Application In Seismic Regions Research Articles

Seismic performance of full-scale prefabricated semi-rigid bolted connection between RC column and composite beam

This paper presents a novel proposal for an assembled bolted joint between precast reinforced concrete (RC) column and steel-concrete composite beams, focusing on its seismic performance. To evaluate the joint's behavior, a comprehensive experimental investigation was conducted on a full-scale RC column to composite beam joint specimen subjected to pseudo-static loading. The study aimed to analyze the joint's failure mode, bearing capacity, ductility, and energy dissipation characteristics. The joint stiffness was assessed by analyzing the bending moment-rotation (M-θ) curve of the beam in accordance with the European standard BS EN 1993-1-8:2005. The experimental results demonstrate that the proposed assembled bolted joint exhibits semi-rigid behavior under positive moments and approaches rigidity under negative moments. To further enhance our understanding of the joint's performance, a finite element model was developed using ABAQUS. The stress distribution in each joint component, as well as the failure mode and ultimate bearing capacity, were analyzed in conjunction with the experimental results. Based on the findings from both the experimental and finite element analyses, an improved joint design is proposed. Additionally, parametric analysis was conducted on the enhanced joint configuration. The study findings indicate that the improved joint exhibits superior damage resistance, seismic performance, and enhanced assembly efficiency compared to the original design. This research contributes to the advancement of assembled bolted joints between precast RC columns and steel-concrete composite beams, offering valuable insights for practical applications in seismic regions.

Assessment of the engineering properties and economic advantage of recycled aggregate concrete developed from waste clay bricks and coconut shells

Using recycled aggregates to replace natural aggregates in concrete helps preserve nonrenewable resources, promotes recycling, and affords reductions in cost. To this end, experiments were performed to clarify the effects of coarse aggregate systems developed using crushed coconut shell aggregate (CCSA) and recycled brick aggregate (RBA) on the mechanical properties, thermal conductivity, ultrasonic pulse velocity and high temperature resistance of concrete. The results showed that the incorporation of CCSA improved the thermal conductivity, flexural strength and cost ratio of concrete. The mechanical properties of the recycled aggregate concrete also satisfied the requirements of structural lightweight aggregate concrete. In addition, low-rigidity concrete developed using RBA and CCSA imparted the building with a higher strain capacity, suitable for applications in seismic regions. However, under high-temperature environments, the properties of the concrete deteriorated significantly with the incorporation of CCSA; the compressive strength and other properties were also reduced considerably.

Observations on the Seismic Loading of Rigid Inclusions based on 3D Numerical Simulations

Rigid inclusions are increasingly being specified in seismic regions to transmit foundation loads to competent strata at depth due to their ability to provide excellent static performance and potential for cost-savings over other forms of ground improvement and/or deep foundations. Despite their widespread application in seismic regions, the seismic kinematic interaction of rigid inclusions is not well understood. This study presents a series of parametric numerical simulations specifically conducted to capture the kinematic soil-rigid inclusion interaction under seismic loading to identify key mechanisms that contribute to seismic performance. The effect of ground motion variability, area replacement ratio, surface crust thickness, embedment into a competent layer, liquefiable layer thickness, and steel reinforcement is systematically investigated. Although the rigid inclusion may not prevent liquefaction triggering, severe amplification associated with dilation spiking of transiently liquefied soil is mitigated and the onset of liquefaction delayed due to the soil-rigid inclusion interaction. The role of static arching to alter the geostatic stress state prior to and during shaking is shown to be responsible for significant and heretofore unknown coupled fluid-mechanical interaction that drives the performance of the rigid inclusion within the reinforced soil system. The kinematic flexural demand following the triggering of liquefaction and phase transformation associated with cyclic mobility is met through transient increases in axial load, which increases the confinement of the grout comprising the rigid inclusion, and therefore its moment capacity. The complex mechanisms identified in this work should be used to help identify which subsurface conditions may lead to responses, guide design decisions regarding selection of reinforcement and embedment, and provide a basis for assessments of the anticipated kinematic demands in view of the beneficial axial load-moment capacity interaction following soil liquefaction.

Experimental study on interior precast concrete beam–column connections with lap-spliced steel bars in field-cast RPC

Reactive powder concrete (RPC) has an ultra-high bond strength with steel bars, which offers new and innovative opportunities for precast concrete structures. This experimental study aimed to develop an alternative precast interior beam–column connection for moment-resisting frames in seismic regions. A two-stage experimental program involved a series of lap-splice tests and two beam–column connection tests to assess the viability of lap-spliced steel bars in field-cast RPC (LS-RPC) used in a precast beam–column connection. In the first part of the study, the lap-splice tests were conducted to determine the minimum lap length of LS-RPC and the influences of embedment length, hoop ratio, and hoop type (rectangular or spiral). In the second part, the application of LS-RPC in the precast beam–column connection was performed to verify its reliability and its seismic performance with the expectation that this alternative precast interior beam–column connection for moment-resisting frames would be practical for application in seismic regions. It was determined that the application of highly ductile fiber-reinforced concrete in the potential plastic hinge zone could improve the seismic performance of the connection.

Seismic performance of mid-to-high rise modular steel construction - A critical review

Modular steel construction (MSC) comprises off-site manufactured volumetric modules and on-site assembly, leading to reduced construction periods, improved quality, and reduced waste of resources. This environmentally friendly solution has been extensively used for low-rise buildings as an alternative to traditional on-site construction. The popularity of MSC has now spread to mid-to-high rise applications in seismic regions to meet the increasing urban construction demand, owing to its significant technical advantages. The influence of earthquake becomes critical as the height of the building increases. Hence, this paper presents a state-of-the-art review of the seismic performance of mid-to-high MSC and articulates the key technical issues. The module classification is presented as a brief introduction of MSC, followed by discussion of the structural system. Afterwards, the seismic performance of the lateral force resisting system and recent innovations on the connection system are reviewed in detail, on which the seismic performance of MSC highly depend. The global seismic response analysis methodology, characteristics, failure mode as well as the current design criteria are evaluated, providing a more comprehensive understanding of the seismic performance of MSC. Finally, the recently developed isolation systems for MSC are introduced. As a currently developing area, there is great potential for innovation in mid-to-high rise MSC. Despite progressively increasing research exploring the seismic performance of MSC, a comprehensive understanding of this topic has not been achieved, hindering the further prevalence of mid-to-high rise MSC in areas with potential seismic hazards. Given this situation, several key research areas are suggested thereupon at last, aiming to promote the further extended application of MSC in seismic regions.

Behavior of eccentrically loaded square spiral-confined high-strength concrete-filled steel tube columns

Concrete-filled steel tube (CFST) columns have been widely used in super tall buildings. Since these columns are subjected to very high axial loads, the use of high-strength concrete (HSC) is preferred in order to reduce their cross-sectional size. For applications in seismic regions, additional confinement to the HSC may be needed to ensure ductility. Among various approaches, spiral confinement is an effective and practical way for square CFST columns. Six spiral-confined concrete-filled steel tube (SCCFST) columns and three CFST columns with the concrete compressive strength of 111 MPa were tested under eccentric axial loading. The behavior of the columns under different levels of eccentricity ratio was investigated, and the use of high-strength spirals to further enhance confinement was also examined. Concrete crushing was found to be the main cause for the loss of the load-carrying capacity. Spiral reinforcement is not effective in increasing the load-carrying capacity; however, it can considerably improve ductility, which is improved with an increase of the yield strength of spiral reinforcement. Based on the test results, an equivalent uniaxial stress–strain model was developed for the HSC in CFST and SCCFST columns. A fiber beam-column element using the proposed stress–strain models was found to provide good predictions of the measured load–displacement responses. Such fiber element can be used for modeling of SCCCFST columns with HSC in nonlinear structural analysis of tall buildings.

Field investigation of lateral monotonic and cyclic performance of reinforced helical pulldown micropiles

Different forms of grouted helical piles are increasingly used to support new and existing foundations. In particular, different methods are used to enhance the lateral and cyclic performance of helical piles for applications in seismic regions. This paper presents a field study on the lateral monotonic and cyclic behaviour of steel fibre–reinforced helical pulldown micropiles (RHPM) and fibre-reinforced polymer – steel fibre–reinforced helical pulldown micropiles (FRP–RHPM). The study shows that the grout shaft and (or) the fibre-reinforced polymer (FRP) sleeve significantly improve the helical pile lateral performance. In addition, the piles showed a significant ductility (no observed failure up to 75 mm displacement or 50% of pile diameter). Two-way cyclic loading resulted in overall degradation in pile response relative to its static performance. Degradation is found to stem from the formation of gaps between the pile and soil, rather than soil stiffness degradation. Formation of gaps leads to the piles having a “preferential direction” with one side providing higher resistance (i.e., stiffness) than the other side. Design charts of various pile configurations are presented.

Single precast concrete rocking walls as earthquake force‐resisting elements

SummaryPrecast concrete walls with unbonded post‐tensioning provide a simple self‐centering system. Yet, its application in seismic regions is not permitted as it is assumed to have no energy dissipation through a hysteretic mechanism. These walls, however, dissipate energy imparted to them because of the wall impacting the foundation during rocking and limited hysteretic action resulting from concrete nonlinearity. The energy dissipated due to rocking was ignored in previous experimental studies because they were conducted primarily using quasi‐static loading. Relying only on limited energy dissipation, a shake table study was conducted on four single rocking walls (SRWs) using multiple‐level earthquake input motions. All walls generally performed satisfactorily up to the design‐level earthquakes when their performance was assessed in terms of the maximum transient drift, maximum absolute acceleration, and residual drift. However, for the maximum considered earthquakes, the walls experienced peak lateral drifts greater than the permissible limits. Combining the experimental results with an analytical investigation, it is shown that SRWs can be designed as earthquake force‐resisting elements to produce satisfactory performance under design‐level and higher‐intensity earthquake motions. Copyright © 2016 John Wiley & Sons, Ltd.

Seismic Behavior of Posttensioned Self-Centering Precast Concrete Dual-Shell Steel Columns

This paper describes an innovative bridge column technology for application in seismic regions. The proposed technology combines a precast posttensioned composite steel-concrete hollow-core column, with supplemental energy dissipation, in a way to minimize postearthquake residual lateral displacements. The column consists of two steel cylindrical shells, with high-performance concrete cast in between. Both shells act as permanent formwork; the outer shell substitutes for the longitudinal and transverse reinforcement, because it works in composite action with the concrete, whereas the inner shell removes unnecessary concrete volume from the column, prevents concrete implosion, and prevents buckling of energy dissipating dowels when embedded in the concrete. Large inelastic rotations can be accommodated at the end joints with minimal structural damage, since gaps are allowed to open at these locations and to close upon load reversal. Longitudinal posttensioned high-strength steel threaded bars, designed to respond elastically, in combination with gravity forces ensure self-centering behavior. Internal or external steel devices provide energy dissipation by axial yielding. This paper describes the main requirements for the design of these columns and also discusses the experimental findings from two quasi-static tests.

Large‐scale seismic tests of tall concrete bridge columns with precast segmental construction

AbstractPast experimental studies have shown that existing precast segmental concrete bridge columns possess unsatisfactory hysteretic energy dissipation capacity, which is an undesirable feature for applications in seismic regions. In this research, we propose new methods of precast segment construction for tall concrete bridge columns to enhance the columns' hysteretic energy dissipation capacity and lateral strength. This is accomplished by adding bonded mild steel reinforcing bars across the segment joints, strengthening the joint at the base of the column and increasing the height of the base segment (hinge segment). Four large‐scale column specimens were fabricated and tested with lateral cyclic loading in the laboratory. Each specimen consisted of a foundation and 9 or 10 precast column segments. Test results of specimens with the proposed design concepts showed ductile behavior and satisfactory hysteretic energy dissipation capacity. In addition to the experimental study, an analytical study using the finite element method was conducted to understand the bond conditions, strain contours and deformation patterns of the specimens tested. Good agreement was found between the experimental observations and the results of the calibrated analytical study. Copyright © 2008 John Wiley & Sons, Ltd.

Innovative seismic design of a post-tensioned concrete masonry houseThis article is one of a selection of papers published in this Special Issue on Masonry.

Post-tensioned concrete masonry walls provide improved seismic performance, but have had limited application in seismic regions because of a lack of research pertaining to their in-plane response. Following focused research over recent years, a consortium of product suppliers has collaborated with the University of Auckland to construct New Zealand’s first post-tensioned concrete masonry house. A feature of this innovative design was that all incorporated products were commercially available, with no proprietary products being specifically developed for the prestressed masonry system used. Consequently, it is hoped that this house will be a showcase, and provide exposure for the technology in New Zealand and elsewhere. This paper provides a brief review of previous post-tensioned concrete masonry research applications, then discusses post-tensioning details and their application to house design and construction.

Seismic Behavior of a Concrete/Steel Integral Bridge Pier System

This paper summarizes an experimental study on an integral bridge pier system consisting of a concrete column, steel girders, and a box-shaped steel cap beam that is suitable for applications in seismic regions. Using two 1 / 3-scale test units, the research examined suitable connections between the concrete column and the steel cap beam and between the steel cap beam and steel girders as well as the overall seismic behavior of the proposed system. The anchorage length requirement for the column longitudinal bars governed the depths of the cap beam and girders in the first unit. Employing mechanical anchorage at the ends of the column longitudinal bars, the required anchorage length for the column bars was reduced in the second unit, thereby enabling the use of shallower and lighter cap beam and girders. Both test units exhibited satisfactory seismic response up to the target displacement ductilities with the intentional formation of plastic hinges in the columns. The description of the test units and key experimental results are included in this paper.

Use of foundations and artificial bases in punched (tamped-out) trenches in seismic regions (using South Kazakhstan as an example)

Field and experimental investigations as well as full-scale tests of foundations and artificial bases in punched (tamped-out) trenches at specific projects in South Kazakhstan have once again confirmed the effectiveness of their application in seismic regions with similar soil conditions.