ConfinedMasonry.org - Complementary Norms Mexico En

COMPLEMENTARY TECHNICAL NORMS FOR DESIGN AND CONSTRUCTION

OF MASONRY STRUCTURES

INDEXComple men tary Te chni cal Norms for De sign and Cons truc tion of Ma son ry Struc tu res

NOTATION

1. GE NE RAL1.1 Sco pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.2 Masonry units . . . . . . . . . . . . . . . . . . . . . . .1.3 Other type of ele ments and other ma nners ofre in for ce ment and wall cons truc tion. . . . . . . . . .

2. MA TE RIALS FOR MA SON RY 2.1 Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1.1 Types of units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1.1.1 So lid units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1.2 Ho llow units . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1.2 Com pres si ve strength . . . . . . . . . . . . . . . . . . . . . . . .

2.2 Ce men ti tious ma te rials . . . . . . . . . . . . . . . . .2.2.1 Hydrau lic ce ment . . . . . . . . . . . . . . . . . . . . . . . . . .2.2.2 Ma son ry ce ment . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2.3 Hydra ted lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.3 Stone aggre ga tes . . . . . . . . . . . . . . . . . . . . .2.4 Mi xing wa ter . . . . . . . . . . . . . . . . . . . . . . . .2.5 Mor tars . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.1 Com pres si ve strength . . . . . . . . . . . . . . . . . . . . . . . .2.5.2 Mor tar for bin ding units . . . . . . . . . . . . . . . . . . . . . .2.5.3 Grouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.6 Ad mix tu res . . . . . . . . . . . . . . . . . . . . . . . . . .2.7 Re in for cing ste el . . . . . . . . . . . . . . . . . . . . .2.8 Ma son ry . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.1 Com pres si ve strength . . . . . . . . . . . . . . . . . . . . . . .

2.8.1.1 Tests of pri sm made of units and mor tars that will be used in the job . . . . . . . . . . . . . . . .2.8.1.2 From the de sign strength of units and mor tars 2.8.1.3 In di ca ti ve va lues. . . . . . . . . . . . . . . . . . . . . . . .

2.8.2 Dia go nal com pres si ve strength . . . . . . . . . . . . . . . . . 2.8.2.1 Tests of wall specimens made of units and mor tars that will be used in the job . . . . . .2.8.2.2 In di ca ti ve va lues . . . . . . . . . . . . . . . . . . . . . . .

2.8.3 Bearing strength . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.8.4 Ten si le strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.5 Mo du lus of elas ti city. . . . . . . . . . . . . . . . . . . . . . . . .

2.8.5.1 Tests of prism made of with units and mor tarsthat will be used in the job . . . . . . . . . . . . . . . . . . . . . .2.8.5.2 De ter mi na tion from de sign com pres si vestrength of ma son ry . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.8.6 Shear mo du lus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.6.1 Tests of wall specimens made of units andmor tars that will be used in the job . . . . . . . . . . . . . . .2.8.6.2 De ter mi na tion from the ma son ry mo du lus ofelas ti city . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. GE NE RAL SPE CI FI CA TIONS FORANALYSIS AND DE SIGN.3.1 De sign cri te ria . . . . . . . . . . . . . . . . . . . . . . .3.1.1 Ultimate li mit sta te . . . . . . . . . . . . . . . . . . . . . . . . .3.1.2 Ser vi ceability li mit sta te . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Du ra bi lity de sign 3.1.4 Strength reduction . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1.4.1 Walls sub fected to axial com pres sion3.1.4.2 Walls sub fected to fle xu ral com pres sion out-of- pla ne . . . . . . . . . . . . . . . . .3.1.4.3 Walls sub jected to shear for ce . . . . . . . . . . . .

3.1.5 Con tri bu tion of re in for ce ment to ver ti cal load strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.6 Hypo the sis for ob tai ning de sign fle xu ral strength . .3.1.7 Strength of ma son ry to la te ral loads . . . . . . . . . . . . . 3.1.8 Seis mic beha vior factor. . . . . . . . . . . . . . . . . . . . . . . 3.1.9 De sign of foun da tions . . . . . . . . . . . . . . . . . . . . . . . . 3.1.10 De sign of flo or and roof sys tems . . . . . . . . . . . . . .

3.2 Methods of analysis . . . . . . . . . . . . . . . . . . . 3.2.1 Ge ne ral cri te ria . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.2.2 Analysis for ver ti cal loads . . . . . . . . . . . . . . . . . . . . 3.2.2.1 Ba sic cri te ria . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.2.2 De sign for ces and mo ments . . . . . . . . . . . . . . .3.2.2.3 Re duc tion fac tor due to ec cen tri city and slen der ness effects . . . . . . . . . . . . . . . . . . 3.2.2.4 Effect of res tra ints to la te ral de for ma tions

3.2.3 Analysis for la te ral loads . . . . . . . . . . . . . . . . . . . . .3.2.3.1 Ba sic cri te ria . . . . . . . . . . . . . . . . . . . . . . . . . .3.2.3.2 Static and dyna mic analysis method. . . . . . . . . 3.2.3.3 Sim pli fied method . . . . . . . . . . . . . . . . . . . . . .

3.2.4 Tem pe ra tu re analysis . . . . . . . . . . . . . . . . . . . . . . . .

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3.3 De tai ling of re in for ce ment . . . . . . . . . . . . . .3.3.1 Ge ne ral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.2 Size of re in for cing ste el . . . . . . . . . . . . . . . . . . . . .

3.3.2.1 Dia me ter of lon gi tu di nal re in for cing ste el . . . .3.3.2.2 Dia me ter of ho ri zon tal re in for cing ste el . . . . .

3.3.3 Pla ce ment and s pa cing of lon gi tu di nal re in for cing ste el . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3.3.1 Spacing bet ween bars . . . . . . . . . . . . . . . . . . .3.3.3.2 Bar bundle . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.3.3 Thickness of grout and re in for ce ment . . . . . . .

3.3.4 Pro tec tion of re in for cing ste el . . . . . . . . . . . . . . . . . .3.3.4.1 Co ve r in ex ter nal tie-co lumn and bond beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.4.2 Co ve r in in ter nal tie-co lumn and in walls with in ter nal re in for ce ment . . . . . . . . . . . . . . .3.3.4.3 Co ve r of ho ri zon tal re in for ce ment . . . . . . . . .

3.3.5 Ben ding of re in for ce ment 3.3.5.1 In straight bars . . . . . . . . . . . . . . . . . . . . . . . .3.3.5.2 In sti rrups . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.5.3 In crossties . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3.6 Bond and development . . . . . . . . . . . . . . . . . . . . . .3.3.6.1 Ge ne ral re qui re ments . . . . . . . . . . . . . . . . . . . .3.3.6.2 Straight in bars ten si on . . . . . . . . . . . . . . . . . .3.3.6.3 Hooked un der ten sion. . . . . . . . . . . . . . . . . . . .3.3.6.4 Ho ri zon tal re in for ce ment in mor tar joints . . . . 3.3.6.5 Wel ded wire meshes . . . . . . . . . . . . . . . . . . . .3.3.6.6 Bar spleus . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4. INFILL WALLS 4.1 Sco pe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.2 De sign for ces . . . . . . . . . . . . . . . . . . . . . . . . 4.3 In-pla ne shear strength . . . . . . . . . . . . . . . . .4.3.1 Shear for ce re sis ted by ma son ry . . . . . . . . . . . . . . .4.3.2 Shear for ce re sis ted by ho ri zon tal re in for cing ste el .

4.4 Over tur ning . . . . . . . . . . . . . . . . . . . . . . . . .4.5 In-plane infill-fra me in te rac tion . . . . . . . . . .

5. CON FI NED MA SON RY 5.1 Sco pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.1.1 Ex ter nal tie-co lumns and bond beams . . . . . . . . . . .5.1.2 Walls with internal tie-co lumns . . . . . . . . . . . . . . . .

5.1.3 Walls with ope nings . . . . . . . . . . . . . . . . . . . . . . . . .

5.1.4 Thickness and heigh t- to-thickness ra tio in walls . . .

5.2 De sign for ces and mo ments . . . . . . . . . . . . .5.3 In-plane com pres si ve strength in plane bending strength of walls . . . . . . . . . . . . . . .5.3.1 Com pres si ve strength of con fi ned walls . . . . . . . . . . 5.3.2 In-plane fle xu ral strength . . . . . . . . . . . . . . . . . . . . .

5.3.2.1 Ge ne ral method of de sign . . . . . . . . . . . . . . . .5.3.2.2 Op tio nal method . . . . . . . . . . . . . . . . . . . . . . .

5.4 Strength to la te ral loads . . . . . . . . . . . . . . . .5.4.1 Ge ne ral con si de ra tions . . . . . . . . . . . . . . . . . . . . . . . 5.4.2 Shear for ce re sis ted by ma son ry . . . . . . . . . . . . . . .5.4.3 Shear for ce re sis ted by ho ri zon tal re in for cing ste el .

5.4.3.1 Types of re in for cing ste el. . . . . . . . . . . . . . . . .5.4.3.2 Spacing of ho ri zon tal re in for cing ste el. . . . . . .5.4.3.3 Mi ni mum and ma xi mum amounts of ho ri zon talre in for cing ste el . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.4.3.4 De sign of ho ri zon tal re in for ce ment . . . . . . . . .

5.4.4 Shear for ce re sis ted by wel ded wire mesh co ve red by mor tar

5.4.4.1 Type of re in for ce ment and mor tar . . . . . . . . . .5.4.4.2 Mi ni mum and ma xi mum amount of re in for ce ment . . . . . . . . . . . . . . . . . . . . . . .5.4.4.3 De sign of welded wire mesh . . . . . . . . . . . . . .

6. RE IN FOR CED MA SON RY 6.1 Sco pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6.1.1 Amount of ho ri zon tal and ver ti cal re in for cing ste el 6.1.2 Size, pla ce ment and spacing of re in for ce ment

6.1.2.1 Ver ti cal re in for ce ment . . . . . . . . . . . . . . . . . .6.1.2.2 Re in for ce ment at wall ends . . . . . . . . . . . . . .

6.1.3 Fine and course grouts . . . . . . . . . . . . . . . . . . . . . . .6.1.4 An cho ra ge of ho ri zon tal and ver ti cal re in for ce ment6.1.5 Trans ver se walls . . . . . . . . . . . . . . . . . . . . . . . . . . . .6.1.6 Walls with ope nings . . . . . . . . . . . . . . . . . . . . . . . . .6.1.7 Thickness and heigh t- thickness ra tio of walls. . . . . . 6.1.8 Pa ra pets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6.1.9 Ins pec tion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.2 De sign for ces and mo ments . . . . . . . . . . . . .6.3 Com pres si ve and fle xu ral com pres si vestrength in the wall pla ne . . . . . . . . . . . . . . . . . .6.3.1 Com pres si ve strength of ma son ry with in ter nal re in for ce ment6.3.2 Fle xu ral com pres si ve strength in the wall pla ne . . .

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6.3.2.1 Ge ne ral method of de sign . . . . . . . . . . . . . . . .6.3.2.2 Op tio nal method . . . . . . . . . . . . . . . . . . . . . . .

6.4 Re sis tan ce to la te ral loads . . . . . . . . . . . . . .6.4.1 Ge ne ral con si de ra tions . . . . . . . . . . . . . . . . . . . . . . .6.4.2 Shear for ce re sis ted by ma son ry . . . . . . . . . . . . . . .6.4.3 Shear for ce re sis ted by ho ri zon tal re in for cing ste el

6.4.3.1 Types of re in for cing ste el . . . . . . . . . . . . . . . .6.4.3.2 Spacing of ho ri zon tal re in for cing ste el . . . . . .6.4.3.3 Mi ni mum and ma xi mum amounts of ho ri zon tal re in for cing ste el . . . . . . . . . . . . . . . .6.4.3.4 De sign of ho ri zon tal re in for ce ment . . . . . . . . .

7. UN CON FI NED MA SON RY WITHOUT RE IN FOR CE MENT 7.1 Sco pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.2 De sign for ces and mo ments . . . . . . . . . . . . .7.3 Re in for ce ment for struc tu ral in te grity 7.3.1 Ver ti cal re in for ce ment . . . . . . . . . . . . . . . . . . . . . . .7.3.2 Ho ri zon tal re in for ce ment . . . . . . . . . . . . . . . . . . . . .7.3.3 Trans ver se re in for ce ment . . . . . . . . . . . . . . . . . . . . .

7.4 In plane com pres si ve and fle xu ralcom pres si ve strength in the wall pla ne . . . . . . .7.4.1 Com pres si ve strength . . . . . . . . . . . . . . . . . . . . . . . . 7.4.2 Fle xu ral com pres si ve strength. . . . . . . . . . . . . . . . . .

7.5 Re sis tan ce to la te ral loads. . . . . . . . . . . . . . .

8. MA SON RY MADE OF NA TU RAL STO NES

8.1 Sco pe8.2 Ma te rials . . . . . . . . . . . . . . . . . . . . . . . . . . .8.2.1 Sto nes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.2 Mor tars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8.3 De sign . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.3.1 De sign stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.3.2 Strength calculation . . . . . . . . . . . . . . . . . . . . . . . . .

8.4 Foun da tions. . . . . . . . . . . . . . . . . . . . . . . . . .8.5 Re tai ning walls . . . . . . . . . . . . . . . . . . . . . .

9. CONS TRUC TION 9.1 Cons truc tion dra wings . . . . . . . . . . . . . . . . .9.2 Cons truc tion with fabricated ma son ry units . . . . . . . . . . . . . . . . . . . . . . . .

9.2.1 Ma te rials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.2.1.1 Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.2.1.2 Mor tars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.2.1.3 Con cre tes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.2.2 Cons truc tion pro ce du res . . . . . . . . . . . . . . . . . . . . .9.2.2.1 Mor tar joints . . . . . . . . . . . . . . . . . . . . . . . . . . .9.2.2.2 La ying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.2.2.3 Coarse and fine grouts . . . . . . . . . . . . . . . . . . .9.2.2.4 Re in for ce ment . . . . . . . . . . . . . . . . . . . . . . . . .9.2.2.5 Pi ping and ducts . . . . . . . . . . . . . . . . . . . . . . .9.2.2.6 Cons truc tion of walls . . . . . . . . . . . . . . . . . . . .9.2.2.7 To le ran ces . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9.3 Cons truc tion of na tu ral sto ne ma son ry 9.3.1 Sto nes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.3.2 Mor tar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.3.3 Cons truc tion pro ce du res . . . . . . . . . . . . . . . . . . . . .

9.4 Cons truc tion of foun da tions . . . . . . . . . . . . .

10. INS PEC TION AND CON TROL 10.1 Ins pec tion . . . . . . . . . . . . . . . . . . . . . . . . . .10.1.1 Prior to cons truc tion of ma son ry walls . . . . . . . . .10.1.2 Du ring cons truc tion . . . . . . . . . . . . . . . . . . . . . . . .

10.2 Quality con trol . . . . . . . . . . . . . . . . . . . . .10.2.1 Sco pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10.2.2 Sam pling and tes ting . . . . . . . . . . . . . . . . . . . . . . .

10.2.2.1 Mor tar for bin ding pie ces . . . . . . . . . . . . . . .10.2.2.2 Fine and coarse grouts . . . . . . . . . . . . . . . . . .10.2.2.3 Ma son ry . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10.2.2.4 Pe ne tra tion of mor tar in mul ti - per fo ra tedpie ces . . . . . . . . . . . . . . . . . . . . . .

10.2.3 Ac cep tan ce cri te ria . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.3.1 Mor tars and ma son ry . . . . . . . . . . . . . . . . . . .10.2.3.2 Mor tar pe ne tra tion in mul ti- per fo ra ted pie ces

10.3 Ins pec tion and quality con trol for buil dings un der reha bi li ta tion . . . . . . . .

11.EVA LUA TION AND REHA BI LI TA TION11.1 Sco pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.2 Eva lua tion . . . . . . . . . . . . . . . . . . . . . . . . .11.2.1 Need for eva lua tion . . . . . . . . . . . . . . . . . . . . . . . .

11.2.2 Eva lua tion pro cess . . . . . . . . . . . . . . . . . . . . . . . .

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11.2.3 In ves ti ga tion and do cu men ta tion of the buil ding and ac tions that cau sed da ma ge . . . . . . . .

11.2.3.1 Ba sic in for ma tion . . . . . . . . . . . . . . . . . . . . .11.2.3.2 De ter mi na tion of ma te rial pro per ties . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.2.4 Clas si fi ca tion of da ma ge in buil ding ele ments

11.2.4.1 Performance mode . . . . . . . . . . . . . . . . . . . . .11.2.4.2 Mag ni tu de of da ma ge . . . . . . . . . . . . . . . . . .

11.2.5 Im pact eva lua tion of damaged ele ments on building beha vior . . . . . . . . . . . . . . . . . . . . . . . . . .

11.2.5.1 Da ma ge im pact. . . . . . . . . . . . . . . . . . . . . . . .11.2.5.2 Buil dings without struc tu ral da ma ge . . . . . . .11.2.5.3 Re si dual ca pa city . . . . . . . . . . . . . . . . . . . . . .11.2.5.4 Determina tion of struc tu ral ca pa city . . . . . . .11.2.5.5 Con si de ra tions for eva lua ting struc tu ral ca pa city . . . . . . . . . . . . . . . . . . . . . .

11.2.6 De ter mi na tion of the need for reha bi li ta tion . . . . .11.2.6.1 Mi nor da ma ge . . . . . . . . . . . . . . . . . . . . . . . .11.2.6.2 Ma jor da ma ge . . . . . . . . . . . . . . . . . . . . . . . .

11.3 Reha bi li ta tion . . . . . . . . . . . . . . . . . . . . . .11.3.1 Sho ring, tem po rary reha bi li ta tion and de mo li tion .

11.3.1.1 Ac cess con trol . . . . . . . . . . . . . . . . . . . . . . . .11.3.1.2 Tem po rary reha bi li ta tion . . . . . . . . . . . . . . . .11.3.1.3 Sa fety du ring reha bi li ta tion . . . . . . . . . . . . . .

11.3.2 Con nec tion bet ween exis ting ele ments and new ma te rials or ele ments . . . . . . . . . . . . . . . . . . . .11.3.3 Re pair of ele ments . . . . . . . . . . . . . . . . . . . . . . . . .

11.3.3.1 Sco pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11.3.3.2 Re pla ce ment of da ma ged pie ces, mor tar, bars and con cre te . . . . . . . . . . . . . . . . . . . . . .11.3.3.3 Re pair of cracks . . . . . . . . . . . . . . . . . . . . . . .11.3.3.4 Re pair of da ma ge due to co rro sion . . . . . . . .

11.3.4 Re in for ce ment . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.3.4.1 Ge ne ral . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11.3.4.2 Jacketing of con cre te and ma son ry ele ments . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11.3.4.3 Addi tion of re in for ced con cre te con fi ning ele ments . . . . . . . . . . . . . . . . . . . . . . . .

11.3.4.4 Addi tion or removal of walls . . . . . . . . . . . . .11.3.5 Cons truc tion, ins pec tion and qua lity con trol. . . . . .

NOR MA TI VE APPEN DIX A -AC CEP TAN CE CRI TE RIA FOR SEIS MICDE SIGN OF MA SON RY SYSTEMSA.1 De fi ni tions . . . . . . . . . . . . . . . . . . . . . . . . .A.2 No ta tion . . . . . . . . . . . . . . . . . . . . . . . . . . .A.3 Sco pe . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A.4 Cri te ria for de sign of spe ci mens . . . . . . . .A.5 Test spe ci mens . . . . . . . . . . . . . . . . . . . . . .A.6 La bo ra tory. . . . . . . . . . . . . . . . . . . . . . . . . .A.7 Tes ting pro to col . . . . . . . . . . . . . . . . . . . . .A.8 Tests re port . . . . . . . . . . . . . . . . . . . . . . . . .A.9 Acceptance criteria . . . . . . . . . . . . . . . . . . .

4

Complementary Technical Norms for the Design and Construction of Masonry Structures

NOTATION

As total area of longitudinal reinforcing steel placed oneach of a end tie-columns of a wall in confinedmasonry; area of ver ti cal reinforcing steel ininternally reinforced masonry, mm2 (cm)

Asc area of trans ver sal reinforcing steel of tie-columnsplaced at a spa cing s, mm (cm)

Ash area of ho ri zon tal reinforcement placed at a spacingsh, mm (cm)

Ast area of ste el devices or connectors, placed at a spa -cing s, necessary for con ti nuity to trans ver se wallswith flushed end, mm (cm)

Asv area of ver ti cal reinforcing steel placed at a spa cing sv, (mm (cm)

AT gross area of cross section of wall or wall segment,including tie-columns, mm (cm)

B flo or di men sion, measured parallel to static to rsio naleccentricity, es mm (cm)

b bearing length of slab supported by wall, mm (cm)cj coefficient of variation of the compressive strength

of fill mortar or groutcm coefficient of variation of the compressive strength

of masonry prismycp coefficient of variation of the compressive strength

of unitscv coefficient of variation of the diagonal compressive

strength of masonry spe ci men wallscz coefficient of variation of the strength of interest of

samplesd distance bet ween centroid of tensile steel and

extreme fiber un der com pres sion, mm (cm)d distance between centroids of steel placed at both

ends of a wall, mm (cm)db diameter of reinforcing bars, mm (cm)Em modulus of elasticity of masonry for compressive

stresses per pe ni cu lar to joints, MPa (kg/cm)Es modulus of elasticity of re in for cing steel, MPa

(kg/cm)e eccentricity with which the load acts on na tu ral- sto ne

ma sonry, including effects of lateral pressu re, if any,mm (cm)

ec eccentricity with which the load is transmitted fromslab to end walls, mm (cm)

es static torsional eccentricity, mm (cm)e eccentricity calculated for obtaining the re duc tion

fac tor for eccentricity and slenderness, mm (cm)

FAE factor of effective area of load bea ring walls,FE re duc tion fac tor due to ec cen tri city and slenderness

effectsFR Strength re duc tion fac tor fc specified compressive strength of concrete, MPa

(kg/cm)f j mean com pres si ve strength of mortar cubes or grout

cylinders, MPa (kg/cm)fj* design compressive strength of grout, MPa (kg/cm)fm mean com pres si ve strength of masonry prism,

corrected due to its heigh t- to-thickness ratio andreferred to gross area, MPa (kg/cm)

fm* design compressive strength of masonry, referred togross area, MPa (kg/cm)

fp mean com pres si ve strength of units, referred to grossarea, MPa (kg/cm)

fp* design compressive strength of units, referred to thegross area, MPa (kg/cm)

fy specified yield stress of reinforcing steel, MPa(kg/cm)

fyh specified yield stress of horizontal reinforcing steelor welded wire mesh, MPa (kg/cm)

Gm modulus of shear of masonry, MPa (kg/cm)H free height of wall between bra cing ele ment, mm

(cm)Ho minimum length, measured at the ends of

tie-columns, over which sti rrups at clo ser spacingless must be placed, mm (cm)

hc sec tio nal di men sion of tie-columns or bond beamthat pro vi de in- pla ne con fi nement to the wall, mm(cm)

k wall effec ti ve height fac tor L wall effective length (mm (cm)L spacing of elements that brace the wall in the trans -

ver se direction, mm (cm)Ld development length of a straight reinforcing bar un -

der tension, mm (cm)MR in- pla ne de sign fle xu ral mo ment strength, on a wall

subjected to axial and ben ding moment, N-mm(kg-cm)

Mo in- pla ne de sign fle xu ral mo ment strength, on a wallsub jec ted to pure bending, N-mm (kg-cm)

5

NOTATION

P total axial load acting on the wall, without mul ti -plying by the load factor, N (kg)

PR ver ti cal load de sign strength, N (kg)Pu design axial load, N (kg)ph amount of horizontal reinforcing steel in wall,

calculated as Ash/sht pv amount of vertical reinforcing steel in wall,

computed as Asv/svtQ seismic behavior fac tor R computed la te ral strength of specimen (Normative

Appendix A), N (kg)Ra approximate la te ral strength of specimen (Normative

Appendix A), N (kg)Rmax strength (maximum lateral load) of specimen

measured in laboratory (Normative Appendix A), N(kg)

s stress of trans verse reinforcing steel or connectors,mm (cm)

sh stress of horizontal reinforcing steel in the wall or ofhorizontal wire of a welded wire mesh, mm (cm)

sv stress of vertical reinforcing steel in the wall, mm(cm)

t thickness of wall masonry, mm (cm)VmR design shear for ce resisted by the masonry, N (kg)VsR design shear for ce re sis ted by horizontal reinforcing

steel or welded wire mesh, N (kg)vm* design diagonal compressive strength of wall spe ci -

men, over gross area measured along the diagonalparallel to load, MPa (kg/cm)

vm mean dia go nal compressive strength of wallspecimen, over gross area measured along thediagonal parallel to load, MPa (kg/cm)

x distance between shear cen ter at a flo or and wall ofinterest, with sign, orthogonal to the direction ofanalysis, used for calculating the static torsionaleccentricity, es , mm (cm)

z* de sign strength of interest, MPa (kg/cm)z mean strength of samples, MPa (kg/cm) lateral displacement applied at the top of spe ci men

(Normative Appendix A), mm (cm) efficiency fac tor of horizontal reinforcement over- strength fac tor of connections (Normative

Appendix A) drift angle (Normative Appendix A)

1. GE NE RAL CON SI DE RA TIONS1.1 Sco peThe se Norms con tain mi ni mum re qui re ments for theanalysis, de sign, and cons truc tion of ma son ry struc tu res.

Chap ters 2 through 10 of the se pro vi sions apply to theanalysis, de sign, cons truc tion and ins pec tion of ma son ry

struc tu res made with walls cons truc ted with pris ma tic unitsof fabricated so lid or ho llow units, or with na tu ral sto nesjoined with a bin ding mor tar. They in clu de walls re in for cedwith in ter nal reinforcement, tie- co lumns, bond beams, orbuttresses.

Chap ters 4 through 7 re fer to diffe rent cons truc tion sys temsba sed on ma son ry with fa bri ca ted units. Whi le the beha viorof cons truc tion sys tems is, ge ne ra lly, si mi lar to each other, adi vi sion is es ta blished in chap ters to ease analysis and de signpro cesses.

Chap ter 8 applies to the de sign of struc tu res made with na tu -ral sto nes.

Chap ters 9 and 10 re fer to the cons truc tion, ins pec tion andqua lity con trol of the job.

Chap ter 11 applies to the eva lua tion and reha bi li ta tion of ma -son ry struc tu res.

In the Nor ma ti ve Appen dix A, ac cep tan ce cri te ria for cons -truc tion sys tems ba sed on ma son ry de sig ned for ear thqua kesare pre sen ted.

1.2 Measurement unitsPro vi sions in the se Norms are sta ted in the Inter na tio nalSystem (SI) units, and in pa rent he sis in the usual me tricsystem (who se ba sic units are me ter, ki lo gram for ce, and se -cond).

The co rres pon ding va lues in the two sys tems are not exac tlyequi va lent, for this rea son, each sys tem must be used in de -pen dently from each the other, without com bi nig them.

1.3 Other types of masonry units and other re in for ce ment and wall cons truc tion layoutAny other type of units, re in for ce ment or cons truc tionprocedure basd on ma son ry, diffe rent from tho se re fe rred tohere, shall be eva lua ted accor ding to the Code and the Nor -ma ti ve Appen dix A of the se Norms.

2.MA TE RIALS FOR MA SON RY 2.1 Masonry units2.1.1 Type of masonry units

Ma son ry units used in struc tu ral ele ments of ma son ry mustcom ply with NMX- C- 404- ONNC CE, ex cept as sta ted for the lower li mit of the net area of ho llow units re fe rred to in 2.1.1.2 (fig. 2.1)

The minimum net unit weight of the ma son ry units, in drystate, shall be as indicated in table 2.1.

In Chap ter 5 of Comple men tary Te chni cal Norms for Seis mic De sign, diffe rent seis mic beha vior factors, Q, are sta ted, as afunc tion, among others, of the type of units used in the wall.

6

NOTATION

2.1.1.1 So lid units

For masonry units pur poses of Chap ter 5 of the Complemen-

tary Te chnical Norms for Seismic De sign, and of the se Stan -

dards, solid units are tho se having in their most un favorable

cross section a net area at least 75% of the gross area, and

whose exterior shells have a thickness no less than 20 mm.

2.1.1.2 Hollow masonry units

The ho llow units re ferred to in these Norms and in Chap ter 5

of the Complementary Te chnical Norms for Seismic De sign

are those having, in their most un favorable cross section, a net

area at least 50% the gross area; in addi tion, thickness of their

outer fa ces is no less than 15 mm (fig. 2). For ho llow units

with two, up to four cells, minimum thickness of the in ner

nerves shall be 13 mm. For multi-perforated pieces, who se

perforations are of the same di mension and even distribution,

minimum thickness of the in ner ner ves shall be 7 mm. Mul-

ti-perforated units are those with more than seven per fora-

tions or cells (fig. 2.1).

For pur poses of the se norms, ho llow units with cells or perfo-

ra tions or tho go nal to bea ring sides are per mi tted.

2.1.2 Com pres si ve strength

The Compressive strength is determined for each type of unit

according to the test method in NMX- C-036.

For de sign, strength, fp*, shall be used, measured over gross

area, which shall be determined as that rea ched by at least

98% of the units pro duced.

The design strength shell be determined based on the existing

statistical information on the product or from sampling of

units, whether in plant or in site. If sampling is chosen, at least

three samples shall be obtained, each from ten units, from

different batches of production. The 30 units shall be tested in

a laboratory accredited by the recognized accreditation entity

according to the Federal Law on Metrology and

Standardization. The design strength shall be computed as

ff

cp

p

p

*.

1 25

(2.1)

whe re

fp

mean com pressive strength of units, re ferred to

gross area; and

cp coe ffi cient of va ria tion of the com pres si ve strength

of units

The value of cp shall not be taken less than 0.20 for units me-

chanical plants evidencing a qua lity con trol system like that

re qui red in the NMX- C- 404- ONNC CE stan dard, nor 0.30 for

units from industrialized fabrication, but not ha ving a quality

control system, nor 0.35 for units from hand-made pro duc-

tion.

The qua lity con trol sys tem re fers to se ve ral do cu men ted pro-

ce du res of the pro duc tion line of in te rest, in clu ding rou ti ne

testes and their re cords.

For pur po ses of the se Norms, the mi ni mum com pres si ve

strength of units of the Mexican Norms NMX-C-404-

ONNC CE co rres ponds to strength fp*.

2.2 Ce men ti tious ma te rials

2.2.1 Hydraulic ce ment

In the fa brication of con crete and mortar, any type of hydrau-

lic ce ment com plying with the spe ci fied re qui re ments in

NMX- C- 414- ONNC CE shall be used.

2.2.2 Ma son ry ce ment

In the fa bri ca tion of mor tars, ma son ry ce ment com plying

with re qui re ments spe ci fied in NMX- C- 021 may be used.

7

NOTATION

Fi gu re 2.1 Ma son ry units

Table 2.1 Minimum net unit weight of

ma son ry u nits in dry con di tion

Masonry-unitValues in kN/m

(kg/m)

Burnt clay brick 13 (1300)

Clay brick with vertical holes 17 (1700)

Concrete block 17 (1700)

Concrete brick 15 (1500)

cp

f p mean compressive strength of units, referred togross area; and

cp coefficient of variation of the compressive strengthof units

2.2.3 Hydrated lime

In dosification of mortars, hydrated lime complying with re-

qui re ments spe ci fied in NMX- C- 003- ONNC CE may be

used.

2.3 Stone aggre ga tes

Aggre ga tes shall com ply with spe ci fi ca tions of NMX- C- 111.

2.4 Mi xing wa ter

Mixing water for mortar or con crete shall comply with spe ci-

fications of the NMX- C-122 . Wa ter shall be stored in clean

and co ve red con tai ners.

2.5 Mor tars

2.5.1 Compressive Resistance

Compressive strength of mortar, whether for binding units or

for lime grouts, shall be de termined according to the test spe -

ci fied in the NMX- C- 061- ONNC CE.

Compressive strength of coarse grouts shall be determined

from test cylin ders made, cu red, and tes ted accor ding to

NMX- C- 160 and NMX- C- 083- ONNC CE.

For de sign strength va lue fj*, determined as that rea ched by at

least 98 % of the samples, shall be used. De sign strength shall

be computed from mortar samples, from mortar used for joi-

ning masonry units or to fill cavities, or from the coarse grout

to be used.

In case of mor tar, at least three sam ples shall be obtained,

each one from at least three cube specimens units. The nine

test specimens shall be tes ted following NMX-C-061-

ONNC CE.

In case of coarse grouts, at least three cylin drical test

specimens shall be obtained. The test specimens shall be

made, cured, and tested, according to the above mentioned

stan dards.

The design strength shall be

ff

cj

j

j

*.

1 25

(2.2)

whe re

fj

mean com pressive strength of mor tar cu bes or con-

crete cylin ders for coarse grouts; and

cj coe ffi cient of va ria tion of the com pres si ve strength

of mor tar or; in no case it shall be ta ken less than 0.2

2.5.2 Mor tar for binding pieces

Mortars used in masonry structural elements shall comply

with the fo llowing re qui re ments:

a) Mortar the com pressive strength shall be at least 4 MPa (40

kg/cm2)

b) Mortar they shall always contain cement with the mi ni-

mum amount indicated in ta ble 2.2.

c) Vo lumetric ra tio bet ween sand and the to tal of ce menti-

tious material shall be between 2.25 and 3. The sand vo lu-

me shall be measured in dry condition.

d) The minimum amount of water re sulting in an easily

workable mortar shall be used.

If mortar includes masonry cement, the minimum quan tity, to

be used in combination with hydrauliccement, shall be as

indicated in table 2.2

2.5.2 Fine and course grouts

Fine and cour se grouts used in masonry structural elements

for fi lling cells in hollow pie ces shall com ply with the fo-

llowing re qui re ments:

a) Compressive strength shall be at least 12.5 MPa (125

kg/cm)

b) Minimum size of aggregate shall not be greater than 10

mm.

c) The minimum amount of water allowing the mixture to be

fluid enough for filling cells and completely covering the

ver ti cal re in for cing bars in case of ha ving in ter nal re in for -

cement, shall be used. Ad mixtures that enhance workabi-

lity shall be ac cepted.

8

NOTATION

Ta ble 2.2 Pro por tio ning, in vo lu me, re com men ded for

fine and cour se grouts in structural elements

Type

of

mortar

Parts or

hydraulic

cement

Parts of

masonry

cement

Parts of

hydrated

lime

Parts of

sand

Nominal

compressive

strength, fj*,

MPa

(kg/cm)

I

1 0 to

se

mit3

na

hter

om

ro

n,

52.

2n

aht

ss

elo

N

ov

nil

ai re t

am

su

oi ti tn

e m

ec

fo

la t

ote

ht-

e m

ul

12.5 (125)

1 0

II

1 to

7.5 (75)

1 to 1

III 1 to 4.0 (40)

The sand vo lume shall be mea sured in the bulk con dition

f j

cj

mean compressive strength of mortar cubes or concrete cylin ders for coar se grouts; and

coefficient of variation of the compressive strengthof mortar or; in no case it shall be taken less than 0.2

d) In ta ble 2.3, no mi nal slumps re com men ded for fine and cour -se grouts ba sed on ab sorption ma son ry units, are in clu ded.

The volumetric ratios recommended among the variouscomponents are shown in table 2.4

2.6 Ad mix tu res Du ring con cre te fa bri ca tion, fine and cour se grouts, ad mix tu -res enhan cing worka bi lity and com plying with re qui re mentsspe ci fied in NMX- C- 255 can be used. Set ac ce le ra ting ad -mix tu res shall not be used.

2.7 Re in for cing ste el Re in for ce ment used in tie-co lumns, bond beams, ele mentspla ced in si de the wall or and/or outsi de the wall, shall con sistof de for med bars, ste el mesh, cold la mi na ted de for med wire,or by elec tri ca lly wel ded trusses, made of ste el wire fortie-co lumns and bond beams, com plying with the co rres pon -ding Me xi can Stan dards. Plain bars, such as wi res, shall beper mi tted only in sti rrups, in wel ded wire mesh or in con nec -tors. The mi ni mum dia me ter for wi res to be used in sti rrups is5.5 mm. Other types of ste el can be used as long as its effi -ciency as a struc tu ral re in for ce ment is de mons tra ted to thego ver ment sa tis fac tion.

The mo du lus of elas ti city for re in for ce ment ste el, Es , shall beassu med equal to 2x105 MPa (2x106 kg/cm)

For de sign, the mi ni mum yield stress, fy, es ta blished in theabo ve men tio ned Stan dards, shall be con si de red.

2.8 Ma son ry 2.8.1Com pres si ve strength

The de sign com pres si ve strength of ma son ry, fm*, ba sed ongross area, shall be de ter mi ned with one of the three pro ce du -

res in di ca ted in 2.8.1.1 through 2.8.1.3. Strength in this Norms is re fe rred to 28 days. If it is con si de red that wall will be loa -ded with de sign ac tions be fo re this age, strength of the time ofloa ding shall be eva lua ted in fo llowing 2.8.1.1.2.8.1.1Tes ting of pri sm cons truc ted with units and mor tars

to be used in the work.

The prisms (fig. 2.2) shall be made al at least three stacke- bon ded units. The heigh t- to-thickness ratio of the pile shall be between two and five; the piles shall be tested at the age of 28days. In the fabrication, curing, transportation, storage,capping, and testing procedure of specimens the co rres pon -ding Mexican Standards shall be followed.

Strength de ter mi na tion shall be made on a mi ni mum of nineprisms in to tal, made up with ma son ry units co ming from atleast three diffe rent bat ches of the same pro duct.

The average stress obtained, computed over the gross area,shall be corrected multiplying by the factors given in table 2.5

The design compressive strength shall be computed as

f fcm

m

m

*.

=

+1 25 (2.3)

whe re

fm mean com pres si ve strength of prism, co rrec ted due to its heigh t- to-thickness ra tio and re fe rred to gross area; and

cm coe ffi cient of va ria tion of com pres si ve strength of ma -son ry prismy, which in no case shall be less than 0.15

2.8.1.1 From de sign strength of masonry units and mor tar

Ma son ry units and mor tar shall com ply with qua lity re qui re -ments spe ci fied in 2.1 and 2.5, res pec ti vely.

9

NOTATION

Figure 2.2 Prism for compressive strength test method

Ta ble 2.4 Pro por tio ning, in vo lu me, re com men ded forfine and cour se grouts in struc tu ral ele ments

TypeParts of

hydrauliccement

Parts ofhydrated

lime

Parts ofsand

Parts ofgravel

Mortar 1 0 to 0.25 2.25 to 3 Concrete 1 0 to 0.1 2.25 to 3 1 to 2 Volume of sand shall be measured in bulk state

Ta ble 2.5 Co rrec ti ve fac tors for strength of pi les withdiffe rent heigh t- to-thickness ra tios

Height thickness ratio 2 3 4 5Co rrec tion fac tor 0.75 0.90 1.00 1.05 For in ter me dia te heightto-thickness ra tios correction fac tor shallbe li near ly in ter po la ted

Ta ble 2.3 Per mis si ble slump for fine and cour se grouts, asa func tion of ab sorption of ma sonsy units

Absorption of masonry units, %

Nominal slump, mm

8 to 10 15010 to 15 17515 to 20 200

Slumps with to le ran ces of 25 mm.

a) For con cre te blocks and bricks with heigh t-t o-thickness ra -tio no less than 0.5, and with fp* = 10 MPa (100 kg/cm), thede sign com pres si ve strength may be that in di ca ted in ta ble2.6.

The va lues of fm* of this ta ble are va lid for ma son ry unitscom plying with fp* sta ted in the table and with 2.1, and forma son ry with ho ri zon tal joint thickness bet ween 10 and 12mm if the pie ces are industrialized, or 15 mm if they are hand --ma de. For other ca ses strength must be de ter mi ned accor -ding to 2.8.1.1.

b) For clay ma son ry units with height-to-thickness ratio noless than 0.5, the design compressive strength may be thatobtained from table 2.7.

The va lues of fm* of this ta ble are va lid for ma son ry unitscom plying with strength fp* sta ted in it and with 2.1, and forma son ry with ho ri zon tal joints bet ween 10 and 12 mm, if thepie ces are industrialized, or 15 mm if they are hand-made.For other ca ses, the strength must be de ter mi ned accor ding to2.8.1.1.2.8.1.3 In di ca ti ve va lues

If ex pe ri men tal de ter mi na tions are not made, va lues of fm* shown in ta ble 2.8 for diffe rent types of pie ces and mor tarsmay be used.

The va lues of fm* in this ta ble are va lid for ma son ry unitscom plying with strength fp* shown in the ta ble and with 2.1,and for ma son ry with ho ri zon tal joint thickness bet ween 10and 12 mm if the ma son ry units are industrialized, or 15 mm if they are hand-made. For other ca ses, the strength must be de -ter mi ned accor ding to 2.8.1.1.

2.8.2 Dia go nal com pres si ve strength

The de sign dia go nal com pres si ve strength of ma son ry, vm*,over gross area of dia go nal, shall be de ter mi ned with one ofthe two pro ce du res in di ca ted in sec tions 2.8.2.1 and 2.8.2.2.The va lue of strength in this Stan dard is re fe rred at 28 days. If it is con si de red that wall will be loa ded with de sign ac tionsprior to this age, strength must be cal cu la ted at this age accor -ding to sec tion 2.8.2.1.2.8.2.1 Tes ting of walls spe ci mens made of masonry units

and mor tars that will be used in the job.

The walls spe ci mens (fig. 2.3) shall have a length at least oneand a half times the length of the ma son ry unit and the number of courses needed so that the height is about the same as thelength. The walls spe ci mens shall be tested subjecting themto a mo no tonic compression along its diagonal and the meanshear strength shall be determined dividing the maximumload by the gross area of the wall spe ci mens measured alongthe same diagonal.

Walls spe ci mens shall be tes ted at 28 days of age. In the fa -bri ca tion, cu ring, trans por ta tion, sto ra ge, capping, and testpro ce du res of spe ci mens, the co rres pon ding Me xi can Stan -dard shall be fo llowed.

The de ter mi na tion shall be made on a mi ni mum of nine wallsmade of ma son ry units from at least three diffe rent lots.

The design diagonal compressive strength, vm*, shall beequal to

10

NOTATION

Ta ble 2.7 De sign com pres si ve strength of clay ma son ry units (fm*, over gross area)

fp*, MPa(kg/cm)

fm* , MPa (kg/cm)Mortar I Mortar II Mortar III

6 (60) 2 (20) 2 (20 2 (20)7.5 (75) 3 (30) 3 (30) 2.5 (25)10 (100) 4 (40) 4 (40) 3 (30)15 (150) 6 (60) 6 (60) 4 (40)20 (200) 8 (80) 7 (70) 5 (50)30 (300) 12 (120) 9 (90) 7 (70)40 (400) 14 (140) 11 (112) 9 (90)

50 (500) 16 (160) 13 (130) 11 (110) For in ter me dia te va lues of fp* , li near ly in ter po la te for the sametype of mor tar.

Ta ble 2.8 De sign com pres si ve strength of ma son ry, fm*,for some types of ma son ry units, over gross area.

Masonry unitfm*, MPa (kg/cm)

Mortar I Mortar II Mortar IIIBurnt clay brick (fp* = 6 Mpa, 60 kg/cm)

1.5 (15) 1.5 (15) 1.5 (15)

Clay brick with verticalvoids (fp* = 12 MPa, 120kg/cm)

4 (40) 4 (40) 3 (30)

Concrete block(heavyweight) (fp* = 10 Mpa, 100 kg/cm)

2 (20) 1.5 (15) 1.5 (15)

Concrete brick (fp* = 10 Mpa, 100 kg/cm)

2 (20) 1.5 (15) 1.5 (15)

With net unit weight, in dry con di tion, no less than 20 kN/m (2 000 kg/m)

Ta ble 2.6 De sign com pres si ve strength of con cre te ma -son ry units (fm*, over gross area)

Fp*, MPa(kg/cm)

fm*, MPa (kg/cm)Mortar I Mortar II Mortar III

10 (100) 5 (50) 4.5 (45) 4 (40)15 (150) 7.5 (75) 6 (60) 6 )60)

20 (200) 10 (100) 9 (90) 8 (80)

For intermediate values of fp* , linearly interpolate forsame type of mortar.

vv

cm

m

v

*.

1 25

(2.4)

whe re

vm mean dia gonal com pressive strength of walls spe ci-

mens, over gross area mea sured along the diagonal

parallel to load; and

cv coe ffi cient of va ria tion of dia go nal com pres si ve

strength of walls specimens, which in no case shall be

less than 0.20.

For walls having some re inforcing system who se contribu-

tion to strength in required to be evaluated, or ha ving charac-

teristics that cannot be re presented in the size of the wall

specimen, the dia go nal com pres si ve tests des cri bed abo ve

shall be made in squa re walls of at least 2 m side.

2.8.2.2 In di ca ti ve va lues

If testing of walls is not performed, de sign diagonal compressive

strength shall be that indicated in table 2.9. Specimen ho llow

units referred to in the table shall comply with section 2.1.1.

The values vm* in this table are va lid for masonry units com-

plying with strength fp* shown in the table and in section 2.1,

and for masonry with ho rizontal joint thickness between 10

and 12 mm. For other cases, the strength shall be de termined

according to section 2.8.2.1.

2.8.3 Bearing strength

When a con cen tra ted load is trans mi tted di rec tly to ma son ry,

bearing strength shall not ex ceed 0.6 fm*.

2.8.4 Ten si le strength

Ma son ry ten si le strength per pen di cu lar to joints shall be con-

sidered equal to zero. When this strength is required, the ne -

ces sary re in for cing ste el shall be supplied.

2.8.5 Mo du lus of elas ti city

The mo du lus of elas ti city of ma son ry, Em, shall be determi-

ned with one of the procedures indicated in sections 2.8.5.1

and 2.8.5.2.

2.8.5.1 Testing of pri sms made of masonry units andmortar that will be used in the job.

Prism of the type, age, and number indicated in 2.8.1.1 shall be

tested. The modulus of elasticity for short term loads shall be

de ter mi ned accor ding to the co rres pon ding Me xi can Stan dard.

For ob taining the modulus of elasticity for sustained loads,

long-term deformations due to plastic flow of masonry units

and mor tar shall be con si de red. Op tio na lly, the mo du lus of

elasticity for short term loads obtained from pris my tes ting

can be di vided by 2.3 if concrete unit are used, and 1.7 if clay

units or any other material different from con crete is used.

2.8.5.2 De ter mi na tion from de sign of ma son ry.

a)For masonry of concrete bricks or blocks:

Em = 800 fm* for short term loadsb (2.5)

Em = 350 fm* for sus tained loads (2.6)

b)For masonry of clay bricks or other units, ex cept con crete:

Em = 600 fm* for short term loads (2.7)

Em = 350 fm* for sus tained loads (2.8)

2.8.6 Shear mo dulus

The ma son ry shear mo du lus, Gm, shall be determined with

one of the pro cedures indicated in sections 2.8.6.1 and

2.8.6.2. Section 2.8.6.2 shall be applied if the modulus of

elas ti city is de ter mi ned accor ding to sec tion 2.8.5.2.

2.8.6.1 Testing of walls specimens made of masonry unitsand mortar to be used in the job.

11

NOTATION

Table 2.9 De sign diagonal compressive strength for some

types of masonry, over gross area

Masonry unit Type of mortar vm* , MPa (kg/cm)

Burnt clay brick (fp*

= 6 Mpa,

60 kg/cm)

I

II III

0.35 (3.5)

0.3 (3)

Clay brick with

vertical voids

(fp* = 12 MPa, 120

kg/cm)

I

II III

0.3 (3)

0.2 (2)

Concrete block

(heavyweight )

(fp* = 10 MPa, 100

kg/cm)

I

II III

0.35 (3.5)

0.25 (2.5)

Concrete bricks (fp*

= 10 MPa , 100

kg/cm)

I

II III

0.3 (3)

0.2 (2)

When the va lue in table is grea ter than 0.25 fm

* , in MPa (0.8

fm

* , in kg/cm) the latter va lue shall be ta ken as vm*.

With net unit weight, in dry con dition, no less than 20 kN/m

( 2 000 kg/m)

Figure 2.3 Wall spe cimen for diagonal compression testing

mean diagonal compressive strength of walls speci -mens, over gross area measured along the diagonalparallel to load; and

coefficient of variation of diagonal compressivestrength of walls specimens, which in no case shall beless than 0.20.

vm

cv

Wall spe ci mens of the type, age, and number shown in sec -tion 2.8.2.1 shall be tes ted. The shear mo du lus shall be de ter -mi ned accor ding to the co rres pon ding Me xi can Stan dard.2.8.6.2 De ter mi na tion from mo du lus of elas ti city of

ma son ry

If section 2.8.5.2 is chosen to be used for determining themodulus of elasticity of masonry, the shear modulus of ma -son ry may be taken as

Gm = 0.4 Em (2.9)

3. GE NE RAL SPE CI FI CA TIONS FOR ANALYSIS AND DE SIGN 3.1 De sign cri te riaDi men sio ning and de tai ling of struc tu ral ele ments shall sa tis -fy accor ding to the cri te ria re lated to ultimated and ser vi cia bi -lity li mit sta tes es ta blished in the Tit le Six of the Code andthe se Stan dards, or by some op tio nal pro ce du re com plyingwith the re qui re ments of the tit le six. In addi tion, struc tu resshall be de sig ned for du ra bi lity.

In ter nal for ces and mo ments pro du ced by the ac tions towhich the struc tu res are sub jected shall be de ter mi ned accor -ding to cri te ria pres cri bed in sec tion 3.2.

3.1.1 Ultimate li mit sta tes

Accor ding to ultimate li mit sta te cri te ria, struc tu res and struc -tu ral ele ments shall be di men sio ned and de tai led in such away that de sign strength in any sec tion shall be at least equalto the de sign va lue of the in ter nal for ce or mo ment.

De sign strengths shall in clu de the co rres pon ding strength re -duc tion fac tor, FR, pres cri bed in sec tion 3.1.4.

De sign in ter nal for ces and mo ments are ob tai ned by mul ti -plying by the co rres pon ding load fac tor, the va lues of such in -ter nal for ces and mo ments com pu ted un der ac tions spe ci fiedin the Tit le Six of the Code Re gu la tions and the Com ple men -tary Te chni cal Norms on Cri te ria and Ac tions for Struc tu ralDe sign of Buil dings.

3.1.2 Servicianility limit sta tes

It must be ve ri fied that the struc tu re res pon ses (settle ment,stra ins, cracking, vi bra tions, etc.) shall be li mi ted to va luessuch that ope ra tions in ser vi ce con di tions is sa tis fac tory.

3.1.3 De sign for du ra bi lity

Struc tu res shall be de sig ned and de tai led for du ra bi lity /or anins pec ted useful lyfe ti me of the struc tu re is 50 years.

The mi ni mum re qui re ments in the se Stan dards are applicablefor ele ments ex po sed to non- aggres si ve en vi ron ments, bothin do ors or out do ors, and co rres pon ding to ex po si tion A1 andA2, accor ding to Comple men tary Te chni cal Norms of De sign and Cons truc tion of Con cre te Struc tu res.

If the ele ment will be ex po sed to more aggres si ve en vi ron -ments, the de sign cri te ria for du ra bi lity of con cre te struc tu resshall apply.

3.1.4 Strength reduction fac tors

Strengths shall be re du ced by a strength re duc tion fac tor, FR.It is ac cep ta ble to apply the se va lues in tho se cons truc tion and re in for cing schemes who se ex pe ri men tal beha vior has beeneva lua ted and sa tis fies Nor ma ti ve Appen dix A. The va lues of the strength reduction fac tor shall be the fo llowing.

3.1.4.1 In walls sub jected to axial com pres sion

FR = 0.6 for con fi ned walls (Chap ter 5) or in ter na lly re in -for ced walls (Cap. 6).

FR = 0.3 for un con fi ned masonry without re in for ce ment(Chap ter 7)

3.1.4.2 In walls sub jected to in plane or out-of-plan, axialforce and bending.

For con fined walls (Chap ter 5) or in ter na lly re in for ced(Chap ter 6).

FR = 0.8 if PP

uR3

FR = 0.6 if PP

uR>3

For un con fi ned masonry without re in for ce ment (Chap ter 7).

FR = 0.3

3.1.4.3 In walls sub jected to shear for ce

FR = 0.7 for infill walls (Chap ter 4), con fi ned walls (Chap.5) and walls with in te rior re in for ce ment (Chap.6).

FR = 0.4 un con fi ned masonry without re in for ce ment (Chap. 7)

3.1.5 Con tri bu tion of re in for ce ment to ver ti cal loadstrength

The con tri bu tion to strength un der ver ti cal load of tie-co lumnsand bond beams (Chap. 5) or of in ter nal re in for ce ment (Chap.6) shall be con si de red accor ding to sec tions 5.3.1 and 6.3.1.

3.1.6 Hypo the sis for ob tai ning de sign fle xu ral strength

The de ter mi na tion of strength of any form of sec tion sub jec -ted to flexure, axial load or a com bi na tion of both, shall bemade fo llowing the cri te ria spe ci fied for re in for ced con cre te,and ba sed on the fo llowing hypo the sis:

a) Ma son ry beha ves like a ho mo ge neous ma te rial.

b) The dis tri bu tion of lon gi tu di nal stra ins in any cross sec tionof an ele ment is pla ne.

12

NOTATION

c) Ten si le strengths are re sis ted only by the re in for cing ste el.

d) The re is a per fect bond bet ween the ver ti cal re in for cingste el and su rron ding grout.

e) Sec tion fails when, in ma son ry, a ma xi mum com pres si ve stra in, ta ken equal to 0.003 is attained.

f) Un less tests in prism allow a bet ter de ter mi na tion of thestress- stra in cur ve for ma son ry, a li near un til fai lu re shallbe assumed.

In walls with ho llow ma son ry units whe re not all cells are fi -lled with grout, the va lue of fm* of ho llow ma son ry unitswithout grout in the com pres sion zone shall be con si de red.

Walls sub jected to out- of- pla ne fle xu ral mo ments, may becon fi ned o in ter na lly re in for ced. In the lat ter case, thebending strength may be de ter mi ned ta king into account thever ti cal re in for ce ment of the wall, when its spa cing does notex ce eds six ti mes the ma son ry wall thickness.

3.1.7 Strength of ma son ry to la te ral loads

The shear for ce re sis ted by ma son ry, accor ding to systemsdes cri bed in Chap ters 4 through 8, is ba sed on the de signshear strength stress which, in the ses Stan dards, is ta kenequal to dia go nal com pres si ve strength, vm*.

3.1.8 Fac tor of seis mic beha vior

For seis mic de sign, the seis mic beha vior fac tor Q, in di ca tedin the Comple men tary Te chni cal Norms for Seis mic De signand the se Stan dards shall be used. The seis mic beha vior fac -tor de pends on the type of ma son ry unit used in the walls(2.1.1), the re in for cing sche me (Chap ters 5 through 8), aswell as the struc tural la yout of the buil ding.

When combination of struc tu ral sys tems is used, i.e. con cre teor ste el at the ground story fra mes and load-bearing walls (asin the case of low rise buil dings with fra mes suppor ting ma -son ry walls), the sma llest seis mic beha vior fac tor in each di -rec tion of analysis shall be used. In addi tion, there qui re ments indicated in the Comple men tary Te chni calNorms for Seis mic De sign shall be sa tis fied.

3.1.9 De sign of foun da tions

Foun da tion of ma son ry struc tu res shall be di men sio ned andde tai led accor ding to the re qui re ments spe ci fied in the Tit leSix of the Code, the Comple men tary Te chni cal Norms onCri te ria and Ac tions for Struc tu ral De sign of Buil dings, theComple men tary Te chni cal Norms for De sign and Cons truc -tion of Foun da tions, the Comple men tary Te chni cal Normsfor De sign and Cons truc tion of Con cre te Struc tu res, and insec tion 8.4 of the se Stan dards, as per ti nent.

Foun da tion ele ments shall be de sig ned to re sist the de sign presand mo ment and soil reac tions, without ex ce eding the soilstrngth. Ma xi mum allowable settle ments shall be re vi sed.

Ver ti cal re in for ce ment of walls and other ele ments shall ex -tend into foo tings, whether of con cre te or ma son ry, or into the

foun da tion slab, and shall be an cho red so that the spe ci fied ten -sion yield stress may be developed. An cho ra ge shall bechecked accor ding to sec tion 5.1 of the Comple men tary Te -chni cal Norms for De sign and Cons truc tion of Con cre te Struc -tu res. The ver ti cal re in for ce ment shall be ter mi na ted with at90- de greeshooks near the bo ttom of foun da tion, with hookex ten sion orien ted towards the in te rior of the ver ti cal ele ment.

Re in for ced con cre te foun da tion slabs shall be de sig ned asdiaph ragms, accor ding to in sec tion 6.6 of the Com ple men -tary Te chni cal Norms for De sign and Cons truc tion of Con -cre te Struc tu res.

3.1.10 De sign of flo or and roof sys tems

Flo or and roof sys tems of ma son ry struc tu res shall be di men -sio ned and de tai led accor ding to the ul ti ma te and ser vi cia bi -lity li mit sta tes criteria, as well as du ra bi lity, es ta blished in the Tit le Six of the Code. Also, the appli ca ble re qui re ments ofthe co rres pon ding Comple men tary Te chni cal Norms shall beapplied, de pen ding up on to the ma te rial used.

In any case, the transfer of for ces and mo ments bet ween walls and flo or and roof sys tems shall not de pend on fric tion bet -ween ele ments.

If it is the case, re in for cing bars of re sis ting ele ments in flo orsand roof shall be an cho red into the walls, in such that the spe -ci fied ten sion yield stress may be developed.

If the flo or or roof sys tems are to trans fer la te ral for ces in itsown pla ne, to or bet ween ele ments re sis ting la te ral for ces suchas tho se in du ced by ear thqua kes, re qui re ments for diaph ragmsshall be met, de pen ding on the ma te rial used.

If flo or and roof sys tems are made of pa nels, the re qui re ments in NMX- C- 405- ONNC CE shall be met.

If joist and vault sys tems are used, re qui re ments of NMX- C- 406- ONNC CE shall be met. When vaults are suppor ted on walls pa ra -llel to joists, bea ring length shall be at least 50 mm. In no case, thevaults and joists shall obs truct pas sa ge of bond beams.

3.2 Methods of analysis 3.2.1 Ge ne ral

De ter mi na tion of in ter nal for ces and mo ments in walls shallbe made, in ge ne ral, by means of first or der elas tic analysis.When de ter mi ning the elas tic pro per ties of walls, it shall becon si de red that ma son ry does not re sist ten sions in a di rec tion per pen di cu lar to joints and, the re fo re, cracked and trans for -med sec tions pro per ties shall be used, when such ten sionsoccur.

The mo du lus of elas ti city of ste el re in for ce ment and ma son -ry, and the shear mo du lus of ma son ry, shall be ta ken as in di -ca ted in sec tions 2.7, 2.8.5 and 2.8.6, res pec ti vely. Forcon cre te, the va lue suppo sed in sec tion 1.5.1.4 of Comple -men tary Te chni cal Norms for De sign and Cons truc tion ofCon cre te Struc tu res shall be used.

13

NOTATION

3.2.2 Analysis under ver tical loads

3.2.2.1 Ba sic cri te ria

For analysis un der ver tical loads lo cal ro tations due to mortar

crushing in wall and floor element joints, shall be taken into

con si de ra tion. The re fo re, for walls suppor ting mo no lithic or

precast con crete slabs, it may be assu med that the joint has

enough ro tation ca pacity so that, for effects of moments dis tri-

bu tion in the wa ll- slab con nec tion, theout- of- pla ne wall fle xu ral

stiffness is zero and that walls are axia lly loa ded only.

In the analysis in teraction among soil, foun dation and walls

shall be considered. When long term effects are considered,

the modulus of elasticity and modulus shear for sustrained

loads in sections 2.8.5 and 2.8.6 shall be used.

3.2.2.2 De sign for ces and moments

Vertical loads ac ting on each wall may be ob tained from ana -

lisys ba sed on tributary areas.

For de sign, the following flexural moments shall be

considered.

a) Flexural moments that must be re sisted for static con di-

tions and that fixed to a cannot be re- distributed through

joint rotation, as those in a can tilever fixed to a wall and

tho se in du ced by wind or ear thqua ke loads, per pen di cu lar

to the wall.

b) Flexural mo ments due to eccentricity with which the load

of the flo or immediately above is transfered to end walls.

Such ec cen tri city, ec, shall be ta ken as

ec = t b

2 3(3.1)

where t is the wall masonry thickness and b is the bea ring

length of slab supported by wall (fig. 3.1).

3.2.2.3 Re duc tion fac tor by ec cen tri city and slen der nesseffects

Ec cen tri city and slen der ness effects shall be con si de red in

design. Op tio na lly effects may be con si de red the appro xi ma-

te values of the re duction fac tor FE.

a) FE is equal to 0.7 for in terior walls suppor ting ad yacent

span not differing more than 50%. FE can be ta ken equal

to 0.6 for end walls or with ad yacent span differing more

than 50%, as well as for ca ses whe re the ra tio of design live

loads to dead loads ex ceedes 1.0. For both cases, it shall

be si mul ta neous ly sa tis fied that:

1) Strains at the top and bo ttom ends of a wall in a perpen-

dicular di rection to the wall plane shall be constrained

by the floor system, bond beams, or by other elements.

2) Eccentricity in the applied axial load is less than or

equal to t/6 and there are no sig nificant for ces ac ting

perpendiculary to the wall pla ne; and

3) The free height-to-thickness ra tio of wall masonry,

H/t, does not ex ceed 20.

b) When con ditions of 3.2.2.3.a are not sa tisfied, the re duc-

tion fac tor by ec centricity and slen derness shall be de ter-

mined as the smaller of that specified in 3.2.2.3.a, and that

obtained from the following equation

Fe

t

kH

tE

12

130

2

(3.2)

whe re

H free height of a wall bet ween ele ments capable of

pro vi din wall la te ral support;

e ec cen tri city cal cu la ted for ver ti cal load plus an ac ci -

dental ec centricity that shall be ta ken equal to t/24;

and

k wall effec tive height factor to be equal to :

k = 2 for walls without restraint lateral displace-

ment in its upper edge;

k = 1 for end walls that su pport slabs; and

k =

0.8

for walls restrained by two continuous slabs

on spanning on both si des of the wall.

3.2.2.4 Effect of res traints to la teral di splacements

Where wall is connected to transverse walls, buttresses, co -

lumns or tie-columns (satisfying sec tion 5.1) to res train its la -

te ral dis pla ce ment, the fac tor FE shall be computed as

Fe

t

kH

t

H

L

HE

1

21

301

2

L09. (3.3)

where L is the spacing bet ween transverse ele ments res tran-

ting wall displacement (fig. 3.2).

3.2.3 Analysis for lateral loads

3.2.3.1 Ba sic cri te ria

For de ter mi ning the in ter nal for ces and mo ments ac ting on

the walls, ma sonry struc tures may be analyzed applying

14

NOTATION

Figure 3.1 Eccentricity of vertical load

free height of a wall between elements capable ofprovidin wall lateral support;

eccentricity calculated for vertical load plus an acci -dental eccentricity that shall be taken equal to t/24;and

wall effective height factor to be equal to :

for walls without restraint lateral displace -ment in its upper edge;

for end walls that support slabs; and

for walls restrained by two continuous slabson spanning on both sides of the wall.

H

e

k

k = 2

k = 1

k =0.8

dyna mic or sta tic methods (sec tion 3.2.3.2), or by using thesim pli fied method of analysis des cri bed in sec tion 3.2.3.3.The effect of ope nings in la te ral stiff ness and strength shall be con si de red.

3.2.3.2 Methods for dyna mic and sta tic analysis

Analysis applying dyna mic or sta tic methods com plying with Chap ter 2 of the Com ple mentry Te chni cal Norms for Seis -mic De sign shall be ac cep ted.

La te ral load effects in du ced by ear thqua ke shall bedetermined ba sed on the re la ti ve stiff ness of the diffe rentwalls and wall seg ments. The ses shall be de ter mi ned ta kinginto account the de for ma tions by shear and fle xion. For re vi -sion of the ultimate li mit sta te and for eva lua ting shear de for -ma tions, cracked pro per ties in the cross sec tions of the mostde man ded walls or seg ments. When eva lua ting fle xu ral stra -ins, the cracked cross sec tion of the wall or seg ment shall becon si de red when net ver ti cal loads in ten sion occur.

Res tra ints on wall ro ta tions, stiff ness of flo or and roof sys -tems, as well as tho se of lin tels and pa ra pets shall be ta keninto account.

In struc tu res de sig ned as confined ma son ry or internallyreinforced masonry, the walls and segments without ope -nings may be modeled as wide columns (fig. 3.3), with mo -ments of inertia moments and shear areas equal to those of theactual wall or segment. In long walls, as those withintermediate tie-columns, the expected behavior shall be

evaluated to decide if, for analysis purposes, the wall isdivided into segments, to each of which the correspondingmo ment iner tia and shear area shall be assigned.

The wide co lumns shall be cou pled by beams with the slabmo ment of iner tia of co rres pon ding from an effec ti ve width,to which the mo ment of iner tia the lin tel and pa ra pet shall beadded (fig. 3.4).

Mo du lus of elas ti city and shear mo du lus of ma son ry, Em andGm, for short term loads shall be used, (sec tions 2.8.5 and2.8.6). These va lues shall re flect the axial and shear stiff nessex pec ted to be ob tai ned from the ma son ry in the job. The va -lues used in the analysis shall be in di ca ted in the dra wings(sec tion 9.1).

For calculation the slab fle xu ral stiff ness, with or without pa -ra pets, con si der a width four ti mes the slab depth at each sideof the gir der or bond beam, or three ti mes the slab depth whenthe re is no gir der or bond beam, or when the bond beam is in -clu ded in the slab depth (fig. 3.4).

In the pla ne fra me analysis, when calculation the flexuralstiff ness of wall with flan ges, a width of compressive flan gean each side of the web not exceeding six times the flangethickness shall be con si de red (fig. 3.5)

In the case of walls with ope nings, ope nings may be mo de ledas equi va lent wide co lumns, only if the ope ning pat tern is re -gu lar in ele va tion (fig. 3.3), in which case so lid seg ments ofthe wall shall be mo de led as wide co lumns and the se shall becou pled by means of beams, as es ta blished abo ve. If ope ning

15

NOTATION

Figure 3.3 Model of a wide column

Figure 3.4 Effec ti ve width of slabs

Figure 3.2 Restraint to lateral displacement

dis tri bu tion is irre gu lar or com plex in ele va tion, more re fi ned

methods for modeling such walls shall be used. Finite ele-

ment method, the strut and tie method or other si milar analyti-

cal pro ce du res ai ming to ade qua tely mo del ope nings

distribution in walls and its im pact on stiffness, strains, and

stress distribution along the length and height of walls shall

be permitted.

The infill walls may be modeled as equivalent dia gonals or as

panels joi ned at cor ners to beams and columns of the

surrounding frame.

If both masonry and concrete walls are used, differences in

the mechanical properties of both ma terials shall be

considered.

Inelastic la teral drift an gles, i.e. equal to the one com puted

through the set of reduced ho rizontal for ces, and multiplied

by the seismic behavior factor Q, shall not ex ceed the fo -

llowing values:

0.006 for in fill walls.

0.0035 for load bea ring walls of confined masonry

made of so lid ma sonry units with horizon-

tal re in for ce ment or wel ded wire mesh

(Chap. 5)

0.0025 in load bea ring walls made of:

a) con fi ned ma son ry of so lid ma son ry units

(Chap. 5)

b) ma son ry of ho llow ma son ry units con fi-

ned and ho ri zon ta lly re in for ced (Chap.

5); or

c) ma son ry of ho llow ma son ry units con fi-

ned and re inforced with mesh (Chap. 5)

0.002 in bearing walls of hollow masonry units

with in ter nal re in for ce ment (Chap. 6).

0.0015 in bearing ma sonry walls not complying

with spe ci fi ca tions for con fi ned ma son ry

or in ter na lly re in for ced ma son ry (Chaps. 7

and 8)

3.2.3.3 Sim pli fied method

It shall be per mitted to consider that the shear for ce taken by

each wall or segment is pro portional to its cross area, to dis re-

gard the effects of tor sion, the overturning moment, and flexi-

bility of diaphragm, and to use the simplified method for

seismic analysis specified in Chapter 7 of the Complementary

Technical Norms for Seismic De sign, when the requirements

specified in Chapter 2 of such Norms are met. The se are:

a) At each story in cluding that supported by the foundation,

at least 75% of the ver tical loads are carried by continuous

walls in ele vation which are connected bet ween them by

means of monolithic re inforced slabs or by other floor sys-

tems sufficiently strong and stiff under shear. Such walls

shall have story an appro xi ma te sym me tri cal dis tri bu tion

with res pect to two or thogonal building axes. For that pur-

po se, cal cu la ted sta te tor sion ec cen tri city es, shall not ex -

ce ed ten per cent the di men sion mea su red pa ra llel to such

ec cen tri city, c. Tor sio nal ec cen tri city es may be cal cu la ted

as the ratio of the ab solute value of the algebraic sum of the

moments of the effec tive areas of walls with respect to the

shear interstory cen ter, and the to tal effec tive area of the

walls in the direction of analysis (fig. 3.6). The effective

area is the pro duct of the gross area of the cross section of

wall, AT, and the fac tor FAE , gi ven by

FH

LAE

1 133; .if

FL

HiH

LAE

133 133

2

. ; .f (3.4)

Where H is the wall free height and L is the effective length of

the wall. In all stories, at least two parallel load bea ring walls

shall be pla ced in the perimeter, with total length at least equal

to one half the story dimension in the direction of analysis

(fig. 3.7)

b) The length-to-width ratio of the flo or of the building does

not ex ceed 2, un less that, for seismic analysis pur poses, it

may be assumed that such flo or is divided in independent

segments where the length-to-width ratio sa tisfies this res-

triction and tho se mentioned abo ve (3.4), and each

segments is independently checked for seismic strength.

c) The height-to-minimum di mension ratio at the base of buil-

ding does not ex ceed 1.5 and the overall height of the buil-

ding is not greater than 13 m.

16

Figure 3.5 Effective width of flange in com pression of walls.

0.006

0.0035

0.0025

for in fill walls.

for load bearing walls of confined masonrymade of solid masonry units with horizon -tal reinforcement or welded wire mesh(Chap. 5)

in load bearing walls made of:

confined masonry of solid masonry units(Chap. 5)

masonry of hollow masonry units confi-ned and horizontally reinforced (Chap.5); or

a)

b)

masonry of hollow masonry units confi-ned and reinforced with mesh (Chap. 5)

in bearing walls of hollow masonry units with internal reinforcement (Chap. 6).

in bearing masonry walls not complyingwith specifications for confined masonryor internally reinforced mason ry (Chaps. 7 and 8)

c)

0.002

0.0015

3.2.4 Tem pe ra tu re analysis

Effects of tem pe ra tu re in de for ma tion and for ces shall bycon si de red when diffe ren ces in tem pe ra tu re may occur, orwhen the structure has a length grea ter than 40 m. Specialattention should be given to mechanical properties ofmasonry when eva lua ting tem pe ra tu re effects.

3.3 De tai ling of re in for ce ment 3.3.1 Ge ne ral

Cons truc tion dra wings shall have fi gu res or no tes with re in -for ce ment de tails (sec tion 9.1). Every re in for cing bar shall be su rroun ded by mor tar, or grout (fine or coar se) along thewho le length, ex cept ho ri zon tal re in for cing bars an cho redaccor ding to sec tion 3.3.6.4.

3.3.2 Si zes of re in for cing bars

3.3.2.1Dia me ter of lon gi tu di nal re in for cing bars

Dia me ter of the longest re in for cing bar size shall not ex ce edhalf size of the sma llest clear di men sion of a cell. In the co -lumns and bond beams, the dia me ter of the longest bar shallnot ex ce ed one sixth of the smallest di men sion (fig. 3.8)

3.3.2.2 Dia me ter of the ho ri zon tal re in for cing bars

Dia me tersr of the ho ri zon tal rein for ce ment shall not be sma -ller than 3.5 mm nor grea ter than three fourths the joint thick -ness (see sec tion 9.2.2.1) (fig. 3.8)

3.3.3 Pla ce ment and s pa cing of lon gi tu di nal re in for cingbars

3.3.3.1Clear s pa ce bet ween bars

The clear space between parallel bars, bar splices, or betweenbars and splices shall not be smaller than the nominaldiameter of the longest bar size, or 25 mm (fig. 3.8).3.3.3.2 Bar bun dles

A ma xi mum two- bar bundles shall be ac cep ted 3.3.3.3 Thickness of grout and re in for ce ment

Thickness of grout, bet ween bars or spli ces and the face of the pie ce shall be at least 6 mm (fig. 3.8)

3.3.4 Pro tec tion of re in for cing ste el

3.3.4.1Co ve r in ex te rior tie-co lumns and bond beams

In con fi ned walls with ex te rior tie- co lumns, lon gi tu di nal re -in for cing bars of tie-co lumns and bond beams shall have ami ni mum con cre te co ver of 20 mm (fig. 3.8).3.3.4.2 Co ve r in in te rior tie-co lumns and in walls with

in ter nal re in for ce ment

If the face of the wall is ex po sed to earth, co ver shall be 35mm for bars no larger than No. 5 (15.9 mm in dia me ter) or 50mm for longer bars (fig. 3.8).3.3.4.3 Co ve r of ho ri zon tal re in for ce ment

Mi ni mum clear dis tan ce bet ween ho ri zon tal re in for cing baror wel ded wire mesh and the outsi de face of a wall shall be atleast 10 mm or one-time the bar dia me ter (fig. 3.8).

3.3.5 Bends of re in for ce ment

The in ner ra dius of a bend shall be that spe ci fied for re in for -ced con cre te.3.3.5.1 In straight bars

Bars in tor sion may be ter mi na ted with 90 or 180 de greeshooks. Hook extension shall not be less than 12 db for de greehooks, nor than 4 db for 180 de gree hooks, whe re db is the bardia me ter (fig. 3.9).3.3.5.2 In sti rrups

Sti rrups shall be clo sed, made of one pie ce, and shall ter mi na -te in a cor ner with 135 de gree hooks, fo llowed by hookextension not sma ller than 6 db long nor 35 mm (fig. 3.9).

3.3.5.3 In crossties

The crossties shall terminate with 180- de grees hooks,followed by hook ex ten sions not smaller than 6 db long northan 35 mm (fig. 3.9).

17

Figure 3.6 Requirement for considering sym me tri cal storyof walls in one direction

Figure 3.7 Requirement for pa ra llel load bearing walls inthe perimeter

3.3.6 Bond and development

3.3.6.1 Ge ne ral re qui re ments

Ten si le or com pres si ve for ces ac ting on the re in for cing ste elat a crti cal sec tion shall be de ve lo ped on each side of the sec -tion con si de red, by means of bond whi tin a suffi cient lengthof the bar.

In ge ne ral, re qui re ments of the Comple men tary Te chni calNorms for De sign and Cons truc tion of Con cre te Struc tu resshall apply.3.3.6.2 Straight bars under tension

De ve lopment length, Ld , in which it is con si de red that a bar in ten sion is de ve lo ped such that the spe ci fied yield stress is rea -ched, shall be re qui red for re in for ced con cre te.3.3.6.3 Bars with 90 or180 de gree hooks

De ve lopment of bars un der ten sion shall satisfy requirements for re in for ced con cre te structures.3.3.6.4 Ho ri zon tal re in for ce ment in mor tar joints

Ho ri zon tal re in for ce ment pla ced in mor tar joints (5.4.3 and6.4.3) shall be con ti nuous along the wall, bet ween two tie-co -lumns if con fi ned ma son ry is con si de red, or bet ween twocells fi lled and re in for ced with ver ti cal bars in in ter na lly re in -for ced walls. If re qui red, two or more bars or wi res from co -pla nar or trans ver se walls may be an cho red in the sametie-co lumn or cell. Wire or ho ri zon tal re in for cing bars lapsalong walls shall not be per mi tted.

Ho ri zon tal re in for ce ment shall be developed in tie-co lumns,whether ex ter nal or in ter nal, or in grou ted re in for ced cells(fig. 3.10). An cho ra ge shall be made of 90- de grees hoo kedbars pla ced in si de the tie-co lumns or cells. The hook shall bepla ced ver ti ca lly in si de the tie- co lumns orgrouted cell the far -thest pos si ble from the tie-co lumn face from grou ted cell facein con tact with ma son ry.

If the design axial load, Pu , acting on the wall is tensile or null, the anchorage length shall satisfy the requirements inComple men tary Technical Norms for Design andConstruction of Concrete Structures. For re vi sing the

18

Figure 3.8 Size, placement and protection of reinforcement

development length, the critical section shall be the face ofthe tie-column in contact with ma son ry or wall of the groutcell (fig. 3.10).

3.3.6.5 Wel ded wire mesh

Welded wire meshes shall be anchored to masonry, as well asto tie-columns and beams if any, so that it can attain itsspecified yield stress may be rea ched (fig. 3.11). It may beaccepted to embed the mesh in concrete; for that purpose, atleast two vertical wires perpendicular to the direction ofanalysis shall be embedded, the shortest being at a distance no less than 50 mm from the critical section (fig. 3.11), powder- dri ven con nec tors or steel nails are used for attaching thewelded wire mesh, ma xi mum separation shall be 450 mm.

The mesh shall reinforced ver ti cal edges of walls and edges of ope nings by su rroun ding the edges. If the mesh is pla ced on aface of the wall, that segment of the mesh su rroun ding thebor ders shall ex tend at least two ti mes the trans verse wirespacing. This segment edges shall be an cho red so that themesh spe ci fied yield stress is reached.

If the wire dia me ter of the mesh does not a allow bendingaround, C- sha pe re in for ce ment made of mesh with wire gagenot smaller than 10 (3.45 mm dia me ter) may be over lappedwith the main mesh accor ding to sec tion 3.3.6.6.

It is per mi tted to at tach the mesh di rec tly in con tact with ma -son ry.

3.3.6.6 Bar splices

a) Bars un der ten sion

Lap length of bars in con cre te shall be de ter mi ned accor -ding to spe ci fi ca tion for re in for ced con cre te. Wel dedconection shall not be ac cep ted. If bars are lapped in si deho llow ma son ry units, lap length shall be at least 50 db inbars with spe ci fied yield stress up to 412 MPa (4,200kg/cm) and at least equal to 60 db in bars and wire withlarger spe ci fied yield stress; whe re db is the dia me ter of the lo ngest lapped bar size. Spli ce shall be lo ca ted in the midd -le third of the wall height. Splices of more than 50% of thelon gi tu di nal ste el of the ele ment (tie-co lumn, bond beam,wall) in the same sec tion shall not be ac cep ted.

Spli ces at both ends of tie-co lumns (whether ex ter nal or in -ter nal) splices the first flo or abo ve gra de along length Ho ,de fi ned in 5.1.1.h., shall not be ac cep ted.

19

Figure 3.9 Bends of reinforcement

Figure 3.10 Development of horizontal reinforcement

Figure 3.11 Reinforcement with welded wire mesh andmortar cover

Spli des in ver ti cal re in for ce ment at the base of in ter na llyre in for ced ma son ry walls along the cal cu la ted height ofthe fle xu ral plas tic hinge shall not be per mi tted.

b) Wel ded wire mesh

Wel ded wire meshes shall be con ti nuous, without spli ces,along the wall. Mesh may be overlapped it wall height re -quie res it. The over lap shall be pla ced in a zone whe re ex -pec ted stresses in wi res are low. Over lap mea su redbet ween trans verse end wi res of the adjoi ning meshes shall not be less than twi ce the spacing bet ween trans verse wi res plus 50 mm.

4. INFILL WALLS4.1 Sco peInfill walls are tho se walls su rroun ded by beams and co lumnsof a struc tu ral fra me, to which they pro vi de stiff ness againstla te ral loads. Infills may be made of con fi ned ma son ry (Chap. 5), in ter na lly re in for ced (Chap. 6), without re in for ce ment(Chap. 7) or of na tu ral sto nes (Cha