Timber provides attractive earthquake performance characteristics for regions of high seismic risk, particularly its high strength-to-weight ratio; however, current timber structural systems are associated with relatively low design force reduction factors due to their low inherent ductility when compared to high-performance concrete and steel...
Results from a series of blast tests performed in October 2016 on three two-story, single-bay cross-laminated timber (CLT) structures demonstrated the ability of CLT construction to resist airblast loads in a predictable fashion. These tests were performed on structures without superimposed load to limit inertial resistance. Subsequently, a follow-on series of tests was performed to investigate the response of axially-loaded CLT construction. Panels damaged during the preceding test were removed and replaced. Axial load was applied using precast concrete blocks to simulate the loaded condition of a five-story building at the first-floor front panel of the structures. These test structures were exposed to two shots: the first was designed to keep the structures within their respective elastic ranges while the second was designed to push the structures beyond their elastic limits. Reflected pressure and peak deflections were recorded at the front panels of the test structures to document the two-way panel load distribution behavior under a dynamic load event and the clearing of the shock wave. Prior to conducting the blast tests, a small number of tests were performed on a load tree test apparatus to aid in test planning by investigating the post-peak response of individual CLT panels of various lengths to quasi-static out-of-plane and axial loads applied simultaneously. This paper provides an overview of the results obtained from both the quasi-static and blast tests of axially-loaded CLT. Additionally, the paper compares CLT structure, component, and connection response across the suite of data. Conclusions are offered to assist engineers in the design of load bearing CLT construction exposed to airblast loads.
The paper presents the design and detailing, and the experimental quasi-static 2/3 scale tests of two posttensioned wall systems: a single (more traditional) wall system (Figure 2) and a new configuration comprising of a column-wall-column coupled system (Figure 3). The latter allows avoiding displacement incompatibilities issues between the wall and the diaphragm by using the boundary columns as supports.
This paper presents selected results of connector testing and wall testing which were part of a Forest Products Lab-funded project undertaken at Colorado State University in an effort to determine seismic performance factors for cross laminated timber (CLT) shear walls in the United States. Archetype development, which is required as part of the process, is also discussed. Connector tests were performed on generic angle brackets which were tested under shear and uplift and performed as expected with consistent nail withdrawal observed. Quasi-static cyclic tests were conducted on CLT shear walls to systematically investigate the effects of various parameters. Boundary constraints and gravity loading were both found to have a beneficial effect on the wall performance, i.e. higher strength and deformation capacity. Specific gravity also had a significant effect on wall behaviour while CLT thickness was less influential. Higher aspect ratio panels (4:1) demonstrated lower stiffness and substantially larger deformation capacity compared to moderate aspect ratio panels (2:1). However, based on the test results there is likely a lower bound of 2:1 for aspect ratio where it ceases to have any beneficial effect on wall behaviour. This is likely due to the transition from the dominant rocking behaviour to sliding behaviour.
Multi-storey platform cross laminated timber (CLT) structures are becoming progressively desirable for engineers and owners. This is because they offer many significant advantages such as speed of fabrication, ease of construction, and excellent strength to weight ratio. With platform construction, stories are fixed together in a way that...
This paper summarises the experimental and numerical investigation conducted on the main connection of a novel steel-timber hybrid system called FFTT. The component behaviour of the hybrid system was investigated using quasi-static monotonic and reversed cyclic tests. Different steel profiles (wide flange I-sections and hollow rectangular sections) and embedment approaches for the steel profiles (partial and full embedment) were tested. The results demonstrated that when using an appropriate connection layout, the desired strong-column weak-beam failure mechanism was initiated and excessive wood crushing was avoided. A numerical model was developed that reasonably reflected the real component behaviour and can subsequently be used for numerical sensitivity studies and parameter optimization. The research presented herein serves as a precursor for providing design guidance for the FFTT system as an option for tall wood-hybrid buildings in seismic regions.
IASS WORKING GROUPS 12 + 18 International Colloquium 2015
April 10-13, 2015, Tokyo, Japan
This paper summarizes an experimental investigation on several innovative reinforcing techniques for the “Single Large Diameter Dowel Connection”, SLDDC in timber truss structures. Besides lateral reinforcing or prestressing, also steel plates glued on two sides of the glulam specimens were used as reinforcing measure. To study the efficiency of these techniques, 15 full-scale quasi-static tensile tests on glulam members with a SLDDC on either ends of each member were performed. It was found that the reinforcement significantly enhanced the bearing capacity of the SLDDCs. All of the reinforcing techniques showed a satisfactory efficiency, preventing splitting of wood. Moreover, most of the specimens remains showed a remarkable post failure strength.
The structural use of wood in North America is dominated by light wood-frame construction used in low-rise and – more recently – mid-rise residential buildings. Mass timber engineered wood products such as laminatedveneer-lumber and cross-laminated timber (CLT) panels enable to use the material in tall and large wood and woodbased hybrid buildings. The prospect of constructing taller buildings creates challenges, one of them being the increasein lateral forces created by winds and earthquakes, thus requiring stronger hold-down devices. This paper summarises the experimental investigation on the performance a high-capacity hold-down for resisting seismic loads in tall timberbased structural systems. The connection consists of the Holz-Stahl-Komposit-System (HSK)™ glued into CLT with the modification that ductile steel yielding was allowed to occur inside the CLT panel. The strength, stiffness, ductility and failure mechanisms of this connection were evaluated under quasi-static monotonic and reversed cyclic loading. The results demonstrate that the modified hold-down-assembly provides a possible solution for use in tall timber-based structures in high seismic zones
The research presented in this paper examines the performance of a shear connection using self-tapping screws (STS) in 3-ply Cross-Laminated Timber (CLT) panels. CLT panels were connected with STS assemblies at an inclined angle in two directions. The capacity of the STS assemblies was tested for the purpose of designing a CLT roof diaphragm of a large storage facility where a high-performance and low-manufacturing-cost solution was required. A total of eleven full-scale specimens were subjected to quasi-static and reversed-cyclic shear loading. Resulting forcedisplacement and hysteretic curves were used to determine an equivalent energy elastic-plastic curve based on ASTM E2126-11 procedures to estimate assembly yield strength, yield displacement, and ductility ratio. The performance in terms of strength and stiffness was excellent, and the STS provided the required ductility for the system to be used in seismic applications. Static yield strength averaged 80kN/m with an average ductility ratio of 7.7 while cyclic yield strength averaged 68kN/m with an average ductility ratio of 4.1. The data obtained allows engineers to specify low-cost lateral load resisting connection systems for large scale CLT structures.