The Hollow Core Floor - Design and Applications


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ASSAP was founded to promote and enhance the prestige of the pressurised hollow core floor.

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the hollow core floor design and applications assap hollow core slabs association of manufacturers of prestressed hollow core floors


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the hollow core floor design and applications manual assap 1st edition hollow core slabs a ssociation of m anufacturers of p restressed h ollow c ore f loors


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assap assap association of manufacturers of prestressed hollow core floors offices via castelletto 5 37050 belfiore verona italy telephone 0039 045 8780533 ­ fax 0039 045 8780544 e-mail web site


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list of assap members june 2002 centro italia prefabbricati s.r.l via campo di marte,14-h 06124 perugia italy tel 39.075.5002743 fax 39.075.50003285 edilgori precompressi s.r.l via del maglio 10 05100 terni italy tel 39.0761.402196 fax 39.0761.402197 e.p edilizia prefabbricata s.r.l via campobello 10 00040 pomezia roma italy tel 39.06.9120256 fax 39.06.91603111 esse solai s.r.l strada delle fornaci 13 36031 vivaro dueville vicenza italy tel 39.0444.985481 fax 39.0444.986558 europrefabbricati s.r.l zona ind di castelnuovo vomano 64020 castellalto teramo italy tel 39.0861.57737 fax 39.0861.507063 giuliane solai s.r.l via della fornace 16 loc mortesins 33050 ruda udine italy tel 39.0431.99588/9 fax 39.0431.999990 hormipresa s.a ctra de igualada s/n s-43420 sta coloma de queralt terragona españa tel 34.977.880124 fax 34.977.880534 iapiter s.r.l via campo di fiume 14 83030 montefredane avellino italy tel 39.0825.607168 fax 39.0825.607041 s.r.l via b da montefeltro 28/d 52100 arezzo italy tel 39.0575.24288 fax 39.0575.22860 immobiliare centro nord s.p.a via castelletto 5 37050 belfiore verona italy tel 39.045.8780533 fax 39.045.8780544 s.r.l via 2 giugno 51-a 13063 masserano biella italy tel 39.015.99120 fax 39.015.99474 laterizi fauci s.p.a contrada bordea 92019 sciacca agrigento italy tel 39.0925.26122 fax 39.0925.26931 marchetti morandi s.a.s via camporcioni 58 51019 ponte buggianese pistoia italy tel 39.0572.635367 fax 39.0572.635369 pavicentro s.a apartado 2 38015-501 eixo aveiro portugal tel 00351.234920200 fax 00351.234920201 precompressi centro nord s.p.a via mulino vecchio 28065 cerano novara italy tel 39.0321.726873 fax 39.0321.728026 prefabbricati dignani s.a.s via s egidio 5-a 62010 montecassiano macerata italy tel 39.0733.599427 fax 39.0733.599087 pretensados industriales s.a av charles de gaulle ave hipica santo domingo rep dominicana tel 001.809.7661151 fax 001.809.7661154 rdb s.p.a via dell edilizia 1 29010 pontenure piacenza italy tel 39.0523.5181 fax 39.0523.518270 s.g.c s.r.l contrada baronia 74021 s giorgio jonico taranto italy tel 39.099.5926815 fax 39.099.5916739


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capitolo 1° editorial staff gennaro capuano ­ university federico ii napoli bruno della bella ­ precompressi centro nord s.p.a novara giorgio della bella ­ immobiliare centro nord s.p.a verona pierluigi ghittoni piercarlo morandi ­ professional piacenza ­ marchetti morandi s.a.s pistoia english translation david c nilson ­ cagliari first published in english 2002 published by offset print veneta verona italy all rights including translation reserved to assap members d 1.1 notizie storiche


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assap assap the association of manufacturers of prestressed hollow core floors a non-profit association for the promotion safeguarding and defence of the hollow core floor and the legitimate interests of associated producers from article 2 of the articles of association associates at the time they are admitted commit themselves to orient their company s policies in the direction of quality and to respect the technical and ethical criteria established by the association from article 4 of the articles of association assap was founded in june 1982 in ponte taro parma italy with the participation of almost half of the producers then present on the italian market the guiding idea was to promote and enhance the prestige of the prestressed hollow core floor the members of assap in alphabetical order are the following companies some of which in italics no longer exist or have left the association for having ceased the production of hollow core floors antares in frosinone bonetti prefabbricati in castenedolo brescia cementedile in lauriano po turin centro italia prefabbricati in frosinone concari prefabbricati in parma dignani prefabbricati in montecassiano macerata edilcemento in gubbio perugia edilgori precompressi in terni e.p edilizia prefabbricata in pomezia rome esse solai in dueville vicenza europrefabbricati in castellalto teramo giuliane solai in ruda udine hormipresa in tarragona spain iapiter in avellino icienne in arezzo immobiliare centro nord in san martino b.a verona inpredil in masserano biella inprevib in chivasso turin laterizi fauci in sciacca agrigento marchetti morandi in ponte buggianese pistoia mubemi in valencia spain pavicentro in aveiro portugal pavinorte in penafiel portugal precompressi centro nord in cerano novara precompressi metauro in calcinelli di saltara pesaro pretensados industriales in santo domingo rep dominicana r.d.b in piacenza s.g.c in taranto s.i.c.s in lodi sun block in kuala lumpur malaysia vibrocemento sarda in cagliari.


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assap soon after its creation assap turned to prof franco levi of the politecnico of turin for his expert advice he strengthened the scientific basis of the engineering techniques and applications that the association s proposers belonging to the gruppo centro nord had previously developed and shared with all assap members from 1982 to 1986 the testing laboratory of the politecnico of turin directed by prof pier giorgio debernardi devoted its energies to the experimental testing of the restraint of continuity established between hollow core floors on several supports by means of normal reinforcement resistant to negative moment and inserted in situ in the slab ends prepared specifically for the purpose the second task was the study of the mechanical model to explain the unexpected experimental behaviour of the restraint of continuity between hollow core slabs during the cracking phase effectively once the positive and negative moments of cracking had been reached and passed experimentally in the laboratory it was noted that these cracks never joined one another and thus caused no structural collapse it was found that cracks remained separate owing to the presence at the ends of the arch and tie system of compression struts in the concrete see fig 4.10 in chapter 4 which inhibited their coming together thus collapse is avoided in the cracking phase prof franco levi politecnico of turin italy


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assap thanks to this formidable and reassuring scientific diagnosis prof levi opened the doors to italian and later european codes dealing with hollow core floors laid in continuity among the many innovative applications introduced by assap we also find the clear span connection between hollow core slabs and bearing beams cast in situ see paragraphs 4.4.2 and 4.4.3 what are the conditions within which these connections can be assured without support once again it was the testing laboratory of the politecnico of turin that addressed this new research challenge through the construction of beam models both depressed and in floor thickness cast in situ with hollow core slabs in continuity but not lying on the beam itself results of the tests confirmed the validity of the engineering idea although with the limits and precautions dictated by prof levi see paragraph 4.4.4 the last research project which dealt with spalling stresses see paragraph 3.5.2 required a three-year effort if in normal prestressed beams vertical tensions in the web-end are absorbed by the specific stirrups in hollow core slabs they must be opposed by the tensile strength of the concrete alone spalling stresses must also be specifically restricted if the hollow core slab is inserted as a clear span between bearing structures cast in situ this manual which represents self-regulation document for companies producing prestressed hollow core slab floors and assap associates is an instrument containing the knowledge acquired by the association through specific studies and research and which has supplied to associates the know-how necessary not only for the production but also for the design of hollow core slab floors on innovative and precise technological and scientific bases.


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foreword foreword after thirty years of continuous and enthusiastic work in a specific field a technician unknowingly and inevitably becomes a specialist in that sector and finds what he has been dealing with for many years so obvious that he or she is dumbfounded when professional colleagues do not show the same level of expertise in such a congenial subject in the case of the technicians who formed the nucleus that led to the founding of assap they were too often perplexed by the inaccuracy of some producers and many designers in the specific field of the production and application of hollow core floors for these reasons starting from the 1980s assap began thinking of writing a manual in which to state the principles for the correct design and application of this universally known component which is sometimes not fully appreciated owing to preconceptions and improper applications the sum of the experience gained by the technicians of the assap committee was found to be so vast that it could not be contained in a sort of instant guide to because while putting it into hard copy form it became more like a treatise the obvious consequence was that its preparation would require far more time and many more revisions than were originally planned the book you are now reading is thus a complete compendium perhaps even too detailed but undoubtedly useful of important information providing in-depth knowledge of the hollow core floor and its prefabricated component which is the prestressed hollow core slab the purpose of this publication is thus to provide designers producers and users of hollow core floors with an instrument to assist them in finding solutions to problems they come across professionally problems that must be solved by bringing together theory and codes with correct constructive intuition taking into account the real necessities of practical construction work over the years designers have developed many innovative engineering solutions in the use of this prefabricated element these must be well understood before its special characteristics can be fully exploited while


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foreword maintaining safe structural conditions and complying with the rules of good building practice with this publication assap the association of manufacturers of prestressed hollow core floors has brought together the general design criteria which have been amply verified experimentally to provide designers with a practical instrument for use when dealing with all morphological types of hollow core slabs methods of calculation are standardized and practical rules for implementation in conformity with italian and european codes now in force are given with great dedication the following technicians participated in the preparation of this publication in doing so they have earned the unconditional gratitude of assap gennaro capuano bruno della bella pierluigi ghittoni piercarlo morandi and stanislaw pereswiet-soltan assap offers special thanks to prof franco levi prof pier giorgio debernardi prof crescentino bosco prof piero contini of the structural engineering department of the politecnico of turin and the late renzo perazzone who starting from 1982 conducted many experiments to verify a large amount of the technical and engineering formulations contained herein many thanks to bruno della bella for having completed the chapter 5th with the deformations argument about hollow core floors deserving of special mention are prof antonio migliacci of the politecnico of milan who as far back as 1967 formulated on an experimental basis the theory of transverse transmission of concentrated loads and prof marco menegotto of the university la sapienza of rome who conducted many experimental investigations on extruded hollow core floor slabs with special emphasis on diaphragm behaviour verona september 2002 giorgio della bella assap chairman


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contents contents notations references 1 4 chapter 1 1.1 1.2 1.3 1.4 hollow core slab floors 6 6 3 10 15 15 19 21 historical background general information reasons for choosing hollow core floors reference to codes 1.4.1 italian building standards 1.4.2 european building standards 1.4.3 important international documents chapter 2 2.1 2.2 production 23 23 29 29 30 31 32 notes on production technologies cross section geometry 2.2.1 types of hollow cores 2.2.2 typical shapes of lateral join faces 2.2.3 thickness of webs and flanges 2.2.4 distribution and cover of prestressing strands 2.2.5 examples of cross-sections of hollow core slabs relevant weights and geometric characteristics with simple support and without resistance to fire production details 2.3.1 open cores at slab ends 2.3.2 sheaths for strand neutralization 2.3.3 additional reinforcement bars 2.3.4 cut-outs in hollow core slabs 2.3.5 ways of lifting 2.3.6 holes for draining rainwater 2.3.7 plugs for hollow cores 2.3.8 devices for eliminating camber deviations dimensional tolerances 2.4.1 tolerances in dimensions and assembling 38 40 42 43 44 46 48 50 51 52 54 55 2.3 2.4


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contents chapter 3 3.1 3.2 3.3 3.4 static peculiarities 59 59 60 62 67 68 72 74 79 88 89 92 94 98 99 101 introduction floor depth longitudinal join shape concrete topping on the hollow core floor 3.4.1 interface shear capacity between in situ topping and precast slab prestressing 3.5.1 tensile forces in the transmission zone 3.5.2 control of spalling tensile stress in the webs 3.5.3 reduction of prestressing by means of sheaths 3.5.4 slippage of strands into slab ends rules and devices for the support of hollow core slabs 3.6.1 minimum design support length 3.6.2 additional reinforcement in the transmission zone for flexural and shear capacity 3.6.3 prestressing in the transmission zone for flexural and shear capacity increase in shear capacity with concrete filled cores 3.5 3.6 3.7 chapter 4 4.1 connections and structural schemes 102 102 104 107 108 109 112 119 121 123 123 126 127 129 130 131 connections and ties 4.1.1 connections in hollow core floors 4.1.2 anchoring capacity of connecting bars in the hollow core slab the execution of structural restraints 4.2.1 simple support 4.2.2 continuity in a multispan floor 4.2.3 redistribution of moments due to connection ductility 4.2.4 restraint for cantilevers the beam-floor connection 4.3.1 premise 4.3.2 inverted t and l-shaped precast beams 4.3.3 precast i beams 4.3.4 semi-precast beams 4.3.5 steel h-beams 4.3.6 steel reticular beams 4.2 4.3.


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contents 4.4 beams cast in situ 4.4.1 slabs with support on beam 4.4.2 clear span floor without support on beam 4.4.3 flat beam having depth equal to hollow core floor 4.4.4 design of the composite connection between cast in situ beam and hollow core slab without direct support the connection between hollow core floor and reinforced concrete loadbearing wall the large holes in hollow core floors 132 133 135 137 139 159 162 4.5 4.6 chapter 5 5.1 5.2 design principles 165 165 166 166 169 172 172 174 175 177 179 181 185 185 188 188 193 194 196 198 203 205 207 216 220 general considerations properties of materials and partial safety factors 5.2.1 properties of concrete 5.2.2 steel properties static and geometric preliminary dimensioning 5.3.1 use-graphs 5.3.2 limits of slenderness 5.3.3 analytical method for preliminary dimensioning 5.3.4 design rules for floors laid in continuity or with fixed ends 5.3.5 design of the corroborant topping transverse load distribution design of fire resistance 5.5.1 general considerations and calculations 5.5.2 the tabulated data method 5.5.3 analytical methods diaphragm behaviour 5.6.1 model for diaphragm calculation calculation of deformations 5.7.1 applications and pratical references 5.7.2 initial camber 0 at time t0 5.7.3 camber 1 after installation at time t1 5.7.4 in-service and long-term deformations 5.7.5 elastic sag at the time of final testing graphic representations 5.3 5.4 5.5 5.6 5.7 5.8.


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notations notations symbols used in this text comply with ec2 european code env 1992-1-1 ac afl ap efgimpqrsv vrd ved a b bc bi bw c d eo v h hf total cross-section area area of reinforcement bars area of prestressing tendons modulus of elasticity effect of action action general permanent action moment of inertia bending moment prestressing force variable action structure internal resistance effect of action shear force design value of the internal resistance to shear force design value of the applied shear force distance width width of a hollow core full of concrete width of a single web total width of slab webs distance concrete cover of tendons effective depth of a cross-section prestressing tendon eccentricity deflection depth of a cross-section depth 1



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