With the rapid development of transportation infrastructure construction, the construction scale of bridge engineering continues to expand, and the requirements for construction technology are increasing day by day. As an important component of the bridge superstructure, precast T-girders have construction quality that directly affects the bearing capacity and service life of the entire bridge. This paper introduces the problems existing in the traditional construction technology of precast T-girders.

1. Problems of the Formwork System

In the construction of precast T-girders, the formwork system is critical to guaranteeing the geometric dimensions and surface quality of girders. Steel formwork is mostly adopted in traditional schemes. Although it features high strength and rigidity, the following defects often occur during formwork design and fabrication:First, unreasonable design of formwork joints and poor sealing performance at spliced positions easily cause grout leakage during concrete pouring, resulting in honeycombing and pitting on the girder surface. These defects impair not only the appearance quality but also potentially weaken the structural strength of the girder.Second, insufficient stability of the formwork support structure may lead to formwork displacement or deformation under construction loads or external disturbances, making the geometric dimension deviations of girders exceed specification limits.Third, improper timing of formwork removal: premature stripping takes place when concrete strength is inadequate, which tends to cause surface cracking and corner spalling of girders; delayed stripping slows construction progress and raises construction costs.

2. Problems in Steel Bar Fabrication and Installation

As the primary load-bearing components of precast T-girders, steel bars rely on fabrication precision and installation quality to determine the girder’s bearing capacity. Traditional steel bar processing mainly depends on manual work, which suffers from low efficiency. It is difficult to guarantee the accuracy of cutting length, bending angle and other parameters to meet design requirements. During steel bar installation, the lack of effective positioning devices makes it hard to control the spacing of steel bar skeletons and the thickness of concrete cover. Steel bar offset, insufficient or excessive cover thickness frequently occur. Insufficient cover thickness exposes steel bars to external corrosion and shortens the service life of girders; excessive cover thickness reduces the effective load-bearing section and impairs structural bearing capacity.

3. Problems in Concrete Construction

Concrete construction serves as the core procedure for precast T-girders, and its quality directly determines the strength, durability and overall performance of girders. The main problems in traditional concrete construction are as follows:First, unreasonable mix proportion design. Targeted design is not carried out according to actual project demands and raw material properties, so indicators such as strength, workability and durability fail to satisfy requirements.Second, inadequate control over concrete mixing and transportation. Insufficient or excessive mixing time results in poor concrete homogeneity. Segregation and premature setting tend to happen during transportation and impair pouring quality.Third, imperfect pouring procedures. Improper pouring sequence and inadequate vibration easily generate air voids, cavities and cracks inside girders, damaging structural integrity and bearing capacity.Fourth, delayed or inadequate curing. This slows strength development of concrete and triggers drying shrinkage cracks on surfaces, reducing concrete durability.

4. Problems in Prestressed Tensioning

Prestressed tensioning is a key procedure in precast T-girder construction, and its quality directly affects the crack resistance and bearing capacity of girders. The main drawbacks of traditional prestressed tensioning technology are listed below:First, improper selection of tensioning equipment or infrequent calibration leads to low control accuracy of tension force, with large deviations between actual tension and design values, weakening the prestressing effect of girders.Second, unreasonable tensioning sequence and rate. An improper sequence causes uneven stress distribution and additional internal forces in girders; an excessively fast tensioning rate brings about excessive stress loss of prestressing tendons and reduces the prestressing effect.Third, real-time monitoring and recording of girder deformation are absent during tensioning, so abnormal conditions such as lateral bending and excessive camber of girders cannot be detected in a timely manner.

In conclusion, the traditional construction mode for precast T-girders has numerous quality control deficiencies in four core procedures: formwork system, steel bar fabrication and installation, concrete construction, and prestressed tensioning. Such defects not only ruin the surface appearance of girders but also degrade structural durability and bearing reliability, failing to meet the high-standard construction requirements of current bridge projects. In response to the above pain points, systematic optimization strategies for precast T-girder construction technology will be proposed in the following text.