The Benefits and Challenges of Plastic Design to BS 5950
Plastic Design To Bs 5950 Pdf Download
If you are a civil engineer, a structural designer, or a student of these fields, you might be interested in learning more about plastic design to BS 5950. This is a method of designing steel structures that allows for more efficient use of material and greater flexibility in design. In this article, we will explain what plastic design is, what BS 5950 is, how to apply plastic design to BS 5950, how to download plastic design to BS 5950 pdf, and how to use it effectively. By the end of this article, you will have a better understanding of this topic and be able to access the relevant resources for further study.
Plastic Design To Bs 5950 Pdf Download
What is Plastic Design?
Plastic design is a method of designing steel structures that considers the plastic behavior of the material under load. Unlike elastic design, which assumes that the material remains within its elastic limit and returns to its original shape after unloading, plastic design allows for some permanent deformation of the material beyond its yield point. This means that the structure can redistribute the internal forces and moments among its members, resulting in more uniform stress distribution and lower stress concentrations.
Plastic design has several advantages over elastic design, such as:
It reduces the amount of steel required for a given load capacity, thus saving material cost and weight.
It allows for more creative and aesthetic design solutions, as the structure can have different shapes and forms without compromising its strength.
It increases the ductility and robustness of the structure, as it can absorb more energy before failure and resist progressive collapse.
It simplifies the analysis and design process, as it only requires checking the ultimate limit state (ULS) rather than both the serviceability limit state (SLS) and the ULS.
What is BS 5950?
BS 5950 is a British standard that specifies the rules and guidelines for the design of steel structures. It covers various aspects of structural design, such as materials, loads, analysis, design, fabrication, erection, inspection, testing, and maintenance. It also provides recommendations for different types of structures, such as buildings, bridges, towers, masts, cranes, offshore structures, etc.
BS 5950 was first published in 1985 and has been revised several times since then. The latest version is BS 5950-1:2000, which incorporates amendments up to 2011. It is compatible with other international standards, such as Eurocode 3 (EC3) and American Institute of Steel Construction (AISC) specifications. However, it also has some differences and specific features that reflect the British practice and experience.
How to Apply Plastic Design to BS 5950?
To apply plastic design to BS 5950, you need to follow the general principles and methods outlined in the standard. These include:
Choosing an appropriate structural system and layout that can achieve plastic behavior and stability.
Selecting suitable steel grades and sections that can provide adequate plastic moment capacity and ductility.
Applying appropriate load combinations and factors that account for the ultimate limit state and the partial safety factors.
Performing plastic analysis to determine the internal forces and moments in the structure and its members.
Checking the plastic design criteria, such as plastic moment capacity, plastic section modulus, plastic hinge formation, and plastic collapse mechanisms.
Designing the connections and details to ensure sufficient strength, stiffness, and continuity.
Let's look at each of these steps in more detail.
Plastic Moment Capacity
The plastic moment capacity (Mp) of a cross-section is the maximum moment that it can resist when it reaches its full plasticity. It depends on the shape, size, and material of the section. For a rectangular section, the formula for Mp is:
$$M_p = f_ybh^2/4$$ where fy is the yield stress of the material, b is the width of the section, and h is the depth of the section. For other shapes, such as I-sections, T-sections, circular sections, etc., you can use tables or software tools to find Mp.
For example, consider a simply supported beam with a span of 6 m and a uniform distributed load of 20 kN/m. The beam has an I-section with a flange width of 200 mm, a flange thickness of 20 mm, a web depth of 300 mm, and a web thickness of 10 mm. The material has a yield stress of 275 MPa. The plastic moment capacity of the section is:
$$M_p = f_ybh^2/4 = 275 \times 200 \times (300 + 2 \times 20)^2/4 = 1.24 \times 10^6 Nm$$ Plastic Section Modulus
The plastic section modulus (Z) of a cross-section is a measure of its resistance to bending. It is defined as the ratio of the plastic moment capacity to the yield stress of the material. For a rectangular section, the formula for Z is:
$$Z = bh^2/4f_y$$ For other shapes, you can use tables or software tools to find Z. The plastic section modulus is useful for comparing different sections with the same material or different materials with the same section.
For example, consider two beams with different I-sections but the same material. Beam A has a flange width of 200 mm, a flange thickness of 20 mm, a web depth of 300 mm, and a web thickness of 10 mm. Beam B has a flange width of 250 mm, a flange thickness of 25 mm, a web depth of 350 mm, and a web thickness of 12 mm. The material has a yield stress of 275 MPa. The plastic section modulus of beam A is:
$$Z_A = bh^2/4f_y = (200 \times (300 + 2 \times 20)^2)/(4 \times 275) = 4500 \times 10^3 mm^3$$ The plastic section modulus of beam B is:
$$Z_B = bh^2/4f_y = (250 \times (350 + 2 \times 25)^2)/(4 \times 275) = 6900 \times 10^3 mm^3$$ Therefore, beam B has a higher plastic section modulus than beam A and can resist more bending moment for the same material.
Plastic Hinge Formation
A plastic hinge is a point in a member where it reaches its full plasticity and rotates freely without increasing its moment. Plastic hinges form when the applied moment exceeds the plastic moment capacity of the cross-section. The formation of plastic hinges is essential for achieving plastic behavior and redistribution in the structure.
The criteria for plastic hinge formation depend on the type and shape of the member. For beams, plastic hinges form at locations where the bending moment diagram has maximum or minimum values. For columns, plastic hinges form at locations where the axial force diagram has zero or minimum values. For frames, plastic hinges form at locations where both bending moment and axial force diagrams have extreme values.
The cross-sectional shape and size of the member, which determine its plastic moment capacity and ductility.
The load distribution and pattern on the member, which affect the shape and magnitude of the bending moment and axial force diagrams.
The boundary conditions and support reactions of the member, which influence the location and number of plastic hinges.
The connection details and continuity of the member, which enable or prevent the transfer of forces and moments between adjacent members.
Plastic Analysis Methods
Plastic analysis is a method of determining the internal forces and moments in a structure by assuming that it behaves plastically under load. Plastic analysis can be performed by two main methods: the moment distribution method and the mechanism method.
The moment distribution method is a iterative procedure that distributes the applied moments among the members of the structure based on their relative stiffness and plastic moment capacity. The steps of this method are:
Divide the structure into segments at potential plastic hinge locations.
Assign a stiffness factor to each segment based on its length and section properties.
Apply the external loads and calculate the fixed-end moments for each segment.
Assume an initial distribution of moments among the segments based on their stiffness factors.
Check if any segment has reached its plastic moment capacity. If yes, mark it as a plastic hinge and redistribute its excess moment to the adjacent segments.
Repeat steps 4 and 5 until no more plastic hinges are formed or all segments have become plastic hinges.
Draw the bending moment diagram for the structure based on the final distribution of moments.
The mechanism method is a direct procedure that identifies the possible collapse mechanisms of the structure based on the formation of plastic hinges. The steps of this method are:
Divide the structure into segments at potential plastic hinge locations.
Apply a unit load to the structure in the direction of collapse and calculate the fixed-end moments for each segment.
Find the segment with the lowest ratio of plastic moment capacity to fixed-end moment. This segment will form a plastic hinge first.
Mark this segment as a plastic hinge and remove its contribution from the fixed-end moments of the adjacent segments.
Repeat steps 3 and 4 until the number of plastic hinges equals the degree of indeterminacy of the structure. This is the collapse mechanism of the structure.
Calculate the collapse load by summing up the products of plastic moment capacity and fixed-end moment for each segment in the collapse mechanism.
How to Download Plastic Design to BS 5950 Pdf?
If you want to download plastic design to BS 5950 pdf, you have several options to choose from. Here are some sources and steps to download it:
Official Website of BSI Group
The BSI Group is the organization that publishes and maintains BS 5950. You can visit their official website at https://www.bsigroup.com/ and search for BS 5950-1:2000 in their online shop. You can purchase and download it as a pdf file for 254.00. You will need to create an account and provide your payment details to complete the transaction.
Online Library of Civil Engineering Books
If you are looking for a cheaper or free option, you can try some online libraries that offer civil engineering books in pdf format. One example is https://www.civilax.com/, which has a collection of over 10,000 books on various topics related to civil engineering. You can search for plastic design to BS 5950 pdf in their search bar and find several results. You can download them for free or for a small fee depending on the source. You may need to register or sign up for some sites to access their content.
Free Ebook Download Sites
Another option is to use some free ebook download sites that offer a wide range of books in different genres and languages. One example is https://www.pdfdrive.com/, which has over 90 million books available for free download. You can search for plastic design to BS 5950 pdf in their search bar and find several results. You can download them by clicking on the download button or the book title. You do not need to register or sign up for this site.
How to Use Plastic Design to BS 5950 Pdf?
Once you have downloaded plastic design to BS 5950 pdf, you can use it as a reference and a guide for your structural design projects. Here are some tips and best practices to use it effectively:
Software Tools for Plastic Design
While you can perform plastic design manually using the methods and formulas in the pdf, it is more convenient and efficient to use some software tools that can automate the process and provide more accurate and reliable results. Some examples of software tools that can perform plastic design to BS 5950 are:
Tekla Structural Designer: This is a comprehensive software that can design and analyze steel structures according to various standards, including BS 5950. It can perform plastic analysis, design, and optimization of steel frames, beams, columns, connections, and details. It can also generate detailed reports and drawings for documentation and presentation.
Oasys GSA Suite: This is a versatile software that can model and analyze various types of structures, such as buildings, bridges, shells, towers, etc. It can perform plastic analysis and design of steel structures according to BS 5950. It can also handle nonlinear effects, such as large displacements, buckling, and post-buckling.
SCIA Engineer: This is a powerful software that can handle complex and multi-material structures, such as steel-concrete composite structures, timber structures, glass structures, etc. It can perform plastic analysis and design of steel structures according to BS 5950. It can also integrate with other software tools, such as Revit, AutoCAD, SketchUp, etc.
Case Studies of Plastic Design Projects
To learn from the practical application of plastic design to BS 5950, you can look at some case studies of real-world projects that have used this method. Some examples are:
The British Library: This is a large public library in London that has a steel-framed structure with a span of 50 m and a height of 25 m. It was designed using plastic design to BS 5950 to achieve an efficient and elegant solution. The structure consists of four main trusses that support the roof and the floors. The trusses have tapered sections and curved profiles to optimize the material usage and the aesthetic appearance.
The Millennium Dome: This is a massive dome-shaped structure in London that was built to celebrate the turn of the millennium. It has a diameter of 365 m and a height of 52 m. It was designed using plastic design to BS 5950 to achieve a lightweight and flexible solution. The structure consists of 12 main masts that support a tensioned fabric roof. The masts have circular hollow sections and are connected by ring beams and cables.
The Eden Project: This is a unique attraction in Cornwall that features two large biomes that house different plants from around the world. The biomes have a hexagonal shape and a span of up to 110 m. They were designed using plastic design to BS 5950 to achieve a durable and sustainable solution. The structure consists of tubular steel members that form a geodesic dome pattern. The members have varying sizes and angles to accommodate the complex geometry and loading.
Common Mistakes and Challenges in Plastic Design
While plastic design has many advantages, it also has some challenges and limitations that need to be considered and avoided. Some common mistakes and challenges in plastic design are:
Ignoring the serviceability limit state (SLS): Although plastic design only requires checking the ultimate limit state (ULS), it does not mean that the serviceability limit state (SLS) can be neglected. The SLS refers to the performance of the structure under normal service conditions, such as deflection, vibration, cracking, etc. These aspects can affect the functionality, comfort, and appearance of the structure and need to be checked separately.
can achieve plastic behavior and redistribution without losing its stability. However, this may not always be the case, especially for slender or complex structures that are prone to buckling or lateral-torsional instability. These effects can reduce the load-carrying capacity and ductility of the structure and need to be checked using appropriate methods and factors.
Using inappropriate sections or materials: Plastic design requires that the sections and materials used for the structure can provide sufficient plastic moment capacity and ductility. This means that they should have a high yield stress and a low ratio of ultimate stress to yield stress. However, some sections or materials may not meet these criteria, such as cold-formed sections, high-strength steels, brittle materials, etc. These sections or materials may not be suitable for plastic design and need to be modified or replaced.
Conclusion
In this article, we have explained what plastic design is, what BS 5950 is, how to apply plastic design to BS 5950, how to download plastic design to BS 5950 pdf, and how to use it effectively. We have also provided some examples, tips, and best practices for plastic design. We hope that this article has been informative and helpful for you.
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FAQs
Here are some frequently asked questions about plastic design to BS 5950:
What is the difference between plastic design and limit state design?
Plastic design is a method of designing steel structures that considers the plastic behavior of the material under load. Limit state design is a general approach of designing structures that considers different failure modes or limit states of the structure under load. Plastic design is a specific type of limit state design that focuses on the ultimate limit state (ULS) of the structure.
What are the advantages and disadvantages of plastic design?
Plastic design has several advantages over elastic design, such as reducing the amount of steel required, allowing for more creative and aesthetic design solutions, increasing the ductility and robustness of the structure, and simplifying the analysis and design process. However, plastic design also has some disadvantages, such as ignoring the serviceability limit state (SLS), overlooking the stability requirements, and using inappropriate sections or materials.
What are some applications of plastic design?
Plastic design can be applied to various types of steel structures, such as buildings, bridges, towers, masts, cranes, offshore structures, etc. Plastic design can also be combined with other methods or materials, such as composite structures, prestressed structures, reinforced concrete structures, etc.
How can I learn more about plastic design?
You can learn more about plastic design by reading books, articles, journals, manuals, standards, etc. on this topic. You can also watch videos, podcasts, webinars, lectures, etc. on this topic. You can also take courses, workshops, seminars, etc. on this topic. You can also practice plastic design by using software tools or doing projects on this topic.
Where can I find more examples of plastic design?
You can find more examples of plastic design by looking at some case studies of real-world projects that have used this method. You can also find more examples of plastic design by using software tools that can generate different scenarios and solutions for this method. You can also find more examples of plastic design by asking expert