4. (10) 2. George N. Wade Memorial Bridge • Carries I-81 and the Capital Beltway across the Susquehanna River in Harrisburg, Pennsylvania • 5,188 feet (1,581 m) long • Construction completed in early 1970’s • $42 million Repair Project from 2009-2012. Shear keys are designed and provided in various structures to provide resistance against lateral loads like earthquake loads and sliding forces in various structure such as bridges, retaining walls, basement of residential buildings, precast buildings and culverts, masonry wall in seismic regions, and steel columns. A gravity wall can also be used as a pier or an abutment wall with piles. (1.9 and 2.2 m) in length, respectively. The lateral post-tension was divided into two steps: initial and final. The height of the shear keys is 0.48 m and the thickness is 0.24 m. The widths are 0.96 and 1.56 m for shear keys at abutments and central pier respectively. The gap between shear key and corresponding bridge girder is 60 mm as shown in Fig. and 7 ft I in. A pier essentially consists of two parts i.ee a column shaft and the foundation. This case report presents a simple method of rehabilitating a patient with a pier abutment in the upper right posterior region of the mouth. this could produce a pathologic mobility in the canine or failure of the canine retainer. In addition, lateral post-tension was used at abutments, intermediate diaphragms and at the pier. The initial post-tension was done prior to grouting the shear keys with the intent of repositioning the girders in their theoretical position as girders were erected along the cross slope of the road. Use a non-rigid dovetail connector between the molar pontic and the second premolar. Contents1 Pier:2 Function Of Pier:3 Types Of Piers:4 Abutments:5 Function Of Abutments:6 Types Of Abutments:7 Also Read- TYPES OF CULVERTS Pier: The intermediate supports for the superstructure of a multi-span bridge are known as piers. It is sometimes provided with projections, […] Exterior shear keys have the demerit of the ease of inspection and repair. Semi-retaining abutments generally are designed with a fixed base, allowing wing walls to be rigidly attached to the abutment body . In the event of a severe earthquake, shear keys should function as structural fuses to prevent the transmission of large seismic forces to the abutment piles. The keyway seat of the inverted orientation is farther from the long axis of the anterior abutment, so concern may arise about distal torquing of this tooth. The segment weights vary from 140 tons (127 t) for the Type "A" seg ments to 150 tons (136 t) for the pier and abutment units. Steel 460 ft. Cast-in-Place Concrete 460 ft. Precast and Post Tensioned Concrete As calculated (460 ft. shoulder pier and sill abutment. • If the keyway of the connector is placed on the distal side of the pier abutment, mesial movement seats the key into the keyway more solidly. Cross pin and wing connectors. Split connectors. The male component or the key is attached to the mesial surface of mesialpontic of distal edentulous space. With rigid connectors, an occlusal load applied on the abutment tooth at one end of an FDP (mainly the molar retainer) with a pier abutment, the pier may act as a fulcrum. 3. If the key way of the connector is placed on the distal side of the pier abutment Mesial movement seats the key into the key way more solidly. Causes the key to be unseated during its mesial movements. Tensile forces may then be generated between the retainer and abutment at the other end of the restoration (in the premolar retainer). Read article at publisher's site (DOI): 10.4103/npmj.npmj_184_20. Multiple shear keys without any re-inforcement and spread over the seg-ment faces were provided to resist the vertical shear forces … To restrain excessive lateral displacement during service and earthquake loads, one shear key is introduced at each side of the pier bent and abutments. The keyway of the connector should be placed within the normal distal contours of the pier abutment, and the key should be placed on the mesial side of the distal pontic. Abutment, Bent, Pier, and Bearing. 2017 409-2.04(02), 409-3.03, Figure 409-2G 19-03 May 2019 409-2.04(01), Figure 409-2F (deleted) 19-04 . The solution is fixed removable bridge(a bridge with non rigid connector on the distal side of the retainer) If a nonrigid connector is placed on the distal side of the retainer on a middle abutment, movement in a mesial direction will seat the key into the keyway. The NRCs are mainly used to relieve stress on the abutment and to accommodate malaligned FPD abutments. To the right is shown the first concrete pier completed with the island of Knight's Key in the background. Non rigid connectors for Fixed partial dentures. The thickness of the top slab is 8 in. There are a variety of non-rigid connectors used in dentistry, while the most common ones are the dove tail or key-keyway 4, split pontics type (connectors placed inside the pontics) and tapered pin 2. pier abutment, and the key should be placed on the mesial side of the distal pontic. The state-of-the-art for abutment scour estimation is considerably less advanced than for pier scour. The height of the shear keys is 0.48 m and the thicknessis 0.24 m. The widths are 0.96 and 1.56 m for shear keys at abutments and central pier respectively. The keyway of the should be placed within the normal distal contours of the pier abutment, and the key should be placed on the mesial side of the distalpontic. The sill abutment (Type A1) is constructed at the top of the slope after the roadway embankment is close to final grade, as shown in . Shillingberg H.T, Fisher D.W. After the Abutments were Repaired, the Superstructure was Removed and Replaced Overnight. In DeepEX, we can select to add piles (fixed to a pile cap or not), define the pile positions (X and Y coordinates), length, inclination and local rotation, and select to edit the pile structural section. Similar Articles . The keyway of the connector should be placed within the normal distal contours of the pier abutment, and the key should be placed on the mesial side of the distal pontic. Design of bridge in case of pier abutment: 1. Sections Affected . The shear keys are designed as sacrificial and it is assumed that once their capacity has been exceeded, the shear keys would not provide further support. The long axes of the posterior teeth usually lean slightly in a mesial direction, and vertically applied occlusal forces produce further movement in this direction. This completed pier lends credence to the theory that construction of the final part of the Key West Extension began on January 1, 1909. Soil springs are used to model foundation stiffness. The goal of this case report is to discuss the use of key and keyway, a type of non-rigid connector to rehabilitate a patient with a pier abutment situation. (203 mm) within the box and 9 in. key strips ___ are chamfered 2x4's used to form keyways: ... pier caps, and abutments: coffer dam a ___ is constructued to restrain water when constructing footing forms in rivers, lakes, and other bodys of water: Generated by Koofers.com. 2017 409-2.04(02), 409-3.03, Figure 409-2G 19-03 May 2019 409-2.04(01), Figure 409-2F (deleted) 19-04 . 2. 13-11 May 2013 409-7.03(03), Figure 409-7F 16-32 Sep. 2016 409-2.04, Figures 409-2C, 409-2D, 409-3A, 409-3B, 409-3D 17-03 Mar. The keyway is usually placed on the distal surface of the pier abutment. A comprehensive study was carried out in a project supported by Caltrans to acquire a good understanding of the behavior and lateral load resisting mechanisms of external shear keys in bridge abutments. - place DISTAL of pier abutment retainer - most commonly used design contains T-SHAPED KEY attached to pontic and dovetail key within retainer - the KEYWAY should be placed in the distal contours of the pier abutment - the KEY should be placed on the MESIAL side of the distal pontic. The main cause of concern in stability of bridges founded in river-beds is the lowering of river-bed level caused by river flow around bridge elements such as piers, abutments and spur dikes and is termed ‘local scour’. Tilted molar abutments Revision Date . 3. The concrete in the diaphragms was placed after erection of these segments to keep the segment weights within the capacity of the launching truss. Because it will tend to exert much forces on this pier abutment. Shillingburg and Fisher (1973) – forces are transmitted to the terminal retainers as a result of the middle abutment acting as a fulcrum causing failure of the weaker retainer. Rehabilitation was done by FPD with an inverted key-keyway type NRC. Align the path of the keyway to that of distal abutment. The non-rigid connector design assembly consisted of, (a) a T-shaped extension key or a Tenon attached to the distal side of the retainer of the pier abutment (mandibular left second premolar), and (b) a Dove tail or keyway receptacle (Mortise) placed within the contours of … If the keyway of the connector is placed on the distal side of the pier abutment, mesial movement seats the key into the keyway more solidly. Nearly 98% of posterior teeth tilt mesially when subjected to occlusal forces. To complete the steel truss portion of the Seven Mile Bridge 334 more piers were constructed. at a pier from an adjacent unit by an expansion device or a fixed gap. Pier abutment is characterized by a lone standing abutment with edentulous regions on either side of it. Table 11-1: Limiting Structure Lengths for Integral Abutments Girder Material Maximum Unit Length . The gap between shear key and corresponding bridge girder is 60 mm as shown in Fig. Design Memo . The long axes of the posterior teeth usually lean slightly in a mesial direction, and vertically applied occlusal forces produce further movement in this direction. max.) J AM Dent Ass 1973;87:1195-99 45 46. The abutment and pier segments in-clude transversely post-tensioned solid diaphragms with access openings. Shear keys in bridge abutment are divided into two types, exterior or interior. Sections Affected : 13-11 May 2013 409-7.03(03), Figure 409-7F 16-32 Sep. 2016 409-2.04, Figures 409-2C, 409-2D, 409-3A, 409-3B, 409-3D 17-03 Mar. Concrete Deterioration • Pier caps were … The long axes of the posterior teeth usually lean slightly in a mesial direction, and vertically applied occlusal forces produce further movement in this direction. Follow up was done up to 11 months. displacement during service and earthquake loads, oneshear key is introduced at each side of the pier bent and abutments. During occlusion molar tend to tip mesially and hence excessive stress is transferred through the connector to pier abutment. in length with the pier and abutment segments being 6 ft 2 in. The four types of NRCs, are the 1. 12.2.3 Sill . Loop connectors. • Placement of the keyway on the mesial side, however, causes the key to be unseated during its mesial movements. Placement of the keyway on the mesial side. Abutment, Bent, Pier, and Bearing. Pier ( intermediate) abutment: An edentulous space can occur on both sides of a tooth creating a lone , free standing pier abutment. Placement of the keyway on the mesial side, however, causes the key to be unseated during its mesial movements. Placement of the keyway on the mesial side of the pier abutment will cause the key to be unseated during its mesial movements. Internal shear keys are undesirable because they are extremely difficult to repair after a seismic event. Shear key can be constructed from concrete as in precast […] abutment is too wide for the external keys to resist all the force, internal shear keys may be provided. Dovetail (key-keyway) or (Tenon-Mortise) connectors. the keyway mesial to the pier abutment retainer will tend to dislodge the key from the keyway on application of occlusal forces which in time might lead to fracture of the canine retainer or bone loss around the canine abutment. Design Memo . Among these connectors, dove tail is most commonly used one in day to day practice. Full text links . The wings and the body of the abutment are usually poured monolithically. Revision Date . The goal of this case report is to discuss the use of key and keyway, a type of non-rigid connector to rehabilitate a patient with a pier abutment situation.
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