Petros Sideris

Quasi-Static Cyclic Testing of a Large-Scale Hybrid Sliding-Rocking Segmental Column with Slip-Dominant Joints

This paper presents the findings of an experimental study that investigated the response properties of segmental cantilever columns incorporating internal unbonded posttensioning (PT) and slip-dominant (SD) joints. The SD joints exhibited controlled sliding that provided energy dissipation with low damage. All joints of these columns, except for the bottom one, were designed to be SD. The bottom joint was designed to be rocking dominant (RD) and exhibited rocking that offered self-centering to the system. Design objectives and equations are presented. These equations were used for the design of a large-scale cantilever column that was subjected to reverse lateral cyclic loading at its top end, reaching a maximum drift ratio of 14.9%. At small drift ratios (≤3%), the response was dominated by sliding of the SD joints that provided energy dissipation (damping). For medium drift ratios (between 3 and 10%), rocking at the bottom joint increased and provided self-centering properties to the system. For large drift ratios (>10%), the self-centering properties decreased, but the damping properties remained practically constant. Rocking at the SD joints remained small at all times. Minor spalling was observed in the SD joints, while concrete crushing was observed at the bottom joint.

Experimental Investigation on the Seismic Behavior of Palletized Merchandise in Steel Storage Racks

The seismic hazard associated with failure of storage racks in retail facilities open to public depends on the behavior of the rack frames and the response of stored merchandise. In this study, the seismic behavior of palletized merchandise stored on shelves of pallet-type steel storage racks is investigated and the concept of incorporating slightly inclined shelving is proposed as a measure for mitigating merchandise shedding. Pull tests and shake table tests are conducted. The main objective of the pull tests is to investigate the frictional behavior at the interface between loaded pallets and rack shelves. The major objective of the shake table tests is to characterize the dynamic response of the palletized merchandise under earthquake excitation imposed at the base of rack structures, and determine experimentally the pallet shedding fragility under an ensemble of ground excitations representative of the seismicity of the Western United States. The combination of wooden pallets and shelves with wire decking of waterfall type, typical of many rack installations, is considered. The results of the pull tests indicate that the frictional coefficient at the pallet-to-shelf interface varies between 0.37 and 0.45 for a range of loads between 0.55 kN and 13.00 kN. From the results of the shake table tests, the concept of inclined shelving appears to be very effective. An inclination of only 3.5° reduced the observed seismic merchandise shedding fragility to zero for the ground excitations considered.

Experimental Seismic Performance of a Hybrid Sliding–Rocking Bridge for Various Specimen Configurations and Seismic Loading Conditions

AbstractThis paper presents the major findings of a shake table testing program on a large-scale (1:2.39) novel segmental concrete single-span bridge specimen. Emphasis is given on various specimen configurations and seismic loading conditions. The bridge specimen, termed hybrid sliding–rocking bridge, incorporated a box-girder superstructure with rocking joints and internal unbonded posttensioning (PT), and two single-column piers with internal unbonded PT. The pier columns included end rocking joints and intermediate sliding joints along the column height. Various configurations of the bridge specimen were considered with respect to the seismic mass and the superstructure-to-substructure connectivity. These configurations were subjected to far-field (F-F) and near-fault (N-F) ground motion ensembles scaled to various seismic hazard intensities. Asynchronous support excitation was also considered. The testing program included approximately 145 seismic tests. The dynamic response of the specimen was found...

Refined Gradient Inelastic Flexibility-Based Formulation for Members Subjected to Arbitrary Loading

AbstractThis paper advances the gradient inelastic (GI) flexibility-based (FB) frame element formulation, which focused on monotonic loading conditions, to capture member responses to arbitrary (no...

Experimental Performance Assessment of Nearly Full-Scale Reinforced Concrete Columns with Partially Debonded Longitudinal Reinforcement

AbstractThis paper presents an experimental study investigating the effect of partial debonding of longitudinal reinforcement at the location of the plastic hinge on the performance of reinforced c...

Seismic Response of Squat Rigid Bodies on Inclined Planes with Rigid Boundaries

AbstractA planar rigid-body dynamics formulation describing the seismic behavior of a squat rectangular rigid body initially resting on an inclined rigid plane is presented. The downslope motion of the body is limited by a rigid boundary perpendicular to the inclined plane. This type of problem appears in several practical applications. Coulomb and hysteretic friction with velocity- and pressure-dependent properties are considered at the body-to-ground interface. The weaknesses of hysteretic friction models incorporating static and kinetic velocity-dependent components are identified and remedied. Impact models for collision of the body with the rigid boundary and the inclined plane are also derived. The formulation is embodied in a numerical model through a dedicated computer code. A comparative study is conducted to demonstrate the effects on the body response of major model characteristics, including the rigid boundary; inclination angle; Coulomb, hysteretic, and combined Coulomb-hysteretic friction; a...

Low-Damage Posttensioned Segmental Bridge Columns with Flexible End Joints for Seismic Accelerated Bridge Construction

A computational parametric study leading toward the development of a new type of low-damage precast concrete segmental column for accelerated bridge construction in seismic areas is outlined. In contrast to conventional monolithic concrete construction, accelerated bridge construction significantly reduces on-site construction time, total project delivery time, weather-related construction delays, and environmental impact, and it provides improved work zone safety for the traveling public and contractor personnel and high product quality and durability. Low-damage systems provide significantly reduced postearthquake downtimes, repair costs, and casualties. The proposed column design will incorporate internal unbonded posttensioning and flexible joints at the column ends, where large flexural demands occur. These joints will be (flexurally) deformable enough to accommodate large column lateral deformations (drift ratios of 10% or higher) without damage, and (axially) stiff enough to limit initial axial deformations due to initial posttensioning and gravity loads. To investigate this concept, a three-dimensional finite element model of a cantilever segmental concrete column incorporating a flexible joint segment at the bottom was generated, and a comprehensive parametric study was conducted. The parametric study investigated three types of polyurethane elastomers for the flexible joint and various geometric properties of the flexible joint in reference to the column geometry. The findings of this study, as supported by preliminary material testing, have shown that hyperelastic materials, such as stiff rubbers and polyurethanes, are good candidates for the proposed application.

Numerical Simulation of Hybrid Sliding-Rocking Columns Subjected to Earthquake Excitation

AbstractThis paper introduces a novel element formulation for the dynamic analysis of bridges incorporating posttensioned segmental columns with hybrid sliding-rocking (HSR) joints distributed over...

Nonlinear Dynamic Analysis of Hybrid Sliding-Rocking Bridges

This paper introduces an innovative joint element to model the hybrid sliding-rocking (HSR) joints utilized in substructure columns of HSR segmental bridges. HSR joints allow both sliding and rocking of the connected segments with respect to each other, which makes their simulation challenging. The proposed element is capable of capturing the interaction of the adjacent segments by combining a force-based (FB) beam element formulation with a hysteretic friction model and an empirical formulation for joint rocking. The empirical rocking formulation is incorporated at the element mid-length, where rocking occurs, through adaptive modification of the corresponding integration weight, which is varied throughout the analysis as the segments’ contact depth changes. The results obtained from the numerical simulations of a HSR pier using this element are in a good agreement with the past experimental data.

Direct Displacement-Based Seismic Design and Validation for Hybrid Sliding-Rocking Bridge Substructure Systems

In this paper, a direct displacement-based seismic design method for the hybrid sliding-rocking (HSR) segmental bridge piers is presented. The HSR bridges consist of unbonded post-tensioning, end rocking joints and intermediate sliding joints (or slip-dominant joints) along the column height. Joint sliding provides energy dissipation with small damage and control of the applied seismic loading. Residual joint sliding is small and restorable after an intense earthquake event. Force-based seismic design of the HSR columns is difficult to apply because representative R-factors are not available and are difficult to estimate. For this reason, displacement-based design methods are investigated. The proposed method involves an iterative scheme that builds on the capacity spectrum method. In the proposed method, a pushover curve for the HSR columns is computed analytically. Then, the equivalent viscous damping ratio is computed as a function of the column displacement. Eventually, the spectral demand obtained from the FEMA 356 is compared to the spectral capacity obtained from the pushover curve. The computed performance is compared with intended performance objectives and iterations are conducted to obtain economical designs. A preliminary comparison of the proposed design method with the results of an experimental study is presented.