A concrete-filled steel tube (CFT) column system has many advantages compared with ordinary sttel or reinforced concrete system. One of the main advantages is the interaction between steel tube and concrete: occurrence of the local buckling of steel tube is delayed by the restraint of concrete, and the strength of concrete is increased by the confining effect provided from the steel tube. Extensive research work has been done in Japan over the last 15 years, including "New Urban Housing Project" and "US-Japan Cooperative Earthquake Research Program", in addition to the work done by individual universities and industries, which has been presented at the annual meeting of Architectural Institute of Japan (AIJ). This paper introduces the merits, design provisions and recent construction trends of CFT column systems in Japan, and discusses the results of trial designs of CFT theme structures which have been carried out to look for the advantages in the performance and construction cost compared with other constructional system.
The paper presents some experimental data and phenomenon on bracket anchor connections for Cross-Laminated-Timber. The goal of this research is to provide a better understanding of the seismic performance of bracket connections subjected to seismic actions and how to choose and design bracket connections for Cross-Laminated-Timber structures. Test configuration and experimental setups are illustrated in details; cyclic displacement schedules of the connections in two directions are presented considering that CLT wall has horizontal sliding in the plane and uplift at the end in quasi-state tests. Different failure modes and force transmission mechanisms of different connections under the loading protocol were analysed. And important quantities for seismic design such as strength, and stiffness, equivalent yield load, peak load and ductility of the connections are evaluated and compared among different kinds of connections; an excellent connector is revealed in ductility and load capacity by test data analysis. In addition, some suggestions to choose and design bracket anchor connections are given.
The wood engineering community has dedicated a significant amount of effort over the last decades to establish a reliable predictive model for the load-carrying capacity of timber connections under wood failure mechanisms. Test results from various sources (Foschi and Longworth 1975; Johnsson 2003; Quenneville and Mohammad 2000; Stahl et al. 2004; Zarnani and Quenneville 2012a) demonstrate that for multi-fastener connections, failure of wood can be the dominant mode. In existing wood strength prediction models for parallel to grain failure in timber connections using dowel-type fasteners, different methods consider the minimum, maximum or the summation of the tensile and shear capacities of the failed wood block planes. This results in disagreements between the experimental values and the predictions. It is postulated that these methods are not appropriate since the stiffness in the wood blocks adjacent to the tensile and shear planes differs and this leads to uneven load distribution amongst the resisting planes (Johnsson 2004; Zarnani and Quenneville 2012a). The present study focuses on the nailed connections. A closed-form analytical method to determine the load-carrying capacity of wood under parallel-to-grain loading in small dowel-type connections in timber products is thus proposed. The proposed stiffness-based model has already been verified in brittle and mixed failure modes of timber rivet connections (Zarnani and Quenneville 2013b).
An investigation was carried out on CLT panels made from Sitka spruce in order to establish the effect of the thickness of CLT panels on the bending stiffness and strength and the rolling shear. Bending and shear tests on 3-layer and 5-layer panels were performed with loading in the out-of-plane and in-plane directions. ‘Global’ stiffness measurements were found to correlate well with theoretical values. Based on the results, there was a general tendency that both the bending strength and rolling shear decreased with panel thickness. Mean values for rolling shear ranged from 1.0 N/mm2 to 2.0 N/mm2.
Performance-Based Earthquake Engineering (PBEE) has been developed mainly for the region of high seismicity for the last three decades. Though abundant information on PBEE is available throughout the world, the application of this PBEE to the moderate-seismicity regions such as their maximum considered earthquake being less than magnitude 6.5 is not always straightforward because some portion of the PBEE may not be appropriate in these regions due to the environment different from the high-seismicity regions. This paper reviews the state-of-art in PBEE briefly. Then, the seismic hazard in moderate-seismicity regions including Korean Peninsula is introduced with its unique characteristics. With this seismic hazard, representative lowrise RC MRF structures and high-rise RC residential wall structures are evaluated by using PBEE approach. Also, the range of forces and deformations of the representative building structures in Korea is given. Based on these reviews, some ideas for the use of PBEE to improve the state-of-practice in moderate-seismicity regions are proposed.
Cross-Laminated Timber (CLT) structures exhibit satisfactory performance under seismic conditions. This ispossible because of the high strength-to-weight ratio and in-plane stiffness of the CLT panels, and the capacity ofconnections to resist the loads with ductile deformations and limited impairment of strength. This study sum-marises a part of the activities conducted by the Working Group 2 of COST Action FP1402, by presenting an in-depth review of the research works that have analysed the seismic behaviour of CLT structural systems. Thefirstpart of the paper discusses the outcomes of the testing programmes carried out in the lastfifteen years anddescribes the modelling strategies recommended in the literature. The second part of the paper introduces theq-behaviour factor of CLT structures and provides capacity-based principles for their seismic design.
Cross-laminated timber (CLT) is a relatively new heavy timber construction material (also referred to as massive timber) that originated in central Europe and quickly spread to building applications around the world over the past two decades. Using dimension lumber (typically in the range of 1× or 2× sizes) glue laminated with each lamination layer oriented at 90° to the adjacent layer, CLT panels can be manufactured into virtually any size (with one dimension limited by the width of the press), precut and pregrooved into desirable shapes, and then shipped to the construction site for quick installation. Panelized CLT buildings are robust in resisting gravity load (compared to light-frame wood buildings) because CLT walls are effectively like solid wood pieces in load bearing. The design of CLT for gravity is relatively straightforward for residential and light commercial applications where there are plenty of wall lines in the floor plan. However, the behavior of panelized CLT systems under lateral load is not well understood especially when there is high seismic demand. Compared to light-frame wood shear walls, it is relatively difficult for panelized CLT shear walls to achieve similar levels of lateral deflection without paying special attention to design details, i.e., connections. A design lacking ductility or energy dissipating mechanism will result in high acceleration amplifications and excessive global overturning demands for multistory buildings, and even more so for tall wood buildings. Although a number of studies have been conducted on CLT shear walls and building assemblies since the 1990s, the wood design community’s understanding of the seismic behavior of panelized CLT systems is still in the learning phase, hence the impetus for this article and the tall CLT building workshop, which will be introduced herein. For example, there has been a recent trend in engineering to improve resiliency, which seeks to design a building system such that it can be restored to normal functionality sooner after an earthquake than previously possible, i.e., it is a resilient system. While various resilient lateral system concepts have been explored for concrete and steel construction, this concept has not yet been realized for multistory CLT systems. This forum article presents a review of past research developments on CLT as a lateral force-resisting system, the current trend toward design and construction of tall buildings with CLT worldwide, and attempts to summarize the societal needs and challenges in developing resilient CLT construction in regions of high seismicity in the United States.
The material presented in this paper refers to a part of the investigation on cross-laminated (XLam) wall panel systems subjected to seismic excitation, carried out within the bilateral project realized by the Institute of Earthquake Engineering and Engineering Seismology (IZIIS) and the Faculty of Civil and Geodetic Engineering at the University of Ljubljana (UL FCGE). The full program of the research consista of basic tests of small XLam wooden blocks and quasi-static tests of anchors, then quasi-static tests of full-scale wall panels with given anchors, shaking-table tests of two types of XLam systems including ambient-vibration tests, and finally analytical research for the definition of the computational model for the analysis of these structural systems. In this paper, the full-scale shaking-table tests for one XLam system type (i.e. specimen 1 consisting of two single-unit massive wooden XLam panels) that have been performed in the IZIIS laboratory are discussed. The principal objectives of the shaking-table tests have been to get an insight into the behavior of the investigated XLam panel systems under seismic excitations, develop a physical and practical computational model for simutalion of the dynamic response based on the tests, and finally correlate the results with those from the previously performed quasi-static tests on the same wooden panel types. The obtained experimental results have been verified using a proposed computational model that included new contitutive relationships for anchors and contact zones between panels and foundations. Because a reasonable agreement between the numerical and experimental results has been achieved, the proposed computational model is expected to provide a solid basis for future research on the practical design of these relatively new materials and systems.
In this paper, the behaviour of cross-lam (CLT) wall systems under cyclic loads is examined. Experimental investigations of single walls and adjacent wall panels (coupled walls) in terms of cyclic behaviour under lateral loading carried out ìn Italy at IVALSA Trees and Timber Institute and in Canada at FPInnovations are presented. Different classifications of the global behaviour of CLT wall systems are introduced. Typical failure mechanisms are discussed and provisions for a proper CLT wall seismic design are given. The influences of different types of global behaviour on mechanical properties and energy dissipation of the CLT wall systems are critically discussed. The outcomes of this experimental study provides better understanding of the seismic behaviour and energy dissipation capacities of CLT wall systems.