There are two methods used to design steel structures: limit state method and working stress method.

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The limit state method is a safety-based approach that considers the effects of external loads on a structure. It aims to ensure that the structure can resist any possible loads that could be applied to it without failing.

The working stress method is a more economic approach that designs for loads that are less than the yield strength of the material. This allows for some deformation of the structure under load, but the deformation is kept within acceptable limits.

The working stress method is a method of calculating the allowable stress in a structural member that takes into account the occasional or accidental loads that the member may experience in addition to the regular or design loads. The limit state method is a method of calculating the allowable stress in a structural member that only considers the regular or design loads and ignores any occasional or accidental loads.

## What is working stress method?

The working stress method (WSM) is a widely used approach for designing structures. The method basically assumes that the structural material behaves in a linear elastic manner, and that adequate safety can be ensured by suitably restricting the stresses in the material induced by the expected “working loads” on the structure.

The WSM is a simple and straightforward approach that can be easily understood and applied by engineers. However, there are some limitations of the method that should be considered. Firstly, the assumption of linear elastic behaviour of the material may not be valid in many cases, especially for materials like concrete which exhibit non-linear behaviour. Secondly, the method does not consider the effects of fatigue and creep, which can lead to failure of the structure over time.

Despite these limitations, the WSM is still widely used due to its simplicity and ease of use. It is also generally considered to be a reasonably accurate and safe approach for designing structures.

Limit state design (LSD) is a type of design approach that considers all loads and deformations that may occur during construction and normal use of a structure. LSD also takes into account a structure’s durability, or how well it will withstand wear and tear over time.

### What is LSM and WSM

Both Working Stress Method (WSM) and Limit State Method (LSM) are civil design methods that are used to assess the strength of a structure.

WSM is a traditional method that uses allowable stresses that are based on the material’s yield strength. LSM is a more modern approach that uses ultimate strength values.

Both methods have their own advantages and disadvantages, but ultimately it is up to the designer to decide which method is more appropriate for the project at hand.

There are two main methods used for designing structures: the working state method (WSM) and the limit state method (LSM).

The main difference between the two methods is that WSM is an elastic design method while LSM is a plastic design method. This means that the WSM takes into account the elastic properties of the materials used in the structure, while the LSM uses the plastic properties.

The advantage of using the LSM is that it is a more accurate method, as it takes into account the non-linear behaviour of materials under load. This makes the LSM more suitable for designing structures that are subject to large loads, such as bridges and skyscrapers.

The WSM is a simpler method and is more suited to smaller structures or those that are not subject to large loads. It is also a more economic method, as it utilises the moment-rotation capacity of beams, for example.

## Where is working stress method used?

The Working Stress Design Method is a method used for the reinforced concrete design where concrete is assumed as elastic, steel and concrete act together elastically where the relation ship between loads and stresses is linear. This method is also called the Elastic Method.

The limit state method is a more accurate method of predicting the strength of a structure, as it takes into account the material’s ultimate strength. This results in a more reliable design.

The limit state method is also easier to use and understand, as it is based on simple principles. This makes it more user-friendly, especially for novice engineers.

## What are the two types of limit state method?

The two different limit states are the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS). The ULS is the limit state beyond which the structure will no longer be able to fulfil its design function, while the SLS is the limit state beyond which the structure will no longer be able to fulfil its intended purpose due to excessive deformation or vibration. In the code SANS10160: 51, distinction is made between these two limit states.

1) Serviceability check in case of LSM is required because after the elastic region strain is higher, which results in more deformation, hence a check is necessary.

2) LSM is strain based method whereas WSM is stress based method.

3) LSM is non-deterministic method whereas WSM is deterministic approach.

### What is WSM also known as

There are two main methods used to design concrete structures: the working stress method (WSM) and the limit state method (LSM).

The working stress method was the traditional approach used in the past, and it is still used in some cases today. With this method, the concrete is designed to resist the forces that are expected to act on it during its lifetime. Once the allowable stresses are determined, the concrete is proportioned so that it can resist these loads without failing.

The limit state method is the more modern approach, and it is the method that is most commonly used today. With this method, the concrete is designed to resist the loads that will cause it to fail. The allowable stresses are based on the strength of the concrete, and the concrete is proportioned so that it will not fail under the expected loads.

There are 3 methods of design an RCC structure:

1. Working stress method

2. Ultimate load method

3. Limit state method

The working stress method was the traditional method of design but it has some limitations. The ultimate load method is sometimes also referred to as the Load factor method. The limit state method is the most commonly used method nowadays.

## What is LSM method of design?

The limit state method (LSM) is a method used to design structures such that they will not reach limit states and will not become unfit for use. This is done by ensuring that the safety and serviceability requirements of the structure are within acceptable limits before failure occurs.

The assumption made according to IS 456 in limit states of collapse are:

1. plane section normal to the axis remains plane after bending

2. The maximum strain in the concrete at the outermost compression fiber can be taken as 0.0035 in bending

3. The tensile strength of the concrete is ignored.

### What is factor of safety in WSM and LSM

In WSM, the load factor of safety is considered as ‘1’. This means that the allowable stress is equal to the actual stress. In LSM, the load factor of safety is considered as ’15’. This means that the allowable stress is 15 times the actual stress.

The limit state method is a modern way of designing a structure that encompasses a wide range of logical and technical considerations. It includes separate considerations of different kinds of failure, types of material, and types of load. This provides an economical design of the structure.

## What is USD vs WSD?

The working stress design method is a means of designing structural elements in which the allowable stress in the element is determined by dividing the ultimate strength of the material by a factor of safety. The ultimate strength is the point at which the material fails. The factor of safety is a number that is used to account for uncertainties in the strength of the material and the loads that will be applied to the element. The ultimate strength of the material is typically much higher than the working strength, so the factor of safety provides a significant margin of safety.

The ultimate stress design method is a means of designing structural elements in which the allowable stress in the element is determined by dividing the ultimate strength of the material by a margin of safety. The ultimate strength is the point at which the material fails. The margin of safety is a number that is used to account for uncertainties in the strength of the material and the loads that will be applied to the element. The ultimate strength of the material is typically much higher than the working strength, so the margin of safety provides a significant margin of safety.

LSD is a design method that considers both the strength of a structure and the loads that it will experience. This approach is different from the traditional method of design, which only considered the strength of a structure.

Loads can come from many sources, including gravity, wind, and earthquakes. They can also come from the weight of the structure itself, as well as from the people and things inside the structure.

In order to design a safe and strong structure, engineers must consider all of the loads that the structure will experience. LSD is an approach that allows engineers to do this in a systematic way.

The LSD method is based on the principle that a structure must be designed to resist the effects of loads without failing. This means that the structure must be strong enough to support the loads without collapsing.

To do this, engineers use a factor of safety. This is a number that is used to multiply the strength of the structure. The factor of safety ensures that the structure is strong enough to resist the loads, even if some of the load is not known.

The LSD method is a more accurate way of designing structures than the traditional method. It is also a more conservative approach, which means that it is more likely to result

## Warp Up

The limit state method is a safety-based approach to design that considers the probability of failure of a structure or component. The working stress method, on the other hand, is a strength-based approach that designs for a specific level of stress.

In conclusion, the limit state method and working stress method are two important methods used in structural engineering. They both have their advantages and disadvantages, but the limit state method is generally considered to be more accurate.