Jason Martinez and Ann Jeffers
A methodology for producing an elevated-temperature tension stiffening model is presented.
Abstract
Purpose
A methodology for producing an elevated-temperature tension stiffening model is presented.
Design/methodology/approach
The energy-based stress–strain model of plain concrete developed by Bažant and Oh (1983) was extended to the elevated-temperature domain by developing an analytical formulation for the temperature-dependence of the fracture energy Gf. Then, an elevated-temperature tension stiffening model was developed based on the modification of the proposed elevated-temperature tension softening model.
Findings
The proposed tension stiffening model can be used to predict the response of composite floor slabs exposed to fire with great accuracy, provided that the global parameters TS and Kres are adequately calibrated against global structural response data.
Originality/value
In a finite element analysis of reinforced concrete, a tension stiffening model is required as input for concrete to account for actions such as bond slip and tension stiffening. However, an elevated-temperature tension stiffening model does not exist in the research literature. An approach for developing an elevated-temperature tension stiffening model is presented.
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Ha Nguyen, Ann E. Jeffers and Venkatesh Kodur
This paper aims to address a need for improving the structural resilience to multi-hazard threats including fire and progressive collapse caused by the loss of a column.
Abstract
Purpose
This paper aims to address a need for improving the structural resilience to multi-hazard threats including fire and progressive collapse caused by the loss of a column.
Design/methodology/approach
The focus is on a steel moment frame that uses welded-unreinforced flange-bolted web connections between the beams and columns. A three-dimensional finite element (FE) model was created in ABAQUS with temperature-dependent properties for steel based on the Eurocode. The model was validated against experimental data at ambient and elevated temperature.
Findings
The failure mechanisms in the FE model were consistent with experimental observations. Two scenarios were considered: fixed load with increasing temperature (i.e. simulating column failure prior to fire) and fixed temperature with increasing load (i.e. simulating column failure during fire).
Originality/value
A macro element (or component-based) model was also introduced and validated against the FE model and the experimental data, offering the possibility of analyzing large-scale structural systems with reasonable accuracy and improved computational efficiency.
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Ann Jeffers and Elisa Sotelino
This paper considers the extension of the force-based element formulation to simulate the nonlinear, temperature-dependent response of structural frames exposed to fire. The…
Abstract
This paper considers the extension of the force-based element formulation to simulate the nonlinear, temperature-dependent response of structural frames exposed to fire. The two-dimensional formulation presented here accounts for thermal expansion, temperature-dependent material properties, and residual stresses. The element utilizes a fiber discretization to simulate the gradual plastification of the section. Geometric nonlinearities are included through coordinate transformations of the corotational reference frame. Analyses of benchmark experimental tests demonstrate that the force-based element formulation is computationally stable and provides accurate results for structures exposed to fire. In addition, comparisons to traditional displacement-based elements indicate that the force-based element may offer improved computational efficiency because fewer elements are needed per member.
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Kaihang Shi, Qianru Guo and Ann Jeffers
This paper describes a preliminary study to explore the use of Monte Carlo simulation to assess the reliability of structures in fire given uncertainty in the fire, thermal, and…
Abstract
This paper describes a preliminary study to explore the use of Monte Carlo simulation to assess the reliability of structures in fire given uncertainty in the fire, thermal, and structural model parameters. The methodology requires (1) the probabilistic characterization of the uncertain parameters in the system, (2) a stochastic model for the thermo-structural response, and (3) a limit state function that describes the failure of the system. The study focuses on assessing the failure probability of a protected steel beam under natural fire exposure. The system was modeled stochastically using a series of sequentially coupled thermo-structural finite element analyses that were embedded within a Monte Carlo simulation. Although the example considered here is relatively simplistic in that it focuses on member level performance, it effectively demonstrates the application of the proposed reliability method and provides insight into the practicalities of extending the approach to more complex structural systems.
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R. Surya Prakash and N. Parthasarathi
The purpose of this study is to perform a numerical analysis of fiber-reinforced polymer (FRP) retrofitting in reinforced concrete (RC) joints at high temperatures and predict…
Abstract
Purpose
The purpose of this study is to perform a numerical analysis of fiber-reinforced polymer (FRP) retrofitting in reinforced concrete (RC) joints at high temperatures and predict models using artificial neural networks (ANN). The aim was to gain insights into their structural behavior across a range of loading conditions from room temperature to 800°C. Additionally, the research assessed the efficiency of carbon fiber-reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP) and aramid fiber reinforced polymer (AFRP) strengthening in enhancing the structural performance of the critical sections.
Design/methodology/approach
The linear numerical simulations were conducted to evaluate the performance of RC beam-column joints using finite element modelling (FEM) analysis. The ANN model demonstrated exceptional effectiveness in predicting the stiffness of frames with openings, establishing itself as the premier machine learning algorithm for frame stiffness estimation. In the conventional model, 300°C was proven to be an effective temperature approach. Subsequently, maintaining a constant temperature of 300°C, an in-depth analysis of nearly 30 models of three retrofitting techniques was conducted under thermomechanical loading.
Findings
The CFRP retrofits yielded 15% less deflection and 30% more stress than the remaining FRPs, and the ANN models predicted the deflection, main stresses, bending moment and shear force. The ANN model results were compared with those of other frequently used models. The R thresholds (R = 0.954, 0.981, 0.986, 0.968, 0.978 and 0.936) for training, testing and validation indicated that the ANN model achieved data variability. The findings indicate that the ANN model is more accurate because of the strong connection between the numerical model and the prediction.
Originality/value
To identify the pinpoint of critical segments within the rehabilitation section and determine the most effective wrapping method among the three laminates.
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John E. Tyler, Evan Absher, Kathleen Garman and Anthony Luppino
This chapter demonstrates that social business models do not meaningfully prioritize or impose accountability to “social good” over other purposes in ways that (a) best protect…
Abstract
This chapter demonstrates that social business models do not meaningfully prioritize or impose accountability to “social good” over other purposes in ways that (a) best protect against owners changing their minds or entry of new owners with different priorities and (b) enable reliable accountability over time and across circumstances. This chapter further suggests a model – a “social primacy company” – that actually prioritizes “social good” and meaningful accountability to it. This chapter thus clarifies circumstances under which existing models might be most useful and are not particularly useful, especially as investors, entrepreneurs, employees, regulators, and others pursue shared, common understandings about purposes, priorities, and accountability.
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The purpose of this paper is to expand the empirical literature on the association between non-compete agreement (NCA) enforceability and entrepreneurship by investigating how NCA…
Abstract
Purpose
The purpose of this paper is to expand the empirical literature on the association between non-compete agreement (NCA) enforceability and entrepreneurship by investigating how NCA policies affect different types of entrepreneurship with incorporated and unincorporated businesses.
Design/methodology/approach
The authors estimate difference-in-differences regressions based on individual-level data. This allows to control for heterogeneity at the individual level. Additionally, the authors provide graphical evidence using the synthetic control method (SCM).
Findings
The authors' findings show that the decrease in the enforceability of NCAs in Massachusetts resulted in a higher rate of unincorporated entrepreneurship among low-wage workers. At the same time, there was no sizable effect on the rate of incorporated entrepreneurship. For Utah, the authors' results indicate that the reform increased both types of entrepreneurship. The findings imply that states can promote entrepreneurial activity by reducing the enforceability of NCAs. The way of changing the enforceability of NCAs matters, as different provisions encourage different types of entrepreneurship in a given state.
Originality/value
The authors contribute to the literature on NCA enforceability effects on entrepreneurship in three ways. First, the authors utilize two quasi-experiments, the NCA policy changes in Utah in 2016 and Massachusetts in 2018, limiting NCAs to one year for all workers. Second, to the authors' knowledge, this is the first individual-level analysis that separates self-employment with incorporated and unincorporated businesses as two different types of entrepreneurship to analyze potentially heterogeneous effects of NCAs. Third, this is the first study to utilize American Community Survey (ACS) data in this literature.
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Virginia Nordstrom and Victoria Clayton
The value of allowing children to experience frequently the sheer pleasure of good children's literature has long been acknowledged. For at least the past twenty‐five years…
Abstract
The value of allowing children to experience frequently the sheer pleasure of good children's literature has long been acknowledged. For at least the past twenty‐five years, educational researchers and faculty members in schools of education and library science have advocated the use of children's literature in the elementary school curriculum.
Evelyne Vanpoucke, Ann Vereecke and Steve Muylle
Companies increasingly exchange information to work more closely with supply chain partners. Although information exchange is a critical element for up- and downstream…
Abstract
Purpose
Companies increasingly exchange information to work more closely with supply chain partners. Although information exchange is a critical element for up- and downstream partnerships, the purpose of this paper is to indicate that it is not a guarantee for improved performance and should be combined with other integration tactics to fully capture its benefits.
Design/methodology/approach
Using a global sample in the industrial sector, a moderated mediation framework for both upstream and downstream integration, which links integration tactics to operational performance, was empirically tested.
Findings
This research shows that operational integration is indispensable to capture the benefits of information exchange. In addition, it points out that the impact of the use of information technology (IT) is stronger for upstream integration.
Practical implications
While the data show that the use of IT significantly improves the delivery performance in the supply chain, it also signals to managers how and when to invest in supply chain integration tactics.
Originality/value
This paper contributes to a better understanding of the supply chain integration-performance link, by clarifying some of the inconsistencies in previous literature and by simultaneously analyzing upstream and downstream implications.