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Bidirectional quasi-static cyclic loading was applied to a subassembly of drywall partition walls integrated with cross-laminated timber rocking walls. Details aimed to reduce seismic damage to the partition walls were investigated, such as slip connections of partition walls to the diaphragm and gap detailing for the wall intersections. Telescoping detailing eliminated damage to the framing at the wall ends compared to traditional slip-track detailing. The distributed gap wall delayed the damage to about 1% inter-story drift. In the corner gap wall, the sacrificial corner bead opened up at low drifts (0.43%), but the wall was damage-free until more than a 2% drift. [ABSTRACT FROM AUTHOR]

Prior studies, which have been limited to horizontal ground shaking, have generally concluded that soil–structure interaction (SSI) has a negligible influence on the seismic response of isolated buildings. In this study, the effect of SSI on the response of a computational model of an isolated building using triple friction pendulum bearings is investigated. The analysis shows that SSI can amplify story drifts and accelerations when the model is subjected to 3-D shaking including a vertical component. Amplification occurs due to a vertical-horizontal coupling effect that is explained using the modal properties of the numerical model. Based on a parametric study using the key parameters of foundation system, it is concluded that amplification occurs when the effective shear wave velocity of the soil falls into a specific range. In this case, the response of the computational model is very sensitive to the hysteretic damping ratio of the soil, Poisson's ratio of the soil and the footing size. [ABSTRACT FROM AUTHOR]

Seismic base isolation systems are mainly used to reduce seismic demands and minimize earthquake effect on structure performance. In this study, the fundamental dynamic response of structures with three-dimensional (3D) isolation systems is explored using a simplified rigid block model. A parametric study is carried out to evaluate the effect of different site conditions, structure properties and 3D isolation parameters on structure and bearing response. The results show that the acceptable range of 3D isolation periods is 0.5–1.0 s for vertical direction with horizontal isolation period around 3–4 times the vertical period and 20% damping in both directions. [ABSTRACT FROM AUTHOR]

This paper evaluates factors that may influence slab vibration and/or induce a horizontal–vertical (H-V) coupled response of buildings with mass irregularities. Responses are investigated through computational simulation of a hypothetical three-story building with base isolation and conventionally configured. Induced mass eccentricities are observed to influence, in an unpredictable way, the vertical slab acceleration and the H-V coupled response, which is identified through modal analysis and floor spectral analysis. The implications of vertical slab vibrations and H-V coupling behavior on the design forces for nonstructural components and systems (NCSs) are evaluated, and modifications are proposed for consideration. [ABSTRACT FROM AUTHOR]

Seismic resilience and continued operation of bridges after earthquakes are important seismic design criteria. A new seismic protection concept for integral bridge piers is explored that uses sliding bearings to separate the superstructure from the piers. The influence of sliding bearings on the seismic response of a representative 3-span integral highway bridge is investigated. With sliding bearings, the pier column shear force was limited to the bearing design friction force. Furthermore, the abutment ductility demands were found to be insensitive to the friction forces in the sliding bearings because the bridge displacement demands were controlled by the equal displacement rule. [ABSTRACT FROM PUBLISHER]

The seismic response of a full-scale, 5-story steel moment frame building in base-isolated and fixed-base configurations with an integrated suspended ceiling-partition wall-sprinkler piping system that was shaken at E-Defense is critically assessed. Horizontal floor accelerations were constrained by the isolation systems to relatively low levels, which allowed observation of damage to the integrated system that was directly related to the vertical component of input acceleration. The floor slabs exhibited single mode vibration at their natural periods with widely varying effective damping. Peak vertical accelerations were amplified by an average factor ranging from 3 to 6 from the table to the middle of the floor slabs, at which amplification factors increased as slab vibration periods lengthened. Damage to the ceiling-partion-piping components initiated at slab accelerations of approximately 2 g and became extensive for slab accelerations exceeding 5 g. These metrics establish target vertical accelerations for achieving desired performance objectives. [ABSTRACT FROM AUTHOR]

This paper focuses on a horizontal-vertical coupling effect observed in a full-scale shake table experiment of a 5-story moment frame building isolated with triple pendulum bearings. A significant increase or amplification of the horizontal floor accelerations was observed during three-dimensional (3D) shaking compared to XY (horizontal only) shaking with comparable input motions. The coupling phenomenon is explained by analytical and numerical simulation of a single degree-of-freedom (rigid mass) structure and multistory cantilever structure subjected to simplified sinusoidal motions, both isolated with triple pendulum bearings. The results of the simplified numerical study are extended to explain the horizontal-vertical coupling in the full-scale experiment, which are also validated by numerical modeling of the test structure. The vertical component of ground acceleration is shown to introduce a high-frequency component into the base shear that can excite higher modes of the base-isolated structure. The phenomenon is possible in anymultistory structure isolated with friction bearings, and should be evaluated on a case-by-case basis. [ABSTRACT FROM AUTHOR]

• Combining a flexible rocking wall system and the flexibility of timber can result in a building with considerable flexibility. • This paper investigates how the partition wall detailing affects the dynamic properties of the structural system. • This paper determines when it is beneficial to consider nonstructural walls in the overall building resistance. • Fixed partition walls contribute significantly to the overall seismic resistance while deformation-compatible ones offer little resistance. The structural-nonstructural interaction effects of nonstructural partition walls and post-tensioned CLT rocking walls in mass-timber buildings were evaluated in a parametric study. Representative 2D rocking wall units in 5-story and 12-story mass-timber archetype buildings were modeled in OpenSees. Moreover, concentrated spring models were developed to represent effective force-deformation for four different variations of partition wall detailing, and applied to the building models to represent wall densities associated with apartment and hospitality occupancies. Eigenvalue, pushover, and response-history analyses were performed on 2D models of the bare structure and those with partition wall variations. Including partition walls with fixed connection details was found to decrease story drifts and rocking wall story shears compared to the bare frame model by up to 50% in a service earthquake and up to 30% in a maximum considered earthquake. However, partition walls with deformation-compatible details were found to have negligible influence (less than 5%) on the response. [ABSTRACT FROM AUTHOR]

SUMMARY Base isolation systems generally perform well under design-level ground motions to reduce both interstory drift and acceleration demands. During a maximum considered earthquake, however, large displacements in the base level may cause pounding between the structure and perimeter moat wall, which can lead to very high acceleration in the superstructure. A phased passive control device, or 'gap damper', has been conceived to control base isolator displacement during extreme events while having no effect on the isolation system performance for earthquakes up to design level. It is by introducing an appropriate initial gap that the device triggers additional energy dissipation during large earthquakes to limit displacements. Various combinations of hysteretic and viscous damping mechanisms are utilized to provide desired additional energy dissipation. A numerical study that assesses the ability of various gap damper models to reduce the base displacement by at least 25% while limiting the acceleration increase at the roof level that results from the sudden engagement of a damping device is devised. The energy dissipation level provided by the damper is optimized to provide the best possible performance. For base isolation systems with effective periods of isolation in the 2.5-3.0 s range, gap damper models incorporating a viscous dashpot are very effective in controlling displacement, whereas gap dampers restricted to a hysteretic damping mechanism are ineffective. The gap damper is less effective for systems with longer periods of isolation (3.5-4.0 s) because the lower target acceleration in this range is more difficult to meet. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Seismic isolation systems that mitigate seismic response are generally applied at the base of a building; however, architectural, functional, and cost considerations have motivated the application of isolation systems at inter-story locations. In this article, we systematically examine the effectiveness of inter-story isolation systems as a function of their location, and explore alternative approaches for selecting their properties. Single-story isolation systems are shown to be effective in mitigating force demands above the isolation system but less effective in mitigating forces below the isolation system. Finally, the practical aspects of designing an inter-story isolation system to accommodate light loads are discussed. [ABSTRACT FROM AUTHOR]

Current design codes generally use an equivalent linear approach for preliminary design of a seismic isolation system. The equivalent linear approach is based on effective parameters, rather than physical parameters of the system, and may not accurately account for the nonlinearity of the isolation system. This article evaluates an alternative normalized strength characterization against the equivalent linear characterization. Considerations for evaluation include: (1) ability to effectively account for variations in ground motion intensity; (2) ability to effectively describe the energy dissipation capacity of the isolation system; and (3) conducive to developing design equations that can be implemented within a code framework. [ABSTRACT FROM AUTHOR]

Although current code guidelines specify different seismic performance objectives for fixed-base and isolated buildings, the future of performance-based design will allow user-selected performance objectives, motivating the need for a consistent performance comparison of the two systems. Based on response history analysis to a suite of motions, constant ductility spectra are generated for fixed-base and isolated buildings. Both superstructure force (base shear) and deformation demands in base-isolated buildings are lower than in fixed-base buildings responding with identical deformation ductility. To compare the relative performance of many systems or to predict the best system to achieve a given performance objective, a response index is developed and used for rapid prototyping of response as a function of system characteristics. When evaluated for a life safety performance objective, the superstructure design base shear of an isolated building is competitive with that of a fixed-base building with identical ductility, and the isolated building generally has improved response. Isolated buildings can meet a moderate ductility immediate-occupancy objective at low design strengths, whereas comparable ductility fixed-base buildings fail to meet the objective. [ABSTRACT FROM AUTHOR]

In dynamic analysis, the energy dissipation in a base-isolated building is typically accounted for by allocating damping properties independently to the superstructure and to the isolation system. Rayleigh damping applied to the superstructure component alone is often used to represent the superstructure energy dissipation. At least one study has indicated that when used improperly, superstructure Rayleigh damping leads to excessive damping of the response of a base-isolated structure. As shown here, even when used as recommended for combining subsystems with disparate damping properties, Rayleigh damping results in undesirable suppression of the first mode response. To correct this behavior, stiffness-proportional damping can be used in lieu of Rayleigh damping. Stiffness-proportional damping is demonstrated to negligibly affect the first mode response, yet provide the expected energy dissipation in higher modes. [ABSTRACT FROM AUTHOR]

The ASCE 7 equivalent lateral force method for base-isolated buildings applies a triangular distribution of forces to the superstructure. This distribution attempts to approximately account for the observed effects of isolation system nonlinearity on the superstructure response, but a more rational approximation is needed. Using nonlinear regression analysis of median response data from nonlinear response history analysis of representative systems, improved equations are developed to estimate the lateral force distribution in the superstructure. The ASCE 7 distribution, a revision considered by a SEAONC committee, and the improved distribution developed here are evaluated. Only the improved equations are accurate over many system parameters. [ABSTRACT FROM AUTHOR]

An earlier procedure that estimates the peak deformation in base-isolated buildings is extended to include overturning and thereby estimate the peak axial forces in individual isolators. Such tools can be used as part of a design procedure to predict and subsequently eliminate bearing tension by modifying the design. The procedure is based on nonlinear response history analysis of an isolated block using an advanced bearing model that incorporates the relation between axial load and bearing response, known as axial-load effects. Rocking of the structure and bearing axial-load effects are found to have little influence on the peak lateral bearing deformation; median response spectra are within 10% of those when rocking is neglected entirely. Furthermore, bearing axial-load effects can usually be neglected in determining the maximum and minimum bearing axial forces; cases are identified where the error in neglecting such effects exceed 10%. Because the structure has been modeled as rigid, the limitations of the procedure should be assessed for superstructure designs that allow significant structural deformation. [ABSTRACT FROM AUTHOR]

Existing models for isolation bearings neglect certain aspects of their response behavior. For instance, rubber bearings have been observed to decrease in stiffness with increasing axial load, and soften in the vertical direction at large lateral deformations. The yield strength of lead–rubber bearings has also been observed to vary with axial load, such that a lightly loaded bearing may not achieve its theoretical strength. Models that include these axial-load effects in lead–rubber bearings are developed by extending an existing linear two-spring model to include nonlinear behavior. The nonlinearity includes an empirical equation for the experimentally observed variation of yield strength. For numerical implementation, the bearing forces are found by solving the nonlinear equilibrium and kinematic equations using Newton’s method, and the instantaneous bearing stiffness matrix is formed from the differentials of these equations. The response behavior of the models is confirmed by comparison with experimental data. [ABSTRACT FROM AUTHOR]

A procedure based on rigorous nonlinear analysis that estimates the deformation and force of an isolator due to strong ground motion is presented. The procedure offers an alternative to the iterative equivalent-linear methods used by current U.S. building codes. The governing equation is reduced to a form such that the median normalized deformation of the system due to an ensemble of ground motions with a given corner period T[sub d] is found to depend on only two parameters: the natural period, defined from the postyield stiffness, and the normalized strength, or strength normalized by peak ground velocity. The dispersion of normalized deformation for an ensemble of ground motions is shown to be small, implying that the median normalized deformation is a meaningful estimate of response. The simple trends shown by the median normalized deformation led to the development of suitable design equations for isolator deformation. These design equations reflect a 13% increase when the excitation includes two lateral components of ground motion instead of just one component. For comparison, deformations estimated by the equivalent-linear method are unconservative by up to 50% compared to those found from the more accurate nonlinear spectrum, and building codes include at most a 4.4% increase for a second component. [ABSTRACT FROM AUTHOR]

• The benchmark wall formed multiple flexural cracks for even curvature distribution. • Debonding of reinforcement helped to distribute strain and delay bar buckling. • An improved debonding detail is suggested for future evaluation. • Walls with advanced cementitious materials had increased crack propagation initially. • Walls with advanced cementitious materials fell short of expectations at large drifts. As a consequence of recent earthquakes in New Zealand, many concrete buildings have been demolished due to structural damage. Observations of damage to concrete walls led to substantial research and revisions to design standards to ensure that a satisfactory ductile response was achieved. However, even when the current performance objectives of the design standards are met, reinforced concrete walls may still require extensive or costly post-earthquake repairs. The objective of this project was to evaluate simple modifications to conventional reinforced concrete walls to increase their repairability. Four modified walls were constructed and subjected to cyclic lateral in-plane loading until failure, and compared to a previously tested conventional ductile reinforced concrete benchmark wall that failed at 2.5% drift. The modifications considered included debonding of reinforcement at the wall base, substituting fiber-reinforced concrete (FRC) for conventional concrete, and substituting engineered cementitious composite (ECC) for conventional concrete in the ends of the plastic hinge region (applied in two walls). Debonding delayed vertical reinforcement buckling, but failure occurred shortly thereafter (2.5% drift) due to constricted movement of the buckled bars within the debonding sleeves. The FRC and both ECC walls had increased crack propagation up to a drift demand of 0.5%, but then the cracks localized to a single dominant crack and the walls failed at drifts lower than the benchmark wall (about 1.5%). Modifications of the tested details are recommended for future test programs that investigate the repairability of concrete walls. [ABSTRACT FROM AUTHOR]

A full-scale, 5-story steel moment frame building in base-isolated and fixed-base configurations was subjected to a number of ground motions using the E-Defense shake table. In these experiments, more than 84 m2 (900 ft2) of suspended ceiling with lay-in tiles, 90 m (300 linear ft) of partition walls with individual lengths varying from 1.5 to 9.8 m (5 to 32 ft), and three sprinkler branch lines were installed below the fifth and sixth (roof) floors of the building. Because the horizontal floor accelerations were generally constrained to relatively low values by the base isolation system, several damage states related to vertical floor system acceleration were observed. One key observation is that use of lateral bracing with compression posts did not improve the seismic response of suspended ceilings when subjected to strong vertical excitation. Acceleration amplification factors of the ceiling-partition-partition components relative to structural floor accelerations were computed. The code-prescribed amplification factors for the design of nonstructural components was consistent with the observed amplification in the horizontal direction, but unconservative in the vertical direction, because the code neglects the additional amplification produced by slab vibration. [ABSTRACT FROM AUTHOR]

In this study, the multihazard response of code-designed conventional and base-isolated steel frame buildings is evaluated using nonlinear response history analysis. The results of hazard and structural response analysis for 3-story moment-resisting frame buildings are presented in this paper. Three-dimensional models for both buildings are created, and seismic response is assessed for three scenario earthquakes. The response history analysis results indicate that the performance of the isolated building is superior to the conventional building in the design event. However, for the Maximum Considered Earthquake, the presence of outliers in the response data reduces confidence that the isolated building provides superior performance to its conventional counterpart. The potential causes of the outliers have been carefully evaluated. [ABSTRACT FROM AUTHOR]

This paper presents the use of modern survey techniques, particularly light detection and ranging (LiDAR) scanning, to collect time-sensitive information before and after shake table experiments. Two full-scale, three-story residential buildings were tested simultaneously on the largest shake table in the world. The focus of this study is on the use of LiDAR to document observations during these tests. The challenges experienced during this study prompted the development of a formalized survey procedure using LiDAR scanning techniques, which can be used by other researchers when planning to collect such time-sensitive data from similar experimental programs. In this paper, damage assessment through visual inspection, which is commonly performed during full-scale tests, is compared to postexperiment assessments using postprocessed LiDAR-derived point clouds. Various examples of damage to structural and nonstructural components, including columns, bracing, partition walls, and façades, are illustrated through postshaking visual inspections as well as LiDAR-derived point clouds. The feasibility of making accurate measurements using LiDAR point clouds, and automatically detecting damage using the point-to-point cloud comparison, is presented. Finally, the relationship between observations through traditional instruments (e.g., accelerometers and laser meters) and LiDAR is discussed. In one example, the measurements from eight laser meters around the buildings are used to validate the measurements obtained using LiDAR point clouds. It is concluded that observations through LiDAR are complementary to those from traditional instruments, while permanent/residual displacements after the tests can be measured from both traditional and modern instruments. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive design methodology for a magnetorheological-based damper device for a three-dimensional building isolation. The device acts as a suspension system itself by combining the liquid stiffness and controllable magnetorheological damping features in one unit. The bi-linear liquid stiffness feature enhances resistance to global rocking/overturning of the structural system by increasing the stiffness in the rebound mode compared to the compression mode. In the field, the system is combined with the conventional elastomeric bearings widely employed to mitigate the lateral seismic motions. During a seismic event, the system is subjected to dynamic vertical shaking and large lateral forces. The theoretical and simulation modeling to overcome this major challenge and achieve other system requirements are presented. In addition, a comprehensive optimization program is developed to achieve all design requirements. The modeling procedure is verified with experimental results. Also, the effectiveness of Displacement/Velocity-based control for a single degree-of-freedom system subjected to sinusoidal loading is evaluated. [ABSTRACT FROM AUTHOR]