Collapse performance of two existing buildings was investigated through experimental testing and computational simulations. Each building was tested in the field by physically removing four first-story perimeter columns from each building prior to building's scheduled demolition. Linear static and nonlinear dynamic analyses were performed using two- and three-dimensional building frame models. Experimental data from the field tests of two buildings were used to compare and verify the computational analyses. The measured strain data compared relatively well with the analysis results. In particular, 3-D model was more accurate than the 2-D model. The strain values calculated from the nonlinear dynamic analysis were smaller than those from the linear static analysis, and were closer to the measured strains. Also, linear static analysis resulted in larger remandto- capacity ratios (DCR) and vertical displacements than nonlinear dynamic analysis for both 2-D and 3-D models.
This study investigates the structural performance of industrial buildings following the February 6, 2023, earthquakes in Kahramanmaras, Turkey, focusing mainly on industrial zones. Causes of damage and damage levels were evaluated for 389 industrial structures, including precast concrete and steel structures. This research demonstrates the need for improved construction practices, advanced seismic design, and quality control. Commonly observed structural damage is highlighted. Identifying the critical common structural damage types is essential to developing effective mitigation strategies and enhancing earthquake resilience. It is concluded that advanced seismic design practices can significantly improve the overall structural performance, resilience, and functional recovery.
In this research work, five different types of post-consumer plastics were mechanically ground into fine aggregate, and each type was used to prepare 2 in. (50 mm) mortar cubes by partial volumetric replacement of the sand. The purpose is to evaluate the effect of the plastic type and its shape on the density and the compressive strength of concrete. The plastic products used in this study are usually not collected by curbside recycling facilities and are discarded in landfills or incinerated. The different types of plastics investigated were Polyethylene terephthalate (PET), High-Density Polyethylene (HDPE), Polypropylene (PP), Polystyrene (PS), and Acrylonitrile Butadiene Styrene (ABS). A total of 180 cubes with 5%, 10%, and 15% replacement were prepared and tested for their densities at the age of 28 days and their compressive strengths at the ages of 7 and 28 days. This work concluded by proposing general equations to predict the reduction in the density and compressive strength of the mortar with the increment in the plastic replacement.
Development and evaluation of seismic fragility of structures and components is crucial in seismic probabilistic risk assessment of nuclear power plants. Simulation-based fragility approaches are a prevailing trend in the literature, while industry-recommended methodologies rely heavily on engineering judgment and deterministic analysis. In this paper, four critical components are selected, modeled and analyzed as a case study. Their fragilities are evaluated using both state-of-the-art fragility methods and code-recommended methods with approximate models. The impact of the choice of fragility approaches on the fragilities of the components and conditional core damage probability of the plant are assessed. The findings reveal that the recommended approaches employed with approximate models have limitations in estimating the median capacity of complex equipment. While there is a notable variance in the treatment of uncertainty among fragility approaches, its influence on core damage probability remains limited unless the component is the primary contributor to core damage.
Load-rating factors are used to evaluate the service life or safety of culverts based on the culvert wall strength and soil cover depth over the culvert. Current culvert load-rating methods have deficiencies in identifying potential critical conditions of corrugated metal culverts. Current load-rating procedures do not provide explicit guidance to the engineer for load rating and evaluation of culvert condition. To ensure good performance over the design life, corrugated metal culverts must be designed and regularly evaluated using an effective load-rating method. The main objective of this study was to investigate the effectiveness of current load-rating procedures. Recommendations are made to improve the analysis and evaluation procedures for corrugated metal culverts. The proposed load-rating procedure is based on an extensive review of load-rating procedures and design practices, experimental data, and theoretical investigations. The proposed method does not include a rating factor for cover depth. However, the design cover depth is required to be checked during the initial design stage to ensure structural stability. New capacity reduction factors are introduced for culvert wall and seam, which require different appraisals for wall and seam during annual inspections. The effect of external live loads is not included in the proposed load-rating procedure for deep culverts and for culverts subjected to low live load stresses. Field data from 39 in-service culverts showed that the proposed load-rating procedure is effective in evaluation of the existing condition of culverts.
Six reinforced concrete beam-column joint specimens were constructed and tested under reverse cyclic loading to failure. The six specimens were divided into three groups, each group representing a different joint design. The main objectives of this study are to investigate the response of joints with three different design, reinforcement detailing and beam strengths, and to evaluate and compare the responses of beam-column joints reinforced with traditional steel rebar and a recently proposed steel reinforcement called prefabricated cage system (PCS). Each of the three test specimen designs included equivalent amount of steel reinforcement and had virtually identical details. The results of the research show that the PCS reinforced joints had a slightly higher strength and significantly larger deformation capacity than the equivalent rebar reinforced joints.
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This paper numerically investigates the influence of masonry infill walls on collapse mechanisms of steel frames under fire scenarios. Three six-story by five-bay steel frames were designed in this study. One of these frames had no infill walls, another one had horizontal infill walls, and the last one had vertical infill walls. Load redistribution and fire resistance were investigated under edge bay fire scenario and central bay fire scenario. The numerical results indicated that masonry infill walls provide alternate load paths in fire conditions, causing significantly large variations of axial forces in surrounding columns. Furthermore, the lateral resistance of the infilled frames is provided by the integral loading resisting system under edge bay fire scenario. The infill walls decrease the buckling temperature and increase the collapse temperature of the heated columns. A series of parametric analyses were performed to investigate the factors influencing the fire resistance of the steel frames. Finally, a preliminary design method was proposed with an aim to prevent the collapse of steel frames with infill walls under fire scenarios.
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The main objective of this study was to evaluate and improve the Ohio Department of Transportation's (ODOT's) current load rating procedures for corrugated metal culverts. This objective is achieved by testing 39 in-service culverts under static and dynamic loads, by evaluating the response of test culverts using available theoretical methods and numerical simulations, and by evaluating and advancing the current analysis tools and load rating methods based on the analytical and experimental evidence generated in this research. The experimental program was conducted to investigate the influence of several parameters on the field performance of culverts in Ohio. These parameters include backfill height, various static and dynamic load applications, and existing condition, size, shape, and other properties of corrugated metal culverts. Experimental results show that culvert deflections decrease nonlinearly with increasing backfill height. Deflections and strains were nearly zero in deep culverts with backfill height larger than 13 ft (4 m). Under static and dynamic truck loading, culvert deflections and strains increased significantly when the backfill height was less than about 6.5 ft (2.0 m). Responses of some of the test culverts were simulated using the two-dimensional finite element program CANDE. Deflections predicted from CANDE analysis were larger than deflections measured in the field. However, the moments and thrusts calculated from experimental strains were similar to those calculated using theoretical methods and CANDE. Experimental data and available theoretical studies were used to evaluate the current load rating methods. Recommendations are made to improve the analysis and evaluation procedures for corrugated metal culverts. Recommendations are based on an extensive review of load rating procedures and design practices, experimental data from 39 test culverts, and theoretical and numerical investigations. The recommended load rating procedures do not consider the effect of cover depth. New capacity reduction factors are introduced for culvert wall and seam, which require different appraisals for wall and seam during annual inspections. The authors recommend changes to rating factors for deep culverts and culverts subjected to low live load stresses.
Earthquakes and laboratory experience show that columns with inadequate transverse reinforcement are vulnerable to damage including shear and axial load failure. To study this behavior, four full-scale columns with light transverse reinforcement were tested quasistatically under unidirectional lateral load with either constant or varying axial loads. Test results show that responses of columns with nominally identical properties vary considerably with magnitude and history of axial and lateral loads. Observed behavior is compared with expected behavior based on available analytical models. The FEMA 356 assessment model predicted the column strengths well, but underestimated the displacements.
A new steel reinforcement system is introduced to be used in concrete columns. This new reinforcement, named Prefabricated Cage System (PCS), is an alternative to the rebar cage used in traditional reinforced concrete for faster, easier, and more reliable construction. PCS reinforcement is prefabricated off-site and then placed inside the formwork eliminating the time-consuming and costly labor associated with cutting, bending, and tying steel bars in traditional rebar construction. The axial strength, confinement, and displacement capacity of 15 small-scale column specimens reinforced with PCS and conventional rebar are experimentally investigated. The behavior of PCS specimens is evaluated and compared with that of similar rebar reinforced concrete columns. The effect of several parameters, such as steel tube thickness, opening dimensions, number and spacing of longitudinal and transverse steel, on the strength and displacement capacity is also investigated. Test results have shown that the axial load carrying capacity of specimens reinforced with PCS was similar to or better than that of reinforced concrete specimens. Axial load–displacement relations for the test columns are also predicted and compared with the measured response.
Steel buildings are generally susceptible to the risk of progressive collapse in case one or a few load-carrying members are lost in an extreme event such as blast, impact, or fire. Thus, to avoid the catastrophic collapse of steel structures, it is imperative to investigate and learn from the performance of existing steel buildings for progressive collapse potential. The Ohio Union building, a multi-story steel-framed building that existed on the campus of Ohio State University, was tested earlier before its demolition by one of the co-authors for progressive collapse assessment under the successive removal of four columns located at the first-story level. The aim of this study is to conduct NLD (nonlinear dynamic) analysis for the building considering buckling of columns to numerically assess its potential for progressive collapse and then compare it with test observations. The calibrated finite element (FE) model was then extended to incorporate more hypothetical sequential and simultaneous column-loss scenarios. As one of the most widely accepted documents used among practicing engineers for numerical assessment of progressive collapse potential of buildings, the 2003 GSA (General Services Administration) guidelines were also applied. The simplified LS (linear static) analysis approach of the GSA guidelines was used for assessing the progressive collapse risk of the building, and the results were then compared with both test observations and NLD analysis. New dynamic increase factors (DIFs) are recommended for both force- and deformation-controlled actions to be used with the LS analysis.
The seismic design of super-tall buildings has become an important research topic in earthquake engineering. Limited research has been conducted on the distribution of plastic energy dissipation among the different components of super-tall buildings when subjected to strong earthquakes. A simplified two-dimensional (2D) nonlinear model is developed based on the analysis of Shanghai Tower, an actual super-tall building with a total height of 632 m. The accuracy of the simplified model is validated by comparing the results from modal analyses, and static and dynamic time-history analyses of the refined finite element model. Then, the proposed simplified model is used to determine the plastic energy dissipation of different components and the distribution of the total plastic energy dissipation over the height of the Shanghai Tower under different seismic intensities. The analysis indicates that the total plastic energy is mainly concentrated in the upper four Zones of the building and that the outrigger is the major plastic energy dissipation component in the Shanghai Tower.
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This research is focused on modeling the behavior of reinforced concrete columns subjected to lateral loads. Deformations due to flexure, reinforcement slip, and shear are modeled individually using existing and new models. Columns are classified into five categories based on a comparison of their predicted shear and flexural strengths, and rules for combining the three deformation components are established based on the expected behavior of columns in each category. Shear failure in columns initially dominated by flexural response is considered through the use of a shear capacity model. The proposed model was tested on 37 columns from various experimental studies. In general, the model predicted the lateral deformation response envelope reasonably well.
Progressive collapse performance of steel structure with unreinforced masonry wall and load-bearing wall structure with concrete masonry unit (CMU) have been investigated through field experiments and computational simulations. During the experiments, single or multiple first-story columns or load bearing walls were physically removed from the buildings, which were demolished immediately after the experiments. Due to lack of full-scale building test data, the data produced in this research has been a valuable addition to the state of knowledge on gravity collapse of buildings. The primary goal of field experiments was to simulate the structural dynamic and static response of buildings that may experience collapse after sudden loss of column(s) or wall(s). Another objective was to investigate how the internal forces were redistributed within the building after each wall or column was removed. In this study, finite element models of the buildings were developed and analyzed to simulate the building performance and collapse potential. Computational models and simulations were examined and compared to the experimental data from the field tests. The contribution and effects of infill walls to progressive collapse resistance of frame structures were investigated. This study showed the robustness of existing buildings and the contribution of different structural components to collapse resistance.
