AASHTO HB-17 DIVISION II SEC 3-2002 Division II Construction - Temporary Works《临时作业》.pdf
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1、Section 3 TEMPORARY WORKS 3.1 GENERAL 3.1.1 Description This work shall consist of the construction and re- moval of temporary facilities which are generally de- signed by the Contractor and employed by the Contractor in the execution of the work and whose failure to perform properly could adversely
2、 affect the character of the contract work or endanger the safety of adjacent facil- ities, property, or the public. Appropriate reductions in allowable stresses or loads shall be used for design when other than new or undamaged materials are to be used. Such facilities include, but are not limited
3、to, false- work, forms and form travelers, cofferdams, shoring, water control systems, and temporary bridges. The following publications are useful reference docu- ments in the preparation of specifications for the design, review and inspection of temporary works: Synthesis of Falsework, Formwork, a
4、nd Scafolding for Highway Bridge Structures, November 1991, Guide Standard Specijcations for Bridge Temporary Guide Design SpeciJcation for Bridge Temporary Certijcation Program for Bridge Temporary Works, Construction Handbook for Bridge Temporary (FHWA-RD-9 1-062) Works, November 1993, (FHWA-RD-93
5、-031) Works, November 1993, (FHWA-RD-93-032) November 1993, (FHWA-RD-93-033) Works, November 1993, (FHWA-RD-93-034) 3.1.2 Working Drawings Whenever specified or requested by the Engineer, the Contractor shall provide working drawings with design calculations and supporting data in sufficient detail
6、to per- mit a structural review of the proposed design of a tem- porary work. When concrete is involved, such data shall include the sequence and rate of placement. Sufficient copies shall be furnished to meet the needs of the Engi- neer and other entities with review authority. The working drawings
7、 shall be submitted sufficiently in advance of proposed use to allow for their review, revision, if needed, and approval without delay to the work. The Contractor shall not start the construction of any temporary work for which working drawings are required until the drawings have been approved by t
8、he Engineer. Such approval will not relieve the Contractor of responsi- bility for results obtained by use of these drawings or any of his other responsibilities under the contract. 3.1.3 Design The design of temporary works shall conform to the AASHTO Standard Specijcations for Highway Bridges or t
9、he Guide Design Specijcations for Bridge Temporary Works; or to other established and generally accepted de- sign code or specification for such work. When manufactured devices are to be employed, the design shall not result in loads on such devices in excess of the load ratings recommended by their
10、 manufacturer. For equipment where the rated capacity is determined by load testing, the design load shall be as stated in the Guide Design Specijcations for Bridge Temporary Works. The load rating used for special equipment, such as ac- cess scaffolding, may be under the jurisdiction of OSHA and/or
11、 other State/local regulations. However, in no case shall the rating exceed 80% of the maximum load sus- tained during load testing of the equipment. When required by statute or specified in the contract documents, the design shall be prepared and the drawings signed by a Registered Professional Eng
12、ineer. 3.1.4 Construction Temporary works shall be constructed in conformance with the approved working drawings. The Contractor shall verify that the quality of the materials and workmanship employed are consistent with that assumed in the design. 3.1.5 Removal Unless otherwise permitted, all tempo
13、rary works shall be removed and shall remain the property of the Contrac- tor upon completion of their use. The area shall be re- 483 484 HIGHWAY BRIDGES 3.1.5 stored to its original or planned condition and cleaned of all debris. 3.2 FALSEWORK AND FORMS 3.2.1 General Falsework is considered to be a
14、ny temporary structure which supports structural elements of concrete, steel, ma- sonry, or other materials during their construction or erec- tion. Forms are considered to be the enclosures or panels which contain the fluid concrete and withstand the forces due to its placement and consolidation. F
15、orms may in turn be supported on falsework. Form travelers, as used in seg- mental cantilever construction, are considered to be a combination of falsework and forms. Whenever the height of falsework exceeds 14 feet or whenever traffic, other than workmen involved in con- structing the bridge, will
16、travel under the bridge, the working drawings for the falsework shall be prepared and sealed by a Registered Engineer. Falsework and forms shall be of sufficient rigidity and strength to safely support all loads imposed, and produce in the finished structure the lines and grades indicated on the pla
17、ns. Forms shall also impart the required surface texture and rustication, and shall not detract from the uni- formity of color of formed surfaces. 3.2.2 Falsework Design and Construction 3.2.2.1 Loads The design load for falsework shall consist of the sum of dead and live vertical loads, and any hor
18、izontal loads. As a minimum, dead loads shall include the weight of the falsework and all construction material to be sup- ported. The combined weight of concrete, reinforcing and prestressing steel and forms shall be assumed to be not less than 160 pounds per cubic foot of normal weight con- crete
19、or 130 pounds per cubic foot of lightweight concrete that is supported. Live loads shall consist of the actual weight of any equipment to be supported applied as concentrated loads at the points of contact and a uniform load of not less than 20 pounds per square foot applied over the area supported,
20、 plus 75 pounds per linear foot applied at the outside edge of deck overhangs. The horizontal load used for the design of the falsework bracing system shall be the sum of the horizon- tal loads due to equipment, construction sequence, in- cluding unbalanced hydrostatic forces from fluid concrete, st
21、ream flow when applicable, and an allowance for wind. However, in no case shall the horizontal load to be resisted in any direction be less than 2% of the total dead load. For post-tensioned structures, the falsework shall also be designed to support any increased or redistribution of loads caused b
22、y prestressing of the structure. Loads imposed by falsework onto existing, new or par- tially completed structures shall not exceed those permit- ted in Article 8.15, “Application of Loads.” 3.2.2.2 Foundations Falsework shall be founded on a solid footing safe against undermining, protected from so
23、ftening, and capa- ble of supporting the loads imposed on it. When requested by the Engineer, the Contractor shall demonstrate by suit- able load tests that the soil bearing values assumed for the design of the falsework footings do not exceed the sup- porting capacity of the soil. Falsework which c
24、annot be founded on a satisfactory footing shall be supported on piling which shall be spaced, driven, and removed in an approved manner. 3.2.2.3 Deflections For cast-in-place concrete structures, the calculated de- flection of falsework flexural members shall not exceed U240 of their span irrespect
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