Loads and Load Combinations (NSCP) - Cheat Sheet
Your last-minute rapid-fire reference for NSCP load types, tributary areas, and LRFD/ASD design combinations — directly tested in the PRC Civil Engineer Licensure Exam and all PSAD/structural design problems.
Load Types & Definitions
Common values
Value
1.9 kPa
Symbol
L_res
Quantity
Residential live load (floor)
Value
2.4 kPa
Symbol
L_office
Quantity
Office/general commercial (floor)
Value
1.9–2.9 kPa
Symbol
L_class
Quantity
Classroom
Value
3.8–4.8 kPa
Symbol
L_retail
Quantity
Retail/department store
Value
0.96–1.43 kPa
Symbol
Lr
Quantity
Typical roof live load
Value
40–60 m/s
Symbol
Vb
Quantity
PH typhoon zone design wind speed
Value
0.40g typical
Symbol
Ca
Quantity
Seismic coefficient (Philippines Zone 4)
Important facts
- Dead load is ALWAYS included in every load combination.
- Live load intensity varies by occupancy — check NSCP Table for specific use (residential, office, assembly, garage, etc.).
- Roof live load Lr is typically less than floor live load L.
- In the Philippines (high seismic zone), earthquake load E often controls lateral/overturning design.
- Wind and seismic loads cannot occur simultaneously; use the more critical in design.
- Live load reduction is permitted for columns/footings supporting large tributary areas (check NSCP 203.2.2).
- Tributary width for interior beam = full beam spacing; edge/perimeter beam = half spacing.
- Load combinations are prescribed by code; designer must evaluate ALL and use the governing (most severe) case.
Key definitions
Dead Load (D)
Example
Concrete slab weight, structural steel, mechanical systems.
Permanent self-weight of structure, finishes, and fixed equipment; constant and predictable.
Live Load (L)
Example
Residential 1.9 kPa, office 2.4 kPa, classroom 1.9–2.9 kPa per NSCP.
Temporary occupancy-dependent load from people, furniture, movable equipment; varies with use.
Roof Live Load (Lr)
Example
0.96–1.43 kPa depending on roof slope per NSCP Table.
Temporary maintenance/snow/rain load on roof; typically smaller than floor live load.
Wind Load (W)
Example
PH design wind speed typically 40–50 m/s depending on region (typhoon zones higher).
Lateral pressure/suction from wind; function of basic wind speed, exposure, height, shape factor.
Earthquake Load (E)
Example
Philippines is highly seismic (Zone 4 in NSCP); E often governs lateral design.
Seismic inertia load from ground acceleration; computed from spectral acceleration, building mass, damping.
Rain/Snow Load (R)
Example
Negligible in most PH; included in code for completeness and northern provinces.
Precipitation load on roof; minor in tropical Philippines but included in load combos.
Tributary Area
Example
Interior beam at 3 m spacing carries slab load over 3 m width; edge beam carries 1.5 m width.
Region of floor/roof closer to a member than to any adjacent member; defines load intensity on that member.
Diagrams to know
- Tributary area diagram for interior beam (rectangle at spacing s × span L).
- Tributary area diagram for corner/edge column (rectangular portions on each side).
- Simple supported beam with distributed load w (kN/m) showing shear and moment diagrams.
- Column free-body diagram with axial load P, moment M from wind/seismic.
Tributary Area & Load Distribution
Formulas
w = q × s
Meaning
w = line load (kN/m), q = area load (kPa), s = tributary width/spacing (m)
Watch out
s is the spacing (distance between beams). For edge beam, use s/2. Units: q in kPa (kN/m²); multiply by m to get kN/m.
When to use
Converting area load on a slab to line load on a beam.
P = q × A_t
Meaning
P = axial load on column (kN), q = area load (kPa), A_t = tributary area (m²)
Watch out
A_t is the tributary area (length × width of slab supported by that column). Interior column supports full slab area between midpoints of adjacent spans. Edge/corner column supports only half the adjacent slab panels.
When to use
Finding the load transmitted from floor/roof to a column.
L_reduced = L × (1 - 0.08 × (A_t - 10) / 10)
Meaning
Reduced live load (kPa) for columns/footings; A_t in m², reduction valid only if A_t > 50 m² and L = floor live load.
Watch out
Reduction NOT permitted for assembly, garage, or storage areas. Live load reduction for beams is NOT standard in NSCP; only applies to columns/footings. Check NSCP 203.2.2 limits.
When to use
Designing columns or footings for large tributary areas — NSCP permits reduction to account for low probability of full loading on entire area.
Important facts
- Tributary area is found by drawing 45° or 50%-50% lines from adjacent members.
- Interior (middle) beam: full spacing on both sides → tributary width = s.
- Edge (perimeter) beam: full spacing on one side, half on the other → tributary width ≈ s/2 or s (depending on layout).
- Corner column supports 4 quadrants, each 50% of its slab area.
- Live load reduction (NSCP 203.2.2) applies only to columns and footings, NOT beams, and NOT to assembly/garage areas.
- When computing column axial load, sum dead and live loads from all floors above; include the column's own weight.
Key definitions
Tributary Area (At)
Example
Column at grid intersection of 6 m × 6 m bays has At = 36 m² (interior); edge column At = 18 m².
The floor/roof area from which a structural member carries load; bounded by lines equidistant to adjacent parallel members.
Tributary Width (s)
Example
Beams 3 m apart: interior beam has s = 3 m; edge beam has s = 1.5 m (half spacing).
The distance (spacing) over which a beam collects load from a slab; usually the center-to-center distance between parallel beams.
Line Load (w)
Example
Beam with tributary width 3 m under slab load 4 kPa: w = 4 × 3 = 12 kN/m.
Load intensity on a beam expressed in force per unit length (kN/m).
Diagrams to know
- One-way slab on two or more parallel beams with tributary width marked.
- Two-way slab with column grid; tributary area shaded for interior, edge, and corner columns.
- Beam with width s and span L showing concentrated loads from slab.
LRFD Design Combinations (Ultimate/Factored)
Formulas
U = 1.4D
Meaning
Ultimate/factored load = 1.4 × dead load; pure dead-load case.
Watch out
This combo applies when only dead load acts (e.g., closed storage with no live load). Modern codes rarely use this alone.
When to use
Rarely governs; used when live load is very small or zero.
U = 1.2D + 1.6L + 0.5(L_r or R)
Meaning
Factored load = 1.2×D + 1.6×L + 0.5×(roof live or rain); PRIMARY GRAVITY COMBO.
Watch out
The 0.5 factor on Lr/R is because Lr and L rarely both reach maximum simultaneously. If only floor live L, ignore Lr/R terms. If only roof, use 0.5Lr instead of 0.5L.
When to use
Governs most floor/roof beam and column design in buildings (gravity + roof or rain effects).
U = 1.2D + 1.6(L_r or R) + (L or 0.5W)
Meaning
Factored load when roof live/rain dominates; companion live or 50% wind.
Watch out
Use L (not 0.5L) in the parenthesis for floor live; the live-load factor f₁ is embedded in NSCP but commonly approximated as 1.0 or 0.5 depending on occupancy.
When to use
Roof design when Lr is large; wind effects secondary.
U = 1.2D + 1.0W + 1.0L + 0.5(L_r or R)
Meaning
Gravity + full wind + full live load; wind and live load together.
Watch out
Wind W is already a factored effect (includes Gust Factor in NSCP wind speed formula). Do NOT double-factor W.
When to use
Wind design on a building also subject to normal occupancy (offices, residential).
U = 1.2D + 1.0E + 1.0L
Meaning
Gravity + seismic + full live load; earthquake combination.
Watch out
E is a factored seismic effect (spectral acceleration × mass × design factor already included). Do NOT multiply E by an additional factor. Some codes reduce L to f₁L (≈0.5 for non-assembly), but NSCP uses full L here.
When to use
Seismic design of buildings (Philippines is Zone 4 — this often controls lateral/moment design).
U = 0.9D + 1.0W
Meaning
Reduced dead + full wind; wind uplift/overturning case (dead load now helps resist, not loads member).
Watch out
The 0.9 factor (not 1.2) is intentional: dead load REDUCES the net demand on wind resistance. Governs tension in braces, uplift in roof members, and frame overturning moment. Easy to forget this combination.
When to use
Light structures where wind uplift dominates (tall slender frame, roof diaphragm, sign). D is reduced because it now resists (rather than adds to) the wind force.
U = 0.9D + 1.0E
Meaning
Reduced dead + full seismic; seismic uplift/overturning case.
Watch out
Often controls column axial tension and base shear in moment frames. The 0.9D reflects that dead load now provides restoring capacity, not additional load. Forgotten by many students.
When to use
Seismic design where inertia and overturning are critical (columns in tension, moment-resisting frames). Common in Philippines (high seismic region).
Important facts
- NSCP prescribes 7 primary LRFD combinations; designer must check ALL and use the governing (highest demand).
- The 1.6 factor on L is much larger than 1.2 on D because live load is more uncertain and variable.
- The 0.5 factor on Lr/R in the second combo reflects low probability of simultaneous max Lr and max L.
- Combos 6 and 7 (with 0.9D) are critical for uplift, overturning, and tension-dominant members; often forgotten.
- Wind W and seismic E are treated as lateral forces; they do NOT use the same safety factors as gravity loads.
- In the Philippines (Zone 4), seismic combos 5 and 7 often govern over wind combos 4 and 6.
- The live-load factor f₁ on L in NSCP depends on occupancy: f₁ = 1.0 for assembly/garage/L > 4.8 kPa; f₁ = 0.5 for residential/office. Conservative reviews use 1.0.
Key definitions
LRFD (Load and Resistance Factor Design)
Example
U = 1.2D + 1.6L is compared to φ × Mn (where Mn is nominal moment capacity and φ ≈ 0.85–0.90 for bending).
Ultimate-strength design philosophy: factor loads up (D, L, W, E multiplied by factors), compare to nominal strength × reduction factor φ.
Load Factor
Example
1.2D reflects variability in dead load magnitude; 1.6L accounts for random nature of live load.
Meaning
Multiplier on load type (e.g., 1.2 on D, 1.6 on L) to account for uncertainty in load magnitude and variation.
Reduction Factor (φ)
Example
φ_bending ≈ 0.90 for steel, 0.85 for concrete flexure; φ_compression ≈ 0.65–0.80.
Discount on nominal strength to account for material, fabrication, and model uncertainty; φ typically 0.85–0.95 depending on failure mode.
Diagrams to know
- LRFD combo decision tree: identify D, L, Lr, W, E → apply 7 combos → find max U.
- Schematic showing 0.9D uplift combo vs. 1.2D downward combo for light-framed roof.
ASD Design Combinations (Service/Allowable)
Formulas
S = D
Meaning
Service load = dead load only; pure gravity baseline.
Watch out
Rarely governs alone in occupied buildings. Always check combo 2 (D + L).
When to use
Closed storage, parking garage without live load, or when live load is negligible.
S = D + L
Meaning
Service load = dead + live; PRIMARY gravity combo in ASD.
Watch out
ASD uses service loads (no factoring). Design stress/strain is compared directly to allowable (nominal/FS). Much simpler than LRFD but more conservative for high-load cases.
When to use
Floor beams, columns in buildings under normal occupancy (residential, office, classroom).
S = D + (L_r or R)
Meaning
Service load = dead + roof live (or rain); roof-only case.
Watch out
Lr is typically smaller than floor L. Do NOT mix L and Lr; use one or the other depending on member location.
When to use
Roof structure design when floor live L does not apply.
S = D + 0.75L + 0.75(L_r or R)
Meaning
Combined gravity with reduction factors on L and Lr to account for simultaneous occurrence.
Watch out
The 0.75 reflects reduced probability of simultaneous max L and Lr. This combo is less common than D + L but may govern in multi-use buildings.
When to use
When floor live and roof live both potentially act (e.g., penthouse or mezzanine).
S = D + 0.6W (or D + 0.7E)
Meaning
Service load = dead + reduced wind (0.6 factor) OR dead + reduced seismic (0.7 factor).
Watch out
Do NOT use both W and E; pick the more critical (usually E in Philippines). The 0.6 and 0.7 are reduction factors specific to ASD; they differ from LRFD factors.
When to use
Wind or seismic design in ASD; lateral loads are reduced compared to LRFD.
S = D + 0.75L + 0.75(0.6W) + 0.75(L_r or R)
Meaning
Combined gravity + reduced wind; all loads at once with reductions.
Watch out
Very conservative; typically does not govern. Included in code for completeness.
When to use
Rare; only when floor live, wind, and roof load all potentially act together.
S = D + 0.75L + 0.75(0.7E) + 0.75(L_r or R)
Meaning
Combined gravity + reduced seismic; gravity + seismic + roof load.
Watch out
The 0.7E is seismic-specific reduction in ASD. This combo often governs lateral design in the Philippines (Zone 4).
When to use
Seismic design in ASD when floor and roof live loads also act.
S = 0.6D + 0.6W (or 0.6D + 0.7E)
Meaning
Uplift/overturning case in ASD: reduced dead + reduced wind (or seismic).
Watch out
The 0.6D is intentional: dead load is now helpful, not harmful. Equivalent to LRFD 0.9D combo. Critical for light structures and high-seismic regions (Philippines).
When to use
Tension members, roof uplift, frame overturning — when dead load resistance is critical and we check minimum (0.6D) condition.
Common values
Value
0.6
Symbol
f_W
Quantity
ASD wind reduction factor
Value
0.7
Symbol
f_E
Quantity
ASD seismic reduction factor
Value
0.75
Symbol
f_L
Quantity
ASD live load reduction (with Lr/R)
Value
0.6
Symbol
f_D_uplift
Quantity
ASD uplift dead load factor
Important facts
- ASD uses service-level loads and compares to allowable stresses; LRFD factors loads up and compares to nominal strength × φ.
- The 0.6 or 0.75 reduction factors on wind/seismic in ASD reflect lower probability of occurrence vs. gravity.
- The 0.6D uplift combo (ASD) and 0.9D uplift combo (LRFD) serve the same purpose: checking tension and overturning resistance.
- ASD is simpler conceptually but may be more conservative for heavily loaded members.
- Wind and seismic are mutually exclusive in design; use the more critical for the location.
- ASD combos are fewer and simpler than LRFD but require different (allowable) strength tables from AISC, ACI, etc.
Key definitions
ASD (Allowable Stress Design)
Example
Service load = D + L; design stress f = P/A is limited to f_allow = F_y / FS (e.g., 0.6F_y for steel bending).
Service-level design philosophy: no load factoring; service loads compared directly to allowable stress (nominal/FS).
Allowable Stress (f_allow)
Example
Steel: f_allow_bend ≈ 0.6F_y; Concrete: f_allow_comp ≈ 0.45f'_c.
Maximum permitted working stress, equal to nominal strength divided by a global safety factor (FS ≈ 1.5–2.0).
Service Loads
Example
Residential floor: D + L = 5 + 2 = 7 kPa (no factors applied).
Unfactored, expected in-service loads (D, L, W, E at actual intensity); used directly in ASD without multipliers.
Diagrams to know
- ASD combo flowchart: identify loads → apply 8 combos → find max service demand → compare to allowable.
Key Formulas & Conversions
Formulas
M = wL² / 8 (simple support, UDL)
Meaning
M = maximum mid-span moment (kN·m), w = uniform line load (kN/m), L = span (m).
Watch out
This formula is ONLY for simply supported, uniformly distributed load. For cantilevers, continuous beams, point loads, etc., use different M expressions. Forgetting this limit is a common exam mistake.
When to use
Finding design moment in a beam once the factored line load w_u (LRFD) or service w (ASD) is known.
V = wL / 2 (simple support, UDL)
Meaning
V = maximum shear force (kN) at support, w = uniform line load (kN/m), L = span (m).
Watch out
Shear V is maximum at support, zero at mid-span for uniform load. Always check shear near supports (concentrated loads, bearing plates).
When to use
Finding design shear once w is known; controls beam depth and web design in steel/concrete.
Deflection δ = 5wL⁴ / (384EI) (simple support, UDL)
Meaning
δ = maximum mid-span deflection (m), w = UDL (kN/m), E = modulus of elasticity, I = moment of inertia.
Watch out
Deflection limits vary by occupancy and member type (L/240 for floors, L/180 for cantilevers, etc.). Always check NSCP Table 502 limits AFTER selecting member size.
When to use
Checking serviceability (span-to-depth ratio, L/360 limit, etc.) in ASD design or post-LRFD check.
Area load (kPa) = Line load (kN/m) / tributary width (m)
Meaning
Reverse of w = q × s; useful for converting back to uniform floor load from a beam line load.
Watch out
Ensure units consistency: kPa = kN/m² is area; kN/m is line. Divide kN/m by m (width) to get kN/m² = kPa.
When to use
Verification: checking if a computed line load on a beam matches the intended floor load.
Important facts
- For a cantilever beam (fixed at one end, free at other): M_max = wL² / 2 (at fixed end), V = wL.
- For a continuous beam: use coefficient method or slope-deflection; M and V are different from simple-support case.
- Shear design often controls beam depth more than moment does (especially in seismic or short spans).
- Deflection is not part of LRFD strength design but is checked in serviceability (ASD); use service loads (unfactored) for deflection calculations.
- Always factor (LRFD) or combine (ASD) the loads BEFORE computing M and V; do NOT design for service loads in LRFD or factored loads in ASD.
Diagrams to know
- Cantilever beam with UDL showing fixed end moment and shear diagrams.
- Simple-span beam with various load types (UDL, point load, triangular) and generic M/V expressions.
Common Exam Traps & Distinctions
Important facts
- NEVER mix LRFD and ASD in the same problem: pick one philosophy and stick with it (and its corresponding design provisions).
- The 0.9D and 0.6D (uplift) combos are the MOST FORGOTTEN in student work — always check them, especially for light structures and high-seismic regions.
- Tributary width ≠ beam spacing. Edge beam tributary width ≈ half spacing. Interior beam ≈ full spacing.
- Live load reduction applies ONLY to column/footing axial load (downward), NOT to beam shear/moment, and NOT in assembly areas.
- Wind speed in NSCP includes gust factor; do NOT apply additional gust multiplier to the wind pressure formula result.
- Seismic E is computed from spectral acceleration × mass × design factor; it is NOT the same as acceleration × mass and should NOT be further factored.
- Roof live load Lr ≠ rain load R; Lr is for maintenance, R is for precipitation. Both are usually small and often combined as 'Lr or R' in code expressions.
- Units: always convert area load (kPa) and width (m) properly to get line load (kN/m). 1 kPa = 1 kN/m²; multiply by m to get kN/m.
- Multiple stories: when computing column axial load, stack all floor loads above (D + L on each floor), then apply live load reduction only to the column, if applicable.
- Allowable stress approach (ASD) uses different (lower) stress values from LRFD strength values; do NOT interchange tables.
Key definitions
LRFD vs. ASD Design Path
Example
LRFD: U = 1.2(5) + 1.6(3) = 10.8 kN/m; find φMn ≥ M_u. ASD: w = 5 + 3 = 8 kN/m; find M_allow ≥ M_service.
LRFD: factor loads up (1.2D, 1.6L, etc.), compare factored demand to strength × φ. ASD: use service loads, compare to allowable stress (strength/FS).
Live Load Reduction (NSCP 203.2.2)
Example
Column with A_t = 100 m² under L = 3 kPa: L_reduced = 3(1 − 0.08(100 − 50)/10) ≈ 2.4 kPa.
Permitted only for columns and footings with tributary area A_t > 50 m²; NOT for beams; NOT for assembly/garage/storage areas.
Wind vs. Seismic (Philippines Context)
Example
Check U = 1.2D + 1.0W + L (wind) AND U = 1.2D + 1.0E + L (seismic); use whichever is larger for lateral design.
Wind W and E are mutually exclusive in a single combo; Philippines (Zone 4) is highly seismic, so E often governs over W in lateral design.
Must remember
- Load Combinations are CODE-PRESCRIBED; never invent your own. ALWAYS evaluate all 7 LRFD (or 8 ASD) combos and use the governing one. Mixing or skipping combos is a common exam failure.
- The 0.9D and 0.6D Uplift Combos are the MOST FORGOTTEN. Check them especially for light structures, roofs, and high-seismic regions (Philippines Zone 4). These catch tension and overturning that other combos miss.
- Tributary Area is the FOUNDATION of load distribution. Interior member = full spacing; edge/perimeter = half spacing. Mistakes here cascade to all downstream calculations. Draw the tributary diagram before computing loads.
- LRFD and ASD are MUTUALLY EXCLUSIVE design philosophies. Once you pick LRFD (factored loads, φ factors), use ONLY LRFD combos, LRFD strength tables (ACI 318, AISC 360), and LRFD deflection criteria. Do NOT mix with ASD allowable stresses.
- Live Load Reduction (NSCP 203.2.2) applies ONLY to columns/footings, NOT beams. Allowed only if A_t > 50 m² and NOT in assembly/garage/storage. This is a frequent exam trap.
- In the Philippines (NSCP Zone 4), Seismic Load E often governs over Wind W in lateral/moment design. Always check combo 5 (1.2D + 1.0E + 1.0L) and combo 7 (0.9D + 1.0E); these are not optional.
- Wind W and Seismic E are mutually exclusive. Use BOTH in separate design checks; report whichever is more critical for the location. Do NOT combine W and E in a single combo.
- Load Factors reflect load uncertainty and variability: 1.6 on L (highly variable), 1.2 on D (stable), 0.5 on Lr (rarely reaches max), 1.0 on W and E (rare events, already incorporate safety).
- Convert units correctly: Area load (kPa) × tributary width (m) = line load (kN/m). 1 kPa = 1 kN/m²; forgetting this unit conversion causes cascade errors in M, V, and deflection.
- Roof Live Load Lr ≠ Floor Live Load L. Lr is for maintenance (0.96–1.43 kPa); L is for occupancy (1.9–4.8 kPa depending on use). Always verify which applies to your member (floor vs. roof).
Last minute tips
- Draw the tributary area diagram FIRST. Mark interior vs. edge/corner members. This single step prevents 80% of tributary-area errors on the exam.
- Create a 7-combo checklist on your scratch paper. List all 7 LRFD combos in order: 1.4D, 1.2D+1.6L+0.5Lr, ... , 0.9D+1.0E. Systematically compute U (or service load) for each, circle the maximum. This methodical approach catches missed combos and reduces errors.
- Combo 2 (1.2D + 1.6L) almost always governs for normal gravity design. But ALWAYS check combos 6 and 7 (0.9D + 1.0W and 0.9D + 1.0E); if you skip them and the answer involves uplift/tension, you'll get it wrong. The 0.9D is a red flag: it means dead load is now helpful, not a burden.
- For columns: stack ALL floors above, then apply the one-time live load reduction to the TOTAL column load (if A_t > 50 m² and occupancy allows). Do NOT reduce live load on individual floors. This is a common mistake when designing multi-story buildings.
- If the problem says 'seismic design' or mentions the Philippines without specifying a region, assume Zone 4 (high seismic). This means combo 5 (1.2D + 1.0E + 1.0L) and combo 7 (0.9D + 1.0E) are likely to govern. Wind combos are secondary unless the problem explicitly states a typhoon zone or coastal site.
Comparison tables
LRFD vs. ASD at a Glance
| Aspect | LRFD (Ultimate Strength) | ASD (Allowable Stress) |
|---|---|---|
| Load Treatment | Factor loads up (1.2D, 1.6L, 1.0W, 1.0E, etc.) | Use service (unfactored) loads |
| Design Equation | U ≤ φMn, φVn, φPn (factored demand ≤ reduced strength) | S ≤ f_allow (service demand ≤ allowable stress) |
| Safety Factor | Built into load factors (1.2, 1.6) and φ (0.85–0.95) | Single global FS (typically 1.5–2.0) |
| Uplift Combo | 0.9D + 1.0W or 0.9D + 1.0E (reduced dead load) | 0.6D + 0.6W or 0.6D + 0.7E (reduced dead load) |
| Deflection Check | Separate serviceability check using service loads (D + L) | Built into allowable stress; use service loads |
| Preferred in PH | Modern default; aligns with ACI 318 & AISC 360 | Older method; still permitted but less common in licensure exams |
| Number of Combos | 7 primary (Eqs. 1–7) | 8 primary (Eqs. 1–8) |
Load Factors & Reduction Factors Summary
| Load Type | LRFD Factor | ASD Factor / Reduction |
|---|---|---|
| Dead Load (Gravity Combo) | 1.2 | 1.0 (no reduction) |
| Live Load (Gravity Combo) | 1.6 | 1.0 (no reduction) |
| Roof Live / Rain (with gravity) | 0.5 (when paired with floor L) | 0.75 (when paired with floor L) |
| Wind Load | 1.0 | 0.6 |
| Seismic Load | 1.0 | 0.7 |
| Dead Load (Uplift Combo) | 0.9 (reduces D because it now resists) | 0.6 (reduces D because it now resists) |
Typical Live Loads by Occupancy (NSCP 2015 Table 207)
| Occupancy / Use | Live Load (kPa) | Notes |
|---|---|---|
| Residential (dwelling) | 1.9 | Includes corridors, hallways |
| Office / Commercial | 2.4 | Standard floor; excludes storage |
| Classroom | 1.9–2.9 | Depends on school type & occupancy density |
| Assembly (auditorium, theater) | 3.8–4.8 | Fixed seating or standing; high density |
| Retail / Department Store | 3.8–4.8 | Heavy merchandise; mirrors assembly loads |
| Garage (parking) | 2.4 | For passenger cars; heavier for trucks |
| Storage (light to medium) | 6.0–12.0 | Depends on contents; no reduction allowed |
| Hospital (patient rooms / corridors) | 1.9–2.4 | Varies by area function |
| Roof Live Load (Lr) | 0.96–1.43 | Depends on roof slope; for maintenance |
When to Use Each LRFD Combination
| Combo # | Equation | Most Likely to Govern | Design Element |
|---|---|---|---|
| 1 | 1.4D | Pure gravity (dead only) | Rarely; only very light live load |
| 2 | 1.2D + 1.6L + 0.5(Lr or R) | MAJORITY of gravity problems | Beams, columns, footings (floors/roofs) |
| 3 | 1.2D + 1.6(Lr or R) + (L or 0.5W) | Roof with large Lr; wind secondary | Roof frames; parapets |
| 4 | 1.2D + 1.0W + 1.0L + 0.5(Lr/R) | Gravity + wind together | Buildings in windy areas (coastal, exposed) |
| 5 | 1.2D + 1.0E + 1.0L | Gravity + seismic (Philippines Zone 4!) | Lateral/moment design; often governs in PH |
| 6 | 0.9D + 1.0W | Wind uplift / overturning | Roof uplift, light trusses, moment-frame base shear |
| 7 | 0.9D + 1.0E | Seismic uplift / overturning (Philippines!) | Column tension, frame overturning, lateral shear |
Diagrams
LRFD Load Combination Decision Tree
Step-by-step flowchart showing how to systematically apply all 7 LRFD combos and identify the governing (maximum) case. Start by identifying loads, apply each combo in order, compare results, and design for the largest factored demand U.
Load Types & Tributary Routing
Mind map showing how different load types originate, typical values in the Philippines context, and how they are routed to structural members (beams use line loads, columns use axial loads) via tributary area and width.
Tributary Area Identification (Interior vs. Edge Member)
Decision flowchart for determining tributary width and area based on member location (interior, edge, corner). Shows how to compute line load w and axial load P from tributary geometry, which feed directly into load combination calculations.
Key Milestones in NSCP Load Design Process
Chronological timeline of the load combination and member design workflow from load identification through final serviceability checks. Emphasizes that all combos must be evaluated and that the governing (maximum) demand drives the member size.
LRFD Load Factor Distribution (Typical Gravity Combo 2: 1.2D + 1.6L)
Pie chart showing the relative contribution of dead and live load factors in the most common LRFD combo (1.2D + 1.6L). Emphasizes that live load carries a larger factor (1.6 vs. 1.2) due to higher variability and uncertainty.