Stepped Wedge for Post-Tensioning Concrete
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Solution Overview
Problem
Traditional wedges used in post-tensioned concrete systems have limitations, including a single consistent surface at a single wedge angle, which can lead to uneven pressure distribution and potential failure at the smallest portion of the wedge, as well as inefficiencies in cutting and potential safety hazards.
Innovation Solution
The development of a stepped wedge design with two circumferential halves, featuring a first end with a larger outer diameter, a tapering length, a step on the external surface, and a second end with a smaller outer diameter, which allows for a more even pressure distribution and increased load-bearing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional single-profile wedges are used, then the wedge structure is simple, but the pressure distribution is uneven and failure occurs at the smallest portion
Solution Approach 1:
The wedge is divided into multiple segments along its length, with each segment having a different outer diameter and wedge angle. This segmentation allows each portion to bear load more evenly, preventing stress concentration at the smallest portion while maintaining structural integrity.
Solution Approach 2:
Different portions of the wedge are given different geometric properties - specifically, varying outer diameters and wedge angles along the length. This local differentiation optimizes the load-bearing characteristics at each position, with larger diameters and appropriate angles where higher stresses occur.
2Ease of manufacture
If traditional cutting methods (abrasive saw or sharp edge) are used, then the cutting process is simple, but the cable end becomes frayed and dust is produced
Solution Approach 1:
The patent replaces traditional mechanical cutting methods (abrasive saw or sharp edge cutting) with a deformation-based cutting method. The stepped wedge deforms and crushes the cable material through controlled compression, substituting mechanical cutting with mechanical deformation to achieve clean cuts without fraying or dust.
3Productivity
If conventional acetylene torch is used for cutting, then the cutting speed is fast, but fire or explosion danger exists and cable/wedges become heated causing loss of temper
Solution Approach 1:
The patent replaces thermal cutting (acetylene torch) with mechanical deformation cutting using the stepped wedge. This substitution eliminates fire and explosion dangers by removing the open flame, and prevents heat damage to the cable and wedges by avoiding high-temperature heating, while still achieving efficient cutting through controlled mechanical crushing.
Data Source
AI summary
The present disclosure relates to stepped wedges that used with tendon anchors for maintaining tension on tension in post-tensioned concrete. Exemplary wedges include two halves. Each halve has a first end and a second end. The two halves are assembled to form a wedge having an outer diameter on the first end that is greater than the outer diameter of the second end. Internally, the wedge may have a constant inner diameter to retain a tendon. The inner surface of the wedge has a gripping surface. The wedge may have an external step that is circumferential around the wedge and results in a decrease from the outer diameter between the first and second ends.