Design Based on Working Stress Method
The Working Stress Method (WSM) is a traditional method used in structural engineering for the design of reinforced concrete structures. In this method, the design is based on the concept of permissible stresses in the structural elements under working loads. Here's an overview of the steps involved in designing a reinforced concrete structure using the Working Stress Method:
Determine Design Loads: Calculate and analyze the various loads that the structure will be subjected to during its service life. These loads may include dead loads (permanent loads such as the weight of the structure itself), live loads (temporary loads due to occupancy, furniture, etc.), wind loads, snow loads, and seismic loads.Select Suitable Materials: Specify the materials to be used in the construction, including concrete and reinforcing steel. The properties of these materials, such as strength, modulus of elasticity, and durability, will influence the design calculations.
Assume Section Dimensions: Make initial assumptions about the dimensions and geometry of the structural elements, such as beams, columns, slabs, and footings. These assumptions will be refined and adjusted during the design process to meet strength and serviceability requirements.
Calculate Bending Moments and Shear Forces: Determine the internal forces, such as bending moments and shear forces, acting on the structural elements due to the applied loads. This can be done using structural analysis methods such as the moment distribution method, finite element analysis, or hand calculations.
Design Reinforcement: Based on the calculated internal forces and the assumed dimensions of the structural elements, design the reinforcement layout (i.e., the size, spacing, and arrangement of reinforcing bars) to resist bending, shear, and axial forces. The design should ensure that the stresses in the concrete and steel do not exceed their permissible limits.
Check for Serviceability Criteria: Verify that the structural elements satisfy serviceability criteria, such as deflection limits, crack widths, and vibration frequencies, under the expected service loads. Adjust the dimensions and reinforcement as necessary to meet these criteria.
Iterative Process: The design process may involve several iterations of calculations and adjustments to refine the dimensions and reinforcement layout until the desired level of safety and performance is achieved.
Documentation: Prepare detailed design drawings, specifications, and calculations documenting the structural design and reinforcing details. These documents serve as the basis for construction and provide guidance for contractors and inspectors.
Review and Approval: Review the design with relevant stakeholders, including structural engineers, architects, and building officials, to ensure compliance with applicable building codes, regulations, and standards. Obtain approval from the appropriate authorities before proceeding with construction.
Construction and Quality Control: Monitor the construction process to ensure that the structural elements are built according to the design specifications and quality standards. Perform inspections and testing as necessary to verify the integrity and performance of the completed structure.
It's important to note that while the Working Stress Method has been widely used in the past, modern design codes and standards, such as the Load and Resistance Factor Design (LRFD) method and the Limit State Design (LSD) method, have largely replaced it in many jurisdictions. These newer methods provide a more rigorous and comprehensive approach to structural design, considering both the ultimate strength and serviceability requirements of the structure.