•Structural response of multi-storey steel frame to travelling fires and uniform fires.•Irrespective of the fire floor location structural behaviour trends are the same.•Irregular and cyclic axial ...forces develop during small travelling fire scenarios.•Travelling and uniform fires may trigger substantially different structural responses.
Most of the current understanding of building behaviour in fire is based on the adoption of the standard and parametric temperature-time fire curves. However, these design fires are based on small scale tests and idealize the thermal environment as uniform. Thus, they have important limitations on their applicability to large enclosures. Instead, in large open-plan compartments, travelling fires have been observed. To account for such fires, a design tool called Travelling Fires Methodology (TFM) has been developed and used for design. The aim of the present study is to compare computationally the structural response of a multi-storey steel frame subjected to both uniform design fires (available in current standards) and travelling fires. A two-dimensional 10-storey 5-bay steel frame designed according to ASCE 7-02 is modelled in the general finite element program LS-DYNA. Different fire exposures are investigated. They include travelling fires, Eurocode parametric curves, ISO-834 standard fire and the constant compartment temperature curve from the SFPE standard. These fires are applied to different floors, one at a time, to explore the influence on the structural response, resulting in a total of 80 different scenarios. The development of deflections, axial forces and bending moments is analysed. Uniform fires are found to result in approx. 15–55kN (3–13%) higher compressive axial forces in beams compared to small travelling fires. However, the results show irregular oscillations in member utilization levels in the range of 2–38% for the smallest travelling fire sizes, which are not observed for any of the uniform fires. Peak beam mid-span deflections are similar for both travelling fires and uniform fires and depend mainly on the fire duration, but the locations in the frame and times when these peak displacements occur are different. The results indicate that travelling fires and uniform fires trigger substantially different structural responses which may be important in the structural design and selection of the critical members.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper presents results of a study aimed at evaluating the effect of aftershocks in steel framed buildings. For that purpose, three frame models representing existing steel moment-resisting ...frames were subjected to a set of as-recorded mainshock–aftershock seismic sequences. For this purpose, 64 as-recorded seismic sequences registered as a consequence of the 1994 Northridge and 1980 Mammoth Lakes earthquakes were considered in this study. In particular, this investigation employed 14 seismic sequences recorded in 7 accelerographic stations in the near-fault region. An examination of the as-recorded seismic sequences shows that the frequency content of the mainshock and the main aftershock is weakly correlated. The response of the frame models was measured in terms of the peak and residual (permanent) drift demands at the end of the earthquake’s excitation. From the results of this investigation, unlike previous results based on artificial seismic sequences, it was found that as-recorded aftershocks do not significantly increase peak and residual drift demands since the predominant period of the aftershocks (i.e. frequency content) is very different from the period of vibration of the frame models. In addition, it was shown that artificial seismic sequences could significantly overestimate median peak and residual drift demands as well as the record-to-record variability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
AbstractA facile and effective method for retrofitting simple shear tab connections in a steel gravity frame is presented to improve its overall lateral force-resisting capacity. At a target shear ...tab connection, the existing gap between the beam flange and column face is snugly filled with a tapered steel plate, which is then field-attached to the column face. When a steel gravity frame is subjected to lateral loads (due to, for example, earthquake and strong wind), the retrofitted shear tab connection deforms and promptly engages the beam to bind the column via the filler plate, thereby exerting a horizontal thrust to the column at the retrofitted beam flange level. Hence, the moment arm between horizontal reactions increases and so does the flexural capacity of the connection. Numerical results from detailed finite-element analysis confirm the role of beam binding action enabled by the present method in satisfactorily enhancing both the strength and stiffness of shear tab connections as a gravity frame deforms laterally.
Particle damping (PD) technology has a remarkable effect in reducing vibration and noise for high frequency vibration such as mechanical analysis and aviation, and has been widely applied in some ...engineering practices. However, in the field of low frequency and low amplitude vibration control for building structures, the research and application of particle damper technology is still in the preliminary stage. The deficiencies and problems mainly include the mechanical model of PD is not perfect enough and the mechanism of vibration reduction is not clear enough. In the light of the shortcomings of the existing theoretical model of the PD, a mechanical model of the PD with friction effect between the particle and the structure is proposed, and the analytical solution of the displacement response for the mechanical model subjected to harmonic excitation is obtained. The model can fully represent the collision and non-collision process of PD, and the phase trajectories can embody the complex nonlinear characteristics of PD. The theoretical and motion characteristics of the PD are verified by the electromagnetic shaking table test of a single-story steel frame with PD, which proves the rationality of the theoretical model and the correctness of the analytical results, as well as the necessity of considering the friction effect. The parameters of mass ratio, excitation amplitude, excitation frequency and motion gap are further analyzed, so the mechanism of vibration reduction is clearer. Finally, compared with the traditional model of impact damper, it is obvious that the mechanical model of PD with friction effect can more reasonably evaluate the damping performance in practical engineering.
•Establishing a mechanics model of particle damper considering the friction effect.•Giving and solving analytically dynamic equations for the structure with particle damper.•Assessing the rationality and the correctness of the mechanics model.•Comparing the theoretical models of particle damper with and without friction.•Analyzing the factors affecting the effect of particle damper.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper presents the experimental results of two welded unreinforced flange-welded web (WUF-W) beam-to-column connections that defy the current design paradigm of prequalified welded connections. ...The proposed WUF-W connections feature customized beveled backing bars that are intentionally left in place after the completion of the beam flange-to-column face complete joint penetration welds. The connection design aims at a stable hysteretic response by exploiting the beneficial aspects of appreciable panel zone shear yielding (i.e., inelastic shear distortions of at least 15γy, where γy is the panel zone shear distortion at yield), by considering a shear strength-to-demand ratio of 0.8. To prevent divot fracture in the column, minimum through-thickness toughness requirements were imposed for the steel column material. The experimental results suggest that the proposed WUF-W connections achieve a stable hysteretic response up until lateral drift demands of at least 7% rad, while a non-softening response was assured up to 9% rad. The beveled backing bars minimize the associated fracture potential near the beam web centerline, which is a primary concern in prequalified field welded moment connections when conventional weld backing bars are employed. The tests suggest that, under a symmetric cyclic loading protocol, local buckling near the steel beams is prevented up until a lateral drift demand of 6% rad, which is an important finding from structural repairability and stability standpoints. The ultimate failure modes of the welded connections, which are attributable to ductile crack initiation and propagation, are consistent regardless of the employed lateral loading histories, which involved standard symmetric cyclic and collapse-consistent loading protocols. The implications for the seismic design of steel moment resisting frames (MRFs) and the limitations of the present work are discussed.
In this paper, we propose a probabilistic method for analysing the collapse time of steel frame structures in a fire. The method considers the uncertainty of influencing factors. Tornado diagrams are ...used for sensitivity analysis of random variables. Structural analysis samples are selected by Monte Carlo method, and the collapse times of different structural samples are calculated by fire time history analysis. A collapse time fragility curve is fitted according to the calculated collapse times of the samples. A reliability index of the collapse time is used as a quantitative standard to evaluate the collapse performance of a steel frame in a fire. Finally, this method is applied to analyse the collapse time fragility of an eight-storey 3D steel frame structure under different compartment fire scenarios and fire protection levels. According to the collapse time fragility curve, the effects of the different fire scenarios and protection levels on the collapse resistance of the structure under fire are evaluated.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The strategic issue faced by the Ministry of Public Works and Housing, Republic of Indonesia (PUPR) is the large housing backlog, especially in the urban areas. Low-income communities earning less ...than 2 USD/day are found as the most vulnerable to lack of access to affordable housing. This experiment aims to find an alternative solution on building construction material in accordance with the Ministry of Public Housing regulation No. 11 of 2011 about affordable housing guidelines. The experiment was carried out on an LSF to compare four different wall cladding materials. The building area was 36 m2 and the total wall cladding area was 95 m2. The wall cladding materials used were metal sheet, lightweight concrete brick, gypsum reinforced cement (GRC) board, and unplasticized polyvinyl chloride (uPVC) fiber. The experiment collected data on purchases of materials to develop the S-curve and measure construction progress. Then, the work unit price analysis (WUPA) approach was carried out to simulate the labor coefficient of construction speed and its comparison to the material costs of the four wall cladding materials. The experiment on this 36 m2 house found that metal sheet is the most efficient material, which took 22.7 h to cover a 95 m2 wall. Later, it was followed by uPVC fiber with 46.6 h, GRC board with 59.7 h, and finally lightweight con-bricks with 85.7 h. Apparently, the metal sheet not only presented the most efficient construction time, but also provided the lowest construction cost with 115.960 IDR/m2 (8.24 USD/m2). It was followed by uPVC fiber at 133.37 IDR/m2 (9.48 USD/m2); GRC board at 146.91 IDR/m2 (10.44 USD/m2) and finally lightweight con-bricks at 156.88 IDR/m2 (11.15 USD/m2). Through WUPA, this study also found that efficient workmanship (construction speed) of the labor greatly affects construction costs.
In this paper, a design procedure that combines both progressive collapse design under column removal scenario and capacity design to produce a hierarchy of design strengths is presented. The ...procedure develops in the context of the European Standards, using the classification of European steel sections and considering the seismic design features. Three-dimensional models of typical multi-storey steel frame buildings are employed in numerical analysis. The design for progressive collapse is carried out with three types of analysis, namely linear static, nonlinear static and nonlinear dynamic. Since the behaviour following sudden column loss is likely to be inelastic and possibly implicate catenary effects, both geometric and material nonlinearities are considered. The influence of the fundamental parameters involved in seismic and robustness design is finally investigated.
•Performance-based design optimization of steel moment frames is implemented.•Local and overall damage indices are calculated for the optimal frames.•Overall damage index-based fragility curves are ...generated.•A new damage indicator termed as damage margin ratio is proposed.•Repairability borders are determined for low-, mid-, and high-rise optimal steel moment frames.
This study is devoted to seismic performance assessment of optimally designed steel moment frames (SMFs) in the framework of performance-based design (PBD). The methodology presented in this work includes three phases. The first phase involves the optimization of SMFs by employing an efficient metaheuristic algorithm to meet the PBD requirements according to FEMA-350 code. Subsequently, the overall damage index (ODI) is calculated for the obtained optimal SMFs based on the Park-Ang local damage index (DIPA). In the second phase, incremental dynamic analysis (IDA) is conducted for the optimally designed SMFs and their fragility curves are derived and their collapse margin ratios (CMRs) are determined based on FEMA-P695. In the last phase, the fragility curves of the optimal SMFs are generated for different damage levels ranging from slight damage to collapse state and a new damage measure termed as damage margin ratio (DMR) is introduced to assess the damage-resistance capacity of the SMFs at the different damage levels. In order to illustrate the efficiency of the proposed methodology, three numerical examples of 3-, 6-, and 12-story SMFs are presented and the total cost of optimal SMFs, including initial and seismic damage costs, are determined. The numerical results demonstrate that the SMF with the best total cost has the best CMR, DMR, and degree of repairability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
ABSTRACT
In this paper a new type of beam‐to‐column connection is introduced, which is capable of absorbing both very large rotations and axial movements, due firstly to thermal elongation and ...subsequently to extreme weakening of the connected beam. The main idea is to connect the beam and column using a special connector bolted to the column flange using a face‐plate and to the beam web using a fin‐plate. Between these a highly ductile element, which is in this case a hollow circular tube, is included. This plays the crucial role in absorbing beam‐end movements occurring firstly during the expansion of the beam and secondly during its catenary behaviour at very high temperatures.
This study aims to extend the research on this connection to structural case studies in the context of performance‐based structural fire engineering design. The connection has been modelled using different approaches, starting with 3‐D finite element modelling and proceeding to validated simplifications which feed into a component‐based model. In order to make calculations feasible, the mathematical model of the ductile component is developed and calibrated using the information provided by parametrized numerical FEM computations. The component model is developed to be capable of representing the hysteresis occurring due to deformation‐reversals as temperatures rise, as well as failure corresponding to fracture in tension. Thus, the component model is described as a function of displacement and temperature, including sufficiently realistic plastic deformation and fracture criteria. This model is then implemented into global FEM models and utilized to assemble the stiffness matrix of a special connector element used to join the beam and column nodes. This component‐based connection model is then applied in some comparative studies.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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