Monolithic Joints Research Articles

Seismic performance analysis of a novel demountable precast concrete beam-column connection with multi-slit devices

In this paper, a novel type of precast concrete beam-column connection based on the ideal plastic hinge failure mechanism is proposed. This connection mainly includes a hinge shaft and multi-slit devices (MSDs). In order to investigate the seismic performance of the proposed precast concrete beam-column joint, the theoretical calculation method of MSD was first proposed, and its accuracy was verified based on the finite element (FE) analysis. Then, based on the proposed calculation method, two kinds of MSDs were designed to connect the precast concrete beam-column joint. The seismic performance of the precast joints was analyzed by FE models, and compared with the monolithic joint. The analysis results indicate that the seismic performance of the proposed precast beam-column joint is superior to that of the monolithic joint in terms of strength, stiffness, deformation, and energy dissipation capacity. Meanwhile, the MSD can be replaced after damage in earthquakes, which is convenient for rapid repair of prefabricated structures. Overall, the proposed precast beam-column joint shows excellent seismic performance and repairability. Therefore, the proposed beam-column connection method can provide a reference for the application of prefabricated structures in high seismic intensity regions.

Performance of monolithic and dry joints with GFRP bolts reinforced with different fibres and GFRP bars under impact loading

This study investigates the performance of monolithic and newly proposed dry beam-column joints using GFRP bolts, GFRP reinforcements, and different types of fibres subjected to pendulum impact. Six specimens were cast and tested with increasing impact velocity until failure. The experimental results have shown that the proposed concrete dry joint reinforced with fibres and GFRP bars showed better behaviour in terms of energy dissipation (up to 51%), reduced damage level, and reduced maximum and residual displacement as compared to the monolithic joint with GFRP reinforcements. The test results suggested that steel bolts and steel reinforcements could be effectively replaced by GFRP bolts and GFRP reinforcements to mitigate the corrosion problem while still satisfy the design requirements for beam-column joints in both strength and ductility. Furthermore, the use of steel fibres (StFs) demonstrated impressive performance in the critical indices such as damage level and displacement at high impact energies, compared to synthetic fibres (SyFs). Meanwhile, the application of SyFs led to greater energy dissipation than that of StFs (between 6 and 30%). The proposed dry joints could be potentially applied in practice to reduce the construction costs and the damaged/deteriorated components would be easily replaced.

Experimental and Numerical Study of Lattice Girder Composite Slabs with Monolithic Joint

This paper studies the behavior of lattice girder composite slabs with monolithic joint under bending. A full-scale experiment is performed to investigate the overall bending resistance, deflection and the final crack distribution of latticed girder composite slab under uniformly distributed load. A finite element model is given for the analysis of the latticed girder composite slabs. The effectiveness and correctness of the numerical simulations are verified against experimental results. The experimental and numerical studies conclude that the lattice girder composite slabs conform to the requirement of existing design codes. A parametric study is provided to investigate the effects of lattice girder with following conclusions: (a) the lattice girder significantly increases the stiffness of the slab when comparing with the precast slab without reinforcement crossing the interface; (b) the additional reinforcement near the joint slightly increases the stiffness and resistance, while it prevents damage near the joint.

Experimental and numerical investigation on seismic performance of a composite wide beam-column interior joint

This paper aims to scrutinize the behavior of a typical composite wide beam-column interior joint under lateral cyclic load. The investigated composite structure consists of a precast U beam with rooted A-trusses and U bars, precast columns, and cast-in-situ concrete poured over the precast U beam and in the joint region with post-tensioning. In this study, a half-scale specimen of the post-tensioned precast wide U beam-column interior joint was tested under an incremental displacement controlled lateral cyclic load. A 3D comprehensive numerical model of the tested specimen was developed in LS-DYNA finite element (FE) code, and validated with experimental results. Based on the experimental and numerical results, hysteresis behavior, failure mode, strain distribution in rebars, energy dissipation and interface interaction between the precast and cast-in-situ concrete were investigated. In addition, force transfer mechanism from the composite wide beam to the column core was elucidated with the validated numerical model. The precast wide U beam column interior joint exhibited an equivalent load-displacement behavior with the monolithic joint having the same beam-column width ratio and reinforcement detailing. Cracks and damages were found to be prevalent on the composite wide beam whilst only a few flexural cracks were observed in the precast column. The transverse flexural cracks across the wide beam, diagonal shear cracks on the beam originating at the column corner, and torsional cracks were the major crack types observed on the tested specimen. Furthermore, the interface of precast and cast-in-situ concrete remained intact until the ultimate state.

Seismic performance of a novel prefabricated beam-to-column steel joint considering buckling behaviour of dampers

A novel prefabricated beam-to-column steel joint (PSJ) for precast concrete structures was proposed in this study. The joint had the advantages of easier to fabricate and more environmentally friendly than existing monolithic joint (MJ) cast on site. Low-yield-point steel 100 was used to fabricate the dampers of the joint to provide a high energy dissipation capacity. In addition, the plastic hinge location of the beam can be controlled in the dampers by the buckling energy-dissipation segments (BEDS) of the dampers. Cyclic loading experiments were conducted on three PSJs and an MJ to investigate their seismic performance. The effects of the BEDS’ slenderness ratio on the seismic behaviour of the joints were studied. According to the test results, the PSJs exhibited higher ductility and energy dissipation capacity than the MJ. The BEDS used in the proposed joint were beneficial for concentrating the plastic deformation in the damper, thus preventing the damage to the concrete beams. The decreased slenderness ratio of the BEDS increased the strength of the PSJ. An analytical model that considering the buckling effect was proposed to evaluate the bending moment capacity of the PSJ.

Performance of geopolymer concrete in monolithic and non-corrosive dry joints using CFRP bolts under cyclic loading

This study evaluates the performances of beam-column joints made of geopolymer concrete (GPC). A new dry joint type made of GPC and carbon fibre reinforced polymer (CFRP) bolts was proposed for moment-resisting concrete frames under earthquake loadings. Cyclic loading was applied to test the four specimens which were preparatorily cast by ordinary portland concrete (OPC) and GPC. Compared to monolithic joints, the proposed dry joints showed better performances in the maximum load-carrying and energy dissipation capacity. Additionally, new analytical models to design GPC monolithic and GPC precast joints are proposed. These models well predict the peak loads, main failure modes, failure positions, and horizontal shear strength with a minor variation of 1.3%. The application of GPC promises to effectively recycle a large amount of industrial wastes. Furthermore, the proper design made sure the CFRP bolts survive during the test without brittle failure and shear failure. Therefore, they could be potentially applied in the proposed dry joint to well resolve the corrosive issues in conventional precast joints, as well as satisfying the requirements for construction in sesmic regions.

Analytical Investigation of the Differences between Cast-In-Situ and Precast Beam-Column Connections under Seismic Actions

At present, the engineering designers generally design and analyze the precast structural models according to the equivalent cast-in-situ principle, and have a vague understanding of non-identical problems. However, these issues cannot be ignored, especially for high-intensity areas. This paper considers the differences of the hysteretic relationship between two typical precast joints and cast-in-situ (RC) joints, and researches the influence of these differences on the seismic response of frame structures. For the monolithic precast joint, the force mechanism was analyzed based on its assembly form, and the differences with the RC joint in the testing phenomena were explained accordingly. The dimensionless hysteresis models of two types of joints were proposed, and the rationality of the monolithic precast joint model was verified according to the existing experimental results. Different performances of joints were realized by assigning the constitutive models calculated from sectional reinforcement to the spring elements of analysis models. Considering two possible performance deficiencies of each type of precast joint separately, a total of seven structural analysis models were formed. Nonlinear static analysis and dynamic time-history analysis methods were adopted to reveal the differences between precast frames and the RC frame in terms of structural capacity curve, displacement response, ductility demands of components and structural residual deformation. The results showed that under strong seismic excitation, the response differences between precast frames and the RC frame were significant, so it is worthwhile to establish nonlinear models suitable for precast frames in seismic analysis. This study is valuable for understanding and distinguishing the nonlinear response of precast frames and traditional RC frames.

Ductile and dry exterior joints using CFRP bolts for moment-resisting frames

This study proposes a new dry joint type for moment-resisting frames by using carbon fibre reinforced polymer (CFRP) bolts and plates. This is one of very rare studies focusing on the potential of using CFRP bolts to connect the precast beam-column joints. CFRP bolts have been recognized for their good performances, which could effectively resolve a very costly issue of corrosion in the common dry joints using steel bolts, plates, and tendons. Cyclic loading was applied to test four specimens until 85% of the post-peak load. The results indicated that the proposed dry joints showed better performances compared to the reference monolithic joint in the load-carrying capacity, energy dissipation, and stiffness, which increased by 27–61%, 45–75%, and 27–55%, respectively. Particularly, drift ratio of all the proposed joints exceeded 3%, which is higher than the requirements for ductile joints in various standards. The ductility of the proposed joints was also more preferable than the reference monolithic joint (i.e. 2.2 vs 2.4). These exciting results suggest that these new dry joints can be plausibly applied to prefabricated constructions in non-seismic and seismic-prone areas. In addition, the proposed dry joints offer numerous advantages, compared to the traditional monolithic joints, in terms of construction time and construction-quality control.

Energy-efficient indicators of panel housing mass construction in the climatic conditions of central Russia

For the design of energy-efficient buildings, it is only necessary to ensure balanced energy consumption. The definition of energy efficiency is inextricably linked to compliance with requirements and economic costs. The concept of energy efficiency does not only apply to a new building. The new design used all the necessary elements. The use of single-layer prefabricated panels in new construction allows for external insulation taking into account the overlap of all monolithic joints. One of the potentially promising methods of thermal insulation of outdoor structures is the use of liquid-ceramic (thermal insulation) coatings. In the course of the study, it was concluded that the surface temperature of the reinforced concrete panel when using two different insulation options has similar indicators. But the difference in the values of the heat flux is 36.2%, i.e. when using liquid-ceramic insulation, the amount of heat transferred through the wall panel is more by 9.67 W / m2. Economic calculation shows that the use of liquid-ceramic insulation has a positive economic effect in comparison with the classical method of wall insulation by 19.56%.

Experimental study of precast beam-to-column joints with steel connectors under cyclic loading

This article investigated the seismic performance of a new type of precast concrete beam-to-column joint with a steel connector for easy construction. Five interior beam-to-column joints, four precast concrete specimens, and one monolithic joint were tested under reversed cyclic loading. The main variables were the embedded H-beam length, web plate or stiffening rib usage, and concrete usage in the connection part. The load–displacement hysteresis curves were recorded during the test, and the behavior was investigated based on displacement ductility, deformability, skeleton curves, stiffness degradation, and energy dissipation capacity. The results showed that the proposed beam-to-column joint with the web plate in the steel connector exhibited satisfactory behavior in terms of ductility, load capacity, and energy dissipation capacity under reversed cyclic loading, and the performance was ductile because of the yielding of the web plate. Therefore, the proposed joint with the web plate could be used in high seismic regions. The proposed joint without the web plate exhibited similar behavior to the monolithic specimen, indicating that this joint could be used in low or moderate seismic zones. Furthermore, the utilization of the web plate was vital to the performance of this system.

Seismic Design of Precast Component Beam-Column Joints using Headed Anchors

Precast construction system ensures high degree of quality, safety, and accelerated construction practice in R.C structures. It is well established in non-seismic conditions where gravity loads are predominated. But it is hesitated to implement during seismic conditions by the effect of lateral loads. Most of structural failures in precast framed structures are associated with beam-column joints as the integrated joint system experience high shear, and moments by cyclic action of seismic loads. In this context, researchers found that the joint distortions in precast system is well associated with its location of beam-column sub-assemblage. In beam-column joints the connections are attributed to locate in D-regions (D:Discrete) and B-regions (B:Beam) where the force transfer mechanism follows by strut - tie method (STM) or flexure beam theory(FBT) respectively. This paper analyzed the seismic performance of “Component Based Precast Joints”[CBPJ] located in D& B regions. To meet the convergence requirements, the connection systems are detailed by mechanical couplers and headed anchors. Five numerical models of exterior beam-column joints representing two models (BM1,BM2) of B-region and three models (DM1,DM2,DM3) of D-region are developed and verified their seismic performance with monolithic joint system by non-linear finite element analysis using ABAQUS software .The results indicated that the use of headed anchors in precast joints are effectively contributed to seismic requirements of shear, ductility, stiffness and energy dissipation. Also the precast joints located in D & B regions resembling good performance of joint sustainability during moderate seismic conditions as monolithic system.

Experimental investigation of prefabricated beam-to-column steel joints for precast concrete structures under cyclic loading

In this study, a novel prefabricated beam-to-column steel joint suitable for precast concrete structures was developed. The proposed steel joint with dampers could replace cast-in-situ concrete beam-to-column joints in precast concrete structures. Low-yield-point (LYP) steel was selected for the damper to provide the energy dissipation capacity. The plastic hinge location of the beam can be controlled within the joint by the energy-dissipation segments (EDS) made of the LYP 100 steel. Compared with the monolithic joint, the joint is easier to fabricate and take less time during construction while ensuring satisfactory construction quality. Experimental tests were conducted to evaluate the seismic performance of steel joints subjected to cyclic loading. The effects of the thickness of the non-energy-dissipation segments (NEDS) and the length of the EDS were investigated. The test results showed that the proposed steel joint exhibited better hysteretic performance and higher energy dissipation and ductility than a monolithic joint. The joints had sufficient initial stiffness. In addition, an increase in the thickness of NEDS results in higher strength and lower energy dissipation of the PSJ specimens. The strength decreases and the energy dissipation increases with the increasing of the length of EDS.

Experimental seismic study of precast hybrid SFC/RC beam–column connections with different connection details

A new type of precast hybrid steel fiber concrete (SFC)/reinforced concrete (RC) beam–column connection with different connection details was developed for precast concrete frames. In this study, seven concrete beam–column connections, six precast specimens, and one monolithic joint were subjected to a constant axial load and a reversed cyclic loading. The main test variables were the end-plate connection forms and SFC usage in the core region and the connection section. The construction process of the proposed hybrid connections was convenient and fast. The load–displacement hysteresis curves and failure modes of the precast connections were obtained, and the seismic behaviors in terms of connection stiffness, strength, energy dissipation, and shear deformation in the joint core were evaluated. The results revealed that the proposed precast concrete connections had higher strength, slower stiffness degradation, and greater energy dissipation capacity, thereby illustrating that the specimens had a satisfactory ability to resist seismic loads. The shear deformation of the proposed joints was reduced because of the tensile deformability of the SFC and the yielding steel connectors, while the shear strength was considerably enhanced. The cracking pattern in the core region of the hybrid connections with the SFC was well controlled. The integrity of the connection section was maintained. Furthermore, the SFC and steel-plate connectors were vital to the performance of the system.

ЧИСЛЕННОЕ ИССЛЕДОВАНИЕ РАБОТЫ ЗАМКОВОГО СОЕДИНЕНИЯ СТЕНОВЫХ ПАНЕЛЕЙ НА РАСТЯЖЕНИЕ ДО ОБРАЗОВАНИЯ ТРЕЩИН

A large-panel design scheme includes floor elements, wall panel elements, and joints between them. The rigidity and strength characteristics in tension, compression and shearare required to be knownfor correct modeling of large-panel buildings. Due to the lack of universal formulas in the normative and reference literature for determining the strength and rigidity of various types of joints, it is necessary to conduct additional research. In 2014 a new type of vertical monolithic joint for large-panel buildings was developed: the fastener joint of wall panels, which has significant strength and rigidity. The fastener includes acheck clamp, which connects the loop outlets on panel ends and the steel plate, which connects the ends of the clamp. It isnecessary to correctly evaluate the strength and rigidity of the joint for its fully- functional application. The experimental research on the joint in tension discovered its bilinear force-deformation relationship (with great rigidity before cracking, and with marginal one after). To analyze the large-panel buildings under the influence of the main operational loads, it is enough to model the joint’s work on the first stage (before cracking). The aim of the research is to study the fastener joint in tension before cracking. The paper compares the results of numerical modeling with the sample testing results, and determines the rigidity and cracking load for joints with other values of the grouting concrete strength and the diameters of the loop outlets. The research was carried out using flat finite-element model in the Lira-SAPR CAD software package. The results of calculation of the joint model are generally consistent with the results of samples testing. In addition, the rigidity and cracking load were determined for joints with various parameters (concrete strength and loop outlet diameter). The results of the study can be usedfor designing large-panel buildings with this type of joint.

Mechanical behavior of a replaceable energy dissipation device for precast concrete beam-column connections

A replaceable energy dissipation device for precast concrete beam-column connections is proposed in this paper, which is comprised by a short length of a H-shaped steel section with web opening. Five full scale specimens under different loading conditions were tested, and its performance was evaluated based on the ultimate load-carrying capacity, stiffness, energy dissipation, and ductility. The experimental results proved that the device has excellent energy dissipation capacity, rotation capacity and ductility. Furthermore, the device under pure shear load and bending-shear load exhibits different failure modes. Subsequently, finite element (FE) models were developed and validated by the test results. Based on the verified FE models, a parametric study was carried out to investigate the influence of span-height ratio, type of web opening, and load boundary condition on the performance of the device. The analysis results showed that the crack of the device under pure shear load is mainly concentrated at the chamfers, while the crack of the device under bending-shear load gradually shifts from the welding position between the flange and the end plate to the chamfers of the web opening when the span-height ratio increases from 0.77 to 3.0. Moreover, the type of web opening has a significant effect on the ultimate load-carrying capacity and strength degradation of the device. Finally, a case study of a precast RC beam-column joint connected by the device was investigated, and the results indicated that the seismic performance of the precast joint is better than that of the monolithic joint in terms of the deformation capacity, energy dissipation capacity and ductility. Therefore, it is recommended that the device can be used for the precast concrete beam-column connections.

Seismic performance of innovative hybrid precast reinforced concrete beam-to-column connections

Precast construction of structural buildings requires connection techniques that can shorten the process using only simple on-site activities while still guaranteeing adequate strength, energy dissipation, stiffness, and ductility. The construction methods should decrease the use of formwork and temporary bracing to save time and costs. In this study, innovative hybrid connections using steel tubes, steel plates, and steel couplers to join beams and columns were proposed and tested under reversed cyclic loading. Five half-scale samples of the hybrid precast joints, including the monolithic and precast joints, were examined to evaluate the seismic performance of the connections. The hybrid connections showed better performance in terms of load, displacement, drift ratio, ductility, strength, stiffness, and energy dissipation compared to a monolithic connection. The drift ratio, moment capacity, strength, and total cumulative energy dissipation of the hybrid connections were higher by 12.5–50.0%, 34.68–59.57%, 35.0–60.0%, and 50.99–331.32%, respectively, when compared with a monolithic connection. The failure modes of the hybrid connections were governed by yielding steel reinforcement, yielding steel plate, and flexural failure, with less extensive damage compared to the monolithic joint. The hybrid connections were effective in shifting the plastic hinges to outside the connection zone. Therefore, the hybrid connections can be used in high seismic zones because the superior performance results meet the requirements of the seismic codes.

Experimental Study on Shear Behavior of Precast Concrete Segmental Beams with Hybrid Tendons and Dry Joints

A series of tests were carried out on nine specimens to improve the understanding of the shear behavior of precast concrete segmental beams (PCSBs) with hybrid tendons and dry joints. The influences of the tendon layout (hybrid tendons and external tendons), shear span ratio, and joint type (monolithic joints, and dry joints) on shear behavior of PCSBs were experimentally studied. The test results indicated that hybrid tendons slightly improved the shear strength and stiffness of PCSBs with dry joints compared to external tendons. The shear strengths of PCSBs with hybrid tendons and dry joints reduced with an increasing shear span ratio. Compared to monolithic beams with hybrid tendons, the dry joints slightly decreased the shear strength and enhanced the nonlinear behavior of PCSBs with hybrid tendons. The shear strengths of PCSBs and monolithic beams can be conservatively predicted by the AASHTO, Chinese code, and British Standard. The strut-and-tie model of prestressing force can accurately estimate the shear strengths of all the beams.

Experimental investigation of precast RC interior beam-column-slab joints with grouted spiral-confined lap connection

The behavior of precast concrete (PC) structures subjected to seismic load depends mainly on the type, location, and reliability of the connections between precast components. To investigate these, the precast beam-column joints are usually tested. However, the research on the seismic performance of the precast beam-column joints containing transverse beams and slabs remains limited and most of the adopted connections are expensive. In this paper, a simple and inexpensive grouted spiral-confined lap (GSCL) connection was proposed and forty-five pull-out tests on this connection were carried out to determine the suggested lap length of deformed bars. Based on these results, an experimental study was carried out on four large-scale PC interior beam-column-slab joints containing transverse beams and slabs in order to further verify the reliability of the GSCL connection and explore reasonable precast assembling patterns for such joints. Three precast assembling patterns, that represent three arrangements of precast members and cast-in-place concrete as well as the location of connections, were designed. Four joints, including one monolithic specimen and three precast specimens, were tested under combined constant axial load and reverse lateral loading. The test results confirm that the proposed GSCL connection can significantly reduce the lap length of reinforced bars compared to the traditional lap connection. Moreover, the test results indicate that the GSCL connection can be applied in seismic regions. Two precast assembling patterns for such PC interior joints with the GSCL connection can be recommended to apply in seismic regions because the corresponding precast joints exhibited better seismic performance than the monolithic joint.

Cyclic loading test for interior precast SRC beam-column joints with and without slab

For better constructability, precast joint segments are used in Steel Reinforced Concrete (SRC) beam-column joints. In this study, quasi-static cyclic tests were performed on six precast SRC beam-column joint specimens with or without slab and one monolithic joint specimen with slab to investigate the load-carrying capacity, deformation capacity, failure mode, stiffness degradation, and energy dissipation capacity. For the test parameters, three connection types of weld-connection, high strength bolt-connection, and a combination of weld- and high strength bolt-connections were considered. The connection location was kept away from the column face so as to avoid the inherent plastic hinge at the connection. The test results showed that the precast SRC beam-column joints with slab exhibited better seismic performance than that of the precast joints without slab. The plastic hinge occurred in steel beam brackets without connection failure. The peak strength was not decreased by bolt-slip at the connection in the joint specimen without slab, while bolt-slip decreased the peak strength of the joint specimen with slab. This study results give an insight to structural engineers for design of precast SRC beam-column joints.

Effects of postcast connection locations on the seismic performance of precast concrete frame joints

SummaryFor the precast structure with postcast connections, the location of the connection is usually the midspan of the beam, joint core, and beam end. However, the postcast connections located at the midspan of the beam or the joint core would increase the difficulty of construction because of the large dimension of the precast components or reinforcement congestion at joint core, respectively. A connection located at the beam end could decrease the seismic performance the energy dissipation mechanism being disturbed. To balance the requirements on the transportation, construction, and seismic performance, the connection is proposed to be located at one plastic hinge length from the beam end. A quasi‐static test was conducted on three 6 m × 3 m beam‐column joints, including two precast joints and a monolithic joint. The results show that the joint with connections located outside the plastic hinge zone had good seismic performance. When the connection located at the beam end, the ductility, strength, and energy dissipation reduced 8%, 10%, and 30%, respectively. To optimize the postcast location, finite element analysis was conducted and 2h was suggested for the postcast location according to the analysis results.