Grand Housing Development Program Volume III - Gtz

BUILDING PARTS4 U-shaped HCBs joined together as alintel with reinforcementSection of HCB with typical placementof reinforcementThe pre-cast beam (bottom) and thereinforcement itself (above)Detail of the reinforcementLintels and Ringbeamsmade out of U-shapedHCBsAfter the wall is properly erectedthe U-shaped HCB’s are placedin at the height of the ringbeam;the reinforcement bars and theconcrete will be placed within theU-shape HCB according to thestructural design.Lintels will be prefabricated on aflat ground area in the same wayas the ringbeams.Precast BeamsIn the pre-cast beam production,the reinforcement has to beproperly bent. Especially for thestirrups, the diameter for bendinghas to be 4 times greater than thediameter of the stirrup itself.The stirrups must be welded at thetop with the main reinforcement.The pre-cast beam is then castby using a mould and a vibrationtable so that the concrete is wellcompacted. The beam production(CONTINUED)This technique avoids extra materialfor formwork.The use of wooden formwork hasnegative effects on the environment.Moreover it requires skilledmanpower and time to mantle anddismantle the form work.The concrete used for filling has tomeet or exceed C25.and transport to the place where itis going to be cured can be doneby four people.After having finished the productionof the components, five labourerscan do the proper layingof the pre-cast elements and slabHCB in one day.Considering 40 sqm of slab, thetemperature reinforcement, theelectric and sanitary lines and alsothe formwork around the slab canbe done within 2 days.One can start the construction ofthe walls on the slab three days aftercasting of the concrete.With the usual method one has towait 21 days without dismantlingthe formwork hampering the activitythat could be done above orbelow the slab.FROM TECHNICAL MANUALS VOL I AND II DESIGN BASICS AND DIMENSIONS9Addis AbabaCity Government