Andreas Stavridis

University at Buffalo, The State University of New York | SUNY Buffalo · Department of Civil, Structural and Environmental Engineering

The evaluation of the seismic performance of masonry-infilled reinforced concrete (RC) frames has been a major challenge for structural engineers. This paper addresses pertinent issues on the development and calibration of nonlinear finite-element models for assessing the seismic performance of these structures. The modeling scheme considered here...

This paper presents the shake-table tests of a 2/3-scale, three-story, two-bay, reinforced concrete frame infilled with unreinforced masonry walls. The specimen is representative of the construction practice in California in the 1920s. The reinforced concrete frame had nonductile reinforcement details and it was infilled with solid masonry walls in...

An analytical and experimental study has been conducted to evaluate the seismic performance of a three-story suspended zipper steel frame. The frame was concentrically braced and had zipper struts to transfer the unbalanced forces induced on the beams due to the buckling of the lower-story braces. The experimental study was conducted with the hybri...

This paper introduces a finite element scheme and a systematic calibration approach for masonry infilled RC frames. The modeling scheme combines the smeared crack approach with discrete crack elements to allow for the opening of diffused flexural and dominant shear cracks. It is, therefore, able to capture the nonlinear material behavior and the in...

The performance of a recently proposed innovative retrofit scheme for existing non-ductile RC frames infilled with both newly constructed and existing masonry infill walls is examined here experimentally. The scheme aims at preventing the shear-dominated brittle failure by introducing horizontal sliding joints, which divide the infill into subpanel...

This paper discusses the development and implementation of a cyclic material law for a cohesive interface element. The element is used in numerical simulation of the experimental behavior of four recently tested RC frames with infills with different configurations of sliding subpanels. The numerical models combine the smeared-and discrete crack app...

This study uses a statistical surrogate model to develop fragility curves for an infilled reinforced concrete frame building, considering uncertainties related to the material properties as well as the ground motions. The focal point of this study is a school building in Nepal damaged during the 2015 Gorkha earthquake. The school was instrumented,...

This paper discusses the numerical simulation of the seismic response of two adjacent high-rise buildings which developed considerably different damage patterns during the 2015 Gorkha earthquake in Nepal. During a reconnaissance trip following the earthquake, the two buildings were instrumented, and their ambient vibrations were recorded. In this s...

The accurate estimation of the pullout capacity of adhesive anchor is critical for the seismic retrofit of unreinforced masonry (URM) structures. However, there is a lack of publicly available test data on the performance of these anchors, while a number of factors can influence this performance. This paper presents the results of an extensive expe...

This paper discusses a series of experiments on walls of light wood frame with anchored brick veneers carried out at the University at Buffalo. Eight full-scale specimens were designed and constructed following current design requirements in the United States. Six walls with anchored brick veneer and two bare wood frames were tested quasi-staticall...

This study uses a statistical surrogate model to develop fragility curves for an infilled reinforced concrete frame building, considering uncertainties in both material properties and ground motion parameters. The focal point of this study is a school building in Nepal damaged during the 2015 Gorkha earthquake. The school was instrumented, and its...

Structural Health Monitoring (SHM) enables the rapid assessment of structural integrity in the immediate aftermath of strong ground motions. Data-driven techniques, often relying on damage-sensitive features (DSFs) derived from vibration monitoring, may be deployed to attribute a specific damage class to a structure. In practical applications, indi...

Due to the lack of instruments in Nepal, there is a lack of data on the intensity of the seismic motion during the 2015 Gorkha earthquake around the country. This study addresses this gap and develops intensity maps utilizing damage assessment reports submitted by local engineers, combined with finite element analyses. A recently proposed strut mod...

After a brief overview of how the dimensionless resilience index has been calculated in the past for buildings, and some of the shortcomings of that approach, the use of a resilience deficit index is advocated to overcome some of these shortcomings. An example is provided and the pros and cons of each approach are discussed, with broad recommendati...

This study proposes a novel approach for the computationally efficient numerical modeling of the nonlinear seismic response of entire buildings with infilled RC frames. The proposed modeling framework can be particularly helpful for buildings with multiple stories and complex layouts, for which the current methods can be cumbersome to implement, or...

This paper focuses on the large-scale experimental investigation of a novel, highly efficient, low-cost and easily constructible seismic isolation system, defined as PVC-Rollers Sandwich (PVC-RS) seismic isolation. The proposed system is based on the placement of spherical roller bearings between two PVC surfaces in a sandwich configuration. This c...

This study presents a large-scale shaking table investigation aimed at the development of a dual, low-cost hybrid design approach for the reduction of seismic damage in developing countries. The introduction of a novel seismic isolation strategy, defined as 'PVC sand-wich' seismic isolation lies in the core of the proposed hybrid approach. The latt...

This paper presents a damage identification and performance assessment study of a four-story masonry-infilled reinforced concrete building in Sankhu, Nepal, using ambient vibration and point cloud data measurements. The building was severely damaged during the 2015 Gorkha earthquake. A set of accelerometers was used to record the ambient response o...

Rail breaks frequently cause service interruptions and are a leading cause of train derailments. In this study a new method for predicting the arrival rate of rail breaks is developed. The proposed model incorporates Finite Element Modeling, into an Approximate Bayesian Computation (ABC) framework to predict the arrival rate of rail breaks in a US...

After the 2017 Puebla-Morelos earthquake, the Applied Technology Council (ATC) funded a mission to Mexico City to collect structural, geotechnical, seismological, and damage information on concrete structures. The collected data set includes 70 reinforced concrete buildings and contains photos, design drawings, ground motion records, ambient vibrat...

This paper presents a study on a retrofit technique for masonry infilled reinforced concrete (RC) frames. The proposed retrofit technique involves the addition of reinforcing steel bars into epoxy-filled pre-cut grooves on the surface of infill walls. The feasibility of the developed technique is initially investigated experimentally through pull-o...

This article presents the Applied Technology Council (ATC) team’s observations following the 2017 M w 7.1 Puebla–Morelos, Mexico earthquake. The team was deployed in Mexico City to collect seismological, geotechnical, structural, and overall performance information. The focus was on non-ductile concrete structures, to support implementation of rece...

This paper discusses the application of a novel framework for the simulation of the seismic response of a school building in Sankhu, Nepal, which was damaged by the 2015 Gorkha earthquake. This framework uses a recently proposed methodology to estimate the backbone curve for every bay of the building. It then combines these curves to obtain the for...

Over 2000 buildings were surveyed by members of the Colegio de Ingenieros (CICM) and Sociedad Mexicana de Ingenieria Estructural (SMIE) in Mexico City following the Puebla-Morelos Earthquake of 2017. This inventory of surveyed buildings included nearly 40 collapses and over 600 buildings deemed to have structural damage. Correlation of damage with...

This study presents a large-scale experimental investigation on the seismic performance of an innovative, low-cost seismic isolation system for developing countries. It is based on the beneficial effect of the encapsulation of sand grains between two PVC surfaces on the initiation of sliding and the dissipation of seismic energy between the surface...

This paper discusses the dynamic tests of a two‐story infilled reinforced concrete (RC) frame building using an eccentric‐mass shaker. The building, located in El Centro, CA, was substantially damaged prior to the tests due to the seismic activity in the area. During the testing sequence, five infill walls were removed to introduce additional damag...

This study focuses on the development of a statistical model for buildings with infilled reinforced concrete frames. The cornerstone of this study is the nonlinear numerical model of a school building in Nepal. The model is developed based on the ASCE 14-17 guidelines, and it is extensively validated with field data. Then, it is used in a series of...

Calibrated linear equivalent models of civil structures are often used for response prediction and performance assessment. However, these models are only valid for a narrow range of excitation level for which these models are calibrated. In this paper a hierarchical Bayesian model updating approach is proposed for model calibration and response pre...

This paper proposes a computationally efficient approach to simulate the seismic behavior of masonry-infilled reinforced concrete frames. The proposed framework utilizes frame elements to represent the reinforced concrete members and diagonal struts to simulate the effect of the masonry panels. The struts are systematically calibrated once the back...

This paper proposes a novel material law to simulate the hysteretic behavior of masonry-infilled RC frames. The proposed law utilizes a recently proposed methodology that estimates the backbone curve describing the lateral force-vs.-displacement behavior of an infilled RC frame. Developed based on an extensive study of experimental data, the rule c...

This paper proposes a novel approach for the efficient simulation of the nonlinear performance of buildings with infilled RC frames under seismic loads. The proposed modeling framework can be particularly helpful for actual buildings with multiple stories and bays, for which the current methods can be cumbersome to implement, or inaccurate. This fr...

The interaction between RC frames and masonry infill walls can lead to catastrophic failures as demonstrated by field evidence and research studies. The performance of a recently proposed innovative retrofit scheme for such structures is examined here experimentally. The scheme aims at preventing the shear-dominated brittle failure by introducing h...

This paper proposes a computationally efficient approach to simulate the seismic performance of masonry-infilled reinforced concrete (RC) frames. The proposed framework utilizes diagonal struts to simulate the effect of the masonry panels. The struts are calibrated once the anticipated failure mechanism has been identified and the backbone curve ha...

This paper presents a study conducted to evaluate a recently proposed analytical framework for the prediction of the seismic resistance of infilled RC frames under in-plane lateral loads. The methodology, which has been adopted by ASCE 41-17, initially identifies the anticipated failure mechanism of the infilled frame based on the relative strength...

This study discusses the model updating performed on a two-story reinforced-concrete masonry-infilled building using the dynamic response obtained during ambient vibration measurements. Five infills were demolished at four stages creating four damage states. The numerical model of the building is developed based on the obtained material properties...

Tunnel fires are low-probability high-consequence events that could lead to loss of lives, property damage, and long service disruptions. The rapid rise of gas temperature in excess of 1000 °C within the confined tunnel space can affect the structural integrity of the tunnel. Although tunnel fires may not necessarily cause collapse, significant str...

Caribbean-style hybrid concrete-masonry structures consist of a RC frame infilled with partially grouted and reinforced masonry walls that are connected to the RC frame with cast-in-place dowels along one or more edges of the infill. Currently, there is little guidance in existing codes for the assessment of infills with such connections to the bou...

Following the April 25, 2015 M7.8 Gorkha Nepal earthquake and subsequent aftershocks, field surveys were conducted on medium-to-high rise reinforced concrete (RC) frame buildings with masonry infill located in Kathmandu. Rapid visual assessment, ambient vibration testing, and ground based lidar (GBL) show that these buildings exhibited damage level...

This paper documents and analyzes the seismic behavior of unreinforced masonry (URM) buildings that were damaged by the 2015 Gorkha earthquake in Nepal, and reports on the performance of palaces, giving an overview on the failures suffered by significant examples of these monumental buildings. Field reconnaissance was completed through both rapid,...

This article investigates the performance of finite element model updating to identify the induced damage in a two-story reinforced concrete masonry-infilled building using vibration data as well as lidar (light detection and ranging) scans. The building, located in El Centro, California, was severely damaged due to the 2010 El Mayor–Cucapah (Baja...

This paper proposes a simplified approach to analyze the seismic performance of masonry infills with sliding joints in moment resisting frame structures. The proposed methodology uses the equivalent strut approach, calibrated on the results of a novel analytical formulation, which considers basic geometrical and mechanical properties of the infill....

The 2015 Nepal Earthquake (also known as the Gorkha earthquake), occurred on April 25, 2015, with Mw = 7.8 and a maximum Mercalli Intensity of IX (Violent). Its epicenter was near the village of Barpak, Gorkha district, and its hypocenter was at a shallow depth of approximately 15 km (9.3 mi). This earthquake and the many aftershocks that followed...

This paper discusses the development and validation of the simplified analytical framework for the seismic assessment of infilled RC frames which will be included in ASCE 41-17. The proposed methodology is based on an extensive parametric study using a detailed finite element model. The methodology initially classifies the infilled frames based on...

This paper discusses the development and validation of the simplified analytical framework for the seismic assessment of infilled RC frames which will be included in ASCE 41-17. The proposed methodology is based on an extensive parametric study using a detailed finite element model. The methodology initially classifies the infilled frames based on...

This paper discusses the dynamic tests, system identification, and modeling of a 10-story reinforced concrete building. Six infill walls were demolished in 3 stages during the tests to introduce damage. In each damage stage, dynamic tests were conducted by using an eccentric-mass shaker. Accelerometers were installed to record the torsional and tra...

In this study the modal parameters of a ten-story reinforced concrete (RC) building are estimated from recordings of free, ambient, and forced vibrations, using the eigensystem realization algorithm (ERA), the natural excitation technique combined with the eigensystem realization algorithm (NExT-ERA), and peak-picking method, respectively. The stru...

Few studies have been conducted to assess post-earthquake performance of structures using vibration measurements. This paper presents system identification and finite element modeling of an 18-story apartment building that was damaged during the 2015 Gorkha earthquake in Nepal. In July 2016, a few months after the earthquake, the authors visited th...

n this paper, a finite element model of a school building is calibrated in its linear range using the identified modal parameters from recordings of its ambient vibration. The structure, located in Sankhu, Nepal, is a four-story masonry-infilled reinforced concrete frame which experienced severe damage during the Gorkha earthquake on April 25th, 20...

This paper presents a numerical study on the seismic performance of reinforced concrete (RC) frames with masonry infill walls. The study is based on extensive parametric analyses using a detailed finite element model validated with laboratory tests. The model combines the discrete and smeared crack modeling approaches and can capture the diffused f...

This paper discusses the simulation of the structural performance of a four-story school building in Sankhu, Nepal after the 2015 Gorkha Earthquake. The structure had a masonry-infilled reinforced concrete frame, which was severely damaged during the earthquake. The concentration of damage in the south end of the ground story indicates that the fra...

A number of construction techniques have been proposed to improve the seismic performance of infilled RC frames by increasing the strength and stiffness of the infill and/or the frame. The increase of the seismic capacity of infilled frames with these techniques can improve substantially their seismic performance as long as the demand does not exce...

This paper discusses the dynamic tests of a two-story masonry-infilled RC building. The building was damaged by earthquakes prior to the tests and additional damage was introduced during the testing sequence by demolishing perimeter infill walls in three stages. Dynamic tests were conducted in each damage state using a strong eccentric-mass shaker....

This paper discusses the dynamic testing, system identification, and modeling of a 10-story reinforced concrete building. During the testing sequence, six infill walls were removed in three stages to introduce damage. In each stage, dynamic tests were conducted using an eccentric-mass shaker. The torsional and translational response of the building...

Recent earthquakes have shown that unreinforced masonry structures are vulnerable to lateral loads and can suffer significant damage under seismic forces. Among the methods proposed to retrofit these structures is the application of polymers with fiber reinforcement. The effectiveness of a number of configurations has been investigated in experimen...

Masonry-infilled RC frames can sustain significant damage in the event of strong ground shaking. The introduction of sliding joints in masonry infills can reduce the infill-frame interaction, ensure the infill out-of-plane stability, and minimize the infill damage under both in- and out-of-plane loading as shown by previous experimental and analyti...

This paper presents the shake-table tests of a full-scale, two-story, reinforced masonry shear-wall structure designed by a displacement-based method. The test structure had two T-sectioned and one rectangular-sectioned wall components along the direction of the table motion, and four rectangular-sectioned wall components in the orthogonal directio...

This paper presents the shake-table tests of a full-scale, 3-story, reinforced concrete masonry structure. The structure was a special reinforced masonry shear wall system designed according to current code provisions for an area of high seismicity. It consisted of three lines of walls arranged in an H-shape in plan view, with one lineal and two T-...

Failures of unreinforced masonry infill walls commonly occur during seismic events. One method of preventing such failures is the use of externally applied mesh reinforced mortar (MRM). This paper presents a FE modeling scheme combining smeared crack and interface elements to simulate the seismic response of RC frames with hollow clay tile (HCT) in...