Roof slab

A composite concrete slab or a stressed-skin system can also provide a roof diaphragm, but the latter may severely restrict the provision of subsequent roof penetrations. Concrete roof slabs are unusual, due to the greatly increased mass over the more normal metal decking/in-sulation/waterproof membrane or insulated metal decking options. 

The walls are 12 ft (366 cm) from floor slab to roof. The shorter walls are 66.67 ft (2,032 cm) long, a 5.6 to 1 height to width ratio. Therefore all walls will be analyzed as one way beams pinned at the base by a crossed reinforcing configuration at the slab level (similar to Figure 8.10), and pinned at the top due to a thinner roof slab (Figure 8,11), The wall is assumed to be unrestrained (for axial forces) at the top end and will not respond in tensile membrane action. 

For moment of inertia calculations, to approximate the effect of roof cracking due to out-of-plane loads, use half the roof slab thickness. 

Roof Slab reinforcing could be reduced somewhat. 

Load calculations braced frames 12-39—12-43 columns 11-37—11-40 exterior walls 11 4—11-10 foundations 11-41—11 45, 12-43—12-46 rigid frames 12-31 — 1 2-39 roof beams 1 1-27—1 1-31 roof decking 12-6—12-71 roof girders 1 1-36 roof putins 1 2-16—1 2-26 roof slabs, in-plane 1 1-1 1 — 1 1-16 roof slabs, out-ofplane 1 1-21—1 1-26 side walls, in-plane 11-16—11-20 wall girts 12-26—12-30 wall panels 12-12-12-16... 

A series of separate SDOF dynamic analyses are performed for each of the primary structural components. For example, a typical roof system consists of a roof slab supported on structural steel roof beams which are in turn supported by roof girders. Separate SDOF dynamic analyses are performed for the slab, beams and girders using the reaction time history of the supported member as loading input 10... 

For primary members (external walls, roof slabs, etc.), the load computation is performed in accordance with Chapter 3. Loads on supporting, or interior members, are determined either by I. the tributary area method or 2, from a computed dynamic reaction. In the tributary area method, external blast pressures are multiplied by the exterior surface area tributary to a support location. The resulting force is then applied to the next member. Dynamic reactions result from a numerical time history analysis (refer to Section 6.5.3) and provide a more accurate time-varying load on the supporting member. 

FIGURE 8.5 Precast Pane Connection to Roof Slab... 

FIGURE 8,11 Cast-in-PIacc Wall to Roof Slab Joint... 

Headed studs are normally used to secure a roof slab to a structural steel framing system for rebound loads in new designs. This option may not available for upgrading existing structures. It may be necessary to provide through bolts to the structural frame with a backing plate on the top side of the stab. 

Each interior roof beam supports a roof slab width of 8 feet (244 cm). 

The roof beam is connected to the roof slab to prevent separation during rebound. In this case, the connection is to be designed to prevent composite action between the roof slab and the roof beam. Because composite action greatly increases the bending capacity while not increasing the beam s shear capacity, neglecting this effect could be very unconservative. 

The top shield includes roof slab and two rotatable plugs. Warm roof concept is adopted for top shield to minimise sodium deposition in the annular gaps. The roof slab is a box type structure filled with concrete as the shielding material. It supports the main vessel, primary sodium pumps, IHX, and direct reactor heat exchangers (DHX) of the decay heat removal system. Use of liquid metal seals has been avoided in order to reduce the rotatable support... 

In-service inspection and monitoring is based on the requirements of ASME section XI, Div 3. For the main vessel, in addition to ASME requirements of continuous monitoring, ultrasonic examination is planned to be carried out through the main vessel - safety vessel interspace (300 mm nominal gap). A periscope is provided for visual examination of reactor internals. Eddy current inspection is under development for the SG tubes. SG tube size and expansion bend design takes into account this inspection requirement. Ultrasonic examination is planned for the dissimilar joints of the roof slab - main vessel and SG transition joint. The subject of ISI for other reactor components important to safety is under study. For the safety related reactor assembly components, which are non-inspectable, an additional factor of safety in design is envisaged. 

Clad temperatures are estimated in case the sodium filled pot carrying subassembly gets struck. It is found that the nominal central pin clad temperature exceeds the limit (923 K) when the pot is stmck in roof slab region, rotating shield, secondary ramp and ex-vessel transfer position. Hence cooling is required. However, it remains to be seen whether temperature limits can be raised from the considerations of economy and avoidance of complex cooling arrangement. 

The LCTR was operated at a maximum temperature of 773 K. The rig will be operated at higher temperature (-820 K) after carrying out improvements to the cooling circuit of an EM Pump. During the year the roof slab cooling circuit was commissioned and the heat flux on the... 

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