Paired assumption
Increasing both demands is conservative only for the declared uncertainty story.
Engineering
Retaining Wall Sensitivity Calculator
Stress-test retaining-wall overturning and sliding factors under a paired demand increase.
RETAINING WALL SENSITIVITY
Show how a demand increase changes the governing wall factor
One sensitivity percentage is applied to both overturning and sliding demand so the adverse case is explicit and reproducible.
Decision boundary:For design teams stress-testing a documented paired demand increase; it is deterministic and does not estimate failure probability.
Base governing factor-
Adverse governing factor-
Demand increase-
Threshold status-
DECISION MAP
Retaining Wall Sensitivity Calculator evidence path
Use the adverse factor to decide whether demand uncertainty warrants a more detailed load model or additional resistance.
| Case | Overturning demand (kN*m/m) | Sliding demand (kN/m) | Overturning FS | Sliding FS | Governing FS |
|---|
LIVE CALCULATION PROCESS
Formula, symbols, substitution, and final check
D_adverse = D_base(1 + d/100); FS_gov = min(M_R/M_O, R_SL/H_D)
The base and adverse rows use the same resistance values. Only demands change, making the sensitivity driver visible.
| Symbol | Meaning | Unit | Current input |
|---|---|---|---|
| MR | Resisting moment held constant | kN*m/m | 820 |
| RSL | Sliding resistance held constant | kN/m | 510 |
| MO | Base overturning demand | kN*m/m | 420 |
| HD | Base horizontal demand | kN/m | 280 |
| dD | Paired demand increase | % | 15 |
| FSreq | Entered adverse-case review threshold | dimensionless | 1.5 |
HOW TO USE
Show how a demand increase changes the governing wall factor
- Enter the base resisting actions and the paired overturning and sliding demands.
- Set a non-negative demand increase that represents the documented uncertainty.
- Enter the review threshold used to interpret the adverse governing factor.
- Compare base and adverse mechanisms without changing resistance in the same scenario.
- Record the trigger for a full load model instead of treating the sensitivity as a code factor.
SUBJECT FUNDAMENTALS
Terms behind Retaining Wall Sensitivity Calculator
- Demand increase
- Paired action sensitivity
- Base factor
- Factor before sensitivity
- Adverse factor
- Factor after demand increase
- Resistance
- Stabilizing action held constant
- Governing mode
- Lower of two mechanisms
CALCULATION METHOD
Why this formula fits the topic
D_adverse = D_base(1 + d/100); FS_gov = min(M_R/M_O, R_SL/H_D)
The base and adverse rows use the same resistance values. Only demands change, making the sensitivity driver visible.
DEEPER ANALYSIS
Where professional judgement still matters
Resistance uncertainty
A separate resistance reduction would be a different scenario.
Decision use
Sensitivity identifies what to verify; it does not set a code load.
WORKED DECISION CASES
Two realistic uses
Paired surcharge screen
The 820/420 and 510/280 base ratios govern at 1.821. A 15% increase to both demands reduces the governing factor to 1.584, which remains just above an entered 1.5 review threshold.
Sensitivity trigger for fuller loading
A 30% paired demand increase reduces the same 1.821 base factor to 1.401. The below-threshold result identifies the need for a full water, surcharge, and load-combination model rather than claiming failure probability.
Technical glossary
- Sensitivity
- A deterministic change applied to the declared demand case.
- Demand factor
- One plus the entered percentage increase divided by 100.
- Adverse case
- The paired-demand row after applying the sensitivity.
- Overturning factor
- Resisting moment divided by adverse overturning moment.
- Sliding factor
- Base resistance divided by adverse horizontal drive.
- Trigger
- The documented condition that requires a fuller design check.
EVIDENCE AND DATA LINEAGE
What to retain with the result
Retain the uncertainty source, base load combination, resistance calculation, and threshold.
LIMITS AND EXCLUSIONS
What this model does not establish
- No probabilistic reliability, water-pressure, seismic, or global-stability analysis.
- The demand increase is an assumption, not a measured probability.
- Confirm the project-specific load combinations.
RELIABLE SOURCES
References for method and context
FREQUENTLY ASKED QUESTIONS
Retaining Wall Sensitivity Calculator questions
Why change both demands together?
The page models a declared paired uncertainty; use another model for independent changes.
Can the increase be negative?
No. Enter a non-negative adverse increase.
Does resistance stay constant?
Yes, by design; changing resistance needs a separate case.
Is the result a reliability index?
No, it is a deterministic ratio.
What if the adverse case still passes?
Retain the result and inspect other mechanisms not modeled here.
Who approves the sensitivity?
The project engineer under the governing standard.
IMPORTANT NOTE
Before relying on the exported result
Sensitivity screen, not a final retaining-wall design.
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