PART I. STRUCTURAL RE-ANALYSIS AND MODELING OF PEZA BUILDING

A. INTRODUCTION

The Philippine Export Processing Zone Authority (PEZA) Building is a six (6) storey reinforced concrete building constructed in the 1960’s. The sixth floor level was an additional one-floor office space constructed above the five storey existing building.

In the conduct of the structural evaluation and analysis of the structural stability of the PEZA Building, PSquare & Associates Co. adopted a systematic procedure using the information and results of the Preliminary Evaluation done by RS Ison and Associates which were provided by PEZA. The procedure involves an independent materials property, evaluation/investigation and determination of in-place structural capacity of structural components which included frame analysis and computations of Demand-Capacity Ratios (DCRs). The Structural Analysis was done by creating a structural model using ETABS Software while other analyses were carried out by using MS-Excel worksheets. The results of the materials property evaluation were used in determining the structural capacities of critical members i.e. Beams, Columns. Linear Static Lateral Force Procedure (LSP) was done following code-prescribed procedure while Linear Dynamic Procedure (LDP) using Response Spectrum Analysis was undertaken considering the results of the site specific study which were modified following the code-prescribed procedures for LDP.

B. STRUCTURAL DESIGN CRITERIA USED IN THE EVALUATION

1. Applicable Codes and Standards a. National Structural Code of the Philippines Volume I for Buildings,

Towers and Other Vertical Structures 2010 6th Edition b. National Building Code of the Philippines c. ASEP Earthquake Design Manual d. Building Code Requirements of Structural Concrete, ACI 318-08

2. Gravity Loads a. Dead Load

Concrete = 24 kN/cu.m. Structural Steel = 77.0 kN/cu. m.

b. Superimposed Dead Load Concrete/Floor Finish = 1.2 kPa Partitions = 1.0 kPa CHB 150 mm = 2.7 kPa Ceiling and Fixtures = 0.60 kPa Waterproofing = 0.05 kPa

3. Live Load Office Units = 2.4 kPa Lobby/Corridor/Social Hall = 4.8 kPa Storage = 7.2 kPa Maintenance/Electrical Room = 6.0 kPa

Stairway = 4.8 kPa Machine Room = 6.00 kPa Roof Deck = 2.4 kPa

4. Seismic Load a. Static Lateral Force Procedure

Design Base Shear, V V = (CvI/RT)W

Should not exceed: V = (2.5CaI/R)W

and should not be less than: V = 0.11CaIW or V = (0.8ZNvI/R)W

Where : Cv = seismic coefficient, NSCP Table 208-8 = 0.896 Ca = Sesimci coefficient, NSCP Table 208-7 = 0.484 Nv = near source factor, NSCP Table 208-5/208-6 = 1.4 (distance from source=7.5 km) Z = zone factor 0.40 R = response modification factor = 8.5 I = importance factor – 1.0 W = seismic dead weight Fundamental period, T = Ct hn ¾ Ct = 0.0731 = 0.03 (English unit) hn = building height in meters

4. Load Combinations a. 4.1 U = 1.4 D b. 4.2 U = 1.2D + 1.6L + 0.5 Lr c. 4.3 U = 1.2D + 1.6 Lr + 0.5L d. 4.4 U = 1.2D + 1.6W + 1.0L + 0.5Lr e. 4.5 U = 1.2D + 1.0E + 1.0L f. 4.6 U = 0.90D + 1.0E

Where: D = dead load L = live load Lr = roof live load W = wind load E = seismic load

5. Material Strenghts a. Concrete, fc’ = 11.2 MPa (1,600 psi) b. Reinforcing bars, ASTM Grade 33, fy = 230 MPa (33,000 psi)

C. RESULTS/FINDINGS Based on the results of the analysis of DCR for beams and columns, 72 percent of the second floor beams failed to resist the anticipated loads due to dead, live and seismic loads. For the third floor, 75 percent of the beams failed. For the fourth and fifth floors, 76 percent of the beams failed. For the sixth floor, 81 percent of the beams failed and for the roof, 51 percent of the beams failed. For the columns, 100 percent of the columns failed in required capacities from footings to roof level. In summary, on the average, 74 percent of all beams failed and 100 percent of the columns failed. The beams and columns failed either due to inadequate flexural capacities and/or strength to resist anticipated loads.

D. STRUCTURAL MODELLING

Figure 1. PEZA ETABS Model (Pure Frame with Elevator Shaft)

Figure 2. PEZA ETABS Model with shear walls and elevator shaft

Figure 3. Second floor framing model showing failed beams (in red)

Figure 3. Second floor framing model showing failed beams (in red)

Figure 4. Third floor framing model showing failed beams (in red)

Figure 5. Fourth Floor Framing model showing failed beams (in red)

Figure 6. Fifth Floor Framing model showing failed beams (in red)

Figure 7. Sixth Floor Framing model showing failed beams (in red)

Figure 8. Roof framing model showing failed beams (in red)

Figure 9. Frame 1 elevation model showing failed columns

Figure 10. Frame 2 elevation model showing failed columns

Figure 11. Frame 3 elevation model showing failed columns

Figure 12. Frame 4 elevation model showing failed columns

Figure 13. Frame 5 elevation model showing failed columns

Figure 14. Typical floor framing model

Figure 15. Typical floor framing Model showing beam designations

Figure 16. Typical stress distribution on frames

Figure 17. Typical beams stress distribution

E. COMPUTATIONS OF DEMAND-CAPACITY RATIOS FOR BEAMS

F. COMPUTATIONS OF DEMAND-CAPACITY RATIOS FOR COLUMNS

G. ETABS RUN ANALYSIS

PART II. STRUCTURAL CALCULATIONS FOR THE APPLICATION OF CFRPS AND RECONSTRUCTION OF 6TH FLOOR