Embedment

About: Embedment is a research topic. Over the lifetime, 2441 publications have been published within this topic receiving 31444 citations.

Assessment of Seismic Analysis Methodologies for Deeply Embedded NPP Structures

Abstract: Several of the new generation nuclear power plant designs have structural configurations which are proposed to be deeply embedded. Since current seismic analysis methodologies have been applied to shallow embedded structures (e.g., ASCE 4 suggest that simple formulations may be used to model embedment effect when the depth of embedment is less than 30% of its foundation radius), the US Nuclear Regulatory Commission is sponsoring a program at the Brookhaven National Laboratory with the objective of investigating the extent to which procedures acceptable for shallow embedment depths are adequate for larger embedment depths. This paper presents the results of a study comparing the response spectra obtained from two of the more popular analysis methods for structural configurations varying from shallow embedment to complete embedment. A typical safety related structure embedded in a soil profile representative of a typical nuclear power plant site was utilized in the study and the depths of burial (DOB) considered range from 25-100% the height of the structure. Included in the paper are: (1) the description of a simplified analysis and a detailed approach for the SSI analyses of a structure with various DOB, (2) the comparison of the analysis results for the different DOBs betweenmore » the two methods, and (3) the performance assessment of the analysis methodologies for SSI analyses of deeply embedded structures. The resulting assessment from this study has indicated that simplified methods may be capable of capturing the seismic response for much deeper embedded structures than would be normally allowed by the standard practice.« less

Anchorage devices for large diameter reinforcing bars

Abstract: Results of nineteen pullout tests conducted on #18, #14 and #11, Grade 60 steel reinforcing bars (ASTM A615-68) to evaluate end anchorage provided by an attached steel end-plate are reported. The effects of group action and low cycle dynamic loading are also reported. Short embedment lengths for anchored bars resulted in greater loaded-end slips than those realized by unanchored bars embedded in accordance with current allowable bond stresses. These slips, however, were less than the "critical" value of 0.010 of an inch at an applied steel stress of 24 kips per square inch. The anchor plate design utilizing shallower reinforcing steel embedment reduced the ductility of the system, at stress levels exceeding yield stresses, by limiting the length of bar available for plastic elongation after the occurrence of bond breakdown. The use of an anchorage device on bars with short embedment lengths served to increase ultimate strength capability to that of a fully embedded, unanchored bar. Visible concrete crack patterns were not influenced by the use of anchor plates. Group-action test results indicated greater slip values at values at given stress levels when compared with single bar tests. Multiple bar pullout tests need to be performed on unanchored bars before the group-action phenomenon can be better evaluated. /FHWA/

Estimation of seismic uplift capacity of horizontal strip anchors using pseudo-dynamic approach

Abstract: In this paper, an analytical method to compute the vertical uplift capacity of horizontal strip anchors under both static and seismic conditions is described by using limit equilibrium method and Kotter’s equation. For seismic forces, pseudo-dynamic approach is used to obtain the net seismic vertical uplift capacity factor for unit weight component of soil (F γd ) by considering the distribution of soil reaction on the simplest planar failure surface through the use of Kotter’s equation. Results under static and seismic conditions are determined for various combinations of input parameters, like soil friction angle, embedment ratio, soil amplification and both horizontal and vertical pseudo-dynamic seismic accelerations. It is observed that F γd decreases significantly with increase in both horizontal and vertical seismic accelerations and soil amplification. As expected, the seismic uplift capacity increases with increase in embedment ratio and soil friction angle. Results in terms of non-dimensional net seismic uplift capacity factor are presented in graphical form. Present results are compared and found in good agreement with few similar results available in literature. Present study reveals lowest critical design values of seismic uplift capacity factor which can be used in seismic design of anchors.

Staged construction modeling of steel pipes buried in controlled low-strength material using 3D nonlinear finite-element analysis

Abstract: Several complexities are inherent in numerical simulation of staged construction modeling of large-diameter steel pressure pipes. A comprehensive robust three-dimensional (3D) nonlinear finite-element analysis model was developed and verified using three experimental field tests conducted at the Rolling Hills Booster Pump Station, Fort Worth, Texas, to simulate the behavior of buried steel pipes during staged construction installation. Controlled low-strength material (CLSM) was used as the embedment material, and the depth of the CLSM embedment and the trench width varied. The developed numerical model includes three possible nonlinearities, including geometric, material, and contact nonlinear algorithms. A large deformation algorithm was considered in the finite-element model and its associated analysis using a total Lagrangian formulation. The contact between each soil layer, soil-to-trench wall, and soil to pipe was carefully implemented. The lateral effect of compaction was identified in prev...

Response of embedded footings to vertical vibrations

Abstract: Field vibratory tests have been carried out to study the effect of embedment on the vertical response of footings. Steady-state vibration tests indicate decrease of maximum amplitudes of motion and increase of resonant frequencies as a consequence of embedment. A lumped parameter analog with the inclusion of Coulomb friction damping is suggested to explain the dynamic behavior of embedded footings. A simple procedure by which the constant frictional force of the Coulomb friction damping can be evaluated has been described. The suggested procedure takes into consideration the relevant physical characteristics of the interface between the foundation walls and the surrounding soil. The field test data obtained by the writers as well as those published by other investigators elsewhere are compared with the values predicted by the proposed analog. The correlation between the available experimental data and the predicted values is satisfactory.