Construction Control of 202m Span Concrete-Filled Steel Tube Tied-Arch Bridge

Overview of the Study

This paper by Pan Shengshan, Huang Cailiang, and Zhang Zhe from Dalian University of Technology addresses the construction control of the Dandong Moon Island Bridge, a 202-meter span concrete-filled steel tube (CFST) tied-arch bridge with a width-to-span ratio of 1/22.44. The bridge features a single-truss X-shaped arch rib configuration with steel tendons tensioned within the deck slab serving as the tie members. Published in the Journal of Wuhan University of Technology (Transportation Science and Engineering) in 2004, Volume 28, Issue 4, pages 522-525, the study analyzes the calculation methods and key construction issues to propose a rational construction plan.

Bridge Configuration and Structural Characteristics

The Dandong Moon Island Bridge represents a distinctive structural form combining CFST arch ribs with a deck-integrated tie system. The narrow bridge width (width-to-span ratio of approximately 1/22.44) presents unique challenges for construction control, including increased sensitivity to lateral loads, torsional effects, and geometric imperfections. The single-truss X-shaped arch rib configuration provides structural efficiency but requires careful control of arch rib alignment and concrete filling sequence during construction.

Structural Parameter	Value	Engineering Significance
Main span	202 m	Long-span, requires staged construction
Width-to-span ratio	1/22.44	Narrow, torsionally sensitive
Arch rib type	Single-truss X-shaped	Efficient, requires precise alignment
Tie system	Deck-integrated steel tendons	Integrated with deck, complex sequence
Arch rib material	CFST	Requires concrete filling control

The CFST arch ribs are fabricated from steel tubes filled with concrete, combining the tensile strength of steel with the compressive strength of concrete. This hybrid approach is particularly advantageous for arch ribs, which are primarily subjected to compressive forces with some tensile components at certain sections. The steel tube provides immediate structural integrity during construction, while the concrete filling enhances the long-term load capacity and durability.

Construction Control Methods

The construction control of this bridge involved several key calculation methods and monitoring techniques. The primary methods included the construction stage analysis using finite element methods, the measurement and adjustment of arch rib elevation and alignment, the monitoring of concrete filling effects on arch geometry, and the control of prestress tendon tensioning within the deck.

Construction Phase	Control Method	Key Monitoring Parameter	Acceptance Criteria
Steel tube fabrication	Dimensional inspection	Diameter, wall thickness, straightness	Per GB/T 8162 or equivalent
Steel tube welding	NDT (UT, MT, PT)	Weld seam integrity	No defects exceeding acceptance level
Arch rib erection	Total station surveying	Arch rib elevation, alignment	Within ±10 mm of design
Concrete filling	Pressure monitoring, level measurement	Fill density, void detection	No voids >50 mm
Prestress tensioning	Force meter, displacement measurement	Tendon force, deck deflection	Within design tolerance
Load testing	Strain, displacement, vibration	Structural response	Meets design criteria

The concrete filling of the arch ribs is a critical construction phase that requires careful control. The filling sequence must be planned to minimize differential settlement and geometric distortion of the arch rib. A typical approach involves filling in segments, starting from the crown and progressing toward the haunches and springings, with each segment monitored for settlement and alignment before proceeding to the next. The use of tremie methods with continuous vibration ensures dense concrete placement and minimizes void formation.

Steel Tube Manufacturing Quality Requirements

For CFST bridge applications, the steel tube manufacturing quality is paramount, as the tubes form the primary structural elements of the arch ribs. The tubes must meet strict dimensional tolerances, including diameter tolerance, wall thickness tolerance, straightness, and ovality limits. The welding quality of the longitudinal seams is critical, as any defect in the seam could propagate under the sustained compressive loads experienced by the arch rib.

Manufacturing Parameter	Typical Specification	Inspection Method	Rejection Criteria
Outer diameter tolerance	±0.5% of nominal	Caliper, laser scanner	Exceeds ±0.5%
Wall thickness tolerance	±10% of nominal	Ultrasonic thickness	Exceeds ±10%
Straightness	≤1 mm/m	Straight edge, laser	Exceeds 1 mm/m
Ovality	≤1% of diameter	Caliper at multiple points	Exceeds 1%
Longitudinal seam	Full penetration	UT, MT, PT	Any indication exceeding acceptance level
Surface condition	Free of cracks, laps	Visual, MT	Any surface discontinuity

The steel grade selection for CFST bridge arch ribs typically involves high-strength structural steels such as Q345, Q390, or Q420 (equivalent to ASTM A572 Grade 50, ASTM A992, or ASTM A709 HPS70W). These grades provide adequate yield strength for the arch rib while maintaining good weldability and ductility. The chemical composition, particularly the carbon equivalent (CE), must be controlled to ensure weldability without excessive preheating or post-weld heat treatment.

Key Construction Issues and Solutions

Several key construction issues were identified and addressed in this project. The first is the control of arch rib geometry during concrete filling, where the weight of the wet concrete can cause additional deflection and alignment deviation. The solution involves staged filling with continuous monitoring and adjustment. The second is the control of prestress tendon tensioning within the deck, which must be sequenced to avoid excessive unbalanced forces on the arch rib. The third is the management of construction loads and temporary supports to ensure the structural integrity of the partially constructed bridge.

Construction Issue	Risk Level	Mitigation Strategy	Verification Method
Arch rib deflection during filling	High	Staged filling, temporary supports	Total station surveying
Prestress unbalanced force	Medium	Sequential tensioning, symmetric loading	Force meter, displacement
Temporary support settlement	Medium	Settlement monitoring, staged loading	Level measurement
Concrete void in arch rib	High	Tremie method, vibration, UT inspection	Ultrasonic testing
Weld defect in arch rib tube	High	100% NDT, repair protocol	UT, MT, PT
Thermal distortion during welding	Medium	Controlled welding sequence, stress relief	Strain gauge, measurement

The integration of steel tendon tensioning within the deck slab as the tie system introduces additional complexity to the construction sequence. The tendons must be tensioned after the arch rib has been erected and concreted, and the tensioning sequence must be carefully controlled to avoid inducing excessive bending moments in the arch rib. The force-displacement relationship of each tendon must be monitored and recorded, with adjustments made to achieve the design prestress levels uniformly across the deck.

Engineering Practice Integration

For steel pipe manufacturers supplying tubes for CFST bridge arch ribs, the construction control requirements translate into specific manufacturing and quality control specifications. The tubes must be produced with tight dimensional tolerances to ensure proper fit during arch rib assembly and to provide consistent confinement to the concrete core. The welding quality must meet the highest standards, with full NDT coverage and documented traceability of welding procedures and operator qualifications.

The construction control approach described in this study emphasizes the importance of measurement-based verification at each construction phase. This philosophy aligns with modern quality management practices such as PDCA (Plan-Do-Check-Act) and FMEA (Failure Mode and Effects Analysis), where each construction step is planned, executed, verified, and adjusted as necessary. For steel pipe suppliers, this means providing not only the physical product but also comprehensive quality documentation, including material certificates, welding procedure qualifications, NDT reports, and dimensional inspection records.

Study Insights and Implications

This study demonstrates the successful application of CFST technology in a long-span tied-arch bridge, highlighting the importance of rigorous construction control and steel tube manufacturing quality. The key insights for engineering practice are that CFST arch ribs require careful control of geometry during concrete filling, the construction sequence must be optimized to minimize unbalanced loads, and the steel tube manufacturing quality directly impacts the structural performance and durability of the bridge. The findings support the continued development of CFST bridge technology, provided that manufacturing standards, construction methods, and quality control protocols are rigorously implemented throughout the project lifecycle.