Cyclic Pullout Research Articles

Three-Dimensional Numerical Analysis of Static and Cyclic Pull-out Response of Plate Anchors in Reinforced Soft Clay

Three-Dimensional Numerical Analysis of Static and Cyclic Pull-out Response of Plate Anchors in Reinforced Soft Clay

Effects of cyclic loading on soil-geogrid interaction characteristics

The benefits of geosynthetic-reinforced soil systems over conventional earth-retaining structures are now well established. These reinforced systems are often subjected not only to static loads, but also to seismic and/or traffic loads, in which case the effects of repeated loading on soil-geosynthetic interaction characteristics should be properly considered. This study investigates the behaviour of a geogrid typically used for soil reinforcement under cyclic pullout loading through load-controlled laboratory pullout tests. To examine the influence of cyclic loading amplitude, number of cycles and static pullout force acting on the geogrid at the onset of cyclic loading, distinct loading patterns are considered. A well-graded residual soil from granite is used as backfill material. A comparison between the cyclic and monotonic pullout response of the reinforcement is then established in order to identify any potential strength loss attributed to cyclic loading. The experimental results show that the ultimate pullout resistance of the geogrid embedded in medium dense residual soil from granite may be adversely affected by cyclic loading. The cumulative cyclic displacements of the reinforcement are more pronounced during the initial loading cycles, but tend to stabilize with the increasing number of cycles when the soil is densely compacted. In the presence of dense soil, the cyclic strains of the geogrid specimen are particularly significant at the front section and almost negligible towards the back end.

Fatigue Behavior in the Carbon-Fiber-Reinforced Polymer-to-Concrete Bond by Cyclic Pull-Out Test: Experimental and Analytical Study

Fatigue Behavior in the Carbon-Fiber-Reinforced Polymer-to-Concrete Bond by Cyclic Pull-Out Test: Experimental and Analytical Study

Experimental research on static and cyclic pullout behavior of cast-in-place anchors with steel sleeve

The cast-in-place anchors with steel sleeve are widely used in the anchoring of heavy equipment with dynamic loads. The setting of the steel sleeve allows a higher preload to be applied to the anchor. The preload level of anchors plays a crucial role in the normal operation of equipment with dynamic loads. In this study, 9 groups of single anchor pull-out tests under static or cyclic loading were carried out. The performance differences of anchors at three preload levels (10%, 20% and 30% of the anchor's yield load) were investigated. The test results show that the preload can effectively improve the anchoring performance of the anchor. With the increase of the preload level, the yield displacement of the anchor and the residual deformation after cyclic loading decreased continuously. Under the same preload level, the anchoring effect of the anchor with thick-wall steel sleeve was slightly better than that of the anchor with thin-wall steel sleeve. Finally, the preliminary design process of anchor with steel sleeve were presented.

Displacement recovery and energy dissipation of crimped NiTi SMA fibers during cyclic pullout tests

Abstract This study examines the cyclic pullout behavior of two types of cold-drawn NiTi shape memory alloy fibers, such as paddled and crimped fibers. For this, two diameters of 1.0 and 0.7 mm are considered. The experimental cyclic pullout results show that the deep crimped fibers produce a higher maximum pullout resistance than the shallow crimped fibers. When heated, the shallow crimped fiber increases the diameter more significantly than the deep crimped fiber, whereas the fiber wave depth decreases more than the deep crimped fiber. Thus, the maximum pullout resistance increases for the heated shallow crimped fiber and decreases for the heated deep crimped fiber. The displacement recovery ratio (DRR) reduction with an increasing slip is significant for the fiber with a low anchoring bond. The high anchoring bond fiber also introduces a higher average DRR than the fiber with a relatively low anchoring bond. Under heating treatment, the average DRR increases due to the prestressing in the fiber due to the shape memory effect. However, the anchoring bond of the fiber is enough to produce prestressing in the fiber. The anchoring bond of the fiber and the prestressing also influence the energy dissipation (ED). The higher anchoring bond results in a higher ED value, and the prestressing in the fiber contributes more to the increased ED values.

Effect of heat treatment and end-hook geometry on pullout behaviour of heavily cold worked superelastic NiTi shape memory alloy fibres embedded in concrete

In this study, superelastic fibres were fabricated from heavily cold worked shape memory alloy (SMA) wire followed by heat treatment, with the goal of enhancing fibre pullout performance and simplifying the fibre production process. The effects of annealing at 350 °C, 450 °C, and 550 °C for 20, 40, and 60 min on the tensile properties of the cold worked SMA were studied. Monotonic and cyclic single fibre pullout tests were conducted using an embedment length of 30 mm. The fibres had straight, 3D, 4D, and 5D end-hook geometries and were embedded in normal strength (NS), high performance (HP), and ultra-high-performance (UHP) concrete. The results demonstrated that heat treatment at 350 °C for 20 and 40 min produced significantly higher peak load, pullout energy, average bond strength, and equivalent bond strength values as compared to the properties of fibres exposed to other temperatures and durations. Heat treatment at 350 °C for 40 min showed the highest re-centring and cumulative energy dissipation under cyclic pullout. Pullout performance significantly increased when either mechanical anchorage or concrete strength were increased. Among the SMA fibre geometries, 5D in NS concrete, 4D and 5D in HP concrete, and 3D and 4D fibres in UHP concrete generated sufficient resistance for martensitic transformation that resulted in a significantly higher re-centring ratio and cumulative pullout energy under cyclic loading than was observed for their steel counterparts.

Mechanical Behavior of Shape Memory Alloy Fibers Embedded in Engineered Cementitious Composite Matrix under Cyclic Pullout Loads.

The incorporation of superelastic shape memory alloy (SMA) fibers into engineered cementitious composite (ECC) materials can provide high seismic energy dissipation and deformation self-centering capabilities for ECC materials. Whether the SMA fibers can be sufficiently bonded or anchored in the ECC matrix and whether the mechanical properties of the SMA fibers in the ECC matrix can be effectively utilized are the key scientific issues that urgently need to be studied. In order to study the mechanical behavior of SMA fiber embedded in ECC matrix, four groups of semi-dog-bone pullout specimens were fabricated, and the cyclic pullout tests were conducted in this paper. The pullout stress, displacement, and self-centering capability were analyzed, and different influencing factors were discussed. The results show that the knotted ends can provide sufficient anchorage force for SMA fibers, and the maximum pullout stress of SMA fiber can reach 1100 MPa, thus the superelasticity can be effectively stimulated. The SMA fibers show excellent self-centering capability in the test. The minimum residual deformation in the test is only 0.29 mm, and the maximum self-centering ratio can reach 0.93. Increasing bond length can increase the ultimate strain of SMA fibers with knotted ends, but reduce the maximum pullout stress. Increasing fiber diameter can increase both the ultimate strain and the maximum stress of knotted end SMA fibers. While neither bond length nor fiber diameter has significant effect on the self-centering ratio. This paper provides a theoretical basis for further study of the combination of SMA fibers and ECC materials.

Influence of cyclic load on pullout stiffness of geogrid embedded in well-graded gravel

Railway structures applied to high-speed railways must achieve high performance in terms of strength and deformation characteristics. This requirement has led to the widespread use of geosynthetic-reinforced soil (GRS) structures. For the design of GRS structures, it is important to evaluate not only the tensile strength of the geosynthetic but also the pullout stiffness (spring constant of geosynthetic). Hence, a series of cyclic pullout loading tests were conducted to evaluate the pullout characteristics of various types of reinforcement embedded in the soil. Moreover, these test results were compared with the results of in-isolation tensile tests with the same loading histories. The experiments revealed that the pullout stiffness increased with an increase in the confining pressure and in-isolation tensile stiffness, but decreased with an increase in the relative displacement between the soil and reinforcement. Although the pullout stiffness was found to be affected by factors such as experimental conditions and type of reinforcement, a similar trend was observed in the results of several other tests when examining the relationship between the normalized pullout stiffness and the average strain generated in the reinforcement. This interesting correlation can be taken into account during the design of GRS structures that support bridge girders.

Effect of Clayey Fine Content on Cyclic Deformative Pullout Behavior of PET Geogrid Embedded in Pure Sand

Effect of Clayey Fine Content on Cyclic Deformative Pullout Behavior of PET Geogrid Embedded in Pure Sand

Fatigue deformation and damage characteristics of bolting system under stress-controlled cyclic pullout

This study explored the fatigue mechanical properties and acoustic emission (AE) characteristics of bolting system under cyclic pullout tests controlled by different upper stress levels. A novel compression-pull load conversion device was designed to precisely apply cyclic pullout load on bolting system. Strain gauges and AE sensors were employed to capture the surface strain variations of rock bolts and microfracture development during static and cyclic testing. The fatigue strength, deformation, axial/shear stress distributions and AE characteristics of the bolting system were comprehensively investigated. Fatigue threshold, an important value determining the service life of a bolting system, was supposed to be lower than 85% of the static strength in this study. The bolt residual slip strain curve was S-shaped and comprised three stages: the initial stage, constant-velocity stage and acceleration stage. The constant-velocity stage accounted for most of the fatigue life and was the main stage of fatigue development. The fatigue failure of the anchorage system was presumably controlled by the entire static stress–strain process, and the residual strain at fatigue failure corresponded to the peak strain at the peak stress under static loading. The anchorage fatigue damage development completely coincided with the residual strain evolution, and the turning points were identical between the different deformation stages. Based on the residual slip strain development, nonlinear inverted S-shaped cumulative fatigue damage models were proposed for different upper stress levels. A comparison of the results from different samples revealed that the damage evolution was highly dependent on the upper stress level. The fatigue life of the bolting system decreased as the upper stress level increased due to the increased steepness of the second stage and the decreased proportion of the second stage to the entire fatigue process.

Post-cycling Interface Strength Test of Geogrids

Geosynthetic-reinforced soil structures are commonly used in seismic design in regions. The performance of GRES under seismic conditions can be found to range from very good to catastrophic. This paper presents the implementation of a test to evaluate the influence of pre-cycling on the post-cycling resistance of a soil–geogrid system. Tests were performed on a PVE uniaxial geogrid with a tensile strength of 400 kN/m and a clean sand with 89% compaction and friction angle of 37.5°. The system was subjected to cyclic pullout tests at 40 and 80% of the monotonic strength. After the pre-cycling, a posterior monotonic pullout test was performed to evaluate the influence of the previous cycling on the final post-cycling strength. A test protocol was established to apply 50, 100, 500 and 5000 cycles with 40% and 80% pullout resistance amplitudes. At the 40% amplitude, the system exhibited stable increasing behavior in terms of resistance and cyclic displacement. Failure was not reached during the pre-cycling stage at 40% amplitude. At the 80% amplitude, the system failed at 250 cycles, and cyclic displacement was found to be erratic for all pre-cycling cases. The results suggest a general tendency of the pre-cycling to increase the post-cycling resistance. However, a combination of high cyclic amplitude with large number of cycles may lead to failure. Exposure to seismic events could be considered in the design of GRES though a rationally chosen reduction factor is applied.

HDPE geogrid-residual soil interaction under monotonic and cyclic pullout loading

The understanding of soil-geosynthetic interaction under cyclic loading conditions is essential for the safe design of geosynthetic-reinforced soil structures subjected to repeated loads, such as those induced by road and railway traffic and earthquakes. This paper describes a series of large-scale monotonic and multistage pullout tests carried out to investigate the behaviour of an HDPE uniaxial geogrid embedded in a locally available granite residual soil under monotonic and cyclic pullout loading. The effects of the pullout load level at the start of the cyclic stage, cyclic load frequency and amplitude, number of cycles and soil density on the load-strain-displacement response of the reinforcement are evaluated and discussed. Test results show that the cumulative displacements measured along the length of the geogrid during cyclic loading increased significantly with the pre-cyclic pullout load level and the load amplitude. In contrast, the cumulative cyclic displacements were found to decrease with increasing frequency and soil density. In medium dense soil conditions, the geogrid post-cyclic pullout resistance decreased by up to 20%, with respect to the value obtained in the comparable monotonic test. However, for dense soil, the effect of cyclic loading on the peak pullout forces recorded during the tests was almost negligible.

Cyclic pullout behavior of helical anchors for offshore floating structures under inclined loading condition

Helical anchors are an effective option to support offshore floating structures with mooring and anchoring systems, where wave and tidal forces are the predominant load components leading to cyclic and inclined loading conditions. In this study, the cyclic and inclined pullout load carrying behavior of helical anchors was investigated. Large-deformation finite element (FE) analysis using the coupled Eulerian–Lagrangian (CEL) method was performed to simulate the cyclic pullout load response of helical anchors. Various configuration conditions of the helical anchor and loading direction, including the number and diameter of helical plate, plate arrangement and load inclination angle (θ), were considered in the analysis. Induced displacements were most significant during the first loading cycle, whereas those for subsequent loading cycles were relatively small. The geometry condition of the helical anchor less affected the pullout load carrying behavior as θ increased. The horizontal displacements (δh) were larger than the vertical displacements (δv) when θ was larger than 30°. When θ was smaller than 30°, δv was more dominant component. It was found that the configuration with top-down increasing diameter was more effective to enhance the pullout load carrying behavior than the conventional bottom-up increasing diameter configuration.

Evaluation of Bonding Interface Strength by Cyclic Pullout Test of Soldered Thin Copper Wire

Evaluation of Bonding Interface Strength by Cyclic Pullout Test of Soldered Thin Copper Wire

Performance of Geosynthetic-Reinforced Soils Under Static and Cyclic Loading

This paper investigates and discusses the composite behavior of geosynthetic reinforced soil mass. It presents the results of a series of large-scale laboratory tests supported by analytical methods to examine the performance of geogrid reinforcement subjected to static and cyclic pullout loading. The testing equipment and procedures used for this investigation are outlined. The results show that geosynthetic reinforcement can mobilize great resistance to static pulling load under high confining pressures. The reinforcement exhibits gradual deformation under cyclic loading showing no sign of imminent pullout failure for all levels of applied loads. In general, the results demonstrate that geosynthetic can be used in situations where loads are non-static, although care will be required in ensuring that appropriate factors of safety are applied to control the resulting deformation. A simplified analytical model for calculating the pulling capacity of geosynthetic reinforcement is proposed.

Monotonic and Cyclic Bond Behavior of Deformed CFRP Bars in High Strength Concrete.

Composite reinforcing bars (rebars) that are used in concrete members with high performance (strength and durability) properties could have beneficial effects on the behavior of these members. This is especially vital when a building is constructed in an aggressive environment, for instance a corrosive environment. Although tension capacity/weight (or volume) ratios in composite rebars (carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), etc.) are very high when compared to steel rebars, major weaknesses in concrete members reinforced with these composite rebars may be the potential consequences of relatively poor bonding capacity. This may even be more crucial when the member is subjected to cyclic loading. Although monotonic bond tests are available in the literature, only limited experimental studies exist on bond characteristics under cyclic loading conditions. In order to fill this gap and propose preliminary design recommendations, 10 specimens of 10-mm-diameter ribbed CFRP rebars embedded in specially designed high strength concrete (f’c = 70 MPa) blocks were subjected to monotonic and cyclic pullout tests. The experimental results showed that cyclically loaded CFRP rebars had less bond strength than those companion specimens loaded monotonically.

Geosynthetics Under Cyclic Pullout and Post-cyclic Monotonic Loading

Several real life reinforced soil structures such as traffic supporting embankments and pavements are subjected to cyclic loads. The behaviour of soil-reinforcement interface under cyclic load is different from that under monotonic load. In the investigation reported herein, cyclic pullout tests were conducted on geogrid embedded in sand. A load controlled pullout test apparatus complying with the dimensions suggested by ASTM D-6706-01 was designed and fabricated in-house. Modular units for applying both cyclic and monotonic load were also designed and fabricated. Cyclic load was applied through a pneumatic double acting air cylinder. In addition, the setup consisted of a signal generator and a filter lubricator regulator volume booster. The effect of normal stress and cyclic load on the pullout behaviour was studied. It was found that cyclic loads of a lower magnitude than the monotonic capacity could cause failure. In the case of cyclic loads of small magnitude, the displacements showed tendency to stabilize. In the case of higher magnitudes of cyclic loads, the displacements progressively increased to failure. An initial stiffness was noticed in the system due to the initial densification achieved near the interface due to the dynamic nature of the cyclic pullout forces. Normal load as well as cyclic load played important roles in the number of cycles to cause failure. Post-cyclic monotonic tests showed the effect of degradation of the soil-geosynthetic interface after subjecting the same to certain number of load cycles.

Experimental Study on Injected Anchors for the Seismic Retrofit of Historical Masonry Buildings

ABSTRACTThis article reports the results of a research study on the behavior of injected anchors in historical masonry under cyclic loads. Laboratory tests with masonry specimens (bricks and mortar with low characteristics to replicate real historical masonry) were conducted to analyze the response of steel anchors injected using a special sock and with different types of mortar (cement and lime based). The test benches replicate the real condition of the use of these anchors: they allow simulation of the connection of masonry panels (T and L connections) or the anchor of steel ties to contrast the arch thrust. Monotonic and cyclic pullout tests were conducted on short and long anchors to define the loss of strength under cyclic loads for different situations. The results yielded load-displacement graphs, steel bar deformation graphs of the anchors’ length, a qualitative bond stress curve, and a comparison among maximum strengths obtained under several conditions.

Design Parameters for Seismically Retrofitted Masonry-to-Timber Connections: Injection Anchors

ABSTRACTProper structural connections play an important role in ensuring seismic loads distribution and developing global damage mechanisms of structures. In historical unreinforced masonry buildings, effective connections between masonry walls and timber floors or walls through the use of anchors can prevent the occurrence of out-of-plane mechanisms and promote box-like behavior. Particularly for historic structures, injection anchors can comply with requirements as decreased architectural impact and minimum intervention. Therefore, this article aims at developing structural design parameters and recommendations that allow the design of connections retrofitted with injection anchors, found in historical unreinforced masonry buildings, built during the 19th century, in Portugal. Existing strength prediction formulae based on behavior models, and idealized force-displacement curves were developed to better fit the results obtained from a series of quasi-static monotonic and cyclic pullout tests carried out on pairs of injection anchors. Behavior models were able to approximate the experimental results, if adapted to the specificities of historical masonry. Further validation is needed, particularly for the combined cone-bond model. From the idealized curves, displacement acceptance criteria, expected forces, and behavior factors were proposed, according to the performance-based approaches recommended by EC8-Part 3 and ASCE/SEI 41–13. Finally, retrofit design recommendations were addressed.

Using Acoustic Emission Monitoring to Observe the De-Bonding Behavior of Rebar in Cyclic Pull-Out Tests

This research aimed to reveal the bond behavior and failure mechanism of varying size rebar embedded in concrete with inside pre-crack through a series of quasi-static/cyclic pull-out tests and real-time acoustic emissions monitoring (AE). The obtained AE signal density records of the tests provide potential usage for evaluate the safety of reinforced concrete (RC) structure subjected to cyclic load, as well as quantitative study in the remaining life of RC after earthquake or shake damage.