Land Launching (Steel Erection)

LAND LAUNCHING The purpose of the method statement is to ensure, where safety critical, work is carried out in a particular sequence with better illustration and description to the erector and worker Where they do exist they are predominantly for high-risk activities for steel erection / beam launching. The land launching works involving total of 8 members of steel girders from Pier 2 to Abutment A. Two 45 tonne crane was used to erect then pre-fabricated segment girders G1 & G2 on the ground. Prior to approve for the launching method statement, the safe working load and launching sequence must be submit for review.

SAFE WORKING LOAD Launching Beam (45 Tons Mobile Crane) CASE 1 (Launching At Abutment A to Pier 2 and Abutment B to Pier 7 ONLY ) Condition With outriggers 7.2m extended 360 deg. Working area operating radius -10m (Please show the 6m working radius on the Layout Plan) Boom Length in meter – 17.4m Lifitng capacity = 12.45 Ton (from load chart) Note : Safety Produre : Reduction of 10% of the capacity due to wind factor / swing effect 12.45 tons x 10% = 1.245 Tons 12.45 – 1.245 = 11.205 tons 11.205 x 2 =22.41 Tons ( For 2 Crane) Therefore Total Lifting Capacity = 22.41 Tons Total Weight for 1st set - Girder G1+G2+Lifting Equipment = 9 +8 +1 = 18tons 2nd set - Girder G2+G3+Lifting Equipment = 8 +9+1 = 18 tons Total Lifting Capacity 22.41 Tons > 18 Tons ---------OK

WORK LAUNCHING SEQUENCE (STAGE 1 ) LAND LAUNCHING

Plan view

Cross section view

Elevation View

Position the crane and the Abutment A and bottom of Pier 1 as per described in the launching sequence diagram.

Road closure underneath the existing bridge with plastic barriers and signboard.

Safety toolbox briefed by the KKB Engineering’s safety officer to the crane operator and erector before start launching works.

Shifting the prefabricated G1 & G2 girders to the side of the headstock ready for launching

Hoisting and alignment the position of girders desired position

Aligned and adjusted the girders by measuring the centerline of girders

CHECKING ON GIRDER’S STABILITY UNDER ERECTION There always be the simplified rules of thumb to assesses the stability of the single girders under erector by the L/b ratio where the, L donates the un-braced length and b is the compression flange width. The rules of thumb for simplified supported girders were as follows; 1. For girders with L/b less than 60 stability would not be major concern during erection 2. For girders with L/b value between 60 and 80, stability is marginal; but further stress calculation need to be verified. 3. For girders with L/b more than 80, temporary support will be required during erection. L/b ratio: Span G1+G2 = (

+

)=(

+

)= 46 +25 = 71

Therefore 60 < L/b < 80 the Stability is marginal to the stability, further stress calculation required. A steel girder remains stable without lateral torsional bulking if

≤

, which

is external normal stress cause by banding under self-weight, is the resistance factor to flexure, is elastic lateral torsional bulking stress =

=

=

= The girders added with temporary stiffness to resist the lateral torsion. Observation for the combination of girders G1 and G2 during the land launching shown that the girders were stable and sign of lateral torsional buckling are unlikely to occur.