Fabrication and erection of structural steelwork

FABRICATION AND ERECTION OF STRUCTURAL 41

STEELWORK

1.0 INTRODUCTION

The steel-framed building derives most of its competitive advantage from the virtues of prefabricated components, which can be assembled speedily at site. Unlike concreting, which is usually a wet process conducted at site, steel is produced and subsequently fabricated within a controlled environment. This ensures high quality, manufacture offsite with improved precision and enhanced speed of construction at site.

The efficiency of fabrication and erection in structural steelwork dictates the success of any project involving steel-intensive construction. Current practices of fabrication and erection of steel structures in India are generally antiquated and inefficient. Perhaps, this inadequate infrastructure for fabrication is unable to support a large growth of steel construction. In India, the fabrication and erection of structural steelwork has been out of the purview of the structural designer. Nevertheless, in the future emerging situation, the entire steel chain, i.e. the producer, client, designer, fabricator and contractor should be able to interact with each other and improve their efficiency and productivity for the success of the project involving structural steelwork. Hence it becomes imperative that structural designers also must acquaint themselves with all the aspects of the structural steel work including the “fabrication and erection,” and that is the subject matter of the present chapter to briefly introduce good fabrication and erection practices.

2.0 FABRICATION PROCEDURE

Structural steel fabrication can be carried out in shop or at the construction site. Fabrication of steelwork carried out in shops is precise and of assured quality, whereas field fabrication is comparatively of inferior in quality. In India construction site fabrication is most common even in large projects due to inexpensive field labour, high cost of transportation, difficulty in the transportation of large members, higher excise duty on products from shop. Beneficial taxation for site work is a major financial incentive for site fabrication. The methods followed in site fabrication are similar but the level of sophistication of equipment at site and environmental control would be usually less. The skill of personnel at site also tends to be inferior and hence the quality of finished product tends to be relatively inferior. However, shop fabrication is efficient in terms of cost, time and quality.

Structural steel passes through various operations during the course of its fabrication. Generally, the sequence of activities in fabricating shops is as shown in Table1. The sequence and importance of shop operations will vary depending on the type of fabrication required. All these activities are explained briefly in the subsequent parts of the section.

? Copyright reserved

Table 1: Sequence of activities in fabricating shops S.No. Sequence of Operation

1.

2.

3.

4.

5.

6.

7.

8.

9.

10. Surface cleaning

Cutting and machining

Punching and drilling Straightening, bending and rolling Fitting and reaming

Fastening (bolting, riveting and welding) Finishing

Quality control

Surface treatment

Transportation

2.1 Surface cleaning

Structural sections from the rolling mills may require surface cleaning to remove mill scale prior to fabrication and painting.

Hand preparation, such as wire brushing, does not normally conform to the requirements of modern paint or surface protection system. However in some applications manual cleaning is used and depending on the quality of the cleaned surface they are categorised into Grade St-2 and Grade St-3.

Blast cleaning is the accepted way of carrying out surface preparation in a well-run fabrication shop. Abrasive particles are projected on to the surface of the steel at high speed by either compressed air or centrifugal impeller to remove rust and roughen the surface before applying the coating. By using shot or slag grits, both of which have an angular profile, surface oxides are removed and a rougher surface is obtained to provide an adequate key for metal spraying or special paint. Depending upon the increase in the quality of the cleaned surface, the blast cleaning is categorised into Grade – Sa2, Grade – Sa2? and Grade Sa- 3.

Flame cleaning is another method of surface cleaning. In this method the surface is cleaned using an oxy-acetylene torch which works on the principle of differential thermal expansion between steel and mill scale. In another method called ‘ the steel piece is immersed in a suitable acid and the scale and rust are removed.

2.2 Cutting and Machining

Following surface preparation, cutting to length is always the first process to be carried out, and this is done by any of the following methods.

2.2.1 Shearing and cropping

Sections can be cut to length or width by cropping or shearing using hydraulic shears. Heavy sections or long plates can be shaped and cut to length by specialist plate shears. For smaller plates and sections, machines featuring a range of shearing knives, which can accept the differing section shapes, are available.

2.2.2 Flame Cutting or Burning

In this method, the steel is heated locally by a pressurised mixture of oxygen and a combustible gas such as propane, which passes through a ring of small holes in a cutting nozzle. The heat is focussed on to a very narrow band and the steel melts at 15000 C when a jet of high-pressure oxygen is released through a separate hole in the centre of the nozzle to blast away the molten metal in globules. The desired cuts are obtained quickly by this process. However due to a rapid thermal cycle of heating and cooling, residual stresses and distortion are induced and hence structural sections that are fabricated using flame cutting are treated specially in the design of structural steelwork.

2.2.3 Arc Plasma Cutting

In this method, the cutting energy is produced electrically by heating a gas in an electric arc produced between a tungsten electrode and the workpiece. This ionises the gas, enabling it to conduct an electric current. The high-velocity plasma jet melts the metal of the work piece. The cut produced by plasma jet is very clean and its quality can be improved by using a water injection arc plasma torch. Plasma cutting can be used on thicknesses upto about 150 mm but the process is very slow.

2.2.4 Cold Sawing

When a section cannot be cut to length by cropping or shearing, then it is normally sawn. All saws for structural applications are mechanical and feature some degree of computer control. There are three forms o f mechanical saw - circular, band and hack. The circular saw has a blade rotating in a vertical plane, which can cut either downwards or upwards, though the former is more common. Band saws have less capacity. Sections greater than 600 mm X 600 mm cannot be sawn using band saws. The saw blade is a continuous metal edged, with cutting teeth, which is driven by an electric motor. Hack saws are mechanically driven reciprocating saws. They have normal format blades carried in a heavy duty hack saw frame. They have more productivity than band saws.

2.3 Punching and Drilling

Most fabrication shops have a range of machines, which can form holes for connections in structural steelwork. The traditional drilling machine is the radial drill, a manually operated machine, which drills individual holes in structural steelwork. But this method has become too slow for primary line production. Therefore, larger fabricators have installed NC (Numerically Controlled) tooling, which registers and drills in response to

keyed in data. These can drill many holes in flanges and webs of rolled steel sections simultaneously. It is also possible to punch holes, and this is particularly useful where square holes are specified such as anchor plates for foundation bolts. While this method is faster compared to drilling, punching creates distortion and material strain hardening around the holes, which increase with material thickness. Its use is currently restricted to smaller thickness plates. In order to reduce the effect of strain hardening and the consequent reduction in ductility of material around punched holes, smaller size (2 mm to 4 mm lesser than final size) holes are punched and subsequently reamed to the desired size.

2.4 Straightening, Bending and Rolling

Rolled steel may get distorted after rolling due to cooling process. Further during transportation and handling operations, materials may bend or may even undergo distortion. This may also occur during punching operation. Therefore before attempting further fabrication the material should be straightened. In current practice, either rolls or gag presses are used to straighten structural shapes.

Gag press is generally used for straightening beams, channels, angles, and heavy bars. This machine has a horizontal plunger or ram that applies pressure at points along the bend to bring it into alignment. Long plates, which are cambered out of alignment longitudinally, are frequently straightened by rollers. They are passed through a series of rollers that bend them back and forth with progressively diminishing deformation. Misalignments in structural shapes are sometimes corrected by spot or pattern heating. When heat is applied to a small area of steel, the larger unheated portion of the surrounding material prevents expansion. Upon cooling, the subsequent shrinkage produces a shortening of the member, thus pulling it back into alignment. This method is commonly employed to remove buckles in girder webs between stiffeners and to straighten members. It is frequently used to produce camber in rolled beams. A press brake is used to form angular bends in wide sheets and plates to produce cold formed steel members.

2.5 Fitting and Reaming

Before final assembly, the component parts of a member are fitted-up temporarily with rivets, bolts or small amount of welds. The fitting-up operation includes attachment of previously omitted splice plates and other fittings and the correction of minor defects found by the inspector.

In riveted or bolted work, especially when done manually, some holes in the connecting material may not always be in perfect alignment and small amount of reaming may be required to permit insertion of fasteners. In this operation, the holes are punched, 4 to 6 mm smaller than final size, then after the pieces are assembled, the holes are reamed by electric or pneumatic reamers to the correct diameter, to produce well matched holes.

2.6 Fastening Methods

The strength of the entire structure depends upon the proper use of fastening methods. There are three methods of fastening namely bolting, riveting and welding. A few decades back, it was a common practice to assemble components in the workshop using bolts or rivets. Nowadays welding is the most common method of shop fabrication of steel structures. In addition to being simple to fabricate, welded connection considerably reduce the size of the joint and the additional fixtures and plates. However, there is still a demand for structural members to be bolted arising from a requirement to avoid welding because of the service conditions of the member under consideration. These may be low temperature performance criteria, the need to avoid welding stresses and distortion or the requirement for the component to be taken apart during service e.g. bolts in crane rails or bolted crane rails.

2.7 Finishing

Structural members whose ends must transmit loads by bearing against one another are usually finished to a smooth even surface. Finishing is performed by sawing, milling or other suitable means. Several types of sawing machines are available, which produce very satisfactory finished cuts. One type of milling machine employs a movable head fitted with one or more high-speed carbide tipped rotary cutters. The head moves over a bed, which securely holds the work piece in proper alignment during finishing operation. Bridge specifications require that sheared edges of plates over a certain thickness be edge planed. This is done to remove jagged flame cut edges and the residual stresses at the edges. In this operation, the plate is clamped t o the bed of milling machine or a planer. The cutting head moves along the edge of the plate, planing it to a neat and smooth finish.

The term finish or mill is used on detail drawings to describe any operation that requires steel to be finished to a smooth even surface by milling, planing, sawing or other machines.

2.8 Surface Treatment

Structural steelwork is protected against corrosion by applying metal or paint coating in the shop or at site.

2.8.1 Metal Coatings

The corrosion protection afforded by metallic coating largely depends upon the surface preparation, the choice of coating and its thickness. It is not greatly influenced by the method of application. Commonly used methods of applying metal coating to steel surfaces are hot-dip galvanising, metal spraying, and electroplating. Electroplating is generally used for fittings and other small items.

Galvanising is the most common method of applying a metal coating to structural steelwork. In this method, the cleaned and fluxed steel is dipped in molten zinc at a temperature of about 4500C. The steel reacts with molten zinc to form a series of zinc or iron alloys on its surface. As the steel workpiece is removed, a layer of relatively pure zinc is deposited on top of the alloy layers. For most applications galvanised steel does not require painting.

An alternative method of applying metallic coating to structural steelwork is by metal spraying of either zinc or aluminium. The metal, in powder or wire form, is fed through a special spray gun containing a heat source, which can be either an oxy-gas flame or an electric arc. Molten globules of the metal are blown by a compressive jet on to the previously blast cleaned steel surface. No alloying occurs and the coating, which is produced, consists of porous overlapping platelets of metal. The pores are subsequently sealed, either by applying a thin organic coating which soaks into the surface, or by allowing the metal coating to weather, when corrosion products block the pores.

2.8.2 Paint Coatings

Painting is the principal method of protecting structural steelwork from corrosion. Paints are usually applied one coat on top of another, each coat having a specific function or use.

The primer is applied directly on to the cleaned steel surface. Its purpose is to wet the surface and to provide good adhesion for subsequently applied coats. Primers for steel surfaces are also usually required to provide corrosion inhibition. They are usually classified according to the main corrosion-inhibitive pigments used in their formulation, e.g. zinc phosphate, zinc chromate, red lead, and metallic-zinc. Each of these inhibitive pigments can be incorporated into a range of binder resins e.g. zinc phosphate alkyd primers, zinc phosphate epoxy primers, zinc phosphate chlorinated-rubber primers.

The intermediate coats (or undercoats) are applied to build the total film thickness of the system. This may involve application of several coats. The finishing coats provide the first-line defence against the environment and also determine the final appearance in terms of gloss, colour etc. They also provide UV protection in exposed condition. Intermediate coats and finishing coats are usually classified according to their binders, e.g. vinyl finishes, urethane finishes.

The various superimposed coats within a painting system have, of course, to be compatible with one another. They may be all of the same generic type or may be different, e.g. chlor-rubber base intermediate coats that form a film by solvent evaporation and no oxidative process, may be applied on to an epoxy primer that forms a film by an oxidative process which involves absorption of oxygen from the atmosphere. However, as a first precaution, all paints within a system should normally be obtained from the same manufacturer. The reader may refer to IS:487(1985) to know more about the surface treatment using paints.

Detailed treatment of corrosion protection systems will be found in the Chapter on ‘Corrosion, fire protection and fatigue considerations of steel

2.9 Welded connections

Welding is used extensively for joining metals together and there is no doubt that it has been a most significant factor in the phenomenal growth of many industries. The different terminology used in welds are explained in IS:812(1957).

A welded joint is made by fusing (melting) the steel plates or sections along the line of joint. The metal melted from each member of the joint unites in a pool of molten metal, which bridges the interface. As the pool cools, molten metal at the fusion boundary solidifies, forming a solid bond with the parent metal. When solidification completes, there is a continuity of metal through the joint.

There are five welding process regularly employed namely:

(i) Shielded Metal Arc Welding (SMAW)

(ii) Submerged-Arc Welding (SAW)

(iii) Manual Metal-Arc welding (MMA)

(iv) Metal-Active Gas welding (MAG)

(v) Stud welding

All these methods of welding has been described with illustrations, in the chapter on ‘Welds - Static and Fatigue Strength - I’. Nevertheless, for the sake of completeness, these methods are briefly enumerated below.

2.9.1 Methods of welding

(1) Shielded Metal Arc Welding (SMAW)

This is basically a semi-automated or fully automated welding procedure. The type of welding electrode used would decide the weld properties. Since this welding is carried out under controlled condition, the weld quality is normally good.

(2) Submerged-Arc welding (SAW)

This is fully mechanised process in which the welding head is moved along the joint by a gantry, boom or tractor. The electrode is a bare wire, which is advanced by a motor. Here again, since the welding is carried out in controlled conditions, better quality welds are obtained.

(3) Manual Metal-Arc welding (MMA)

This is the most widely used arc welding process and appears to be advantageous for labour intensive Indian construction practices. As it is manually operated it requires considerable skill to produce good quality welds. Hence in the case of MMA, stringent

quality control and quality assurance procedures are needed. In India, the Welding Research Institute, BHEL, Trichy, Tamil Nadu, conducts periodical courses for welders and weld inspection personnel. Welders who are employed in actual fabrication are, infact, graded according to their training and skills acquired.

(4) Metal-Active Gas welding (MAG)

This process is sometimes referred to as Metal-Inert Gas (MIG) welding. It is also manually operated. A gas that does not react with molten steel shields the arc and the weld pool. This protection ensures that a sound weld is produced free from contamination-induced cracks and porosity. Nevertheless, this procedure also depends on the skills of the welder.

(5) Stud welding

This is an arc welding process and is extensively used for fixing stud shear connectors to beam in the composite construction. The equipment consists of gun hand tool (Fig.1(a) and 1(b)), D.C. power source, auxiliary contractor and controller. The stud is mounted into the chuck of the hand tool and conical tip of the stud is held in contact with the work piece by the pressure of a spring on the chuck. As soon as the current is switched on, the stud is moved away automatically to establish an arc. When a weld pool has been formed and the end of the stud is melted the latter is automatically forced into the steel plate and the current is switched off. The molten metal, which is expelled from the interface, is formed into a fillet by a ceramic collar or ferrule, which is placed around the stud at the beginning of the operation. The ferrule also provides sufficient protection against atmospheric contamination (Figs. 1(a) and 1(b)).

This process offers an accurate and fast method for attaching shear connectors, etc with the minimum distortion. While it requires some skill to set up the weld parameters (voltage, current, arc time and force), the operation of equipment is relatively straight forward.

connection (for Safety) Power Supply Unit (DC) Fig 1(a): Stud Welding (Schematic Diagram)

(a) Shop welding (b) Site welding

Fig.1 (b) Stud Welding on composite beam

3.0 RESIDUAL WELDING STRESSES AND DISTORTION

3.1 Residual welding stresses

When a weld such as a butt weld is completed and begins to cool the hot weld and parent metal contracts longitudinally. The surrounding cold parent metal resists this contraction so that the weld is subjected to a tensile stress. This is balanced by the compressive stresses induced in the cold regions of the parent plate. These self-equilibrating forces introduce residual stresses both in the longitudinal and transverse direction. These stresses can even reach yield stress. Hence, the fabricator should adopt good fabrication practices that reduce the detrimental effect of residual stresses.

3.2 Residual distortions due to welding

3.2.1 Butt welds

Fig. 2 shows a typical angular rotation of the plates due to a single V butt weld. This occurs because the major part of the weld is to one side of the neutral axis of the plate. This induces greater contractile stresses on that side. A double V or double U butt weld preparation reduces this distortion.

Fig 2: Angular distortion of butt weld

The welding sequence for double preparation has an important influence on the resultant distortion. If a few weld runs are first made on one side, and the plate turned over and then the same number of runs are made on the second side (i.e., sequential welding), a 'balanced' weld will be produced with little distortion. This will not, of course, be possible in situations where rotation of the plate is impracticable such as a plate, which is part of a large fabrication.

One aspect of butt-welding that should be noted is where back gouging is necessary to produce a full penetration weld. This can lead to distortion because the back gouging will produce bigger weld on the second side about the neutral axis of the plate. Such distortion can be reduced using an unsymmetrical weld section. Single V butt welds may produce cusping as shown in Fig.3 if the overall plate is restrained. This can be reduced by using a double V butt weld.

3.2.2 Fillet welds

In single and double fillets, shrinkage across the throat area can lead to distortion as shown in Fig.4. The distortion caused by a double fillet weld is important in box or plate girder webs where stiffeners are attached to only one side of the web. The use of a thicker plate can reduce the fillet weld angular distortion due to increased stiffness.

3.3 Control of distortion

Some distortion from welding is due to transverse and longitudinal contraction of weldments. Adopting suitable methods that can resist contraction can control the distortion. Weld distortion of a flat plate with a series of stiffeners on one side can be countered by elastically prebending the plates. In a similar manner two T sections can be welded, prebent back to back, to prevent final curvature in the web plate. Presetting the flange plate at an angle initially as shown in Fig.5 and Fig.6 may reduce the angular rotation due to a single fillet .

Fig 3: Cusping due to transverse butt weld

Fig 4: Angular distortion of fillet welds (b)

(a)

Sometimes both presetting and prebending may be required, e.g. in plate girder fabrication where the web to flange welds are made automatically. When the welds are made manually, it is customary to put the stiffeners into the girder before the web/flange welds are made; in this way the square profile of the web to flange is maintained. Where automatic welding is employed the stiffeners cannot be put first since they would impede the progress of the automatic machine; in this presetting of the flange plates may be required. Welding should preferably be started at the centre of the fabrication and all succeeding welds from the centre outwards. This allows contraction to occur in the free condition. If the welding sequence is not chosen correctly, locked up stresses at either end of a welded portion can lead to uncorrectable distortions.

Restraint procedure to reduce the effect of weld distortion should be carefully planned otherwise it can lead to solidification cracking.

Fig 5: Prebending (b) Prebent T's

Spacer

(a) Prebent Plate Fig 6: Preset for fillet weld

3.4 Methods of correcting distortion

In general, there are two methods available to correct distortion namely:

(a) applying force and (b) heating

Light sections can be corrected by applying force such as by hydraulic presses and local jacking or wedging. While heavier structures will require heating to apply stresses to reduce or eliminate the distortion. The effect of heating is similar to that of welding in which distortion results from the induced stresses. An area of steelwork will e xpand when heated but this expansion will be constrained by the surrounding cold unheated area, causing a plastic upset. On cooling, the area contracts and the element then becomes shorter, this principle can be used to correct or induce any curvature. The heat must be evenly applied right through the material, if not, unwanted curvature may occur in the plan of the section. Fig.7 shows some of the methods to induce and correct distortion. Fig.7(c) shows how it can be applied to a H section in which a camber is required. Rectangular heating across the bottom flange will shorten it compared with the top flange and hence induce camber. Since the shortening of the flange in the heated areas may tend to buckle the web adjacent to the flange, the heat is also applied to the web in a triangular manner such that the most affected part of the web contracts with the flange. In a similar manner a cambered plate may be straightened by applying triangular heating with the bases of the triangles parallel to the plate edges to be shortened. When the plate cools the heated edge will shorten and so reduce the camber. For panels in box girder webs, spot heating as shown in Fig.7(d) may be employed to reduce the concavity produced by the welding around the panel perimeter. Each spot contracts on cooling and induces a local plate shrinkage within the panel boundary and so reduces the dish. If the heat applied and the web panel thickness are such that there is a large temperature difference between the surfaces of the plate at each spot heat, then the resultant contraction on the hotter surface will produce a greater correction of the dish.

Triangular heat

by heating Rectangular heat input across flange

7(a) Camber of beam by heating Triangles heated evenly

through plate thickness

7(b) Cambered Plate

Fig 7. Methods of correction of distortion

3.5 Defects in welds

Faulty welding procedure can lead to defects in the welds, thereby reducing the strength of the weld.

Fig.8 shows some of the common defects in welds. Some of these are:

(i) Undercut

(ii) Porosity

(iii) Incomplete Penetration

(iv) Lack of side wall fusion

(v) Slag inclusions

(vi) cracks

All these weld defects are discussed in the chapter on ‘Weld – Static and Fatigue strength – I’. It should be emphasised that a ‘theoretical 100% error free’ weld is not achievable in practice. While good quality welds are the priority of welders and weld inspectors, minor defects do normally creep in. Hence these defects are assessed during a weld inspection.

If the defects are within acceptable limits, they are accepted. If not, alternative measures of rectification may have to be carried out. Table 2 shows nature of some of the defects and their acceptability limits.

(a) Undercut

(d) Lack of side wall fusion Lack of side

wall fusion

Table 2: Nature of defects and their acceptability limits. Nature of Defect Acceptance Norms Disposition

1. Crack, Lack of

Fusion

2. Crater

3. Undercut

4. Porosity for butt

or fillet welds Not accepted

Not accepted

Upto 0.8mm accepted

One pore of dia. < 2.4mm

every 100 mm length is

permitted. However pores

of dia. > 2.4mm not

accepted

Confirm by Magnetic Particle

Inspection, repair and retest.

Fill by weld deposit.

Fill and grind smooth.

To be repaired.

4.0 QUALITY CONTROL IN FABRICATION

Quality assurance during fabrication assumes utmost importance in ensuring that the completed structure behaves in the manner envisaged during design stage. Any deviation from these design considerations as reflected in detail drawings may introduce additional stresses to the structure and affect its strength and durability. This section discusses the relevant aspects in fabrication and erection, which need to be considered to achieve the desired quality.

4.1 Fabrication

A fabricator's work starts from the point of procurement of raw materials including fasteners and ends with the dispatch of the fabricated items to site for erection.

In order to ensure that the fabrication can be carried out in accordance with the drawings, it is necessary that inspection and checking is carried out in accordance with an agreed Quality Assurance Plan (QAP). The plan should elaborate on checks and inspections of the raw materials and also of the components as they are fabricated, joined etc.

During the last two decades, fabrication activities have increased steadily in yards adjacent to work. In the absence of controlled environment (as in an organised workshop), the quality of workmanship of such fabrication is likely to suffer. It has, therefore, become all the more important to motivate the fabricators to appreciate the usefulness of Quality Assurance Plans and introduce the system in all their works and at site as well.

4.1.1 Imperfections in Fabrication

Structural steelwork cannot be fabricated to exact dimensions and some degree of imperfection is bound to occur during fabrication process. The limits of various imperfections are spelt out in the specifications. In the design, these are accounted by adopting a factor of safety for material. However, in some components an increase of imperfection beyond these limits may lead to reduction in the strength and durability of the structure e.g., imperfections on the straightness of the individual flanges of a rolled beam or a fabricated girder results in the reduction of strength of the girder due to lateral torsional buckling which may cause an overall bow in the girder. This, in turn, may generate twisting moments at the supports.

As a rule all columns and struts should be checked for straightness on completion of fabrication. Also, all rolled and fabricated girders should be checked over a distance in the longitudinal direction equal to the depth of the section in the region and points of concentrated load.

4.1.2 Making holes

Excessive cold working of structural steel can cause reduction in ductility, embrittlement and cracking. Punching holes is a cold-working operation and can, therefore, cause brittle fracture. This becomes critical for the durability of structures subjected to fluctuation of stresses such as railway bridges and crane girders. Under cyclic loading fatigue cracks can initiate from such punched holes. In such cases, holes for bolts may be formed either by drilling or by punching undersize holes followed by reaming to desired size. Drilling is preferable to punching, because it reduces the chances of brittle fracture. Studies show that punching may produce short cracks extending radially from the hole, thereby enhancing the possibility of initiating brittle fracture at the hole when the member is loaded. Even in statically loaded structures the maximum thickness of plates in which holes can be punched is restricted.

4.1.3 Shop assembly and camber check

For important structures particularly for bridges, it is necessary to have the fabricated units temporarily assembled at the place of fabrication before these are dispatched to site for erection. During this operation, the overall dimensions of the structure including alignment, squareness, camber etc. should be confirmed. Inadequate or erroneous camber, in fact, introduces huge secondary stresses in the members instead of eliminating these as originally desired. Shop assembly also ensures that the open holes drilled in various units are within tolerable limits.

4.1.4 Welded joints

As presented in the previous sections, welded joints are very important as far as the quality control of the joints is concerned. It is well known that joints are the last straw of strength in structural steelwork. Any poor quality weld would detrimentally affect the

joint and in turn affect the performance of the whole structure itself. Hence welded joints need thorough inspection during and after the fabrication. Different methods of Non-Destructive Testing (NDT) and evaluation of welds are available. The NDT procedures are elaborated in the chapter on ‘Welds Static and Fatigue Strength – I’. Depending upon the severity of service loading, the QAP may call for the level of NDT to be used. Guidance could be obtained from IS:822(1970) for the inspection of the welded joints.

5.0 ERECTION

5.1 General

Erection of steel structures is the process by which the fabricated structural members are assembled together to form the skeletal structure. The erection is normally carried out by the erection contractor. Generally the steps that are involved in the erection of steel structures are shown in Table 3. The erection process requires considerable planning in terms of material delivery, material handling, member assembly and member connection. Proper planning of material delivery would minimise storage requirement and additional handling from the site storage, particularly heavy items. Erection of structural steel work could be made safe and accurate if temporary support, falsework, staging etc. are erected. Before erection the fabricated materials should be verified at site with respect to mark numbers, key plan and shipping list. The structural components received for erection should be stacked in such a way that erection sequence is not affected due to improper storing. Care also should be taken so that steel structural components should not come in contact with earth or accumulated water. Stacking of the structures should be done in such a way that, erection marks and mark numbers on the components are visible easily and handling do not become difficult. From the earlier discussion it should emphasised that safe transportation of fabricated items to the site, their proper storage and subsequent handling are the pivotal processes for the success of fabrication of structural steel work.

Table 3: Sequence of Activities during Erection

S.No. Sequence of Operation

1.

2.

3.

4.

5.

6. Receiving material from the shop and temporarily stacking them, if necessary.

Lifting and placing the member and temporarily holding in place. Temporarily bracing the system to ensure stability during erection.

Aligning and permanently connecting the members by bolting or welding. Connecting cladding to the steel structural skeleton.

Application of a final coat of painting.

Guidance for handling and storage for material shall be obtained from IS: 7969(1975). The fabrication at shop or site should be so planned that units to be handled weigh nearly the same. The erection drawing should reach the site of construction well in advance to plan the erection sequence and material handling. Erection should be carried out with the help of maximum possible mechanisation. Normally anyone or more of the material

handling systems, such as tower crane; crane mounted on rails, crawling crane, pneumatic tire mounted crane, and derrick crane may be used for handling the material. Details of the above said erection equipments can be found in any standard textbooks on construction equipment.

A variety of methods can be employed for the erection of a structure. Normally, the selection of the method is influenced by the type of the structure, site conditions, equipment, quality of skilled labour, etc. available to the erector.

However, regardless of the method adopted the main aim during erection is the safety and preservation of the stability of the structure at all times. Most structures which collapse do so during erection and these failures are very often due to a lack of understanding on someone's part of what another has assumed about the erection procedure. Hence, it is emphasised that as far as strength and stability of the components during erection are concerned, they must satisfy the provision of IS: 800(1984). For the guidance on general fabrication and erection of structural steel work, Chapter 11 of IS:800 (1984) must be followed. As far as safety is concerned guidance could be obtained from Indian safety code for structural steelwork IS:7205(1974). Before the commencement of the erection, all the erection equipment tools, shackles, ropes etc. should be tested for their load carrying capacity. Such tests if needed may be repeated at intermediate stages also.

5.2 Bracings

During the entire erection period, the steelwork should be securely bolted or otherwise fastened and braced to take care of the stresses from erection equipment or the loads carried during erection. In addition to this, adequate provisions to resist lateral forces and wind loads during erection should also be made according to local conditions.

Normally bracings are built into all types of structures to give them a capability to withstand horizontal forces produced by wind, temperature and the movements of crane and other plant in and on the building. Bracings can be permanent or temporary.

Temporary bracings required at some stages of the work must have properly designed connections and should be specifically referred to in the erection method statement.

The decision on sequence of erection such as which member should be erected first for providing initial stability to the structure or whether temporary bracings should be used for this purpose should be taken at an early stage of planning of the erection process. Fig.9 illustrates this point. As permanent bracings have been provided in AB, bay erection should logically start from AB bay to give stability and ensure proper alignment of the erected structure. In case, for some reason erection has to start from DE bay, it would be necessary to provide temporary bracings in this bay. The bracing system should be retained till the permanent bracings are fixed in the AB bay. Any mis-alignment at initial stage will impair the performance, of the structure when completed. Early or unauthorised removal of temporary bracings is a common cause of collapse in a partially completed frame.

Having considered the need for installing temporary bracings and the need to postpone fixing permanent bracings, consideration should be given to the overall economy of retaining the temporary bracings and perhaps leaving out the permanent bracings. It is a costly and potentially dangerous business to go back into a structure solely in order to take out temporary members, or to insert components that had to be left out temporarily.

5.3 Maintaining tolerances

The best way of erecting a s tructure within the acceptable tolerance limits is to make sure that accuracy is achieved from the very beginning of the job.

Table 4: Maximum permissible tolerance in erected steel structures

S.No Description Tolerance in(mm)

1.

(i)

(ii)

Columns: Out of plumbness of column axis from true vertical axis Heights upto 30 m Heights over 30 m ±l /1000 or ±25 whichever is less ±l /1200 or ±35 whichever is less 2.

Trusses: Lateral shift in location of truss from its true vertical position ±10 3. Crane girders and ribs:

Shift in plane of alignment with

respect to true axis of crane rail.

±5 4.

Chimney and towers:

Out of plumbness (vertically from

true vertical axis) 1/1000 of the height of the chimney or tower Fig 9. Bracing System

Thus quality control must start from the setting out of the foundations and the holding down bolts. This operation is often done at a stage when site conditions are disorderly and most untidy and the environment appears to be incongruous to accuracy. However, inaccuracies in marking the centrelines and the levels of foundations allowed at this stage are likely to cause misfit in the connections and misalignment of the structure leading to secondary stresses in the members. In such areas corrective measure must be taken by way of locally modifying some of the components so as to eliminate the mismatch. Table

4 shows some typical tolerances that are accepted in structural steel work.

5.4 Joints

Most steel structures are fabricated by either bolting or welding in the shop and bolting o r welding in the field. Durability of a structure largely depends on the quality of the joints made at site.

In bolted connections, care should be taken to ensure that all parts intended to be bolted together should be in contact over the whole surface and the surfaces should be thoroughly cleaned and painted with specified primer paint and the two matching plates or sections secured together while the paint is still wet by service bolts. After erection, the joint should be made by filling not less than 50% of the holes with bolts. The service bolts are to be tightened. The holes that need enlargement to admit bolts or rivets should be reamed only after carefully examining the extent of the inaccuracy and the effect on the soundness of the structure. Such holes must not be formed by gas cutting process. The contact surfaces in HSFG connection if painted will develop lesser friction and this should have been accounted for in design. The fundamentals of HSFG connections are elaborated in the chapter on Bolted connections.

For connections to be done by welding, the components should be securely held in position to ensure alignment, camber etc., before welding is commenced.

In the case of field assembly using bolts the number of washers for the permanent bolts should not be more than two (and not less than one) for the nuts and one for the bolt head. It is desirable to use wooden rams and mallet to force the members in position so as to protect steelwork from injury and shock. It should also be ensured that the bolts project through the nut by atleast one thread. In the case of field assembly by welding almost all the precautions needed for shop welding may be followed. In the case of High Strength Friction Grip (HSFG) bolts the material surfaces should be absolutely free from grease, lubricant, dust, rust etc. and shall be thoroughly cleaned before assembling. The nuts should be pretensioned by a torque–wrench or by the turn of the nut method with the help of pneumatic wrench/lever. After tightening the bolt heads, nuts and edges of the mating, surfaces should be sealed with a coat of paint to obviate entry of moisture. In the case of connections such as base plate they must be aligned and levelled using wedges/ shims and subsequently filled by grouting.

脐带干细胞综述

脐带间充质干细胞的研究进展 间充质干细胞（mesenchymal stem cells,MSC S ）是来源于发育早期中胚层 的一类多能干细胞[1-5]，MSC S 由于它的自我更新和多项分化潜能，而具有巨大的 治疗价值 ,日益受到关注。MSC S 有以下特点：(1)多向分化潜能，在适当的诱导条件下可分化为肌细胞[2]、成骨细胞[3、4]、脂肪细胞、神经细胞[9]、肝细胞[6]、心肌细胞[10]和表皮细胞[11, 12]；(2)通过分泌可溶性因子和转分化促进创面愈合；(3) 免疫调控功能，骨髓源（bone marrow ）MSC S 表达MHC-I类分子，不表达MHC-II 类分子，不表达CD80、CD86、CD40等协同刺激分子，体外抑制混合淋巴细胞反应，体内诱导免疫耐受[11, 15]，在预防和治疗移植物抗宿主病、诱导器官移植免疫耐受等领域有较好的应用前景；(4)连续传代培养和冷冻保存后仍具有多向分化潜能，可作为理想的种子细胞用于组织工程和细胞替代治疗。1974年Friedenstein [16] 首先证明了骨髓中存在MSC S ，以后的研究证明MSC S 不仅存在于骨髓中，也存在 于其他一些组织与器官的间质中：如外周血[17]，脐血[5]，松质骨[1, 18]，脂肪组织[1]，滑膜[18]和脐带。在所有这些来源中，脐血(umbilical cord blood)和脐带(umbilical cord)是MSC S 最理想的来源，因为它们可以通过非侵入性手段容易获 得，并且病毒污染的风险低，还可冷冻保存后行自体移植。然而，脐血MSC的培养成功率不高[19, 23-24]，Shetty 的研究认为只有6%，而脐带MSC的培养成功率可 达100%[25]。另外从脐血中分离MSC S ，就浪费了其中的造血干/祖细胞(hematopoietic stem cells/hematopoietic progenitor cells,HSCs/HPCs) [26, 27]，因此，脐带MSC S (umbilical cord mesenchymal stem cells, UC-MSC S )就成 为重要来源。 一．概述 人脐带约40 g, 它的长度约60–65 cm, 足月脐带的平均直径约1.5 cm[28, 29]。脐带被覆着鳞状上皮，叫脐带上皮，是单层或复层结构，这层上皮由羊膜延续过来[30, 31]。脐带的内部是两根动脉和一根静脉，血管之间是粘液样的结缔组织，叫做沃顿胶质，充当血管外膜的功能。脐带中无毛细血管和淋巴系统。沃顿胶质的网状系统是糖蛋白微纤维和胶原纤维。沃顿胶质中最多的葡萄糖胺聚糖是透明质酸，它是包绕在成纤维样细胞和胶原纤维周围的并维持脐带形状的水合凝胶，使脐带免受挤压。沃顿胶质的基质细胞是成纤维样细胞[32]，这种中间丝蛋白表达于间充质来源的细胞如成纤维细胞的，而不表达于平滑肌细胞。共表达波形蛋白和索蛋白提示这些细胞本质上肌纤维母细胞。 脐带基质细胞也是一种具有多能干细胞特点的细胞，具有多项分化潜能，其 形态和生物学特点与骨髓源性MSC S 相似[5, 20, 21, 38, 46]，但脐带MSC S 更原始，是介 于成体干细胞和胚胎干细胞之间的一种干细胞，表达Oct-4, Sox-2和Nanog等多

脐带血造血干细胞库管理办法(试行)

脐带血造血干细胞库管理办法（试行） 第一章总则 第一条为合理利用我国脐带血造血干细胞资源，促进脐带血造血干细胞移植高新技术的发展，确保脐带血 造血干细胞应用的安全性和有效性，特制定本管理办法。 第二条脐带血造血干细胞库是指以人体造血干细胞移植为目的，具有采集、处理、保存和提供造血干细胞 的能力，并具有相当研究实力的特殊血站。 任何单位和个人不得以营利为目的进行脐带血采供活动。 第三条本办法所指脐带血为与孕妇和新生儿血容量和血循环无关的，由新生儿脐带扎断后的远端所采集的 胎盘血。 第四条对脐带血造血干细胞库实行全国统一规划，统一布局，统一标准，统一规范和统一管理制度。 第二章设置审批 第五条国务院卫生行政部门根据我国人口分布、卫生资源、临床造血干细胞移植需要等实际情况，制订我 国脐带血造血干细胞库设置的总体布局和发展规划。 第六条脐带血造血干细胞库的设置必须经国务院卫生行政部门批准。 第七条国务院卫生行政部门成立由有关方面专家组成的脐带血造血干细胞库专家委员会（以下简称专家委

员会），负责对脐带血造血干细胞库设置的申请、验收和考评提出论证意见。专家委员会负责制订脐带血 造血干细胞库建设、操作、运行等技术标准。 第八条脐带血造血干细胞库设置的申请者除符合国家规划和布局要求，具备设置一般血站基本条件之外， 还需具备下列条件： （一）具有基本的血液学研究基础和造血干细胞研究能力； （二）具有符合储存不低于1 万份脐带血的高清洁度的空间和冷冻设备的设计规划； （三）具有血细胞生物学、HLA 配型、相关病原体检测、遗传学和冷冻生物学、专供脐带血处理等符合GMP、 GLP 标准的实验室、资料保存室； （四）具有流式细胞仪、程控冷冻仪、PCR 仪和细胞冷冻及相关检测及计算机网络管理等仪器设备； （五）具有独立开展实验血液学、免疫学、造血细胞培养、检测、HLA 配型、病原体检测、冷冻生物学、 管理、质量控制和监测、仪器操作、资料保管和共享等方面的技术、管理和服务人员； （六）具有安全可靠的脐带血来源保证； （七）具备多渠道筹集建设资金运转经费的能力。 第九条设置脐带血造血干细胞库应向所在地省级卫生行政部门提交设置可行性研究报告，内容包括：

卫生部办公厅关于印发《脐带血造血干细胞治疗技术管理规范(试行)

卫生部办公厅关于印发《脐带血造血干细胞治疗技术管理规 范(试行)》的通知 【法规类别】采供血机构和血液管理 【发文字号】卫办医政发[2009]189号 【失效依据】国家卫生计生委办公厅关于印发造血干细胞移植技术管理规范(2017年版)等15个“限制临床应用”医疗技术管理规范和质量控制指标的通知 【发布部门】卫生部(已撤销) 【发布日期】2009.11.13 【实施日期】2009.11.13 【时效性】失效 【效力级别】部门规范性文件 卫生部办公厅关于印发《脐带血造血干细胞治疗技术管理规范（试行）》的通知 （卫办医政发〔2009〕189号） 各省、自治区、直辖市卫生厅局，新疆生产建设兵团卫生局： 为贯彻落实《医疗技术临床应用管理办法》，做好脐带血造血干细胞治疗技术审核和临床应用管理，保障医疗质量和医疗安全，我部组织制定了《脐带血造血干细胞治疗技术管理规范（试行）》。现印发给你们，请遵照执行。 二〇〇九年十一月十三日

脐带血造血干细胞 治疗技术管理规范（试行） 为规范脐带血造血干细胞治疗技术的临床应用，保证医疗质量和医疗安全，制定本规范。本规范为技术审核机构对医疗机构申请临床应用脐带血造血干细胞治疗技术进行技术审核的依据，是医疗机构及其医师开展脐带血造血干细胞治疗技术的最低要求。 本治疗技术管理规范适用于脐带血造血干细胞移植技术。 一、医疗机构基本要求 （一）开展脐带血造血干细胞治疗技术的医疗机构应当与其功能、任务相适应，有合法脐带血造血干细胞来源。 （二）三级综合医院、血液病医院或儿童医院，具有卫生行政部门核准登记的血液内科或儿科专业诊疗科目。 1.三级综合医院血液内科开展成人脐带血造血干细胞治疗技术的，还应当具备以下条件： （1）近3年内独立开展脐带血造血干细胞和（或）同种异基因造血干细胞移植15例以上。 （2）有4张床位以上的百级层流病房，配备病人呼叫系统、心电监护仪、电动吸引器、供氧设施。 （3）开展儿童脐带血造血干细胞治疗技术的，还应至少有1名具有副主任医师以上专业技术职务任职资格的儿科医师。 2.三级综合医院儿科开展儿童脐带血造血干细胞治疗技术的，还应当具备以下条件：

卫生部关于印发《脐带血造血干细胞库设置管理规范(试行)》的通知

卫生部关于印发《脐带血造血干细胞库设置管理规范(试行)》的通知 发文机关：卫生部(已撤销) 发布日期： 2001.01.09 生效日期： 2001.02.01 时效性：现行有效 文号：卫医发(2001)10号 各省、自治区、直辖市卫生厅局： 为贯彻实施《脐带血造血干细胞库管理办法（试行）》，保证脐带血临床使用的安全、有效，我部制定了《脐带血造血干细胞库设计管理规范（试行）》。现印发给你们，请遵照执行。 附件：《脐带血造血干细胞库设置管理规范（试行）》 二○○一年一月九日 附件： 脐带血造血干细胞库设置管理规范（试行） 脐带血造血干细胞库的设置管理必须符合本规范的规定。 一、机构设置 （一）脐带血造血干细胞库（以下简称脐带血库）实行主任负责制。 （二）部门设置 脐带血库设置业务科室至少应涵盖以下功能：脐带血采运、处理、细胞培养、组织配型、微生物、深低温冻存及融化、脐带血档案资料及独立的质量管理部分。 二、人员要求

（一）脐带血库主任应具有医学高级职称。脐带血库可设副主任，应具有临床医学或生物学中、高级职称。 （二）各部门负责人员要求 1．负责脐带血采运的人员应具有医学中专以上学历，2年以上医护工作经验，经专业培训并考核合格者。 2．负责细胞培养、组织配型、微生物、深低温冻存及融化、质量保证的人员应具有医学或相关学科本科以上学历，4年以上专业工作经历，并具有丰富的相关专业技术经验和较高的业务指导水平。 3．负责档案资料的人员应具相关专业中专以上学历，具有计算机基础知识和一定的医学知识，熟悉脐带血库的生产全过程。 4．负责其它业务工作的人员应具有相关专业大学以上学历，熟悉相关业务，具有2年以上相关专业工作经验。 （三）各部门工作人员任职条件 1．脐带血采集人员为经过严格专业培训的护士或助产士职称以上卫生专业技术人员并经考核合格者。 2．脐带血处理技术人员为医学、生物学专业大专以上学历，经培训并考核合格者。 3．脐带血冻存技术人员为大专以上学历、经培训并考核合格者。 4．脐带血库实验室技术人员为相关专业大专以上学历，经培训并考核合格者。 三、建筑和设施 （一）脐带血库建筑选址应保证周围无污染源。 （二）脐带血库建筑设施应符合国家有关规定，总体结构与装修要符合抗震、消防、安全、合理、坚固的要求。 （三）脐带血库要布局合理，建筑面积应达到至少能够储存一万份脐带血的空间；并具有脐带血处理洁净室、深低温冻存室、组织配型室、细菌检测室、病毒检测室、造血干/祖细胞检测室、流式细胞仪室、档案资料室、收/发血室、消毒室等专业房。 （四）业务工作区域应与行政区域分开。

脐带血间充质干细胞的分离培养和鉴定

脐带血间充质干细胞的分离培养和鉴定 【摘要】目的分离培养脐带血间充质干细胞并检测其生物学特性。方法在无菌条件下用密度梯度离心的方法获得脐血单个核细胞，接种含10%胎牛血清的DMEM培养基中。单个核细胞行贴壁培养后，进行细胞形态学观察，绘制细胞生长曲线，分析细胞周期，检测细胞表面抗原。结果采用Percoll(1.073 g/mL)分离的脐血间充质干细胞大小较为均匀，梭形或星形的成纤维细胞样细胞。细胞生长曲线测定表明接后第5天细胞进入指数增生期，至第9天后数量减少;流式细胞检测表明50%～70%细胞为CD29和CD45阳性。结论体外分离培养脐血间充质干细胞生长稳定，可作为组织工程的种子细胞。 【关键词】脐血;间充质干细胞;细胞周期;免疫细胞化学 Abstract: Objective Isolation and cultivation of mesenchymal stem cells (MSCs) in human umbilical cord in vitro, and determine their biological properties. Methods The mononuclear cells were isolated by density gradient centrifugation from human umbilical cord blood in sterile condition, and cultured in DMEM medium containing 10% fetal bovine serum. After the adherent mononuclear cells were obtained, the shape of cells were observed by microscope, then the cell growth curve, the cell cycle and the cell surface antigens were obtained by immunocytochemistry and flow cytometry methods. Results MSCs obtained by Percoll (1.073 g/mL) were similar in size, spindle-shaped or star-shaped fibroblasts-liked cells. Cell growth curve analysis indicated that MSCs were in the exponential stage after 5d and in the stationary stages after 9d. Flow cytometry analysis showed that the CD29 and CD44 positive cells were about 50%～70%. Conclusions The human umbilical cord derived mesenchymal stem cells were grown stably in vitro and can be used as the seed-cells in tissue engineering. Key words:human umbilical cord blood; mesenchymal stem cells; cell cycle; immunocytochemistry 间充质干细胞(mesenchymal stem cells，MSCs)在一定条件下具有多向分化的潜能，是组织工程研究中重要的种子细胞来源。寻找来源丰富并不受伦理学制约的间充质干细胞成为近年来的研究热点[1]。脐血(umbilical cord blood, UCB)在胚胎娩出后，与胎盘一起存在的医疗废物。与骨髓相比，UCB来源更丰富，取材方便，具有肿瘤和微生物污染机会少等优点。有人认为脐血中也存在间充质干细胞(Umbilical cord blood-derived mesenchymal stem cells，UCB-MSCs)。如果从脐血中培养出MSCs，与胚胎干细胞相比，应用和研究则不受伦理的制约，蕴藏着巨大的临床应用价值[2,3]。本研究将探讨人UCB-MSCs体外培养的方法、细胞的生长曲线、增殖周期和细胞表面标志等方面，分析UCB-MSCs 作为间充质干细胞来源的可行性。

脐带血干细胞检测

脐带血干细胞检测 对每份脐血干细胞进行下列检测： ①母体血样做梅毒、HIV和CMV等病原体检测，这一检测使脐血干细胞适合于其它家庭成员应用。如任何一种病原体测试阳性，需重复测定。 ②每份脐血干细胞样本同时检测确定没有微生物污染。 ③细胞活性检测、有核细胞数、CD34+细胞数、集落形成试验等。CD34是分子量115KD 的糖蛋白分子，使用特定单克隆抗体（抗-CD34）确定，脐血祖细胞的大部分，包括体外培养产生造血集落的细胞都包含在表达CD34抗原的细胞群中。 ④HLA组织配型、ABO血型。 一、采血方式及其优点 再生缘生物科技公司采用最严谨的封闭式血袋收集法，避免在收集脐带血液时可能遭受微生物污染的发生，且以最少之操作步骤，收集最大量之脐带血液方式，在产房内即可完成。 二、脐带血处理与保存 脐带血收集于血袋，经专人运送至再生缘生物科技公司之无菌细胞分离实验室后，由专业的技术人员于完全无菌的环境下，依标准操作程序将血液进行分离，收集具有细胞核的细胞，其中含有丰富的血液干细胞，经加入冷冻保护剂和适当品管检测后，并进行以最适合

血液干细胞的冷冻降温程序方式，进行细胞冷冻程序，达到避免细胞受到冷冻过程之伤害。完成后，冷冻细胞立刻保存于摄氏零下196度的液态氮槽中。所有操作程序记录和细胞保存相关数据，均由计算机条形码系统追踪确认，完全符合国际脐带血库之标准操作程序和品管要求。 母亲血液之检测 为确保所操作和保存的脐带血液细胞，符合国际血液操作规范，并提供客户最大的保障，对于产妇血液必须同时进行一些病毒传染病的检测，以确保没有下列病毒，如艾滋病毒(HIV)、C型肝炎病毒(HCV)、人类T细胞淋巴病毒(HTLV)和梅毒(syphilis)，同时对于B型肝炎病毒(HBV)和巨细胞病毒(CMV)加以侦测和纪录，作为将来可能应用脐带血细胞时之必要参考数据并符合卫生医疗之要求。 脐带血细胞之品管 对于所保存之脐带血细胞均进行多项操作流程监控和品管检测，如微生物污染检测、血液细胞浓度、细胞存活率、细胞活性测定等，每一步骤均有详细之纪录，在操作方法和使用仪器方面均定期进行验证和校验，以符合国际医疗标准。 三、实验室、贮存处所介绍 再生缘生物科技公司拥有符合美国联邦标准(FED-STD-209E)和中华民国优良药品制造标准（一区、二区、三区）的生物安全实验室和无菌操作设备，在专业的技术人员依标准操作程序下进行血液分离和保存步骤，保障客户珍贵样品和权益。 分离后之细胞将依浓度分装入4-6个冷冻管，计算机降温冷冻完成后，即由食品工业发展研究所国家细胞库专业液态氮库房人员，将冷冻细胞分别存放于二个不同的脐带血细胞专属液态氮槽中保存，在安全机制上更有保障。液态氮库房拥有五吨的液态氮供应系统，每一液氮槽均有自动充填装置和异常警报系统，和每日值勤人员监控，确保冷冻细胞处于最佳的冷冻状态。 四、安全管制措施 脐带血液经快递送达无菌细胞分离实验室后，每一步骤均有专业技术人员操作和监督，并将所有分析数值详细填于具有条形码管制之分析表格和计算机数据表中，利用条形码和读码系统确认样品之专一性，避免人为失误，且便于追溯和数据品管。 在冷冻细胞保存上

胎盘干细胞与脐带血干细胞的区别

胎盘干细胞与脐带血干细胞的区别 干细胞是一类具有自我复制和多向分化能力的原始的未分化的细胞，它可以向多种类型细胞分化，并具有相应的功能，可以用来修复和替代受到损伤，病变的组织和器官。目前主要的成体干细胞来源有胎盘来源、脐带来源、脐带血来源和骨髓来源的干细胞，本文主要介绍一下胎盘来源的干细胞和脐带血来源的干细胞的区别： 1、分离部位不同：胎盘干细胞是从胎盘组织中分离提取的干细胞，脐带血干细胞是从脐带里面血液中分离提取的干细胞。 2、种类不同：胎盘中的干细胞主要指的是间充质干细胞，而脐带血干细胞主要指的是造血干细胞。 3、分化能力不同：1）胎盘干细胞分化能力强，在特定的诱导条件下可以分化成血管干细胞、神经干细胞、肝干细胞等多种类型的干细胞，从而修复受损和病变的组织和器官2）脐带血干细胞可以在体内向红细胞、血小板等各种血液细胞分化。 4、数量不同：1）胎盘体积大，从中提取的干细胞数量丰富，并可以在体外培养扩增，扩增培养的子细胞数量达十亿个，可以供成人多次使用2）脐带血干细胞的数量要根据抽取的脐带血多少而定，不可以在体外培养扩增，一份脐带血干细胞可以供40kg以下患者一次使用。 5、治疗使用：1）胎盘干细胞目前在治疗脑瘫、糖尿病、肝硬化、心血管疾病等诸多疾病都显示了良好的效果2）脐带血干细胞可以治疗白血病，再生障碍性贫血等血液系统疾病。不过对于儿童白血病多以先天性为主，所以对于这种情况，自己的脐带血干细胞是不能使用的，需要配型使用捐献的脐血干细胞。 6、配型方面：二者自体使用都不需要配型，如果异体使用，胎盘干细胞由于免疫源性低的特点，所以配型成功率非常高，有血缘关系的亲属都可以使用；脐带血干细胞与父母配型有1/2的几率，与兄弟姐妹有1/4的几率。

脐带血造血干细胞库技术规范

脐带血造血干细胞库技术规范(试行) I 脐带血造血干细胞库(简称脐带血库)的质量控制 1 规章制度和操作规程 脐带血库必须制定脐带血采集、制备、检测、库存、选择和发放的规章制度、操作规程。 1.1 脐带血供者筛选标准和咨询。 1.2 脐带血采集和运送。 1.3 脐带血制备、冷冻、库存。 1.4 标签。 1.5 传染性疾病、人类组织相容性抗原（HLA）分型、造血干细胞和其他检测。 1.6 库存脐带血和脐带血检测标本的确认。 1.7 脐带血的发放。 1.8 脐带血库与移植机构之间的运输。 1.9 数据管理、申请查询、供者与受者配型、脐带血的选择。 1.10 移植随访资料的收集和分析。 1.11 人员培训和继续教育。 1.12 材料、试剂和设备。 1.13 不合格产品、操作错误和事故的报告。 1.14 卫生清洁。 1.15 保密制度。 2 规章制度和操作规程的执行 2.1有脐带血库主任的签字及开始实施的日期。 2.2各项规章制度和操作规程修改，须由脐带血库主任或文件起草人进行审查、签字并标明日期。 2.3 规章制度和操作规程应置于方便工作人员随时取用的位置。 2.4 存档的各种规程和标准记录应长期保留。 2.5 如认为本技术规范不适应当前发展，允许各脐带血库根据情况适当调整，但应报脐带血造血干细胞库专家委员会备案，备案期为30天。专家委员会如不同意备案的规章制度和操作规程，应在备案期间内通知备案单位停止执行。 3 质量控制 3.1 应有专门的质量控制规程，以便对脐带血库工作人员在常规操作中所使用的规程、试剂、设备和材料进行质量控制。 3.2 脐带血库内部的质量控制 3.2.1应由脐带血库主任或指定专人进行质量控制。 3.2.2脐带血库内部的质量控制包括质量评估，改进和修正的措施，错误和事故的处理。 3.2.2.1 脐带血库必须有不合格产品的记录和报告。 3.2.2.2 脐带血库主任应定期召开质量评价会议，对错误和事故进行评价；对重大事故应及时处理。 3.2.2.3 脐带血库主任必须签发对规程的修正。

脐带血干细胞的基础与应用研究

生命科学 Chinese Bulletin of Life Sciences 第18卷 第4期2006年8月 Vol. 18, No. 4Aug., 2006 脐带血干细胞的基础与应用研究 顾东生, 刘 斌, 韩忠朝* （中国医学科学院中国协和医科大学血液学研究所实验血液学国家重点实验室，天津 300020） 摘　要：作为造血干/祖细胞(hematopoietic stem cells/hematopoietic progenitor cells, HSCs/HPCs)的另一 来源，脐带血已经应用于临床治疗多种恶性和非恶性疾病。脐带血中HSCs/HPCs 的质与量是决定其临床应用效果的最重要因素。同时，脐带血中还存在多种非造血的干细胞和前体细胞，如间充质干细胞(mesenchymal stem cells, MSCs)、内皮前体细胞(endothelial progenitor cells, EPCs)和非限制性体干细胞(unrestricted somatic stem cells, USSCs)等，这些细胞可能会在未来的细胞治疗和再生医学中发挥重要作用。本综述还讨论了脐带血的临床应用及HSCs/HPCs 的体外扩增、增加HSCs 归巢和再植能力等提高其临床应用能力的相关研究。关键词：脐带血；造血干细胞；移植 中图分类号：R322.2; R323.3; Q813 文献标识码：A The research and application of cord blood stem cells GU Dong-Sheng, LIU Bin, HAN Zhong-Chao* (State Key Laboratory of Experimental Hematology, Institute of Hematology, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300020, China) Abstract: Umbilical cord blood (UCB), as an alternative source of hematopoietic/progenitor stem cells (HSCs/HPCs), has been used clinically for a large number of malignant and non-malignant disorders. The quality and quantity of HSC and HPC may be the most important factors on which the capacity of UCB to perform clinical function depends. Other non-HSCs/HPCs, such as mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs) and unrestricted somatic stem cells (USSCs), also present in cord blood, which may play a future role in cell therapy and regenerative medicine. This review also covers the efforts to expand HSCs and HPCs ex vivo and recent studies on attempts to enhance the homing and engrafting capability of HSCs as means to enhance the clinical utility of UCB. Key words: umbilical cord blood; hematopoietic stem cells; transplantation 收稿日期：2006-04-25 基金项目：“863”计划(2003AA205060)；“973”项目子项(2001C B5101) 作者简介：顾东生(1981—)，男，硕士研究生；刘 斌(1973—)，男，硕士，助理研究员；韩忠朝(1953—)，男，博士，教授，博士生导师，*通讯作者。 文章编号 ：1004-0374(2006)04-0323-05 1988年，Broxmeyer 首先以实验证明脐带血(umbilical cord blood, UCB)中富含造血干细胞(hematopoietic stem cells, HSCs)。法国Gluckman 等[1]在巴黎圣路易斯医院为一位患有先天性再生不良性贫血的儿童实施了世界上首例脐带血移植术，并取得成功。从此，人们对于一直被当成废弃物丢掉 的胎盘和脐带血有了全新的评价和认识，至今，各国学者对脐带血的基础研究和临床应用进行了大量工作并取得很大成绩。本文对脐带血中存在的多种干/祖细胞的生物学特性及临床应用研究进行综述。1　脐带血干细胞 在现阶段，脐带血之所以能够应用于临床治疗

胎盘干细胞和脐带血干细胞是否需要都保存

胎盘干细胞和脐带血干细胞是否需要都保存？ 近来,保存胎盘干细胞热潮在京城悄然兴起，引起了人们对于保存胎盘干细胞和脐带血干细胞的一番讨论，即究竟该保存哪个更有价值呢？是否需要都保存呢？针对这一问题，记者特意查找了大量专业性新闻报导及相关信息，并就该问题咨询了北京博雅干细胞库技术人员，以求寻获一个明确的答案。 记者了解到，在保存胎盘干细胞热潮兴起之前，保存脐带血干细胞或捐献 脐带血干细胞的观念早已深入人心，而且已经占据了一定的市场。并且大多数人都已知晓利用脐带血干细胞能够治愈血液系统疾病等等诸多好处。但是对于胎盘干细胞在生物医学领域的重大用途却知之甚少。 现如今，胎盘干细胞同脐带血干细胞一样被人们所熟知，可是面临的问题 却使得人们不知该如何选择，那就是胎盘干细胞和脐带血干细胞是否应该都保存呢? 针对此问题,记者经过一番周折终于可以比较专业的为大家解答这个问题了。其实，保存胎盘主要是保存从胎盘中提取的间充质干细胞，而保存脐带血是保存脐带血中的造血干细胞。那么，胎盘间充质干细胞和脐带血造血干细胞有何区别呢？首先，胎盘中含有的间充质干细胞非常丰富，这种间充质干细胞属于多能干细胞，具有强大的增殖能力和多向分化潜能，能培养发育成人体的各个组织器官与神经系统。而脐带血中的造血干细胞含量较少，这种造血干细胞属于单能干细胞，不能进行体外扩增，不能分化成为其他的干细胞。其次，胎盘间充质干细胞治疗疾病范围比较广泛，如对于治疗心、脑血管疾病、神经系统疾病、肝脏疾病、骨组织病、角膜损伤、烧伤烫伤、肌病等多种疾病都有不错的疗效。造血干细胞主要针对治疗血液系统疾病和免疫系统疾病具有较好的疗效。最后，记者想告诉大家的是，胎盘间充质干细胞和脐带血造血干细胞两者同样都具有很高的医学价值，都能治疗多种疾病，虽然造血干细胞治疗疾病范围有限且不能进行体外扩增，导致干细胞数量仅可供30公斤以下儿童一次使用，但是胎盘间充质干细胞可以和造血干细胞共移植治疗血液系统疾病，并可供成人使用。另外，两者在采集的时候都不会给产妇和新生儿带来任何不适的感觉和产生任何不良的影响，并且在未来生物医学研究发展过程中，都将起到不可或缺的作用，并将推动再生医学的发展。那么，人们更应该保存哪个呢？记者建议，如果经济条件许可的话，建议人们将两者一起保存起来，以备将来不时之需。

脐血干细胞移植实施方案

附件3 脐带血造血干细胞移植实施方案

(一）准备 患者准备 1、身体准备全面体检和实验室检查； 2、心理准备移植病人大多数对治疗方法及过程缺乏了解，又因长期接受化疗，造成很大的痛苦，病人对移植既抱有希望，又有焦虑和恐惧的心理。因此，在移植前护理人员应主动与病人及家属进行交谈，尽可能做好心理。 物品准备： 病人入舱前，舱内所有物品包括药品、被服、纸张、卫生材料、医疗器械都要经过灭菌处理后，由传递窗送入无菌舱内。 病人在舱内的生活用品，经灭菌处理后入舱。 环境准备： 无菌层流舱: ?患者舱：100级 ?护士站、治疗室等：1000级 ?手消毒间、备无菌餐间：10，000级 ?更衣间、药浴间：100，000级 ------舱内压力递减 患者入住前环境准备 1、彻底卫生清洁： 2、熏蒸24小时：每立方米用高锰酸钾5mg+40%甲醛10ml，熏蒸24小时，通风24小时。 3、入住前的全面消毒液擦拭。 4、空气培养：达标。目前选用平皿沉降法检测； 5、入室物品一律消毒灭菌：可以高压灭菌或适合环氧乙烷消毒的物品，一律灭菌后进舱，须浸泡消毒的物品要确保浸泡消毒的效果可靠。 患者入住后无菌全环境的保持 （一）入住后患者要求： 1、每日以KL-98消毒液洗头、洗脸、擦身、洗脚，早晚各一次（20分钟）。 2、每日以KL-98消毒液于晨起、睡前、便后坐浴一次（20分钟）。

3、睡前、饭前、饭后（进食任何饮食后）认真漱口。 4、3%双氧水擦洗鼻前庭、外耳道每日三次，然后用碘伏消毒液擦拭，再涂以红霉素软膏等。 5、抗菌及抗病毒的眼药水交替点眼，每日三次。 6、经常以含KL-98消毒液棉球擦手（代替洗手）。 （二）入住后环境要求： 1、净化舱内地面、所有物品表面每日消毒液擦拭一次，发现有污染随时擦拭消毒。 2、室内墙壁隔天消毒液擦拭一次。 3、被服高压消毒更换每日一次。 4、空气喷雾消毒每日一次。 5、坐便桶、污水桶每日更换消毒一次。 （三）无菌饮食要求： 1、食物新鲜，彻底洗净、煮熟、微波炉消毒7分钟。 2、水时须做成水果羹后微波炉消毒，或须经消毒后用无菌刀削皮后方可食用。 3、饼干、馒头放微波炉隔水蒸7分钟。 4、饮水均须用开水经舱内电热水瓶二次沸腾后方可饮用。 5、餐具严格消毒。 工作人员入室要求： 严格控制入室人员。医护人员入室前先淋浴，更换清洁衣裤，戴清洁帽子。在缓冲间用肥皂洗手，清水冲净后，再用手快速消毒剂擦手，然后更换无菌拖鞋进入更衣间。戴一次性无菌手套，按无菌操作要求穿无菌分体式隔离衣，戴无菌口罩，进入消毒间再次消毒手，更换无菌拖鞋方可进入护士站。如果进入病人所在的百级层流病房，还需戴无菌手套，穿无菌隔离衣，更换无菌拖鞋方可进入。(二）预处理 定义：是指在输注造血干细胞前对病人进行的大剂量化疗或放疗。 目的：尽可能杀灭病人体内的异常细胞或肿瘤细胞，最大限度减少复发；破坏病人免疫系统，为造血干细胞的植入提供条件，防止移植物被排斥；为造血干细胞的植入、生长提供必要的空间。