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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 8 Abstracts search results
March 1, 2001
W. H. Dilger and P. Langohr
For long span continuous concrete bridges, haunched box girders are the preferred choice of the structural engineers because they not only look most graceful, but they are also more efficient structurally, and more economical. It is therefore not surprising that the designers of the 12.9 km (8 mile) long Confederation Bridge in Eastern Canada chose the haunched girder configuration for the 43 girders of the 250 m (820 ft) long marine spans as well as 21 girders of the approach spans. In the paper it is demonstrated that the conventional approach to shear design of haunched girders is on the unsafe side. This is so because the compression force, the vertical component of which reduces the shear force in the web, is smaller than the bending moment M, divided by the internal lever arm d,. The relevant equations are derived on the basis of equilibrium in a web with diagonal cracks, sloped at an angle 8. As an example the shear design for the Confederation Bridge is presented.
J. E. Breen
This Symposium honors a man who through a broad range of contributions, clearly carved a worldwide leadership position in the field of Structural Engineering. It is a fitting place to discuss the characteristics of leadership in the formulation of codes of practice and particularly building codes for structural concrete. In our North American democracies, the tradition of developing a clear consensus in support of a proposed change is the rule in formulating concrete design codes. Such a consensus means overwhelming agreement of a committee of strong-willed persons representing a myriad of conflicting interests after consideration and judgment of the merit of every dissenting opinion. In order to obtain such a consensus, code recommendations must not only be technically sound, but they must be practical, workable, and necessary. Above all, they must be patiently and painstakingly presented, defended, revised and re-presented to the committee. Those who shepherd the proposals that ultimately become part of the standards that guide practice and protect the citizenry must be effective leaders.
R. G. Sexsmith
Professor Jim MacGregor began his doctoral studies at the University of Illinois just as his research advisor had become concerned with the safety provisions of the ACI building code. As MacGregor began his teaching and research career at the University of Alberta, developments in the reliability area became suitable for structural applications, especially in providing a basis for load and resistance factors. MacGregor was able to combine his exceptional talents in reinforced concrete behavior and design with the reliability-based code developments. This combination of expertise in reinforced concrete with an interest in safety requirements of codes has resulted in significant advances in the safe and economical design of concrete structures.
This paper describes some of the important aspects of code requirements for the design of structural members made with high-strength concrete. The provisions of the 1994 CSA Standard for the Design of Concrete Structures are highlighted. Comparisons are made between the provisions of the 1999 ACI Code and the 1994 CSA Standard. Some aspects of design from the 1990 CEB-FIP Model Code and the 1995 New Zealand Standard are also discussed.
D. M. Rogowsky
The evolution of strut and tie models is reviewed and their characteristics are discussed. From their evolution it is seen that more design effort should be expended on developing a reasonable truss than on refined calculations of nodal stresses and permissible concrete stresses. Strut and tie models are design tools. They allow engineers to put an appropriate amount of material in an appropriate place, and expeditiously demonstrate that there is at least one way for the structure to safely carry the design load. They are not very useful for checking designs. When one is planning the structural analysis, one needs to know if the design will be done on the basis of strut and tie models. Different models may be required for different load cases. Rather than modeling the whole structure, models may be applied to specific regions of a structure. Designs based on strut and tie models may require slightly more reinforcement than designs based on other methods since, in general, the contribution of concrete tensile strength is ignored. Finely tuned empirical equations will use less reinforcement but are restricted by the limits of the test data. Strut and tie models are general rational design tools that do not have such limitations.
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