Cyclic behavior of precast concrete beam-column connection using steel fiber reinforced cast-in-place concrete

Three equivalent exterior precast concrete beam-column (PCBC) connections have been investigated in this study in orderto analyze the effect of steel fiber reinforced concrete (SFRC) as cast-in-place (CIP) on the seismic performance of the PCBC connection. The connection was designed as a ductile connection for a moment-resisting frame and consists of a precast U-beam, precast column with corbel, interlocking bars, and CIP-concrete to connect the precast beam to precast column. The volume fractions of steel fiber incorporated within the CIP-concrete were 0%, 0.5% and 1%. A quasi-static load was applied vertically to the beam tip of the PCBC specimen. The results showed that the steel fibers contained within the CIP-concrete provided 2% increase of the maximum load, 17.7% increase of the energy dissipation, and increase in the joint stiffness of the PCBC connection. The steel fibers delayed the onset of cracking and slowed down the crack propagation, resulting in shorter cracks in the joint core of PCBC specimen, which correlates well with the deflection-hardening characteristic found from the modulus of rupture test.

Behaviour of Precast Column Foundation Connection under Reverse Cyclic Loading

Precast column foundation connection is one of the critical connections under reverse cyclic loading, and the present study focuses on this connection. Three types of connections were considered, such as (i) base plate connection, (ii) pocket connection, and (iii) grouted sleeve connection. All the above connections were designed, and experimental investigation was carried out on 1 : 2 scaled models by subjecting the column to lateral reverse cyclic loading. Displacement-controlled loading pattern has been adopted for the testing of the specimens. The structural response of the connection was studied for their (i) load-displacement hysteresis behaviour, (ii) stiffness degradation, (iii) energy dissipation, and (iv) ductility. The results were then compared with that of the monolithic connection. The precast connection was more ductile, and the energy dissipated by the pocket connection was high compared to the base plate and grouted sleeve connection. The ductility and the load-carrying of grouted sleeve connection were small compared to other connections. The results of the study showed the precast column foundation can be used in seismic prone areas.

A Novel Precast Concrete Beam–Column Connection With Replaceable Energy-Dissipation Connector: Experimental Investigation and Theoretical Analysis

In order to avoid the damage of the connection due to the overstrength of beam strength, and the alternation of the strength hierarchy in the structural system. The additional bending moment produced by the combined action of the pressure generated by the concrete compression zone and the tension generated by the reinforcements needs to be reduced. A novel precast concrete beam–column connection is proposed herein. In the proposed connection, the precast beam is laid on a steel corbel embedded in the precast column. A novel replaceable energy-dissipation connector (REDC) is placed at the bottom of the steel corbel, which ensures that it is in the same horizontal position aligned with the longitudinal reinforcement at the bottom of the connection. In addition, there is a narrow vertical slot adjacent to the column face. The total yield capacity of the top reinforcement is larger than that of the bottom REDC energy-dissipation connector. Theory study focused on the structural features and mechanical mechanism of this novel precast connection. Three low-cycle quasi-static loading tests were carried out on a single full-scaled specimen by replacing three REDCs with different sizes. The cracking pattern of this novel precast connection, and the effects of different parameters of the REDCs on the energy-dissipation capacity and load capacity of the connections were discussed. By performing a finite-element simulation, a method for reducing the additional bending moment and keeping the top reinforcements always in elastic was developed. In addition, the relevant design suggestions were provided. The conclusion shows that the seismic performance of this novel precast concrete beam–column connection is excellent. The positive and negative bending moments of novel precast concrete beam–column connection both reduce the additional bending moment. In view of this, the bending moment of the novel connection is a controllable variable.

Study on Precast Coconut Shell Concrete Beam-Column Junction Using M-Sand under Static Load

Coconut shell (CS) is one of the sustainable alternative aggregates and coconut shell concrete (CSC) was developed a decade earlier. Prefabricated conventional concrete (CC) and CSC using M-sand, and their research are very limited. Capacity and behavior of the joints are important in precast. Hence in this study, precast column-beam behavior of CSC elements was studied. Two different sizes 12 and 16 mm bolts and nuts connection were chosen and used to connect the precast elements. Also, the same sectional details were used and specimens produced for combination with CC using M-sand (CCM). Specimen failure of both monolithic and prefabricated CSC using M-sand (CSCM) elements was typical structural failure and is comparable to that of CCM. Compared to CCM, high deflection was observed on CSCM element. No crack was developed on both CCM and CSCM prefabricated specimen. All elements were able to sustain their maximum potential for strain. Column-beam joint behavior of CSCM monolithic and prefabricated specimen behavior are comparable to that of CCM.

Mechanical behavior of a novel precast beam-to-column connection with U-shaped bars and engineered cementitious composites

This article investigates a novel precast connection, with U-shaped bars extending from precast column to connect with the longitudinal bars in precast beams. To improve the seismic behavior of the connection, engineered cementitious composites, one kind of highly ductile concrete, were introduced into the core area of the connection, which also act as the cast-in-place material in the beam top and end. Prior to the test, finite element modeling was conducted to determine the proper splice length between U-shaped bars and beam reinforcements and also to evaluate the bonding performance of the proposed connection. The experimental program was then carried out on a monolithic connection, a precast connection with normal concrete as well as a precast connection with engineered cementitious composite, after which the seismic behaviors of the connections including their failure mode, hysteresis characteristic, stiffness degradation, ductility, and energy dissipation were analyzed. All three types of connections underwent typical flexural failure where the joint area remained intact. The negative carrying capacity, ductility, and energy dissipation were slightly lower for the connection with concrete, while the connection with engineered cementitious composite exhibited satisfactory behavior comparable to monolithic specimens. The latter connection with engineered cementitious composite is therefore suggested to be applied in highly seismic region.