Page 192 - Water Standards
P. 192

constructed in advance.
                           4  Simply supported beam structures should be used for the
                       crane beam for the convenience of the prefabrication and installation.
                       The hoisting shall meet the relevant requirements in Section 2   9 of
                       this specification.
                           5  For the construction of the main roof beam, the stiff self⁃sup⁃
                       porting framework method, a upper load bearing framework or a
                       through type load bearing framework should be adopted. When the
                       hoisting conditions are available, precast roofs shall be the priority for
                       selection.
                           6  When the method of stiff self⁃supporting framework or load
                       bearing framework is adopted in construction, their strengths and
                       stiffnesses shall be designed to ensure enough stability and
                       construction convenience. The camber shall be set according to design
                       requirements in construction.
                           7  Reinforced concrete precast slabs should be adopted for the
                       roof, and roof waterproofing shall be done well.
                           8  The reinforced concrete bents in the switch yard should be
                       constructed with precast ones and installed.
                       3   9   8  Second stage concrete in powerhouse construction shall meet
                       the following requirements:
                           1  Second stage concrete in the powerhouse shall meet the provi⁃
                       sions in Section 2   7 of this specification, as well as the following re⁃
                       quirements:
                             1) The strength of the second stage concrete should be 5MPa
                                higher than that of the first stage concrete.
                             2) The aggregate size shall not be larger than 1 / 4 of the
                                thickness of the smallest structure of the second stage con⁃
                                crete, or 1 / 2 of the smallest clear spacing between the
                                steel bars (or embedded parts).
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