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.
Robust Mask R-CNN (Mask Regional Convolu-tional Neural Network) methods are proposed and tested for automatic detection of cracks on structures or their components that may be damaged during extreme events, such as earth-quakes. We curated a new dataset with 2,021 labeled images for training and validation and aimed to find end-to-end deep neural networks for crack detection in the field. With data augmentation and parameters fine-tuning, Path Aggregation Network (PANet) with spatial attention mechanisms and High-resolution Network (HRNet) are introduced into Mask R-CNNs. The tests on three public datasets with low- or high-resolution images demonstrate that the proposed methods can achieve a big improvement over alternative networks, so the proposed method may be sufficient for crack detection for a variety of scales in real applications.
A new reinforcement system, Prefabricated Cage System (PCS), is proposed to perform the function of longitudinal and transverse steel in reinforced concrete members. PCS is made from a solid steel tube or plate acting as transverse and longitudinal steel connected monolithically. PCS reinforcement eliminates some of the weaknesses and detailing problems inherent in traditional rebar reinforced concrete construction resulting in easier, more reliable, and faster construction. The confinement provided by PCS is investigated by comparing the results from 6 small-scale column tests. The specimens were tested by axially loading the concrete core. The effects of PCS tube thickness, and the width and height of transverse and longitudinal steel on the provided confinement and displacement capacity are investigated. Test results show that PCS provides higher confinement capacity than similar rebar reinforcement.
Collapse performance of nine existing multi-story buildings have been investigated through field experiments and computational modelling. Masonry, reinforced concrete and steel frame buildings have been tested. Most of the test buildings were located on the Ohio State University campus. Single or multiple first-story columns were physically removed from each building during the experiments. The data produced in this research has been a valuable addition to the state of knowledge on progressive collapse of buildings because experimental evidence from full-scale structures is either very limited or does not exist. The main goal of field experiments was to simulate the dynamic and static response of buildings that may experience progressive collapse after sudden loss of column(s). Another objective was to investigate how the internal forces would be redistributed within the building after column loss. Experimental data is used to evaluate the design methods and analysis procedures recommended in current design guidelines. Two and three-dimensional building models were analyzed to simulate the progressive collapse response. Computational models and simulations were compared with the experimental data from the field tests. This study showed robustness of existing buildings and potential contribution of structural components to collapse resistance.
The 6 February 2023 Kahramanmaraş earthquakes in Turkiye, which measured 7.8 and 7.5 moment magnitude ( M w ) per the United States Geological Survey (USGS), affected 13 provinces and over 15 million people, according to the Turkish Government. The Earthquake Engineering Research Institute’s (EERI) Buildings Reconnaissance Team visited the populated centers as well as small towns in Turkiye that were most affected by these earthquakes. The team focused on understanding the overall structural performance of buildings, including correlation with maximum spectral acceleration and peak ground velocity at nearby ground motion recording stations. This article discusses the vulnerability of concrete buildings, which constitute most of the building stock in the region, performing an overall assessment of structural systems as well as components. More than 160 individual buildings at about 130 sites were observed. The construction period of these buildings varied from pre-2000s to as new as a few years old. Turkish building codes underwent significant changes after the 1999 Kocaeli earthquake and most recently in 2018. The findings in this article include not only the behavior of critical gravity and lateral structural elements but also the participation of non-structural elements in the seismic response of the structure, such as infills, non–load-bearing partitions, and perimeter unreinforced masonry infill walls. This article discusses the findings from field observations related to design, detailing, and construction practices. Findings illustrating the seismic performance of building systems and individual components such as floor slabs, beams, columns, shear walls, and foundations, with key takeaways to improve the seismic design guidelines, construction, and inspection practices, are summarized.
No abstract is provided for this article.
There are a large number of reinforced concrete buildings in seismically active areas of the world that are not built in accordance with modern seismic design provisions such as those published by American Concrete Institution ([ACI] Committee 318, 2008). In the United States and other parts of the developed world, these buildings were constructed between 1930s to mid 1970s according to the building code requirements of that time. Even today, in low to moderate seismic regions and in some developing countries that are in process of developing and implementing their seismic codes, reinforced concrete structures are being designed and built without essential seismic details deemed vital to withstand large lateral loads. These buildings often have low lateral displacement capacities and undergo rapid degradation of shear strength and axial load carrying capacity during strong ground motions and hence are extremely vulnerable to excessive structural damage or collapse during future earthquakes. In the past, the earthquakes have caused wide spread damage to the reinforced concrete structures with inadequate seismic design and construction practices. For example, during Kashmir (Pakistan) earthquake of 2005 and Haiti earthquake of 2010, extensive structural damage to residential, commercial and government buildings was observed (Earthquake Engineering Research Institute [EERI], 2005; Mid-America Earthquake [MAE] Center, 2005; U.S. Geological Survey [USGS]/EERI, 2010). The damage was attributed largely to lack of earthquake-resistant design, poor standard of construction and inferior quality of building materials. In majority of the collapsed or damaged structures, structural types, member dimensions and detailing practices (insufficient lap length, improper lap location and lack of confinement in columns etc) were found inadequate to resist forces imposed by these earthquakes. The 2011 off The Pacific Coast of Tohoku (Japan) earthquake is a modern day example of large scale devastation to a highly industrial nation in which building and infrastructure is well designed and constructed. Although, majority of causalities and large scale destruction of infrastructure was caused by ensuing tsunami, limited damage to the buildings due to ground shaking was reported (Pacific Earthquake Engineering Research Center [PEER]/EERI/Geotechnical Extreme-Event Reconnaissance [GEER]/Tsunami Field Investigation Team, 2011; Takewaki et al. 2011). However, extensive and severe structural damage was observed in older residential and commercial buildings that were constructed prior to 1978 code revision of Japan, whereas modern structures built to withstand seismic demands did not sustain any substantial and widespread damage (Aydan & Tano, 2011).
Retrofit and rebuilding are two potential solutions for reinforced concrete (RC) structures with columns that have insufficient detailing or strength to withstand seismic loads or other extreme events. Demolition and rebuilding can be expensive and time-consuming. Thus, retrofitting and strengthening of columns can be an efficient solution. Jacketing of reinforced concrete columns is one of the common methods for retrofit and rebuilding. For jacketing method, the main concern is the performance loss between new and old concrete due to interface slip. There are three major options to provide a better performance, as surface roughening, dowels, and both. In this study, the methods to provide coworking of new and old concrete are evaluated with respect to four parameters; strength, energy dissipation, stiffness, and displacement ductility. Additionally, a slip coefficient is proposed to model the friction between new and old concrete. The proposed model is applied into OpenSees and a Finite Element (FE) software. The slip coefficient is simulated numerically by a friction coefficient using a tangential contact behavior definition as well. Finally, a slip coefficient is proposed for each method.
Before the introduction of special requirements in the 1970s, reinforced concrete building frames constructed in zones of high seismicity in the US had details and proportions similar to frames designed solely for gravity loads. Columns generally were not designed to have strengths exceeding beam strengths, so column failure mechanisms often prevail. Relatively wide spacing of transverse reinforcement was common, such that column failures may involve some form of shear or flexure-shear failure, in some cases followed by loss of axial load capacity. This study examines laboratory behavior of columns with light transverse reinforcement and proposes models for shear strength and subsequent axial load failure that may be suitable for evaluation of existing building frames.
Silos are special structures subjected to many different unconventional loading conditions, which result in unusual failure modes. Failure of a silo can be devastating as it can result in loss of the container, contamination of the material it contains, loss of material, cleanup, replacement costs, environmental damage, and possible injury or loss of life. Silo damage and failures that occurred in different regions of the world are presented in the paper using illustrative photos. Also provided are a review and discussion of the common or spectacular silo failures due to explosion and bursting, asymmetrical loads created during filling or discharging, large and nonuniform soil pressure, corrosion of metal silos, deterioration of concrete silos due to silage acids, internal structural collapse, and thermal ratcheting. Silo damage and failures from several earthquakes are also presented.
No abstract is provided for this article.
Modern society is demanding that the use of energy associated with construction and operation of structures be investigated during the planning and design phases. The engineering community has been striving to design more sustainable buildings in an attempt to reduce both raw material requirements and energy use during all phases of design. Structural engineers currently have very limited guidance on how to incorporate sustainability concepts in their designs. Innovative methods are needed to address the environmental impact, energy use, and other sustainability issues faced during planning and design of buildings. This paper investigates and discusses five sustainable structural design methodologies: Minimizing Material Use, Minimizing Material Production Energy, Minimizing Embodied Energy, Life-Cycle Analysis/Inventory/Assessment, and Maximizing Structural System Reuse. The goal of this paper is to describe and address issues associated with the proposed design methodologies to determine which, if any, can produce the most sustainable structural designs. It was determined that no single methodology can address all the issues surrounding sustainable structural design. Also, it was determined that combinations of two or more methodologies may increase the ability of design professionals to produce more sustainable designs.
This paper presents the results of field performance tests of 39 in-service corrugated steel highway culverts in Ohio. The culverts had span lengths varying from 3.23m (10.6ft) to 7.04m (23.1ft) and backfill soil heights over the crown varying from 0.27m (0.9ft) to 7.47m (24.5ft) . Static and dynamic load tests were conducted by driving heavy trucks across the culverts. Static loads were applied at ten different locations above each culvert. Dynamic load tests were conducted at six truck speeds varying from 8km/h (5mi/h)to64km/h (40mi/h) . A portable instrumentation frame was installed inside each test culvert to monitor deflections. Strains on the culvert walls were also measured at 14 locations using strain gauges. Effects of backfill height and loading conditions are investigated. According to the experimental results, a plot of maximum culvert deflection versus backfill height shows a nonlinear relationship. Maximum static load deflections were found to be consistently larger than the maximum dynamic deflections obtained using the same test truck. Deflections were nearly zero for deep culverts with backfill heights exceeding 4m (13ft) . Maximum deflections correlate more closely to equivalent line loads than to total truck weight. The data also indicate that culvert behavior is more difficult to predict when backfill heights are shallow because other factors, such as culvert age and condition and soil type, likely play a significant role.
Lateral response of reinforced concrete (RC) columns can be modeled and simulated considering three displacement components: flexural displacement, displacement due to slippage of longitudinal bars at column ends, and shear displacement. The incorporation of shear displacement in a computational model is essential for accurate calculation of lateral load–displacement relationship. The contribution of shear displacement can be significant for RC columns with low displacement capacity or ductility. An easy-to-apply shear displacement model is proposed in this study, and implemented in the open source software, OpenSees. The proposed model is based on a pre-defined envelope or monotonic model and does not require updating of modeling parameters during each cycle. The model is validated using experimental data. New rules are developed for the cyclic model to capture the effects of cracking and change in stiffness and strength during the loading and unloading cycles. Comparison of the calculated and measured shear displacements indicates that the cyclic shear response can be captured by the proposed model.
This paper presents the results of field performance tests of 39 in-service corrugated steel highway culverts in Ohio. The culverts had span lengths varying from 3.23m(10.6ft)to7.04m(23.1ft) and backfill soil heights over the crown varying from 0.27m(0.9ft)to7.47m(24.5ft). Static and dynamic load tests were conducted by driving heavy trucks across the culverts. Static loads were applied at ten different locations above each culvert. Dynamic load tests were conducted at six truck speeds varying from 8km∕h(5mi∕h)to64km∕h(40mi∕h). A portable instrumentation frame was installed inside each test culvert to monitor deflections. Strains on the culvert walls were also measured at 14 locations using strain gauges. Effects of backfill height and loading conditions are investigated. According to the experimental results, a plot of maximum culvert deflection versus backfill height shows a nonlinear relationship. Maximum static load deflections were found to be consistently larger than the maximum dynamic deflections obtained using the same test truck. Deflections were nearly zero for deep culverts with backfill heights exceeding 4m(13ft). Maximum deflections correlate more closely to equivalent line loads than to total truck weight. The data also indicate that culvert behavior is more difficult to predict when backfill heights are shallow because other factors, such as culvert age and condition and soil type, likely play a significant role.
This paper proposes a pipeline to automatically track and measure displacement and vibration of structural specimens during laboratory experiments. The latest Mask Regional Convolutional Neural Network (Mask R-CNN) can locate the targets and monitor their movements from videos recorded by a stationary camera. To improve precision and remove the noise, techniques such as Scale-invariant Feature Transform (SIFT) and various filters for signal processing are included. Experiments on three small-scale reinforced concrete beams and a shaking table test are utilized to verify the proposed method. Results show that the proposed deep learning method can achieve the goal to automatically and precisely measure the motion of tested structural members during laboratory experiments.
