LA 481 Final Project Documenting the Detail: A Bridge Jeremy Johnson Fall 2017
PROJECT STATEMENT One of the most important tasks of a Landscape Architect is connecting people to outdoor spaces. Landscape Architects commonly use bridges to create connections from place to place that would otherwise be limited by topography and waterways, but in the eyes of a Landscape Architect a bridge is more than an access route. Bridges can be places with character. The materials of the bridge mean something. The way the bridge sits on the site says something. The way the materials connect to one another are purposeful. The smallest details tell a lot of information. Inside Pammel Woods, North of Iowa State’s College of Design, is a bridge that crosses Clear Creek. None of the elements of the bridge, neither in materiality or structural construction, go beyond satisfying the function of a typical bridge. It is a timber decking and GLULAM beam bridge with dimensional lumber for handrails. The biggest issue with this bridge is how it
ignores the site conditions. The major site condition this bridge ignores is the creek it crosses. This bridge sits on a wooden foundation which is poorly suited for a site which floods. The water levels during a flooding event are high enough to have stale water in contact with the beams of the bridge. While the GLULAM beams are water resistant due to their sealant production, the life span of the bridge will be shortened after years of water contact during flooding events. My goal in this project is to design and detail a simple timber beam bridge, similar to the existing bridge, but make construction decisions that will elongate the lifespan of the bridge while showing my knowledge of how the materials connect together. The proposed design focuses on raising the bridge on a concrete foundation to alleviate stress from flooding events.
RESEARCH To begin this project, it was first important to understand the materials that I was working with. The materials that I focused on were GLULAM beams, timber decking, and concrete foundations because I already know enough about concrete ramps and dimensional lumber. GLULAM or Glued Laminated Timber beams are made of “wood laminations bonded with (moisture resistant) adhesives, with the grain approximately parallel in lengthwise.” (Thomas Hodne Architects, Inc) “Pound for pound, a GLULAM board is stronger than steel and PG. 1 has, greater strength