Integrated sensitivity analysis

Standard Design Criteria/Guidelines for Balance of Plant of Thermal Power Project 2 x (500MW or above)

Section- 9 (Civil Works)

Design loads for all structures shall be determined according to the criteria described below, unless the applicable Indian building code requires more severe design conditions.

i) Dead loads

Dead loads shall consist of the weights of the structure and all equipment of a permanent or semi-permanent nature including tanks, silos, bins, wall panels, partitions, roofing, piping, drains, electrical trays, bus ducts, and the contents of tanks measured at full capacity. However, the contents of tanks and other loads of semi-permanent nature shall not be considered as effective in resisting column uplift, overturning and sliding.

ii) Live loads

a) Live loads shall consist of uniform live loads and equipment live loads. Uniform live loads are assumed unit loads which are sufficient to provide for movable and transitory loads, such as the weight of people, portable equipment and tools, plank-ing and small equipment, or parts which may be moved over or placed on floors during maintenance operations. These uniform live loads should not be applied to floor areas which shall be permanently covered with equipment.

b) Equipment live loads are calculated loads based upon the actual weight and size of the equipment and parts to be placed on floors during dismantling and maintenance, or to be temporarily placed on or moved over floors during installation.

c) Floors and supporting members which are subject to heavy equipment live loads shall be designed on the basis of the weight of the equipment in addition to a uni-form load of 500 kg/m², or specifically defined live loads, whichever is greater.

Each member in the floor which may carry these loads shall be designed for the heaviest piece or pieces of equipment arranged in the most critical position. For loads caused by moving equipment over the floor for installation, consideration shall be given to the shoring of beams and floor from floors below. When moving equipment over floors for installation, stress increases of 25 percent are permitted in beams and columns.

d) Live loads shall be used as follows:-

Description Floor slabs

Grade floors slabs 1500 kg/m² (minimum) Maintenance area in ground

floor 3000 kg/m²

Storage areas Actual load of stored material or 1500 kg/m² (minimum)

Suspended floors and

control room floor 1500 kg/m² (minimum ) or actual whichever is higher

Roofs (concrete slab) 250 kg/m²

Standard Design Criteria/Guidelines for Balance of Plant of Thermal Power Project 2 x (500MW or above)

Section- 9 (Civil Works)

Description Floor slabs

Steel grating / chequered

plate platforms - 750 kg/m² for grating/ chequered plate - 500 kg/m² for supporting beams Inclined Roof As per IS – 875 (Part-2)

Areas designated for different loadings on the same floor shall be clearly and permanently marked.

e) Column live loads

Live loads carried from the floors to the columns shall include 100 percent of the roof live load. In addition to the roof live load, the columns must carry floor live load. If the floor live load is 500 kg/m² or less, no reduction in live loads carried from the floors to the columns is allowed. If the floor live load is greater than 500 kg/m², reduction in live loads carried from the floors to the columns shall be considered as per clause 3.2 of IS-875 (Part-2) for design. However, reduction in live load from all floors to be carried by the member under consideration shall not exceed 20% irrespective of the codal provisions.

iii) Impact loads

Impact loads shall be added to other loads for components supporting reciprocating or rotating machines, elevators, hoists, cranes, or other equipment creating dynamic forces. The following impact loads shall be used, unless analysis indicates higher or lower values:-

a) Elevators -- 100 % of lifted load.

b) Hoists and cranes:

• Vertical -- 25 % of the maximum static wheel load.

• Horizontal-lateral -- 20 % of the sum of the lifted load plus the weight of the hoisting component.

• Horizontal-longitudinal -- 10 % of the total moving load.

c) Rotating and reciprocating -- 50 % of the machine weight

equipment

d) Hangers supporting floors -- 33 % of the sum of the dead load

and platforms and reduced live load.

e) Steel members supporting

Standard Design Criteria/Guidelines for Balance of Plant of Thermal Power Project 2 x (500MW or above)

Section- 9 (Civil Works)

boiler drum hangers -- 100 percent..

iv) Equipment loads

Equipment loads shall be specifically determined and located. For major equipment, structural members and bases shall be specifically located and designed to carry the equipment load into the structural system. For equipment weighing less than the live load, the structural system shall be designed for the live load. Equipment loads shall be noted in the design calculations to permit separation in calculation of uplift and stability.

v) Access walkways, stair, handrails, and ladders

Design loads shall conform to the requirements of IS: 875 (part I and II) and the minimum requirements following, whichever are the most severe:

a) The walkways shall be designed for the dead loads of the structure plus a superimposed live load of 500 kg/m² uniformly distributed, or a concentrated load of 500 kg at any point, whichever produces the most severe effect.

b) Stair treads shall be designed for a distributed load of 225 kg/linear meter of tread width or a concentrated load of 100 kg, whichever produces the most severe effect.

c) Handrail forces shall be 100 kg applied outward at the center of the span and vertical between posts. Ladders shall be designed to withstand a line load of 100 kg or, alternatively, a number of line load units of 100 kg, the number of units and their spacing being in accordance with the anticipated usage of the ladder.

vi) Test load

The test load shall be defined as the gravity load imposed by method necessary to test vessels, tanks, equipment or piping.

vii) Wind loads

Wind load for all structures shall be based on IS: 875 (part 3). Basic wind speed shall be as specified in IS: 875(part-3).

viii) Seismic loads

The seismic risk zone for the site shall be determined from the IS: 1893. Under seismic condition, the whole frame except the roof shall be assumed loaded with 50% design live load. No further reduction in column live load shall be considered as per clause 5.3.2.1 under seismic condition.

ix) Construction loads

Standard Design Criteria/Guidelines for Balance of Plant of Thermal Power Project 2 x (500MW or above)

Section- 9 (Civil Works)

The integrity of the structures shall be maintained without use of temporary framing struts or ties and cable bracing insofar as possible. However, construction or crane access considerations may dictate the use of temporary structural systems. Special studies shall be made and documented to ensure the stability and integrity of the structures during any periods involving use of temporary bracing systems.

x) Estimated loads

Loadings imposed by equipment shall be specifically determined or estimated before detailed structural design. Estimated loadings shall be noted as such in hand calculations or computer input and verified as information is made final.

xi) Dust Load

All buildings and structures shall be designed for dust load of 50 kg/m². xii) Thermal load

Thermal loads shall be defined as forces caused by changes in temperature. The primary source of thermal loads in an industrial plant is the expansion or contraction of vessels and piping. Another source of thermal loads in a redundant structure is the expansion or contraction of the entire structure or individual structural components.

xiii) Future load

Loads from future expansion shall be considered when so directed by the purchaser./owner. Future loads may include any of the loads listed above.

xiv) Surge load

Surge loads may occur in some vessels or equipment. In such cases, the magnitude and direction of the load shall be given by the equipment supplier.

xv) Miscellaneous load

Miscellaneous loads shall be defined as loads that do not fit into the categories listed in this section. Typical miscellaneous loads are loads, during erection, maintenance and repair or forces due to creep, shrinkage or settlement.

For the design of individual structural components, realistic load combinations in accordance with the relevant design standards shall be considered.

All loadings considered in the design shall be justified with supporting details.

9.1.6.4 General Requirements