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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 10 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
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.
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.
Hongchun Liu, Jaspal S. Saini, Gang Zhao, Sushil Chauhan, Namgyu Park, Mahi Galagoda, Steven Wu
This paper discusses an innovative retrofit that stabilized a Steam Turbine Generator (STG) pedestal
foundation undergoing unexpected differential settlements during construction. The innovative solution involved
driving steel H-piles around the STG foundation perimeter. A new concrete bracket (a.k.a. corbel) was added around
the STG foundation perimeter to fully engage and integrate the H-piles with the existing pedestal foundation. The pile
layout was established and optimized based on dynamic and static performance analyses of the modified foundation
geometry using finite element (FE) software ANSYS, considering bounding pile and soil dynamic impedances. The
frequency-dependent dynamic pile impedances were calculated using DYNA6. The continuous settlement monitoring
of the STG foundation demonstrated that the retrofit effectively seized the ongoing settlements and stabilized the
foundation enabling the subsequent machine installation.
Ping (Philip) Jiang, Ron McDonel
A more than 50-year old Steam Turbine/Generator (STG) table-top concrete foundation was retrofitted to
support a new STG/Condenser unit. This new machine unit is set on a sub skid with spring/damper assemblies
underneath and located on existing concrete table top columns. This paper presents a case study of the seismic
design and evaluations of the existing foundation structure that were performed to assess and qualify the structure’s
service and strength capabilities. Based on these evaluations, modifications to the existing STG foundation were
minimized allowing the cost effective reuse of the existing foundation resulting in significant savings for the overall
installed cost of the project.
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