Structural Health Monitoring and Post-Occupancy Performance of Mass Timber Buildings

Project Lead: Mariapaola Riggio

 A key question about new generation taller wood buildings is how they will perform over time in terms of durability and livability. This project will determine how best to measure these qualities by selecting sensors, determining testing and measurement protocols, and implementing testing assemblies in selected CLT buildings in Oregon. Future research will use the knowledge developed through this project to carry out post-occupancy monitoring, generating valuable new insights into building performance.

 

Overview

Mass timber construction is still in its infancy in the U.S. and industry professionals aren’t sure how tall wood buildings perform over time in terms of durability and livability. To date, most research on cross-laminated timber (CLT) performance has focused on quantitative, lab- based measures, which have helped establish standards for manufacturing and construction. However, many questions remain about the behavior of full-scale CLT in mass timber buildings, including performance of the material over time and at different stages - from construction through service life. There is a need for both quantitative monitoring data as well as data about the subjective and qualitative performance of mass timber buildings, including post-occupancy feedback.

To address this gap, TDI researchers measured a wide range of performance indicators of CLT, both within a controlled laboratory setting and within occupied buildings out tted with sensors. The goals were to generate monitoring protocols, acquire benchmark data about the holistic performance of CLT buildings (which will ultimately help de ne performance standards for CLT systems) and to explore how monitoring might reduce market barriers for CLT.

 

Research Details

Three studies were performed:

1.)  The analysis and monitoring of the hygrothermal (movement of heat and moisture through buildings) performance of CLT panels.
This study included both accelerated weathering tests of CLT in a large weather simulation chamber, called a Multi-Chambered Modular Environmental Conditioning Chamber (MC-MEC), at OSU’s Green Building Materials Laboratory, as well as onsite measurement of moisture content in CLT structural panels during construction of

the new Peavy Hall on the OSU campus. The aim of this study was to understand the e ects of moisture absorption and desorption cycles on the overall behavior of CLT components, including durability and mechanical performance.

 

2.) The analysis and monitoring of the vibrational performance of CLT panels and mass timber buildings. This study investigated the dynamic behavior of mass timber buildings with the purpose of providing guidance for seismic and wind performance, including safety and serviceability issues.

 

The post-occupancy analysis of mass timber buildings.

This helped researchers understand how the technical characteristics of mass timber systems a ect the occupants’ comfort. The project also tested several di erent sensing techniques to determine the best tools and installation methods for collecting performance data on CLT components and assemblies.

 

Key Findings:

Monitoring protocols were defined, including best-practices for equipping CLT buildings with sensors to collect meaningful data. This information generated the baseline data needed for the monitoring project of the Oregon State University College of Forestry’s new mass timber building, George W. Peavy Forest Science Center.

Potential vulnerability factors were identified for long-term performance and durability of CLT panels when exposed to weathering cycles. This information will help designers and contractors develop better detailing and protection practices during construction.

The first-ever set of data characterizing the dynamic behavior of U.S. mass timber building was generated based on ambient vibration testing on a newly constructed, four-story mass timber building in Portland, Oregon. While this represents the first set of results from mass timber building in the U.S., additional vibration-related studies of mass timber buildings are needed in the future in order to provide guidelines for code development.

 

Effects of Moisture Content on the Dynamic Properties of a Cross-Laminated Timber (CLT) member (Ignace Mugabo Ph.D Civil Engineering, Ph.D Wood Science, 2019)