ANN-based Shear Capacity of Steel Fiber-Reinforced Concrete Beams Without Stirrups

Comparing experimental results on the shear capacity of steel fiber-reinforced concrete (SFRC) beams without mild steel stirrups, to the ones predicted by current design equations and other available formulations, still shows significant differences. In this paper we propose the use of artificial intelligence to estimate the shear capacity of these members. A database of 430 test results reported in the literature is used to develop an artificial neural network-based formula that predicts the shear capacity of SFRC beams without shear reinforcement. The proposed model yields maximum and mean relative errors of 0.0% for the 430 data points, which represents a better prediction (mean Vtest / VANN = 1.00 with a coefficient of variation of 1× 10-15) than the existing expressions, where the best model yields a mean value of Vtest / Vpred = 1.01 and a coefficient of variation of 27%

Enlightening force chains: a review of photoelasticimetry in granular matter

A photoelastic material will reveal its internal stresses when observed through polarizing filters. This eye-catching property has enlightened our understanding of granular materials for over half a century, whether in the service of art, education, or scientific research. In this review article in honor of Robert Behringer, we highlight both his pioneering use of the method in physics research, and its reach into the public sphere through museum exhibits and outreach programs. We aim to provide clear protocols for artists, exhibit-designers, educators, and scientists to use in their own endeavors. It is our hope that this will build awareness about the ubiquitous presence of granular matter in our lives, enlighten its puzzling behavior, and promote conversations about its importance in environmental and industrial contexts. To aid in this endeavor, this paper also serves as a front door to a detailed wiki containing open, community-curated guidance on putting these methods into practice.Comment: 13 page

Challenges and Opportunities for Academic Parents During COVID-19

Parents in academic careers face notable challenges that may go unrecognized by university management and/or policy makers. The COVID-19 pandemic has shed light on some of these challenges, as academic parents shifted to working from home while simultaneously caring for children. On the other hand, many parents found that the shift to working from home offered new opportunities such as working more flexible hours, development of digital skillsets, and increased involvement in the education of their children. In this article we explore the work-related challenges and opportunities experienced by academic parents as a result of the COVID-19 pandemic and offer potential long-term solutions for academic parents and their universities. We use the following methods: (1) a literature review focused on identifying the work-related challenges academic parents faced prior to the pandemic, as well as the impact of the pandemic on scientists and working parents and (2) administer a world-wide survey with the goal of identifying the challenges and opportunities associated with parenting and academic work through the COVID-19 lockdown (304 total responses; 113 complete). Moving forward these findings have enabled conclusions to be drawn in order to shape a new normal. Our aim is to offer university administrators, policy makers, and community service providers with ways to provide additional support for academic parents as well as provide tools for academic parents to learn successful strategies directly from their peers.Concrete Structure

Punching capacity of spread footings using aci 318-19 and the strip model

In design, the sectional depth of reinforced concrete spread footings is usually governed by design code provisions for punching shear, which are derived primarily from experiments on slab-column connections. Previous experiments have shown that the punching behavior of concentrically loaded spread footings differs from that of slab-column connections. This paper describes punching of a concentrically loaded spread footing by combining conventional strut and tie modeling with the concept of an arch strip, part of the Strip Model. By itself, the Strip Model describes the behavior of slab-column connections under a variety of loading conditions. For spread footings, Strip Model concepts need to be combined with conventional strut and tie modeling to adequately describe load transfer in a concentrically loaded spread footing. Two methods are explored, each producing closed-form expressions for the footing capacity that agree well with experimental results (112 tests from the literature). The analyses make it possible to estimate the fraction of footing load that is carried by conventional strut and tie behavior. The experimental results are also compared to punching shear capacities in accordance with ACI 318-19. The Strip Model produces results with roughly the same average test-to-predicted ratio (in the order of 1.3) as ACI 318-19 but with a lower coefficient of variation (10.3% compared to 15.8%). This work shows how a lower-bound plasticity-based model can be used for the practical case of determining the capacity of reinforced concrete spread footings failing in punching shear.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Concrete Structure

Bridge Load Testing: State-of-the-Practice

Bridge load testing can answer a variety of questions about bridge behavior that cannot be answered otherwise. The current governing codes and guidelines for bridge load testing in the United States are the 1998 NCHRP Manual for Bridge Rating through Load Testing and Chapter 8 of the AASHTO Manual for Bridge Evaluation. Over the last two decades, the practice of load testing has evolved, and its intersections with other fields have expanded. The outcomes of load tests have been used to keep bridges open cost-effectively without unnecessarily restricting legal loads, when theoretical analyses cannot yield insights representative of in-service performance. Load testing data can be further used to develop field-verified finite-element models of tested bridges to understand these structures better. In addition, structural reliability concepts can be used to estimate the probability of failure based on the results of load tests, and noncontact measurement techniques capturing large surfaces of bridges allow for better monitoring of structural responses. Given these developments, a new Transportation Research Board (TRB) Circular, Primer on Bridge Load Testing, has been developed. This document contains new proposals for interpreting the results of diagnostic load tests, loading protocols, and the determination of bridge load ratings based on the results of proof load tests. In addition, included provisions provide an estimation of the resulting reliability index and the remaining service life of a bridge based on load testing results. The benefit of load testing is illustrated based on a cost–benefit analysis. The current state-of-the-practice has demonstrated that load testing is an effective means for answering many important questions regarding bridge behavior that are critical to decisions on bridge maintenance or replacement. Load testing has evolved over its history, and the newly developed TRB Circular reflects this evolution in a practical way

Bridge Load Testing: State-of-The-Practice

Bridge load testing can answer a variety of questions about bridge behavior that cannot be answered otherwise. The current governing codes and guidelines for bridge load testing in the United States are the 1998 NCHRP Manual for Bridge Rating through Load Testing and Chapter 8 of the AASHTO Manual for Bridge Evaluation. Over the last two decades, the practice of load testing has evolved, and its intersections with other fields have expanded. The outcomes of load tests have been used to keep bridges open cost-effectively without unnecessarily restricting legal loads, when theoretical analyses cannot yield insights representative of in-service performance. Load testing data can be further used to develop field-verified finite-element models of tested bridges to understand these structures better. In addition, structural reliability concepts can be used to estimate the probability of failure based on the results of load tests, and noncontact measurement techniques capturing large surfaces of bridges allow for better monitoring of structural responses. Given these developments, a new Transportation Research Board (TRB) Circular, Primer on Bridge Load Testing, has been developed. This document contains new proposals for interpreting the results of diagnostic load tests, loading protocols, and the determination of bridge load ratings based on the results of proof load tests. In addition, included provisions provide an estimation of the resulting reliability index and the remaining service life of a bridge based on load testing results. The benefit of load testing is illustrated based on a cost-benefit analysis. The current state-of-The-practice has demonstrated that load testing is an effective means for answering many important questions regarding bridge behavior that are critical to decisions on bridge maintenance or replacement. Load testing has evolved over its history, and the newly developed TRB Circular reflects this evolution in a practical way. </p