Precast Specimens Research Articles

Experimental study of precast dry connections constructed away from beam–column junction under progressive collapse scenario

This paper presents experimental studies conducted on precast dry connections under progressive collapse scenario. Reduced one-third-scale precast beam–column assemblies are constructed as test specimen by providing connection away from beam–column junction. Dimensions of test specimens are extracted from 6-story symmetrical building having overall plan dimensions of 16 m × 12 m. Each specimen consists of two span beams and three columns with removed middle column, which represents progressive collapse scenario. Dry connection between precast elements were constructed by adopting two different types of detailing such as welding and bolting of steel plates at connection region. Monotonic vertical load was applied at the location of removed middle column with the help of hydraulic jack. Behavior of test specimens was measured in terms of ultimate load carrying capacity, deflection profile along the length, failure pattern and crack propagation. The performance of precast specimens having dry connection was also compared with that of monolithic connection. From the results of experimental studies, it was observed that precast dry connection with welded plates was having maximum ultimate load carrying capacity, while the same for precast dry connection with bolted plates was lesser than that of monolithic connection. However, performance of precast dry connection with bolted plates can be enhanced by ensuring appropriate quality of concreting around connection region. Based on the study, it was concluded that building having precast elements connected away from the beam–column junction with adequate connection detailing behaves similar to that of monolithic construction and can be a sustainable alternative of cast-in-place construction.

Experimental study on seismic performance of L‐shaped insulated concrete sandwich shear wall with a horizontal seam

SummaryA series of new L‐shaped insulated concrete sandwich shear walls integrated with heat preservation function are tested for its seismic performance. Those specimens, partially excavated and filled with insulation materials, are made up of three precast specimens and one cast‐in‐situ specimen as a control group. For the three precast specimens, the vertical distributed reinforcements are equivalently spliced to the bottom beam by grouting sleeves arranged along the centerline of the wall, whereas for the compared specimen, they are directly cast‐in‐situ anchored. These specimens are tested under low frequency cyclic loading. The failure mode, yielding load and displacement, skeleton curve, energy dissipation, stiffness degradation, ductility, and so forth, are recorded and analyzed. The result shows that the precast specimens have similar bearing capacity and much better deformation capacity and ductility than that of the control group in this experiment. This indicates that the seismic performance of the proposed L‐shaped insulated concrete sandwich shear wall is desirable and generally meets the requirements of both function and safety, thus can be used as structural elements in practice. The methods in Chinese design code and American Concrete Institute code are adopted to calculate the ultimate shear capacity of this precast insulation shear wall, and it is found that the tested result is larger than the calculated one, indicating the calculation method is reliable.

Experimental study on seismic behavior of precast concrete column with grouted sleeve connections considering ratios of longitudinal reinforcement and stirrups

This manuscript presents the experimental investigations on the seismic behavior of precast grouted sleeve column-to-foundation connections. Six full-scale specimens were constructed with varying longitudinal reinforcement ratios and stirrup ratios. Four specimens were precast with grouted sleeve connections. Two cast-in-place reference specimens were equivalent in design with the precast ones, but only without the grouted sleeve connections. Vertical compression ratio of approximately 0.41 was applied for use in high seismic regions. Damage states, load-carrying capacity, ductility, energy dissipation and strain distributions of the specimens are investigated and are compared with the cast-in-place reference specimens. The test results demonstrate that the sleeve connection exhibited comparable lateral deformation capacity and ductility but lower strength capacity compared to the cast-in-place reference specimens. Among the precast specimens, the increase in stirrup ratio slightly increased both the yield and the ultimate strength. The increase in longitudinal reinforcement ratio showed greater effects by considerably raising the ultimate strength, while increasing the yield strength marginally.

Experimental Investigation of Exterior Mechanbical Precast Beam Column Connections using Internal Dissipators under Seismic Loading

This paper investigates the development and testing of the proposed one-third scaled precast beam column specimens using cleat angle and unbonded threaded rod connection (internal dissipator) under reverse cyclic loading. One monolithic specimen for reference and two precast specimens were studied. The parameters considered in the precast specimens were the presence of stiffener and the action of cement grouting in the predetermined gap of the beam column interface region. The load and displacement were measured for the cyclic loading and thereby strength, hysteretic behaviour, energy dissipation, stiffness, ductility and stiffness degradation were computed and compared. The experimental results showed that the performance of monolithic specimen was superior to precast specimens. The performance of precast specimen with cleat angle and stiffener was found to be superior to precast specimen without stiffener.

CAPACITY DESIGN CRITERIA FOR SEISMIC RESISTANCE OF PRECAST CONCRETE COLUMNS USING STEEL BOX CONNECTION

A variety of advantages of precast concrete adding to benefits of concrete has made the pre-fabrication and assembly systems widely adopted in building construction business. However, theconnections may diminish the increase in the utilization due to their complication in the installation work andseismic design consideration. This paper presents an easy-to-install steel box for column base connectiondesigned based on the standard capacity design criteria. Experimental investigations on the precast concretecolumns using the steel box connection at the column base under cyclic loading were also made. The testresults show the satisfactory seismic performance of the precast specimens both in seismic shear capacity,ductility and energy dissipation compared with the identical cast-in-place specimen. The failure of the precastcolumns, with proper details, was in the flexural ductile mode. The shear capacity was respectively 1.16-1.24times higher than the averaged capacity of the cast-in-place column. The damping ratio was about 18-25percent in the inelastic range, after the drift ratio of 3.0%. Finally, the seismic performance of the designedprecast concrete column using the steel box connection based on the capacity design criteria is guaranteedwithout early brittle failures.

Seismic performance of interior precast concrete beam-column connections with T-section steel inserts under cyclic loading

An experimental investigation was conducted to study the performance of precast beam-column concrete connections using T-section steel inserts into the concrete beam and joint core, under reversed cyclic loading. Six 2/3-scale interior beam-column subassemblies, one monolithic concrete specimen and five precast concrete specimens were tested. One precast specimen was a simple connection for a gravity load resistant design. Other precast specimens were developed with different attributes to improve their seismic performance. The test results showed that the performance of the monolithic specimen M1 represented ductile seismic behavior. Failure of columns and joints could be prevented, and the failure of the frame occurred at the flexural plastic hinge formation at the beam ends, close to the column faces. For the precast specimens, the splitting crack along the longitudinal lapped splice was a major failure. The precast P5 specimen with double steel T-section inserts showed better seismic performance compared to the other precast models. However, the dowel bars connected to the steel inserts were too short to develop a bond. The design of the precast concrete beams with lap splice is needed for longer lap lengths and should be done at the beam mid span or at the low flexural stress region.

Strengthening of precast RC beam-column connections for progressive collapse mitigation using bolted steel plates

Being one of the most critical scenarios in extreme events such as blast attacks, the progressive collapse of reinforced concrete (RC) structures has attracted the attention of structural engineering community. As precast concrete buildings are deficient in structural continuity, they are more vulnerable to progressive collapse than cast-in-situ RC buildings. Hence, effective rehabilitation techniques to upgrade beam-column joints in existing precast RC buildings for progressive collapse mitigation are needed. The goal of this study is to investigate the effectiveness of using bolted steel plates on the behavior of precast beam-column connections under sudden column-loss scenario. This study presents experiments involving one half-scale precast RC beam-column assembly, which represented the most prevalent types of existing precast beam-column joints in Saudi Arabia. One monolithic test specimen having continuity of top and bottom beam rebars was used for the sake of comparison. Another precast specimen similar to the control one was strengthened using bolted steel plates within the connection region. The progressive collapse scenario was simulated by removing the central column support and applying a sudden vertical load on this column at a rate of 100 mm/s until failure. The collapse load of both monolithic and strengthened specimens was predicted using a simplified section analysis procedure. The analysis was then used for some useful parametric studies in which the effect of different steel plate parameters on the response of test frames under middle column-loss scenario was investigated.

Quasi-static cyclic tests of precast bridge columns with different connection details for high seismic zones

In this study, seven 1/3-scale bridge column specimens are investigated under the same quasi-static cyclic loading protocol both experimentally and numerically. The specimens consist of one cast-in-place (CIP) reference column and six precast columns. The precast columns are designed with different connection details, and they are tested for the feasibility study of the urban viaducts of highway S6 in Shanghai, China. The seismic performance of the precast columns needs to be investigated and verified prior to the practical application of these connection designs. Based on the experimental results, the precast specimens solely using mild reinforcement exhibit similar hysteretic behavior to the CIP reference column, though various grouted connection approaches are employed. The differences between these precast specimens and the CIP reference column are less than 15% for all indices. The precast specimens with bonded tendons (prestressing strands or prestressing bars) retain higher strength, but no less than 30% decrease of energy dissipation capacity is found. The bonded prestressing strands give at least 10% increase in strength compared with the CIP reference column, while the bonded prestressing bars provide approximately 50% improvement. The precast specimen utilizing unbonded tendon (prestressing strands) shows unique self-centering capability with equivalent energy dissipation capacity of the CIP reference column, but it has 33% lower ductility. Finite element modeling is performed and calibrated with the test data. Bond-slip behavior near column-to-footing interface is modeled by using a ZeroLength element at the interface. Buckling, fatigue and strength reduction of reinforcement are also considered in the model. Hysteretic behaviors of the specimens can be effectively simulated, and differences of ultimate strengths between the experimental and numerical results are less than 9%.

Experimental study of L‐shaped precast RC shear walls with middle cast‐in‐situ joint

SummaryPrecast shear walls, as an environmentally friendly building system, have been vigorously developed in China. There are many vertical and horizontal joints on precast reinforced concrete shear wall system, which certainly have a significant effect on seismic performance of structures. In this paper, 3 L‐shaped precast reinforced concrete shear walls that were assembled by 2 precast parts through a middle cast‐in‐situ joint and a compared 1 completely cast‐in‐situ were tested under low frequency cyclic loading to investigate their seismic behaviors. The vertical distributed reinforcements in the three precast specimens were equivalently spliced by grouting sleeves arranged along the center line of the wall, and the horizontal reinforcements were directly anchored in cast‐in‐situ joints. The experimental results, including failure mode, yielding load and displacement, skeleton curve, energy dissipation, stiffness degradation, ductility, and so forth were presented in the paper. The results show that the precast specimens have similar bearing capacity whereas much better deformation capacity and ductility compared to the cast‐in‐situ specimen. Additionally, the experimental results of ultimate shear capacity of specimens were also compared with that of the calculation results. These results indicate that the tested precast shear walls have good and reliable seismic performance and can be used as a structural member in engineering projects.

Seismic experimental study on a precast concrete beam-column connection with grout sleeves

The seismic behavior of the beam-column connections in concrete frame is studied in this paper, including five precast specimens and one cast-in-place specimen. For the precast specimens, the column, joint and part of the beam away from the joint are prefabricated, while the part of beam close to the joint is cast-in-place. The rebar is connected by grout sleeve. The specimens were tested under low-reversed cyclic loading, and were evaluated in terms of failure mode, skeleton curves, stiffness, energy dissipation, and drift capacity. Differences in seismic performance between these specimens were also revealed. From the test results, the seismic performance of the precast connection is similar to that of the cast-in-place connection. However, the distribution of cracks, the strain of reinforcements and the deformation of joint are different. The strength ratio between column and beam is an important factor on the failure mode of the precast connections. For precast connection, the seismic behavior of the plastic hinge as well as the core region of the joint are clearly affected by the grout sleeve, the cast-in-place region and the rebar hole. Also in the core region of the joint, slippage of longitudinal rebar is observed.

In-Plane Quasi-Static Cyclic Tests on Emulative Precast Concrete Walls

This paper presents two types of emulative precast concrete walls with dry horizontal connection and semi-dry horizontal connection. As for dry connection, vertical continuity reinforcing bars are grouted in metal bellows embedded in the precast wall panel. As for semi-dry connection, the web reinforcing bars are still grouted in embedded metal bellows while the reinforcing bars within boundary elements are overlapped and anchored in cast-in-place concrete. To assess the seismic performance of the two connections, three full-scale specimens, including one reference monolithic specimen and two precast specimens for each connection, were prefabricated and tested under in-plane quasi-static cyclic loading. The strength, stiffness, displacement ductility, and energy dissipation of the specimens were measured and compared. The experimental results demonstrated that, compared with the monolithic specimen, both precast specimens exhibited satisfactory behavior and the semi-dry precast specimen performed better than the dry precast specimen in terms of ductility and energy dissipation. In addition, the analytical results showed that precast specimens exhibited reliable seismic performance with high bearing capacity and large deformation capacity.

Experimental Study on Seismic Performance of Full Precast Shear Wall-Frame Structures

To study the seismic behaviors of full precast shear wall-frame structures with prefabricated shear wall panels and prefabricated frames. Two geometrically identical half-scale two-story two-bay RC shear wall-frame structure specimens were constructed and tested under quasi-static reversed cyclic loading (One specimen named RC-1 is cast-in-place concrete shear wall-frame structure, the other one is a precast specimen named PC-3). The test results show that the specimen PC-3 have similar failure pattern with the specimen RC-1. The experimental investigation indicates that the reliably connected, well-designed and constructed full prefabricated shear wall-frame structures with prefabricated shear wall panels and prefabricated frames, have good seismic performance and can meet the seismic requirements and be used in anti-seismic zone.

Development and testing of hybrid precast concrete beam-to-column connections under cyclic loading

In general, precast concrete structure has insufficient ductility to resist seismic load. Detailed understanding on the behaviour of precast concrete connections are limited and current researches are focused addressing this. In this study, two precast and two monolithic concrete joints for exterior beam-to-column connection were tested under cyclic loading. The installation of precast specimens was prepared using dry type method while the monolithic joints were casted in-situ. The evaluation of seismic performance of the joints was conducted by applying hysteretic reverse cyclic loading until failure. Information regarding the strength, ductility and stiffness properties of the connection were recorded and analysed. Based on the test results and damage condition, the initial design of the joint was improved. Consequently, a new joint was constructed and tested, which exhibited a better performance. Precast concrete connections showed stable load–displacement cycles and dissipated a higher energy. The structural drift obtained was up to 9.0%. Pinching and deterioration were attained at a drift ratio of 4.5%. Also, there was improvement in the tested precast joints based on deflection, plastic hinges, crack pattern and shear deformation. Thus, the precast joints had a satisfactory resistance to seismic loads.

Quasi-static test and strut-and-tie modeling of precast concrete shear walls with grouted lap-spliced connections

This paper discusses the seismic performance of nine full-scale shear walls including seven precast specimens and two cast-in-place specimens. The precast specimens were designed to emulate monolithic cast-in-place specimens. The precast upper shear wall and the base were connected at their interface through lap splice that one of the spliced bar was embedded into a grout-filled hole, which was reserved by metal bellow or expanded metal mesh. The geometries and reinforcement of precast specimens were identical with those of corresponding cast-in-place specimens in each group. But their stirrups were different. Based on the two types of grouted connections, the specimens were tested under low cyclic lateral loading to study their seismic performance by comparing their carrying capacities, crack patterns, ductility, hysteretic curves and energy dissipation. In general, shear walls with metal bellows at the joint exhibited better structural behaviour than the shear walls with expanded metal mesh due to their well confined effect on the spliced bars and surrounding concrete. Thus, this kind of precast connection may emulate cast-in-place connection. Lastly, a reasonable strut-and-tie model was developed based on ACI 318-14 code to investigate the force transfer mechanism of the precast shear wall. The calculated results were compared with the test results and the shear strength results calculated by empirical expression in the ACI 318-14 code.

Investigation of precast RC beam-column assemblies under column-loss scenario

The progressive collapse of reinforced concrete (RC) buildings, being one of the most critical failure scenarios, is a great concern for the structural engineering community. As precast concrete buildings are deficient in structural continuity, these are more vulnerable to progressive collapse than cast-in-situ RC buildings. The goal of this study is to develop a nonlinear finite element (FE) model using LS-DYNA software to predict the performance of precast non-prestressed RC beam-column assemblies, each comprising three columns and two beams, under column-removal scenario. The model takes into account the nonlinear behavior of concrete and steel, strain rate effect on material properties and contact between surfaces at the joints. The FE models were calibrated against three half-scale specimens tested under middle column-removal scenario. Tests included two precast specimens and one monolithic specimen with continuous top and bottom beam reinforcement. The validated FE modeling was further extended to study the progressive collapse potential of seven revised precast connections. As a result of the FE study, new joint efficiency parameters were introduced in this research.

Development and Seismic Behavior of Precast Concrete Beam-to-Column Connections

A new precast concrete beam-to-column connection for moment-resisting frames was developed in this study. Both longitudinal bar anchoring and lap splicing were used to achieve beam reinforcement continuity. Three full-scale beam-to-column connections, including a reference monolithic specimen, were investigated under reversal cyclic loading. The difference between the two precast specimens was the consideration of additional lap-splicing bars in the calculation of moment-resisting strength. Seismic performance was evaluated based on hysteretic behavior, strength, ductility, stiffness, and energy dissipation. The plastic hinge length of the specimens is also discussed. The results show that the proposed precast system performs satisfactorily under reversal cyclic loading compared with the monolithic specimen, and the additional lap-splicing bars can be included in the strength calculation using the plane cross-section assumption. Furthermore, the plastic hinge length of the proposed precast beam-to-column connection can be estimated using the models for monolithic specimens.

Experimental study of a new beam-to-column connection for precast concrete frames under reversal cyclic loading

A new beam-to-column connection developed for precast concrete-resisting frames was proposed in this article. This connection provided adequate structural integrity in the connections and could be constructed easily and rapidly by eliminating the need for welding, bolting, and post-tensioning, and it also avoided reinforcement congestion or obstruction in connection regions. Five full-scale beam-to-column connections, including a monolithic specimen, were tested under reversal cyclic loading. One precast specimen was manufactured following all the proposed details. For comparison purpose, the other precast specimens were made without one or two structural details like additional bars and making a certain length of the two bottom deformed bars debonded near the end of U-shaped hollow in a precast beam. After analysis on the hysteretic behavior, strength, deformability, stiffness, and energy dissipation, it was showed that the proposed connection exhibited good seismic resistance, thus could be used in seismic regions. Furthermore, the existence of additional bars showed more necessity in such a system than the detail of making a certain length of the two bottom deformed bars debonded. Finally, a theoretical analysis curve was proposed.

Flexural Behavior of UHPFRC Moment Connection for Precast Concrete Decks

This paper presents an experimental investigation of the flexural behavior of precast concrete moment connections filled with ultra-high-performance fiber-reinforced concrete (UHPFRC). The experimental program consisted of two phases. First, the bonding performance of steel reinforcing bars embedded in the UHPFRC was evaluated using lap-spliced beam specimens with three different volumes of steel fibers. Second, the flexural behavior of the UHPFRC moment connections was investigated using 14 precast concrete beam specimens. The precast connections had a narrow joint width ranging from 250 to 100 mm (10 to 4 in.) and included three feasible noncontact splice details: straight bars, 90-degree hooked bars, and U-loop bars. Test results demonstrated the remarkable bonding characteristics of UHPFRC. The precast specimens with a joint width larger than 150 mm (6 in.) exhibited flexural behavior equivalent to that of a monolithic concrete beam specimen. Also, the anchorage provided by the hooked bars and U-loop bars did not appreciably contribute to the bonding strength.

Experimental testing on emulative connections for precast columns using grouted corrugated steel sleeves

Seismic analysis of precast concrete structures requires specific information regarding the behaviour of the connections under large deformation cycles. If a connection is located within the critical region of a structural element, its energy dissipation capacity needs to be confirmed by experimental testing. The use of emulative connections for precast elements is attractive for designers because common conventional design methodologies and assumptions developed for cast in place structures may be readily used. The results of a structural testing program for precast columns connected using grouted corrugated steel sleeves are reported in this paper. A comparison with reference “cast in place” specimens is made and conclusions regarding the emulative characteristic of the connection are drawn. Tests were carried out on scaled concrete columns using the reaction frame at the Technical University of Civil Engineering of Bucharest. Four precast specimens and two reference specimens were tested. Analysis of the recorded data showed that the precast specimens have similar hysteretic response and energy dissipation capacity as the reference ones.

Seismic Performance Research of Connections of Prefabricated Wall and Beam In-Plane

The paper introduces a method for connecting fabricated shear wall with beam in a plane by sleeve, and uses the finite element software to analyze and compare the seismic performance of precast wall beams node and cast wall beam node. It concluded:Seismic performance of prefabricated wall beam node and cast wall beam node are basically the same , while the prefabricated wall beam node has higher strength, which indicates that the connection of precast specimen is reliable. However, before putting it into practical, application, further study on it is still necessary.