A structural design is much more than just drawings on paper or a computer screen. In fact, it's a... complex technical process, methodically structured, This transforms an architectural idea into a safe, functional, and durable structure. Therefore, from the first meeting with the client to the delivery of the final plans, each step plays a crucial role in the quality and safety of the project.
In this article, we will guide you through each phase of the development of a structural project. Furthermore, we will explain what happens at each stage, the objectives, the tools used, and the expected deliverables.
What is a structural project?
Before we begin, it's essential to clarify what characterizes a structural project. In simple terms, it is the... A set of documents, calculations, and drawings that define how a structure will be built., ensuring that it withstands all loads and forces applied during its service life.
A well-developed structural design ensures not only the safety of the people who will use the building, but also the resource savings, a durability and the compliance with Brazilian technical standards. Furthermore, it serves as a communication tool between engineers, architects, and builders, clearly outlining every detail of the project. Therefore, its importance is undeniable.
The Main Stages of a Structural Project
The development of a structural project involves a well-defined sequence of steps. Therefore, each one has its own importance. Furthermore, they all share a calculation methodology that ensures the consistency of the process. Thus, understanding each phase is essential to comprehending how a project comes to life.
Step 1: Preliminary Analysis and Data Collection
ObjectiveGather all the necessary information for the project.
Before any calculations or sketches, the structural engineer needs to gather a series of essential information. In fact, this is the basis of all future work. Therefore, this step requires a great deal of attention.
Required Documentation:
- Complete architectural design to scale.
- Soil investigation report (geotechnical)
- Topographic survey of the area
- Characteristics of neighboring buildings
- Classification of environmental aggressiveness class
- Specification of the desired concrete strength
- Analysis of external factors (wind, earthquakes, if applicable)
- Estimated permanent and variable loads
- Desired timeframe for the start of construction.
This is a critical stage. Indeed, errors or omissions at this stage can compromise the entire subsequent project. The structural engineer works together with the client, the architect and, if necessary, the geotechnical engineer. This ensures that no information is overlooked. This collaboration is vital to the success of the undertaking.
Step 2: Structural Design
ObjectiveDefine the structural system and perform the preliminary dimensioning.
In structural design, the engineer makes crucial decisions about how the structure will be organized. Therefore, this stage will shape the entire future project. It is worth noting that any error here has consequences for the next phases.
Definition of the Structural System
Initially, the engineer defines which structural system will be used. The main options include:
- Reinforced ConcreteThe most common system in Brazil, versatile and economical for most buildings.
- Metal StructureIdeal for large spans and lightweight structures, such as industrial roofs.
- Structural MasonryThe walls function as structural elements, reducing costs in smaller buildings.
- Precast ConcreteIt speeds up construction and reduces waste.
- Steel Frame and Wood FrameIndustrialized systems for rapid construction
In many cases, this choice is made by the client or the architect. However, the structural engineer must assess the technical and economic feasibility. Therefore, this assessment is essential for the success of the project.
Location and Preliminary Sizing of Elements
After defining the system, the engineer performs a preliminary layout of the structural elements. Basically, he distributes:
- PillarsVertical distribution of elements to create an efficient structural grid.
- BeamsDetermining the main beams that will support the slabs.
- SlabsDefinition of the slab type (solid, ribbed, prestressed, etc.)
- FoundationsPreliminary type based on the survey report (shallow or deep)
Preliminary dimensioning consists of estimating the dimensions of these elements based on practical rules and experience. For example, the height of a continuous concrete beam is usually approximately 1/12 of its span. This preliminary dimensioning serves to:
- Establish a rough initial budget.
- Identify any potential technical limitations.
- Create the foundation for the next step.
Generated DocumentationSketch of the structure, location of the main elements, preliminary dimensioning.
Step 3: Defining Actions and Combinations
ObjectiveIdentify and quantify all the forces that will act on the structure.
Before we move on to the calculations, it's necessary to define what actions our structure will be subjected to. That's precisely why this step is so important. Furthermore, it determines the safety of the entire building.
The Brazilian standard ABNT NBR 8681:2003 classifies these actions into three main categories. Specifically, each category has a different behavior. Consequently, they must be treated in different ways.
Permanent Actions
Permanent actions are those that act continuously on the structure. Therefore, they include:
- Self-weight of the structure (concrete, steel)
- Weight of walls and masonry
- Weight of fixed equipment
- Prestressing (in prestressed structures)
Variable Actions
On the other hand, these actions vary over time. In fact, they are expected throughout the structure's lifespan. Typically, they include:
- Occupancy loads (people, furniture, mobile equipment)
- Wind loads
- Snow loads (in applicable regions)
- Thermal loads
Exceptional Actions
Furthermore, exceptional actions are those that occur very infrequently. Although rare, they should be considered in the design. Consequently, examples include:
- Explosions
- Vehicle impacts
- Earthquakes (in seismic regions)
Combinations of Actions
After identifying the actions, the engineer establishes different load combinations for sizing. Therefore, there are two main types. Specifically:
- Combinations for Ultimate Limit State (ULS)They assure that the structure will not collapse.
- Combinations for Service Limit State (SLS)They ensure that the structure will function properly during use, without excessive deformation or cracking.
Generated DocumentationAction report, load combinations, calculation memos.
Step 4: Structural Modeling
ObjectiveRepresenting the structure in analysis software.
With the information from the previous steps in hand, we arrive at the structural modeling. This is the moment when the engineer imports the structure into specific engineering software. Literally, the project leaves the paper and enters the computer.
Tools Used
The most commonly used software in Brazil for this step includes:
- TQS (CAD/TQS)TQS is the most widely used software in major Brazilian engineering firms. It offers complete modeling, structural analysis, and integrated dimensioning. Therefore, approximately 90 out of the 100 largest structural design firms in Brazil use TQS.
- CYPECADWidely used Spanish software, capable of working with multiple structural systems.
- EberickBrazilian software with a user-friendly interface and BIM integration.
- SAP2000Finite element analysis software, widely used in more complex structures.
- RevitBIM software that enables integration between architecture and structure.
Modeling Stages
During the modeling process, the engineer performs several important actions:
- Geometry input: Coordinates of columns, beam lengths, slab areas
- Definition of Materials: Concrete strength, type of reinforcing steel.
- Load Application: Inserting actions and their combinations into the structure.
- Definition of Boundary Conditions: How the structure is supported, where the foundations are located.
Generated DocumentationThree-dimensional model of the structure in the software, preliminary visualizations.
Step 5: Structural Analysis
ObjectiveDetermine the internal forces in each element.
After the structure is modeled, the software processes the structural analysis. This is a crucial step. In fact, it determines all the internal forces that each structural element will undergo. Therefore, its accuracy is vital.
What happens in this stage?
The software uses advanced mathematical methods to calculate several essential parameters:
- Bending moments: Stresses that tend to bend beams and slabs.
- Shear forces: Forces that attempt to cut the cross-section of the element.
- Normal stresses: Compression or tension along the element.
- Displacements and deformations: How much the structure moves under loads.
- Cracks and fissuring: Analysis of potential crack openings in concrete.
Available Analysis Methods
There are different methods of analysis that can be used. Therefore, each one has its own particularities:
- Space PortalThree-dimensional analysis that considers the interaction between all elements (columns, beams, slabs).
- GrillSimplified analysis for structures where the elements are in a plane.
- Finite ElementsA more refined method, dividing the structure into thousands of small elements for precise analysis.
Validation of Results
Before proceeding, the engineer meticulously validates the results. At this stage, he verifies:
- If the horizontal displacements are within acceptable limits
- The global stability parameter (α or γz)
- That no bar reached its resistance limit improperly.
- Possible problems in the model that require correction.
Generated DocumentationEffort diagrams, results spreadsheets, processing reports.
Step 6: Sizing of Structural Elements
ObjectiveCalculate the final dimensions and required reinforcement.
With the efforts clearly defined, the crucial moment arrives: sizing each structural element. In practice, this is one of the most important stages of the project. Therefore, it requires extensive technical knowledge.
Design of Reinforced Concrete Beams
For beams, the engineer specifically determines:
- Section height: Based on positive and negative bending moments.
- Section width: Generally defined by construction criteria (multiples of 5 cm)
- Longitudinal Reinforcement: Quantity and diameter of bars that resist bending.
- Transverse Reinforcement (Stirrups): Bars that resist shear stress.
The TQS software, for example, performs this sizing. automatically, Considering stress envelope diagrams and specific criteria defined by the engineer, the work becomes much faster and more precise.
Column Dimensioning
For pillars, the engineer calculates:
- Section dimensions: Height and width required to resist compression.
- Longitudinal Reinforcement: Vertical steel bars
- Confinement Stirrups: To contain the reinforcement and improve the strength of the concrete.
Slab Dimensioning
The slabs, in turn, require special attention:
- Thickness: Based on deflection and strength criteria.
- Lower Armor: To withstand positive moments.
- Top Reinforcement: Close to the supports (negative moments)
Foundation Design
For the foundations, the engineer calculates:
- Footing Dimensions: Area required to distribute the loads from the columns.
- Depth: Based on the borehole report.
- Armor: Distributed appropriately at the base.
Compliance Checks
All of these dimensions must be strictly adhered to:
- NBR 6118Concrete structure design project
- NBR 8681Actions and safety in structures
- Durability criteria: Appropriate concrete cover thickness for environmental aggressiveness class
Generated Documentation: Floor plans with dimensions, material specifications, and detailed calculation reports.
Step 7: Project Optimization
ObjectiveTo improve technical and economic efficiency.
After the initial sizing, it is often possible optimize the project. There are often opportunities for improvement.
- Adjusting dimensions to reduce material costs without compromising safety.
- Seeking a more architecturally elegant solution
- Increase efficiency in cases where there is unnecessary oversizing.
- Review pillar placements to improve circulation and functionality.
This iteration may involve communication with the architect and the client, especially if changes affect the building's form. Therefore, communication is essential at this stage.
Step 8: Armor Detailing
ObjectiveCreate precise drawings of how each piece of armor will be constructed.
Detailing is a step. extremely important. Essentially, this is where it is specified. exactly how each piece of iron will be cut, bent, and positioned.. In this way, the quality of the work is guaranteed.
What is detailed?
At this stage, the following elements are carefully detailed:
- Bar diameter: Which gauge will be used (10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 32 mm, 40 mm)
- Bar length: Exact cutting measurement
- Positioning: Where each bar will be positioned (reinforcement layers, spacing)
- Amendments: How will the amendments between bars be made (minimum overlap)?
- Bends: Angles and radii of curvature of the bars
- Hooks and spirals: Stirrup arrangement and confinement
Software Automates This Task
Software such as TQS automates much of the detailing. Therefore, this is very beneficial:
- It automatically generates the reinforcement bars based on the sizing.
- Creates cutting and bending lists (iron quantity)
- Check minimum splice lengths.
- Generates drawings automatically.
Generated DocumentationDetailed drawings of each element (beams, columns, slabs), cutting and bending lists, quantities.
Step 9: Compatibility with Other Projects
ObjectiveEnsure that the structural design does not conflict with other disciplines.
A complete project involves multiple specialties: architecture, plumbing, electrical, HVAC, etc. Therefore, coordination is essential. For this reason, this step cannot be neglected.
Compatibility ensures that:
- Electrical, plumbing, and air conditioning pipes run through it. without conflicting with the structure
- The shafts (vertical spaces) were properly planned.
- Equipment loads were taken into account in the structural design.
- All professionals share the same understanding of the project.
In the era of BIM (Building Information Modeling), This has become much more efficient. Certainly, all models are integrated and potential conflicts are identified automatically.
Step 10: Project Review and Validation
ObjectiveTo guarantee quality, safety, and compliance.
Before issuing the final design, the engineer performs a thorough review. At this stage, he checks:
- If all the rules were met
- The main calculations
- Drawings for clarity and completeness
- Material specifications
- If the quantity is correct
Often, an experienced colleague from the office also reviews the project independently. This ensures maximum quality. Therefore, this double review is essential.
Step 11: Issuance of Final Documentation
ObjectiveProvide the client with all the necessary documents for the construction.
The final product of a structural design project is a complete set of documents. Specifically:
For Reinforced Concrete Structures, it Typically Includes:
- Plant ShapeDimensions of all columns, beams, and slabs on each floor.
- Site PlanPrecise indication of where each element is located.
- Cuts and ElevationsVertical view of the structure.
- Armor DetailsSpecific drawings showing how each piece of armor is positioned.
- Quantity of MaterialTotal quantity of concrete, steel, formwork, etc.
- Calculation ReportTechnical document detailing all calculations performed.
- Descriptive ReportExplanation of materials, specifications and procedures.
- ART (Technical Responsibility Annotation)Document that establishes the engineer's technical responsibility.
Delivery Formats:
Currently, projects are delivered in various formats:
- PDF spreadsheetsFor viewing and printing
- CAD/DWG fileFor possible future changes
- 3D ModelsAugmented reality visualization, facilitating comprehension of the artwork.
- Digital reportsMemoranda in editable formats
Step 12: Monitoring During Construction
ObjectiveTo ensure that the work follows the project plan.
The engineer's role doesn't end with the delivery of the drawings. Therefore, he must... monitor the execution actively:
- Check if the dimensions are being respected.
- Evaluate the quality of the materials used.
- Inspect the correct position of the reinforcement bars before pouring the concrete.
- Authorize necessary changes during construction (always documented).
- Perform concrete strength tests.
- Identify and resolve structural problems that arise during construction.
This technical support is essential. In fact, it guarantees the final quality of the structure and the building safety.
Essential Tools and Software
To efficiently execute each step above, the structural engineer uses several specialized tools:
Analysis and Sizing Software:
- TQS (CAD/TQS)Complete, integrated, ABNT standards
- CYPECADVersatile, multiple structural systems
- EberickUser-friendly interface, BIM integration
- SAP2000Advanced analysis of complex structures
- RevitBIM, integration with architecture
3D Modeling Software:
- AutoCADTraditional 2D/3D CAD
- RevitIntegrated BIM
Auxiliary Tools:
- Microsoft ExcelAdditional calculations
- MATLABAdvanced numerical analyses
- SkyCivOnline tools for quick analysis
Technical Standards Governing the Entire Process
All the steps described above must strictly follow Brazilian technical standards. Therefore, here are the main ones:
- NBR 6118:2023Concrete Structure Design – Procedure. This is the fundamental standard for any reinforced concrete project.
- NBR 8681:2003Actions and safety in structures – Procedure. Defines how to calculate the actions on the structure.
- NBR 14931: Execution of concrete structures – Procedure
- NBR 14855Design, execution and control of precast concrete structures.
Estimated Time for Each Step
The total time for a structural project varies depending on its complexity. Therefore, a general estimate is:
- Preliminary Analysis1-2 weeks
- Structural Design1-2 weeks
- Structural Analysis1-2 weeks
- Sizing1-2 weeks
- Details2-4 weeks
- Compatibility1-2 weeks
- Review and Validation: 1 week
Approximate Total8-15 weeks, depending on the complexity.
For simple and small buildings, the process can be faster. Conversely, for complex structures, such as towers, special structures, or those with innovative systems, it can take months.
Common Mistakes and How to Avoid Them
During the development of a structural project, some common errors occur. Fortunately, it is possible to avoid them:
Lack of Initial InformationThis can lead to significant rework. Therefore, the solution is to ensure complete data collection from the start.
Inadequate CommunicationBetween architect, structural engineer, and geotechnical engineer. Therefore, the solution is to hold regular design meetings.
Inadequate MatchingConflicts were discovered during construction. Therefore, the solution is to use BIM and systematically reconcile them.
OversizingThe structure is more expensive than necessary. Therefore, the solution is to review and optimize it after an initial analysis.
Neglecting DurabilityInadequate coverage specification. Therefore, the solution is to consider the aggressiveness class from the beginning.
The Role of the Structural Engineer
Throughout this entire process, the The structural engineer is responsible. for several critical functions:
- Making technical decisions based on standards and experience.
- To guarantee the safety of the structure.
- Optimize costs without compromising quality.
- Communicate clearly with the entire project team.
- To be technically responsible (through the ART) for the structure.
- Monitor execution and ensure compliance.
It's a demanding profession. in-depth technical knowledge, ethical responsibility e commitment to quality and safety. Therefore, it is a challenging and rewarding career.
Conclusion: From Concept to Construction
A structural design project is a living document that evolves through multiple stages. Therefore, each stage has its specific purpose. From the first conversation with the client to the delivery of the final drawings to the construction site, Every detail matters.. Therefore, full attention is required.
Understanding this process helps owners, architects, and builders appreciate the meticulous work involved. Therefore, they recognize the importance of creating a safe, economical, and durable structure. It's not just about designs – it's fundamentally about... to ensure that the buildings where people live and work are safe and well-designed.. Indeed, the responsibility is great.
If you are starting a construction project, now you have a better understanding of what will happen in the structural phase. Therefore, know that the engineer will take your idea from the initial concept until it becomes a real structure.
