Precast concrete structures History of prefarication early 20.century 1904 concrete precast panels system in Liverpool (house.12 flats) 1907 hollow wall and slab panels for low-storey family houses 1926 W. Gropius family houses in Dessau tranversal wall system 1930 Le Corbusier panel house in Geneva great development after World War II to replace houses bombed during WWII Europe 60ties/70ties France, Sweden, Danmark at the end of 70ties the flat shortage in European countries was fixed and prefabricated construction was reduced 1
Philosophy of industrialisation in the building industry economic view manufacture better conditions better material (const. temperature, higher concrete class, better surface) lower cost (reuse of mould, decrease of the cross-section dimension, holes) shorter time of producing (vertical and horizontal at the same time, manufacturing at low temperature - frost) Pozitives of precast structure manufacturing of element mechanization automatization of production better quality control (HPC, HSC) more economic dimensions reuse of mould decrease of weight decrease of labour consumption speeding of building process savings in formwork erection and demoulding 2
shape, self weight Surface quality appearance, durability 3
Graphic Concrete image is printed on the membrane with a surface retarder of concrete setting 4
Negatives od prefabrication abandon of monolitic shape not for complicated plans no rigid joints transport of element form plant to the site special road permits for oversized elements shape of the piece may affect the ease of transportation (beams x complicated shapes) 5
Structural design Standards and Codes EN 1992: Design of concrete structures Section 10 Precast concrete elements and structures old ČSN 73 1201 Clauses on connections and lifting anchors ČSN 73 1211 for panel buildings 6
Specifics of the design of precast structures Design the entire structure, system precast element connections 7
Design of the structural system dividing of the load-bearing structure precast elements, layout of connections modular coordination simplicity of assembling optimal shape and possible weight decrease of the element large-scale production careful elaboration of the design potential of savings Choice of a suitable load-bearing system with respect to manufacturing and assembling Layout of connections where small inner forces are transmitted or where compression forces act end sections of straight elements reduced number of connections 8
Layout of connections where small inner forces are transmitted or where compression forces act big quantity of connections complicated shape of connections differences in elements dimensions Layout of connections end sections of straight elements + simple shape of precast elements + their equal weight connections of elements have usually complicated loading and design 9
Layout of connections reduced number of connections lead to large precast elements with complicated shapes + smaller numer of precast elements is benefitial big weight of precast elements more demanding lifting devices 10
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USL SLS specialities Design load states, load situations (manufacturing, transport, assembling, final acting) lifting anchor systems connections Structural model of precast structures consider simplicity of assembling divide structures into particular elements (position of connections) shapes and weight-decrease of elements modular coordination 12
Design of the structure dividing of the structure to elements design of the precast element Design of the precast element ULS, SLS + special problems consider situations (change of structural system): manufacturing manipulation transport storage assembling final design of lifting anchors for transport and assembling modular and manufacturing dimensions design of connections 13
Dimensions and shape of precast element Modular x manufacturing dimension optimal decrease of the self-weight choice of structurally efficient sections quality concretes utilisation prestressing consider possibilities of transport (dimension limited by possibilities of means of transportˇ) Dimension and shape weight decrease efficient section 14
dimensions of elements, tolerances (for manufacturing, for assembling) work size x coordinate system Load situations manufacturing (lifting from mould) manipulation storage (position, supporting) assembling erection (temporary supporting before connection and grouting) transport (stiffness, spalling of parts sticking out from element) final acting 15
Load cases, transient situations manufacturing (lifting from mould) transport assembling final acting 16
Change of structural model q d (užitné) Lifting Anchors 17
shapes bent bar Lifting anchors notch special devices (screw) Lifting anchors design Design for (load) separation from mould subsequent manipulation type of lifting device 18
N d manipulation force (ČSN 731201) lifting from mould N d = 1,3. (F k + F n,adh ) n.cos a manipulation g man. g G g G N d = 1,8. (F k ) n.cos a! 1 2 kn/m 2 * area 3 19
n lifting spreader beam rigging - 4 ropes (chains) 20
Bent bars steel 11 373 21
strain: tensile, shear Reusable anchors for lifting 22
Lifting 23
Lifting Eye Bolt 24
system BS 25
Possible failures breaking, rupture of the anchor pulling out of the anchor pull out of the whole anchor area due to concentrated load rupture due to tensile stresses load 26
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Assembly 28
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Connections 30
Classification of connections according to way of fabrication: wet, dry, combined according to structural acting hinged, fixed don't transmit forces according to connection close contact (with concrete) dry (plane surface) filled connections (by concrete) thickness of gap min. 2x gravel diameter, max 2x smaller depth of the element glued Connections According to way of fabrication: wet filling of the connection by concrete or glue + simple attached after hardening 31
Connections According to way of fabrication: dry welding, screwing together filling by cement mortar to protect steel + attached immediately after welding (screwing) more complicated more demanding (accuracy, control) tolerance Connections design analytic experimental 32
Connection slab slab grouted connections welded or screwed reinforced concrete topping Connection slab slab shearing 33
Connection slab slab shear key 34
connection wall wall Connection beam slab anchor plate welded bar hook shear tie Welding Shear connection Dowel connection Concrete topping shear hook connectors 35
Connection beam slab connection beam slab 36
connection beam slab connection beam slab 37
connection beam slab 38
connection beam beam 39
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Connection beam to column 41
Connection column beam continuous column without corbels (splicing of beam reinforcement) with corbels continuous beam connection block Connection beam continuous column 42
Connection beam continuous column connection beam continuous column 43
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Connection beam continuous column plate ( knife ) 45
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connection beam continuous column steel plate ( knife ) 47
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connection column column 51
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connection column basement monol precast prefa-monol 54
Halfen-Deha Pfeifer Bolt connectors (Halfen-Deha) 55
System Crazy Brush (SICON) 56