SIXTH EDITION

Plulippines

ilippines

eers of the Phllippincs

1

nes

es

, .,. 511

combinations [rom this chapter in conjun ction with strengthreduc tio n factors of Section 426 shall not be permitted.

CHAPTER ~ - Concre te 4 ·~ 3

the appropr iate load combinations of ASCE I SEI 7 shall beused.

409.3 Required Strength

409.3.1 Required strength U shall be at least equal to theeffects of factored loads in Eq. 409 -1 through Eq, 409-7.The effect of one or more loads not acting simultaneouslyshall be investigated.

409.3.2 If resistance to impact effec ts is taken into accountin de sig n, such effects shall be included with live load L. _

except as follow s:

I. The load factor on the live load L in Eq . 409 ·3 to 409-5shall be permitt ed 10 be reduced to 0.5 except forgarages , are as occupied as places of publi c assemb ly.and all areas where L is grea ter than 4.8 kN/m

2•

2. \Vhere wind load W has not been reduced by adirectionality factor , it shall be pen nined to use 1.3W inplace of 1.611' in Eq . 409-4 and 409·6.

3. Wh ere E, the load effects of eart hquake, is based onse rvice-level seismic forces. 1.4£ shall be used in placeof 1.0£ in Eg' 409·5 and 409-7.

4. The load factor on If. loads due to wcight and pressureof soil , wa ter in so il, or other mater ials. shall be setequ al to zero in Eq. 409-6 and 409 -7 if the structuralaction due to H counteracts that due to W or E. Wherelateral earth pressure provides resistance to structuralac tions from other forces, it shall not be included in Hbut shall be incl uded in the design resistance.

U = 1.4(D + F)

U = L2 (D+ F+T) + 1.6 (L+/i) + O.5(L . or R)

U = 1.2 D + 1.6 (L. or R) + ( 1.0L or 0 .80 II')

U = 1.2 D + 1.6 II' + 1.0 L +0.5 (L. or R)

u = 1.2 D + 1.0 £+ 1.0 L

U = 0.9 D + 1.6 II' + 1.6 H

U = 0 .90 D + 1.0 E + 1.6 If

(409- 1)

(409-2)

(409-3)

(409-4)

(409-5)

(409-6)

(409-7)

409.3.5 For post-tensioned anchorage zone design . a loadfactor of J.2 shall be appli ed to the maximum tendonja cking force .

409.4 Design Strength

409.4 .1 Design strength provided by a member, itsconnections to other members and its cros s sections. interm s of flexure, axial load. shear and torsion , shall be takenas the nomin al strength calculated in acco rdance withrequirements and assumptions of this Sect ion . mult iplied bya strength-reduction factor ¢ in Sections 409.4 .2. 409.4 .4and 409.4.5 .

409.4.2 St re ngt h-Reduct ion Factor

Strength-reduction factor ¢ shall be given in Sections409.4.2. 1 through 409 .4.2.7:

409 .4.2.1 Ten sion controlled sections as defined in Section4 10.4.4 (see also Scct ion 409.4.2.7) 0.90

409 .4.2.2 Compress ion controlled sec tions, as defined inSec tion 4 10.4.3:

I. Members with spiral rein forcementconforming to Section 4 10.10.3 .. .................. 0.75

2. Other reinforced members 0.65

For sect ions in which the net tensile strength, Cr . is betweenthe limits for compress ion-control led an d tension-controlledsections, ¢ shall be permi tted 10 be linearly increased fromthat for compression-con trolled sections to 0 .90 as f.,

increases from the compression-controlled strain limit 10

0.005.

Altern atively , when Section 425 is used, for membe rs inwhich [I ' does not exceed 415 MPa, with symmetricreinforcement, and with (11 • cl')/I! not less than 0.70. ¢ shallbe permitted to be increased linearly to 0.90 as ¢ P,decreases from 0.10 Fe A,( to zero. For other reinforcedmembers. ¢ sha ll be permitted to be increased linearly to0.90 as ¢ P" decreases from 0.10F, A~ or ¢ Ph. whichever issmaller . to zero.

409.4.2.3 Shear and torsion (Sec also Sect ion 409.4.4 (orshear walls and frames in Se ismic Zo ne 4) 0.75

409.4 .2.4 Bearing on concrete (except for post-tensioning anchorage zones) 0.65

409.3.3 Estimations of differential scu lcmcm. creep.shrinkage, expa nsio n of shrinkage-co mpensating concrete ortemperat ure change shall be based on a realistic assessmentof such e ffects occurring in service.

409 .3.4 If a struc ture is in a flood zone. or is subje cted toforces fro m atmospheric precipitat ions . [he flood la nds and

409.4.2.5 Post-tensioned anchorage zones 085

National Structural Code of the Philippines 6th Edition Volume 1

1

me 1

ilippines

ume 1

s of tile Philippines

€