Design Process - Suranaree University of...

Post on 03-May-2018

224 views 4 download

Transcript of Design Process - Suranaree University of...

Reinforced Concrete DesignReinforced Concrete Design

Lecture 2 - Specification, Loads andDesign Methods

�� Structural Design ProcessStructural Design Process

�� Building CodesBuilding Codes

�� Working Stress DesignWorking Stress Design

�� Strength Design MethodStrength Design Method

�� Dead Load & Live LoadDead Load & Live Load

�� Load Transfer in Structure Load Transfer in Structure

Mongkol JIRAVACHARADET

S U R A N A R E E INSTITUTE OF ENGINEERING

UNIVERSITY OF TECHNOLOGY SCHOOL OF CIVIL ENGINEERING

ArchitecturalFunctional Plans

DesignDesign ProcessProcess

Select StructuralSystem

Trial Sections,Assume Selfweight

Analysis for internalforces in member

Member Design

Acceptable?Redesign

NG

Final Design& Detailing

OK

Design LoopDesign Loop

SpecificationsSpecifications

Developed by organizations such as AISC, ACIASCE, and EIT

Recommendations of good practice based onthe accepted body of knowledge

NOT legally enforceable

OrganizationsOrganizations

EIT = Engineering Institute of Thailand

ASCE = American Society of Civil Engineers

AASHTO = American Association of State Highwayand Transportation Officials

UBC = Uniform Building Code

BOCA = Building Officials & Code Administrators

ACI = American Concrete Institute

Building CodesBuilding Codes

���ก������ �������������� ก�� ��

Minimum requirements to protect the public

- �.�.�. ����� ����� 2522

- �����""��#ก���$� �����

- $%��""��#

Design Loads

Dead Loads - stationary loads of constant magnitude

Live Loads - moving loads or loads that vary in magnitude

Caused by the weight of structure

Include both the load bearing and non-load

bearing elements in a structure

Generally can be estimated with reasonable

certainty

�&�����ก����ก���� (Dead Load)

�&�����ก��/�ก0�/�������12

���������� kg/m3

���ก�������� �ก 2,400���ก��� ��� 2,320��� 500-1,200�� �ก 7,850

�������������� kg/m2

ก������� ���!" 14ก������� #�$%�&����' 50�� �ก��( ��, * ก�� 5

���������� 10-30���� 5����ก!""#$�"% 180-360����ก!""#$(�)"� 100-200

Tributary area = 0.5SL sq.m

Load on beam = 0.5wSL kg/m

Floor load = w kg/sq.m

LoadLoad from from PrecastPrecast Concrete SlabConcrete Slab

S

L

Example: Example: CPACCPAC Hollow Core Slab Hollow Core Slab HC100HC100

600 mm

100 mm

SLAB WEIGHT 296 KG/M2

PC WIRE 6 ∅ 4 MM.

SPAN 4 M.

LIVE LOAD 300 KG/M2

4 m

L : Beam span

w = ? kg/m

Floor Loads

Snow and Ice: 50 - 200 kg/sq.m.

Traffic Load & Pedestrian Load for Bridges

Impact Loads

Lateral Loads: Wind & Earthquake

�&������&�����กก����ก3�����ก3� ((Live LoadLive Load))

�&�����ก����ก3����6&������ก�ก������ ��� 6 (�.�. 2527) �.�.. ���������� �.�. 2522

������� �!"�#$"��%&������� '#"�(#)*�'#�ก+�(kg/m2)

(1) ����

(2) ก� ����������� ก���

(3) �����ก���� ������� � ��� ���� ! ������"#

(4) ����%&" �'ก%&"���()���ก���� ��)�� ����ก ���%�# %�*���� +,��-��.,���������

(5) �! �ก� 0 �

(6) (ก) ���2-)�3 �4" ,������%&" �'ก%&"���()������ก��2-)�3#�"-����� "-����� ������� %�*�������

(,) �����&� �� +� )4������- ,����)�� ����ก ���%�#�! �ก� %�*0 �

30

100

150

200

250

300

300

�&�����ก����ก3����6&������ (�0�)ก�ก������ ��� 6 (�.�. 2527) �.�.. ���������� �.�. 2522

������� �!"�#$"��%&������� '#"�(#)*�'#�ก+�(kg/m2)

(7) (ก) ��� �������- � ��7�*)�# ���#���� 8��������7�*)�# �����4 � �����( �����#���������#�����9�������ก:��&� �3 �������9�ก�� � �3

(,) �����&� �� +� )4������- ,�����2-)�3 #�"-����� "-����� %�*�������

(8) (ก) ����- � ���ก�< �-�-08�2=3 ��>9� ��3 ���� �����ก��#����-#�3 �����ก:���ก��%�*�����

(,) �����&� �� +� )4������- ,����� �������- � ����7�*)�# ��7�*)�# ���#���� 8���� �����#�� %�*���#��

(9) �����ก:�� �����,�������#���������#��

400

500

500

600

(10) ���9�������ก:��&�����ก�7�4

500

800

Wind LoadsWind Loads

��� ��� ก���*�ก�0���!�1��'�23103(ก���*�#�4���3�# ��� �ก53ก�65������

25.0 Vq ρ=

��7 � q = stagnation pressure ���3�# � (กก./�.2)

V = basic wind speed ������8� ��7)#9�#��3�� ����!:� 10 ��$� (ก�./=�.)

ASCE 7-98200483.0 VKq =

K = �>ก�$��?!*�'������!:��7 #�� $"��+�ก 10 ��$�

���ก"4 10 5010 < h < 20 8020 < h < 40 120#กก"4 40 160

����!:������ '#"�(��� �(��$�) (กก./$�.�.)

WIND DIRECTION

Windwardside

Leew

ard

side

0 m

10 m

20 m

30 m

Step wind loading

��� �$�� �.�.. ���������� �.�. 2522

��� 19 ��ก�������������ก ����������� ��� �������� ����������������ก ���� �������ก!��������"#$��"�� ���������������ก��� %ก&� ���� �"�$ ��ก����'(�� �'�����'������('�"�$ ��!�������'��"��()��

50(8) �� ���&#'��'&�ก����������'�'/0���� ��"����$�

40(7) �� ���ก��'&�ก����������'�'/0�

30(6) �� �������'&�ก����������'�'/0�

20(5) �� �������'&�ก����������'�'/0�

10(4) �� ����$��'&�ก����������'�'/0�

0(3) �� �������'&�ก����������'�'/0�

0(2) �� ����7����'&�ก����������'�'/0�

0(1) ����������'�'/0�

���ก� ������ก���ก�������������������������

ก��������ก�� ����

����������$���8 ����)�� %$ ��)�� %$ �����$%' ���$%' 8989:;�<= ��>&�� �= �����9���� ������ �%"���ก��$ �����&�'�����ก#�����"= ����&�ก������"= ����9'�����������ก��� %ก&��"#$��"�� %ก ��

Early 1900s: WSD was mainly used.

aci 318

ACI 318-56: USD was first introduced.

ACI 318-63: Treated WSD and USD on equal basis.

ACI 318-71: Based entirely on strength approach (USD)WSD was small part called Alternate Design Method (ADM).

ACI 318-77: ADM moved to Appendix AUSD was called Strength Design Method.

Building Code Requirements forStructural Concrete (ACI318-XX)and Commentary (ACI318R-XX)

ACI 318-95: Unified Design was introduced in Appendix B

ACI 318-05

ACI 318-83: ADM moved to Appendix B

ACI 318-89: ADM back to Appendix A

ACI 318-99: Limit State at Failure Approach was introduced

aci 318Building Code Requirements for

Structural Concrete (ACI318-XX)and Commentary (ACI318R-XX)

ACI 318-02: Change load factor to 1.2DL + 1.6LL

ACI 318-08

Reinforced Concrete

Design MethodsWorking Stress Design

(WSD)

Ultimate Strength Design(USD)

Limit State Design(LSD)

Performance-based Design(PBD)

ACI: Alternate Design Method

Stress fromservice load

Allowable stressFa

Concrete: Fa = 0.45f’c (ACI and "��.),= 0.375 f’c (�.�.�. "��#�� 2522)

Steel: Fa = 0.50Fy

- Design under service load condition

�#7���0��8�������� (Working Stress Design : WSD)

- Apply F.S. to strength of materials forallowable stress level Fa

Disadvantages of WSDDisadvantages of WSD::

-- Inability to deal with groups of loads where one loadInability to deal with groups of loads where one load

increases at a rate different from that of the others.increases at a rate different from that of the others.

-- Not account for the variability of the resistances Not account for the variability of the resistances and loadsand loads

-- Lack of any knowledge of the level of saftyLack of any knowledge of the level of safty

F.S. is not known explicitlyF.S. is not known explicitly

�#*+ก,�����-��. = Ultimate Stress Design (USD)

Design Strength Required Strength (U)≥

�#7�ก����� (Strength Design Method : SDM)

- Factored load condition = Structure is about to fail

(Ultimate load = �/,����ก(����ก�-��. )

- Apply F.S. in design via:

- Load factors (> 1.0)

- Strength reduction factors (< 1.0)

Dead Load Factor = 1.4

Live Load Factor = 1.7

Factored Load = 1.4 DL + 1.7 LL

Service Load = DL + LL

Required Strength (U) = Load Factors × Service load

= Factored Load

= �������ก��ก� ���

Load Factors

General:

U = 1.4 DL + 1.7 LL

Wind Load:

U = 0.75(1.4 DL + 1.7 LL+1.7W)

U = 1.05DL + 1.275W

Lateral Earth Pressure:

U = 1.4 DL + 1.7 LL+1.7H

U = 0.9DL + 1.7H

Factored Load Combinations

Strength reduction factor (φφφφ) :

Bending φ = 0.90

Shear and Torsion φ = 0.85

Compression φ = 0.70 or 0.75

Strength Reduction Factor = factor that account for

(1) Variations in material strengths and dimensions

(2) Inaccuracies in the design equations

(3) Degree of ductility and required reliability of member

(4) Importance of member in the structure

Nominal Strength (N) = Strength of a member calculated usingStrength Design Method.

Strength Reduction Factors

Load Transfer in StructureLoad Transfer in Structure

Floor loads

Slab + Dead loadRoof + Dead load

Snow, Rain, Windand Construction load

Column + Dead load

Wall load

Beam + Dead load

Foundation

Wind load

SoilEarthquake