Beam Modification for Prefabricated Slab Houses
Prefabricated slab houses can undergo beam modification. The construction principle involves using beams to replace load-bearing walls, eliminating the obstruction of walls. The beams serve as support points to bear loads, relying on the foundation and structural columns for support. Different craftsmen may employ varying methods for beam modification, with common approaches including hole-drilling grouting and side-form grouting, as detailed below:
Side-form grouting: During formwork installation, one template is installed vertically, while the other is installed at an angle to facilitate grouting. Nowadays, small concrete conveying machines are available, allowing grout to be poured into the assembled formwork through openings made at the edges of the templates. Reinforcing bars and stirrups must be prepared in advance. The ratio for beam construction typically involves creating beam bars that are a fraction (e.g., one-tenth) of the beam's length. Bottom bars are made of 25mm deformed steel bars, along with secondary bars and waist bars. For wall-to-beam modification, stirrups are placed at a rate of 5 to 7 per meter. When binding waist bars, they are not tied in the middle of the beam's stirrups but rather 15 to 20 centimeters away from the bottom bars.
Hole-drilling grouting: First, reinforce the steel bars and supports, then assemble the formwork. Locate the appropriate position on the floor slab and drill holes. If the floor slab is prefabricated, it must be directly lifted away or broken down; drilling holes in prefabricated slabs is not allowed. The method is similar to that used by carpenters on construction sites for formwork installation. Prior to wall removal, provide support for the entire floor slab underneath to prevent it from bearing excessive weight. Pour the mixed concrete directly through the drilled holes. For longer beams, drill multiple holes to avoid voids or exposed reinforcing bars in the poured beam.
Additionally, after the beam is poured, formwork removal and curing are necessary. The side forms can be removed after 24 hours, while the bottom forms and supports require a minimum of half a month in summer and at least 20 days in winter before removal. Daily watering is required for curing. During the beam modification process for prefabricated slab houses, strict adherence to specifications is essential. Ensure proper temporary support is in place to guarantee construction safety. Simultaneously, the quality of materials such as reinforcing bars and concrete, as well as the accuracy of construction techniques, must be ensured to guarantee the structural safety and functionality of the modified beam.
