Inter-story Drift Research Articles

Experimental and numerical evaluation of seismic behavior of coupled walls connected by post-tensioned, unbonded, precast concrete coupling beams

To investigate the seismic performance of coupled shear walls, which are connected by post-tensioned, unbonded, precast concrete coupling beams (PCCB), two 1/7-scale experiments with 8-story coupled shear walls under cyclic lateral loadings were conducted. Coupling of concrete shear walls is achieved by post-tensioning concrete beams to the wall piers using unbonded post-tensioning tendons (UPT) at the floor and roof levels. Experimental results show that little damage occurs in the coupling beams and the wall regions when the specimen undergoes large nonlinear displacements. The residual displacements of the specimen are small because of the restoring effect of the post-tensioning force. The seismic performance of three systems including CW-RC (coupled wall systems that use traditional RC coupling beams), CW-UP (coupled wall systems which use only post-tensioning tendons without steel reinforcement through the beam-wall joints), and CW-HUP (shear walls and PCCB that use combinations of steel reinforcement and post-tensioning tendons) are evaluated by means of nonlinear dynamic analysis. The calculation results indicate that the inter-story drift and peak lateral displacements of CW-HUP and CW-UP are greater than that of CW-RC, whereas the residual deformations are reduced because of the self-centering effect of the post-tensioning tendons.

Vulnerability assessment of tall isolated steel building under variable earthquake hazard levels using endurance time method

ABSTRACT In this research, the superstructure behavior in isolated structures has been studied based on their ductility. For this purpose, three tall structures isolated by triple friction pendulum isolators (TFPI) have been designed. The ductility of superstructures is different due to their different seismic force-resisting systems. The performance of the structures has been evaluated by endurance time (ET) method. This method significantly reduces nonlinear dynamic analysis time by optimizing the number of desired earthquake records to one to three endurance time excitation functions (ETEFs). Additionally, the seismic response of structures under different earthquake hazard levels can be achieved by this method. Results show that the change in ratio of the isolator period to the superstructure period (TI/TS) can affect floor acceleration, TFPI displacement and interstory drift ratio (IDR). However, TFPI displacement and IDR are also sensitive to the type of superstructure system, whether it is a braced frame or a moment frame. Moreover, there is a possibility of entering the collapse phase of structural components in tall isolated structures with braced or moment frame which are designed by linear static and spectral methods, under an earthquake with a return period equal to the earthquake hazard level considered in the design step.

Study on Seismic Performance of Reinforced Concrete High-Rise Building with Buckling Restrained Braces Dissipation Devices

Performance-based Seismic Engineering is the modem approach to Earthquake Resistant Design to control lateral deflection and inter-story drifts. It is a significant challenge to overcome in the execution of high-rise buildings. Since structures are subjected to lateral loads, the Utilization of dissipation devices such as the bracing, shear wall, and dampers are a possible method to enhance the structural performance of the high-rise building under load cases. These cases are varying to static and dynamic ones as Response Spectrum. Properly designed and detailed structures with dissipation devices have exhibited excellent performance during a severe earthquake. Lateral forces due to will be resisted in its plane. In continuation studies of reinforced concrete structure compared to the absorbing devices, Three essential reinforced concrete buildings were taken for analysis G+ 30 floors to cover the broader spectrum of high-rise building construction. Software ETABS carried out seismic analysis through Response Spectrum Analysis. The result highlights how structural damper systems perform much better than other systems with accuracy and exactness through the parameters of Displacement, Drift, Base shear, and Stiffness. Damper structures are more suitable for high-rise buildings and earthquake zones due to this study's results; maximum height of systems could be possible, which must be economically less expensive than steel structure of the same height.

Comparative analysis of seismic performance enhancement in irregular RC buildings using friction and viscous dampers

The purpose of this study is to demonstrate the impacts of friction dampers (FD) or fluid viscous dampers (FVD) in irregular (in plan and elevation) reinforced concrete (RC) buildings. The buildings (a four-story, a nine-story, and a twenty-story skyscraper) were analyzed using nonlinear dynamic time-history analysis on earthquake-recorded accelerograms, three of which were real while the other four were artificial. For this purpose, 70 nonlinear dynamic analyses were carried out. This paper describes the optimal design of FDs and FVDs, with a focus on minimizing the following parameters: (i) maximum displacement (top of the structures), (ii) building torsion, and (iii) maximum horizontal inter-story drift. Two different placements of the dampers have been studied in each building. The consequences of each strengthening method are shown, and other relevant results were obtained from this creative comparison (optimal design, two passive energy systems, and three different story numbers). The comparable results show that in low-rise structures, FD was more successful than FVD in reducing torsional moment; however, in medium and high-rise buildings, VDF was more effective at improving the seismic performance of the structures.

Investigation of Seismic Response of Irregular Steel Buildings: A Case Study of U-Shaped Structures

Tills paper presents a dynamic analysis focusing on the influence of plan shape on tall steel structures. The study specifically investigates the seismic behavior of two 22-story buildings, one with a square plan and the other adopting a U-shaped configuration. Utilizing OpenSEES platform for nonlinear time history analysis, the research sheds light on the impact of plan irregularities on fundamental time periods, displacements, drift ratios, and base shear. Results reveal that the U-shaped building experiences liiglier dynamic response compared to the square shaped reference building, the U-shaped building experiences liiglier time periods across all modes due to increased mass and irregular stiffness distribution in the building's grid. Top story displacements reveal an increase in maximum displacement by 30% compared to the reference structure, showing a non-linear pattern. Inter-story drift ratios had peaks at the 8th and 18th floors showing increments of 43% and 117%. respectively. The time liistoiy response illustrates a liiglier response over time for the U-shaped building, indicating distinct behavioral differences. Base shear time liistoiy revealed liiglier values for the U-shaped building over time, including a 48% increase in maximum base shear compared to the reference building. These findings reveal the significant effect of plan regularity in tall steel building design on the seismic response and the importance of considering it in building design.

Seismic response prediction using a hybrid unsupervised and supervised machine learning in case of 3D RC frame buildings

The seismic vulnerability assessment represents an important step in monitoring the buildings’ capacity and checking their performance during and after earthquake events. The Nonlinear Time History Analysis (NL-THA) is considered the most reliable method that is used to calculate the exact structural behavior of any building. However, this sophisticated method is known for its complexity, the use of Finite Element (FE) software, and computational time consuming, especially in the case of tall buildings. For that reason, An Artificial Neural network (ANN) is used to develop a new model able to predict the essential Engineering Demand Parameters (EDPs), i.e., the Maximum Base Shear (MBS), the Maximum Inter-story Drift (MIDR) and the Maximum Roof Drift Ratio (RDR). Unsupervised algorithms such as the Principal Component Analysis PCA and the Autoencoder are coupled with the ANN to reduce the dimensionality, improve the dataset quality, and reduce the irrelevant features. More than 192,000 buildings are analyzed using the NL-THA and eighty artificial ground motions (GMs) to generate the dataset. The buildings’ characteristics are generated randomly from the selection range. The results showed that the Autoencoder-ANN model represents the highest performance compared to the PCA-ANN and ANN models. The Autoencoder-ANN model could quickly and accurately predict the seismic responses of unseen ground motions using only the building’s characteristics and the GM parameters without using any FE software.

Post-earthquake fire performance of a steel moment-resisting frame

The effects of earthquakes and fires are typically analyzed separately in structural design. However, historical events highlight that fires following earthquake (FFE) can cause significantly more damage than an earthquake alone. The 1906 San Francisco earthquake exemplifies this, with fires destroying 80% of the city. Other major FFE events include Tokyo (1923), Kobe (1995), and Tohoku (2011) earthquakes. Earthquakes can damage infrastructure, leading to potential ignitions and structural fire performance deterioration. This paper focuses on the post-earthquake fire performance of a four-story five-bay steel frame using a probabilistic FFE framework to develop FFE fragility functions and consider uncertainties in the ground motions, compartmentation measures, fire development, and material properties. Damage to structural and non-structural components is considered. In this respect, the probabilistic FFE framework generates the fire scenarios based on seismic response. The seismic response is assessed through nonlinear time-history analyses. Then, post-earthquake fire ignitions in specific compartments are assessed based on the structural damage, determined by inter-storey drift ratio (IDR) and peak floor acceleration (PFA). Compartmentation and opening characteristics as well as the potential for fire spread are considered based on seismic damage in windows, doors, and partition walls following seismic fragility functions found in the literature. Finally, thermomechanical analyses are performed, and failure criteria based on displacement and displacement rate are applied to the beams and columns. The results of the probabilistic analyses were used to produce fragility functions to evaluate the probability of exceeding a limit state conditioned on an intensity measure in the context of FFE. A higher probability of exceeding the collapse limit state with shorter times to collapse was observed when the structure was subjected to higher values of spectral acceleration.

Prototype silicone rubber based passive seismic damper: Development, characterization and implementation

Passive damping devices are mostly preferred owing to their relatively lower cost, low maintenance, and stability over a wide range of frequencies during seismic events. Currently, these devices with temperature in-sensitive viscoelastic material are being explored. The paper aims to develop a prototype piston-cylinder based passive damper with silicone rubber particles and characterize it with varied amplitude and frequency of sinusoidal input. The device Silicone Rubber Particle Packed Damper, so developed, was then implemented in the benchmark building for seismic response control. Silicone rubber particles with lower hardness were produced through compressed molding technology to improve the damping efficiency of the device. The device was later converted to an Air Damping Device by removing silicone rubber particles for a natural comparison of efficacy. Hysteresis curves of devices, elliptical in shape, obtained through characterization were mathematically modelled using the Kelvin-Voigt model, and parameters were identified using multivariable linear regression to implement them with the benchmark building. Uncontrolled and controlled responses of benchmark building fitted with, both, damping devices were determined under strong motion (El Centro, Hachinohe) and pulse-type (Kobe, Northridge) seismic excitations. Seismic response parameters; peak displacement, peak interstorey drift, peak acceleration, and peak damper force was estimated. Each seismic response parameter yields substantial reduction for controlled benchmark building with Silicone Rubber Particle Packed Damper. The efficacy of damping devices was established by Performance Indices in terms of peak interstorey ratio, level acceleration, base shear, and control force. Though both passive damping devices were found effective in seismic response control of benchmark building, Silicone Rubber Particle Packed Damper outperforms Air Damping Device. The developed prototype damping devices are a low cost and easy to maintain.

Beam-column joint modeling effects on the seismic response of a non-ductile reinforced concrete building

Seismic performance evaluation of existing reinforced concrete buildings requires numerical approaches that reflect the damage modes that may arise from deficiencies in beam-column joints. In this study, the seismic performance of an existing reinforced concrete building with four stories was investigated by applying elastic and deformable beam-column joint models. The deformable beam-column joint model was verified using an exterior non-ductile beam-column joint test. The model included a rotational spring located at the joint with two connected nodes in a zero-length with rigid elements in the vicinity of frame elements. Moment- rotation relationships represent the joint behavior, and they were defined based on shear stresses and strains. After effective modeling of beam-column joints, it was aimed to obtain the cyclic behavior of the building model using non-linear time history analysis. For this purpose, scaled earthquake records were applied to the three-dimensional numerical model, and the results were compared in terms of inter-storey drift ratios, column and beam chord rotations, and base shear. It was determined that the exterior beam-column joints reached their strength and deformation capacity, while the beam and columns remained below their section deformation limits according to the Turkish Earthquake Code.

Damage inference and residual capacity assessment for an E-Defense 2018 ten-story RC test structure

This paper presents an enhanced vision-based, post-earthquake performance assessment framework for RC building structures. This framework incorporates a damage inference method that can estimate the stiffness and strength reduction factors of components in stories without damage inspection based on the inter-story drift. The framework was validated by the application to the full-scale shaking table test of an E-Defense 2018 ten-story RC structure. The vision-based damage detection method effectively detected multicategory seismic damage on the component surfaces, and the damage states estimated by the vision-based method were consistent with the results estimated by the measured plastic hinge rotation. The proposed inter-story drift-based damage inference method reasonably estimated the reduction factors of components in the stories without damage photos. The numerical model updated by the reduction factors of damaged components provided accurate estimates of the fundamental vibrational frequencies after different levels of seismic shaking, and the drift-based inference method significantly improved the results compared with the trivial linear interpolation method. The residual capacity curves provided by pushover analysis of the updated model using the reduction factors as per FEMA 306 & Chiu et al. reasonably captured the hysteretic responses of the structure.

ЭФФЕКТИВНОСТЬ КВАДРАТНОГО АРМИРОВАННОГО ВОЛОКНОМ ЭЛАСТОМЕРНОГО ИЗОЛЯТОРА ДЛЯ ЖЕЛЕЗОБЕТОННОГО ЗДАНИЯ ПРИ ЗЕМЛЯТРЕСЕНИЯХ

Un-bonded fiber reinforced elastomeric isolator (U-FREI) is a relatively new type of multi-layer elastomeric isolator in which fiber layers are used as reinforcement to replace steel sheets in conventional steel reinforced elastomeric isolators. It is installed directly between the substructure and superstructure without any connection at the interfaces. Most of the previous studies on the U-FREIs supported to the base-isolated buildings are masonry or stone structures. In this study, the dynamic responses of a reinforced concrete (RC) building supported on square U-FREIs under the action of recorded real time-history ground motions of earthquakes are investigated by finite element analysis using SAP2000 software. A hypothetical 4-storey reinforced concrete building constructed in Vietnam is selected for the study. Comparison of the dynamic responses of the base-isolated building and corresponding fixed-base building is carried out to evaluate the seismic vulnerability of the base-isolated building under earthquakes. Finite element analysis results show that peak values of floor acceleration and inter-storey drifts at different floor levels, and peak value of base shear of the base-isolated building are lower than those of the corresponding fixed-base building. The U-FREIs are found to be very effective in reducing seismic vulnerability of low and mid-rise RC buildings.

Optimal design of self-centering bi-rocking braced frames using metaheuristic algorithms

Residual drift of structural systems after seismic events can make buildings uninhabitable and may cause their collapse in aftershocks, as seen in the 2023 Turkey-Syria earthquake. Self-centering rocking-core systems can eliminate plastic deformation of structures after earthquakes. In the current study, a bi-rocking steel-braced frame was designed using the modified modal superposition (MMS) method. The optimal location of the secondary joint was found to minimize the base shear, overturning moment, peak floor acceleration and inter-story drift. Damage to non-structural components has been considered. The models included 12-, 18- and 24- story frames that were subjected to far-field (FF), near-field-pulse (NP) and near-field-no-pulse (N) ground motion records. The seismic records were scaled to the maximum credible earthquake level. Nonlinear time-history analyses were performed using OpenSees open-source finite element software. Additionally, post-tensioned cables and energy dissipation fuses as variable parameters were optimized using particle swarm optimization. The performance of seven metaheuristic algorithms was compared and the results showed that placing the secondary joint at the mid-height of the structure reduced all seismic demand. The results also suggest that the story moment and FF records were most sensitive to the location of the secondary joint. It was observed that frames with lower stiffness and yield strength of the damper exhibited better seismic performance. Based on this, corrective percentages have been proposed for the design of the cable and dampers. A self-centering ratio of 1.07 was suggested at the mid-height and 1.19 for the base damper. The colliding bodies optimization algorithm performed best for time-history analysis-based optimization.

Dynamic responses of multi-story structural systems with separated gravity and lateral resisting systems under seismic action considering connection semi-rigidity effects

This paper investigates the dynamic behaviour of an innovative structural system with separated gravity and lateral resisting systems (SGLR system), which is proposed for the prefabricated structures in multi-story buildings by enhancing the standardization of beams, under earthquake excitation. The seismic performance of SGLR system is benchmarked against the conventional rigid frame system (RF system) designed with the same maximum inter-story drift ratios, and the influences of connection semi-rigidity on the dynamic responses of SGLR system are focused on. Numerical models are built using the self-developed fiber beam-column elements for composite frames, beam elements for semi-rigid connections and multi-layer shell elements for shear walls based on a six-story prototype structure. The modal analysis indicates that the natural vibration periods of SGLR system are smaller than those of RF system and the connection semi-rigidity will further significantly decrease the periods for the first three orders. Nonlinear time history analysis is conducted under eight sets of ground motions at two different levels in two horizontal directions. The shear walls in SGLR system bear the majority of seismic action with damage concentrated in the bottom. The connection semi-rigidity will decrease the lateral deformation and increase the involvement of the frame part in the lateral resisting mechanism of SGLR system, which can be more significant when the semi-rigidity is higher. SGLR system exhibits better control of inter-story drift ratios considering connection semi-rigidity in low-rise buildings and higher economic efficiency in mid-rise buildings.

Seismic performance and collapse analysis of RC framed-wall structure excited with Turkey/Syria destructive earthquake

Due to the increasingly serious threat of natural disasters, it is crucial to examine the ability of buildings to withstand such catastrophes. The damaged structures observed in the recent Turkey/Syria destructive earthquake on February 6th, 2023, attracted the attention of experts and stirred controversy regarding the main causes of this extensive damage. Since numerical simulation is widely utilized as a powerful tool to investigate the buildings’ seismic response, an efficient simulation procedure is presented to investigate the structural response and capture the damage induced in RC framed-wall structure excited by the Turkey/Syria earthquake and aims to present valuable remarks to avoid or even mitigate the damage that may occur in future events. Moreover, the ground motion vertical component is typically neglected in structural design/analysis, and the recent seismic codes did not consider it adequately, leading to a lack of general understanding of the structural response and threatening the structures’ safety. However, the results revealed that considering vertical components substantially impacts the structural response where significant amplification is recorded. A comprehensive comparison between the two cases (excitation with HL component and combined HL and VL components), when the building is excited with two records of this event, is presented in terms of displacement time history, inter-story drift, and straining actions. For instance, the amplification index AISR for the shear forces ranges between 13% to 387% and 35% to 47% for the axial compression force at the first record and ranges between 13% to 62% for the shear forces and 12% to 50% for the axial compression force at the second record. Furthermore, the collapse analysis is performed to explore the structural collapse pattern under this earthquake, which affects the adjacent road network resilience and evacuation plans. This study is crucial for implementing effective risk mitigation measures, enhancing the buildings’ resilience, and is of great importance for the performance-based design concept since damage anticipation and domination are the main objectives of this design concept.

Enhancing Seismic Performance of Multi-story Steel Buildings Using Inner Mega Braced Frames

damage to buildings. In this study, a multi-story steel building is designed using the ETABS v16 software under vertical loads only. Subsequently, seismic performance was enhanced by employing five different Mega braced frames (MBFs) systems in two cases: in the first case, the five bracing systems are placed within a frame located 6 meters away from the outer frame, while in the second case; the bracing systems were placed within a frame located 12 meters away from the outer frame. The building was then analyzed using nonlinear time history analysis with SAP 2000 V20 software, utilizing seismic data from the El-Centro earthquake available in SAP 2000 V20. The results were compared based on various parameters such as maximum roof displacement, maximum inter-story drift ratio, and maximum base shear. The findings demonstrated an improvement in the building's response, in the first case maximum roof displacement reduction ranging from 36.08% to 48.29% in both directions, and from 36% to 44% for maximum roof displacement in the second case. Maximum inter story- drift ratio also reduced by percentages ranging from 25% to 46% in the first case and 25% to 39% in the second case. From the analysis results, it is evident that the best pattern in the first case is pattern5, while in the second case pattern4 is the best.

Mechanical performance study of coupled partially encased composite shear walls with double replaceable fuse components

The partially encased composite (PEC) shear wall is a promising resistance structure. To focus structural post-earthquake damage on replaceable components and facilitate convenient repair after an earthquake, this paper introduces replaceable footings and replaceable coupling beams into the coupled PEC shear wall, forming a double replaceable component coupled PEC (RCPEC) shear wall. The design methodology for the replaceable components is presented, emphasizing theoretical analysis to control the bearing capacity and ensure equal stiffness after replacement. The validity of the coupled PEC (CPEC) shear wall is verified through ABAQUS. Additionally, based on the coupling ratio (CR) theory, three six-story CPEC shear walls and three six-story RCPEC shear walls are designed for pushover analysis. This paper investigates the influence of the coupling ratio and replaceable components on mechanical and seismic performance. Furthermore, the post-earthquake rehabilitation of CPEC and RCPEC shear walls is evaluated, specifying the evaluation method. Based on research results, the installation of replaceable coupling beams and replaceable wall footings effectively controls damage, with the RCPEC shear walls exhibiting earlier coupling beam yielding compared to wall limb yielding. As the CR increases, the inter-story drift ratio of all shear walls gradually decreases. To ensure satisfactory structural post-earthquake recovery performance, the CR for CPEC shear walls to be 0.35, and for RCPEC shear walls to be within the range of 0.35 to 0.45 are recommended.

Seismic performance evaluation of reinforced concrete hilly buildings under sequence of earthquakes

SummaryThe present study investigates the effect of earthquake sequences on the response of reinforced concrete hilly buildings having typical configurations, that is, stepback and split‐foundation, with three different story ratios. A set of 30 as‐recorded mainshock‐aftershock sequence of earthquake ground motions is considered for this study. Mainshock acceleration time histories are scaled at two distinct intensity levels to obtain the mainshock‐damaged building. These mainshock‐damaged hilly buildings are then subjected to aftershocks. A comparative study is performed for various response quantities, such as peak interstory drift ratio, peak floor acceleration, and peak roof displacement of undamaged and mainshock‐damaged buildings under aftershocks. Further, fragility analysis is carried out to study the effect of aftershocks on undamaged and mainshock‐damaged hilly buildings. Subsequently, component‐wise seismic loss estimation due to damage in the non‐structural and structural components is performed. It is concluded from the study that the building components that contribute maximum to the expected repair cost ratio vary with respect to the intensity of the aftershocks. Also, the estimated seismic loss is higher in mainshock‐damaged split‐foundation buildings in comparison to stepback buildings.

Experimental study on seismic performance of internal cruciform joints of grouting sleeve connection for modular integrated construction

Modular integrated construction (MiC) adopts room units that integrate maintenance structure, decoration and equipment pipelines in the factory-made modules, resulting in a lack of operating space for connecting modules at the construction site. In the previous research, the joints between modules are usually hinged or semi-rigid connections and partial strength joints. In this paper, a new type of joint with the grouting sleeve connection is proposed to connect modules horizontally and vertically, which is more convenient for construction and does not conflict with interior decoration. Six full-scale cruciform joints were tested to study the effect of axial compression ratio and different structural details. The test results presented the failure mode, stiffness, ductility, and energy dissipation of the specimens. The ultimate inter-story drift ratio is between 4.78 % rad and 5.96 % rad, which is larger than the requirement of 4 % rad in the special moment frame (SMF) system. The horizontal connection plate between modules can cooperate the deformation of left and right beams and columns, and significantly improve the lateral resistance of the joint. The vertical connection between modules did not slip or open and the grouting material is not broken. The inner and outer reinforced plates in the beam-to-column connection can transfer the tensile force of the beam flange well so the outer sleeve does not tear, and the wedge-shaped stiffener can inhibit the cracking of the beam-to-column connection. EC3 Part 1–8 was adopted to evaluate the stiffness characteristic of the proposed connection, indicating that the proposed joint can be classified as rigid joint for the non-sway frame. Finally, the theoretical ultimate resistance of the joint under the ideal failure mode is obtained, which is lower than the test results, indicating that the plastic development of the joint is sufficient and can be classified as full-strength joint.

Evaluation of Soil Structure Interaction Effects on Seismic Response of RC Framed Buildings Using Simplified Method

In the current practice for the design of the building structure is done by considering the footing as fixed based. The mid-rise buildings having variation in storey height from 3- to 10-storey were selected for the research. In this research, analysis was done to study into the interaction between the seismic response of RC-framed buildings and the soil-structure for various soil types. To study the linear responses of the structures, the model was developed in FEM software SAP2000. The underneath soil was modelled by using direct method, where the soil is considered as solid element. The considered depth of soil was considered 30 m and the viscous spring dashpot were applied to avoid the reflection of seismic waves in soil medium along the effective horizontal soil boundaries. The seismic response variables such as maximum lateral deflection, inter-storey drift and fundamental time periods have been studied. SSI amplified the lateral deflection, inter-storey drift and time period of structure shifting the performance level from life safety to near collapse level. Fundamental time period of the first mode was increased by 23 % for very soft soil. The maximum lateral deflection of 10-storey building for very soft soil was amplified up to 282 % for Kobe and the performance level was shifted from life safety (1.5 %) to collapse level for all the considered model for soil type D . The performance level of structure was checked against the different soil types on varying storey height and finally a simplified method has been proposed to incorporate the effects of SSI in fixed base structures.

Deformation behavior of rectangular underground structures in liquefiable deposits correlated to ground motion intensity measures

Rectangular underground structures in liquefiable deposits are susceptible to larger deformation during earthquake events. The intensity of earthquake motions, as one of the critical factors that would induce large deformation of underground structures in liquefiable deposits, however, was not received enough recognitions. In this paper, nonlinear dynamic analyses with a probabilistic seismic demand model (PSDM) were conducted for a two-dimensional liquefied soil-structure system, considering a variable thickness of liquefiable layer below the structure. The nonlinear soil behavior was simulated by the nonlinear constitutive model PDMY02. The constitutive parameters of saturated sand were calibrated by a slope model in the centrifuge test from LEAP-2017. Interstory drift ratio (IDR) and uplift ratio (UR) of underground structures were selected as engineering demand parameters (EDP). There were totally 18 recorded earthquake motions and 8 intensity measures (IMs) included for the PSDM. Numerical results show that the uplift behavior of underground structures is more sensitive to the variable thickness of liquefiable deposits compared to the horizontal drift of the structure. According to the performance of correlation, efficiency, practicality and proficiency, the velocity-related IMs are more appropriate than the acceleration-related IMs for the evaluation of seismic deformation behavior of underground structures. The deformation response as well as the adaptability of velocity-related IMs are further discussed and evaluated by considering more general cases including different buried depths and height-width ratios for rectangular underground structures.