Showing papers on "Embedment published in 1990"

Buried Pipe Design

Abstract: Introduction and Overview External Loads Design of Gravity Flow Pipes Design of Pressure Pipes Buried Pipe Products

Performance of piles with enlarged bases subject to uplift forces

Abstract: The influence of embedment, base diameter, and backfill density on the uplift behaviour of piles with enlarged bases embedded in sand was investigated in a centrifuge. Comparitive tests on straight...

On the axisymmetric interaction of a rigid disc with a semi-infinite solid

Abstract: An analytical treatment is presented for the determination of the response of a vertically-loaded disc embedded in a semi-infinite elastic medium By means of Love's method of potential and a set of relaxed boundary conditions, the mixed boundary value problem is formulated as dual integral equations with the aid of Hankel transforms On the reduction of the dual integral equations to a Fredholm integral equation which features a closed-form kernel, solutions to the inclusion problem are computed In addition to including existing solutions for zero and infinite embedment as degenerate cases, the present analysis reveals a severe boundary-layer phenomenon which is apt to be of significance to this class of problems in general As illustrations, numerical results on the load-displacement relation, the response of the embedding medium, as well as the contact load distribution are included

Numerical analysis of headed studs embedded in large plain concrete blocks

Abstract: Anchoring elements such as headed studs, expansion, grouted or undercut anchors are used for local transfer of loads into concrete members. Parameter study of the behavior of headed stud anchors with embedment depth h v= 130 mm and failing by pulling out a concrete cone, is performed through numerical analysis. Compression and tension strength, fracture energy and the head diameter are varied. Numerical analysis is performed using nonlocal microplane model and axisymmetric finite elements. Results of the analysis are compared with experimental results.

Effects of geometrical and material properties on the vertical vibration of three-dimensional foundations by BEM

Abstract: The dynamic response of foundation is influenced by various mechanical properties of soil as well as the geometrical properties of the foundation. In this paper, the effects of Poisson's ratio and material damping, as well as the influences of aspect ratio and embedment depth on the dynamic stiffness of rectangular foundations are studied. Studies are also conducted to investigate the influence of the type of contact at the soil–foundation interface and the soil layer overlaying a half-space. These studies were conducted using an advanced algorithm of the boundary element method incorporating isoparameteric quadratic boundary elements. Higher-order elements (quadratic) were used since they can model the wavy nature of the dynamic problem accurately.

Mechanics and performance of a tied-back wall under seismic loads

Abstract: In this paper the stability of a tied-back wall subjected to seismic loads is analysed for a predetermined mode of failure (rotation about the top of the wall) and the analysis is compared with data from tests on this type of wall using the seismic simulator at the State University of New York at Buffalo. We carried out a pseudo-static analysis of the problem using the Mononobe-Okabe earth pressure coefficients, wherein the dynamic effects due to the seismic loading are converted into equivalent static loads. The acceleration ratio at which the wall fails by rotation about the top was obtained by considering the moments due to the various lateral earth pressure resultants and the inertial forces induced in the soil due to the seismic loading. We found that the presence of wall friction on the passive side significantly enhances the stability of the flexible retaining wall under seismic loads. Thus, flexible retaining walls supporting dry cohesionless soil can be very efficient during earthquakes. Under moderate earthquakes, an increase in the depth of embedment increases the dynamic factor of safety significantly. However, beyond a certain acceleration ratio for a soil with a particular value of o, any increase in the depth of emdedment has no effect in impeding failure, irrespective of any change in the geometry of the system. Seismic design charts are presented to evaluate the stability of, and to design, flexible retaining walls embedded in dry cohesionless soils under seismic loading.

Sound barrier wall foundations in granular material

Abstract: Sound barrier walls are necessary for highways when alignments cross residential areas. Drilled shafts (caissons) are simple foundations for sound barrier walls. Four different design methods for drilled shafts are discussed and compared. All methods result in comparable capacities for shafts up to certain embedment depths, as is indicated by the analysis. Two of the methods, which originally were developed only for level ground, are modified to accommodate sloped ground surfaces.

Hybrid experiments on non‐linear earthquake‐induced soil‐structure interaction

Abstract: Non-linear seismic soil-structure interaction is studied through a hybrid procedure using the pseudo-dynamic testing (PDT) method which is modified to take into account frequency dependence and developed for foundation-soil systems. The numerical scheme used in conventional PDT is improved by introduction of a time-dependent pseudo-forcing function which is derived from frequency-dependent dynamic characteristics of the system by means of Hilbert transformation in the frequency domain. Surface, shallow and caisson foundation models that differed in size and depth of embedment were used. The mechanical characteristics of the systems were determined from static and forced vibration dynamic tests. An amplitude scaling technique was used for three recorded accelerograms.

Evaluation of Bond Performance of Epoxy-Coated Reinforcing Steel Using Nonlinear Finite Element Analysis

Abstract: The role played by epoxy coatings on the failure of standard beam-end specimens is explored. The specimen consists of a reinforcing bar embedded in concrete. As the bar is loaded, the specimen is placed in flexure, resulting in simultaneous tension in both the reinforcing steel and the concrete. The specimen is designed to duplicate the stress field that occurs in beams. Experimental results show that bond strength increases with additional cover and embedment length, but that bond strength per unit length decreases as embedment length increases. The results also show that epoxy coatings reduce bond strength, but that the effect is dependent on the bar size and the deformation pattern. The finite element model for the beam-end specimen includes representations for the deformed steel bar, the concrete, and the interfacial material. The interface is represented by special link elements that can be varied to match the stiffness and friction properties of the interfacial material. Cracking within the concrete is represented using A. Hillerborg's fictitious crack model. The goal of the model is to incorporate the key aspects of material behavior in as simple a representation as possible while duplicating the principal behavior of the test specimen.

Production of in-vivo implanting material

Abstract: PURPOSE:To produce the implanting material for in-vivo embedment by fixing a porous body consisting of Ti or Ti alloy into a casting mold, then pouring the melt of the Ti or Ti alloy into the mold to internally chill the porous body and exposing a part of the porous body by processing, such as machining, after solidifying the melt. CONSTITUTION:The porous sintered body 1 is produced by compressing and molding the fine powder of the Ti or Ti alloy, then sintering the molding. After this body is fixed into a cavity 6 in a casting mold 5, the melt of the Ti or Ti alloy is poured into the casting mold 5 to internally chill a part of the porous body 1 made of the Ti by which a casting 4 is formed. This casting is taken out of the casting mold 5 and the part which is not internally chilled is ground or polished or is chemically treated by an acid, alkali, etc., at need, by which a part of the porous body 1 is exposed and the implanting material for in-vivo embedment, such as artificial bones for plastic surgery and artificial fang for dental purposes is produced.

Constructing method for underground structure

Abstract: PURPOSE: To dispense with making a PC plate longer by inserting an assembled body formed of the PC plate, an earth retaining member and an embedment member into a slot formed in the earth as stabilizing liquid is filled in the slot, and solidifying the stabilizing liquid to widenedly dig the ground for building a structure. CONSTITUTION: A pair of slots 12 are digged as stabilizing liquid is filled in the slots 12, and an assembled body 22 formed of a PC plate 16, an earth retaining member 18 and an embedment member 20 is inserted into a slot 12. The other assembled bodies 22 are then inserted into the slot 12 in order, and the adjacent PC plates 16 are therefore mutually abutted. While each of the assembled bodies is suspended from a supporting plate 24, grout is applied to the bottom of the slot 12 to partially cover each of the embedment members 20. The stabilizing liquid is then solidified to form an united body, and a sheet pile is arranged between the earth retaining members 16 for widenedly digging the ground between the slots 12, and the PC plates 16 re used as a side wall to build a structure 42. Thus the structure 42 can be supported through the PC plate 16. COPYRIGHT: (C)1992,JPO&Japio

Direct embedment foundation research: Load test summaries

Abstract: This project involved the development of a design/analysis model for direct embedment foundations subject to high overturning moments and moderate compressive axial and lateral forces. The final report discusses the semiempirical model developed by modifying the four-spring nonlinear subgrade modulus'' model for laterally loaded drilled shaft foundations previously developed for EPRI. The design/analysis model for direct embedment foundations considers the stiffness of the pole, the multilayer soil system, and the annulus backfill to estimate deflections and rotations. The model also considers the influence of the backfill in the resistance to the applied loads. The model has been incorporated in the EPRI computer program MFAD (Moment Foundation Analysis and Design) contained in TLWorkstation, which is now capable of analyzing/designing laterally loaded drilled shafts and direct embedment foundations. The final report also presents comparisons between model predictions of load-deflection/rotation behavior and the actual behavior observed in twelve full-scale load tests. This supplemental volume was prepared to document data gathered from the twelve full-scale laterally loaded direct embedment foundation tests conducted during the project.

Uplift behaviour of circular plate anchors in cohesionless soils

Abstract: The work presented in this thesis describes an investigation into the behaviour of circular plate anchors embedded in dry cohesionless soils and subjected to vertical static uplift loading. A review of previous theoretical and experimental work provides a good insight into, and justification for, this study. A small-scale laboratory test model was constructed for experimentation purposes. A large circular steel tank was used to contain sand which was uniformly deposited using a raining device except for the dense well graded sand). A total of one hundred and thirty tests were completed in five different sands at densities varying from loose to very dense and using depth/diameter ratio (D/B) ranging from 2 to 12. A further 20 tests have been performed in a two layered system. A stereo photogrammetry technique was used to establish the different zone of displaced sand mass for shallow and deep anchors and a computer program was developed to facilitate computation of the results. From the analysis of the results, it appears that the sand grain shape and grading have a profound influence on the behaviour of circular plate anchors embedded in sand. However, it was found that grain size did not have any effect on the pull out behaviour. Other influencing factors, such as the depth of embedment and relative density have also been examined. The stereo photogrammetry results showed that the extent and the shape of the zone of disturbed sand is also a function of the aformentioned parameters. Tests in the two layered system indicated that the ultimate uplift load and the mode of failure were dependent on the thickness of the upper layer and the strength of the different layers. A theoretical analysis based on Fadl's (1981) work, was formulated in order to predict the maximum uplift load in a two layered system. Design charts for homogeneous soil have also been put forward. The validity of the design procedure was examined by comparing it with both model and field test results reported by previous investigators. A reasonable correlation has been achieved. Finally, a number of areas of related research considered suitable for further study have been outlined for the benefit of future investigators.

Variability of Fiber/Resin Interfacial Shear Strengths

Abstract: The microbond pullout technique for the measurement of interfacial shear strength in fiber-reinforced composites has provided data to support the hypothesis that observed bond strength variations for a fiber/resin system are mainly the consequence of fiber surface heterogeneities This conclusion is based upon two observations First, there is closer agreement in bond strength associated with near-neighbor fiber sites than for more widely separated sites Second, shear strength distributions become narrower as embedment areas are increased Since fiber surface defects and variations tend to average out when larger embedment areas are used, broad shear strength distributions may not be observed with macro pullout experiments

Investigation of pile anchors for flexible hydrobiotechnical structures

Abstract: 1. Experimental investigations established the main characteristics of the interaction of pile anchors of HBTSs with the soil, in particular, the dependence of the limit load on the depth of embedment, anchor rigidity, cyclicity of loading, etc., was established. 2. An approximate method is proposed for determining the limit load on the anchor (separation load) with consideration of the slope of the acting load and rotation of the anchor. The results of the calculations by the proposed method agree satisfactorily with the data of experiments and on-site measurements.

Foundation construction of building

Abstract: PURPOSE:To make it possible to greatly reduce the volume of earth to be excavated by making underground beams in a direction necessary for the depth of embedment, and making a mat slab in a direction unnecessary for the depth of embedment. CONSTITUTION:Both underground beams 11 and 11 are connected with a mat slab 12 to form a foundation construction having a gantry type section, and in consideration of inversion, a Y direction necessary for the depth of embedment is made resistant to moment of inversion in case of an earthquake by underground beams 11. In an X direction, it is not necessary to consider the inversion so that the depth of embedment is not required, and the moment of inversion in the X-direction is treated with the mat slab 12. According to this constitution, the resistance of the ground against the inversion in case of an earthquake can be safely secured.