Sessions & Events

All sessions and events take place in Eastern Daylight Time - EDT (UTC - 4). 

Effective Use of the Strut-and-Tie Method per ACI 318-19, Part 1 of 2

Tue, October 19, 2021 8:30 AM - 10:30 AM, 313-314

The Strut-and-Tie Method is an approach to evaluate or design any structural concrete member, or discontinuity region in a member, by modeling the member or region as an idealized truss. The concepts behind the development of the Strut-and-Tie Method (STM) will be presented as well as “What’s New” in the ACI 318-19 code. The session will include the fundamentals of STM as well as practical examples; accordingly, the session is geared toward practitioners and educators who utilize or would like to learn more about the strut and tie provisions in the ACI 318 code.
Learning Objectives:
(1) Describe the fundamentals of the strut-and-tie method;
(2) Identify the new provisions for strut-and-tie in the ACI 318-19 as well as the latest related research;
(3) Describe the use of strut-and-tie method for bridge applications;
(4) Evaluate the ability of the strut-and-tie method for identifying and providing a suitable internal load path.

Strut-and-Tie Fundamentals

Presented By: Daniel Kuchma
Affiliation: Tufts University
Description: The use of strut-and-tie models, as both a design and analysis tool, is examined. The application of this very simple model for a wide breadth of applications is illustrated along with the key steps in establishing a suitable model. The limitations of this model as a plastic truss are explored. The differences in stress limits and dimensional definitions used in codes of practice are also compared. The contrast with sectional design approaches is also discussed.

Changes in the Strut-and-Tie Method for ACI 318-19

Presented By: Gary Klein
Affiliation: Wiss, Janney, Elstner Associates, Inc.
Description: ACI 318-19 includes about a dozen technical changes to Chapter 23 on the strut-and-tie method. The most significant changes include new provisions for curved-bar nodes, requirements for minimum reinforcement of discontinuity regions, and changes in the provisions for allowable strut strength. This presentation will describe the changes, including the underlying research and testing.

Solution to a Complex Beam – What’s New & Form Finding Methodology

Presented By: Lawrence Novak
Affiliation: International Code Council
Description: The Strut and Tie Method (STM) is a versatile design technique for all structural engineers to have readily available in their ‘toolbox’. A flowchart of steps to design and detail any concrete element by STM will be the offered and utilized to solve a complex notched beam with an opening and to showcase “What’s New” in the ACI 318 Code. Important topics such as intuitive model “form finding” will be discussed to enrich the understanding of the process.

Strut-and-Tie Model for Extradosed Cable Stayed Bridge Diaphragm

Presented By: Robert Anderson
Affiliation: AECOM
Description: The new Pearl Harbor Memorial Bridge is an extradosed cable stayed bridges carrying I-95 over the Quinnipiac River in New Haven, Connecticut. The new bridge is comprised of a pair of twin bridges each with a main span of 515.0 ft. and sides spans of 249.0 ft. The width of each of the twin bridges varies from 107.6 ft. to 95.6 ft. Because of its width, internal diaphragms were used to stiffen the box cross-section at each stay. Additionally, extradosed bridge cables have a high dead load to live load ratio. This presentation discusses: 1) strut-and-tie modeling of the internal diaphragm by the AASHTO bridge code for both strength and service level conditions: 2) application of post-tensioning and stay cable forces; 3) staged construction; and 4), and constructability issues related to this element.

Design of a Hammerhead Bent Cap using ACI 318-19

Presented By: Robin Tuchscherer
Affiliation: Northern Arizona University
Description: The objective of this presentation is to present a design example of a Hammerhead Bent Cap using the ACI 318-19 strut-and-tie method. These provisions contain significant updates from previous versions. The implications of these changes will be demonstrated through their application in designing a hammerhead bent cap. In addition, this example will highlight the strength of the strut-and-tie method for identifying and providing an adequate path for transferring loading; as well as address designer’s questions regarding reinforcement details and transitioning between strut-and-tie and other design methods.

Upper Level Sponsors

Brasfield Gorrie
Concrete Sealants, Inc.
Euclid Chemical
Martin Concrete Construction
Master Builders
Metromont Corporation
Thomas Concrete

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