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Rebar cages are the skeletons of reinforced concrete structures. These temporary structures consist of longitudinal and transverse reinforcing bars connected by tie-wires. Given the relatively low strength of tie-wire connections, replacing tie-wires with mechanical connectors such as U-bolts can improve the stability and strength of rebar cages. This paper aims to understand the behavior of large prefabricated rebar cages reinforced with mechanical U-bolt connectors through experimental and analytical investigations. Twenty-six full-scale experimental tests are performed on five different underground pile-shaft rebar cages with tie-wire and U-bolt connectors to determine their behavior during different site handling conditions. The data obtained from the experiments are used to develop and calibrate detailed finite element models that can predict the complex response behavior of rebar cages reinforced with U-bolt connectors. The results show that U-bolt connectors can effectively ensure rebar cage integrity even under extreme loading conditions. Additionally, it is concluded that the presence of U-bolt connectors allows for the elimination of internal stiffening elements, which are common for large rebar cages, adding to the simplicity and efficiency of the construction process. The results of this study can be used as a basis for establishing analysis, design, fabrication, and handling guidelines for rebar cages. [ABSTRACT FROM AUTHOR]

Plate steel shear links offer enhanced design freedom, including the ability to use steel grades that are not available in rolled shapes. This paper discusses the cyclic response of five types of shear links designed using steel grades that ranged from 485 to 100 MPa yield strength. The design and subsequent performance was categorized into two groups; conventional design and those designed without stiffeners using low yield point steels. Ductile failure modes and desirable hysteretic behavior that resulted in efficient cyclic energy dissipation were observed for all specimens. The links designed without stiffeners using low yield point steel reached shear deformations exceeding 0.20 rad, outperforming the conventional designs that exhibited approximately 0.12 rad capacity. The enhanced performance was the result of shifting the failure mode by excluding intermediate stiffeners and providing low web compactness. This combination eliminated welding and decreased measured plastic strain demands on the face of the inelastically deforming webs. DOI: 10.1061/(ASCE)ST.1943-541X.0000131 CE Database subject headings: Steel plates; Experimentation; Stiffening; Failure modes; Energy dissipation. Author keywords: Shear link; Cyclic experiment; High-performance steel; Low yield point steel.

This paper discusses the superelastic behavior of shape memory alloy, Nitinol (NiTi), when used as reinforcement in concrete beams. The ability of NiTi to recover and reduce permanent deformations of concrete beams was investigated. Small-scale concrete beams, with NiTi reinforcement were tested under half-cycle loads. The reinforcement ratio varied from 0.1 to about 0.9%. The experimental results showed that the average residual displacement in the NiTi reinforced beams was less than one-fifth of that of the steel reinforced test beams. The stiffness of NiTi reinforced test beams however was lower than those of the steel reinforced test beams. An analytical study of load-deflection relationship for a series of hybrid beams was undertaken. It was found that a hybrid system that incorporated NiTi combined with high strength steel or carbon fiber reinforced plastic bars was a better choice for design because of their relatively high stiffness. DOI: 10.1061/(ASCE)0899-1561(2007)19:6(454) CE Database subject headings: Deflection; Concrete beams; Cracking; Shape memory effect; Ductility; Flexural strength; Deformation.

Unstiffened, unbraced steel beams used in bridge falsework are subjected to patch loads from timber or steel posts. This paper investigates the critical web limit states in these types of beams experimentally and through finite-element analysis. Existing equations were appropriate for calculating the web yielding and crippling capacity, as observed in experiments, except that a 1:1 stress gradient through the flange and fillet of the web is found to be more appropriate and conservative for web yielding than the 2.5:1 gradient assumed in the current AISC specifications. Lateral deformation of a beam flange, due to buckling of the web, was also observed experimentally. The capacity of the web for resisting lateral buckling can be calculated assuming that the web of the beam acts like a column with an appropriate effective area and length factor. The effect of accidental eccentricity between the flange and post is not significant if limited to three times the web thickness. Blocking is approximately 50% effective in increasing the web yielding and crippling capacity. Bracing or stiffeners should be used to prevent lateral buckling of a web where necessary. DOI: 10.1061/(ASCE)0733-9445(2007)133:5(665) CE Database subject headings: Webs; Bridges; Falsework; Limit states; Buckling; Steel beams; Deformation.

Ductile end cross frames have been proposed in the past as a seismic design and retrofit strategy for steel plate girder bridges. In this paper it is shown that with good connection details, single angles are able to undergo large cyclic deformations in excess of 6% average axial strain before failure occurs. Large-scale shake table experiments were performed on a straight steel I-girder bridge model to evaluate the performance of a superstructure with ductile end cross frames using single angle X braces. The cross frames exhibited no apparent overall strength degradation, but also a comparatively low postyield stiffness, allowing the cross frames to act as effective structural fuses. The measured base shear was 61% of the elastic base shear in response to 2.0 times the El Centro earthquake at an average drift of 3.4%. Large girder drifts were achieved without distress in the deck slab by removing selected studs between the slab and top flange of the girders at the end cross frame locations, with axial deformations in the angles well below their deformation capacity based on component experiments. DOI: 10.1061/(ASCE)0733-9445(2006) 132:3(329) CE Database subject headings: Buckling; Bracing; Seismic effects; Bridges, Girder; Frames.

Ductile end cross frames have been proposed in the past for seismic design of steel plate girder bridges. In this paper buckling-restrained braces (BRBs) are investigated as ductile end cross frames and compared against the performance of yielding X braces. Component experiments on the BRBs showed that these braces dissipated energy very efficiently and have stable hysteretic behavior. Shake-table experiments on a large scale bridge model investigated the performance of braces with both pin-ended connections and fixed-end connections. Despite slippage, the pin-ended connections are considered more effective as flexural action in the relatively short braces is prevented. The base shear in the bridge model in response to 2.0 times the El Centro earthquake was 69% of the elastic base shear at an average drift of 2.5% during experiments. The relatively large deformation capacity of the BRBs, although not as great as the X braces, is necessary to achieve a significant reduction in base shear. The maximum cross frame displacements with the BRBs are consistently smaller than those in X braces at the same level of base shear. DOI: 10.1061/(ASCE)0733-9445(2006) 132:3(338) CE Database subject headings: Buckling; Bracing; Seismic effects; Bridges, Girder; Frames.

Introduction: Starting December 2019, the world has been devastated by the rapid spread of coronavirus disease 2019 (Covid-19). Many risk factors have been associated with worse outcomes and death from Covid-19 pneumonia including having diabetes mellitus. To date, it is not clear if all group of diabetics share the same risk of complications with COVID-19 infection. This study aims to compare disease severity and mortality rate in insulin users versus non-insulin users. Methods: In this retrospective case–control study conducted at the largest health care network in New York state, we included adult, diabetic patients admitted from March 2020 to October 2020 with Covid-19 pneumonia. We compared the baseline characteristics in addition to outcomes of diabetic patients on home insulin (cases) and non-insulin user diabetics (controls). In addition, to determine if home insulin use is associated with an increased mortality, we conducted a cox regression analysis. Results: We included 696 patients in the study period with a median age of 57 years, interquartile range [IQR] 51–62, and median body mass index 29.9 (IQR: 26–34.7). The majority (476 [68%]) were males. We identified 227 cases (33%) and 469 controls (67%). More cases than controls were hypertensive (74% vs 67%, p = 0.03), on ACE/ARB (50% vs 42%, p = 0.05), and had a hemoglobin A1c > 8.1 (71% vs 44%, p < 0.001). More cases had AKI (52% vs 38%, p < 0.001), however no significant differences were found in intubation rates (26% vs 24%, p = 0.54), detection of pulmonary embolism (4% vs 6%, p = 0.19) or death rate (15% vs 11%, p = 0.22) comparing cases and controls. In a multivariate analysis, we found that home insulin use was independently associated with increased risk of death: Hazard ratio: 1.92, 95% confidence interval (1.13–3.23). Conclusion: We showed herein that diabetic patients on home insulin with COVID-19 pneumonia, have worse outcomes and increased mortality compared to diabetics on oral antihyperglycemic agents. Close monitoring of insulin-dependent type II diabetic patients is needed in the current pandemic. [ABSTRACT FROM AUTHOR]