Welded Reinforcement Mat Rib Spot Welding Fatigue Strength
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Solution Overview
Problem
Welded reinforcing steel mats used in reinforced concrete components under non-predominantly static loads suffer from material fatigue due to structural changes and notch effects, failing to meet DIN 1045-1 fatigue strength requirements, necessitating additional material or high-quality steels and labor-intensive manual connections.
Innovation Solution
A method and machine for producing welded reinforcing steel mats that minimize structural changes by using areas of increased material thickness, such as transverse ribs, for spot welding, allowing the mats to withstand dynamic loads without material addition, using mechanical sensors for precise positioning and energy-controlled welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If welded connections are used in reinforced steel mats for non-predominantly static loads, then productivity and ease of manufacture are improved, but fatigue strength and reliability deteriorate due to structural changes and notch effects during welding
Solution Approach 1:
The patent applies local quality by concentrating the weld material specifically at the rib locations where it is most needed for fatigue resistance, rather than uniformly distributing weld material across the entire bar surface. The ribs act as localized reinforcement zones that provide both structural support and fatigue-resistant welding areas.
Solution Approach 2:
The patent creates a composite structure by combining the base steel bar material with additional weld material at the rib locations. This composite approach allows the welded joint to achieve fatigue strength comparable to or exceeding the base material, resolving the contradiction between welding-induced weaknesses and required reliability.
2Loss of time
If welded reinforcing steel mats are used instead of manual connections, then labor costs and manufacturing time are reduced, but material consumption increases significantly to compensate for reduced fatigue strength
Solution Approach 1:
Instead of adding material uniformly or excessively to compensate for welding weaknesses, the patent applies material locally at the rib positions where it provides maximum fatigue resistance. This localized approach achieves the required reliability without the significant material overconsumption that would result from uniform material addition.
3Ease of manufacture
If welding is performed on standard reinforcing steel bars, then ease of manufacture is improved, but fatigue strength falls below DIN 1045-1 requirements due to notch effects and structural changes
Solution Approach 1:
The patent employs preliminary action by pre-forming ribs on the reinforcing steel bars before the welding process. These ribs are specifically designed to serve as optimal welding locations, preparing the bar surface in advance to receive weld material in a way that maximizes fatigue resistance and minimizes notch effects.
Solution Approach 2:
The patent changes the geometric parameters of the bar surface by adding ribs with specific dimensions and configurations. This parameter change creates localized areas with enhanced material thickness and optimized stress distribution, allowing standard bars to achieve the fatigue strength required by DIN 1045-1 when welded.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The mats produced exhibit fatigue strength above the Wöhler line for DIN 1045-1 at 175 N/mm² and 10⁶ load cycles, eliminating the need for additional material and manual connections, thus overcoming the suitability prejudice for non-static loads.
Implementation Method 1
a welding device (1) which connects the at least one reinforcing steel bar (2) to the support strip (4) in an area of increased material thickness
Implementation Method 2
mechanical sensors for precise positioning
Data Source
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AI summary
The present invention relates to a method and to a machine for producing welded reinforcing steel rod mats for use in the production of DIN-conforming reinforced concrete components having primarily not static loads, and to such a reinforcing steel rod mat, wherein, among other things, a welding device (1), one or more reinforcing steel rods (2), and one or more stay braces (4) in the case of uniaxial reinforcing steel mats, are positioned relative to each other with position control and optionally with position correction of the reinforcing steel rod(s) to be welded together, and a reinforcing steel rod (2) is welded in the area of at least one of the ribs (3) thereof to a stay brace (4), or to another reinforcing steel rod (2) in the area of at least one of the ribs (3') of said rod.