Slab Reinforcement Research Articles

Interpretable Machine Learning Models for Punching Shear Strength Estimation of FRP Reinforced Concrete Slabs

Fiber reinforced polymer (FRP) serves as a prospective alternative to reinforcement in concrete slabs. However, similarly to traditional reinforced concrete slabs, FRP reinforced concrete slabs are susceptible to punching shear failure. Accounts of the insufficient consideration of impact factors, existing empirical models and design provisions for punching strength of FRP reinforced concrete slabs have some problems such as high bias and variance. This study established machine learning-based models to accurately predict the punching shear strength of FRP reinforced concrete slabs. A database of 121 groups of experimental results of FRP reinforced concrete slabs are collected from a literature review. Several machine learning algorithms, such as artificial neural network, support vector machine, decision tree, and adaptive boosting, are selected to build models and compare the performance between them. To demonstrate the predicted accuracy of machine learning, this paper also introduces 6 empirical models and design codes for comparative analysis. The comparative results demonstrate that adaptive boosting has the highest predicted precision, in which the root mean squared error, mean absolute error and coefficient of determination of which are 29.83, 23.00 and 0.99, respectively. GB 50010-2010 (2015) has the best predicted performance among these empirical models and design codes, and ACI 318-19 has the similar result. In addition, among these empirical models, the model proposed by El-Ghandour et al. (1999) has the highest predicted accuracy. According to the results obtained above, SHapley Additive exPlanation (SHAP) is adopted to illustrate the predicted process of AdaBoost. SHAP not only provides global and individual interpretations, but also carries out feature dependency analysis for each input variable. The interpretation results of the model reflect the importance and contribution of the factors that influence the punching shear strength in the machine learning model.

Effect of reinforcement on the response of continuous steel-concrete composite beams

This paper presents a comprehensive assessment on inelastic behavior of continuous steel-concrete composite (SCC) beams, focusing on the effect of reinforcement in slab. A finite element model is formulated and verified against laboratory tests. Numerical assessment is conducted on two-span SCC beams with various reinforcement types and areas. The results indicate that using carbon fiber reinforced polymer (CFRP) reinforcement is more effective in reducing the crack width in concrete slab over the center support than using glass fiber reinforced polymer (GFRP) or steel reinforcement. The reinforcement hardly influences the ultimate response at midspan but markedly affects that at the center support. The ultimate load of SCC beams with steel reinforcement is close to that with CFRP reinforcement while higher than that with GFRP reinforcement. At ultimate, CFRP reinforcement leads to greater support moment but substantially lower moment redistribution while GFRP reinforcement results in lower moment but comparable moment redistribution, when compared to steel reinforcement.

Seismic behavior of single plate shear connection between steel-concrete composite beam and RC column

This paper aims to investigate the seismic behavior of single plate shear (SPS) connection between steel–concrete composite (SCC) beam and reinforced-concrete (RC) column. A total of four SCC beam to RC column composite joints were fabricated: one specimen was tested under monotonic loading, and three specimens were tested under cyclic loading. The failure modes, hysteretic and skeleton curves, strain distribution of anchor bars, RC slab and longitudinal reinforcement, ductility, energy dissipation and stiffness degradation were discussed, and the influence of longitudinal reinforcement ratio ρsl and the type of embedded parts on the seismic performance of joint were studied. The results indicated that the joint exhibited good seismic behavior. With the increase of ρsl, the initial stiffness, hogging moment and rotation capacities increased, while the ductility and energy dissipation capacity decreased slightly. The type of embedded parts had influence on the failure modes and initial stiffness, but had little effect on the moment and rotation capacities, ductility and energy dissipation capacity of joint. Finally, based on the Zhang’s model, considering the composite action of the floor slab and the contribution of additional bending moment, a calculation method was proposed to predict the ultimate sagging moment capacity of the joint, and the strength of the embedded parts of all specimens in this study and open literature were checked. The results showed that the Zhang’s model and the proposed model have a good prediction accuracy, and it is suggested that when designing the embedded parts of the joint under sagging moment, the cross-sectional area of anchor bars should be checked to avoid early failure.

EXPERIMENTAL STUDIES OF DEFORMABILITY AND FRACTURE RESISTANCE OF AIRFIELD SLABS ON MODELS

The results of experimental studies of deformability and crack resistance of models of aerodrome slabs made of reinforced concrete and steel-fiber concrete, made on the basis of serial slab PAG-18 taking into account the scale factor, are presented. Two series of slabs were tested - two models of reinforced concrete and two models with one-percent dispersed reinforcement. The load was applied in steps, the instrument readings were recorded twice at each step and the crack opening width was measured starting from the moment of the first crack formation. Dial gauges, deflectometer and microscope MPB-3 were used as measuring instruments. In accordance with the normative documents acting in Ukraine, one of two possible loading schemes was considered - with the loading by the concentrated force applied in the span part of a plate which had a hinged support along its short sides. Plate models were tested on a specially made stand. Each load step ended with a five-minute dwell time, at the beginning and the end of which readings were taken on the measuring instruments. The deformations at the same levels were measured with dial gauges. The process of crack formation was observed with a Brinell tube in the places of the greatest crack opening. Breaking load for fiber concrete slab was 1.52 times higher than for reinforced concrete slab, and the moment of cracking initiation was 1.22 times higher. The process of cracking in the fiber concrete slab begins at higher loads than in the reinforced concrete slab. The initial crack opening width of the slabs is almost the same, and the final crack opening width of all the cracks in the fiber concrete slab is significantly lower than in the reinforced concrete slab. The deformations in steel-fiber concrete slabs when the load is applied in the span, both for compressed and stretched fibers, are higher than in reinforced concrete slabs. The experimental studies indicate that dispersed reinforcement of airfield slabs with steel fiber leads to their higher crack resistance.

DEFORMABILITY AND CRACK RESISTANCE OF AIRFIELD SLABS

Abstract. The results of experimental studies of deformability and crack resistance of models of airfield slabs made of reinforced concrete and steel fiber concrete are presented. Two series of plates were tested ‒ three models of reinforced concrete and three models with steel fiber added to the concrete mixture in amount of 1% of the total volume of the product. The load was applied in small steps, the instrument readings were recorded twice at each step, and the crack opening width was measured starting from the moment of the first crack formation. Dial gauges and deflectometers were used as measuring instruments. According to the normative documents acting in Ukraine, one of two possible loading schemes was considered ‒ with the loading by the concentrated force applied on the cantilever part of a plate. The plate models were tested on a specially made stand which consisted of four supporting struts connected in pairs by beams. The airfield slab was supported by the beams. The load was applied along the width of the plate in steps ‒ 0.05 of the destructive load, along two concentrated vertical strips. Each degree of load ended with a five-minute dwell time, at the beginning and end of which readings were taken on the measuring instruments. The deformations at the same levels were measured with dial gauges. The process of crack formation was observed with a Brinell tube in the places of the greatest crack opening. It follows from the obtained results that the process of cracking in the fiber concrete slab begins at higher loads than in the reinforced concrete slab. The final and initial crack opening widths of all cracks in the fiber concrete slab are significantly lower than in the reinforced concrete slab. The deformations in steel-fiber concrete slabs during the application of load in the cantilever part, both for compressed and stretched fibers are higher than in reinforced concrete slabs. At the initial stages of load application in the cantilevered part of the slabs, the deflections increase in a linear relationship. The curves get non-linear character for airfield slabs made of reinforced concrete when the load reaches the level of 10÷25 kN, for steel-fiber-concrete slabs ‒ 15÷30 kN. In reinforced concrete slabs, the non-linearity starts a little earlier and is expressed more clearly. Experimental studies show that dispersed reinforcement of airfield slabs with steel fiber leads to their higher crack resistance.

Investigation of force redistribution in the foundation slab of complex configuration in low-rise buildings

A study of the redistribution of forces in the foundation slab of a complex configuration in the plan for the installation and non-installation of deformation seams between blocks of low-rise building using numerical simulation by the finite element method (FEM). Two variants of the foundation slab are considered - with the installation and non-installation of deformation seams.
 Due to the large difference in loads in different rooms and areas of the building to prevent uneven deformation of the bases as a foundation was adopted monolithic reinforced concrete foundation slab type with a thickness of 400 mm. The frame of the building is monolithic reinforced concrete with vertical load-bearing elements in the form of columns, pylons and walls, which are united by monolithic floor slabs, which create stiffness disks.
 The basis for the slab foundation are sandy soils dusty and small, medium density with lenses of plastic sands.
 After the calculations, the stress-strain state (SSS) of the foundation structures of the building was analyzed, namely: subsidence of the foundation slab, redistribution of bending moments in the foundation slab in the X and Y directions and selected the appropriate area of working reinforcement of the foundation slab. As a result of calculations, it was found that the presence of deformation seams significantly affects the redistribution of forces in the foundation slab of complex configuration in low-rise buildings. When installing them, there is an increase in bending moments in areas away from the junction of building blocks from 5% to 20%. A significant increase in bending moments occurs in the joint zone of the building blocks when installing deformation seams. In these areas, an increase in bending moments from 10% to 3 times, which significantly affects the cost of reinforcement of the foundation slab. It is also shown that the device of deformation seams practically does not affect the maximum values of subsidence of the foundation slab.
 Therefore, for low-rise buildings it is recommended to arrange a version of the foundation slab without deformation seams.

USING AND MODELING GROUND PENETRATING RADAR ON DENSELY REINFORCED SLABS

<jats:p>Ground Penetrating Radar - GPR by modern equipment has grown in importance in recent years in non-destructive testing. Estimating steel rebar position and diameter is the main focus for assessment of existing reinforcement concrete facilities. This paper presents the latest modern non-destructive technique – suitable for testing reinforcement concrete members. The capabilities of this technique for locating reinforcement bars in unilaterally accessible, densely reinforcement slab are described.</jats:p>

Experiment and Simulation Study on the Dynamic Response of RC Slab under Impact Loading

Reinforced concrete (RC) slab is an important component in civil construction and protection engineering, and its dynamic response under impact loading is a complex mechanical problem, especially for two or multiple continuous impact loads. In this paper, a series of drop hammer impact tests were carried out to investigate the dynamic response of RC slabs with two successive impacts. The time history of impact force and the failure characteristic of the slab surface were recorded. Moreover, four influence factors, including slab thickness, reinforcement ratio, impact location, and drop hammer height have been discussed. Besides, a 3D numerical model based on the finite element method (FEM) was established to expand the research of constrained force, deflection, and vertical stress of an RC slab. The results show that increasing the slab thickness and reinforcement ratio can improve the impact resistance of an RC slab. The impact point location and drop hammer height have a great influence on the dynamic response of the RC slab. In addition, the RC slab will have more obvious damage under the second impact, but the dynamic response becomes weaker. It may be because of the local damage in the concrete caused by the first impact that would weaken the propagation of vibration.

Influence of fiber orientation and structural-integrity reinforcement on the flexural behavior of elevated slabs

In the last decades, research works regarding the behavior of Fiber-Reinforced Concrete (FRC) showed that the use of fibers enhances the mechanical behavior of Reinforced Concrete (RC) structures both at Serviceability Limit State (SLS) and Ultimate Limit State (ULS). It is also well recognized that the design of these elements should take into consideration fiber orientation since the residual properties of the material can be different depending on the fiber inclination with respect to the cracking plane. This article presents the results of an experimental program aimed at evaluating the influence of fiber orientation on the flexural response of elevated slabs. Both Vibrated Fiber-Reinforced Concrete (VFRC) and Self-Compacting Fiber-Reinforced Concrete (SCFRC) were analyzed. Seven elevated slabs (250 × 250 × 15 cm) were cast following the most common casting process adopted in practice by using VFRC (2 specimens), SCFRC (4 specimens) and plain concrete (1 specimen). The post-cracking mechanical properties evaluated by three-point bending tests on 192 notched beams sawn from three FRC slabs showed that, for a given fiber type and amount, the fiber orientation in slabs was comparable varying both concrete workability and casting procedure. The structural behavior of the remaining four slabs was studied both by experimental tests and numerical analyses. The slabs were simply supported at the corners and subjected to center-point loading. Results showed that the response in flexure was related to the average residual properties obtained from small beams sawn from slabs. Finally, the importance of having a structural-integrity reinforcement in FRC elevated slabs under flexure was also underlined by the numerical study.

Effect of slab gravity load on slab-column connection with different compressive strengths

Current design codes specify the effective compressive strength of a column-slab connection when columns and slabs have different concrete compressive strengths. However, this approach assumes that no gravity load is applied to the slab. The gravity loads acting on the slab weakens the confinement of the slab-column connection and reduces the effective compressive strength of the column. Therefore, the effective compressive strength of the column specified in the current design code can be considered unsafe when gravity loads act on the slab, similar to the case of an actual structure. In this paper, the existing studies on slab-column connection, in which the gravity loads act on the slab, were comprehensively reviewed, and an effective compressive strength of the column based on the strain in the top slab reinforcement was proposed. In addition, three slab-column connections were fabricated, where the gravity loads acting on the slab and constraint condition of the slab were set as test variables, and axial load tests were conducted.

Unbalanced Moment Transfer in GFRP-RC Slab–Column Connections

When reinforced concrete (RC) slabs are supported directly on columns, a combination of shear forces and unbalanced bending moments is transferred between the slab and the columns at slab–column connections. The unbalanced moment transferred between a slab and a column can be significantly increased by the application of horizontal loads, such as wind and seismic loads. According to current design codes and standards for steel–RC structures in North America, a portion of the unbalanced moment is assumed to be transferred by the eccentricity of shear, while the remaining portion is assumed to be transferred by flexure. Previous research shows that the slab width that contributes to transferring the flexure portion is bounded by lines located at a distance of 1.5 times the slab thickness on each side of the column. This study investigates whether the same slab width can be used to transfer the unbalanced moments in slab–column connections reinforced with glass fiber–reinforced polymer (GFRP) reinforcement. A similar approach to that used for steel–RC connections is followed to analyze data from 27 GFRP-RC connections without shear reinforcement reported in the literature. Furthermore, a previously validated finite-element model is used to investigate the strain distribution in the longitudinal slab reinforcement along the transverse direction of the slab. The results show that a smaller slab width bounded by lines located at a distance of 0.5 times the slab thickness on each side of the column is recommended for GFRP-RC slabs.

ANALISIS PERENCANAAN GEDUNG PERPUSTAKAAN STAIN PAREPARE DENGAN MENGGUNAKAN MODIFIKASI METODE FLAT SLAB

The Analysis of Library Building Plan of Sekolah Tinggi Agama Islam Parepare by using A Modication of Flat Slab Method.
 The research aimed to know the dimensions of main structure, create construction structure using at slab based on ETABS Program that was analyzed according to SNI 2847:2013. Counting the reinforcement needed by main structure and create a nal design based on the modication result of Library Building as well as analyze the mass participation in earthquake areas.
 The analysis result showed that the thickness of the whole flat floor was 22 cm and drop panel was 120 cm x 120 cm with 12 cm thick, column dimension K1 for Floor 1 with 70/70, K1 floor 2-4 with 60/60, K1 floor 5 with 50/50, column 2 floor 1-5 with 50/35 and K3 floor 1-5 with 30 x 30, the thickness of shear wall was 30 cm. The reinforcement of flat slab produced reinforcement D16 mm, main column reinforcement K1 22D22, column K2 9D22, column K8D12. Final Plan of library building modification based on technical drawing form consisted of the Picture of structure plan, pieces, and detail of the reinforcement. In earthquake area with Category C, it was showed by mass partition control on mode 4 and 5 had achieved 93% and 94% and was able to restrain the load of earthquake plan.

Behavior of Composite Floor Assemblies Subject to Fire: Influence of Slab Reinforcement

AbstractA series of fire experiments are being conducted on the 2‐story steel framed building with composite floors in the National Fire Research Laboratory. This paper presents a brief overview of experimental design and discusses some results of the first test conducted on 6.1 m by 9.1 m composite floor assembly exposed to a standard fire. The test floor slab was constructed with lightweight concrete cast on 7.7 cm deep formed steel deck units and welded wire fabric (60 mm/m2) as the minimum shrinkage reinforcement required in the U.S. practice. The structural steel beams and girders were sprayed with a cementitious fire resistive material for a 2‐hour restrained fire resistance rating. While the test floor assembly resisted mechanical loads (2.7 kN/m2) applied using hydraulic actuators, its underside was exposed to a natural gas‐fueled compartment fire that was equivalent to the standard gas temperature‐time relationship. The study revealed that the test floor assembly could withstand an imposed load at a large vertical deflection on the order of span / 16, but the concrete slab failed due to limited ductility and strength prior to 2 hours in a standard fire. Simple post‐test predictions were performed incorporating tensile membrane action in the floor slab to compare with the measured behavior. Limited comparisons discuss the contribution of steel decking and slab reinforcement to the load‐carrying capacity of a floor assembly in fire.

Enhancing shear capacity of thin slabs with CFRP shear reinforcement: Experimental study

AbstractEmploying non‐metallic reinforcement made of fiber‐reinforced polymers (FRPs) as textile grids is one promising extension of the utilization range of FRP in concrete construction, and thin planar elements reinforced in this manner have high application potential in bridge or parking garage decks, in façades, or in webs and flanges of hollow core cross‐sections. Existing models for predicting the shear resistance of such elements were derived for solid cross‐sectional dimensions similar to conventional steel‐reinforced structures, and their application to thin slabs is debatable. This paper presents the results of an extensive experimental program on the one‐way shear capacity of slabs without and with carbon FPR textile shear reinforcement. A variation of member height, shear slenderness, and shear reinforcement ratio allowed for analysis of the most relevant influencing factors on shear resistance. Both planar and preformed C‐shaped grids enhance the shear capacity and are suitable as shear reinforcement in thin slabs. The experimental results are the foundation for the extension of shear models to thin slabs with FRP reinforcement and for derivation of new unifying shear models that are applicable to a wider range of reinforcement materials and member dimensions.

Analysis of the shear strength mechanism of slender precast concrete beams with cast-in-place slab and web reinforcement

Precast concrete beams with cast-in-place slabs on top, namely concrete composite beams are frequently used for building concrete bridge decks. In designs, the contribution of cast-in-place slabs to shear strength tends to be omitted. However, given the vast number of existent bridges with this deck typology, significant cost savings could be made when assessing these structures if the slab’s shear strength is considered. This paper analyses how cast-in-place slab influences the shear behaviour of concrete composite beams with web reinforcement. For this purpose, an experimental programme of 18 concrete specimens with web reinforcement and rectangular cross-sections was run, in which the following parameters varied: cross-sectional depth; existence of an interface between concretes; compressive strengths of the concrete of beams and slabs; differential shrinkage between concretes. It was observed that: the slab contributed to resist shear; the existence of an interface between concretes led to a crack appearing along it that caused the transmitted shear to be divided into two load paths: one through the precast beam and another one through the slab; the slab’s concrete strength was that which mainly influenced the element’s shear strength; differential shrinkage did not reduce shear strength. Based on experimental observations, a mechanical model is proposed in this paper to assess the composite elements’ shear strength, which considers the yielding of both stirrups and the slab’s longitudinal reinforcement to be a failure criterion, which well predicted the experimental results. The shear formulations of Eurocode 2, the Level III Approximation of Model Code 2010 and the (b) Formula of ACI 318-19 offered a similar result to the herein proposed method when using the entire composite element effective depth and the weighted average of the concrete strengths of both the beam and slab estimated from the area ratio. Codes significantly underestimated specimens’ interface shear.

Effect of uniform temperature load on design of long reinforced concrete structures without expansion joints

This study presents an investigation on the design of long reinforced concrete (RC) structures subjected to uniform temperature load by considering three RC frame building models with different lengths of 45 m, 135 m, and 270 m using Etabs. The uniform temperature load is considered being the change from the annual average highest to lowest air temperature at the construction site in the case of unavailable temperature data of concrete. The analysis results indicate that the uniform temperature load mainly influences on the internal forces of RC members at storey 1 and slightly effects on the internal forces of RC members at storey 2. For short-length RC structures, the effect of temperature load can be ignored in the design of RC elements, whereas it must be taken into account in design of slab, beams and some column positions at storey 1 of medium-length and long RC structures without expansion joints. For the present RC frame building models, the required slab reinforcement in long direction increases about 33.4% for medium-length RC structures (135 m) and about 48.2% for long RC structures (270 m) without expansion joints. The required reinforcement for positive moment at mid-span increases from 33.7 to 39.4%, whereas the total required reinforcement for negative moment at the supports of beams increases from 19.4 to 34.9% in long direction of 270 m long RC structures without expansion joints due to uniform temperature load. Column design of long RC structures without expansion joints under uniform temperature load must be concerned, especially for columns in the corners.

Factors affecting slip and stress distribution of concrete slabs in composite beams

An experimental program is carried out to examine the effects of different factors on the slip and stress distribution of concrete slabs in composite beams. A total of ten steel–concrete composite beams with a span of 4.80 m are tested to find the effects of the type of shear connectors and the concrete slab reinforcement on the behaviour of composite beams. All beams consist of monosymmetric steel cross-sections connected to 120 cm wide concrete slabs. Welded shear connectors (angles or channels) spaced at 20 cm are used to connect the concrete slabs to the steel beams. The concrete slabs of eight beams are provided with a lower steel reinforcement only while two beams are provided with both lower and upper steel reinforcement. The results showed that the ultimate load capacity of composite beam with channel connectors is 14% higher than the counterpart beam with angle connectors and 30% stiffer in resisting the slip of the concrete slab. Moreover, composite beams with channel connectors tend to maintain strain compatibility at the interface between concrete slab and steel section better than the counterpart beams with angle connectors. It is also found that using upper steel reinforcement mesh enhances the stress distribution in the concrete slab until failure. It is found that increasing the reinforcement ratio of the concrete slab from 0.18% to 0.46% increases the flexural strength of the composite beams by 7.45%, while decreases the deflection values by 23%. Moreover, using upper steel reinforcement prevented the longitudinal cracking of the top surface of the concrete slab and allowed for full plastification of the steel cross-sections.

Električno zavarena armaturna rešetka u armiranobetonskim rebrastim pločama

Shear strength of precast concrete ribbed slabs reinforced with electro-welded lattice girders of variable height is experimentally verified. Technical justification is given for the use of high latticework in the reinforcement of precast lightweight double-tee ribbed slabs and precast reinforced concrete slabs 30 cm in thickness. It was established that the contribution of concrete to shear strength was always higher than the expected values according to Spanish standards. Furthermore, as low lattice ribbed slabs exhibited lower ultimate shear strength values than the ones expected based on the standards, the need arose to provide an adequate height of lattices in ribbed slabs to ensure anchorage of the compressed area in order to develop the strut-and-tie mechanisms. Consequently, lattice girders with approximately 80% of specimen height are highly recommended in reinforced concrete ribbed slabs, when the length of lattice chords is 20 cm.

Lightweight and slender timber-concrete composite floors made of CLT-HPC and CLT-UHPC with ductile notch connectors

Cross-Laminated Timber (CLT) structures have been emerging worldwide for residential floors in multi-storey buildings thanks to their lightness, fast construction and low ecological footprint. This work aims at fostering this application, which is often limited by vibrational and deflection limits, by investigating composite slab floors made of CLT and High-Performance Concrete (HPC) slab as well as CLT and Ultra High-Performance Fiber Reinforced Concrete (UHPFRC).Firstly, the composite floors CLT-HPC and CLT-UHPFRC with a span of 8 m were designed by considering a multicriteria analysis. To assure a certain structural ductility, previously developed ductile notch connectors were employed. As an economic choice, no shear reinforcement in the concrete slab was employed. Then, full-scale composite beams were fabricated in order to verify the predicted flexural behaviour and natural frequency. A numerical analysis was carried out to verify the connectors could effectively yield before the timber collapse. The comparison between the numerical simulation and the slip measurements confirmed that about 50% of the notch connections fully yielded and underwent inelastic deformation which favors the structural ductility. In the case of the CLT-HPC floor, a reduction of the notch contact surface due to the use of plastic sheet waterproofing as well as shear cracks developing in the concrete close to the notch corner both reduced the expected structural stiffness. Finally, the CLT-UHPFRC floor is endowed with outstanding values of slenderness ratio (∼35) and lightness (∼2 kPa), while eliminating the use of shear reinforcement and sheet waterproofing.

Waffle Slab Behavior Subjected to Blast Load

Over the previous years, the use of structure roof systems which can be implemented with long column spans has been welcomed by manufacturers. One of the most widely used roofs is the waffle slab system. Therefore, by reviewing previous studies in the field of roof collapse in reinforced concrete structures under blast, the absence of studies on the performance of waffle slab and comparing its behavior with blast affected RC slabs is observed. Laboratory simulation of this problem requires high cost, high accuracy in model building and much time. In this study, after preliminary model validation with experimental research and two numerical studies in LS-DYNA software, the behavior of waffle slab subjected to blast load and compare its performance with RC slab is investigated. It should be noted that because the blast load is applied to the structure in a very short time, it has a high loading rate. Therefore, the strain rate effects on concrete and reinforcement are considered for achieving real material behavior. The identical volume of concrete and reinforcement used in all roofs is considered in order to evaluate and compare the behavior of the roofs reasonably. Then, the effect of the geometric dimension of waffle molds and the effect of the supporting condition on the Waffle slab responses are studied. Other parameter investigated in this study includes the effect of concrete compressive strength on the behavior of roof under blast load. The mass of the explosive and its distance from the roof surface are other parameters considered in this study. The effect of bar size on the behavior of the roof is also investigated. The results of this study are presented as diagrams and tables showing that given the same volume of concrete and reinforcement in the RC slab and the waffle slab, the central displacement of Waffle slab are reduced to a desirable level. This shows the better behavior of the waffle slab in comparison with the RC slab with the same volume of material under the blast load.