Hollow Core Slabs Research Articles

КОНСТРУКТИВНАЯ СИСТЕМА БЫСТРОВОЗВОДИМОГО ЗДАНИЯ ИЗ ИНДУСТРИАЛЬНЫХ ПАНЕЛЬНО-РАМНЫХ ЭЛЕМЕНТОВ

The paper presents a new structural solution of the precast-monolithic frame for prefabricated residential and civil buildings of various storeys manufactured from prefabricated industrial reinforced concrete elements. The precast frame structures include L-shaped and inverted U-shaped precast elements, installed in the longitudinal and transverse directions and forming a frame, hollow-core slabs and bracing perforated beams of the outer contour, on which fencing non-bearing wall structures are supported within each storey. The computational model of the precast-monolithic building frame was developed using different degrees of discretization at different stages of the analysis. This allowed to obtain both a general picture of structural system deformation in the limiting and over limit states caused by special and emergency actions, and a detailed picture of the stressed state in concrete and reinforcement of structural elements before and after cracking. The paper provides the results of the comparative analysis of the effectiveness of application of the proposed structural system in the mass construction as compared with the applied constructions of large-panel buildings. It has been shown that the application of the proposed structures of panel-frame elements allows considerably reduce the material capacity, cost and transportation expenses of the reinforced concrete frame by up to 30 %, ensuring the mechanical safety of the building.

A Method of Evaluating the Destruction of a Reinforced Concrete Hollow Core Slab for Ensuring Fire Resistance

Fire tests of reinforced concrete floor slabs do not allow the detection of the onset of the boundary state due to loss of entirety because blocks are installed on the unheated surface to reproduce the design load. This prevents the formation of cracks through which toxic combustion products, smoke, and temperature spread can penetrate. Determining a building structure’s actual fire resistance limit was fixed at the onset of any fire resistance boundary state. It was proven that calculation methods for fire resistance assessment have significant advantages over experimental methods. To reduce the number of finite elements for a rational calculation of the fire resistance assessment of a reinforced concrete hollow core slab, a geometric model of 1/4 of this structure was built. The possibility of visualizing the studied structure at full scale was realized when obtaining the calculation results. The stress-strain state of the studied structure was evaluated based on the thermal and mechanical loading results applied to the reinforced concrete hollow core slab. Thus, the work’s objective was achieved based on the calculation experiments’ results. A methodology was developed for calculating the destruction of a reinforced concrete hollow core slab while assessing its fire resistance. Scientific fundamentals for determining the onset of the boundary state of loss of entirety were developed. The proposed methodology allowed for a reliable assessment of the fire resistance of such structures.

Shear Strength of Extruded, Prestressed Steel Fiber-Reinforced Concrete Hollow-Core Slabs

Shear Strength of Extruded, Prestressed Steel Fiber-Reinforced Concrete Hollow-Core Slabs

Reinforcement of cracked hollow-core slabs during the construction of the building

During the implementation of investment processes with the use of ready-made prefabricated elements, undesirable situations may occur that cause scratches, excessive deflections or damage. This is due to the fact that defects occur during transport, storage or incorrect loading of the elements. The conducted tests and technical assessments often allow the use of built-in elements, however, under the conditions of the need to make their reinforcements. This may be due to the scale of damage or defects made during molding and, as a consequence, the implementation of prefabricated elements with too low load capacity. Taking action each time should allow for the implementation of reinforcements of the elements, limiting the need to dismantle them, which would result in their irretrievable destruction. The implementation of reinforcements allows to reduce the generation of waste from new elements and allows for the proper management of already produced prefabricated elements. Used elements with reinforcements should be subject to technical inspection in the same periods as other structural elements. Proper implementation of repairs allows for the final effect to be similar to the parameters of elements free of technical defects. Due to the existing problem of damage to new elements of prefabricated channel ceilings, solutions have been developed that can be used to reinforce the elements without the need to dismantle them from the places of installation, while reducing the time spent on the process.

Evaluation of Web Shear Design Procedures for Precast Prestressed Hollow Core Slabs

Precast, prestressed hollow core slabs (HCS) are commonly used by the construction industry for floor and roof systems worldwide. Generally, the web shear strength governs the shear design of such members. This is because the web width resisting shear stresses is relatively small and the prestressing force at the bottom of the slabs restrains flexural cracking. Although most of the available design codes follow Mohr’s circle of stress for estimating the web shear cracking capacity of HCS, they produce different and scattered predictions. This paper gives more insight into the web shear design provisions of prestressed HCS in five of the available design codes. These codes include ACI 318, Eurocode 2, European standard EN 1168, CSA-A23.3, and AASHTO LRFD design specifications. A set of 229 data points was established from experimental investigations available in the literature on prestressed HCS that failed in the web shear. The dataset was used for evaluating the web shear design methods in the five codes. The results of the analysis indicated that both the simplified method of AASHTO and the ACI 318-19 method produced very conservative predictions. In contrast, the Eurocode 2 method produced unconservative predictions for most of the specimens in the dataset, whereas the ACI 318-05 method gave unconservative predictions for deeper sections. On the other hand, reasonable predictions were obtained by the EN 1168 method while the CSA-A23.3 method provided better predictions. Proposed modifications were presented for improving the predictions of the ACI 318, Eurocode 2, and EN 1168 web shear design methods for prestressed HCS.

Structural behavior of Lightweight and High strength Layered Hollow Core Slabs

A new technique of Layered Hollow Core Slab (LHCS) has been used to obtain a slab with an optimum weight-to-strength ratio. Specimens with a 90 mm top layer of High Strength Concrete (HSC) and a 90 mm bottom layer of Lightweight Aggregate Concrete (LWAC) were examined. Nine full-scale slabs with dimensions of 1600* 450* 180 mm were tested under a 4-point loading test. The %core, a/d, RFT ratio, and connection method were the different studied parameters. A push-out test was conducted on triplet specimens to study the bond strength at the interface between HSC jacket and LWAC cubes using bond agent material or shear dowels, or without treatment, to determine which method of them is suitable for connecting the two layers of the tested slabs. Load, deflection, ductility, strain, crack pattern, and mode of failure were studied. The results indicate that ultimate strength is enhanced with decreasing a/d and %core and with an increasing RFT ratio of the LHCS specimens. Using shear dowels ensures an efficient bond between the two layers of the tested slabs. ANSYS program used for modelling the slab. The numerical study accepted the experimental data with a variation of less than 10% for all slabs.

OPTIMALISASI BIAYA PELAKSANAAN PEMBANGUNAN ADMINISTRATION BUILDING MENGGUNAKAN METODE VALUE ENGINEERING

Value Engineering is a multidisciplinary-based systematic approach that is carried out creatively,innovatively and systematically to find a functional balance between cost, reliability and performance toachieve the concept of value for money. In value engineering there are six stages. The information stagecarried out 2 analyzes, namely cost breakdown and Pareto diagram analysis, resulting in the largestwork being owned by concrete work with a weight of 37% and a weight of 28% of floor slab work fromthe total concrete work. The function analysis stage produces 1 primary function and 4 secondaryfunctions. The creative stage produces 3 creative ideas, namely the Conventional Method (PA-1),Floordeck and Wiremesh Method (PA-2), and Hollow Core Slab Method (PA-3). The evaluation stageresulted in 2 creative ideas that passed. In the development stage, several calculations are carried outthat support all creative ideas. In the evaluation criteria stage, each alternative choice is assessed withthe help of the Expert Choice application, resulting in a total PA-2 value of 20% greater than PA-1. Thecalculation of the floor slab design results in the serviceability of PA-2 being 12.67% higher than that ofPA-1. PA-1's NPV is 5% greater than PA-2's. The PA-2 index value is 2.17 smaller than PA-1. The use ofPA-2 can save RAB of IDR 101,372,430.00 or 5%.

Mechanical properties and reinforcement technology of deep joints under static and fatigue loads

Fabricated hollow-core slab bridges inevitably contain joints that should be made structurally stable. With the increase in traffic and vehicle loads, the joints are prone to damage. Four new joint reinforcement schemes are proposed to improve the durability of the joint. These reinforcement schemes include pinned rebar reinforcement, prestressing tendon reinforcement, carbon fiber cloth reinforcement after cracking, and carbon fiber cloth reinforcement before cracking. Nine concrete beams with joints were subjected to bending tests under static load and cyclic dynamic load. Results show that under static load, the cracking load and ultimate load of the reinforced joints were higher than those of the control joints. Under cyclic load, the damage process after joint cracking can be divided into three stages: rapid development, slow development, and failure. The fatigue life and integrity of the reinforced joints are higher than those of the control joints. In particular, the fatigue life of the joints reinforced with carbon fiber cloth before cracking is increased by 157.6 times.

Model validation of hollow core slab with overlay using Response-2000

Hollow Core Slab (HCS) is a precast slab with prestressing system and voids along the span of the slab which serves to reduce its self-weight. For HCS to be able to increase its flexural and shear capacity, an overlay is used on the interface along the length of HCS. Overlay serves to create a continuous surface level and increase the load capacity of the slab. The advantage of using an overlay system, namely strength and serviceability, is available after the element is fully composite against the parent concrete. An analytical study will be carried out using Response-2000 version 1.0.5 program related to flexural behavior using two research configurations. The first configuration is HCS with overlay, with an overlay thickness of 50 mm. The second configuration is HCS without using an overlay. Therefore, the second specimen is referred to as a control specimen. The evaluation of the analysis results was reviewed based on the load-displacement curve, cracking load, displacement at cracking load, peak load, displacement at peak load, and cracking mode. The final result of this study is a form of validation to ensure the flexural behavior of the specimen in analytical modeling is consistent with the specimen in experimental studies.

Vibration Serviceability of Large-Span Steel–Concrete Composite Beam with Precast Hollow Core Slabs Under Walking Impact

A large-span steel–concrete composite beam with precast hollow core slabs (CBHCSs) is a relatively new floor structure that can be applied to various long-span structures. However, human-induced vibrations may present serviceability issues in such structures. To alleviate vibrations, both the walking forces excited by humans and the associated floor responses must be elucidated. In this study, 150 load–time histories of walking, excited by 25 test participants, are obtained using a force measuring plate. The dynamic loading factors and phase angles in the Fourier series functions for one-step walking are determined. Subsequently, walking tests are performed on seven CBHCS specimens to capture the essential dynamic properties of mode shapes, natural frequencies, damping ratios, and acceleration time histories. The CBHCS floor system generally exhibits a high frequency (> 10 Hz) and low damping (damping ratio < 2%). Sensitivity studies using the finite element method are conducted to investigate the vibration performance of the CBHCS floor system, where the floor thickness, steel beam type, contact time, and human weight are considered. Finally, analytical expressions derived for the fundamental frequency and peak acceleration agree well with the experimental results and are hence proposed for practical use.

Low-Cost Assessment Method for Existing Adjacent Beam Bridges

Damage in grouted joints is an unavoidable early disease in adjacent box beam bridges and hollow-core slab bridges. Joint damage will lead to degradation of the transverse load transmission capacity of the bridge, causing beams of the bridge superstructure to bear loads higher than the designed value, and eventually fail prematurely. Precise assessment of bearing--capacity degradation degree of adjacent box beam bridges and hollow-core slab bridges that are of great number is the keypoint to maintaining the serviceability of traffic network. The current specifications regard grouted joints as individual components and cannot correctly assess the degradation degree of bearing capacity caused by joint damage. In this paper, the traditional hinge connected beam method is improved by modifying deformation compatibility conditions at grouted joints. By using a modified hinge connected beam method, the relationship of joints at different locations with the lateral load distribution factor (LLDF) is analyzed. Based on analysis results, this paper proposes a new low-cost assessment method and a new assessment index that can utilize visual inspection results. Based on the concept of standard deviation, the proposed method assesses the degradation degree of the lateral load transmission performance of bridge superstructures by calculating the variation in LLDFs of beams, which is expressed by the lateral load distribution performance rating number LDN. The proposed method is applied to three real bridges. The accuracy of the calculation results is verified by comparing the ranking of LDNs of three bridges with the ranking of the variation degrees of lateral deflection influence lines of three bridges obtained from static-load test results.

Post-Cracking Web-Shear Response of Hollow Core Slabs with Low Steel Fiber-Volume Fractions

Post-Cracking Web-Shear Response of Hollow Core Slabs with Low Steel Fiber-Volume Fractions

COMPARISON OF COST AND TIME OF FLOOR SLAB WORKS ON CONVENTIONAL AND BUBBLE DECK SLAB METHODS

Floor slab is one of the most important structure members in a building and one of the largest members consuming concrete. Conventional floor slab has been used for years and has disadvantages that can be improved with alternate methods. There is lot of alternative methods that have been used in the construction world such as precast slab, half precast, hollow core slab, and many more. One of the alternative methods is bubble deck slab. The spherical hollow reinforced concrete slab has been patented named Bubble Deck Slab is a method that removes concrete from the center part of a slab which doesn't do any structure functional, so it can reduce the dead load significantly. High-density polyethylene hollow sphere is used to replace the ineffective part of the slab, so it reduces the dead load and increases efficiency. With the HDPE ball substitution, there will be differences in cost and time compared to the conventional method. This research is taking the case research in Central Control Building of Power Plant Muara Tawar Project with quantitative method approach. The analysis is calculating the budget plan and scheduling with Microsoft Project. After the analysis, there is differences in cost and time between the methods. The bubble deck slab method has the advantages which have the cheaper cost of IDR. 142,128,506.44 or 14,442% and 1 day or 3,846% faster compared to the conventional. Even so, the conventional method is still the first choice because the very common methods in Indonesia and the ease of execution.

Behavior of Reinforcing Bar Connection of Hollow-Core Slabs to Steel Beams under In-Plane Forces

Hollow-core slab (HCS) floors supported on steel beams require the use of steel reinforcement as connections to avoid slab displacement caused by lateral loads. However, current North American design codes offer limited provisions on the design and behavior of such connections. In this study, the results of an experimental investigation conducted on such connections to assess their capacity and mode of failure are presented. Eleven full-scale assemblies of HCS reinforcing bar connections to steel beams were tested to failure under monotonic in-plane loading (compression, tension, or shear). Test results revealed that connections tested under compression failed by bar buckling without yielding. Under tension, the connection bar reached close-to-yielding or yielding strains at the unrestrained portion of the bar, followed by grout splitting in the shear key or the grouted core. Finally, the mechanism of failure of specimens subjected to shear was governed by bar yielding.

Damage mechanism of conventional joints and proposal of a novel joint for hollow-core slab bridges

Damage mechanism of conventional joints and proposal of a novel joint for hollow-core slab bridges

High-Birefringence Low-Loss Hollow-Core THz Waveguide Embedded Parallel Slab Cladding

A novel high-birefringence and low-loss hollow-core (HC) antiresonant (AR) THz waveguide is proposed and experimental demonstrated. The waveguide is a circular tube embedded with two pairs of symmetrical parallel slabs. With the support of a circular tube, one pair of slabs near the waveguide center is used to form a rectangular-like core to achieve high birefringence, and another pair of slabs is placed in the cladding to further reduce the waveguide loss. Simulation results indicate that the birefringence reaches the magnitude order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> within the transmission window from 0.38 to 0.50 THz. The highest birefringence reaches 3.42 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> at 0.38 THz with a loss of 0.09 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> . We manufacture the HC-AR THz waveguide with photosensitive resin by using three-dimensional printing technology. And the waveguide properties are investigated by THz time-domain spectroscopy system. Experimental results demonstrate that the birefringence variation of the HC-AR THz waveguide is within the range of 1.57 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> to 4.77 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> in the 0.39 to 0.51 THz transmission window. The highest birefringence is up to 4.77 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> at 0.39 THz and the corresponding loss is 0.12 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> . To the best of authors’ knowledge, the proposed HC-AR THz waveguide achieves the highest birefringence and relatively low loss in current HC-AR THz waveguides.

Structural reliability of hollow core slabs considering compressive membrane action

Compressive membrane action can considerably improve the load bearing capacity of concrete slabs and beams in case of excessive loaded due to an accidental event. Currently, only limited research has been focusing on compressive membrane action in prestressed concrete elements, or on concrete elements with large cavities, such as precast concrete hollow core slabs. Therefore, a novel real-scale test setup has been developed in order to assess this effect in precast hollow core slabs, and how it can enhance the load-carrying capacity in accidental events. In parallel with these tests, a numerical finite element model has been developed in order to perform a more detailed structural analysis of this phenomenon, and to study the influence of various input parameters. The details of this test setup are briefly explained, and some relevant experimental test results are provided. Considering the experimental findings and validated numerical model, this contribution aims to quantify the influence of compressive membrane action on the structural reliability of precast concrete hollow core slabs. To this end, probabilistic models for the most important material and geometric variables are gathered, and the structural reliability is assessed using Latin Hypercube sampling. Overall, the results indicate that considering the formation of compressive membrane action strongly influences the variability of the ultimate load-carrying capacity of precast concrete hollow core slabs.

Flexural behavior of precast concrete hollow-core slabs with high-strength tendons

Precast concrete hollow core (PHC) slabs have been widely used in brick and concrete structures of rural buildings due to their economic and rapid construction in China. A new PHC slab with high-strength tendons and spliced slab made of the short slabs were proposed in this paper. To investigate the flexural behavior of the slabs, full-scale tests were conducted on three PHC slabs, including one long slab and two spliced slabs with side beams. In detail, the spliced slab was assembled by two short slabs through U-type bars, anchorage bars, and post-pouring concrete. The mechanical properties of specimens were evaluated including the failure modes, strain of concrete and bars, flexural capacity and deflection. The tests results shows that the flexural performance of the spliced slab is close to that of the long slab. Subsequently, finite element models were established and validated by the test data. Based on the validated models, an additional specimen made up of long slab and side beams, was studied to further verify the reliability of the spliced slab. And parametric analysis were carried out on the spliced slab to investigate the influence of prestress of tendons, diameter of tendons, concrete strength, etc. Moreover, the cracking and failure moment of the slabs were calculated by the formulas of GB50010 and ACI318, respectively. The calculated results were compared with the test and simulation results. The results proves that the prediction values calculated by the codes on the flexural capacity of the spliced slab is not conservative. Therefore, considering a reduction factor to correct the results calculated by the codes is necessary.

Toward Consistent Prediction of Web-Shear Capacity for Hollow-Core Slabs Using Strut-and-Tie Models

Toward Consistent Prediction of Web-Shear Capacity for Hollow-Core Slabs Using Strut-and-Tie Models

Analysis of The Most Affecting Factors in The Selection of Conventional and Precast Concrete Floor Slabs on Time Performance

One of the efforts to achieve the goals of construction project in terms of cost, quality and time is to replace conventional methods with more modern ones, namely by applying precast concrete. Precast concrete products, especially for buildings, are quite varied, one of them is Hollow Core Slab (HCS). Supported by previous research which explains that precast concrete floor slabs can save processing time compared to conventional floor slabs. Therefore, it is necessary to identify factors and variables that affecting the selection of conventional and precast&#x0D; floor plates on time performance and how the influence of the X variable (Factors) on the Y variable (Time performance).The results showed that the most affecting factors in the selection of conventional floor slabs on time performance were manpower factor with variable number of workers (41.3%), location factor with variable distance of batching plant to project site (19.8%), and also technical factors with shop drawing revision variable (by 41.8%). As for, the most affecting factors in the selection of precast concrete floor slabs on time performance include manpower factors with worker’s expertise variable (29.7%), and technical factors with shop drawing revision variable (by 38.4%).