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A.M Barszcz

Abstract

This paper deals with a Continuous Stiffness Degradation (CSD) version of advanced analysis of braced steel framing. It is based on the gradual stiffness degradation concept of frame and truss members. A novelty of the approach presented herein is related to the introduction of the bracing member response in the whole range of its behaviour in tension and compression, including the post-limit range. The validation of the proposed advanced analysis is performed for braced framework with rolled angle section braces. The validation of the brace force-deformation model has been presented in the author’s earlier publication. The basis for the presented CSD advanced analysis is briefly summarized and its difference with regard to the Refined Plastic Hinge (RPH) version of advanced analysis is emphasized. Experimental investigations dealing with tests on portal braced sub-frame specimens are referred to briefly. Results of the experimental investigations are presented in the form of a frame global response and they are used for the validation of the developed computational model.

Open access

J. J. Sokołowska and K. Zalegowski

Abstract

Elaborating composites containing waste materials requires study of basic mechanical properties and assessment of their structure quality. The subject of investigation was PPC concrete where aggregate was substituted with PET remaining after beverages bottles grinding. Substitution was done up to 25% (by volume). Waste material was fractioned and applied in various granulations. The main goal was to indicate the influence of such modification on the composite mechanical properties and to examine composite structure quality at macro level. Since PET and quartz differ greatly in density, to perform such examination it was possible to apply the nondestructive ultrasonic method, one of the most common NDT techniques used in material science and industry. The paper presents the effects of substitution of quartz with PET on ultrasonic wave propagation in PCC. The ultrasonic test results (measurements of wave velocity) compared with results of destructive tests (flexural and compressive strength) showed great correlation.

Open access

Muhaned A. Shallal and Aqil Mousa K. Al Musawi

Abstract

Reinforced concrete is one of the most widely used structural components about which much scientific research has been conducted; however, some of its characteristics still require further research. The main focus of this study is the effect of direct fire on the shear transfer strength of concrete. It was investigated under several parameters including concrete strength, number of stirrup legs (the steel area across the shear plane), and fire duration. The experimental program involved the testing of two sets (groups) of specimens (12 specimens each) with different concrete strengths. Each set contained specimens of two or four stirrup legs exposed to direct fire from one side (the fire was in an open area to simulate a real-life event) for a duration of one, two, and three hours. The results of the comparison showed the importance of using high-performance concrete (instead of increasing the number of stirrup legs) to resist shear stress for the purpose of safety. A significant reduction in shear strength occurred due to the deterioration of the concrete cover after three hours of direct fire exposure.

Open access

C. Sivakumar, R. Malathy and P. Sivaprakash

Abstract

The construction industry in India is the country’s second largest industrial sector, after agriculture. The construction industry makes a remarkable contribution to the Indian economy and provides employment to a large number of people of India. Fire is a chemical reaction of a combustible substance with oxygen, involving heat and is usually accompanied by a visual flame or incandescence. Ensuring fire safety has always been a challenge to the stakeholders, i.e. building owners, construction companies, contractors and sub-contractors, and government employees due to the multiplicity of the factors involved and their complexity. There are various legal standards and requirements for ensuring fire safety on construction sites. The buildings are normally provided with firewalls during construction and these firewalls separate two structures or divide a structure into smaller portions to prevent the spread of fire. The lightweight construction and trusses are designed to support only their own weight. During a fire, if one fails, a domino effect happens and all fail rapidly within 5 to 10 minutes. Prolonged exposure to fire may result in structural collapse and injury or death of the occupants of the building under construction. Fire safety on construction sites is still in its primitive stages in India. There is a great necessity to improve fire safety on construction sites to protect construction workers and other occupants of the buildings. This study aims to design and implement fire safety systems for construction sites, thereby enhancing the standards to meet the system requirements at par with global standards.

Open access

V. Jayanthi and C. Umarani

Abstract

Shear connectors are designed in steel-concrete composite construction to transmit the longitudinal shear, to prevent separation of steel and concrete slabs, and also to increase the structural efficiency of the whole system. In this study, the performances of different types of shear connectors in steel-concrete composite specimens are evaluated by conducting push-out tests under monotonic loading conditions. An ISMB 200 @ 25.4 kg/m universal steel beam measuring 400 mm and a reinforced cement concrete slab measuring 300 mm with a breadth of 200 mm and a thickness of 200 mm reinforced with 8 mm diameter steel rods are used for the experimental study. The results reveal that the load-slip relationships for various types of shear connectors and failure mechanisms are obtained to identify those shear connectors which are more relevant to the steel - concrete composite members.

Open access

Yabo Wang, H. T. Liu, G. F. Dou, C. H. Xi and L. Qian

Abstract

This paper aims to study the effect of reinforcement configuration (steel fibre and rebar) on the mechanical performance of composite slabs of the same total steel contents. We manufactured four pieces of fullscale multi-ribbed composite prefabricated slabs with different reinforcement configurations by using steel fibrereinforced concrete, foam concrete, and normal concrete. The multi-ribbed composite prefabricated slab has many excellent properties, such as light weight, good thermal and sound insulation. Thus, it can be applied to fabricated structures. In addition, the composite prefabricated slabs with the same total steel contents but with different reinforcement configurations were studied under the same static load, and many technical indicators such as crack resistance capacity, yield load, ultimate load capacity, maximum deflection, destructive pattern, and stress of steel rebar were obtained. Results indicate reinforcement configuration has a significant effect on the mechanical performance of composite prefabricated slabs with the same total steel contents, and composite prefabricated slabs reinforced with longitudinal rebar and steel fibre (volume fraction is 1.5%) have the best mechanical performance and ductility.

Open access

Zhi Wang, Jiajia Zhou, Linjian Song and Long Li

Abstract

In order to improve the toughness of traditional epoxy resin, dibutyl phthalate (DBP) was introduced into the epoxy resin. The static mechanical performance of plasticized and unplasticized epoxy resin was evaluated. The test results showed that the DBP modified epoxy resin can obtain a higher toughness than conventional epoxy resin, but the elastic modulus and the tensile strength were slightly reduced. The low cycle fatigue test results indicated that the stress ratio and the stress level were two critical factors of fatigue life, which was increased with the growth of stress ratio. It was also found that the fatigue life of plasticized specimen was much less than that of the unplasticized specimen because of the plastic deformation. A logarithmic linear relationship was then established to predict the fatigue life for plasticized epoxy resin. The strain energy density was also applied to demonstrate the accumulation of energy loss. In addition, the fatigue toughness can be obtained by the hysteresis loop area method.

Open access

Yonggang Wang and Jingfeng Ma

Abstract

To examine the correlation of driver visual behaviors and subjective levels of fatigue, a total of 36 commercial drivers were invited to participate in 2-h, 3-h, and 4-h naturalistic driving tests during which their eye fixation, saccade, blinking variables, and self-awareness of their fatigue levels were recorded. Then, one-way ANOVA was applied to analyze the variations of each variable among different age groups over varying time periods. The statistical analysis revealed that driving duration had a significant effect on the variation of visual behaviors and feelings of fatigue. After 2h of driving, only the average closure duration value and subjective level of fatigue had an increase of one-fifth or more. After 4h of driving, however, all these variables had a significant change except for the number of saccades and pupil diameter measurements. Particularly, driver saccadic eye movement was more sensitive to driving fatigue, and the elderly were more likely to be affected by the duration of the drive. Finally, a predictor of driver fatigue was determined to detect the real-time level of fatigue and alert at the critical moment.

Open access

Robert Matyszkiel, Bogusław Grochowina, Adam Dobkowski, Marcin Wiśniewski and Paweł Domaros

Abstract

Accomplishment of basic services implementation with specific quality is one of the main challenges of the command and communication systems for modern maritime safety and defense. The specificity of the marine environment imposes the use of narrowband HF (High Frequency) and VHF (Very High Frequency) radio communication devices which are capable to implement IP transmission. This paper presents the requirements for the HF and VHF radio systems according to the IP protocol requirements. At the beginning basic properties of narrowband HF and VHF waveforms in context of their operational scenarios has been described. Then results of experimental research (implementation of narrowband services — voice and data) has been presented. Finally further research directions with contribution of the authors, in NATO working groups related to the development of NBWF (Narrowband Waveform) for coalition communication has been presented.