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Several studies have revealed that slabs with cast-in-place over precast, prestressed panels (CIP-PCP) behave differently from traditional concrete slabs because of the panel joints between the PCP components. While high-strength reinforcing bars can improve load capacity or reduce bar quantity in traditional slabs, limited research has focused on their application in CIP-PCP slabs. This study addressed this gap by conducting four-point bending tests on CIP-PCP slabs with normal- and high-strength reinforcing bars. Two configurations of high-strength steel were used: one with the same bar layout as normal-strength reinforcing bars, and another with increased bar spacing to reduce the bar quantity. Additionally, slab specimens were designed to replicate real-world bridge deck conditions, including longitudinal and transverse joints, for detailed analysis. The results indicated that reducing reinforcing bar quantity by adjusting bar spacing based on the specified yield strength ratio between normal- and high-strength steels maintained a comparable load capacity, with crack widths' magnitude similar to those in normal-strength steel layout in the service state. Keywords: cast-in-place over precast, prestressed panel (CIP-PCP) slabs; crack control; crack width; high-strength reinforcing bar; serviceability.

Cast-in-place is the anchor’s installation method where the anchors are installed together with the casting of the concrete, while post-installed is the method of installing the anchors after the concrete has hardened, namely by drilling holes in the concrete with a concrete drill and then injecting the holes with chemical epoxy paste then immersing the anchors to the holes. In general, concrete drilled holes will produce a plain concrete surface, while drill bit extractor concrete (DBEC) will produce screw-textured concrete holes which are expected to increase the pullout capacity of the post-installed anchor. The pullout capacity test of cast-in-place, post-installed, and post-installed (DBEC) anchor studs 12x160 mm anchors planted with various depths (h ef ) of 70 mm, 80 mm, 90 mm, and 100 mm injected with chemical epoxy paste in the borehole concrete and drill bit extractor concrete (DBEC). The pullout capacity of the post-installed with drilled holes concrete (concrete drill model) and pullout capacity drill bit extractor concrete (DBEC) will be compared with the pullout capacities of cast-in-place and post-installed concrete with drilled holes. The result of the study showed that the pullout capacity of cast-in-place increased by 64.05% compared to theory, the pullout capacity of the post-installed concrete drill model increased by 68.23% compared to theory, and the pullout capacity of post-installed DBEC increased by 71.51% compared to theory while the pullout capacity of post-installed concrete drill model increased by 11.64% compared to the pullout capacity of cast-in-place and pullout capacity of post-installed DBEC increased by 20.75% compared to pullout capacity of cast-in-place while the pullout capacity of post-installed DBEC increased by 10.3% compared to the pullout capacity of the post-installed concrete drill model. The results of the t-test pullout capacity increased significantly for all variations of anchor h ef depth and anchor installation methods.

The post-pressure grouting technique has proven to be an effective method to enhance axial resistance. In this paper, field tests were conducted to investigate the performances of large-diameter cast-in-place bored piles for six combined side-and-tip grouting piles and two side-grouting piles in extra-thick fine sand layers. The load–displacement response, shaft resistance, and mobilization of unit base resistance were discussed. The field results indicate that compared with the piles before post-grouting both the shaft resistance and base resistance for the piles after post-grouting are significantly improved. The piles after post-grouting have higher load-bearing capacity. Meanwhile, the load-bearing capacity of combined-grouting piles is also greater than that of side-grouting piles. Additionally, the strengthening effect of the surrounding soil improvement due to side grouting on the base resistance can enhance the unit base resistance, and the unit shaft resistance can also be increased by the soil improvement at the pile tip due to tip grouting. Moreover, the distribution of the injected pressurized grout at the pile tip and side is detected by an electromagnetic wave computerized tomography (EWCT) technique. The results reveal that EWCT can detect the distribution pattern of the pile, injected grout and geotechnical interface and evaluate the diffusion range of the grout of the soil at the pile tip and side, which can be used to assess the grouting effect of grouted piles. Finally, an in situ standard penetration test is employed to evaluate the grouting effect of grouted pile by variation of the SPT N value before and after post-grouting. The research results have reference value and guiding significance for the design and effect detection of post-grouting piles.

In order to study the direct shear properties of ultra-high performance concrete (UHPC) structures, 15 Z-shaped monolithic placement specimens (MPSs) and 12 Z-shaped waterjet treated specimens (WJTSs) were tested to study the shear behavior and failure modes. The effects of steel fiber shape, steel fiber volume fraction and interface treatment on the direct shear properties of UHPC were investigated. The test results demonstrate that the MPSs were reinforced with steel fibers and underwent ductile failure. The ultimate load of the MPS is about 166.9% of the initial cracking load. However, the WJTSs failed in a typical brittle mode. Increasing the fiber volume fraction significantly improves the shear strength, which can reach 24.72 MPa. The steel fiber type has little effect on the shear strength and ductility, while increasing the length of steel fibers improves its ductility and slightly reduces the shear strength. The direct shear strength of the WJTSs made from 16 mm hooked-type steel fibers can reach 9.15 MPa, which is 2.47 times the direct shear strength of the specimens without fibers. Finally, an interaction formula for the shear and compressive strength was proposed on the basis of the experimental results, to predict the shear load-carrying capacity of the cast-in-place UHPC structures.

There is a drastic change in design and construction trends of underground structures, where a precast concrete (PC) shear wall system is quickly replacing a cast-in-place (CIP) diaphragm wall (that is, the so-called slurry wall) system in urban areas for better constructability and reliable performances. However, it is challenging to achieve the proper coupling action or composite performance through vertical connections between adjacent PC walls and that in horizontal connection between PC walls and foundations to satisfy the seismic design criteria specified in codes. To this end, this study introduces cast-in-place (CIP) cap beam and waling beam at the top and midheight of PC walls to connect individual precast wall panels by means of a coupling action. Precast specimens were carefully designed to be code-compliant as intermediate precast shear wall systems, and were then fabricated and tested under the reversed cyclic loads to evaluate seismic performances. Detailed numerical models were also developed to identify how CIP beams can effectively improve the seismic performance of a precast shear wall system by restraining the free rotation and axial deformation of individual precast wall panels.

The hydration heat generated during the concreting of cast-in-place piles causes thermal disturbance to the surrounding permafrost, leading to its thawing. This further affects the stability of the pile foundation and degrades the construction progress. To explore the influence mechanisms of the concrete hydration heat on the permafrost temperature field around the pile, as well as that of different construction seasons on the pile-side boundary conditions and permafrost temperature field, monitoring results of on-site tests and numerical simulation were used to analyze the distribution law of the pile soil temperature field in space and time, and the pile-side boundary conditions and permafrost temperature field during construction seasons. The results show that the temperature trend of the pile foundation can be divided into three stages: a rapid rise phase (0∼2 d), a rapid decline phase (2∼10 d), and a slow decline and stabilization phase (10∼90 d). As the radial distance from the pile center decreases, there occur a corresponding acceleration in temperature increase and an elevated maximum temperature rise (MTR). The influence range of the molding temperature and the hydration heat is about 1∼2 times the pile diameter and less than 1.5 m in the depth direction. Compared to the atmospheric temperature, there is a lag in the change in the permafrost temperature caused by accumulation of ground temperature, and the significant difference between the two leads to an increased rate of heat exchange at the boundary condition. Conducting drilling operation and cast-in-place pile construction in the cold seasons is conducive to reducing the thermal disturbance to the permafrost around the pile in permafrost areas.

As the most widely used construction material worldwide, concrete is the main cause of greenhouse gas emissions, material depletion, and waste generation by the construction industry. Typically, concrete waste is crushed and, at best, reclaimed into recycled aggregate or used as gravel. This process is energy-intensive and results in a reduction in material properties. In contrast, the direct reuse of concrete elements from obsolete structures offers great potential for significantly reducing the environmental impact of new constructions. To be reused, concrete elements are carefully sawn out of soon-to-be-demolished buildings. Elements are then used without other major transformations for another service cycle in a new assembly. This paper analyses two recent projects in Switzerland that showcase innovative applications of concrete reuse: a post-tensioned segmented arch footbridge and a parking pavement. Both projects reuse blocks extracted from cast-in-place concrete buildings undergoing transformation or demolition. In this paper, environmental and economic analyses provide a comprehensive understanding of the alleviations and costs involved. Results are compared to those of alternatives with conventional construction methods. The two projects reusing concrete globally showcase a drastically lower environmental impacts for comparable or higher construction costs, hence calling for future developments of such new circular construction strategies.

The field static load test method was adopted for two test piles in a project in Zhejiang area of China, analyze the effect of post-grouting technique on super-long cast-in-place bored pile and its internal mechanism. Q-s curves and pile axial force curves were drawn based on test data to show that post-grouting technique played a prominent role in improving bearing capacity of single pile and pile skin friction. In addition, pile skin friction at upper soil layer around super-long pile was fully used, but that at lower soil layer was not. For the design of super-long pile, the compression of pile body should be considered to make the best use of pile skin friction caused by relative displacement between pile and soil.

To clarify the bearing characteristics and load transfer mechanisms of long large-diameter pile foundations in dense silty fine sand strata within the middle and lower reaches of the Yellow River, a graded tension–compression anchor reaction loading test method was devised and implemented using a field-configured apparatus. This approach enables graded static load testing on large-tonnage long bored cast-in-place piles. Then, the relative displacement and settlement between pile and soil under vertical cyclic loading were analyzed. Finally, numerical simulations were adopted to study the settlement behavior of pile tops and ends under cyclic loads representative of beam yard operational conditions (20 cycles). Results indicate that, under vertical loading, the shaft friction resistance and tip resistance of large-diameter long bored cast-in-place piles are not mobilized simultaneously, but sequentially. The degree of shaft friction is related to the magnitude of pile top loading, soil properties, burial depth, and construction methods. The soil between piles generates vertical resistance to horizontal force-transfer rods, becoming part of the pile foundation’s bearing capacity and sharing the load. Moreover, in dense silty fine sand strata, long large-diameter pile foundations exhibit pure friction pile behavior. When calculating the bearing capacity of such piles, parameters from geotechnical reports based on code-specified values should be multiplied with corresponding correction coefficients. In addition, the shaft friction resistance in dense silty fine sand layers remains under-mobilized. Limited loading–unloading cycles in permanent–temporary integrated beam yard operations do not induce significant deformation in pile foundations, indicating minimal impact on their bearing performance.

The phenomena of induced seismicity have recently become of increasing interest for public/private authorities and stakeholders due to the impact that some of these low-intensity earthquakes might have on the built environment of regions that were not historically prone to hazard from natural seismicity. This has led to the deployment of experimental campaigns aimed at investigating and assessing the seismic response of existing structures in such now-seismically active regions, which were typically built without any particular seismic design and/or detailing criteria. A pseudostatic cyclic test on a full-scale one-storey two-bay cast-in-place reinforced concrete (RC) wall-slab-wall structure, representative of a building typology that is a very common form of housing in the Netherlands, was thus carried out. The test specimen was designed according to Dutch building practice and tried to combine several common characteristics as well as customary detailing of multi-unit cast-in-place RC terraced houses, which, together with precast ones, constitute the vast majority of the Groningen RC building stock. The present paper describes the main features of the building mock-up and discusses the foremost results obtained by the testing, which was performed in a bi-directional fashion and was therefore meant to address several open questions regarding the seismic behaviour/performance of this specific structural typology in both longitudinal/weak and transverse/strong directions. Hysteretic response curves of the specimen and key parts of it are provided, along with a discussion of the building damage evolution during the phases of testing, showing how rocking of walls around their base was the dominating response mechanism for both directions of loading. Issues of strength degradation and energy dissipation were also addressed, illustrating the main trends observed with the changing of imposed drift level as well as with the number of applied cycles for a given drift amplitude. Finally, a simple yet reliable fibre-based finite element model was developed, with a view to allow the readily assessment of the seismic response of structures of this type; feasibility and limitations of such numerical model were evaluated through comparison with the obtained test data.