Seismic Behavior Research Articles

Experimental Investigation on the Seismic Behavior of RC Double‐Column Medium‐Height Bents Retrofitted With SCEB‐Us

Experimental Investigation on the Seismic Behavior of RC Double‐Column Medium‐Height Bents Retrofitted With SCEB‐Us

A shaking table study on seismic behavior of pier of bridge in sand

Dynamic Soil-Bridge interaction (DSBI) is an important seismic design for bridges. The behavior of pier under earthquake loading is an important factor affecting the performance of such structures. Two series of laboratory tests were conducted to measure the response of structure when subjected to dynamic loads the first test the model was made of Aluminium and the second just the piles were made with Steel. A small shaking table was manufactured. The measurements taken in these experiments are horizontal displacement and strain of superstructure, acceleration in three dimensions in soil, pile, cap and superstructure. The soil used is sand and the model pile group (5x4) used has a diameter of 1 cm. It was concluded that the acceleration amplitudes increase with frequency for both model Aluminium and steel and the reaction of superstructure on aluminium piles is more than the steel ones.

SaniSand model performance evaluation for liquefaction simulation and liquefaction remediation actions for liquefiable sand

Soil liquefaction is a major element influencing the behaviour of piles built in seismically active places. As a result, the first goal of this research is to investigate the seismic behavior of a soil-pile system in liquefiable soil using ABAQUS 3D and SANISAND as the constitutive model to simulate the seismic behavior of a liquefiable sand layer, including soil-pile interaction; the second goal is to apply an improved method of mitigating liquefaction potential in a sandy soil profile subjected to shaking. First, the finite element model was validated by comparing variations in pile reaction to measured data from the centrifuge test, and the numerical and experimental results were quite similar. Second, the effectiveness of consolidation in both the mitigation of a liquefiable soil and the reduction of induced pile relative settlement is showed.

Softening index‐based equivalent linear modeling approach for bolt‐connected precast concrete frame

AbstractPrecast concrete structures with bolt‐connected joints have been widely constructed in the world, and their prospective application market is still considerable. Considering the clear load transferring path and damage mechanism, simplified analysis method is feasible for the bolt‐connected precast concrete frame. This paper proposes an equivalent linear modeling approach (ELMA) for this type of structure, which is convenient and high efficiency to help the preliminary design of structures and seismic assessment of existing buildings. In this method, a series of linear models are established to simulate the real structure in different seismic intensity levels. The softening indices summarized from the variation of modal frequencies are defined to represent the stiffness degradation of structures. In order to obtain specific softening indices, a shaking table test for a bolt‐connected precast concrete frame was implemented. Based on the test results, the recommended softening indices, applicable to bolt‐connected frames with similar design performance objectives, are 0.325, 0.713, and 0.816 for the minor, moderate, and major earthquake levels, respectively. Following the ELMA, the numerical model of the test frame was constructed and its equivalent seismic behaviors were analyzed. By comparison with the test results, the convenience and effectiveness of this method is validated, and the precision of simulation meets the requirement of engineering application. The ELMA is also applicable for precast frames with different joints or design requirements, if the softening indices are appropriately defined by shaking table test of the structure or cyclic loading test of its single‐connection model.

Influence of Mass Irregularities on the Seismic Behavior of Multi-Storied Using STAAD.Pro Connect Edition

The seismic behavior of multi-story buildings is greatly influenced by their structural configuration. Irregularities in plan or elevation, particularly mass irregularities, are critical factors contributing to structural failure during earthquakes. Proper identification and management of such irregularities are essential to optimize a building's functionality and aesthetics. This study examines the seismic response of a G+14 reinforced concrete (RC) frame structure with and without mass irregularity. The analysis focuses on storey drift, storey displacement, lateral loads, maximum bending moments, and shear forces. A swimming pool placed on the 7th floor introduces a heavy mass, creating mass irregularity as per IS 1893 (Part 1):2016, where a floor’s seismic weight exceeds 150% of the floors above and below. Using STAAD.Pro Connect Edition software, the structures are analysed through dynamic response spectrum analysis. The residential building, with dimensions of 35.45 m × 30.56 m, is subjected to seismic loads according to IS code standards. Results indicate that the inclusion of mass irregularity significantly impacts the seismic response, leading to notable variations in drift, displacement, and internal force distribution. This study highlights the importance of addressing mass irregularities in seismic design to ensure structural safety and performance in earthquake-prone areas. Keywords: Mass irregularity, seismic response, RC frame, STAAD.Pro, storey drift, response spectrum, IS 1893:2016, dynamic analysis.

EFFECT OF MECHANICAL PROPERTIES OF FILLING MATERIAL ON STATIC AND DYNAMIC BEHAVIOR OF MASONRY ARCH BRIDGES

The present study examined the impacts of the mechanical properties of the filling material on the seismic behaviour of masonry arch bridges (MAB). A bridge model that did not exist was selected to achieve this objective. Using this model, bridge models with different filling material properties were created in the SAP2000 computer program. Modal analysis and linear time history analysis (THA) were conducted on the aforementioned models to ascertain the filling material's influence on the bridge's dynamic behavior. The findings of the modal analysis indicated that an increase in the density of the filling material increased in the period, while an increase in the elasticity modulus led to a decrease in the period. As a result of linear THA, it was determined that as the density of the filling material increases, the displacements and stresses increase, and as the elastic modulus increases, the displacements and stresses decrease. As a result of static analysis, it was determined that as the density of the filling material increases, the displacement and stress values increase, and as the elastic modulus increases, these values decrease.

Seismic performance of continuous rigid-frame bridges affected by flood-induced scour

River-crossing bridges in high-intensity seismic regions can be vulnerable to the combined action of earthquake and flood hazards; in particular, flood-induced scour of the substructure can have a notable influence on the seismic behavior of bridge structures. Currently, long-span continuous rigid-frame bridges are widely used to cross large rivers worldwide, yet related studies on their seismic performance under flood-induced scour have been lacking. This paper focuses on the effects of time-varying flood-induced scour on the seismic performance of long-span continuous rigid-frame bridges incorporating complex thin-walled reinforced concrete piers with pile group foundations. A detailed finite element (FE) model for a representative bridge structure is developed and the scour depth risk of the bridge is evaluated under several flood events for different return periods. The influence of flood-induced scour on the pile-soil interaction is examined throughout the bridge service life. Detailed seismic fragility assessment is carried out through nonlinear time-history analyses using a large suite of 100 seismic records. Particular focus is given to evaluate the time-varying scour effects on the pile and soil deformations as well as on the component and system level seismic fragility functions. It is shown that the total flood-induced scour depth exhibits a nonlinear increasing trend with the increase in service time, particularly in the initial 10 years of the bridge service life. The deformations of the scoured piles, within a depth of 20 m, are also shown to increase significantly with the increase in service time. The results indicate that the scour has a pronounced effect on both the component and system level seismic fragility functions. Importantly, although the piles (or pile groups) are typically designed to remain elastic under seismic loading, they are shown to be subjected to significant inelastic demands and governing damage levels as a result of time-varying flood-induced scour effect. Overall, this study provides a methodology to assess the time-varying seismic fragility of the scoured long-span rigid-frame bridges with complex thin-walled reinforced concrete piers, which can enhance the multi-hazard time-varying seismic resilience assessment for bridge structures with similar configurations.

Experimental Study on Seismic Behavior of a New Separately‐Anchored Self‐Centering Beam‐Column Connection

ABSTRACTPost‐tensioned self‐centering (PTSC) structures that use PT tendons to assemble precast members and provide structural resistance have demonstrated superior seismic performance and self‐centering capacity. Current PTSC frames generally serially connect all beams in a floor. This assembly method would induce interferences among different spans and increase the risk of progressive failure once local damage occurs in a bay. This paper proposes a new type of PTSC joint to avoid such serial connection of beams. By employing steel beams to serve as the anchorages of PT tendons, each bay of the frame is separately prestressed. The composite prestressed beams can be readily fixed to columns by high‐strength bolts, hence facilitating the construction of such separately‐anchored self‐centering (SASC) frame building. External friction dampers are installed to enhance the energy dissipation capacity of SASC connections. Eight full‐scale cyclic loading tests are performed to compare the performance of the new SASC connections with conventional PTSC joints and also comprehensively evaluate the seismic behavior of SASC connections with different parameters. The test results validate the excellent damage mitigation abilities of both types of connections while the superior mechanical performance of the new SASC connections. In addition, the effects of key design parameters such as initial prestress level, damper force, and tendon number on the seismic behavior of the SASC connection are evaluated, and design recommendations for the application of the proposed precast beam‐column connection are also provided.

Uncovering implicit Seismogenic associated regions towards promoting urban resilience

Earthquakes pose a significant threat to urban environments, highlighting the need for enhanced seismic resilience. To improve understanding of earthquake dynamics and the interplay of seismic activity across space, this study introduces a novel approach for identifying associated regions that exhibit interdependence seismic behavior, revealing a network structure of earthquake interplays. This model was applied to earthquakes exceeding 3.0 Mw in Iran (1976–2023), using a 1° × 1° grid. Monthly and seasonal timespans were evaluated to capture potential short-term and long-term interactions. The model revealed a network of interdependent seismic regions in southern and southwestern Iran, predominantly located within the Zagros belt. Notably, the strongest associations were observed between spatial units 45 and 36, located approximately 6° apart in southern Iran. These units exhibited significant association in both monthly and seasonal scenarios, with support values of 0.28 and 0.65, and average confidence values of 0.58 and 0.84, respectively. The second significant bilateral relation was detected between neighboring spatial units 22 and 36, with support values of 0.26 and 0.59, and average confidence values of 0.57 and 0.80, respectively. The recognized structure was compared to the established seismotectonic zoning. This network aligns with established seismotectonic provinces, particularly in the seasonal scenario. The model also identified potential interactions between distinct zones in the monthly scenario, highlighting areas where urban development strategies might need reevaluation. Additionally, the analysis revealed implicit causal relationships between spatial units, pinpointing areas susceptible to or influencing seismic activities elsewhere. These results contribute to a deeper understanding of crustal structure, earthquake propagation, and the potential for seismic activity to trigger earthquakes in nearby or distant areas. This knowledge is crucial for developing effective strategies to build earthquake-resilient cities.

Experimental study on the post-fire seismic behavior of exterior beam-column joints in reinforced concrete frames

This study outlines the post-fire seismic behavior of reinforced concrete beam-column joints. Due to the lack of sufficient research data regarding the seismic vulnerability of exterior reinforced concrete beam-column joints after fire exposure, experimental investigations were carried out to assess variations in the seismic performance of these joints after experiencing high temperatures. In this way, five scaled beam-column joints were considered for examinations and were designed according to the seismic provisions of ordinary moment frames. One benchmark specimen was subjected to reverse cyclic loading at ambient temperature without prior fire exposure. Four others were exposed to the heating regimes with various target temperatures and then examined by reverse cyclic loading after cooling to the ambient temperature. Damage patterns were exhibited with substantial alterations from flexural beam-end hinging for the benchmark specimen to the shear ruptures for the fired specimens exposed to the high temperatures of 400°C, 600°C, and 800°C. The quantitative results indicated minor changes in the load-bearing capacity, ductility factor, and energy dissipation by the effect of the 200°C heating regime. On the other hand, other three heating regimes led to noticeable reductions of 16–62% in the load-bearing capacity, 25–65% in the cumulative energy dissipation, and 14–42% in the ductility factor by propagating diagonal cracks and developing shear ruptures inside the joint core. Trends in variations of investigated parameters were also discussed, and novel findings were presented in this regard. The results and observations in this study can be employed as the applicable data for retrofitting decisions of fired exterior beam-column joints in reinforced concrete ordinary moment frame buildings.

Experimental study on the seismic behavior of all-steel buckling-restrained brace with constrained coupler

This study proposes a novel all-steel buckling-restrained brace (BRB), in which cross-shaped (or H-shaped) steel members and double steel tubes are employed for the core members and buckling-restraining members, respectively. The core members are equipped with a constrained coupler in the central region. The square outer tube, welded to one end of the bracing system, uses spacers to prevent buckling of the inner tube. The hexagonal inner tube is connected to a constrained coupler by welding, thereby preventing the buckling of the core members. The constraint system provides a quadruple restraint mechanism comprising the inner tube, outer tube, constrained coupler, and spacers. Global and local stability are analyzed based on Eulerian theory, the principle of virtual work, and yield line theory, respectively. Cyclic loading tests were performed on four test specimens of the proposed BRB and four traditional BRBs without constrained couplers. Comparative analysis, through cyclic loading tests, reveals that the proposed BRB exhibits a stable energy dissipation performance post-yielding under compression, outperforming the specimens without constrained couplers in terms of the equivalent viscous damping ratio, cumulative plastic deformation, and the compression-strength adjustment factor. Furthermore, the numerical model was constructed and validated using the test results. The effects of the core width-to-thickness ratio and the gap size between the core member and inner tube on hysteretic behaviors were investigated. The contributions of this study can provide a reference for the application of BRBs in the engineering of more complex high-rise buildings and mega-spatial structures.

Seismic Behavior of GFRP-RC Circular Bridge Columns under Eccentric Lateral Cyclic Loading: Influence of Transverse Reinforcement Ratio and Configuration

Seismic Behavior of GFRP-RC Circular Bridge Columns under Eccentric Lateral Cyclic Loading: Influence of Transverse Reinforcement Ratio and Configuration

Seismic behaviour of reinforced concrete buildings: Impact of inter-story pounding with adjacent structures on one and both sides

Seismic behaviour of reinforced concrete buildings: Impact of inter-story pounding with adjacent structures on one and both sides

Experimental study on seismic behavior of a novel RC slab- SC wall joint based on UHPC and rebar – steel plate lap splices

Steel plate concrete shear walls (SC walls) have been widely used in practical projects because of great mechanical properties. For the application in nuclear power plant containment, the joint of specially shaped reinforced concrete slab and SC walls is difficult to design and construct. By using ultra-high performance concrete (UHPC), a new type of joint with the non-contact lapping method is proposed in this paper, which has advantages of simple construction, superior performance, suitable cost, and wide application range. Five RC-UHPC slab-shear wall joints were designed and tested under reciprocating load to study the effects of structures of lapping steel plate, shear-resisting methods, and interfacial reinforcing methods on the mechanical properties of the joints. The test results showed that the joints adopting the new structures were damaged for the flexural failure of the concrete area, with no damage to the joint zone, while the other specimens failed in the shear failure of the joint zone. It can be demonstrated that the ribs formed by bars and studs on the lapping steel plates are effective measures for non-contact force transferring, and interfacial reinforcing bars can improve the strength of the interface between concrete and UHPC. The force transferring efficiency of the new joints was close to or more than 90%, which indicates that the proposed joint structures can effectively realize the non-contact lapping force transferring. The design formulas and suggestions are proposed based on the analysis of the mechanism of new structures.

Seismic Behavior of Concrete Columns Reinforced with BFRP, GFRP, Steel, and Hybrid Steel–FRP Reinforcement

Seismic Behavior of Concrete Columns Reinforced with BFRP, GFRP, Steel, and Hybrid Steel–FRP Reinforcement

Effect of Vertical Location of Post-Opening on Seismic Behaviour of RC Shear Wall: Experimental and Numerical Analysis

The seismic performance of reinforced concrete (RC) shear walls with post-openings is critical in civil engineering. This study investigates the influence of post-opening positions on the seismic behaviour of RC shear walls through both experimental and numerical approaches. Four shear wall specimens with varying positions of post-openings were subjected to pseudo-static tests. Additionally, Finite Element Method (FEM) simulations were employed to further analyse the structural responses of shear walls with post-openings. The results show that the vertical position of post-openings significantly affects the failure mode, peak bearing capacity, and overall seismic performance. Peak bearing capacity reductions were observed, with central and bottom openings diminishing capacity by up to 17.5% and 15.1%, respectively, while top openings had a minimal impact. Openings also influenced pre-crack initiation, yielding behaviour, and stiffness degradation, with central openings causing the most significant effects. The ductility and energy dissipation capacities of the shear walls were also affected by opening positions. Bottom post-openings led to a maximum ductility reduction of 18.4%, while top openings increased ductility by up to 24.6%. Energy dissipation capacity decreased with lower post-opening locations, with central and bottom openings reducing capacity by 78.9% and 63.0%, respectively. These findings emphasize the importance of considering opening location in the seismic design of RC shear walls to optimize structural performance.

Seismic Behavior of a Concrete Rocking Wall with Controllable SMA Dampers: Concept and Experimental Evaluation

Seismic Behavior of a Concrete Rocking Wall with Controllable SMA Dampers: Concept and Experimental Evaluation

Seismic performance and failure mechanisms evaluation of multi-story elliptic and mega-elliptic bracing frames: Experimental and numerical investigation

In recent decades, researchers have evaluated the seismic performance of the innovative Elliptic-Braced Resisting Frames (ELBRFs) only in single-story single-span configurations. Although numerical studies have investigated the behavior of multi-story ELBRF configurations, the lack of laboratory data has cast doubt on the reliability of these numerical results. To address this gap in knowledge, this article evaluates the seismic performance and failure mechanisms of multi-story ELBRFs through a laboratory program and compares them with a developed type of this bracing system known as Mega Elliptic-Braced Resisting Frames (MELBRF). The key contribution of this research is the provision of laboratory test data for multi-story ELBRF and MELBRF systems, which can be utilized to validate numerical models and investigate their seismic characteristics. In this study, laboratory tests are used to examine the cyclic behavior and to calculate parameters such as strength, ductility, stiffness, energy dissipation, seismic performance, and failure modes in multi-story specimens. To this end, an experimental test of a 1/6 scale single-span four-story ELBRF specimen and a two-span four-story MELBRF specimen under cyclic quasi-static loading was conducted. Next, the seismic behavior of the proposed specimens is compared with other types of bracing systems such as X-, V-, Inverted-V, Two-Story X-, and Two-tiered diagonal braced frames in a story-base model under cyclic quasi-static loading through nonlinear FEM analyses. The results indicated that the yielding of elliptic braces would delay the failure mode of adjacent elliptic columns and thus help tolerate significant nonlinear deformation to the point of ultimate failure. The response modification factor in ELBRF and MELBRF is 7.3 and 6.5, respectively. Symmetrical behavior, high energy absorption, appropriate stiffness, and high ductility in comparison with conventional systems are some of the advantages of the proposed systems.

Experimental seismic behavior of novel inorganic-bonded bamboo composite beam-to-column moment-resisting connections

In this study, an innovative method of gluing the slot and the bolt holes was proposed to enhance the seismic performance of the inorganic-bonded bamboo beam-to-column connections. Four different types of inorganic-bonded bamboo composite beam-to-column connections were designed. They included the conventional bolted connection with slotted-in L-shaped steel plates, the bolted connection with slotted-in L-shaped steel plates (the slots and the bolt holes are glued), the bolted connection with slotted-in T-shaped steel plates and bolt anchorage in column (the slots and the bolt holes are glued), and the bolted connection with slotted-in T-shaped steel plates and glued-in rods in column (the slots and the bolt holes are glued). Monotonic and cyclic loading tests were conducted to evaluate the seismic behavior of the novel inorganic-bonded bamboo beam-to-column connections. The test results showed that the bearing capacity of the connections whose holes and slots are filled with glue increased by 40%–120 %, compared with the conventional bolted connection. The initial stiffness of the glued connections was about 5–15 times that of the conventional connection. The ductility and energy dissipation capacity of the conventional bolted connection with slotted-in steel plates was lower than that of the glued connections. Under the joint action of the adhesive in bolt holes and slots, the steel plate and the bamboo composite worked together as a whole until adhesive failure occurred. Therefore, gluing the slot and the bolt holes was an effective method for improving the seismic performance of the inorganic-bonded bamboo composite connections. The bolted and glued connection with slotted-in T-shaped steel plates in the beam and glued-in rods in the column showed a better seismic performance and was found to be suitable for practical engineering after taking some measures on the end anchorage. In addition, it was conservative to estimate the bearing capacity of the bolted connection with glue-filled holes and slots according to Eurocode 5.

Geophysical downhole logging analysis within the shallow-depth ICDP STAR drilling project (central Italy)

Abstract. The International Continental Scientific Drilling Program (ICDP) STAR (A Strainmeter Array Along the Alto Tiberina Fault System) drilling project aims to study the seismic and aseismic fault slip behavior of the active low-angle Alto Tiberina normal fault (ATF) in the northern Apennines, central Italy, by drilling and instrumenting six shallow boreholes (maximum depth 160 m) with seismometers and strainmeters. During the STAR fieldwork, a geophysical downhole logging campaign was carried out to define the optimal target depth for instrument deployment and formation rock characterization. In particular, the main objectives of this study were to define in situ physical properties of the rocks and the tectonic discontinuity geometry along the boreholes. The downhole logging data provide new findings and knowledge, especially with regards to physical properties such as resistivity and gamma-ray and wave velocity. The collected parameters were compared to the results of literature data collected in similar lithologies, as well as with the results of logging performed in deeper wells drilled for commercial purposes. The physical properties of the Mesozoic–early Tertiary calcareous formations show low gamma-ray values and high compressional (Vp) and shear wave (Vs) velocities (up to 5.3 and 2.9 km s−1, respectively), whereas the overlying clay-rich Late Tertiary formations exhibit high gamma-ray and low resistivity values as well as relatively low Vp and Vs values (up to 3.5 and 2.0 km s−1, respectively). The results obtained from the analysis of the orientations of the tectonic structures, measured along the six boreholes, show good agreement with the orientations of the present-day extensional stress field, which is NE–SW-oriented. Our study allowed us to bridge the gap between the physical properties obtained from literature data and those obtained from the deep well measurements, representing a possible case history for future projects. These new outcomes represent an almost unexplored window of data and will contribute to the advancement of knowledge of the physical properties of the rocks at shallow depths, which are typically overlooked.