Lattice Beam Diagonal Strut Angles for Concrete Punching Shear
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Solution Overview
Problem
Existing lattice beams for point-supported concrete ceilings fail to achieve sufficient reinforcement efficacy and high punching shear increase factors, leading to premature failure and damage in the concrete pressure zone during loading.
Innovation Solution
The lattice beam design features diagonal struts inclined at specific angles, with the strut closest to the support at a steeper angle (70°-85°) and the next strut at a flatter angle (45°-75°), creating an overhang that prevents crack propagation and enhances anchoring, combined with ribbed surfaces and larger lower chords for improved engagement with the concrete.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If diagonal struts are inclined at standard angles (45° or 90°) in existing lattice beam designs, then the structure is simple to manufacture and install, but the reinforcement efficacy is insufficient and punching shear increase factors are limited
Solution Approach 1:
The patent applies local quality by varying the inclination angles of diagonal struts at different locations along the lattice beam. The first diagonal strut is inclined at 45° to the chords, while the second diagonal strut is inclined at a different angle (not 45°), creating locally optimized stress distribution patterns that enhance punching shear resistance without requiring complete redesign of the entire structure.
Solution Approach 2:
The invention changes the geometric parameters of the lattice beam by introducing variable inclination angles for diagonal struts. Specifically, the angle between the second diagonal strut and the chords is deliberately set to be different from 45°, which alters the stress distribution and creates more effective concrete anchoring zones, thereby improving punching shear resistance.
2Reliability
If diagonal struts are configured with equal inclinations in existing designs, then the manufacturing process is simplified, but crack propagation cannot be effectively prevented and the concrete pressure zone becomes severely damaged
Solution Approach 1:
The patent implements local quality by making the inclination angles of different diagonal struts non-uniform. The first diagonal strut maintains a 45° inclination for ease of manufacture, while the second diagonal strut uses a different angle to locally optimize crack propagation resistance in critical regions of the concrete ceiling.
Solution Approach 2:
The invention introduces asymmetry in the lattice beam configuration by using different inclination angles for successive diagonal struts. This asymmetric arrangement disrupts the uniform stress patterns that lead to crack propagation, while maintaining sufficient symmetry for practical manufacturing purposes.
3Strength
If traditional reinforcement systems like double-headed bolts are used, then punching shear resistance is achieved, but the increase factors are higher than lattice beams and the structural efficiency is lower
Solution Approach 1:
The patent achieves superior structural efficiency by optimizing the geometric parameters of the lattice beam, specifically the inclination angles of diagonal struts. This parameter optimization allows the lattice beam to achieve higher punching shear increase factors compared to traditional reinforcement systems, making it more productive and efficient.
Solution Approach 2:
The invention effectively creates a composite action between the lattice beam structure and the concrete ceiling. The variable angle diagonal struts work together with the concrete to form an integrated reinforcement system that outperforms traditional discrete reinforcement elements like double-headed bolts.
Data Source
AI summary
The invention relates to a point-supported element or flat concrete ceiling (BD) that comprises a transverse force and punching reinforcement (B) into which a lattice beam (1) that tapers on a support vertical axis (A) is integrated, wherein the lattice beam comprises lower chords (U) and a continuous upper chord (O) or anchoring elements (10) arranged with open spaces (Z) between one another and at least one serpentine diagonal strut section (D) with upper and lower bent portions (11, 12) between each two successive diagonal struts (S1, S2), said bent portions being secured in securing points (SO, SU). The diagonal struts (S1, S2) are angled in the same manner upwards and in the direction of the support (T). The diagonal strut (S1) nearest to the support is inclined at a steeper angle (α)<90° relative to the lower chords (U), and the preceding diagonal strut (S2) further from the support is inclined at an angle, which is flatter by at least 10°, of 45°≦(α2)<90° such that, of the concrete anchoring zones (VO, VU) formed by the diagonal strut (S1) nearest to the support, the upper concrete anchoring zone (VO) lies closer to the support vertical axis (A) than the lower concrete anchoring zone (VU).