Search Results (7)

The adoption of prefabricated elements and systems (PBES) in accelerating bridge construction (ABC) and rapidly replacing aging infrastructure has attracted considerable attention from bridge authorities. These prefabricated components facilitate quick assembly, which diminishes the environmental footprint at the construction site, alleviates delays and lane closures, reduces disruption for the traveling public, and ultimately conserves both time and taxpayer resources. The current paper explores the structural behavior of a reinforced concrete (RC) precast full-depth deck panel (FDDP) having 175 mm projected glass-fiber-reinforced polymer (GFRP) bars embedded into a 200 mm wide closure strip filled with ultra-high-performance fiber-reinforced concrete (UHPFRC). Three joint details for moment-resisting connections (MRCs), named the angle joint, C-joint, and zigzag joint, were constructed and loaded to collapse. The controlled slabs and mid-span-connected precast FDDPs were statically loaded to collapse under concentric or eccentric wheel loading. The moment capacity of the controlled slab reinforced with GFRP bars compared with the concrete slab reinforced with steel reinforcing bars was less than 15% for the same reinforcement ratio. The precast FDDPs showed very similar results to those of the controlled slab reinforced with GFRP bars. The RC slab reinforced by steel reinforcing bars failed in the flexural mode, while the slab reinforced by GFRP bars failed in flexural-shear one. Full article

The present study proposed novel prefabricated composite RC shear walls with a concrete-filled steel tube frame (CCRCSW-CFST) because of the superior seismic performance of shear walls incorporating CFSTs as boundary-restrained members. One cast-in-place reinforced concrete shear wall (RCSW) and seven CRCSW-CFSTs, each varying in axial compression ratios, concrete strengths, and shear span ratios, were designed for experimental analysis. Cyclic loading tests were performed on these specimens, yielding the following results: (1) Compared to reinforced concrete shear walls, CCRCSW-CFSTs demonstrated superior seismic performance, with 14.2% increased ductility and 47.5% greater energy dissipation capacity. (2) Elevating the axial compression ratio in CCRCSW-CFSTs resulted in increased yield strength, peak strength, and stiffness. Conversely, this adjustment also expedited the degradation of stiffness with displacement and decreased both ductility and ultimate deformation. (3) The peak displacement and ultimate displacement of CCRCSW-CFSTs were both increased with an increase in concrete strength. Increasing the axial compression ratio enhanced the initial stiffness of CCRCSW-CFSTs and mitigated the rate at which stiffness deteriorated with increasing displacement. (4) The stiffness, peak and ultimate displacements, peak and ultimate loads, and shear span ratio of CCRCSW-CFSTs were significantly reduced as the shear span ratio was increased. (5) The minor slip between the reinforced concrete panel of the precast slab and the encasing C-shaped steel contributed to an increase in early-stage energy dissipation of the CCRCSW-CFSTs. Full article

Prefabricated composite shear walls (PCSW) consisting of steel plate clapped by single-sided or double-sided prefabricated reinforced concrete (RC) panels have enormous advantages for application as lateral-resisting structures in prefabricated high-rising residential buildings. In this paper, three 1/3-scaled PCSW were manufactured and tested to investigate the seismic performance of PCSW with single-sided or double-sided prefabricated RC panels. The experimental results, including hysteretic and skeleton curves, stiffness and strength degradation, ductility, energy dissipation capability and steel frame effects, were interpreted, compared and summarized. In spite of the RC panels being the same thickness, PCSW with double-sided RC panels had the most outstanding lateral-resisting properties: the highest yield strength and bearing capacity, adequate ductility, plumper and stable hysteresis loop and excellent energy absorption capacity. Finally, a simple predicting equation with a modification coefficient to calculate the effects of boundary steel frame was summarized and proposed to calculate the lateral yield load of the PCSW. All efforts were made to give reliable technical references for the design and construction of the PCSW. Full article

Construction with precast or prefabricated elements requires the connecting of structural joints. This study presents an accelerated construction method to strengthen reinforced concrete (RC) slab-type elements in flexure using precast lap-spliced textile-reinforced concrete (TRC) panels. The objectives of this study are to identify the tensile behavior of a TRC system with lap-spliced textile, and to experimentally validate the performance of the proposed connecting method by flexural failure test for the concrete slabs strengthened by TRC panels with lap-spliced textile. Twenty-one coupon specimens were tested in tension with two different matrix systems and three different lap splice lengths. The influence of the lap splice length and matrix properties on the tensile performance of the TRC system was significant. Five full-scale RC slabs were strengthened by the precast TRC panels with and without the lap splice, and was tested in flexure. The results of the failure test for the strengthened specimens showed that the ultimate load of the strengthened specimen with the TRC panel increased by a maximum of 24%, compared to that of the unstrengthened specimen. Moreover, the failure-tested specimens were re-strengthened by a new TRC panel system and tested again in flexure. The objective of the re-strengthening of the damaged RC slabs by the TRC panel is to investigate whether the yielded steel reinforcement can be replaced by the TRC panel. The initial cracking load and the stiffness of the re-strengthened specimens were significantly increased by re-strengthening. Full article

Textile reinforced concrete (TRC) has widely been used for strengthening work for deteriorated reinforced concrete (RC) structures. The structural strengthening often requires accelerated construction with the aid of precast or prefabricated elements. This study presents an innovative method to strengthen an RC slab-type element in flexure using a precast panel made of carbon TRC. A total of five RC slabs were fabricated to examine the flexural strengthening effect. Two of them were strengthened with the precast panel and grouting material and another set of two slabs was additionally strengthened by tensile steel reinforcement. The full-scale slab specimens were tested by a three-point bending test and the test results were compared with the theoretical solutions. The results revealed that the ultimate load of the specimens strengthened with the TRC panel increased by at least 1.5 times compared to that of the unstrengthened specimen. The application of the precast TRC panel and grouting material for the strengthening of a prototype RC structure verified its outstanding constructability. Full article

Pilotis buildings have widely spread out in developed countries since World War II onwards. From the structural point of view, Pilotis RC frames exhibit substantial lack in ductility capacity and shear resistance localized at the first floor, since they have been mainly realized before the seismic codes’ era. The present study shows the performance comparison of four advanced retrofit techniques when applied to typical Pilotis RC frame designed for gravity loads only according to Italian building code of ‘60s. A preliminary investigation has been performed to select non-linear numerical models suitable to describe the considered RC frame behavior, involving flexural inelastic hinges of RC beams and columns and in-plane axial inelastic hinges of masonry infill panels. Two seismic retrofit projects have been designed at a local level, by strengthening the masonry infilled panels with Fiber Reinforced Cementitious Matrix (FRCM) technique and alternatively by replacing infilled panels with prefabricated panels disconnected from the structure, so that no infill/frame interaction occurs. Two more retrofit projects have been designed at a global level, in order to improve the overall structural performance making use of energy dissipation and, alternatively, base isolation techniques. Nonlinear time history analysis and structural assessment have been carried out for the as-built case as well as for the four retrofit solutions according to Eurocode 8 and Italian Building Code, in order to highlight the structural deficiencies and relative improvements, respectively. Performances offered by the proposed retrofit techniques have been finally compared in terms of structural behavior, expected damage, and economic impact. Full article

In seismic European countries most of the residential building stock is highly energy-intensive and earthquake-prone because it was built before the enforcement of the most recent energy and seismic codes. Furthermore, this stock often shows a low architectural quality due to poor maintenance and/or construction and design deficiencies: for all these reasons, it needs deep renovation, but the use of common energy and seismic upgrading techniques is often unsustainable in terms of costs, work duration, and occupants’ disturbance. Therefore, new integrated, affordable, fast, and low-disruptive renovation actions are strongly needed. This study proposes an innovative energy, seismic, and architectural renovation solution for reinforced concrete (RC) framed buildings, based on the addition of cross-laminated timber (CLT) panels to the outer walls, in combination with wooden-framed panels. The two panels integrate insulation and cladding materials in order to improve the energy performance and the architectural image of the renovated building. Moreover, the CLT panels are connected to the existing RC frame through innovative seismic energy dissipation devices. In case of an earthquake, these devices in combination with the CLT panels reduce the drift demand of the building, preventing or reducing structural damages and consequent repair costs. In particular, this paper investigates the technical feasibility, the energy efficiency, and the architectural enhancement of the proposed retrofitting system. To this purpose, dynamic thermal simulations were conducted on a typical multi-story residential building from the 1960s, located in Catania, Italy. The results indicated that this retrofitting technique considerably improved the energy performance of the selected building, with a reduction of the global energy demand up to nearly 60%. The presented study is part of a larger research project aimed at also investigating, in a further stage, the seismic performance achievable by the above-mentioned renovation solution. Full article