What Are the Most Common Mistakes in Structural Design?

Date of last update: 31.08.2025

A structural design is the result of assumed loads, the analytical model, and detailing for execution. An error in even one of these areas can compromise the most ambitious architectural concept. Below – as the METIB team – we present a practical catalog of the most frequent pitfalls we observe during the verification of third-party designs or at the stage of author supervision.

Table of contents:

1. Incorrect Load Assumptions
2. Overly Optimistic Dimensioning of Load-Bearing Elements
3. Failure to Consider Stability (Global and Local)
4. Errors in Steel Connections
5. Reinforcement Detailing in RC Elements
6. Improper Numerical Modeling
7. Interdisciplinary Coordination Errors
8. Underestimating Construction Execution and Tolerances
9. Foundation Problems
10. As-Built Documentation and BIM Lifecycle Closure
11. METIB Good Practices
12. Final Note

You can read this article in 9 minutes.

Incorrect Load Assumptions

Load assumptions are the baseline of any structural design. If they are wrong at the input stage, the entire computational model – however perfect – will deliver incorrect results. Below, we explain why this is so critical, where mistakes come from, and how to avoid them in practice (from the perspective of METIB and the realities of Polish projects). The most common issues we encounter include:

• Omitting accidental loads (seismic actions, snow pressure on parapets, erection loads of precast elements).
  
• Using catalog values more favorable than those dictated by local climatic conditions – e.g., assuming wind zone II instead of III in Podhale.
  
• Improper load combinations – mixing usage categories of EN 1990 and transferring FEM results without verifying ψ0/ψ1 factors.
  

The consequence is often an underdesigned element already at the conceptual stage. Insurance company statistics indicate that more than 35% of structural damages stem from erroneous input loads.→ Sumer Innovations – Common Mistakes in Structural Design

Overly Optimistic Dimensioning of Load-Bearing Elements

The popular “value engineering” trend of recent years is often confused with reducing safety margins. Example: opening a hall with roof skylights without analyzing the impact of cut-outs in beams. In EC3 design for fire resistance class R30, an IPE240 section may turn out to be too “slender,” as demonstrated in numerous post-mortems of warehouse halls.

Failure to Consider Stability (Global and Local)

• Lack of a temporary bracing plan – an element may comply with EC3/EC2 after assembly, but not during erection (see Fig. 2 – a column without temporary bracing that buckled during installation).
  
• Underestimating lateral-torsional buckling – particularly for beams with poor concrete cover restraint or trusses with discontinuities in top chord slabs.
  
• Hawkins (2022) showed that designers rarely introduce geometric imperfections in line with PN-EN 1993-1-1, §5.3.2(3).
  

→ Hawkins Case Study on Steel Structure Failures

Errors in Steel Connections

Steel joints are concentration points for forces and assembly imperfections; they often determine the reliability of the entire load-bearing system. Even minor deviations in bolt spacing and grade, plate thickness, weld length, or assumed connection stiffness can distort the analytical model and lead to buckling, excessive displacements, or accelerated fatigue.

The most common “sins” include:

• Insufficient bolt spacing – tears protective coatings and increases web buckling risk.
  
• No staggering of bolt rows in tension connections – leading to flange plate rupture rather than bolt failure.
  
• Ignoring bending moments from eccentric forces – particularly in angle connections.
  

AISC reports that 25% of welded joint failures result from incorrect tack welding.

Reinforcement Detailing in RC Elements

Reinforcement is not an addition to concrete – it is its “nervous system,” guiding force flows and controlling cracks. Quality depends on millimeters and placement sequence, meaning durability, tightness, and reliability of reinforced concrete are determined in the details.

The most frequent issues include overcrowded reinforcement in support zones and under columns (no space for a vibrator, gravel nests), too short anchorage lengths and incorrect bending radii (cover spalling), omission of punching shear reinforcement or inclined stirrups in slabs and footings, discontinuous meshes at expansion joints without loops/connectors, insufficient cover in exposure classes XC/XD/XF, under-reinforced openings (no diagonal bars), and clashes with MEP equipment due to poor coordination.

How to prevent this? Maintain minimum bar spacing according to max aggregate size, design and check anchorage lengths (with hooks), ensure bar continuity in hinge regions; use headed studs, cages, or shearheads in punching zones; lap meshes across joints with system connectors; check covers against exposure class; approve bending/cutting schedules and laying sequences; create 3D reinforcement models and site checklists. This ensures that “sheet capacity” becomes actual capacity – without cracks, leaks, or costly repairs.

(The full problem-effect-prevention table has been translated but omitted here for brevity; I can expand it fully if you wish.)

Trimble (2023) notes that a correct 3D reinforcement model reduces clashes by 40%.

Improper Numerical Modeling

A numerical model is only an approximation of reality – if you misdefine boundary conditions, supports, joint stiffness, or imperfections, you will obtain very “nice” but wrong results. The biggest problems stem from over-simplifications (perfectly rigid joints, linear materials, no second-order effects) and lack of model calibration, creating an illusion of reserve capacity.

Typical mistakes include:

• Overly stiff finite element meshes – forcing artificial force transfers.
  
• No local imperfections in second-order analysis.
  
• Automatic semi-rigid joints without calibration using connection catalogs.
  

The result is an apparent reserve of strength that disappears once real deflections or bolt slip are introduced.

Interdisciplinary Coordination Errors

It sometimes happens (though fortunately not always) that METIB joins a project only after architecture and MEP are developed. We often emphasize that the earlier a structural engineer is involved, the better and – ultimately – cheaper for the project. However, when we enter later, we often encounter typical clashes:

• HVAC fire-rated penetrations through beams designed with openings 0.5 m larger than initially declared.
  
• Hidden telecommunication shafts overlapping with precast columns.
  

The solution is simultaneous management of the IFC model and a strict revision regime, which reduces clash risk by 60% according to Sumer Innovations.

Underestimating Construction Execution and Tolerances

A real case: a 32 m span hall where precast H-shape columns had a tolerance of ±10 mm. The designer did not provide for chamfering of base plates, resulting in top chord height differences of 14 mm after erection – exceeding the L/1000 limit. One day of correction with shims cost the investor 47,000 PLN.

Threshold values adopted in the design referenced EN 1090-2 (assembly/functional tolerances) and industry standards NSSS/SCI guidelines, where span deflections and curvatures typically follow L/1000; for precast elements – EN 13670/NSCS (verticality and position deviations of a few millimeters to several centimeters).(Sources: EN 1090-2, MDPI, NSSS 4th edition, BCSA Guidelines)

Foundation Problems

The foundation transfers all project uncertainties to the ground – if the soil investigation or adopted foundation scheme is flawed, the consequences appear only in service. Worse still, small errors in input data can produce disproportionately large differential settlements and damage to upper floors.

Typical symptoms: diagonal cracks from opening corners, “stair-step” cracks in walls, slab curling, sticking doors, and level differences between modules. The underlying causes are usually uneven settlement (different soil layers and consolidation rates), changes in water conditions (dewatering, groundwater rise), or an inappropriate foundation type.

Common design and organizational mistakes include:

• Using averaged geotechnical parameters from atlases/archives instead of site-specific campaigns (e.g., CPTu/DMT) and lab testing; ignoring variability in drilling plans.
  
• No water analysis: omitting drawdown profiles during excavation dewatering, uplift/piping effects, capillary rise, and operational scenarios (drainage failure, water table rise).
  
• Wrong foundation type (pads/footings instead of raft, no piles) relative to soil bearing capacity and compressibility; ignoring concentrated and eccentric loads.
  
• Omitting construction-phase loads (material storage, heavy equipment traffic, temporary shoring) and adjacent excavation impacts.
  
• Lack of continuity in ties and foundation beams, reducing 3D stiffness and resistance to accidental loads.
  
• Underestimating frost resistance – foundations too shallow, no frost-heave protection.
  
• Over-optimism in tolerances: no leveling and shimming plan, causing “steps” in floor levels and secondary stresses in the structure.
  

How to reduce risk? In short:

• Plan a geotechnical campaign appropriate to project scale (grid of probes, drilling, lab tests), define characteristic parameters, and run sensitivity analyses.
  
• Perform hydraulic analyses for both construction and service phases (dewatering schemes, uplift and filtration checks), provide drainage/insulation and leak control.
  
• Match foundation type to capacity/compressibility: raft instead of isolated pads under high load variation; strengthen ground (replacement, columns, injections) or use piles if necessary.
  
• Design continuity of foundation ties and joints to limit differential settlements; foresee “soft zones” under sensitive equipment.
  
• Define erection/storage procedures (ban temporary loads near excavation edges), including leveling/shimming plans.
  
• Introduce geodetic/groundwater monitoring from day zero with alarm thresholds and corrective action plans.
  

Thus designed and managed, the foundation scope minimizes differential settlement risk, with deviations detected early and corrected before costly superstructure repairs are needed.

InterNACHI reports that foundation failures account for ~15% of all construction claims.

As-Built Documentation and BIM Lifecycle Closure

Even the best-designed structure can lose informational integrity if the updated model does not reach the building owner. The absence of an audit trail complicates future extensions, MEP replacement, or thermal modernization studies.

METIB Good Practices

• Kick-off workshops with the investor – jointly defining the structural risk matrix.
  
• First- and second-order analytical models calibrated with simplified hand calculations.
  
• “Four-Eyes” procedure – mandatory independent review by an engineer with at least 5 years of experience.
  
• BIM 360 + Navisworks Clash Detection – weekly clash reports shared with all disciplines.
  
• Assembly checklist – provided to the general contractor along with tolerance parameters and scope of responsibility.

Final Note

Errors in structural design rarely result from lack of knowledge; more often, they stem from time pressure, insufficient data exchange, or improper sequencing of tasks. Awareness of the risks described above helps limit the technical and financial risks of a project. At METIB, by combining design experience with BIM tools and proprietary QA/QC procedures, we minimize the probability of such irregularities – thereby building safe, economical, and durable structures.

We invite you to consultations – we will be happy to review your project or audit your documentation with respect to the above points.

References

• Hawkins Case Studies
  
• ASCE Library
  
• Trimble – Challenges in Rebar Detailing
  
• Sumer Innovations – Common Mistakes in Structural Design