Closed Stirrup Connecting Rings for Precast Beam Installation
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Solution Overview
Problem
The existing construction methods for prefabricated concrete buildings with composite floor slabs and precast reinforced concrete composite beams face challenges with small rib widths, where open stirrups restrict the placement of beam surface longitudinal rebars, limiting practical applications and requiring poor workmanship adjustments.
Innovation Solution
The use of closed stirrups in rib beams, which connect with rebar cages through extending connecting rings, allowing beam surface longitudinal rebars to be placed outside the stirrups, facilitating easier on-site installation and seismic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If open stirrups with bent ends are used in rib beams, then connection strength with concrete is enhanced, but beam surface longitudinal rebars cannot be properly disposed when rib width is small
Solution Approach 1:
The stirrup is segmented into two functional parts: the main body within the rib beam providing connection strength, and the extended tail portions protruding outward to receive and secure the beam surface longitudinal rebars. This segmentation allows the stirrup to simultaneously achieve strong concrete connection and feasible rebar disposal.
Solution Approach 2:
The stirrup design extends from the two-dimensional plane within the rib beam cross-section into the third dimension by having tail portions protrude outward. This dimensional extension creates space for rebar placement outside the rib beam, solving the spatial conflict caused by small rib width.
2Ease of operation
If rib width of rib beams is increased to accommodate open stirrups, then beam surface longitudinal rebars can be disposed, but structural efficiency is reduced
Solution Approach 1:
The stirrup functionality is segmented between the enclosed portion within the rib beam (providing structural strength) and the extended tail portions (providing rebar disposal space). This allows the rib beam to maintain its optimized small cross-section while the stirrup extends outward to accommodate rebars.
Solution Approach 2:
Instead of increasing the rib beam width (two-dimensional solution), the stirrup extends in the third dimension (outward protrusion) to create rebar disposal space, thereby maintaining the compact rib beam volume while achieving feasible rebar installation.
3Ease of manufacture
If rebar diameters are adjusted to fit open stirrups, then construction feasibility is improved, but design flexibility is limited
Solution Approach 1:
The stirrup design separates the connection function (main body within rib beam) from the rebar disposal function (extended tails). This segmentation allows standard rebar diameters to be used while maintaining construction feasibility, as the extended tails provide adequate space for rebar placement without requiring custom rebar sizes.
4Ease of operation
If exposed parts of open stirrups are pulled apart after construction, then rebar disposal is enabled, but workmanship quality deteriorates
Solution Approach 1:
The stirrup is pre-formed with extended tail portions that protrude outward, creating ready-to-use receptacles for beam surface longitudinal rebars. This preliminary preparation eliminates the need for post-construction manipulation and pulling apart operations, thereby maintaining high workmanship quality while enabling easy rebar disposal.
Data Source
AI summary
A reinforced concrete composite beam structure based on precast concrete beam-slab integrated units include rib beams and rebar cages; stirrups in the rib beams are closed stirrups; upper parts of the closed stirrups in each rib beam are extended from the rib beam and taken as connecting rings; the rebar cages are disposed on upper parts of two connected rib beams; the connecting rings are lapped with beam surface closed stirrups to form the reinforced concrete composite beam structure with the rib beams after casting concrete. Its construction method includes: installing the precast concrete beam-slab integrated units; hoisting the rebar cages on the rib beams to tie two corresponding connecting rings with the corresponding beam surface closed stirrup in a staggered and overlapped manner; and casting concrete to submerge the rebar cages. A form of the closed stirrups is proposed when rib width of the rib beams is small.