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Theoretical and experimental comparison between straight and curved continuous box girders

  • Asala Asaad Dawood EMAIL logo , Khattab Saleem Abdul-Razzaq und Wael Shawky Abdulsahib
Veröffentlicht/Copyright: 30. September 2024
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Aus der Zeitschrift Open Engineering Band 14 Heft 1

Abstract

The curvature causes a variation in the deflection of the outer and inner sides. The effect of curvature was investigated by casting and testing two specimens with the same section – one straight and the other horizontally curved continuous box girder. ABAQUS software was used to numerically model the box girder in order to verify the model and investigate additional parameters. Numerical modeling is successful with less effort, cost, and time because good results are obtained. The effect of the span-to-depth ratio, the compressive strength of concrete, and the percentage of stirrup steel reinforcement was studied numerically. Increasing the height, compressive strength, and percentage of stirrup steel led to a significant increase in load capacity and stiffness. The load capacity in the curved specimen decreased by 11% compared to the straight one due to the effect of torsional moments. A mathematical model was proposed based on the theory of strut-and-tie modeling (STM), where the span was divided into several panels, the effect of torsion was added, and then the results were compared with the traditional sectional method according to ACI and CEB-FIB. For the straight specimen, the sectional ACI, CEB-FIB, and STM methods were used, which gave theoretical results less than the experimental by 31, 48 and 13%, respectively. For the curved specimen, to get closer to reality, the sectional and STM methods were modified by adding the effect of torsion, and the results were less than the experimental tests by 43, 61 and 22%, respectively.

Keywords: continuous bridges; curved box girder; reinforced concrete; shear; strut-and-tie model; torsion

Notations

a

Shear span measured from the loading to supporting points (mm)

A b

Area of reinforcing bars ( mm 2 )

A s

Area of main longitudinal tension reinforcement ( mm 2 )

b

Width of box girder (mm)

b w

Web width (mm)

d

Effective depth of box girder, distance from the centroid of flexural reinforcement to the extreme compression fiber (mm)

E c

Modulus of elasticity of concrete (MPa)

E s

Modulus of elasticity of steel reinforcement (MPa)

f′c

Cylinder compressive strength of concrete (MPa)

f ct

Indirect tensile strength (splitting tensile strength) (MPa)

f r

Modulus of rupture (MPa)

f y

Yield stress of main steel reinforcement (MPa)

f yv

Yield stress of stirrup vertical reinforcement (MPa)

h

Overall depth of the box girder (mm)

j d

Distance between the centers of the top and bottom nodes (mm)

L

Total length of the box girder (mm)

L b

Length of load-bearing block (mm)

L s

Length of support-bearing block (mm)

P

Ultimate load failure (kN)

P FE

Ultimate load failure of finite element analysis (kN)

P cr − diag .

First diagonal cracking load (kN)

P cr − flex , Neg .

First negative flexural cracking load (kN)

P cr − flex , Pos .

First positive flexural cracking load (kN)

P STM

Theoretical load according to chapter 23, ACI 318M-14, strut-and-tie method (kN)

s

Stirrup reinforcement spacing (mm)

Δ cr − diag

Deflection corresponding to the first diagonal crack load (mm)

Δ FE

Deflection of finite element analysis (mm)

Δ inner

Deflection corresponding to the ultimate of the box girder inner side (mm)

Δ outer

Deflection corresponding to the ultimate of the box girder outer side (mm)

1 Introduction

Recently, transportation networks have started to favor the development of box-girder bridges. Their popularity is due to a variety of factors, including an increase in traffic, economic parameters, and aesthetic design choices. Because modern highway bridges are frequently subject to severe geometric restraints in urban areas where elevated highways and multi-level structures are required, they must be constructed as a curved alignment. The use of straight segmental construction has decreased in comparison to curved girders [1,2,3]. Although it is more expensive to construct the superstructure using curved girders, the overall cost of the curved girder system has decreased dramatically since there are fewer intermediate supports, expansion joints, and bearing details. Additionally, the continuous curving girder provides a more attractive structure. Although horizontally curved girders provide the advantages mentioned above, they are more complicated than straight girders. Because of the girder’s curvature, curved girders are sensitive to torsion as well as vertical bending and shear [4,5,6,7]. In the 1960s, researchers concentrated on the challenges presented by curved girders and developed rough assumptions for the study of curved bridges [8,9]. Previously, it was believed that curved girders were made of a number of straight segments that were joined together to make a curved alignment. The study of curved bridges is quite simple now because of readily available analytical software.

Strut-and-tie modeling (STM) provides design engineers with a more flexible and intuitive option for designing structures, or portions thereof, that are heavily influenced by shear. The method allows for the stress flows within a structure to be approximated with simple truss elements that can be designed using basic structural mechanics. The 1989 AASHTO Guide Specifications for Design and Construction of Segmental Concrete Bridges was the first American code provision to use STM. STM may be used to design for shear, torsion, and the forces brought on by the anchoring of post-tensioned prestressing forces in the segmental guide specification. STM has gained popularity in recent years as a method for designing and specifying structural concrete elements exposed to high shear stresses [10,11,12]. The STM of ACI 318-19 code standards have been incorporated for design [13] and the AASHTO LRFD Bridge Design Specifications [14].

Truss members are loaded with uniaxial stresses. Struts and ties are the names given to the force courses in compression and tension, respectively, of truss components. The nodes are formed by strut and tie junctions. A truss mechanism or model is a group of struts, ties, and nodes [15,16]. Prismatic struts are the most fundamental strut type, and over their length, they have a constant cross-section. Such a strut can develop in beam-bending situations when the neutral axis confines compressive stresses. Compression fans are the second type of struts. Stresses that concentrate in a tiny area define a compression fan. A huge region experiences radial stress flow into a much smaller one. A bottle-shaped strut can develop when the flow of compressive loads is not restricted to a specific area of a structural part. In this instance, a tiny area receives the force, and the stresses spread out as they pass through the member. As the compression dissipates, it alters course and forms an angle with the strut’s axis. A tensile force is created to oppose the lateral component of the angled compression forces in order to maintain balance [17]. To appropriately account for the tensile stresses, a collection of struts and ties can be used to model a bottle-shaped strut.

The presence of horizontal curvature causes a non-centralization of the applied loads with the longitudinal main axis, which produces torsional moments [18,19]. The torsional moments are transmitted at an angle of 45° in a spiral manner along the longitudinal main axis. Those torsional moments are mainly located in the outer layers, i.e., they are not affected by the amount of core concrete, and therefore, new compressive struts are produced in addition to the STM truss for shear [20,21,22].

The early 1970s saw a revival of STM usage in the United States. At that time, concrete members exposed to both shear and torsion were the first to get STM treatment. In this instance, a tubular truss was utilized, forming a hollow box close to the outside face of the members [23]. Later, the space truss model was developed from the tubular truss model [24,25,26]. The space truss was capable of accounting for all bending, shear, torsion, and axial loads.

Yoo et al. [27] provided an analytical method utilizing the CURSYS computer software to determine the loads applied to box bridges with horizontal curves. Although the torsional rigidity of the closed section was much higher than that of the open section – about 200–1,000 times higher – the bending stiffness remained roughly the same. A unified theory technique was proposed by Arici et al. [28] for the analysis of curved thin-walled girders having both open and closed cross sections. For both straight and horizontally curved beams, the precise solution is discovered, and the box section distortion is resolved without the need for an analysis using the beam on elastic foundation analogy. In order to demonstrate the wide range of applicability of the suggested strategy and to validate it through comparisons with data from the literature, numerical applications are provided. Granata [29] presented an approach that takes bimoment effects and warping into account when evaluating non-uniform torsion using the Hamiltonian structural analysis method. In comparison to finite element approaches, this approach minimizes computational effort and provides fast solutions for numerous launching phases. Comparisons with the current literature and finite element analysis are used to perform validation. The results demonstrate distinct behaviors of thin-walled sections under non-uniform torsion. Mokos and Sapountzakis [30] established a boundary element technique that takes secondary torsional moment deformation into account when analyzing non-uniform torsion in bars with constant, doubly symmetrical cross-sections. It solves primary and secondary twist angles as well as warping functions using boundary discretization and handles bars under different twisting and warping moments. By using boundary integration and automatic domain integration, the technique effectively computes torsion constants; numerical examples show that this method is more accurate and effective than finite element methods (FEMs).

Engineers need many numerical methods to model the behavior of engineering structures, especially when the stresses in them are complex [31,32]. For example, in the current study, shear stresses interact with flexure in addition to torsion.

There are few experimental studies that investigate the behavior and load capacity of horizontally curved box bridges. The current research provides experimental results that are currently useful in addition to being data for future studies to develop the analysis and design of box bridges. By reviewing previous studies, it becomes clear that the behavior of horizontally curved box bridges is complex and, therefore, requires a complex analysis process. Consequently, the authors tried to resort to a simpler process that designers can use owing to its simplicity, time-saving, and safety at the same time.

2 Significance of the study

The current study aims to determine the experimental behavior of continuous box girder bridges under the influence of horizontal curvature by comparison with a straight specimen. More parameters of the curved model were studied numerically using the ABAQUS software, including the span-to-depth ratio (L/h), the compressive strength of the concrete, and the stirrups steel reinforcement. Because of the complexities in the stresses that curved box girders are exposed to, the authors suggested modifying the STM and sectional methods by subtracting the shear values resulting from the torque in order to be more realistic in dealing with such members.

3 Experimental program

Two reinforced concrete continuous box girders, straight (SB) and curved (CB) specimens, were tested under a concentrated mid-span load, as shown in Figures 1 and 2. The total length (L) is 2 m along the longitudinal centerline with different length-to-radius of curvature (L/R) ratios of ∞ and 1.7 for straight and curved specimens, respectively. Height is 200 mm, web width is 50 mm, and total width is 300 mm. The curved specimen’s radius of curvature is 1,000 mm. The flexural reinforcing steel at the top and bottom is 5Ø12 mm and 3Ø12 mm, respectively, while the shear reinforcing steel is Ø6 mm@90 mm. A pressed cork was used to form the box void along the specimens. After preparing the reinforcing steel cages and placing the cork inside them, they were placed in molds and poured, as shown in Figure 3.

Figure 1 Reinforcement details of the SB specimen; all dimensions are in mm.
Figure 1

Reinforcement details of the SB specimen; all dimensions are in mm.

Figure 2 Reinforcement details of the CB specimen; all dimensions are in mm.
Figure 2

Reinforcement details of the CB specimen; all dimensions are in mm.

Figure 3 The reinforcing cages in molds: (a) SB specimen and (b) CB specimen.
Figure 3

The reinforcing cages in molds: (a) SB specimen and (b) CB specimen.

3.1 Material properties

Ordinary Portland cement type I was used in the construction of the box girders. Mixed materials included crushed gravel with a maximum particle size of 12 mm, as shown in Table 1. Graded natural sand with a specific gravity of 2.6, sulfate content of 0.08%, and absorption of 0.7% was used, and the sieve analysis is shown in Table 2. Deformed steel bars of diameter 12 mm were used as flexural top and bottom reinforcements. Deformed steel bars of a diameter 6 mm were used for the shear reinforcement. To determine the actual yielding strength (f y) of the used steel reinforcement, experimental testing was conducted (Table 3). According to test findings, the flexural and shear steel that were utilized complied with ASTM A615/A615M-05 [33] and ASTM A496-02 [34] standards, respectively.

Table 1

Grading of the coarse aggregate

Sieve size (mm) %Passing Iraqi specification No. 45/1984 [38]
12.5 100 90–100
10 83 50–85
4.75 0.51 0–10
Pan Zero Zero
Table 2

Grading of the fine aggregate*

Sieve size Passing% Iraqi specification No. 45/1984 for zone(2) [38]
4.75 mm 95 90–100
2.7 mm 82.3 75–100
1.18 mm 67 55–90
600 μ m 49.23 35–59
300 μ m 17.05 8–30
150 μ m 0.924 0–10
Pan Zero Zero

*Grading analysis was conducted at the Structural Laboratory of the College of Engineering\University of Technology.

Table 3

Mechanical properties of reinforcing steel bars*

Type of used bars Nominal bar diameter (mm) Measured bar diameter (mm) Yield stress (MPa) Ultimate stress (MPa)
Flexural reinforcement 12 12.97 575 625
Shear reinforcement 6 5.95 480 530

*Steel bars were tested at the Laboratory of Structural Engineering at the College of Engineering\University of Technology.

Six 150 mm × 300 mm standard cylinders were cast to accompany the casting of the two box girder specimens. As per ASTM C496-96 [35], three cylinders were cast to measure splitting tensile strength ( f ct ), while the remaining three were cast to evaluate concrete compressive strength (f′ c) as per ASTM C39M-03 [36]. In accordance with ASTM C78-02 [37], three 500 mm × 100 mm × 100 mm prisms were cast to evaluate the concrete’s modulus of rupture ( f r ). Both specimens were demolded around 24 h after casting. They were then continuously covered with damp, thick canvas for 28 days to cure. After that, the box girders were painted white to make it easier to see the cracks. Cement, fine aggregates, and coarse aggregates were utilized in this study in the ratios of 1:1.86:1.95 (Table 4).

Table 4

Mix proportions of concrete

Cement content (kg/m3) Sand content (kg/m3) Gravel content (kg/m3) Water (kg/m3) Water/cement ratio (w/c) Cylinder compressive strength, f′c (MPa) Splitting tensile strength, f ct (MPa)
400 740 780 240 0.60 25 2.47

3.2 Test setup and instrumentation

The strain values in the concrete and steel bars were measured in each box girder using strain gauges. For both specimens, strains were measured using PFL-30-11-3LJC-F and FLAB-6-11-3LJC-F for concrete and steel, respectively. The strain gauge is a wire-type of size 30 mm × 2.3 mm for concrete and 6 mm × 2.3 mm for steel reinforcement with a resistance of 118.5 ± 0.5 Ω and a gauge factor of 2.08 ± 1%.

Flexural steel strain gauges were placed in the zones of maximum positive moment (at the loading point in the lower flange reinforcement) and maximum negative moment (at the middle support zone in the upper flange reinforcement), in addition to shear steel strain gauges in the inner span part (between the load and the middle support) on both webs. Concrete strain gauges were placed in the compression zone (near loading points) to measure the compression produced by the flexural stresses in the upper flange.

Deflection values were measured using two linear voltage displacement transducers at the midspan inner and outer sides of the tested specimens. Vertical loading was applied to each specimen using a 2,000 kN hydraulic universal testing machine (AVERY), as shown in Figure 4. Each specimen rested on three equally spaced supports, forming two spans, each of which was subjected to one central load. To test the curved specimen, a special frame was fabricated to ensure that it was tested in the same way as the straight specimen. This frame was used because the supports of the curved specimen do not lie in one straight line. Therefore, two I-section steel beams were welded at an angle of 125° to form an appropriate steel supporting frame. This frame was strengthened with stiffeners in the load application zones, as shown in Figure 4. Bearing plates of 430 mm × 60 mm × 20 mm and 300 mm × 60 mm × 20 mm were used at loading and supporting points, respectively. The load was recorded using an electronic load cell until failure.

Figure 4 Test setup of specimens. (a) Experimental test setup and (b) numerical load and boundary conditions.
Figure 4

Test setup of specimens. (a) Experimental test setup and (b) numerical load and boundary conditions.

4 Finite element modeling

The experimental specimens were modeled using ABAQUS software, where the experimental properties of concrete and reinforcing steel were adopted and represented in the software, as shown in Figure 5. Concrete damage plasticity (CDP) was adopted for the concrete to study cracks and the failure criterion, as shown in Table 5. A 3D solid element (C3D8R) was also adopted to represent the concrete, load, and support plates. A linear 3D truss element with two nodes and three degrees of freedom (T3D2) was used to represent the steel bars. To make the concrete and steel bars work together, they are bonded using an embedding technique. The load and support plates were connected using typical hard contact behavior with tangential behavior between the two surfaces, with a friction value of 0.35. On the top surface of the steel loading plates, the load is applied as a pressure load, as shown in Figure 4(b). The edge support plates were constrained in the x and y directions (i.e., U x = U y = 0), whereas the center support was treated as a hinge support (U x = U y = U z = 0) to replicate the displacement boundary conditions. Several attempts were made to obtain a mesh, as shown in Table 6, that provides accuracy and speed in analysis using a size of 30 mm, as shown in Table 7.

Figure 5 Material properties for concrete and steel. (a) Relationship of stress–strain in compression and tension for concrete and (b) relationship of stress–inelastic strain in steel reinforcement.
Figure 5

Material properties for concrete and steel. (a) Relationship of stress–strain in compression and tension for concrete and (b) relationship of stress–inelastic strain in steel reinforcement.

Table 5

CDP parameters

Dilation angle (deg) Eccentricity f b0/f c0 k Viscosity
49 0.1 1.16 0.667 0.001
Table 6

Results of the convergence study

Mesh size (mm) Deflection of the CB specimen (mm)
40 8.24
35 9.05
30 10.55
25 10.62
Table 7

Total number of nodes and elements in the ABAQUS model

Component No. of elements No. of nodes
Concrete 4,615 6,680
Steel plates 116 375
Reinforcement 1,869 1,885

5 Experimental and numerical results

Both box girders were tested under incremental static monatomic loads up to the failure point, as shown in Figures 6 and 7. Cracking load, failure load, midspan deflection, and strain values were studied in both concrete and reinforcing steel.

Figure 6 SB specimen after the test.
Figure 6

SB specimen after the test.

Figure 7 CB specimen after the test.
Figure 7

CB specimen after the test.

5.1 General behavior and crack patterns

The experimental test results for the box girder specimens are shown in Table 8, while Figure 8 shows the values of the flexural and diagonal cracking loads. Flexural cracks appeared vertically and gradually developed at the beginning of loading, but their development decreased when diagonal cracks appeared. By increasing the load, several diagonal cracks appeared between the loading and supporting points at an angle of 45°. In the straight specimen, at about 10% of the experimental load capacity (P), the positive flexural cracks appeared in the middle of the span first, while in the curved specimen, they appeared at 8%P in the inner side. The negative flexural cracks appeared at the middle support at 24%P in the straight specimen and 28%P in the curved specimen. In general, flexural cracks appeared with approximately similar values in both specimens. On the other hand, in the straight specimen, the first diagonal cracking load was 37%P, while in the curved specimen, it was 22%P due to the curvature, i.e., a decrease of 47%.

Table 8

Test results of the specimens

Specimen P cr ‒ fl ex , Pos . (kN) P cr ‒ diag . (kN) P cr ‒ flex , Neg . (kN) P ( kN ) P FE ( kN ) P cr ‒ flex , Pos . / P (%) P cr ‒ diag . / P (%) P cr ‒ flex Neg . / P (%) P FE / P Δ cr ‒ diag . (mm) Δ inner (mm) Δ outer (mm)
SB 40 150 100 404 416 9.9 37.1 24.8 1.03 4.99 10.87 10.87
CB 30 80 100 359 355 8.4 22.3 27.9 0.99 2.69 8.61 11.47
Figure 8 Flexural cracking, diagonal cracking, and ultimate loads.
Figure 8

Flexural cracking, diagonal cracking, and ultimate loads.

The number of diagonal cracks was almost equal in the two webs of the straight specimen, while in the curved specimen, the number of cracks on the outer side was more than on the inner side. This occurred because, in the curved specimen, the shear span is shorter on the inner side compared to the outer side. By increasing the loading, the width of the diagonal cracks increased on both webs between the loading point and the middle support, and failure occurred as a result.

The straight specimen failed by shear, while the curved specimen failed by torsional shear. As a result of the presence of torsional moments in the curved specimen, a concrete cover separation occurred upon failure; more specifically, one side of the crack was displaced outward relative to the other. The curved specimen load capacity decreased by 11% compared to the straight specimen due to the effect of torsional moments.

The FEM results showed consistency with the experimental results in terms of crack appearance, development, and distribution, in addition to the failure zone. This makes the FEM an effective way to accurately follow the development of cracks and reveal the most critical zones where failure occurs.

5.2 Load–deflection behavior

Through the response of the load–deflection, it was possible to determine the behavior of the specimens during the various stages of loading (Figures 9 and 10). In the straight specimen, the deflection increased at the beginning of loading as a result of the flexural stresses that caused the flexural cracks. With more loading, diagonal cracks appeared, the deflection increases slowed down, and the load–deflection response became less curved, which indicates shear predominance. About failure, the deflection increased significantly, and the curve became more bent. This occurred because the concrete failed to bear the shear stresses, so those stresses were transferred to the reinforcing steel.

Figure 9 Load–deflection for SB.
Figure 9

Load–deflection for SB.

Figure 10 Load–deflection for CB.
Figure 10

Load–deflection for CB.

In the curved specimen, at the beginning of loading, the deflection increased on both the inner and outer sides as a result of the bending moments. By increasing the loading, the deflection decreased due to the appearance of shear cracks, i.e., the distribution of stresses along the span. With more loading, the deflection on the outer side was superior to the inner one due to the effect of torsional moments that caused additional compression and twisting angle, as shown in Figure 11. After the appearance of more cracks, the curvature of the load–deflection response increased due to the increased role of steel, which is more ductile than concrete.

Figure 11 Torsional moment–twisting angle for CB.
Figure 11

Torsional moment–twisting angle for CB.

The ultimate deflection increased in the curved specimen by 6% on the outer side while decreasing by 21% on the inner side compared to the straight specimen. It is worth mentioning that there was a sudden increase in deflection at about 75%P due to the development of torsional cracks.

By comparing the load–deflection behavior of both the straight and curved specimens to the results of the finite elements, it becomes clear that there is an agreement between them. This indicates the possibility of representing this type of structure using finite elements efficiently. The results of the finite elements showed the difference in deflection between the outer and inner sides with good accuracy.

5.3 Average concrete surface and steel reinforcement strain values

Concrete strain gauges were installed at the top flanges (c, co, and ci) (Figures 12 and 13). In the same way, steel strain gauges were installed on shear and flexural reinforcement (So and Si) and (M + o, M + i, M-o, and M-i), respectively (Figures 14 and 15).

Figure 12 Applied load versus average concrete compressive surface strains for the straight box girder SB.
Figure 12

Applied load versus average concrete compressive surface strains for the straight box girder SB.

Figure 13 Applied load versus average concrete compressive surface strains for the curved box girder CB.
Figure 13

Applied load versus average concrete compressive surface strains for the curved box girder CB.

Figure 14 Applied load versus steel strain for the straight box girder SB.
Figure 14

Applied load versus steel strain for the straight box girder SB.

Figure 15 Applied load versus steel strain for the curved box girder CB.
Figure 15

Applied load versus steel strain for the curved box girder CB.

Before the cracks appeared, the steel strain did not give any noticeable readings, while the concrete strain gave few readings. This is because, at the beginning of loading, the concrete works to resist the applied stresses almost on its own. Once cracks appear, almost all the stresses are transferred to the steel reinforcement. In other words, once cracks occur, there is a sudden increase in the strain of the steel and concrete. After the appearance of cracks, the increase in strain continues in an almost linear manner because the steel is in the elastic stage. The increase in concrete strain also occurs in a non-linear manner resulting from the non-linear behavior of the concrete. Near failure, greater increases in the strain of the steel occur because the elastic stage exceeds and moves to the plastic stage, resulting in failure.

From the results of the concrete strain readings, it was found that the compressive stresses in the curved specimen were greater than those in the straight specimen, although both specimens did not reach the maximum concrete strain (0.003). That is, the failure did not occur due to the compression resulting from the flexure. On the other hand, the flexural reinforcement did not reach the yield, i.e., the flexural cracks did not develop to cause failure. Through the strain readings of the flexural reinforcement, it was found that the positive moments were higher than the negative ones.

In general, the readings of strain, whether concrete or reinforcing steel, were superior in the curved specimen over the straight one. This makes sense because torsional moments affect bending moments. The shear steel strain reached the yield, which means that the failure was shear in both specimens. It is worth mentioning that the yield strain ( ε yield ) of Ø6mm bas is 2,400 με and ε yield of the Ø12mm bar is 2,875 με.

6 Finite element parametric study

Variables, including the changing span/depth ratio, compressive strength, and stirrups steel ratio, were studied using ABAQUA software, as shown in Table 9. The failure load and maximum deflection were investigated by comparing them with the reference curved specimen to determine the effect of each variable, as shown in Table 10. The load–deflection behavior was also studied due to the change in every variable.

Table 9

A parametric study using finite element analysis

No. Specimen Parameter L/h f′c Steel ratio
1 CBF Reference 4.25 25 0.0063
2 CBF250 Effect of span/depth 3.40
3 CBF300 2.83
4 CBF30 Effect of concrete strength (f′c) 200 30
5 CBF35 35
6 CBF0.011 Effect of steel ratio 25 0.011
7 CBF0.017 0.017
Table 10

Results of finite element analysis

No. Specimen P FE %Variation in load Δ FE %Variation in deflection
1 CBF 355 — 10.55 —
2 CBF250 409 15.21 10.27 −2.65
3 CBF300 548 54.37 9.79 −7.20
4 CBF30 404 13.80 10.30 −2.37
5 CBF35 424 19.44 9.74 −7.68
6 CBF0.011 413 16.34 10.59 0.38
7 CBF0.017 449 26.48 10.76 1.99

6.1 Effect of span/depth

The effect of the span-to-depth ratio is important because it affects bending, torsional, and shear moments. Its decrease leads to an increase in the resistance of the section. For example, increasing the height greatly increases the bending resistance, making shear failure more likely. The lower the percentage with increasing height, the greater the load capacity and greater the stiffness, as shown in Figure 16. The reason for this is that the decrease in the L/h ratio causes the structure to behave like a deep beam in which stresses are transferred directly from the load to the support zones. By increasing the height by 25 and 50%, the load capacity increased by 15 and 54%, respectively, while the deflection decreased by 2.7 and 7.2%, respectively. The behavior did not differ much because all of the specimens failed by shear, that is, shear failure with relatively little deflection.

Figure 16 Effect of span to depth ratio.
Figure 16

Effect of span to depth ratio.

6.2 Effect of concrete strength

Concrete compressive strength values of 25, 30, and 35 MPa were chosen for the current study. Changes in the concrete’s compressive strength at the start of the load application had less effect on the behavior; however, as additional load was applied, there was an increase in stiffness and load capacity, as shown in Figure 17. Concrete’s ductility decreased and it grew more brittle as its compressive strength increased. There was an approximate 20 and 40% increase in the concrete’s compressive strength, an increase in its load capacity by about 14 and 19%, respectively, and a decrease of about 2.4 and 7.7% in its deflection, respectively.

Figure 17 Effect of the concrete compressive strength.
Figure 17

Effect of the concrete compressive strength.

6.3 Effect of steel ratio

The stirrups reinforcement ratio was increased by increasing the diameter of the bars from 6 to 8 mm and then to 10 mm while fixing the spacing between them. By increasing the stirrups reinforcement ratio, the load capacity and stiffness increased because the shear forces produce tensile forces that the reinforcement steel resists, as shown in Figure 18. On the other hand, the large increase in the stirrups reinforcement ratio has little impact because the shear forces are exerted on the concrete. Since concrete resistance is relatively low and the resistance of steel is high, failure occurs in the concrete. By increasing the stirrups reinforcement ratio by 75 and 170%, the load capacity increased by 16 and 26%, respectively, while the deflection increased by 0.38 and 2%, respectively. The increase in deflection results from the contribution of the reinforcement steel as a more ductile material.

Figure 18 Effect of steel ratio.
Figure 18

Effect of steel ratio.

7 Discussion of the results

The most notable difference between the straight and curved specimens is the difference in the behavior of the outer side from the inner one in the curved specimen. This difference did not occur in the straight specimen. This difference results from the torsional moments and the difference in the lengths of the span between the outer and inner sides. Torsion moments lead to a difference between the two webs, which results in the generation of a twist angle.

The general behavior of both specimens did not differ much because both failed in shear. In the load–deflection response, linear behavior dominated in most stages of loading except for the beginning and end of the load application. The appearance and development of cracks occurred in the zones between the loading and supporting points at an angle of 45°. The failure occurred in one of these cracks, specifically between the loading point and the middle support. It turns out that this zone is more subjected to stresses than the zone between the loading point and the end support, despite the presence of cracks. The reason for this is the presence of two adjacent spans, which together contributed to an increase in the concentration of stresses coming from each of them to the middle support; in addition, this specimen continuity caused a decrease in the deflection values.

In deep beams, stresses tend to pass directly between loading and supporting points [39,40,41], while in shallow beams, this is not possible because the distance between loading and supporting points is large, so a multi-panel truss is formed. The importance of the flexural reinforcing steel is highlighted in resisting the tensile forces resulting in the tie, as well as the role of the shear reinforcement in resisting the perpendicular tensile forces on the inclined struts. The shear reinforcement restricts the development of cracks, reduces their width, and makes the failure more ductile. The difference in load capacity between the straight and curved specimens resulted from the effect of torsional moments. These torsional moments cause shear forces that increase the shear forces on the outer side and decrease them on the inner side (Figure 19). The reason for this is that, on the outer side of the girder, the conventional shear forces are combined with the shear forces caused by the torque because they are in the same direction, while on the inner side, they are in opposite directions, so they are subtracted from each other. The effect of torsional moments is not limited to shear but also affects bending moments, as indicated by the strain readings in concrete and reinforcing steel. Despite the decrease in load capacity in the curved specimen compared to the straight one, the strain readings were superior in the curved specimen. This is due to the fact that the horizontal component of the inclined struts resulting from the torsional moments affects the flexural stresses.

Figure 19 Shear stresses in curved box girders.
Figure 19

Shear stresses in curved box girders.

8 A proposed mathematical model

It is a reasonable assumption that the diagonal tension’s intensity can be determined by measuring the vertical shear’s intensity. Therefore, the diagonal tension stresses are what we actually mean when we use the term “shear.” Concrete buildings must be designed for shear since the material’s strength in tension is much less than that of compression. Owing to the complex shear resistance mechanism found in reinforced concrete beams, many codes provide an empirical equation between the fundamental ideas derived from comprehensive test data.

According to the propagation of the cracks at an angle of 45°, which were distributed along the shear span between the loading and the supporting points, it is seen that the behavior of the curved specimen takes the form of a truss. More specifically, the load is transmitted to the support by several struts in sequence according to the length of the shear span (Figure 20). Each strut resists the compression forces applied to it. As a result of these applied compression forces, perpendicular tension occurs on the strut, forming a bottle-shaped strut. In addition to that, at the nodes, the inclined strut axial force has two components: the vertical one is resisted by the concrete, while the horizontal one forms a longitudinal tensile force that is resisted by flexural reinforcement.

Figure 20 Strut and tie model for specimens.
Figure 20

Strut and tie model for specimens.

A truss is formed that represents the transition of stresses inside the specimens, which can also explain the shearing behavior [42,43]. Accordingly, the STM theory was used here to find the theoretical load capacity for the straight and curved specimens. The following steps are adopted here to find the load capacity:

  1. The dimensions of the strut are found by finding the dimensions of the nodes (Figure 20). The perpendicular face of the node (w t) represents twice the distance between the flexural reinforcement center and the end of the concrete cover. The horizontal face of the node represents the width of the support or the width of the loading plate, while the inclined face represents the section of the strut.

    (1) w t = 2 × ( h − d ) ,

    (2) jd = h − 0.5 × w t − 0.5 × w t ,

    where jd is the lever arm, which represents the distance between flexure negative and positive reinforcement

    (3) θ = tan − 1 j d a ,

    where θ is the angle of the strut with the horizon:

    (4) Strut width ( w s ) = L b × sin θ + w t × cos θ .

  2. Finding shear force at the nodal zone, CCT:

    (5) β n = 0.8 , f ce = 0.85 β n × f ′ c ,

    (6) Capacity of the vertical face of node , V n , A 1 = f c e × L b × b ,

    (7) Capacity of the horizontal face of node , V n , A 2 = f ce × w t × b × tan θ ,

    (8) Capacity of the inclined face of node , V n , A 3 = f ce × w s × b w × sin θ .

  3. Finding shear force at Strut AB, interior strut.

    (9) f ce = 0.85 β s × f ′ c .

    According to the provisions of the ACI 318-19 code, β s is a value for converting the compression stresses in the strut into normal tension. β s is 0.75 if the strut is adequately reinforced. A reinforcing steel ratio of 0.0025/sin2 θ was allocated in the case of vertical reinforcement only.

    (10) V n , A B = f ce × w s × b w × sin θ .

  4. Finding shear force at Tie AD.

(11) F n , AC = A s f y ,

(12) V n , AC = F n , AC × tan θ ,

(13) V n = min ( V n , A 1 ; V n , A 2 ; V n , A 3 ; V n , AB ; V n , AC ) .

It is possible to find the shear strength using the sectional method according to the ACI 318-19 code for both concrete and reinforcement, as follows:

(14) V s = A v f yv d S ,

(15) V c = 1 6 f ′ c b w d ,

(16) V n = V s + V c .

The sectional method, according to the CEB-FIB code [44], contains more details than the ACI code, as shown in the following equations:

(17) V s = A v f yv jd S ,

(18) V c = k v f ′ c γ c b w jd , where γ c = 1.5

(19) k v = 0.4 1 + 1 , 500 ε x × 1 , 300 1 , 000 + k dg jd ,

(20) k d g = 32 16 + d g ,

where d g is the specified maximum size of the aggregate

(21) V n = V s + V c .

Comparing the load capacity according to the ACI and CEB-FIB codes, it is clear that the CEB-FIB method is more conservative than the ACI method. The load capacity according to the CEB-FIB method is 23–27% lower than the load capacity according to the ACI method.

As discussed earlier, in the curved specimen, in addition to the shear resulting from the shear forces, there is also shear resulting from the torsional moments [45,46,47,48]. Torsional moments form another strut with an angle of 45° (Figure 20). These torsional struts are not in the same direction on the opposite web. In each strut, the formed tensile forces cause the formation of torsional cracks. According to ACI 318-19, cracking is assumed to occur when the principal tensile stress reaches 0.33. Since the tension that causes cracks reduces the load capacity, the shear resulting from the torque can be subtracted from the conventional shear of sectional and STM methods, as follows:

(22) α = 26.565 degree,

(23) V t = 0.33 f ′ c b w s sin θ tan α ,

(24) V t = 2 × 0.33 f ′ c b w s sin θ ,

(25) then the nominal strut strength is P / 4 = V prop . = V n − V t .

For the curved specimen, two mathematical models were proposed here. The idea is to subtract torsional shear from the sectional and STM method calculations. The differences between the proposed models and the experimental load capacities were 43 and 22%, respectively (Table 11). As for the straight specimen, both the sectional and STM methods were used as they are, i.e., without any development; therefore, the differences were 31 and 13% compared with the experimental tests.

Table 11

Verification of the box girder specimens

Specimens P (kN) P FE (kN) P Sec.,ACI (kN) P Sec.,CEB-FIB (kN) P STM (kN) P torsion (kN) P prop.,Sec.ACI (kN) P prop.,Sec.CEB−FIB (kN) P prop.,STM (kN) P/P prop.,Sec.ACI P/P prop.,Sec.CEB−FIB P/P prop.,STM
SB 404 416 278 212 350.6 — 278 212 350.6 1.45 1.91 1.15
CB 359 355 72.6 205.4 139 278 1.75 2.58 1.29
CB1 [49] 407 372 563 412 466 76 487 336 390 0.83 1.21 1.04

The proposed model was applied to the results of a previous study [49] of a horizontally curved model in the shape of a semicircle with a radius of 1.15 m. The specimen has a cross-sectional measurement total depth of 250 mm, width of 250 mm, and top flange width of 360 mm. Every beam’s end protruded 50 mm past the centerlines of the support. At a 45° angle, two-point loads were applied to these beams in the middle of each span. There were deformed steel reinforcement bars measuring 6 mm × 12 mm for the top negative moment regions, 4 mm × 10 mm for the bottom positive moment regions, and 6 × 10 + 2 Ø 8 mm for longitudinal torsion reinforcement with a 20 mm clear cover. Throughout the length of the beam for each span, the closed stirrups of Ø8 mm reinforcing bar were positioned 90 mm center to center from angle (0) to angle (40°) and 45 mm center to center from angle (40°) to angle (90°). By comparing the experimental results of the study with the theoretical analysis using the proposed model, it becomes clear that there is agreement between them.

9 Conclusions

The current research work included the study of two box girder specimens, one of which is straight and the other horizontally curved, in terms of cracks, midspan deflection, strain values, and load capacity. The two specimens were numerically modeled using the finite element ABAQUS software for the purpose of verifying the numerical model to study more variables, including changing span/depth ratio, compressive strength, and stirrups steel ratio. For the curved specimen, the current study includes proposing two mathematical models based on subtracting torsional effects mathematically from both STM and sectional methods. Accordingly, the following conclusions were reached:

  1. The experimental and numerical load capacity in the curved specimen decreased by 11 and 15%, respectively, compared to the straight specimen due to the effect of torsional moments. The midspan deflection increased in the curved specimen by 6% on the outer side and decreased by 21% on the inner side compared to the straight specimen. More specifically, the torsional moments add shear to the outer side and subtract shear from the inner side.

  2. Good results were obtained when comparing numerical modeling with experimental results, which makes numerical modeling effective with less time, effort, and cost. Increasing the height, compressive strength, and steel reinforcement ratio of stirrups led to an increase in load capacity and stiffness.

  3. Comparing the sectional load capacity according to the ACI code and the CEB-FIB code, it is clear that the CEB-FIB method is more conservative than the ACI method. The CEB-FIB load capacity is 23–27% lower than the ACI load capacity.

  4. The proposed model calculations using the sectional ACI, CEB-FIB, and STM methods are intended to subtract torsional capacity from them. The differences were 43, 61, and 22% between the proposed models and the experimental load capabilities in the curved specimen according to the sectional ACI, CEB-FIB, and STM methods, respectively. For the straight specimen, the sectional ACI, CEB-FIB, and STM methods were used just as they are, that is, without any development. Therefore, the differences from the experimental testing were 31, 48, and 13%, respectively.

  5. The presence of horizontal curvature generates torsional moments, which seem to produce additional shear forces (the effect of which is significant). This requires care in their analysis and design, as it is recommended to add additional horizontal and vertical shear reinforcement to resist them.

Acknowledgements

The authors appreciate the College of Engineering at the University of Technology’s Civil Engineering Department team for their great moral support.

  1. Funding information: The authors state no funding involved.

  2. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and consented to its submission to the journal, reviewed all the results, and approved the final version of the manuscript. AAD: conceptualization, methodology, formal analysis, investigation, resources, writing of original draft, and editing, and correspondence. KSA-R: formal analysis, investigation, supervision, review, and editing. WSA: investigation, supervision, and review.

  3. Conflict of interest: The authors state no conflict of interest.

  4. Data availability statement: Some or all data, models, or codes generated or used during the study are available from the corresponding author by request.

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Received: 2024-04-20
Revised: 2024-08-03
Accepted: 2024-08-29
Published Online: 2024-09-30

© 2024 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  106. Effect of internal and external recycle ratios on the nutrient removal efficiency of anaerobic/anoxic/oxic (VIP) wastewater treatment plant
  107. Enhancing structural behaviour of polypropylene fibre concrete columns longitudinally reinforced with fibreglass bars
  108. Sustainable road paving: Enhancing concrete paver blocks with zeolite-enhanced cement
  109. Evaluation of the operational performance of Karbala waste water treatment plant under variable flow using GPS-X model
  110. Design and simulation of photonic crystal fiber for highly sensitive chemical sensing applications
  111. Optimization and design of a new column sequencing for crude oil distillation at Basrah refinery
  112. Inductive 3D numerical modelling of the tibia bone using MRI to examine von Mises stress and overall deformation
  113. An image encryption method based on modified elliptic curve Diffie-Hellman key exchange protocol and Hill Cipher
  114. Experimental investigation of generating superheated steam using a parabolic dish with a cylindrical cavity receiver: A case study
  115. Effect of surface roughness on the interface behavior of clayey soils
  116. Investigated of the optical properties for SiO2 by using Lorentz model
  117. Measurements of induced vibrations due to steel pipe pile driving in Al-Fao soil: Effect of partial end closure
  118. Experimental and numerical studies of ballistic resistance of hybrid sandwich composite body armor
  119. Evaluation of clay layer presence on shallow foundation settlement in dry sand under an earthquake
  120. Optimal design of mechanical performances of asphalt mixtures comprising nano-clay additives
  121. Advancing seismic performance: Isolators, TMDs, and multi-level strategies in reinforced concrete buildings
  122. Predicted evaporation in Basrah using artificial neural networks
  123. Energy management system for a small town to enhance quality of life
  124. Numerical study on entropy minimization in pipes with helical airfoil and CuO nanoparticle integration
  125. Equations and methodologies of inlet drainage system discharge coefficients: A review
  126. Thermal buckling analysis for hybrid and composite laminated plate by using new displacement function
  127. Investigation into the mechanical and thermal properties of lightweight mortar using commercial beads or recycled expanded polystyrene
  128. Experimental and theoretical analysis of single-jet column and concrete column using double-jet grouting technique applied at Al-Rashdia site
  129. The impact of incorporating waste materials on the mechanical and physical characteristics of tile adhesive materials
  130. Seismic resilience: Innovations in structural engineering for earthquake-prone areas
  131. Automatic human identification using fingerprint images based on Gabor filter and SIFT features fusion
  132. Performance of GRKM-method for solving classes of ordinary and partial differential equations of sixth-orders
  133. Visible light-boosted photodegradation activity of Ag–AgVO3/Zn0.5Mn0.5Fe2O4 supported heterojunctions for effective degradation of organic contaminates
  134. Production of sustainable concrete with treated cement kiln dust and iron slag waste aggregate
  135. Key effects on the structural behavior of fiber-reinforced lightweight concrete-ribbed slabs: A review
  136. A comparative analysis of the energy dissipation efficiency of various piano key weir types
  137. Special Issue: Transport 2022 - Part II
  138. Variability in road surface temperature in urban road network – A case study making use of mobile measurements
  139. Special Issue: BCEE5-2023
  140. Evaluation of reclaimed asphalt mixtures rejuvenated with waste engine oil to resist rutting deformation
  141. Assessment of potential resistance to moisture damage and fatigue cracks of asphalt mixture modified with ground granulated blast furnace slag
  142. Investigating seismic response in adjacent structures: A study on the impact of buildings’ orientation and distance considering soil–structure interaction
  143. Improvement of porosity of mortar using polyethylene glycol pre-polymer-impregnated mortar
  144. Three-dimensional analysis of steel beam-column bolted connections
  145. Assessment of agricultural drought in Iraq employing Landsat and MODIS imagery
  146. Performance evaluation of grouted porous asphalt concrete
  147. Optimization of local modified metakaolin-based geopolymer concrete by Taguchi method
  148. Effect of waste tire products on some characteristics of roller-compacted concrete
  149. Studying the lateral displacement of retaining wall supporting sandy soil under dynamic loads
  150. Seismic performance evaluation of concrete buttress dram (Dynamic linear analysis)
  151. Behavior of soil reinforced with micropiles
  152. Possibility of production high strength lightweight concrete containing organic waste aggregate and recycled steel fibers
  153. An investigation of self-sensing and mechanical properties of smart engineered cementitious composites reinforced with functional materials
  154. Forecasting changes in precipitation and temperatures of a regional watershed in Northern Iraq using LARS-WG model
  155. Experimental investigation of dynamic soil properties for modeling energy-absorbing layers
  156. Numerical investigation of the effect of longitudinal steel reinforcement ratio on the ductility of concrete beams
  157. An experimental study on the tensile properties of reinforced asphalt pavement
  158. Self-sensing behavior of hot asphalt mixture with steel fiber-based additive
  159. Behavior of ultra-high-performance concrete deep beams reinforced by basalt fibers
  160. Optimizing asphalt binder performance with various PET types
  161. Investigation of the hydraulic characteristics and homogeneity of the microstructure of the air voids in the sustainable rigid pavement
  162. Enhanced biogas production from municipal solid waste via digestion with cow manure: A case study
  163. Special Issue: AESMT-7 - Part I
  164. Preparation and investigation of cobalt nanoparticles by laser ablation: Structure, linear, and nonlinear optical properties
  165. Seismic analysis of RC building with plan irregularity in Baghdad/Iraq to obtain the optimal behavior
  166. The effect of urban environment on large-scale path loss model’s main parameters for mmWave 5G mobile network in Iraq
  167. Formatting a questionnaire for the quality control of river bank roads
  168. Vibration suppression of smart composite beam using model predictive controller
  169. Machine learning-based compressive strength estimation in nanomaterial-modified lightweight concrete
  170. In-depth analysis of critical factors affecting Iraqi construction projects performance
  171. Behavior of container berth structure under the influence of environmental and operational loads
  172. Energy absorption and impact response of ballistic resistance laminate
  173. Effect of water-absorbent polymer balls in internal curing on punching shear behavior of bubble slabs
  174. Effect of surface roughness on interface shear strength parameters of sandy soils
  175. Evaluating the interaction for embedded H-steel section in normal concrete under monotonic and repeated loads
  176. Estimation of the settlement of pile head using ANN and multivariate linear regression based on the results of load transfer method
  177. Enhancing communication: Deep learning for Arabic sign language translation
  178. A review of recent studies of both heat pipe and evaporative cooling in passive heat recovery
  179. Effect of nano-silica on the mechanical properties of LWC
  180. An experimental study of some mechanical properties and absorption for polymer-modified cement mortar modified with superplasticizer
  181. Digital beamforming enhancement with LSTM-based deep learning for millimeter wave transmission
  182. Developing an efficient planning process for heritage buildings maintenance in Iraq
  183. Design and optimization of two-stage controller for three-phase multi-converter/multi-machine electric vehicle
  184. Evaluation of microstructure and mechanical properties of Al1050/Al2O3/Gr composite processed by forming operation ECAP
  185. Calculations of mass stopping power and range of protons in organic compounds (CH3OH, CH2O, and CO2) at energy range of 0.01–1,000 MeV
  186. Investigation of in vitro behavior of composite coating hydroxyapatite-nano silver on 316L stainless steel substrate by electrophoretic technic for biomedical tools
  187. A review: Enhancing tribological properties of journal bearings composite materials
  188. Improvements in the randomness and security of digital currency using the photon sponge hash function through Maiorana–McFarland S-box replacement
  189. Design a new scheme for image security using a deep learning technique of hierarchical parameters
  190. Special Issue: ICES 2023
  191. Comparative geotechnical analysis for ultimate bearing capacity of precast concrete piles using cone resistance measurements
  192. Visualizing sustainable rainwater harvesting: A case study of Karbala Province
  193. Geogrid reinforcement for improving bearing capacity and stability of square foundations
  194. Evaluation of the effluent concentrations of Karbala wastewater treatment plant using reliability analysis
  195. Adsorbent made with inexpensive, local resources
  196. Effect of drain pipes on seepage and slope stability through a zoned earth dam
  197. Sediment accumulation in an 8 inch sewer pipe for a sample of various particles obtained from the streets of Karbala city, Iraq
  198. Special Issue: IETAS 2024 - Part I
  199. Analyzing the impact of transfer learning on explanation accuracy in deep learning-based ECG recognition systems
  200. Effect of scale factor on the dynamic response of frame foundations
  201. Improving multi-object detection and tracking with deep learning, DeepSORT, and frame cancellation techniques
  202. The impact of using prestressed CFRP bars on the development of flexural strength
  203. Assessment of surface hardness and impact strength of denture base resins reinforced with silver–titanium dioxide and silver–zirconium dioxide nanoparticles: In vitro study
  204. A data augmentation approach to enhance breast cancer detection using generative adversarial and artificial neural networks
  205. Modification of the 5D Lorenz chaotic map with fuzzy numbers for video encryption in cloud computing
  206. Special Issue: 51st KKBN - Part I
  207. Evaluation of static bending caused damage of glass-fiber composite structure using terahertz inspection
https://doi.org/10.1515/eng-2024-0085
Schlagwörter für diesen Artikel
continuous bridges; curved box girder; reinforced concrete; shear; strut-and-tie model; torsion
Creative Commons
BY 4.0

Artikel in diesem Heft

  1. Regular Articles
  2. Methodology of automated quality management
  3. Influence of vibratory conveyor design parameters on the trough motion and the self-synchronization of inertial vibrators
  4. Application of finite element method in industrial design, example of an electric motorcycle design project
  5. Correlative evaluation of the corrosion resilience and passivation properties of zinc and aluminum alloys in neutral chloride and acid-chloride solutions
  6. Will COVID “encourage” B2B and data exchange engineering in logistic firms?
  7. Influence of unsupported sleepers on flange climb derailment of two freight wagons
  8. A hybrid detection algorithm for 5G OTFS waveform for 64 and 256 QAM with Rayleigh and Rician channels
  9. Effect of short heat treatment on mechanical properties and shape memory properties of Cu–Al–Ni shape memory alloy
  10. Exploring the potential of ammonia and hydrogen as alternative fuels for transportation
  11. Impact of insulation on energy consumption and CO2 emissions in high-rise commercial buildings at various climate zones
  12. Advanced autopilot design with extremum-seeking control for aircraft control
  13. Adaptive multidimensional trust-based recommendation model for peer to peer applications
  14. Effects of CFRP sheets on the flexural behavior of high-strength concrete beam
  15. Enhancing urban sustainability through industrial synergy: A multidisciplinary framework for integrating sustainable industrial practices within urban settings – The case of Hamadan industrial city
  16. Advanced vibrant controller results of an energetic framework structure
  17. Application of the Taguchi method and RSM for process parameter optimization in AWSJ machining of CFRP composite-based orthopedic implants
  18. Improved correlation of soil modulus with SPT N values
  19. Technologies for high-temperature batch annealing of grain-oriented electrical steel: An overview
  20. Assessing the need for the adoption of digitalization in Indian small and medium enterprises
  21. A non-ideal hybridization issue for vertical TFET-based dielectric-modulated biosensor
  22. Optimizing data retrieval for enhanced data integrity verification in cloud environments
  23. Performance analysis of nonlinear crosstalk of WDM systems using modulation schemes criteria
  24. Nonlinear finite-element analysis of RC beams with various opening near supports
  25. Thermal analysis of Fe3O4–Cu/water over a cone: a fractional Maxwell model
  26. Radial–axial runner blade design using the coordinate slice technique
  27. Theoretical and experimental comparison between straight and curved continuous box girders
  28. Effect of the reinforcement ratio on the mechanical behaviour of textile-reinforced concrete composite: Experiment and numerical modeling
  29. Experimental and numerical investigation on composite beam–column joint connection behavior using different types of connection schemes
  30. Enhanced performance and robustness in anti-lock brake systems using barrier function-based integral sliding mode control
  31. Evaluation of the creep strength of samples produced by fused deposition modeling
  32. A combined feedforward-feedback controller design for nonlinear systems
  33. Effect of adjacent structures on footing settlement for different multi-building arrangements
  34. Analyzing the impact of curved tracks on wheel flange thickness reduction in railway systems
  35. Review Articles
  36. Mechanical and smart properties of cement nanocomposites containing nanomaterials: A brief review
  37. Applications of nanotechnology and nanoproduction techniques
  38. Relationship between indoor environmental quality and guests’ comfort and satisfaction at green hotels: A comprehensive review
  39. Communication
  40. Techniques to mitigate the admission of radon inside buildings
  41. Erratum
  42. Erratum to “Effect of short heat treatment on mechanical properties and shape memory properties of Cu–Al–Ni shape memory alloy”
  43. Special Issue: AESMT-3 - Part II
  44. Integrated fuzzy logic and multicriteria decision model methods for selecting suitable sites for wastewater treatment plant: A case study in the center of Basrah, Iraq
  45. Physical and mechanical response of porous metals composites with nano-natural additives
  46. Special Issue: AESMT-4 - Part II
  47. New recycling method of lubricant oil and the effect on the viscosity and viscous shear as an environmentally friendly
  48. Identify the effect of Fe2O3 nanoparticles on mechanical and microstructural characteristics of aluminum matrix composite produced by powder metallurgy technique
  49. Static behavior of piled raft foundation in clay
  50. Ultra-low-power CMOS ring oscillator with minimum power consumption of 2.9 pW using low-voltage biasing technique
  51. Using ANN for well type identifying and increasing production from Sa’di formation of Halfaya oil field – Iraq
  52. Optimizing the performance of concrete tiles using nano-papyrus and carbon fibers
  53. Special Issue: AESMT-5 - Part II
  54. Comparative the effect of distribution transformer coil shape on electromagnetic forces and their distribution using the FEM
  55. The complex of Weyl module in free characteristic in the event of a partition (7,5,3)
  56. Restrained captive domination number
  57. Experimental study of improving hot mix asphalt reinforced with carbon fibers
  58. Asphalt binder modified with recycled tyre rubber
  59. Thermal performance of radiant floor cooling with phase change material for energy-efficient buildings
  60. Surveying the prediction of risks in cryptocurrency investments using recurrent neural networks
  61. A deep reinforcement learning framework to modify LQR for an active vibration control applied to 2D building models
  62. Evaluation of mechanically stabilized earth retaining walls for different soil–structure interaction methods: A review
  63. Assessment of heat transfer in a triangular duct with different configurations of ribs using computational fluid dynamics
  64. Sulfate removal from wastewater by using waste material as an adsorbent
  65. Experimental investigation on strengthening lap joints subjected to bending in glulam timber beams using CFRP sheets
  66. A study of the vibrations of a rotor bearing suspended by a hybrid spring system of shape memory alloys
  67. Stability analysis of Hub dam under rapid drawdown
  68. Developing ANFIS-FMEA model for assessment and prioritization of potential trouble factors in Iraqi building projects
  69. Numerical and experimental comparison study of piled raft foundation
  70. Effect of asphalt modified with waste engine oil on the durability properties of hot asphalt mixtures with reclaimed asphalt pavement
  71. Hydraulic model for flood inundation in Diyala River Basin using HEC-RAS, PMP, and neural network
  72. Numerical study on discharge capacity of piano key side weir with various ratios of the crest length to the width
  73. The optimal allocation of thyristor-controlled series compensators for enhancement HVAC transmission lines Iraqi super grid by using seeker optimization algorithm
  74. Numerical and experimental study of the impact on aerodynamic characteristics of the NACA0012 airfoil
  75. Effect of nano-TiO2 on physical and rheological properties of asphalt cement
  76. Performance evolution of novel palm leaf powder used for enhancing hot mix asphalt
  77. Performance analysis, evaluation, and improvement of selected unsignalized intersection using SIDRA software – Case study
  78. Flexural behavior of RC beams externally reinforced with CFRP composites using various strategies
  79. Influence of fiber types on the properties of the artificial cold-bonded lightweight aggregates
  80. Experimental investigation of RC beams strengthened with externally bonded BFRP composites
  81. Generalized RKM methods for solving fifth-order quasi-linear fractional partial differential equation
  82. An experimental and numerical study investigating sediment transport position in the bed of sewer pipes in Karbala
  83. Role of individual component failure in the performance of a 1-out-of-3 cold standby system: A Markov model approach
  84. Implementation for the cases (5, 4) and (5, 4)/(2, 0)
  85. Center group actions and related concepts
  86. Experimental investigation of the effect of horizontal construction joints on the behavior of deep beams
  87. Deletion of a vertex in even sum domination
  88. Deep learning techniques in concrete powder mix designing
  89. Effect of loading type in concrete deep beam with strut reinforcement
  90. Studying the effect of using CFRP warping on strength of husk rice concrete columns
  91. Parametric analysis of the influence of climatic factors on the formation of traditional buildings in the city of Al Najaf
  92. Suitability location for landfill using a fuzzy-GIS model: A case study in Hillah, Iraq
  93. Hybrid approach for cost estimation of sustainable building projects using artificial neural networks
  94. Assessment of indirect tensile stress and tensile–strength ratio and creep compliance in HMA mixes with micro-silica and PMB
  95. Density functional theory to study stopping power of proton in water, lung, bladder, and intestine
  96. A review of single flow, flow boiling, and coating microchannel studies
  97. Effect of GFRP bar length on the flexural behavior of hybrid concrete beams strengthened with NSM bars
  98. Exploring the impact of parameters on flow boiling heat transfer in microchannels and coated microtubes: A comprehensive review
  99. Crumb rubber modification for enhanced rutting resistance in asphalt mixtures
  100. Special Issue: AESMT-6
  101. Design of a new sorting colors system based on PLC, TIA portal, and factory I/O programs
  102. Forecasting empirical formula for suspended sediment load prediction at upstream of Al-Kufa barrage, Kufa City, Iraq
  103. Optimization and characterization of sustainable geopolymer mortars based on palygorskite clay, water glass, and sodium hydroxide
  104. Sediment transport modelling upstream of Al Kufa Barrage
  105. Study of energy loss, range, and stopping time for proton in germanium and copper materials
  106. Effect of internal and external recycle ratios on the nutrient removal efficiency of anaerobic/anoxic/oxic (VIP) wastewater treatment plant
  107. Enhancing structural behaviour of polypropylene fibre concrete columns longitudinally reinforced with fibreglass bars
  108. Sustainable road paving: Enhancing concrete paver blocks with zeolite-enhanced cement
  109. Evaluation of the operational performance of Karbala waste water treatment plant under variable flow using GPS-X model
  110. Design and simulation of photonic crystal fiber for highly sensitive chemical sensing applications
  111. Optimization and design of a new column sequencing for crude oil distillation at Basrah refinery
  112. Inductive 3D numerical modelling of the tibia bone using MRI to examine von Mises stress and overall deformation
  113. An image encryption method based on modified elliptic curve Diffie-Hellman key exchange protocol and Hill Cipher
  114. Experimental investigation of generating superheated steam using a parabolic dish with a cylindrical cavity receiver: A case study
  115. Effect of surface roughness on the interface behavior of clayey soils
  116. Investigated of the optical properties for SiO2 by using Lorentz model
  117. Measurements of induced vibrations due to steel pipe pile driving in Al-Fao soil: Effect of partial end closure
  118. Experimental and numerical studies of ballistic resistance of hybrid sandwich composite body armor
  119. Evaluation of clay layer presence on shallow foundation settlement in dry sand under an earthquake
  120. Optimal design of mechanical performances of asphalt mixtures comprising nano-clay additives
  121. Advancing seismic performance: Isolators, TMDs, and multi-level strategies in reinforced concrete buildings
  122. Predicted evaporation in Basrah using artificial neural networks
  123. Energy management system for a small town to enhance quality of life
  124. Numerical study on entropy minimization in pipes with helical airfoil and CuO nanoparticle integration
  125. Equations and methodologies of inlet drainage system discharge coefficients: A review
  126. Thermal buckling analysis for hybrid and composite laminated plate by using new displacement function
  127. Investigation into the mechanical and thermal properties of lightweight mortar using commercial beads or recycled expanded polystyrene
  128. Experimental and theoretical analysis of single-jet column and concrete column using double-jet grouting technique applied at Al-Rashdia site
  129. The impact of incorporating waste materials on the mechanical and physical characteristics of tile adhesive materials
  130. Seismic resilience: Innovations in structural engineering for earthquake-prone areas
  131. Automatic human identification using fingerprint images based on Gabor filter and SIFT features fusion
  132. Performance of GRKM-method for solving classes of ordinary and partial differential equations of sixth-orders
  133. Visible light-boosted photodegradation activity of Ag–AgVO3/Zn0.5Mn0.5Fe2O4 supported heterojunctions for effective degradation of organic contaminates
  134. Production of sustainable concrete with treated cement kiln dust and iron slag waste aggregate
  135. Key effects on the structural behavior of fiber-reinforced lightweight concrete-ribbed slabs: A review
  136. A comparative analysis of the energy dissipation efficiency of various piano key weir types
  137. Special Issue: Transport 2022 - Part II
  138. Variability in road surface temperature in urban road network – A case study making use of mobile measurements
  139. Special Issue: BCEE5-2023
  140. Evaluation of reclaimed asphalt mixtures rejuvenated with waste engine oil to resist rutting deformation
  141. Assessment of potential resistance to moisture damage and fatigue cracks of asphalt mixture modified with ground granulated blast furnace slag
  142. Investigating seismic response in adjacent structures: A study on the impact of buildings’ orientation and distance considering soil–structure interaction
  143. Improvement of porosity of mortar using polyethylene glycol pre-polymer-impregnated mortar
  144. Three-dimensional analysis of steel beam-column bolted connections
  145. Assessment of agricultural drought in Iraq employing Landsat and MODIS imagery
  146. Performance evaluation of grouted porous asphalt concrete
  147. Optimization of local modified metakaolin-based geopolymer concrete by Taguchi method
  148. Effect of waste tire products on some characteristics of roller-compacted concrete
  149. Studying the lateral displacement of retaining wall supporting sandy soil under dynamic loads
  150. Seismic performance evaluation of concrete buttress dram (Dynamic linear analysis)
  151. Behavior of soil reinforced with micropiles
  152. Possibility of production high strength lightweight concrete containing organic waste aggregate and recycled steel fibers
  153. An investigation of self-sensing and mechanical properties of smart engineered cementitious composites reinforced with functional materials
  154. Forecasting changes in precipitation and temperatures of a regional watershed in Northern Iraq using LARS-WG model
  155. Experimental investigation of dynamic soil properties for modeling energy-absorbing layers
  156. Numerical investigation of the effect of longitudinal steel reinforcement ratio on the ductility of concrete beams
  157. An experimental study on the tensile properties of reinforced asphalt pavement
  158. Self-sensing behavior of hot asphalt mixture with steel fiber-based additive
  159. Behavior of ultra-high-performance concrete deep beams reinforced by basalt fibers
  160. Optimizing asphalt binder performance with various PET types
  161. Investigation of the hydraulic characteristics and homogeneity of the microstructure of the air voids in the sustainable rigid pavement
  162. Enhanced biogas production from municipal solid waste via digestion with cow manure: A case study
  163. Special Issue: AESMT-7 - Part I
  164. Preparation and investigation of cobalt nanoparticles by laser ablation: Structure, linear, and nonlinear optical properties
  165. Seismic analysis of RC building with plan irregularity in Baghdad/Iraq to obtain the optimal behavior
  166. The effect of urban environment on large-scale path loss model’s main parameters for mmWave 5G mobile network in Iraq
  167. Formatting a questionnaire for the quality control of river bank roads
  168. Vibration suppression of smart composite beam using model predictive controller
  169. Machine learning-based compressive strength estimation in nanomaterial-modified lightweight concrete
  170. In-depth analysis of critical factors affecting Iraqi construction projects performance
  171. Behavior of container berth structure under the influence of environmental and operational loads
  172. Energy absorption and impact response of ballistic resistance laminate
  173. Effect of water-absorbent polymer balls in internal curing on punching shear behavior of bubble slabs
  174. Effect of surface roughness on interface shear strength parameters of sandy soils
  175. Evaluating the interaction for embedded H-steel section in normal concrete under monotonic and repeated loads
  176. Estimation of the settlement of pile head using ANN and multivariate linear regression based on the results of load transfer method
  177. Enhancing communication: Deep learning for Arabic sign language translation
  178. A review of recent studies of both heat pipe and evaporative cooling in passive heat recovery
  179. Effect of nano-silica on the mechanical properties of LWC
  180. An experimental study of some mechanical properties and absorption for polymer-modified cement mortar modified with superplasticizer
  181. Digital beamforming enhancement with LSTM-based deep learning for millimeter wave transmission
  182. Developing an efficient planning process for heritage buildings maintenance in Iraq
  183. Design and optimization of two-stage controller for three-phase multi-converter/multi-machine electric vehicle
  184. Evaluation of microstructure and mechanical properties of Al1050/Al2O3/Gr composite processed by forming operation ECAP
  185. Calculations of mass stopping power and range of protons in organic compounds (CH3OH, CH2O, and CO2) at energy range of 0.01–1,000 MeV
  186. Investigation of in vitro behavior of composite coating hydroxyapatite-nano silver on 316L stainless steel substrate by electrophoretic technic for biomedical tools
  187. A review: Enhancing tribological properties of journal bearings composite materials
  188. Improvements in the randomness and security of digital currency using the photon sponge hash function through Maiorana–McFarland S-box replacement
  189. Design a new scheme for image security using a deep learning technique of hierarchical parameters
  190. Special Issue: ICES 2023
  191. Comparative geotechnical analysis for ultimate bearing capacity of precast concrete piles using cone resistance measurements
  192. Visualizing sustainable rainwater harvesting: A case study of Karbala Province
  193. Geogrid reinforcement for improving bearing capacity and stability of square foundations
  194. Evaluation of the effluent concentrations of Karbala wastewater treatment plant using reliability analysis
  195. Adsorbent made with inexpensive, local resources
  196. Effect of drain pipes on seepage and slope stability through a zoned earth dam
  197. Sediment accumulation in an 8 inch sewer pipe for a sample of various particles obtained from the streets of Karbala city, Iraq
  198. Special Issue: IETAS 2024 - Part I
  199. Analyzing the impact of transfer learning on explanation accuracy in deep learning-based ECG recognition systems
  200. Effect of scale factor on the dynamic response of frame foundations
  201. Improving multi-object detection and tracking with deep learning, DeepSORT, and frame cancellation techniques
  202. The impact of using prestressed CFRP bars on the development of flexural strength
  203. Assessment of surface hardness and impact strength of denture base resins reinforced with silver–titanium dioxide and silver–zirconium dioxide nanoparticles: In vitro study
  204. A data augmentation approach to enhance breast cancer detection using generative adversarial and artificial neural networks
  205. Modification of the 5D Lorenz chaotic map with fuzzy numbers for video encryption in cloud computing
  206. Special Issue: 51st KKBN - Part I
  207. Evaluation of static bending caused damage of glass-fiber composite structure using terahertz inspection
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Heruntergeladen am 4.11.2025 von https://www.degruyterbrill.com/document/doi/10.1515/eng-2024-0085/html
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