Search

The failure mode of concrete columns in subway stations during seismic events can be affected by the dynamic fluctuation of the axial forces. This study conducted quasi-static tests with bidirectional loading on three scaled rectangular columns to investigate the influence of highly variable axial compression ratio (ACR). A detailed analysis was conducted of the impact of the highly variable ACR on the column failure mode, reinforcement strains, and hysteretic behavior, and the repairability assessment was discussed. Numerical analysis of the effect of ACR variations was carried out based on the experimental results. In these experiments, the failure modes of central columns in Dakai Station, Japan, during the Kobe earthquake were reproduced, and three columns exhibited compressive-bending-shear damage and compressive-bending damage. As the ACR varied up to three cycles during one horizontal loading cycle, the hysteresis curve of the columns exhibited notable asymmetry. Furthermore, with a large variation of ACR amplitude, the stirrups of the column were fractured due to excessive shear effects. The bearing capacity, energy dissipation, and stiffness degradation of the columns were significantly adversely affected. A reparability assessment of the columns, based on the distribution of reinforcement strains, residual displacements, and concrete damage, is proposed. The effects of varying frequency and amplitude of different vertical ACRs on the hysteretic behavior of columns were analyzed numerically. [ABSTRACT FROM AUTHOR]

A method to calculate structural functionality for building structures based on structural natural frequency was proposed for seismic loading events. Structural functionality loss and recovery were determined by monitoring the change of structural natural frequency during the earthquake events or repair activities. A shape factor was introduced, structural functionality recovery function (SFRF), to consider the repair strategy and repair speed. As an example, this method was applied to obtain the structural functionality curve and seismic resilience of a half scale two-story reinforced concrete (RC) frame structure. This structure was subjected to a series of ground motions on a shake table and then repaired by carbon fiber cloth a total of four times. The results indicate that the SFRF is able to capture the recovery trend of a structure in the repair process. Meanwhile, a damage index-repair target (DI-RT) curve, representing the 5% difference between the proposed and traditional SFRFs, was used to investigate the impact of structural damage degree and repair target. The areas above the curve indicates that the difference between the proposed and traditional SFRFs cannot be ignored. [ABSTRACT FROM AUTHOR]

The safety of railway vehicles running on bridges needs to be evaluated in the seismic design of bridges. This study examined the spectral intensity calculated from the lateral vibration of the bridge deck during earthquakes, a Japanese code-based index to measure bridge vibration's strength. In addition, the effect of the torsion of the bridge deck on vehicle derailment is investigated using a nonlinear vehicle–track–bridge model. The bridge deck torsion increases the derailment risk, especially for bridges with a low natural frequency. The reason lies in that the lateral and torsional deck motions are highly correlated for bridges with lower frequency. Based on this observation, a code-type formula was proposed to evaluate the vehicle running safety including both lateral and torsional motions of the bridge deck. The accuracy of the proposed formula was demonstrated by comparison with vehicle–track–bridge simulation excited by ground motion records. The new procedure overcomes the non-conservative assessment of derailment caused by ignoring bridge torsion. [ABSTRACT FROM AUTHOR]

Displacement-based seismic design often requires nonlinear time history simulation of building responses which is computationally intensive. This technical note presents an artificial neural network (ANN) designed to generate max inter-story drift for buildings with post-tensioned mass timber (MT) rocking walls systems. This particular lateral system was selected because it is an innovative system with limited physical design parameters, making it an ideal candidate for ANN. The proposed model achieved significantly higher computational efficiency than time history simulation, while maintaining similar level of accuracy. The proposed method could potentially be used for automated design of MT rocking wall lateral systems. [ABSTRACT FROM AUTHOR]

With two producers in operation and over 20 buildings already constructed or in planning process, use of cross-laminated timber (CLT) is gaining popularity in Canada. Since CLT as a structural system is currently not included in the National Building Code of Canada (NBCC), one of the most important issues are the values for the force modification factors for seismic design of CLT structures when NBCC equivalent static force procedure is used. In this study, a test-calibrated numerical model for CLT shear walls was applied to develop the design resistances for typical CLT wall configurations. An estimation of a possible range of [R.sub.d]-factors was obtained by developing design variations for three multi-storey CLT apartment buildings. By specifying the desired seismic performance in terms of inter-storey drift, it is concluded that an Rd-factor of 2.0 will likely provide desirable building performance during the design earthquake level event in Vancouver, B.C. Key words: cross-laminated timber, force modification factors, [R.sub.d]-factor, mid-rise building, seismic design, NBCC. Avec deux producteurs en operation et plus de 20 batiments deja construits ou au stade de planification, l'utilisation des poutres stratifiees croisees (CLT) gagne en popularite au Canada. Puisque les CLT ne sont pas incluses dans le Code national du batiment du Canada (CNBC) en tant que systeme structural, l'une des plus importantes questions est les valeurs des facteurs de modification des forces pour la conception sismique des structures en CLT lorsque la procedure de force statique equivalente du CNBC est utilisee. Dans la presente etude, un modele numerique etalonne par essais pour des murs de contreventement en CLT est utilise pour developper les resistances de calcul pour des configurations typiques de murs en CLT. Une estimation d'une plage potentielle des facteurs Rd a ete obtenue en developpant des variations de calcul pour trois immeubles a appartements de plusieurs etages avec structure en CLT. En specifiant le rendement sismique desire en termes de deplacement inter-etage, nous avons conclu qu'un facteur Rd de 2,0 fournira probablement le rendement desire de l'immeuble durant un seisme de calcul du niveau ressenti a Vancouver, C.-B. [Traduit par la Redaction] Mots-cles: poutre stratifiee croisee, facteurs de modification de force, facteur Rd, immeuble de moyenne hauteur, calcul sismique, CNBC., Introduction Cross-laminated timber (CLT) was first developed some 20 years ago in Austria and Germany. European experience shows that this mass timber panelized system can be competitive not only in [...]

In July 2009, a full-scale midrise light-frame wood apartment building was subjected to a series of earthquakes at the word's largest shake table in Miki, Japan. This article focuses on the test results of that full-scale six-story light-frame wood building. The objectives of the testing program were to (1) demonstrate that the performance-based seismic design procedure developed as part of the NEESWood project worked on the full-scale building, i.e., validate the design philosophy to the extent one test can and (2) gain a better understanding of how midrise light-frame wood buildings respond, in general, to a major earthquake while providing a landmark data set to the seismic engineering research community. The building consisted of l,350 [m.sup.2] (14,000 [ft.sup.2]) of living space and had 23 apartment units; approximately one-half one-bedroom units and one-half two-bedroom units. The building was subjected to three earthquakes ranging from seismic intensities corresponding to the 72-year event to the 2,500-year event for Los Angeles. In this paper, the construction of the NEESWood Capstone Building is explained and the resulting seismic response in terms of base shears, selected wall drifts, global interstory drifts, accelerations, hold-down forces, and roof drifts are presented. Detailed damage inspection was performed following each test and those results are summarized also. The building performed excellently with little damage even following the 2,500-year earthquake. The global drift at roof level was approximately 0.25 m and maximum interstory drifts were approximately 2% for the floor average with individual wall drifts reaching just over 3% in one corner of the building at the fifth story. DOI: 10.1061/(ASCE)ST.1943-541X.0000222 CE Database subject headings: Shake table testing; Seismic tests; Earthquake; Frames; Buildings, multistory. Author keywords: Shake table testing; Seismic tests; Earthquake; Woodframe; Light-frame wood; Midrise building.

In July 2009, a full-scale six-storey platform wood frame apartment building was subjected to a series of earthquakes at the world's largest shake table in Miki, Japan. Two double-midply shear wall stacks were installed in the building from the first storey through to the fifth storey. A continuous anchor tie-down system (ATS) was used to prevent overturning and allow the shear walls to develop their full lateral load capacities. This paper focuses on the behavior of the stacked double-midply shear wall in a full-scale midrise building during a series of triaxial shakes scaled for the city of Los Angeles, California. The stacked midply shear wall achieved a maximum interstorey deformation of 40.4 mm (equivalent to 1.64% drift). The uplift forces measured at the bottom storey of the stacked wall exceeded 760 kN, indicating the need for substantial tie-down systems for this type of wall when utilized in a midrise platform wood frame building. Key words: shake table testing, seismic tests, earthquake, wood frame, light-frame wood, midply wall. En juillet 2009, un immeuble residentiel a charpente en bois a plateforme de six etages a plein echelle a ete soumis a une serie de seismes sur la plus grande table de vibration au monde a Miki, au Japon. Deux empilements de murs de contreventement a doubles contreplaques au centre ont ete installees dans l'immeuble du premier jusqu'au cinquieme etage. Un systeme d'ancrage a fixation continue (<< ATS >>) a ete utilise; pour prevenir le renversement et permettre aux murs de contreventement de developper leur pleine capacite de porter la charge laterale. Le present article porte sur le comportement d'un mur de contreventement empile a doubles contreplaques dans un immeuble de hauteur moyenne a pleine echelle durant une serie de secousses triaxiales mises a l'echelle pour la Ville de Los Angeles, Californie. Le mur empile; de contreventement a doubles contreplaques au centre a atteint une deformation maximale de 40,4 mm entre les etages (equivalent a une derive de 1,64 %). Les forces de soulevement mesureees a l'etage inferieur du mur empile ont depasse 760 kN, indiquant le besoin d'avoir des systemes de fixation importants pour ce type de mur lorsqu'il est utilise; dans un immeuble de hauteur moyenne a charpente de bois a plateforme. Mots-cles: essais sur table de vibration, essais sismiques, seisme, charpente de bois, charpente legere en bois, mur a doubles contreplaques au centre. [Traduit par la Redaction], Introduction Platform wood frame construction has been the dominant type of construction for low-rise residential buildings in North America for many decades. With wood shear walls as the primary lateral [...]

This paper presents a simplified direct displacement design (DDD) procedure which was used to design the shear walls for a six-story woodframe structure. The building was tested in the final phase of a Network for Earthquake Engineering Simulation (NEES) project. Specifically, NEESWood Capstone Building was designed to meet four performance expectations: damage limitation, life safety, far-field collapse prevention (CP), and near-fault CE The performance expectations are defined in terms of combinations of interstory drift limits and prescribed seismic hazard levels associated with predefined nonexceedance probabilities. To verify that design requirements were met, a series of nonlinear time-history analyses (NLTHAs) was performed using suits of both far-field and near-fault ground motion records. The distributions of interstory drifts obtained from the NLTHA confirm that the Capstone Building designed using DDD meets all four target performance expectations, thereby validating the DDD procedure. Additionally, collapse analysis in accordance with the recently proposed Applied Technology Council project 63 (ATC-63) methodology was performed. The results of incremental dynamic analyses confirmed that the Capstone Building designed using the DDD procedure has adequate capacity margin against collapse, as dictated by the ATC-63 methodology. DOI: 10.1061/(ASCE)ST.1943-541X.0000181 CE Database subject headings: Displacement; Wood structures; Structural design; Shear walls; Earthquake engineering; Seismic effects. Author keywords: Displacement-based design; Wood structures; Shear walls; Earthquake engineering; Seismic hazard; Structural engineering; Performance-based design.

The experimental seismic responses of a full-scale two-story light-frame wood townhouse building, designed to modern U.S. engineered seismic design requirements, were compared against the predictions of a new software package entitled seismic analysis package for woodframe structures (SAPWood) developed recently within the NEESWood Project. The main objective of this paper was to verify the accuracy of the predictions from the SAPWood model, which incorporates shear deformations of shear walls as well as cumulative floor displacements caused by the out-of-plane rotations of the floor and ceiling diaphragms. A comparison was conducted on interstory drifts and shear wall deformations for various structural configurations (construction phases) of the test building and excitation levels. Good agreement was found between the numerical predictions and test results for the four different construction phases. The SAPWood model was shown to be a promising numerical tool for predicting the seismic response of light-frame wood structures. DOI: 10.1061/(ASCE)ST.1943-541X.0000086 CE Database subject headings: Seismic analysis; Numerical models; Earthquakes; Frames; Wood structures; Computer software. Author keywords: Seismic analysis; Numerical model; Time history; Earthquakes; Wood structures.