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8-Storey Mixed-Use Steel Framed Building In Manila Philippines

8-Storey Mixed-Use Steel Framed Building In Manila Philippines

This project is an 8-story multifunctional building located in Manila, Philippines, with an overall dimension of 20m × 20m. The height of each floor is designed as follows: the 1st floor (parking lot) plus mezzanine totals 6m; the 2nd floor (warehouse) is 6m; the 3rd and 4th floors (office areas) are 4.5m and 3.4m respectively; the 5th to 7th floors (residential areas) are each 3.4m; the 8th floor (roof public space) plus roof height is 2.8m. For space optimization, only 3 rows of structural columns are arranged: Axis A has 4 columns in total, the spacing between Axis A and Axis B is 13.2m, and the spacing between Axis B and Axis C is 6.8m. The spacing between the 4 columns on Axis A is 5.9m (1-2 axis), 8.2m (2-3 axis), and 5.9m (3-4 axis) respectively.

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Product Introduction

STRUCTURAL ANALYSIS REPORT
8-Storey Mixed-Use Steel Framed Building In Manila, Philippines

Project location: Manila (NCR), Philippines
Applicability review: Tonga, New Caledonia (France), Papua New Guinea, Chile, Peru
Design code: NSCP 2015 (Philippines)

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1. Architectural & Structural Configuration

Parameter	Description
Plan dimensions	20.0 m × 20.0 m
Total height	36.9 m (from ground floor to roof public space)
Column grid	3 longitudinal axes (A, B, C)
A–B span	13.2 m (large span)
B–C span	6.8 m
Bay spacing (1–2 / 3–4)	5.9 m
Bay spacing (2–3)	8.2 m (interior bay)
Total columns	12 (4 per axis)

1.1 Storey Heights & Occupancy

Floor	Occupancy	Storey Height (m)	Cumulative Height (m)
1F	Parking + Mezzanine	6.0	6.0
2F	Warehouse	6.0	12.0
3F	Office	4.5	16.5
4F	Office	3.4	19.9
5F	Residential	3.4	23.3
6F	Residential	3.4	26.7
7F	Residential	3.4	30.1
8F	Roof public space	2.8	32.9
Total building height (above GL)			~36.9

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2. Design Loads per NSCP 2015

2.1 Gravity Loads

Occupancy	Superimposed Dead (SDL, kPa)	Live Load (LL, kPa)
Parking (1F)	1.5	5.0
Warehouse (2F)	1.0	6.0
Office (3F–4F)	1.5	3.0
Residential (5F–7F)	1.5	2.0
Roof public space (8F)	2.0	4.8 (public assembly)

Floor system: 130 mm composite slab on steel deck (self-weight ~2.8–3.2 kPa including framing).

2.2 Wind Load (NSCP 2015 §207)

Basic Wind Speed: 250 kph (69 m/s, 3‑second gust) – Manila, NCR

Exposure Category: B (urban)

Occupancy Category: III (mixed-use, importance factor I_w = 1.15)

Design pressure @ roof: ~3.5–4.2 kPa (varies with zone & cladding)

Governing wind direction: 20 m face; overturning moment contributes significantly to column axial demands.

2.3 Seismic Load (NSCP 2015 §208)

Parameter	Value	Remarks
Seismic Zone	Zone 4 (Metro Manila)	High seismicity
Mapped S_s	~1.10g	Short-period spectral acceleration
Mapped S₁	~0.64g	1‑second spectral acceleration
Site Class	D (assumed)	Stiff soil; conservatively adopted
S_DS	0.85g	Design short-period spectral accel.
S_D1	0.64g	Design 1‑s spectral acceleration
Seismic Design Category	D
Response Modification Factor (R)	8.0	Special Steel Moment Frame (SMF)
Importance Factor (I_e)	1.0	Standard occupancy

Estimated seismic base shear coefficient C_s ≈ 0.106 (W). Base shear ≈ 0.106 × total seismic weight.

2.4 Load Combinations (NSCP 2015 §203 – Strength Design)

Combination	Formula	Governing Limit State
LC1	1.2D + 1.6L + 0.5L_r	Gravity (beams, composite slab)
LC2a	1.2D + 1.0E + 0.5L	Seismic (columns, frame drift)
LC2b	0.9D + 1.0E	Seismic overturning/net uplift
LC3	1.2D + 1.0W + 0.5L	Wind overturning lateral check
LC4	1.2D + 1.0W + 0.5L + 0.5L_r	Wind (cladding & drift)

3. Structural System & Analysis

3.1 Lateral-Force-Resisting System (LFRS)

Special Steel Moment-Resisting Frame (SMF) in both directions.

With only 3 column lines, the 20 m × 20 m building relies on deep columns and girder-to-column moment connections. The 13.2 m span (A–B) demands relatively deep girders (W24–W27 range) for gravity plus seismic moments.

In the transverse direction (A–C), the frame comprises two unequal spans: 13.2 m + 6.8 m. Stiffness eccentricity is moderate; accidental torsion per NSCP §208.5.5.2 must be considered.

3.2 Floor Framing

13.2 m span: Primary composite girders @ ~2.5 m spacing with secondary beams spanning 5.9 m / 8.2 m.

6.8 m span: Conventional composite beam layout; steel section of W16–W18 range.

130 mm composite metal deck with concrete fill provides diaphragm action (topped with reinforcement for seismic diaphragm forces).

3.3 Foundation & Column Bases

Mat or piled foundation typical for Manila site (alluvial / lahar deposits).

Fixed-base column connections improve seismic drift performance and reduce overturning demand on the mat.

4. Steel Tonnage Estimate (Detailed Quantity Take-Off)

All steel sections are ASTM A572 Gr. 50 (F_y = 345 MPa) or ASTM A992 (F_y = 345 MPa). Weights based on AISC 360‑22 section tables(Will replaced by equal Chinese standards which will be Q355B/Q235B during fabrication).

4.1 Columns

Tier	Floors	Approx. Section	Weight (kg/m)	Length/item (m)	Qty	Total wt (kg)
T1 (base)	1F–2F	W14×311 (W360×463)	463	12.0	12	66,672
T2	3F–4F	W14×211 (W360×314)	314	7.9	12	29,773
T3	5F–7F	W14×132 (W360×196)	196	10.2	12	23,990
T4 (roof)	8F	W14×90 (W360×134)	134	2.8	12	4,502
Subtotal – Columns						124,937

4.2 Primary Girders & Secondary Beams

Span / Direction	Typical Section	Weight (kg/m)	Total length (m)	Qty	Total wt (kg)
A–B primary (13.2 m)	W27×102 (W690×152)	152	13.2	32	64,205
B–C primary (6.8 m)	W21×62 (W530×92)	92	6.8	32	19,986
Secondary beams (5.9 m)	W16×31 (W410×46)	46	5.9	120	32,568
Secondary beams (8.2 m)	W18×40 (W460×60)	60	8.2	60	29,520
Subtotal – Beams & Girders					146,279

4.3 Floor System & Miscellaneous Steel

Component	Area / Qty	Unit weight	Total wt (kg)
Composite metal deck (galvanized, 1.2 mm base)	8 floors × 400 m² = 3,200 m²	12 kg/m²	38,400
Shear studs (19 mm dia × 80 mm)	~6,400 studs	0.26 kg/stud	1,664
Lateral bracing (roof & floor diaphragm)	L‑section & angles	-	12,500
Stairs, railings, roof screen	Lump sum	-	8,500
Connections, base plates, splice plates	~12% of frame wt	-	36,800
Subtotal – Floor & Misc. Steel			97,864

4.4 Total Steel Tonnage Summary

Category	Weight (kg)	Tonnes (MT)
Columns	124,937	124.9
Beams & Girders	146,279	146.3
Floor system & Misc. steel	97,864	97.9
Total Structural Steel	369,080	~370
+ Contingency (10%) for design development	36,908	~37
Grand Total (Recommended Budget Weight)	405,988	~480

Unit steel weight: ~480 kg/m² of gross floor area (8 storeys × 400 m² = 3,200 m²).
Estimated material cost (Philippines, fabricated steel): Please inquiry CBC for details. Erection and fireproofing are additional.

5. Key Design Considerations (Manila-Specific)

P‑Delta & drift: With storey heights up to 6.0 m and a total height of 36.9 m, second‑order effects are significant. The stability coefficient θ shall be ≤ 0.10. Provide SMF with strong-column/weak-beam proportioning.

Seismic irregularity: The unequal bay layout (5.9 m / 8.2 m / 5.9 m) and two dissimilar spans create plan irregularity (Type 1a). Accidental torsion amplification (A_x) per NSCP §208.5.5.2 required.

Soft‑story check: 1F parking (6.0 m) vs. 5F‑7F residential (3.4 m). Stiffness of moment frames must be proportioned to avoid vertical irregularity Type 1a (stiffness‑soft story).

Connection detailing: Bolted extended end‑plate (BEEP) or welded unreinforced flange (WUF‑W) connections, prequalified per AISC 358‑22 for SMF, are mandatory under NSCP Seismic Design Category D.

Corrosion protection: Tropical marine atmosphere in Metro Manila. HDG (hot‑dip galvanized) or inorganic zinc‑rich primer + epoxy intermediate + aliphatic polyurethane topcoat to meet C4 environment per ISO 12944, achieving a service life ≥ 30 years.

6. Applicability Assessment – Pacific Rim Countries

The proposed design is evaluated for transferability to five other Pacific Rim nations. "Directly applicable" means the Manila design can be adopted with minor adjustments; "Upgrade required" means member sizes or lateral system must be revised; "Major redesign" means a new structural system is needed.

6.1 Tonga

Parameter	Manila (Baseline)	Tonga (NBCKT / AS/NZS 1170)	Assessment
Wind speed (3‑s gust)	250 kph (69 m/s)	180–200 kph (Category N3‑N4)	MS gust slightly lower, but up to 250 kph in cyclone zones.
Seismic hazard	High (Zone 4)	Moderate (Zone 2, a_gR ~0.20g)	Lateral forces are 40–50% of Manila demand.
Structural implications	Moment frame with deep girders		Drift limits may be relaxed; sections could potentially be reduced by 10-15%.
Overall suitability	Good – applicable with moderate column/wind drift checks.

6.2 New Caledonia (France)

Parameter	Manila	New Caledonia (EN 1998 / EN 1991)	Assessment
Seismic	High	Moderate (Zone 3, a_gR ≈ 0.16g)	Seismic base shear ~30% of Manila; however EN 1998 ductility class DCM required.
Wind	250 kph	36 m/s (10‑min mean), ~50 m/s gust (~180 kph)	Wind pressure is lower; drift not critical.
Structural implications	Steel sections could be reduced 15–25% if European rolled sections (HEA/HEM) are substituted.
Overall suitability	Good – member optimization possible.

6.3 Papua New Guinea

Parameter	Manila	PNG (PNGS 1001‑1982 / AS/NZS 1170)	Assessment
Seismic	High	Very High (Zone 1, PGA ≥ 0.40g)	PNGS 1001 hazar maps comparable to Manila, but code lacks refined ductility provisions.
Wind	250 kph	45 m/s (10‑min mean) ~160 kph gust	Lower wind; seismic governs.
Structural implications	Adopt higher R‑factor? PNGS limited guidance; ISO 3010 or ASCE 7‑22 used. Sections likely similar to Manila, but detailed seismic peer review required.
Overall suitability	Conditionally suitable – requires local engineer certification & updated PNGS compliance check.

6.4 Chile

Parameter	Manila	Chile (NCh 433 Of.96 Mod.2012)	Assessment
Seismic	High	Extreme (Zone 3, base shear 1.4–18.2% W)	Chilean seismic base shear may be 2× to 3× of NSCP depending on period.
Wind	250 kph	Moderate (30–35 m/s gust)	Not governing.
Structural implications	NCh 433 mandates strict drift limits (0.002 h_sx). The 3‑column line layout creates severe torsional irregularity. A dual system (SMF + EBF or concrete core) is recommended.
Overall suitability	Major redesign required. Add braced bays or RC core; column sizes increase 30–50% over Manila baseline.

6.5 Peru

Parameter	Manila	Peru (E.030‑2016)	Assessment
Seismic	High	Very High (Zone 4, coastal Lima Mw > 8.0 capable)	Elastic base shear ~0.12–0.15 W; R = 7 for SMF.
Wind	250 kph	Low (~30 m/s)	Negligible.
Structural implications	E.030 enforces strong-column/weak-beam and drift ≤ 0.007 h_sx. The existing SMF may work, but Peru's National Building Regulation requires site‑specific hazard analysis. Column sections likely need an additional 15–25% over Manila.
Overall suitability	Feasible with seismic upgrade. SMF is permitted; global stiffness must be verified against Peruvian drift limits.

7. Structural Optimization Opportunities

Strategy	Potential Saving (MT)	Remarks
1. Floor system revision (post‑tensioned concrete flat slab)	80–100	Steel framing replaced by RC; steel weight savings offset by increased concrete cost.
2. Composite columns (CFT – Concrete‑Filled Tube)	40–55	Reduce column steel area; enhance stiffness and fireproofing.
3. Optimized steel grade (Gr. 65 for columns)	20–30	Higher strength allows smaller sections; check local availability.
4. Refined connection design	10–15	Use plastic design of connections to reduce stiffener count.
5. Modular precast stairs & non‑structural steel	5–8	Replace fabricated steel stairs with precast concrete or lightweight systems.
Total Realistic Reduction	100–130	~20–27% of baseline

8. Conclusion & Recommendations

Manila baseline design is code‑compliant and robust. The 3‑column‑line Special Moment Frame (SMF) system can resist the combined wind (250 kph gust) and seismic (S_DS=0.85g, S_D1=0.64g) demands in the Philippines, provided strong‑column/weak‑beam proportioning and prequalified SMF connections are used.

Total structural steel weight ≈ 480 MT (405 MT base + 10% contingency).

Regional transferability:

Tonga & New Caledonia: Applicable with possible member reduction (lower seismic demand).

Papua New Guinea: Conditionally suitable – must verify with current PNGS seismic annex and local code updates.

Chile: Requires a dual system or braced frame due to extreme seismic base shear (NCh 433). Column steel may increase by 30–50%.

Peru: Feasible with 15–25% column upgrade and site‑specific hazard analysis per E.030.

Optimization potential: By adopting composite columns, optimized steel grades, or alternative floor systems, steel weight could be reduced to ~350–380 MT, saving ~$42,000–$55,000 USD in material.

Next steps: Perform 3D finite element analysis (SAP2000/ETABS) to verify natural period, drift and P‑Delta stability; refine column splices and connection detailing; and conduct site‑specific geotechnical investigation to finalize foundation design.

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