..

" ! \

1 )

\ ' '

NSFjRA-800497

"\;! '\ 1

i 1 j ~ _/ j

'-~'. '.-'.. -:-

EARTHQUAKE RESrSTAWi.' STRUCTURAL'f'lALLS".

TESTS OF LAP SPLICES

R£PRODUCED BYNATIONAL TECHNICALINFORMATION SERVICE

u.s. DEPARTMENT Of COMMERCESPRINGfiELD, VA. 22161

Fi 0 rat0 '-.)1 .,---'G"-'.'----'C~o~r'-l.'...:e"'-yL_ __J. D. Aristizabal-Ochoa, A. E.t ~;a Performing Organization Name and Address

I 7..~uthor(sl

50272 'j 0 I ,..,_._._•... 'M" ._•••__._._.__.... '._._... _ .. -,. ••

f, REPORT DOCUMENTATION \1. REPORT NO. 1 2, \ 3~.;,,~;,~;Pient·r8eir3 6°'9

i PAGE , NSFjRA-800497 I , ~ (:J,:hI:. Title and Subtitle 1-5-.-R-ep-o-rt-O-a-te--------

, Earthquake Resistant Structural Walls--Tests of lap Splices, I December 1980Final Report ~

------- ----- 1--------- ,

1

8. Perlorming Organization Rept, No. i

PCA ROSer. 166D__!10. project/Task/Work Unit No.

11. Contract(Cl or Grant(G) No.

Portland Cement AssociationConstruction Technology laboratories5420 Old Orchard RoadSkokie, Il 60077

(Cl

(G) ENV771533313. Type of Report &. Period Covered

I FinalI~-----

----------------'-, -----------------115. Supplementary Notes

t 12. Sponsoring Organization Name and Address

Office of Planning and Resources ~lanagement (OPRM)National Science Foundation1800 G Street, N.W.Washington, D.C. 20550

-----------------,------ .- ---------------1j- IS. Abstract (Limit: 200 words)

A test program to develop seismic design criteria for lap splices of reinforcing barsis described. Specifically, the effectiveness of tension lap splices under inelasticstress reversals is evaluated. Variables include load history, amount and configurationof lapped reinforcement, and amount of transverse hoop reinforcement around theiappedbars. Tests were performed on eight reinforced concrete column elements. Columnshad cross-sectional dimensions of 12 x 12 in. (305 x 305 mm). Longitudinal reinforce­ment consisted of either four No.8 bars or eight NO.6 bars. Results indicate thatdistribution of transverse hoop reinforcement significantly influences performance.Offset reinforcing bars also have a significant effect. Specimens with Class Clapsplices and special transverse hoop reinforcement performed well under monotonic andreversing axial loads.

StressesDucti 1i tyColumns (supports)

LoadsDesign criteriaWalls

b.. tdentifiers/Opel1·E,,,ded Terms

(S"e }\NSI-Z39.1B)

II 1~'. Oocumen~ }\nalysis '3. Descriptors

Earthquake resistant scructuresI Concrete structuresI i~ei nforced concrete

II Lap splices

'

:1: III"

Earthquake Hazards MitigationI c. COSAT: .<j,eid/Gr·)up ILI ----, --,-. _

1 18• "",ai/ability Slatem"nt i \9. Secl.Hity Cta", (This Reoof't) 21. No. 01 Pages -Jj NTlSi20. Security Class (This Page) ! 22. Price '

I !i.- ..•.<> __ .,_..... , ...... p •• __ .~._'."' ••• " ••••_.o<"~_._.~..,,.~..._..__...,._~._ .~.~_ ....__~..._, ... <O', .•.,•••.,~.•'""_, •••_._._••~-.' ••__ ._._.__.__• __......_,

OFTH.iN.A.\.. fORM ,:7'~ (!J,-i7)(Forme'iy NTI S-35lOepartment of Comme(~-;~

TABLE OF CONTENTS

HIGHI,IGHTS. . .

CURRENT BUILDING CODE PROVISIONS . .

LITERATURE REVIEW

OBJECTIVES AND SCOPE •

OUTLINE OF TEST PROGR~

Test Specimen

Specimen Design

Materials

Construction 1 •

Test Setup ..

Instrumentation

Loading

OBSERVED BEHAVIOR

Force Transfer Mechanisms in Lap Splices , .

Effects of Load History

Effects of Longitudinal Reinforcement

Effects of Transverse Reinforcement

1

4

7

10

12

12

12

17

17

21

21

22

24

24

29

30

32

SU~lARY AND CONCLUSIONS

ACKNm<lLEDGMENTS

40

44

REFERENCES . 45

APPENDIX A - ADDITIONAL REFERENCES

APPENDIX B ~ TEST RESULTS

S6 Specimens , ,

S 8 Spec imens .

-i- ct

A-I

8 .,

B-·l

8-8

EARTHQUAKE RESISTANT STRUCTURAL WALLS -

TESTS OF LAP SPLICES

by

J. D. Aristizabal-Ochoa, A. E. Fiorato,and W. G. Corley*

HIGHLIGHTS

This report describes results of a test program to develop

seismic design criteria for lap splices of reinforcing bars.

The full-scale tests are part of an investigation of reinforced

concrete structural walls used as lateral bracing in earthquake-

resistant buildings.

The specific problem considered in this investigation is

use of tension lap splices in regions of potentially severe

stress reversals. This situation occurs, for example, at the

base of tall structural walls where splices of vertical rein-

forcing bars are often used. Figure 1 illustrates this condi-

tion. During severe earthquakes, overturning forces can induce

inelastic stress reversals in the vertical bars. At present,

the designer has no guidance on effectiveness of splices in this

critical region.

This report presents results of a test ptogram to evaluate

effectiveness of lap splices under inelastic stress reversals.

It includes a description of eight 12-in. (30S-rnrn) square column

elements subjected to axial loads.

*Respectively, Former structural Engineer, Structural Develop­ment Section; Manager, Construction Methods Section; andDivisional Director, Engineering Development Division, PortlandCement Association, Skokie, Illinois.

-1-

PotentialHinging

Region

FoundatIon

-I I

I

I III

I II I Floor Slab !,I II II III I

III iII WALL II II II I

:>\I IIlice ./ tr\ II

"'-\ II . II+.J III II

Lap Sp

Fig. 1 Splice in Critical Region NearBase of Structural Wall

-2-

Variables were amount and configuration of lapped longitu-

dinal reinforcement, amount of transverse hoop reinforcement

around the longitudinal reinforcement, and load history.

Specimens had Class C tension lap splices in conformance

with the 1977 ACI Building Code. (1)* Lapped longitudinal

reinforcement included No. 8 and No.6 bars. In each case 100%

of the bars were spliced at the same location. Following common

practice, corner bars were offset at the end of the lap. Offset

length was six times the bar diameter. Amount of transverse

reinforcement varied from that required for seismic design con-

ditions to maximum spacing for column ties. Four tests under

monotonic loading and four under severe reversing loading were

made. Reinforcement with a nominal yield of 60 ksi (414 MPa)

was used. Nominal concrete strength was 3,000 psi (20.7 MPa).

* Numbers in parentheses correspond to references at the end ofthe report.

-3-

CURRENT BUILDING CODE PROVISIONS

The 1977 ACI Building Code(l) provisions for tension lap

splices of flexural members are summarized in Table 1. These

provisions are similar to those in the 1976 Uniform Building

Code. (2) Three classes of lap splices are defined. No lap

splices are permitted for bars larger than No. 11.

For sections where the area of tensile steel pr.ovided is

equal to or greater than two times that required, two cases are

considered. When 75% or less of the bars at the section in

question are interrupted, a Class A splice is required. This

splice has a lap length equal to the bar development length,

Qd' When more than 75% of the bars at a section are inter­

rupted, a Class B splice is required. The lap length is then

1.3 Qo'

For sections where the area of tensile steel provided is

less than two times that required, two more cases are defined.

When 50% or less of the bars are interrupted, a Class B splice

is required. When more than 50% of the bars are spliced, a

Class C splice must be used. This splice has a lap length of

1.7 Qo'

Seismic design provisions in Appendix A of the 1977 ACT

Building Code(l) also require that lap lengths be at least 24

nominal bar diameters or 12 in. (305 mm).

The basic intent of the building code provisions is to dis­

courage use of tensile splices in regions of critical stress

and to encourage staggering of splices.

-4-

TABLE 1 - TENSION LAP SPLICES ACCORDING TO 1977ACI BUILDING CODE

A provided Maximum percent of As spliceds within required lap length

A requireds 50 75 100

Equal to or Class A Class A Class Bgreater than 2

Less than 2 Class B Class C Class C

Where:

As provided/As required :::

Class A splice ::: 1.0 Qd

Class B splice ::: 1.3 Qd

Class C splice ::: 1.7 Qd

ratio of area of reinforce­ment provided to area ofreinforcement required byanalysis of splice location.

Qd::: development length, in.

f :::y

db :=

Ab:::

ft :::C

0.04 Abf y

Jftc

but not less than 0.0004 dbf y for No. 11 bars

or smaller in normal weight concrete.

specified yield strength of reinforcement, psi

nominal diameter of bar, in.

area of individual bar, sq. in.

specified compressive strength of concrete, psi

-5-

For seismic conditions, applicability of current code pro­

visions for tensile laps needs to be clarified. The following

questions arise:

(1) Code lap lengths are based on development of 125% of

the yield stress of the ba~. Is this appropriate Eor

seismic conditions where severe overloads can occur?

(2) Experimental investigations(3) indicate a significant

improvement in performance with ordinary transverse

reinforcement. For seismic design, unusually large

amounts of transverse reinforcement are used. Wh&t is

the effect of such reinforcement on performance of lap

splices?

(3) What are effects of load reversals on the performance

of lap splices?

-6-

LITERATURE REVIEW

A review of literature on lap splices of reinforcing bars

indicates that very little work has been done to determine per­

formance under seismic loaning conditions. Appendix A is a

list of references covering the topic of lap splices.

An evaluation of nevelopment length and lap splices has

been reported by Orangun et ale (3) This paper describes der­

ivation of an equation for development length that includes

effects of concrete cover, bar spacing, and amount of uniformly

distributed transverse reinforcement. However, the recommenda­

tions are based on tests of monotonically loaded members. They

must be reevaluated for members subjected to seismic loading.

Test of lap splices under monotonic compressive loads have

been reported by Arthur and Cairns. (4) They concluded that:

(1) Forces in compression lap splices are transferred by

bond stresses around the circumference of the bars and

by end-bearing of the bars on the concrete.

(2) Transfer of forces causes bursting stresses on the sur­

rounding concrete.

(3) Strength in bond and end-bearing is dependent on the

resistance available to counteract bursting stresses.

(4) Transverse reinforcement located at ends of the splice

is most effective in resisting bursting stresses.

Arthur 'and Cairns developed an expression to predict stresses

in the main steel. This expression includes contributions of

lateral reinforcement, bond, and end bearing. They also recom­

mended that one third of required transverse reinforcement be

-7-

placed within a distance of 15% of the lap length from each end

of the splice.

Tests of tension lap splices in beams have recently been

reported by Betzle. (5) His tests included beams longitudi­

nally reinforced with No. 5 and No.9 bars without transverse

reinforcement. Specimens were subjected to monotonic loading.

Betzle concluded that bond stresses in the concrete and force

transfer between lapped bars are mainly concentrated at the

ends of the splice.

Tests of bond and anchorage of reinforcing bars under ine­

lastic reversals of load have been reported by Ismail and

Jirsa, (6) Hassan and Hawkins, (7) and Popov. (8) These tests

indicate that rate of bond deterioration and response of

anchored bars are significantly affected by loading history.

Slip and deformation of anchored bars under load reversals were

observed to have substantial influence on hysteretic response

of the members tested. This was also observed in cantilever

beam tests by Brown and Jirsa. (9) They concluded "Deformation

of the steel in the anchorage zone (within the fixed end) con­

tributed significantly to the total deformation and to the

energy absorbing capacity of the specimens."

The conclusion is that, for seismic conditions, the load

versus slip relationship of bars is of prime importance. Brown

and Jirsa, (9) and Hawkins(lO) also conclude that for cyclic ine­

lastic loads it may be necessary to increase embedment lengths

required by the 1977 ACI Building Code. (1)

-8-

Tests to determine effects of inelastic stress reversals on

bond and anchorage are relevant to the problem of using lap

splices under seismic conditions. However, a comprehensive

evaluation of performance of lap splices under load rever.sals

requires data from tests of spliced members under loading con­

ditions simulating those that could occur during an earthquake.

It is for this purpose that the current program was undertaken.

-9-

OBJECTIVES AND SCOPE

Objectives of this investigation were:

(1) To determine effects of reversing loads on behavior of

tension lap splices.

(2) To develop design criteria for tension lap splices in

earthquake-resistant structures.

To achieve these objectives, a series of reversing load

tests on specimens containing lap splices were performed. Var­

iables included:

(1) Load History - Tests using load histories corresponding

to monotonic and severe reversing loads were made.

(2) Longitudinal Reinforcement - Variations in longitudinal

reinforcement included bar size and number of bars in

the cross section.

(3) Transverse Reinforcement - The amount and configuration

of transverse reinforcement ranged from that required

for ordinary column ties to that required ror special

seismic confinement hoops.

Table 2 lists the variables considered in this experimental

program.

-10-

TABLE 2 - TEST SPECIMENS

Specimen(l) Load Transverse Longitudinal(2)History Reinf. Reinf.

S6-l Monotonic No. 3 @ 2" 8 No. 6

S6-2 Reversing No. 3 @ 2" 8 No. 6

S6-3 Reversing No. 3 @ 4" 8 No. 6

S6-4 Monotonic No. 3 @ 4" 8 No. 6

S8-l Monotonic No. 3 @ 2" 4 No. 8

S8-2 Reversing No. 3 @ 2" 4 No. B

S8-3 Monotonic No. 3 @ 12" 4 No. S

S8-4 Reversing No. 3 @ 4" 4 No. 8

Notes: (1) All specimens 3,000 psi (20.7 MPa) design com-

pressive strength concrete.

(2) All bars spliced at the same location.

100% Bar Splicing.

(3) 1 in. = 25.4 mm

-11-

OUTLINE OF TEST PROGRAM

A total of eight specimens were tested. Amount of longitu­

dinal reinforcement within the splice length was 4.4% for spec­

imens with No.8 bars and 4.9% for specimens with No.6 bars.

Reinforcement with a nominal yield of 60 ksi (414 MPa) was used.

Nominal concrete strength was 3,000 psi (20.7 MPa). Four spec­

imens were subjected to monotonic loading and four were sub­

jected to severe loading reversals. Test specimens, test setup,

and test procedure are described below.

Test Specimen

Tests were performed on I-shaped specimens as shown in Figs.

2, 3, and 4. Axial loads were applied through the two end

blocks using two hydraulic rams. The splice test region was at

the center of the column portion of the specimen.

The column portion had cross-sectional dimensions of l2x12 in.

(305x305 mm) and a length of 96 in. (2.44 m). End blockS had

dimensions of 48x56x12 in. (1.22xl.42xO.3l m).

Specimen Design

Cross sections at the location of the splices for the two

types of specimens selected for testing are shown in Fig. 4.

Specimens designated S6 consisted of eight No. 6 bars all

spliced at the same location. Specimens designated S8 consisted

of four No. 8 bars all spliced at the same location. The number

and size of the reinforcing bars were selected within capacity

-12-

Fig. 2 Test Setup

Reproduced frombest availa ble copy.

-13-

I I--'

.~ I

o ----

jF

ixe

dE

nd

DC

DT

(D

o Lo

ad

Ce

llE

yeB

racke

t

Fig

.3

Test

Setu

p

DC

DT

®

Fre

eE

nd

DC

DT

®

I--_..~---

iD.~~~1!!l

__~~_

----t..

.---~~------.-----~--~-

56

"(2

44

m)

..I_

4B~J1.22ml

·1

---+

--

l=::=

r::--_

-__=_

_==-=

':::~~

=-=-:

:1=J

=-.

e::--:1

-=-=-~

-_-==_

-=-_~

~-::=

-T_T

_~

~tt

..=DE

We

ld

~:t-

-::-::.

-::._::

.-==-

_-_-_-

_=--_

-L-_

~:J-

-:.__

-_-_

-::_-.-

_-_-_=

__=t==

=

Sp

lice

Lel\

glh

Secli

on

AA

12"

r(0

.30

ml"I

,.~[[fJ}'.

"".,17

.5"(

O.1

9m

l

~g~

[--

13

3"

(08

4m

l(0

11m

)

:O

ff",

-3

15

"(0

80

m)

oo

oo_:t

_-_~

c:::

::.c

:::

-=.::t::

--=

56

"(1

.42

ml

g~r~n_n~_-----

.------

--

---

----

----

--

.---

l-=-1

--=1

---

--_

_=__

-=_=__

_::.-_

-_-:::-

1=::=

Wel

d(0

)S

6S

peci

men

I-'

l;l I

Wel

d--

r---

----

---

r=~

1--

of=

:::

-=-_

-..=

-=_=

_

ot--

-=!-.

: o

12"

t""(0

.3O

m)"

I

,"~·lJCJ}r,.,".,

~8

"8

See

Ta

ble

2fo

rho

opsp

aci

ng

Wel

d

r-=:-1

-=~_=_-_-_-=-

__::._

::.-=.

-:E

We

ld

I-=--:i

::L-_

-_---=

-_--::-

-_=.

1:

r-B

ISM

(O.4

6m

)

o

=-=.

-_-_-

=-==

=-=--=

=.t::

:....4.

.-=

tJt::1

I41

3H

oop

~~-

B_

6"

12

"(0

30

m)

-(0

15

m)

-.,=

c·-.

~·c'

C=l=

.1C,

._J

,:~::;;;

:;"0,

,,,,=

-=--

--

o

-1,=0+=

56

"ll

.'l2

m)

~~-_._---~--

--~

~----------~

-~

----

--

--

--

--

"--

---

6·:=

-_'::

:-=-=

--=-=-

-==-

=-=.

.::-.

-=-

--.-

----

----

--=

-.

(b)

S8

Spe

cim

en

Fig

.4

Rein

forc

em

en

tD

eta

ils

of

Test

Sp

ecim

en

s

limits of existing laboratory equipment. The four bar and eight

bar arrangements provide flexibility for considering different

splice configurations.

Lap lengths corresponded to Class C tension lap splices

according to the 1977 ACI Building Code. (1) This resulted in

a 33-in. (0.84 m) lap for S6 specimens and a 60-in. (1.52 m)

lap for 8a specimens.

Transverse reinforcement in Specimens S6-l, 86-2, S8-l, and

S8-2 consisted of confinement hoops spaced 2 in. (51 mm) on

centers. Rectangular hoops were made of No.3 reinforcing bars.

The volumetric hoop reinforcement ratio in these specimens met

requirements of the 1976 Uniform Building Code. (2) It was 70%

of that required by the 1977 ACT Building Code. (1)

To investigate effects of amount of transverse reinforcement

on strength and behavior, Specimens S6-3, S6-4, Sa-3, and S8-4

were built with less confinement. In Specimens S6-3, S6-4 and

S8-4, transverse reinforcement consisted of No.3 hoops spaced

4 in. (102 rom) on centers. In Specimen S8-3, it consisted of

No.3 hoops spaced 12 in. (305 rom) on centers. Confinement

spacing in Specimen S8-3 corresponded to the maximum permitted

for column ties in the 1976 Uniform Building Code and the 1977

ACI Building Code.

Corner longitudinal bars had offsets at the start of the

lap as shown in Fig. 4. Slope of the inclined portion of the

bars with the longitudinal axis of the specimen was 1:6, the

maximum permitted by the 1977 ACI Building Code. Interior bars

were not offset. Photographs of reinforcing cages at the loca-

-15-

tion of the offsets are shown in Fig. 5. It was anticipated

that local stress conditions at the offset would be critical to

performance of the specimens.

The two end blocks were designed to avoid premature termi­

nation of tests because of failure of loading or supporting

elements. Main longitudinal reinforcement in the specimens was

anchored in the end blocks as indicated in Fig. 4.

Materials

Concrete contained a blend of Type I portland cements, Elgin

sand, and Elgin gravel aggregates. (11) Maximum aggregate size

was 3/8 in. (10 mm). Compressive and splitting tensile

strengths of the concrete were determined from tests on 6xI2-in.

(152x305 mm) cylinders. Modulus of rupture was determined from

tests on 6x6x30-in. (152x152x762 mm) beams. Average properties

of concrete used in each specimen are given in Table 3.

Bars conforming to ASTM Designation A61S Grade 60 were used

as reinforcement. Measured physical properties of the rein­

forcement are summarized in Table 4.

Construction

Test specimens were constructed and cast in a horizontal

position as shown in Fig. 6. Reinforcing cages for the center

part of the specimen and for the two ends were fabricated as a

unit and then placed in the form. Before casting, lifting eyes

and inserts for attaching the loading system were placed in

position.

-17-

I l-'

()) I

Off

set

Off

se

t

(a)

Off

set

in8

6S

pecim

en

s

58-3

(b)

Off

set

inS

8S

pecim

en

s

Off

set

'..

Fig

.5

Off

set

of

Lo

ng

itu

din

al

Rein

forc

em

en

t

TABLE 3 - CONCRETE PROPERTIES FOR TEST SPECIMENS

Age Compressive Modulus of Split

Specimen At Test Strength Rupture Cylinder Testf' f fDays c r s

psi psi psi

S6-1 24 3300 510 430

S6-2 28 3980 460 340

S6-3 43 3520 410 490

S6-4 41 3280 370 420

88-1 50 3340 460 430

S8-2 34 4480 420 560

88-3 35 4520 400 540

88-4 24 3530 490 450

Notes: (1) Average properties for center part of the specimen.

(2) 1000 ps i = 6. 895 MP a •

TABLE 4 - REINFORCING BAR PROPERTIES FOR TEST SPECIMENS

Bar f f I Es Elongationy suSize ksi ksi I

1 • %,{SlI II

No. 3 73.7 109.8 29,800 I 13

No. 6 69.9 107.4 29,600 I 13\

I No.I

8 68.2I

111. 4 30,100 I 13I I

I

1.0 ksi = 6.895 MPa

-19-

(a) Reinforcing Cage

(b) Reinforcing Cage in Form

Fig. 6 Test Specimen S8-1 Prior to Casting

Reproduced frombest available copy.

-20-

Each specimen was cast using ten batches of concrete. Prop­

erties of the concrete were determined from batches used in the

center part of the specimen. After casting, specimens were

covered with polyethylene sheets and cured for one week. Spec­

imens were then stripped and moved to the test location.

Test Setup

A photograph of a specimen ready for testing is shown in

Fig. 2. Specimens were tested in a horizontal position. One

end was fixed to the floor. The other was supported on thrust

bearings and guided by rollers to prevent end rotation. Speci­

mens were subjected to axial loading using two hydraulic rams

controlled by a hydraulic pump.

Instrumentation

Specimens were instrumented to measure applied loads, axial

elongations, and steel strains. Readings from each sensor were

recorded by a VIDAR digital data acquisition system interfaced

with an HP9830A calculator. Data were stored on tape cassettes

Ear subsequent analysis.

Total and relative axial elongation of the column portion

of the each specimen were measured using the system of external

gages shown in Fig. 3. Elongations were measured with direct

current differential transducers (DCDT).

Strain gages were placed on both longitudinal and trans­

verse reinforcement.

-21-

Loading

Each test specimen was loaded axially with forces applied

through the end blocks. Two loading histories were used. These

are termed tensile monotonic (M), and severe reversing loading

(SR) •

In tensile monotonic loading tests, specimens were initially

loaded in increasing force increments. Increments were deter­

mined by dividing the calculated yield load by 15. The first

three or four increments were below the cracking load. Subse­

quent to yielding, loading was controlled by increments of axial

elongation. Elongation, which was controlled by manually clos­

ing a valve in the hydraulic pressure line,was increased until

the specimen was destroyed.

In the severe reversing loading tests, specimens were sub­

jected to six reversing cycles. A representative SR loading

history is shown in Fig. 7. In tension, three cycles at yield

were alternated with three cycles at 1.25 times yield. In com­

pression, six cycles at a peak load of approximately 200 kips

(890 kN) were applied. After six cycles, specimens were sub­

jected to monotonic tensile loading until they were destroyed.

Specimens were inspected visually for cracking and evidence

of distress after each load increment. Crack widths were mea­

sured and recorded after initial cracking, and before and after

yielding of the longitudinal steel. Crack patterns were also

recorded.

-22-

Loa

d~

2.0

P y t gP y

(/) c (j)

i-

0I

['.)

CW

0I

(/)

(/)

(j)

l- n.. E

'f0 0 ~

Mo

no

ton

ic I1.

25Py

/ / /\

I\

I\1

\'

\1

\t

~

,-

1~

il:"

tC

ycle

No.

Leve

lo

fC

om

pre

ssiv

eL

oa

dV

ari

ed

f~om

0.7

2P y

for

S6'

Spe

cim

ens

to1.

0P y

for

S8

Spe

cim

ens.

Fig

.7

Rep

resen

tati

ve

SR

Lo

ad

ing

His

tory

OBSERVED BEHAVIOR

Amount and distribution of hoop reinforcement, and arrange­

ment of longitudinal reinforcement were primary factors affect­

ing observed strength, ductility and behavior. Capacity of the

specimens was limited either by bar fracture or pull-out of

spliced bars. Bar fracture occurred at the offset. Pull-out

of spliced bars was associated with longitudinal splitting of

the concrete.

A general discussion of force transfer mechanisms and

effects of significant variables is presented in the following

sections. Test results are summarized in Table 5. Detailed

data for each specimen are given in Appendix B.

Force Transfer Mechanisms in Lap Splices

Forces between lapped bars in tension are transferred by

bond stresses around the circumference of the bars. The bond

stresses cause radial or "bursting" forces on the concrete sur­

rounding the splice. These forces are concentrated at ends of

the splice. (5)

Crack widths and strains measured in longitudinal and trans­

verse reinforcement are shown in Figs. 8, 9, and 10. These

figures are representative of all tests. They indicate the

concentration of deformations and bursting forces at each end

of the splice.

Strains in concrete and reinforcement were more heavily

concentrated at the offset end of the splice than at the straight

end. This resulted because the offset tended to "straighten

-24-

J N VI I

TAB

LE5

-SU

MM

ARY

OF

TE

STS

RES

ULT

S

--C

rack

ing

Loa

dF

ull

Yie

ldL

oad

Max

imum

Loa

dO

bse

rved

Sp

ecim

en(k

ips)

(kip

s)(k

ips)

Mod

eo

f"-

----~---

Fail

ure

(c)

(a)

Calc

ula

ted

(b)

Calc

ula

ted

(b)

Ob

serv

edC

alc

ula

ted

Ob

serv

edO

bse

rved

...~--_.

__._

---

----

----

-_.

---

.>--

86

-147

6124

624

635

737

8S

pli

ce

(M)

S6

-247

4924

624

635

737

8B

arF

ractu

re(6

)

S6

-346

71

246

246

302

378

Sp

lice

(6)

86

-446

6024

624

629

837

8S

pli

ce

(5)

88

-144

6221

621

633

035

2B

arF

ractu

re(M

)

88

-2(d

)46

8021

621

632

535

2--

(6)

88--

346

7821

121

628

035

2S

pli

ce

(M)

S8

-4(e

)46

6521

221

626

135

2B

arF

ractu

re(3

)

(a)

Bas

edon

sp

lit

cy

lin

der

ten

sil

est

ren

gth

.

(b)

Bas

edon

aver

age

pro

pert

ies

of

rein

forc

ing

ste

el.

(c)

Num

ber

wit

hin

pare

nth

ese

sin

dic

ate

snu

mbe

ro

ffu

lly

rev

ers

ed

cy

cle

sap

pli

ed

to

the

spec

imen

pri

or

tofa

ilu

re.

Mm

on

oto

nic

load

.

(d)

Lo

adin

gap

para

tus

beca

me

un

stab

leaft

er

init

ial

six

cy

cle

sap

pli

ed

.

(e)

Aco

rner

bar

fractu

red

at

the

off

set

du

rin

gth

efir

st

half

of

the

fou

rth

cy

cle

.

(f)

1k

ip=

1000

Ib=

4.4

48

kN

Tens

ilelo

ad=

24

2ki

ps(1

076

kN)

at

cycl

esI,

2,

3,

and

4

Cra

ckW

idth

,m

m

1.0

2.0 a

(\ 1\ /\ ,' I\

I...

..C

yde

41

I(

\

1\

Cyc

le3-J

>i/'\\

II

I,

I,C

ycle

2-r

!'.

\\/;1

\\'

f/I

\\

'//

\

'I:\

1/I

III

I

~~----=-=

,t::....

II\ \ X'---

\I

\\

\,.

,I

'\\ \I \, \\ \1 Y.

a

0.0

50

Cra

ck0.

100

Wid

th,

in.

---,

Vi

~-J

_.-

•

1IV

-,

--------

Spl

ice

----

--

- "

-------

-----

--

-.--

----

r

---

-

1-0(

:."-

-....1~O

ffse

t1

--------

33

"

-

L--

-l(

0.8

4m

).L

--'

I N CY\ I

Fig

.8

Cra

ck

Wid

ths

Alo

ng

Sp

lice

inS

pecim

en

S6

-2

I in. 25.4 mm

I kip 4.448 kN

Level

Strain

Offset Bar

I

Yield Level

0.001 Strain

0.001

0.002

oo

30"

P~154kips(l)

_________ .,.... __ - - -- Yield

p: 337 kips / / /

(M) \ /, 0.0027 ./ ,

/ / JP:300kiPSfr ..-"-

(2) r..- ........ ..-/,,"-P:245kips// (I)

,f/IF P=154 kips

,/." (I)

20"

..,:;

///

~----~r- ~ P=300kips

p: 2<15 kips I~ "? (2 )

(I) '/./:' i"

/p= 337 kips (M)II

----'-~---------

0.002

o

0.002

Strain 0.001

I 0Straight Bar

Strain 0.001

Note: Number within parenthesis indicates cycle

M = monotonic loading after sixth cycle

Fig. 9 Strains In Longitudinal Reinforcement of Specimen S6-2

-27-

II

tI

II

II 1

:::::

Off

set

Spl

ice

I.-{'

~3"..I

IYie

ld

0.0

1 0/()

AO?

n~

00

Jt

I,

I'

30

0f-

/,'/

,_

-

I/

"~"'--

Ip

.....---

1/r/

'<"//

.'/~

/20

0~1

I/®

//I

/.:

/

".:

/

I(//

/1/

j/,/'

100U

f:'

/1!

Lo

ad,

kips

I tv 00 I

Str

ain

Fig

.1

0T

en

sil

eS

train

sin

Tra

nsv

ers

eR

ein

forc

em

en

tin

Sp

ecim

en

S6

-2

out" when the longitudinal reinforcement was in tension. There­

fore, an outward component of thrust was generated.

End bearing of bars at the offset also contributed to force

transfer when longitudinal steel was in compression.

Severity and extent of bursting, and the load at which

bursting occurred, depended on the relative size of the offset

bars with respect to the size of the cross section. The amount

and distribution of the transverse reinforcement was also a

significant factor. Propagation of concrete spalling from end

regions into the splice depended on the amount and distribution

of the transverse reinforcement.

Bursting forces within the splice produced splitting cracks

along the longitudinal lapped reinforcement. These forces were

resisted by the transverse reinforcement. Some initial resist­

ance was also obtained from concrete cover. Lap splices with

very light transverse reinforcement failed violently with split­

ting propagating from the ends into the splice. Lap splices

with heavy transverse reinforcement failed at the offset by bar

fracture. Bar fracture was precipitated by pullout of interior

bars.

Effects of Load History

One of the main objectives ?f this experimental investiga­

tion was to determine effects of severe load reversals on

performance of tension lap splices. Performance of specimens

-29-

subjected to the loading history shown in Fig. 7 did not vary

significantly from that for specimens subjected to monotonic

tensile loading.

Figure 11 shows load versus total elongation of nominally

identical specimens subjected to different loading histories.

The hysteresis loops correspond to specimens subjected to

reversing loading and the broken lines correspond to companion

monotonic tests. Results in Fig. 11 and Table 5 show that

strength was not affected by the applied load history. However,

final elongation was slightly affected by the applied load.

Specimens subjected to monotonic loading had slightly larger

ductilities than companion specimens subjected to load reversals.

All specimens except Specimen S8-4 attained a final strength

larger than 1.25 times the calculated yield strength. Specimen

S8-4 failed by bar fracture at the offset. One of the offset

bars fractured during the first half of the fourth cycle.

Effects of Longitudinal Reinforcement

Amount and distribution of lapped reinforcement were impor­

tant factors. The larger the lapped bars relative to the size

of the cross-section, the larger the bursting forces in the

concrete, particularly at the offset end.

Specimens tested in this program show effects of bar size

and bar configuration. The main differences between S8 Speci­

mens and S6 Specimens were bar size, presence of interior bars

in S6 Specimens, and relative size of the offset with respect

-30-

_~_--4<

=~-~--Specimen S6-1

Tafof elongafion, In.-100

Load,kips

, I3.0 4.0

in.

·/00

-200 (a)

300

Load,kips

S6-3

200

100

-200 (b'

300

Load,kips

200

100

-100

-200

58 - I

2.0

Toial elongation I lfl.

3.0 4.0

(e)

Fig. 11 Effects of Load Reversals

-31-

to the cross section. Figure 4 shows the reinforcement in S8

and S6 Specimens.

Figure 12 shows Specimens S6-l and S8-l after testing.

Failure in S8 Specimens occurred at the offset except for Spec­

imen S8-3 which had very light transverse reinforcement. The

extent of bursting at the offset was more severe in S8 Speci­

mens than in S6 Specimens.

Failure in S6 Specimens, except for Specimen S6-2, was ini­

tiated by slip of interior bars. Splitting cracks appeared

along interior bars near the offset as first yield of longitu­

dinal reinforcement occurred. At very high inelastic tensile

loads, longitudinal splitting propagated from both end regions

into the splice. As loads approached ultimate, interior spliced

bars slipped, and load was transferred to corner bars which

fractured. Longitudinal splitting was not as well contained

for the interior bars as it was for the corner bars, which were

confined within corners of transverse hoops.

Effects of Transverse Reinforcement

Amount and distribution of transverse reinforcement were

critical to ductility, strength and behavior. Transverse rein­

forcement controlled longitudinal splitting and bar slip as

well as yield penetration along the spliced reinforcement. In

particular, longitudinal lapped bars located within corners of

hoops had less tendency to slip.

Figures 9 and 10 show strains in the longitudinal and trans­

verse reinforcement along a splice. Intensity of strains at

-32-

0-;<

:>m

m~~

010

<0

...

01C

_.n

iiJm

0-0

...

CD~

nO

03

"0 -::.

(a)

Ov

era

llV

iew

-S

pec

imen

S6

-1

Sp

lice

.'.'

J

(b)

Ov

era

llV

iew

-S

pec

imen

S8

-1

I w w I

Off

set

..~~_i

~,

Off

set

,

., ~~ ....,

(c)

Off

set

Reg

ion

-S

pec

imen

S6

-1(d

)O

ffset

Reg

ion

-S

pec

imen

S8

-1

Fig

.1

2S

pec

imen

sS

6-1

and

S8

-1A

fter

Testi

ng

end regions of the splice indicated that location of transverse

reinforcement is "a critical factor. It appears that closely

spaced hoops at the ends of a splice would improve ductility and

performance. Concentration of hoops at the ends would contain

splitting and loss of bond.

For the amounts of transverse reinforcement used in the

tests, reduction in the number of uniformly distributed hoops

caused only a slight reduction in load carrying capacity of the

tension lap splice. Comparison of Specimens S6-2 and S6-3 in

Table 5 shows that a 50% reduction in transverse reinforcement

required by the UEC Code for seismic conditions caused a reduc­

tion of only 15% in strength of the splice. Similar effects

were observed in monotonically loaded Specimens S6-1 and S6-4.

Comparison of Specimens S8-1 and S8-3 shows that an 83%

reduction in transverse reinforcement caused a reduction of

only 15% in strength for monotonically loaded Class C tension

laps. Similar comparisons for Specimens S8-2 and S8-4 indicate

a 20% reduction for a 50% reduction in hoops.

Although reduction in transverse reinforcement did not sig­

nificantly affect strength, it did affect behavior and ductility.

Figure 13 shows Specimens S6-2 and S6-3 after testing. Specimen

S6-2,' which had 100% of the required transverse reinforcement,

failed by bar fracture at the offset. Specimen S6-3, which had

50% of the required transverse reinforcement, failed by slip of

the inner bars. The corner bars fractured after the inner bars

pulled out.

-34-

Splice

(a) Specimen S6-2

Splice

(b) Specimen S6-3

Fig. 13 Specimens S6-2 and S6-3 After Testing

Reproduced frombest available copy.

-35-

Figures 14 and 15 show Specimens S8-l and S8-3 after test­

ing. Specimen S8-l, which had 100% of the required transverse

reinforcement, failed by bar fracture. Specimen S8-3, which had

17% of the required seismic confinement reinforcement, failed by

slip of the lapped reinforcement. Longitudinal bars pulled out

at the straight end of the splice. Figures 13, 14, and 15 show

that the extent of damage in S6 Specimens was not as severe as

that in S8 Specimens, particularly at the offset end.

Figure l6a shows applied axial load versus total elongation

envelope for Specimens S6-2 and S6-3. As expected, Specimen

S6-2, which had more hoops, attained a higher ductility than

Specimen S6-3. A similar trend was observed for Specimens S6-1

and S6-4, as shown in Fig. 16b, and Specimens 88-2 and S8-4, as

shown in Fig. l6c.

-36-

Fig. 14 Specimen S8-1 After Testing

Reproduced frombest availa ble copy.

-37-

Fig. 15 TestingS8-3 AfterSpecimen

d d fromRepro u~iable copy.be5t av, da~1:::..::.- _

-38-

400

Load,kips

--

Specimen S6-3

L - Specimen S6-2

( a )

1.0 2.0 3.0 4.0

400

Load,kips

Total elongation, in.

Specimen S6-1

Specimen S6-4

( b )

oo!:.------~-----...L-------1.-----....l1.0 2.0 3.0 4.0

Total elongation, in.

400

Load,kips

200

_- -r-/----- "-Specimen

//

//

S8-4

Specimen 58-2

( c )

0 11::------,,-.1.,-,:-----__4.-1------'~ --'Io 1.0 2.0 3.0 4.0

Total elongation, in.

Fig. 16 Effects of Transverse Reinforcement

-39-

SUMMARY AND CONCLUSIONS

This report describes results of a test program to evaluate

effectiveness of tension lap splices under inelastic stress

reversals. Results of eight tests are included.

variables considered were amount and configuration of lapped

reinforcement, amount of transverse reinforcement, and load

history.

Specimens were designed as Class C tension lap splices

according to the 1977 ACI Building Code. (1) Lapped reinforce-

ment included No.6 and No. 8 bars. Specimens with No.6 and

No. 8 bars were termed S6 Specimens and S8 Specimens, respec­

tively. Four specimens of each series were built and tested.

In each case 100% of the reinforcement was spliced at the same

location.

Following common practice, lapped bars were offset at one

end of the lap over a length equal to six times the bar diameter.

The amount of transverse reinforcement varied from that required

for seismic design conditions to maximum column tie spacing.

Four tests under tensile monotonic loading and four tests under

reversing loading were made. Reinforcement with a nominal yield

of 60,000 psi (414 MPa) and concrete with a nominal compressive

strength of 3,000 psi (20.7 MPa) were used in design of the

specimens.

Tests were performed on column elements that had cross-

sectional dimensions of 12x12 in. (305 x 305 mm) and a length

of 96 in. (2.44 m). Axial loads were applied to the column

-40-

through two end blocks using hydraulic rams. Series S6 Speci­

mens had eight No.6 bars with a 33 in. (0.84 m) lap splice.

Series S8 Specimens had four No.8 bars with a 60 in. (1.52 m)

lap.

Specimens were instrumented to measure loads, axial elonga­

tions, crack widths, and longitudinal and transverse steel

strains.

The following observations are based on the eight tests:

(1) Specimens designed as Class C lap splices with trans-

verse reinforcement for seismic conditions according

to the 1976 UBC Code (2) performed very well under

monotonic and reversing loads. Strength of these

specimens varied from 92% to 94% of average tensile

strength of the longitudinal reinforcement. Strengths

varied from 169% to 174% of the design yield load.

(2) Strength of specimens was not affected significantly

by load history.

(3) All specimens experienced large post-yield elongations.

Specimens subjected to monotonic loading exhibited

slightly larger ductility than those subjected to load

reversals.

(4) The use of offset bars at the end of the lap caused

severe local distress. The extent of damage was larger

in specimens with large bars. Moreover, this detail

may lead to low cycle fatigue failure in the reinforce-

ment in structures under reversing loads.

-41-

(5) In an eight bar arrangement with 100% of the bars

spliced, slip of interior bars controlled capacity.

Splitting cracks first appeared along interior bars at

the offset and then propagated from both end regions

into the splice. They were first obser~ed as the load

approached yield. As the tensile load approached

ultimate, interior spliced bars slipped and transferred

load to the corner bars. Longitudinal splitting was

not as well contained for interior bars as it was for

corner bars.

(6) Transverse reinforcement was effective in controlling

longitudinal splitting and bar slip as well as yield

penetration along the spliced bars.

(7) The amount and distribution of transverse reinforcement

have a critical effect on ductility, strength and

behavior of lap splices. An insufficient amount of

hoop reinforcement at the ends of a splice can lead to

reduction in ductility and strength, and to severe

damage within the splice region. From measurements of

strains in transverse reinforcement, it appears that

closely spaced hoops at the ends of a splice would .

improve performance. Hoops at the ends of the splice

were more effective than interior hoops in resisting

splitting and bursting of the concrete.

(8) If the design criteria for lap splices is strength,

the 1976 UBC Code requirements for confinement in

seismic regions are conservative with regard to amount

-42-

of transverse reinforcement around the splices. In S8

Specimens, which had a four corner bar arrangement, a

reduction of 83% in the required transverse reinforce­

ment caused a reduction of only 15% in strength. In

S6 Specimens, which had an eight bar arrangement, a

reduction of 50% in the required transverse reinforce­

ment caused a reduction of 15% in strength.

(9) Transverse hoops must be in contact with longitudinal

bars to be effective.

-43-

ACKNOWLEDGMENTS

This investigation was carried out in the Structural Devel­

opment Department of the Portland Cement Association, Dr. H. G.

Russell, Director. Fabrication and testing of specimens were

performed by B. J. Doepp, B. W. Fullhart, W. Hummerich, A. S.

Evans, W. H. Graves.

J. Julien assisted with preparation of the manuscript.

E. M. Ringquist provided editorial assistance.

The research was supported by the National Science Founda­

tion under Grant No. ENV 77-15333 and by the Portland Cement

Association. Any opinions, findings, and conclusions expressed

in this publication are those of the authors and do not neces­

sarily reflect the views of the National Science Foundation.

-44-

REFERENCES

1. "Building Code Requirements for Reinforced Concrete (ACI318-77)", American Concrete Institute, Detroit, 1977, 102 pp.

2. "Uniform Building Code", 1976 Ed., International Conference ofBuilding Officials, Whittier, California, 1976, pp. 300-406.

3. Orangun, C. 0., Jirsa, J. 0., and Breen, J. E., "A Reevalu­ation of Test Data on Development Length and Splices",Journal of the American Concrete Institute, Proc. Vol. 74,No.3, March 1977, pp. 114-122.

4. Arthur, P. D., and Cairns, J. W., "Compression Laps of Rein­forcement in Concrete Columns", The Structural Engineer,No.1, Vol. 56B, March 1978, pp. 9-12.

5. Betzle, M., "Bond Slip and Strength of Lapped Bar Splices",American Concrete Institute, SP 55-20, Douglas McHenry Inter­national Symposium on Concrete and Concrete Structures, 1978,pp . 49 3- 514 .

6. Ismail, M. A. F. and Jirsa, J. 0., "Behavior of AnchoredBars Under Low Cycle Overloads Producing InelasticStrains", Journal of the American Concrete Institute, Proc.Vol. 69, No.7, July 1971, pp. 433-438.

7. Hassan, F. M. and Hawkins, N. M., "Effects of post-YieldLoading Reversals on Bond Between Reinforcing Bars andConcrete", Report SM 73-2, Department of Civil Engineering,University of Washington, March 1973, 244 pp.

8. Popov, E. P., "Mechanical Characteristics and Bond of Rein­forcing Steel Under Seismic Conditions", Proceedings, Work­shop on Earthquake-Resistant Reinforced Concrete BuildingConstruction, Berkeley, July 1977, pp. 658-682.

9. Brown, R. H. and Jirsa, J. 0., "Reinforced Concrete BeamsUnder Load Reversals", Journal of the American ConcreteInstitute, Proc. Vol. 68, No.5, May 1971, pp. 380-390.

10. Hawkins, N. M., "Development Length Requirements forReinforcing Bars Under Seismic Conditions", Proceedings,Workshop on Earthquake-Resistant Reinforced Concre~e

Building Construction, Berkeley, July 1977, 696-704.

11. Oesterle, R. G., Fiorato, A. E., Johal, L. S., Carpenter,J. E., Russell, H. G., and Corley, W. G., "EarthquakeResistant Structural Walls - Tests of Isolated Walls",Report to National Science Foundation, Portland CementAssociation, Skokie Nov. 1976, pp. 315. (Available throughNational Technical Information Service, U.S. Department ofCommerce, 5285 Port Royal Rd., Springfield, Va., 22161,NTIS Accession No. PB271467.)

-45-

APPENDIX A - ADDITIONAL REFERENCES

1. ACI Committee 318, "Commentary on Building Code Requirementsfor Reinforced Concrete (ACI 318-77)", American ConcreteInstitute, Detroit, 1977, 102 pp.

2. ACI Committee 408, "Bond Stress - The State of the Art",Journal of the American Concrete Institute, Proc. Vol. 63,No. 11, November 1966, pp. 1161-1189.

3. ACI Committee 408, "Opportunities in Bond Research", Journalof the American Concrete Institute, Proc. Vol. 67, No. 11,November 1970, pp. 857-867.

4. ACI Committee 408, "Interaction Between Steel and Concrete",Journal of the American Concrete Institute, Proc. Vols. 76and 77, No.1 and 2, January and February 1979.

5. Bresler, B. and Bertero, V. V., "Behavior of ReinforcedConcrete Under Repeated Load", Journal of the StructuralDivision, ASCE, Vo. 94, No. ST6, June 1968, pp. 1567-1590.

6. "Building Code Requirements for Reinforced Concrete (ACT318-71)", American Concrete Institute, Detroit, 1970, 78 pp.

7. Chinn, J., Ferguson, P. M., and Thompson, J. N., "LappedSplices in Reinforced Concrete Beams", Journal of theAmerican Concrete Institute, Proc. Vol. 52, No.2, October1955, pp. 201-213.

8. Colaco, J. P. and Siess, C. P., "Behavior of Splices inBeam-Column Connections", Journal of the Structural Divi­sion, ASCE, Vol. 93, No. ST5, October 1967, pp. 175-193.

9. Ferguson, P. M., "Small Bar Spacing or Cover - A Bond Prob­lem for the Designer", Journal of the American ConcreteInstitute, Proc~ Vol. 74, No.9, September 1977, pp. 435-439.

10. Ferguson, P. M. and Breen, J. E., "Lapped Splices for HighStrength Reinforcing Bars", Journal of the American ConcreteInstitute, Proc. Vol. 62, No.9, September 1965, pp. 1063­1077.

11. Goto, Y., "Cracks Formed in Concrete Around Deformed Ten­sion Bars", Journal of the American Concrete Institute,Proc. Vol. 68, No.4, April 1971, pp. 244-251.

12. Ismail, M. A. F. and Jirsa, J. 0., "Bond Deterioration inReinforced Concrete Subject to Low Cycle Loads", Journal ofthe American Concrete Institute, Proc. Vol. 69, No.6, June1972, pp. 334-343.

A-I

13. Lutz, L. A. and Gergely, P., "Mechanics of Bond and Slip ofDeformed Bars in Concrete", Journal of the American ConcreteInstitute, Proc. Vol. 64, No. 11, November 1967, pp. 711­721.

14. Nilson, A. H., "Internal Measurement of Bond Slip", Journalof the American Concrete Institute, Proc. Vol. 69, No.7,July 1972, pp. 439-441.

15. Orr, D. M. F., "Lap Splicing of Deformed Reinforcing Bars",Journal of the American Concrete Institute, Proc. Vol. 73,No. 11, November 1976, pp. 622-627.

16. Perry, E. S. and Jundi, N., "Pullout Bond Stress Distribu­tion Under Static and Dynamic Repeated Loadings", Journalof the American Concrete Institute, Proc. Vol. 66, No.5,May 1969, pp. 377-380.

17. Pfister, J. F. and Mattock, A. H., "High Strength Bars asConcrete Reinforcement Park 5. Lapped Splices in Concen­trically Loaded Columns", Journal of the PCA Research andDevelopment Laboratories, Vol. 5, No.2, May 1963, pp. 27­40. Also reprinted as PCA Development Department BulletinD63.

18. "Reinforcing Bar Splices", Third Ed., Concrete ReinforcingSteel Institute, Chicago, 1975, 30 pp.

19. Rezansoff, T., Bufkin, M. P., Jirsa, J. 0., and Breen, J.E., "The Performance of Lapped Splices Under Rapid Loading",Research Report 154-2, Center for Highway Research, TheUniversity of Texas at Austin, January 1975, 92 pp.

20. Rice, P. F., "Rebar Splices: Cutting Costs, AvoidingErrors", Civil Engineering - ASCE, Vol. 47, No.8, August1977, pp. 73-74.

21. Somerville, G. and Taylor, H. P. J., "The Influence of Rein­forcement Detailing on the Strength of Concrete Structures",The Structural Engineer, Vol. 50, No.1, January 1972, pp.7-19.

22. Tepfers, R., "A Theory of Bond Applied to Overlapped Ten­sile Reinforcement Splices for Deformed Bars", Publication73:2, Division of Concrete Structures, Chalmers Universityof Technology, Goteborg, 1973, 328 pp. -

23. Thompson, M. A., Jirsa, J. D., Breen, J. E., and Meinheit,D. F., "The Behavior of Multiple Lap Splices in Wide Sec­tions", Research Report 154-1, Center for Highway Research,The University of Texas at Austin, January 1975, 75 pp.

A-2

24. "Uniform Building Code", 1976 Ed., International Conferenceof Building Officials, Whittier, California, 1976, pp. 300­406.

25. Untrauer, R. E. and Warren, G. E., "Stress Development ofTension Steel in Beams", Journal of the American ConcreteInstitute, Proc. Vol. 74, No.8, August 1977, pp. 368-372.

A-3

APPENDIX B - TEST RESULTS

In this section results for each test are presented in

detail. Specimen behavior during testing is described and

supporting data are presented.

The following results are included:

a. Load vs. axial elongations

b. Crack patterns and distribution of crack widths.

c. Load vs. strain, and strain distribution along longi­

tudinal reinforcement.

d. Load vs. strain of transverse reinforcement.

The test program and results are summarized in Tables 2 and 5,

of the main text.

S6 Specimens

Four Specimens S6-l, S6-2, S6-3, and S6-4 were built using

No.6 bars as longitudinal reinforcement. Controlled variables

included type of loading and amount of transverse reinforce­

ment. Specimens S6-l and S6-4, tested under monotonic loading,

were companions to Specimens S6-2 and S6-3, which were tested

under load reversals.

Specimens S6-l, S6-2, S6-3, and S6-4 differed in amount of

lateral reinforcement. Specimens S6-l and S6-2 were built with

confinement according to seismic provisions of the 1976 Uniform

Building Code. (2) To investigate effects of amount of

transverse reinforcement, Specimens 36-3 and S6-4 were built

with 50% of the code required transverse reinforcement.

B-1

Details of specimens are given in Fig. 4b and Table 2. The

splice length was 33 in. (0.84 m). Material properties are

summarized in Tables 3 and 4. Calculated and observed yield,

and maximum loads and modes of failure, are summarized in

Table 5.

Specimen S6-l

Plots of load versus elongation are shown in Fig. B-1.

Initial and final crack patterns are shown in Fig. B-2.

Cracking was first observed at a load of 47 kips (209 kN).

Distribution of initial cracks was uniform over the column

portion of the specimen. As loading progressed, cracks at the

ends of the lap were observed to grow wider than those at other

locations. Widest cracks were observed at the location of the

offset. Measured crack widths are presented in Fig. B-3.

Initial yielding of the longitudinal reinforcement was

indicated by strain gage measurements at a load of 225 kips

(1001 kN). Full yielding was measured at 246 kips (1094 kN).

This is evident in the load versus elongation curves shown in

Fig. B-l.

Measured strains in the longitudinal reinforcement are

plotted in Figs. B-4, B-5, and B-6. The plot of strains along

corner bars, as shown in Fig. B-6, indicates a consistent

"anti-symmetric" distribution along each bar in the splice. As

load increased the strain distribution tended to become linear.

At a load of 200 kips (890 kN) spalling of concrete cover

was observed at the offset as a result of bursting forces that

developed. This was also evident from measured strains in

B-2

load,I<ips

Elongation. mm

400 rO .:.;10;- -=,20:=.-. ---. Load,

I<N

300

200

100

o

DeDr 2 X 1500

DeDr l - - ---'XX--'" .,. ==-- ' 15Ci)i- 3-'-'1000

X Gage out

500

o 0.2 0.4 0.6 0.8

Efonga tioo, in.

Pot I

124" D./5m)

0 C DeDr I DeDr 2 DeDr 334.5" 1 33" I 34.5" I

I = ~ = =/ I

0 0 10.88ml . /084ml (0.88ml ISplice

Toto I E.longation, mm

load, 400 0r- ~-----"'5~0'-----~----_..!'10e;.0:!.-----_,k. ips

__--.... PoLl

300

200

100

-~Cracking

Load.

kN

1500

1000

500

o l..- -"" .-i- -'-- --' ..JO° 1.0 2.0 3.0 4.0 5.0

Total Elongation I in.

Fig. B-1 Axial Deformations of Specimen 56-1

B--3

tJ:J I ot:>-

Splic

e(O

ffset

i-I1

Jt-j

(a)

In

itia

lC

rack

Patt

ern

Spli

ceIO

ffset

,......

....,

(b)

Fin

al

Cra

ck

Patt

ern

Fig

.B

-2C

rack

Patt

ern

so

fS

pecim

en

S6

-1

CONSTRUCTIO~J TECHNOLOGY LABORl\fORiES

Oat8 _

A Division of the PORTLAND CEi'v1ENT ASSOCIAT!Of\JOld Orchard Road, Skokie, Illinois 60076/ Area Code 312/966-6200

Title _

Project Sheet of _

Initials _

Checked Dat8 Revised Oate _

ttl I U1

Cra

ck

Wid

th,

in.

0.2

1'\

/\

"I

\"

I\

0.1

f-"

I\

"I

\\.

I,

I,

I,

I"

I"

I__

,I

ot=

-:--

---:---:---",

I--_.::.::~--

----

"'<

'

-===

====

==="

:...._

-'"

Cra

ck

5.0

Wid

th,

mm

p::

311

Kip

s(1

38

3kN

)

P=

24

7K

ips

(10

98

kN)

p::

22

9K

ips

(101

9kN

)P

::15

2K

ips

(67

6k

N)

p=

61K

ips

(271

kN)

..--

----

--.......

.---

--

-,....'

--

----

----

:"'7

\,------

-------

Off

se

tI..

...!

33

"(O

.84

m)

Fig

.B

-3M

easu

red

Cra

ck

Wid

ths

inS

pecim

en

S6

-1

Load, 400 Load,

kips kN

GI GZ

1500

300

G3

1000

ZOO

500[00

0 0

0 2500 5000 7500 [0000 [2500

Strain, millionths

II"

Gt

II" f II" J OffsetG5

j!- ! : ~bor

! \ ! i ! !

'~SlraightG3 G2 GI

bar Splice

Load, 400 Load,

\( ips I kN

G4 G5

JI500G6 I

300

11000

200I

II

I[00

~~0a 2500 5000 7500 10000 [Z500

Strain, millionths

Fig. B-4 Load versus Steel Strains in Corner Barsfor S':leciDen S6-1

3-6

G9

GIO

I',

I,

/"

""

""

""

""

""

""

,I

I,

I')

G8

G7

Lo

ad

,ki

ps

40

0I

I(

,I

,t

G7

Lo

ad,

kN

50

0

15

00

10

00

G8

GIO

12

50

0

G9

1000

0

-_

.-.-.-_

.--

-----

--'

-_.

75

00

50

00

-----------

-_.-

_.-

_.-

.

25

00

/If'

oI

10

II

or

II

15

00

0

20

0

100

30

0

tel J -J

Str

ain

Im

illio

nth

s

Fig

.B

-5L

oad

vers

us

Ste

el

Str

ain

sin

Inn

er

Bars

for

Sp

ecim

en

S6

-1

- Yield Level

0.002

0.00/ Strain

0.001 Stra in

o

o

0.002

- Yield Level

1 f I ! I IIII

I I ! ! I I ! II

20Distance, in.

10

---------7------

<:'P=350 kip s/ (1557kN) /

/ //

P=229 kips/

/ !~O~~

II __?~P=213 ki"ps

//" (947 kN)

//I ~ -----.::'-P-=-12-1 kip s

(538 kN)

o 3,Q

//P= 121 kips /;/ /

{538 k~ _.,;::.:/

r--;:-- /P=213kiPJ/Y I(947~ /

\,/ / P=350 kips

0.002 //A / (1557 kN)

/ / P=229 kiP~ ,__ L _ JI019~N.2.. _

o

0.002

0.001

Strain 0.001

Strain

I I I I I I I I I I II I I I I I I I I I I I I I I I I !I

Fig. B-6 Strain Distribution Along Corner Spliceof Specimen S6-1

transverse hoop reinforcement. Figure B-7 is a plot of applied

load versus strains in selected hoops. Measured strains in Gage

No.2, on a hoop at the offset, indicate that this hoop was

effective almost from the onset of loading. The hoop instru­

mented with Gage No.1 was ineffective throughout the test.

This hoop was not in contact with longitudinal reinforcement.

Significant longitudinal splitting cracks were observed at

the ends of the splice and along the interior bars at a load of

326 kips (1450 kN). Hoop strains in Fig. B-7 indicate that

transverse expansion began at an earlier load stage, but was

not visually evident. As load approached ultimate, interior

spliced bars slipped and transferred load to corner bars. At a

load of 357 kips (1588 kN), corner bars fractured at the offset

bend. It was apparent that longitudinal splitting was not as

well contained for interior bars as it was for exterior bars.

This is attributed to the fact that the exterior bars were

located within the corners of transverse hoops.

The specimen reached a capacity equivalent to 94% of its

calculated strength. Calculated yield and maximum loads, based

on average reinforcement properties, are listed in Table 5.

Specimen 56-2

Plots of load versus elongation are shown in Fig. B-8.

Initial and final crack patterns are shown in Fig. B-9.

Cracking was first observed at a load of 47 kips (209 kN).

Initial cracking was uniform. Cracks at the ends of the splice

were observed to grow wider than those at other locations.

B-9

Loa

d,

kN

50

0

1500

10

00

2

Sp

lice

dS

tee

l

3

2

45

I1

/7,-

)001

• \1/

r\!I

'\i

\ ~\ \

\

Lo

ad

,4

00

I

iii5

kip

s

30

0rIlf / It I:

20

0If!

'lJ

j I f....

0

10

0

o1

00

02

00

03

00

04

00

05

00

06

00

0

Str

ain

,m

illio

nth

s

Fig

.B

-7L

oad

vers

us

Ho

op

Str

ain

sfo

rS

pec

imen

S6

-1

Load.l\ips

300

200

100

-100

Deor CD

0.5 La

Relative elonqotion. in.

(a)

300

\.ocor C?)

10

(b)

-200 -200

Deer 2 , oeeT~3I .33' ,34.5" II

<= S

Deer (4)102" ( 2.59 m) .. I:-

o~ .=~/ :. J t

o (O.88m) j(O.84m) (O.88m) I I'-- ..J Spite. .

o

Load.kips

300

200

a i

°1I

-100 I

I

Load,lei".,

300

200

1.0

elonqation~ in.

=100

(e)

2.0 3'0

Totof elongation, in.

( d )

-200 -200

Fig. B-3 Axial Deformations of Specimen 86-2

B-ll

tJ:) ! }--'

N

/ ~~

I.....

Sp

lice

I

(a)

Init

ial

crac

kp

att

ern

(b

)F

ina

lc

rac

kp

att

ern

Off

se

t

~~ "

Fig

.B

-9C

rack

Patt

ern

so

fS

pecim

en

S6

-2

Figure B-lO shows crack widths at the peaks of tensile loading

cycles. As expected, inelastic load reversals caused progres­

sive permanent deformations and subsequent growth of the

specimen.

Full yield load and ultimate strength were identical to

those measured in monotonic test 56-I. Full yield load was 246

kips (1094 kN) and load capacity was 357 kips (1588 kN).

Measured strains in longitudinal reinforcement are shown in

Figs. B-ll, B-12, B-13, and B-14. Strains along the inner bars

shown in Fig. B-14 indicate an "anti-symmetric" distribution

along each bar in the splice. As tensile loads increased the

strain distribution became linear. A similar strain distribu­

tion in the longitudinal reinforcement was observed in Specimen

56-I, as shown in Fig. B-6. Yield "penetration" within the

lapped bars varied from 1/3 to 1/2 of the splice length.

Figures B-15 and B-16 show measured strains in transverse

reinforcement. Strain readings in hoop No.1, which was located

at the edge of the offset, indicates that transverse expansion

began from the first load stage. Strains in hoop Nos. 1, 2,

and 3, which were at the offset end of the splice, indicate that

these hoops were more effective than other hoops along the

splice. The closer the hoop to the ends of the splice, the more

effective it was, particularly at the offset end. This is clear

from the sequence of yielding in the hoops. Hoops 1, 2, and 3

yielded as applied tensile load reached 307 kips (1366 kN), 314

kips (1397 kN), and 346 kips (1539 kN), respectively.

Strains in the hoop at the edge of the straight end of the

splice indicated that this hoop was not as effective as those

B-13

Tensile load = 242 kips (1076 kNl

in cycles I, 2, 3, and 4

Crockwidth,mm

2.0

1.0

'\I.I \I ~

: \I \\ :1\ \ (4)X'-', I. \1

\. i :/ ',\(31" ' Ii 1\ I

~'~ '\\. il/ \~21

/ ~' [II \, II \I {II

OL-.----.......:::.~~---.....JO

0.100

0.050

Crackwidth,in.

____________~:_=====_-=_='_=--==_~_:-=-=:_=-~-==='="----.JI - _

------------------ -------'"::"'"

I. .1\33" (O.84m) I '--Offset

( a I Tensile load = 242 kips ( 1076 kN )

0.250

Crackwidth,in.

0.125

Crock5.0 width,

mm

Tension load = 302 kips (1343 kN)in cycles 2, 4, and 4

M = monotonic loading after

cycle 6

OL----~=~--'----.....JO

--------------- - ~---=-_-=..::="'~---=- ...-----------------

r=======~I-~-=-~-~-=-~$~=====----------

• 33" (0,84;) "'-Offset

( b) Tensile load 302 kips (1343 kN)

Fig. B-10 Measurpd Crack Widths in Specimen 56-2

B-14

Load, Load,kips kips

300 300

"GI G2

200 200

100 100 Gage G3 Out

5 00 5000

Strain, millionths Strain, millionths

-100 -100

-200 -200

I"II" II"

9" IG6"':4...1 ..

IGS: : : : : : : 4('~; 'IG3 G2 GI

Splice

Loads,kips

3°°1G5

200

0: Gage out

Strain, millionths

100

)

Loads,kips

300

200

-100

5000

4

Strain, millionths

Loads,kips,300

-100

Fig. B-ll Load versus Steel Strains inCorner Bars for Specimen S6-2

B-15

Lo

ad,

Loa

d,

kips

kipb

30

03

00

G7

I/}G

8

20

02

00

10

010

0

50

00

Sif

oin

,m

illio

nths

-20

0

-'0

0

o-Il

Io

-100

-20

0

Lood

ki~S

'I

Loa

d,

OO

Tki

ps

"-3

00

ifjf

"2

00

100

69

}XG

oge

out

°01~_I_

_I

L!S

ifo

in,

100

Loa

d,

kips

30

0

-'0

0

-20

0

50

00

Stf

oin

,m

illio

nths

O-.f----<

-10

0

-20

0

0"I

015

00

0S

lrai

n,

mill

ionl

h$

-10

0

-20

0tJ

j I f-'

m

!"."'~

i',

,,~;

II

;1&'I

II':C:="~

,,,,

'IG

9G

BG

7

Sp

lici

° 0'

lI_

!__

If1

1/1

....-;/

I/

~-'--

-100

·

10

0

20

0

Lo

ad,

kips

30

0

-20

0

Fig

.B

-12

Lo

adv

ers

us

Ste

el

Str

ain

sin

Inn

er

Bars

for

Sp

ecim

en

S6

-2

1kip = 4.448 kN

'* Numbers within parenthesesindicate cycle

I I II I ! I I

Strain

- Yield Level

Strain

0.001

0.001

0.002

.......

- ---- - ---7-' ,- --• ,*. • I

P =337 kips (M~/ I ,'P= 245 kips/,; I (I)

/ ,,/" I.' /' I

/ . I...~P=300 kips

//- -~~- I

/ /1///(/ / '-P-=-15-4-k-jp-s""'":(-I)::-'

if~

Distance, in.

Gages Out

0.001

0.001

0.002

Strain

Strain

I I I

0.002I /

I .________ Ll _0.002

- Yield Level

Fig. B-13 Strain Distribution AlongCorner Splices of Specimen S6-2

B-17

1kip == 4.448 kN

* Numbers within parenthesesindicate cycle

j]

aIii I I J i I ! \ ! I ! I I J I I 1 I I I

Strain

- Yield Level

0.002

o

0.001

Strain

- Yield Level

0.001

0.002

I i II I I

I20

Distance, in.

- --- - - --.T -71----p= 337 kips (Mi" /' J P=300 kips (2)

.. /' I

/. ..././ ......... ..../~-P:245 kips (i)

;(5/p/ P= /54 kips (I)

/;/'

0.001

oI I I I

0.002

/'

P== 154 kips "

0.001 i7'P =245 kj';'~/----/.

J-- ~.I .

1I ......... P=300 kipsI r .'

0.002 ",' ./p = 337 kipsI •

- ----~~-----------

Strain

Strain

I I I

Fig. B-14 Strain Distribution AlongInner Splice of Specimen S6-2

B-18

Load,kips

300

200

-/00

Strain, millionths

-200

d

Spliced Sleel(0.30m) d (0.25m)

12" /.//,. /0"

(0.2.5 m)10"

SlrOI(~11t end

I ,.: . II . • II I I

, I

I -T / I I I j I I f I I ! I -1

= ill tIl I I I I [J I II .li1' I I I I<h',1' 1- \~' I

1/

~ ~l~ 2)~~OffsetI

5 ..n

load,kips

300

200

-100

Slroin, millionths

-200

Fig. B-15 Load versus Hoop Strains forSpecimen 56-2: Gages 1 and 2

B-19

d

4

°Offif-------'-----I1000

Strain, mfllionfh,

300

roo

-100

Load,kips

-200 •

Spliced Steel(a.30m} d (0.25 m)

12" / /I. 0 10":-"

3 a

3

2 00

, . .; , 1;7 I

I i / I

I I L ! I I l I I I I=- I'! I III I I I., f ~ ',I I I Ifl

I I I 'to IIf \

~ ~~~OffsetI

( ® 0)3 en

Strain, millionths

{025m}

10"

-100

-200

Slraight end

-100 -\00

Load,kip.

300

200

100

Load,kip.30

a 2000Strain, millionth'S

-200 -200

Fig. B-16 Load versus Hoop Strains forSpecimen S6-2: Gages 3, 4, 5,and 6

B-20

at the offset end, and that this hoop became effective after

yielding of the longitudinal reinforcement occurred. Since

both ends of the splice are practically identical except for

the presence of the offset and the relative position of the

lapped bars, the main source of transverse expansion within the

splice is the internal moment induced by the eccentricity of

the lapped bars. Offsetting bars causes bursting forces at the

offset-end and concentrates bursting of the concrete in a small

region.

Bursting or radial forces are resisted by concrete cover,

hoop reinforcement, and dowel action of the exterior corner

bar. At the offset end, radial forces are resisted mainly by

hoop reinforcement. The contribution of the concrete cover at

the offset-end is reduced by the bursting forces induced by

offsetting of bars. This explains the high concentration of

damage at the offset end region of the splices.

splitting cracks were first observed at the ends of the

splice and along the interior lapped bars at a load of 232 kips

(1032 kN) during first half cycle. This is also the load at

which yielding of interior lapped bars was first observed.

Specimen S6-2, after being SUbjected to six load reversals,

reached a load capacity identical to that of Specimen 56-1.

However, the final mode of failure was by bar fracture. All

eight bars fractured at the offset-end. Calculated yield and

maximum loads are listed in Table 5.

B-21

Specimen S6-3

The main difference between Specimen S6-3 and previous

specimens was the amount of transverse reinforcement. Specimen

S6-3 had 50% of the hoop reinforcement that was used in

Specimens S6-l and S6-2. Specimen S6-3 was subjected to load

reversals.

plots of load versus elongation are shown in Fig. B-17.

Initial and final crack patterns are shown in Fig. B-18.

Cracking of the concrete was first observed at a load of

46 kips (205 kN),. Figure B-19 shows crack widths along the

splice. The magnitude and distribution of cracks were similar

to those observed in Specimens S6-l and S6-2. As in Specimen

S6-2, load reversals caused progressive permanent deformations.

Figures B-20, B-2l, and B-22 show strains along the spliced

reinforcement. Figure B-23 shows strains along the corner bars

at load stages of the first two cycles. The anti-symmetry and

the tendency of the strain distribution to become linear are

apparent. Yield penetration was eventually equivalent to about

2/3 of the splice length.

Strains in hoop reinforcement are shown in Figs. B-24 and

B-25. The effectiveness and sequence of yielding of the hoop

reinforcement were similar to those observed in Specimen S6-2.

As in Specimen S6-1, hoop No. 1 was not effective. Hoops at

the ends of the splice were effective, particularly those at

the offset end.

Splitting cracks were first observed at the offset end of

the splice and along the interior lapped bars at a tensile load

of 233 kips (1036 kN) during the first cycle. These splitting

B-22

Load,Load,kips

kips 300300

200 200

100 100

I

B 1.0

Ielonqotion, in.

I -100-100

-200 -200

DeDT@., (102 2.59m)

0 oj ocoTffi I oeor6:I1345 I 33' I 345" iJ

:::::s S!'

0 0 to. 88m} (~4m) (0.88m)Splice

Load,!cios

300

200

-100

in.

-200

Fig. B-17 Axial Deformations of Specimen S6-3

B-23

tJj I N ~

Sp

lice

1(of

tset

I"I

\ \\

(a)

Init

ial

crac

kp

atte

rn

(b

)F

inal

crac

kp

att

ern

Fig

.B

-18

Cra

ck

Patt

ern

so

fS

pecim

en

S6

-3

Tensile lood = 248 kips (1103 kN)

in cycles I, 3, and 5

Crockwidth,mm

50(316(S~\

. \.I \

y(SJ / iI \ I i

1.0 //),..-{31 .I i 2.S

A'\\ I \- '\ .1\.

0.2Crockwidth,in.

--------__ -!=--=~==-=-=_-=_=-=-=:_=_::-__--:-::-::-=-===-=.J _

----------------~~===~~~=~~===,--------

\t-.....----........~j Offset

, 33" {0.84m .

{a 1 Tensile load = 248 kips (1103 kN)

Crack 0.2width,in.

0.\

Crackwidth,mm

Tensile laod = 304 kips (I352 kNI

in cycles 2, and 4

----------------~~~-~~----------------

- - -- - --------- -~~-=--=-..='"-==----------- -------

133" (0.84m) I Offsel

(b) Tensile load =304 kips (1352 kN)

Fig. B-19 Measured Crack Widths in Specimen S6-3

B-25

Load, Load,kips kips

300 300

GI

200 200

0-1''-----------j'---:..--------/10,000 20,000

Strain, millionths

100

5000Strain, millionths

100

-100 -100.

-200 -200

I)

II" " ",'~ 1!"~-4-,-11_•.J .. ':J -iI IG5 G6L! i 'E ! ; ,::::.::r:C:====:::::::lG3 G2 GI t

Splice

Load,kips

300

-100

30,000

-200

Fig. B-20 Load versus Steel Strains in Corner Barsfor Specimen S6-3: Gages Gl, G2, and G3

B-26

Load,kips

300

200

G4

5000

Load,kips

300

200

G5

100

O......~----io 5000

Strain, millionths Strain, millionths

-100 -100

-200 -200

J

Load,kips

30

200

-100

1-200 .....

r II"

L'G3 G2.

Fig. B-2~ Load versus Steel Strains in Corner Barsfor Specimen S6-3; Gages G4, GS, and G6

B-27

Gag

eG

7D

amag

edD

uri

ng

Test

Lo

ad

,ki

ps 30

0

G8

20

0

100 °o

f5

00

010

.boo

Sir

oin

,m

illio

nth

s

-10

0

-2

0J

Loa

d.ki

ps 30

0

Str

oin

,m

illio

nth

s

-10

0'-

-20

0

10:0

00

txJ I tv coL

oad

,L

oad

,L

oad

,ki

pski

pski

ps

30

0...

•

'O°ff

30

0-

GIO

Gil

i..J

I/G

12

20

02

00

200-

100

10

0

0.:

50

00

0 05d

oo

'1-

Str

oin

,m

illio

nlh

sS

troi

n.m

illio

nths

Str

oin

,m

illio

nth

s

-'''I-1

00

-10

0

-20

0-2

00

-20

0

II"

II"

,,"

1-"!~IO

~I;II

"IGI2

2'

/I

IIIii1i

!:E

.§'

iI

II

,I

~1

'1

11

III

II!

11

,1I~

G9

G8

G7S

plic

e

Fig

.B

-22

Lo

adv

ers

us

Ste

el

Str

ain

sin

Inn

er

Bars

for

Sp

ecim

en

S6

-3

1kip:: 4.448 kN

* Numbers within parenthesesindicate cycle

Strain

0.002

0.001

-----------;-T---- - Yield Level

I /p:: 250 kips

/• I (I) 0.002

* IP = 301 kips (2)/' /I

/ .,...1, .,..""

.(~.,.. ..../ .... _ Strain

:/ 0.001/. ".----~,---Io P=146kips(l)

/.

/;,9­61'

Strain

0.001Strain

o 0OII~I=I~I~III~I~IIlrIII~II~:~:~:~:~:~:~:~:~:~:~I:~:~:~:3:~:E:~:~:~I~:~:~:~:~:~:~:§l~:~:,P'~11 II! II III I

o 10 20 30 0Distance, in. /y

/.

//// .

///' , 0.00/

,// .~= 301 kips (2)

P=250 kips (I) ,.- / . /\,,.-/ // .

/ /0.002 /// /' 0.002

/' 1_-.l_-.! L - Yield Level

Fig. B-23 Strain Distribution AlongCorner Splice of Specimen S6-3

B-29

Load, Load,kias kips

300 300

200 I 200

100

°0I

1000 4000Strain, mtllionthos

-100

~~-100

\

-200 -200

6000

Offset.I

4000Strain, millionths

33"Splice

2000

I·

I

L I I I I I I I I I I~I I I 1 1 I I I I

? l

-100

Load,kias

- 200 .L

Fig. B-24 Load versus Hoop Strains forSpecimen S6-3: Gages 1, 2,and 3

B-30

Load,kips

300

4

200

100

Strain, millionths

-100

4000 6000

-200

2000

if Sfroin, millionths

~t

Offset

-200

-100

Load,kips

300

.133"

Splice

I.

I

Q I I I I I I I L-::,I I I I I I I I !

? lI

Load,

"::t~,oof

9]*"1-+U+-I'--------'-2.0"!'""0:-::0--------:4"':-OOO.,...,,---

\ Sirain, millionths

-100 \

-2.001Fig. B-25 Load versus Hoop Strains for

Specimen S6-3; Gages 4, 5,and 6

B-31

cracks penetrated 8 in. (0.20 m) into the splice at the peak

tensile load of the second cycle. At the peak tensile load of

the sixth cycle, splitting cracks crossed most of the splice

causing the inner bars to pullout. Splitting cracks were also

observed along the corner bars as shown in Fig. B-18. The

corner splitting cracks were first observed at the peak tensile

load of the third cycle. It is important to note that immedi­

ately before the inner bars pulled out, hoop Nos. 3, 4, and 5

yielded. This may have permitted propagation of splitting

cracks along the splice.

Specimen S6-3 failed at the peak tensile load of the sixth

cycle. The mode of failure was by "splitting-bond" of the

inner bars. Corner bars fractured after inner bars pulled out.

Calculated and measured strength~ are listed in Table 5.

Specimen S6-4

Specimen S6-4 was a companion to Specimen S6-3, but

Specimen S6-4 was monotonically loaded. Strength, ductility,

and behavior of S6-4 were similar to those of S6-3.

plots of load versus elongation are shown in Fig. B-26.

Initial and final crack patterns are shown in Fig. B-27.

Figure B-28 shows crack widths along the splice. Most of

the axial deformation was concentrated at the offset end.

Figures B-29, B-30, and B-3l show strains along the spliced

reinforcement. Figure B-3l shows the anti-symmetry and the

tendency of the strain distribution to become linear. The data

indicate a yield penetration of about 2/3 of the splice length.

B-32

Lood,kips

DeoTeD

0,2.0 0.40 0,60 0,80Relative elongation, in.

1.00 1.2.0

o

o

OI+----i-.,..--r-~-(-O.-8-8-m':""iIEJ'-----_....Load,

kics

300

200

0;to-----~0~,:t50;:;------~I"""J,O;-;:0:-------'71.'=50::------2.:-00

Relative elonqation1

in.

Fig. B-26 Axial Deformations of Specimen 86-4

B-33

Off

set

(a)

Init

ial

crac

kp

atte

rn

ttl r w .t>-

Off

set

~1(b

)F

inal

crac

kp

atte

rn

Fig

.B

-27

Cra

ck

Patt

ern

so

fS

pecim

en

S6

-4

5.0

tJj I W lFl

Cra

ck0

.2w

idth

,in

.

0.1

P=

27

2'k

ip,. \;\

/I I

II

P=

24

6ki

ps~'

\~2.5

P=

23

2~iP6]X\\

P=

18

4kI

ps

I\

\

P=

12

3kiP

Sm:-\

:•

I

--'-_-=:.~~-~

----

Cra

ckw

idth

,m

m

II

--

-------

--

----

----

---

--

=--=

---=

--=---=

...-==

---

----

----

----

----

----

---

-

---

----

----

----

----

----

---=

====

-=--=

--=-:

:---

I..

..-I )

Off

se

t

Fig

.B

-28

Mea

sure

dC

rack

Wid

ths

inS

pecim

en

S6

-4

Load,"kips

load.kips

300

10

OJ------------:IO::','::"OO::'O:::-------.-----,2,;;t";,o;;:;ono-----<

Strain, millionths

II" Ililt

I 11" !

[G4 LG5 iG6""'" IG3 ~2. t GI

Sgjlea

G4 (G5300 ;./ J-----­

! I! Ii Ji Ii Ii Ji I

2.00 !Iif;1!IitilIIII

100 I ifq

11

V°6:!:-------I-------:10"..,"'"000::-::------------::2,-:'0:'="00"..0=------

Slrain, millionths

B-29 Load versus Steel Strains inCorner Bars for Specimen 56-4

B-36

xG

age

ou

t

II"

II".

1\"

1----:

....:...-

t1G

9"\

G10

)!I

II

::

::

:I

:I

II

::

II

II

11

II

l

·e:

(X7

.13

3"

Sp

lice

tJj I w -...

.J

Loa

d,ki

ps 30

0

20

0

10

0

G7

II::

:":="/

"~'_

.r

G10

"~

~._._-L

.

.G

8I····

....,Gil'

.-

f.

:

IIt

'--------

JG9

II

)---

~.

....---

------

I/,4

r~·-·-~-><

./'

/'

G12

:f/

/...

//

~///

j:>/

/.y

:!~

/ /~/ ~

.

00

50

00

10

,00

01

5,0

00

Str

ain

,m

illio

nth

s

Fig

.B

-3:0

S-t

rain

Dis

trib

uti

on

Alo

ng

Inn

er

Bars

for

Sp

ecim

en

S6

-4

1kip =: 4.448 kN

//Strain

0.002

0.001

-------r---j----P =288 kips/ /

/P=246 kips

I/

//

"./

",..

)",..//./

~/./

~/y

~

- Yield Level

0.002

Strain

0.001

It I

oI I I I ! II: : : : : : : : : : : : : : : : : : : i :

Io 10 20Distance, in.

P= 123 kips

Strain

0.001

0.002

//

/

0.001Strain

0.002

- Yield Level

Fig. B-3l Strain Distribution Along CornerSplice of Specimen 86-4

B-38

Strains in hoop reinforcement are shown in Fig. B-32. The

effectiveness and sequence of yielding of the hoop reinforce­

ment were similar to those observed in Specimen S6-3. As in

previous specimens, hoop No. 1 was ineffective.

Splitting cracks were first observed at the offset end

along the corner and interior lapped bars at a load of 184 kips

(818 kN). The splitting propagated along corner bars and inner

bars causing the bars to pullout at the offset. As in

Specimen S6-3, hoop Nos. 3, 4, and 5 yielded immediately prior

to bar pullout.

Specimen S6-4 failed by "splitting-bond" of lapped bars.

Calculated and measured strengths are listed in Table 5.

S- 8 Spec imens

Four Specimens, 88-1, S8-2, 88-3, and 88-4, were built and

tested. Variables included type of loading and amount of

lateral reinforcement. Specimen 88-1 was a companion mono­

tonic loading test to Specimen S8-2.

Transverse reinforcement in Specimens S8-1 and S8-2 con­

sisted of No. 3 confinement hoops spaced 2 in. (51 rom) on cen-

ters. This amount of confinement met seismic provisions of the

1976 Uniform Building Code. (2) To investigate effects of trans-

verse reinforcement, Specimens S8-3 and S8-4 had No.3 hoops

spaced 12 in. (305 rom) and 4 in. (102 rom) I respectively.

Specimen S8-3 was subjected to monotonic loading and Speci­

men S8-4 to reversing loading.

B-39

10~

T ~I

c:;

I~

.I'O

ffse

'

...3

3"

III1

il

Loa

d,ki

ps 30

0.,

.(i

)>:-

r--;

;-;'

f-...

.~-/~~-==---~~--------~

---

/I.../~'~

///

/',/

//6

/I

'/

/

I/

.;

//~

//

,LW

1/

®,I

/II

200-

11f/

/:

~I

/

I!I/

"I

/11/

1/:I

I'I

,)/

/:/

/I

10

0{/

1'

:I I}/

OJ I ,!,,> o

06

20

'00

4doo

66

00

80

00

Str

ain

,m

illio

nth

s

Fig

.D

-32

Lo

adv

ers

us

Hoo

pS

train

sfo

rS

pec

imen

S6

-4•

Details of 58 Specimens are given in Figs. 4a and Table 2.

The splice length was 60 in. (1.52 m). Material properties are

summarized in Tables 3 and 4. Calculated and observed yield, and

maximum loads and modes of failure, are summarized in Table 5.

Specimen 58-1

Load versus total and relative elongations are plotted in

Fig. B-33. Initial and final crack patterns are shown in Fig.

B-34.

Cracking was first obser~ed at a load of 44 kips (196 kN).

Initial cracks were located outside the splice length as shown

in Fig. B-34(a). Under increasing load, cracks at the offset

end grew much wider than those at other locations, as can be

seen in Figs. B-34(b) and B-35.

Initial yielding occurred at a load of 200 kips (890 kN).

This was followed by full yielding at 216 kips (961 kN). Mea­

sured longitudinal strains are plotted as a function of applied

load in Fig. B-36. The distribution of longitudinal bar strains

along the splice is shown in Fig. B-37. Similar to 56 Speci­

mens, the strain distribution became linear as loads increased.

At a load of approximately 120 kips (534 kN), severe crack­

ing of concrete co~er was observed at the location of the

offset. This cracking was associated with bursting stresses

caused by the offset. As loading progressed the cover at the

offset spalled.

Figure B-38 contains load versus strain curves for the hoop

reinforcement. It is evident from the measured strains that

B-41

Elongation, mm

Lood, 4000r:- .-----:..-----.,10~ __r------'2T0'------,kips

1500

load,kN

300

200

100

....-:.:::-...:../

II• I

I I. f

1/. I

DC DT 2 DCDT 3 DCDT I.---- --­---- .. ---=--- -- - -----0 __ -'-::::'~-----

1000

500

0 00 0.2 0.4 0.6 0.8 1.0

Relative Elongation. in.

joq OCOT 4]101124" (3.15m)

0 DeDT 2 DeDT 3 (0.5Im)(0.5Iml 60"(1.52ml 22"

=::; =c:::J

0 0Spli ce

Load,400

0 50 Total elongation mm lOG Lood,kips kN

1500

300 OCDT 4

200

100

1000

500

O"- --l.. -'- --'- ~O

o 1.0 2.0 3.0 4.0

Totol Elongotion ,in.

Fig. B-33 Axial Deformation of Specimen S8-1

B-42

tJ:I I ,Po

W

SP

lice/O

ffset

"'1

r"'ll(

\1IT

\l~

(a)In

itia

lC

rack

Patt

ern

/'

r--

,<-

'>1

11

""\

I~\~~,

,••

ll\

•.

"•

II

(b)

Fin

al

Cra

ck

Patt

ern

Fig

.B

-34

Cra

ck

Patt

ern

so

fS

pecim

en

83

-1

0.0

50

.....

Cra

ck

Wid

th)

in

p=

197

Kip

s/\

(87

6kN

)/

\

')/

\JC

rack

/\

Wid

th)

/\

1.0

mm

/\

/\

/p

=12

01<

lps

.\

0.0

25~-

----

/L(5

34

kN

)_

_.

~0.5

'"//

.--'-

-'\.

,"

.\

'.-.-."""

'/.--'

P=

44

KIp

s

---

---:

--/

_L~I~~~~_----,o

t--

-r

0tJ

j I .Po

.Po

I I , I \l-

J

......_--

----

----

----

-------------------=..:~.....-

----

----

----

--

I'"

'"

60

"_

IO

ffse

t

(1.5

2m

)

/---

----

-_...._

----

----

--_

..::.:==.==-=====--=:::..-...:-_---==-==--=~-------------------

Ir

,I

I I I t I

Fig

.B

-·3

5B

easu

red

Cra

ck

~'Jidths

inS

pecim

en

58

-1

load,kips

400 r--------,------,.-------.------,------, Load,kN

1500

------ ----------------------

500

1000G4

G3.,.....--G2

i-

GI

/

/I

II

II

/

//

I/,

"

100

200

300

0 00 2500 5000 7500 10000 12500

Sirain. milliont hs

12" 18" 18" 12" 18"

rJ; ., .. -I" T IG6 G7G8

} I 1 1 1 I IJ 1

I\-G:\I f:::t:::, j ! , I

I ')G4 G3 G2

SplIce

load,kips

400 r-------,.--------,r--------r------,.-------, Load,kN

1500

300

200

100

---------G8 1000

500

Ol..- --L ..L- --Jl.-- -L. --JO

o 2500 5000 7500 10000 12500

Strain. millionths

Fig. B-36 Load versus Steel Strains for Specimen S3-l

B-45

"j

Str

ain

Str

oin

-Y

ield

Le

ve

l

0.0

02

0.0

01

0.0

02

0.0

01

-Y

ield

Le

ve

l

Dis

tan

ce.

in4

0 I

---(53

'

P=

12

0kip

s

....-

20 I

P=

12

0kip

s(5

34

kN)

----

----

//

/P

=2

90

kip

s/

/(1

29

0kN

).

:L

_

--------------------------~---

p~2

90

ki

s.----

•/

---

(I2

90

.ktJ

--.---

/_

__

_•

p~2

12

kip

s/

"j~

(94

3kN

)-

/.

v

.~

0.0

02

0.0

02

Str

ain

0.0

0I

Str

ain

0.0

01

td I~r-::.

m

Fig

.B

-37

Str

ain

Dis

trib

uti

on

Alo

ng

Sp

lice

of

Sp

ecim

en

58

-1

'.'

r

1500

I1

<::

.It

lIt

l(/

Ie.

II

I-

I_.

11

11

11

J1.<

~cL<

II

IIc>

-L"

-.

\)

\

Lo

ad,

kN

50

0

1000

2.

Sp

lice

dS

tee

l(0

.30

m)

34

5

-5

100

Lo

ad,

40

0I

rk

ips

I2

3

300'r~4

I r PIII

I'2

00

tv t,~

'.J

60

00

50

00

40

00

30

00

20

00

10

00

__

__

__

_.L

1_

_I

I1

II

10

70

00

oo

Str

ain

,mil

lio

nth

s

Fi~.

B-3

8L

oad

vers

us

HO

Op

Str

ain

sfo

rS

pecim

en

88

-1

/..

the hoop at the offset was working to contain the outward

thrust component of the offset longitudinal bars. Bursting of

the concrete at the offset was more severe in Specimen S8-1

than in Specimen S6-1.

Longitudinal splitting cracks were observed at the ends of

the lap, but they did not propagate along the splice. Capacity

of the specimen was 330 kips (1468 kN). At this load one of

the welds that anchored a longitudinal bar in the end block

failed. The measured maximum load was 94% of that calculated

based on average material properties.

If the weld failure had not limited capacity of this

specimen, it is possible that the full calculated strength of

the longitudinal reinforcement would have been developed.

Specimen S 8-2

Specimen S8-2 was nominally identical to Specimen S8-1, but

was subjected to six load reversals.

Load versus elongations are plotted in Fig. B-39. Initial

and final crack patterns are shown in Fig. B-40.

Cracking was first observed at a load of 46 kips (205 kN) .

Under load reversals, cracks at the splice ends grew much T,qider

than those at other locations, as shown in Fig. B-41.

Longitudinal steel strains are plotted as a function of

applied load in Fig. B-42. Distribution of longitudinal steel

strains along the splice is shown in Fig. B-43. The strain

distribution and yield penetration in Specimen S8-2 were simi­

lar to those observed in the monotonic test of S8-1. It is

B-48

Load, Load,kips kips

300 300

DCDT I OCDT(2)

200 200

100

00 1.0 1.0elongation, in. Relative elongation. in.

-100 -100

-200 -200

o

o

Load,kiP'30

OCOT Q)

Relotive elonqation. in.1.0

Load,kips

300

'-DeOT@

e!onqation, in.

,2.0

Fig. B-39 Axial Deformations of Specimen S8-2

B-49

tJJ I Ul

o

\I

Spl

ice

Offs

ol

·1~

\)

)~

()

)l

l.."

)

(0

)In

i1ia

lcr

ock

paH

ern

Off

se

t

(b

)F

ino

/cr

ack

pat

tern

Fig

.B

-40

Cra

ck

Patt

ern

so

fS

pecim

en

88

-2

P=2

14ki

ps(

5)

Cra

ckw

idth

,4

.0m

m

IIIA

tpe

aks

of

cycl

es

4,

5,

and

fin

al

mon

oton

iclo

adin

g2

.0

¥l'J\

p=2

80

kips

(M)

!\

P=

26

5ki

PS(4

).~~

\,/

\\

0.1

Cra

ck0

.2w

idth

,in

.

•0

I~.s;;

_'n

-=

J10

i

W I(J

l

I-'

I I I I '---------------------------.------------

--

------,

....1

(---

I...

....

I I I

Off

set

Fig

.B

-41

Measu

red

Cra

ck

Wid

ths

inS

pecim

en

S8

-2

001

(7'

If

f.~,

t~/

///

~)~M

,~I

-100

-20

0

12"

18"

18"

12"

Il::1

:tJG

BJ.

[;mgI

Hd2'

:<:;1P

'::.:r:

:x:·:

c·:c·:

c.CI:

CI:C

':C'rf'

l

Sp

lice

20

0

Lo

ad

,ki

ps 30

0

!sp

00

[0,0

00

~

-wT

--7

Loa

d,ki

ps 30

0

-200

1

20

0

100 'tJf

~ooo

[d,O

OO

Str

ain

,m

illio

nlh

s

Lo

ad,

kips 3

00

-10

0

-20

0

-20

01

1·-

-10

0

---5

{j0

0S

lro

in,

mill

io.o

1hs

100T~ II

-100

-20

0

QI-

----sO

OO

Sh

ain

,m

illio

nth

s

100-

'-

-10

0

-20

0

Lo

ad,

Lo

ad,

kips

kips

30

03

00

~

I1"62

GI

20

02

00

"

100

10

0

----5

00

0

t~"

Str

ain

,rn

itlio

nlh

sS

tro

in,

mill

ion

ths

-lO

Ot"

-10

0-

-20

0p

.--2

00

td I U1

Lo

ad,

Lo

ad,

Nki

pski

ps

30

'11

,3

00

IJ~6

G5

20

0+

I2

00

Fig

.B

-42

Lo

adv

ers

us

Ste

el

Str

ain

sfo

rS

pecim

en

S3

-2

to I ta

-Y

ield

Leve

l

0.0

02

~p

=2

99

kips

(Mt.

·---

----:,--,/

J0.0

02

kips

(2)

I-

----

----

--S

trai

nI

.r-'.~

--

-----

-P=

20

9ki

ps(I

)--l

Str

ain

0.0

01

~.h

--

~0

.00

1

p=

107

kips

(I)

Str

ain

0.0

01

0.0

02

0.0

01

Str

ain

0.0

02

-Y

ield

Leve

l

Fig

.B

-43

Str

ain

Dis

trib

uti

on

Alo

ng

Sp

lice

of

Sp

ecim

en

88

-2

interesting to note that in Specimen 88-2 a greater yield

penetration occurred at the straight end of the splice than at

the offset end.

Figure B-44 contains load versus strain curves for the

transverse reinforcement. Strains indicate that only hoops at

the offset end region were effective.

At a load of approximately 163 kips (725 kN) splitting

cracks were observed at the offset. These cracks did not prop­

agate along the splice. Maximum load applied to the specimen

was 325 kips (1446 kN). Because the test apparatus became

unstable, loading was discontinued during the monotonic incre­

ment that was being applied after the six load reversals.

Observed behavior of Specimens S8-1 and S8-2 indicated that

the applied reversing load history did not have a significant

effect on strength or performance.

Specimen S8-3

Specimen S8-3 was nominally identical to Specimens S8-l and

S8-2 except for the amount of confinement. Confinement in

Specimen S8-3 corresponded to the maximum spacing of column

ties according to the 1976 Uniform Building Code(2) and the 1977

ACI Building Code. (1)

Load versus elongation curves are plotted in Fig. B-45.

Initial and final crack patterns are shown in Fig. B-46.

Cracking was first observed at a load of 46 kips (205 kN).

At a load of 60 kips (267 kN), cracks were observed every 12

in. (305 ~~). This spacing coincided with the location of

B-54

tJj I

(Jl

(Jl

Lo

ad

.ki~s

30

0

-10

0

-20

0

Str

ain.

mill

ion

ths

2"\

5Im

ml

(03

0m

l(0

.46

ml

-11-

\.1

2"

.1.

18"

20

00

Off

set

1000

-10

0

-20

0

Str

ain

.m

illio

nth

s

0411

5~00

-10

0

-20

0

50

00

Str

ain

,m

illio

nth

s

-10

0

-20

0

Str

ain

,m

illio

nth

s

oI

50

00

Lo

ad

.Lo

ad,

Lo

ad

,L

oa

d.

kips

kips

kips

kips

30

0"

30

01

®300

f3

00

®f~

200-

112

00

11

20

0~

20

0

10

01

100-

11II

100

-,]

lobo

2000

Str

ain

.m

illio

nth

s

20

0

-10

0

-20

0

Lo

ad

.ki

ps

30

0

Fig

.B

-44

Lo

adv

ers

us

Ho

op

Str

ain

sfo

rS

pecim

en

S8

-2

E.foo~alion.

Load,400

iO 20i,ip1

Load.'N

J~OO

300... Gaqa "".

-~_..:-"''';':':''''''''''''----''-_ ............ , ., J

-., I< 1000,.......I ,

'.I '-.I .............I ,I

III

100 J / ... ~OO

II OCOT 2

:""OCOT J j oeOT ,0

0 0.2 0.4 0·6 00.8 10

ElorujJ01loo , in.

o

o

TotC2t

(0:~6,"11.1 ...l

Load,kio'S :::lr----~----~,f-~------,----~9

Lood.'If

200

oeOT •

1000

0IOO---CQt5---,I7i.01----;~;'<---.,,27. ...----.z.-:.:j-----,.J8Totot ,l(lnqoth,". in.

Fig. B-45 Axial Deformations of Specimen S8-3

B-56

t:J:J I Ul

--J

\ ()

I'S

plic

eO

ffse

t.j/ I

\

(a)

Initi

alcr

ack

pat

tern

Off

se

t

-(b

)F

inal

cra

ck

pat

tern

Fig

.B

-46

Cra

ck

Patt

ern

so

fS

pecim

en

S8

-3

transverse hoops. Cracks at the ends of the splice grew much

wider than those at other locations as shown in Fig. B-47.

Initial yielding in spliced reinforcement occurred at a

load of 211 kips (939 kN). Measured longitudinal strains are

plotted in Figs. B-48 and B-49. As expected, a greater yield

penetration occurred in this specimen than in Specimens 58-1

and 58-2, particularly at the offset end region.

Figure B-SO shows load versus strain curves for the hoop .

reinforcement. Hoops at the straight end region were subjected

to higher strains than those at the offset end region.

At a load of 114 kips (507 kN), splitting cracks were

observed at the offset. As load was increased, splitting cracks

penetrated the splice. Capacity of the specimen was 280 kips

(1245 kN). At this load, bars pulled out at the straight-end

region of the splice. The behavior of Specimen S8-3 indicated

that minimum column hoop reinforcement was not sufficient to

prevent splice failure. Additional reinforcement concentrated

at the ends of the splice might have been sufficient to develop

the strength of the bars.

Specimen S8-4

Specimen S8-4 was identical to S8-l and S8-2 except for the

amount of hoop reinforcement. This was reduced to 50% of that

required by the 1976 DBC Building Code. (2)

Load versus elongtion curves are plotted in Fig. B-5l.

Initial and final crack patterns are shown in Fig. B-52.

B-58

Iki

p=

4.4

48

kN

Cra

ckw

idth

,m

m4

.0 20

kips

P=

55

kips

0.1

Cra

ck0

.2w

idth

,in

.

/\ \

t:=-:-

.;:;---

----

:=l?

-~~-~\

~I

0--

--~=-

=........---.-0

-----~~O

.

t;dII

....

.=-=

_--

-I

I_

-=-

_Lf

1_-

-=--:

:::.....

._w

I~~

__

I_

'------

I.....

60

11(1

.52

m)

...1

Off

set

/------------------------------

--r--

--------------

If

,"

I I I I

Fig

.B

-47

Measu

red

Cra

ck

Width~

inS

pecim

en

S8

-3

Load,!<ips' 4oor------,-------,------,-------r--------, Load,

kN

1500300

200

_.-.-.-.--.-.~~..L.-.---.-~._.-- ---"-. ....---__..- ..- ..- ..--G4J".-..-.. 1000

"---'

500

°O~----;;2::50::;-;0~-----;;5:;::00~0;;-----:7:;-;50~0----:-:10:-':,O:-::0:-=0---12-.s...J&

Slrain, millionths

12." 18" 18". Ii'

}:::z::=~f.~:i~5,~i~G6i~'I~~7~~1g,g~====9(\. Solice

Load,kN

500

1000

G5 G6

\f' .__,G7J.-._.-.-·-·-I --.--.-J --' _.-:-~G8

J!1r - ,Go,. ~,y ,'j

~Tri/If

°O~------;2:-::5-=00:::------:5~0-:::'00-=------;7::::5:'::0-::-0----1:-=0-':,00:-=-::-0----:,-::-::I2,S30

200

Load,kips

Slraln, milllanlll$

Fig. B-48 Load versus Steel Strainsin Splice of specimen 38-3

B-60

to I 0"1

I-'

Str

ain

Str

ain

0.0

02

0.0

01

0.0

01

0.0

02

P=

120

kips

(53

4kN

)

~.

.,j'

P-

120

kips

(53

4kN

);:

P"

/--;:

:;--.

.P

=2

08

kips

(92

6kN

l-;:

.:::

:::':

::::

--·

/'

---.."'

':::'-

......

---:--

-/

-----

1---

---'

f:"-"-"-"

1.-

--'

:P=

26

2ki

ps(1

166

kN

)I/

P=

21

8kip

sI

I·(

1/

97

0k

N)

:_

__~

L_

-Y

ield

Leve

l

0.0

02

Str

ain

0.0

0/

0.0

01

Str

ain

0.0

02

-Y

ield

Leve

l

Iki

p=

4.4

48

kN

Fig

.B

-49

Str

ain

Dis

trib

uti

on

Alo

ng

Sp

lice

of

Sp

ecim

en

S8

-3

000r0

MI

coC/)

>::(j)

S0.-1U(j)0..

C/)

~

0~

00 Ul0 >::C\J (/l 0.-1

J::. mC ~

0 +lC/)

-E 0...

0c 0.....0

........Ul<7i :::lUl~(j):>

'1j0 m0 00 H

0LI')

It:Q

.tJ1

0.-1Ii.

(J)

u

a.(J)

N~-0

-nr

- J-

:

uv-~

f>.------+------1-....::::=~~~"""_+O

~ 0 000~(/lO 0 0o a. r0 C\Jo ._

.-J":::::'

B-62

Load,kips

300

Load,kips

300

-200

DCOT @

LO<:ld,kips

300

200

-10

-200

elon<jOllon, In.

__--r-...... failure

2.0

Fig. B-5l Axial Deformations of Specimen S8-4

B-63

to I 01

>f;:>

Off

set

I'"S

plic

e-I. (

(0)

Initi

alcr

ock

pat

tern

Offs

e1S

plic

e

"1///

1--

~/1

(.....

...JI

"\-

~r-

1I

\\.

(,

I7

\

W(b

)Fi

nal

crac

kp

atte

rn

Fig

.B

-52

Cra

ck

Patt

ern

so

fS

pecim

en

58

-4

Cracking was first observed at a load of 46 kips (205 kN).

Severe spalling and bursting of concrete was observed at the

first peak of first load cycle. Under increasing load, cracks

at the offset grew wider than those at other location as shown

in Fig. B-53.

Figures B-54 and B-55 show measured longitudinal strains.

The yield penetration was similar to that observed in Specimen

S 8-3.

Figures B-56 and B-57 show load versus strain curves for

the hoop reinforcement. It is evident that hoops at the offset

region were effective.

Longitudinal splitting cracks were observed at the offset

at a load of 261 kips (1161 kN) during the first peak of the

second load cycle. The splitting cracks did not propagate

along the entire splice length. At the end of the third load

cycle, the specimen was severely damaged at the offset end

region. In the first half of the fourth cycle, load carrying

capacity was lost by fracture at the offset of one of the

spliced bars. This may have been related to the bend in the-

bar at the offset. with only three bars remaining, load on the

specimen was 235 kips (1046 kN). This is 90% of that cal-

culated for three bars based on average material properties.

B-65

4.0

*Cyc

len

um

be

rsh

own

inp

are

nth

ese

s

Cra

ckw

idth

,8

.0m

mpt

261

kip

s(2

)

*".

P=2

12ki

ps(9

43

(I)

2.0

Cra

ck0

.4w

idth

,in

.

I I I II

'-----

1-

-=--

=-_

__

__

__

__

__

_

I / /(1

161

kN)~!

/ / / Nt)k, / / /

--,

/

\I

,L_

_-'::

::::::

'~'~==

::::==

-=-=-~

-:::::

'-f/

IIO"-

---\

---------0

1I

to I m m

/---

!----,--

,:'\

-----

I6

0"

(1.5

2m

)..

.,O

ffse

t-

----

Fig

.B

-53

Heasu

red

Cra

ck

Wid

ths

inS

pecim

en

88

-4

gooo

10;W

OSi

foin

.m

illlo

n,h,

67

--'

10:0

00

-20

0

t~t

1ft

leu

Itt

~G8

""

IU

I~~

,1'5}~\'''''=.===::sf{

Spl

iCO

Ott

aot

Loa

d,ki

ps3

00

-'00

-10

0

-20

0

-20

0,

5OdO

Sh"o

in,

mil

lion

lha

-10

0

-20

0

5110

4_.

UIIU

J("1

1Iui

-20

0

tt,I---5

do

o

-tOO

-20

0

load

,to

ad,

load

.lo

ad.

kip

,ki

p'

~IP'

kips

30

0

:::1j

'""I3

00

'""II

?O

f\·

/Jj

20

0-

,G

lG

2'_

J_

J

100

lr

10

0

tJ:J I 0\

looe

J.L

oad.

loa

d,

-..-J

kip:

kki

p.k

ipi

30

°'1

W]3

00

·

G5

kG

6

'Wr

20

0,.J

100

100

tt,1-·--~0J-

-~$

liaW

l,m

iltio

nlJu

.S

:wio

,Ill

.illk

t.lh

l

-100

1-tO

o

Fig

.B

-54

Lo

adv

ers

us

inB

ars

for

Ste

el

Str

ain

sS

pecim

en

S8

-4

0.0

02

Str

ain

-Y

ield

Leve

l

Str

ain

0.0

0/

0.0

0/

0.0

02

-Y

ield

Leve

l

/----_.

/---

//"

P==

1/4

kip

s/.

/.

....../

_.// -.

",.-/

/-/'

P=

214

kip

s/.

/,"

./

.//

/p=2

61ki

ps

.//

./.

__

__

_--

-./

L-

-

------------r------7

---

../

P=

26

Ikip

s(2

)//'

././

.//'

.//'

P==

212

kips

(I)

/'

./

,/

0.0

02

0.0

01

0.0

01

0.0

02

Str

ain

Str

ain

ttl I 0'1 co

Iki

p;-;

4.4

48

kN

l?ig

.B

-55

Str

ain

Dis

trib

uti

on

Alo

ng

Sp

lice

of

Sp

ecim

en

S8

-4

Loa

d,ki

ps3

00

Loa

d,ki

ps 30

0

20

00

mill

ion

ths

°0

100

-10

04

•

20

0··

,t

30

00

20

00

-20

0

~~...

.1

Str

ain

.Ill

illio

nth

s

20

0·'

·

-/0

0•.

_~J

10

0

20

0

load

.ki

ps3

00

001-

'----

----

--1

01

50

2000

30

00

Slr

oln

,m

illio

nih

s

100

-20

0

-100

-20

0

td I <J\ \0

Fig

.B

-56

Lo

adv

ers

us

Ho

op

Str

ain

sfo

rS

pecim

en

S8

-4:

Gag

es1

,2

,an

d3

-100

-100

-200

1000

Sfrain, millionths

2000

Load,kios

300

-100

-200

1000Strain. millionths

1000/ Sfrain. miilianth.

/

~

-100

-200

rTf ~I02mml 1m(Offset

~lllll! i! IIIIII!: i nm:'II __ I'

60· (1.52 m)Load.kips

1000Strain, milltOnths

Load.I<i~

Fig. B-57 Load versus Hoop Strains forSpecimen S8-4: Gages 4, 5, 6,and 7

B-70