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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 202 Abstracts search results
March 19, 2021
Sponsors: Sponsored by ACI Committee 351
Editor: Carl A. Nelson
This special publication grew out of the Technical Session entitled “Application of ACI 351-C Report on Dynamic Foundations,” held at the ACI Spring 2019 Convention in Québec City, Québec. Following this event, Committee 351 decided to undertake a special publication with contributions from those session participants willing to develop their presentations into full-length papers. Three papers included in the current publication were contributed by these presenters and their coauthors, with six additional papers provided by others. All but one of the papers deal with the subject matter of ACI 351.3—Foundations for Dynamic Equipment—updated in 2018. The one exception (the paper of Wang and Fang on wind turbine foundations) provides valuable information to engineers dealing with a lack of consistent design criteria among various codes for reinforced concrete foundations subjected to high-cycle fatigue loads.
I would like to thank the members of ACI Committee 351 for their support, in particular the current main Committee and Subcommittee C Chairpersons Susan Isble and Dr. Mukti L. Das, respectively. I also wish to express my gratitude to the authors for their perseverance through the difficult circumstances of 2020, and to the reviewers who generously contributed their time and expertise to this publication.
Last, but not least, I want to thank my wife Cindy for tolerating me (and the growing piles of paper) over the past several months as the deadline approached.
Carl A. Nelson
On behalf of ACI Committee 351
Minneapolis, December 2020
March 1, 2021
Pericles C. Stivaros and Pablo A. Bruno
This paper presents a case study involving the structural analysis and design of an elevated foundation
plinth to support multiple pieces of rotating machines with different operating weights and speeds. The equipment is
used to operate a high-speed balancing testing facility for turbines and rotors that are located within an adjacent
testing chamber. This project comprised of several layout and design challenges, including vibration and resonance
concerns, effects of multiple operating frequencies, plinth shape, and pile foundation effects. Major concern was to
maintain the high precision and strict tolerance limitations required by the high-speed balancing operations. Elevated
machine foundations integral with other structures possess many natural frequencies, both locally and globally. The
traditional design rules-of-thumb are not adequate for analyzing and designing elevated machine foundations. A
computer-based finite element analysis method is required to identify the multiple natural frequencies of a
complicated foundation structure. The strength design of a machine foundation can become very challenging when
trying to implement code requirements that are mostly applicable to building elements and not to massive concrete
foundations. This study recognizes the need for the development of a design standard to include special design
requirements for mass concrete machine foundations.
O.S. Ali Ahmed
Dynamic pile group effect can either increase or decrease the response of pile-supported structures. This
paper presents the results of a three-dimensional finite element model of the pile-to-pile interaction that considers the
effect of the surrounding soil to determine the dynamic stiffness and damping for vertical end bearing pile groups
subjected to vertical harmonic loading. The results were generated for a wide range of the dimensionless frequency
parameter (ao) for a 9x9-pile group with three different spacings: 2-, 4-, and 6-pile diameter. Both the stiffness and
the damping showed an oscillatory behavior with the dimensionless frequency parameter ao, as well as with the soil
shear modulus. Also, the group efficiency was determined as a function of the pile spacing and the soil shear modulus.
The efficiency factor for the stiffness can be as high as 1.15 and as low as 0.7 and for the damping as high as 3.75 and
as low as 0.4 as a function of the dimensionless frequency parameter ao.
Xuan Wang and Shu-jin Fang
One of major challenges for the US wind industry is the lack of consistent fatigue design criteria.
ASCE/AWEA RP2011 recommends several design codes for fatigue analysis of land-based wind turbine support
structures. However, it does not provide discussions on the differences and limitations of these codes. The purpose of
this paper is to present our findings on the application of fatigue design codes including Model Code 2010 (MC10),
Eurocode 2 (EC2), Det Norske Veritas (DNV), and ACI 215. Comparison of the design results from using these
codes/standards are summarized. Due to lack of consistency in the design standards, evaluation results may vary
greatly, which can be confusing and inconclusive at times. In addition, this study shows that there will be significant
differences on fatigue design adequacy depending on which analysis method is used: the average sectional method or
finite element method, the two principal methods used to analyze fatigue. A number of suggestions and critical
comments are also provided in this paper for helping development of more consistent fatigue analysis and design
criteria for wind turbine foundations.
O. S. Ali Ahmed and Damon G. Reigles
This paper discusses the factors that affect the dynamic response of machine foundation systems,
which include (1) the soil dynamic properties, (2) the geometric properties of the foundation, (3) mass of the machine
and foundation, and (4) the amplitude and frequency of the applied dynamic loads. The primary objective in any
machine foundation design is to limit the foundation response below a specific amplitude threshold. A foundation
response exceeding this limit may adversely affect the performance of the machine and damage the machine internals,
resulting in costly repairs and lost revenue. Also, the excessive vibrations may result in structural degradation of the
foundation, additional excitation stresses on the machine, and increase the compressor unbalance loading. This paper
presents dynamic analysis results of a four-cylinder compressor foundation originally designed without consideration
for soil-foundation interaction and suffering from excessive vibration. The foundation block supports a 4-cylinder
Dresser-Rand compressor, suction and discharge bottles, a crank, and a driving motor with a total weight of
approximately 300 kip (1334 kN). A three-dimensional, finite element model representing the soil–foundation system
was developed to determine the dynamic characteristics and assess the foundation response under applied dynamic
loading from the compressor crank. Results showed that the response of the soil-foundation system is governed by the
response of the individual support piers (blocks) and not the global foundation response. This paper also provides a
recommended modification to the foundation geometry to reduce the effect of the individual piers' local modes and
enhance the foundation dynamic performance.
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