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Über dieses Buch

Structures placed on hillsides often present a number of challenges and a limited number of economical choices for site design. An option sometimes employed is to use the building frame as a retaining element, comprising a Rigidly Framed Earth Retaining Structure (RFERS). The relationship between temperature and earth pressure acting on RFERS, is explored in this monograph through a 4.5 year monitoring program of a heavily instrumented in service structure. The data indicated that the coefficient of earth pressure behind the monitored RFERS had a strong linear correlation with temperature. The study also revealed that thermal cycles, rather than lateral earth pressure, were the cause of failure in many structural elements.

The book demonstrates that depending on the relative stiffness of the retained soil mass and that of the structural frame, the developed lateral earth pressure, during thermal expansion, can reach magnitudes several times larger than those determined using classical earth pressure theories. Additionally, a nearly perpetual lateral displacement away from the retained soil mass may occur at the free end of the RFERS leading to unacceptable serviceability problems. These results suggest that reinforced concrete structures designed for the flexural stresses imposed by the backfill soil will be inadequately reinforced to resist stresses produced during the expansion cycles.

Parametric studies of single and multi-story RFERS with varying geometries and properties are also presented to investigate the effects of structural stiffness on the displacement of RFERS and the lateral earth pressure developed in the soil mass. These studies can aid the reader in selecting appropriate values of lateral earth pressure for the design of RFERS. Finally, simplified closed form equations that can be used to predict the lateral drift of RFERS are presented.

KEY WORDS: Earth Pressure; Soil-Structure Interaction; Mechanics; Failure; Distress; Temperature; Thermal Effects; Concrete; Coefficient of Thermal Expansion; Segmental Bridges; Jointless Bridges; Integral Bridges; Geotechnical Instrumentation; Finite Element Modeling; FEM; Numerical Modeling.

Inhaltsverzeichnis

Frontmatter

Introduction to Rigidly Framed Earth Retaining Structures (RFERS)

Abstract
Structures placed on hillsides often employ the building frame to retain earth on one side only and derive their resistance to lateral earth pressure from rigid frame action, without the presence of any other restraining elements or forces against lateral displacement. The relationship between temperature and earth pressure acting on rigidly framed earth-retaining structures (RFERS), subject to wide temperature variations, is explored in this book through a 4.5 year monitoring program of an instrumented RFERS, as well as numerical analyses and parametric studies. The study demonstrates the important role of thermal cycles on earth pressure and structural integrity.
Walid Aboumoussa, Magued Iskander

Classical Earth Pressure Theory Related to Framed Structures

Abstract
The development of earth pressure theory as it relates to rigidly framed earth retaining structures is chronicled in this chapter. Inadequacies of classical theories are explored along with studies related to earth pressure acting against integral bridges, which resemble, in some ways, a single story rigidly framed earth retaining structure.
Walid Aboumoussa, Magued Iskander

Closed-Form Expressions for Lateral Deflection of Rigid Frames

Abstract
Determining the magnitude of the lateral deflection of the building frame of low-rise rigidly framed structures, due to external loads, is needed in order to meet appropriate serviceability and design code requirements. In this chapter, a simplified rational closed form analytical expression is formulated for calculating the lateral deflection of low rise rigidly framed structures subjected to different lateral force distributions varying with the height of the frame.
Walid Aboumoussa, Magued Iskander

Case Study of a Full Scale RFERS in Service

Abstract
A distressed Rigidly Framed Earth Retaining Structure (RFERS) open concrete garage that retains 11 m (36 ft) of soil was instrumented. After some repairs, movement of the building was monitored and recorded hourly. The monitoring revealed complex temperature-dependent soil structure interactions, which are reported in this chapter.
Walid Aboumoussa, Magued Iskander

Relationship between Temperature and Earth Pressure for RFERS

Abstract
The relationship between temperature and earth pressure acting on a Rigidly Framed Earth Retaining Structure (RFERS) subject to wide temperature variation was explored in this chapter. The open concrete garage RFERS presented in Chapter 4 was instrumented and monitored for a period of four and a half years. The structure retains 11 m (36 ft) of soil on one side only. The measured displacements were used to calculate the earth pressure coefficient using closed form equations that were developed in Chapter 3. The data indicated that the coefficient of earth pressure behind the monitored RFERS had a strong linear correlation with temperature. The study also reveals that thermal cycles, rather than lateral earth pressure, caused some of the structural elements to fail.
Walid Aboumoussa, Magued Iskander

Numerical Analysis of Instrumented RFERS

Abstract
This chapter presents the finite element analysis of the building monitored in Chapters 4 and 5. A plane strain model was employed through dividing the column properties by the tributary width of the frame, and utilizing the equivalent area and moment of inertia per foot of length of the waffle slab. The analysis confirms many of the results gleaned from the discrete instrumentation measurements. In particular, the lateral earth pressure exerted on the rigid frame developed during the thermal expansion cycles is considerably larger than the lateral earth pressure at rest.
Walid Aboumoussa, Magued Iskander

Parametric Study of Earth Pressure behind RFERS at Backfill Stage

Abstract
This chapter presents the results of parametric finite element analyses performed to explore the relationship between earth pressure and the stiffness of Rigidly Framed Earth Retaining Structures (RFERS). A plane strain model was employed. The stages of construction were incorporated in the analysis to simulate an initial stage where a structural frame is first completed followed by the addition of backfill soil in several stages. The displacement of the structures, as well as the earth pressure and resultant load developed behind them were obtained to examine the relationship between the stiffness of the retaining structure and the development of lateral earth pressure in the retained soil mass.
Walid Aboumoussa, Magued Iskander

Analysis of Single Story RFERS Subject to Temperature Variations

Abstract
This chapter presents the results of numerical parametric analysis of single-story structures with varying geometries and properties. The primary purpose of this analysis is to investigate the effect of thermal movements of Rigidly Framed Earth Retaining Structures (RFERS) on (1) the displacement of the rigid frames, (2) the stresses developed in the structural elements, and (3) the lateral earth pressure developed in the soil mass. The results are reported for 1, 10, 20 bay frames in this Chapter and for 3, 6, 15 bay frames in Appendix A for φ = 30°. Results for φ = 40° are also presented in Appendix A.
Walid Aboumoussa, Magued Iskander

Multi-story RFERS Subject to Temperature Variation

Abstract
This chapter presents the results of numerical parametric analysis of multi-story structures with varying geometries and properties. The primary purpose of this analysis is to investigate the effects of thermal movements of Rigidly Framed Earth Retaining Structures (RFERS) on (1) the displacement of the rigid frames, (2) the stresses developed in the structural elements, and (3) the lateral earth pressure developed in the soil mass. The results are reported for three and five story structures in this Chapter and for two and four story structures in Appendix B.
Walid Aboumoussa, Magued Iskander

Conclusions and Recommendations

Abstract
This chapter summarizes the methodology and typical results of the (1) experimental investigations, (2) numerical analyses, and (3) parametric studies conducted to investigate the thermal soil structure interaction of Rigidly Framed Earth Retaining Structures (RFERS). Recommendations for the design of such structures are also presented.
Comparison of the lateral displacement and corresponding earth pressures as well as structural stresses developed at the backfill stage in the absence of temperature changes, and those after the application of thermal movements, suggests that structural frames designed without the inclusion of the soil-structure interaction effects due to temperature changes will likely undergo undesirable response in service.
Preliminary recommendations regarding the analysis and design of RFERS at back fill stage and due to exposure to thermal cycles are also made in this section.
Walid Aboumoussa, Magued Iskander

Backmatter

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