Limit State Method is based on calculations at working loads and ultimate loads

The Limit State Method is a design philosophy used in structural engineering that aims to ensure the safety and serviceability of structures under both normal working loads and extreme ultimate loads. It is widely adopted in the design of various types of structures such as buildings, bridges, dams, and tunnels.

Calculation at Working Loads
The first aspect that the Limit State Method considers is the calculation at working loads. Working loads refer to the loads that a structure is expected to experience during its intended use. These loads include dead loads (self-weight of the structure and permanent loads), live loads (loads due to occupancy, furniture, equipment, etc.), and environmental loads (wind, snow, temperature variations, etc.).

When designing a structure using the Limit State Method, calculations are performed to ensure that the structure can safely withstand these working loads without experiencing excessive deflections, deformations, or failure. This is done by determining the appropriate size and distribution of structural members, selecting suitable construction materials, and considering factors of safety.

Calculation at Ultimate Loads
In addition to working loads, the Limit State Method also takes into account calculations at ultimate loads. Ultimate loads represent extreme events that a structure may encounter, such as earthquakes, strong winds, or accidental loads. These loads are typically much higher than the working loads and are considered rare but possible events.

The calculations at ultimate loads involve assessing the structure's capacity to withstand these extreme loads without collapsing or suffering significant damage. The design is based on ensuring that the structure reaches a state where it is on the verge of failure but does not actually fail. This state is known as the "limit state."

Safety Factors
To ensure a sufficient level of safety, the Limit State Method incorporates safety factors that account for uncertainties in material properties, construction quality, and loadings. These safety factors are applied to both working loads and ultimate loads and are determined based on extensive research, empirical data, and engineering judgment.

By considering both working loads and ultimate loads, the Limit State Method provides a comprehensive approach to structural design that ensures the safety, functionality, and durability of structures under a wide range of load conditions. It allows engineers to optimize the design by considering different load scenarios and selecting appropriate structural elements and materials to achieve an efficient and cost-effective solution.