[Abstract] steel house is the fifth period will focus on the promotion of the project, its high strength, structure, small size, light weight, speed of construction, seismic performance and features of a high degree of industrialization. In this paper, major domestic and foreign steel structure of residential structure were reviewed and summarized the various structural systems were reviewed, and the steel structure housing the main problems existing in the design recommendations.
[Key words]
a steel residential structure system . Overview
reform and opening up, China's steel production has been greatly improved, especially after 1997, China's steel output reached over million tons, but the total amount of China's steel production steel steel compared to just 2% in steel consumption in the steel, construction steel and steel consumption accounted for only 10%, steel production in China as a great power is not commensurate with the position, for which the State Economic and Trade Commission developed in conjunction with the Ministry of Metallurgy in the promoting the use of steel construction projects a series of policy measures aimed at the 6% of the total steel output, while the Ministry of Construction will be steel housing development and application of steel construction industry as a breakthrough in China, and to develop a Technical guidelines for residential building systems. So steel housing is in line with national industrial policy to promote the project. As the state and restrict the use of solid clay brick disabled hollow clay brick introduction of policies to speed up the process of the housing industry, actively promote the steel housing is imminent. However, China's steel residential structure is still in the initial stage of exploring this system in the steel structure fire, beam-column joints practices, floor forms and supporting wall material, economic, and market acceptability of the still many imperfections. In the past few years beginning National Steel has been found in a number of pilot projects in housing, such as in Shandong Laiwu Steel Sakura Park residential district, Tianjin m steel frame shear wall high-rise residential, metal structure Ltd. Beijing Saibo Si core tube steel frame multi-storey residential, Shanghai Metallurgical Design Institute of the land and sea city, in Fujian City project, Maanshan Iron & Steel Co., Ltd. designed 18-storey residential building and other model experiments. steel housing design in our hospital has just started, to make everyone have a comprehensive understanding of residential steel for future Design accumulated the necessary technical information, is on the domestic steel housing as an introduction.
II. structural system
steel residential structure system can be divided into the following types:
1. steel frame and concrete cylinder (wall) of the hybrid structure system
2. plus supporting steel frame structural system
3. steel frame with precast concrete wall frame structure system
4. Pure Steel frame structure
5. staggered truss structural system
6. metal frame structure system
1) steel frame and concrete cylinder (wall) of the mixed characteristics of structural system
m concrete hybrid structure of steel layout of the elevator or bathroom floor is generally reinforced concrete to form the main lateral force resisting structure, the outer framework of the week by steel frame, this structure system will be high strength steel, light weight, speed of construction, and concrete compressive strength high strength, fire performance, lateral stiffness characteristics of the organic combination of peripheral connections generally use rigid beam, and floor with steel beams and concrete walls are hinged end, the concrete bear most of the horizontal force and therefore the displacement control indices mixed structure of reinforced concrete structures can be used with reference, but the framework part of the commitment of the seismic force not less than 20% of the bottom shear structure and the floor was 1.8 times the maximum shear force the smaller of the two, in large In most cases, the latter often play a controlling role in this system, the plane should be limited to non-residential part of the framework of the length of the wall, or floor just assumed would be infinitely difficult to meet. that the whole structure is characterized by the force damage is bending shear type, structural damage mainly in the concrete core tube, in particular the lower part of the concrete shell structure of the four corners of these areas should be strengthened to ensure the ductility of the cylinder, in addition to steel beams and concrete walls of connected parts of the force complex, is also the most easily damaged areas should ensure that the node may be able to withstand the axial force beam.
the inadequacies of this system for the core tube is concrete, not a lot of weight reduction, on-site pouring concrete The workload is still large. From the perspective of building layout, the general layout of pillars or corner in the balcony area, in order to facilitate handling household decoration.
2) steel frame support system for multi-storey and high-rise
building the wall in the building, location of windows and doors decorated with two-way cross-support, support can be angle, channel or bar, according to rod design, but also in the light steel residential structure, the support does not necessarily have to be from the bottom Set the same location, but also jump gingham set, its main purpose is to increase the stiffness of the structure, has opened the doors and windows for the exterior can also be arranged within the window height to form a similar band around the truss structure, the structure as a whole enhance rigidity.
of high-rise residential, and interior layout of choice braced gable or eccentric support, it is worth noting that, when using a single inclined column system should be set to different tilt directions of the two single-diagonals to bi-directional earthquake resistance, in terms of nodes, if the support of all buildings to withstand the lateral force, the beam can be made into the hinge, such as insufficient to support all of the buildings to withstand the lateral force, the beam can be partially or all made of rigid.
in the highly seismic region, if a relatively slender column, the most eccentric frame system, this system is characterized by small or medium-intensity earthquake under earthquake lateral stiffness to withstand the horizontal force , under the action of the earthquake but also has good ductility and energy dissipation capacity. braced frames under horizontal force, similar to the vertical cantilever trusses, columns bear the same chord as the external load produced bending moment, as the sway brace and the beam braces to withstand the horizontal force, shear braces exposure level, the axial chord lateral deformation of the framework of the deformation of the structure of structure of lower support structure, the shear deformation is most important, and sometimes it basically determines the structure of the lateral deformation, so the bottom layers of this structure between the large deformation; in the high-level structure, the column axial force and deformation of the larger and the significant accumulation of the two along the height of the dominant bending deformation in high aspect ratio greater than 8 single-cell in the support area on the corner, all the horizontal displacement of 60% to 70% is usually caused by bending deformation, so that kind of structure or near the top of the top most layer deformation, thus believe that the lower structure for the shear, should pay attention to the bottom of the structure set in the energy support; for bending-type high-level structure, the top of the structure can not be ignored Wing of energy support, support arrangements, the anchor should not be used in the column of the K-shaped support, while support members should control the axial compression ratio, 7 degrees generally not large and 120r235/fy.
If a residential structure of the lower storey, inter-section of smaller components, leading to support members and the number of nodes are large, and the power transmission line is longer, the side effects of anti-poor, support the structural system can also consider cross-layer support.
3 . m steel frame prefabricated concrete wall
this system are generally pre-cast concrete wall buried in the support plate, which is only connected to the anchor in the steel frame and concrete wall panels and beams frame the gap left from the subject power on, it is still a support. but the feature is built-in plate by intensity control setting, does not consider buckling.
should be double reinforced concrete wall, and both sides should be mutually reinforced Rachel, in the end bracing within the structure should be set up to strengthen steel, such as the use of plum-shaped steel, spiral steel, steel hoop. This system forces good performance, relatively economic support members, and can combine with the wall layout. But the on-site installation more difficult, more complex production.
4.
steel frame system explicitly force this system, the use of flexible, making installation simple, fast construction, but required for the beam to resist lateral forces larger column section, and can be used for multi-storey building below the 6th floor, and under normal circumstances, should be rigid beam-column joints. This system is poor economy for the high-rise buildings.
5. staggered truss structure system of staggered truss structural system
produced in the 20th century, 60 years, first proposed by the Massachusetts Institute of Technology, and successfully used in several apartments and hotel buildings. The system is outside of the pillars by the Housing and span equal to the housing composition of the width of the truss, truss-storey height is equal to, in the adjacent column for the staggered arrangement on the bottom, hold the floor in the truss winding one end, other end of the shelving in the adjacent bottom chords of trusses. a Pin layout of the two bay truss, and the middle No columns, so is ideal for residential, hotel construction and flexible layout requirements of each unit. This system is characterized by force: the level of force is mainly transmitted through the floor adjacent to the oblique abdominal truss rod, so the level of the ultimate load ramp through the floor truss spread support braces or the underlying basis of the main pillars between floors to bear axial force, shear and moment they suffered were minimal. Since truss, a whole story, so the system stiffness, generally do not need to increase the column stiffness to control the displacement, the staggered truss structural system to withstand the axial force in the main column, the column section can be arranged in the strong axis vertical, so the vertical lateral stiffness is also larger, the amount of such a system of steel frame structures can be reduced by 30 compared with ~ 40%, so the system is an economical, practical and highly efficient structural system, the system is currently being made Hunan University System.
6.
metal frame metal frame structure system the main structural system for the lower house or villa can be divided into two categories, one for the cold formed steel frame system C, and the other to form the keel of a small hot-rolled steel structural system. metal frame system in general by the column, Leung, Tin keel, the keel and the middle supporting the fastener through the lumbar support stiffening pieces connected together with a self-tapping screws, beam elements between 1 ~ 3mm thickness, column spacing of about 400 ~ 600mm.
its main The mechanism of force: the keel and the upper and lower support columns or partition walls formed by the force, vertical force transmitted to the wall by the floor beam day of the keel, and then spread through the column base; horizontal force transmitted from the floor as the division foundation wall and then spread to the force. As power transmission process, the wall panels to withstand a certain amount of shear, and provide the necessary stiffness, so the wall panels should meet certain requirements. floor floor light steel frame system can be used, overlying layer of particle board and the floor surface, the lower set gypsum board ceiling, can easily walk through the pipeline, but also meets the noise requirements. The advantages of the system composed of smaller component system, structural elements can be hidden in the wall Internally, is conducive to building layout and interior appearance, and good insulation properties, are hinged beam, field welding and save the cost of high-strength bolts and force the whole wall can be assembled in the factory to speed up the construction schedule. The disadvantage is beam articulated a strong earthquake area is not suitable for high-rise buildings, the system is still a lack of domestic experience in engineering, fewer varieties of cold-formed steel.
III.
for steel columns in the form of residential in the form of columns are the following: ① circular steel tube, ② CFRT, ③ square steel tube, ④ rolled H section steel.
1. circular steel tube: round steel tube with the force of good performance, small size cross-section columns, fire resistance and easy processing advantages For circular concrete filled steel tube we generally do not control the axial compression ratio, and control the slenderness ratio, so that the steel has the necessary ductility of concrete columns, requiring ductility greater than 5, the general control of the slenderness ratio L / D is less than 8.25 can meet the requirement, the story is less than 2.9 meters of housing, if the girder is taken as 400 steel is taken as 300, the L / D = 8.3, meet the ductility requirements. If the residential floors is greater than 2.9 meters, the proposed pipe diameter is taken as 350.
2. CFRT: square steel tubular beam-column connections are easy, fire performance advantages, although the force slightly worse performance than the circular tube, but its mechanical properties and stiffness was still better than H-type steel column .
other steel tube, the ductility and the axial load ratio, slenderness ratio, steel ratio, steel yield strength and compressive strength of concrete.
other steel tube, normally control the axial load ratio should be such as the slenderness ratio l = 30, the steel ratio
a = 0.2, Q345 steel Fy = 345Mpa, allowing axial compression ratio [n] = 0.889, this ensures the column ductility factor greater than 6.0.
The steel square tubular column axial compression ratio n = N / (pASCfScy) for the average residential structure
p = 1.0 fScy = (1.212 + Bx + Cx2) fck
B = 0.1381 (fy/235 +0.7646 )
C =- 0.0727 (fck/20) +0.0216
ASCm sectional area of concrete filled steel tube over
on C40 concrete, axial load ratio should be properly tightened
as 400X400 square steel tube, wall thickness t = 20mm to meet the ductility requirements.
3. square steel: square steel tube beam main advantage is ease of access, better performance two-way force, torsional capacity; its defects and processing for the fire is too much trouble, column connections nodes difficult, if not readily available sizes of steel pipes, welding larger workload.
4. hot-rolled H section steel: its main advantage is relatively full supply of materials, processing and production convenient, simple connection, in particular, development of Shanghai Datong Steel Structure Co., Ltd. high-frequency welding H beam processing is simple, the use of materials than the province, better economy; but weak axis stiffness of steel is poor, if you want to meet the requirements of strong column and weak beam, the column size to be increased a lot.
III.
wall materials to reflect the superiority of high-rise steel structure housing, reduce the structural weight, the general use of lightweight composite outer wall panels, beams and columns are connected with the main use of plug-in type, for the following 6 layers multi-residential, but also can be embedded aerated concrete block. exterior wall materials varieties are: IT lightweight aerated concrete panel, lightweight autoclaved aerated concrete (ALC) board, GRC composite sandwich board, ferrocement sandwich panels. interior wall materials in general can be aerated concrete block, may also have plaster board, fiber gypsum board, glass fiber reinforced cement board, paper straw panels. The following introduces the ALC board aerated concrete panels, some physical properties and construction requirements:
1. ALC board:
calculated density 650kg/M2
0.11W/MK thermal conductivity of thermal insulation thickness of the plate is equivalent to 370 125 bricks thick wall insulation performance, with 150 thick ALC board to meet the requirements of thermal insulation in Shanghai.
thick plate of 150 fire resistance is greater than 4 hours fire resistance.
sound insulation performance of thick plate 150 index greater than 46.4dB, 45 dB to meet regulatory requirements.
drift angle seismic performance of 1 / 20, the sheet metal with no loss.
construction requirements of external construction, the slab must use a suitable seal between the caulking material and outside and then cover with a layer of sealing liquid synthetic resin emulsion, a slurry out of the brush, heavy with water within 5% ~ 10% 107 Glue, the outermost and the appropriate use of paint finishes.
when used outside the ALC board walls, generally use a two-story board, a length of 5600 ~ 6000, the actual selection of the building area should be based on the wind load the appropriate choice of model, as the external walls of the hole to open the doors and windows are angle steel lintel, door and window openings at the same time on both sides of the angle also used to strengthen 100cm. In addition ALC also be used for lightweight roof panels, and the board easy to cut.
IV.
steel residential floor systems, floor systems generally have the following: pressure-type steel concrete composite slabs, precast concrete composite plate, place reinforced concrete slab.
(1) steel plate concrete floor: 1.5 hours due to the fire floor to meet the requirements to be poured on 80 of its thick concrete, the use of butterfly Type the total thickness of steel plate floor to reach 130 ~ 150mm, and for residential buildings, indoor and are subject to the ceiling, such as using fresh button pressure plate slab thickness can be reduced to 110mm, can be used on the steel structure housing the bardeck BD-40 model fresh button pressure plate, the fin height of only 40mm, and the mouth closed, do not do the ceiling, just in the crevice can be affixed to the bandage. As the level of composite slab bears a passing role in force and therefore connected steel beams and steel plate should be set at the necessary stud, designed with a combination of steel beams and floor effects, can significantly increase the capacity and stability of the beam, effectively reducing the high beam. generally lower floor without portfolio plus a bar, but for a dynamic load and the more humid areas, the lower floors still need to configure the necessary structural reinforcement. but the floor should meet the weighted combination of standardized impact sound pressure level is less than 75dB requirements. floor insulation requirements in foreign countries in residential design it has become increasingly important.
(2) Composite Concrete Slabs: concrete composite slab structure is to place the time of manufacture in accordance with the requirements and change the force characteristics of the individual components and pre-cast parts, of which individual components of prefabricated manufactured in the factory, then shipped to the field assembly, and then poured in the pound concrete, composite assembly to form the overall structure of the main advantages of this structure; high degree of mechanization, short construction period can be technology and high-strength prestressed steel, prefabricated parts of small size, light weight, easy to transport lifting; but some of the concrete and precast concrete cast on the existence of age differences exist between the shrinkage stress, and between slab prone to fracture.
(3) use of instrumental support casting slab floor, the advantage of good integrity, easy fitting, but still higher than costs, reinforced with steel beams and construction of the connection is complex, and a longer construction period , as well as ensure the concrete floor and the combined effect of steel beams, steel beam flange must also set the necessary stud.
five. beam-column joints and columns in steel frames
foot node m of concrete or steel tube frame m lateral support system, the beam-column joints can be hinged, rigid or semi-rigid, multi-storey steel structures for residential, high frequency welding steel column most of the H beam, H-section of the web is thin, so in the weak axis connection with the multi-hinged beam, beam in the strong axis connection with the use of rigid, semi-rigid connections can sometimes, but its mechanical properties is complex, in addition to multi-storey steel structure is relatively thin, should be avoided the construction site welding, speed up the construction schedule. floor beams and concrete cylinder can be hinged connection. residential high-rise steel structure, to ensure the concrete cylinder split open, there is still enough capacity steel frame, usually the outer steel frame is rigid, and floor beams and concrete cylinder is hinged. structural arrangement, the general framework of the spindle set in the plane of steel. beam using rigid, should meet the requirements of strong column and weak beam, large bay house To meet this condition, the column size will be relatively large, so where possible, the external columns should maximize the use of small bays, judging from the existing engineering, structural arrangement, in addition to the floor outside the elevator set into the cylinder, can also be arranged into a concrete cylinder bathroom. As for the foot steel column connections also can be hinged or rigid, high-level and multi-layer and the basement of a small number of layers can be used when more articulated, but the column should be considered part of the foot in the ground corrosion, while the high-rise residential, should adopt the rigid column base. Steel concrete practice of the connection node.
connection diagram of a horizontal beam (strong axis)
Figure II longitudinal beam connections (weak axis)
Figure III Figure beam and four-wall connections steel column column foot
Figure V steel tube connected nodes
3) wall and the steel beams and steel columns connected nodes
layer below the 6 multi-storey residential, fly ash aerated concrete wall can be blocks or concrete hollow block. As smaller cross-section columns, the general outsourcing can be a pillar of the way of concrete block, to be completely encased steel columns, block wall thickness of not too small, usually not less than 240, Concrete outsourcing of parts of block columns should also be coated with fire retardant paint, the outermost supplemented by steel mesh plaster. interior walls with brick, the brick masonry on the floor in layers, on both sides of beam web filled with concrete block outside covered with plaster or externally bonded steel mesh fire board.
high rise residential and small multi-use peg board or the entire bay strip plug the board, but must pay attention to the design and installation of joint regulation. For the height high building (18 m) beam and plate elements can be embedded on the welding to be resolved, more than 18 meters for the height of the building, in addition to embedded parts of the joints with steel beams welded plate, the board should also set hook bolts and steel pull access. walls and steel beams and steel columns under the connection node can refer to Figure six to ten chart.
Figure Six Figure seven independent families steel column fire wall side column node
Figure Eight Wall and floor steel columns connected nodes in Figure IX
Figure X framework and plug board connections
VI.
steel structure under fire, 19 floors above the fire rating of the residential level, the components required for a column of fire time: 3 hours, Beam: 2 hours, floor: 1.5 hours; 19 floors below the residential fire rating of two, members of the fire-resistant time requirements for a column : 2.5 hours, beam: 1.5 hours, floor: 1.0 hours. on fire coating, the general thin fire resistant coating for no more than 1.5 hours, more than 1.5 hours should be thick fire retardant paints.
fire steel components can be use of coated concrete (or masonry brick method), fire retardant paint, fire panels and composite structure coated in several ways, fire board can be divided into thick and thin fire, fire plate thickness 20 ~ 50mm, mainly silicon calcium and expanded vermiculite fireproof board fireproof board, the main varieties KB board, GF board; fire at 6 ~ 15mm plate thickness between the main varieties are short-fiber reinforced cement pressure plate, fiber-reinforced calcium silicate board and glass of ordinary cloth reinforced inorganic panels.
on steel columns, pillars of fire safety requirements due to the higher, the general outsourcing of concrete (or masonry brick method), thick fire retardant paint, fire plate and composite structures in several ways, + / The following should be outsourced -0.000 concrete way, when the plate coated with fire when, in most cases the thickness of 4 ~ 5cm 3 hours to meet the requirements of fire safety when using the composite structure, the steel beam steel columns through thick fire retardant coating After the fire sheet coated with a decorative panel. steel column and steel beam joint fire board can be used to refer to Figure 11 Figure 14.
the fire resistance of concrete filled steel tubular steel columns have been greatly improved over type, and the larger diameter pipe, fire The longer, whereas the smaller diameter, the time required to achieve the same fire retardant coating thicker, according to Shenzhen SEG Plaza, test and engineering practice, the pipe diameter of 500 fire-resistant coating thickness of 15mm of concrete to meet the fire resistance time of 3 hours , while the diameter of 300mm of steel tubular column, the thickness of fire-resistant coating is required 25mm.
H beam steel beam flange fire can be filled with aerated concrete block, and then wipe the metal thickness of vermiculite concrete coating of 25 , may also fire board or fire retardant coating, consider the special nature of housing in general, fire-resistant plate coated with the decoration.
with the smelting of iron and steel enterprises to improve technology, to meet the needs of the market, Baosteel, Wuhan Iron and Steel and other steel companies the successful development of resistant weathering steel, it is through appropriate technology, the steel containing specific components (such as addition of molybdenum, etc.), the steel structure and microstructure of the apparent changes, so that the steel itself to generate the required fire resistance and weather resistance. weathering weathering steel for ordinary steel from 2 to 8 times the fire resistance of steel at 600 degrees can yield strength decreased less than 1 / 3, the use of weathering steel can reduce the coating 1 / 3, eliminating the need for anti- rust paint, 30% overall cost savings, but its price is only increased by 10% compared with ordinary steel, so fire-resistant weathering steel has a bright future.
VII. steel structure residential steel housing economics economy
hindering the development of steel structure housing the biggest obstacle, according to our level of development of country's existing steel structure, steel structure housing the civil construction cost of reinforced concrete residential high than 10% to 20%, but more concrete steel residential construction costs in the base 30% savings on, and the steel structure housing the room rate was 7% higher than the concrete house 10%, in addition to steel structure housing the construction period can be reduced by about 30%, consider the above combination of factors, roughly the cost of steel structure house and concrete residential flat, especially with the housing increase, the steel structure housing better reflect its superiority, for the northern region, steel structure housing more energy cost savings of 8%, so the steel residential areas in the economy still has certain competitiveness, the key is that developers should consider the reduction of construction period, area increased, and banks to reduce loan interest to measure a combination of factors such as steel housing economy. the basis of existing experience in engineering, usually 9 to 14 layers of steel Civil construction cost of housing in 1100 to about 1,300 yuan / M2 or so, roughly the amount of steel steel 40 ~ 50kg / M2 so we work on Building 17, East Garden City (12 floors) using steel and concrete structure an economic comparison , a specific data table below
Table Oriental City Garden and economic comparison of different structural alternatives
concrete cylinder, steel concrete column, H steel beam steel
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