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Static Force Procedure: CE 305- Principles of Earthquake Engineering Lesson 3: Static Force ProcedureStatic Force ProcedureAll structures is subjected to static forces, of varying degree based on the structures properties, design, location, as well as their purpose. In earthquake engineering, it is ...

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3.2. Static Force Procedure: CE 305- Principles of Earthquake Engineering

Lesson 3.1: Static Force Procedure Static Force Procedure All structures is subjected to static forces, of varying degree based on the structures properties, design, location, as well as their purpose. In earthquake engineering, it is important to understand the seismic considerations when it comes to the computation of the total weight of each floor, computation of the Structural Period (T), and solving the Base Shear (V) and the Lateral Seismic Force (Fx). This topic intends to give a guide on how to come up with these computations based on the provisions of the National Structural Code of the Philippines (NSCP) 2015.

NSCP 2015 Section 208.4.2 - Static The Static lateral force procedure of 208.5 may be used for the following structures: 1. All structures, regular or irregular in Occupancy Categories IV and V in Seismic Zone 2. 2. Regular Structures under 75 m in height with lateral force resistance provided by systems listed in table 208-11, except where 208.4.8.3, Item 4, applies. 3. Irregular structures not more than 5 stories or 20 m in height. 4. Structures having a flexible upper portion supported on a rigid lower portion where both portions of the structure considered separately can be classified as being regular, the average storey stiffness of the lower portion is at least 10 times the average storey stiffness of the upper portion and the period of the entire structure is not greater than 1.1 times the period of the upper portion considered as a separate structure fixed at the base.

General Procedure 1. List all the Seismic Considerations: Occupancy Category Importance Factor Soil Profile Type Seismic Zone Factor Seismic Source Type Seismic Coefficient: Ca & Cv Near Source Factor: N a & Nv Structural Design Response Modification Factor: R

2. Compute the total weight of each floor 3. Compute for the Structural Period (T) 4. Solve for the Base Shear (V) 5. Solve the Lateral Seismic Force (Fx)

Example Problem: Given: Profile and Information of the Structure 4 – Storey Residential Manila City, NCR Reinforced Concrete Building Structural System: Special-Moment Resisting Frame System (SMRF) Storey Height, h = [email protected] + 3@3m = 13.5 m Building Dimension: 5 m x 12 m Weight per Floor = 7.2 kPa Building Seismic Information Seismic Source Type: B Distance to nearest fault line: 5 km Soil Profile Type: SD TB = 1 sec Requirement: Period (T) Base Shear (V) Lateral Seismic Force (Fx) at the roof

Solution: 1. Identify Occupancy Category.

Occupancy Category = IV 2. Identify the Seismic Zone Factor and Seismic Importance Factor.

Seismic Zone Factor: 0.40 Seismic Importance Factor: 1.00

3. Identify the Near-Source Factors.

Na: 1.0 Nv: 1.2

4. Compute for the Seismic Coefficients

Ca: 0.44Na = 0.44(1.0) = 0.44 Cv: 0.64Nv = 0.64(1.2) = 0.768

5. Identify Ct

Ct: 0.0731

6. Identify the Response Modification Factor (R)

R: 8.5

7. Compute for the Total Weight (W)

Total Weight (W): 1,728 kN

8. Compute for the Total Weight (W)

9. Compute for the Total Weight (W)

10. Compute for the lateral seismic force, Fx....