Load Inclination Research Articles

Undrained capacity of surface foundations with zero-tension interface under planar V-H-M loading

Undrained capacity of strip and circular surface foundations with a zero-tension interface on a deposit with varying degrees of strength heterogeneity is investigated by finite element analyses. The method for simulating the zero-tension interface numerically is validated. Failure envelopes for strip and circular surface foundations under undrained planar V-H-M loading are presented and compared with predictions from traditional bearing capacity theory. Similar capacity is predicted with both methods in V-H and V-M loading space while the traditional bearing capacity approach under-estimates the V-H-M capacity derived from the numerical analyses due to superposition of solutions for load inclination and eccentricity not adequately capturing the true soil response. An approximating expression is proposed to describe the shape of normalised V-H-M failure envelopes for strip and circular foundations with a zero-tension interface. The unifying expression enables implementation in an automated calculation tool resulting in essentially instantaneous generation of combined loading failure envelopes and optimisation of a foundation design as a function of foundation size or material factor. In contrast, the traditional bearing capacity theory approach or direct numerical analyses for a given scenario requires ad-hoc analyses covering a range of input variables in order to obtain the ‘best’ design.

Skew Bending of Aircraft Fuselage Panels with “L” and “C” Stringers Mounted by Hybrid Joint / Ukośne Zginanie Poszycia Samolotu Z U Sztywnieniami Typu “L” I “C”, Mocowanymi Za Pomocą Złącza Hybrydowego

A section of fuselage skin with dimension 30 x 200 mm was subjected to numerical study and loaded by skew bending (Fig. 3). The thickness of the skin was 0,6 mm, the length of a leg of an angle “L” profile stringer was 12 mm with 1mm thickness. The angle of inclination α of the load plane to the skin plane varies in the range from 10° to 90° with 10° increment. The elastic - plastic material model of D16T aluminum alloy was used in simulations of the fuselage skin as well as for “L” and “C” profile stringers. In the material model description damage of aluminum alloy was taken into account. An adhesive layer with thickness of 0,1mm was modeled using cohesive elements with the failure mode depending on the shear strength and the tensile strength.The paper presents a comparative analysis of the considered structural elements with application of the unsymmetrical “L” profile or the symmetrical “C” profile with the same cross section area.All numerical studies were performed in Abaqus program. Finally, one can conclude that the stiffness of the structural element with application of the symmetrical “C” profile stringer is stronger, whereas the mechanical response of both versions of the hybrid joint significantly depends on the angle of load inclination α.

Influence of loading path on cyclic mechanical response of small-scale shallow strip footing on loose sand

This paper aims at experimentally exploring the behaviour of a small-scale 1g shallow strip footing on loose dry sand, subjected to vertical and horizontal cyclic loads. An experimental apparatus has been developed and calibrated, and some series of monotonic and cyclic tests with different combinations of load direction and cycle amplitudes have been carried out. Results are presented and discussed in terms of evolution of foundation global stiffness, damping properties, and settlement accumulation along both vertical and horizontal directions with increase in the load cycle’s number. The coupling effect between vertical and horizontal loads is highlighted, underlying its important role even at a low number of cycles, when, in the design practice, the behaviour of the system is often considered to be linear elastic and path independent. The observation also allowed the inference that a variation of the inclination of the cyclic loads may induce significant differences (up to one order of magnitude) in the global stiffness and damping properties. Far from having exhaustively investigated the subject and from the aim of proposing a new empirical quantitative relationship to be directly employed in the design practice, this paper was primarily focused on highlighting some aspects of the mechanical behaviour of the system that are still rather unknown. A further in-depth study allowed the analysis of experimental results within the framework of a meaningful physical interpretation, showing the results to be particularly useful in the perspective of a displacement-based design approach, as required by the current design standards.

매입된 석션앵커의 인발력에 대한 분석적 매개변수의 연구

The Embedded Suction Anchor (ESA) is a type of permanent offshore foundation that is installed by a suction pile. To increase the loading capacity against pullout, three wings (vertical flanges) are attached along the circumference at 120 degrees apart. Analytical parametric study using the proposed analytical solution method has been conducted to identify the effects of several parameters that are thought to influence the behavior of ESAs. The analysis results show that the pullout capacity increases as the anchor depth and the soil strength increase, and decreases as the load inclination angle increases. The anchor having square projectional area and being pulled horizontally at the middle of its length provides the highest pullout capacity.

Behaviour of flexible piles subjected to inclined loads

The behaviour of the piles under inclined loads is a topic not fully investigated in the literature. No experimental results from full-scale pile tests are available so that numerical analysis can be an interesting tool to provide useful results about the pile behaviour under this loading condition. In this study, a three-dimensional finite element approach is used to analyse the response of reinforced concrete flexible piles to inclined loads. Appropriate constitutive models are adopted to account for the nonlinear behaviour of the pile and the soil. In particular, the occurrence of plastic strains in the soil, concrete cracking and steel yielding in the pile as well as the occurrence of slip and gap at the pile–soil interface are adequately modelled. To assess the reliability of the method, some loading tests documented in the literature concerning axially or laterally loaded piles are first simulated. A fairly good agreement is found between numerical and experimental results. The geotechnical model and the pile from the above-mentioned tests are considered to highlight some characteristic aspects of the response of flexible piles to inclined loads. In particular, the analysis results show that a flexible pile can experience a flexural or an axial behaviour depending on the load inclination. Load inclination also influences significantly both the stiffness and the bearing capacity of the soil–pile system. Comparisons with the results from some empirical solutions proposed in the literature to evaluate the bearing capacity of the piles under inclined loads are also shown.

Capacity of dynamically installed anchors as assessed through field testing and three-dimensional large-deformation finite element analyses

The capacity of dynamically installed anchors in soft normally consolidated clay was examined experimentally through a series of field tests on a 1:20 reduced-scale anchor. The anchors were installed through free fall in water, achieving tip embedment of 1.5–2.6 times the anchor length, before being loaded under undrained conditions at various load inclinations. Vertical anchor capacities were between 2.4 and 4.1 times the anchor dry weight and were satisfactorily predicted using the American Petroleum Institute approach for driven piles. Anchor capacity under inclined loading increased as the load inclination approached horizontal; the field data indicated this increase to be up to 30% for the minimum achievable inclination of about 20° to the horizontal. Corresponding large-deformation finite element analyses showed a similar response, with the maximum capacity occurring at a load inclination between 30° and 45° to the horizontal. The finite element results demonstrate that, for the anchor geometry considered, an inclined load at the anchor padeye could be decomposed into ultimate vertical and moment loading at the anchor centroid. The establishment of a vertical and moment loading yield envelope for the geometry investigated forms the basis of a simple design procedure presented in the paper.

Effect of load inclination on the undrained bearing capacity of surface spread footings above voids

Footings are often situated on ground that includes voids that were either undetected or had not formed at the time of construction. In this study, small-strain finite element analyses are conducted to investigate the influence of load inclination on the bearing capacity of surface spread footings on undrained homogeneous clay with single and double continuous voids. The numerical solutions are compared with existing theoretical and empirical predictions. The results are presented as failure envelopes expressed in terms of loads that are non-dimensionalised by the footing width and the undrained soil shear strength (these are known as bearing capacity factors) and loads that are normalized by the uniaxial ultimate load. If underground voids exist under the footing, the shape and the size of the failure envelope defining the undrained bearing capacity of the footing subjected to combined horizontal and vertical loading depends on the location, the geometry and the number of voids.

Dynamic installation and monotonic pullout of a torpedo anchor in calcareous silt

Challenges associated with dynamically installed anchors include prediction of the anchor embedment depth, which dictates the anchor's holding capacity. This is particularly true for calcareous sediments, as very little performance data exist for this anchor type in these soils. This paper reports results from a series of model tests undertaken to provide insight into the behaviour of a torpedo anchor during dynamic installation and monotonic pullout in lightly overconsolidated calcareous silt. The tests were carried out in a beam centrifuge, varying the drop height and consequently the impact velocity, and the consolidation period prior to anchor pullout. The mudline load inclination was also varied to encompass various mooring configurations. The centrifuge model test data were used to calibrate: (a) an analytical dynamic embedment model, based on conventional bearing and frictional resistance factors but with strain-rate-dependent undrained shear strength for the soil; and (b) an analytical quasi-static vertical pullout capacity model, accounting for reverse end bearing and frictional resistance. A total energy based expression, appropriate for calcareous silts, was proposed for predicting anchor embedment depth for a given anchor geometry, mass and impact velocity. For assessing anchor vertical holding capacity, a piezocone based direct design approach was also proposed, deriving anchor end bearing and frictional resistance from cone tip resistance and sleeve friction, respectively. Anchor capacity under inclined loading was presented as failure envelopes expressed in terms of dimensionless vertical and horizontal components of anchor net resistance, which agreed well with a finite-element based envelope developed for embedded foundations. The regain of anchor capacity was found to be in good agreement with predictions based on the cavity expansion framework.

Pile capacity under oblique loads – evaluation from load–displacement curves

Evaluation of pile capacity from load–displacement curves under oblique loads is an intricate task. Because under oblique loads, load–displacement curves do not exhibit a distinct plunge point. Several methods have been adopted by different researchers to evaluate pile capacity from load–displacement curves under oblique loads. A summary of all these methods has been presented in this paper. To delineate the effect of load inclination on pile capacity, the method opted, always plays an important role. It is the main factor which significantly affects the pile capacity quantitatively and leads to establish a distinct trend of load inclination on pile capacity. To illustrate the significance of opted method, an experimental study was conducted on 20 mm diameter and 600 mm length piles under oblique pullout loads of different inclinations. Pile capacity at each load inclination has been evaluated from load–displacement curves using three different methods. Results of one method indicate that there is an increase in pile capacity up to 10° of load inclination and thereafter it decreases as load inclination increases. Whereas, results of second method show that pile capacity continuously decreases as load inclination increases with pile axis. Decrease in pile capacity with increase in load inclination was also observed in the results of third method, but pile capacity at certain loads' inclinations significantly differs as compared to the second method with minimum at 45°. The paper also deliberates on the applicability of adopted methods as per serviceability and functionality requirements of system or structure to be supported by pile.

Influence of Load Obliquity on Pullout Capacity of Micropile in Sand

An experimental study was undertaken to understand the influence of load obliquity on ultimate pullout capacity of pile. Twenty, single free-head vertical piles in the form of micropiles of 20 mm diameter and 600 mm lengths were drilled using an auger and grouted under gravity in uniform sand bed. Ample cured micropiles were tested at 0°, 5°, 10°, 15°, 20°, 30°, 45°, 60°, 75° and 90° load inclinations with respect to axis of micropile i.e. vertical. Ultimate pullout capacity at each load inclination was determined from load-displacement curves using double tangent intersection method. It is found that ultimate oblique pullout capacity as well as vertical pullout capacity of micropile decreases as load inclination increases with axis of micropile. To understand the relationship between the two components of oblique pullout load an interaction diagram has been derived from test results which show that horizontal load significantly affects vertical pullout capacity than vice versa. Test results of similar studies on micropiles have been presented through a polar diagram. An attempt has also been made to assess the applicability of existing theories to estimate the ultimate pullout capacity of micropiles under oblique loads.

Ultimate capacity of battered micropiles under oblique pullout loads

To understand the influence of load inclination and pile batter on ultimate pullout capacity, an experimental study was carried out on single, free head vertical (0°) and battered (±15°, ±30°) model micropiles under central in-plane pullout loads of different inclinations. Auger drilled, centrally reinforced, and grouted micropiles of 20 mm diameter and 600 mm length (L/D = 30) were casted and tested in uniform sand bed. Load–displacement curves were plotted for average displacements in horizontal and vertical directions. Ultimate pullout capacity for each load inclination was determined from load–displacement curves using double tangent interaction method. Test results indicate that ultimate pullout capacity of vertical and battered micropiles decreases as load inclination increases with the micropile axis. Vertical micropiles have more pullout capacity than ±15° battered micropiles at all inclinations of load. Whereas 30° negative battered micropiles beyond 5° of load inclinations have more pullout capacity than vertical micropiles. In general, negative batter micropiles offer more pullout capacity than positive battered micropiles at corresponding load inclinations and axial pullout capacity of the micropile decreases slightly as a result of increase in batter angle.

Numerical Analysis of the Mechanical Properties of Batter Piles under Inclined Loads

AbstractA three-dimensional elastic-plastic finite element model based on the elastic-plastic constitutive relation of the non-associated flow Mohr-Coulomb criterion is constructed to analyze the influence of inclination angles of loads and piles on the mechanical properties of batter piles under inclined loads. The results indicate that (1) the stiffness of batter pile depends on both its axial and horizontal stiffness under a smaller inclined load and does not become maximum under an axial force because of the existing stiffness balance in the axial and horizontal directions. (2) The relationship between the ultimate compressive bearing capacity of batter pile and the load inclination angle exhibits an M shape. The peak of this capacity appears near a small load inclination angle rather than under axial load. (3) The stiffness and bearing capacity of batter pile increase with pile inclination under positive inclined loads, whereas the results show the opposite behavior under negative inclined loads. (4)...

Reliability Analyses at Ultimate and Serviceability Limit States of Obliquely Loaded Circular Foundations

This paper aims at determining the failure probability and the corresponding most predominant failure mode at both ultimate (ULS) and serviceability (SLS) limit states of a circular foundation resting on a (c, φ) soil and subjected to an inclined loading. The failure modes at ULS are the footing sliding and the soil punching while those at SLS are the exceedance of tolerable horizontal and vertical footing displacements. The probabilistic results based on the response surface methodology have shown that at both ULS and SLS, there is a load inclination where neither mode of failure is predominant. This inclination corresponds to the loading configurations situated on the line joining the origin and the maximal point of the interaction diagram. In a second stage, the results of a sensitivity analysis showing the effect of the different statistical parameters of the uncertain variables on the value of the failure probability were presented and discussed.

Experimental Investigation of Installation and Pullout of Dynamically Penetrating Anchors in Clay and Silt

This paper reports the results from a series of model tests undertaken to provide insight into the behavior of torpedo anchors during dynamic installation and pullout in lightly overconsolidated kaolin clay and calcareous silt. The tests were carried out in a drum centrifuge at 200g, varying the drop height (hence the impact velocity) and the time delay for consolidation before pullout. The pullout angle at the mudline was also varied to encompass various mooring systems, including catenary (0°), taut leg (45°), and tension leg (∼80°). Two geometries of torpedo anchors were explored, varying the fin and tip geometry. The results demonstrated that the anchor embedment depth increased as the drop height (and hence the impact velocity) increased and the soil undrained shear strength decreased. In stronger silt, the cavity above the installing anchor remained open, whereas in soft clay, it was fully backfilled and replenished. The corresponding anchor embedment depth was also about 0.63 times compared with that in clay. The anchor holding capacity was found to increase with increasing postinstallation consolidation time, depth of embedment, and soil undrained shear strength and with reducing pullout angle at the mudline. The anchor rotation during pullout, and hence the pullout distance for attaining the maximum capacity, reduced as the load inclination at the mudline increased. The fin geometry (rectangular or elliptical) and tip geometry (conical or ellipsoid) were shown to have remarkable influence on the holding capacity, with rectangular fins and conical tip proving to be more effective. The negligible adherence of silt along the anchor sides and the presence of semiliquid material around the extracting anchor resulted in a significantly (34–47%) lower holding capacity in the calcareous silt, with significantly higher intact undrained shear strength.

Effect of Pile and Load Inclination on the Pile Resistance In both Compression and Tension

According to this theoretical study which was about loading of piles under different condition of loading (compression and up-lift forces ) and for deferent pile installation (vertical and inclined pile ) by which it called (positive batter pile ) when the inclination of the load and pile is in the same direction and called (negative batter pile) when the inclination of load is opposite to the pile inclination, and from studying these cases the results of analysis can be summarize in the flowing points:
 1-Variation of load inclination on piles effects on the bearing capacity and uplift resistance. It was found that bearing capacity of the piles increase with increasing of load inclination up to the inclination angle (37.5ͦ) which represents the maximum bearing capacity and then the bearing capacity decrease with increasing of load inclination.
 2- Variation of batter pile affects the bearing capacity of the pile and up-lift resistance. by which equivalent angle will be used as result between the load and piles inclination and this angle will be used in calculation of piles resistance .
 3- It was noticed the shape of soil failure is highly affected by the inclination of pile.
 The shape of failure for the soil which is in contact with pile and this include (vertical and batter piles) is highly affected by the angle of inclination.

The influence of padeye offset on plate anchor re-embedding behaviour

Equations that can be used to predict the trajectory of a plate anchor under pull-out load are derived from a simple combined loading yield surface assuming associated flow. They are used to directly predict the behaviour of plate anchors with different padeye offsets and under loads of varying inclinations. It is demonstrated that there is an optimal padeye offset that depends on the load inclination and causes the anchor to increase its embedment, and hence its capacity, under pull-out. The equations represent an elegant and efficient method to assist in the design of plate anchors, notably in optimising the padeye location.

Study on Pullout Behavior of Embedded Suction Anchors in Sand using ALE (Arbitrary Lagrangian Eulerian) Technique

석션 매입 앵커(Embedded Suction Anchor; ESA)는 석션 기초(Suction Pile or Caisson)을 이용하여 앵커를 지중에 매설한 후 인발에 저항하는 계류앵커형식이다. 본 연구에서는 ALE (Arbitrary Larangan Eulerian) Adpative Meshing 기법을 이용한 수치해석을 통해 석션 매입 앵커의 인발 거동을 모사하고, 그 결과를 기존 연구에서 수행된 원심모형 실험 및 한계 평형법을 이용한 해석적 방법의 결과와 비교 분석 하였다. 이를 통해 앵커의 수평 연직 경사 방향의 인발 거동을 평가하였으며, 수치 해석 결과, 수평 재하 시 중간 위치에서 가장 큰 저항력을 발휘하는 것으로 나타났다. 연직 재하의 경우 재하 위치와 무관하게 유사한 저항력이 발휘 되었으며, 수평 저항력이 가장 큰 중간 위치에서 경사 하중을 가한 결과 경사각이 증가할수록 인발 저항력이 감소하는 것으로 나타났다. The embedded suction anchor, ESA, is one type of mooring anchor systems which utilizes the suction pile or caisson to penetrate the anchor into the sea bed and develops its capacity under pullout load. In this study, the numerical analysis using ALE (Arbitrary Lagrangian Eulerian) Adaptive Meshing technique was performed to simulate the pullout behavior of the ESA, and the results were compared to those of the previous research, centrifuge model tests and the analytical method based on limit equilibrium theory. The pullout behaviors of the ESA under horizontal, vertical, and inclined loading were evaluated. The analysis results showed that the maximum horizontal pullout load was developed when the location of loading point was at the mid-point, and the each vertical pullout load gave the similar value regardless of the locations of the loading points. The pullout load decreased as the load inclination angle increased at the mid-point of the anchor.

Mixed-Mode I/III Fracture Characterization of Aluminum Alloy

Aluminum alloy 5083 is taken for the study of fracture parameters in mixed-mode I/III. Three point bend specimens with load inclination and notch inclination are fabricated and precracked. They are tested with various inclination angles and for two different thicknesses. The results are analyzed and found that the fracture toughness decreases for larger inclination angles. Also, it is found that the thinner specimens are found to be tougher than the thicker specimens. Material and methods Symmetrical three-point bend cracked specimens have been used extensively in fracture mechanics to study mode I fracture properties because they are one of the standard types of specimens used in the ASTM codes for determining the fracture toughness JIc..In the mixed-mode I/III fracture, there is only a limited amount of experimental work done so far. The observations on combined mode I - mode III fracture have been very scarce and there is no general agreement among researchers on the effect of the addition of a mode III component to pure mode I loading. Limited study (Avci et al 2005 [, Kamat and Hirth 1996 [) has been done on bend specimens subjected to mixed-mode I/III when compared to the mode I case, i.e., a center-loaded specimen.

Non-dimensional correlations for design of eccentrically obliquely loaded footings on cohesionless soils

In this paper, a comprehensive parametric study has been carried out to evaluate the behavior of footings on cohesionless soils and subjected to eccentric-inclined loads considering the non-linear elastic soil behavior and the soil-footing interface characteristics. The methodology for ultimate load criterion reported by was chosen to calculate the ultimate bearing capacity of sand having a relative density of 84% and depth to width ratios of 0·0 and 0·5. The values of ultimate bearing capacity agree very well with those of Meyerhof (1956). A detail parametric study was undertaken for different widths of footings and for different values of depth to width ratio, eccentricity to width ratio, load inclination, factor of safety, and relative density of sand. Based on the data obtained from this parametric study, non-dimensional correlations have been developed for predicting the values of settlement, horizontal displacement, and tilt of eccentrically obliquely loaded footings. These correlations have been found to be independent of the size of footing, factor of safety, and depth to width ratio and are dependent on the eccentricity to width ratio of the footing and the inclination of the applied load. To use these correlations, the settlement of the footing subjected to central load is required which can be obtained using the conventional methods.

Seismic uplift capacity of shallow horizontal strip anchor under oblique load using pseudo-dynamic approach

In this paper, an analytical method to compute the uplift capacity of an obliquely loaded horizontal strip anchor under both static and seismic conditions is described using the limit equilibrium method. The distribution of the soil reactions on a simple planar failure surface is obtained through the use of Kötter's equation, and the pseudo-dynamic approach is used to obtain the net seismic vertical uplift capacity factor for the unit weight component of the soil (Fγd). The results for the static and seismic vertical uplift capacity factors are determined for various combinations of input parameters, such as the load inclination, the soil friction angle, the embedment ratio, the soil amplification and both horizontal and vertical pseudo-dynamic seismic accelerations. It is observed that the orientation of the load significantly affects the seismic uplift capacity of the horizontal strip anchor. Fγd is seen to decrease with an increase in both horizontal and vertical seismic accelerations and soil amplification, whereas it is seen to increase with an increase in the embedment ratio and the soil friction angle, as expected. The results in terms of the non-dimensional net seismic uplift capacity factor are presented in graphical and tabular forms. The present results are compared and found to be in good agreement with similar results available in literature.