Pipe piles, such as offshore monopiles, may suffer from considerable damage at the pile tip during installation because of contact with an obstacle such as a boulder or a stiff soil layer but also because of amplification of a pre-deformation or pre-dent. This damage is often referred to as pile tip buckling initiation in the former situation and extrusion buckling in the latter. This paper reports on a series of model tests carried out to verify the numerical model and understand pile tip buckling during impact driving in saturated, dense sand. The test program includes three different scenarios: tests with an initial dent at the pile tip, tests with a fixed rigid body and tests with free-moving rigid bodies (boulders) placed at a certain depth in the sand. The results show that the soil stress level strongly influences pile tip buckling. At high soil stress levels, the penetration rate of the pile decreases progressively. Notably, the wall thickness of the pile has a significant effect on the penetration curve in the case of pre-dented piles. The tests with boulders at low soil stress levels show that the buckling behavior is strongly influenced by the shape of the boulder, by the point of initial contact and by the movement of the boulder. Only small deformations can be observed at the pile tip due to the contact with a spherical steel boulder, whereas the test with the imperfectly shaped stone boulder caused considerable damage to the pile under otherwise equal test conditions.

Integral abutment bridges (IABs) provide a viable solution to address durability concerns associated with bearings and expansion joints. Yet, they present challenges in optimizing pile foundation design, particularly concerning horizontal stiffness. While previous studies have focused on the behaviour of various piles supporting IABs in non-liquefied soils under cyclic loading, research on their seismic performance in liquefied soils remains limited. This study addresses the gap by systematically comparing the performance of various pile foundations in liquefied soil, focusing on buckling mechanisms and hinge formation. Using the Pyliq1 material model and zero-length elements in OpenSees, soil liquefaction around the piles was simulated, with numerical results validated against experimental centrifuge tests. The findings indicate that IABs supported by reinforced concrete piles with a 0.8 m diameter (RCC8) experience greater displacement at the abutment top, while alternative piles, such as 0.5 m (RCC5), HP piles with weak and strong axis (HPS and HPW), steel pipes (HSST) and concrete-filled steel tubes (CFST), show pronounced rotational displacement at the abutment bottom. Maximum stress, strain and bending moments occurred at the pile tops and at the interface between liquefied and non-liquefied soil. Notably, CFST piles resisted buckling under seismic excitation, suggesting their superiority for supporting IABs in liquefied soil.

Local buckling of pipeline walls is a common failure mode for buried pipelines crossing reverse faults. The damage evolution of pipelines from initial buckling to severe failure under reverse fault displacement is closely related to soil properties, fault mechanism, and pipeline geometry. The performance-based design methodology proposed by the Pacific Earthquake Engineering Research Center has become well-recognized worldwide. However, current safety-based design codes for buried steel pipelines generally provide operable limits corresponding to the initiation of local buckling of the pipeline walls, and cannot be used to effectively assess the damage states and performance levels of pipelines. To address the local buckling of pipeline walls under fault displacement, a performance criterion is proposed based on the critical compressive strain and the change rate of pipeline compressive strain. Three performance levels corresponding to pipeline wall local buckling are identified, namely, buckling initiation, buckling development, and buckling failure. Moreover, the ductility coefficient that characterizes the nonlinear behavior of the pipeline wall prior to buckling failure is proposed in this study to quantify the damage state threshold values. Three-dimensional finite element models of the largediameter pipeline crossing a reverse fault are developed and validated against the existing experiment study. Parametric analysis is performed to comprehensively assess the effects of pipeline burial depth, fault mechanism, and pipeline geometry on the performance of the buried steel pipeline under reverse fault displacement. Finally, the empirical equation for critical displacements between performance levels under different conditions is developed. The numerical results indicate that as the diameter-to-thickness ratio and burial depth of the pipeline increase, the structure ductility of the pipeline wall prior to buckling failure decreases. The structural ductility of the pipeline wall increases by 94.7 % as the fault dip angle increases from 30 degrees to 90 degrees. Moreover, the structural ductility increases when the internal pressure increases from 0 MPa to 6 MPa, but decreases as the internal pressure changes further from 6 MPa to 12 MPa.

The traditional design criterion for buckling restrained braces (BRB) is established based on the fixed base model, which is appropriate for situations where significant soil-structure interaction (SSI) effects are absent. This paper presents a study considering the SSI effect of the 4, 6, and 8-story BRB structures with split X and Chevron V invert configurations. The study includes fragility seismic analysis, considering the SSI effects on BRB structures at different performance levels, such as immediate occupancy (IO), life safety (LS), and collapse prevention (CP). The nonlinear soil behavior is represented using the Drucker-Prager model, and the soil boundary conditions are determined based on the Leismer theory. The BRB structures are subjected to incremental dynamic analysis (IDA) using 22 far-field ground motions from FEMA P695 to create seismic fragility curves. The study findings indicate a significant rise in axial deformation of BRBs at various performance levels when the SSI effect is present. The increase in axial deformation of BRB has caused earlier damage and failure of this structure. Therefore, it is highly advisable to consider the SSI effects in the analysis and design of buckling restrained braced (BRB) structures with six stories or fewer to ensure the desired structural response during seismic events.

Steel thin-walled tanks have been of particular interest in the tank industry from the past to the present due to their unique features. Settlement is one of the most critical conditions that causes widespread damage in reservoirs, and the reason for that is the large volume of reservoirs, improper design, and poor soil condition. According to API 653, differential settlement is the most important cause of failure among them, and local one of the shell edges is a subset of this type of settlement. On this basis, the main objective of this research endeavor is to investigate the nonlinear response of steel storage tanks with and without a roof under local edge settlement. For this purpose, an experimental and numerical study was conducted to investigate the settlement capacity, nonlinear response, and out-of-plane behavior. In this regard, various regulations, and standards, including API 650, API 653, API 625, EEMUA 159 and PIP STE03020, were examined. The findings revealed that the allowable settlement takes place before the initial buckling and snap-through phenomenon occurs in tanks under local edge settlement.

The Kugino wind farm at Japan was seriously damaged in the severe Kumamoto earthquake, characterizing as all three pile group cracks but only one tower buckling. This study aims to reveal the failure mechanism underlying such damage pattern through the Beam on Nonlinear Winkler Foundation (BNWF) analyses, where the soilfooting interaction is considered with a new q-z model (QzSimple6). It identifies three parameters in a hyperbolic function to match any desired modulus reduction curve, whereas adjusts the unloading-reloading curves iteratively with the Ishihara-Yoshida rule to achieve site-specific soil damping curve. The QzSimple6-based BNWF analyses quantitatively reproduces centrifuge test results of a pile group foundation system, and newly reveals the soil-footing interaction does not influence pile bending moments but reduces the point mass acceleration. A parametric study is conducted on the full BNWF model with identifying pile group supported wind turbine, but with scaling soil stiffness and strength. The thrust force is attracted from the aero-elastic analysis in OpenFAST and the free-filed seismic displacement are calculated with the site response analysis in OpenSees. The simulation shows consistency with site observations that the No.2 wind turbine tower is destined to buckling at the height of around 13.9 m due to the sudden reduction of tower thickness, while No.1 and No.3 towers could remain safe potentially because soil properties under them are softer than that under the No.2 tower. In contrast, all three pile groups are found to be cracked under the Kumamoto earthquake intensity since the pile bending moment relies on the footing rigidity rather than the footing-soil interaction.

Dynamic response of soil-pile system in liquefiable layered sloping ground under the effect of static axial load as well as ground motions simultaneously is an issue of utmost importance. The present study is performed using an advanced nonlinear finite element-based 3D numerical model for filling up this research gap. Two typical soil profiles of Kolkata city such as Normal Kolkata Deposit and River Channel Deposit (RCD) have been chosen for this study. The input motions considered for present analysis are 1940 Imperial Valley and 2001 Bhuj earthquakes. Multi-yield surface plasticity model is adopted to incorporate soil nonlinearity. Fully coupled u-p formulation is used to simulate pore water pressure generation because of soil-fluid interaction. The applicability of the present numerical model is verified using the past experimental works. Then, parametric study has been conducted to evaluate the effect of different vital parameters on dynamic response of soil-pile system. It is observed that the residual soil displacement in RCD soil increases with an increase in ground slopes indicating liquefaction-induced lateral spreading. Parametric studies also showed that the amplification factors of bending moment for sloping ground with respect to level ground due kinematic and combined loading are 3.50, 5.50, 6.75 and 1.09, 1.13, 1.18 for 2.5-, 5.0- and 10.0-degree ground slopes, respectively. The combined peak lateral displacement and bending moment coefficient decrease by 62.60% and 44.20%, respectively, when slenderness ratio decreases from 42 to 21. Also, the peak combined lateral displacement decreases by 48.7% and combined bending moment coefficient increases by 14.3% when soil condition changes from liquefiable state to dry condition. Finally, bending-buckling interaction diagram is presented for safe and economical designing of piles in liquefiable sloping ground under combined loading condition.

Architectural aspects of buildings, such as the shape of the plan, play an important role in defining the seismic behavior of the building and the future damages structural and non-structural elements may go through. Several items, like the aesthetic aspects and limitations in the field under construction, make an irregular plan shape to be selected as a desirable option. Correctly understanding the building's behavior on the irregular plan is necessary in this case. With that being said, this research aims to evaluate the seismic performance of buckling restrained braced frames (BRBFs) steel structures having an L-shaped irregular plan. An irregular L-shaped plan amplifies the torsional response of the building and causes stress concentration because of the re-entrant corners. Since the lack of a comprehensive study on the L-shaped plan irregularity in buildings equipped with BRBs and the effect of Soil-structure interaction (SSI) would be felt, three types of buildings, low-, mid-, and high-rise, were considered to study the demands of this system on an L-shaped plan. SSI effects were also considered by the cone method in the frequency domain for a more accurate evaluation of the building's behavior during an earthquake event. Each building is studied having three different base conditions: 1- fixed base, 2- SSI with soil type C, and 3- SSI with soil type D. Structural demands, including base shear, overturning and torsional moment, lateral displacement, inter-story drift, and column capacity were measured for different models with fixed and flexible bases by performing time history analyses. The results signify the significant SSI's impact on the building's demands.

Large earthquakes in the last 25 years have caused significant damage to buildings and infrastructure, including the partial or total collapse of storage tanks in various industries. Elephant foot buckling, or local buckling at the base, is one of the main failure modes observed in these structures, and this failure mode can lead to their collapse and/or complete loss of contents. Although hydrostatic and hydrodynamic loads typically affect the seismic response of tanks, the effect of soil type on tank buckling behavior has not been widely studied or recognized. This research aims to evaluate the effect of soil type on seismic fragility of tanks by analyzing typical storage tanks used in the wine industry. The work focuses on elephant foot buckling for tanks with both unanchored and anchored bases and compares the influence of three different types of soil and two different tank geometries. The approach uses the capacity spectrum method, as opposed to the more commonly used incremental dynamic analysis, to determine a critical peak ground acceleration to cause buckling at the tank. The tanks were subjected to 21 Chilean seismic records with three different soil types and a no-soil condition. From the results a lognormal fragility curve, and its median and standard deviation, are calculated. The results indicate that unanchored tanks built softer soils exhibit poorer performance, while tanks in competent soils and rock exhibit good performance. Anchored tanks show less sensitivity to soil types than unanchored tanks. The study demonstrates the importance of considering soil-foundation-structure interaction for wine storage tanks, but the results indicate that many comparable storage structures will be similarly affected.

The absence of a defined allowable pile ductility in integral abutment bridges (IABs) creates a critical gap in determining the maximum safe bridge length. This paper introduces a design aid procedure to assist bridge engineers in establishing the length limits of jointless bridges. Numerical and analytical approaches were used in formulating the design aid procedure. A total of 66 finite difference models were established to obtain pile equivalent cantilever length considering various design parameters (soil stiffness, pile size, pile orientation, axial compressive load, and lateral displacement magnitude). The analytical approach incorporates a strain compatibility and equilibrium model to generate moment -curvature diagrams and load -deflection curves for standard HP sections commonly used in IABs construction. The validity of the developed design aid procedure was examined and tested with available experimental and numerical results. Lateral buckling displacement capacity of HP sections ranged from 50 to 100 mm (2 - 4 in.). Based on these displacement capacities, length limits for IABs were established and compared with existing studies. The maximum length limits for steel integral bridges fall within the range of 162 - 320 m (530 - 1050 ft), while concrete integral bridges have limits ranging from 210 to 390 m (680 - 1285 ft). These limits depend on factors such as pile size, soil stiffness, and climate conditions.