Traffic speed, allowable loads, or both were reduced on crete superstructure construction where the deflection occurs the existing bridge during and immediately after placing new when the falsework is released. The traffic lane adjacent to the connecting joint was the different stages of simple-span precast or steel-girder de- closed for a few days after placing new deck concrete.
Temporary shoring was installed under the existing girder to the other. The concept is the same for continuous bridge during this period. Observed perfor- mance, however, indicates that no distress occurs if the pro- illustrates the importance of using a closure placement be- cedures in this guide are followed.
It is probable that tween the new deck and the existing deck so that the grade of relaxation in the concrete allows these theoretical overstress- the widening will match that of the existing bridge. For ex- es to dissipate before damage is caused to the structures. This is discussed in more width to make a smooth transition between the final detail in Section 3. ACI Sec- 3. Deflection due to creep is the result of creases the difficulty of getting a good grade match between many variables, such as the dimensions of the girder, the new and existing decks.
However, the use of prestressed con- quality of the concrete, the concrete age, and the rate of load- crete design does not eliminate the need for a closure place- ing; no single formula will suffice. Differential longitudinal elastic shortening during more complete discussion of this topic. This longitudinal short- deflection of cast-in-place concrete structures, which is only ening continues as a result of creep. For some structures, about one-fourth to one-third of the total deflection, occurs creep can be of sufficient magnitude to warrant a greater de- immediately after the falsework is released.
The remaining lay in placing the closure. Accurate prediction of dead load deflection creep continues at a diminishing rate, which be- deflection is more important for widenings than for new comes negligible after about 4 years.
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A theoretical analysis bridges, as it is essential that the deck grades match. Therefore, when determining the camber to be cast into widenings for long spans, it is neces- sary to consider the length of time the falsework will support the widening. This time period should be included in the contract documents. When the design calls for connecting new and existing substructures on continuous, multiple-span, post-tensioned rigid-frame structures, the piers, caps, and superstructure of the existing bridge must remain unconnected to the new structure until after the new structure is stressed.
The only exceptions are piers or caps at the point of zero movement during stressing for example, the center pier of a symmetrical three-pier frame. When the junction of the widening to the existing deck falls within the traveled way, however, longitudinal expansion joints are generally avoided because such joints create maintenance problems Fig.
Closure placements may not be needed on short spans or on very narrow widenings if deck concrete is placed fast enough to permit dead load deflection and the concrete placement is completed before final strikeoff and initial set of the concrete. Retarding admixtures can be used to ensure that initial elastic deflections have completely taken place before the concrete begins to set. When closure placements between the new deck and the existing deck are used, the construction sequence and details employed are critical to the successful performance of the structure.
Their degree of importance varies from bridge to bridge due to the many variables involved. The recommended width of closure placements is approximately 18 in. A closure placement accomplishes two purposes: 1 it per- Fig. All existing reinforcement may of the widening to reach a stage where the portion of the not be weldable and preheating may be required. When deck closure placements are employed, dia- culty in reinforcing the area around the seat. Dowels can be smooth or deformed and the placement of the closure. The diaphragms are then con- can be anchored into the existing concrete with grout or ad- nected just before placement of the closure.
Although presized encapsulated resin cartridges have 3. This method requires a hole sloped one vertical transverse deck reinforcing with that of the widening. Several types should not exceed 0.
They should be Longitudinal reinforcing bars should be placed in the clo- located at least 3 in. The holes 3. The holes are then the closure. They then act as an articulated ramp to spread the filled with grout or epoxy before the dowels are inserted. The dowel is has been placed and the shoring released. A gasket is used around the dowel at the face of the bration from external forces during the first few days after hole to retain the grout while allowing the air to escape.
This 3. Reinforcing 3. For steel girders or precast concrete girder bridges, clo- proved mechanical connections or full-strength welds. Weld- sure placements can be made as soon as the full dead load is ing can be used when the extension being welded is free from on the widening.www.hiphopenation.com/mu-plugins/choctaw/early-dating-poems.php
ACI Manual of Concrete Practice Volume 3, 2016
For widenings consisting of more than one restraint during the welding process to permit shortening of girder, the exterior railing need not be placed before closure. The length of the delay period, along with the to determine its weldability and gives procedures for welding width of the closure placement, should be engineered to ac- splices if chemical composition is unknown. This deflection is pri- marily the result of creep in the concrete superstructure.
In concrete, the amount of creep deflection is a direct func- Fig.
ACI Manual of Concrete Practice Volume 3, 2016
The rate of creep de- to connect the deck of the widening to the deck of the exist- creases with the age of the concrete and the length of time since ing bridge, and the method and sequence of making such the formwork was removed. Any creep deflection of the girders connections. It is recommended that the decks be closure concrete. Thus, the rate of deflection of the girders must structurally connected. The type of bridge used for the wid- be permitted to decrease to a level that can be tolerated by the ening does not have to be the same as the existing.
Economy, closure concrete before closure concrete is placed. If the two than in the widening, make the required delay period very diffi- spans are to be connected structurally, however, the live load cult to calculate. It is therefore normally based on experience. TRANS has required for several years that whenever the When the deck of a widening is to be connected structur- falsework is removed at the earliest permitted date, the clo- ally to the existing deck, it is generally recommended that the sure concrete should not be placed until at least 60 days af- final connection be delayed until the widening is nearly com- ter the falsework is removed.
This will avoid the possibility of damage to the new falsework is left in place for at least 28 days after casting, work caused by 1 vibrations of traffic on the existing bridge; then the closure concrete should not be placed sooner than 2 dead load deflection of the widening that occurs as deck 14 days after falsework removal.
ACI R Guide to Maintenance of Concrete Bridge Members on Apple Books
For 3. In cases where bridge in any way that would prevent the longitudinal shorten- considerable settlement is anticipated, closure placements in ing of the new work. For cast-in-place spans, it may be advis- footing and substructures have been used to prevent transfer able to delay making this final connection for several days after of load from new to old structures Interstate, For ex- the falsework is released to allow for some of the more rapid ample, elastic shortening of the piles at the Hackensack early dead load deflection caused by creep in the concrete to oc- Bridge Soto, due to the dead load of the new pier was cur see Section 3.
Dusel, J. Such rein- Roads and Bridges, V. Likewise, the connection , Texas Transportation Institute, State Department of High- of diaphragms between the existing bridge and the widening, ways and Public Transportation, College Station. P, Kansas Department of Transportation. McMahon, J. Officials 2, No. Reay, G. Scordelis, A. Soto, M. Construction Sprinkel, M.
Concrete Repair American Concrete Institute Bridge Superstructures, Department of Transportation Weyers, R. American Welding Society Read Free For 30 Days. Flag for inappropriate content. Original Title: ACI Related titles.
Carousel Previous Carousel Next. Jump to Page. Search inside document. Weyers Many highway bridges become functionally obsolete due to inadequate Chapter 2—General design considerations, p. Lampard Chen. Annur Kamarudin. Peter Nobrega. Muhammad Al-Ani. Any applicable errata are included with individual documents at the time of purchase. Errata are not included for collections or sets of documents such as the ACI Collection. For a listing of and access to all product errata, visit the Errata page. Choose Product Language English.
PDF free access to members. Anyone knows, or have any idea, how much they are selling ProtaStructure products? Bearing capacity of shallow foundations Size: KB Bearing capacity of shallow foundations is a common check engineers have to perform during their design of structures. Most software packages, including more expensive ones, usually don't contain an appropriate or separate module to analyze the structure's foundation for bearing capacity check.
Therefore an engineer is usually forced to use another software, where he must import design loads from his main software and iteratively look for the appropriate dimension of foundation to fulfill the bearing capacity checks. The purpose of this Excel spreadsheet is to allow engineers a quick, graphically supported, design of rectangular foundations for bearing capacity check based on Eurocode 7, Annex D.
Related ACI 345.2R-13: Guide for Widening Highway Bridges
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