Huaca de la Luna is a monumental earthen complex near Trujillo, Peru built by the Moche civilization from 200 to 850 C.E. Its principal structure, a stepped pyramid constructed with millions of adobe bricks on sloping bedrock and sandy soil, presents severe structural damage at the northwest corner. A sensitivity study of the static and dynamic response of the pyramid is conducted in Abaqus/CAE Explicit using 2D and 3D nonlinear finite element models derived from archaeological, material, and geotechnical data. Concrete damaged plasticity and Mohr-Coulomb formulations are adopted to represent adobe and sandy soil, respectively. Models undergo quasi-static gravitational loading followed by dynamic application of lateral ground accelerations. Lateral capacity is defined as the applied acceleration that produces collapse and is identified from the time-evolution of elastic strain and plastic dissipation energies. Initial 2D sensitivity analysis investigates the effect on lateral capacity of adobe tensile strength, bedrock/soil configuration, west fa & ccedil;ade profile, eastward architecture, and plastic dilation angle. Critical configurations identified from 2D analysis are expanded into 3D models. All results show stability under gravitational load. At dynamically induced failure, damage corresponds closely to the extant collapse of the northwest corner of the pyramid, suggesting that present damage is due to seismic activity.

Investigations of seismic response of underground structures often assume homogeneous or layered homogeneous sites. However, significant spatial variability in soil parameters may lead to vastly different underground structure performance from that obtained for homogeneous sites. Based on random field theory, this study models the spatial variability of the soil elastic modulus, cohesion, and friction angle using the Karhunen-Loe`ve (K-L) expansion method. Target acceleration response spectra are generated according to standards, and the trigonometric series method is employed to create artificial seismic waves of four different intensities. Nonlinear dynamic analyses of underground structures under deterministic and random field conditions are conducted using ABAQUS software. The study comprehensively analyzes the structural damage state, internal forces, interstory displacement, and drift ratio to evaluate the station structure's performance under different seismic intensities. Results show that the spatial variability of soil parameters significantly impacts the dynamic response of underground structures, especially for stronger earthquakes. The variability of soil stiffness and strength parameters leads to greater fluctuations and uncertainties in displacement and internal force responses, exacerbating structural damage. It is recommended that when the peak ground acceleration (PGA) reaches or exceeds 0.5 g, the spatial variability of soil parameters should be incorporated into the analysis to ensure a reliable assessment of the structural seismic performance.

Internal soil erosion in urban environments is a significant factor contributing to the chronic uneven settlement of subway stations. This paper investigates the seismic failure mechanisms of subway stations affected by prior soil internal erosion. Erosion is modeled via a practical approach based on the Cap plasticity model. A 2D finite element model of a two-layer, three-span subway station is developed to simulate its seismic response under various factors, including the seismic incidence angle, soil erosion, and earthquake motions. The vertical load transfer and damage assessment of the vertical elements are thoroughly analyzed across all the scenarios. The results show that after the adverse internal force redistribution caused by soil erosion in the corners of the underlying soil, the subway station experiences a progressive seismic failure process. As the seismic incidence angle increases, the deformation mode of the station shifts from a bilateral shear mode to a unilateral pushover mode, requiring more seismic energy for structural collapse.

Nonlinear dynamic analyses are required to account for the structural performance of mid- to high-rise buildings and complex structures. Generally, time history analyses are carried out considering several ground motions for a certain seismic action. These analyses are often very time-consuming, mainly because of the high resolution of the ground motion signal. Therefore, performing these calculations based on lower resolution accelerograms can be very useful, especially when dealing with large sets of buildings (e.g., seismic vulnerability studies on an urban scale). In this paper, two methods for signal reduction are tested against each other: i) an open-source Fourier-based resampling implementation; and, ii) a simple reduction algorithm that preserves both the highest and lowest peaks of the signal. The experiments compare the two methods at several levels of resolution reduction and for three different accelerograms. The influence of amplitude scaling on important earthquake demand parameters (EDPs), namely, the peak floor displacements and accelerations have been studied for three reinforced concrete case study buildings modelled in OpenSees: low- (5-storey), mid- (8-storey) and high-rise (11-storey). The results allow establishing a set of criteria to choose the appropriate reduction method and level. This depends on the balance desired of computation time versus calculation accuracy. Real accelerograms without baseline corrections have been for the tests. The simple reduction algorithm method appears to capture better the accelerograms by avoiding excessive interpolation. This results in peaks and areas closer to the original signal. However, it presents greater variability in energy preservation, introducing large abrupt changes in acceleration. These large fluctuations have led to inducing significantly larger displacements in OpenSees, causing greater structural damage. The Fourier method led to better and consistent results than the reduction algorithm proposed. Resolution 50 provided a reduction in time of up to 30% and an error margin of the engineering demand parameters of around +/- 15%.

Owing to the repeatedly observed long-duration ground motions (GMs), the duration effect is becoming increasingly critical for the seismic design and assessment of important infrastructures. In this study, dynamic analyses are performed to evaluate the influence of GM duration on the inelastic seismic response of subway stations. Based on the Daikai subway station in Kobe, Japan, a two-dimensional numerical model incorporating a concrete damage plasticity model and a soil nonlinear model is developed. Twenty-five spectrally matched records with different significant durations (D 5-95 ) are selected for dynamic analyses. The responses are evaluated based on various engineering demand parameters (EDPs) including the internal force, drift ratio, element damage index, and the total damage of the structural member. The results show that for weak earthquakes (PGA = 0.15 g) the duration has a negligible influence, while for strong earthquakes (PGA = 0.45 g) the duration effect is particularly pronounced due to the significant cyclic degradation of stiffness and strength of the material. Compared to the location-dependent maximum internal forces and the element damage index, the maximum drift ratio and the total compressive damage index are suitable EDPs, since they correlate well with D 5-95 . On average, for every 10-s increase in D 5-95 of strong GMs used in this study (PGA = 0.45 g), the maximum drift ratio of the side wall and center column increases by 0.12 % and 0.2 % while the total compressive damage index of the side wall and center column increases by 0.01 and 0.04, respectively. The duration effect is more pronounced for the center column implying that damage to the weak structural member is exacerbated by long-duration GMs. The increased column stiffness or elastic soil behavior may reduce the duration effect. This study highlights that strong GMs having similar amplitude and response spectrum with different significant durations can significantly affect the inelastic seismic response of subway stations.

The effects of evolutionary Arias intensity are thoroughly investigated based on ground motion simulation and nonlinear dynamic response. A new methodology is developed to generate a series of spectral-equivalent synthetic motions with different energy accumulation paths using wavelet packets. Systematic studies are performed on dynamic responses of hysteretic systems and liquefiable grounds using the simulated motions and actual recordings. An attempt is made to develop the relationship between liquefaction-induced deformation and shaking intensity rate which is used to quantify the rate of Arias intensity accumulation. The results indicate the need of considering evolutionary Arias intensity in nonlinear dynamic analysis.

Kathmandu, located in a high seismic zone, predominantly features irregular structures among its building stock. These structures are particularly susceptible to severe damage during seismic events, primarily due to torsional effects. Traditional seismic designs rely particularly on fixed -base conditions that underestimate forces and displacement primarily on soft soil conditions leading to irrational design practices. This study aims to quantify the seismic performance of buildings on various base conditions through fully nonlinear Soil -structure Interaction (SSI). The soil nonlinear behaviour was modelled using the Pressure-Independ-Multi-Yield (PIMY) material with an octahedral shear stress -strain backbone curve. Three distinct soil types were considered, and structures with irregular plan configurations were modelled using finite elements in both Opensees and STKO platforms. Structural performance was analyzed through nonlinear dynamic analysis, and outputs were evaluated based on seismic parameters. Comparing nonlinear SSI with linear SSI and fixed -base conditions revealed a significant increase in structural response, expressed in terms of displacement, drift ratio, and base shear. The magnitude of diaphragm rotation was found to be influenced by a combination of building torsional irregularity and SSI effects. It is suggested that the conventional practice of using the torsional irregularity ratio as a measure of torsional irregularity be revised and enhanced to better account for these influences. It has been quantified that torsional irregularity has a relatively lesser impact on displacements, drifts, and base shear compared to SSI. In all cases, fixed -base conditions consistently exhibited the minimum response. The study explored that linear SSI and fixed -base conditions tend to underestimate structural responses, while nonlinear SSI coupled with dynamic analysis provides a more accurate representation of realistic structural behaviour for seismic design particularly in soft soil cases.

This paper presents an experimental and analytical study on a steel slit damper designed as an energy dissipative device for earthquake protection of structures considering soil-structure interaction. The steel slit damper is made of a steel plate with a number of slits cut out of it. The slit damper has an advantage as a seismic energy dissipation device in that the stiffness and the yield force of the damper can be easily controlled by changing the number and size of the vertical strips. Cyclic loading tests of the slit damper are carried out to verify its energy dissipation capability, and an analytical model is developed validated based on the test results. The seismic performance of a case study building is then assessed using nonlinear dynamic analysis with and without soil-structure interaction. The soil-structure system turns out to show larger seismic responses and thus seismic retrofit is required to satisfy a predefined performance limit state. The developed slit dampers are employed as a seismic energy dissipation device for retrofitting the case study structure taking into account the soil-structure interaction. The seismic performance evaluation of the model structure shows that the device works stably and dissipates significant amount of seismic energy during earthquake excitations, and is effective in lowering the seismic response of structures standing on soft soil.