International Concrete Abstracts Portal

Because of the presence of lateral loads and high-end eccentricities, the ACI 318-83 empirical design method cannot be used for design of tilt-up walls. Analysis must be performed during design to account for the P-{delta} effects. To confirm various design concepts and to evaluate the slenderness limitations, a series of tests on concrete wall panels was conducted. Several simplified design procedures were used to compare analytical results to test observations of slender load-bearing walls. Results of computer program TILT for IBM-PC (or compatible) computers were compared with the results of simplified design procedure calculations and test observations. Investigations show that the actual strength of load-bearing tilt-up walls are considerably higher than predicted by simplified analysis. The paper briefly discusses the theory of geometrical and material nonlinearities and presents methods for solutions that are incorporated in the program TILT. Conclusions and effectiveness of the TILT computer program for analyses of tilt-up load-bearing walls are shown.

A computational procedure is described for determining nonlinear response of a building system subjected to earthquake motion. The method is sufficiently simple for use with a microcomputer because system response is expressed in terms of a single generalized coordinate. Deflected shapes for the systems are assumed to be invariant for all amplitudes of motion. The equation of motion is integrated for each instant of response on the basis of a normalized relation between base shear and top-level deflection. The hysteretic relation is constructed for each new cycle using cubic segments to express a path from initial unloading through force and deflection reversals to the point of maximum deflection. The base motion is selected from a menu of earthquake records stored on diskette. Results displayed on screen consist of histories of acceleration at the top-level and maximum interstory drift, and the computed force-deflection relation.

A large amount of specialized factual and heuristic knowledge on the relations between the design of concrete mixtures, including the constituents, and the durability of concrete has been gained through research and field experience. Effective dissemination of this knowledge should result in fewer incidents of premature deterioration of concrete. Expert systems appear to be an effective means for transferring the knowledge on the durability of concrete obtained through laboratory and field studies and experiences to engineers and designers responsible for the design, construction, and maintenance of concrete structures. Durcon is a prototype expert system being developed to give recommendations on the selection of constituents for durable concrete. The purpose of developing Durcon is to demonstrate the application of expert systems to improve the process of selecting construction materials. Four major deterioration problems are covered by Durcon: freezing and thawing, corrosion of reinforcing steel, sulfate attack, and alkali-aggregate reactions. This report discusses the approach being followed and the progress being made in developing Durcon. In addition, model systems for recommendations for concrete exposed to corrosive environments and for preventing alkali-aggregate reactions are presented.

SP-98 Because the design of concrete structures and proportioning concrete mixtures can be complex, you need state-of-the-art knowledge when selecting structural systems and construction materials. Computer Applications in Concrete Technology has been especially prepared to aid designers and engineers in all facets of concrete design and technology. Providing a source of "know-how" for the entire civil engineering community, this symposium volume of 13 papers covers a broad spectrum of computer applications. Some of the subjects include: expert systems for selecting concrete constituents, analysis of reinforced concrete shear walls, analysis and design of load-bearing tilt-up walls, decision support systems for design, and spreadsheet programming for structural design. Other topics include: monitoring construction with microcomputers as you build, analysis and design of reinforced and prestressed concrete compression members using desktop computers, and integrated design environment for concrete structures.

The microcomputer and associated digital technology has changed the way things are done both in the structural laboratory and in the field. The impact of microcomputers on the science of field measurement is mainly with regard to cost and time. The many benefits of field monitoring of structures are now available at an acceptable cost. Cost is reduced due to automatic recording rather than manual methods. This paper discusses the benefits of field monitoring during construction and the life of the structure. Two proven measuring systems are described in detail. The paper also describes a system for dynamic analysis of structures. The reduced cost of determining the behavior of buildings and bridges is not the only benefit of these three new measuring systems. Data returned for analysis are in a form that can be quickly reduced and evaluated by computer. A short turn-around time means that the behavior data are available when needed.