Anchor Rod Research Articles

Numerical Simulation Research for Stress and Distortion of Pile-Anchor Support Structure of the Deep Foundation

This article has used the ADINA numerical calculus software to simulate the deep foundation excavation and supports process, as well as analyzing the analogue result in the project of the Xia Gong in ShenYang City. The results illustrate that (1) it is essential to optimize the pile earth's horizontal displacement and the mechanical situation of anchor rod. (2) It makes soil’s horizontal displacement and the mechanical situation of anchor rod more reasonable by changing the anchor rod vertical spacing and length ，hence obtains that the anchor parameter change has the great influence on the distortion of the support structure.

Analysis on Qinyu Landslide and Treatment Measures in G212 Highway

G212 highway is a primary route from Gansu to Sichuan province. Landslides and debris flows along G212 highway often occurred in Longnan region of Gansu province. According to finite element method of saturated-unsaturated seepage, variation of pore water pressure of saturated-unsaturated slope under transient seepage field was simulated in the cases of rainfall and groundwater and safe factor of the slope stability was obtained, based on Fredlund’s strength theory of unsaturated soil and Bishop’s method. As an example of the Qinyu west landslide, the drainage, guarding face wall and frame structure with pre-stress anchor rod were very effective and feasible for the landslide treatment measures.

A practical method of design of concrete pedestals for columns for anchor rod tension breakout

This technical note considers concrete pedestals bearing steel and concrete columns attached to the foundation with cast-in anchor rods. One mechanism of pedestal failure — the anchor rod breakout in tension — is considered. Uplift and shear forces and bending moments in the base cause tension in the anchor rods. Classical methods of statics and finite element analysis (FEA) are applicable to establish the anchor likely to fail first. For the design of the anchor rod embedment in the concrete, the new “cone balancing” method is proposed. It considers equilibrium of the pullout cone of concrete, ascertained by development of vertical reinforcing bars into the pullout cone and below the failure plane. The method allows determination of tensile force in each individual rebar and direct checking of its size and development length.

Influence of Flexibility on the Fatigue Performance of the Base Plate Connection in High-Mast Lighting Towers

This study investigates the effect of base connection geometry on base plate flexibility and the fatigue performance of multisided high-mast lighting towers. Three parametric studies investigating the effect of base plate thickness, tube wall thickness, and anchor rod configuration are discussed in this paper. The results of this study show that of the geometric parameters considered, base plate thickness has the largest influence on the stresses in the tube wall adjacent to the weld toe. By increasing the base plate thickness of the tower, significant improvement to the fatigue life is observed because the maximum stress, and hence stress range, at the base plate-to-tube wall thickness is reduced due to a reduction in local bending in the tube wall.

Numerical modelling of anchor bolts under pullout and relaxation tests

The anchoring of structure elements in a reinforced concrete foundation is often performed by means of cast-in-place anchors. Their main function is to transfer normal loads, tension and compression, and possible shear loads according to the force transferred to the base of the structure. This study is limited to the study of long and smooth anchor rods with an anchor washer on the end, embedded in concrete. The anchor rods are prestressed in order to minimize the effects of fatigue. In normal practice to design these anchors the long-term behaviour of concrete is not taken into account although concrete creep involves a decrease in the initial prestress level. This paper presents the experimental results of pullout and relaxation tests and a finite element modelling of the joint. The time-dependent behaviour of concrete is taken into account in a visco-elastic analysis using the creep laws given in Eurocode 2. The numerical results are coherent with the measurements obtained in experimental tests. The decrease in the prestress is correctly simulated and its evolution in time can be estimated.

Experimental behaviour of anchor bolts under pullout and relaxation tests

The anchoring between a metallic component and a concrete block is an essential point in stability and durability of the structure. This joint has to transfer the deadweight of the structure and tensile, compressive and shearing loads created by the structure in service. This study focuses on the joint constituted of long anchor bolts cast-in-place. The anchor rods are prestressed in order to minimize the effects of fatigue stress. To design these anchors the long-term behaviour of concrete is not taken into account whereas the concrete creep and shrinkage involves a decrease in the initial prestress level. This paper presents experimental results of pull-out tests and mass-spring modelling of the joint is proposed. In this model the long-term behaviour of the joint is taken into account using the creep and shrinkage laws given in Eurocode 2. The modelling of the evolution in time of the rod prestress shows good agreement with the measurements obtained in relaxation tests.

EXPERIMENTAL AND ANALYTICAL INVESTIGATIONS OF SCAFFOLDS WITH ANCHOR ROD AND PLANK

This paper investigates the influence of anchor rods, planks and inner knee braces on the critical load of scaffolding systems under concentric and eccentric loads in construction. The steel rebar of grade 3 is used in place of the patent anchor rod in this study. The results show that the critical load of the scaffolding system increases by 1.5 times when anchor rods of a length of 30 cm are used on two sides of each story of the scaffolding system. The critical load increases by 4 times when the scaffolding system has both the anchor rods and plank. The critical load of the scaffolding system with the anchor rods placed on each story is twice as large as that with anchor rods added every two stories; the failure mode of the system also switches from the in-plane to out-of-plane mode. The 30-cm-long anchor rod, used in place of a steel bar of grade 3, provides a good lateral restraint to the scaffolding system. Moreover, the setup plank can significantly elevate the critical load of the scaffolding system; the critical load increases approximately 1.5 times under the concentric load, and increases up to 2.2 times under the TL/4 eccentric load, defined as a load applied at a quarter distance from the end. The anchor rod and the plank should always be included in a scaffolding system to improve its stability, especially under the eccentric loads in construction.

Experimental Determination of Resistance Characteristics of Support Details Used in Prestressed Concrete Bridge Girders

Static load tests were performed on support details used at the ends of prestressed concrete pedestrian bridge girders to determine the resistance characteristics of girder supports in the direction perpendicular to the longitudinal axis of the girders. The specimens tested represent support details that have also been widely used in prestressed concrete highway bridges in Minnesota and in other states. Two specimens, one representing the free-end detail and one representing the restrained-end detail were subjected to a combination of vertical and lateral loads. The applied loading was intended to simulate the loading conditions to which the girder ends would be subjected in the event of an over-height vehicle collision with the bridge. The tests revealed two types of lateral load resisting mechanisms depending on the type of support detail. The specimen with the free-end detail resisted the lateral loading through sliding friction between the components of the support assembly. Deformation of this specimen was a combination of shear deformation of the bearing pad and sliding of various support components. The restrained-end detail exhibited larger lateral load capacity than the free-end detail due to the resistance provided by the anchor rods that were intended to prevent the lateral movement of the girder ends. Failure of the specimen with restrained-end detail was due to the concrete breakout and bending of the anchor rods.

Seismic Column Demands in Ductile Braced Frames

In ductile braced frames, column seismic demands depend on the strength of ductile elements and yielding patterns that occur during earthquake loading. Column demands were investigated in buckling restrained braced frames (BRBFs), special concentrically braced frames (SCBFs), and eccentrically braced frames (EBFs) with different heights (3, 9, and 18 story) and strength levels using nonlinear time history analysis. For columns at the base of 9- and 18-story BRBFs and EBFs, axial demands observed from the analyses were 55–70% of demands commonly used in design, indicating potential cost savings on columns, anchor rods, base plates, and foundations in tall buildings; however, in low-rise SCBFs with braces in the 2-story X-configuration, column axial demands were up to 100% greater than those commonly used in design because of force redistribution that occurs after brace buckling. Column rotations in all frames were less than 0.03rad. These rotation demands are lower than rotation capacities that have been demonstrated in other work.

FEM analyses of stress and deformation of a flexible inner pressure bolt

The flexible inner pressure bolt is a new kind and new structural bolt (anchor rod). A number of structural improvements and performance test have been carried out. The bolt has superior compatibility to the soft crag and the large distortion tunnel with its flexibility. In order to study its stress, deformation and interaction mechanism thoroughly, a number of large distortion calculations and analyses have been carried out on the bolt by FEM (finite element method), especially with the ANSYS software, based on the updated Lagrangian law. The results show that the maximum stress of the inner wall of the bolt is consistent with an elastic analytic solution. The maximum stress on the body occurs in the vicinity of the enhancement material. The link enhancement of the body seems to be quite essential. The experimental results indicate that the maximum injection pressure in the bolt is 2.5 MPa without link enhancement and 8.3 MPa with the enhancement. This link enhancement effect is highly significant. These results provide some basis for the design, application and anchoring stress analysis of the bolt.

Target reliability based design optimization of anchored cantilever sheet pile walls

In this study, the stability of anchored cantilever sheet pile wall in sandy soils is investigated using reliability analysis. Targeted stability is formulated as an optimization problem in the framework of an inverse first order reliability method. A sensitivity analysis is conducted to investigate the effect of parameters influencing the stability of sheet pile wall. Backfill soil properties, soil – steel pile interface friction angle, depth of the water table from the top of the sheet pile wall, total depth of embedment below the dredge line, yield strength of steel, section modulus of steel sheet pile, and anchor pull are all treated as random variables. The sheet pile wall system is modeled as a series of failure mode combination. Penetration depth, anchor pull, and section modulus are calculated for various target component and system reliability indices based on three limit states. These are: rotational failure about the position of the anchor rod, expressed in terms of moment ratio; sliding failure mode, expressed in terms of force ratio; and flexural failure of the steel sheet pile wall, expressed in terms of the section modulus ratio. An attempt is made to propose reliability based design charts considering the failure criteria as well as the variability in the parameters. The results of the study are compared with studies in the literature.

Fracture of high carbon high strength anchor rods

During a heavy windstorm, there was failure of anchors supporting transmission towers. We were given the mandate to examine the reasons for the failure of the anchor rods and suggest measures to prevent such failures from occurring. The study involved the in-depth examination of the chemical composition, microstructures, mechanical properties and fracture morphologies of specimens from failed anchors. Results indicated that the chemical composition, yield and tensile strengths of the anchor rods are within the norm of ASTM standard A722. The chemical composition corresponds to that of AISI 1070 with slightly higher manganese and silicon levels. Microstructure is ferrite–pearlite with dominance of pearlite due to the relatively high carbon content. Fracture surfaces of failed anchor rods exhibited pronounced cleavage facets (cleavage steps and river pattern) indicating that failure mode is brittle and the mechanism of fracture is cleavage. There were no signs for the occurrence of fatigue – any beach mark or striations. Final area of fracture showed traces of ductility (small shallow dimples). To prevent brittle failure of anchor rods, their toughness has to be improved. To achieve this, the potentiality of applying HSLA steel technology of micro alloying and TMCP (thermo mechanical control process) has been suggested.

Experimental study on coupling effect of model anchor rod corrosion

Experimental study on coupling effect of model anchor rod corrosion

Discussion on Several Technical Issues in the Technical Regulations for Rock and Soil Anchor Rods (Cables)

Discussion on Several Technical Issues in the Technical Regulations for Rock and Soil Anchor Rods (Cables)

Discussion of “Suspension Cable Design of the New San Franscisco–Oakland Bay Bridge” by John Sun, Rafael Manzanarez, and Marwan Nader

A discussion of a paper with the aforementioned title by J. Sun et al., published in this journal (Volume 9, Number 1, January/February 2004), is presented. The discusser suggests that the octagon strand arrangement, proposed in the original paper to deal with some of the problems created by the unusual cable geometry of the San Francisco-Oakland Bay Bridge, may lead to other difficulties in construction. He also expresses concern about the lack of design details of strand separators in the saddles, cable strand geometry during erection stages and its relationship to the cable final position, and the limited clear space between a strand socket and its anchor rod. He concludes that these problems would make this a very difficult and expensive bridge to build.

Closure to “Suspension Cable Design of the New San Francisco–Oakland Bay Bridge” by John Sun, Rafael Manzanarez, and Marwan Nader

This article presents a closure to a discussion by H. Knox of a paper with the aforementioned title. The original paper was published in this journal (Volume 9, Number 1, January/February 2004) and the discussion was published in this journal (Volume 10, Number 3, May/June 2005). The authors believe that their proposed octagon strand arrangement for the San Francisco-Oakland Bay Bridge is an effective way to alleviate potential strand twist. Space limitations in the original paper prevented presentation of some of the other issues that concerned the discusser, such as the lack of design details of strand separators in the saddles and the limited clear space between a strand socket and its anchor rod. The authors do present a possible solution to a problem concerning cable strand geometry during erection stages.

Project-Specific Steel Sheet Piling Applications

Hot-rolled, heavy-gauge steel sheet piling has advantages over other available products including concrete, vinyl, and fiberglass-reinforced polymers for bulkhead and deep-excavation applications. For FEMA seawall bulkheads, steel sheet piling provides the only practical structural solution available. For deep excavations, steel sheet piling typically provides the most economical solution for the conditions encountered in braced trench and cofferdam construction. A steel sheet pile wall consists of a continuous row of interlock- ing vertical segments that form essentially a straight wall that is capable of acting integrally. There are two primary types of steel sheet pile wall structures: cantilevered and anchored. Walers are commonly used in conjunction with tiebacks to construct anchored sheet pile walls. Tiebacks are typically installed as either ground anchors or anchor rods secured to deadmen. Cofferdams are a special form of steel sheet pile construction in which the method of resistance to soil forces is provided through the ability of the circular footprint to function either as a compression or tension ring. The design of sheet pile walls involves the evaluation of loads imposed by soil, water, surcharging, and other externally applied forces. The analysis of a sheet pile wall includes a determination of the required depth of embedment, sizing of any anchorage systems, and verification that the actual flexural stresses do not exceed the allowable. Safety factors are typically included in the determination of the minimum embedment depth.

Electro-Magnetic-Acoustic Transducers for Automatic Monitoring and Health Assessment of Transmission Lines

This paper presents analysis, design, development, and experimental verification of a non-destructive monitoring system for diagnosis of mechanical integrity of electric conductors based on the concept of Electro-Magnetic-Acoustic Transducers (EMAT). Electric conductors, in general, are exposed to harsh environments. Such conductors include electric transmission lines, anchor rods, and ground mat risers. For automatic failure detection and assessment of mechanical integrity of these conductors, in addition to an effective transducer, feature extraction and pattern recognition techniques have to be employed. Details of the sensor design, neural-based signature analysis, feature extraction, and experimental results of fault detection techniques are presented.

Granular Pile Anchor Foundation (GPAF) System for Improving the Engineering Behavior of Expansive Clay Beds

Abstract Several innovative foundation techniques have been suggested for reducing the detrimental heave of foundations in expansive clays. This paper presents another innovative technique in the form of a granular pile anchor-foundation (GPAF) system for arresting heave and for improving the overall engineering behavior of expansive clay beds. In the GPAF system, the foundation is anchored at the bottom of the granular pile to an anchor plate through an anchor rod. As a result, heave of the foundation is reduced. The laboratory model tests using this new concept of the GPAF system revealed that the heave of the expansive clay beds was reduced by about 96 %. The development of final heave was faster in the case of the expansive clay beds reinforced with the GPAF system. The undrained strength of the clay surrounding the granular pile anchor improved by about 20 %. The tests on two-group granular pile anchors indicated that heave was reduced to a minimum value when the spacing between the granular pile anchors was kept at twice the pile diameter. The compressive load response of the expansive clay bed reinforced with granular pile anchors also improved. The pull-out load of the granular pile anchors increased with increasing diameter and the relative density of the pile.

Some experiences of rock slope protection engineering construction with anchor rod

Some experiences of rock slope protection engineering construction with anchor rod