Analysis and Development of an Innovative Prefabricated Beam-to-Column Joint

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University of Padova University of Trieste University of Udine Università IUAV di Venezia

Enrico Mazzarolo

A

NALYSIS AND

D

EVELOPMENT OF AN

I

NNOVATIVE

P

REFABRICATED

B

EAM

-

TO

-C

OLUMN

J

OINT

Advisor: Prof. Enzo Siviero Università IUAV di Venezia, Venice, Italy

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Civil and Mechanical Structural Systems Engineering

Ph. D. Head’s: Prof. Davide Bigoni

24 / April / 2012

Board of Examiners

Prof. Enzo Siviero (Università IUAV di Venezia) Prof. Antonio Tralli (Università degli Studi di Ferrara)

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First and foremost, I would like to express sincere gratitude to my advisor Prof. Enzo Siviero for the support to my Ph.D study and research. His knowledge and expertise have been a precious reference during these three years.

I can not find words to express thankfulness to my co-tutors Prof. Bruno Briseghella and Prof. Tobia Zordan. They have been a source of friendships as well as enriching and stimulating collaboration. This thesis would have not been possible unless their precious contribution.

Thanks to Dr. Eng. Lan Cheng, irreplaceable workfellow during writing of many papers.

The research has been jointly supported by IUAV and Tecnostrutture S.R.L., that has provided the test structures. This support is gratefully acknowledged.

Assistance for experimental studies from State Key Laboratory for Disaster Reduction in Civil Engineering (SLDRCE) in Tongji University has been also appreciated.

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CHAPTER 1

1. LITERATURE SURVEY 1

1.1. Introduction 1

1.2. Initial development of precast technology 1

1.3. Former precast earthquake resisting frames experiences 5

1.4. New Zealand approach to precast framing 9

1.4.1. The emulative approach 9

1.4.2. Precast system n°1 11

1.4.6. Benefits and drawbacks of emulative approach 23

1.5. United States approach to precast framing 24

1.5.1. The dry connection approach 24

1.5.2. Non linear elastic systems 25

1.5.3. Tension-compression yielding systems 29

1.5.4. Energy dissipating systems 33

1.5.5. Hybrid frame system 35

1.5.6. Benefits and drawbacks of dry-connection approach 40

1.6. Italian approach to precast framing 40

1.6.1. The precast CSTC beam technology 40

1.6.2. CSTC beam specifications 43

1.6.3. Experimental testing on CSTC beam 44

1.6.4. Code design provisions for CSTC beam 49

1.6.5. Beam-to-column joint testing 50

1.6.6. Current CSTC beam application on framing system 58

CHAPTER 2

2. PROPOSED PRECAST JOINT LAYOUT 61

CHAPTER 3

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viii

3.2.1. Concrete 69

3.2.2. Steel 71

3.3. Static testing 73

3.3.1. Specimens description and test setup 73

3.3.2. Force vs. displacement curves 76

3.3.3. Horizontal strain sensor on column concrete 78

3.3.4. Vertical strain sensor on concrete 79

3.3.5. Strain sensor on lower horizontal steel plate 82 3.3.6. Vertical strain sensors on vertical steel plate 83

3.3.7. Conclusions 85

3.4. Cyclic testing 86

3.4.1. Specimens description and test setup 86

3.4.2. Force vs. displacement curves 92

3.4.3. Strain gauges on CSTC beam’s truss 97

3.4.4. Strain gauges on truss girder 98

3.4.5. Strain gauges on vertical plate 100

3.4.6. Displacement gauges on outer beam surface 102

3.4.7. Conclusions 103

CHAPTER 4

4. CONCRETE MODELLING 105

4.1. Introduction 105

4.2. Compression models 106

4.2.1. Mander model (1988) 107

4.2.2. Nagashima Model (1992) 112

4.2.3. Cusson and Paultre Model (1995) 113

4.2.4. Razvi model (1999) 116

4.2.5. Legeron model (2003) 119

4.2.6. Cusson model (2008) 121

4.2.7. Cui and Sheick model (2010) 123

4.2.8. Provisions for concrete ductility 124

4.2.9. Provisions for concrete strength 125

4.2.10. Models’ validation 127

4.3. Numerical implementation of concrete models 132

4.3.1. Tensile behaviour 132

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5. LATTICE GIRDERS’ PARAMETRIC OPTIMIZATION 137

5.2. Numerical parametric pull-out tests 139

5.3. Bending strength 149

5.4. Conclusion 153

CHAPTER 6

6. COMPOSITE-COLUMN’S FE MODEL CALIBRATION 155

6.2. FE model 155

6.3. Experimental vs. numerical response 157

6.4. Conclusions 166

CHAPTER 7

7. OPTIMIZATION OF COMPOSITE-COLUMNS 169

7.2. HSC column numerical analyses 170

7.3. Core-joint numerical analyses 172

7.4. Column-joint connected with welded flanges 175

7.5. Column plus bolt-connection (4 bolts) 179

7.6. Column plus bolts-connection (6 bolts) 183

7.7. Conclusion 186

CHAPTER 8

8. ROTATIONAL STIFFNESS OF COLUMNS’ COUPLING SYSTEMS 189

8.2. Reverse component approach 190

8.3. Analytical component approach 191

8.4. Rotational stiffness of column-to-joint interface 193

8.5. Column-to-joint interface classification 194

CHAPTER 9

9. ANALYTICAL STUDY OF COMPOSITE-COLUMNS 199

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x

9.3.2. HSC column 204

9.3.3. Composite-core-joint 205

9.3.4. Bolted connection 206

9.4. Design domain for composite-column 207

CHAPTER 10

10. NUMERICAL JOINT CYCLIC PERFORMANCE 213

10.2. Numerical model 214

10.3. Implementation of experimental static test 216 10.4. Expected cyclic behaviour for precast joint 218

10.5. Conclusion 223

CHAPTER 11

11. ESTIMATION OF SEISMIC VULNERABILITY 225

11.2. Plastic hinges’ reference theory 226

11.3. Beams’ plastic hinges 230

11.3.1. Adopted formulations 230

11.3.2. Computed plastic hinges 231

11.4. Columns’ plastic hinges 234

11.4.1. Adopted formulations 234

11.4.2. Lateral confining steel 235

11.4.3. Column plastic hinge 237

11.5. Vulnerability-based approach 241

11.5.1. Frame models 241

11.5.2. Reference seismic action 243

11.5.3. Verification procedure 245

11.6. Seismic analyses results 252

11.6.1. Layout A frames 252

11.6.2. Layout B frames 256

11.6.3. Layout C frames 258

11.6.4. Layout D frames 261

11.7. Reduction factor identification 263

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12. PRACTICAL DESIGN PROVISIONS 267

12.2. Continuity lattice girder design 268

12.2.1. Design for bending 268

12.2.2. Design for shear 269

12.2.3. Shear-connection design 271

12.3. CSTC beam design 272

12.4. HSC column axial and bending strength 273

12.4.1. Flexural strength for seismic design 273 12.4.2. Shear strength design and minimum confinement 274 12.4.3. Lateral reinforcement to provide confinement 276

12.5. Bolted connection 277

12.5.1. Bending strength 277

12.5.2. Shear strength 277

12.6. Core-joint M-N domain strength 278

12.7. Core-joint shear strength 278

12.7.1. Design for shear 279

12.7.2. Design for confinement 285

12.8. Improved layout for exterior joints 286

CHAPTER 13

13. REAL CASE-STUDY APPLICATION 289

CONCLUSION 291

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CHAPTER 1

1. LITERATURE SURVEY

1.1. Introduction

Presented in this chapter is a detailed literature survey about implementation of precast framing technologies in seismic area, which deal with the topic of this thesis. Introducing the different solutions developed through the years in different geographical areas helps not only to deepen the knowledge on the subject and to recognize past and actual building trends, but mainly to emphasize advantages and disadvantages of previous experiences, so to give researchers space for further improvements.

To provide a unitary framework, an historical overview is presented. In the first part is reported a rapid introduction on preliminary worldwide precast technology development since the ‘50s. In the second part, attention is focused on the evolution of precast moment resisting frame structures through two main chapters, as many as the countries characterized by major progress on this topic. These are New Zealand, where the monolithic emulative approach developed since the ’80 and Unites States which promoted the dry connection approach since the ‘90s. Finally, the Italian trend is considered, characterized by an emulative approach, reinterpreted through a patented hybrid truss beam born in the ’60 and topical still nowadays.

1.2. Initial development of precast technology

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buildings increased. The high cost of structural steel promoted the adoption of reinforced concrete as base material, with a cost advantage 1 to 10 when resisting compressive columns are considered (Griffis, 1992). The need for reducing construction costs, led to moving out from site-construction long time spending casting and scaffolding operations. More conveniently, these could be brought off into factory plants, where monolithic, easy to transport and assemble modular RC element started being produced.

In Canada structural precast concrete construction started in the 1950’s with a number of notable buildings. Early examples include a 10000 m2 one-storey structure, with column and girder framing system and double tee roof members in Edmonton in 1955 and eight storey precast frames building built in Winnipeg in 1960. Contemporarily the use of precast concrete in flooring systems (prestressed hollow core sections) was becoming commonplace also in Japan and New Zealand, in the 60’s leaving cast-in place floor construction generally uncommon in these countries (Park, 2002).

Based on the concept that maximum economy is achieved with maximum repetition and mass production, development of standard products was one of the major activities through the 1950s and the 1960s in United States. Initial applications dealt with pre-tensioned precast units such as single or double T section and hollow core section. Afterward long-line beds for precasting/prestressing (Fig. 1), high strength concrete and steam curing were also introduced.

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Fig. 1: Long-l casting

Fig. 3: Dry joi

In Italy parti 1950’s and t costs and th rapidly towa based on g resisting wal storey comm for multi-stor residential b truss-concret parallel also systems, due Conversely t Union Repub 5), to provide 1990). Altern precast colum

line prestressed g bed

ints for precast fr

cularly succes the 1970’s. Th

e high deman rds precast co ravity load re ls (either prec mercial (storeho

rey parking ga uilding, thank te beams, pate load-bearing e to their functio

his solution be blics for urban e low-income h natively, structu mn appeared (F

double tee F

rames F

ssful was the e introduction d for industria oncrete solutio

sisting skeleto cast or cast-in-ouses, markets arage, municip to the develo ented in the lat

precast wall-p onal rigidity, ha ecame rather p residential buil ousing for the ural systems c Fig. 6).

Fig. 2: Example o

Fig. 4: Load-bear

development of prestressing l building of a on (CEB-FIP, on structures -place) became s, malls) and in pal facilities (s

opment of pre te ‘60s by Salv panels appear ave been no lon popular in East dings, usually growing urban combining load

of typical precast

ring wall structure

of precasters g, the growth ll kinds turned 2003). Precas in combination e popular not ndustrial buildi chools, hospit efabricated com

vatore Leone ( red (Fig. 4) e nger widely use

t Europe and f five to ten stor population (Br -bearing preca

t frame layout

e

between the of manpower d construction st technology n with shear only for low-ngs, but also als, etc) and mposite steel cf.ch. 1.6). In even if these

ed.

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A te gi w

F

nother solution echnology”, co rders), directly walls to withstan

Fig. 5: Seria 135 Perez, 199

Fig. 7: IMS preca

n employed in E onsisting in ca y post-tensione nd seismic indu

precast system, 90

ast frame techno

Eastern Europe antilever floor ed against col uced solicitation

, Brzev & Fig. 6

logy: post-tensio

e since the 60’s slabs (totally umn (Fig. 7) a ns.

6: Precast frame Brzev & Perez

oning of floor slab

s was the so-c y replacing be

and coupled w

e system of Seria z, 1990

b

alled “IMS eams and with shear

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1.3. Forme

The adoption framing techn combination to provide s apartment bu represent the Some except In New Zeala post-tensione sometimes u conducted by comprehende this topic (Ch

Fig. 8: Gener tension

Since the 60 incorporating design prov assembled w (“windowed c longitudinal r continuity in t the first time suggesting th

er precast earth

n of precast mo nology was ma with shear pan strength agains uilding in Calga e tallest total pr

tions are howe and and Japan ed together sed (Fig. 8, Fig y Park & Blake ed until the beg heok & Lew, 19

ral reinforcing de ned system

’s in Mexico a g precast conc ision covering with multi-level columns”). Bea reinforcement a

the joint region e some provis

he emulation c

hquake resisting

oment resisting ainly employed nel or load-bea st seismic act

ary, a 31 store recast building

ver revisable in , for example, i to form cont g. 9). Experime eley, 1971 (se ginning of the ‘9 991).

tails of

post-limited numbe crete elements g this aspect. columns with am’s through jo and by subseq n. Just in 1976, ions for mome concept (emula

g frames exper

g frames was lim d as gravity res aring panels, bo ion. An exam ey building, com

in Canada . n the worldwide

in the 1960’s a tinuos momen ental research o e par 1.5.2), b 90s, when Unit

Fig. 9: Building c with

post-r of building wi s have been c Precast con h voids in the oint connection uent concrete , Mexico City B ent resisting p ation of cast-in

riences

mited until the sistant skeleton oth precast or

ple is the Bro mpleted in 198

e panorama. and 1970’s prec

nt resisting f on this precast but potentiality ted States first

constructed in Ne -tensioned syste

ith moment res constructed, de ncrete frame

beam-column was provided casting to rest Building Code i precast structur n-place frames)

80’s. Precast n structure, in cast-in-place, omley Palace

85, which still

cast elements frames were t solution was

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welding for connections in precast elements was common practice in Mexico until designers were aware of failures of welded connections during the 1994 Northridge earthquake in California. Alternative methods were used more recently for connecting precast elements in frames (par. 1.4.2).

An appreciable development of moment resisting frame technology is revisable in Soviet Union Republics. In particular the “Seria 106 system”, developed in Kyrgyzstan in 1975, represented one of the former system adopting cruciform precast beam-to-column sub-assembly (Fig. 10a). The frame was constructed using two main modular elements: the cruciform element and a linear beam element (Fig. 10b). The precast elements were joined by welding the reinforcement bars at midspan and casting the concrete in place.

Fig. 10: a) Cruciform precast units “Seria 106”; b) building example with highlighted cruciform and transversal beam elements

Moment resisting frames with beams substituted by concrete slab, were implemented in the last decade of the Soviet Union (1980-1989). This type of precast construction is known as “Seria KUB”. Frames were usually 5 to 12 storeys high, with multi-level precast columns, normally two storeys long (Fig. 11). Precast square slab elements were used as flooring system. Some of these slabs presented a central hole with dimension 680 by 680 mm that was used to thread the slab along the column, from the top down to the joint level. Here some longitudinal rebars in the upper and lower face of the slab were welded to assure continuity of longitudinal rebars and self-bearing capabilities. The other slabs were placed beneath the central one and welded together. Cast-in-site concrete at connections was completing the structure. “Seria111” technology was similar, with the main difference that floor slabs were larger panels casted on the ground and then lifted and erected to the final position.

BEAM

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Fig. 11: Floor

Fig. 12: “Seria

Fig. 13: Seria

Hence, a ce considered p

ring element and

a KUD” joint ass

a KUD frame und

ertain evolutio period, especia

d column of “Seri

sembling

der construction i

on in precast lly in the Asian

ia KUD” precast

in Kyrgyzstan

framing techn n region. Despi

system

nology is revi te these progre

3000

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kn fa ca C fra w Se Ea (M w po co F F Ba co m ex A nowledge abo ailures, jointed atastrophic con hinese earthqu ame buildings were damaged i everal precast arthquake (Ma Magnitude 7.5) with precast fram

oorly connecte onfinement (20

Fig. 14: Tangsha

Fig. 16: Armenian

ased on these ommunity, rega matter of fact th

xample, the po rmenian Earthq

ut seismic de to low quality nsequences du uake in 1976 (Fig. 14). In th n the second G t concrete fram agnitude 7.2), . In the latter c me systems “S ed to the fram 003).

an (China) Earthq

n (Turkey) Earth

e evidences, th arding the sei hat “bad news oor performanc quake were we

esign and req of adopted ma ring several ea at Tangshan he same year Gazly earthqua mes collapsed

, as well as case, collapsed Seria 111” (Fig me elements a

quake in 1976 F

hquake in 1988

here was a ge smic performa ” are more wid ces of precast f

ell known. Con

quired details aterials and co arthquake even

caused the co in Russia, ma ke of 1976 (Ma

during the 19 in the 1988 d frames were g. 11 to Fig. 13 and columns d

Fig. 15: Gazli (R

eneral concern ances of preca dely publicized frame systems nversely, few e

to prevent un nstruction cont nts.

ollapse of man any large-pane

agnitude 7.3, F 977 Vrancea ( Armenian E generally 9-st 3) with floor di detailed with in

ussia) Earthquak

among the en ast construction d than “good n s “Seria 111” in engineers were

nexpected trol, led to

ny precast l buildings Fig. 15). (Romania) Earthquake torey, built aphragms nadequate

ke in 1976

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the good seismic performance of several large-panel buildings under construction in the same site (background buildings in Fig. 16).

Fintel, 1986 reports that after Mexico City Earthquake (1985) only 5 of 265 buildings that either collapsed or were severely damaged, used precast concrete elements. Besides, many of the precast buildings and multi-storey parking garage in Mexico City survived the severe ground shaking without damage or distress.

Nevertheless, the bad feeling raised around precast systems caused the use of precast concrete in earthquake-resisting structures to be view with suspicion in several countries as for example United States and Chile for many years. In this latter in particular, still nowadays precast concrete elements are being used mainly in gravity load resisting skeleton systems, just in combination with cast-in-place reinforced concrete walls. Even the use of precast concrete in flooring systems is seldom used, preferring using cast-in-place floors solution (2003).

1.4. New Zealand approach to precast framing

1.4.1. The emulative approach

Since the ‘60s in New Zealand there was a steady increase in the use of precast concrete in buildings, in particular for flooring system (hollow core slab) and non-structural cladding. On the contrary, the adoption of totally precast frames in such a high seismicity region was still uncommon at the beginning of the ‘80s for two main motivations: the bad feeling about the poor seismic performances of poorly designed precast buildings in the Russian and Asian regions and the absence of specific seismic provisions for precast structures. A significant growth in use of precast concrete in moment resisting frames and structural walls took place during the boom-years of building construction in the mid-to-late 1980s.

The main input was given by economical motivations. Incorporation of precast concrete elements had several advantages like high quality control, reduction of in site formwork and site labour and increased speed of construction. High interest rates and demand for new building space in the mid ‘80s, highlighted the benefits of precast technology over cast solutions. Contractors readily adapted to precast concrete and the new construction techniques resulting from off-site fabrication of building components (Park, 2002).

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ad m st le su un re fa m Th Ze re de 31 po Th m pr cr C w el bu co m co w to dequate seism mid 1970s, it wa

tructural analys east strong en

ubjected to a s npredictable. F egions of maxim ailures could a members and jo

he capacity de ealand Nation ecommended b efinitively formu 101:1982). For ost-elastic defo he preferred mechanism sho reclude develo ritical regions is

Fig. 17: Post-ela

onfidence in th wall required th

ements togeth uildings provis onnections be monolithic concr onsist on capa was to find eco ogether to ensu

ic performance as customary in sis to determin ough to resist severe earthqua

Flexural yieldin mum bending lso occur, dep oints were first r esign method w Society for E by the New Z ulated in the N r moment resis ormations is by

mechanism is uld be prevent opment of any s required agai

astic deformation

he use precast he developmen her. Being cu sions (NZS 31

tween precast rete structure. acity design ap onomical and p ure adequate st

e) may be achi n the seismic d ne internal forc

t those action ake, the mann ng of structura moment (eithe pending on wh

reached. was first introdu

Earthquake En Zealand Loadi

ew Zealand Co sting frame bui

y flexural yield s the beam-si

ted since the p y ductile respo nst brittle failur

n mechanisms fo

t concrete in m nt of satisfacto

rrent design c 101:1982), the t elements ai This is called c

pproach applied practical mean tiffness, streng

ieved in precas design of struct

ce and design ns. As a resul er of post-elas l members co er beams or co

ere the flexura

uced by a discu ngineering in t

ing Standards oncrete Design

ldings, the bes ding at selecte desway (Fig. possibility to ge onse. In additi

res, due to she

or framed structu

moment resistin ory method for code mainly d e design meth med to achie

cast-in-place em

d to precast st ns of connectin th ductility and

st frame struct tures to use line n the members

lt, when struct stic behaviour w

uld occur at a olumn’s ends) a

al and shear s

ussion group o the 1970s. It (NZS 4203:1 n Standard in 1 st way to achie d plastic hinge 17). Column et a soft storey

on, specific d ear mechanisms

ures

ng frames and connecting th devoted to cas hods introduce eve behaviour

mulation techn

tructures. The ng the precast

stability (Park,

ures. Until ear elastic s to be at tures was was totally any of the and shear strength of

of the New was later 1976) and 1982 (NZS eve ductile e location. sidesway y response etailing in s. structural he precast st-in-place ed for the

as for a

nology and

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A Study Group of the New Zealand Concrete Society, the New Zealand National Society for Earthquake Engineering and the Centre for Advanced Engineering of the University of Canterbury was formed in 1988 to summarize and present data on precast concrete design and construction, to identify special concerns and to indicate recommended practices (Restrepo et al., 1989). The outcome of the deliberations of the Study Group was the publication of a manual entitled “Guidelines for the Use of Structural Precast Concrete in Buildings,” which was first printed in August 1991. A second edition incorporating experimental research evidences undertook in the first half of the ‘90s in Japan by Kurose et al., 1991 and New Zealand by Restrepo et al., 1995a was published in 1999. Two main connections categories are identified: strong and ductile. Strong connections of limited ductility are designed to be sufficiently strong, so that the connection remain in the elastic range, when the building is satisfying the ductility demand imposed by earthquake (Ghosh et al., 1997). Ductile connections of equivalent monolithic system are designed for the required strength and with longitudinal bars, grouted post-tensioned tendons or mechanical connections located in the regions that are expected to enter the post-elastic range in a severe earthquake (Park, 2002). Depending on the arrangement of precast concrete members forming moment resisting frames, 4 different approaches may be identified as suggested by

“Guidelines for the Use of Structural Precast Concrete in Buildings (1999)”:

 System 1, precast beam units between columns;  System 2, precast beam units through columns;  System 3, cruciform elements;

 System 4, pretensioned precast U-beam units between columns.

This approaches represent even today a reference in the field of emulative precasting. In the following, a brief description of each system is reported together with most recent experimental researches.

1.4.2. Precast system n°1

Layout of this system is shown in Fig. 19. The arrangement involves the adoption of precast reinforced members to form the lower part of the beams. These are placed between column and seated on the cover concrete of the previously cast-in-place or precast column (Fig. 21). Propped erection is usually required (Fig. 19 right).

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F

Lo at re co to to th ov co

Fig. 18: Vertical r

Fig. 19: Precast s

Fig. 20: Joint’s re

ower longitudin t the far face o easonably large

ongestion caus op of the beam opping slab ove he system. To

verdesigned, l onnection) as r

rebar splice syst

system n°1 layou

einforcement for

nal reinforceme of the cast-in-p

e to accommod sed by hooked ms, over the pr er the precast assure a ducti eaving the be required by the

a)

tems; a) grouted

ut

system n°1 Fig

ent is spliced in place joint. Hen

date the requir rebars (Fig. 20 recast floor an

floor system a le frame behav eams’ end to capacity desig

steel sleeve; b)

g. 21: System n°

n the joint core nce the column red developme 0). Reinforcem nd in the beam and the cast of viour the colum

behave in a gn approach.

b) corrugated steel

1 before casting

e using 90-deg n dimensions n ent length and ment is then pla m-column joint f the joint core mn connection ductile manne

) l ducts

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Full-scale lab 1995b eviden from cast-in-p

Fig. 22: Expe the en

Main drawba units slightly usually very s Dimensioning

Fig. 23: Lap

A slightly mo in Mexico. It the numerou Northridge an layout of prec order to inc strengthening common prac column voids when limited

boratory tests nce excellent e place-members

erimental tests on nd of tests, Rest

ack of this prec longer than an small tolerance g detail can be

p splicing design

odified version o replaces the p us failures of nd 1995 Kobe cast system n° crease mount g. To overcom ctice in Mexico s, to provide st d column dime

reported by R energy dissipa

s (Fig. 22).

n precast system trepo et al., 1995

cast system is nticipated could es are left for th

found in Restr

detail (Restrepo

of this system practice of in-si fully welded earthquakes. S 1, are replaced ting speed, a me the issue o to hook bottom

tructural contin ension does n

a)

Restrepo et al., tion capabilitie

m n°1: a) hysteres 5b

related to con d restrict the p his purpose. repo et al., 198

o et al., 1989)

is being widely ite beam longit moment con Single-storey co d with multi-lev and reduce tim

related to co m beams’ long nuity. This solu not comply wit

1989 and Re es similar to tho

sis cycle; b) Crac

nstruction toler placement of jo

9, Restrepo et

y adopted in the tudinal rebars w nnections durin

olumns used fo el “window typ me required nstruction tole itudinal reinforc tion is adopted th the Code p

estrepo et al., ose expected

ck pattern at

ances. Beam oint hoops, as

al., 1995a.

e last decade welding, after ng the 1994 or the original

e” columns in for concrete erances, it is

cement in the d in particular provisions for

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an B Ex A ca ex ho co fu st ho F F Th fra te nchorage lengt uilding Code (A xperimental cy lcocer et al. apability is goo xpected level f oops used to ontributed to in urther beam ro torey performe oops in the hoo

Fig. 24: Reinforci 2002

Fig. 25: a) plastic

his issue could ames subjecte esting two sam

th, despite this ACI 318-08),no yclic tests on re (2002) do no od for drift lev from equivalen achieve con itial joint dama otation inside t ed by Rodrigu oked bars could

ing details of a w

c mechanism at

d be overcome d only to gravit mples, the firs

s approach is n or in the Mexico eal-scale beam ot provide enc

vel lower than nt monolithic sa

tinuity, as we age. Joint mech he joint (Fig. 2 uez & Blandon

d not provide th

window-type beam

failure; b) experi

e adopting pre ty loads. Rahm st representativ

not explicitly al o City Building m-to-column join couraging resu 3% but stren ample. Premat ell as pullout hanisms of resi

25). Further te n, 2005 confir

he required con

m-to-column con

imental cyclic loo

ecast system n man et al., 2008 ve of the prec

lowed neither Code (MCBC-nt (Fig. 24) per ults. Energy d ngth is only 80 ture bending fl

of beam bott stance were im ests on a half

med that the ntinuity for thes

nnection, Alcocer

ops (Alcocer et a

n°1 for momen 8 investigated t cast frame, th

in the ACI -93). rformed by dissipation 0% of the

exibility of tom bars, mpaired by scale two continuity se bars.

r et al.,

al., 2002)

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correspondin and lower reb was placed response in specimen wit limited dama the corbel. S Moreover fo connection. connections Elliott et al., evidence sug totally rigid co

Fig. 26: Beam

Fig. 27: Expe at ulti

ng to an equiva bar through the at core-joint Fig. 27 indic th respect to ca age in compres

plitting failure o orce deflection There are s in reducing glo

2004 and Fer ggests to class

onnection.

m-to-column joint

erimental results imate load; b) loa

alent monolithic e joint. No spec level. Experim cates compar ast-in-place sp ssion of the pre of compressive n curve allow several studie

obal framed st rreira et al., 20 sify the solution

t samples tested

by Rahman et a ad-deflection cur a)

c cast-in-place cific confineme mental eviden able or highe ecimen. Crack ecast frame, p e concrete took

s to estimate es investigatin tructure stiffnes 011. In the con n proposed by

d by Rahman et a

l. (2008); a)crack rve

frame with con ent or hooking r nce from mon er performance k pattern at failu robably due to

place in mono e stiffness of ng the effect

ss, like those nsidered case

Rahman et al

al., 2008

k pattern of prec

ntinuos upper reinforcement notonic curve

e of precast ure points out o the effect of olithic frame.

the precast t of precast

presented by experimental ., 2008 like a

cast specimen

(32)

1. P ca po th re to cl pr w pl ha To th pr im .4.3. Precast recast system ast-in-place co ortion of the be he precast elem einforcement. T olerances, due

ear height betw rotrude up thro where they are astic tubes are as been place o

Fig. 28: Precast

Fig. 29: Precast

o complete the he beam. Des rovided by lite mplemented co

 Straight

system n°2

n°2 takes mor oncrete in the eam extends fr ment over the The success

to the fact that ween beams w ough vertical co grouted and pa e placed over t

over the colum

t system n°2 layo

t system n°2; a)

e frame system sign informatio

erature (Restr nnection techn and double-str

re extensive us congested be om midspan to column the co of the system t precast or cas without gaps. T

orrugated steel assed into the he bars (Fig. 2 mn.

out

a) mounting phase

m, connections on on a variet

repo et al., 1 niques is report raight bar laps

se of precast a am-column joi o midspan and omplex arrange m depends o st-in-place colu he vertical colu duct located i

column above 29a) and then r

e; b)column bars

have to be cre ty of beam-to 995a). A revi ed from Fig. 30

and avoids the nt Fig. 28. Th hence, it inclu ement of joint c on smaller tha

umns need to o umn bars below

n the precast b e. To help this

removed, once

b)

after joint groutin

eated at the m o-beam connec

ew of most c 0 to Fig. 32:

placing of he precast des within core hoop an normal occupy the

(33)

 Drop  Weld  Mech Some exam reported in F

Fig. 30: a) Be c) exa from

Fig. 31: Beam

Fig. 32: a) Be

p-in double hoo ded connection hanical coupler ples about co ig. 34.

eam-to-beam con ample of connec cyclic test from R

m-to-beam conne

eam-to-beam con

oked bars s r

onstruction in

a)

c) nnection using s ction using doubl Restrepo et al., 1

a) ection using drop

a) nnection using m

New Zealand

straight bar laps; le-straight bar lap 1995b

p-in double hook

mechanical coup

adopting sys

b) double straigh ps; d) experimen

ked bars, 2003

ler, 2003

stem n°2 are

b)

d) ht bar laps; ntal results

b)

(34)

F

Fig. 33: a) Beam welded r

Fig. 34: a) 22-st tall ANZ

m-to-beam conne rebars, 2003

torey Prince Wat Z Tower in Auckla

b) ection using weld

a) terhouse-Coope and (NZ), Park,

ded bars; b)weldi

r building in Chri 2002

a)

ing operation set

ristchurch (NZ); b c) t-up; c)

(35)

1.4.4. Preca

Precast syste cruciform or 35). It appea

Fig. 35: Preca

Fig. 36: 13-st

Vertical colum or grouting t

ast system n°3

em n°3 is given multi-storey c rs as an update

ast system n°3: p

tory Unisys Hous

mn bars in the hem into corru

3

n by an arrang cruciform units, e of original “Se

precast T-shape

se in Wellington

precast units ugated steel d

ement incorpo , depending o eria 106” techn

d element, 2003

(NZ), Park, 2002

are connected ucts, at core-jo

orating T-shape n precaster’s nology(Fig. 10)

3

2

d using grouted oint or mid-spa

ed, H-shaped, solution (Fig. .

(36)

18 (F co M pr he 1. In ha ar co In th co C se th br th F

8).Cast in plac Fig. 30 to Fig. oncrete and th Mounting ease,

recast element eavy and bulky

.4.5. Precast

n this precast s as U-shaped c re seated on t oncrete is cast n the early deve he formwork fo

ore concrete en yclic experime evere seismic l he cast-in-plac reakdown of bo his precast syst

Fig. 37: Precast

ce beams conn 32). Main ben he elimination

on the contr ts, in particular y and difficult to

system n°4

system, widely cross section ( the column. Lo t monolithically elopment by Pa r core concret nclosed by the ental tests perf oading, there w ce reinforced

ond. This had tem.

system n°4, Par

nection are ide efits of system

of complex re rary, might be r when provide o manage.

adopted in Ne (U-shell). In the ongitudinal reb

in the beam c ark & Bull, 1986

e in the tempo stirrups is used formed by Par was a tendency

concrete core a negative imp

rk and Bull (1986

ntical to those m n°3 are the e einforcing deta e sensibly affe ed in multi-leve

w Zealand, the e construction bars are placed core and the be 6, the precast c orary construct

d for structural rk & Bull, 1986 y for the plastic e within the p pact on energy

6)

employed for extensive use ails on constru ected by dime el layout, resul

e precast conc site, the U-sh d inside the U eam-column co concrete shell tion phase, and

purpose Fig. 3 6 evidenced th c hinging to spr precast U-beam y dissipation ca

System 2 of precast ction site. ensions of ting those rete beam hell beams -shell and onnection. is used as d only the 38 (left),. hat, during

(37)

Lee et al., 2 placed in the favor a full-s precast fram is filled with U-shell after improved lay severe pinch A recent exp this aspect. 5 confinement and energy d and deforma monolithic re capacity and cast-in-place slippage of re

Fig. 38: U-she 2004

Fig. 39: Cycl cyclic

2004 develope e precast concr section strengt e, one-piece m cast-in-place c

the two contin yout, experimen

ing.

erimental camp 5 different spe

details to impr dissipation capa

ation capacity einforced conc d stiffness of th specimen. Th ebars occurred

ell joint layout de (right)

lic behaviour of U c hysteresis loop

ed an updated rete are conne th (Fig. 38). T multi-level colu concrete. Long nuous beams ntal tests exhib

paign performe ecimens were a

rove the joint p ability. The spe y, which were

crete specime he specimens his is mainly d

at the beam-c

eveloped by Park

a) U-shell joint (spe ps, Park et al., 20

version of th cted to the cas To enhance th mns are adopt itudinal bottom are seated on bited poor energ

ed by Park et a arranged with performance in ecimens show e comparable en. On the co are significan ue to the diag column connect

k & Bull, 1986 (le

ecimen SP1); a) c 008

he U-shaped s st-in-place core he mounting s ted. The beam m bars are plac the column v gy dissipation c

al., 2008 furthe different reinfo terms of stiffn good load-carr to those of ontrary, energ

tly lower than gonal shear cra

tion.

eft) and updated

crack pattern at

shell. Stirrups e concrete, to speed of the m-column joint

ced inside the oids. Despite capacity, with r investigated orcement and ness, strength rying capacity conventional y dissipation

those of the acks and the

by Lee et al.,

(38)

A na an Ex on of cy th A th 20 similar beam ame “APE sys nd additional re

xperimental tes n interior (Fig. f strength and yclic loading ca he absence of s

Fig. 40: a) cyclic assembl

Fig. 41: Cyclic b b)cyclic

further confirm his kind of prec

010. Both inter

to column join stem”. U-shell ebars are plac sts performed 40) and exterio

ductility (Fig. 4 ause an appre smeared cracks

c tests configurat ly, Mazzotti et al

behaviour of U-sh hysteresis loops

mation of the r ast solution is rior and exterio

t was develop beam acts as ed in the joint at University o or joints indicat 41b), but bond eciable “pinchin s inside

a) tion for U-shell jo ., 2011

a) hell joint from AP s, Mazzotti et al.,

rebar debondin given by third p or U-shell joint

ed recently in scaffolding fo to assure beam f Bologna by M te as the samp

failure of reba ng” effect. This -to-column joint

oint from APE sy

PE system; a) cra 2011

ng phenomena party tests, per were tested. T

Italy under the or cast-in-place m-to-column co Mazzotti et al., ples behave we ars inside the j s is further con

t (Fig. 41a).

ystem; b) details

ack pattern at fai

under cyclic lo rformed by Lign The experimen

e patented e concrete onnection.

(39)

evidenced th performance To reduce th concrete grad as suggested increase of jo was about respectively f

Fig. 42: Cycl

1.4.6. Bene

A general po tradition. Sinc properly det provisions u general the r RC frames, debonding du Further aspe the ease of a generally de scaffoldings d concrete is n sensibly the strengthening then necessa

hat un-proper compared to a he pinching effe

de is increased d by Park et oint performan 5% and 10% for interior and

lic behaviour of in

efits and drawb

ositive aspect f ce the 80’s the tailed. Their d usually adopte restoring of ade

with the exc uring cyclic loa ects to conside assembly and m eal with self

during construc necessary to p

erection spee g after each c ary not to slow

detailing ma an equivalent c

ect resulting fro d to improve b

al., 2008. The ce in term of e % lower than exterior joints.

nterior U-shell jo

backs of emulat

for emulative m ey demonstrat design is reas

d for cast-in-equate strength ception of sys

ding.

r to check effe mounting spee bearing capa ction. Neverthe provide global s ed of frames, b casting. An ac

down excessiv

ay lead to a ast-in-place mo om the first tes ond and the U ese improveme energy dissipat n the equival

oint, Lignola et al

tive approach

monolithic syst ed to perform w sonably simple -place constru h and ductility l stem n°4, suff

ectiveness of a d. Considered acity, thus no eless considera structural stren being required curate plannin vely the rising o

dramatically onolithic solutio st series, both U-shell thicknes ents led to a tion, despite jo lent cast-in-pl

l., 2010

ems is related well under seis e, being requ uctions. This g

evel, analogou fering conside

a precast soluti emulative prec ot requiring fo able amount of ngth and stabi d enough time ng of construct

of the building.

worst joint’s on (Fig. 42).

cast-in-place ss is reduced, considerable oint’s strength ace sample,

d to their long smic action, if uired to fulfil

guarantee in us to classical

rable rebars’

on should be cast solutions or temporary f cast-in-place

lity. This limit for concrete tion phase is

(40)

To improve this issue, multi-level precast columns may be adopted. In this way, up to 3-4 storeys can be assembled contemporarily. Limitation in the maximum storey number is given by the dimension of the precast elements, which might become bulky and difficult to transport and manage.

1.5. United States approach to precast framing

1.5.1. The dry connection approach

Differently from other countries like New Zealand, Mexico and Japan, where the monolithic-emulative precast technology has been widely adopted since the middle of the 80’s (par. 1.4), in the United States this solution didn’t found the approval of precasters and contractors (Stone et al., 1995).

Main motivation was that mixing of precast concrete and cast-in-place concrete could result in scheduling conflicts between construction phases when the cast-in-place concrete is required for structural stability of the system, with increased construction time and with economical impact on construction costs (Saqan, 1995) As a result, during the 80s and the whole 90s, the implementation of precast construction in high-seismicity area was seldom used (Stone et al., 1995).

Beyond practical application, even the American research community opposed strictly to emulative approach for precast system. As reported by Stanton et al., 1997, this approach was perceived like “a limitation that inhibits innovation without

considering peculiarities and potentialities of precast system”. The basic idea that

marked US research during the whole 90s was that of moving inelastic response from members to connections. These are detailed to be weaker than the precast elements, and are intended like locations of inelastic deformations. As a consequence, the precast members should not be detailed for ductility and should remain elastic during seismic action.

Two multi-year multi-phase research programs were arranged with the aim of investigating this topic: the National Institute for Standards and Technology (NIST) program (1987-1995) and PRESSS (Precast Seismic Structural System) program (1991-1999) (Sritharan et al., 2000).

(41)

connections, emulative sys Developed “j namely:

 Post- Tens  Hybr NLE solution prestressed elastic. The dissipate ene Hybrid syste mentioned sy devices to dis Further detai reported in ne

Fig. 43: Preca

1.5.2. Non

For this conn closing at the related to g connection ty

in contrast to stems.

ointed systems

-tensioned/pret sion-compressio rid connections

n consists su central tendon second conne ergy and emula em is a third ystems. It cons ssipate energy ls on these tec ext chapters.

ast joint classifica

linear elastic sy

nection type, no e interface betw geometrical rat

ype are prestre

the “wet” conn

s” may be grou

tensioned conn on-yielding (TC ;

ubstantially in . The typical b ection type us ate cast-in-plac

category whic sists in post-ten y

chnologies, the

ation (2003)

ystems

onlinear behav ween beams a ther than ma essed with cab

nections typica

uped into three

nection (NLE); CY) and energy

a rocking sy behaviour of th se yielding of e behaviour. ch merge toge

nsioned connec

eir past develop

ior is achieved and adjoining c terial nonlinea bles passing th

l of cast-in-pla

e main categor

y dissipating co

ystem, charact his connection rebar or othe

ether character ction with mild

pment and actu

through crack columns. This n

arity. Beams hough the bea

ce monolithic

ries (Fig. 43),

onnection;

terized by a is non linear er devices to

ristics of two steel or other

ual trends are

(42)

th pr th Ea Th to co pa F Fu pr Th co co jo w

he column. Cra roduce flexural he face of the c arly study on th he authors obs o spread into

oncrete, energ assing though t

Fig. 44: Connect

urther investiga rogram (Cheok he tested sub-a onnections an onnected in a c oint with post-te with different arr

acks or joints l stresses large column.

his type of conn served that yie

the beam as gy dissipation the column cau

tions tested at Un

ations on simil k & Lew, 1993, assemblages w nd consisted

cruciform shap ensioned fully b

rangements (Fi

at the column e enough to ex

nection were co elding of the ca

a consequenc was minimal. used a reductio

niversity of Cant

ar specimens w Cheok & Stone were 1/3 scale

of one preca pe. Connection bonded cables

ig. 45).

n face open w xceed the prec

onducted by Pa ables occurred ce of debondin Progressive d on of bending r

terbury, Park & B

were carried o e, 1993)

models of plan ast column an between mem passing throug

when bending compression s

ark & Blakeley at column fac ng. Prior to cr debonding of resistance.

Blakeley, 1971

out during NIST

nar interior bea nd two preca mbers was give gh column and

(43)

Note: 1in. = 25

Fig. 45: Beam

It was conc connections connection s degradation (

Note: 1in. = 25.4

Fig. 46: Hyste Cheok

A considerab given by Prie performances following adv

 prest lengt  the g  Sma As a result, th

5.4mm

m cross-sections

cluded that po could perform strength. Howe

(Fig. 46).

4mm 1kip = 4.44kN

eresis curve from k & Lew, 1991

ble contribute estley & Tao, 1

s was to use vantages:

tressing steel th;

global response ll residual drifts his connection

for connections

ost-tensioned as well than eq ver these suba

N

m a precast prest

to full underst 1993. The solu e partially deb

should not yi

e of frame build s are expected

is described as

tested at NIST, S

bonded preca quivalent mono assemblages s

tressed beam-co

tanding of res ution proposed bonded tendon

eld if it is un

ding should be .

s “self-righting”

Saqan, 1995

ast concrete b olithic specimen suffered exces

olumn joint tested

sults obtained d by the author

ns through th

bonded over

elastic, even if

” or “rocking” sy

beam-column ns in terms of ssive stiffness

d at NIST,

at NIST was rs to improve he joint, with

an adequate

f non linear;

(44)

Li eq vs F Ba an di be co do pr ca le F mited dissipat quivalent damp s. drift expected

Fig. 47: Typical p

ased on above nd University fferent prestre eams and sing olumns and s ogbone to sim rototype follow ables in centra evel lower than

Fig. 48: Pretensi

tion capabilitie ping factor  u d response is r

prestressed prec

e reported expe of Minnesota ssed (NLE) pr gle-story colum single-bay bea

mplify reinforc w similar provis

al position. Also 2%. Self-cente

ioned system; Un

es should be sually compris reported in Fig.

cast system force

eriences, Unive (Palmieri, 19 ecast system l mns (Fig. 48 ams. Post-tens cement arrang

sions and ado o the experime ering capabilitie

niversity of Texa

expected by sed between 5

. 47

e-drift response (

ersity of Texas 996; Palmieri layouts. The fir and Fig. 50). sioning cables

ement (Fig. 4 opt partially un ental evidence es are revisable

as at Austin (Saq

y this technol and 10%. Typ

(Priestley, 1996)

at Austin (Saq et al., 1996) rst frame uses

The second m s are located

49 and Fig. nbonded post-t

is similar for s e in both specim

(45)

Fig. 49: Prete

Fig. 50: Poss betwe

1.5.3. Tens

In this kind o connecting e hence the na The basic ide (i.e. high ene damage effec beam plastic Major efforts phases of P (Saqan, 1995 51 and Fig. 5 The first on longitudinal c

ensioned system

sible arrangemen een columns; b)

sion-compressio

of precast joint elements. Thes ame tension/co ea is that of sim

ergy dissipatio ct in the joint s

hinging). in the develop PRESSS progra 5) and Minneso 52.

ne adopt vert continuity of re

m; University of M

a) nt of pretensione

beam through c

on yielding sys

connection, en se are allowed

mpression yield mulating the no on capabilities, section, withou

pment of this k am. Solutions ota University

ical dogbone ebars. Ducts th

Minnesota (Palmi

ed connection in columns

stems

nergy is dissipa to yield in both ding.

on-linear behav =25-35%), c t spread it alon

kind of connect proposed by (Palmieri et al.

and mechan at contained th

ieri et al., 1996)

frame buildings;

ated through y h tension and

vior of monolith concentrating c

ng the beam (a

tion were done Texas Univers ., 1996) are re

ical coupler t he high-strengt

b) a) beam

yielding of the compression,

hic connection contemporary avoiding then

e during initial sity at Austin ported in Fig.

(46)

w w ar Th ev re en (u F F Th 53 if re st in D

were grouted af was reasonably round connecti he prototype p ven if is revisa egions were re nergy dissipatio usually lower th

Fig. 51: TCY sys

Fig. 52: TCY sys

he TCY concep 3). The solution the adoption ebars reduce d

train concentra terface. etails about the

fter threadbars y acceptable u on system cau roposed by Pa able a conside ebar are locat

on capability d han 2% in the d

stem with vertica

tem; University o

pt has been fur n appears simi

of corrugated drastically cast ation, rebars

e test arrangem

were snug tig until 1% storey used an anticipa almieri et al., 19 erable use of c ted. The spec

uring the whole design practice)

l “dogbones”; Un

of Minnesota (Pa

rtherly improve lar to the one p steel duct ins t-in-place oper are wraped fo

ment and result

ghtened . Even y drift, some ated failure of s 996 appears si

cast-in place c cimen performe e test and for d ).

niversity of Texas

almieri et al., 199

ed by PRESSS proposed by Pa stead of

block-rations. Furthe or a limited le

ts are reported

if connection local concrete specimen.

mpler than the concrete to fill ed very good drift level bigge

s at Austin (Saqa

96)

S research prog almieri et al., 1 -out to locate rmore to avoid ength near th

in par. 0.

behaviour e crushing

e previous, block-out with high er than 4%

an, 1995)

(47)

Fig. 53: Layo

A further e construction number of si imposed on t the once ov compression The adopted frame beam is made poss placed in the end of the d proposed to Englekirk, 2 resistance m specific strut transfer betw friction mech consider frict has been u (Englekirk &

confirmed hig ratio between depending on

ut for TCY joint t

volution of T of Paramou ingle bay beam the unconfined verstrained rei

loads. d solution in D

and into the co sible through t e precast colum

ductile rod (F connect single 002). Particul mechanism and

t-and-tie mode ween beam an

hanisms. Diffe tion as resistin updated and s Wang, 2008)

gh seismic per n 16% and 22% n reinforcemen

tested at PRESS

TCY system f nt tower (Fig. ms. Normally in d cover of the b inforcing bars

DR system is olumn where hi

the developme mn. A high stre

ig. 54). A pre e span beams i ar attention h d assure adeq el has been ide

d joint is assu erently from o ng mechanism specific formu . Experimenta

rformance from % and maximu nt arrangement

SS (Sritharan et a

found an inte 65) as conn n plastic hinge beam are exac to buckle ou

to move the y gh confinemen ent of a forged ength bar woul eliminary versio

in the Paramou has been dev quate confining entified for this red by bolt pre other regulatio

fro shear tran lations for de l tests perform

m this technolog um storey drift

.

al., 2000)

eresting applic ection system es the high con cerbated by the utward when

yielding eleme nt is possible T ductile rod wh ld then be scre on of this tec unt Tower (Eng voted to dime g (Fig. 55. Ins s purpose (Fig etensioning an ns, ACI 318-0 nsfer. Recently esign have be med by Chang

gy with equiva between 5,47%

cation during in a limited ncrete strains e tendency of subjected to

ent out of the This relocation hich could be ewed into the chnology was

glekirk, 1995; ension shear side the joint g. 56). Shear nd associated 08 allows to y the solution een provided g et al., 2008

(48)

D be pr F F M sy sh re pr in co te by Th jo be espite encoura e recognised: recision require

Fig. 54: DDB pre

Fig. 56: DDB stru

Metelli & Riva, ystem. Main ch hould increase esults easy an

recast element terface, both i olumn should ensile force thro

y Roeder & Ha he experimenta oint, in term of

ehaviour up to

aging structura the high reba ed for assembli

ecast system

ut-and-tie model;

2008 have rec haracteristic of shear resistan d damage sho ts. Specific hig

n tension and guarantee forc ough steel stu wkins, 1981 an al results on a f moment ver o 2.0% drift. Co

l performances ars congestion ing process be

; top view

cently propose f the connectio nce of connectio ould concentra

h-strength (24 compression. ce transfer fro ds embedded nd recently inve

full-scale spec sus curvature oncerning high

s, some import n in the core-j tween beam a

Fig. 55: D

Fig. 57:

Load-d a Load-dry joint p on is a Z-shap on (Fig. 58). Th ate at interface

4) rebars shou Specific embe m beam. The inside concret estigated by Za cimen show a g response, ch her drift values

tant limiting fac oint zone and nd columns.

DDB joint details

-deflection relatio

prototype base ped plates inte

he joint assem e without sprea uld yield at bea

edded connect idea is that o te as originally anchettin et al.,

good performa aracterized by s, the joint has

ctors could d the high

onship

d on TCY erface that bly should ads inside am-column tion inside of transfer proposed , 2011

(49)

limited dissip at 2.5% drift, pull-out of a c Further deve obtain an ef provide the d earthquake in

Fig. 58: Dry jo behav

1.5.4. Ener

In this conn between con behavior. Th yield, resultin large displa tension/comp the other side occur in both experimental

pative capacity due to the brit conical fracture elopment of the ffective bar an ductility and d ntensity

oint developed a viour

rgy dissipating s

ection type, e nnecting eleme e advantage o ng in cracking acement level

pression conne e permits only h directions (F

tests (>35%)

because of the ttle failure of th e surface radiat

e joint detail o nchorage syste

issipative capa

at University of B

systems

energy is diss ents. Special m of this connect

in the precast s. The same ections where s rotation. Then Fig. 59). Very )

e early collapse he connection o

ting from the an n the column em allowing th acity of the joi

rescia: a) joint la

ipated through material can be

ion type is tha t members tha e concept c slip occurs on a gap must be high energy d

a)

ed, reached du on the column nchored end.

side is require he bar yield w int, even in ca

ayout; b)Experim

h friction when e used to enh at reinforcing st

t is relatively s an be used one side of the

provided to all dissipation is e

ring the cycle side with the

ed in order to which should ase of a high

b) mental cyclic

(50)

F A co th D ca an F R to on co us be in co

Fig. 59: Friction c

similar energy onnection at be hat connection

isadvantages o apability. This i nd energy diss

Fig. 60: Friction c

ecently an ene o improve seism

ne to three s ommercial build sed to connec etween these put energy ge olumns’ base.

connection; Univ

y dissipation c eam mid-span.

can be easily r of energy dissi s probably the ipation have be

connection, Univ

ergy dissipation mic performanc storey height,

ding. The energ ct the beam to

two monolithic et dissipated, t

versity of Texas a

concept though A main advan repaired or sub pation systems

reason why th een limited con

versity of Texas a

n system has b ce of a typology widely adopte gy dissipation d o the column e c element durin thus reducing

at Austin (Saqan

h friction can b tage of this sys bstituted after e

s are related to is kind of conn nsidered in PRE

at Austin; Saqan

been developed y of skeleton pr ed in Italy m devices consis elements. Thro ng seismic eve frame’s total d

n, 1995)

be implemented stem above the arthquake eve o limited self re nections based

ESSS program

n, 1995

d by Marinini e recast structure

ainly for indu st in a friction m

ough the relati ent a certain a drift and solicit

d in shear e others is

nt. ecentering

on friction m.

(51)

1.5.5. Hybr

The basic ide that can pro energy dissip The hybrid jo program betw In developed equivalent m level bigger capability we MacRae, 199

Fig. 61: Typic

Fig. 62: Hybr

Unbon

rid frame system

ea in this syste ovide self-cent pation capability

oint technology ween 1992 and d specimens monolithic speci than 2%). How ere demonstra 96.

cal NLE system f

rid connection de

NLE system

M

θ

nded post-tension (PT tendons/bars

m

em is to comb tering capabilit

y.

y was mainly d d 1994 (Stanton energy dissip imen and failur wever limited d

ted. Similar re

force-drift respon

eveloped at NIST

T) Mild

M

TCY s

bine two differe ties and TCY

developed dur n et al., 1997).

ation capabilit re was achieve damage in co esults were als

nse

T; Stone et al., 1

steel

θ

ystem

ent technology: system, that

ring the last ph

ty was slightly ed with bar fra ncrete and se so obtained by

995

Hybrid system

M

NLE system can provide

hase of NIST

y lower than acture (at drift

lf recentering y Priestley &

m

(52)

F

A P la te Sy (D Pa co se

Fig. 63: Experim of cyclic

Fig. 64: Layout fo

slightly modifie RESS program ayout was adop esting was requ ystem (Fig. 66 Day, 1999; Kim aramount tow ompleted in 16 eismicity area.

ental performanc load test; b) hys

for hybrid joint tes

ed version of t m (Fig. 64), im pted for the 39 uired to develop 6), and this eff m, 2000).

wer superstruc 6 month. Actua

a) ce of hybrid spec

teresis curve; St

sted during PRE

the NIST hybrid mproving self r

storey Paramo p a performanc fort was undert

cture build-up ally it represen

cimen OPZ4; a) tone et al., 1995

ESSS program; S

d system, was recentering cap ount tower (Eng ce based desig

taken at the U

started on ts the highest

crack pattern at

Sritharan et al., 2

further develo pabilities. A si glekirk, 2002). gn criterion for t University of W

March 2001 precast buildin

b) the end

2000

ped in the milar joint Additional the Hybrid Washington

(53)

Fig. 65: Para CA (E

Together with specific code 2008). With t of the type d widely used i social use. T Beside the o tensioned ca performances Morgen & Ku mild steel Displacemen friction surfa dissipating e connections installation, th

 close dissip 

post-colum exter  the d

until  damp

interf

amount tower in S Englekirk, 2002)

h experimental e regulation we this publication

eveloped by N in the US regio he Park Plaza original hybrid ables, new solu

s.

urama, 2004 de reinforcement nts at the beam

aces between energy. The

to the beam he use of the p e-to-rectangula pation per cycl -earthquake in mn joints can rnal to the joint dampers can a the post-tensio pers contribute faces.

San Francisco

l and in site va ere approved

, the technolog IST and Panko on, in particular

in Daly City (C frame layout c utions have be

eveloped a typo is replaced m-to-column int

the beam a proposed da m and column proposed damp ar force-displa

e;

nspections and be easily co ;

act as corbels t oning force is a e to the transfe

Fig. 66: Hystere cast sys

alidation of hyb in the ACI T1 gy transfer proc

ow, was compl r for high-storey California) is a e