AbstractThis paper presents the experimental evaluation of an earthquake-resilient rocking damage-free steel column base, previously proposed and numerically investigated by the authors. The column ...base uses post-tensioned high-strength steel bars to control its rocking behavior, and friction devices to dissipate seismic energy. It is equipped with a circular steel plate with rounded edges, which is used as a rocking base. The rounded edges prevent stress concentration and damage of the contact surfaces, whereas the circular shape allows rocking toward all plan directions. In contrast to conventional steel column bases, the proposed column base exhibits monotonic and cyclic moment–rotation behaviors that are easily described by analytical equations. This allows the definition of a step-by-step design procedure which ensures damage-free behavior, self-centering capability, and energy dissipation capacity for a target design base rotation. The experimental tests, presented in this study, were conducted under monotonic and cyclic loads demonstrating the damage-free behavior even under large rotations. The experimental results were used to validate the design procedure and to calibrate refined three-dimensional (3D) nonlinear finite-element models that will allow further investigations.
AbstractThis paper presents ultralow cycle fatigue tests and the calibration of different fracture models for duplex stainless-steel devices of high seismic performance braced frames. Two different ...geometries of the devices were tested in full scale under 14 cyclic loading protocols up to fracture. The imposed protocols consisted of standard, constant-amplitude, and randomly generated loading histories. The test results show that the devices have stable hysteresis, high postyield stiffness, and large energy-dissipation and fracture capacities. Following the tests, two micromechanics-based models, i.e., the cyclic void growth model and the built-in ABAQUS ductile fracture model, were calibrated using monotonic and cyclic tests on circumferentially notched coupons and complementary finite-element simulations. In addition, Coffin-Manson-like relationships were fitted to the results of the constant-amplitude tests of the devices, and the Palmgren-Miner’s rule was used to predict fracture of the devices under the randomly generated loading protocols. Comparisons of the experimental and numerical results show that the calibrated models can predict ductile fracture of the devices due to ultralow cycle fatigue with acceptable accuracy.
AbstractA new self-centering beam-to-column connection is proposed. The connection uses posttensioned high-strength steel bars to provide self-centering capability and carefully designed ...energy-dissipation (ED) elements that consist of steel cylindrical pins with an hourglass shape. The proposed ED elements have superior ED and fracture capacity, and are placed between the upper and the bottom flanges of the beam such that they do not interfere with the composite slab. A simplified performance-based procedure was used to design the proposed connection. The connection performance was experimentally validated under quasi-static cyclic loading. The specimens were imposed to drift levels beyond the expected design ones to identify all possible failure modes. The experimental results show that the proposed connection eliminates residual drifts and beam damage for drifts lower than or equal to 6%. A simplified analytical procedure using plastic analysis and simple mechanics was found to accurately predict the connection behavior. Repeated tests on a connection specimen were conducted, along with replacing damaged ED elements. These tests showed that the proposed ED elements can be easily replaced without welding or bolting, and hence the proposed connection can be repaired with minimal disturbance to building use or occupation in the aftermath of a major earthquake.
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DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A dual seismic-resistant steel frame, which consists of a moment-resisting frame equipped with high post-yield stiffness energy-dissipative braces, is proposed and numerically evaluated. Replaceable ...hourglass shape pins made of duplex stainless steel with high post-yield stiffness and large energy dissipation and fracture capacity are in series connected to conventional steel braces. Moreover, replaceable fuses are introduced in the beams at the locations where plastic hinges are expected to develop. A performance-based seismic design procedure and appropriate capacity design rules are used to design the dual frame, while its seismic performance is evaluated with advanced numerical simulations using experimentally validated shell–solid finite element models and simplified beam element models. The numerical results show that the dual frame has adequate stiffness and energy dissipation capacity to control peak storey drifts (i.e. non-structural damage), while plastic deformations (i.e. structural damage) are isolated within the replaceable pins of the braces and the beam fuses. In addition, the high post-yield stiffness of the pins, combined with the appreciable elastic deformation capacity of the moment-resisting frame, results in significant reduction of residual storey drifts, which are found to have a mean value of 0.06% under the design earthquake and a mean value of 0.12% under the maximum considered earthquake. These values indicate a superior residual storey drift performance compared to steel frames equipped with buckling restrained braces, and highlight the potential of the proposed dual frame to help steel buildings to return to service within an acceptable short time in the aftermath of a strong earthquake.
•A novel dual seismic-resistant steel frame for drift reduction is proposed.•Braces are equipped with stainless steel pins with high post-yield stiffness.•Stiffness and strength comparable with conventional steel systems•Advanced numerical models show a superior residual storey drift performance.•Structural and non-structural damage are drastically reduced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Nonlinear behavior of continuous prestressed composite beams is evaluated.•Secondary moments in continuous prestressed composite beams are significant.•External prestressing improves moment ...redistribution ability of composite beams.
This paper evaluates the flexural performance and quantifies the secondary moments in two-span prestressed steel-concrete composite beams. A nonlinear model capable of simulating the full-range nonlinear behavior of continuous prestressed composite beams is validated against experimental results. A parametric numerical investigation is then conducted to examine the effectiveness of strengthening a continuous steel-concrete composite beam with external tendons of different cross section areas. In addition, secondary moments in continuous prestressed composite beams having different tendon layouts under symmetrical and unsymmetrical loads are investigated. The results indicate that external prestressing not only increases significantly the ultimate load-carrying capacity but also improves the moment redistribution ability of continuous steel-concrete composite beams. Moreover, the analysis shows that significant secondary moments are present in continuous prestressed composite beams throughout the loading history. It is therefore necessary to consider secondary moments in the strength design of this structural typology.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
► A previously proposed and tested post-tensioned connection was simulated. ► Simple mechanics model predicts the behavior of the proposed connection. ► Finite element models were developed to ...capture the cyclic behavior. ► Parametric studies on different beam and column sizes were conducted. ► The stress state and weak points of the post-tensioned connection were studied.
A new self-centering steel post-tensioned connection has been proposed by the authors. The connection uses high-strength steel post-tensioned bars to provide self-centering behavior and steel energy dissipation elements that consist of cylindrical pins with hourglass shape to provide enhanced deformation capacity. Large-scale experimental tests showed that the connection has robust self-centering behavior by eliminating residual drifts and beam damage for drifts lower or equal to 6%. This paper presents finite element models which can be used to reliably assess the design and behavior of the connection. A simplified connection model was first developed using simple mechanics. This model can predict the connection stiffness and strength with reasonable accuracy, and enables the preliminary design of self-centering steel moment-resisting frames using the proposed connection. A detailed nonlinear finite element model was also developed. This model was calibrated against experimental results and found capable to trace the nonlinear cyclic behavior of the connection and capture all possible local failure modes. The calibrated finite element model was used to conduct a series of simulations to study the effect of different parameters on the connection behavior. The parameters studied include the adopted design procedure, beam reinforcing detailing, and the beam and column section sizes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Previous research showed that steel moment-resisting frames (MRFs) with viscous dampers may experience column plastic hinges under strong earthquakes and highlighted the need to further assess the ...efficiency of capacity design rules. To partially address this need, three alternatives of a prototype building having five, 10 and 20 stories are designed according to Eurocode 8 using either steel MRFs or steel MRFs with dampers. Incremental dynamic analysis (IDA) is conducted for all MRFs and their collapse resistance and plastic mechanism is evaluated. The results show that steel MRFs with dampers are prone to column plastic hinging in comparison to steel MRFs. The steel MRFs with dampers are then iteratively re-designed with stricter capacity design rules to achieve a plastic mechanism that is approximately similar to that of steel MRFs. The performance of these re-designed steel MRFs with dampers indicates, that overall, enforcement of stricter capacity design rules for columns is not justified neither from a collapse resistance or a reparability perspective.
•The capacity design of columns of steel MRFs with viscous dampers is evaluated.•Tall steel MRFs with viscous dampers experience column plastic hinges.•Stricter capacity design of columns for MRFs with viscous dampers is not justified.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A novel steel joint is experimentally evaluated against progressive collapse.•Stainless steel pins are used to improve the robustness of typical steel joints.•The proposed structural details provide ...the required tie force and rotation capacity.•An analytical model can accurately predict the behaviour of the tested joints.
This paper presents static and dynamic tests on nominally-pinned steel joints equipped with novel structural details for progressive collapse mitigation. The proposed structural details utilise the exceptional ductility and strength of stainless steel pins to enhance both the tie force and the rotational capacity of a vulnerable steel joint. The stainless steel pins along with additional supporting elements are installed in the joint region without interfering with the design for gravity loads, and they can be used for both new designs and to retrofit existing steel buildings. A static test on a vulnerable industry-standard steel fin-plate connection is first presented followed by two static tests on the same connection retrofitted with the proposed structural details. The retrofitted connections were subsequently tested under dynamic conditions with increasing imposed loading using a test setup that simulates a sudden column loss scenario. The test results showed that nominally-pinned joints equipped with the proposed structural details can achieve the required tie force capacity while undergoing rotations larger than 0.2 rad. Analytical equations based on simple joint equilibrium are used to validate the results of the static tests. An analytical method based on the energy conservation principle is also proposed and comparison with the dynamic tests shows very good predictive capability when the assumed loss of energy is 22%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Robustness of a steel building with self-centering moment resisting frames.•The investigation is based on nonlinear quasi-static and dynamic analyses.•The composite floor contributes significantly ...to the robustness of the building.•Dynamic Increase Factor values are estimated based on displacements and forces.•A significant safety factor against progressive collapse is observed.•Column buckling is found to govern the ultimate collapse resistance of the building.
This paper presents progressive collapse simulations to assess the robustness of a seismic-resistant building using self-centering moment resisting frames (SC-MRFs) under a sudden column loss scenario. The first floor of the building, including the composite floor, was modelled in ABAQUS using a mixture of finite element types and simulation methods to balance computational cost and accuracy. First, key components of the numerical model, including the composite beams, the fin-plate beam-column connections, and the perimeter SC-MRFs, were validated against available experimental results to ensure a reliable simulation. The validated model was then used to study the robustness of the building under a sudden column loss event. Both nonlinear static and dynamic analyses were employed. The simulations allowed for the identification of all possible failure modes and the quantification of the contribution of the composite floor to the robustness of the frame. The results show that the building can withstand the code-prescribed load with a safety factor of 2 and that the structural limit state that triggers progressive collapse is the buckling of the gravity columns. The Dynamic Increase Factor (DIF) was also identified by comparing the static and dynamic responses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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