Showing papers on "Embedment published in 2000"

Failure behavior of riprap layer at bridge piers under live-bed conditions

Abstract: Experiments conducted under live-bed conditions show that a riprap layer at a cylindrical bridge pier will fail in either one of the following two modes: Total disintegration or embedment. The former refers to the break-up of the entire riprap layer where the stones are washed away by the flow field generated at the pier. The latter relates to the embedment of the riprap layer where it is buried in the sediment bed. The study proposes a criterion to demarcate the limiting condition between the two types of failure. It also identifies that embedment failure is a more common failure mode of riprap layer under live-bed conditions. The causes of embedment failure are twofold: (1) bed feature destabilization; and (2) differential mobility. Bed level fluctuations caused by the propagating bed features resulted in bed feature destabilization, whereas differential mobility is due to the different response of the riprap stones and bed sediments to the flow field. Experimental results also show that the riprap layer can degrade to an equilibrium level for a given flow condition. Finally, the study proposes a semiempirical equation to compute the maximum depth of riprap degradation, which occurs at the upper end of dune regime.

Concrete Strain Monitoring with Fabry-Pérot Fiber-Optic Sensor

Abstract: The field of instrumentation is now going through new developments with the advent of fiber-optic strain gauges. Fabry-Perot is one type of fiber-optic sensing technology that can be used for microstrain measurement of concrete. However, this new generation of strain gauges first needs laboratory investigation. The Fabry-Perot type of sensor, specially designed for embedment in concrete, is evaluated. The sensor is protected by a steel sleeve that allows its installation in concrete elements. Laboratory experiments, including compressive and thermal loading, are performed on a high-performance concrete cylinder containing this new type of strain gauge. The fast response of these strain gauges allows monitoring of the dynamic load test up to 5 Hz. The strain gauge sleeve is made of steel, and numerical simulations using a finite-element method are performed to verify strain distribution in a concrete cylinder with an embedment fiber-optic strain gauge. Results show that this type of strain gauge performs well for strain measurement of concrete and seems not to be affected by temperature variations.

Load–Deflection response of transversely isotropic piles under lateral loads

Abstract: In general, pile materials are assumed to be isotropic during the analysis of the load–deflection response of piles under lateral loads. However, commonly used materials such as reinforced concrete and timber as well as potentially promising new pile materials such as fiber reinforced polymers are typically transversely isotropic materials. Experimental studies have shown that transversely isotropic materials have a high ratio of section longitudinal modulus to the section in-plane shear modulus (Ezz/Gxz) compared to the value for isotropic materials. The high modulus ratio leads to a more significant shear deformation effect in beam bending. To account for the shear deformation effect, the Timoshenko Beam Theory has been adopted in deriving the solutions for the load–deflection response of transversely isotropic piles under lateral loads instead of the Classical (Euler–Bernoulli) Beam Theory. The load–deflection responses depend on the shear effect coefficient, the lateral soil resistance, the embedment ratio, and the boundary conditions. The deflection of the pile, if the shear deformation effect is considered, is always larger than if it is neglected. Copyright © 2000 John Wiley & Sons, Ltd.

Progress on monitoring of adhesive joints using multiaxis fiber grating sensors

Abstract: Previously, the results of embedding multi-axis fiber gratings into adhesively bonded joints were discussed. This paper presents more information on the testing of the adhesive joints and techniques employed to successfully embed a fiber grating sensor into such structures. These techniques include orienting the fiber, marking its orientation, and preparing it for embedment into the adhesive. Also discussed are strain relief methods for the egress of the fiber.

Behavior of laterally loaded piles supporting bridge abutments

Abstract: This final report describes the work performed in research related to the behavior of laterally loaded piles supporting abutments in which the piles and abutment are built integrally. Pile-abutment systems were built and loaded laterally in a way that simulated the load induced in an integral abutment as a bridge is subjected to changes in temperature. Two areas of particular interest were (1) the embedment zone of the pile in the concrete abutment and (2) the embedment zone of the pile in the soil. Five pile-abutment systems were built and tested. All of the piles had strain gages applied at regular intervals for the first 20 ft of the 38-ft embedded depth, and the first four piles also had pressure sensors affixed to attempt to locate the point along the pile where the lateral pressure was zero. The primary conclusion drawn from the tests was that the Tennessee Department of Transportation (TDOT) design approach for integral abutments is reasonable. While some cracking did occur in the abutments at deflections of 1 in. and greater, the pile-abutment interface maintained its structural integrity for deflections as much as 2 in. and beyond. Four of the test systems had 1-ft pile embedments consistent with TDOT practice. The fifth had a 2-ft embedment. While there were no data suggesting a need for anything greater than a 1-ft embedment, the extra 1 ft of embedment depth did provide the capability of sustaining significantly larger lateral deflections without loss of structural integrity.

Determining Embedment Response Parameters from Connector Tests

Abstract: A method is proposed for the determination of parameters in a model for embedment response of mechanical connectors in wood. The parameters are extracted from results of a common connection test, in which the connector not only compresses the wood medium but also bends, contaminating the “embedment” response. The parameter identification is implemented using a general model for calculating the hysteretic response of connectors. The method is illustrated with examples.

The embedment of co-integration in time series analysis : problems and cases for single equation approach to exchange rate modelling

Abstract: In this thesis, the long-run Purchasing Power Parity model and the Flexible Price Monetary Approach to the exchange rate are studied. The purching power parity (hereafter the PPP) model is a two country model and basically assumes that, the same goods or basket of goods should sell for the same price in any two countries when measured in a common currency. This implies that the exchange rate depends upon the price levels. Similarly, the flexible price monetasry approach (hereafter the FPMA) is also a two country model, however, it assumes that the exchange rate is influenced by relative money supplies, relative income and relative interest rates instead of the relative price levels. These models are examined via the estimation of a single equation using co­ integration analysis techniques developed by Engle and Granger (1987). Co­ integration is a very powerful and reliable technique in investigations involving non-stationary series. By their nature, non-stationary series fluctuate up and down away from their mean, implying that they have the tendency to possess different mean at different point in time. However, the linear combination of two or more non-stationary series integrated of the same order (have the same property) is expected to change to stationary (stability), and co­ integration technique was developed to achieve this transformation (change non-stationary series to stationary series). The Engle and Granger (1987) two stage procedure for co-integration analysis has been widely applied in cases involving up to two variables (nonstationary time series). The present study involves more than two variables in a single equation. Therefore it makes an original contribution to the literature in that it has successfully applied the single equation approach widely used for estimations of up to two variables. Thus, the study provides a bridge between the conventional approaches that adopt standard testing procedures, and the more recent sophisticated approaches that adopt multivariate equations or the full information maximum likelihood (FIML). Stationarity properties of individual series including exchange rates are analysed via a unit root test by means of both the Dickey Fuller (DF) and Augmented Dickey Fuller (ADF) procedures. The Lagrange Multiplier (LM) was applied to select an appropriate number of augmentations in the case of the ADF tests. When initially tested in levels, all series showed the property of non-stationary 1(1) variable, but were all changed to stationary variables when tested in first difference form. The period-by-period deviations of the models from their respective equilibrium positions are analysed via the error correction mechanisms (ECMs). The ECMs encompass the variables of the short-run dynamic model as well as those of the long-run static model, all of which are estimated in a single error correction equation. The robustness of this approach (single equation estimation) shed a great light on the treatment of the PPP model and FPMA respectively as long-run models of exchange rate determination.

Propagation of waves from a spherical cavity with and without a shell embedment

Abstract: A spherical cavity in an infinite, elastic medium with and without a shell embedment is subjected to axisymmetric, non-torsional surface loads in the radial and meridional directions. The so-called Residual Variable Method (RVM) is used to obtain exact, closed-form solutions of the wave propagation problems. Some representative numerical results are presented graphically for the stresses created in two realistic loading situations.

Seal slab/pile interface bond

Abstract: This report presents results from a two-year experimental study to evaluate the interface bond between a cast-in-place seal slab and prestressed concrete or steel piles. Both scale model and full-scale tests were conducted and several cofferdam conditions were simulated. These were (1) marine environment, (2) fresh water conditions, and (3) drilling fluid condition. Normal pile surfaces were investigated. Additionally, the situation of "soil-caked" piles was also investigated. In the model tests, a total of 36 one-third scale specimens were tested - 28 prestressed concrete and 8 steel. Bonded embedment depth in the seal slab was varied between d to 2d where d was the size of the pile. The results of these tests indicated that shear stress variation was non-uniform leading to larger computed bond stresses with shallower embedment. Values were least for drilling fluid. Concrete piles had better bond with the seal concrete than steel piles. "Soil-caked" condition was found to be relevant for the drilling fluid situation only. In other cases, it was washed away from the pile surface. In the full-scale tests, a total of 32 specimens were tested divided equally between steel and concrete. The prestressed piles were 14 in. square and the steel piles were 14 in. deep wide flange sections. Embedment depth was varied between 0.5d to 2d, i.e., 7 to 28 in., with the larger depth reserved for the drilling fluid condition. Four of the 16 prestressed piles were cast with embedded gages located at the top, middle and bottom of the interface region. The results of the full-scale tests were similar to those from the one-third scale tests. The most important findings were (1) loads were transferred over a distance equal to the depth of the pile, (2) scale effects were present - the average calculated bond stresses were lower for the full-scale tests than from the corresponding scale model tests, (3) prestressed piles cracked prior to bond failure, and (4) the seal slab cracked prior to bond failure. Based on the test results it is proposed that the interface bond between piles and the seal slab be restricted to an effective area in contact with the cast-in-place seal slab. The effective area is calculated using the actual embedment depth or the size of the pile, whichever is smaller. The average bond stress over this region is limited to 300 psi for concrete piles and 150 psi for steel piles. These values are reduced by a third in cases where drilling fluid is used. Application of the proposed values to the conditions related to the full-scale tests led to average factors of safety in excess of two for both the prestressed and steel piles. However, tension loads taken by the piles should not lead to cracking (concrete) or exceed the allowable tension load (steel) of the piles. Nor should the seal slab crack.

Precast concrete member joining structure

Abstract: PROBLEM TO BE SOLVED: To provide a precast concrete joining structure wherewith an embedded metal can be produced without welding a stud and a high accuracy can be ensured for execution of works without the need for embedment of a sleeve material for forming an insertion hole for high strength bolt. SOLUTION: A joining steel plate 27 is caught from both sides with each of edge parts 21a of a pair of precast concrete members 21 each of which is divided into two in the direction of thickness, and the precast concrete members 21 facing each other are joined together by tightening a high strength bolt 29 which is pierced through the edge part 21a and the joining steel plate 27. In this case, a closed-end cylindrical embedding cap 23 is embedded at the edge part 21a of the precast concrete member 21. With the joining steel plate 27 caught between the bottoms 23a of the embedding caps 23 fastened tight with the high strength bolt 29, the edge parts 21a are stuck fast to the joining steel plate 27.

Numerical modelling of the uplift behaviour of circular plate anchors in sand

Abstract: Axisymmetric finite element analyses of the uplift behaviour of circular anchors in sand using the ANSYS package are reported. The non-linear behaviour of soil was incorporated in the analysis by using the MISO (Multi-linear Isotropic Hardening Material) model. The influence of soil type, friction angle and depth of anchor embedment on uplift response was investigated. The load-displacement relationship obtained from the non-linear finite element analyses compares well with published results. The ultimate pullout load increased with embedment ratio and soil friction angle. Critical embedment ratios of 5, 6.5 and 7.5 were obtained for anchors in sand with friction angles consistent with loose, medium-dense and dense packings. Computed breakout factors compared fairly well with predictions from various theories, Meyerhof and Adams theory providing best overall agreement, particularly for shallow anchors in loose sand and for deeper ones in medium-dense and dense sand. Comparisons with previously reported experimental work were also reasonable.

Embedment sign, display implement and their main bodies

Abstract: PROBLEM TO BE SOLVED: To provide an embedment sign which may be easily produced at a low cost and makes display easily visible without the easy peeling of a display plate. SOLUTION: This embedment sign has the display plate 3 and a main body 2 for mounting the display plate 3. This main body 2 has a recessed part 6 for accepting the display plate 3 in a manner as to prevent the generation of a clearance from the outer peripheral edge 7 of the display plate 3 on its front surface 5. The depth of the recessed part 6 and the thickness of the display plate 3 are so set that the surface 8 of the display plate 3 attains a height below the front surface 5 of the main body 2 at its circumference when the display plate 3 is fixed into the recessed part 6.

Accuracy of Post-frame Building Construction

Abstract: Thirty-nine post-frame buildings were extensively measured to determine the accuracy of their construction. The buildings were all located in southern Wisconsin and were constructed by 12 different dealers/companies. Deviations between measured and ideal values were calculated for the embedment, alignment, spacing, plumbness and height of posts, as well as for building length and squareness, truss bearing height, and girt height and spacing. This report does not make judgments concerning the acceptability of any tolerance measured nor does it recommend tolerance limits.

Analysis of Reliability of Optimal Embedment of Cantilever Supporting Structure

Abstract: Based upon the reliability analysis, this paper present s a new method of the optimal des ign embedment length of cantilever supporting structure in deep excavation engin eering by second-order moment theory. The different control factors for retaining wall an d pile supporting structure are also analyzed．