The influence of different factors on steel strand prestressed concrete beams: -----Analysis of the influence of tension center and aspect ratio in steel strand prestressed concrete beams

The tension center position and the cross-sectional aspect ratio are key parameters affecting the performance of prestressed concrete beams. Different tension centers and aspect ratios have different effects on the structural performance of concrete beams. 

The two have different effects on structural deformation, stress distribution and construction safety through different mechanisms. The specific performance is as follows:

PC Steel Strand

Ⅰ. Structural Effect of Spect Ratio

1. Overall deformation and prestress transfer

The change of aspect ratio has limited effect on the direct deformation of the beam, but it will change the layout space of the prestressed tendons. When the aspect ratio increases, the torsional stiffness of the beam may be weakened. It is necessary to optimize the prestress distribution by adjusting the tensioning sequence (such as the radial force control of the bottom plate joint of the large-span wide beam) to avoid the risk of concrete cracking.

2. Construction adaptability and durability

A smaller aspect ratio (such as a short T-beam) can improve the durability of the structure and reduce the difficulty of hoisting, but it is necessary to balance the effect of prestressing under the restriction of cross-sectional size; on the contrary, a beam with a large aspect ratio needs to coordinate the tensioning process and cross-sectional parameter design to ensure stability.

Ⅱ. Key Influence of Tensioning Center

1. Deformation control and stress distribution

The adjustment of tensioning center can significantly improve the deformation of beam body. By optimizing the distribution, the additional bending moment caused by prestress eccentricity can be reduced and deflection can be suppressed. The eccentric or symmetrical arrangement of tensioning position will directly lead to stress concentration or uniform transmission of concrete. In particular, attention should be paid to the risk of mid-span bottom plate cracking caused by the radial effect of tensioning force.

2. Construction constraints and safety hazards

Before tensioning, the constraint formwork and brackets must be removed to avoid axial contraction obstruction, resulting in cracks or support deformation. In engineering examples, failure to remove constraints in time has caused accidents such as support rollover, highlighting the importance of construction process control.

Ⅲ. Collaborative Optimization Strategy

1. Parameter refinement matching

Use finite element tools such as ABAQUS to simulate stress and deformation responses under different working conditions, dynamically adapt tensioning position and aspect ratio parameters, and achieve mechanical performance optimization.

2. Intelligent monitoring and construction control

Fiber optic sensing technology is used to monitor the tension stress of steel strands in real time to avoid prestress deviation caused by empirical parameters; for large-span continuous beams, segmented tensioning is required and the order of post-casting strip and formwork removal is strictly followed to reduce the constraint effect.

Conclusion:

The tension center is the core variable for optimizing structural performance, and the aspect ratio needs to be designed in accordance with engineering requirements. The synergy of the two directly affects the mechanical properties and durability of prestressed concrete beams, and comprehensive control needs to be achieved through parameter simulation, construction monitoring and process optimization.