DIGITAL CORRUGATED
CONCRETE SHELL

Form Finding and Digital Fabrication Using Knitted Formwork

TIME:

2021

location:

Tongji University, Shanghai, China

INSTRUCTORS:

Prof. Dr. Philippe Block, Prof. Dr. Philip F. Yuan, Dr. Tom Van Mele, Dr. Mariana Popescu

ta:

Prof. Dr. Xiang Wang, Chaoyu Du, Lotte Aldinger, Sam Bouten

TEAMMATE:

Pan Miaozi, Wu Yuheng, Wu Zihao, Yang Haozhuo, Xue Zihan,Wu Dao, Zheng Min, Lee Yang, Wang Xinru

The design and construction of the bridge is divided into three layers, which respectively are steel frame, shell and tread. First, design the 3D printing form, determine the anchor points according to the terrain, then determine the steel frame structure line to generate the tensioning surface, then determine the construction sequence: decompose the steel frame and customize, use UHPC pouring in the cloth test to determine the amount of concrete, design the base and cloth. In the fabric design, first of all, to carry out tensile ability test, make machine weaving drawings to control the robot weaving.

Design Workflow

Research on Fabric Weaving Techniques

Different Weaving Methods : (a) orthogonal weaving; (b) skew weaving; (c) weft knitting; (d) Non-woven weaving

Knitting Control : (a) coil addition; (b) coil reduction; (c) short line weaving

Generation of Curved Shell Structures

Generate handrail profiles from steel frame lines

Form handrail and step surfaces from steel pipes

Folded form enables self-supporting handrail

Bridge Deck Shell Generation

Handrail profiles from steel-frame control lines

Handrail and step surfaces from steel pipes

Folded form for self-supporting handrail

Material and Construction Detail Design

Steel Frame + Tensioned Fabric System

UHPC Shell

Overall Structure

Structural Analysis Diagram

Loading Process & Calculation Results

Initial Geometry → Pre-tension Applied by Cooling → UHPC Self-Weight → Additional Loads + Crowd Load

1.0 Dead Load + 1.0 Full-Span Live Load

1.3 Dead Load + 1.5 Full-Span Live Load

1.0 Dead Load + 1.0 Full-Span Live Load 1

1.3 Dead Load + 1.5 Full-Span Live Load 1

1.0 Dead Load + 1.0 Full-Span Live Load 2

1.3 Dead Load + 1.5 Full-Span Live Load 2

Cable Force and Deformation Analysis in Unhardened UHPC

Before tensioning, the steel frame must be fully fixed, and any deformation is not permitted. During the tensioning stage, the free-edge cables at mid-span remain slack. After the UHPC is cast—while still in its unhardened state—all cables are in tension, with the free-edge cables carrying higher pretension forces than the inner cables.Both the tensioning process and the UHPC casting will cause deformation of the cable net and increase the pretension forces; such deformation will not significantly decrease afterward. To reduce this deformation, a 1 cm layer of fast-setting mortar may be sprayed onto the cable net prior to UHPC casting.The Wen’s method provides only a qualitative simulation of the changes in cable forces and deformations during pretensioning, serving as guidance for construction and fabrication.

Simulating Cable Prestress Application Using the Cooling Method

Casting UHPC, Not Yet Hardened

CONCLUSION：
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1. After the UHPC hardens, the structural system formed with the steel frame provides sufficient load-bearing capacity. Under the considered loads, both deformation and capacity meet service requirements.
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2. Before tensioning the cable net, the steel frame must be fully fixed with supports, allowing no deformation. The supports should only be removed after the UHPC has hardened.

3. At the connections between the UHPC shell and the steel frame, as well as at both ends of the UHPC shell, it is recommended to use double-layer reinforcement of φ8@100. The reinforcement should be welded to the steel frame and anchored into the shell with a length of ≥500 mm.

Support Analysis

Plan Development

Axonometric view

Laser Cutting Exploded Diagram

Section Drawing

Fabric Design, Fabrication, and Installation

3D-to-2D Conversion

Weaving Logic Design

3D-Printed Bridge Deck Design

Shell Generation

Printing Segmentation

Design of the Joint with the Steel Frame

Fabric Tension Tests

To begin, the shape of the tensioning frame is defined, and turnbuckles are installed at the tension points for fixation. The structure is then reinforced according to the tension points on the underside, threading steel cables through the fabric test sample to form an integrated load-bearing system. Additional reinforcement is applied based on the top tension points. Finally, the load-bearing corners of the woven fabric sample are attached to the turnbuckles using fasteners, completing the test setup.