4 . c . 3

COMPRES SION TESTS ON WALL TIES

CO LI N AfWE RSON

PoZJtedzm:c ::l .+' ·the SDuth Bcr-1k> Lo'2don, Great 13Y'itain

COMPRESSION TESTS ON WALL TIES

CDdes Df practice geneY'ally specify wDY'king loads.

foY' wall ties in tensiDn and shear although they

are vulnerable to failure in compY'ession . This

papel' describes a series of tests to deteY'mine the

load carl'ying capacity of butteY'fly and fishtail

ties under compression.

The test specimens used foY' alI the tests consisted

of four wall ties embedded at each end in a bZock

of mortal' 150 mm square by 100 mm thick . The ties

were arranged in "square " formation for stability .

Specimens with a Y'ange of spacings between the blocks

were tested to studY the effect of different cavity

thicknesses upon the compressive strength of the

ties .

The tests weY'e caY'ried out between the platens of a

testing machine and load/deflection Y'eadings were

taken for some of the specimens . Load/def[e~tion

graphs will be included in the report o During the

tests the two end blocks for each specimen were pre ­

vented from potating by being inseY'ted in a "s leeve ">

this sleeve being the sides of a 150 mm cube mould

fastened lightly round the specimen .

DRllCKVEFlSUCHE .IvJIT MAUERANKERN

In NO Pm8n findet man gewohnlich zulassige Bean­

spruchungen für Mauerwerksanke r für Zug- und Scher­

beanspruchung> wahrond sie in Wirklichkeit auf

Druck versagen konnen . Diesel' Beitrag beschl~ibt

eine VersuchsY'eihe zur FeststelIung der Tragfãhig­

keit von Schmette r Zing- und Fischschwanzzankern

unteI' Dluck .

Die für alIe Versuche verwendeten Probekorper be ­

standen aus vier MaueY'ankerr'l> die an beidEn Enden

in einem Mor telblock mit 150 mm Seitenlange und

100 mm Dicke eingebettet waron . Die Anker wurdEn

aus Stabilitatsg1"Ünaen im Viereck angeordnet . Es

wuraen ProbekorpeY' mit verschiedenem Abstand

zwischen den Mortelblocken geprüft um den Einfluss

unters chiedlicher Luftspaltbrei te (Zweischalen ­

mauerwerk) auf die Druckf estigkeit dEr AnkeY' fest ­

z v.s te llen .

me Versuche wurden zwischen dEn Plcrtten einer

PY'Üfmaschine ausgef ührt und Jia> einige P"robekorper

wumen Last- Ve r [ormungswerte aufgezeichnet . Ent ­

sprechende Diagramme u'e raen diesem Beitrag beige ­

fiig t . Durch eine entsprechende Vorrichtung wv.rdEn

die Probekorper gehindert sich zu verdrehen .

4 . c . 3-Q

ESSAIS DE COMPRESSION SUR ANCRAGES DE MURS

Les Nor~s, en généra~ spécifient Zes taux admis ­

sibZes des ancrages sous des efforts de traction

et de cisailZe~nt . Mais ces ancrages sont vuZné­

rahZes en compression. Ce docu~nt décrit une

série d 'essais pour déterminer Za capacité por­

tante des ancrages, en forme de papiZZons et en

forme de queues de poi sson, en compres sion.

Les échantilZons utiUsés pour tous Zes essais

se composaient de quatre ancrages de murs , dont

Zes extrémités étaient noyées dans un bZoc de mor­

tier de 150 mm2 sur 100 mm d 'épaisseur . Les ancra­

ges étaient pZacés en forme de carré pour la stabi- ,

ZiU. Des essais ont été effectuéB Bur des bZocs à

entredistances différentes afin d 'étudier l 'influ­

ence de la largeur du vide du mur sur la résistance

à la compression des différents ancrages . Les essais

ont été exécutés entre les plateaux d ' une presse et

on a enregistré les rapports entre la charge et la

déformation pour quelques échantiZZons . Les diagram­

mes de ceS rapportB seront inclus dans le rapport .

Pendant les essais , on a empêché la rotation deB

deux blocs de chaque échantilZon, en les insérant

dans un "corset" qui était comp08é des côtés d ' un

cw:;e de 150 mm mouZé et maintenant légerement

l ' échantiUon .

DRUIGPROEVEN OP MUURANKERS

Normen en voorschriften geven meestaZ wer kbeZast-ingen

voor muurankers op trek en op schuif., terwijl deze

ankers kwetsbaar zijn bij druk . Deze mededeling be­

schrijft een r eeks testen om de belastbaarheid van

vlinderankers en vissestaartankers onder druk te be­

palen .

De testspec-imens gebruikt voor aUe proeven waren vier

ankers gebed in twee mortelblokken van 15OX15OX100 mm.

De ankers werden vierkant opgesteld voor de stabili­

teit .

Verschillende reeksen, met verschillende afstand tus­

sen de blokken werden geteBt om het effekt van ver­

Bchillende spouwbreedte op de drukBterkte van de an­

kers na te gaan .

De proeven werden gedaan in een drukper s , en de last/

vervorming werd gemeten. Grafieken met last/vervor­

ming zijn inbegrepen in het rapport .

Tijdens de proef werden de blokken vaBtgezet in een

"mal ", beBtaande uit een UchtjeB vaBtgezette beton­

varm van 150 mm zijde, om rotatie tijdenB de proef

te beletten .

1 . I NTRODUCnDr·j

As their name suggests wall ties are usually con­sidered to act in t~nsj.Jn ~~d C~dcs of Practice such as the British Standard CP 121 give working loads for butterfly typ e ties and fishtail ties in tensio~ and shear . lhe draft specificBtion, 74/ 104 83 De, for the structural use Df masonry dnes h~wevBr suggest that the stated tension values may be used where ties are arranged to operate in compression .

It is cons i de red that ties in cavity walls operate in compressicn at lease as frequently as in tension , it WiJ5 th8rsfoY'8 declLied to carrv Ol.!t a seri2s of tests to d~~~rnline ~hc sGllap~ c'~r3ct8ristics of wall ties acting in cO~1pr~~s.i.Gr dr(j to s-:udV the offect of "lhe c.=\/jty \I'idtn on th'? collrlpse loads .

2 . 1 Mortar BlocK SDeclmens

lhe firs: tes~ 3Decimens consisted Df fou r wall ties cast i nto blDcks of 1 : 1 : 6 morta r in a "square " for­mation as sh~wn in Fig . 1 , t~is arrangempnt was chasen to minimise la+eral c oll apse . lo simulate the situ­a ti on in a wall lt was desirable to prRvent one bloc k rot ating ralative to the othar and tt was also de­sirable to ensure that the ~locks would rema in pa r al lel during t~E rest , tnese Dbjectives wer a acnieved by placir; the sidns of a 150 mm cuoe mould around t he specimen as shown in Fig . 2 . The specimens were tested batween rigid platens in an Amsler 300 kN un iversal tcstirg machine . Closure of the gap be­tween thq blocKs was measured by a pai r of dia l gauges .

This arrangement wo rke d very well with the butterfly type ti'lS as the mortar blocks r ema ined intact , the fafl ure ~eing entirely by buckling Df the ties .

VJhen the metr.od was used fo r the fisht ail type ties the mortar blocks spIit but they "lere prevented from disintegratinf by tne cube mould su rroun d . Thi s splitt ing ~ould nave been saused by the flexing Df the tiP3 in lhe cavity ar by the fishtail ends being forced into the ffiortar b 1ocks . Obv iously this test arrangement wo~ld nct ellow the ties to push through ths mortar so an aI 1:srn,'lti ve specimen type was de­veleped .

2 . 2 "Three Brick" _Specirnens

lhe arrangement shown in Fig . 3 was used as an alter­nativa matnod Df testing fishtail ties as it s imu­lated the situation in a wall more closely tha n the rnortar block sDecim~n . ro pr event the brieks separ ­ati~g by ourstin~ along the joints a rigid clamp was placed aerDss each 581: Df bricks, the clamps were hsld initi311y ''1 B light pressure without indu c ing a prest r ess tnto the joints . lhe load was app lied around the edge Df tne bricK layers and the tie failure could be by bL ckling or by punching .

Thes e specimens were too la rge for the Amsler machine 50 they we re tested under a Mayes Servo-hydraulic jack .

3. RESULTS

The mortar ussd in alI the specimens was a 1 :1:6 mix with an average cuba crushing strangt h at the time Df the tia tests of 10. 4 N/rnm 2

•

TYPlcal load ~ gap clo~ure cha~acteristics are shown on Fig . 4.

4 . c .3-1

lables 1 and 2 summarise the results Df alI the tests so far carried and Fig . 5 shows t he collapse loads plotted against the cavity gap for both types Df t ie .

l he mortar used in these tests was designation (iii) by pro portions and designation (ii) by strength using the cri teri a gi ven in Table 6 Df CP 121: Part 1 : 1973 and lable 2 Df draft code 74/10483 DC extract s from wh ich are given below :

28 day compressive Proportions by

Mo rtar streng th N/mm 2

volume designation

laboratory works cement : lime : tests t ests sa nd

(i) 16 . 0 11 . O 1 : O-~ : 3

(ii) 6 . 5 4 . 5 1 : 1 2 : 4-4 i

(iii) 3 . 6 2 . 5 1 : 1 : 5-6

( iv) 1 . 5 1 . O 1 : 2 : 8-9

lable 2 Df CP 1 21 and lable 7 Df 74/10483 DC give working loads for ties embedded in mortar , the ten ­sion values being given for morta r designations (i) , (iii) and (iv) . lhe values for wire butterfly ties and fishtail ties for mort ar designation (iii) are listed in the fourth co lumn Df Table 3 Df this report and these have been used for calculating the ratios Df col lapse load to work ing load given in the fifth column Df lab le 3 .

4 . CONCLUSIDNS

The tests with butterfly ties in mortar blocks are considered to g i ve a good simulation Df the condition in service and the results were very consistent . The tests on the fishtail ties probably sli ght ly under­estimate the buckling st ren gth in service due to the splitting Df the morta r blocks in the first type Df test and due to the fact that there was no restra i nt from rotation or lateral collapse in the 3 brick specimens eve n though there was little evidence Df such movements i n the actual tests carried out .

lhe results do indicate that the fishtail ties are about 5 times as strong in compression as the butter­fly ties and that the safety factors for the fishta il ties are over gene rous for comp ressi on alone .

Further wo r k is required in testing:

(a) other types and sizes of ties

(b) t he effect Df mortar strength on t he compression strength Df the ties and

(c) the same type Df specimens in tension .

It is hoped to develop the t es t a r rangement Df the bric k specimen to prevent lateral movement and rota ­tion Df one end relative to the other .

4 . c . 3-2

TABLE 1

CoLLAPSE LoAoS oN BUTTERF LY WALL TIES

These tests were all carried out with t he "Mort ar 81oc k" type of specimen

CAVITY COLLAPSE LoAo LoAo PER TIE MEAN LoAo PER TIE mm oN 4 TIES kN kN kN

60 6 . 25 1 . 56 1 . 66 7.00 1 . 75

:,0 8 . 00 2 . 00 8 . 13 2 . 03 9 . 00 2 . 25 2 . 08 8 . 38 2 . 10 8 . 00 2 . 00

40 8 . 75 2 .1 9 2 . 23 9 .1 0 2 . 28

30 10 . 50 2 . 63 2 . 60 10 . 25 2 . 56

TABLE 2

COL LAPSE LO AOS ON FISHTAIL WAL L TIES

Si'ECIr1EN UIVITY COLLAPSE LoAO LoAO PER TIE MEAN LO AO FISH ' L LoAO --- --TYrt mrn oN 4 TIES kN PER TIE kN kN 8UTT ' Y LoAo

r10RTAR 60 34 . 2 8 . 55 9 . 55 5 . 8 BLoCI(S 42 . 2 10 . 55

r---51J 40 . 5 10 . 13

39 . 0 9 .75 10 . 04 4 . 8 41 . 0 10 . 25

40 31. 4 7 . 85 45 . 0 11. 25 9 . 96 4 . 5 38 . 0 9.50 45 . 0 11. 25

30 51 . 8 12 . 95 13 . 35 5.1 55 .0 13 . 75

8RI CKS 50 50 . 0 12 . 50 55 . 0 13 . 75 48 . B 12 . 20 12 .1 6 5 . 8 40 . 6 10 . 15 48 . 8 12 . 20

TIE TYPE

BUTTERFLY

FISHTA I L I MORTA?

FISHTAIL I N BIUCKS

TABLE 3

RATI oS DF CoLLAPSE LoAo TO WoRKING LoAo

CAVITY mm MEAN LoAD PER TIE kN

50 2 . 08

40 2 . 23

30 2 . 60

50 10 . 04

40 9 . 96

30 13 . 35

50 12 . 16

-+ + -t----+­

~-

Oial GaugE'

WoRK ING LDAD PER TIE kN

(FRoM CP 121 )

0 . 65

0 . 65

0 . 65

1 . 00

1 . 00

1.00

1 . 00

4 . c . 3 -3

CoLLAPSE LDAD

WoRKING LD AD

3 . 20

3 . 43

4 . 00

10 . 04

9 . 96

13 . 35

12 . 16

Sides of 150 mm cube mould

FIG. 1. MORTA R BLOCK SPECIMEN F IG. 2. TEST ON MORTAR BLOCK SPECIMEN

Load applied on a 150 mm square I

Two t iE's i n_-"-4-+-~--r Clampsto prevent bursting of j oints each joint

/

FIG 3 THREE BRIC K TEST SPECIMEN

~ I

crJ

u

~

::l

.. ~ +>

I-l .. p.

'd «I o H

14

12

10

8

6

4

2

• Butterfly ties

~ Fishtail ties in mortar blocks

• Fishtail ties in brick

~ t

~r" _____ .t - -"t;-- Fishtail type

~--------j!lr--..

-.........

-

Butterfly type -r------ r--___ ..t1 -----1

1 30 40 50 60

Cavity mm

FIG. 5 COMPRESSION STRENGTH Y CAVITY

50

45

40

35

30

~

III 25 ., ..... +>

• ~ 20 o 'd (\1 o H

15

10

5

O

I I -----Fishtail type ,,/ 10-'"

brick specimen ---50 = cavity ~ I'"

I

1/ I

/ / 1 I .l

Ir / 1/ ./

Fishtail type / !

I I mortar blocks I J

30 mm cavity I / ~ I I

I I T

I I

/ / I I

I / I

/ Butterfly type

./ , 50 mm gap

/' / \ / ---/ I .----

/ / ---/1 ?--~ ~ 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Gap closure mm

FIG. 4. TYPICAL LOAD-GAP CLOSURE CURVES