Abstract
Steel trestle bridges have become an important technical solution for addressing construction challenges in top-down deep foundation pits with limited working space, difficulties in excavation removal and construction material transportation, due to their characteristics of convenient assembly and disassembly, as well as easy recycling and reuse. This paper investigates the design and construction of steel trestle bridges in water-rich sand stratum deep foundation pits using the top-down method, studies the connection form between steel pipe column tops and Bailey beams, and develops a "slope-type" connection end that is welded after the steel pipe columns are excavated, ensuring the installation accuracy of the steel trestle bridge and improving construction efficiency. The construction method and structural form of the pile-column support were optimized, employing a pre-insertion method to reliably connect the steel pipe columns with the anti-uplift pile reinforcement cages before hoisting them to the design elevation at the construction working face, ensuring the verticality of both the anti-uplift piles and steel pipe columns. The Bailey beams of the steel trestle bridge and the supports between steel pipe columns are installed concurrently with excavation, ensuring the overall safety and stability of the steel trestle bridge. Using Midas finite element analysis software, loading numerical simulations were conducted on the main components of the steel trestle bridge and the stability of the steel pipe columns. The results demonstrate that the steel trestle bridge is safe and reliable, meeting construction requirements.
Full Text
Preamble
Research on Key Technologies for the Design and Construction of Steel Trestle Bridges in Top-Down Deep Foundation Pit Engineering
LIU Jiazhen
China Railway 16th Bureau Group Co., Ltd., Beijing 100018, China
Abstract
Steel trestle bridges have emerged as a critical technical solution for addressing construction challenges in top-down deep foundation pits, including limited workspace and difficulties in soil excavation and construction material transportation, owing to their convenient installation, removal, and recyclability. This paper investigates the design and construction of steel trestle bridges for deep foundation pits in water-rich sandy strata using the top-down method. The study focuses on the connection between steel pipe column tops and Bailey beams, leading to the development of a novel "slope-type" connection end that is welded after column excavation. This approach ensures installation precision and significantly improves construction efficiency.
The construction method and structural configuration of pile-column supports were optimized through a pre-insertion technique, wherein steel pipe columns are reliably connected to uplift pile reinforcement cages before being hoisted to design elevation at the working face, thereby guaranteeing the verticality of both elements. The Bailey beams and inter-column supports are installed progressively during excavation, ensuring the overall safety and stability of the steel trestle bridge system. Numerical loading simulations of the main structural components and steel pipe column stability were performed using Midas finite element analysis software. The results demonstrate that the steel trestle bridge is safe, reliable, and fully meets construction requirements.
Keywords: top-down construction; deep foundation pit; steel trestle bridge; Bailey beam