Advancements in Anchoring to Concrete Construction, Part 4 of 4

Tuesday, November 5, 2024  4:00 PM - 6:00 PM, Grand BR Salon C

Advancements in Anchoring to Concrete Construction – Commemorating the lifetime contributions of Prof. Dr.-Ing. Rolf Eligehausen

We have & will be receiving abstracts from Germany and other European countries. Prof. Dr.-Ing. Rolf Eligehausen is a name synonymous with anchorage to concrete and bond, and his research contributions for the last 50 years have been paramount to advancing the state-of-the-art in anchorage technology. This symposium will recognize and celebrate the extraordinary contributions of Prof. Dr.-Ing. Eligehausen in the field of anchorages in concrete construction.

This symposium and the proposed peer-reviewed Special Publication (SP) will target several current issues on the topic of anchorage to concrete. This SP is anticipated to provide a reference document for the present state-of-the-art.

Learning Objectives:
(1) Learn about nonlinear modelling of anchorages;
(2) Learn about design techniques of anchor groups with arbitrary anchor layouts;
(3) Learn about opportunities for improvement in anchoring to concrete design;
(4) Learn about fire resistance design of mechanical and bonded anchors.

Opportunities for Improvement in Anchoring to Concrete Design

Presented By: Kenton McBride
Affiliation: Hilti Corp
Description: Strength design provisions for anchoring to concrete were introduced directly in the first edition of the IBC in 2000 and subsequently in ACI 318-02 as Appendix D based on the then-newly formulated CCD method for concrete breakout capacity of anchors. As we approach a quarter century of strength design in anchorage, it is useful to take stock and identify potential areas for structural improvement. While incremental adjustments will continue to be made in the provisions, this paper focuses on larger issues. These include: 1. The need for a generalized approach to breakout of anchor groups unconstrained by rectilinear anchor placements, uniform diameter and embedment, etc. 2. Harmonization of the provisions for development of reinforcing bars and anchorage. 3. Recognition of the use of numerical analysis techniques using advanced concrete fracture models in code-compliant design. 4. Calibration of anchorage provisions for use with higher-strength concrete and concrete with alternative materials, including low-carbon Portland cement substitutes. 5. Improved treatment of shear loading. 6. Harmonization between AISC and ACI, including stand-off and multi-axial loading. This paper is intended as a roadmap for future technical committees as they grapple with the increasing complexity of the built environment.

Engineering Challenges in Anchorage Design

Presented By: BENJAMIN WORSFOLD
Affiliation: University of Minnesota
Description: This paper describes knowledge gaps in addressing complex anchorage scenarios commonly encountered by practicing engineers. Without standardized design methodologies, anchorage details may, at best, be highly conservative and, at worst, result in questionable load paths. Some pressing issues include: • The growing popularity of higher-grade reinforcement may result in more concentrated anchorage loads potentially exacerbating anchorage issues. • Deep anchor groups rely on extrapolation of limited test data. • Reliance on development length provisions has been observed to be insufficient to prevent anchorage failure in some cases. • If the headed reinforcing bar bearing area is not scaled with bar grade, anchorage issues may occur. • Embedment plates are a common detail but are excluded from some codes. Detailed simulations can provide guidance to designers who have access to them. However, the absence of a vetting process or minimum performance requirements for software packages poses a significant challenge, underscoring the necessity for standardized benchmark problems to evaluate the models. Addressing these challenges is imperative for advancing anchorage design practices, ensuring structural safety, and fostering innovation in the field.

Advances in Fire Resistance Design of Mechanical and Bonded Anchors

Presented By: Hitesh Lakhani
Affiliation: University of Stuttgart, Institute of Construction
Description: The paper provides insights into new experimental observations on the Concrete Cone (CC) capacity of mechanical anchors during fire and advances made in the field of Numerical simulation Assisted Design “NAD” for fire resistance of mechanical anchors to CC failure and for Pull-Out (PO) failure of bonded anchors. The new results shown that the current design guidelines in EN1992-4 are too conservative for small fire resistance durations. This conservatism in the current guidelines is because in past very limited experimental results only around R90 fire resistance were available. In view of new results, a new step function is proposed to determine the CC capacity under standard fire exposure. Furthermore, to harmonise the fast-developing performance-based fire design of structures and fire design of fasteners, recent advances in the NAD of fasteners is presented with application to mechanical and bonded anchors. Main advantages and novelties of NAD includes: 1) Evaluate the CC capacity for realistic fire exposure; 2) Consider the interaction between the structural member deformation and the CC capacity; 3) Overcome the limitation of the “strength integration method” for PO capacity of bonded anchors namely, shear lag effect and effect of structural cracking on the pull-out capacity.

Developing Anchor Design: Introducing a Method for Accurate and Flexible Design of Fasteners in Structural Constructions

Presented By: Michael Eckstein
Affiliation: University of Stuttgart
Description: Since more than 20 years the Concrete Capacity Method is established for the design of fastenings failing with a concrete cone. In this model the projected areas of the developing cones are determined and are used to calculate the anchor capacity. Influences on the capacity are considered if the projected area is reduced by e.g. small edge distances small spacing’s. In this case the projected areas are reduced compared to the reference area of a single anchor placed in the middle of a concrete block. In this concept factors like holes in the concrete, multileveled edges and any other cut outs in the breakout area are not considered in the design since the projected areas does not change. The developed method presented in this work shows an approach that can account for any potential cross-sectional cut out of the concrete in the areas of the cone development. This enables the safe design of fastenings in areas with cut-outs due to e. g. holed due to climbing formwork or pipe installations. In the past engineering judgment was necessary to design such scenarios. The method standardizes such cases and represents therefore a significant improvement for safe and economic design of modern fas-tenings.

The New Model for Anchors with Anchor Reinforcement in Fib and EN1992-4

Presented By: Akanshu Sharma
Affiliation: Purdue University
Description: Anchor reinforcement is known to enhance the performance of the anchorages against concrete breakout failure modes. The current models for the design of anchors with anchor reinforcement are quite conservative in Europe as well as in the US. Based on recent research carried out on anchor groups with different configurations of anchor reinforcement, a new model proposed by the authors have been incorporated in the upcoming versions of the EN1992-4 and fib Design Guide. The model gives recommendations to calculate the breakout capacity of anchorages with anchor reinforcement subjected to tension, shear or combined tension and shear (interaction) loading. The novelty of the model lies in the fact that it separates out the contribution of the hook and bond for the anchor reinforcement, allows to consider the contribution of both concrete and reinforcement for the anchorage resistance, and also recognizes an upper limit to the capacity enhancement of the anchorage due to the so-called strut failure. The model is validated against large number of test results and provides much better predictions of the capacity of anchors with anchor reinforcement compared to the current models. This paper provides the background and the basis of the formulations of the model.