Pseudo-static Test Research Articles

Experimental Assessment of the Influence of Boundary Conditions on the Out-of-Plane Response of Unreinforced Masonry Infill Walls

ABSTRACTExperimental pseudo-static tests aimed at investigating the influence of boundary conditions on the out-of-plane response of unreinforced masonry (URM) infill walls in terms of stiffness, strength and displacement capacity are presented. URM infills bounded to the confining Reinforced Concrete frame along two, three or four edges are tested. Predictions of literature formulations are compared to experimental values of strength and secant stiffness at first macro-cracking and peak load. Models predicting displacement capacity are discussed and interpreted based on the experimental results presented.

Experimental investigation on seismic performance of endplate composite joints to CFST columns

The aim of this research is to carry out pseudo-static tests and investigate the seismic behaviour of the endplate composite joints of concrete-filled steel tubular (CFST) columns using blind bolts. Four full-scale blind-bolted endplate composite joints of a reinforced concrete (RC) slab to circular or square CFST columns were subjected to lateral cyclic displacements. Thereafter, the data obtained were used to evaluate the seismic performance of the typical composite joints from many aspects, such as hysteretic response, strength and rigidity degradation, ductility and energy dissipation capacity. In addition, failure modes were summarized based on the test phenomena; the influence of the column section and endplate types on the seismic performance of the joints was discussed in detail. The findings of the experiment demonstrate that the blind-bolted endplate composite joints possess appropriate ductility and adequate energy dissipation and, through reasonable design, they can satisfy the anti-seismic requirements in most seismic zones.

Pseudo-static low cycle test on the mechanical behavior of PHC pipe piles with consideration of soil-pile interaction

Pre-stressed high-strength concrete (PHC) pipe piles have been widely used in the pile foundations of buildings and bridges which are usually designed elastic based on the capacity design principle. However, when the PHC pipe pile comes to the foundations of Integral Abutment Jointless Bridges (IAJBs), limited ductility might apply in order to accommodate the relatively large deformation demand under the effect of temperature fluctuations or earthquake. The conventional design methods for PHC pipe piles remain in doubt. This paper focuses on low cycle pseudo-static tests on 4 PHC pipe-pile models with various pre-stress levels to gain insight into their mechanical behaviors with consideration of soil-pile interaction. Medium sand was employed in the tests. The details of the experiments are introduced, including design of the models, instrumentation and loading scheme. The testing results indicate that the damages of the PHC pipe piles are mainly concentrated at 4D to 8D of embedded depths. Moreover, the pre-stress level and reinforcement ratio have a significant influence on the failure mode of PHC pipe piles, especially on the distribution of internal force and moment along piles. It is found that the interaction effect of pile-soil strengthens with the pre-stress level which is beneficial to the seismic performance. Furthermore, the backbone of the PHC pipe piles model has four stages: elastic, elastic-plastic, plastic hardening, and failure. It is concluded that PHC pipe piles perform favorably plastic and ductile behavior, and their failure modes are flexural (bending) not brittle (shear). Finally, the PHC pipe pile has an appreciable energy dissipation and deformation capacity, and hence can be used for pile foundations in IAJBs.

EXPERIMENTAL STUDY ON THE SEISMIC PERFORMANCE OF DAMPED OUTRIGGERS

The outriggers are the key components of super tall buildings. Increasing the energy dissipation capacities of outriggers has significant value on improving the structural seismic performance. Based on the pseudo-static test of a conventional outrigger, the seismic performance of outriggers with different dampers was investigated through experiments in this study. The results indicated that the auxiliary devices should be installed to ensure the pure shear deformation state of the dampers. Installing either mild steel dampers or friction dampers at the end of the outrigger could improve its energy dissipation capacity and prevent its components from being damaged. As the stiffness and strength of a friction damper can be decoupled, the design process of such damper in the outriggers was much operable, making it more adoptable and promotable in engineering practice. Moreover, the feasibility of using mild steel dampers in the outriggers was also analyzed in this study. It was found that due to the coupling of stiffness and strength of mild steel dampers, the design requirements for the stiffness and strength of outriggers were hard to meet simultaneously. Therefore, further in-depth studies on the application of outrigger with mild steel dampers are needed.

Experimental study on seismic performance of rocking buckling-restrained brace steel frame with liftable column base

An innovative frame system called rocking buckling-restrained brace frame (RBRBF), which is characterized by allowing the column base uplifting during strong earthquakes, has been proposed to decrease seismic damage and reduce repair cost of building structures after the disaster. According to the working mechanism and functional objectives of this new type of structure system, four buckling-restrained brace steel frames including two rocking ones were designed as half-scale specimens considering various parameters. Pseudo-static tests were conducted on the model specimens to investigate their seismic performance, the yielding mechanism and the damage mode. The experimental results illustrated that the lateral resisting capacity and initial stiffness between the rocking structural models and non-rocking ones were nearly same at the elastic stage due to the reasonable design of rocking column base. The reduced beam sections (RBS) used at the beam-column joints could effectively control the damage location, and the liftable column bases with friction dampers could improve the energy absorption capacity of the rocking structure model. Comparing with the non-rocking models, the plastic damage on rocking specimens was greatly reduced under large lateral deformation. Furthermore, there was no local buckling on the structural elements of the rocking steel frame even under 2.5% drift ratio, which showed that the rocking structures with rational design would perform well under server seismic.

Pseudo-static tests of terminal stirrup-confined concrete-filled rectangular steel tubular columns

This paper mainly presents a pseudo-static test program on 12 terminal stirrup-confined square concrete-filled steel tube (SCFT) columns and 14 rectangular SCFT columns under constant axial pressure. The effects of various factors on the hysteretic behavior of specimens are investigated. These factors include with or without stirrups, height of terminal stirrup region, equivalent stirrup ratio, stirrup form, loading direction, height-length ratio (L/B), length-width ratio (B/D), axial compression ratio (n) and sliding support. The failure mode, strain ratio, hysteretic curve, skeleton curve, ultimate bearing capacity, ductility, stiffness degradation, energy dissipation, as well as the residual deformation of the specimens are analyzed. The results indicate that: (1) When n is relatively larger, the bidirectional stirrups can effectively delay the local buckling of steel tube and greatly increase the ultimate bearing capacity, stiffness, equivalent damping viscosity index, residual deformation rate and ductility index, and further significantly improve the seismic behavior of the rectangular SCFT columns; (2) Axial pressure can improve the confinement effect from the steel tube to the core concrete, also bidirectional stirrups can directly confine the core concrete to decrease strain ratio of the steel tube; (3) With the same value of n, increasing the height of terminal stirrup region or increasing the equivalent stirrup ratio can effectively improve the seismic behavior of the rectangular SCFT columns; (4) The influence of loading direction, L/B and B/D on the ductility of rectangular SCFT columns are not obvious.

Model test study on seismic performance of new type column-plate hollow high pier

There are many disadvantages in the design of high pier in high intensity zone for traditional circular end-shaped hollow pier. The design concept of multi-column grid pier can improve the seismic performance of high-strength pier. The column-plate hollow high piers not only retain the good seismic performance of the lattice pier, but also improve the longitudinal and transverse stiffness of the hollow high piers, which lays a foundation for the application of the column plate bridge piers to the design of railway bridges. To understand the seismic performance of such piers systematically, a local model of plate pier is made on the basis of the column plate pier of the Zongmu Gou Bridge in this paper. The destructive mode and hysteresis characteristics of the pier are studied by means of pseudo-static test. It provides reference for the seismic design of the piers. The test results show that the column-plate structure as a whole has strong seismic performance. Under seismic loading, the inter-column plates can be completely sheared and destroyed, and the frame columns remain flexible. The energy consumption of the inter-column plate during the destruction process ensures the normal operation of the frame column.

Degradation laws of hysteretic behaviour for historical timber buildings based on pseudo-static tests

This paper reports on the pseudo-static tests (PSTs) with a single storey full-scale timber building with architectural details that are prevailing in the Song dynasty, China (A.D. 960–1279). The PSTs were conducted under three levels of vertical load. The force and displacement relationship at selected points in the backbone curves were analysed for the structural stiffness and the accumulated energy dissipation with varying ductility coefficient. The degradation ratios of the bearing capacity, lateral stiffness, and the accumulated energy dissipation of the structure under different vertical loads were obtained. The trilinear backbone curve in PST1 is different from the bilinear relationship in PST2. The stiffness degradation can be modelled with a power function while it is accompanied with a reduced maximum accumulated energy dissipation.

Reinforcement Technology for Foundation Beams of Shear Wall Specimens and Example Analysis

Background: The accuracy of test result could be affected by the cracking of foundation beam in the pseudo-static test of shear walls. Objective: In the paper, the reinforcement method combing external pre-stress method and adding steel bars method was used to reinforce the foundation beam. Conclusion: The study proved that the reinforcement method could reduce the strain of longitudinal steel and slow down the cracking of foundation beam. So that,the method can gain expected goal and offer some help for similar situations.

The influence of microstructure on the mechanical properties of polycrystalline diamond: a literature review

ABSTRACTPolycrystalline diamond (PCD) is an extremely high-performance cutting tool material used in the machining of rock, high-strength, non-ferrous metal alloys and carbon-fibre-reinforced composites. It is favoured for its exceptional hardness and wear resistance which results in at least an order of magnitude improvement in performance over previous technologies in almost all metrics. However, PCD suffers from unpredictable brittle fracture and degradation at high temperature during service which limits its capabilities in cutting applications. The literature on the link between its microstructure and its mechanical properties, including strength, toughness and flaw size distribution as measured by pseudo-static tests, is investigated. The conclusions of the seminal paper on this topic are re-examined in the light of modern ceramics research and an alternative explanation is put forth for the strength–grain size relationship published in this paper. All known literature values for strength and toughness vs. grain size and binder content are collated showing no overall trend in strength with binder content but moderate trends in all other combinations. The common claim of weak grain boundaries is brought into question in the light of the lack of any evidence of this fracture mode being evident in pseudo-static tests. The industrial literature on wear testing and failure modes of PCD in service and service-like tests is examined to bridge the gap between pseudo-static and dynamic, application-based experiments. Six main failure modes are recorded and summarised with intergranular fracture being the most conspicuously absent from the pseudo-static tests. It is suggested that the temperature generated by friction in dynamic tests causes the weakening of grain boundaries, resulting in a transition from transgranular to intergranular fracture and a call for further research in this area is made.

Experimental study of a fabricated confined concrete beam-to-column connection with end-plates

At present, the building industrialization has become the development direction of construction industry, the precast prefabricated buildings become the focus of the construction industry once again because of its unique characteristics. A new-type of fabricated beam-column connections with end-plates is presented and introduced on this background. To investigate the seismic behavior of the new-type precast connection, seven specimens are tested by pseudo-static test. The hysteresis curves are recorded during the test, and the seismic indicators, such as ductility and energy dissipation capacity, are determined. The test results indicate that the hysteresis curves of precast connection are plump, and all specimens failed in bending in a malleable way with a beam plastic hinge, which is fully consistent with the criterion of strong column weak beams. Additionally, the fabricated connection exhibits satisfactory ductility and energy dissipation capacity, showing better seismic performance. Besides, the flexural capacity of unbonded prestressed confined concrete beam is analyzed, and the formula of flexural bearing capacity is proposed based on the theory of concentrated plastic zone. The theoretical results agree well with the experimental data, which can provide reference for theoretical research.

Experimental and Numerical Researches on the Seismic Behavior of Tubular Reinforced Concrete Columns of Air-Cooling Structures

Tubular reinforced concrete columns of air-cooling condenser structures, which undertake the most weight of air cooling equipment, are the major components to resist lateral forces under earthquake. Once collapsed, huge casualties and economic loss would be caused. Thus, four 1/8 scaled specimens were fabricated and tested through the pseudo-static testing method. Failure modes and crack patterns of the specimens under cyclic loading were observed. Then, finite element models of tubular reinforced concrete columns were established using OpenSees and were verified with the experimental results. Finally, the influence of axial compression ratio and longitudinal reinforcement on energy dissipation capacity and stiffness degradation were studied based on the validated finite element modes. It is confirmed that tubular reinforced concrete columns of air-cooling condenser structure exhibit a moderate ability of energy dissipation, and the nonlinear finite element model could reasonably simulate its seismic behavior. Furthermore, axial compression ratio and longitudinal reinforcement are main factors which affect the seismic behavior of the tubular reinforced concrete columns. The experimental results and simulation method provide an available way to design this kind of large tubular reinforced concrete columns with thin-wall.

Performance of a transfer beam with hybrid reinforcement of CFRP bars and steel bars under reversed cyclic loading

AbstractHybrid carbon fiber reinforced plastic (CFRP) and steel bar reinforcement concrete were applied in a transfer beam. Three specimens (ZHL-2, ZHL-3, and ZHL-4) corresponded to different forms of reinforcement, reinforcement ratio, and reinforced root number, respectively. The pseudo static test of the three specimens was carried out under the condition of vertical loading and horizontal reversed cyclic loading. The flexural property and failure mode of the transfer beams were demonstrated. Further, the ductility, energy dissipation capability, hysteretic characteristics, structural yield mechanism, and failure mechanism were also studied. The exploration of these factors was aimed to study the bearing capacity and seismic performance of the transfer beam with hybrid CFRP and steel bars. The test results show that if both the upper and lower longitudinal reinforcements were replaced by CFRP bars with a symmetrical reinforcement, the mechanical property and deformation performance would be superior. The performance would be better than the reinforcements with single upper and lower replacement by CFRP bars. Both the upper and lower longitudinal bars of the transfer beam should be replaced by CFRP bars with a symmetrical form of reinforcement. The ductility performance would be better for the transfer beam with the hybrid reinforcement of CFRP bars and steel bars. It showed a seismic performance. The transfer beam with the hybrid reinforcement of CFRP bars and steel bars could meet the design requirements for the ductile frame “strong column, weak beam and strong node.”

Jatropha curcas crude oil as heat transfer fluid or thermal energy storage material for concentrating solar power plants

Valorisation of local and low cost eco-materials has become an imperative for the sustainable development of Concentrating Solar Power (CSP) in West Africa. In this study, Jatropha curcas crude oil is studied as alternative heat transfer fluid or thermal energy storage material, particularly as a thermal oil substitute. The thermal stability of Jatropha curcas crude oil was experimentally investigated. The crude oil was aged by through thermal treatments, using galvanised steel and 316L stainless steel reactor under steady-state and dynamic conditions up to 210°C. The change in physico-chemical parameters of Jatropha curcas crude oil, such as viscosity, flash point, acidity number, water content, iodine value, peroxide value and chemical composition was monitored. The results indicate a relative stability of the total acid number during the dynamic and pseudo-static tests both in galvanised steel and in 316L stainless steel reactors. The results also show that the measured viscosity at 40°C remains practically constant after tests in steady-state conditions. This is also the case of the total acidity number. The evolution of iron and zinc contents of the oil shows that the use of 316L stainless steel material highly limits the degradation process of Jatropha curcas crude oil. Therefore, the main benefits of Jatropha curcas crude oil are its sustainable character, wide availability, good energy storage density, low cost and absence of use conflict. The oil can, therefore, be considered a suitable candidate for thermal applications up to 210°C, such as small scale CSP plants.

Seismic Failure Modes and Deformation Capacity of Reinforced Concrete Columns under Cyclic Loads

This paper investigates the seismic failure modes and horizontal deformation capacity of reinforced concrete square columns based on the pseudo-static test. The controlled variables include shear aspect ratio, axial load ratio and stirrup spacing. The seismic failure modes, the inelastic deformation capacity after yielding and the deformation components due to flexure, shear and anchorage slip of the RC columns were analyzed, especially flexural-shear failure. The results show that decreasing shear aspect ratio, or increasing axial load or stirrup spacing can result in the change of column failure mode from flexural failure to flexural- shear failure or shear failure, the pinching of hysteresis loops, the reductions of hysteresis loop area and deformation capacity. With the increase of total displacement, all three displacement components increased; the contribution of flexure displacement in total displacement reduced, the contribution of shear displacement increased, the contribution of anchorage slip displacement changed in the range of 30%- 40%.

Studies on Seismic Performance of Precast Concrete Columns with Grouted Splice Sleeve

In order to validate the seismic performance of precast concrete members with steel sleeve connections, pseudo-static tests on four prefabricated columns with vertical grouted splice sleeve connections and on a control group of two cast-in-situ columns have been conducted. The test results indicated that the failure modes of the prefabricated columns and of the cast-in-situ columns are basically identical but differences exist in their crack distribution. The cast-in-situ columns mainly crack horizontally at the bottom of the column, whereas the prefabricated columns have horizontal cracks above the sleeves, and then form diagonal cracks downwards and develop many wider cracks within the range of height of 300 mm at the bottom of the column. The hysteresis curves of the prefabricated columns are plump, which demonstrates that prefabricated columns have satisfactory energy-dissipating capacity. Moreover, the stiffness degradation of the prefabricated specimens is slower than that of the cast-in-situ specimens. The ultimate displacement angle of the prefabricated columns is up to 1/104–1/54, which satisfies the requirements of the inter-story drift ratio during major earthquakes. Finally, some recommendations on practical seismic design pertinent to the precast concrete members with grouted splice sleeves are proposed.

Seismic tests of RC shear walls confined with high-strength rectangular spiral reinforcement

In order to improve the deformation capacity of the high-strength concrete shear wall, five high-strength concrete shear wall specimens confined with high-strength rectangular spiral reinforcement (HRSR) possessing different parameters, were designed in this paper. One specimen was only adopted high-strength rectangular spiral hoops in embedded columns, the rest of the four specimens were used high-strength rectangular spiral hoops in embedded columns, and high-strength spiral horizontal distribution reinforcement were used in the wall body. Pseudo-static test were carried out on high-strength concrete shear wall specimens confined with HRSR, to study the influence of the factors of longitudinal reinforcement ratio, hoop reinforcement form and the spiral stirrups outer the wall on the failure modes, failure mechanism, ductility, hysteresis characteristics, stiffness degradation and energy dissipation capacity of the shear wall. Results showed that using HRSR as hoops and transverse reinforcements could restrain concrete, slow load carrying capacity degeneration, improve the load carrying capacity and ductility of shear walls; under the vertical force, seismic performance of the RC shear wall with high axial compression ratio can be significantly improved through plastic hinge area or the whole body of the shear wall equipped with outer HRSR.

Experimental study of cross stiffened steel plate shear wall with semi-rigid connected frame

There is complex interaction between the infill steel plate and frame edges in the steel plate shear wall structure. The bearing capacity and stiffness of SPSW structure not only depends on the section sizes of frame and wall, but also relates to the stiffness of joint connection. The beam-to-column connection is easy to construct using semi-rigid joints which enhances the deformation and energy dissipation capacities of SPSW structure and effectively avoids the brittle failure of traditional welded joint. Based on the pseudo static test of cross stiffened SPSW structure with semi-rigid connected frame, this paper analyzes the failure mode and energy dissipation mechanism of the structure, discusses the influence of joint connecting forms and arrangement of stiffeners on the seismic performance of the structure. According to the results, the effect of the beam-to-column connection stiffness on the bearing capacity of SPSW structure is small and the differences among the ultimate bearing capacities are less than 5%. When the inter-story displacement angle is 1/50, the ductility factor is between 3.69 and 4.4, which indicates that SPSW structure is good in plastic deformation capacity. The cross stiffeners divide the thin steel plate into small cell plates. By setting the cross stiffeners, the thin steel plate is divide into small cell plates, and mainly pattern of local buckling.

Investigation of the Influences of Asymmetric Damages on Seismic Assessments for Existing Masonry Structures

Masonry structures have been widely used in residences and in commercial and public buildings around the world. Most existing masonry structures have asymmetric damages that significantly influence their safety in earthquakes. Their seismic assessment would not be reliable without considering the influences of these asymmetric damages. To address the issue, the authors conduct a pseudo-static test on a masonry model with asymmetric damages. Before the test, the authors apply asymmetric damages by weakening one of the load-bearing walls of the model. In the test, the authors apply synchronized horizontal displacements on top of the load-bearing walls in a cyclical manner, and record the deformation, crack distributions, and reaction forces. Based on the records, the authors analyze the deformation patterns, failure procedure, cracking pattern, hysteretic behaviors, and stiffness degradation of the model. The test results indicate that asymmetric damages cause nontrivial structural rotation under horizontal loading, and then make the walls fail in different patterns. The structural rotation significantly influences the distribution of the seismic internal forces. Excluding the rotation in the calculation, one can underestimate the seismic internal forces for walls without damages and overestimate the forces for walls with damages. The structural rotation also influences the seismic strengthening scheme. One should apply strengthening measures both in the member scale and in the structural scale. The findings can be referred to in seismic assessment for most existing masonry structures.

EXPERIMENTAL RESEARCH ON SEISMIC PEFORMANCE OF FRAME PIERS OF DOUBLE-DECK VIADUCTS

Based on a double-deck viaduct, two double-deck viaduct piers with different column longitudinal reinforcement ratios are designed and the influence of the longitudinal reinforcement ratio on the seismic performance of double-deck viaducts is investigated with pseudo-static test and numerical analysis. The experiment results show that the beam and lower-level beam-column joints of the high reinforced pier suffer severe damage. When the reinforcement ratio is reduced, damage mainly appears on the column, and the level of damage on the beam and the joint is mitigated effectively. Based on the experiment results, a finite element model of the pier is built and used for parametric analysis. The analysis results indicate that when the column longitudinal reinforcement ratio increases, the ductility capacity of double-deck viaducts decreases and the beam would collapse before the column, which disobeys the performance objective of strong beam and weak column.