1. Failing to Define Project Requirements Early
1.1 Building Use and Space Requirements
The intended use of the building affects many structural decisions. A warehouse, workshop, production facility, and multi-purpose building may have very different requirements for:
- Clear span and column spacing
- Storage areas and circulation routes
- Equipment and machinery
- Overhead cranes
- Doors and openings
- Floor levels and loading requirements
- Future expansion
For example, a workshop with heavy equipment or an overhead crane may require different structural provisions from a warehouse used primarily for storage.
1.2 Future Changes Should Be Considered
A building may also need to accommodate future changes in production, storage, equipment, or internal layout.
This does not mean every possible future requirement should be designed into the structure. Instead, important foreseeable changes should be identified early so engineers can evaluate whether they affect the structural grid, foundations, crane provisions, or other major elements.
2. Using Incomplete or Incorrect Design Criteria
Once the building requirements are established, the next step is to define the design criteria that govern the structure.
2.1 Loads Must Reflect the Actual Project
Structural design may need to consider combinations of:
- Dead loads
- Live or imposed loads
- Wind loads
- Snow loads
- Seismic actions
- Equipment or crane loads
- Temperature or other project-specific actions
The applicable loads depend on the project location, building use, geometry, and governing design standard. For projects designed under the U.S. system, ASCE/SEI 7-22 provides provisions for design loads and load combinations.
For a deeper explanation of how different actions are considered together, see Load Combination in Steel Structure Design.
2.2 Site Conditions Matter
Design criteria should also reflect actual site conditions rather than generic assumptions.
Depending on the project, this may include:
- Local wind conditions
- Snow or rainfall
- Seismic conditions
- Exposure and environmental conditions
- Soil and foundation information
- Building importance and occupancy
Accurate information at this stage reduces the risk of significant changes after structural design has already begun.
3. Choosing a Structural System Without Considering the Whole Building
Selecting a structural system based only on building type or span can lead to an inefficient design.
3.1 The Structural System Should Match the Requirements
Portal frames, trusses, rigid framing, multi-story framing systems, and other structural arrangements each have different characteristics.
The appropriate solution depends on factors such as:
- Building span
- Number of floors
- Required clear space
- Applied loads
- Building height
- Crane requirements
- Architectural constraints
- Fabrication and erection considerations
- Potential future modifications
A portal frame may be an effective solution for many single-story industrial buildings, while other structural arrangements may be more appropriate when the building has multiple floors, unusual loading, or different spatial requirements.
For a comparison of two common systems, see Portal Frame vs Truss System in Steel Structures.
3.2 Avoid Choosing a System Too Early
The goal is not to select the most sophisticated structural system. It is to select a system that provides the required structural performance and usable space without unnecessary complexity.
A system that appears economical at the structural level may create additional fabrication, transportation, erection, or operational requirements. These factors should be considered together.
4. Treating Materials and Environmental Conditions as Separate Issues
Material selection and environmental exposure are closely connected. Choosing a steel grade without considering the project's design requirements or selecting a coating system without considering the environment can create problems later.
4.1 Specify the Required Steel Grade
The required steel grade should be defined according to the applicable design standard and project requirements.
Depending on the project, specifications may refer to grades such as Q235 or Q355 under Chinese standards, ASTM specifications used in the U.S. system, or S235 and S355 under European standards. The applicable material specification should be confirmed as part of the project requirements.
For U.S.-based projects, ASTM steel standards provide specifications for different types of steel, including structural steel used in construction.
See Structural Steel Grades for Buildings for a more detailed discussion of common structural steel grades.
4.2 Consider the Exposure Environment
Steel protection requirements depend on where and how the structure will be used.
Coastal environments, industrial atmospheres, high humidity, chemical exposure, and other aggressive conditions can increase corrosion risk. The appropriate protection system should therefore be considered during design rather than added as an afterthought.
ISO 12944-3 addresses design considerations for steel structures that will be protected by paint systems, including measures intended to reduce premature corrosion and facilitate inspection and maintenance.
For practical information on protection methods, see Corrosion Protection and Coatings for Steel Buildings.
4.3 Consider Sustainability Requirements When They Apply
If the project is targeting a green building certification or has specific sustainability requirements, these requirements should also be identified during planning. They may affect material documentation, environmental product information, energy-related design decisions, or other project deliverables.
For projects pursuing LEED certification, sustainability requirements should be considered early enough to coordinate them with the overall building design and documentation process.
5. Separating Budget and Schedule From Design Decisions
A common planning mistake is treating budget and schedule as separate from engineering.
In reality, early design decisions can influence fabrication complexity, material quantities, transportation, erection, and long-term maintenance.
5.1 Define the Cost Drivers Early
A realistic project budget should consider more than the weight of structural steel.
Depending on the project scope, important cost factors may include:
- Structural steel
- Cladding and roofing
- Insulation
- Doors and openings
- Crane systems
- Corrosion protection
- Foundations
- Fabrication
- Transportation
- Erection
- Future maintenance
A low initial structural cost does not necessarily mean a lower overall project cost if it creates additional requirements elsewhere.
5.2 Design Information Affects Schedule
Steel fabrication depends on sufficiently defined engineering information. Changes to dimensions, openings, loads, connections, materials, or other major requirements after fabrication has started can result in redesign, production changes, or delays.
For this reason, the project should establish key design requirements before final fabrication information is released.
6. Failing to Confirm the Applicable Codes and Project Deliverables
Another important planning mistake is assuming that one familiar set of standards can be applied to every project.
The governing requirements may depend on the project location, local authorities, contract documents, client requirements, and the scope of engineering services.
For projects using the U.S. structural steel design framework, AISC 360 provides generally applicable requirements for the design and construction of structural steel buildings. In Europe, the EN Eurocodes provide a coordinated series of standards for structural design.
The important point is not simply to name a standard. The project team should establish:
- Which design codes apply
- Which edition is required
- Which loads and combinations govern
- Which material standards apply
- What drawings and calculations are required
- What inspection and certification documents are required
- Who is responsible for design approval and local compliance
These decisions should be clarified before detailed engineering and procurement progress too far.
