Cyclic Lateral Load Tests Research Articles

Experimental and Numerical Analysis of the Bolt Connections in a Low‐Rise Precast Wall Panel Structure System

This paper develops a novel dry connection utilizing high‐strength bolts and introduces the corresponding low‐rise precast wall panel structure system. To investigate the seismic performance of the structure system with full bolt connections, monotonic loading tests of the connection joint and cyclic lateral loading tests of three full‐scaled precast shear walls are both conducted. Based on the test data, axial and shear mechanical models of the connection are given. Meanwhile, experimental results show that the failure mode of the connection is dominated by anchored rebar ductile rupture, and the precast structure system presents a stable energy dissipation capacity and a good seismic ductility. The numerical model of the precast shear wall is then developed and validated by the cyclic loading test. Also a simplified calculation method to predict the lateral strength of the precast shear wall is proposed. According to the calculation results, the distance between the center of the connection and the edge of the shear wall is suggested to be 150 mm, while the wall thickness is recommended to be 120 mm or 150 mm. Finally, a three‐story precast wall panel structure is employed to assess the collapse performance of the proposed precast structure system by using the presented numerical model. The results indicate that the proposed structure system with full bolt connections has high stiffness and high seismic resistance against collapse.

Pile lateral subgrade reaction modulus for Jakarta

The behavior of laterally loaded piles could be simulated by the subgrade reaction model. The primary soil parameter for this model is the subgrade reaction modulus, and in this paper, the correlation between the subgrade reaction modulus and the soil N-SPT value is examined by conducting numerical analyses of 34 pile cyclic lateral load tests in Jakarta. In each analysis, the pile is modeled as a series of beam elements, while the surrounding soil is modeled as a series of linear elastic springs. The moduli are varied according to the N-SPT values recorded in the associated deep boring data. In each load cycle, a trial and error process is conducted to match the resulting pile head lateral deflection to the measured value. The resulting correlation between the subgrade reaction modulus and the pile lateral deflection is presented for the 34 case studies and compared to a correlation in the literature. Furthermore, the analyses reveal that subgrade reaction modulus is affected by the magnitude of measured deflection, by the applied lateral loads, as well as by the construction methods.

Behaviour of Cyclic Laterally Loaded Pile Group in Soft Clay

The capacity of laterally loaded piles is mainly governed by the strength of soil at the proximity of top level of the piles. In coastal areas, the topsoil mostly comprises of soft clay and they extend for a considerable depth, offering low resistance against lateral loads. In addition to static loads, the piles are subjected to cyclic loads. Experimental study of single pile and pile group for varying L/D ratios, number of piles in a group and spacing between the piles under static and cyclic lateral load is studied. Cyclic lateral load tests were conducted for L/D ratios of 12, 18 and 24 under cyclic load ratio of 0.6. Cyclic load tests were performed by embedding the piles in a clay bed of consistency 0.2. The experimental results showed that for pile of L/D ratios the 12, 18 and 24 displacement at pile head becomes nearly constant after 300 hundred cycles. From the pattern of displacement versus number of cycles, it is observed that shorter piles exhibit higher magnitudes of displacement compared to longer piles upon cyclic loading. However, longer piles show higher rate of increase in displacement with number of cycles compared to shorter piles.

Cyclic testing of unreinforced masonry walls retrofitted with engineered cementitious composites

The results of in-plane static cyclic lateral loading tests conducted on unreinforced masonry walls retrofitted with trowelling engineered cementitious composites (ECC) are presented in this paper. Six 1/2 scale testing specimens including unretrofitted and retrofitted walls were constructed. The first and second unretrofitted masonry walls were control specimens. The third and fourth walls were retrofitted applying ECC with strip type and the other two walls were retrofitted with ECC coatings. Every batch of tested walls was constructed with two different mortar strengths. The failure modes, lateral strength, ductility, stiffness, and the energy dissipation capacity of the tested walls were examined and compared. Furthermore, the experimental envelope curves were idealized and reasonable overstrength factors of the retrofitted walls were obtained. The results indicated that these retrofit techniques can effectively improve the lateral strength and the displacement ductility of unreinforced masonry (URM) walls, convert the brittle failure mode to a more ductile one, and provide an effective constraint for the walls, resulting in preserved integrity of the wall at large lateral displacements. Finally, the calculation methods for each retrofitting scheme were proposed to estimate the ultimate lateral strengths of ECC retrofitted masonry walls.

Cyclic tests on composite plate shear walls–concrete encased before and after fire exposure

Cyclic lateral loading tests were conducted on six composite plate shear walls–concrete encased and two conventionally reinforced concrete walls. The composite plate shear walls–concrete encased were constructed using high-performance concrete and different steel configurations with a same steel content ratio. These walls were divided into two batches. Three composite plate shear walls–concrete encased and one conventional wall were first exposed to the ISO 834 standard fire before the cyclic tests. To their comparison, the other four walls were only tested under the cyclic loading at room temperature. During the fire tests, the four walls experienced the spalling of concrete. The composite plate shear walls–concrete encased suffered more explosive spalling than the conventional wall. After the fire tests, all walls were tested under the cyclic loading. Based on the test results, analysis and discussions were made on the lateral load, lateral stiffness, and energy dissipation ability of walls. The difference was identified between the behavior of composite plate shear walls–concrete encased and that of conventional wall. Moreover, the influences of fire exposure were analyzed on seismic behavior of shear walls. Generally, the high temperatures reduce the yield, peak, and ultimate loads of walls and degrade the lateral stiffness. No significant difference can be found in energy dissipation ability between the heated and unheated walls before the drift ratio 1/120.

Shear strengthening of RC short columns with ECC jacket: Cyclic behavior tests

This study aims at developing an easy-to-apply strengthening method for reinforced concrete (RC) short columns by using Engineered cementitious composite (ECC), which is a high-performance composite material with tensile strain-hardening behavior and multiple cracking mechanism in tension. Seven identical RC short columns were prepared, and five of them were strengthened with ECC jackets or ferrocement jacket. The main experimental parameters involve the jacketing schemes and the axial load. The failure modes, hysteresis response, deformation capacity, stiffness degradation and energy dissipation capacity of the specimens were studied by the lateral cyclic loading tests. The tests results show that the ECC jacketed columns failed in ductile modes, and exhibited significant improvement in plastic deformation ability and energy dissipation capacity compared with the control specimens. At the ultimate displacement point, the increase of the drift ratio and cumulative energy dissipation of the ECC jacketed columns were 19–111% and 102–549%, respectively, compared with the corresponding control specimens. Under higher axial loads, the ECC jacketing was still certified to be effectively in enhancing the seismic behavior of the original columns. The shear deformation and the shear strength of the original RC columns were effectively improved by the external ECC jacket, and a prediction method for the shear strength of the ECC jacketed columns was given based on the current Chinese codes.

Battened Steel Columns with Semi-Continuous Base Plate Connections: Experimental Results vs. Theoretical Predictions

The paper describes a comparison of experimental results and theoretical predictions regarding the lateral force-displacement response of built-up battened steel columns including semi-rigid and partial-strength base plate connections. Two specimens, representing samples of columns extracted from an existing industrial building, were fabricated and tested. Different types of both the battens and the base-plate connections characterized the two specimens. Preliminary lateral-loading tests in a range of elastic response, under varying levels of the concomitant axial force, allowed both exploring initial (elastic) stiffness and estimating yield displacements. Subsequently, cyclic lateral-loading tests with a given value of the axial force allowed investigating the restoring force characteristics in case of seismic actions. First, the paper describes and comments on the experimental performance of the two specimens. Second, numerical finite-element model predictions are illustrated and compared with experimental results. Third, based on the experimental results, as well as on the FE model analysis, the study looks for possible extensions and adaptations to current Eurocode 3 prediction models.

Study on seismic performance of prestressed precast concrete walls through cyclic lateral loading test

This paper presents experimental results from three prestressed precast concrete walls in comparison with a conventional reinforced concrete (RC) wall. The prestressed specimens utilise a combination of high-strength post-tensioned (PT) steel and mild reinforcing steel for lateral resistance, whereas the RC specimen retains a conventional code-compliant design. The major advantage of the prestressed specimens incorporating PT steel is a self-centring capability after a large lateral excursion. At the same time, PT steel facilitates construction by post-tensioning and connecting wall panels together. In this study, all the test walls had an identical overall geometry and were tested under the same reversed cyclic lateral loading. Comparisons of the seismic performance of prestressed and RC specimens were made in relation to progression of damage, failure mechanism, strength and drift capacity, energy dissipation and residual drift. The PT steel and base joint behaviours of the prestressed specimens were also recorded. Results show that the prestressed precast concrete walls feature minimal structural damage and excellent self-centring tendency compared to their RC counterpart; these features are essential to achieve a resilient structural system for use in seismic regions.

강섬유 혼입률에 따른 고강도 철근콘크리트 기둥의 전단강도에 대한 실험적 연구

The purpose of this study is to evaluate the shear strength of steel fiber reinforced concrete columns quantitatively through the experimental program. For this purpose, the volume fraction of steel fiber is determined to main parameter (0%, 1%, 2%), and the cyclic lateral loading tests of columns were performed with constant axial loads. According to the test results, the shear strength of the column with 1% of steel fiber increased 1.61 times and shear strength of the column with 2% of steel fiber increased 1.67 times compared to RC column. Also, it was investigated that the cracks are distributed and angle of cracks is reduced in specimens with steel fiber. This resulted in an increase of the number of transverse reinforcement located on the crack face. Therefore, the shear strength of columns was evaluated by dividing the shear strength contribution by the concrete, transverse reinforcement, and the shear strength increase by the steel fiber. As a result, the shear strength contributions of concrete increased about 29% with 1% of steel fiber and increased about 36% with 2%. Also, the shear strength contributions of transverse reinforcement increased when steel fiber is mixed.

Monotonic and cyclic lateral tests on driven piles in Chalk

This paper describes the results of a pile-testing campaign on open-ended tubular steel instrumented piles driven into the Chalk formation in the UK. The testing campaign comprised the performance of both monotonic and one-way cyclic lateral load tests, performed at different times after pile installation. The tests were performed on five piles with uniform outer diameters of 762 mm and embedded lengths of 4 m and 10 m to investigate the difference in response between short and long piles. Lateral pile head load–displacement behaviour to failure has been analysed. The tangent stiffness evolution during monotonic loading has been evaluated at different times after pile installation and the chalk set-up has been found to have no effect on pile behaviour under lateral loading. The pile secant stiffness during cyclic lateral loading is also investigated. Accumulated pile head lateral displacements are discussed and their pattern is described by a logarithmic function that varies with number of cycles. The creation of a gap between the Chalk and the pile during cyclic lateral loading was observed, which influenced the shape of the load–displacement loops. The influence of the instrument protection system was taken into account in analysing the results.

Cyclic testing of unbonded post-tensioned concrete wall systems with and without supplemental damping

A series of cyclic lateral-load tests were conducted on four different unbonded post-tensioned precast concrete wall systems, including two Single Rocking Walls (SRW) and two PREcast Wall with End Columns (PreWEC). The main purpose of these tests was to systematically investigate the cyclic response of post-tensioned concrete walls with varying amounts of supplemental damping while keeping the initial post-tensioning force, wall dimensions, and confinement details constant. A secondary objective was to validate the wall panel design including the appropriate selection of axial force ratio and design of confinement and armouring details. All of the test walls exhibited excellent performance with uplift and rocking at the wall base with only minor damage observed, consisting of small amounts of spalling in the wall toes. There were consistent observations and measurements of the wall damage, concrete compressive strains, and wall neutral axis depths for both the SRW and PreWEC systems with the same wall panel dimensions. Based on these observations it is concluded that the behaviour of the wall panel in a PreWEC system is independent of the number of energy dissipating O-connectors. The O-connectors increased the hysteretic energy dissipation in the wall system and provided between 1.1% and 1.4% of additional equivalent viscous damping per connector for the PreWEC walls tested. Overall, the behaviour of the four walls tested confirmed the design procedures used, with both the global force-displacement response and local response parameters predicted with sufficient accuracy using an existing simplified analysis method.

Experimental and Numerical Investigations of Composite Frames with Innovative Composite Transfer Beams

Experimental and numerical studies were conducted to investigate the vertical load-carrying behavior and seismic performance of a composite frame structure with an innovative composite transfer beam, which was proposed to overcome the disadvantages of traditional reinforced concrete or steel reinforced concrete transfer beams. In the experimental study, a vertical monotonic loading test and a lateral cyclic loading test were conducted. The test observations, load–displacement curves, and strain measurements were discussed to investigate the structural performance and failure mechanism. The experimental results demonstrated the excellent vertical load-carrying behavior and seismic performance of the composite transfer frame. The characteristics of the plastic hinge distribution were investigated based on extensive data of the steel strains measured to reveal the typical failure mechanism of the composite transfer frame. In the numerical simulation analysis, a multiscale modeling scheme was developed to make full use of the fiber beam–column elements and multilayer shell elements. Comparisons with the experimental results showed that the developed model predicted the overall structural behavior, the individual story and component behavior, and the failure mechanism with a reasonable level of accuracy. In addition, both the experimental tests and numerical analyses indicated that the shear deformation mode and the energy dissipation in the composite joint core were also significant mechanical characteristics of the composite transfer frame.

Evaluation of FRP Confinement Models for Substandard Rectangular RC Columns Based on Full-Scale Reversed Cyclic Lateral Loading Tests in Strong and Weak Directions.

Although many theoretical and experimental studies are available on external confinement of columns using fiber-reinforced polymer (FRP) jackets, as well as numerous models proposed for the axial stress-axial strain relation of concrete confined with FRP jackets, they have not been validated with a sufficient amount and variety of experimental data obtained through full-scale tests of reinforced concrete (RC) columns with different geometrical and mechanical characteristics. Particularly, no systematical experimental data have been presented on full-scale rectangular substandard RC columns subjected to reversed cyclic lateral loads along either their strong or weak axes. In this study, firstly, test results of five full-scale rectangular substandard RC columns with a cross-sectional aspect ratio of two (300 mm × 600 mm) are briefly summarized. The columns were tested under constant axial load and reversed cyclic lateral loads along their strong or weak axes before and after retrofitting with external FRP jackets. In the second stage, inelastic lateral force-displacement relationships of the columns are obtained analytically, making use of the plastic hinge assumption and different FRP confinement models available in the literature. Finally, the analytical findings are compared with the test results for both strong and weak directions of the columns. Comparisons showed that use of different models for the stress-strain relationship of FRP-confined concrete can yield significantly non-conservative or too conservative retrofit designs, particularly in terms of deformation capacity.

Experimental performance of reinforced double H-block masonry shear walls under cyclic loading

Ordinary reinforced concrete block masonry shear walls have some shortcomings such as abrupt change in the grout core cross section and permeation of grout concrete resulting in reduced integrity and seismic performance of masonry structure. To overcome these issues, the authors used a special type of core-aligned block (termed as double H-block) to construct shear wall, and the seismic performance of double H-block reinforced masonry shear walls was investigated by lateral cyclic loading test. Two large-sized double H-block reinforced masonry shear walls were designed and fabricated. Two axial compression ratios and two grout ratios were considered. The failure pattern, shear strength, hysteretic energy, and ductility capacity of the walls were analyzed. The test results showed that the double H-block masonry shear wall constructed in running bond exhibited integrity, high ductility and energy dissipation capacity. The bearing capacity of H-block shear walls decreased with the reduction of axial compression ratio, while the ductility increased. A model was also proposed to predict the shear strength of the grouted double H-block based on mechanical analysis of the internally grouted concrete. The accuracy of the model was verified through 30 H-block specimens under shear tests and it was found the grout ratio had a significant effect on the shear strength of the grouted double H-block. The model proposed by the Chinese masonry code was over-conservative when the grout ratio was high. Finally, a modified shear capacity model was proposed and was found to be effective to predict the shear capacity of double H-block reinforced masonry shear wall.

Axial Load and Cyclic Lateral Load Tests for Composite Columns with Steel Angles

AbstractTo enhance the structural capacity and constructability of composite columns, a prefabricated steel-reinforced concrete (PSRC) column was developed. By using the prefabricated steel cage, field rebar work is unnecessary, and the self-erectable steel cage can provide sufficient strength and rigidity to support the construction loads of beams and slabs. In the present study, various steel angle ratios, transverse bar spacings, and prefabrication details were considered for better structural capacity and constructability. To investigate the performance of the proposed method, axial loading tests and cyclic lateral loading tests were performed. In the axial loading test, the structural performance of the PSRC columns was comparable to, or even better than, that of the conventional composite column using the wide flange steel section, when early spalling of the cover concrete was restrained by closely spaced hoops. Under cyclic lateral loading, on the other hand, the PSRC columns were more susceptible ...

Effect of Corrosion on Bond Mechanism between Extremely Low-Strength Concrete and Plain Reinforcing Bars

AbstractIn this study, a bond-slip model is proposed to take into account the effects of corrosion on the bond characteristics between extremely low-strength concrete and plain reinforcing bars. The proposed bond-slip model is based on reversed cyclic lateral loading tests of nearly full-scale reinforced concrete columns with reinforcing bars corroded to different levels. The columns taken into consideration during the current study were part of an extensive experimental program designed to study the performance of older columns at Istanbul Technical University. The columns were representative of a large number of underperforming reinforced concrete buildings prone to seismic actions throughout the world. Test results demonstrated that the corrosion of reinforcing bars had a significant effect on the strength and deformability characteristics of substandard reinforced concrete columns subjected to the combined actions of axial and reversed cyclic lateral loads. Taking this aspect into consideration, a nov...

Quasi-Static Cyclic Testing of Elevated RC Pile-Cap Foundation for Bridge Structures

In current practices, the elastic design principle for the seismic design of pile foundations is an overly conservative strategy. In this regard, cyclic lateral loading tests were conducted to investigate the seismic failure mechanism and ductile behaviors of elevated RC pile-cap foundations. Two six-pile specimens with different aboveground heights were constructed and embedded in a single layer of cohesionless soil. Hysteretic characteristics and observed damages of the pile groups were presented, together with the corresponding soil pressure and pile curvature responses. From the test results, the sequence and positions of the pile plastic hinges were established. Ultimate limit states of the pile groups were determined according to test data, as well as numerical analysis results. Test results revealed a ductile flexural failure mode for both specimens. Plastic hinges were detected first at the top of outer piles, then underground at a depth of 4–6 times the section width. A displacement ductility capacity of 3.5 was observed for the elevated pile-cap foundation. Test results also indicated a linear relation between the displacement ductility factor and the cap rotation, which was important for determining the displacement at the top of piers.

사질토 지반에서 수평하중에 따른 단일강관말뚝의 거동특성에 관한 실험적 연구

해상풍력기초를 설계함에 있어 사용하중에 대해 극한적인 조건뿐만 아니라 지속적인 동적하중에 대해 기초의 거동을 정확하게 파악하여 안정적이고 경제적인 기초를 개발할 필요성이 있다. 이를 위하여 강관말뚝을 일정비율로 축소시켜 모형말뚝을 제작하고, 모형토조에 모래층을 500mm의 높이로 포설한 후 모형말뚝을 모델링하여 정적 및 반복 수평재하실험을 실시하였다. 그 결과, 정적수평재하시 모형말뚝의 길이/직경(L/D)이 클수록 하중에 따른 변위는 증가하는 반면, 반복수평재하시 하중재하 횟수가 증가할수록 반복수평하중 1회당 발생하는 말뚝의 수평변위는 감소하였고 지반이 조밀할수록 반복수평하중에 의한 말뚝의 극한수평지지력의 증가율이 작아지는 것으로 나타났다. 또한 휨모멘트의 분포형상은 지반의 상대밀도에 상관없이 유사한 형태를 보였으며, 최대휨모멘트는 지표면으로부터 170mm지점에서 발생하는 것으로 나타났다. 그리고 지반의 상대밀도가 증가할수록 정적수평재하와 반복수평재하 조건에서 발생하는 최대휨모멘트는 증가했다. In order to fulfill the needs of reliable and economically feasible foundation, engineers should consider not only the working load that can endure extreme conditions but also apprehending precise behavior of continuous dynamic load while designing the foundation of offshore wind power generators. To actualize the foundation, a model pile was made in miniature. Also, calibration chamber was made and a 500mm height of sand-bed was made to perform "static lateral load experiment" and "repetitive loading experiment", total of two Lateral load tests. As a result, in Static Lateral load test, the bigger length/diameter of model pile led an increase in load displacement. However, when performing "Cyclic Lateral load test", the increase in number of under loading led the decrease in horizontal displacement from each repeated lateral load. While performing Static Lateral load test and repeated loading experiment, we could observe the decreasing in the rate of ultimate lateral load capacity increase of the pile. Also, it turned out that the higher relative density of the ground, the lower ultimate lateral load capacity by repeated horizontal loading.

Performance of Hollow Bar Micropiles under Monotonic and Cyclic Lateral Loads

AbstractHollow bar micropiles are becoming a popular option for foundation retrofitting because of their fast installation and effectiveness as both a foundation system and ground improvement at the same time. This paper presents a field study and numerical investigation of the lateral behavior of single hollow bar micropiles embedded in stiff silty clay deposits. Two monotonic and six cyclic lateral load tests were conducted on four micropiles, and the results were used to calibrate/verify a numerical model that was then used in a numerical investigation. The observed load-displacement curves demonstrated that the micropile behavior was flexible and was governed by the properties of soil along a depth equal to 10 times the pile diameter. The parametric study suggested that hollow bar micropiles can carry moderate lateral loads with proper reinforcement configurations and pile head fixity condition. During cyclic loading, the micropile head stiffness degraded initially as the number of load cycles increas...

Earthquake resistance of structural walls confined by conventional tie hoops and steel fiber reinforced concrete

In the present study, the seismic performance of structural walls with boundary elements confined by conventional tie hoops and steel fiber concrete (SFC) was investigated. Cyclic lateral loading tests on four wall specimens under constant axial load were performed. The primary test parameters considered were the spacing of boundary element transverse reinforcement and the use of steel fiber concrete. Test results showed that the wall specimen with boundary elements complying with ACI 318-11 21.9.6 failed at a high drift ratio of 4.5% due to concrete crushing and re-bar buckling. For the specimens where SFC was selectively used in the plastic hinge region, the spalling and crushing of concrete were substantially alleviated. However, sliding shear failure occurred at the interface of SFC and plain concrete at a moderate drift ratio of 3.0% as tensile plastic strains of longitudinal bars were accumulated during cyclic loading. The behaviors of wall specimens were examined through nonlinear section analysis adopting the stress-strain relationships of confined concrete and SFC.