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Precast reinforced and prestressed concrete frames provide a high strength, stable, durable and robust solution for any multi-storey structure. Precast reinforced and prestressed concrete frames provide a high strength, stable, durable and robust solution for any multi-storey structure, and are widely. Have you looked for this ebook Multi Storey Precast Concrete Framed Structures Pdf by ronaldweinland.info Study Group Or you intend to review it online?.
Precast reinforced and prestressed concrete frames provide a high strength, stable, durable and robust solution for any multi-storey structure, and are widely regarded as a high quality, economic and architecturally versatile technology for the construction of multi-storey buildings. The resulting buildings satisfy a wide range of commercial and industrial needs. Precast concrete buildings behave in a different way to those where the concrete is cast in-situ, with the components subject to different forces and movements. These factors are explored in detail in the second edition of Multi-Storey Precast Concrete Framed Structures, providing a detailed understanding of the procedures involved in precast structural design. Civil and structural engineers as well as final year undergraduate and postgraduate students of civil and structural engineering will all find this book to be thorough overview of this important construction technology.
If the address matches an existing account you will receive an email with instructions to retrieve your username. Skip to Main Content. First published: Print ISBN: Elliott and Colin K. About this book Precast reinforced and prestressed concrete frames provide a high strength, stable, durable and robust solution for any multi-storey structure, and are widely regarded as a high quality, economic and architecturally versatile technology for the construction of multi-storey buildings.
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Your password has been changed. Portal Frames are economical to produce and are often associated with industrial or warehouse buildings where a clear span of up to 35m or more is required.
It is straightforward to design, provided the flexural rotations at the end of the main portal are achieved. Generally a neoprene pad or other durable pad is inserted at the bearing to facilitate this flexibility and to avoid potential damage to the bearing ledge. Industrial - Portal Frame Additional Floors In the case of Portal Frames, first floors or mezzanines can be easily constructed by creating a corbel in the column element to facilitate the installation of a secondary post and beam.
Dowel bar or pinned connections are generally applied between the column and rafter sections. The horizontal load acting on the gable walls is distributed to the outer columns by single bay sometimes multi-bay roof bracing and gable bracing at each end of the building.
The diaphragm action of the roof also contributes to the stability of the building. In particular, jointing techniques and composite action between columns, floors and beams have been developed.
These have contributed greatly to increases in span capability, material efficiency and reduced costs. Multi-storey buildings can have different column configurations. The most common type of structure is composed of a Multi-Storey Precast Frame combination of continuous multi-storey columns at the perimeter and floor to floor single storey columns on the inner structure.
Other options are to use either single storey or multi-storey columns throughout the structure. Continuous columns bypassing each floor have a corbel at each floor level to support the surrounding beams.
Spandrel beams are typically positioned between the continuous columns on each elevation. Columns can be manufactured in lengths of up to 24m. However, the most economic length in terms of cost and handling is 15m. The key advantage of continuous columns is speed of installation. Spine beams are typically erected over these columns and are connected using single Storey Columns high strength dowel bars in grouted dowel tubes, cast into the beams and columns.
Continuous spine beams, resting on and connected to several columns are commonly used. These often cantilever over the end of the last column to facilitate a drop-in beam. See Detail, page With this method of precast construction, buildings are erected one floor at a time with beams placed at the head of columns at one level before the upper level columns are erected and connected through the beams to the columns below.
These structures have continuous edge beams which are jointed to the columns using high tension steel dowels grouted into dowel tubes cast into both columns and beams. This Column in turn reduces the height of the building which Grout Tubes results in cost savings. Minimising beam depth is particularly important where a computer floor Reinforcing Bars or other raised floor is required, increasing the overall floor height.
However, with a composite beam the final loading capacity Column will not be achieved until the screed is applied. Therefore, in the temporary condition, temporary propping may be required to avoid over-stressing or excessive deflection of the beam.
This type of construction is ideal for buildings of a cellular structure, for example hotels, offices, student accommodation, housing and apartment developments. Apartments - Cross Wall Construction Cross wall multi-storey structures consist of precast floors and load bearing walls, where the walls are designed as the means of primary support.
The system provides a structurally efficient building with main division walls offering a high degree of sound insulation between adjacent dwellings, offices, etc. These walling systems can produce buildings in excess of 20 storeys. However, in the Irish context, structures greater than 10 storeys are rarely required, primarily due to planning restrictions. The majority of car parks in Ireland are concrete column and deck structures. These are specialist structures, but their layout is ideally suited to a precast solution.
A typical layout allows a standard bay size in the region of The 7. The Car Park use of deep hollowcore units generally negates the need for inboard columns which inhibit vehicle manoeuvrability and obstruct the opening of vehicle doors.
Spandrel panels are combined beam and wall panel units. Spandrel panels also act as internal vehicle barriers or as external vehicle barriers when used at the perimeter of the structure. Tried and tested standard details for the interfacing of concrete and other construction materials are well established. Combining precast concrete with steel, cast in situ concrete, masonry and glass maximises the benefits of each material. The most economical result can sometimes be achieved by mixed construction methods.
Mixed construction requires a considered approach. Nowadays there is increased emphasis Industrial - on fire resistance, acoustics, low maintenance Precast Wall Panels and aesthetics.
These properties are substantially inherent in concrete, but are not necessarily inherent in substitute materials.
Steel, for example, needs substantial fire protection. The substitution of precast elements with steel must be carefully appraised. A good example of mixed construction is steel frame and precast concrete wall panels and floors. Using precast as the dominant form of construction in mixed construction reduces construction time, shuttering and wet trades. The number of reinforcing bars is greatly reduced and site safety is greatly improved by the installation of precast floors which act as safe working platforms.
Since most of the construction is carried out in the factory, there is less down-time and noise disturbance. The number of operatives on site is also greatly reduced. Consideration of the interaction and relationship between the frame, floors and cladding is critical to the overall building design and particularly to achieving a buildable, cost effective structure. When general requirements including the architectural design have been decided, the structural design can proceed in stages.
The following aspects must be considered: Other methods of achieving stability are sometimes employed. In frames up to three storeys high, it may be possible to consider the frame unbraced and to rely for stability on cantilever action in the columns and moment fixity at the foundations. The precast concrete floor is analysed by considering the slab to be a deep horizontal beam. The floor units must be tied and grouted together at the joints to ensure full plate action of the floor.
Office Blocks - 4. Structural integrity in the context of avoiding progressive collapse is normally obtained by using the fully tied solution incorporating full horizontal and vertical ties.
The function of a tie system is to enable the structure to bridge over a section failure and limit the extent of the damage to a localised area. In relation to the robustness of structures B.
In particular, situations should be avoided where damage to small areas of a structure or failure of a single element may lead to collapse of major parts of a structure. These ties must withstand accidental loads such as fire, explosion or subsidence or the collapse of an adjacent component.
There are a number of different methods for connecting units including tie-bars, steel billets or plates, in conjunction with the use of high strength grouts. The joint must also be capable of withstanding abnormal loads caused by fire, impact, explosion or subsidence.
The failure of a single joint should never lead to structural instability. These factors include: There are three main methods of fixing precast columns to the in situ foundation: Projecting Starter-Bars. Bolt or Baseplate Connections. In situ Pocket Foundation. The starter-bars are cast into the in situ base by the main contractor at locations specified on the drawings. The precast columns can then be erected on the base, with the starter-bars projecting into dowel tubes provided in the precast columns.
This method of fixing a precast column to an in situ base is extensively used in medium to high rise buildings where the complete structure is designed as a braced frame and thus a pinned connection is required at the base.
When structural requirements determine that the column must have a large foot dimension, the in situ pocket 1. The main contractor is responsible for the preparation of column foundations. This work must be carried out to a high degree of accuracy to avoid Engineering Brick mm min. Alternatively, mild steel bars can be welded to the baseplate and cast onto the foot of the column during the curing process. The column is then fixed to the in situ foundation using cast-in holding down bolts to form a pinned base connection.
Alternatively, the precast column can be fixed onto an existing base using holding down bolts which are drilled into place and fixed using a chemical anchor resin. The beam may be composite or non-composite. Composite beams act with the floor, column and screed to form a monolithic structure. Beams generally span from column to column.
Alternatively, the beam can cantilever over the end of the column to facilitate a drop-in beam. See diagram page Precast beam profiles are generally inverted T-Beams or l-Beams designed to facilitate the support of the precast concrete floor units. The billet is cast into the body of the column and projects from the column face to form a seating for the floor beam. Another common method of column to beam connection is the formation of a concrete corbel in the column. Precast concrete units have significant time-saving advantages over propped formwork flooring methods.
Reducing the construction programme and presenting the building ahead of schedule for rental are important cost-saving factors. In addition, openings can be left for services such as cabling and service hangers and fixings installed as part of the precast sub-contract package. Precast floor units are typically supported by concrete or steel beams or on solid block walls. Precast concrete floors are particularly valued for their excellent sound insulation and fireproofing qualities. The specific structural characteristics of each type must be taken into account in assessing the most suitable option for a particular application.
In some applications the structural capabilities such as spanning ability will determine the choice. In short-span buildings, structural and material efficiency or proximity to site might be the determining factor.
The most suitable choice is relative to the specific project requirements and conditions. Units are available in standard mm widths and in depths of mm to mm. Hollowcore slabs have excellent long-span capabilities, achieving a maximum capacity of 2.
The long-span capability is ideal for office, retail or car park developments. Units are installed with or without a structural screed, depending on requirements.
Slabs arrive on site with a smooth pre-finished soffit. In car parks and other open structures, pre-finished soffits offer a maintenance free solution. Hollowcore Floor Units 5. Apartments - Wideslab Floors There are two distinct types of wideslab: These slabs are generally for upper floors and have smooth self-finishing soffits. Some manufacturers can apply a specialist painted finish to the soffit as part of the contract. Generally a 75mm structural screed is required.
A triangular steel lattice girder reinforcement which projects into the screed can be used to increase the spanning capabilities of the wideslab unit and the overall robustness of the floor. The pre-camber of prestressed units should be discussed with the technical department of the selected precast company. Maximum spans of 7.
The system offers greater structural capacity at longer spans than hollowcore or wideslabs, but often requires a deeper floor zone. The Double-Tee system is the only system which offers a solution for spans over 16m. Double-Tee Floor Units 5. The advantage of Precast Composite Floors is the increased bending and flexural stiffness. Structural toppings can also be specified to improve acoustic performance and reduce vibration. In situ toppings will also improve thermal performance.
Structural toppings are generally 75mm to mm thick and it is recommended that their thickness should not be less than 50mm. For example, the drawings should confirm the designed reinforcement strand pattern, whether open cores are required for forming stability tie details and if temporary propping is required while pouring the structural screed.
Slab Widths All three flooring systems can be produced in narrower widths than the standard widths indicated. However, sq. Consequently, buildings designed on grids which are a multiple of mm will maximise the cost benefit of precast floors. Stair units are connected to floors and landings using steel angle joints.
Other connections such as continuous halving joints and intermittent halving joints are sometimes used. Combined stairs and landing units are also available. Once installed, precast stairs allow immediate, safe access to upper floors for following trades. Precast stairs are particularly cost effective when duplicated. The greater the number of identical units required, the lower the cost.
Units have steel bars projecting from the back which tie-in with the steel mesh in the structural screed of the precast floor units. Balcony units are temporarily supported while the structural floor screed is being poured.
When the screed has set, the supports are removed leaving the balcony unit cantilevered from the floor edge. Precast balcony units typically have integral drainage slots to receive drainage outlets and an upstand to facilitate Apartments - proper weatherproofing details at door threshholds. There is a wide range of high durability, low maintenance surfaces, including both integral and applied finishes.
Both highly polished and textured finishes are achievable. Brick, tile, marble and granite are typical finishes, but virtually any decorative stone can be applied. The most cost effective wall panels comprise of reconstituted stone, i.
Panels are typically mm thick and may be up to 9m in length and 3. Panel sizes are generally only limited by transport and cranage constraints. When installed, cladding panels may be either stacked off the ground, one above the other, thus transferring all vertical loads directly to the ground, or alternatively they may be independently supported at each floor level by means of localised concrete corbels.
Lateral fixings are secured to either beams or columns.
The main advantages of precast cladding are: Tight quality control measures are in place both pre and post casting. Installation is swift and panels are typically sized so that they can span grid to grid and floor to floor, allowing a large area of the building to be weathered in the shortest time possible. No scaffolding is required as all fixings are accessed from the rear of the panels.
In most cases, glazing units and insulation may be fitted to the precast units in the factory, speeding up the work of following trades. To make precast units more cost effective, it is important that panel sizes are maximised and a degree of repetition exists.
This approach ensures that a number of panels may be cast from a single mould. Natural stone blend, reconstituted stone and terracotta -faced panels are available. Panels arrive on site complete with fixing brackets. The wall is lifted into position and attached to the column which can be either concrete or steel. Because the loads acting on the panel are transferred into the column, no strip foundation is required.
However, Composite Panels are now being manufactured which comprise of an outer leaf of finished concrete or terracotta tile , a layer of insulation and a backing leaf of plain grey concrete, cast as a single unit.
The insulation is Office - Precast Brick-Faced Panel installed under controlled factory conditions and is protected from the elements by the concrete outer leaf. To fully optimise the system, the inner leaf of the sandwich panel can be used as a load-bearing element to support floor units, thus offering further economies in the building and minimising the need for co-ordination of different trades.
Wall panels can eliminate the following on-site activities: When technical and production issues have been resolved, production is then scheduled. As the project progresses, correspondence is referenced and stored. All relevant information, such as the position of fixings, penetrations, cast-in items, openings, lifting anchors, etc.
The production details are then forwarded to the consultants for approval. Production can take place when formal approval has been received from the project principals. Machine changes and mould alterations are kept to a minimum to achieve the most efficient batch production. This can only be achieved with the Apartments - Precast Cladding co-operation of the entire project team.
Panels 6. Complex mixes for a variety of different concrete products are stored in the batching plant systems. Precast components are reinforced by inserting steel bars or cages into the mould. Steel is generally cut and bent into the required shape. This can be done manually or by automated means.
An alternative to steel cages or strands is the use of fibre reinforcement. The fibres used can be produced from steel, glass or synthetic materials such as polypropylene. Certification of all materials is available from the precaster on request. The flexibility to pour sections, in a range of sizes, from one mould, ensures optimum productivity and facilitates the quick turnaround of precast components required on fast-track construction programmes.
These sections open apart to allow preparatory work and are then mechanically closed and clamped together to form a multi-cast mould. Typical applications would include retainer wall panels and other panel sections complete with door and window openings, suitable for apartment or housing developments. Moulds can be manufactured from different materials such as plywood, steel or fibreglass and may be lined with a range of purpose-made patterned liners to imitate natural finishes.
The choice of mould material is usually determined by the number of casts required and the complexity of the shape and size of the finished product. Specialised moulds can be adjusted and may be used for similar projects in the future. The mix design and volumes of concrete required are programmed into the system. The steel beds are thoroughly cleaned prior to use and a release agent is applied to produce a quality surface finish.
Reinforcing strands are placed on the bed and hydraulically tensioned.