What are frames?
The trusses and frames are the two most important structural members of civil engineering. Trusses are the interconnection of links and other structural members. The interconnection with other members makes the system behave as a single member that supports and transfers loads. Trusses are generally two types, plane truss, and space truss. Frames on the other hand form the skeleton of any building construction. Frames are structures formed by the connection of beams, columns, slabs, and joists. These members provide the building with the required structural support.
In civil engineering construction, a framing system can be classified into three different types, convention framing system, advanced framing system, and concrete framing system. Out of the three, the advanced framing system is the optimized way of framing system, it consumes less material during its construction and also, it supports efficient energy management.
Here in this article, a brief introduction has been provided about frames and their usages in different civil engineering applications.
Basic terminologies of a framing system
As stated in the quick introduction, a framing system is composed of four basic parts beams, columns, slabs, and joists. Here in this section, some of the basic terminologies of a framing system have been outlined including basic components.
Columns are the vertical structural members that carry axial compressive loads. Columns form the fundamental structure of a framing system, including the foundation of a building. Columns carry an entire load of a building including its own structural members like beams, slabs, and joists, and transfer the load to the foundation. A column can have multiple cross-sections like circular, square, rectangular, etc. The square cross-sectional column provides the highest modulus of rigidity. Damaging a single column will cause the entire building to fall.
Beams are the structural members that are intended to carry transverse shear loads. Shear loads are those loading systems that are parallel to the cross-section of the member and perpendicular to the longitudinal axis. Beams are always placed in between the columns, and directly transfer the loads to the columns. The majority of the framing system uses simply supported beam conditions, but sometimes cantilever beams are also used. The loads that act on the beam can be a point load or a distributed load.
Slabs are the flat structural members which are built above the beams. The weight of the entire slab is supported by beams and columns. They are witnessed by both dead and live loads. They are the area made of reinforced concrete where occupants use it for walking, standing, and other purposes. According to building codes, the standard thickness of a slab is between 100 mm to 500 mm.
Reinforcement is a process to induce strength and durability in concrete. Concrete is a brittle substance that has excellent compressive strength, but they have extremely weak tensile strength. A high tensile load will lead to the sudden failure of the concrete. So to enhance the tensile strength property of the concrete, reinforcement is provided. reinforcement is done by the use of steel bars which are ductile materials. A ductile material has superior tensile strength properties, this is what makes steel bars mostly used for reinforcements. A network of bars or grid is formed, where the concrete mixture is poured, upon hardening, they behave like a single member having strong compressive and tensile strength.
Joists are another structural member specially made of wood. They are used to support the floor with the foundation. Joists are mainly provided above the columns above which the floor is constructed. They mainly carry vertical loads.
Types of framing systems
In building construction, there are two types of framing systems, these framing systems are discussed below.
Rigid frame system
These frames have the ability to resist superior deformations. These frames are characterized by a lack of pin joints, which means, most of the joints are fixed type. These kinds of framing systems find their application in the steel-concrete system, and they are statically indeterminate. The beams and columns undergo bending to take care of both lateral and vertical loads. Hence, the strength and the stiffness of these frames largely depend on the rigidity properties of beams and columns.
Castigliano's theorem and force method are used in the analysis of such frames. The rigid frame is further classified into two types, they are:
- Fixed end rigid frame: The supports of these kinds of framed structures are fixed type, hence the structure is constrained to move in both directions (X and Y direction). Due to such boundary conditions, three types of support reactions are induced; vertical reactions, horizontal reactions, and bending moments.
- Pin-ended rigid frame: In the pin-ended rigid frame, instead of making the supports fixed, they are pin jointed or hinge jointed. Due to the pin joint, the frame has only two degrees of freedom. This gives rise to horizontal and vertical reactions.
Braced frame system
The frames of this kind of system have braces that are pin-connected, i.e. an additional link connects the beam and column members via pin joints. This arrangement allows the structure to carry lateral loads. This framing system provides more resistance to earthquakes and is more efficient than rigid frames. Different types of bracing in this category can be used like knee-bracing, diagonal bracing, X bracing, K bracing, and shear walls.
There are generally two types of braced frame systems, they are:
- Gabled frames: These kinds of framing systems have a peek at the top. These are mostly used in areas where the possibility of rain is high.
- Portal frames: These kinds of frames are widely used in industrial constructions. The vertical supports are attached to the beams by fixed supports. These kinds of structures have a wide span and floor area.
Advanced framing systems
Advanced framing is a technique that uses predefined methodologies to build framing structures that are highly optimized in terms of strength and durability. The framing system uses minimum material and labor in the construction. It is also known as optimum value engineering. The below-mentioned points outline some of the major benefits of using advanced framing systems.
- Structural integrity
- Energy efficiency
It also outlines a set of rules which account for maximum building insulation and sheathing.
Context and Applications
This topic is widely taught in many undergraduate and postgraduate degree courses of:
- Bachelors in Technology in Civil Engineering
- Bachelors in Technology in Mechanical Engineering
- Masters in Technology in Civil Engineering
- Masters in Technology in Building and Construction
- Masters in Technology in Construction Technology
1. Which of the following is a part of the framing system?
- All of these
Answer: Option d
Explanation: Joists, beams, and columns are part of framing systems.
2. What kind of load is carried by a column?
- Axial tensile load
- Axial compressive load
- Both axial tensile and axial compressive loads
- None of these
Answer: Option b
Explanation: Columns are the structural members that carry axial compressive loads.
3. Which of the following is true for rigid frame systems?
- They are statically determinate.
- They are statically indeterminate.
- They have fixed supports.
- Both b and c.
Answer: Option d
Explanation: A rigid frame system is a statically indeterminate system having fixed type supports.
4. Why steel reinforcement is done?
- To induce shear strength.
- To induce high seismic load resistance.
- To induce tensile strength.
- To induce torsional resistance.
Answer: Option c
Explanation: Steel reinforcement is done to induce tensile strength to the concrete structure.
5. Which of the following is true for concrete?
- It is a brittle substance.
- It has high compressive strength.
- Both a and b.
- It hardens on heating.
Answer: Option c
Explanation: A concrete is a brittle substance that has superior compressive strength.
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