Quasi-static Cyclic Tests Research Articles

Cyclic shear-compression tests on two stone masonry piers strengthened with CRM and FRCM

This paper discusses the results of an experimental campaign on Composite-Reinforced Mortar (CRM) and Fabric-Reinforced Cementitious Matrix (FRCM) jacketing for the retrofit of stone masonry structures. Two double-leaf natural stone masonry piers were built with the same materials and geometry, including portions of adjoining spandrels above and below. Then CRM was applied to both faces of one of the specimens, using a natural hydraulic-lime mortar, glass-fiber-reinforced polymer meshes, and helicoidal steel connectors. The other pier, instead, was retrofitted with FRCM on both sides, combining a glass-fiber-reinforced cementitious mortar, bidirectional PBO textiles, and PBO connectors. Both specimens were subjected to the same vertical overburden load and to a quasi-static cyclic shear-compression test in double-curvature conditions, up to failure conditions. Different collapse mechanisms were triggered by the two retrofit systems, with flexure dominating the CRM specimen and shear controlling the FRCM one. The displacement capacity was enhanced by factors of about 2.5 in flexure and 3.0 in shear, compared to typical values for unstrengthened piers.

Experimental and numerical investigations into seismic behavior of corroded steel frame beams and columns in offshore atmospheric environment

With the strong promoting of “national carbon peak and carbon neutrality” strategy and the continuous deepening of “performance-based seismic design” concept, the seismic performance evaluation field of Chinese steel structures has developed rapidly. Nevertheless, previous studies are generally aimed at new building structures, ignoring the seismic performance degradation characteristics caused by the durability loss of existing structures under environmental erosion. Thus, in this paper, accelerated offshore atmospheric corrosion and quasi-static cyclic loading tests were carried out on five steel frame beams and four steel frame columns. The effects of corrosion level on the failure mechanism, hysteretic behavior, skeleton curve, bearing capacity, ductility, stiffness degradation and energy dissipation of steel frame members were revealed and analyzed in detail. The test results indicate that with an increase in corrosion level, the appearance of plate local buckling, steel cracking and final failure shows a forward tendency, and all seismic performance indexes significantly decrease. Moreover, the deterioration models of the maximum load, ultimate displacement and cumulative energy dissipation with weight loss rate for corroded steel frame beams and columns were proposed. In addition, a finite element analysis method for corroded steel frame members was established and validated, which considered the corrosion damage and introduced a nonlinear mixed hardening constitutive model and a stress triaxiality dependent ductile damage criterion. On this basis, the parametric analysis was further presented to systematically study the influence of corrosion level, plate width - thickness ratio and its assembly factors, and stress conditions on the mechanical performance of H-shaped steel members, then obtaining the regular expressions of bending capacity and plastic rotation capacity.

Hysteretic restoring force model of high damping rubber bearings including thermo-mechanical coupled effect

In the application of High Damping Rubber (HDR) bearings as seismic isolation devices for bridges in cold regions, there are concerns about the low temperature effect on the hysteresis performance of HDR bearings and the resulting deterioration in bridge performance under strong ground motions. The stiffness and damping ratio of the HDR bearing significantly increase at lower ambient temperatures, and the stiffness reduces as the inner temperature of the bearing increases due to the self-heating of rubber material under repeated cyclic loading, resulting in a complicated thermo-mechanical coupled hysteresis behavior which is not expressed by the currently available restoring force models of HDR bearings. In this study, a simplified thermo-mechanical coupled hysteretic restoring force model of HDR bearings is newly developed. The model parameters are identified from the shear strain–stress curves of HDR bearings obtained in quasi-static cyclic loading tests at three different ambient temperatures. Accuracy of the improved model is verified by comparing the numerical result of seismic response analysis of a bridge model using the proposed restoring force model with the result of hybrid simulation of the same bridge model including the HDR bearing loading test under low-temperature conditions.

Effect of beam elongation phenomenon on lateral load resistance of RC frame

In this study, a quasi-static cyclic loading test was conducted on a two-span reinforced concrete frame to investigate the beam elongation phenomenon. The load–drift ratio responses and failure modes of the test specimens were examined, and the local response of the column members was analyzed to calculate the force and displacement caused by beam elongation. Based on the results, constitutive equations representing the beam elongation phenomenon were derived, and the design implications were proposed for the criteria of the beam-column strength ratio and joint shear strength presented in the ACI 318–19 code. The proposed design implications were found to accurately simulate the experimental results.

Wire Rope Isolators for the Vibration Protection of Heavy Equipment: Exploratory Research

Wire rope isolators (WRI) are devices that dissipate vibrational energy. They are used in various industrial applications to protect equipment and machinery. Heavy machinery and limited space are still some of the constraints engineers face when designing the WRI system. Heavy equipment requires increased vertical stiffness; however, using larger WRIs decreases their lateral flexibility, which is the target property in the first place. Using several small-sized WRIs is not possible in the case of limited space. Therefore, the present study proposes two improvements to WRIs to overcome the challenges caused by heavy-weight equipment and a lack of the space required to insert the appropriate number and size of WRIs. Two new configurations for WRIs are proposed, Spring-WRI (S-WRI) and Double-WRI (D-WRI), to improve the stiffness and damping properties in order to expand their applications. Monotonic and quasi-static cyclic loading tests were performed on the conventional and proposed WRI variants. Exploratory tests showed that the WRI’s stiffness greatly depends on the wire rope diameter. Adding springs inside a conventional WRI (S-WRI) can improve vertical stiffness while maintaining the required lateral flexibility. The D-WRI was found to preserve the necessary flexibility and to be capable of solving the problem of limited space. The hysteresis behavior of the D-WRI can be expressed as the sum of the hysteresis of each WRI. The proposed configurations effectively improve the stiffness and damping properties of WRIs and expand their applicability for the vibration isolation of heavy equipment and in limited space.

Response of steel frame filled by prefabricated RC infill walls with eccentric opening: Experimental study

A steel frame filled by prefabricated RC infill wall (SFRCW) is an effective lateral load-resisting system wherein RC infill walls are embedded inside. The presence of eccentric opening (EO) such as door or window usually significantly reduces the lateral stiffness and strength. In order to accurately evaluate the effect of the EO on the seismic performance of the SFRCW structure, the cyclic quasi-static tests on two, 1/3-scaled, two-story, single-span SFRCW-EO specimens were performed. Both specimens showed the shear-dominated failure mode, moderate ductile behavior, and pinching hysteretic feature. The concrete cracks were induced from the corners of the EO and were attributed to stress concentration phenomena. The initial lateral stiffness was approximately 50 kN/mm, overall ductility ranged from 2.48 to 2.95, and the overstrength factor reached 2.5. The interface slips and separations between RC infill wall and surrounding steel frame in SFRCW-EO specimens were considerably tiny that could be neglected. The flushed end-plate connection, which had the enough rotation capacity and tension-resisting capacity, was an effective partially-restrained (PR) connection used in the SFRCW-EO. The overall seismic behavior of SFRCW-EO was weaker compared to that of the steel frame with solid RC infill walls because it failed by serious concrete crush. In addition, the on-site assembly was more convenient for the SFRCW-EO specimen. Further, strengthening measures such as the use of an embedded beam were essential for ensuring the integrity of infill walls and improving their overall seismic behavior.

Seismic Response Analysis of Steel–Concrete Composite Frame Structures with URSP Connectors

The uplift-restricted and slip-permitted (URSP) connector is a new type of connector used in steel-concrete composite structures that has been proven to improve the structural performance of negative moment regions. Since this connector changes the interface restraint between the slab and steel beam, there is an imperative to study the seismic performance of steel-concrete composite frame systems with this new type of connector. In this study, the dynamic behavior of composite frame structures with URSP connectors under seismic loads was numerically investigated. First, a beam-shell mixed model was used and complex interfaces of different connectors were considered while establishing a numerical model to conduct elasto-plastic time history analysis under various seismic loads. This numerical model was validated with the frame sub-assemblage experimental results of quasi-static cyclic tests. Second, the model analysis results of structures with URSP connectors were obtained and compared with those of traditional structures. Third, dynamic response results including roof displacement, inter-story displacement, and the distribution and failure modes of plastic hinges were analyzed and compared. The comparisons indicated that the arrangement of full-span URSP connectors had a non-negligible influence on the dynamic behavior of the systems. The arrangement increased the maximum inter-story displacement by 31.5% and induced adverse effects in certain cases, which is not suggested in the application of URSP connectors. The partial arrangement of URSP connectors had little influence on the dynamic behavior of the systems, and the frame systems still showed a good seismic performance, which was the same as the traditional composite structural system. These findings may promote the application of URSP connectors in composite structures.

Comparative seismic behavior assessment of a new damper-equipped and conventional chevron-braced frames

This paper presents the results of experimental studies performed on three 1/3-scale steel building frames for comparative assessment of the cyclic behavior of a Chevron frame equipped with a newly-developed damper, THDF (Torsional Hysteretic Damper for Frames) in relation to a Chevron special concentrically braced frame (SCBF) and an eccentrically braced frame with a vertical H-link. THDF is a damper with a displacement-dependent post-elastic stiffness, developed for Chevron frames. First, the SCBF was designed as a full-scale frame according to the requirements of AISC 360–16 and AISC 341–16, and scaled down to 1/3-scale according to similitude requirements due to limitations of the testing facilities. The other two frames are designed as scaled frames by adjusting their braces and energy dissipation elements so that the frames have similar levels of yield force. The frames are subjected to quasi-static cyclic tests of increasing amplitude until failure. In the case of SCBF and H-link frames, the force levels observed in the tests were higher than predicted due to oversight in the fabrication of the test specimens, which may not be the case in practice. In the case of the H-link frame, this led to early failure of the connection before the full plasticization of H-link. SCBF was tested up to low-cycle fatigue failure of both braces. The THDF-equipped frame showed stable force-displacement loops with little variation in force levels and a better distribution of energy among the stories.

Quasi-static cyclic tests on a half-scaled two-storey steel frame equipped with Crescent Shaped Braces at both storeys: Experimental vs. numerical response

This paper discusses the results of quasi-static cyclic tests performed on a half-scaled two-storey one-bay steel pendular frame equipped with Crescent Shaped Braces (CSBs) at both storeys. The same steel pendular frame was previously tested with only one CSB device located at the first storey to validate the structural response of a single device when inserted into a realistic frame. The CSB seismic design procedure and the experimental results of this first configuration were presented and discussed in a companion paper which proved that the experimental behaviour of the single CSB matched the theoretical predictions and that the effect of connection plates was not negligible. Here the attention is focused, for the first time, on a structure fully braced along the height by CSBs as in a realistic building configuration. During the tests, the global and local responses of the structure were monitored by means of inductive displacement transducers, strain gauges and Digital Image Correlation technique. Non-linear Finite Element models were also developed to provide an in-depth interpretation of the experimental results. The objective is twofold: (i) the experimental assessment of the global performances of the braced structure in terms of stiffness, strength, ductility and energy dissipation, and (ii) the comparison between the experimental and the numerically-simulated response of the structure, with specific focus on the response of the two CSBs and on the effects of realistic connections (parasitic bending moments and bolt slippage). In conclusion, the results of the experimental test carried out on a two-storey building structure fully braced with CSBs proved that the CSB seismic design procedure is effective and the use of CSBs as diagonal braces could represent a feasible solution for buildings to achieve multiple seismic performance objectives.

Test of Novel Self-Centering Energy Dissipative Braces with Pre-Pressed Disc Springs and U-Shaped Steel Plates

ABSTRACT To control the residual displacement of the structure after strong earthquakes, this paper develops and validates a novel brace, i.e. the self-centering energy dissipative brace with pre-pressed disc springs and U-shaped steel plates (SCEDB-U). The pre-pressed disc springs are used for recovering nonlinear deformation and the U-shaped steel plates are used for dissipating energy. Initially, the configuration and working principle are described in detail. Then the analytical equations governing the cyclic behavior of the brace are derived. To confirm the concept, the large-scale bracing specimens are designed and manufactured for the quasi-static cyclic loading tests. In the tests, the varied parameters included the plate width of the U-shaped steel plates and the pre-pressure magnitude of the stacked disc springs. Besides, the high-fidelity three-dimensional finite element (FE) models of SCEDB-U are established. According to the experimental data, the SCEDB-U has typical flag-shaped hysteresis, which is characterized by excellent self-centering capability and stable energy dissipation ability. It also indicates that increasing the plate width of U-shaped steel plates can effectively improve the energy dissipation capacity, but may induce residual displacement; increasing the pre-pressure magnitude of disc springs could improve self-centering ability. The numerical results are in good agreement with the experimental data; hence, the FE models can be further utilized for parametric analysis, initial design and optimization.

Overturning effects on seismic performance of the hybrid friction-based seismic isolation system

The safety and reliability of the double-deck variable-depth composite truss bridge (DDVD-CTB) during earthquakes can be ensured by a hybrid friction-based seismic isolation system (HFBSIS). However, the overturning effects on seismic performance of HFBSIS is a significant concern, as it can induce vertical actions of isolation bearings. In this study, a single-degree-of-freedom (SDOF) system was first employed to describe the isolation system with the consideration of overturning effects. Following the nondimensionalization of motion equation, it indicated that the ratio of total axial load variations of spherical bearings to deadweight of the girder (γ) was a good indicator for the overturning effects on seismic performance. Then, the finite element (FE) model of SDOF system was developed and verified by the quasi-static cyclic test results. Finally, parametric sensitivity analyses were carried out to evaluate the degree of overturning effects on the seismic performance of the isolation system under different design parameters. Therefore, the maximum value γ of was less than 5 × 10−7 degree in the engineering practice. The nondimensionalization of motion equation considering overturning effects was approximately the same as that neglecting overturning effects, suggesting that overturning effects could be neglected when designing the HFBSIS in DDVD-CTB.

Seismic performance of short precast bridge columns with grouted splice sleeve (GSS) connectors for shear study: Quasi-static cyclic test and analytical estimation

In this study, shear damage development of four precast bridge columns with different connection design details are first examined via quasi-static test. The short columns are of identical dimension and reinforcement arrangement for both pier and footing segments, and the span-to-depth ratio is 0.85 for shear study. The connection utilizes grouted splice sleeve (GSS) couplers for all four specimens. Different bonding materials are compared, effectiveness of shear keys is investigated, and variation of steel rebar grades is carried out. It is found that epoxy retain lower bond strength than high strength mortar, lower grade of longitudinal rebar significantly reduces shear strength of bridge column, and shear keys are of limited effectiveness on the overall shear damage development. An analytical method for shear strength calculation is then proposed and calibrated based on different test results, which incorporates possible influencing factors for shear strength estimation. Maximum difference between the test results and estimated strength values are less than 10%, and it indicates that the proposed method can be used as a reference for shear strength estimation of short precast bridge columns for seismic strength estimation.

A generalized method for numerical modeling of seismically resilient friction dampers using flat slider bearing element

There has been a growing interest in recent years by both researchers and industry in developing friction dampers that have enhanced seismic performance by using inclined friction interfaces (i.e., not colinear with the plane of loading) in combination with a re-centering mechanism such as steel disc springs and/or SMA materials. These friction and friction-hybrid dampers provide both energy dissipation and self-centering characteristics. Compared to conventional flat-slider friction dampers (where friction interface is colinear with the plane of loading), numerical modeling of these types of friction devices is not straightforward and requires unique material models or complex element configurations to predict earthquake building responses. This technical note provides a generalized numerical model implemented in the OpenSees structural analyses framework that could be broadly applied to the numerical modeling of seismically resilient type friction dampers. The modeling scheme presented in this study utilizes readily available elements (i.e., flat-slider bearing element), eliminating the need and complexity of creating new material models. Given the increased interest found in the literature in the development of friction dampers with re-centering characteristics, this technical note could be useful for both researchers and engineers. Illustrative examples using two distinctly different seismically resilient friction dampers are presented for validation of the proposed modeling scheme. The first comparison is made with a cross-laminated timber rocking wall detailed with a newly proposed Uplift Friction Damper (UFD). Comparisons are made with both quasi-static cyclic tests and a continuum finite element numerical model in the ABAQUS software program. The second validation example compares results with a quasi-static uniaxial cyclic test of a Friction Spring Damper (FSD) device. Predictions of the proposed generalized numerical model are in good agreement with the results of both validation examples.

Experimental study on the normal deformation of joint under dynamic compressions

Understanding the effect of loading rate on the normal deformation characteristics of joints has been an important topic for rock dynamics and rock engineering activities. In this paper, a series of static and quasi-static cyclic compression tests are performed on intact and jointed specimens, to reveal the mechanism of the dynamic normal behaviour of joints. The rate and peak value of the compression loading in each cycle are carefully determined to relate the dynamic normal characteristics of joint to the damage of joint asperities. The effect of loading rate on the normal stress-closure curve in different cycles of loading is analyzed. The results indicate that the loading rate has little or no effect on the normal deformation of joint under compression when the joint behaves in an elastic manner and no damage is caused to joint asperities. And the rate-dependent normal behaviour of joint, on the other hand, is found to be due to the failure of joint asperities, arising from the rate-dependent strength of the material.

Experimental and numerical study on seismic performance of square and l-shaped Concrete-filled steel tubes column Frame-Buckling steel plate shear walls

To boost the application of concrete-filled steel tubes (CFTs) in high-rise buildings, square and l-shaped CFT are used as boundary columns in frame-buckling steel plate shear walls (SPSWs). This study presents an eco-friendly and sustainable solution for using tailings and recycled aggregate concrete as the infill concrete in CFT columns. Cyclic quasi-static tests are performed on two one-span, two-story specimens. A four-corner gusset connection connects the shear wall to the boundary columns. Subsequently, the failure modes, hysteretic curves, and characteristic capacities are analyzed. The failure and hysteretic behaviors of the two tested specimens are simulated using the finite element (FE) software ABAQUS and verified against the experimental results. Based on validated models, parametric studies are established and analyzed. The results imply that the frame-buckling SPSW exhibits good seismic performance. The failure modes of the two specimens are similar; however, the specimen using the l-shaped column exhibits more excessive deformation. In addition, the use of an l-shaped column increases the bearing capacity and ductility by approximately 10 %; simultaneously, the stiffness increases by 30 %. The buckling of the steel plates primarily consumes seismic energy. The results of this study can be used as a reference for engineering practice.

Seismic Performance of Flat Steel Plate Shear Walls with Atmospheric Corrosion

The seismic performance of four different kinds of steel plate shear walls (SPSWs) before and after corrosion are investigated in this paper, including flat steel plate shear walls (FSPSWs), SPSWs with vertical slots in the middle (VSSPSWs), SPSWs with orthogonal stiffeners (OSPSWs) and SPSWs with silts on both sides (BSPSWs). A numerical model that can be validated by existing quasi-static cyclic tests is developed by ABAQUS 6.13. The seismic performance of SPSWs under cyclic loading and atmospheric corrosion is investigated. The results show that (1) compared with FSPSWs, the ultimate shearing strength, initial stiffness, energy dissipation, and ductility of OSPSWs are significantly improved under cyclic loads when both VSSPSWs and BSPSWs are reduced in ultimate shearing strength and energy dissipation. (2) The performance of the FSPSW is most affected by atmospheric corrosion but setting stiffeners can significantly improve the hysteretic performance after corrosion. Meanwhile, the effect of the VSSPSW is better than that of the BSPSW in decreasing the ultimate shearing strength, although both decrease more tardily than that of the FSPSW. (3) The relationships between the ultimate shearing strength and corrosion time of SPSWs are fitted into four equations in this paper, which can be used in practical situations.

Seismic analysis of a base-isolated reinforced concrete frame using high damping rubber bearings considering hardening characteristics and bidirectional coupling effect

High damping rubber bearings (HDRBs) are commonly used in base isolation systems, which can protect the structures from heavy earthquake damage by elongating natural vibration periods of the structures and improving the energy dissipation capacity of the systems. For the HDRBs, the stiffness hardening effect is exhibited at large shear strain, which is favorable to control the displacement of the bearings. Meanwhile, the horizontal hysteretic behavior in the two orthogonal directions is coupled and related to the path history. Here, the influence of the stiffness hardening and bidirectional coupling effects of the bearings on the seismic responses of the isolation system is studied. The full-scale quasistatic cyclic tests of two HDRB specimens with different dimensions were carried out under unidirectional and bidirectional loads. In the numerical analysis, the DHI and the classical Bouc-Wen model are used to simulate the hysteretic behavior of the HDRBs, in which the DHI model can capture the increased damping and stiffness, and bidirectional coupling properties. The parameters of both bearing models are determined according to the test results. Time-history analyses of a six-story reinforced concrete (RC) frame building with an HDRB isolation system are carried out for a suite of earthquake ground motions. The influence on seismic response of superstructure and isolation layer is analyzed with or without considering the hardening effect and bidirectional coupling effect of HDRBs. The results demonstrate that with consideration of the stiffness hardening and coupling effects, the peak responses of the superstructure significantly increase under high-intensity earthquakes. The analytical results suggest that the stiffness hardening and the effect of bidirectional coupling of the HDRBs should be considered in the design for HDRB isolation systems.

Energy dissipation estimation of steel slit shear panel dampers with tapered links considering the effect of out-of-plane buckling

The steel slit shear panel (SSSP) with tapered links is one type of efficient energy-dissipating devices, with tapered shape of the links accommodating the bending moment demand when subjected to lateral shear deformation. To dissipate the maximum amount of seismic energy, full plasticity is expected to be developed. However, out-of-plane buckling, which is almost inevitable for thin plates, significantly reduces its energy dissipation capacity. This work aims to quantify the amount of energy dissipation of SSSPs with tapered links considering the effect of out-of-plane buckling. Quasi-static cyclic loading tests on five SSSP specimens with different design parameters are conducted, based on which the refined numerical model is built and validated. In estimating the energy dissipation, the effect of out-of-plane buckling needs to be considered. Otherwise, the estimated energy dissipation can be as much as over two times the tested value. To consider the effect of out-of-plane buckling, the index of average pinching parameter is adopted. A new method is derived for estimating the energy dissipation of SSSPs with considering the effect of out-of-plane buckling, feasibility of which is validated using the obtained test results.

Quasi-Static Cyclic Testing of Hybrid Posttensioned Bridge Column Supported on a Monopile Foundation

In this research, a low-damage posttensioned rocking solution referred to as dissipative controlled rocking (DCR) connection is proposed for bridge columns supported on monopile foundations. The DCR connection is a low-damage system that replaces the plastic hinge mechanism in a column and aims to minimize and potentially eliminate the repair time and costs after an earthquake. A DCR bridge system combines unbonded posttensioning and replaceable dissipaters to provide self-centering and energy absorption capabilities, respectively. Current research on DCR column systems has focused on the performance of bridge bents founded on a fixed foundation, neglecting soil damping effects. In this research, a one-third scaled bent supported on a monopile with passive soil resistance was tested under quasi-static cyclic loading to validate the lateral seismic response of a DCR bridge bent with the contribution of the soil–foundation–structure interaction. When developing the details for the DCR connection, particular emphasis was made on utilizing conventional construction materials and forms for a low-damage bent that yields a similar construction cost to a monolithic joint. Nevertheless, the proposed DCR connection can be easily and quickly repaired or replaced after a significant seismic event. The performance of the bent was compared against a benchmark structure with an emulative connection type that resembles a monolithic cast-in-place joint. Results from testing suggest a greater performance of the low-damage DCR column. The dynamic response of the DCR column built on a flexible foundation differed from that of a fixed-base structure, which is primarily due to the energy dissipation capability of the flexibly supported structure. Flexibility in the soil foundation increased the structural period of the structure and reduced the seismic response of the DCR column. Damage to the DCR bent was limited to concrete crushing at the rocking interface, which proved to be easily repairable. In contrast, the bent with an emulative connection developed plastic hinging at the bottom of the column, which was nonrepairable.

Seismic responses of infill walls with sliding joints and openings in semi-rigid steel frame

Forming door and window openings in partition infill walls is a frequent activity in engineering practices, while the complexity of the mechanical behavior of such infill systems with openings due to the destructive damage to the infill walls has not been thoroughly considered. To protect the vulnerable door and window openings and mitigate the detrimental multiple diagonal struts effect of infill around the opening, the paper presents two novel precast infill walls with sliding joints and door and window openings for semi-rigid steel frames. The quasi-static cyclic tests are performed on three specimens: a reference bare steel frame and two infilled steel frames with door or window opening. Test results confirm that the developed infill systems effectively prevent potential cracking or deformation of the openings and release the adverse multiple diagonal struts effect of infill with a door or window opening. Because of the working mechanism of the developed infills, the two infilled steel frames behave with similar seismic responses to the bare steel frame, while the novel infills are significantly undamaged and no detectable opening deformation is observed even at the inter-story drift ratio of 3.33%. Furthermore, both experimental and numerical responses of the developed innovative infill systems confirm the effectiveness of the infill systems without any additional fixtures to protect the fragile door and window openings.