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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 16 Abstracts search results
Document:
SP273-07
Date:
September 20, 2010
Author(s):
Gary J. Klein
Publication:
Symposium Papers
Volume:
273
Abstract:
This example describes the design of the support region of dapped-end double-tee beam, the type of beam typically used in parking structures. The strut-and-tie model (STM) employs curved-bar nodes, the bend region of a continuous reinforcing bar (or bars) whose straight extensions form two ties in a strut-and-tie model.
DOI:
10.14359/51682295
SP273-08
Katrin Habel, Matthias F. Andermatt, and Adam S. Lubell
The load carrying capacity of the hinge region of an existing highway overpass is evaluated using the strut-and-tie modeling techniques of ACI 318-08 Appendix A. The overpass consists of a series of drop-in span girders supported at the center by doubly cantilevered pier girders. The hinge is achieved through the use of an incorporated steel piece, the so-called Cazaly hanger, in the ends of the span girders. This example examines the disturbed end regions of both the span girders and the pier girders. The strut-and-tie model demonstrates how the Cazaly hanger can be incorporated into the model. In addition, the girders are prestressed which is taken into account by modeling the prestressing as equivalent forces applied to the concrete. This example demonstrates how to evaluate the load carrying capacity of an existing concrete structure and how to develop a strut-and-tie model based on the existing reinforcement configuration.
10.14359/51682296
SP273-09
Hakim Bouadi and Asif Wahidi
Utilizing the real world project of a 6-story tall reinforced concrete building located in a moderate seismic zone, this example demonstrates the design of coupling beams (or as often named link beams) by application of the strut and tie provisions of ACI 318 Appendix A. A coupling beam with a moderate shear level and a 2nd coupling beam with a high shear levels are designed. The former beam is designed using longitudinal and web reinforcement while the latter utilizes diagonal reinforcement. For demonstration purposes, the beam design utilizing diagonal reinforcement incorporates parts of ACI 318-08 chapter 21.9; however, for moderate seismic zones, section 21.9 need not apply.
10.14359/51682297
SP273-10
Daniel Kuchma, Sukit Yindeesuk, and Tjen Tjhin
This example presents a strut-and-tie design for a storey-high propped cantilever beam that supports a single concentrated load near midspan and has a large rectangular opening between this point of loading and the fixed-ended support. The internal truss that is selected to carry the imposed loading to the supports is both externally and internally indeterminate. This creates a condition in which the calculated capacity of the STM designed region is affected by the relative stiffness of truss members and the degree of plasticity attributed to the truss. The design is investigated and validated by plastic and non-linear truss analyses, finite element analysis, and the results from a scale model test of the designed structure. This paper examines the influence of design and analysis assumptions on the performance of this structure under service and factored loads.
10.14359/51682298
SP273-04
Daniel Kuchma and Thomas Nagle
A sectional approach is typically taken in US bridge engineering practice for the design of end regions in precast/prestressed I-Beams. However, these end regions are clearly discontinuity regions as there is a complex distribution of stresses created by reaction forces and the anchorage of prestressing strands. In accordance with ACI318-08, the design of these regions should satisfy the strut-and-tie provisions in Appendix A. There are several factors that make these apparently simple regions worthy of careful consideration in design. These include: (i) that the combination of shape and prestressing allow these members to be designed by sectional methods to resist very large shear forces that in turn leads to severe diagonal compressive stresses above supports, (ii) that longitudinal tie capacity at supports is most commonly provided by prestressing steel that is still within its calculated transfer length from the end of these members; (iii) that significant fanning action and changes in angle of diagonal compression occur throughout these end regions; and finally (iv) that these regions can often be the weak and brittle link in a very common class of members. This example presents how the strut-and-tie model provisions of ACI318-08 can be used to ensure the adequate design of end regions in large prestressed bulb-tee girders. Special attention is given to the influence of nodal zone dimensions and designer assumptions on the calculated capacity of these end regions.
10.14359/51682292
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