Search Results (16)

Nuclear power plant (NPP) shear walls are typically ultra-thick and heavily reinforced, posing significant challenges for conventional cast-in-place (CIP) construction. To overcome these issues, this study proposes a precast concrete shear wall (PCSW) system with bolted connections. Owing to orthogonal wall layouts dictated by functional requirements, these structures are subjected to significant out-of-plane seismic demands, making their performance under such loading a critical design concern. Therefore, this paper investigates the out-of-plane seismic performance of scaled (1:2) models of PCSWs (300 mm thick) under an axial pressure ratio of 0.2 and without axial pressure through low-cycle repeated load tests, and compares them with corresponding CIP shear walls. All specimens exhibited flexural failure, while damage in PCSWs was relatively minor and concentrated within the grouting layer. Compared with CIP specimens, the precast specimens showed more pinching and smaller residual deformation, with cumulative energy dissipation reaching 70–80% of CIP specimens. The flexural load-bearing capacity of the precast specimens was close to that of the CIP specimens, with differences within 5%. The ductility of the precast specimens under axial pressure ratios of 0 and 0.2 was 4.54 and 2.68, respectively, differing from the CIP specimens by 16% and −10%. The stiffness degradation trends of both systems were essentially consistent. Overall, the results demonstrate that the out-of-plane seismic performance of PCSWs with bolted connections is broadly equivalent to that of CIP counterparts, confirming their feasibility for application in NPPs. Full article

With the continuous improvement of the prefabricated modular technology system, the prefabricated subway station structures are widely used in underground engineering projects. However, prefabricated subway stations in soft soil can suffer significant adverse effects under seismic action. In order to study the seismic performance of a prefabricated subway station, this work is based on an actual project of a subway station in soft soil. And the nonlinear static and dynamic coupling two-dimensional finite element models of cast-in-place structures (CIPs), assembly splicing structures (ASSs), and assembly monolithic structures (AMSs) are established, respectively. The soil-structure interaction is considered, and different peak ground accelerations (PGA) are selected for incremental dynamic analysis. The displacement response, internal force characteristics, and structural damage distribution for three structural forms are compared. The research results show that the inter-story displacement of the AMS is slightly greater than that of the CIP, while the inter-story displacement of the ASS is the largest. The CIP has the highest internal force in the middle column, the ASS has the lowest internal force in the middle column, and the AMS is between the two. The damage to the CIP is concentrated at the bottom of the middle column and sidewall. The AMS compression damage moves upward, but the tensile damage mode is similar to the CIP. The ASS can effectively reduce damage to the middle column and achieve redistribution of internal force. Further analysis shows that the joint splicing interface between cast-in-place and prefabricated components is the key to controlling the overall deformation and seismic performance of the structure. The research results can provide a theoretical basis for the seismic design optimization of subway stations in earthquake-prone areas. Full article

To reduce the cast in place work of concrete and realize the industrial production of a bamboo–concrete composite (BCC), innovative connection systems composed of an assembled bamboo–lightweight concrete composite (ABLCC) structure featuring perforated steel plate connectors are presented for use in engineering structures. This study examined the shear performance of connection systems composed of an assembled BCC structure featuring perforated steel plate connectors based on the design and fabrication of three groups of shear connectors with nine different parameters using bamboo scrimber, lightweight concrete, perforated steel plates, and grout. Push-out tests were conducted on these shear connectors. A linear variable differential transformer (LVDT) and digital image correlation (DIC) were utilized for measurements. The test parameters comprised fabrication techniques (assembled and cast-in-place/CIP) and connector size (steel plate thickness). This study investigated mechanical performance indicators, including the failure mode, load–slip relationship, shear stiffness, and shear capacity of the shear connectors. The experimental results showed that the shear connector failure modes involved concrete spalling near the connectors and deformation of the perforated steel plates. The load–slip curves generally included three stages: high slope linear increase, low slope nonlinear increase, and rapid decrease. The shear capacity and stiffness of the assembled shear connectors were 0.84 times and 2.46 times those of the CIP connectors, respectively. The stiffness of the 4 mm steel plate connectors increased by 42% compared to the 2 mm steel plate connectors. Analysis showed that the shear capacity of the BBC primarily consisted of four aspects: the end bearing force of the steel plate, contact friction, and forces due to the influence of tenon columns and the reinforcing impact of through-rebars. This study proposes a simple and suitable formula for obtaining the shear capacity of perforated steel plate connectors in the BCC structure, with the analytical values being in good agreement with the test results. Full article

In this study, three prefabricated integral shear wall specimens with strength differences were constructed based on a real engineering project to investigate the impact of these strength disparities on the structural performance of shear walls. The results indicate that all three prefabricated integral shear wall specimens with strength differences between precast (PC) and cast-in-place (CIP) concrete exhibited bending-shear failure. Moreover, the experimental axial-bearing capacity of the specimens was higher than the calculated axial-bearing capacity obtained using the reduced concrete strength according to the shear wall calculation formula in the code. The ultimate displacement angles of all three specimens exceeded the limit elastic–plastic displacement angle specified for shear wall structures under large seismic motions in the code, and the ductility factors were greater than 3. Furthermore, this paper presents a calculation formula for the axial-bearing capacity of the plane section of prefabricated integral shear walls with strength differences and compares it with experimental results. This paper presents a calculation formula for the axial-bearing capacity of the plane section of prefabricated integral shear walls with strength variations, compares the calculated results with experimental values, and shows that the relative error between the calculated and experimental values is nearly within 10%, which provides a design basis and reference for engineers in calculating the axial-bearing capacity of such shear walls with strength variations. Full article

Four full-scale specimens were constructed, including two hybrid precast specimens with a haunch (height: 150 mm, PUT-H) and without a haunch (PUT). Additionally, two cast-in-place (CIP) comparative specimens (referred to as RUT-H and RUT) were included, all of which underwent reversed cyclic loading. The results showed that the four specimens suffered flexural damage at the ends of the sidewall and displayed similar hysteresis loops shapes. The bearing capacity of the PUT specimen was 2.7% higher than that of the RUT, while the bearing capacity of the PUT-H specimen was 8.5% lower than that of the RUT-H. Additionally, the displacement ductility values of the precast specimens PUT and PUT-H were 2.98 and 2.46, respectively, which are 11.3% and 3.53% lower than those of the corresponding CIP specimens. The haunch increases the local stiffness of the component, exerting a notable influence on the bearing capacity and displacement ductility of the specimens, increasing the bearing capacity by 20% and decreasing the ductility by 21%. Moreover, an assessment conducted using the criteria outlined in ACI 374.1-05 indicated that the four specimens exhibit excellent seismic performance. Full article

This paper introduces a new type of hybrid precast MUT, consisting of precast composite top slab and double-skin sidewalls with reserved rebar. The seismic behavior of the top joints was examined through pseudo-static tests. Four full-scale specimens, including both exterior and interior precast joints, in addition to two corresponding cast-in-place (CIP) joints, were fabricated and subjected to reversed cyclic loading. The results showed that both the precast and CIP joints exhibited flexure failure, characterized by the formation of a plastic hinge at the end of the sidewall. The hysteresis curves of both precast and CIP joints exhibited comparable shapes and quantities of hysteresis loops. The load-carrying capacities for exterior precast joints and corresponding CIP joints were 141.25 kN and 143.5 kN, exhibiting a difference of less than 1.6%. The load-carrying capacities for interior precast and corresponding CIP joints were 60.5 kN and 62.75 kN, displaying a variance of less than 3.6%. The precast specimens demonstrated comparable levels of ductility, energy dissipation, and structural integrity as the CIP specimens. These findings provide validation for designing and analyzing the hybrid precast utility tunnel using identical principles and models as applied CIP structures. Full article

Accelerated bridge construction (ABC) has attracted much attention in China as a new and efficient construction method. However, the seismic performance of the connections between precast piers and other structures limits the application of ABC in medium and high seismic zones. In this paper, a quasi-static test was conducted to investigate the seismic performance differences between a cap–column socket connection (PSC) specimen, which reinforced an embedded RC column-to-precast cap beam with a socket connection, and a cast-in-place (CIP) cap–column specimen. A fiber-based finite element model that considers bond slippage between the connection reinforcement and wet joint concrete is proposed. The numerical simulation results compared with the experimental results show an error of about 12% in peak bearing capacity and about 2% in initial stiffness. The experimental and numerical results show that the PSC specimen demonstrates comparable seismic performance to the CIP specimen. Experimental results verified that the finite element model in this paper is adequate to predict the seismic responses of a precast column with a reinforcement-embedded socket connection. A reinforcement-embedded RC column-to-precast cap beam with socket connection can be an effective solution for construction in medium and high seismic areas. Full article

Although the anchorage location of longitudinal reinforcing bars is a significant design element for flexural behavior, the conventional anchorage method of using longitudinal reinforcing bars has limited applications in new types of structures, such as composite structures. Therefore, this study examined the effect of the anchorage location of longitudinal reinforcing bars on the flexural behavior of slabs at the junctions of developed composite basement walls (SCBW) under monotonic loads at the top free end of the slab. The test results showed that the slab with longitudinal reinforcing bars anchored to the cast-in-place pile (CIP) in the composite basement wall exhibited ductile behavior accompanied by the yielding of the longitudinal reinforcing bars, a relatively wide area of vertical cracks propagating along the slab length, and a plastic plateau flow in the load–deflection relationships. In particular, the slab with longitudinal reinforcing bars anchored to the basement wall experienced severe crack concentration localized at the junction of the composite basement walls and concrete spalling in the basement walls, which resulted in no yielding of the longitudinal reinforcing bars and no cracks in the slab. Consequently, in a slab, it is recommended that longitudinal reinforcing bars be anchored into the CIP by penetrating the steel plate. Full article

In the era of energy conservation and environmental protection, as well as the industrialization of buildings, precast concrete (PC) structures have been developed and increasingly applied in construction industries due to their advantages of outstanding workability and ecofriendliness. In order to verify the reliability of overlapping U-bar loop connections and a modified form of these connections, and study the seismic performance of PC wall–beam–slab joints with these connection methods, three full-scale wall–beam–slab joints were designed and tested under low reversed cyclic loading, including one cast-in-place (CIP) specimen and two PC specimens. Based on the test results, the seismic performance of the PC joints was studied by comparing their damage process, hysteretic loops and skeleton curves, load-carrying capacity, ductility, equivalent stiffness, and energy dissipation with those of the CIP joint. After analyzing the experimental results, the following conclusions can be drawn: the overlapping U-bar loop connection and its modified form are effective and reasonable; the specimen with the modified connection form showed slightly better mechanical properties; the failure mode of the PC joints was consistent with that of the CIP joint; and the generation, distribution, and development of cracks in the PC specimens were similar to those in the CIP specimen. In addition, the stiffness of the PC joints was similar to that of the CIP joint, and the load-carrying capacity, ductility, and energy dissipation of the PC joints were better than those of the CIP joint. Moreover, the research in this paper can also provide some guidance for assembling wall–beam–slab joints in PC shear wall structures. Full article

Congested reinforcement may lead to difficulties with compacting concrete and reduce the connection efficiency. To overcome this problem, using large-diameter longitudinal rebar to replace medium-diameter longitudinal rebar to reduce the number of longitudinal rebars may be a useful mean. However, the seismic behavior of precast concrete (PC) columns with different-diameter longitudinal rebars was still unclear. In order to evaluate the influence of large-diameter longitudinal rebar replacement on the seismic behavior of PC columns, a series of large-scale reinforced concrete (RC) columns adopting similar concrete strength, longitudinal rebar ratio, and transverse rebar ratio was fabricated and tested. Six of the columns were prefabricated with grouted sleeve connections and the remaining two were cast in place (CIP) for reference. The longitudinal rebar diameter varied from 18 mm to 32 mm. A low-cycle reversed horizontal load was applied to study their seismic performance, including failure modes, load-bearing capacity, hysteresis behavior, stiffness degeneration, and energy-dissipation capacity. The test results showed that the PC column with large-diameter longitudinal rebar replacement performed similarly to CIP columns in general. The column with large-diameter longitudinal rebar suffered significant bond-slip between longitudinal rebar and concrete, especially for columns with a high axial compressive ratio of 0.6. It may be of detriment to the seismic behavior of the columns to some extent. Additionally, with the increase in the diameter of longitudinal rebar, the ductility and energy-dissipation capacity of PC columns were reduced slightly. In the grouted sleeve region, a local rigid zone was formed, making its overall lateral stiffness higher than that of corresponding CIP columns. It is recommended to extend the strengthening zone, with closer transverse reinforcement, to two times the column depth of the PC columns with grouted sleeve connections, as the plastic hinges may be shifted upward. Full article

Precast concrete bridge structures have been extensively used because of the mature construction techniques, fast construction, and their economy. Considerable practical applications, however, present certain disadvantages, such as cracking and water infiltration in their normal strength concrete (NSC, compressive strength 40 MPa) joints connecting prefabricated deck panels. Ultra-high performance fiber reinforced concrete (UHPFRC, compressive strength 143 MPa) has been proven highly effective in replacing the conventional cementitious grout materials in precast bridge structures. In the present study, three types of UHPFRC connections, rectangular, zigzag-shaped, and diamond-shaped, were experimentally evaluated on their flexural capacities, interface bonding performances, and failure modes through four-point bending tests (loading rate 0.1 kN/s). The results showed that all the UHPFRC connections exhibited apparently higher flexural capacities than an intact precast NSC member and had such strong UHPFRC-NSC interfacial bonding that the interfacial first-crack strengths were not less than the NSC member. Having the capability of modeling the UHPFRC connections and their interface properties, the developed finite element (FE) models of the precast slabs with UHPFRC connections produce numerical results in good agreement with the flexural tests. By means of the FE models, parametric investigations were carried out to make suggestions on optimizing the UHPFRC connection designs for practical use. Full article

To investigate the seismic performance of prefabricated piers with a grouting sleeve connection, two scaled model specimens of symmetrical prefabricated piers with different reinforcement anchorage lengths, and two cast-in-place (CIP) comparison symmetrical specimens, were designed and manufactured. The fabricated specimens were connected by a grouting sleeve, which was in the column of the pier. The height of the pier column of the test piece was 1.425 m, the diameter of the pier column was 0.25 m, and the size of the bearing platform was 0.85 m × 0.85 m × 0.5 m. Shake table tests were performed on the specimens to evaluate crack development, dynamic characteristics, acceleration response and relative displacement of the pier tops, as well as strain in the plastic hinge area. The results revealed the dominant failure mode of the test piers was bending failure, while the cracks were generally horizontal through-cracks. The failure location of the prefabricated specimens with the grouting sleeve was concentrated within one diameter of the pier in the upper sleeve region. Compared with the CIP specimens, the plastic hinge exhibited an obvious upward movement. Under a maximum test loading condition, the peak acceleration at the pier top of the fabricated pier was 11.0% smaller than that of the CIP specimen, the peak relative displacement was 34.2% smaller than that of the CIP specimen, and the peak tensile strain of the pier body was 46.8% smaller. The seismic performance of the prefabricated pier connected via the grouting sleeves was barely affected by changing the anchoring length of the reinforcements in the grouting sleeves. An ABAQUS finite element model was established for the specimens, with good agreement between the model and experimental results. When the seismic load was 0.65 g, the difference between the peak acceleration of the pier top in the X direction and the Y direction of the numerical simulation and the experimental data was less than 15%. Full article

To study the seismic performance of prefabricated single-segment steel jacket piers connected by grouting sleeves, two scaled symmetrical pier models with different anchorage lengths of the longitudinal reinforcement in the grouting sleeves and a comparative symmetrical cast-in-place (CIP) model were designed. OpenSees finite element models were established and shaking table tests were carried out on the three scaled pier models. The seismic response of each pier was compared and analyzed. Results showed the stiffness of the two prefabricated piers was greater than that of the CIP pier, and other seismic responses were less than those of the CIP piers, The dynamic responses of the two prefabricated bridge models were similar and changing the anchorage length of the reinforcement in the grouting sleeve had little effect on the seismic performance of the prefabricated pier. The simulation results were in good agreement with the experimental results. In the parameter analysis, the counterweight of the pier top had the greatest influence on the seismic performance of the prefabricated pier. The anchorage length of the longitudinal reinforcement in the grouting sleeve could be 6–14 times the diameter of the longitudinal reinforcement. Moreover, the seismic performance was found to be optimal when the thickness of the steel jacket was 5–7 mm. Full article

In a precast concrete (PC) composite beam, the horizontal interface between the PC beam and the cast-in-place (CIP) slab is located either on the compression side or on the tensile side of the cross-section. If the CIP slab is on the compression side, it becomes C-type interface, and if it is on the tensile side, it becomes T-type interface. Tensile cracks in the CIP slab may cause the horizontal shear strength of composite beams to decrease because of the reduced anchorage performance of shear reinforcements as well as the sliding on the interface. Such a tendency can be found from previous test results of specimens having T-type interface. In this study, the results of the push-off test and the beam flexure test were collected and analyzed to evaluate effects on the horizontal shear strength depending on the interface conditions, such as the interface location, surface roughness, concrete compressive strength, and clamping stress by shear connectors. The horizontal shear strength equations of ACI, PCI, AASHTO LRFD, and MC 2010 were evaluated with a database composed of 84 push-off tests and 95 beam tests from previous studies. According to the evaluation, evaluation results show that the design codes predict the horizontal shear strength conservatively for conditions other than the interface location. The horizontal shear strength deviated largely depending on the interface locations. The design codes conservatively estimate the horizontal shear strength for C-type interface, but the horizontal shear strength of T-type interface is overestimated. Based on current studies, it is recommended to use a friction coefficient of 0.7 as MC 2010 when calculating the horizontal shear strength of a composite beam with roughened T-type interface. Full article

In this study, experiments and numerical analyses were carried out to examine the flexural and shear performance of a double composite wall (DCW) manufactured using a precast concrete (PC) method. One flexural specimen and three shear specimens were fabricated, and the effect of the bolts used for the assembly of the PC panels on the shear strength of the DCW was investigated. The failure mode, flexural and shear behavior, and composite behavior of the PC panel and cast-in-place (CIP) concrete were analyzed in detail, and the behavioral characteristics of the DCW were clearly identified by comparing the results of tests with those obtained from a non-linear flexural analysis and finite element analysis. Based on the test and analysis results, this study proposed a practical equation for reasonably estimating the shear strength of a DCW section composed of PC, CIP concrete, and bolts utilizing the current code equations. Full article