Reinforced Concrete Design / An integrated design: one structure, end to end
Every check, and the one that governs
Compare the checks that can be calculated, and state which acceptance decisions still need project information.
Lesson review: expert verification remains open
This lesson has received a full-context editorial review and a check of its technical explanations. Selected arithmetic has been checked separately. This is not independent engineering sign-off.
Corrections checked in this pass
- Rebuilt the load take-down and dependent beam, column and pad results; removed unsupported overall pass claims.
Checks needed for project use
- A concrete-design reviewer must check the stated first-generation clauses, National Annex choices, detailing rules and factor sets. Numerical agreement alone does not establish code compliance.
- Column end moments, effective length, creep and governing combinations remain needed for N-M and stability. Check ground resistance, settlement and full detailing.
These are educational models and exercises. Check their assumptions before using the results. The full technical content and every diagram have not yet been independently verified.
Concrete and steel calculations retain their stated first-generation Eurocode teaching basis. Use the standards and amendments specified for your project; do not mix generations without an appropriate design basis.
Read the lesson register and outstanding review notesWhy this matters
A utilisation is useful only when its demand, resistance and scope are clear. Record the calculated ratios and keep unresolved checks visible; a low axial ratio cannot stand in for a column stability assessment.
By the end of this lesson you should be able to
- Check the reinforcement actually provided
- Use the applicable flanged span/depth ratio
- Reconcile an optional depth change throughout the take-down
- Report unresolved acceptance checks separately
Worked example
Stage 1 — the slab
Given
- 200 mm one-way slab, 5.0 m span, C30/37
- w = 14.63 kN/m² from the take-down
- 25 mm cover, H12 bars
Find
The reinforcement, and which check decides it.
Assumptions
- First-generation teaching material values: fcd 17 MPa, fyd 434.783 MPa; no redistribution
- Member span/depth checks use required reinforcement, with excess provided-steel credit capped at 1.5
- The beam flange ratio exceeds 3, so the flanged factor is 0.8; assumed brittle partitions over 7 m also require 7/7.5
- The illustrated checks do not replace continuity, support detailing, lateral stability, fire or durability design
Worked example
Stage 2 — the baseline beam
Given
- 350 ×550 mm downstand beam with 200 mm monolithic slab;7.5 m simple span
- MEd 543.230 kNm; VEd 289.723 kN;35 mm cover, H10 links,4H32 bottom bars
Find
Check the baseline T-beam using its flange in both bending and the prescribed span/depth calculation.
Assumptions
- First-generation teaching material values: fcd 17 MPa, fyd 434.783 MPa; no redistribution
- Member span/depth checks use required reinforcement, with excess provided-steel credit capped at 1.5
- The beam flange ratio exceeds 3, so the flanged factor is 0.8; assumed brittle partitions over 7 m also require 7/7.5
- The illustrated checks do not replace continuity, support detailing, lateral stability, fire or durability design
Worked example
Stage 3 — optional depth change and downstream checks
Given
- Optional 350 ×650 mm beam on all three levels; other dimensions and loading categories unchanged
- Retain 4H32 bottom bars and H10 two-leg links at 250 mm;2.6 m square pad 600 mm thick
- Pad reinforcement 14H16 in each of two orthogonal layers, equally spaced 191.077 mm
Find
Compare an optional deeper beam and recalculate the column loads and pad checks. The 550 mm baseline did not fail the corrected span/depth check.
Assumptions
- First-generation teaching material values: fcd 17 MPa, fyd 434.783 MPa; no redistribution
- Member span/depth checks use required reinforcement, with excess provided-steel credit capped at 1.5
- The beam flange ratio exceeds 3, so the flanged factor is 0.8; assumed brittle partitions over 7 m also require 7/7.5
- The illustrated checks do not replace continuity, support detailing, lateral stability, fire or durability design
Try it
The whole building, in one picture
Calculated gravity checks, ranked by their reported utilisation. Column combined bending and stability, ground resistance, settlement and detailing still require separate inputs.
- Slab permanent load gk
- 7.50 kN/m²
- Beam design load w
- 77.3 kN/m
- Beam moment MEd
- 543 kNm
- Beam effective depth d
- 489 mm
- Steel required / provided
- 2620 / 3217 mm²
- H10 link spacing
- 250 mm
- Column NEd
- 1660 kN
- Imposed-load reduction
- None applied
- Characteristic load on the pad
- 1198 kN
- Bearing pressure
- 192 kN/m²
Acceptance remains open: column combined bending and stability, geotechnical ultimate resistance, settlement and reinforcement anchorage are not calculated here.
Compare the options
- At the defaults, the corrected flanged span/depth check passes at about 64%. The conservative full-shear check uses H10 links at 250 mm.
- Deepen all beams to 650 mm. The column action rises from 1660.04 to 1686.61 kN and service pad pressure from 192.28 to 195.19 kPa.
- Change slab thickness and follow its self-weight through the take-down. Recheck steel demand as well as serviceability.
- A smaller pad may require clipped punching perimeters, which this centred full-perimeter model does not evaluate.
- Close utilisation values do not predict which check will fail first after a change. Recalculate each model.
Revised option: calculated checks
| Member | Check | Utilisation |
|---|---|---|
| Pad | Supplied allowable service pressure | 0.9760 |
| Slab | Span/depth | 0.9406 |
| Slab | Bending | 0.8749 |
| Beam | Selected-link shear | 0.8125 |
| Pad | Beam shear | 0.6910 |
| Beam | Bending | 0.6867 |
| Pad | Searched punching perimeters | 0.5944 |
| Beam | Span/depth | 0.3213 |
The largest of these calculated ratios is the pad service-pressure comparison. That remains informative even though the plan size was chosen using the same criterion. None of these ratios closes the outstanding column, ground or detailing checks. Their different load relationships mean that the current ordering does not predict which limit is reached first after a change.
Practice
For the revised option Gk =936.84375 kN and Qk =281.25 kN, with no imposed-load reduction. What is NEd under 1.35G +1.5Q, in kN?
Practice
The revised pad carries characteristic column load 1218.09375 kN, weighs 101.4 kN and is 2.6 m square. What is its service ground pressure in kPa?
Practice
Deepening the beam from 550 to 650 mm adds 0.875 kN/m of self-weight. Two beam half-spans of 3.75 m frame into each column, on three storeys. How much factored load does that add to the column, in kN?
Check yourself
The slab's bending utilisation is 0.87, yet K = 0.053 is only a third of Klim. How can both be true?
Check yourself
A beam is at 0.95 in bending and 0.92 in shear. What does that tell you that a pass/fail would not?
Summary
- The example carries two office floors and a roof with no imposed-load reduction
- The beam take-down includes only its downstand self-weight
- Use required steel and the flanged concrete area in the T-beam span/depth calculation
- The initial 550 mm beam passes the illustrated checks;650 mm is an optional sensitivity study
- The optional deepening adds 19.6875 kN characteristic permanent load at the column base
- A foundation requires geotechnical and settlement verification in addition to these structural checks
- The column combined bending and stability assessment remains open