STEEL CONSTRUCTION

BUILDING CONSTRUCTION

IN EVERY REGION OF THE WORLD, BUILDINGS HAVE TRADITIONALLY BEEN CONSTRUCTED FROM MATERIALS AVAILABLE LOCALLY. THUS THE FORMS OF BUILDINGS AND THE MATERIALS USED VARY FROM ONE REGION TO ANOTHER.

AS SOCIETY DEVELOPS, THERE ARE CHANGES IN THE KINDS OF BUILDINGS IT REQUIRE. IN THE MODERN INDUSTRIAL SOCIETY, THE DEMAND FOR OFFICE AND FACTORY BUILDINGS OFTEN EXCEEDS THAT FOR HOUSING. FOR MANY YEARS, MOST OFFICE AND FACTORY BUILDINGS HAVE BEING BUILD OF REINFORCED CONCRETE – USING CEMENT AND AGGREGATES THAT MAY BE AVAILABLE LOCALLY, TOGEATHER WITH A SMALL AMOUNT OF STEEL BARS FOR REINFORCEMENT.

RECENTLY, THE NEED HAS BEEN GROWING IN MOST AREAS FOR STILL LARGER BUILDINGS: GRATER HEIGHT, WIDER SPAN AND HEAVIER LOAD-BEARING CAPACITY. MASS CONSTRUCTION, SHORTER CONSTRUCTION PERIOD, HIGHER PRECISION OF CONSTRUCTION AND GREATER DEPENDABILITY ARE BECOMING STEADILY MORE IMPORTANT FACTORS.

STEEL-FRAME CONSTRUCTION ANSWERS MANY OF THESE NEED, IN SOUTHEAST ASIA, DUE TO LACK OF STEEL BUILDING AND EXPERIENCE WITH MORE COMPLEX TECHNOLOGY IN THEIR CONSTRUCTION COMPARED WITH REINFORCED CONCRETE CONSTRUCTION, STEEL-FRAME CONSTRUCTION IS SAID TO BE LESS POPULAR. 

STEEL PRODUCTS

STEEL PRODUCTS AS STRUCTURAL MEMBERS

STEEL STRUCTURE MEMBERS CAN BE SMALL IN SECTIONAL AREA, BECAUSE STEEL IS FAR STRONGER THAN WOOD OR CONCRETE. THE DEAD LOAD OF STRUCTURE (ITS OWN WEIGHT) IS THEREFORE RELATIVELY SMALL, AND PROPORTION OF DEAD LOAD IS ALSO SMALL. THIS MEANS, HOWEVER, THAT IT IS NECESSARY TO ESTIMATE THE EXTERNAL LOAD ACTING ON THE STEEL STRUCTURE MEMBER AS PRECISELY AS POSSIBLE. TO ENCLOSE A LARGE SPACE SUCH AS GYMANSIUM, FOR EXAMPLE, A STEEL TRUSS STRUCTURE IS FREQUENTLY EMPLOYED SINCE IT HAS A LOW DEAD LOAD THOUGH IT IS LARGE, AND IS THUS AN ECONOMICAL CHOISE.

FOR STEEL MEMBERS, WITH THEIR SMALL SECTIONAL AREAS, BUCKLING AND OTHER KINDS OF DEFORMATION MUST BE PREVENT. OTHERWISE, SUCH MEMBERS MAY BE SUBJECT TO BENDING, BUCKLING OR TORSIONAL DEFORMATION EVEN THOUGH SIMPLE CALCULATIONS INDICATE A SUFFICENT YEILD STRENGTH. IN THE DESIGNING A STEEL-FRAME BUILDING, DEFORMATION MUST BE CONSIDERED IN ADDITIONAL TO STRUCTURE CALCULATIONS. AN IMPORTANT PART OF THE STUDY OF DEFORMATION OF STEEL STRUCTURE AND THEIR MEMBER IS THE METHODS OF JOINTING MEMBERS AND COLUMN BASE, AND THE DESIGN CONDITIONS OF THE JOINTS. NEGLECT OF THESE CONSIDERATIONS MAY RESULT IN DEFORMATION OF STEEL STRUCUTRE TO MEET THE DESIGN REQUIREMENTS.

NEVERTHELESS, THE LOW DEAD LOAD OF STEEL STRUCTURE OFFERS ADVANTAGES. REGARDING THE BUILDING FOUNDATION, FOR EXAMPLE, ON SOIL OF LOW BEARING CAPACITY WHERE REINFORCED CONCRETE BUILDING WOULD REQUIRE A PILE FOUNDATION, A DIRECT FOUNDATION IS SUFFICIENT FOR STEEL-FRAME BUILDING. SUCH A FOUNDATION IS LESS EXPENSIVE AND IS COMPLETED MORE QUICKLY. IN AN ULTRA-HIGH-RISE BUILDING, STEEL STRUCTURE IS USED BECAUSE, IN ADDITION TO HIGHER TOUGHNESS OF A STEEL-FRAME, ITS DEAD LOAD MEMBERS ARE SMALLER IN SECTIONAL AREA, LEAVING MORE OF THE INTERIOR SPACE IN THE BUILDING FREE TO USE.

FRAME DESIGN

CONSTRUCTION OF STEEL STRUCTURES

CONTRACTOR PROCEDURE

WHEN PEPRARING THE STRUCTURE DESIGN OF A STEEL STRUCTURE, ONE SHOULD KEEP IN MIND ALWAYS THE PROCEDURE BY WHICH A BUILDING IS ERECTED. AS A GOOD UNDERSTANDING BY THE DESIGNER OF HOW STEEL MEMBERS ARE MADE, FABRICATED AND ERECTED TO FORM THE COMPLETED STRUCTURE LEADS TO SUPERIOR STRUCTURAL DESIGN. LACK OF SUCH UNDERSTANDING CAN LEAD TO COSTLY MISTAKES AT THE DESIGN STAGE: JOINTS WITH HIGH-STRENGTH BOLTS THAT ARE UNFASTENABLE MANUALLY; DETAILS THAT ARE IMPOSSIBLE TO WELD; STEEL PRODUCTS CUT IN WAYS THAT MAKE THAM DIFFICULT TO TRANSPORT; MEMBERS SO SHAPED THAT CONCENTRATED STRESS IS UNAVOIDABLE; JOINTS FOR WHICH THE STRESS TRANSMISSION MECHANISM IS NOT CLEAR; AND SO ON. THE CONSTRUCTION OF STEEL STRUCTURE IS OUTLINED BELOW, WHICH REFERENCE TO GENERAL PRECAUTIONS THAT SHOULD BE OBSERVED.

STEEL IS NORMALLY DIVIDED INTO SHOP WORK AND FIELD WORK.THE FLOWCHART BELOW INDICATES THE SERIES OF STEPS FROM RECEIPT OF DESIGN DOCUMENT BY STEEL FRAME FABRICATOR THROUGH THE CUTTING AND FABRICATION OF STEEL FRAME, THEIR ASSEMBLY AND SHIPPING FROM SHOP. 

COLUMN BASES

THE COLUMN BASES OF A BUILDING ARE HIGHLY IMPORTANT STRUCTURAL ELEMENTS SINCE THEY TRANSMIT THE VERTICAL LOAD OF THE FRAME TO THE FOUNDATION AND ARE ALSO REQUIRED TO WITHSTAND LARGE HORIZONTAL SHEARING FORCES AT TIMES OF EARTHQUAKE OR STRONG WIND.

THE COLUMN BASES OF A STEEL-FRAME BUILDINGS ARE ACTED UPON BY A COMPLEX STRESS PATTERN BECAUSE THEY ARE THE CONTACT POINT BETWEEN TWO DIFFRERNT KINDS OF STRUCTURE: THE REINFORCED-CONCRETE FOUNDATION AND THE STEEL SUPERSTRUCTURE. THIS IS LIABLE TO CAUSE PROBLEMS AT THE WORK STAGE IF DUE CARE IS NOT TAKEN.

THE TWO CLASSES OF COLUMN BASE – THE FIXED TYPE AND THE PIN TYPE – ARE DECRIBED BELOW.

1. FIXED COLUMN BASE

TYPICAL FIXED COLUMN BASES ARE SHOWN BELOW. WHEN THE BENDING MOMENT OF THE COLOUMN BASE IS SMALL, A BASE PLATE WELDED TO THE COLUMN SECTION AND FIXED BY ANCHOR BOLTS TO THE FOUNDATION.

                   EXAMPLE OF FIXED COLUMN BASE FOR STEEL-FRAME STRUCTURE

ANOTHER DESIGN METHOD FOR FIXED COLUMN BASES IS THE “ROOT COVERING” APPROACH. THIS METHOD, AS INDICATED BELOW, IS TO COVER THE STEEL COLUMN BASE WITH CONCRETE, WHICH IS A KIND OF STEEL-REINFORCED CONCRETE STRUCTURE. THE COLUMN BASE, BEING EMBEDDED IN CONCRETE, HAS VERY HIGH RIGIDITY.

 EXAMPLE OF ‘ROOT-COVERED’ COLUMN BASE

2. PIN-TYPE COLUMN BASE

STEEL STRUCTURE IS WIDELY EMPLOYED FOR LARGE-SPAN BUILDINGS. IN THE STRUCTURE DESIGN OF SUCH A BUILDING, IT IS DIFFICULTY TO DESIGN A FOOTING BEAM HAVING HIGH RIGIDITY. THE FOUNDATION MUST BE A TIE-ROD TYPE, AIMED AT PREVENTING OPENING OF THE FRAME, OR AN INDEPENDENT TYPE BELOW. 

                                        EXAMPLE OF PIN-TYPE COLOUMN BASES

BEAM TO COLUMN CONNECTIONS

IN DESIGNING THE CONNECTIONS OF BEAMS TO COLUMNS, THEREFORE, ADEQUATE RIGIDITY SHOULD RECEIVE AS MUCH ATTENTION AS ADEQUATE STRENGTH. ONLY THEN CAN BE BEAMS AND COLUMN THAT COMPRISE THE FRAMEWORK DELIVER THEIR FULL SECTIONAL PERFORMANCE. FROM THIS STANDPOINT. PROVISION OF A HAUNCH AT THE END OF THE BEAM IS VERY ADVANTAGEOUS FOR WIND AND EARTHQUAKE RESISTANT DESIGN. DIAGRAM BELOW SHOWS A BRACKETS-TYPE CONNECTION USING WIDE-FLANGE BEAMS.  

                 EXAMPLE OF BRACKET-TYPE CONNECTION USING WIDE-FLANG BEAMS

BEAM TO GIRDER CONNECTIONS

IT SHOULD BE NOTED THAT BEAM TO GIRDER CONNECTIONS, TRUSS JOINT AND BRACE JOINTS ARE USALLY TREATED AS PIN JOINTS. ILLUSTRATES BELOW SHOWN BEAM TO GIRDER CONNECTION. NORMALLY IT IS SUFFICENT TO CONNECT THE WEB OF THE BEAM THROUGH A GUSSET PLATE TO THE GIRDER FOR TRANSMISSION OF THE SHEARING FORCE.

                                   EXAMPLES OF BEAM TO GIRDER CONNECTIONS

FRAME DESIGN

STRUCTURAL STEEL MEMBERS

1.SINGLE MEMBERS AND ASSAMBLED MEMBERS

  STEEL SECTION CAN BE CLASSIFIED ACCORDING TO METHODS OF APPLICATION INTO PRODUCTS USED AS SINGLE MEMBERS AND PRODUCTS USED MAINLY IN COMBINATION TO FORM ASSEMBLED MEMBERS. CLASSIFIED BY TYPES OF SECTION, THE MAIN PRODUCTS ARE FLAT BAR, ANGLES, CUT-TEES AND ROUND BARS. STEEL PROUDCTS OF THESE TYPES ARE REARLY USED SINGLY AS COLUMNS OR BEAMS, BUT ARE COMBINED IN LATTICE GIRDER OR TRUSS TO FORM MEMBERS.

2.WIDE-FLANGE BEAMS

  WIDE-FLANGE BEAMS ARE SIMILAR IN APPERANCE TO I-BEAMS

  (1)     THE FLANGES OF WIDE-FLANGE BEAMS HAVE INNER AND OUTER SURFACE IS PARALLED,WHILE THE FLANGES OF I-BEAMS ARE TAPERED.

  (2)      THE INSIDE DEMENSIONS OF WIDE-FLANGE BEAMS OF THE SAME SERIES ARE FIXED, WHEREAS FOR I-BEAMS THE OUTSIDE DIMENSIONS ARE FIXED.

                           CROSS SECTIONS OF WIDE-FLANGE BEAM AND I-BEAM

CONNECTIONS - JOINING BY HIGH-STRENGTH BOLTS

METHODS OF JOINING WITH BOLTS ARE CLASSIFIED INTO THREE TYPES.

1.  SHEARING JOINT

            THE STRESS-TRANSMISSION MECHANISM OF A SHERING JOINT IS ILLUSTRATED BELOW. SECTIONAL FORCE  N  ACTING ON THE JOINED MEMBERS IS TRANSMITTED BY CONTACT PRESSURE (BEARING PRESSURE) BETWEEN THE SIDE BOLT AN THE BOLT HOLE. A SHERING FORCE IS THUS APPLIED TO THE SECTION OF THE BOLT. ACCORDINGLY, THE YIELD STRENGTH OF A SHERING JOINT SHOULD BE EITHER THE SHEARING STRENGTH OF THE BOLT, DETERMINED BY ITS DIAMETER, OR THE BEARING STRENGTH OF THE JOINED MEMBERS,WHICHEVER IS SMALLER IN VALUE.

                                    SHEARING JOINT

2.  FRICTION JOINT

            ILLUSTRATED BELOW SHOW THE CONCEPT OF THE FRICTION JOINT. AS IN THE SHEARING JOINT, THE SECTIONAL FORCE  N  IS TRANSMITTED AT RIGHT ANGLES TO THE AXIS OF THE BOLT, BUT ITS STRESS-TRANSMISSION MECHANISM IS COMPLETELY DIFFERENT FROM THE SHERING JOINT. IN THE FRICTION JOINT, A LARGE CLAMPING FORCE IS APPLIED TO THE BOLT, WHEREBY A COMPRESSIVE STRESS IS PRODUCED BETWEEN THE JOINED MEMBERS. THE SECTIONAL FORCE  N  IS THUS COUNTERED BY THE FRICTIONAL RESISTANCE OF THE SURFACES OF THE JOINTED MEMBERS.  

FRICTION JOINT

3.   TENSION JOINT

            ILLUSTRATED SHOW THE CONCEPT OF THE TENSION JOINT, ANOTHER WAY IN WHICH HIGH-STRENGTH BOLT CAN BE APPLIED. THE TENSION JOINT DIFFERS FROM THE PRECEDING TWO TYPES IN THAT THE SECTIONAL N  IS TRANSMITTED THROUGH THE BOLTS AS AXIAL STRESS. IF A TENSILE STRESS IS CREATED IN THE BOLT IN ADVANCE, THEN THE JOINED MEMBERS DO NOT SEPARATE UNTUL THAT TENSILE STRESS IS OFFSET BY AXIAL FORCE N . THIS MAKES IT POSSIBLE TO DESIGN JOINTS HAVING HIGH RIGIDITY.

TENSION JOINT

JOINING BY WELDING

BASIC POINTS ABOUT WELDING

BRAZING (HARD SOLDERING) IS A JOINING METHOD SIMILLAR TO WELDING. IN BOTH METHODS, AN EASILY MELTABLE METAL, SOLDER OR WELDING ROD, IS FILLED BETWEEN TWO METAL MEMBERS AND ALLOWED TO HARDEN, JOINING THE MEMBERS TOGEATHER. THE FUNDAMENTAL DIFFERENCE IS THAT IN BRAZING THE JOINED MEMBERS (BASE METAL) THEMSELVES ARE NOT MELTED, WHILE IN WELDING THE BASE METAL AT THE JOINT IS MELTED AND UNITED WITH MOLTEN FILLER METAL.

THESE METHODS ARE CLASSIFIED ITO THREE GROUPS, ACCORDING TO THE TYPE OF WELDING EQUIPMET USED: MANUAL ARCH WELDING, SEMIAUTOMATIC WELDING AND AUTOMATIC WELDING.

MANUAL ARC WELDING

A COVERED ELECTRODE CONSISTING OF A CORE WIRE COATED WITH FLUX IS USED IN MANUAL ARC WELDING. THE FLUX COATING MELTS UNDER THE HEAT OF THE ARC AND PRODUCES A SIELDING GAS THAT PROTECTS THE MOLTEN METAL AND IMPROVES IT WELDABILITY. IN MOST CASES, IT IS NECESSARY TO CHANGE WELDING ROD DURING THE WELDING OPERATION. THIS METHOD IS WIDELY USED FOR WELDING OF INTRICATE PORTIONS.

SEMIAUTOMATIC WELDING

THIS METHOD INVOLVES THE USE OF A MACHINE EQUIPPED WITH AN AUTOMATIC DEVICE FOR FEEDING CORE WIRE IN COIL FORM TO THE WELDING TORCH, ELIMINATING THE NEED TO CHANGE WELDING RODS MANUALLY. THE TORCH  ITSELF CAN BE MOVED AND OPERATED MANUALLY. SEMIAUTOMATIC WELDING METHODS ARE DIVIVED BROADLY INTO CO2, GAS ARC WELDING, WHICH USES CARBON DIOXIDE GAS AS A SHIELDING GAS, AND NON-GAS ARC WELDING, IN WHICH THE SHIELDING GAS IS GENERATED BY FLUX ON THE CORE WIRE.

AUTOMATIC WELDING

AUTOMATIC WELDING USUALLY MEANS SUBMERGED ARC WELDING. A COMPOUND SIMILAR IN COMPOSITION TO THE FLUX IS APPLIED TO THE AREA IN ADVANCE, AND THE CORE WIRE IS SUBMERGED IN THIS COMPOUND DURING WELDING. THIS IS GENERALLY CALLED UNION WELDING. AUTOMATIC WELDING FEATURES HIGH PRODUCTIVITI AND IS SUITABLE FOR WELDING THICK PLATES. IT IS WIDELY USED IN FACTORY WELDING OF LONG PIECES SUCH AS PLATE GIRDER AND COLUMN MEMBERS. 

FILLET WELD

THE TYPES OF WELDING JOINTS MOST COMMONLY USED IN STEEL-FRAME BUILDINGS ARE FILLET WELDS AND BUTT WELDS. EXAMPLES OF FILLET WELD ARE SHOWN BELOW. 

                                              EXAMPLES OF FILLET WELDS

BUTT WELDS

WHEN PLATES ARE TO BE BUTT WELDED, EDGE PREPARATION CALL GROOVING IS FIRST CARRIED OUT ON THE END FACES OF THE PLATES, THE RESULT CAN BE SEEN IN DIAGRAM BELOW. EDGE PREPARATION ENSURES FULL PENETRATION OF THE MOLTEN METAL THROUGH THE CROSS SECTION DURING WELDING.  

                                             EXAMPLES OF BUTT WELDS

TYPES OF GROOVES

QUALITY CONTROL OF WELDS

DURING WELDING, THERE IS A HIGH POSSIBILITY THAT COMPLEX THERMALEFFECTS WILL CAUSE CHANGES IN STEEL PROPERTIES, RESULTING IN WELDING DEFECTS. IT CANNOT BE OVEREMPHASIZED THAT POOR-QUALITY WELDING PREVENT STEEL MEMBERS FROM EXHIBITING THE EXPECTED YIELD STRENGTH, AND IN SOME CASES THE RESUT MAY BE COLLASE OF THE ENTIRE BUILDING. THEREFOR, INSPECTION OF WELDS IS A VITAL PART OF STEEL-FRAME FABRICATION.

WELD DEFECTS ARE BROADLY DIVIDED INTO THREE KINDS:

1. INSUFFICENT DIMENSIONS (WELD LENGTH TOO SHORT, SIZE TOO SMALL)

2. SURFACE DEFECTS (PITS, SURFACE CRACKS)

3. INTERNAL DEFECTS.

SURFACE DEFECTS AND INSUFFICENT DIMENSIONS CAN BE DETECTED VISUALLY. FOR INTERNAL DEFECTS, ULTRASONIC FLAW DETECTION IS WIDELY USED.

SPACE STRUCTURE

ALL THE FRAMES DESCRIBED SO FAR ARE COMBINATIONS OF SIGLE-PLANE FRAMES, DESIGED BY SEPARATING THE LOADS ACTING ON THE BUILDING INTO THOSE ACTING IN THE RESPECTIVE PLANE OF THESE FRAMES. BUT IT IS ALSO POSSIBLE TO DESIGN A BUILDING FRAME AS A SINGLE, INTERGRAL THREE-DIMENSIONAL SHAPE. THIS IS CALLED A SPACE STRUCTURE, AND SUCH STRUCTURE CAN BE BUILD TO ENCLOSE A HUGE SPACE.

SPACE STRUCTURE ARE CLASSIFIED AS FOLLOWS:

                                          COMPOSITION OF SPACE TRUSS

CORROSION PROTECTION

CORROSION PROTECTION METHODS

CLASSFICATION OF METHODS

            THE METHODS USED TO PROTECT STEEL EMPLOYED IN CONSTRACTION FROM CORROSION ARE LISTED BELOW. AMONG THEM, THE COATING METHOD  (2) A) IS MOST COMMONLY USED.

1.         PRIMARY CORROSION PROTECTION METHODS, GENERALLY EXPENSIVE METHODS IN WHICH ALLOYING ELEMENTS ARE ADDED TO INCREASE THE CORROSION RESISTANCE OF THE PRODUCTS, SUCH AS STAINLESS STEEL AND WEATHERING STEEL.

2.         SECONDARY CORROSION PROTECTION METHODS

  a)  COATING METHODS.

  b)  ELETRICAL METHODS.

COATING METHOD

  IN THIS APPROCH, A COATING IS FORMED ON THE SURFACE OF THE STEEL TO ISOLATE IRON FROM WATER CONTAINING OXYGEN. THE COATING IS FORMED IN FOLLWING WAYS.

•          OILING: TEMPORARY PROTECTION BY NON-DRYING OIL, VASELINE OR OTHER PROTECTIVE OIL.

•           RUST PREVENTIVE PAINT: THE MOST COMMONLY USED METHOD

•           METAL COATING: FORMATION OF A COATING OF METAL, SUCH AS ZINC, TIN OR COPPER, BY PLATING. PLATING IS CLASSIFIED AS HOT-DIP PLATING OR ELECTROPLATING.

•           LINING: RUBBER, PLASTIC OR PORCELIN ENAMEL, WHICH ALSO SERVES AS A SURFACE FINISH.

ELETRIC PROTECTION

            THIS METHOD IS USED WHERE HIGH CORROSION RESISTANCE IS ESSENTIAL OR FOR STRUCTURE SUCH AS A STEEL PILES THAT CANNOT BE REPAIRED. THEREARE TWO TYPES: CATHODIC PROTECTION AND ANODIC PROTECTION.

PAINTING METHODS

PAINTING PROCESS AND METHOD.

1. BRUSH PANTING

            BRUSHING IS THE MOST WIDELY-USED MEANS OF APPLYING PAINT. IT IS SUITABLE FOR SLOW-DRYING PAINTS SUCH AS OIL PAINT AND OIL VARNISH. PAINT ROLLER ARE GENERALLY USED FOR THE PAINTING OF STEEL FRAMES.

2.SPRAYING PAINTING (COLD SPRAY)

            THIS WIDELY USED METHOD IS SUITABLE FOR ALMOST ANY KIND OF PAINT AND PRODUCES A UNIFORM, BEAUTIFULLY FINISHED COATING. COMPRESSED AIR IS USED TO ATOMIZE THE PAINT FOR SPRAYING ON THE SURFACE TO BE COATED. 

3. AIRLESS SPRAY PAINTING

            PRESSURIZED PAINT IS JETTED THROUGH A SPECIAL NOZZLE AND APPLIED AS A MIST, BUT COMPRESSED AIR IS NOT USED. AIRLESS SPRAY DEVICES ARE OF TWO TYPES HOT-SPRAY AND COLD-SPRAY. THE PAINT, PRESSURIZED TO 20 – 50 kg/cm2 (HOT TYPE) OR 80 – 120 kg/cm2 (COLD TYPE) IN A CLOSED CIRCULATING DEVICE. JETS FROM NOZZLE OF A SPECIAL SPRAY GUN RAPIDLY EXPANDING IN VOLUME AND ATOMZING. THERE IS LESS SPLASHING BACK OF PAINT THAN IN ORDINARY SPRAY PAINTING, MAKING THIS PROCESS MORE HYGIENIC AND LESS WASTEFUL OF PAINT.  

FIRE PROTECTION


PURPOSE OF FIRE PROTECTION

DESPITE THE GREAT STRENGTH OF STEEL MATERIALS UNDER ORDINARY CONDITIONS, THEIR YIELD POINT COEFFICIENT OF ELESTICITY ARE GREATLY LOWERED WHEN THEY ARE EXPOSED TO HIGH TEMPERATURES, SUCH AS IN A BUILDING FIRE. TO PREVENT LOSS OF STRENGTH UNDER SUCH CIRCUMSTANCES, STEEL SURFACES MUST BE COVERED WITH HEAT-INSULATING MATERIAL TO AVOID THEIR TEMPERATURE FROM EXCEEDING A SPECIFIED LEVEL DURING A FIRE. THIS IS THE PURPOSE OF FIRE PROTECTION.

FIRE PROTECTION MATERIALS AND APPLICATION METHODS

CONCRETE ENCASEMENT METHOD

STEEL COLUMNS AND BEAMS ARE ENCASED IN LIGHTWEIGHT CONCRETE. 

                                         CONCRETE PLACEMENT FIREPROOFING

METAL LATH METHOD.


A METAL LATH IS FIRST APPLIED TO STEEL MEMBERS, AND LIGHTWEIGHT MORTAR IS APPLIED OVER. 

                                                            METAL LATH FIREPROOFING

PROTECTIVE BOARD INSTALLATION

FIRE-PROTECTION BOARDS SUCH AS ROCKWOOD, ASBESTOS, CALCIUM SILICATE, AND OTHER BOARDS ARE BONDED TO STEEL COLUMNS AND BEAMS. THIS METHOD IS SHOWN BELOW HOW CLAMPS, CLIPS AND NAILS ARE EMPLOYED. 

                                                                      FORMED PLATE BONDING FIREPROOFING

                                                                                                                        

SPRAY METHOD

THERE ARE TWO METHODS, DRY AND WET. THE WET METHOD IS COMMONLY USED. IN THE DRY SPRAY METHOD, A DRY MATERIAL SUCH AS ASBESTOS OR ROCKWOOL AND A LIQUID BONDING AGENT ARE SPRAYED FROM SEPARATE NOZZLES BY MEANS OF COMPRESSED AIR. IN THE WET METHOD, WHICH IS COMMONLY USED, THE FIRE PROTECTIVE MATERIAL AND BONDING AGENT ARE SPRAYED AS A MIXTURE. IN SOME CASES THE STEEL MEMBERS ARE SPRAYED DIRECTLY, AS SHOWN BELOW.

SPRAY FIREPROOFING