Abutment Rotation Research Articles

Effect of inclined pile on seismic response of bridge abutments undergoing liquefaction—Induced lateral displacement: Case study of Nishikawa bridge in the 2011 Great East Japan earthquake

It is reported that the inclined pile could be either beneficial or detrimental for the abutment they support in the condition of liquefaction—induced lateral displacement. To clarify the effect of inclined pile on seismic response of bridge abutments undergoing liquefaction—induced lateral displacement, numerical analyses were carried out on the damaged abutment that was supported by inclined piles and that was displaced riverwards 100 mm–150 mm due to soil liquefaction during 2011 Great East Japan earthquake. Accordingly, a fully coupled dynamic effective stress finite element model was developed for the soil—pile—superstructure system. It was found that the shear failure of the bridge abutment was initialized from the inclined piles and then followed by the middle vertical pile. Moreover, the earthquake—induced liquefaction caused substantial lateral displacement of soils around the piles and thus dominated the backward rotation of the abutments supported by inclined piles. Additionally, the exclusion of the deck pinning effect may lead to a marked increase in the lateral displacement and rotation of abutments. If the abutment were supported by vertical piles, a much larger lateral displacement was expected and the promotion of the earth pressure behind the abutment was the main cause of the forward rotation of the piled abutment.

Effects of seasonal temperature change-induced abutment movements on backfill surface settlements behind integral bridge abutments – Numerical analysis

For an integral abutment bridge (IAB), expansion of its bridge deck at high temperature pushes the integral bridge abutment (IBA) toward the backfill, while contraction of the bridge deck at low temperature pulls the IBA away from the backfill. Over years, these repeated processes may cause large backfill surface settlements behind the abutment. The IBA supported by a single row of H-piles reacts to seasonal temperature changes in a combined behavior of abutment rotation and abutment translation. This paper presents a numerical study, in which the abutment model had limited translation but free rotation. Parametric studies showed that the backfill behind the IAB constructed in summer had the largest settlement right behind the abutment but the backfill behind the IAB constructed in winter had the most significant backfill heave away from the abutment. Smooth abutments and short span of IABs reduced the backfill surface settlements significantly.

Calibration and parametric investigation of integral abutment bridges

Integral abutment bridges (IABs) are a special type of bridges that are built free of joints on the superstructure to overcome the undesirable consequences associated with conventional jointed bridges. Despite of the proven advantages of IABs, no consensus exists among bridge engineers about design guidelines. This paper presents a parametric study validated to a field monitored concrete IAB using a three-dimensional finite-element model to study the parameters that affects the bridge response. Bridge length, pile size and orientation, and soil type were included in the study. Bridge components were simulated using 3D solid elements for best reflection of the real behavior of the IAB. Nonlinear p-y method was employed to model soil-pile and soil-abutment interactions. Several shrinkage models, earth pressure theories and temperature distribution across the bridge superstructure were considered in simulating the field response of the IAB. The outcomes of the calibration process were utilized in building sound models for the parametric study. The soil stiffness around the pile was found to has more impact than the pile orientation on the pile displacement. Pile stresses were found to be proportional to the soil stiffness and inversely proportional to the pile stiffness. Moreover, the maximum stresses occurred within the middle segment of the pile rather than the pile-abutment interface due to apparent abutment rotation. The study promotes understanding of important facts which could assist in a better IAB design.

The Influence of a Positioning Hex on Abutment Rotation in Tapered Internal Implants: A 3D Finite Element Model Study

The purpose of this study was to investigate the resistance against rotation of a two-piece abutment with or without the presence of a positioning hex in tapered internal connection implant systems. A tapered internal connection implant with an 11-degree internal oblique angle was placed into a constructed three-dimensional (3D) bone model. Two types of abutments were compared: hex-type abutments with a positioning hex and two-piece round-type nonhex abutments. Vertical compressions equivalent to the screw tightening torque of 30 Ncm and 40 Ncm were applied to the abutment screws. A horizontal load of 150 N was applied to the superstructure to create moments. The contact area between the implant and abutment was compared and analyzed. The rotational displacement of the abutments was investigated as well. When a preload equivalent to 40 Ncm of tightening torque was applied, the round-type abutment exhibited a larger contact area than the hex-type abutment by approximately 2.5% to 3.5% in contrast to the internal surface area of the implant. When the screw tightening torque of 30 Ncm was applied, the rotational displacement of the hex-type abutment was approximately 0.54 degrees and the round-type was approximately 1.16 degrees under clockwise moment loading. Within the limitations of this study, it can be assumed that the hexagonal design of the abutment acts as rotational resistance against moments.

Experiment on Interaction of Abutment, Steel H-Pile and Soil in Integral Abutment Jointless Bridges (IAJBs) under Low-Cycle Pseudo-Static Displacement Loads

Soil-abutment or soil-pile interactions under cyclic static loads have been widely studied in integral abutment jointless bridges (IAJBs). However, the IAJB has the combinational interaction of soil-abutment and soil-pile, and the soil-abutment-pile interaction is lack of comprehensively study. Therefore, a reciprocating low-cycle pseudo-static test was carried out under an cyclic horizontal displacement load (DL) to gain insight into the mechanical behavior of the soil-abutment-pile system. Test results indicate that the earth pressure of backfill behind abutment has the ratcheting effect, which induced a large earth pressure. The soil-abutment-pile system has a favorable energy dissipation capacity and seismic behavior with relatively large equivalent viscous damping. The accumulative horizontal deformation in pile will be occurred by the effect of abutment and unbalance soil pressure of backfill. The test shows that the maximum horizontal deformation of pile occurs in the pile depth of 1.0b~3.0b of pile body rather than at the pile head due to the accumulative deformation of pile, which is significantly different from those of previous test results of soil-pile interaction. The time-history curve for abutment is relatively symmetrical and its accumulative deformation is small. However, the time-history curve of pile is asymmetrical and its accumulative deformation is dramatically large. The traditional theory of deformation applies only to the calculation of noncumulative deformation of pile, and the influence of accumulative deformation should be considered in practical engineering. A significant difference of inclinations in the positive and negative directions increases when the displacement load is relatively large. The rotation of abutment when bridge expands is larger than that when bridge contracts due to earth pressure of backfill.

Mechanical stability of all-ceramic abutments retained with three different screw materials in two-piece zirconia implants-an in vitro study.

To measure the abutment rotation and fracture load of two-piece zirconia implants screwed with three different abutment screw materials. Thirty-six zirconia implants with 36 zirconia abutments were distributed into 3 test groups: group G connected with gold screws, group T with titanium screws, and group P with peek screws. In the first part of the study, the rotation angle of the abutments was measured. The second part of the study measured the maximum fracture force of adhesively bonded lithium disilicate crowns after artificial aging and fracture modes were reported. In group G, the median rotation angle was 8.0°, in group T 11.6°, and in group P 9.5°. After artificial aging, no screw loosening, crown, abutment, or implant fracture occurred. The median fracture force in group G was 250N, in group T 263N, and in group P 196N. Rotation angles and fracture loads of two-piece zirconia implants with gold, titanium, or peek screws showed no significant differences; however, fracture loads showed inferior results for group P. The indication for the material peek as an abutment screw is still questionable and should be considered carefully.

The influence of a positioning hex on abutment rotation in tapered internal implants‐A 3‐D finite element model study

The influence of a positioning hex on abutment rotation in tapered internal implants‐A 3‐D finite element model study

Seismic damage of gravity abutment in liquefied ground

Purpose Abutment damage in liquefied ground is an important form of seismic damage of bridge structure. This paper aims to further research the effect of beam restriction on seismic damage mode of abutment in liquefied ground. Design/methodology/approach Based on the investigation of the seismic damage of Shengli Bridge in Tangshan earthquake, the finite element software dynamic effective stress analysis for ground (UWLC) is used to simulate the seismic damage of Shengli Bridge, and the results were compared with the actual seismic damage results. Then, the influences of the horizontal binding force of the beam, the liquefaction layer thickness, the top weight of the abutment, the peak acceleration, the liquefaction layer buried depth and the type of the foundation soil on the abutment seismic damage model are studied. Findings The results show that numerical simulation results are consistent with the actual seismic damage, and it is feasible to use UWLC software to simulate seismic damage. The results show that the seismic failure mode of the gravity abutment in liquefied ground is slip–rotation coupling type, not single slip type or rotation type. The large deformation of abutment bottom layer, horizontal binding force of the beam and post-stage soil pressure are the main reasons for abutment rotation or even destruction. Research limitations/implications A series of basic assumptions are used in the calculation process in this paper. The gravity abutment is defined as the elastic body and neglects its local deformation. The soil layer is a homogeneous isotropic. The consolidation process and the drainage boundary problem are not considered in the calculation process. Therefore, the paper may have some limitations. Originality/value To further research the seismic damage mode and influencing factors of abutment in liquefied ground, in this paper, based on the investigation of the seismic damage of Shengli Bridge in Tangshan earthquake, the finite element software UWLC is used to simulate the seismic damage of Shengli Bridge, and the results were compared with the actual seismic damage results. The seismic damage mode and influencing factors of gravity abutment in liquefied ground have been studied.

Lateral spreading-induced abutment rotation in the 2011 Christchurch earthquake: observations and analysis

A series of strong earthquakes near Christchurch, New Zealand, occurred between September 2010 and December 2011, causing widespread liquefaction throughout the city's suburbs. Lateral spreading developed along the city's Avon River, damaging many of the bridges east of the city centre. The short- to medium-span bridges exhibited a similar pattern of deformation, involving back-rotation of their abutments and compression of their decks. By explicitly considering the rotational equilibrium of the abutments about their point of contact with the rigid bridge decks, it is shown that relatively small kinematic demands from the laterally spreading backfill soil are needed to initiate pile yielding, and that this mode of deformation should be taken into account in the design of the abutments and abutment piles.

Monitoring and Analysis of Abutment-Soil Interaction of Two Integral Bridges

Field tests of two jointless bridges are presented, focusing on the magnitude and significance of earth pressure behind the abutments. The Haavistonjoki Bridge is a 56-m-long, continuous three-span bridge. Instrumentation was used to measure the horizontal displacement of an abutment, abutment rotation, abutment pile strains, earth pressures behind the abutments, superstructure displacements, frost depth, and air temperature. The measured earth pressures were compared with pressures that had been calculated on the basis of Nordic codes of practice and the Eurocodes pertaining to bridges. The bridge over the Leduan is a single-span composite bridge with a cast-in-place concrete deck on top of two steel beams. This bridge, spanning 40 m, is slender, with a 1.7-m-high superstructure. The bridge was fitted with strain and displacement gauges and short-term measurements were made using a loaded truck. The field test results for this bridge were verified with calculations based on an abutment rotation stiffness calculation model developed during the research presented in this paper.

Behavior of an Integral Abutment Bridge in Minnesota, US

The behavior of an integral abutment (IA) bridge near Rochester, Minnesota, was investigated from the beginning of construction through approximately 7 years of service using data collected from more than 150 instruments installed in the bridge during construction. Long-term bridge shortening was observed to increase with time, based on the readings of horizontal extensometers installed behind the abutments and strains measured using concrete embedment gauges in the girders. Abutment rotations and measured pile curvatures also steadily increased with time. The time-dependent behavior of the bridge can be explained from a combination of factors including the concrete creep and shrinkage, the increase of backfill soil pressure, the yielding of the reinforcement across the joint between diaphragm and pile cap, and the alternation of the relative humidity and temperature. In comparing the measured pile axial force and moment data to axial force–moment interaction capacity curves, it was estimated that approximately 20% of the pile flange cross section yielded in compression under the abutment. The likelihood of low-cycle fatigue was determined to be small. On the basis of the findings of this research, it is recommended that the time-dependent effects of concrete IA bridges should be considered in structural design and analysis for both long-term bridge shortening and abutment rotation if these long-term effects are anticipated to be significant. More research is needed to determine the parameters for the cases when a time-dependent analysis of an entire integral bridge system is warranted, that is, bridge length limit and soil condition.

ガイドプレーンの設定条件がエーカースクラスプ装着時の支台歯変位に及ぼす影響

Three types of guide plane were compared to clarify the effect of guide plane setting conditions on abutment displacement which arises when an Akers clasp is inserted. An experimental model with an artificial periodontal membrane made of hydrophilic vinyl polysiloxane impression material was created. Abutments given a guide plane with only a clasp body (G1), a guide plane whose span extended as far as the reciprocal clasp arm shoulder region diametrically opposite the retention area (G2), and a guide plane for the entire reciprocal clasp arm region (G3) were created, and an Akers clasp was made for each abutment. The amount of abutment displacement and the degree of rotation that arose in the abutment when the Akers clasp was inserted were detected with three laser displacement sensors for comparison. The amount of abutment displacement that arose when the clasp was inserted was higher with G1 than with G2 and G3 in the lingual and distal directions, and no difference was seen between G2 and G3. It was lower with G1 than with G2 and G3 in the buccal direction, and no difference was seen between G2 and G3. It was high with G1 in the mesial direction, and the abutment rotation was high, whereas they were low in the case of G3. A difference was seen between each condition. Differences in guide plane setting conditions affected the abutment displacement that arose when an Akers clasp was inserted, suggesting that a difference in reciprocal action is seen depending on the setting conditions of the guide plane.

Predicted and Measured Response of an Integral Abutment Bridge

This project examined several uncertainties of integral abutment bridge design and analysis through field-monitoring of an integral abutment bridge and three levels of numerical modeling. Field monitoring data from a Pennsylvania bridge site was used to refine the numerical models that were then used to predict the integral abutment bridge behavior of other Pennsylvania bridges of similar construction. The instrumented bridge was monitored with 64 gages; monitoring pile strains, soil pressure behind abutments, abutment displacement, abutment rotation, girder rotation, and girder strains during construction and continuously thereafter. Three levels of numerical analysis were performed in order to evaluate prediction methods of bridge behavior. The analysis levels included laterally loaded pile models using commercially available software, two-dimensional (2D) single bent models, and 3D finite element models. In addition, a weather station was constructed within the immediate vicinity of the monitored bridg...

A locating splint for placing implant abutments

The prosthodontic phase of many implant techniques uses the following protocol: (1) making an implant-level impression, (2) the selection and preparation of abutments, (3) abutment placement and making the definitive impression, and (4) the fabrication and placement of the definitive restoration. After placement of the abutment, a definitive impression is required because slight rotation of the abutment is commonly observed during the torquing procedure. This article presents a technique to avoid abutment rotation and, hence, the additional definitive impression procedure can be omitted. It reduces the number of clinical visits and also avoids the need for the fabrication of a provisional restoration after abutment insertion. The definitive restoration may be fabricated directly on the abutment and inserted at the same visit as abutment connection. This technique may be used with any implant system where conventional machined or prepared abutments are used, as well as custom-made abutments with CAD/CAM. Only simple laboratory procedures and materials are required. The technique can also be applied in multiunit implant situations.

Cyclic loading of loose backfill placed adjacent to integral bridge abutments

Abutments for integral (or jointless) bridge decks experience cyclic rotations/translations due to temperature induced expansion and contraction of the decks. These movements generate cyclic displacements within the backfill placed adjacent to the abutment. To assist understanding of the consequences of such displacements, an experiment is described here in which the movements within a laboratory scale model of an abutment and loose backfill are measured. The distributions of displacements and strains within the backfill are recorded using an optical measurement technique. It is found that the cyclic rotations of an abutment in loose sand results in significant volumetric contraction of the sand mass in the area where an active wedge is created. The degree of contraction is related to the abutment rotation and the number of such rotations. Many of the observed features, including the trend for large increases in lateral stresses on the abutments, may be attributed to the tendency of loose backfill to experience strain hardening due to repeated cyclic straining.

Field Performance of Integral Abutment Bridge

The behavior of an integral abutment bridge near Rochester, Minnesota, was investigated from the beginning of construction through several years of service by monitoring more than 180 instruments that were installed in the bridge during construction. The instrumentation was used to measure abutment horizontal movement, abutment rotation, abutment pile strains, earth pressure behind abutments, pier pile strains, prestressed girder strains, concrete deck strains, thermal gradients, steel reinforcement strains, girder displacements, approach panel settlement, frost depth, and weather. In addition to determining the seasonal and daily trends of bridge behavior, live-load tests were conducted. All of the bridge components performed within the design parameters. The effects from the environmental loading of solar radiation and changing ambient temperature were found to be as large as or larger than live-load effects. The abutment was found to accommodate superstructure expansion and contraction through horizontal translation instead of rotation. The abutment piles appeared to be deforming in double curvature, with measured pile strains on the approach panel side of the piles indicating the onset of yielding.

Failure of All-ceramic Fixed Partial Dentures in vitro and in vivo: Analysis and Modeling

Hertzian cone cracks visible at the loading site of 20 all-ceramic fixed partial dentures (FPDs), tested in vitro, led to the hypotheses that failure was due to the propagation of localized contact damage crack systems (Hertzian stress state) and that such damage was an unlikely clinical failure mode. Fractographic analysis of the 20 laboratory-failed and nine clinically-failed all-ceramic FPDs allowed for definitive testing of these hypotheses and a comparison between in vitro and in vivo failure behavior. In all cases, failure occurred in the FPD connectors (none from contact damage), with approximately 70 to 78% originating from the interface between the core and veneer ceramics. The coincidence between failure origins provides strong evidence that the in vitro test modeled aspects of structural behavior having clinical importance. The fractographic observations, coupled with the in vitro failure load data, furnished very specific boundary conditions which were applied to constrain mathematical models of FPD connector failure. Finite element analysis (FEA) of the laboratory FPDs found that maximum principal tensile stresses would occur at locations consistent with the fractographic observations only if: (1) there were appropriate elastic moduli differences between the ceramics; and (2) a small amount of abutment rotation was allowed. Weibull failure probability (Pf) calculations, incorporating FEA stress profiles, very closely replicated the laboratory failure distribution only when: (1) the veneer ceramic was much weaker than the core ceramic; and (2) the Weibull modulus of the core-veneer interface was much lower than that for the free veneer surface (i.e., the interface is of lower quality with regard to defects).(ABSTRACT TRUNCATED AT 250 WORDS)