Research On The Construction Technique Of Site-Manufacturing Simpiy-Supported T Beam With Pre-Tensioning Prestressed Durability Concrete On Qinghai-Tibet Railway

In this thesis, the construction technique, safety and quality control method of manufacture are researched for the spot-manufacturing simple-supported T beam with pre-tensioned prestressed durability concrete, under the conditions of serious cold, low pressure, a lack of oxygen, strong radiation and special weather on the Qingzang Plateau.1.Research on the spot location for manufacture. Through field investigating, the manufacture spot for T beam is selected at Dagangou, which covers 530m long, 120m wide, about 63600m2; locates on the right side of Qing-Zang highway GK2796+100-630; 10m away from Qing-Zang highway; 260m away from the new-builded Gangou Station on QING-ZANG railway. The first pre-tensioned T beam was produced on June, 2002. Up to November, 2003, the total production amouts to 412 pieces of T beam.2.Research and design of prestressing bed for T beam. Two prestressing bed are builded for 8nu 16m T beam, and one bed for 12m T beam. The structure and main design items for the beds are emphasized.3.Investigation on the steel bar construction of T beam. Synthesis analysis and research are given to the construction technique and quantity controls of the proceedures for T beam steel bar.4.Emphasized researches are given to the construction of T beam durability concrete. Because of the special weather on of Qingzang Plateau, eight durability concrete indices are firstly proposed for the bridges in jelly soil area of Qingzang Railway. They are anti-jelly melts circulation, anti-permeability, anti-rust for steel bar, crack resistance, anti-Cl- ion permeates, corrosion resistance, anti-alkali-aggregate reaction, anti-wind corrosion. The concrete design, construction technique and quality control measures are summarized for the durability concrete, primarily through the choice of original materials, the tests for selecting the concrete design, the examination of the samples, and the quantity control of construction process.5.Emphasized researches are made to the construction pre-tensioned prestressed T beam. Through construction practice, the following several works should done well to assure the construction quantity of T beam prestress. The oil jack and oil pump should be well maintained. The oil pressure gauge should be periodically inspected. The construction personnel must make operations strictly according to the standards of prestressing. When the oil jack works, the insurance card must be established, and the person for measure must be sent to prevent that the oil jack appears unloading and breaking down suddenly during the beam body maintenance. After releasing pretress, theperiodic inspection should be made for the camber, the deviation between the actual camber and design camber, which are important data for perfecting and adjusting the prestress.6. The control of the concrete construction crack are investigated. The concrete construction cracks are mainly resulted by the original materials and construction technique.7.The construction methodes of the construction of T beam are summarized and developed.