Structural fire performance of wood-steel-wood bolted connections with and without perpendicular-to-wood grain reinforcement

2019 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Adam Roman Petrycki ◽  
Osama (Sam) Salem
Keyword(s):  
Time To Failure ◽  
Bolted Connections ◽  
Content Type ◽  
Structural Fire ◽  
Fire Condition ◽  
Glued Laminated Timber ◽  
End Distance ◽  
Wood Grain ◽  
Mass Timber ◽  
In Fire

Purpose In fire condition, the time to failure of a timber connection is mainly reliant on the wood charring rate, the strength of the residual wood section, and the limiting temperature of the steel connectors involved in the connection. The purpose of this study is to experimentally investigate the effects of loaded bolt end distance, number of bolt rows, and the existence of perpendicular-to-wood grain reinforcement on the structural fire behavior of semi-rigid glued-laminated timber (glulam) beam-to-column connections that used steel bolts and concealed steel plate connectors. Design/methodology/approach In total, 16 beam-to-column connections, which were fabricated in wood-steel-wood bolted connection configurations, in eight large-scale sub-frame test assemblies were exposed to elevated temperatures that followed CAN/ULC-S101 standard time-temperature curve, while being subjected to monotonic loading. The beam-to-column connections of four of the eight test assemblies were reinforced perpendicular to the wood grain using self-tapping screws (STS). Fire tests were terminated upon achieving the failure criterion, which predominantly was dependent on the connection’s maximum allowed rotation. Findings Experimental results revealed that increasing the number of bolt rows from two to three, each of two bolts, increased the connection’s time to failure by a greater time increment than that achieved by increasing the bolt end distance from four- to five-times the bolt diameter. Also, the use of STS reinforcement increased the connection’s time to failure by greater time increments than those achieved by increasing the number of bolt rows or the bolt end distance. Originality/value The invaluable experimental data obtained from this study can be effectively used to provide insight and better understanding on how mass-timber glulam bolted connections can behave in fire condition. This can also help in further improving the existing design guidelines for mass-timber structures. Currently, beam-to-column wood connections are designed mainly as axially loaded connections with no guidelines available for determining the fire resistance of timber connections exerting any degree of moment-resisting capability.

Fire performance of hybrid mass timber beam-end connections with perpendicular-to-wood grain reinforcement

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Oluwamuyiwa Okunrounmu ◽  
Osama (Sam) Salem ◽  
George Hadjisophocleous
Keyword(s):  
Fire Resistance ◽  
Elevated Temperatures ◽  
Time To Failure ◽  
Rotational Behaviour ◽  
Fire Performance ◽  
Timber Beam ◽  
Content Type ◽  
Glued Laminated Timber ◽  
Wood Grain ◽  
Mass Timber

PurposeThe fire resistance of timber structures is heavily dependent on the fire behaviour of the connections between its structural elements. The experimental study presented in this paper aimed to investigate the fire performance of glued-laminated timber beam connections reinforced perpendicular-to-wood grain with self-tapping screws (STS).Design/methodology/approachTwo full-size fire experiments were conducted on glulam beam-end connections loaded in flexure bending. Two connection configurations, each utilizing four steel bolts arranged in two different patterns, were reinforced perpendicular to wood grain using STS. The bolt heads and nuts and the steel plate top and bottom edges were fire protected using wood plugs and strips, respectively. Each connection configuration was loaded to 100% of the ultimate design load of the weakest unreinforced configuration. The test assemblies were exposed to elevated temperatures that followed the CAN/ULC-S101 standard fire time–temperature curve.FindingsThe experimental results show that the influence of the STS was significant as it prevented the occurrence of wood splitting and row shear-out and as a result, increased the fire resistance time of the connections. The time to failure of both connection configurations exceeded the minimum fire resistance rating specified as 45 min for combustible construction in applicable building codes.Originality/valueThe experimental data show the effectiveness of a simple fire protection system (i.e. wood plugs and strips) along with the utilization of STS on the rotational behaviour, charring rate, fire resistance time and failure mode of the proposed hybrid mass timber beam-end connection configurations.

Temperature analysis of extended end plate joints to square CFST columns in fire

2016 ◽  
Vol 7 (4) ◽  
pp. 306-315
Author(s):  
Jing-feng Wang ◽  
Hai-Tao Wang ◽  
Wei-Wei Shi ◽  
Hong-Yu Sheng
Keyword(s):  
Temperature Distribution ◽  
Test Results ◽  
Content Type ◽  
Composite Frames ◽  
Composite Joint ◽  
Fire Condition ◽  
Temperature Filed ◽  
Cfst Columns ◽  
Rigid Joints ◽  
In Fire

Purpose This paper aims to obtain fire resistance of semi-rigid joints for concrete-filled steel tubular (CFST) composite frames and temperature filed distribution of composite joints in fire. Design/methodology/approach The temperature filed model of semi-rigid joints to CFST columns with slabs was made by using ABAQUS finite element (FE) software, in considering temperature heating-up stage of fire modelling. The effects of composite slab, fire type and construction location were discussed, and the model was verified by the test results. The temperature distribution of composite joint under three-side or four-side fire condition was studied by the sequentially coupled thermal analysis method. The temperature versus time curves and temperature distribution of various construction and location were analyzed. Findings The paper provides FE analysis and numerical simulation on temperature field of semi-rigid joints for CFST composite frames in fire. The effects of composite slab, fire type and construction location were discussed, and the model was verified by the test results. It suggests that the temperature distribution of composite joint in three- or four-side fire condition showed a different development trend. Research limitations/implications Because of the chosen FE analysis approach, the research results may lack generalizability. Therefore, researchers are encouraged to test the proposed propositions further. Practical implications The research results will become the scientific foundation of mechanical behavior and design method of semi-rigid CFST composite frames in fire. Originality/value This paper fulfils an identified need to study the temperature field distribution of the semi-rigid joints to CFST columns and investigate the mechanical behavior of the semi-rigid CFST joints in fire.

Modelling of unstiffened flush end-plate bolted connections in fire

2006 ◽  
Vol 62 (1-2) ◽  
pp. 151-159 ◽  
Author(s):  
K.S. Al-Jabri ◽  
A. Seibi ◽  
A. Karrech
Keyword(s):  
Bolted Connections ◽  
End Plate ◽  
In Fire

Structural Fire Integrity Testing of Lightweight Structures

2016 ◽  
Author(s):  
Michael Rahm ◽  
Franz Evegren
Keyword(s):  
Safety Factor ◽  
Fire Resistance ◽  
High Speed ◽  
Time To Failure ◽  
Test Procedures ◽  
Structural Fire ◽  
Lightweight Structures ◽  
Applied Loading ◽  
Frp Composite ◽  
Starting Point

To reduce environmental impact and to manage weight in shipping and offshore, lightweight structures are becoming increasingly important. A critical issue for loadbearing structures is their structural fire integrity. It is generally evaluated by loaded furnace fire resistance tests based on ISO 834. As part of the EU project BESST, a series of such tests were performed with typical lightweight fiber reinforced polymer (FRP) composite sandwich structures. The purpose was to determine whether structural fire integrity is sensitive to the design load, design method and safety factor against buckling. In particular was examined whether the temperature at the interface between the exposed laminate and the core is critical for structural integrity and how it depends on the applied loading. Independence of the applied load would make performance solely a matter of heat transfer, which would significantly reduce necessary testing. The tests were carried out with starting point in an insulated sandwich panel system, certified as a 60 minute Fire Resisting Division (FRD-60) for high-speed craft in accordance with the Fire Test Procedures (FTP) Code. The structure consisted of 1.3 mm glass fiber reinforced polyester laminates surrounding a cross linked PVC foam core called Divinycell H80 (80 kg/m3). It was constructed for a 7 kN/m design load, which is the loading applied in the FTP Code furnace test for high-speed craft. Hence, with a conventional safety factor against buckling of 2.5 it was designed to resist a critical load of 17.4 kN/m. With basis in this design, tests were performed with structures where the thickness of the laminates or core had been altered and with adjusted safety factor against the applied loading. In addition, a test was performed with a stiffened panel. Firstly it was noted that 60 minutes of fire resistance was not achieved in most of the tests, which was a consequence of an alteration in the FTP Code test procedures. The FRD-60 structure used as starting point was certified before the 2010 edition of the FTP Code was ratified. This harmonized the test procedure between laboratories and gave a slightly tougher temperature development than when the structure was certified. However, the test results are still valid and show a small variation in the time to failure in the tests with unstiffened sandwich structures, ranging between 51 and 58.5 minutes. Changing the safety factor from 2.5 to 1.5 resulted in a relatively small decrease in time to failure of 3 minutes. The stiffened test showed that structural resistance is better achieved by use of stiffeners than by thick laminates. Furthermore, applying this as a design principle and using a safety factor of 2.5 leaves a test variation between 55 and 58.5 minutes. The temperature at the exposed laminate-core interface was quite similar in the tests at the time of failure. This excludes the test when the laminate thickness was increased as a measure for structural improvement. In conclusion, the test series shows that fire resistance bulkhead testing of insulated FRP composite panels can be simplified and does not have to be performed with varying design loads. To achieve conservative evaluation, a design concept should be evaluated by testing the panel designed for the highest applicable load level, not by testing a weak panel at 7 kN/m loading. This applies to non-stiffened solutions.

scholarly journals Deformations of R.C.Circular Slabs in Fire Condition

2018 ◽  
Vol 4 (4) ◽  
pp. 712 ◽  
Author(s):  
Abdelraouf Tawfik Kassem
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Slenderness Ratio ◽  
High Surface ◽  
High Surface Area ◽  
Concrete Slabs ◽  
Finite Element Models ◽  
Reinforced Concrete Slabs ◽  
Fire Condition ◽  
In Fire

Reinforced concrete slabs are elements in direct contact with superimposed loads, having high surface area and small thickness. Such a condition makes slabs highly vulnerable to fire conditions. Fire results in exaggerated deformations in reinforced concrete slabs, as a result of material deterioration and thermal induced stresses. The main objective of this paper is to deeply investigate how circular R.C. slabs, of different configurations, behave in fire condition. That objective has been achieved through finite element modelling. Thermal-structural finite element models have been prepared, using "Ansys". Finite element models used solid elements to model both thermal and structural slab behaviour. Structural loads had been applied, representing slab operational loads, then thermal loads were applied in accordance with ISO 843 fire curve. Outputs in the form of deflection profile and edge rotation have been extracted out of the models to present slab deformations. A parametric study has been conducted to figure out the significance of various parameters such as; slab depth, slenderness ratio, load ratio, and opening size; regarding slab deformations. It was found that deformational behaviour differs significantly for slabs of thickness equal or below 100 mm, than slabs of thickness equal or above 200 mm. On the other hand considerable changes in slabs behaviour take place after 30 minutes of fire exposure for slabs of thickness equals or below 100 mm, while such changes delay till 60 minutes for slabs of thickness equals or above 200 mm.

A study on the effects of electrical and thermal stresses on void formation and migration lifetime of Sn3.0Ag0.5Cu solder joints

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yanruoyue Li ◽  
Guicui Fu ◽  
Bo Wan ◽  
Zhaoxi Wu ◽  
Xiaojun Yan ◽  
...  
Keyword(s):  
Solder Joint ◽  
Thermal Stresses ◽  
Solder Joints ◽  
Void Formation ◽  
Model Parameters ◽  
Time To Failure ◽  
Current Crowding ◽  
Theoretical Derivation ◽  
Content Type ◽  
And Migration

Purpose The purpose of this study is to investigate the effect of electrical and thermal stresses on the void formation of the Sn3.0Ag0.5Cu (SAC305) lead-free ball grid array (BGA) solder joints and to propose a modified mean-time-to-failure (MTTF) equation when joints are subjected to coupling stress. Design/methodology/approach The samples of the BGA package were subjected to a migration test at different currents and temperatures. Voltage variation was recorded for analysis. Scanning electron microscope and electron back-scattered diffraction were applied to achieve the micromorphological observations. Additionally, the experimental and simulation results were combined to fit the modified model parameters. Findings Voids appeared at the corner of the cathode. The resistance of the daisy chain increased. Two stages of resistance variation were confirmed. The crystal lattice orientation rotated and became consistent and ordered. Electrical and thermal stresses had an impact on the void formation. As the current density and temperature increased, the void increased. The lifetime of the solder joint decreased as the electrical and thermal stresses increased. A modified MTTF model was proposed and its parameters were confirmed by theoretical derivation and test data fitting. Originality/value This study focuses on the effects of coupling stress on the void formation of the SAC305 BGA solder joint. The microstructure and macroscopic performance were studied to identify the effects of different stresses with the use of a variety of analytical methods. The modified MTTF model was constructed for application to SAC305 BGA solder joints. It was found suitable for larger current densities and larger influences of Joule heating and for the welding ball structure with current crowding.

The influence of ethical leadership on the organizational commitment in fire organizations

2021 ◽  
Vol 37 (1) ◽  
pp. 145-156
Author(s):  
Mohammadkarim Bahadori ◽  
Matina Ghasemi ◽  
Edris Hasanpoor ◽  
Seyed Mojtaba Hosseini ◽  
Khalil Alimohammadzadeh
Keyword(s):  
Organizational Commitment ◽  
Ethical Leadership ◽  
Affective Commitment ◽  
Role Model ◽  
Fire Department ◽  
Average Score ◽  
Normative Commitment ◽  
Continuance Commitment ◽  
Content Type ◽  
In Fire

Purpose It is necessary for organizations to have committed employees to perform properly and be able to survive in a competitive world. One of the key components of organizational commitment is implementation of ethical leadership. The purpose of this study is to examine the relationship between ethical leadership and organizational commitment in fire organizations of Tehran. Design/methodology/approach A descriptive-correlational study was carried out in 2019. The sample consisted of 200 randomly selected participants, active in executive and headquarters divisions of fire department in Tehran. To collect data, a questionnaire with three different parts: demographics, organizational commitment questionnaire and the ethical leadership scale, was used. Data analysis were performed by AMOS24 and SPSS software, and data are presented as descriptive statistics of frequency, percentages, mean ± standard deviation (SD) and Pearson’s correlation coefficient. Findings Mean and SD for organizational commitment and ethical leadership were 3.44 ± 0.7 and 3.66 ± 0.62, respectively. Affective commitment had the highest average score among organizational commitment dimensions (3.63 ± 0.75). Among ethical leadership dimensions, ethical management showed the highest average (3.79 ± 0.70). Each component of organizational commitment, i.e. affective commitment, continuance commitment and normative commitment, also showed a significant relationship with ethical leadership (p < 0.05). Model fit results revealed that independent variables could anticipate 87% of changes of dependent variables in organizational commitment. Originality/value The results show a significantly positive relationship between ethical leadership and organizational commitment among the firefighters. Therefore, by using ethical leadership method, i.e. being a role model, improving the relations between management and employees, establishing trust and mutual respect, managers of fire departments can increase firefighters’ organizational commitment, affective commitment, continuance commitment and normative commitment and prevent them from quitting.

scholarly journals A detailed investigation on thermal behaviour of slim floor beams with web openings at elevated temperatures

2019 ◽  
Vol 10 (4) ◽  
pp. 446-467
Author(s):  
Naveed Alam ◽  
Ali Nadjai ◽  
Olivier Vassart ◽  
Francois Hanus
Keyword(s):  
Finite Element ◽  
Thermal Behaviour ◽  
Elevated Temperatures ◽  
Major Influence ◽  
Web Openings ◽  
Content Type ◽  
Composite Action ◽  
Temperature Development ◽  
In Fire ◽  
Steel Section

Purpose In recent times, the use of steel sections with web openings has become common as slim floor beams because they offer a reduction in weight of the steelwork, accommodate services within the floor depth and provide the composite action. The composite action in these beams is achieved either through the concrete dowels or through concrete plugs. Though these web openings offer several benefits in slim floor beams, they induce the material discontinuity in the steel web, which may affect their shear capacity and/or thermal behaviour. The purpose of this study is to investigate the thermal behaviour of slim floor beams with web openings in fire. Design/methodology/approach This research presents findings from experimental and analytical investigations conducted to study the thermal behaviour of slim floor beams with web openings in fire. For this purpose, an experimental investigation was conducted, which shows that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. The behaviour of the tested slim floor beam is validated using finite element modelling. The validated finite element model is then used to conduct a sensitivity study to analyse the influence of different opening spacings, sizes and shapes on the thermal performance of slim floor beams in fire. Findings Test results show that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. Temperatures on the web below the openings are found to be higher as compared to those recorded on the adjacent solid steel web. It is also observed that temperatures on the steel web above the openings are lesser than those on the adjacent solid steel web. Parametric studies conducted using the verified analytical modelling methods show that different opening spacings, sizes and shapes have a variable impact on the thermal behaviour of slim floor beams in fire. Closely spaced and larger opening sizes were found to have a more severe influence on their thermal behaviour in fire as compared to widely spaced and smaller openings. It was also found that the behaviour of these beams is influenced by the shape of the openings with rectangular openings resulting in more severe thermal distributions as compared to circular openings. Originality/value The findings from this research study are highly valuable as they contribute to the existing knowledge database. There is a lack of experimental and analytical investigation on performance of slim floor beams with web openings at elevated temperatures. The results and conclusions from this study will help in developing innovative designs for slim floor beams and will help in reducing the fire related risk associated with structures comprising of slim floor beams with web openings.

Barriers and enablers to women in fire and emergency leadership roles

2019 ◽  
Vol 34 (2) ◽  
pp. 78-93 ◽  
Author(s):  
Debra Parkinson ◽  
Alyssa Duncan ◽  
Frank Archer
Keyword(s):  
Role Models ◽  
Online Survey ◽  
Leadership Roles ◽  
Structured Interviews ◽  
Family Responsibilities ◽  
Content Type ◽  
Management Leadership ◽  
Senior Women ◽  
Qualitative Component ◽  
In Fire

Purpose The purpose of this paper is to understand what (if any) actual and perceived barriers exist for women to take on fire and emergency management leadership roles within the Department of Environment, Land, Water and Planning, Victoria, Australia. Design/methodology/approach An anonymous quantitative online survey was used to collect data about opinions and thoughts of staff. This informed the qualitative component of the research – in-depth, semi-structured interviews and a focus group. The combination of these techniques provides deeper insight into the nature of the barriers for women. Findings Respondents identified real barriers for women accessing leadership roles in fire and emergency. Reflecting the wider literature on barriers to women in executive roles, those identified related to sexism, career penalties not faced by men for family responsibilities, and assumptions of women helping other women’s careers. There were more men in senior roles, leaving senior women isolated and often overlooked. Women had fewer role models and sponsors than men and less developed networks, finding it harder to access training and deployments. The context was described by most as “a boys’ club”, where men were seen to dominate meetings and stereotype the abilities of women. Originality/value This paper analyses the barriers to women in fire and emergency leadership roles within a masculine workplace and is rare in including a qualitative aspect to the issue in the Australian context.

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