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...
Hybrid composite glulam timber reinforced using deformed steel bars and epoxy resin adhesive (RGTSB), was significantly developed in Kagoshima University. In this paper, a beam-to-beam connection for RGTSB and experimental data on the connection are presented. Two 2:3-scaled simply-supported beams under four-point flexural bending in short-term loading, connection elements under short and long-term tension loading were tested. The connection for RGTSB beam performed on bending behaviour such as non-connection RGTSB beam, especially better on ductility.
This paper investigates the risk of disproportionate collapse following extreme loading events. The methodology mimics a sudden removal of a loadbearing wall of a twelve-storey CLT building. The ductility-demand from the dynamic simulation is checked against the ductility supplied by the structural components and their connections. The analyses focus on rotational stiffness (k) of the joints by considering three different sub-structural idealisations according to the required modelling details and the feasibility of model reductions. To resist the imposed dynamic forces, the required k-values may be too large to be practically achieved by means of off-the-shelf brackets and screw connections. Improved structural detailing as well as adequate thickness of structural elements need to be considered in order to reduce the probability of disproportionate collapse.
To improve the seismic performance of mid-rise heavy timber moment-resisting frames, a hybrid timbersteel moment-resisting connection was developed that incorporates specially detailed replaceable steel yielding link elements fastened to timber beams and columns using self-tapping screws (STS). Performance of the connection was verified using four 2/3 scale experimental tests. The connection reached a moment of 142 kN m at the column face while reaching a storey drift angle of 0.05 rad. Two specimens utilizing a dogbone detail in the steel link avoided fracture of the link, while two specimens absent of the dogbone detail underwent brittle failure at 0.05 rad drift. All four test specimens met the acceptance criteria in the AISC 341-10 provisions for steel moment frames. The STS connections exhibited high strength and stiffness, and all timber members and self-tapping screw connections remained elastic. The results of the experimental program indicated that this hybrid connection is capable of achieving a ductility factor similar to that of a steel-only moment-resisting connection. This research suggests that the use of high ductility factors in the design of timber systems that use the proposed hybrid connection would be appropriate, thus lowering seismic design base shears and increasing structure economy.
We propose the high productivity timber joint system based on combining the medium-sized wood lumber as assembly large cross-section member. In general, the wood frame structures are required high ductility performance. In this study, the surfaces of the member joints are covered with fiber reinforced plastics (FRP) to improve the mechanical properties to achieve high ductility wood joints. It will be construction of outstanding architectural space to earthquake resistance by these wood frame structure. The purpose of this study is to investigate the seismic performance of joint and to propose the assembling large cross-section timber joint system by high ductility wood frame structure
This paper presents an experimental study on ductility and overstrength of dowelled connections. Connection ductility and overstrength derived from monotonic testing are often used in timber connection design in the context of seismic loading, based on the assumption that these properties are similar under monotonic and cyclic loading. This assumption could possibly lead to non-conservative connection design. Therefore, it is necessary to quantify ductility and overstrength for cyclic loading and contrast them with their monotonic performance. For this purpose, monotonic and quasi-static cyclic experimental tests were performed on dowelled LVL and CLT connections. The experimental results were also compared with strength predictions from state-of-the-art analytical models in literature that were verified for ductile and brittle failure under monotonic loading. This work also allowed investigation into a generally applicable overstrength factor for push-pull loaded dowelled connections.
Second European Conference on Earthquake Engineering and Seismology
August 25-29, 2014, Istanbul, Turkey
Cross-laminated timber (CLT) as a structural system has not been fully introduced in European or North American building codes. One of the most important issues for designers of CLT structures in earthquake prone regions when equivalent static design procedure is used, are the values for the force modification factors (R-factors) for this structural system. Consequently, the objective of this study was to derive suitable ductility-based force modification factors (Rd-factors) for seismic design of CLT buildings for the National Building Code of Canada (NBCC). For that purpose, the six-storey NEESWood Capstone wood-frame building was redesigned as a CLT structure and was used as a reference symmetrical structure for the analyses. The same floor plan was used to develop models for ten and fifteen storey buildings. Non-linear analytical models of the buildings designed with different Rd-factors were developed using the SAPWood computer program. CLT walls were modelled using the output from mechanics models developed in Matlab that were verified against CLT wall tests conducted at FPInnovations. Two design methodologies for determining the CLT wall design resistance (to include and exclude the influence of the hold-downs), were used. To study the effects of fastener behaviour on the R-factors, three different fasteners (16d nails, 4x70mm and 5x90mm screws) used to connect the CLT walls, were used in the analyses. Each of the 3-D building models was subjected to a series of 22 bi-axial input earthquake motions suggested in the FEMA P-695 procedure. Based on the results, the fragility curves were developed for the analysed buildings. Results showed that an Rd-factor of 2.0 is appropriate conservative estimate for the symmetrical CLT buildings studied, for the chosen level of seismic performance.