Cyclic Lateral Load Tests Research Articles

Nonlinear cyclic behavior of laterally loaded pile in cohesive soil

Pile foundations may be subjected to lateral dynamic loads due to different hazards, such as impact of ships on bridge piers or jetties during berthing, wave and wind actions on offshore structures, and seismic wave motion on different buildings. The beam on nonlinear Winkler foundation (BNWF) approach is widely employed for predicting the response of piles under lateral loading because of its simplicity and practical accuracy. p–y curves are employed to represent the nonlinear soil reactions within the framework of the BNWF approach. However, they are empirically obtained from limited full-scale field tests and are not unique, accounting only for the pile width and not its mechanical properties. On the other hand, the strain wedge (SW) method allows the assessment of three-dimensional (3-D) soil–pile interaction of laterally loaded piles by incorporating soil continuity and pile properties as well as soil properties. In this study, the nonlinear p–y curves generated by the SW model are implemented as the backbone curve of developed BNWF model to effectively account for different response features of the pile–soil system. These features include the soil and pile nonlinear behavior, cyclic degradation of soil stiffness and strength, formation of soil–pile gap, and radiation damping. Two case studies of cyclic lateral load tests for single piles are investigated to examine the effects of soil degradation and gap formation on the response of laterally loaded piles embedded in cohesive soil. The developed model is shown to be capable of representing different soil–pile interaction features observed in experiments. The predictions of the developed BNWF model are in good agreement with experimental results. Finally, a comprehensive parametric study is performed to compare the predictions of the SWM-based model of the pile response under cyclic loading with that obtained from the conventional p–y curve–based model for different pile cross-section configurations, mechanical properties (strength and stiffness), and soil strength–stiffness.

Seismic and Power Generation Performance of U-Shaped Steel Connected PV-Shear Wall under Lateral Cyclic Loading

BIPV is now widely used in office and residential buildings, but its seismic performance still remained vague especially when the photovoltaic (PV) modules are installed on high-rise building facades. A new form of reinforced concrete shear wall integrated with photovoltaic module is proposed in this paper, aiming to apply PV module to the facades of high-rise buildings. In this new form, the PV module is integrated with the reinforced concrete wall by U-shaped steel connectors through embedded steel plates. The lateral cyclic loading test is executed to investigate the seismic behavior and the electric and thermal performance with different drift angles. The seismic behavior, including failure pattern, lateral force-top displacement relationship, and deformation capacity, was investigated. The power generation and temperature variation on the back of the PV module and both sides of the shear wall were also tested. Two main results are demonstrated through the experiment: (1) the U-shaped steel connectors provide enough deformation capacity for the compatibility of the PV module to the shear wall during the whole cyclic test; (2) the electricity generation capacity is effective and stable during this seismic simulation test.

Cyclic Lateral Load Test on T-Shaped Reinforced Concrete Columns

Based on the experiment of eight reinforced concrete T-shaped columns under low cyclic load, the factors which affect bearing capacity and seismic behavior, such as limb length, axial load ratio, stirrup ratio and the arrangement of longitudinal bars, etc., are analyzed. Tests results show that the bearing capacity of the columns increases, but the ductility is decreased with an increase of axial load ratio. The bearing capacity of T-shaped column increases when the web gets longer, while its deformability and ductility decrease. Besides, increase of stirrup ratio and longitudinal bars in the end of the web also have effect on the ductility of the columns.

Influence of masonry infill on the seismic performance of concentrically braced frames

This paper presents an experimental and analytical study to investigate the effect of masonry infill on the seismic performance of special Concentrically Braced Frames (CBFs). Cyclic lateral load tests are conducted on three half-scale specimens including two special CBFs with and without masonry infill and a moment resisting steel frame with masonry infill for comparison purposes. Companion analyses are performed to study the influence of masonry infill on the potential rupture of gusset plates and top-seat angle connections by using detailed FE models validated with experimental results. It is shown that the presence of masonry infill could increase the lateral stiffness and load carrying capacity of the special CBF by 33% and 41%, respectively. However, the interaction between masonry infill and the frame significantly increased the strain demands and failure potential of the connections. The results of the experimental tests and analytical simulations indicate that ignoring the influence of masonry infill in the seismic design process of CBFs results in a premature fracture of the connection weld lines and a significant reduction in the deformation capacity and ductility of the frame. This can adversely influence the seismic performance of the structure under strong earthquakes. The results of this study compare well with the damage observations after the 2003 earthquake in Bam, Iran.

H형강 프레임으로 보강한 철근 콘크리트 골조의 내진성능 평가

This study proposed proposes a retrofitting method using an H-beam frame to improve the seismic performance of non-seismic designed reinforced concrete frames. To evaluate the seismic performance with the H-beam frames, a cyclic lateral load test was performed and the experimental result was compared with the bared frame, and a masonry infilled RC frame. The results was were analyzed regarding aspects of the load-displacement hysteresis behavior, effective stiffness, displacement ductility, and cumulative energy dissipation. AlsoIn addition, it was possible to prove both an increase of in the maximum load capacity, effective stiffness, and energy dissipation capacity using the H-beam frame.

횡방향 가력실험 및 충격실험을 통한 강판콘크리트(SC) 전단벽의 감쇠비 평가

Steel plate concrete (SC) composite structure is now being recognized as a promising technology applicable to nuclear power plants as it is faster and suitable for modular construction. It is required to identify its dynamic characteristics prior to perform the seismic design of the SC structure. Particularly, the damping ratio of the structure is one of the critical design factors to control the dynamic response of structure. This paper compares the criteria for the damping ratios of each type of structures which are prescribed in the regulatory guide for the nuclear power plant. In order to identify the damping ratio of SC shear wall, this study made SC wall specimens and conducted experiments by cyclic lateral load tests and vibration tests with impact hammer. During the lateral loading test, SC wall specimens exhibited large ductile capacities with increasing amplitude of loading due to the confinement effects by the steel plate and the damping ratios increased until failure. The experimental results show that the damping ratios increased from about 6% to about 20% by increasing the load from the safe shutdown earthquake level to the ultimate strength level.

Experimental study on the seismic performance of new sandwich masonry walls

Sandwich masonry walls are widely used as energy-saving panels since the interlayer between the outer leaves can act as an insulation layer. New types of sandwich walls are continually being introduced in research and applications, and due to their unique bond patterns, experimental studies have been performed to investigate their mechanical properties, especially with regard to their seismic performance. In this study, three new types of sandwich masonry wall have been designed, and cyclic lateral loading tests were carried out on five specimens. The results showed that the specimens failed mainly due to slippage along the bottom cracks or the development of diagonal cracks, and the failure patterns were considerably influenced by the aspect ratio. Analysis was undertaken on the seismic response of the new walls, which included ductility, stiffness degradation and energy dissipation capacity, and no obvious difference was observed between the seismic performance of the new walls and traditional walls. Comparisons were made between the experimental results and the calculated results of the shear capacity. It is concluded that the formulas in the two Chinese codes (GB 50011 and GB 50003) are suitable for the calculation of the shear capacity for the new types of walls, and the formula in GB 50011 tends to be more conservative.

Cyclic Loading Tests for Prefabricated Composite Columns Using Steel Angle and Reinforcing Bar

PSRC 기둥은 앵글을 콘크리트에 매입시킨 기둥으로, 단면의 외곽 코너에 배치되는 앵글이 기둥의 휨-압축에 저항한다. 본 연구에서는 KBC 2009에 따라 압축력을 가한 기둥에 대하여 횡방향 반복가력 실험을 통하여 내진성능을 검증하였다. 기둥 종류, 연속후프근 적용, 앵글에 스터드 적용을 실험 변수로 고려하였으며, 2/3 스케일을 갖는 한 개의 SRC 합성기둥과 세 개의 PSRC 합성기둥을 실험하였다. 실험결과, KBC 2009로 예측한 PSRC 합성기둥의 하중재하능력은 실험결과와 잘 일치하였으며, 변형능력과 에너지 소산에 있어서 우수한 성능을 보여주었다. PSRC 합성기둥은 반복하중으로 인한 콘크리트 피복 탈락 이후, 앵글 및 주철근의 좌굴에 의해 실험체의 하중재하능력이 감소하였다. 특히, 연속후프근을 적용한 PSRC 합성기둥은 앵글의 조기 국부좌굴이 억제되어 기존 PSRC 합성기둥에 비해 연성능력이 향상되었다. PSRC composite column is a concrete encased steel angle column. In the PSRC composite column, the steel angles placed at the corner of the cross-section resists bending moment and compression load. In the present study, using the performance criteria in KBC 2009, cyclic lateral loading test was performed for PSRC columns to verify the seismic performance. The test parameters were the column type, the use of continuous hoop, and the use of studs for steel angle. 2/3 scale specimens of a conventional composite column and three PSRC columns were tested. The test results showed that the load-carrying capacity predicted by KBC 2009 correlated well with the test results. The specimens also exhibited good deformation and energy dissipation capacities. After concrete cover spalling under cyclic loading, the load-carrying capacity were decreased by buckling of longitudinal bars and steel angles. When continuous hoop was used, the deformability of the PSRC column was improved, preventing early buckling of the steel angles.

Development of multi-spiral confinements in rectangular columns for construction automation

Proper design of confinement reinforcement in columns is critically important for buildings that need to survive strong earthquakes. This paper presents the development of an innovative multispiral confinement design for rectangular reinforced concrete columns through testing and evaluation of a large number of concrete column specimens in axial compression and lateral cyclic loadings. In the first phase of this test program, 10 confinement designs, including four rectilinear configurations and six different multispiral configurations, were evaluated in a series of axial compression tests. The test results show that the specimens with multispiral configurations exhibited higher compressive strengths, energy capacities, and ductility than those with rectilinear confinement designs. Among them, two multispiral confinement designs (i.e., combinations of four spirals and five spirals) and a design with a spiral and cross ties exhibited better confinement effectiveness and, therefore, were selected for further study in the Phase II study. In the Phase II study, detailed axial compression tests and lateral cyclic loading tests were carried out for four confinement designs that include one conventional stirrup design, combinations of four spirals and five spirals designs, and a spiral with cross ties. Test variables include various strengths of concrete, spiral pitches, the sizes and yield strengths of the spiral reinforcement, and the volumetric ratio of the confinement reinforcement. The test results clearly indicate that the multispiral reinforced concrete specimens exhibited higher compressive strengths and ductility capacities as compared to the columns with the conventional stirrup design. Among the specimens tested, the five-spiral confinement design (consisting of one large spiral at the center and four small ones at the four corners) shows the highest compressive strength, and ductility capacity.

STRUCTURAL CHARACTERISTIC OF RC COLUMNS RETROFITTED WITH A COMBINATION OF ARAMID FIBER SHEETS AND STEEL PLATES

We have developed a new seismic reinforcing method that combines aramid fiber sheets and steel plates for existing RC columns. In order to investigate structure characteristic of RC columns retrofitted with this technique, cyclic lateral loading test was carried out. As a test results, the tendency of hysteretic loops were generally similar for all specimens;longitudinal bar was yielding at drift angle of 1/100rad, the strength started to decrease when the maximum strength was achieved at drift angle of about 1/50rad. Flexural cracks after the test were observed at the top and bottom of column. However, the strength decrease was very small and cracks was few. Furthermore, it was found that this method can be used for enhancing the flexural strength compared with RC columns retrofitted only by aramid fiber sheets. Therefore, the calculated values by current ultimate flexural capacity formula were underestimate test results. This paper was discussed about the flexural strength and the ductile behavior obtained form the skeleton curve, which was converted into the elastic-plastic restoring force characteristics based on principle of the ultimate energy equilibrium. In conclusion, the experimental evaluation methods of seismic performance for columns retrofitted with this technique was estimated considering the increasing effect of flexural strength and equivalent viscous damping factor.

RC造柱梁部分架構の柱曲げ強度増大を図るための外付け補強法とその実験検討

In this paper, new seismic retrofitting methods by external reinforcement is proposed. Main objectives of this technique is to increase the flexural strength of existing RC columns detailing weak column and strong beam joint type in RC connection and to ensure the seismic performance subjected to large deformation under cyclic lateral loads. The proposed methods herein is the combined the steel plates and continuous fiber sheets with grout mortar layer. Furthermore, additional external longitudinal bar through the beam-column joint which is encased in mortar layer. These members are connected with the existing RC columns together with bonded anchor.In order to investigate the increasing flexural strength, the lateral cyclic loading tests were conducted for the five specimens with two different joint type of exterior and interior columns which the different mechanical properties of beam were planned, and respectively, compared them with the original RC frame. Test results shows that this method was very effective in enhancing the flexural strength of column. But its strength for all specimens of interior columns were almost similar, because hysteresis characteristics were hardly affected by mechanical properties of beam.

Seismic Behavior of Concrete Columns Reinforced by Steel-FRP Composite Bars

Steel-fiber-reinforced polymer (FRP) composite bars (SFCBs) are a novel reinforcement for concrete structures. Because of the FRP’s linear elastic characteristic and high ultimate strength, they can achieve a stable postyield stiffness even after the inner steel bar has yielded, which subsequently enables a performance-based seismic design to easily be implemented. In this study, lateral cyclic loading tests of concrete columns reinforced either by SFCBs or by ordinary steel bars were conducted with axial compression ratios of 0.12. The main variable parameters were the FRP type (basalt or carbon FRP) and the steel/FRP ratio of the SFCBs. The test results showed the following: (1) compared with ordinary RC columns, SFCB-reinforced concrete columns had a stable postyield stiffness after the SFCB’s inner steel bar yielded; (2) because of the postyield stiffness of the SFCB, the SFCB-reinforced concrete columns exhibited less column-base curvature demand than ordinary RC columns for a given column cap lateral deformation. Thus, reduced unloading residual deformation (i.e., higher postearthquake reparability) of SFCB columns could be achieved; (3) the outer FRP type of SFCB had a direct influence on the performance of SFCB-reinforced concrete columns, and concrete columns reinforced with steel-basalt FRP (BFRP) composite bars exhibited better ductility (i.e., a longer effective length of postyield stiffness) and a smaller unloading residual deformation under the same unloading displacement when compared with steel-carbon FRP (CFRP) composite bar columns; (4) the degradation of the unloading stiffness by an ordinary RC column based on the Takeda (TK) model was only suitable at a certain lateral displacement. In evaluating the reparability of important structures at the small plastic deformation stage, the TK model estimated a much smaller residual displacement, which is unsafe for important structures.

Synergetic effect of steel fibers and shear-reinforcing bars on the shear-resistance mechanisms of RC linear members

Reinforced concrete with steel fibers (RSF) is one type of a hybrid structure that can improve the shear-load capacity of conventional reinforced concrete (RC) structures. This paper studies the synergetic effect of shear-reinforcing bars and steel fibers on the shear-resistance of RSF beams and columns, based on the shape and the distribution of diagonal cracks. A series of bending and lateral cyclic-loading tests were conducted to consider the effect of loading and support conditions on the shear-resistance mechanism. As a result, the optimum ratio of steel fibers to shear-reinforcing bars for the shear-load capacity is determined for the RSF linear members.

Experimental Investigations on the Behaviour of Pile Groups in Clay Under Lateral Cyclic Loading

This paper presents the results of two-way cyclic lateral load tests carried out on model pile groups embedded in soft marine clay. The tests are conducted on 1 × 2, 2 × 2 and 3 × 3 pile groups having length to diameter ratio (L/D) of 15, 30 and 40 with the spacing to diameter ratio (S/D) of 3, 5, 7 and 9. The experimental results are presented in the form of load–deflection curves and bending moment profiles. Cyclic group efficiency, critical spacing, critical cyclic load level and cyclic p-multipliers are evaluated. It is found that the lateral capacity of the 3 × 3 group reduces by about 42% after 50 cycles of loading. The cyclic p-multipliers of 3 × 3 pile group are found to be 0.41, 0.25 and 0.29 for leading, intermediate and rear rows respectively. The test results are compared with the numerical analysis carried out by p–y method using GROUP program. The analysis carried out with experimentally evaluated p-multipliers predicts load—deflection and bending profiles of pile groups reasonably well, but underestimates the depth to maximum bending moment by about 15%.

Ductility Evaluation of Concrete-Encased Steel Bridge Piers Subjected to Lateral Cyclic Loading

An experimental and analytical study was conducted to investigate the ductility of concrete-encased steel piers, referred to as “steel-reinforced concrete (SRC) construction.” Based on the cyclic lateral loading tests of SRC column specimens, the restorable and ultimate limit states are defined as the point when concrete cover spalling occurs (equivalent to longitudinal bar buckling) and the point when flange buckling of the H-shaped steel occurs, respectively. To estimate the lateral displacement capacity at both the restorable and ultimate limit states, the curvature distribution of the column was calculated based on the buckling analysis of the longitudinal bar, which was restrained by a concrete cover and transverse reinforcement, and of the steel flange encased in concrete. The lateral displacement was obtained by integrating the curvature distribution. Comparison of the computed results with experimental results, including other writers’ reports, confirmed that the proposed method can appropriately ...

Damage Avoidance Design Steel Beam-Column Moment Connection Using High-Force-to-Volume Dissipators

Existing welded steel moment frames are designed to tolerate substantial yielding and plastic rotation under earthquake loads. This sacrificial design approach can lead to permanent, and often irreparable damage when interstory drifts exceed 2%. The experimental seismic performance of a 50% full-scale damage avoidance designed structural steel beam-column connection is presented. The beam-column joint region consists of a top flange-hung beam connected to the column by an angle bracket. High-force-to-volume (HF2V) devices are attached from the column to the beam to provide joint rigidity and energy dissipation as the joint opens and closes. The HF2V devices are connected either below the beam flange or concealed above the beam's lower flange. Reversed cyclic lateral load tests are conducted with drift amplitudes up to 4%. No damage is observed in the principal beam and column structural elements. The need for stiff device connections to achieve optimal device performance is demonstrated, and potential design solutions presented. Stable hysteresis and repeatable energy dissipation for a large number of cycles up to the 4% drift level is observed. It is concluded that superior and repeatable energy dissipation without damage can be achieved for every dynamic motion cycle, in contrast to conventional sacrificially designed welded moment frame connections.

Lateral Performance of Full-Scale Bridge Abutment Wall with Granular Backfill

Bridge abutments typically contain a backwall element that is designed to break free of its base support when struck by a bridge deck during an earthquake event and push into the abutment backfill soils. Results are presented for a full-scale cyclic lateral load test of an abutment backwall configured to represent the dimensions ( 1.7 m height), boundary conditions, and backfill materials (compacted silty sand) that are typical of California bridge design practice. An innovative loading system was utilized that operates under displacement control and that assures horizontal wall displacement with minimal vertical displacement. The applied horizontal displacement ranged from null to approximately 11% of the wall height (0.11H) . The maximum earth pressure occurred at a wall displacement of 0.03H and corresponded to a passive earth pressure coefficient of Kp =16.3 . The measured force distribution applied to the wall from hydraulic actuators allowed the soil pressure distribution to be inferred as triangula...

EXPERIMENTAL STUDY ON LATERAL RESISTANCE MECHANISM OF COMPOSITE FOUNDATION OF PILE WITH REUSING EXISTING PILES

This paper investigates the lateral resistance of a composite foundation of pile with reusing existing piles by cyclic lateral loading tests and simulation analysis. In this foundation, existing piles are not jointed to the raft with shallow soil improvement between a new pile and existing piles. The major findings obtained from tests and simulation analysis are summarized as follows; 1) Existing piles left in the soil have almost no effect on lateral resistance of a new pile. On the other hand, due to shallow soil improvement between a new pile and existing piles, existing piles are displaced together with a new pile and therefore lateral resistance of a new pile increases. 2) The test results, such as lateral resistance of a new pile and stresses in piles, are precisely simulated by 3-D finite element analysis. Furthermore, ultimate stress in improved soil can be approximately predicted.

반복 횡하중을 받는 유공 PC 기둥 접합부의 구조성능 평가

In order to improve the workability in erecting Precast Concrete (PC) members and enhance the seismic resistance capacity of the joints in PC moment frames, a new PC column and its construction process are introduced in this paper. This column is manufactured by centrifugal force in keeping the hollow tube inside; the hollow is little bit wide and the grout can be poured from top to bottom after erection at site so that more compact grouting is possible in horizontal joint. The repeated cyclic loading test for four full scaled specimens was conducted to evaluate the seismic resistance capacity of the joint designed by the proposed system. For the continuity of main reinforcements in column, two connecting methods are used in designing specimens; one is to use mechanical connector and other is lab splice. From the cyclic lateral loading test, it was found that the seismic capacity of the developed PC column joint is comparable to that of monolithic joint.

Centrifuge Seismic Modeling of Pile-Supported Wharves

Abstract Five pile-supported wharf models were dynamically tested in a large-scale geotechnical centrifuge at UC Davis, California. Models representing pile-supported wharf configurations common in the United States were subjected to recorded acceleration time histories. Model variations included single-lift, multi-lift, and cut-slope rock dike configurations with foundation layers of loose liquefiable sand, marine clay, or dense sand, or a combination thereof. In addition, zones of soil were placed to model soil improvement. Structural elements representing pile-supported wharf geometries were placed within the models; some models included all vertical piles, while two of the models included batter piles. In addition, single piles were placed in two of the models and subjected to static cyclic lateral load tests. All models were extensively instrumented with nearly 100 instruments recording accelerations, pore pressures, linear deformations, and pile strains. This paper summarizes the design, construction, and testing of these complex models, and includes a brief summary of the results and recommendations for future modeling.