International Concrete Abstracts Portal

Design and construction of bridges composed of simple-span, pretensioned girders made continuous for composite dead and live loads have become widespread. The design of these structures in the U.S. has been generally based on the procedure outlined in "Design of Continuous Highway Bridges with Precast, Prestressed Concrete Girders," published by the Portland Cement Association (PCA) in 1969. Although existing bridges designed by this procedure are generally performing well, it is believed that this method may not accurately predict the true behavior of these structures. One of the major uncertainties in the design of these structures is prediction of positive and negative moments in the cast-in-place connections at the piers. This uncertainty is due to the different loading and construction stages, time-dependent effects, and details used to make the connection. To resolve such uncertainties, an analytical study was conducted to develop guidelines for more rational design of the continuity connections. Paper summarizes results of an extensive parametric study to consider the effects of 1) construction sequence, including simple span behavior before and continuous behavior after casting the deck and diaphragms; 2) time-dependent behavior, including concrete creep and shrinkage, and steel relaxation; 3) live load applied at any stage of service life; 4) cracking resulting from both positive and negative moment, including "tension stiffened" stress-strain relationships for reinforcement; and 5) closing of cracks when combined dead load plus time-dependent moments are reversed by application of live loads.

The knowledge contained in Computer Applications in Concrete Technology will prove invaluable. This symposium volume of 10 papers will provide you with the information you need to build high-quality, cost efficient structures. Presenting various practical applications of computer technology, the topics covered include: computer analysis of time-dependent behavior of continuous precast prestressed bridges; substructure modeling of two-way slab systems; an automatic quantitative image analysis system for cement and concrete research; maintenance and implementation of an expert system for durable concrete; and prediction of shear failure in concrete structures using nonlinear finite element analysis. Other subjects covered include: a three-dimensional stability analysis/ design computer program for concrete monolithic structures; and a programming environment for structural engineering applications based on interactive computer graphics." Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP106

Paper describes the capabilities and techniques used in a Three-Dimensional Stability Analysis/Design (3DSAD) computer program for concrete monolithic structures. The program was designed to do both nonstandard-shaped structures and specific structure types such as dams, locks, cooling towers, power houses, etc. The philosophy of the program was to first develop general geometry, loads, and analysis modules and then develop modules for specific structures using the general modules as tools. Another general purpose capability, the Free-Body Module, was then added to the collection of tools. Specific modules were also enhanced with a Design Memorandum (DM) Plate capability for final reporting of results. Paper describes the general modules and the specific modules for dams with emphasis on algorithms and procedure for the general modules.

A brief overview of current research undertaken on computer-aided design of reinforced concrete is presented. The following research projects, related to concrete structures, are briefly discussed: 1) interactive graphics optimum design of reinforced concrete frames; 2) interactive graphics optimization-based design of partially prestressed concrete beams; 3) hybrid design program for the design of reinforced concrete frames; and 4) usage of expert systems as quality assurance programs for the design of reinforced concrete to check their compliance with all the appropriate ACI Building Code provisions.

Computers are becoming a day-to-day tool in the Corps of Engineers design offices for analyzing and designing concrete structures. These structures vary from specialized hydraulic structures, such as locks and dams, to conventional retaining walls and buildings. The Corps uses both general purpose, as well as special purpose, computer programs for the design/analysis of these structures. Many of the special purpose programs are developed under a very successful project called Computer-Aided Structural Engineering (CASE). The Corps is also active in performing research toward developing ideal engineering workstations for design engineers using microcomputers as tools. Some of the Corps' activities in these areas are highlighted.