The 1987 edition of IS 875 Part 2 outlines the essential minimum live loads (imposed loads) that must be factored into the design of various types of buildings and structures across India, excluding seismic loads. It offers comprehensive instructions for calculating imposed loads for a range of occupancy categories including residential, industrial, educational, commercial, and storage facilities.
Overview
The 1987 edition of IS 875 Part 2 outlines the essential minimum live loads (imposed loads) that must be factored into the design of various types of buildings and structures across India, excluding seismic loads. It offers comprehensive instructions for calculating imposed loads for a range of occupancy categories including residential, industrial, educational, commercial, and storage facilities.
Audience
Contents
Structure
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This section defines the scope of IS 875 Part 2, covering imposed loads (live loads) applicable to floors, roofs, stairs, balconies, and similar building components. It specifies the loads due to occupants, movable furniture, partitions, and maintenance activities. The code addresses flat, sloping, and curved roofs with appropriate slope adjustments, as well as horizontal loads applicable to parapets, balustrades, and staircases.
Defines key terms and presents a summary of imposed loads categorized by occupancy. It includes tables of uniformly distributed loads (UDL) and point loads for residential, institutional, assembly, business, and office buildings. Notes cover special load conditions, including concentrated loads on balconies and corridors, and the application of load factors for design.
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This part provides key formulas and tabulated values for calculating imposed loads on roofs and floors. It covers uniform and concentrated load applications, guidelines on load distribution for bending and shear, and specific values for horizontal forces on parapets and balustrades. The section also addresses impact and vibration considerations.
Explains how uniform loads are applied as static loads over entire or partial floor areas to produce critical structural effects. Concentrated loads are treated as point loads for bending and shear and as distributed loads over a 0.3 m by 0.3 m area for local effects such as crushing or punching.
Specifies that when the exact load from light partitions is unknown, a uniformly distributed load of at least 0.34 kN/m² should be considered in the design of floors and supporting members. This load is supplemental to other imposed loads.
Describes the permissible reductions in imposed loads for structural members supporting multiple floors. Reduction percentages are based on the number of floors supported, with detailed tables and formulas. Exclusions to reductions are also specified, such as for moving loads and machinery.
Details the imposed loads applicable to different roof types and slopes, including flat, sloping, and curved roofs. It includes formulas for slope-based load reduction and minimum load values. The section also clarifies considerations for loads due to occupancy and environmental factors.
Outlines the design requirements for members supporting roof coverings, ensuring they are designed for the most critical imposed loads, whether uniform or concentrated. It specifies minimum load values and provides formulas relevant to curved and sloping roofs.
Covers the impact factors and vibration allowances to be added to concentrated loads from machinery and equipment. It includes minimum impact factors, guidance on load application points, and requirements for installation and maintenance loading.
Summarizes imposed load values for roofs and horizontal loads on parapets related to equipment. Emphasizes impact and vibration effects, as well as provisions for concentrated loads during installation and servicing.
Provides guidelines for combining loads from multiple cranes, including tandem cranes and long-span gantries. Describes the overloading factors to be applied and the consideration of lateral and longitudinal forces.
Introduces special load cases such as seismic and crane loads. Refers to IS 875 Part 5 for detailed combination rules and includes tables for imposed loads on roofs and parapet horizontal forces. Discusses impact allowances and the methodology for combining various loads.
Presents an example calculation demonstrating how imposed loads can be reduced in columns supporting multiple floors. Includes reduction factors and formulas, emphasizing that design loads should not decrease with descending floors.
Frequently Asked
As per IS 875 Part 2 (1987), minimum imposed loads vary by occupancy type, with residential floors typically designed for 1.5 kN/m², office areas for 2.0 kN/m² plus a concentrated load of 2.0 kN over an area of 0.3 m by 0.3 m, and assembly spaces such as theatres for 4.0 kN/m² with a concentrated load of 4.0 kN. Industrial buildings range from 3.0 to 10.0 kN/m² depending on usage intensity, and storage areas are designed at 5.0 kN/m² per meter of stack height with a minimum of 15 kN/m². Concentrated loads act over a 0.3 m by 0.3 m area, and when occupancy is unlisted, loads should be estimated based on expected occupancy, equipment, and storage. Load reductions up to 50% may be applied for vertical members in multi-storey buildings to account for diversity.
According to IS 875 Part 2, imposed loads on beams, girders, and trusses can be decreased by 5% for every 50 m² of supported floor area, up to a maximum reduction of 25%, provided the floor area is at least 50 m². This reduction does not apply to moving loads, concentrated loads, partition wall loads, impact or vibration loads, or roof loads. For columns, load reductions are applied cumulatively based on the number of floors supported, as exemplified in Appendix A. It is important that the reduced load on a lower floor is not less than that on an upper floor to maintain a non-decreasing load pattern.
IS 875 Part 2 specifies that concentrated loads from machinery must include a minimum impact factor of 20% to account for dynamic effects, with higher values for heavier or vibrating machinery. Loads should be applied at points causing maximum bending or shear, considered as point loads for structural analysis, and spread over a 0.3 m by 0.3 m area for local effects such as crushing. Additionally, provisions must be made for increased loads during equipment installation or maintenance. Where data is available, actual impact and vibration factors should be used; otherwise, the minimum prescribed values apply.
The code mandates that structural members directly supporting roof coverings must be designed for the most critical imposed load scenario, which is the greater of the uniform imposed load on the roof surface or the minimum uniformly distributed load specified for beams, trusses, or walls. Roof types including flat, sloping (≤10°), and curved roofs have specific load values and formulas, such as reductions for slopes greater than 10° and calculations based on roof geometry for curved roofs. Access to roofs affects load values, with higher loads assumed for roofs with access.
IS 875 Part 2 requires that when two cranes operate in tandem, the design must consider both cranes fully loaded with an overloading factor typically set at 10-25%, depending on the clause referenced. For long-span gantries supporting multiple cranes, the girder should be designed for one crane fully loaded with overloading plus additional cranes at full rated load without overloading to maximize effects. Vertical loads, impact factors, and lateral and longitudinal braking forces must all be included in the design. The overloading factor ensures safety against production overloads and dynamic effects.
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