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Since the 1980s, calcium silicate element masonry has been commonly used in Dutch buildings, and vertical continuous joints have been usually located at the corner of perpendicular walls. Since the shear failure of these joints may significantly reduce the seismic performance of the flanged wall and therefore of the entire building, the assumption of rigid connection may be inaccurate, unlike for the traditional interlocking of bricks in running bond textures. In this paper, analytical and numerical approaches to study the failure of vertical joints in the seismic assessment of URM buildings are presented. The first part of the work focuses on two different numerical models to study the nonlinear behaviour of the vertical connection; the related critical numerical issues are then discussed. The second part introduces an analytical method able to estimate the lateral force–displacement curve of a flanged wall, which considers the possible failure of the connection. In particular, the method is derived from the section analysis approach developed for controlled rocking deformable systems. The comparison between the numerical simulations and the analytical method proves the capacity of the latter to provide a quick but sufficiently accurate estimate of the force–displacement curve of a URM U-Shaped wall. [ABSTRACT FROM AUTHOR]

An increasing interest in the development of high-performance seismic resisting systems based on posttensioned, jointed ductile connections has been observed in the last decade. The extensive experimental and numerical studies carried out under the PRESSS program developed efficient alternative solutions for seismic resisting frame or wall systems in precast concrete building construction, typically referred to as jointed ductile connections. Low structural damage and self-centering behavior, leading to negligible residual displacements after an earthquake event, were recognized to be the main features of such systems. Recently, the extension and application of similar technology and seismic design methodologies to bridge piers and systems have been proposed in the literature as a viable and promising alternative to traditional cast-in situ or precast construction. However, a broad acceptance of these solutions in the bridge design and construction industry has yet to be observed. Valid justifications can be found in the lack of official guidelines for design and construction detailing as well as in the general apparent complexity of the design procedure and analytical models presented by the scientific community. In this contribution, confirmations of the unique design flexibility, the ease of construction, and the high seismic performance of jointed ductile hybrid systems, combining recentering and dissipation capabilities, are presented. After a presentation of simple design methodologies and modeling aspects herein adopted to fully control the seismic response of these systems, the experimental results of quasistatic cyclic tests on five 1:3 scaled, bridge pier specimens are reported and discussed. Four alternative hybrid configurations are implemented by varying the ratio between the posttensioning steel and the internal mild steel as well as the initial posttensioning load. Lower levels of damage and negligible residual/permanent deformations are observed in the hybrid solutions when compared to the experimental response of the benchmark specimen, representing a typical monolithic (cast-in situ) ductile solution. In addition, the efficiency of the simple analytical procedure adopted for design and modeling is further validated. DOI: 10.1061/(ASCE)0733-9445(2007) 133:11(1648) CE Database subject headings: Bridges, piers; Post tensioning; Energy; Seismic tests; Mathematical models; Model verification; Connections.

Summary: By utilizing a modified Hu‐Washizu principle, a new mixed variational framework and a corresponding high‐performing four‐node membrane element with drilling degrees of freedom, named as GCMQ element, are proposed. In this work, the generalized conforming concept, which is originally proposed within a displacement‐based formulation, is extended to a mixed formulation. The new element is able to handle higher‐order displacement, strain, and stress distributions. The interpolations are complete up to second order for stress and strain. The enhanced strain field is optimized so that a complete cubic displacement field can be represented. For numerical integration, a five‐point scheme is proposed to minimize computational cost. Compared to other four‐node elements in existing literature, numerical examples show that the proposed element has a better performance regarding predictions of both displacements and internal forces, particularly with coarse meshes. The new element is also free from shear locking and volumetric locking. Due to the nature of the mixed framework, GCMQ can be directly used in elastoplastic applications. [ABSTRACT FROM AUTHOR]

Prestressed-laminated timber (Pres-Lam) design has recently been adopted for multistory timber buildings based on ongoing research at the University of Canterbury, New Zealand. This system combines large timber members with unbonded posttensioning for recentering and ductile connections for energy dissipation. This paper describes the experimental, analytical, and numerical investigation of posttensioned laminated veneer lumber (LVL) walls coupled with plywood sheets subjected to both quasi-static cyclic and pseudodynamic seismic testing protocols. Different arrangements of nails, used to connect the plywood coupling panels with the posttensioned timber walls, have been tested to compare their energy dissipation characteristics. Simplified numerical macromodels with rotational spring elements have been developed to accurately represent the recentering contribution from the posttensioning and the pinched hysteric contribution of the nailed connections. The testing results provided good seismic performance, characterized by negligible damage of the structural members and very small residual deformations following drift levels of 2-2.5%. The only components significantly damaged, as designed, were the nailed connections between the plywood sheets and the LVL walls. These plywood sheets can be easily and cheaply removed and replaced with new sheets after an earthquake, creating a major reduction in postearthquake downtime. Combining these benefits together, the concept has potential for consideration as a cost-effective, high-performance solution for multistory timber buildings. [ABSTRACT FROM AUTHOR]

This article presents recent research on the seismic resistance of coupled post-tensioned timber walls for use in multi-story buildings. The walls are constructed from laminated veneer lumber (LVL), post-tensioned with unbonded vertical tendons, and coupled together with mild steel U-shaped flexural plates (UFPs) as energy dissipating elements. The timber wall design follows the same principles as used for post-tensioned precast concrete wall systems, using U-shaped plates to obtain a “hybrid” system, where energy is dissipated through yielding of the plates, while the vertical post-tensioning provides the restoring force. In this project, the same principles are applied to timber coupled walls. A series of quasi-static cyclic and pseudo-dynamic tests have been carried out to verify the applicability of the concept and the feasibility of the construction technology in timber buildings. The U-shaped plates showed stable energy dissipation characteristics and, in combination with the post-tensioning, desirable re-centering hysteretic behavior typically referred to as “flag-shape”. Because of the simplicity of these elements and the low cost of implementation, they have good prospects for practical application. [ABSTRACT FROM AUTHOR]

The paper is focusing the attention on the important aspects related not only to the acceptable safety level avoiding catastrophic failures and loss of life, but even to higher performance level requested for some important buildings, like hospital, police station, communication centers. Such buildings need to be designed to remain functional after the earthquake event. The paper, moving from the current philosophy for seismic engineering, aims to recall and underline how the different levels of Performance Based Design of such buildings are still requesting investigation concerning the design and realization of technical devices. It is known that a building is able to respond with a predictable performance level if designed with ductility capacity, developed as response mostly by the structure. An alternative is to modify externally the building to reduce the demand or the response. This can be achieved either isolating the building from the ground, or dissipating the incoming energy. The paper introduce the work done by the authors, mostly developed at the University of Canterbury, by following the second design technique, describing and testing dissipating devices for wood structures. [ABSTRACT FROM AUTHOR]

Haunch retrofit solution (HRS) has been investigated as a viable alternative for retrofitting of beam-column joints of reinforced concrete (RC) frame structures. For connecting the haunch elements to the frame members, partially prestressed rods were used. This solution, however, makes it difficult for implementation in practice due to the requirement of drilling holes through the slab. A more practical solution is to connect the haunch elements using post-installed anchors, resulting in fully fastened HRS (FFHRS). The solution has been tested at the subassembly level, and encouraging results were obtained. To verify the performance of the FFHRS to retrofit the frame structures subjected to real-life seismic loads, shake-table tests were performed on non-seismically detailed two-dimensional (2-D) RC frame structures. This paper presents the results of the experiments with the detailed discussion of the performance of the FFHRS under earthquake ground motions. [ABSTRACT FROM AUTHOR]

This article analyses 1.36 million realistic soil-structure interaction (SSI) scenarios in a systematic fashion to define the correlation between soil, structural, and system parameters and interaction effects on the structural response. In the analyses, a soil-shallow foundation-structure model that satisfies design building code requirements is utilized. It has been identified that soil shear wave velocity, shear wave velocity degradation ratio, structure-to-soil stiffness ratio, and structural aspect ratio combined with the system stiffness are the key parameters whose variation significantly affects variation in structural response. The critical range of variation of these parameters resulting in a detrimental SSI effects is also defined. [ABSTRACT FROM PUBLISHER]

This article highlights soil-structure interaction (SSI) effects on the seismic structural response accounting for uncertainties in the model parameters and input ground motions. A probabilistic Monte Carlo methodology was used to conduct approximately six million dynamic time-history simulations using an established rheological soil-shallow foundation-structure model. Considering the results yields outcomes that contradict prevailing views of the always beneficial role of SSI. In other words, the likelihood of having amplification in structural response due to SSI is large enough that it cannot be readily ignored. This research provides a significant first step towards reliability-based seismic design procedures incorporating foundation flexibility. [ABSTRACT FROM AUTHOR]

A new seismic resisting system for multi-story timber buildings has been recently developed and proposed by the authors based on refinement and adaptation of jointed ductile connections, using post-tensioning technology, originally developed for precast concrete construction. Successful implementation of the concept and confirmation of the high structural and seismic performance of such systems has been obtained through extensive experimental testing on system subassemblies carried out at the University of Canterbury in the past few years. In this contribution, a simplified analytical model for the analysis of the section and overall connections behavior is proposed based on the extension of existing procedures proposed and adopted for the design and analysis of jointed ductile precast concrete walls and frames. Particular focus will thus be given to the specific modifications required when dealing with the peculiarity of post-tensioned connections using orthotropic timber engineered wood materials such as Laminated Veneer Lumber or Glu Laminated systems. The modified procedure, suitable for both analysis and design, is herein verified using the aforementioned extensive experimental test data from quasi-static cyclic tests on wall, column, and beam-column subassemblies. Based on detailed analytical-experimental comparison, looking at both local and global connection behavior, suggestions are given in terms of (a) strain penetration contribution when dealing with internally glued mild steel reinforcement, (b) actual stiffness of the connection when accounting for the bearing effects in the parallel or perpendicular-to-the-grain directions. These considerations are then implemented into the design procedure in order to guarantee control over the re-centering/dissipative system mechanism [ABSTRACT FROM AUTHOR]