What is the difference between dynamic loads and dead loads in structural design?
When it comes to structural design, there are a number of different loads that you need to be aware of. These loads include vertical loads, horizontal loads, and longitudinal loads, and they all fall into even more load categories.
Today we will focus on live loads and permanent loads, which are part of the broader group of vertical loads. Dead loads are the first vertical load that always needs to be considered. These loads are always permanent and will always be inside the building. A permanent load is often a permanent partition wall, a structural part, and permanent equipment. Often this type of load includes all the beams, roof, columns, walls and more.
Dynamic loads are also called imposed loads and are moving loads, or live loads, that do not have any impact or acceleration. All of these loads are part of what the occupant brings into the building. These items are typically furniture and movable partitions.
Dynamic loads will continually change within a building as people bring things in and out of the space. Therefore, it is important that the slabs can support a concentrated load or an evenly distributed load at any time. However, because there is virtually no way for the floor to support the maximum load at the same time, you have some leeway when it comes to designing columns, load-bearing walls, pillar supports, and even the foundation.
It is necessary to determine what the dead load of a building will be before any of the live loads are brought inside. Most people forget to include systems like HVAC, ducts, elevators, plumbing, and even fixed manufacturing equipment when calculating live load. But these items are equally important and can really change the calculation you make tremendously.
You will need load numbers for both dead loads and live loads before you begin constructing any building because these numbers can also potentially change the cost of construction. The reason for this is that you may need to use different materials than you initially thought of and this could mean the construction process will cost more in the long run. This is especially true if you need to use concrete instead of wood or steel.
To calculate load numbers, you must consult the limits and permitted loads for the location in which you are building. These will often be the numbers you find in the International Residential Code book.
Of course, you'll also need to check local building codes before starting any construction because there may be specific dead and live load requirements that you need to be aware of. What may be acceptable in one part of the country may not be acceptable in another and you need to be aware of any nuances that could mean the difference between a building passing inspection and not passing inspection.
Questions to Ask When Determining Which Building Codes to Use for Your Building Design
- What is the occupancy category of the building?
A structure used to store hay or other livestock feed will have different requirements than an elementary school or office building. The risk category would be significantly lower for the former than for the latter.
- What material will be used for the dead weight?
Many homes are built from wood, but most commercial buildings can be constructed from wood, steel, or concrete.
- What is the design of dynamic loads?
You must know the live load requirements for the structure you are building so you know which materials to use during the construction process. After all, the dynamic loads of a house will be very different from those of a restaurant or office building. It's also important to note that different rooms will have different dynamic loads, so it can be helpful to know how each specific room will be used before construction begins.
Steps to follow when using Span tables
- Check your plans to determine the span as well as center spacing
- Check codes for dead load, live load, snow load and even deflection
- Choose the appropriate span table
- Determine the minimum values of Fb and E by matching your design condition with the range in the table
- Choose the class from the values listed in the design value table
- Determine the required compression perpendicular according to the grain design value in the table
- Always make sure that the numbers selected in steps five and six are the correct numbers and will match in the end
Some active load numbers from the International Residential Code
Outdoor balconies 60
Deck 40
Garages for 50 passenger cars
Attics without storage 10
Sleeping 30
Rooms that do not accommodate 40 people
It is important to note that these are all uniformly distributed minimum live loads for these spaces.
Failure to use the proper numbers of dynamic loads and dead loads can result in dangerous conditions in any building. Buildings that are not built to withstand both permanent and dynamic loads can collapse over time. It will also not be safe for anyone to be inside buildings that do not follow codes for live loads and dead loads.
Many people think that the stability of any building is abundant, regardless of the materials from which it was constructed. However, not using the appropriate materials for permanent and dynamic loads can make any building unsafe and uninhabitable. Therefore, it is absolutely necessary to learn more about live loads and dead loads so that you can construct buildings properly in the future.
After all, people are bringing more items into buildings than ever before, and you'll want to make sure those items are safe and won't cause any part of the building to collapse.
If you haven't given much thought to dead loads and live loads in the past, now is the time to make sure you know as much as possible about them all. It will just make everything you build in the future safer than ever.
