UPDATES ON CHAPTER 2 : MINIMUM DESIGN LOADS NATIONAL STRUCTURAL CODE OF THE PHILIPPINES NSCP 2015, VOLUME 1
Ronaldo S. Ison, F.ASEP, PP 2002‐2004, FPICE Chancellor, College of Fellows
Significant Changes to Chapter 2 Minimum Design Loads
Load combinations for are changed due to the use of strength‐based wind loading based on ASCE 7‐10 Additional live load designations for parking, garage, and ramp live loading Basic wind speed are revised based on latest studies For communication towers, ANSI TIA/EIA 222G latest edition is fully referenced in the NSCP
Significant Changes to Chapter 2 Minimum Design Loads
Near‐source factors are revised to consider distance to source <2 km to be distinct and with higher values Revision of magnitude limits for Seismic Source Type A Use of spectral acceleration based on ASCE/SEI 7‐10 is recognized as an alternative procedure for determining earthquake forces Rest of the Sections in Chapter 2 are unchanged with reference to NSCP 2010 6th Edition
Material Densities
Loadings Dead Loads
Loadings Live Loads
Loadings Live Loads
Loadings Live Loads
Live Load Reduction
Live Load Reduction
Loadings Roof Loads
Loadings Earthquake Loads SCOPE ‐ Structures or portions thereof shall be, as a minimum, be designed and constructed to resist the effects of seismic ground motion SEISMIC AND WIND DESIGN ‐ When the code prescribed produces greater effects, the wind design shall govern, but detailing requirements and limitations of Section 208 Earthquake Loads shall be followed.
Earthquake Loads Design Base Shear – Static Force Procedure
Cv I V W RT
(208‐9)
The total design base shear need not exceed the following: 2.5Ca I (208‐10) V W R
Earthquake Loads Design Base Shear – Static Force Procedure The total design base shear shall not be less than the following: (208‐11) V 0.11Ca I W In addition, for Seismic Zone 4, the total base shear shall also not be less than the following: (208‐12) 0.8ZN v I V W R
Occupancy Categories
Occupancy Categories
Seismic Importance Factors
NSCP 2015 and NSCP 2010
Soil Profile Types
NSCP 2015 and NSCP 2010
Seismic Source Types
NSCP 2015
NSCP 2010
Near Source Factors
NSCP 2015
NSCP 2010
Seismic Coefficients
NSCP 2015
NSCP 2010
Seismic Coefficients
NSCP 2015
NSCP 2010
Response Modification and Overstrength Factors
Seismic Map of the Philippines The Philippines is divided into two (2) Seismic Zones : Seismic Zone 2 (Z=0.2) Islands oF Palawan, Tawi‐ Tawi and Sulu Seismic Zone 4 (Z=0.4) Rest of the Philippine Islands
Fault Map of the Philippines Distribution of Active Faults and Trenches (PHIVOLCS)
Fault Map of the Philippines Active Faults in the Cordillera Administrative Region (CAR)
Fault Map of the Philippines Active Faults and Trenches in Region 1
Fault Map of the Philippines Active Faults and Trenches in Region 2
Fault Map of the Philippines
Active Faults in Region 3
Fault Map of the Philippines Active Faults and Trenches in Region 4A
Fault Map of the Philippines
Active Faults in Region 4B
Fault Map of the Philippines Active Faults and Trenches in Region 5
Fault Map of the Philippines Active Faults and Trenches in Region 6
Fault Map of the Philippines Active Faults and Trenches in Region 7
Fault Map of the Philippines Active Faults and Trenches in Region 8
Fault Map of the Philippines Active Faults and Trenches in Region 9
Fault Map of the Philippines Active Faults and Trenches in Region 10
Fault Map of the Philippines Active Faults and Trenches in Region 11
Fault Map of the Philippines Active Faults and Trenches in Region 12
Fault Map of the Philippines Active Faults and Trenches in Region 13
Fault Map of the Philippines
Active Faults and Trenches in Autonomous Region of Muslim Mindanao (ARMM)
Fault Map of the Philippines Active Faults in National Capital Region (NCR)
Earthquake Loads Design Base Shear – Static Force Procedure
Cv I V W RT
(208‐9)
The total design base shear need not exceed the following: 2.5Ca I (208‐10) V W R
Earthquake Loads Design Base Shear – Static Force Procedure The total design base shear shall not be less than the following: (208‐11) V 0.11Ca I W In addition, for Seismic Zone 4, the total base shear shall also not be less than the following: (208‐12) 0.8ZN v I V W R
Earthquake Loads Building Period, T
T = Ct(hn)3/4 = 0.0853(30)3/4 = 1.093 sec
30 m
Ct = 0.0853 for steel SMRF
Ct = 0.0731 for concrete SMRF T = Ct(hn)3/4 = 0.0731(30)3/4 = 0.937 sec Ct = 0.0488 for other systems T = Ct(hn)3/4 = 0.0488(30)3/4 = 0.626 sec
6m
Ground
Earthquake Loads Sample Problem – Design Base Shear
Zone 4, Z = 0.4 Seismic Source Type = A Distance to seismic source = 10 km Soil Profile Type = Sc I = 1.0 R = 8.5 W = 7300 kN
25m
Given:
Earthquake Loads Sample Problem – Design Base Shear Determine the structure period T using Method A. For concrete moment –resisting frames, Ct is 0.0731 T = Ct(hn)3/4 = 0.0731(25)3/4 = 0.81 sec. Find near source factors Na and Nv from Tables 208‐9 and 208‐10 for Seismic Source Type A and distance to seismic source of 10 km. Na = 1.0 Nv = 1.2
Earthquake Loads Sample Problem – Design Base Shear Determine seismic coefficients Ca and Cv from Tables 208‐11 and 208‐12 for soil profile type Sc and Zone 4. Ca = 0.40 Na Cv = 0.56 Nv = 0.4x1.0 = 0.56x1.2 = 0.4 = 0.672
Earthquake Loads Sample Problem – Design Base Shear The total design base shear in a given direction is: V = CVI/RT x W (NSCP 208‐4) = 0.672(1.0)/(8.5x.81) x 7300 = 712 kN (GOVERNS) the total design base shear need not exceed the following: V = 2.5(CaI)/R x W (NSCP 208‐5) = 2.5(0.40)1.0/8.5 x 7300 = 858 kN
Earthquake Loads Sample Problem – Design Base Shear the base shear shall not be less than the following: V = 0.11CaIW (NSCP 208‐6) = 0.11(0.40)(1.0)(7300) = 321 kN in Seismic Zone 4, the total design base shear shall also be not less than: V = 0.8NvI/R x W (NSCP 208‐7) = 0.8(0.40)(1.20)(1.0)/8.5 x 7300 = 330 kN
Earthquake Loads Vertical Distribution The total design base shear, V, shall be distributed at different floor levels according to the following: Fx = (V‐Ft) x wxhx wxhx where: V : design base shear Ft : .07TV, when period, T > 0.7 second, else Ft = 0 wx : mass at floor level hx : height of floor from ground level
Earthquake Loads Dynamic Analysis – Response Spectrum
Load Combinations Buildings, towers and other vertical structures and all portions thereof shall be designed to resist the load combinations in NSCP Section 203. The critical effect can occur when one or more of the contributing loads are not acting.
Load Definitions
D = dead load E = earthquake load Em = estimated maximum earthquake force that can be developed in the structure F = load due to fluids with well‐defined pressures and maximum heights H = load due to lateral pressure of soil and water in soil L = live load, except roof live load, including any permitted live load reduction Lr = roof live load, including any permitted live load reduction
Load Definitions
L
= live load, except roof live load, including any permitted live load reduction Lr = roof live load, including any permitted live load reduction R = rain load on the undeflected roof T = self‐straining force and effects arising from contraction or expansion resulting from temperature change, shrinkage, moisture change, creep in component materials, movement due to differential settlement, or combinations thereof W = load due to wind pressure
Load Combinations for RC Design and Steel Design
U = 1.4 (D + F) U = 1.2 (D+ F+T ) + 1.6 (L+H) + 0.5(Lr or R) U = 1.2 D + 1.6 (Lr or R) + (f1L or 0.50 W) U = 1.2 D + 1.0 W + f1 L +0.5 (Lr or R) U = 1.2 D + 1.0 E+ f1 L U = 0.9 D + 1.0 W + 1.6 H U = 0.9 D + 1.0 E + 1.6 H f1 = 1.0 for floors in places of public assembly, for live loads in excess of 4.8 kPa, and for garage live load = 0.5 for other live loads
Load Combination for Strength Design Application of the strength design load combinations that involve the seismic load E for the moment resisting frame Z = 0.4 Ca = 0.44 I = 1.0 ρ = 1.1 f1 = 0.5
Load Combination for Strength Design Beam A‐B and Column C‐D are elements of the special moment‐ resisting frame. Structural analysis has provided the following individual beam moments at A, and the column axial loads and moments at C due to dead load, office building live load, and lateral seismic forces. Dead Load D Live Load L Lateral Seismic Load Eh Beam Moment at A 135 kN‐m 65 kN‐m 165 kN‐m Column C‐D axial load 400 kN 180 kN 490 kN Column Moment at C 55 kN‐m 30 kN‐m 220 kN‐m PROBLEM : Find the strength design moment at beam end A and strength design axial load and moment at column top C.
Load Combination for Strength Design
Strength design moment at beam end A. Determine earthquake load E: The earthquake load E consists of two components as shown below in equation (208‐1). Eh is due to horizontal forces, and Ev is due to vertical forces. E = ρEh + Ev (Section 208‐1) The moment due to vertical earthquake forces is calculated Ev = 0.5CaID = 0.5(0.44)(1.0)(135) = 29.7 kN‐m
Load Combination for Strength Design The moment due to horizontal earthquake forces is given as Eh = 165 kN‐m Therefore = ρEh + Ev = 1.1(165)+29.7 = 211 kN‐m
Load Combination for Strength Design
U = 1.4 (D + F) = 1.4D U = 1.2 (D+ F+T ) + 1.6 (L+H) + 0.5(Lr or R) = 1.2D + 1.6L U = 1.2 D + 1.6 (Lr or R) + (f1L or 0.50 W) = 1.2D + 0.5L U = 1.2 D + 1.0 W + f1 L +0.5 (Lr or R) = 1.2D +0.5L U = 1.2 D + 1.0 E+ f1 L = 1.2D + 1.0E + 0.5L U = 0.9 D + 1.0 W + 1.6 H = 0.9D U = 0.9 D + 1.0 E + 1.6 H = 0.9D +1.0E
Load Combination for Strength Design
Apply earthquake load combinations The basic load combinations for strength design (or LRFD) are given in Section 203.3.1. For this example, the applicable equations are:
1.2D + 1.0E + f1L (Section 203‐5) 0.9D 1.0E (Section 203‐6) Using Equation (203‐5) and Equation (203‐6), the strength design moment at A for combined dead, live, and seismic forces are determined.
MA = 1.2MD +1.0ME + f1ML = 1.2(135)+1.0(211)+0.5(65) = 406 kN‐m
MA = 0.9MD 1.0ME = 0.9(135)1.0(211) = 333 kN‐m or –90 kN‐m Therefore, MA = 406 kN‐m or –90 kN‐m
Load Combination for Strength Design Apply earthquake load combinations, continuation… MA = 0.9MD 1.0ME = 0.9(135) 1.0(211) = 333 kN‐m or –90 kN‐m MA = 1.2MD + 1.6ML = 1.2(135)+1.6(65) = 266 kN‐m Therefore, MA = 406 kN‐m or –90 kN‐m
Strength design axial load and moment at column top C. Determine Earthquake load E: E = ρEh + Ev where
Ev = 0.5CaID = 0.22D for axial load
E = ρEh + Ev = 1.1(490)+0.22(400) = 627 kN for moment
E = ρEh + Ev = 1.1(220)+0.22(55) = 254 kN
Apply Earthquake Load combinations: 1.2D + 1.0E + f1L 0.9D 1.0E
(Section 203‐5) (Section 203‐6)
Design axial force Pc at point C is calculated as Pc = 1.2D + 1.0E + f1L = 1.2(400)+1.0(627)+0.5(180) = 1197 kN
Pc = 0.9D 1.0E = 0.9(400) 1.0(627) = 987 kN‐m or ‐267 kN Therefore, Pc = 1197 kN or –267 kN
Apply Earthquake Load combinations, continued 1.2D + 1.0E + f1L (Section 203‐5) 0.9D 1.0E (Section 203‐6) Design axial force Pc at point C is calculated as Pc = 0.9D 1.0E = 0.9(400) 1.0(627) = 987 kN‐m or ‐267 kN Therefore, Pc = 1197 kN or –267 kN
Design moment Mc at point C is calculated : Mc = 1.2D + 1.0E + f1L = 1.2(55)+1.0(254)+0.5(30) = 335 kN‐m Mc = 0.9D 1.0E = 0.9(55) 1.0(254) = 304 kN‐m or ‐205 kN‐m Therefore, Mc = 335 kN‐m or –205 kN‐m
Note that the column section capacity must be designed for the interaction of Pc = 1197 kN compression and Mc = 335 kN‐m (for dead, live and earthquake), and the interaction of Pc = 267 kN tension and Mc = ‐205 kN‐m (for dead and earthquake).
Design moment Mc at point C is calculated , continued Note that the column section capacity must be designed for the interaction of Pc = 1197 kN compression and Mc = 335 kN‐m (for dead, live and earthquake), and the interaction of Pc = 267 kN tension and Mc = ‐205 kN‐m (for dead and earthquake).
Significant Changes to Chapter 2 Minimum Design Loads
Load combinations for are changed due to the use of strength‐based wind loading based on ASCE 7‐10 Additional live load designations for parking, garage, and ramp live loading Basic wind speed are revised based on latest studies For communication towers, ANSI TIA/EIA 222G latest edition is fully referenced in the NSCP
Significant Changes to Chapter 2 Loads and Actions
Near‐source factors are revised to consider distance to source <2 km to be distinct and with higher values Revision of magnitude limits for Seismic Source Type A Use of spectral acceleration based on ASCE/SEI 7‐10 is recognized as an alternative procedure for determining earthquake forces Rest of the Sections in Chapter 2 are unchanged with reference to NSCP 2010 6th Edition
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