Reinforced Recycled-Aggregate Precast Columns With One-Bar Hinge Confinement
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Solution Overview
Problem
Existing reinforced concrete columns face issues such as low recycling ratio of construction and demolition wastes, inadequate restraint of column-end concrete covers, limited improvement in stirrup restraint capability, and cumbersome construction processes due to multiple binding steps.
Innovation Solution
A reinforced recycled lump/aggregate concrete precast column using high-strength one-bar confinements and recycled materials, including recycled coarse aggregates and excavated soil, with a construction method that simplifies stirrup placement and enhances concrete cover restraint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional recycled aggregate concrete or recycled lump concrete is used, then waste concrete is recycled, but the overall recycling ratio of construction and demolition wastes remains low because excavated soil is not recycled
Solution Approach 1:
The patent applies multi-functionality by creating a recycled lump concrete that simultaneously recycles both waste concrete and excavated soil. The excavated soil serves dual purposes: as a filler material and as a partial replacement for fine aggregate, thereby expanding the recycling scope from just waste concrete to include both types of construction and demolition waste in a single concrete system.
Solution Approach 2:
The patent changes the compositional parameters of the concrete by incorporating excavated soil at controlled proportions (30-70% of fine aggregate volume) and adjusting the mix design to account for the soil's properties. This parameter modification enables the concrete to achieve both high recycling ratio and adequate mechanical performance.
2Strength
If conventional stirrups with yield strength no more than 500 MPa are used, then the construction is simple, but the restraint capability on concrete cover is insufficient and columns are prone to concrete cover shedding under earthquake
Solution Approach 1:
The patent applies local quality by concentrating high-strength one-bar confinements specifically at the column-end plastic hinge regions where concrete cover shedding is most critical. The confinements are strategically positioned at spacing of 50-200mm in these high-stress zones, while using conventional stirrups in less critical regions, thereby providing enhanced restraint capability where needed without unnecessarily complicating the entire column structure.
Solution Approach 2:
The patent uses composite reinforcement by combining high-strength one-bar confinements (made from high-strength steel bars with yield strength ≥500 MPa) with conventional stirrups and longitudinal bars. This composite reinforcement system leverages the superior restraint capability of the high-strength confinements at critical locations while maintaining the overall structural integrity through conventional materials.
3Reliability
If multiple rectangular closed stirrups and tie bars are used in conventional columns, then the column structure is stable, but the construction flow is cumbersome with multiple binding processes required
Solution Approach 1:
The patent applies segmentation by dividing the column into distinct zones: plastic hinge regions requiring high-strength one-bar confinements and other regions using conventional stirrups. This zonal segmentation allows optimized reinforcement in critical areas while simplifying construction in non-critical areas, thereby maintaining structural stability without requiring multiple binding processes throughout the entire column.
Solution Approach 2:
The patent inverts the conventional approach by placing high-strength one-bar confinements on the outside of the column rather than using them internally. This external placement simplifies the construction process as the confinements can be installed after the core concrete is placed, eliminating the need for complex internal binding operations while still providing effective restraint against concrete cover shedding.
Data Source
AI summary
A reinforced recycled block/aggregate concrete precast column and a construction method are provided. The reinforced recycled block/aggregate concrete precast column includes several first one-bar hoops, vertical reinforcement bars, several second one-bar hoops, a flexible hinge area, and recycled block/aggregate concrete; the first one-bar hoops and second one-bar hoops are each provided with an anchor end; the first one-bar hoops and second one-bar hoops are disposed in the flexible hinge area, and only the second one-bar hoops are disposed outside the flexible hinge area; the outer edge of each first one-bar hoop is flush with the outer surface of the reinforced recycled block/aggregate concrete precast column; and the interior of the reinforced recycled block/aggregate concrete precast column is filled with the recycled block/aggregate concrete, thereby greatly increasing the recycling rate of engineering waste, reducing shedding of a concrete protective layer in the flexible hinge area of the column.