Principal Architectural Ideas For Steel Erectors, Fabricators & Supervisors
The Erection of structural steelwork consists of the assembling of the steel components into a frame on the site.
It involves lifting the individual steel component from its position and placing it into another position specified by the frame drawing as it makes connections with other components in the frame.
The connections that exist in any frame are usually made through welding or bolts or a combination of both.
“According to the information shared by the steel construction, whirlwind steel and Osha Oregon websites concerning steel frame construction.”
The process of creating the connection in the frame involves making sure that the steels components were properly aligned before welding or tightening the bolts and nuts.
This process can be ignored by some inexperienced in the structural erection jobs but such action will lead to unbalanced frame structure which will not fit the desired designs and may lead to job repetition.
There are things builders must consider the frame and its designs while carrying out the construction on site.
Steel frames are usually made of column and beam steels, such that a frame is made up of steel beams and columns connected together by bolts or welds.
The frame will act as support to the entire structure after the building project irrespective of the type of building.
A frame made of column and beam steels can either be braced or continuous.
A braced frame will have sets of other small-sized steel components in a web format such that those components will act as support to provide stability and rigidity to the entire frame.
While the continuous frame will have no bracing rather bolts or welds will create rigidity in the connections such that the entire frame can be able to withstand the designed loads without any need for additional steel component.
The advantage continuous frame offers is to minimize the depth of the beams or the entire quantity. Besides that, the continuous frame has better look than the braced frame and it creates more space for accessibility.
It is believed that a good architectural designer or architect can make a good combination of the braced frame and the continuous frame methods to come up with quality and economical structural designs.
DIFFERENCES BETWEEN THE CONTINUOUS FRAME AND BRACED FRAME
|1. It is a moment resisting frame where the beam to column connections can be classified as being rigid.
2. It does not the local beam to column connection rotation in the global frame analysis into account.
3. It the type of frame recommended for special buildings like medicals, research institute, and housing for sensitive equipment.
4. The connections that exist in this frame are designed to transmit the end beam moments and shear forces into a column without the need for bracing to resist the lateral load.
5. The frame stability and rigidity comes from the connections and the stiffness of the members.
6. It has lower beam deflection and the floors are less sensitive to vibration.
7. The rigid connections of the frame can perform better than the braced frame in load reversal situations.
|1. A braced frame can be less expensive than a continuous frame.
2. Responsibility for temporary stability lies with the erectors.
3. As soon as the steel bracing is properly connected, the structure is stable.
4. Bracing of frame happens in the periphery of the building and ensures it’s in a plane, also it is mainly used in steel structural frames.
5. Due to the bracing of buildings, the lateral displacement or drift, as well as axial force and bending moment in columns, will reduce to a remarkable level.
6. The reduction in lateral displacement is a major advantage. Therefore the Concentric (X) bracing is more effective in this case than Eccentric (V) bracing.
7. Braced frames resist the wind and seismic forces, much more than non-braced buildings.
8. Steel bracing is economical, easy to erect, and has the flexibility to design for meeting the required strength and stiffness.
The above differentiation has given us the real idea of the differences that exist between the continuous frame and the braced frame. Now let us discuss the issue of the frame connections.
IMPORTANCE OF STRUCTURAL FRAME CONNECTIONS
Just as it was mentioned earlier that the connections are usually created with welds and bolts. There are cases a combination of the two can be done, and that is where there will be a likelihood of the frame failure due to continuous load impacts or vibrations.
The connections that exist in the frame are the weakest locations of the frame and most frame failure or accident occur due to the disconnections at the connection or connections.
Supervisors of structural erection jobs must pay much attention to the connections that exist in any frame design during construction projects.
For the above reason, experts in the construction field due make it compulsory that an experienced and qualified structural engineer should work alongside with the structural erectors for the purpose of procedural corrections, identification of errors and maintaining of standards.
According to whirlwind steels, the procedure specifies it as follows:
- The structural engineer sizes the members.
- The steel fabricator designs the connections.
- The structural engineer reviews and approves the connections
There are three basic connections that exist for frame design during structural erections and they are specified as follows:
PINNED CONNECTION: this is a connection design meant for transmission of end shear only, it is simple and has negligible resistance to rotation. In this type of connection, the beam can rotate at the point of connection but it cannot move in or out or up and down.
The connection is known to create weakness in the frame. It can be formed with flexible end plates and fin plates. However, stability can be added by bracing or with a concrete core.
FIXED CONNECTION: this type of frame connection counters that of the pinned connection because it resists the usual rotation of the beam at the point of connection. It is a moment-resisting connection. This connection can be formed by having plates of metal welded to the flanges at the bottom and the top of the column.
SPLICED CONNECTION: spliced connections offers a solution for strength and continuity of stiffness around both axes of the column. It holds the frame beams in line and allows for easy access from the adjacent floor for bolting up onsite. The spliced connection provides more convenient beam lengths for fabrication, transport, and erection.
The above ideas are meant to enlighten structural engineers, fabricators, and erectors in the site operation of frame erection, if you have any personal idea or contribution in regard to the idea, you can drop it through the comment form below this post.