Glued-laminated timber arches are widely used in gymnasiums, bridges, and roof trusses. However, studies on their mechanical behaviours and design methods are still insufficient. This paper investigates the in-plane loading capacity of circular glued-laminated timber arches made of Douglas fir. Experiments were conducted on four timber-arch models with different rise-to-span ratios under concentrated loads at mid-span and quarter-point locations. The structural responses, failure modes, and loading capacity of the timber arch specimens were obtained. The results show that the timber arches presented symmetric and antisymmetric deformation under mid-point and quarter-point loading conditions, respectively. The downward shifting of the neutral axis of the cross section was observed under mid-point loading condition, which contributes to higher loading capacity compared to that under quarter-point loading condition. The loading condition significantly affects the ultimate loads and the strain distribution in the cross section. Based on the design formula in current standards for timber structures, an equivalent beam-column method was introduced to estimate the loading capacity of the laminated timber arches under vertical concentrated loads. The moment amplification factor in the formula was compared and discussed, and the value provided in the National Design Specification for Wood Construction was recommended with acceptable accuracy.
Glued laminated timber Tudor arches have been in wide use in the United States since the 1930s, but detailed knowledge related to seismic design in modern U.S. building codes is lacking. FEMA P-695 (P-695) is a methodology to determine seismic performance factors for a seismic force resisting system. A limited P-695 study for glued laminated timber arch structures highlighted the lack of lateral load testing; therefore, critical modelling information was not available and assumptions based on available research were used. In this study, full-scale lateral load testing of the glued laminated timber arch is used to fill in gaps in test-based information and assess the following characteristics: damping, deformation behaviour, and failure modes.
This paper discusses the determination of the ASCE 7 seismic response modification factor R for three-hinge glulam Tudor arches. In an attempt to meet this objective, a limited application of the methods and procedures outlined in FEMA P-695 were used to assess the performance of a variety of arch designs. Computational models were created using finite elements within OpenSees to accurately depict the behaviour of the arch. When the crown connections were redesigned using load combinations incorporating over-strength, all of the light gravity load designs systems were successfully able to demonstrate a probability of collapse of less than ten percent when subjected to Maximum Considered Earthquake (MCE) level of ground shaking. Systems designed for heavy gravity did not pass; however, a variety of sidestudies on the influence of inelastic behaviour in the base connections, and varied levels of damping indicate that acceptance criteria of FEMA P-695 may be met through refined modeling assumptions based on results of testing.
April 3-5, 2014, Boston, Massachusetts, United States
Summary
The second glued-laminated structure built in the United States was constructed at the USDA Forest Products Laboratory (FPL) in 1934 to demonstrate the performance of wooden arch buildings. After 75 years of use the structure was decommissioned in 2010. Shortly after construction, researchers structurally evaluated the gluedlaminated arch structure for uniform loading on the center arch. This structural system evaluation was added to the existing laboratory work on glued-laminated arches to develop the foundation on which the current glued-laminated arch design criteria is based. After 75 years of service and decommisioning, recovered arches were tested in the laboratory to evaluate the loss of structural performance. Loss of structural performance was evaluated by comparing original and current deformation. Based on a preliminary visual and structural assessment, the degradation of structural performance was minimal in the arches, except for two arch that were affected by the building fire.
