Bottom Tensile Stress Research Articles

Design and mechanical response analysis of asphalt steel plastic pavement structure

In order to further study the mechanical properties of new asphalt steel plastic (ASP) pavement and explore optimal ASP pavement structures, this study analyzed the bottom tensile strain of asphalt mixture layer, the bottom tensile stress of steel plate layer, the bottom tensile stress of acrylonitrile butadiene styrene (ABS) layer, the top vertical compressive strain of subgrade and deflection. The results show that when the pavement structure adopts an 8 cm thick SMA layer, a 0.5 cm thick insulation layer, a 20 cm thick ABS layer, and 0.6 cm, 1.0 cm and 1.2 cm thick steel plate layers respectively, the mechanical properties of the ASP pavement are relatively good. The variation in the thickness of the steel plate layer has a greater impact on the bottom stress of steel plate layer. For the same pavement structure, when the dynamic load increases from 0.5 MPa to 0.9 MPa, the maximum values of the design indexes are linearly related to the dynamic load values. Under the static load, the shear stress generated in the steel plate layer is significantly lower than that in asphalt and ABS layers. The new asphalt steel plastic pavement has good mechanical properties and great application potential.

Study on Mechanical Properties of Tunnel Flame Retardant Asphalt Pavement Considering the Ablative Effect

With the widespread utilization of composite pavements in highway tunnel projects, the flammability issue of asphalt layers has garnered increasing attention. Previous research has demonstrated that the addition of flame retardants effectively reduces the occurrence of pavement fires. However, there are few studies combining asphalt flame retardant technology with tunnel composite pavement structures. Therefore, this paper, considering the context of actual engineering projects, uses ABAQUS software to analyze and calculate the mechanical response of the tunnel composite pavement, considering the thickness of various asphalt layers under the ablation depth. Key design indexes such as shear stress and lower tensile strain of the asphalt layer, the bottom tensile stress of the cement concrete subgrade, and interlayer shear stress between the asphalt layer and cement concrete subgrade of composite pavements are analyzed using the nonlinear finite element analysis method. The findings enable the determination of the optimal thickness of the composite pavement asphalt layer combination after ablation, thus contributing to enhancing the safety of tunnel pavements.

Structural response analysis of conductive ethylene–propylene–diene monomer rubber composite pavement under validated temperature field

Conductive ethylene–propylene–diene monomer rubber composite material (EPDM) is a new type of active electric heating deicing material. It has good heat generation and mechanical properties. In this study, in order to study the effect of the addition of EPDM on the response of the pavement structure, the composite material was laid under the asphalt layer in the pavement structure in a full-width paving method. A three-dimensional finite element model of EPDM pavement structure was established and the pavement heating temperature field was simulated. The simulated temperature field of road surface was verified by an outdoor heating test. The structural response of EPDM pavement under three different loading conditions was analyzed by using the ANSYS static structural analysis module. The structure response was analyzed from three indicators of bottom tensile stress, surface deformation, and equivalent stress. The results show that under the static load of the vehicle, the addition of EPDM composite material can reduce the cracking risk of the asphalt pavement; The temperature load caused by the active heating of the road surface is the main factor causing the damage of the EPDM road surface; The weakest part of the entire pavement structure is the lower asphalt layer close to the composite material, especially at the center of the wheel load action spacing. This study can provide a reference for future practical engineering applications of EPDM pavements and attract attention to the effect of temperature loads generated by active snow-melting pavement heating on the structural response of the pavement.

Numerical Analysis of Reflective Cracking of Continuous Reinforced Composite Pavement under Multifactor Coupling

The occurrence and expansion of reflective cracking is a typical problem associated with the composite pavement that has a proven impact on the life of the continuous reinforced composite pavement. The current research studies a 3D finite element model to preset cracks at the top of the continuously reinforced concrete (CRC) layer’s transverse crack and at the bottom of the asphalt concrete (AC) layer based on the theory of linear elastic fracture mechanics in order to explore the factors responsible for the reflective cracking formation mechanism and expansion law. Considering the main stress parameters that affect the formation of reflective cracking (layer bottom tensile stress and vertical shear stress), the most unfavorable load position and the most unfavorable point of the corresponding stress parameter are determined that are then used to calculate the stress intensity factor of the crack tip under the coupling effect of multiple factors based upon the position and point above the crack, by using the confinement integral. The variance analysis of the stress intensity factor of the crack tip under the multifactor coupling effect is conducted via an orthogonal test in order to determine the main factors affecting the formation and development of reflective cracking. Meanwhile, the analysis of single-factor sensitivity is carried out on all these factors, which reveal the real contribution in the formation and expansion of reflective cracking in the continuous reinforced composite pavement. The results show that the most unfavorable load position for reflective cracking is when the load is on the side of the CRC layer’s lateral crack, while the most unfavorable point of the stress parameter is concentrated within the range of the wheel track. At the same time, analysis of multifactor variance and that of single-factor sensitivity show that the cracking mode of reflective cracking in the continuous reinforced composite pavement is a mixed one, dominated by K2 (slip type), supplemented by K1 (open type), and participated by K3 (tear type), whereas the AC layer’s preset-crack depth ratio, instantaneous temperature drop, and CRC-transverse-crack load transfer capacity are the main factors that affect the formation and development of the reflective cracking. Moreover, a better bonding state between the AC layer and the CRC layer improves the stress intensity factor of the preset crack tip on the bottom of the AC layer.

A structural design for semi-rigid base asphalt pavement based on modulus optimization

The early damage of the semi-rigid base asphalt pavement is related to the pavement structure modulus's unreasonable matching. In this study, three typical pavement structures were selected to analyze the pavement structures' influence on the pavement service life. A three-dimensional finite element pavement structure model was established. The independent variables are subgrade modulus, base course modulus, and subbase modulus. The deflection, the bottom tensile stress, and maximum shear stress were chosen as the evaluation indexes. The effect of the modulus on the mechanical response of the pavement structure was analyzed. The optimal modulus combination of the pavement structure was determined through multi-factor range analysis. The mechanical response and fatigue life before and after the optimization pavement structure were compared. The results showed that the field measured modulus of Structure 1 and 2 was higher than the design modulus. Moreover, while the modulus of base course and subbase course was increased, the deflection gradually reduced. The base course's bottom tensile stress and the subbase were increased, and the maximum shear stress was basically unchanged. After the modulus combination optimized pavement structure, the mechanical response was significantly reduced. The fatigue life based on the deflection and bottom tensile stress, and the laboratory normalized fatigue equation were significantly increased. By the combination of fatigue performance of pavement materials and pavement structure, it was possible to provide an effective optimization method for the design of semi-rigid base asphalt pavement in this research work.

Fatigue damage analysis of cement stabilized sub-base during construction period

When cement stabilized gravel materials are used as pavement base and sub-base, irreversible fatigue damage often occurs due to insufficient maintenance days during the construction period and overload of vehicle load. In order to obtain the fatigue damage caused by the construction load on the cement stabilized gravel sub-base, the flexural tensile strength test and the fatigue test are carried out based on Miner theory and ABAQUS software. Under 9 kinds of vehicle load, we analyze both the relationship between the maximum tensile stress of the sub-base layer and the substrate thickness when the substrate thickness is 16, 20, 24, 28, and 32 cm and the relationship between the maximum tensile stress of the sub-base layer and the modulus of the sub-base when the modulus of the subbase is 400, 800, 1 200, 1 600, and 2 000 MPa, respectively. The research results show that with the increase of the thickness of the sub-base layer, the tensile stress of the sub-base decreases gradually, and the maximum reduction rate is 8.8%. With the growth of the sub-base modulus, the bottom tensile stress of the sub-base layer increases gradually, but the growth rate continues to decrease. Relying on the actual engineering project, the fatigue prediction equation of the cement stabilized gravel sub-base can be obtained by using Miner theory to calculate the fatigue damage degree of the subbase caused by different construction loads under different working conditions, which provides guidance for the design and construction of the pavement.

Structural response analysis of road pavement solar collector (RPSC) with serpentine heat pipes under validated temperature field

Road Pavement Solar Collector (RPSC) is one of the inevitable products of the diversified development of pavement, which can reduce the temperature of the road surface to mitigate the urban heat island (UHI) effect. The arrangement of the heat pipes in RPSC mainly includes the straight arrangement and the serpentine arrangement. In this study, in order to study the influence of the serpentine heat pipes on the structural response of pavement, the 3D Computational Fluid Dynamics (CFD) - finite element model (FEM) is established and verified. The structural response of conventional pavement and RPSC under three different loading conditions is analysed and compared using ANSYS static structural module. The structural response is analysed from the three indexes of the bottom tensile stress, surface deformation, and equivalent stress. The results show the introduction of heat pipes has a significant effect on the mechanical response, thermal response, and coupling response, and the weakest part of the overall pavement structure is the surrounding of the heat pipe specifically at the bending zone. This study can be a reference for future work to attract the attention of balance the efficiency of heat collection and the structural response for RPSC.

A Discussion of Stability and Engineering Verification of Thin Immediate Roof under Uniform Load of the Rectangular Coal Roadway

Roadway roof is a key factor in roadway stability. At present, the analysis of roof stability is mainly based on numerical calculations and field measurements with a relatively weak theoretical basis and inadequate research studies on the loading mechanism of the roof. In this paper, a mechanical calculation model of immediate direct roof under uniform load of rectangular coal roadway is established. The stress distribution and roof subsidence in the roof are calculated theoretically and verified by the numerical calculation, physical tests, and engineering applications. Based on the classical beam solution theory, the stress distribution and sinking of the thin immediate roof under uniform load are obtained and verified by numerical calculations. The results are highly consistent. Two types of thin direct roof failure under uniform load are analyzed: the failure of the normal cross section caused by the bottom tensile stress and the failure of the inclined section caused by the combined effect of the tensile stress in the abdominal area and compressive stress. The stability of thin immediate roof under uniform load of the rectangular coal roadway was tested in 1905s mining roadway of Great Wall Number #3 coal excavation field. This research can further fill in blanks of the loading mechanism of the roadway roof and provide theoretical and pragmatic values to control the roadway pressure and rock stratum as well as the scientific references to the design of the anchor bolt supporting system.

Fatigue Damage Analysis of Cement-Stabilized Base under Construction Loading

Cement-stabilized macadam is commonly used in pavement base courses. The disadvantage of this material is that it easily cracks because construction vehicles cause irreversible fatigue damage to the pavement. Fatigue damage is caused by an insufficient number of maintenance days and overloading by construction vehicles. In order to analyze the influence of the number of maintenance days and overloading by construction vehicles, Miner theory and ABAQUS software were used, and an unconfined compressive strength test, an indirect tensile strength test, a bending tensile strength test, and a fatigue test were carried out simultaneously. The relationship between compressive strength and the splitting strength of water-stabilized macadam as well as compactness, water content, and temperature at different ages were determined. Fitting shows that the bottom tensile stress of the most disadvantageous layer increased with increasing subbase modulus, and its reduction rate increased slowly with the increasing of cement-stabilized macadam subbase thickness. The fatigue prediction equation for cement-stabilized macadam was obtained using bending tensile strength and fatigue tests. Subbase fatigue damage caused by different construction loads under different working conditions was calculated using Miner theory according to actual engineering data. Therefore, the number of pavement maintenance days should be increased. For harsh natural environments and strict time constraints, the design should increase the strength and thickness of the subbase material. When laying the base, overloaded vehicles should be limited, and the construction period of the loaded vehicles should be reduced to minimize road damage.

Experimental Analysis of Stress in Cement Concrete Pavement with Base Cracks

AbstractIn order to analyze the stress varieties in cement pavement slabs caused by load with the existence of base cracks, the influences of moduli, crack locations and quantities of semi-rigid base and lean concrete base, thickness of cement concrete slab and size of load and other factors on the load stress of cement concrete pavement slab were analyzed through experimental simulation methods. The analysis result indicates that: (1) The road surface deflection increases with the number of base cracks increasing; (2) The tensile stress at the bottom of concrete slab decreases with the increase of base modulus and slab thickness, the increase in slab thickness more substantially minimizes stress than does the increase in base modulus; (3) The stress of concrete slab increases sharply with the presence of base cracks, and the slab bottom tensile stress increases with the number of base cracks increasing; (4) The load increase is an important factor causing load stress increase; so overload must be strictl...

The Influence of Different Subbase Materials on the Crack of Cement Stabilized Macadam Base during Construction

According to actual axle load data and the measured mechanical parameters of cement stabilized macadam material with different cement dosages, the bottom tensile stresses of different subbase structures are calculated and the results show that: to graded gravel subbase, the weight of construction vehicle is inadvisable to be more than 35t and the cement dosage of base course shall be more than 3.0%; and, the maximum bottom tensile stress of graded gravel subbase shall be much more than that of lime-flyash soil subbase. According to the measured dry shrinkage strain and dry shrinkage coefficient, the dry shrinkage crack space of base course is analyzed and the results show that: under the same cement dosage, the crack space of the base course with graded gravel subbase is smaller than that of lime-flyash soil subbase; with the increase of cement dosage, the crack space of base course increase first and then decrease, and when the cement dosage is 3.5%, the dry shrinkage strain and dry shrinkage coefficient is minimum and the crack space of base course is maximum.

Prediction of Potential Cracking Failure Modes in Three-Dimensional Airfield Rigid Pavements with Existing Cracks and Flaws

This paper predicts the potential for crack propagation in concrete pavements under aircraft loading given a starter fatigue crack at the bottom of the concrete slab or a surface-initiated shrinkage crack on top of the slab. The generalized finite element method was used to evaluate the stress intensity factors for quarter elliptical cracks placed at the critical top and bottom tensile stress locations. The pavement was loaded with a single triple-dualtandem (TDT) gear and two TDTs accounting for the entire belly gears. When the pavement was loaded with the two TDT gear configuration, the analyses showed significantly higher KI (shear mode) values for surface-initiated cracks than for bottom-initiated cracks for the same crack size. Therefore, concrete slabs with preexisting surface cracks are more likely to exhibit top-down crack growth despite being designed for bottom-up fatigue cracking under certain loading conditions. The theoretical framework allows for improved assessment of the fracture susceptibility of concrete slabs under aircraft loading, specifically the potential for top-down over bottom-up cracking.

Impact of Subgrade Resilience Modulus on Heavy Load Asphalt Pavement Mechanical Properties

Subgrade resilience modulus is an important mechanical parameter in pavement design. It will directly influence the design result of pavement structure. Using BISAR3 of SHELL design method, the impacts of subgrade resilience modulus on pavement surface deflection, base and subbase bottom tensile stress, surface layer bottom tensile stress of the heavy load asphalt pavement structure were analyzed. And the influencing laws were analyzed, too. The results show that the mechanical and deforming characteristics of heavy load asphalt pavement were influnced significantly by subgrade resilience modulus. With the increasing of subgrade resilience modulus, the pavement surface deflection, base bottom tensile stress would significantly decrease, and fatigue life would be improved.

Load Testing of Prestressed Concrete Double Tees Without Web Reinforcement

This paper describes three static load tests that were conducted on full-scale pretopped 12DT30 double tees. All specimens were typical production double tees spanning 62 ft (18.9 m) and representing typical units used in parking structures. Design of the units used heavy live loads and the ACI 318-02 Building Code for load and resistance factors. The bottom tensile stress under full live load was in the range of 10.3 √∫' c to 11.9√∫' c , which places these units in the Class T category of ACI 318-02, Section 18.3.3. Although the specimens' stem dimensions varied, the double tees shared many common features, including total omission of shear reinforcement in the web. The paper concludes with appropriate recommendations related to the omission of web reinforcement in prestressed concrete double tees of similar geometry.

Bond Interaction Between Concrete Pavement and Lean Concrete Base

In the past, concrete pavement design procedures have been based on stresses computed with the assumption of either a frictionless or a fully bonded interface between pavement layers. It is recognized that neither of these assumptions is realistic for layers not intentionally bonded. Information on the degree of interaction between pavement layers is provided. Full-scale load-induced strain and falling weight deflectometer testing was conducted to measure the degree of bonding between portland cement concrete pavement and a lean concrete base (LCB) layer prepared using five commonly specified interface treatments. For each interface treatment, the effect of extending the LCB layer beyond the slab edge was also evaluated. Strain gauges installed at different pavement depths measured the load-induced edge and wheelpath stress profiles, which allowed the degree of layer interaction to be evaluated. By analysis of load-induced stress and deflection, it was verified that a double layer of polyethylene promotes an unbonded interface with very little frictional interaction. Other interface treatments create varying degrees of friction or partial bond between the layers, reducing the loadinduced stress. Slab bottom tensile stress reductions were computed in comparison with measured slab top compressive stress, measured polyethylene interface tensile stress, and theoretically calculated unbonded stress. Overall, the most effective stress-reducing interface treatments were asphalt emulsion and plain (no treatment) conditions, where tensile stress reductions of more than 40 percent were measured.