Structural design to NSCP 2015 (Philippines)

The National Structural Code of the Philippines 2015 (NSCP 2015, 7th edition, Volume 1) is the structural code for buildings in the Philippines. It has its own load chapters — combinations (203), live loads (205), wind (207) and earthquake (208) — and adopts the American material standards for design: ACI 318-14 for concrete (Chapter 4) and AISC 360-10 for steel (Chapter 5). Choosing NSCP 2015 in Struxt3D applies the NSCP load rules and runs the members through the ACI and AISC engines. This tutorial shows each rule, works a typical Metro Manila example and lists what you must still check.

Members, connections, walls, footings and composite beams are checked with the ACI 318-19 and AISC 360-22 equations that Struxt3D implements. These are the later editions of the standards NSCP 2015 adopts; the basic strength equations are the same, and the design results show this note so it appears in your report.

What Struxt3D takes from NSCP 2015

NSCP section	Topic	Used for
203.3.1 (eqs. 203-1 to 203-7)	Load combinations	Strength combinations with f₁ and H
205, Tables 205-1, 205-3	Live loads	Floor, roof and deck live loads
207 (Figure 207A.5-1)	Wind	3-s gust basic wind speed
208, Tables 208-2 to 208-8, 208-11	Earthquake	Zone Z, soil profile, near-source Na and Nv, Ca and Cv, R
Chapter 4 (ACI 318-14)	Concrete	Beams, columns, slabs, walls, footings
Chapter 5 (AISC 360-10)	Steel	Members (504 for cables), connections

Load combinations (203.3.1)

Combination	NSCP eq.
1.4D (+ 1.4H)	203-1
1.2D + 1.6L (+ 1.6H)	203-2
1.2D + 1.0W + f₁L	203-4
0.9D + 1.0W (+ 1.6H)	203-6
1.2D + 1.0E + f₁L	203-5
0.9D + 1.0E (+ 1.6H)	203-7
D + L (service)	deflections

f₁ is 1.0 for floors with a live load over 4.8 kPa (and for garages and places of public assembly) and 0.5 otherwise. Struxt3D sets it from the floor use: storage (6.0 kPa) gets 1.0, the other uses 0.5, and the combination name shows the value used, for example 1.2D + 1.0W + 0.5L. H, the earth pressure on retaining walls, is factored 1.6 (1.4 in eq. 203-1). Wind and earthquake are at strength level. Each wind combination is made for four directions, and each earthquake combination for ±(E_X + 0.3E_Y) and ±(0.3E_X + E_Y).

Live loads (205)

Use	L (kPa)	f₁
Office	2.4	0.5
Residential	1.9	0.5
Retail	4.8	0.5
Storage	6.0	1.0
Roof	1.0	—
Footbridge deck (NSCP Vol. 2 / AASHTO LRFD 3.6.1.6)	4.3	—

Wind (207)

NSCP 2015 follows the ASCE 7-10 method with a 3-second gust basic wind speed from the contour maps of Figure 207A.5-1. The default is 69 m/s (250 km/h), a typical value; areas on the eastern seaboard can be higher and parts of Mindanao lower, so read the map for your site and occupancy category.

q = 0.613 K_z V² G, K_z = 2.01 (z/274)^2/9.5 (exposure C), G = 0.85z at least 4.6 m. Walls: 0.8q windward, 0.5q leeward. K_zt = K_d = 1.0.

Earthquake (208)

NSCP 2015 keeps the 1997 UBC form of the spectrum. You choose:

Seismic zone: zone 4 (Z = 0.4) for most of the country, or zone 2 (Z = 0.2) for Palawan and the Sulu islands.
Soil profile: S_A to S_E (Table 208-2).
Seismic source type A, B or C and the distance to it in km (zone 4 only). These give the near-source factors N_a and N_v (Tables 208-5 and 208-6), interpolated in the distance.
Structural system, which sets R (Table 208-11).

Struxt3D shows the resulting C_a and C_v (Tables 208-7 and 208-8) under the inputs.

Soil profile	C_a zone 4	C_v zone 4	C_a zone 2	C_v zone 2
S_A hard rock	0.32N_a	0.32N_v	0.16	0.16
S_B rock	0.40N_a	0.40N_v	0.20	0.20
S_C very dense soil, soft rock	0.40N_a	0.56N_v	0.24	0.32
S_D stiff soil	0.44N_a	0.64N_v	0.28	0.40
S_E soft soil	0.36N_a	0.96N_v	0.34	0.64

Source type	N_a at 2 / 5 / 10 km	N_v at 2 / 5 / 10 / 15 km
A (M ≥ 7, high slip rate)	1.5 / 1.2 / 1.0	2.0 / 1.6 / 1.2 / 1.0
B (other faults)	1.3 / 1.0 / 1.0	1.6 / 1.2 / 1.0 / 1.0
C (M < 6.5, low slip rate)	1.0	1.0

The design spectrum (Figure 208-3) rises from C_a at T = 0 to 2.5C_a at T₀ = 0.2T_s, stays flat to T_s = C_v/2.5C_a, then falls as C_v/T. Struxt3D divides it by R and keeps it above the static base-shear limits 0.11C_a (eq. 208-6) and, in zone 4, 0.8ZN_v/R (eq. 208-7).

The default seismic inputs (Zone 4, soil SC, Ca = 0.40, Cv = 0.56): elastic spectrum dashed, the design spectrum Struxt3D applies in blue. Change the inputs in Supports & loads › Earthquake.

Structural system	R	Table 208-11 system
Ductile moment frame	8.5	Special moment-resisting frame (SMRF)
Ordinary moment frame	3.5	Concrete OMRF (steel OMRF is 4.5)
Braced frame	6.4	Special concentrically braced frame, building frame system
Walls or core	5.5	Concrete shear walls, building frame system
Elastic	1.0	—

Materials and sections

Material	Grades offered (default first)
Steel	ASTM A992 Gr 50 (345 MPa), A36 (248 MPa), A572 Gr 50 (345 MPa)
Concrete	f′_c 28 MPa (4000 psi), 21 MPa (3000 psi), 35 MPa; E_c = 4700√f′_c
Reinforcement	f_y = 414 MPa (PNS 49 Grade 60)
Glulam	24F-V4, 20F-V7

Sections are the US W-shapes and HSS, as in AISC. φ factors are the ACI and AISC ones: 0.90 for steel flexure, 0.90 / 0.65 / 0.75 for concrete flexure, tied columns and shear.

Worked example: a five-storey office in Metro Manila

Open the Multi-storey frame template; set five storeys.
In Materials, choose NSCP 2015. Concrete becomes f′_c 28 MPa and bars Grade 60.
In Supports & loads, pick Office, keep wind at 69 m/s, turn on Earthquake: zone 4, soil S_D, source type A at 8 km (a site near the West Valley Fault, for example), SMRF.
Press F5 and F6. The design results and the report show the NSCP basis note and the ACI/AISC clauses.

Check 1: near-source factors and coefficients

N_a = 1.2 + (8 − 5)/(10 − 5) × (1.0 − 1.2) = 1.08; N_v = 1.6 + 0.6 × (1.2 − 1.6) = 1.36C_a = 0.44 × 1.08 = 0.475, C_v = 0.64 × 1.36 = 0.870

Check 2: spectrum ordinates

T_s = 0.870 / (2.5 × 0.475) = 0.73 s; plateau 2.5C_a/R = 1.188 / 8.5 = 0.140 gAt T = 1.2 s: C_v/(T R) = 0.870 / (1.2 × 8.5) = 0.085 g. Floor: max(0.11 × 0.475, 0.8 × 0.4 × 1.36 / 8.5) = 0.052 g, which governs beyond T ≈ 2 s.

Check 3: combinations on the floor

D = 6.41 kPa, L = 2.4 kPa (f₁ = 0.5); 1.2D + 1.6L = 7.69 + 3.84 = 11.53 kPa; 1.2D + 0.5L = 8.89 kPa with E or W

Check 4: wind pressure at 10 m

q = 0.613 × 1.00 × 69² × 0.85 = 2.48 kPa; windward wall 0.8q = 1.99 kPa

What you still need to check

Importance factor I (Table 208-1): Struxt3D uses I = 1.0. For essential or hazardous facilities (I = 1.5 or 1.25), scale your result or check by hand.
Vertical earthquake E_v and the redundancy factor ρ are not included in E.
Scaling the response spectrum to the static base shear (90 % for regular, 100 % for irregular structures) is not done; compare the reactions' total with V from eqs. 208-4 to 208-7.
Storey drift limits, accidental torsion, irregularity checks and the Ω_o combinations.
Seismic detailing to ACI 318 Chapter 18 / NSCP 418 for SMRF beams, columns and joints, and AISC 341 for steel.
Wind: site-specific speed, exposure B or D, topography (K_zt) and components and cladding.

The response spectrum tutorial explains how the spectrum becomes member forces, and accuracy and limitations lists the solver's assumptions.

#What Struxt3D takes from NSCP 2015

#Load combinations (203.3.1)

#Live loads (205)

#Wind (207)

#Earthquake (208)

#Materials and sections

#Worked example: a five-storey office in Metro Manila

#Check 1: near-source factors and coefficients

#Check 2: spectrum ordinates

#Check 3: combinations on the floor

#Check 4: wind pressure at 10 m

#What you still need to check

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