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STEEL TRUSS BRIDGE CONTENT : INCLUDE CONTENT: - PART 1: GENERAL LAYOUT DESIGN - PART 2: ABUTMENT CONSTRUCTION - PART 3: PIER CÓNTRUCTION - PART 4: EXECUTING SPANS STRUCTURE IN STEEL BRIDGE CONSTRUCTION PART 1: GENERAL LAYOUT DESIGN 1.The concept of the steel truss bridge  Steel truss bridge is one of the types often used now because of lighter weight and construction of the bridge faster than the reinforced concrete bridge Also, About shape steel truss bridge architecture is quite diverse line with modern urban  This is Forth bridge Forth Bridge in Queensferry, Scotland, was put into use in 1890 and is the bridge "heavyweight" in the world with 54,000 tons of steel, 21,000 tons of concrete, length 2.529m For over a century, the bridge was carrying 200 trains per day Some steel truss bridge in Vietnam - - - - Long Bien Bridge is the first steel bridge across the Red River linking the two districts of Hoan Kiem with Long Bien district, built by the French (1898-1902) Chuong Duong bridge across the Red River, on Highway 1A at km170 + 200, diocese of Hanoi, Hoan Kiem district centers connected with Long Bien District This is the first big bridge was designed and constructed in Vietnam without the technical assistance of foreign engineers Thang Long bridge across the Red River at km6 + 300 positions on Ring Road 3, connecting with Dong Anh Tu Liem district north of Hanoi, capital of Vietnam Bridge construction is considered the century of the Vietnam-Soviet friendship Nguyen Van Troi - are firm RMK American builders constructed, including 14 steel truss spans a total length 513,8m Poni, bridge width 10.5 m, 8.5 m vehicle parts, there is no margin for riders butter 2.Superstructures  The major spans are arranged steel truss with length 140 meters  Two side spans are arranged with length 100 meters  Two approach spans are 72 meters, one approach span is divided two spans, each span is 36m, slope i = 2%  expansion gap expansion joints in the first beams 10mm, 100mm expansion joints  Length of bridge is 484m The material characteristics:     Concrete deck have Compressive strength at 28 days age Compressive strength: 30 MPa = 30 f'c = 000KN / m ^ bulk weight of concrete : Ɣc = 2500 Kg/m^3 = 25 KN/m^3 Asphalt pavement covered with 10cm thick, 0.5cm thick layer of water proofing layer Structural sections below: • Abutments : M0 AND M1 abutments made of reinforced concrete u abutment , pier foundation made of reinforced concrete pile used with a diameter of 1500 mm is poured in place by BT grade 30Mpa • bridge pier : length of the bridge is expected bridge pier T1-T6 which includes two intermediate supports, adjacent pier and guide post pier foundation use pile diameter = 1.5 m with T1, T6 uses pile with a length of 17m, T2, T3, T4, T5 used 12 bored piles with a length of 45m PART 2: ABUTMENT CONSTRUCTION Abutment structure: The structure of U steel-enforced abutment is lighter concrete abutment because the abutment parts have reinforcing steel bearing participation Wing wall, coping thickness of abutment less than 50 cm The inside and outside of abutment wall surface are vertical Abutment construction methods and construction technology: Step 1: The site preparation - Gathering materials and equipment for construction sites Preparation of human resources and other activities serving the construction process Ground leveling to the design elevation by bulldozers combined manually Step 2: Construction of cast-in-situ bored piles A B - - Positioning drill: the machine must be stood on a 20 mm thick sheet and check the balance status of the machine  Put, shift and balance the machine so that the heart of the placements to drill coincide with the heart of boreholes  Equipment positioning drill include: cranes, jacket, chain hoist, theodolite, gradienter and plumb  Check the heart of location by theodolite before drill  Chocking certainly the whole machine to insert drill is not tilted, shifted during drilling Setting the hammer casing by vibration: Pile casing diameter in order to construct cast-in-situ bored piles is 20-30 cm bigger than piles, length from 2-6m Positioning pile casing + Digging the ground to the foot of pile casing is circular, excavation can deep 1.2 - 1.5 m, the center is the heart of drill hole + Adjust pile casing by machine and plumb We prepare vibrator: used hydraulic crane to transfer pumping stations, pipes and vibrators to the construction site The casing test track to be concerned during closed walls, to limit the situation was skewed C - Drilling the pile to the designed height The drill hole by the conveniently circulatory method + Drilling hole is created by circulation method with the speed 26 cycles/ minute + In the process, depending on the kind of geological drill that drills right to choose when to take their head long drill stop drilling when drilling down to the bottom of the first hole and withdraw up to hold the rods in place properly and to turn attention slow speed with 2-4 m / + During drilling encountered large rocks if we must proceed according to the following processing: • Use breakers • Use grab grab onto rocks • Use a drill to drill out the rock Clean the drill hole: + Borehole can be cleaned by the method of reverse circulation by pumps D + Water is pumped into the piles of clean water pump to ensure compensation in the water column above the water boreholes outside static + When a bottom hole drilling and reviewing all bottom hole section, suck out enough water flow and sand inside the stone is no longer satisfactory E Setting the casing: The basic steps for installation and reinforcement cage segments as follows: - - Dredging holes Setting slowly reinforcement cage into the borehole to a determined altitude Check altitude above the steel cage and bottom of the drill hole Anchoring the Reinforcement cages to make sure the concrete works are not washed F Install tramie pipes: We use methods vertical tube Require for material - Cement: cement M300 - Water: Clean water should be no impurities, - Additives: use quick hardening admixture - Transiting concrete:under guaranteed time from the concrete mixing is complete until put into piles should not exceed 30 minutes Concrete Shipping: - Transportation of concrete to ensure tight, not lose grout - The time when mix concrete until decant into the pile no more than 30 minutes The hopper: angles between two kerb are 60-80 degrees to easy to decant concrete, hopper volume is 1m3 Pile concreting work: Pouring the concrete pile by vertical extubation method Step 3: Dig the soil in hole - Digging drainage trench, pit water accumulation Arranging the water pump if necessary - Coordinate machine and handmade Step 4: Install formwork - Construction of the cushion concrete layer with 10cm thick - Pile concrete dam, then bending the pile - Clean the nail holes, erect scaffolding, formwork, reinforcing steel pedestal Requirement: - Transportation, shaft up, lowered gently to avoid collisions, making formwork pushing deformed Day had not been forced to hang strong, ingrained into the formwork - Method formwork assembly must ensure the principles of simplicity and ease of dismantling; remove the front part should not be dependent on the parts to be removed later - When fixed formwork by ligaments and grappling hook, rope and hook must certainly not slip Wires must really stretch to the bearing does not make formwork deformed Step 5: Construction of hole - - Pouring the concrete footings: Request concreting must uniformity and continue, the concreting height must be less than 1.5 meters to the concrete without lose material Time for concreting less than time for precipitate (4h) Equipment beams: Using beams puncher Concrete Maintenance: To ensure the maintenance requirements for the construction of concrete in normal conditions - Concrete Pour combined spit pile casing: Concreting of bentonite vertical tube method… + spit pile casing • Use a vibrator to extubation up slowly • To avoid pulling into the air ducts vertically changing section arranged piles need theodolite to track two during extubation - Check the quality of the pile after landing: at roadworks pile quality is evaluated by the method of ultrasound STEP 3: Dig highway pouring concrete pile - moving the machines out of the position - excavating until we reach the designed height by the excavator and hydraulic erosion STEP 4: Concreting bottom seal - Pour concrete sealing floor: the thickness of concrete layer is m, the intensity 200Pa - After concreting day,we can can drain water, pouring one concrete layer about 10cm to create flat STEP 5: Absorbent and struck the pile - Suction dried after pouring the concrete floor covering struck the concrete pile, handling the pile reinforcement STEP 6: constructing footing pier -Fitting construction formwork, splash resistant, reinforced cylindrical pedestal - On the concrete layer covering the bottom, along the cardiac exact location and horizontal heart, which determine and trace the edges of the foundation blocks - Moving the location cylindrical concrete barge - Proceed pour concrete on cylindrical pedestal STEP 7: constructing body pier - For Achieve concrete cylindrical pedestal intensity, dismantle and conduct cylindrical pedestal reinforced molds, formwork cylindrical body - Conduct concreting cylindrical body with crane or by hose elephants avoid free fall height of the concrete, use vibrator for compacting concrete during pouring - Construction of concrete maintenance done to the intensity allowed STEP 8: Completing the cylinder - Dismantling of scaffolding, formwork - Extraction of positioning spindles - Extraction of steel pile - Pouring the concrete pedestal pillows - Create slope on the crossbar caps PART 4: EXECUTING SPANS STRUCTURE IN STEEL BRIDGE CONSTRUCTION General methods used in executing bridge decks ON-SITE ERECTION + Erecting on temporary piers + Balanced outtrigger erection + Half-outtrigger erection VERTICAL LAUNCHING + Vertical launching by sliding + Vertical launching on floating system HORIZONTAL LAUNCHING + Horizontal launching by sliding + Horizontal launching on floating system Choosing balanced outtrigger erection method to execute steel decks structure: Cantilever method based on anchor spans to erect cantilever gradually to the front Anchor span is started from pier position or mid-span, and then erecting on either side so cantilever erection method called balancing cantilever erection to distinguish from half-cantilever erection method and one side-cantilever erection method When the bridge span has reached the limit of state stability, need add temporary pier to support the cantilever head before erecting the next one Cantilever erection from two sides to mid-span, and then match two parts to each other, this process is called closure Cantilever erection from beginning until the the last arch of bridge overlaps the pier top, it is called erecting without closure - - - - - a Diagram of outtriggers erection without closure (erecting from pier top) Diagram of outtriggers erection without closure (erecting from pier top) b Diagram of balanced outtriggers erection with closure (erecting from midspan) Diagram of balanced outtriggers erection with closure (erecting from midspan) c Diagram of balanced outtriggers erection with closure Diagram of balanced outtriggers erection with closure Group chose: EXECUTING STEEL BRIDGE DECKS STRUCTURE BY USING BALANCED OUTTRIGGER ERECTION METHOD WITH CLOSURE STEP 1: - Erecting the scaffolds to widen piers and temporary piers - Using the crane on flotation system to erect anchor cages on scaffolds - Launching the approach spans by the tripod In where: Scaffolds and temporary piers structure:  Widen pier scaffolds function: - Creating space for on-site anchor spans installation - Ensuring anti-roll stability during balancing cantilever erection  - Widen pier structure is a structure which has two temporary piers erected on two sides of main pier, temporary pier is bearing point of scaffold cage knot Temporary piers are the main bearing pier, scaffolds role is just a working platform in this case Temporary piers structure: Temporary pier foundation: Erecting by using rootball on natural base - Pier body: Erecting by using multipurpose bar in UYKM or MYK form Cape head: On temporary pier top, there are some bats which are adjusted by screws to transmit force to the top of the vertical bar and create space STEP 2: - Assembling the hard-foot crane on the upper chord of anchor bar, erecting cranes on each pier top Assembling the hard-foot crane on the upper chord of anchor bar, erecting cranes on each pier top STEP 3: Erecting balanced outtriggers symmetric with pier top ultil two erecting parts prepare to meet each other Anchor bars erecting procedure : Erecting rule: Lower bars  Upper bars  Bearing rods  Sag rods  Sroos bars Closing quickly the joint of truss, aberration is not allowed STEP 4: Closure in the middle of the bridge STEP 5: Keeping on erecting side spans, each span is located on one side until the last arch of bridge overlaps the pier top STEP 6: Dismounting the hard-foot crane。  Dismounting the pier extension  Pouring concrete slab on bridge floor  Executing the wearing coat  Executing the sildwalk, balcony and sewage system  Completing all the bridge construction, clearing the site after completion, purifying the river bed