Precast Beam-column Connections Research Articles

Experimental study on the progressive collapse resistance of emulative precast concrete beam-column subassemblies with various anchorage details

In this study, seven emulative precast concrete (PC) beam-column subassemblies with or without connecting bars and one concrete (RC) were fabricated and tested to investigate the effect of various types of anchorage detailing for reinforcing and connecting bars on the progressive collapse resistances. Two anchorage detailing formats for steel bars with bending and straight ends were used in the PC specimens for both the reinforcing and connecting bars. Test results show that, as found in the RC specimen, resisting mechanisms including pure flexure, compressive arch action (CAA) and tensile catenary action (TCA) were sequentially activated in all PC specimens. It is demonstrated that the connecting bars improved the progressive collapse resistance in both the CAA and TCA stages. The effect of the anchorage detailing was found to be negligible in CAA stage. However, in the TCA stage, the proper usage of the straight end for steel bars was helpful to improve the deformation capacity and thereafter enhanced the progressive collapse resistance. When the loading resistance, the deformation capacity as well as the construction flexibility are taken into account, the configuration consisting of both reinforcing and connecting bars with straight end as anchorage detailing is recommended for the design of precast beam-column connections in case a central column removal scenario is assumed.

Cyclic behaviour of precast beam-column connections with shear key and hybrid rebar coupler: An experimental study

The current work attempts to examine the cyclic behaviour of the proposed shear key based precast beam-column wet connections. The configurations consist of shear keys, fiber reinforced composites and interface treatment between beam & column. The rebar continuity between the precast beam and column was established using hybrid rebar couplers. Six precast specimens and one monolithic joint were cast and tested under reversed cyclic loading. The seismic performance of the connections was assessed and discussed in terms of hysteretic behaviour, stiffness and strength degradation, damage tolerance, displacement ductility, energy dissipation characteristics, and joint principal tensile stresses. The strength enhancement, dissipated energy, stiffness retention of precast specimens was similar to monolithic specimen. The crack patterns revealed the influence of stiffness of coupler in the plastic hinge region with shifting of cracks next to coupler and joint region. Also, the presence of fiber reinforced composites, shear key and interface treatment in the connection region exhibited controlled cracking in the plastic hinge region and restricted the joint shear failure. The obtained results were validated through ACI 374.1–05 requirements criteria, which shows the acceptable seismic behaviour. The findings obtained from this study demonstrated the integrity of proposed beam-column connections against seismic forces and could achieve emulative design philosophy.

Seismic behavior and restoring force model of precast beam-column connections with locally reactive powder concrete

In this study, an innovative approach to enhance the seismic performance of prefabricated concrete frame beam-column joints, incorporating high-strength steel bars and reactive powder concrete (RPC), was developed. The research involved the construction of four prefabricated joints and one cast-in-place node, subjecting them to low-cycle reverse load tests. The findings indicate that the inclusion of high-strength steel bars in the node core area led to a notable increase in load-bearing capacity, ranging from 9.5 % to 9.7 %. Moreover, when RPC and high-strength steel bars were simultaneously used in the node core area, the load-bearing capacity improved even further, with an increase of 19.1 %–20.8 %. Additionally, RPC was found to enhance crack resistance in columns and beams, reducing the severity of node failures. Comparing specimens with different spacing of hoops in the core area, it was observed that RPC not only ensured the seismic performance of the nodes but also addressed the issue of excessive hoop density in the core area. Through experimental data, a restoring force model for prefabricated RPC/RC composite frame beam-column joints was established using theoretical analysis. This model exhibited strong agreement with experimental results and effectively depicted the stress distribution within the proposed joints at various stages.

Cyclic behavior of a slit damper proposed for precast concrete beam-column connections

Since the 2017 Puebla-Morelos Earthquake, interest in limiting damage to structural components has exponentially increased in Mexico. Consequently, the use of energy dissipation devices has received renewed attention. Following that line, this paper studies an attractive solution, which is a slit damper proposed as a passive energy dissipation device for, but not limited to, precast beam-column connections. Slit dampers have been studied for their cost-effectiveness and ease of application. They present stable hysteretic behavior and dissipate substantial amounts of energy under cyclic loading while maintaining less ductile elements essentially elastic. The structural behavior of the proposed device was evaluated theoretically, followed by experimental verification. Quasi-static incremental and constant-amplitude cyclic tests were conducted on eight specimens, with two of them having non-uniform struts. Test results are presented and discussed, emphasizing ductility and energy dissipation capacity. The proposed damper showed stable hysteretic behavior and adequate seismic performance. Using non-uniform struts significantly increased the damper's deformation capacity and fatigue performance, which is desirable for seismic zones where long-duration earthquakes are expected, such as in Mexico City. Numerical modeling techniques were also validated with finite element analyses. It was shown that the proposed damper's hysteretic response could be accurately predicted using the combined non-linear isotropic and kinematic hardening model.

A practical multiscale modeling strategy to model wet-type beam–column connections for seismic analysis of precast RC frame structures

Numerical models of beam–column connections are widely used in the seismic analysis of wet-type precast concrete frame structures. However, because of the trade-off between computational accuracy and efficiency, it is difficult to appropriately consider wet-type precast features by using existing numerical approaches. Therefore, this paper presents a multiscale modeling strategy based on OpenSees software, in which frame and solid elements are adopted to model the flexural behavior of precast members (beams/columns) and cast-in-place joint panels, respectively. Moreover, a multiscale interface is developed and implemented in OpenSees to establish the displacement compatibility and force equilibrium conditions of the interface between the frame and solid elements. The proposed strategy can capture the features of wet-type precast beam–column connections, including grouted splice sleeves, bond–slip, pre- and postcast concrete interfaces and shear deformations in the joint panel. The strategy is validated by experimental results on both the member and structural levels. Finally, an inelastic seismic analysis case study is developed to assess the computational efficiency of the proposed strategy.

A detachable configuration for the precast beam-column connection using metallic damper as connector: Experimental investigation

A beam-column connection with satisfactory seismic performance and assembly efficiency is preferred in prefabricated structures. An evolved detachable configuration for the precast beam-column connection using metallic damper as connector (PCF-MDC-nuts) is proposed. The detachable connection significantly reduces the labor cost of building demolition, repair, and recycling. A specimen PCF-MDC-nuts was designed and constructed based on a precast “wet” connection (specimen PC)). A dog-bone damper was adopted in PCF-MDC-nuts as a sacrificial element. First, a laboratory test was performed on the damper, followed by the beam-column connection. The dominant failure pattern of the dog-bone damper, both in the damper and connection tests, was mainly out-of-plane flexural-torsional buckling. The test results show that PCF-MDC-nuts has a similar flexural strength as PC. The maximum in-elastic drift ratio of PCF-MDC-nuts has been improved to 5.48% compared to that of PC (3.27%). The degradation of PC-MDC-nuts was alleviated compared with PC. The cumulated absorbed energy and maximum equivalent viscous damping ratio of the PCF-MDC-nuts were 41.04 kN·m and 44.17%, respectively, while those of PC were 11.06 kN·m and 19.48%. The seismic performance of PCF-MDC-nuts was superior to PC. The concept of the proposed detachable configuration was justified.

Seismic behavior of a friction-type artificial plastic hinge for the precast beam–column connection

Seismic behavior of a friction-type artificial plastic hinge for the precast beam–column connection

Experimental Study of Emulative Precast Concrete Beam-to-Column Connections Locally Reinforced by U-Shaped UHPC Shells.

Precast beam–column connections act as vital elements of precast concrete frames. To enhance the resistance to the earthquake-induced damage and environment-induced deterioration of precast beam–column connections, an innovative precast concrete beam-to-column connection locally enhanced by prefabricated ultra-high-performance concrete (UHPC) shells was proposed. For studying the seismic behaviors of these novel connections and the influence caused by the prefabricated UHPC shell length, full-scale precast specimens were experimentally investigated using low-cyclic reversed loading tests. The obtained results were analyzed and discussed, including hysteresis curves, skeleton curves, strength and deformability, performance degradation, energy dissipation capacities, and plastic hinge length. The results reveal that the novel precast concrete beam–column connections with UHPC shells behaved satisfactorily under seismic loadings. The damage in the concrete near the lower part of the beam end is reduced by the prefabricated UHPC shells. The longer prefabricated UHPC shells were more useful for decreasing the damage to the precast concrete components and improved the structural performance. The precast specimen with 600-mm long UHPC shells can achieve a ductility of 4.87 and 4.0% higher strength than the monolithic reference specimen.

Numerical Investigation of Beam-Column Connections in Precast Concrete Buildings

The progressive collapse of structures has been the concern of many studies. Efforts have been made to develop methodologies of analysis and design for the mitigation of progressive collapse. As precast structures lack of structural continuity in the load paths, they are more responsive to progressive collapse than the cast-in-situ monolithic reinforced concrete (RC) buildings. In this paper, Analytical study has been conducted to develop a nonlinear finite element FE model using ABAQUS 6.12 software to investigate the behavior of precast non-prestressed reinforced concrete beam-column connection in case of sudden column removal. The FE model consider the nonlinear behavior of concrete and steel. In addition, it takes into account the contact properties between surfaces at joints. A calibration was performed between the numerical and the experimental results, using three half-scale specimens tested under mid column lose, to verify that the FE model could be used for simulating precast beam column connections. There was a good agreement between experimental and numerical results.

Numerical Investigation of Beam-Column Connections in Precast Concrete Buildings

The progressive collapse of structures has been the concern of many studies. Efforts have been made to develop methodologies of analysis and design for the mitigation of progressive collapse. As precast structures lack of structural continuity in the load paths, they are more responsive to progressive collapse than the cast-in-situ monolithic reinforced concrete (RC) buildings. In this paper, Analytical study has been conducted to develop a nonlinear finite element FE model using ABAQUS 6.12 software to investigate the behavior of precast non-prestressed reinforced concrete beam-column connection in case of sudden column removal. The FE model consider the nonlinear behavior of concrete and steel. In addition, it takes into account the contact properties between surfaces at joints. A calibration was performed between the numerical and the experimental results, using three half-scale specimens tested under mid column lose, to verify that the FE model could be used for simulating precast beam column connections. There was a good agreement between experimental and numerical results.

Nonlinear Numerical Evaluation of Dry Precast Beam Column Connection with Embedded Bolts

Precast dry connected frame systems are faster to construct with less erection efforts. These frame systems are considered non-emulate frame systems. The lateral load behaviour of these connections needs to be evaluated to ensure the desired performance. The performance of these dry connections with embedded bolts proposed was studied by finite elemental analysis. The nonlinear FEM analysis results obtained by considering appropriate elements, and material definition parameters, including failure and interactions, were validated with the experimental results available in the literature. The rigidity of the joints was evaluated using the beamline method. The beamline plot unveils that the joints can be classified as rigid joints. The results reveal that the joints under study have satisfactory stiffness degradation, energy dissipation characteristics, and failure modes like monolithic connection. The numerical procedure developed provide an efficient solution for performance evaluation and seismic design of these precast joints

Precast Concrete Column Beam Connection Using Dowels Due to Cyclic Load

The beam-column connection plays an important role in the building structure, especially when the load is cyclic. The main problem that must be solved is the beam and column connection panels. The purpose of this study was to analyze the characteristics of the hysteresis loop of the displacement load relationship with the control displacement of the precast beam-column connection due to cyclic loading. The research method used is the experimental method with a measurable object design test and a special testing method. The results of this study indicate that normal concrete has a compressive strength of 26.43 MPa, while grouted concrete has a compressive strength of 36.97 MPa. The findings of this study also show that the bond stress grouted concrete increases by 102.4% from normal concrete for D13 diameter screw reinforcement, while for D16 diameter, the adhesive stress increases by 51.63%. The findings of this study also show that in the ultimate condition, the load obtained in the tensile load is 13.58 kN with a displacement of 87.58 mm, while the compressive load is 12.62 kN with a displacement of 88.30 mm. This study concludes that the behavior of precast beam-column joints with dowels is stronger in resisting cyclic loads.

Quantification of Moment–Rotation Relationship of Monolithic Precast Beam–Column Connections

The accurate prediction of nonlinear structural behaviors under different seismic intensities is an important basis for seismic resilience assessments of building structures. The moment–rotation relationship is often used to characterize the seismic performance of connections, and is widely used in high-efficiency nonlinear structural analysis. In this paper, a method of calculating the curve using a four-linear equivalent model is presented, aiming to quantify the characteristic point parameters of the moment–rotation curves of monolithic precast beam–column (MPBC) connections for engineering design purposes. The method considered the contribution of the elastic flexure of beams and columns, the relative slip of beam longitudinal bars in the core zone, and the formation of plastic hinges at beam ends to the total deflection. Due to the presence of local complex configurations in MPBC connections, the fine fiber section method was used for moment–curvature analysis of critical beam sections. The determination of the sectional analysis processes was controlled by the strain of steel bars or concrete or their coupling effect. In addition, a two-step method was proposed to construct the moment–rotation relationship of cruciform beam–column connections for solving the deformation compatibility of beams on both sides of the column caused by asymmetric reinforcement and the strength difference between new and old concrete. To reflect the current manufacturing level of MPBC connections, 58 representative specimens reported in recent years were analyzed and classified as type 1–5. All types of MPBC connections and their 18 cast-in situ counterparts were calculated using the proposed method for both verification and quantification. The verification showed that the proposed method had good applicability to both cast-in situ and precast beam–column connections. The quantification showed that the characteristic point parameters were slightly different between these two connections. Accordingly, modification coefficients were suggested for MPBC connections to facilitate design.

A post-tensioned hybrid beam-column connection with a web friction device: Experimental study and theoretical analysis

An innovative post-tensioned hybrid beam-column connection with a web friction device (PTH-WFD) was proposed to mitigate concrete crushing of precast members and to avoid the onsite aerial tension of steel strands in reinforced concrete (RC) structural systems. The proposed PTH-WFD connection was assembled using a precast hybrid (PH) beam and a precast RC column with high-strength bolts. The PH beam consisted of an RC beam and two short steel arms on both sides, and post-tensioned (PT) steel strands and WFDs were employed in the PH beam to provide a self-centering capacity and an energy dissipation capacity, respectively. To explore the seismic behavior of the proposed connection, cyclic tests were conducted on five specimens to evaluate the seismic behavior of the proposed connection, and the effects of the initial PT force on the steel strands and the clamping force in the WFDs were investigated. During the test process, few cracks were observed on the primary structural components, namely the RC beam and column, and the damage was primarily concentrated on the steel arms. The test results indicated that the proposed connection could exhibit a typical two-stage hysteretic behavior, namely, a self-centering stage and an energy consumption stage. In the first stage, the contact interface between the steel arms and the RC beams presented a continuous opening-to-closing mechanism when the drift ratio was less than 1.5%, indicating that the residual deformation was controllable and that a self-centering behavior could be achieved. In the second stage, the short steel arms yielded when the drift ratio was larger than 1.5%, indicating that the residual deformation increased and the energy dissipation significantly increased. In addition, the peak load and displacement ductility ratio increased with an increasing clamping force in the WFDs, and the peak load also increased with an increasing initial PT force. Based on the test results, a theoretical moment-rotation model was proposed, and the calculated results were in good agreement with the test results. • We conducted the test on seismic behavior of a novel precast beam-column connection. • The proposed connection could exhibit a typical two-stage hysteretic behavior. • The theoretical cyclic behavior was proposed.

Energy dissipation capacity of precast concrete beam-column joint connected by double notch subjected to cyclic lateral loading

This paper presents the experimental investigation of full-scale precast concrete beam-column connections subjected to cyclic lateral loading. The specimen consists of three models. Two of which are precast beam-column connections and one is monolith. The precast and monolith specimen were designed for the same strength. The cross-sectional dimensions of the beam 250 mm x 300 mm and column 300 mm x 300 mm. Connections are placed in plastic hinge area, with a distance of h (beam height) from the face of the column which is expected to occur first destruction. Precast construction joints are distinguished, with 3 different models, namely monolith, double notch type 1 (STR-1), and double notch type 2 (STR-2). Maximum load capacity, hysterical behavior and energy dissipation are measured, and capacity is compared. The results showed that beam-column joint STR-2 are better able to absorb energy than beam column joint monolith and beam-column joint STR-1. Kumulative energy dissipation of monolith about 9333.07 kN-mm, STR-1 is 8336.76 kN-mm, and STR-2 is 10162.52 kN-mm. The use of dual notch connections (STR-1 and STR-2) provides satisfactory performance, which is marked by meeting the minimum relative energy dissipation ratio at a 3.5% drift according to the ACI Committee 374.1-05. The results show that the STR-2 beam-column connection is more capable of absorbing energy than the monolith beam-column connection and STR-1 beam connection. the value of monolithic cumulative energy dissipation is around 9333.07 kN-mm, STR-1 is 8336.76 kN-mm, and STR-2 is 10162.52 kN-mm. in principle, all three test specimens, monoliths, STR-1 and STR-2 provide satisfactory stability performance under lateral cyclic loads, because they still meet the minimum relative energy dissipation ratio at a deviation of 3.5% according to the ACI Committee 374.1 -05

Experimental study on internal precast beam–column ultra-high-performance concrete connection and shear capacity of its joint

Precast reinforced concrete structures are increasingly being studied and adopted for their potential advantages. In this study, we tested five precast beam–column connections whose regular shape beams and columns were connected with lap-spliced steel bars in ultra-high-performance concrete (UHPC). A monolithic beam–column connection as a control specimen was also tested under reverse cyclic loading. The results showed that the application of lap-spliced steel bars in UHPC is feasible for connecting the beam and column in the joint. It is recommended that the minimum straight bar lap length in UHPC can be determined as 15db (db is the bar diameter), and the minimum hooked bar lap length was determined as 11db (with a straight extension length of 8db, inside bend diameter of 4db, and tail extension length of 5db). UHPC significantly enhanced the shear capacity of the joint owing to its high shear strength. The increases in the fiber volume fraction and stirrup volume ratio enhanced the damage-resistance property of the joint, which is beneficial for the development of beam-end plastic hinges. Therefore, the ductility of the beam–column connection can be further increased. The increase in axial load enhanced the shear capacity. To design a “strong joint,” a theoretical strut-and-tie model was proposed based on Mohr–Coulomb theory applied to the joint core to accurately calculate the UHPC joint shear capacity.

Hysteretic performance of precast beam-column connections fabricated with high-strength materials

The current work attempts to characterize the hysteretic performance of precast 100 MPa grade HSC beam-column connections incorporating rebars with a nominal yield strength of 500 MPa. Four full-scale subassemblies (precast interior and exterior connections, and two corresponding cast-in-place (CIP) connections) were constructed and tested under reversed cyclic loading with a fixed axial compression ratio n of 0.4. The precast connections encompass precast column, composite beam (precast part and CIP part), and CIP joint core, in which, the longitudinal rebars in column and beam were connected using grouting sleeve and welding, respectively. Results show that four beam-column subassemblies suffered the flexural failure of beam end with no joint core spalling or cracking, and arch-shaped hysteresis curves and stable hysteretic behavior up to 3.0% drift ratio were captured. Precast beam-column connections could achieve an emulative (equivalent to CIP) design philosophy, concluded from the similar bearing capacity, ductility and dissipated energy of precast and CIP specimens. Moreover, an evaluation based on the criteria presented in ACI 374.1-05 validates the satisfactory seismic performance of beam-column connections with high-strength materials.

Study on Comprehensive Evaluation Method for Construction Suitability of Precast Concrete Beam-column Connections

The key difference between prefabricated structure and cast-in-place structure is the connection of components. The comprehensive reliability of the connection directly determines the overall performance of the structure, and also affects its application scope in the building structure. It is particularly important to select the appropriate beam-column connections in the construction. In recent years, with the continuous development of precast concrete structure, a large number of precast beam-column connections have been invented. However, in view of different construction environment, construction cost and building function requirements, the selection of precast beam column connections is often difficult to choose. Therefore, this paper is based on the Analytical Hierarchy Process (AHP) evaluation model, combined with the evaluation index of the precast concrete beam-column connections, to provide a scientific method for selecting suitable precast beam-column connections for engineering construction.

LOAD RESISTING MECHANISM OF PRECAST STRUCTURE UNDER EXTERIOR COLUMN FAILURE

In order to study the anti-continuous collapse mechanism of an unbonded post-tensioning precast structure with prestressed spliced connections under the condition of side column failure, four one-half scaled precast beam-column substructures were tested in the laboratory. The performance of three types of precast beam-column connections are investigated by using a pushdown loading approach. The test results demonstrated that different connection types exhibit different failure modes. The installation of unbonded post-tensioning connections is an effective way to resist the progressive collapse of precast concrete frames. The hybrid connection achieved greater load resistance than the summation of the load resistance of the unbonded post-tensioning connection and steel angle connection individually. Higher effective prestress in unbonded post-tensioning tendons could increase the load resistance in a relatively small deformation stage. However, the higher effective prestress may decrease the ultimate load capacity of the frame at a large deformation stage. Finally, high-fidelity finite element models, which were relied on commercial software ANSYS/LSDYNA, were developed. After validation, the results, which could not be measured during tests, were presented and discussed. Then, parametric studies were carried out based on the validated models. The numerical results showed that bonded post-tensioning tendons could increase the resistance of the specimen with unbounded post-tensioning tendons. Increasing the concrete strength could also increase the load resistance significantly. However, higher axial compressive forces at side columns will aggregate the P-Δ effects, which leads to lower deformation capacity and ultimate load resistance capacity.

Experimental study on interior precast concrete beam-column connections with UHPC core shells

High-performance materials are increasingly being used in precast connections to improve their mechanical performance and simplify the construction process. In this study, a novel precast beam-column connection with an ultrahigh-performance concrete (UHPC) core shell is proposed, which works as the permanent joint formwork in the precast stage and the strengthening overlay during normal service. To investigate the seismic performance of the proposed connection, a total of three precast specimens and one reference monolithic specimen were tested through the quasi-static method. The main variables in this study were the thickness of the UHPC shell and the layout and ratio of stirrups in the joint zone. The test results indicated that the UHPC core shells effectively limited the shear behavior, delayed cracking in the joint zone, and provided plump hysteretic performance. With the assembly configuration, the proposed connection had good ductility and an efficient energy dissipation capacity. The UHPC shell configurations with variable stirrup layouts and ratios led to different crack patterns in the joint core zone. In addition, strengthened by the UHPC shells, the joint cores could be reinforced with fewer stirrups than demanded by code.