent behavior of sand-lightweight concrete as a material and as used in prestressed structures. This includes the loss of prestress and camber of members that undergo rather high initial strains (due to both high initial stresses and relatively low modulus of elasticity); the effect of the composite deck in reducing the stress level and corresponding creep rate and loss of prestress; and the effect of the time of casting the composite slab, since the rate of creep, loss of prestress, and camber growth are quite different before and after the slab is cast. Design procedures are presented for the following: 1. Calculation of creep and shrinkage of the sand-lightweight concrete of this project at any time after casting, including ultimate values. An indication is also given of the calculation of creep and shrinkage at any time after casting, including ultimate values, for normal weight, sand-lightweight, and all-lightweight concrete in general. 2. Both theoretical and approximate methods for calculating camber of non-composite and composite prestressed structures. Results computed by these methods are shown to be in reasonably good agreement with the control specimen data, the laboratory beam data, and the bridge girder data.