Design and Construction Technology of Prefabricated Reinforced Concrete Slab Culverts

Compared with traditional cast-in-situ concrete slab culverts,prefabricated reinforced concrete slab culverts can be produced more quickly and has strong quality controllability,strong earthquake resistance,and repeatability.They will be the primary production method of slab culverts in the future.This article offers a comprehensive review of the design and construction technology associated with prefabricated reinforced concrete slab culverts.The objective is to provide a valuable reference for related enterprises,enhance the quality of design and construction in precast pile configuration,and,in turn,contribute to the advancement of construction projects within our country.

Exploring the Synergy: Experimental and Theoretical Investigation of Steel and Glass Fiber Reinforced Polymer (GFRP) Reinforced Slab Incorporating Alccofine and M-Sand

Introduction: This study investigates the Experimental and Theoretical Investigation of Steel and Glass Fiber Reinforced Polymer (GFRP) Reinforced Slab Incorporating Alccofine and M-sand. Objective: Specific objectives include evaluating the mechanical properties and structural behaviour of steel and GFRP-reinforced one-way slabs and comparing experimental and theoretical predictions. Methods: Four different mix proportions were arrived at, comprising both conventional concrete and Alccofine-based concrete. In each formulation, a combination of normal river sand and M-sand was utilized. Results: Concrete with Alccofine exhibits superior mechanical properties, while M-sand incorporation minimally affects strength but reduces reliance on natural sand. GFRP-reinforced slabs display distinct brittle behaviour with significant deflections post-cracking, contrasting steel-reinforced slabs’ gradual, ductile failure. Discrepancies between experimental data and design recommendations underscore the need for guideline refinement. Conclusion: Alccofine and M-sand enhance concrete properties, but reinforcement type significantly influences slab behaviour. GFRP-reinforced slabs, though exhibiting lower values than steel, offer advantages in harsh environments, warranting further optimization.

Pressure-impulse diagram with multiple failure modes of one-way reinforced concrete slab under blast loading using SDOF method

Two loosely coupled single degree of freedom (SDOF) systems were used to model the flexural and direct shear responses of one-way reinforced concrete slabs subjected to explosive loading. Blast test results show that the SDOF systems are accurate in predicting the failure mode of the slab under blast loads by incorporating the effects of the strain rate effect caused by rapid load application. Based on different damage criteria, pressure-impulse (P-I) diagrams of the two failure modes were analyzed with the SDOF systems. The effects of span length, concrete strength, and reinforcement ratio of the slab on the P-I diagram were also investigated. Results indicate that a slab tends to fail in direct shear mode when it is of a smaller span length and tends to fail in flexure mode when it is of a larger span length. With the increase of the concrete strength or reinforced ratio, both the flexure and shear capacity increase. Based on numerical results, a simplified method and a semi analytical equation for deriving the P-I diagram are proposed for different failure modes and damage levels.

Damage analysis of POZD coated square reinforced concrete slab under contact blast

High efficiency, environmental protection and sustainability have become the main theme of the development of the protection engineering, requiring that the components not only meet the basic functions, but also have chemical properties such as acid and alkali corrosion resistance and aging resistance. Polyisocyanate-oxazodone(POZD) polymer has the above characteristics, it also has the advantages of strong toughness, high strength and high elongation. The concrete slab sprayed with POZD material has excellent anti-blast performance. In order to explore the damage characteristics of POZD sprayed concrete slabs under the action of contact explosion thoroughly, the contact explosion test of POZD concrete slabs with different charges were carried out. On the basis of experimental verification,numerical simulation were used to study the influence of the thickness of the POZD on the blast resistance of the concrete slab. According to the test and numerical simulation results that as the thickness of the coating increases, the anti-blast performance of the concrete slab gradually increases,and the TNT equivalent required for critical failure is larger. Based on the above analysis, empirical expressions on normalized crater diameter, the normalized spall diameter and normalized spall diameter are obtained.

Analytical Solutions to Strain Rates of Reinforced Concrete Simply Supported Slabs under Blast Loads

Based on the Duhamel integral, a couple of analytical solutions are derived to predict the strain rates of concrete and steel reinforcement in reinforced concrete slabs under blast loads and to estimate their variation over depth of a cross-section along the entire length of the member. The analytical approach utilizes the single-degree-of-freedom mode for the analysis of reinforced concrete simply supported one-way panels subjected to blast loads. These analytical solutions can give the strain rate profile for any cross-section at any time and permit variations of strain rate in each time step of numerical iteration method, thus making it possible to directly incorporate strain rate effects into non-linear dynamic response analysis of structural members subjected to blast loads.

NONLINEAR ANALYSIS OF REINFORCED CONCRETE RECTANGULAR SLABS USING FINITE ELEMENT METHOD

The nonlinear analysis of reinforced concrete rectangular slabs undermonotonic transverse loads is performed by finite element method.The layered rectangu-lar element with 4 nodes and 20 degrees of freedom is developed,in whichbending-stretching coupling effect is taken into account.An orthotropic equivalentuniaxial stress-strain constitutive model of concrete is used.A program is worked out andused to calculate two reinforced concrete slabs.The results of calculation are in goodconformity with the corresponding test results.In addition,the influence of tension stif-fening effect of cracked concrete on the results of calculation is discussed.

Performance Evaluation of One-Way Concrete Slabs Reinforced with New Developed GFRP Bars

The incorporation of fiber-reinforced-polymer (FRP) bars in construction as a replacement to steel bars provides a superior material which is capable to overcome corrosion problems. However, serviceability requirements are important issues to be considered in the design of concrete elements reinforced with glass-FRP (GFRP) bars which are known to have larger deflections and wider crack widths as well as weaker bond compared with steel reinforced concrete. As a solution to this problem, square GFRP bars are proposed. This paper presents the results of an experimental investigation that was performed, in which newly developed square and circular GFRP bars were fabricated in the lab. Also, the GFRP bars were tested and used to reinforce concrete slabs. A total of nine full-scale GFRP-reinforced concrete (RC) one-way slabs were constructed, tested and analyzed, considering the most influencing parameters such as the cross sectional shape of GFRP bars, reinforcement ratio, the concrete characteristics strength, and adding polypropylene fibers to the concrete mixture. The test results were showed that, the tested slabs with GFRP square bars improved the deflection and cracking behavior as well as the ultimate load.

Effects of edge beams on mechanic behavior under lateral load in reinforced concrete hollow slab-column structure

In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic analysis of reinforced concrete hollow slab-column structure with different dimensions to study internal relationship between effective beam width and the frame dimensions.In addition,the formulas for calculating the increasing coefficient of edge beam were also obtained.

Structural Glass Fiber Reinforced Concrete for Slabs on Ground

This paper aims to contribute to the classification and specification of glass fiber reinforced concrete (GFRC) and to deal with the question if structural glass fiber reinforced concrete as a special kind of glass fiber reinforced concrete is suited for use in load-bearing members. Despite excellent material properties, the use of glass fibers in a concrete matrix is carried out so far only in non- structural elements or as a modification for the prevention of shrinkage cracks. The aim of re- search at the University of Applied Sciences in Leipzig is the use of alkali-resistant macro glass fibers as concrete reinforcement in structural elements as an alternative to steel fiber reinforcement. Slabs on ground, as an example for structural members, provide a sensible application for the new material because they can be casted as load bearing and non-load bearing and are mostly made of steel fiber reinforced concrete. In the future, structural glass fiber reinforced concrete shall provide a simple and visually appealing alternative to conventional steel bar or steel fiber reinforced concrete. The glass fibers can also be used in combination with conventional reinforcing bars or mat reinforcements. Initial investigations have announced some potential.

Analysis and Prediction Model Reinforced UHPC Shrinkage Property

This paper explores the shrinkage of reinforced UHPC under high-temperature steam curing and natural curing conditions.The results are compared with the existing shrinkage prediction models.The results show that the maximum shrinkage strain of reinforced UHPC after steam curing is 164μεand gradually becomes zero.As for natural curing,the maximum shrinkage strain is 173μεand the value stabilizes on the 10th day after pouring.This indicated that steam curing can significantly reduce shrinkage time.Compared with the plain UHPC tested in the previous literature,the structural reinforcement can significantly inhibit the UHPC shrinkage and greatly reduce the risk of cracking due to shrinkage.By comparing the results in this paper with the existing models for predicting the shrinkage strain development,it is found that the formula recommended in the French UHPC structural and technical specification is suitable for the shrinkage curve in the present paper.

Lead spall velocity of fragments of ultra-high-performance concrete slabs under partially embedded cylindrical charge-induced explosion

When an explosion occurs close to or partially within the face of a concrete structure, fragments are rapidly launched from the opposite face of the structure owing to concrete spalling, posing a significant risk to nearby personnel and equipment. To study the lead fragment velocity of ultra-high-performance concrete(UHPC), partially embedded explosion experiments were performed on UHPC slabs of limited thickness using a cylindrical trinitrotoluene charge. The launch angles and velocities of the resulting fragments were the determined using images collected by high-speed camera to document the concrete spalling and fragment launching process. The results showed that UHPC slabs without fiber reinforcement had a fragment velocity distribution of 0-118.3 m/s, which are largely identical to that for a normal-strength concrete(NSC) slab. In addition, the fragment velocity was negatively correlated to the angle between the velocity vector and vertical direction. An empirical Eq. for the lead spall velocity of UHPC and NSC slabs was then proposed based on a large volume of existing experimental data.

Possible Collapse Mode for Slender Reinforced Concrete Plates Subjected to Blast Load

This paper discusses the collapse mode of thin reinforced concrete (RC) plates sub-jected to blast load. To extend the well known plastic-mode method to analyze, not only perfect-plastic plates , but also RC plates, it is needed to investigate the effect of material cracking on the collapse mode because the plate might have been cracked on both upper and lower surface before the plastic-mode fully develops, creating an unexpected type of collapse mode shape. A new fail-ure mode is proposed and verified by numerical analysis in this paper. The new mode is a result of the material cracking and has an un-negligible effect on the reaction mechanism of the RC plate to the blast load.

Numerical study on local failures of reinforced concrete slabs against underwater close-in explosions

Reinforced concrete(RC)slabs are the primary load-carrying member of underwater facilities.They can suffer severe local failures such as cratering,spalling,or breaching as a result of underwater close-in(UWCI)explosions.In this study,we established a fully validated high-fidelity finite element analysis approach to precisely reproduce the local failures of RC slabs after a UWCI explosion.A recently proposed dynamic constitutive model is used to describe wet concrete.The effects of free water content on the material properties,including the tensile/compressive strength,elastic modulus,strain rate effect,failure strength surface,and equation of state,are comprehensively calibrated based on existing test data.The calibrated material parameters are then verified by a single-element test.A high-fidelity finite element analysis(FEA)approach of an RC slab subjected to a UWCI explosion is established using an arbitrary Lagrangian-Eulerian(ALE)algorithm.Simulating previous UWCI explosion tests on RC orifice targets and underwater contact explosion tests on saturated concrete slabs showed that the established FEA approach could accurately reproduce the pressure-time history in water and damage patterns,including the cracking,cratering,and spalling,of the RC orifice target and saturated concrete slab.Furthermore,parametric studies conducted by simulating an RC slab subjected to a UWCI explosion showed that:(i)the local failure of an RC slab enlarges with increased charge weight,reduced standoff distance,and reduced structural thickness;(ii)compared to a water-backed RC slab,an air-backed RC slab exhibits much more obvious local and structural failure.Lastly,to aid the anti-explosion design of relevant underwater facilities,based on over 90 simulation cases empirical formulae are summarized to predict local failure modes,i.e.,no spall,spall,and breach,of water-and air-backed RC slabs subjected to a UWCI explosion.

Sensor location in concrete slabs with various layout of opening using modified ‘FEMS-COMAC’ approach

Two-way concrete slabs are widely used around the world for the construction of many types of infrastructures and common buildings. The optimal sensor placement(OSP) in slabs with various opening positions is the most important issue in structural health monitoring(SHM) to increase reliability. In this study, a novel approach of OSP was evaluated to obtain the number and placement of sensors using examination of the closed loop performance. The nonlinear finite element(NFE) was used to discretize the mechanism behavior of slab. Multi-Objective Optimization based on the coordinate modal assurance criterion(COMAC) and cost considerations was considered in the optimization processes. All of the analysis, discretization and optimization process was designed and developed as a novel approach in Matlab by the author under the name ‘FEMS-COMAC’(FEM analysis of slab with COMAC). The points in the finite element method(FEM) mesh were classified as line by line information along the slab. The OSP in each line was optimized according to the objective function. The slabs with various width, thickness, aspect ratio and opening position were selected as case studies. The results of the OSP using the COMAC algorithm around the slab openings were compared with the novel ‘FEMS-COMAC’ method. The statistical analysis according Mann-Whitney criteria shows that there were significant differences between them in some of the case studies(mean P-value=0.54).

Behavior of RC two-way slabs strengthened with CFRP-steel grid under concentrated loading

A novel composite technique of orthogonally bonding carbon fiber-reinforced polymer （CFRP） strips and steel strips is proposed to improve the performance of reinforced concrete （RC） structures based on co-working of CFRP strips and steel strips. To verify the effectiveness of the method for strengthening RC two-way slabs, seven flat slabs with the dimensions of i 500 mm x 1 500 mm x 70 mm and an internal reinforcement ratio of 0.22% were prepared and tested until failure under concentrated loading, of which one was unstrengthened, one was strengthened with CFRP strips bonded to its soffit making a grid pattern （termed the CFRP grid）, and five were strengthened with a hybrid grid of CFRP strips and steel strips in two orthogonal directions （termed the CFRP-steel grid） to the bottom with steel bolt anchorage. The investigation parameters are the strengthening method, the strip spacing （150, 200, and 250 mm） and the layers of CFRP strips （one layer, two layers, and three layers of CFRP strips are applied for CFRP-steel grid）. The experimental results show that the strengthening RC two-way slabs with CFRP-steel grid are effective in delaying concrete cracking and enhancing the load-carrying capacity and deformability in comparison to the CFRP grid strengthening. The yield-line analysis model is proposed to predict the load-carrying capacity of the strengthened slabs. The prediction results are in good agreement with the experimental results.

基于声发射技术的高强全珊瑚钢筋混凝土板破坏特性研究

为了探究全珊瑚钢筋混凝土板破坏特性,设计了3种不同配筋率(0.85%、1.13%和1.41%)的高强全珊瑚钢筋混凝土板构件.结合声发射技术,开展了全珊瑚混凝土板构件四点弯曲加载试验,揭示了配筋率对高强全珊瑚钢筋混凝土板力学性能的影响.基于声发射参数速率过程理论,建立了损伤定量评估模型,并进一步提出了可用于工程实践的损伤评估准则.结果表明:随配筋率增大,高强全珊瑚混凝土板构件起裂荷载、起裂时间与峰值荷载均增大,但中心挠度降低了11.29%;单位时间声发射参数变化均存在2个峰值区,可作为板构件的起裂评判和破坏预兆;根据声发射参数累计值变化可将高强全珊瑚混凝土板构件破坏过程划分为轻度(<0.35)、中度(0.35~0.66)、高度(0.66~0.84)和重度(>0.84)损伤4个程度.所建立模型适用于不同配筋率的全珊瑚混凝土板构件损伤评估.

钢纤维细石混凝土-钢组合板抗弯性能试验研究

钢纤维细石混凝土是一种具有优异力学性能和良好工作性的高性能混凝土复合材料。本试验针对正交异性钢桥面铺装层裂缝病害问题,对4组采用不同钢筋配筋率和保护层厚度的横桥向钢纤维细石混凝土-钢组合桥面板进行了抗弯破坏试验,研究了组合板的荷载-挠度关系与裂缝开展特征;用等效截面法计算了开裂应力、裂缝宽度和钢筋应力,验证了钢纤维细石混凝土-钢组合板的抗裂性能。结果表明:60 mm厚钢纤维细石混凝土铺装层在小配筋率(2.6%)和低于规范要求的保护层厚度(15 mm)条件下呈现出多缝开裂的破坏形态,具备较高的延性和开裂应力,满足规范和工程应用的要求。

RC框架梁端负弯矩纵筋部分置于梁侧楼板对性能的影响及构造问题分析

为适应建筑多功能、大跨度、重荷载、高抗震的发展要求,框架梁端部负弯矩纵筋配筋率通常较高,节点区钢筋过于密集,混凝土施工质量不易保证,对结构综合性能有不利影响。先对梁端负弯矩纵筋部分设置于梁侧楼板内(简称APNRFS)的布筋方式进行阐述,然后基于试验结果分析探讨了该配筋方式对结构性能带来的变化及相关构造问题。研究表明:梁端采用APNRFS布筋方式一般不会降低框架梁的承载力;梁端的弯曲变形能力和结构抗震性能有一定提高;移至板内的梁负筋布置宽度宜小于有效翼缘宽度范围;移至板内的梁端负筋宜同时兼作楼板负筋;横向分布筋参与受力,设计中应适当增配。

波纹钢形状与拱效应对加固盖板涵承载力的影响

为了探索波纹钢形状对加固盖板涵承载力的影响及填充混凝土的拱效应形成机制,采用室内试验与数值分析相结合的研究方法,以一个室内模型试验结果为基准,建立了72个箱形、圆弧及其之间的过渡形状的波纹钢加固盖板涵的数值模型,探明了加固体系承载力随波纹钢形状参数的变化规律;基于合理拱轴的概念,探明了填充混凝土的拱效应形成机理,并采用5个数值模型进行了验证。结果表明:拱腋半径保持不变时,加固体系的承载力随着拱顶、侧墙半径的增加而减小;拱顶、侧墙半径不变时,加固体系的承载力随着拱腋半径的增加而增大;提升加固体系承载力最有效的方式是增加拱腋半径,其次是减小拱顶和侧墙半径;填充混凝土的拱效应与荷载类型有关,当波纹钢的形状能保持拱轴连续并且在素混凝土刚性角以内时,加固体系的承载力最高。在设计波纹钢加固盖板涵结构时,应根据实际工程需要综合考虑波纹钢形状与填充混凝土的拱效应,尽量避免紧贴原盖板涵的加固设计。

UHPC加固空心板梁现场足尺抗弯试验研究

为分析UHPC加固受损空心板梁的抗弯性能,设计制作了2片空心板梁以开展现场足尺抗弯试验研究.基于现场试验结果对比分析了未加固和加固空心板梁的破坏模式和荷载-跨中位移曲线.试验结果表明UHPC加固层可以有效改善受损空心板梁的破坏模式,并且加固空心板梁呈现出更好的抗弯和变形能力.与未加固空心板梁相比,加固空心板梁的开裂和极限荷载均得到明显提升,提升幅度分别达到11.5%和23.8%.此外讨论了UHPC层的加固机理,同时推导了加固空心板梁的抗弯极限承载能力公式,并将理论值与试验值进行对比.结果表明抗弯承载能力计算值和试验值的最大误差仅为1.1%,证明了理论公式的准确性.