International Concrete Abstracts Portal

Editor: Yail J. Kim and Nien-Yin Chang

Soil-structure interaction has been of interest over several decades; however, many challenging issues remain. Because all structural systems are founded on soil strata, transient and long-term foundation displacements, particularly differential settlement, can severely influence the behavior of structural members in buildings and bridges. This is particularly important when a structure is constructed in earthquake-prone areas or unstable soil regions. Adequate subsurface investigation, design, and construction methods are required to avoid various damage types from structural and architectural perspectives. Typical research approaches include laboratory testing and numerical modeling. The results of on-site examinations are often reported. Recent advances in the-state-of-the-art of soil-structure interaction contribute to accomplishing the safe, reliable, and affordable performance of concrete structures. This Special Publication (SP) encompasses nine papers selected from two technical sessions held in the ACI Fall convention at Denver, CO, in Nov. 2015. All manuscripts submitted are reviewed by at least two experts in accordance with the ACI publication policy. The Editors wish to thank all contributing authors and anonymous reviewers for their rigorous efforts. The Editors also gratefully acknowledge Ms. Barbara Coleman at ACI for her knowledgeable guidance.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-316

Because of the complexity of the soil-structure interaction (SSI) effect on high-rise buildings, contemporary design codes allow the use of results from an advanced numerical analysis in the design of structures without providing further stipulation. The information on SSI effects, however, is only available for low rise buildings with simple analysis procedures. Two hypothetical 20-story buildings and one 30-story real building were subjected to seismic response analyses using SSI3D under the following conditions: rigid base, flexible base with linear foundation springs, flexible base with linear soil, flexible base with nonlinear springs, and the full SSI analysis with flexible base with nonlinear soils for two hypothetical buildings. For the real building, the calculated natural periods, base shears, and top-floor displacements were compared to the values evaluated using the recorded building motions. It was observed that the natural periods increase and the base shears decrease as the base becomes more flexible, but further study is needed to examine the top-floor side sway.

Two concrete masonry buildings, at adjacent sites in Glenwood Springs, Colorado, are located atop existing collapsible debris fan soils. Both buildings were constructed on concrete foundations with spread footings, and both suffered serious and damaging differential settlements. Compaction grouting was utilized for underpinning and lifting both buildings. Compaction grout columns are comprised of a low slump and low strength grout made from a combination of sand, soil, pea gravel, cement, and water. When installed under pressure, the grout densifies the surrounding soils supporting the building foundation, and when carried to the underside of footings, the grout can offer direct support. The grout was also used to lift and partially level the buildings. But here the similarity ends; each had unique circumstances and the repair designs were custom tailored. One was underpinned with deep (100’) compaction grout columns while the other received a much shallower underpinning treatment. Each had unique drainage problems. Both projects were challenging and required cooperation among the Owners, Structural, Geotechnical and Civil Engineers, and the Contractors. The geotechnical studies, the structural design for repair, the drainage provisions for each, and the construction are described, with a focus on structural damage, design of the underpinning to be compatible with the structural capacities, and control systems utilized during construction.

In LNG plants and refineries, foundations for heavy rotating machines are required to be designed to limit the vibration induced by the unbalanced force and the moment of the machines to be within allowable amplitude for designated performance. When designing a pile-supported foundation for those dynamic machines, soil-pile spring constant to be used for dynamic analysis is calculated by conventional methods. However, there have been few studies of examining the accuracy of these methods and comparing them with the actual vibration data. The authors had an opportunity to carry out the vibration-proof design of reciprocating-type compressor foundation of which supporting PC piles were tested by rapid load test with a single mass model analysis. Moreover, vibration measurement was conducted at the Commissioning and multiple-point vibration data were obtained and studied by FFT analysis. Consequently, soil-pile spring constant was estimated from the rapid load test and the vibration analysis was conducted by 3D FEM software (STAAD. Pro)1. In particular, the vibration amplitude and the mode of various wave components calculated based on the rapid load test and conventional methods, and those measured by actual vibration, were compared. From this result, we confirmed the validity of the analysis method based on the rapid load test result, which can be proposed for dynamic machine foundation design.

Bridges are consistently subjected to various hazards throughout their expected lifespan while being subjected to constant use as a vital component of the national transportation network. Scour effects around the abutments and pier columns are one of the most common causes of bridge damage in the United States. Therefore, a multi-hazard analysis is necessary to evaluate if the bridges are capable of resisting scour and seismic loadings. This is of high importance as several earthquake-prone states regularly undergo flooding where extreme scour depths have been found. The current study employs non-linear time history analysis using 30 synthetic ground motions applied to a 3D analytical bridge model to simulate the responses of the combined effects of an earthquake and scour. The soil-structure interaction behaviors are taken into account using soil springs underneath the foundations in the model. To quantify probabilistic performance results, analytical fragility analysis is conducted to compute the probability of exceeding predetermined damage states. Comparisons are made between various levels of scour. Results indicate that as scour increases the response of bridge components increase, meaning the bridge becomes more fragile, specifically an increase in scour depths made the columns the most susceptible component at all damage levels. As scour increases, PGA required to achieve 50% exceedance probability were about two or three times lower for each damage state compared to the zero scour case.