HANOI UNIVERSITY OF CIVIL ENGINEERING -
HANOI UNIVERSITY OF CIVIL ENGINEERING -🙞🙜🕮🙞🙜 - MINI – PROJECT CONSTRUCTION METHOD Lecturer : Lê Hồng Hà Student : Trần Minh Giang Class : 63KTE Student ID : 56663 Hanoi, 2022 Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner Choosing construction equpment 5.1 Tower crane - The crane is used as the vertical transport equipment for massive objects and volumes such as fresh concrete, reinforcement, and formwork to remarkable heights - Rail travelling tower crane is used for this building because of great building height and large concrete volume transportation 5.1.1 Tower crane requirements - The criteria to select tower crane is specified below a Required lifting height (hoisting level) Figure Required lifting height of tower crane Hrequired = Hbuilding + H1 + H2 + H3 + H4 Where: - Hbuilding : building height, Hbuilding = H1 + Ht x + Hm = 4,5 + 4,2 x + 3,8 = 29,3 (m) - H1: the covering scaffolding protrudes from the roof, choose H1 = 2m - H2: safety distance, choose H2 = 1m - H3: Height of structure components or concreting hopper, choose H3 = 1,5m - H4: Height of hanging kit, choose H4 = 1,5m => Hrequired = 29,3 + + + 1,5 + 1,5 = 35,3 (m) b Required lifting capacity The tower crane is installed to carry fresh concrete, formwork and reinforcement to required level Among which, fresh concrete has the largest weight, then the load capacity of crane is computed when the concreting hopper is full of concrete: Qrequired = Vhopper x γconcrete x n + qhopper Where: Vhopper: maximum volume of concreting hopper, Vhopper = 0,8 m3 γconcrete: unit weight of concrete, γconcrete = 2,5 T/m3 n: safety factor, n = 1,2 qhopper: self-weight of concreting hopper, qhopper = 200 kg = 0,2T => Qrequired = 0,8 x 2,5 x 1,2 + 0,2 = 2,6 (T) c Required working radius Figure Required working radius of rail travelling tower crane Where: - 𝑅𝑟𝑎𝑖𝑙 : 𝑅𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 = 𝑅𝑟𝑎𝑖𝑙 + 𝐿𝑠𝑎𝑓𝑒𝑡𝑦 + ∗ 𝐵𝑠𝑐𝑎𝑓𝑓𝑜𝑙𝑑 + 𝐵𝑏𝑢𝑖𝑙𝑑𝑖𝑛𝑔 the distance between the slewing axis of crane to the side edge of the counterweight, choose Rrail = 8m - Lsafety : safety distance, choose Lsafety = 1m - Bscaffold : width of scaffold system and clearance, choose Bscaffold = 1,4m - Bbuilding : building width, Bbuilding = (7 + 7,5) x = 29 (m) 𝑅𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 = + + ∗ 1,4 + 29 = 36,8 (𝑚) d Required summary - Required lifting height (hoisting level): Hrequired = 35,3m - Required lifting capacity: Qrequired = 2,6T - Required working radius: Rrequired = 36,8m 5.1.2 Selecting tower crane Based on the manual note of choosing construction machines written by Nguyen Tien Thu, I chose rail travelling tower crane code KB-504 with specifications: - Lifting height: H = 77m > Hrequired = 35,3m - Lifting capacity: Q = 6,2 – 10T > Qrequired = 2,6T - Working radius: R = 40m > Rrequired = 36,8m - Lifting/lowering speed: vlifting = 60 m/min → m/s - Lowering things speed: vdrop = m/min → 0,05 m/s - Trolley speed: vtrolley = 27,5 m/min → 0,458 m/s - Slewing speed: vslewing = 0,6 r/min → 0,01 r/s - Width of rail track: Rrail = 8m 5.1.3 Checking crane productivity per working shift a Crane cycle 𝑛 Where: 𝑇𝑐𝑘 = 𝐸 × ∑ 𝑡𝑖 - E: simultaneous gestures factor, E = 0.8 𝑖=1 - ti: time for gesture number i with speed vi, 𝑡𝑖 = brake, gear shift, etc 𝑆𝑖 𝑣𝑖 + (3 − 4)𝑠 with (3-4)s is time for - t1: time for hanging the hopper on the lifting hook, t1 = 10s - t2: lifting time 𝑡2 = 𝐻𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 35,3 + 4𝑠 = + = 39,3(𝑠) 𝑣𝑙𝑖𝑓𝑡𝑖𝑛𝑔 - t3: slewing time to pouring position 𝑡3 = 0,5 𝑣𝑠𝑙𝑒𝑤𝑖𝑛𝑔 + 4𝑠 = - t4 : time for trolley get to pouring position 𝑡4 = 0,5 + = 54(𝑠) 0,01 𝑅𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 36,8 + 4𝑠 = + = 84,3(𝑠) 𝑣𝑡𝑟𝑜𝑙𝑙𝑒𝑦 0,458 - t5 : time for lowering the hopper to constructing position 𝑡5 = 𝐻𝑠𝑐𝑎𝑓𝑓𝑜𝑙𝑑 + 𝐻𝑠𝑎𝑓𝑒𝑡𝑦 2+1 + 4𝑠 = + = 7(𝑠) 𝑣𝑙𝑜𝑤𝑒𝑟𝑖𝑛𝑔 - t6 : pouring concrete time, t6 = 120s - t7: time for lifting bucket to former position, t7 = t5 = 7s - t8: time for trolley to return former position, t8 = t4 = 84,3s - t9: time for crane jib to return previous position (slewing back) t9 = t3 = 54s - t10: time for taking a new hopper, t10 = t2 = 39,3s → 499,2𝑠 𝑇𝐶𝐾 = 0,8 × (10 + 39,3 + 54 + 84,3 + + 120 + + 84,3 + 54 + 39,3) = b Checking crane productivity per working shift * Productivity of tower crane selected per working shift N = Qmin x nck x ktt x ktg x T (T/shift) Where: - Qmin : lifting capacity at maximum working radius, Qmin = 6,2T - nck: number of cycles in an hour 𝑛𝑐𝑘 = 3600 3600 = = 7,2 𝑇𝑐𝑘 499,2 - ktt: weighting factor, ktt = (0,6-0,8), choose ktt = 0,8 - ktg: factor considering time-used of crane in a shift, ktg = 0,8 - T: time of a working shift, T =8h → Ncrane = 6,2 x 7,2 x 0,8 x 0,8 x = 288,55 (T/shift) *Required productivity of tower crane per working shift This is total weight of materials for the day that need to be transported the most, which is the 31st day The task in the 31st day is: Dismantling column formwork of segment Z4 of floor F.3 Installing formwork of beam and slab of segment Z3 of floor F.3 Installing reinforcement of beam and slab of segment Z2 of floor F.3 Pouring beam and slab of segment Z1 of floor F.3 Dismantling beam and slab formworks of segment Z5 of floor F1 => Required productivity of tower crane in the 31st day: Z4F3 Z3F3 N required =Q column +Q Z3F3 +Qstringer&shore +Q Z2F3 formwork beam &slabformwork beam &slab reinf Z5F1 Z5F1 +Q Z1F3 +Q beam +Qstringer&shore ( T/segment ) beam &slabconcrete &slabformwork Where: - Qconcrete : concrete weight, Qconcrete = Vconcrete x γconcrete - Qreinforcement : reinforcement weight - Qformwork : formwork weight, Qformwork = Vformwork x γwood - Qstringer : stringer weight, Qstringer = Vstringer x γwood - Qshore : shore weight, Qshore = Vshore x γwood - γconcrete : unit weight of concrete, γconcrete = 2,5 T/m3 - γwood : unit weight of wood, γwood = 600 kg/m3 = 0,6 T/m3 Construction method 6.1 Installing and dismantling formwork 6.1.1 Technical requirement for formwork - General requirements for formwork are detailed in issue 3.1 in TCVN 4453:1995 Table 18 Technical requirement for formwork No Requirement Inspection Result Observation by eyes, Size and shape measurement Follow construction design equipment Formwork structure Flatness at connection Close and tightness Observation by eyes Observation by eyes Observation by eyes Follow issue 3.3.3 in TCVN 4453:1995 Allowed difference is 3mm No leaking of cement paste during placing Non-stick coating must be Anti-stick Observation by eyes lubricated on formwork’s surface No rubbish, debris or other Cleaning Observation by eyes dust allowed inside formwork Observation by eyes, Dimension and benchmarked by total slope station or other relevant equipment Allowed differences not exceed the value in table in TCVN 4453:1995 Water the wooden Moisture Observation by eyes formwork before pouring concrete 10 Scaffolding and Observation by eyes, supporting system strongly shake shoring Strength and Observation by eyes, stability compare to design Size, number and position of components must follow the design Size, number and position of components must follow the design 6.1.2 Column formwork *Installation - Firstly, identify column center (ex using the wire…) and the limitation of the height for concrete pouring (painting the column steel…) - Adjust the standby steels of the column and install the column structure - Pouring high strength concrete as the column base at the column-foot mark with its section-dimension similar to that of column and 3÷5cm height - The formwork boards at column sides are nailed to make a box with sides (1 side has large width and sides have smaller width) Afterward, the box is installed in the column location and install with formwork boards of the remain side of the column - Adjust the accuracy of the center of the column formwork and ensure the vertical position of the column formwork Use the braces/struts, foot-props… to fix the column formwork *Removal - Follow the principle: first installed, second removed – first removed, seconded installed - Make sure to avoid formwork being stuck to the column that may cause damaged on concrete surface during removal 6.1.3 Beam and slab formwork *Installation - Identify the location of beam and slab formwork by the geodesic machine of steel meter tape - Install the beam formwork Main beam is installed prior to the supporting beams The sides of the boards are usually left with openings for the supporting beams + The beam’s bottom board (which is protected by the cover board, then if the formwork is deflected, the beam will not be affected) is install first Two top parts of the board are temporarily laid on the frame at the main column or beam Next, insert the props to the middle to support the bottom boards Adjust the bottom board to be correct in height and designed position + Continue by installing beam’s edge board (after installing beam’s reinforcement): after laying the beam’s edge board to its location, adjust the located formwork and use the flying post/prop, brace/strut and foot-hold bar to fix the formwork boards The edge boards must be perpendicular to the bottom ones + Adjust the height and location and bind the props together - Install the joists for slabs and posts/props Adjust the height and location by the geodesic machine and the wedges Installation of slab joists: First, joists are temporarily laid on ledgers to determine the height of joists Afterward, install the posts/props for the joists (using the wedge) - Spread the slab boards/sheeting and edge sheeting - Adjust the height of slab formwork to comply with the design by using wedges at the foot of the slab joists posts/props *Removal - The dismantlement sequence is reversed to the installation sequence - First, lower the slab posts/props and beam by moving the wedges Afterward, strip the sheeting out of the concrete slab Incline the slab boards/sheeting to remove it from the posts/props Because the edge sheeting is covered by concrete, we need to use the crowbar to break the concrete Similar techniques are used for beam’s bottom board 6.2 Reinforcement work - Imported steel will be fabricated to make reinforcement steels of RC structures The steps of fabricating are straightening, measuring, cutting and bending based on design These steps maybe executed by hands or machines Technical requirements for fabrication and installation are illustrated below: 6.2.1 Straightening - For steel roll with Ø ≤ 10mm, we use capstan (whether electrical capstan of hand-control capstan) for straightening It is requested to have a flat floor of 30÷50m length Steel roll will be placed on a support with rotating axle to avoid twisting for the steel bar - For steel roll with Ø > 10mm (11.7 and folded in two), we use worker’s force to adjust the bar to be relatively straight, the use hammer to complete straightening 6.2.2 Rust scraping - Reinforcement steel before fabricating, installation or pouring concrete must be scarped rust - Iron brushes or steel-whittling tools maybe used in rust scraping 6.2.3 Measuring, cutting and bending - Before cutting or bending, steel bar must be measured and marked for the fabricating to be accurate The marker is by white chalk or paint - Steel bar before bending must be studied in term of the allowable extension while bending: + Bending angle 450, the extension is 0.5Ø + Bending angle 900, the extension is 1Ø + Bending angle 1800, the extension is 1.5Ø - When the cutting is executed, we can make a spacer, or take one bar as the standard for cutting the others The standard bar should be used from beginning to end to avoid the accumulated tolerances - May use bending machine and bar bender for bending 6.2.4 Splicing - RC structures are designed to behave monolithically Properly designed splices of individual reinforcing bars are key element in transmitting forces through the structure and creating a load path The architect/engineer provides location, lap length and related information on structural drawings + No joining at the positions where major loading and bending exist + On each section, the joining should not be over 25% of the number of steel bar with smooth/undeformed bars and should not be over 50% of the number of steel bar with deformed bars + The lap length (L) of the reinforcement steel in frames and wire fabric is not shorter than 250mm for steel in tension area, 200mm for steel in compression area and the figures shown below: Table 18 Lap length of reinforcement Lap length Reinforcement steel types In tension area In compression area Beam Others With hook Without hook Smooth/undeformed bars 40Ø 30Ø 20Ø 30Ø Hot rolled steel bars with 40Ø 30Ø 20Ø 20Ø ridges 45Ø 35Ø 20Ø 30Ø Cold rolled 6.3 Concrete placement 6.3.1 Technical requirement for concrete - The principles governing proper placement of concrete are detailed in TCVN 4453:1995, but not limited to some notes as following: + Segregation must be avoided during all operations between the mixer and the point of placement including final consolidation and finishing + The concrete must be thoroughly consolidated, worked solidly around all embedded items, and should fill all angles and corners of the form + Where fresh concrete is placed against or on hardened concrete, a good bond must be developed + Unconfined concrete must not be placed under water + The temperature of fresh concrete must be controlled from the time of mixing through final placement and protected after placement 6.3.2 General procedure for placement Currently, ready-mix concrete is often preferred on site Ready mix concrete is concrete which is manufactured as per required mix ratio in batching plant, and then is transported to construction site on truck mixers As being produced under factory conditions, this type of concrete guarantees the highest possible quality On the other hand, site-mixed concrete is notoriously difficult to control the quality Material storage and mixing conditions are unavoidably far from ideal Even if uniform high quality is maintained at the mixer, it is recently lost during subsequent handling before it reaches the formwork * Placement method - The placement methods of ready-mix concrete play an important role as it affects the strength and durability of concrete structures The time of delivery, quality checks and time of placement affect the ready-mix concrete In normal condition, concrete should be placed within hours since it is mixed at the batching plant Concrete maybe conveyed from a mixer to point of placement by any of a variety of methods and equipment, if properly transported to avoid segregation The most appropriate technique for placing concrete depends on jobsite conditions, especially project size, equipment, and the contractors’ experience In building construction, concrete usually is placed with hand- or power-operated buggies, drop-bottom buckets with a crane, inclined chutes, flexible and rigid pipe by pumping and for underwater placing, tremie chutes (closed flexible tubes) *Consolidation - The purpose of consolidation is to eliminate voids of entrapped air and to ensure intimate complete contact of the concrete with the surfaces of the formworks and the reinforcement Intense vibration, however, may also reduce the volume of desirable entrained air, but this reduction can be compensated by adjustment of the mix proportions Powered internal vibrators are usually used to achieve consolidation For thin slabs, however, high-quality, low-slump concrete can be effectively consolidated, without excess water, by mechanical surface vibrators If concrete is not consolidated well, defects will appear after removing formwork Some precautions necessary to avoid ill effects are: (1) Place concrete in level layers through closely spaced trunks or chutes (2) Do not place concrete full depth at each placing point (3) Do not move concrete laterally with vibrators (4) On any delay between placing of layers, vibrate the concrete thoroughly at the interface (5) If concreting must be suspended between planned horizontal construction joints, level off the layer cast, remove any laitance, excess water and make a straight, level construction joints, if possible, with a small cleat attached to the formwork on the exposed face (6) The depth of each concrete layer should not exceed ¾ times the vibrator head length Time for each consolidation is from 15 to 60s, until the concrete is not slumped anymore, and cement paste shows on surface *Inspection of concrete placement - Concrete should be inspected before, during and after casting Before concrete is placed, it is required to inspect the formwork, rebars and concrete’s performance The formwork must be free of dust, debris and properly coated with bond-breaker oil The reinforcing bars must be in place, properly supported to bear any traffic they will receive during concrete placing Conduit, inserts and other items to be embedded must be in position, fixed against displacement As concrete is cast, the slump of the concrete must be observed and regulated within prescribed limits to ensure specified strength - There should be at least one placing inspector who is also responsible for sampling and making cylinders should test slump, entrained air, temperatures and unit weight Any field adjustment of slump, water and cement added must be controlled The inspector should also ascertain that the approved construction procedure is properly followed - Inspection is complete only when concrete is cast, finished, protected for curing and attains full strength ... 26 398.96 (6)=[(3)+(4)]x2x(5) Floor (1) F.1 F .2 to F.6 F.7 Structural Element (2) D1 b D1 b D1 g D1 g D2 D2 D3 D3 Sb Sb Sg Sg C1 C2 D1 b D1 b D1 g D1 g D2 D2 D3 D3 Sb Sb Sg Sg C1 C2 Dmb Dmb Dmg Dmg D2 ... 11.97 20 . 52 Code Grade worker (4) (5) AF .22 335 3,5/7 AF .22 235 AF .22 275 3,5/7 AF .22 335 3,5/7 AF .22 235 AF .22 275 3,5/7 AF .22 335 3,5/7 AF .22 235 3,5/7 AF .22 335 3,5/7 AF .22 235 3,5/7 Quota (man3 day/m... 324 25 2 324 28 8 26 6 399 380 380 418 418 540 540 4 32 4 32 324 25 2 324 28 8 26 6 399 340 340 418 418 540 540 4 32 4 32 324 25 2 324 28 8 22 8 3 42 (10) 380 380 418 418 540 540 4 32 4 32 324 25 2 324 28 8 26 6