Optimized Green Wall

A Tensioned Laser Cut Plate Structure

Overview

Authors

Photo of Algis Lencus

Algis Lencus

M. Ludvik Consulting Engineering

al@mludvik.com


Keywords


Abstract

A Catmull-Clark algorithm (used in 3D computer graphics for smoothing polygon surfaces) was used to create a unique design for an over 208ft by 30ft green wall mesh attached to the side of The Sheldon Concert Hall in St Louis, Missouri. The resultant mesh is an organic geometry with long, slender members in an array of varying angles, rather than the orthogonal design often found in green walls. The mesh is pretensioned to create structural stiffness and imbues the structure with an ethereal quality. The Catmull-Clark design is not linear, nor is it repeating and this posed a significant challenge as a tension structure – analysis of the design showed that the irregular Catmull-Clark design would have failed under design loads without significant structural optimization. Form-finding and sizing optimization algorithms were developed and used to reshape the mesh and resize members based on tension and stress level. The resulting design sees ½ inch thick laser cut steel plate form a resilient continuous mesh expanse supported by nothing more than its outer perimeter. The plate was cut on a 100ft long laser cutting machine. Laser cut panels measuring approximately 10ft by 30ft are to be welded together on site to form the completed mesh. The project is currently under construction.

Introduction

The Sheldon Concert Hall has served its patrons for over one hundred years. Located in the “Grand Center” theater and art district in St Louis, Missouri, it has evolved in

Members Only

Algorithmic Design - Catmull-Clark

The use of the Catmull-Clark algorithm proved ideal in generating organic-like automatically generated mesh designs. The Catmull-Clark algorithm is a technique used in three-dimensional computer graphics for the subdivision of

Members Only

Structural Engineering - Tensile Structure

M Ludvik Engineering were engaged as the green wall structural engineers. A clear mandate for the design that would present a significant engineering challenge was to have a thin mesh

Members Only

Algorithmic Design - Structural Optimization

A tensile mesh is ordinarily of a relatively simple orthogonal design and would form a net with each member set to a tension great enough to deflect less than a

Members Only

Laser Cut Mesh Design

The nodes that form the intersections of members in a tensioned plate are moment bearing, which results in additional bending stress compared to pinned connections in a cable-and-node design, which

Members Only

Mesh Framework

The perimeter frame is composed of a double channel arrangement with mesh termination anchor plates welded within the cross section. It is galvanized to ensure the relatively inaccessible internal surfaces

Members Only

Welding of Mesh Panels

The 208ft long green wall is composed of 22 full height laser cut panels that are welded together to form a seamless mesh. The panel width was optimized for transport

Members Only

Construction

As at January 2017, all mesh, columns and frames were fabricated, with a number of frame members galvanized. The relatively soft subgrade surrounding the building necessitated the use of compact

Members Only