Design Criteria Steel

7/28/2019 Design Criteria Steel

1/7

NECC ADDITIONAL FIRE EXIT

NECC Building, Gozar St. Cor. Sales St., Newport City, Pasay City

STRUCTURAL DESIGN CRITERIA

1.1 APPLICABLE CODES AND STANDARD

The following codes, standards, and references were used in the design of the Structural Works.

1) National Structural Code of the Philippines (NSCP) C101-10, 6th Edition, 2010

2) Uniform Building Code (UBC) 1997 Edition, International Conference of Building Officials

3) American Concrete Institute (ACI) Publications

a. Building Code Requirements for Structural Concrete and Commentary American ConcreteInstitute (ACI 318) 2002 Edition

b. Details and Detailing of Reinforcement for Concrete

4) Manual of Steel Construction American Institute of Steel Construction (AISC) 9th Edition

5) Earthquake Resistant Design of Structures, ASEP Guide, 1991 Edition

6) Foundation Analysis and Design, Fifth Edition, by Joseph E. Bowles

1.2 DESIGN LOADINGS

1.2.1 Live Loads

Room Name kPa

Stairs 4.80

1.2.2 Live Load Reduction

The design live load was reduced on members supporting more than 14 m2, except for floors inplaces of public assembly and for floor live loads greater than 4.80 kPa, in accordance with thefollowing equation:

R = r (A-14)

The reduction shall not exceed 40 percent for members receiving load from one level only, 60percent for other members or R, as determined by the following equation:

R = 23.1 (1 + D/L)

Where:

A = area of floor or roof supported by the member, square meter.D = dead load per square meter of area supported by the member.L = unit live load per square meter of area supported by the member.R = reduction in percentage.r = rate of reduction equal to 0.08 percent for floors.

G.E. ORIGENES AND ASSOCIATESStructural Engineers

1


2/7



For storage loads exceeding 4.80 kPa, no reduction shall be made, except that design live loadon columns may be reduced 20 percent.

The live load reduction shall not exceed 40 percent in garages for the storage of privatepleasure cars having a capacity of not more than nine passengers per vehicle.

1.2.3 Dead Loads

Self-Weight kN/m3

Concrete 23.6

Steel 77.0

Soil 16.0

1.2.4 Superimposed Dead Load

Material kPa

Partitions :

Masonry Movable Partition

2.730.96

Floor Finish + Topping 1.20

Membrane Waterproofing + Topping 1.80

Ceiling + Utilities 0.5

1.2.5 Lateral Loads

1.2.5.1 Wind Load

Design Code: NSCP 2010Wind Pressure Zone: Zone II

Basic Wind Speed: 200 kphVelocity Pressure, q: 47.3x10-6 Kz Kzt V

2 IwImportance Factor, Iw : 1.0Exposure Category: BDesign Wind Pressure, P: P = q G Cp qh (GCpi)

1.2.5.2 Earthquake Loads

Seismic Code: Uniform Building Code 1997 / NSCP 2010

Seismic Zone: Zone 4, Z=0.4Soil Profile Type: SD (Stiff Soil Profile)Building Base: Ground Level

Seismic Source Proximity: < 5 km from Valley Fault System (Seismic Source Type A)

Design Earthquake Load, E = Eh + Ev

where :

E = the earthquake load on an element of the structure resulting from the combinationof the horizontal component, Eh, and the vertical component, Ev

Eh = the earthquake load due to the base shear, V or the design lateral force, Fp.


2


3/7



Ev = the load effect resulting from the vertical component of the earthquake groundmotion and is equal to an addition of 0.5CaID to the dead load effect, D, forStrength Design, and may be taken as zero for Allowable Stress Design.

= Reliability/Redundancy factor as given by the following equation:

= 1, when calculating drift or when the structure is located in Seismic Zone 0,1 or 2

BAmaxr

6.12 =

where : rmax = the maximum element-story shear ratio. For a given direction ofloading, the element-story shear ratio is the ratio of the designstory shear in the most heavily loaded single element dividedby the total design story shear.

AB = the ground floor area of the structure in square meter. For any

given Story Level i, the element-story shear ratio is denoted asri. The maximum element-story shear ratio rmax is defined asthe largest of the element story shear ratios, ri, which occurs inany of the story levels at or below the two-thirds height level ofthe building.

Design Base Shear for Static Force Procedure:

WRT

ICV v= W

R

I2.5Ca

IW0.11Ca

WR

I0.8ZNv

where :

V = Total Design Lateral Force or Shear at the BaseZ = Seismic Zone FactorI = Importance FactorT= Ct(hn)

3/4, Elastic Fundamental Period of Vibration of the Structure, in seconds, in thedirection under consideration.

Ct= Numerical Coefficient for Structure= 0.085 for steel moment-resisting frames.= 0.073 for reinforced concrete moment-resisting frames.= 0.0488 for other structures

hn= the height of structureCa = 0.40Na, Seismic Coefficient for StructureCv = 0.672Nv, Seismic Coefficient for StructureNa = 1.0Nv = 1.0R= Numerical Coefficient Representative of the Inherent Overstrength and Global

Ductility Capacity of the Lateral-Force-Resisting SystemW = Total Seismic Dead Load


3


4/7



Seismic Parameters

Seismic Zone, Z 0.4

Importance Factor 1.0

Seismic Source Type A

R (Shear-Wall-Frame Interaction System) 8.5

1.3 MATERIAL SPECIFICATIONS

1.3.1.1 Structural Steel

Yield strength, FyRolled Sections (ASTM A36) 248 MPa

Cold-formed Sections (ASTM A446) 276 MPa

Tensile strength, Fu

High Strength Bolts (ASTM A325) 830 MPaNormal Bolts (ASTM A307) 414 MPa

Welding Electrodes (E70XX) 414 MPa

1.4 Load Combinations

1.4.1 For Allowable Stress Design of Steel

1.4.1.1 Dead Load + Live Load

DL + LL

1.4.1.2 Dead Load + Live Load + Wind Load

0.75 * (DL + LL WL)

0.75 * (0.85 * DL WL)

1.4.1.3 Dead Load + Live Load + Seismic Load

0.75* (DL + LL EQ)

0.75 * (0.85 * DL EQ)

where:

D = Dead LoadL = Live LoadWL = Wind LoadEQ = Earthquake Force


4


5/7


6/7



1.6.3 Lateral Load Analysis

1.6.3.1 Wind Load Analysis

Wind load analysis was carried out on the basis of the loads given in 1.2.5.1. Wind was

assumed to come from any horizontal direction. No reduction in wind pressure for shieldingeffect of adjacent structures.

The base overturning moment for the entire structure, or for any one of its primary lateral-resisting elements, was checked and shall not exceed two thirds of the dead-load-resistingmoment. For an entire structure with a height-to-width ratio of 0.5 or less in the winddirection and a maximum height of 60 feet (18,290 mm), the combination of the effects ofuplift and overturning was reduced by one-third as allowed by NSCP / UBC. The weight ofearth superimposed over footings was used to calculate the dead-load-resisting moment.

Procedure is as follows:

9. Determine design wind pressure at each level.

10. Apply wind load to the three dimensional model.

1.6.3.2 Earthquake Load Analysis

Earthquake load analysis was carried out on the basis of the loads given in 1.2.5.2. Anequivalent static seismic analysis was carried out to obtain the scaling factors for thedynamic lateral forces. The dynamic analysis was performed as required and the detailedprocedure illustrated in UBC 1631. The forces from the dynamic analysis multiplied by thescaling factor, was be used throughout the design.

Below are the effective moment of inertia used for the structural members.

Columns: Ieffective = 0.70 * IgrossBeams: Ieffective = 0.35 * Igross

Procedure is as follows:11. Determine building mass12. Determine design base shear for static force procedure.13. Determine minimum accidental torsion.14. Perform dynamic lateral response spectrum analysis


6


7/7



Description of Dynamic Analysis Procedure:

14.1 Perform the dynamic analysis using the normalized response spectra shapes givenby UBC 1997 using an initial acceleration of one (1) g.

14.2 Determine number of modes shapes required to attain a mass participation of at least90%. UBC requires that at least 90 percent of the participating mass of the structureshould be included in the calculation of response for each principal horizontaldirection

14.3 Check base shear from dynamic analysis using an acceleration of one (1) g. Scalethe results.

14.4 Rerun dynamic analysis using the scaled acceleration from Step 14.3.

14.5 Apply minimum accidental torsion requirements.

14.6 Perform design for structural members.

14.7 Determine the fundamental period (TB) using the structural properties anddeformational characteristics of the resisting elements (Method B).

14.8 Check approximate T of Method A (TA) versus Method B (TB). If TB is smaller than TA,use TB and recalculate the minimum required base shear in Step 12 and redo theanalysis. If TB is larger than TA, we can use TB in formula in Step 12 and reduce theminimum required base shear. The value of TB shall not be over 40 percent inSeismic Zones 1,2 and 3.

14.9 Check the story drift.


7

Documents

Design Criteria Steel