Pullout Load Capacity Research Articles

Experimental investigation of the behaviour of injection anchors in rubble stone masonry

The seismic response of historical masonry buildings is largely controlled by the effectiveness of wall-to-diaphragm connections, which can be improved using injection anchors. Despite their use, there is a need for a better understanding of the performance of such anchoring system in stone masonry walls. This paper presents quasi-static pull-out tests performed on twelve specimens to investigate the behaviour of injection anchors in rubble stone masonry walls when breakout failure occurs. For each specimen, the experimental results are presented in terms of force–displacement curves, propagation of damage and crack pattern. It is shown that the anchoring details adopted in this study had a negligible influence on the pull-out force capacity of the anchoring system, while an increase in peak pull-out force was observed with increasing overburden stress applied. Because stone masonry specific capacity formulations have not yet been presented in the literature, the capacity is predicted using state-of-the art formulations for the pull-out load capacity of anchors installed in brick masonry. The limits of their applicability are discussed using the obtained experimental results.

Pullout behavior of helical soil nails in cohesionless soil: a laboratory investigation

The soil reinforcing method of incorporating helical soil nails is a technique involving the introduction of passive elements into the soil. The combined action of helical bearing and shaft skin friction from helical soil nails gives better reinforcement against failure of the composite soil mass. The current study is aimed to explore the laboratory pullout response of helical soil nails in cohesionless soil (river sand) under varying shaft cross-section (Circular & Square), shaft type (Hollow & Solid), transition in the position of the third helix, and overburden pressure to optimize the most suitable soil nail. In this study, pullout tests are conducted on the soil nails in the laboratory using the physical model setup. The pullout capacity of circular nails is higher than the corresponding square nail. Moreover, a solid shaft nail depicts a higher pullout load capacity than a hollow shaft soil nail. Maximum pullout load is achieved at third helix spacing of about 3.8 Dh and gives a 7.40% increase in pullout load as compared to the reference soil nail. SSCN1. Further, as the overburden pressure is increased, the pullout capacity also increases.

Effect of Curing Age on Pull-Out Response of Carbon, Steel, and Synthetic Fiber Embedded in Cementitious Mortar Matrix

Fiber-matrix interface bonding is an important area of concern in fiber-reinforced composites because it is directly related to the mechanical behavior of composites. In this study, interfacial bond properties of four types of fiber at different curing ages were investigated by analyzing fiber pull-out responses. Special attention was given to the fiber–matrix bonding behavior, including fiber tensile strength, average bond strength, equivalent bond strength, and average pull-out energy. Pull-out tests were conducted at 7, 14, 28, and 56 days of curing. Different failure modes in steel fiber, synthetic macrofiber, polyacrylonitrile (PAN)-based carbon fiber, and pitch-based carbon fiber were investigated. According to the pull-out force versus slip curves, different failure patterns were recorded based on the fiber type. Carbon fibers experienced a sudden drop after reaching the peak load, whereas the load decrease in steel and synthetic fiber was not as abrupt. Results also confirmed that steel fibers exhibited the highest pull-out load and energy absorption capacity followed by lower values for synthetic and carbon fibers. While monofilament of steel fiber was able to absorb 1,050 N·mm, monofilament of synthetic fiber and twisted bundles of carbon fibers could absorb 277 and 55 N·mm, respectively. However, the bond strength of straight carbon fibers was comparable to that of synthetic fiber and still lower than steel fiber. It was also derived from the experimental data that an increase in cement matrix age correlates to an improvement in fiber maximum pull-out load, bond strength, and tensile strength. These parameters were identified and compared in all fiber types.

Enhancing Pullout Load Capacity of Helical Anchor in Clay with Adjusted Load Application Point under Inclined Loading Condition

Enhancing Pullout Load Capacity of Helical Anchor in Clay with Adjusted Load Application Point under Inclined Loading Condition

Finite Element Analysis on Behavior of Single Battered Pile in Sandy Soil Under Pullout Loading

Batter piles are the piles driven in the soil at an inclination with the vertical to withstand oblique loads or large horizontal loads and have been widely used to support high buildings, offshore buildings, and bridges. These constructions are risky because of the exposure to moments and overturning resulting from winds, waves, and ship impact. A 3D FEA using PLAXIS 3D software was used to investigate the effect of several variables that affect the behavior of single batter piles under pull-out loads. The study is achieved on a steel pipe pile model embedded in a dry sandy soil with three relative densities (loose, medium, and dense) at different inclination angles and three embedment ratios, L/D of 25, 37.5, and 50, respectively. The numerical results showed that the ultimate pull-out resistance of the battered pile raise as the battered angle increases reaches a maximum value, then decreases. The ultimate pull-out load capacity of a single battered pile is directly proportional to the slenderness ratio and relative density; the ultimate pull-out load increases with the increase in the ratio of slenderness and relative density. The ultimate uplift load of the battered pile was less affected by the free-standing length. Vertical and battered piles at a battered angle of (10ᵒ and 20ᵒ) and free-standing lengths equal to zero have higher ultimate pull-out capacity; by increasing the free-standing length, the ultimate pull-out capacity decreased.

Moisture transport and steel rebar corrosion in repair composites incorporating Nano-Fibrillated Cellulose (NFC)

Repair of deteriorating concrete infrastructure remains a major challenge. The concern is that current repair materials are not able to prevent premature failure after a repair has been performed. Thus, an engineered repair mortar that can enhance the durability of repaired composites by mitigating moisture transport and its debilitating influence on deterioration mechanisms such as steel rebar corrosion would be highly coveted. In this study, the influence of reinforcing a repair mortar with 0.1% by volume of Nano-Fibrillated Cellulose (NFC) on the capillary water transport in monolithic and composite specimens was investigated. Micro Computed Tomography (CT) imaging was also utilized in evaluating the microstructure of sorptivity test specimens. Thereafter, the influence of repair mortars on the corrosion behavior of deformed steel rebar was investigated via natural and accelerated tests. In these tests, concrete substrates had an embedded rebar in it, and repair mortars were applied on the top creating a composite specimen with a repair interface. Some of the parameters measured were surface resistivity, half-cell potential, overlay delamination time, residual rebar pullout load and rebar corrosion degree.Sorptivity tests indicated that the NFC is indeed capable of refining the pore structure through internal curing and thus reducing the capillary uptake of water. Moreover, the tendency of the NFC to entrap micro voids, especially near the repair interface, thereby indirectly reducing moisture transport and saturation of composite specimens was confirmed by CT imaging. Natural and accelerated corrosion test results demonstrated that NFC addition inhibited rebar corrosion as indicated by reduced rebar corrosion degree and delayed delamination of the repair overlay. The NFC also provided superior surface resistivity and a higher rebar pullout load capacity after corrosion.

Mechanical Behavior of Hybrid Soil Nail-Anchor System

Prestressed soil-nail system has two reinforcing components: steel bar and PC strands. The steel bar with relatively less elongation yields earlier than PC strands. Thus, yield displacements of these two components should be matched to maximize the design load (capacity) of prestressed soil-nail. To achieve this, PC strands need to be prestressed before applying pullout load. In this study, load transfer mechanisms of soil-nail and prestressed soil-nail were determined based on skin friction theory and load transfer theory. The load transfer was derived analytically based on the assumption that skin friction at the interface was fully mobilized. It was then compared with results from field pullout tests performed to identify in-situ load transfer mechanism. Additionally, optimum prestress level required to maximize the pullout loading capacity was evaluated and compared with those obtained from field tests.

Investigation of pullout load capacity for helical anchors subjected to inclined loading conditions using coupled Eulerian-Lagrangian analyses

The pullout load carrying behavior of helical anchors for inclined loading conditions was investigated based on the coupled Eulerian-Lagrangian (CEL) analyses. Various types of helical anchors, specified as Types 1 to 6, were adopted in the analyses. Types 1, 2 and 3 represent those with one, two, and three equal-diameter helical plates and Type 4 was a helical anchor type with two helical plates of different diameters. Types 5 and 6 were both with three helical plates of different diameters in opposite diameter configurations. Inclined loading conditions affected the pullout capacity (Qu) of helical anchors producing lower Qu with increasing load inclination. The patterns of the Qu decrease with increasing load inclination were similar for all helical anchor types considered in this study. The values of Qu were approximately similar up to θ = 60° and then decreased continually with furthering increasing θ. Qu was lowest at θ = 90°. The top-down increasing diameter configuration of helical plates was more efficient than the bottom-up increasing diameter configuration. A normalized load capacity relationship was proposed, which can be used to evaluate Qu for inclined loading conditions. The pullout behavior of helical anchors was governed by helical plates with marked effects of helical plate configuration, which was however less pronounced with increasing θ.

Performance of Multi-Helix Pile Embedded in Organic Soil Under Pull-out Load

The performance of multi-helix plate piles under pull-out load in organic soils is tested through an experimental investigation on helical piles. On the basis of experimental tests, this study presents the feasibility of multi-helix pile behavior installed in organic soil. Tests were carried out on two different densities of organic soil. The helix piles were made of 16-mm-diameter mild steel shafts to which mild steel plates of 50 mm for both diameter and pitch were welded. Tests were performed on single-, double-, triple-, and quadruple-helix cylindrical screw piles with helix spacing to diameter ratios varying from 0.1 to 0.5. A set of tests was also performed to evaluate efficiency. The results of the tests are used to illustrate the difference in ultimate capacity for the different geometry anchors. The results showed that the helical pile behavior depends essentially on pile geometric characteristics and soil density. According to the achievements, pull-out load capacity of helical piles depends on spacing ratio (S/D) and number of plates.

Evaluating the pull-out load capacity of steel bolt using Schmidt hammer and ultrasonic pulse velocity test

Steel bolts are used in the construction industry for a large variety of applications that range from fixing permanent installations to temporary fixtures. In the past much research has been focused on developing destructive testing techniques to estimate their pull-out load carrying capacity with very little attention to develop non-destructive techniques. In this regards the presented research work details the combined use of ultrasonic pulse velocity and Schmidt hammer tests to identify anchor bolts with faculty installation and to estimate their pull-out strength by relating it to the Schmidt hammer rebound value. From experimentation, it was observed that the load capacity of bolt depends on its embedment length, diameter, bond quality/concrete strength and alignment. Ultrasonic pulse velocity test is used to judge the quality of bond of embedded anchor bolt by relating the increase in ultrasonic pulse transit time to the presence of internal pours and cracks in the vicinity of steel bolt and the surrounding concrete. This information combined with the Schmidt hammer rebound number, R, can be used to accurately identify defective bolts which resulted in lower pull-out strength. 12 mm diameter bolts with embedment length of 70 mm and 50 mm were investigated using constant strength concrete. Pull-out load capacity versus the Schmidt hammer rebound number for each embedment length is presented.

Analysis of pullout load capacity of suction caissons in clay by a three-dimensional displacement approach

ABSTRACTA study was made to present analytical solutions of pullout load capacity for a suction caisson subjected to inclined tension in clay. The inclined tension on the skirt of the suction caisson is transformed into an equivalent system comprised of the vertical, horizontal, and moment load applied on the center of the lid. The vertical and horizontal stiffness coefficients along the skirt of the suction caisson in clay are presented by three-dimensional elastic solutions considering the nonhomogeneous and nonlinear property of clay. The vertical, horizontal, and rocking stiffness coefficient of the suction caisson on the base are presented considering the solutions of a hollow rigid cylindrical punch acting on the surface of clay. The envelopes of the horizontal and vertical ultimate load capacity for clay are presented. The yield, pullout, and failure for clay are taken into consideration. The effects of load inclination, loading depth, and aspect ratio on the pullout load capacity are shown. Behavior of the suction caisson in clay up to failure is investigated using the relationship between tensile load and displacement and that between depth, vertical, and horizontal pressure.

Evaluation of pullout load capacity of suction caissons in sand using a three-dimensional displacement approach

ABSTRACTAn investigation was conducted to obtain analytical solutions for the pullout behavior of a suction caisson undergoing inclined loads in sand. The inclined load is transformed into an equivalent load system in which the vertical, horizontal, and moment loads are applied on the center of the lid of the suction caisson. The vertical and lateral stiffness coefficients along the skirt of the suction caisson in sands are presented using the new three-dimensional elastic solutions taking into account the nonhomogeneous and nonlinear properties of the sand. The vertical, lateral, and rocking stiffness coefficients on the base of the suction caisson are presented considering the solutions of a hollow rigid cylindrical punch acting on the surface of a soil. The yield, pullout, and failure for sands with the nonhomogeneous and nonlinear characteristics are taken into consideration. The effects of the load inclination, the loading depth, and the aspect ratio on the pullout load capacity of the suction caisson are presented. Behaviour of the suction caisson in sand prior to failure is clarified from the relationship between tensile load, displacement, and rotation and that between depth, vertical pressure, and lateral pressure.

PVCO Pipeline Performance Under Large Ground Deformation

Technological advances have improved pipeline capacity to accommodate large ground deformation associated with earthquakes, floods, landslides, tunneling, deep excavations, mining, and subsidence. The fabrication of polyvinyl chloride (PVC) piping, for example, can be modified by expanding PVC pipe stock to approximately twice its original diameter, thus causing PVC molecular chains to realign in the circumferential direction. This process yields biaxially oriented polyvinyl chloride (PVCO) pipe with increased circumferential strength, reduced pipe wall thickness, and enhanced cross-sectional flexibility. This paper reports on experiments performed at the Cornell University Large-Scale Lifelines Testing Facility characterizing PVCO pipeline performance in response to large ground deformation. The evaluation was performed on 150-mm (6-in.)-diameter PVCO pipelines with bell-and-spigot joints. The testing procedure included determination of fundamental PVCO material properties, axial joint tension and compression tests, four-point bending tests, and a full-scale fault rupture simulation. The test results show that the performance of segmental PVCO pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of the joints, as well as their ability to accommodate deflection and joint rotation. The PVCO pipeline performance is quantified in terms of its capacity to accommodate horizontal ground strain, and compared with a statistical characterization of lateral ground strains caused by soil liquefaction during the Canterbury earthquake sequence in New Zealand.

Statistical analysis of the effective stress method and modifications for prediction of ultimate bond strength of soil nails

Uncertainty in the predicted ultimate pullout strength of soil nails can be significant due to the complexity of nail–soil interactions, inherent variability in soil properties and the effects of nail installation. The paper first presents a statistical evaluation of the accuracy of ultimate bond strength of soil nails using the effective stress method (ESM) equation that has been adopted in Hong Kong. A total of 113 ultimate nail capacity data points from field pullout tests were collected from the literature and used to estimate the accuracy of the current ESM. Based on the available data, the current ESM default pullout model is found to be excessively conservative (on average) by at least a factor of three. The spread in prediction accuracy measured by the coefficient of variation (COV) of bias is in the range of 36–43 % after removing anomalous test data. Here, bias is the ratio of measured to predicted pullout load capacity. In addition, the accuracy of the current ESM equation for prediction of nail bond strength is shown to be dependent on the magnitude of predicted ultimate bond strength and magnitude of nominal vertical effective stress which is undesirable. The paper examines four candidate-modified bond strength equations with empirical coefficients that have been back-fitted to measured bond strengths to improve the overall accuracy of the equation and to reduce or remove the undesirable dependencies noted above. One equation with an empirically corrected stress-dependent term is judged to be the best candidate model based on the mean of bias values, spread (COV) of bias values, lack of dependencies and simplicity. Finally, the relative contributions of random variability in soil shear strength to measurement bias in bond strength (prediction accuracy) for each soil type are computed for the best bond strength model. Analysis of the contribution of soil shear strength to prediction accuracy showed that the combination of variability due to factors other than soil shear strength was greater than the variability in soil shear strength alone, where the latter is defined by the soil secant friction coefficient.

Jointed Pipeline Response to Large Ground Deformation

AbstractThe performance of segmental pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of their joints, as well as by the limits on joint rotation during permanent and transient ground deformation. Although ductile iron (DI) pipelines with push-on joints are commonly used in water distribution systems, experimental data and numerical simulation related to their performance under large ground movements are lacking. This paper reports on a series of specially designed four-point bending experiments and finite-element (FE) simulations to characterize 150-mm (6-in.) diameter DI push-on joints. The results were used to develop a relationship between rotation and metal binding as a function of axial pullout, as well as to determine the magnitudes of rotation and moment that initiate joint leakage. FE simulations were performed to investigate the deformation associated with joint leakage. Uniaxial tension and one-dimensional compression tests were ...

Uplift Response of Irregular-Shaped Anchor in Cohesionless Soil

This paper presents an innovative soil anchor in loose and dense sand. Many studies on the anchor plates, both theoretical and experimental, have been conducted, although the existing works were mainly performed on regular and symmetrical anchor plates. A new anchor system is an irregular and non-symmetry shape anchor. This is an innovative system due to the special shape and the penetration into soils. Two sizes of irregular-shaped anchors, 159 and 297 mm, were used. The non-symmetry anchor employed in the system contributes to its good performance and high pullout load capacity. The maximum resistance increased based on the embedment ratio and the density of the sand. An important innovation of this system is the installation method, where it does not require excavation and grouting. The main objective of this research is to validate the break-out factors and the ultimate uplift capacity load of the irregular-shaped anchor with the existing researches related to anchor plates. The experimental research was performed on the models in a chamber box. For the 159 mm-width irregular-shaped anchor, an embedment ratio L/D between 1 and 7 and for the 297 mm-width embedment ratio L/D between 1 and 4 were employed. The irregular-shaped anchors were used in dry, loose and dense sand. The new irregular-shaped anchors are compatible with the symmetrical anchor plates as determined by existing researchers.

A multi-layer parallel crack extension model for deformational response of post-installed anchor

A simultaneous crack extension pull-out model for post-installed anchor bar is presented. The anchor bar is such that used in various strengthening techniques to strengthen reinforced concrete structures. The properties of the infill material used for post-installed anchor bar are characterized by a nonlinear interface between the surrounding concrete and the anchor bar. This is a new type of anchor-infill assembly in which the infill material is divided into two layers for the purpose of providing a larger failure path length resulting in increase of the energy absorption and pull-out load capacity. The mechanical properties of the infill layer are different from the surrounding concrete. Therefore the existing pull-out model of deformed bars cannot be applied directly in this case. The interfacial de-bonding is examined by the strength criterion expressed in terms of interfacial shear stress. Pre-existing cracks representing artificial notches are assumed at the top of infill layers for identifying crack location and stabilizing its propagation direction. All the possibilities associated with two-cracks in the close vicinity have been investigated in detail. The objective of the analysis is to predict a set of material properties which result in simultaneous crack extension at the two interfaces and also to identify a simultaneous crack extension length which results in increasing the pull-out load capacity, increase in energy absorption and increased failure path length but achieved at lowest increase in pull-out deformation thereby proving the effectiveness of two-layer model. Limiting the pull-out deformation is desirable from the point of view of limiting damage.

Experimental Performance of Soil Hook System as an Innovative Soil Anchors in Sand

Soil Hook System (SHS) is an innovative soil anchor. This paper presents an innovative and efficient system of anchor in loose sand. However the previous works were mainly performed on regular and symmetrical anchor plates but SHS is an irregular shape anchor. Two sizes of irregular shape anchors, 159 mm and 297 mm were used the non-symmetry anchor employed in the system contribute to its good performance and high pull-out load capacity. An important innovation of this system is due to its special shape and the method of installation where is does not require excavation and grouting. The experimental research included in the research was performed on Soil Hook System which was conducted in a chamber box based on embedded ratio 1-7. SHS is compatible withstand the symmetrical anchor plates as determined by other researchers.

TWO-LAYER SIMULTANEOUS CRACK EXTENSION MODEL FOR PULL-OUT BEHAVIOR OF POST-INSTALLED ANCHOR

A simultaneous crack extension pull-out model for post-installed anchor is presented. The anchor is such that used in various strengthening techniques for reinforced concrete structures. The properties of the infill material used for post-installed anchor are characterized by a nonlinear interface between the surrounding concrete and the anchor. This is a new type of anchor-infill assembly in which the infill material is divided into two layers for the purpose of providing a larger failure path length resulting in increase of energy absorption and pull-out load capacity. The mechanical properties of the infill layer are different from the surrounding concrete. Therefore, the existing pull-out model of deformed bars cannot be applied directly in this case. The interfacial de-bonding is examined by the strength criterion expressed in terms of interfacial shear stress. Pre-existing cracks representing artificial notches are assumed at the top of infill layers for identifying crack location and stabilizing its propagation direction. All the possibilities associated with two-cracks in the close vicinity have been investigated in detail. The objective of the analysis is to predict a set of material properties which result in simultaneous crack extension at the two interfaces and also to identify a simultaneous crack extension length which results in increasing the pull-out load capacity, energy absorption and failure path length, achieved at lowest increase in pull-out deformation. Limiting the pull-out deformation is desirable from the point of view of limiting damage. From the analysis, using proposed material properties and dimension parameters, simultaneous crack extension length, Ld equal to 0.3 is identified as the ideal length which results in increasing the pull-out load capacity by 31%, increasing the failure path length by 30% and increase the energy absorption capacity by 47% achieved at an limited increase in pull-out displacements of 20%.

모래지반에 근입된 석션파일의 인발저항력 및 변위거동 분석

모래지반에서 석션파일의 최대인발저항력 산정을 위한 일련의 원심모형실험이 수행되었다. 최대인발저항력 산정을 위한 실험인자인 석션파일의 인발각과 인발작용점의 위치에 대하여 실험을 수행하였다. 인발작용점의 경우 75%에서 최대인발저항력이 관찰되었다. 모든 경사각에 대하여 전체파일 높이에서 50%에서 75%사이에 석션파일의 회전각이 변함을 알 수 있었다. 인발각이 증가함에 따라 최대 인발저항력 발생 시까지의 변위가 점점 작아짐을 알 수 있었다. 석션파일의 형상중심의 수직변위를 최대인발저항력이 작용한 시점에서 관찰한 결과 모두 지표 쪽으로 이동한 것을 알 수 있었다. A series of centrifuge model tests to investigate the suction pile pullout loading capacity in sand have been performed. The main parameters that affect the pullout loading capacity of a suction pile include the mooring line inclination angle and the padeye position of the suction pile. With respect to the padeye position, the maximum pullout loading capacity is obtained when the padeye position is near 75% of the pile length from the top. The direction of the pile rotation changes when the padeye position reaches somewhere near 50~75% for all mooring line inclination angles. The translation displacement of suction pile to develop the time of maximum pullout loading capacity decreased as the mooring line inclination angle increased. In addition, the vertical displacements of the center of a suction piles for all cases appeared to develop toward the ground surface.