This paper investigates the impact of configuration parameters on the seismic performance of the modular prefabricated two-side connected composite shear wall. Firstly, the finite element model of ...the modular prefabricated two-side connected composite shear wall was established and validated by Xu’s experimental results. Secondly, three aspects of parameter investigations were discussed in detail based on the validated numerical technology, namely the design parameter of ISP, design parameter of the stud, and design parameter of reinforced concrete faceplate (RCF). Then, the computation formula of shear capacity is deduced on the basis of the finite element model for reference to structural design. The results of parameter analysis displayed that the seismic performance of the modular prefabricated two-side connected composite shear wall has excellent seismic performance with the array studs of the length-diameter ratio of 4 which the center distance of 150 mm, and RCF with the thickness of 75 mm. A satisfactory but unadventurous estimation of the shear capacity of a modular prefabricated two-side connected composite shear wall is supplied by the advised technique.
•Saturated poroelastic medium dynamic theory was introduced into calculate EDZ.•The transient response was obtained by introducing equivalent blasting curve.•High frequency incident waves were more ...likely to cause tensile damage.•Dynamic stress transfer process in the EDZ under transient load was investigated.
The stability analysis of a deep buried tunnel subjected to dynamic disturbance is an important issue. In this study, the transient response has been obtained by establishing a water-rich tunnel model considering excavation damage zone (EDZ). Based on Biot’s two-phase dynamic theory and wave function expansion method, the analytical solution of dynamic response around the water-rich tunnel containing EDZ subjected to P wave is derived. Moreover, Fourier transform and Duhamel’s integral technique is introduced to calculate the transient response, and the equivalent blasting curve is adopted to input excitation function. The dimensionless parameters thickness N and shear modulus ratio μ∼ are defined to characterize the degree of damage in the surrounding rock, investigating the influencing factors, such as the parameters and the incident source frequencies. The results indicate that the dynamic stress concentration factor (DSCF) gradually decreases as the dimensionless parameters increase. Additionally, it is observed that the DSCF is more sensitive to changes in the thickness parameter N. Finally, the influence of the waveform parameters has been taken into account in the analysis of transient response, and the stress state and transfer process in each time stage of the EDZ are analyzed. This study establishes a theoretical foundation for comprehending the mechanical behavior and support design considerations associated with a deep-buried water-rich tunnel containing EDZ.
This study investigated the impact of a non-causative fault on the dynamic response of a nearby lined tunnel under the incidence of plane SV waves using the indirect boundary element method. The ...effects of several critical parameters, such as the incident frequency, the inclination degree of the fault, the distance between the fault and the tunnel on the hoop stress of the lined inner and outer walls, were explored intensively. The numerical results indicated that the non-causative fault could significantly change the hoop stress distribution of inner and outer surfaces of the tunnels. In general, for the vertically incident seismic waves, when the tunnel was located in the foot wall (under the fault), the hoop stress within the tunnel was significantly greater than that of the tunnels in the non-fault half space, with an amplification factor of up to 117%. The amplification effect became more pronounced as the fault dip angle increased. However, when the tunnel was located in the hanging wall (above the fault), the non-causative fault could produce a significant shielding effect on the dynamic response of the tunnel under high frequency wave incidence, with the reduction of hoop stress being up to 81%. For low-frequency waves, though, the fault could lead to an increase of the hoop stress of the tunnel of up to 152%. The research results will provide a reference for the seismic design and safety protection of underground structures in non-causative fault sites.
Terrorist attacks using improvised explosive devices on reinforced concrete buildings create a rapid release of energy in the form of a shock wave. Most casualties and injuries resulting from such an ...attack are not caused by the blast itself, but rather by the disintegration and fragmentation of the RC member due to concrete spallation on the opposite side of the member and which is propelled at high velocities depending on the size of the fragments. Therefore, it is important to analyze the size distributions of the concrete fragments from spallation. In this paper, two RC specimens were tested under explosive loading in a blast chamber: the first, a reinforced concrete (RC) specimen; and the second, an identical RC specimen retrofitted with 6 near surface mounted (NSM) carbon fibre reinforced polymer (CFRP) plates on both the top and bottom faces. Both specimens were subjected to the equivalent 2.1
kg of TNT at a standoff distance of 0.6
m, resulting in significant scabbing of the concrete. All fragments resulting from the blast tests were collected and analyzed. A sieve analysis was carried out to investigate the size distributions of the fragments from the two specimens. It was found that the fragment size followed both a Weibull distribution and a Rosin–Rammler–Sperling–Bennet (RRSB) distribution. The distribution of the fragment shape factor was also studied. The fragment shape factors were distributed according to the lognormal distribution. Furthermore, the influence of fragment size distribution on energy density dissipation was evaluated.
•The deformation variation law is a direct indicator of dam overall stability.•A geometric center of an irregular deformation plane is proposed.•The unified egg-shaped ellipse equations are developed ...for ultrahigh arch dams.•The critical indexes are estimated considering the abnormal probabilities.
This paper presents an innovative critical threshold estimation approach using unified egg-shaped ellipsoid modelling to study the deformation behavior of ultrahigh arch dams. First, the deformation variation law is regarded as a direct indicator of the overall stability and potential damage of ultrahigh arch dams based on comprehensively comparison with the results of theoretical calculations, experimental tests, numerical simulations and monitoring data. Subsequently, a novel geometric center of an irregular deformation plane constituted by all the deflection curves is proposed according to the measured distribution characteristics of the deformation spatial fields of the Xiaowan and Jinping I arch dams. Furthermore, unified egg-shaped ellipse equations are proposed to systematically identify the deformation critical attributes of Jinping I dam. Eventually, based on the peaks over threshold model, critical indexes are estimated considering the abnormal probabilities. The proposed methods are applied to Xiaowan dam as well. Results demonstrate that unified ellipsoid modelling can uniformly describe the abnormal features of the deformation behaviors of different ultrahigh arch dams, thereby the universal structural evolution characteristics to be understood in a wider range during their long-term operations.
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•Slab made of normal strength concrete underwent severe damage against blast loads.•Lower structural damage was observed on slabs made of ultra-high performance concrete.•Smaller ...central deflections were recorded from ultra-high performance concrete slabs.•Numerical simulations gave good agreement with field observations.
Ultra-high performance concrete (UHPC) which is characterized by high strength, high ductility and high toughness has been widely applied in modern structure construction. Outstanding mechanical feature of UHPC not only enables strong yet slim structure design but also highlights its potential in protective engineering against extreme loads like impact or explosion. In this research a series of reinforced concrete slabs are tested to determine their response under explosive loading conditions. Concrete materials used in the slab construction are ultra-high strength concrete (UHPC) and normal strength concrete (NSC). In total five slabs are tested including four UHPC slabs with varying reinforcement ratios and one control NSC slab with normal reinforcement. Explosive charges with TNT equivalent weights ranging from 1.0 to 14.0kg at scaled distances ranging from 0.41 to 3.05m/kg1/3 are used in the current experiments. Test results verified the effectiveness of UHPC slabs against blast loads. Numerical models are established in LS-DYNA to reproduce the field blast tests on UHPC slabs. The numerical results are compared with the field test data, and the feasibility and validity of the numerical predictions of UHPC slab responses are demonstrated.
A terrorist attack on a long-span spatial structure would cause horrible results. Therefore, it is important to determine the characteristics of blast pressure fields to protect such structures. In ...this study, fully confined blast loading tests were conducted using a rigid curved shell model, which had an inner space similar to that of a reticulated dome. Four different scenarios were carried out to record the blast loading on five typical positions. The blast pressure-time data were compared and analyzed. In addition, a suitable numerical simulation method was proposed for the issues involved in interior blast loading. This numerical model was verified by comparing with the test data. A parametrical analysis of the interior blast simulations was conducted based on this numerical method. The blast loading values at specific positions were obtained with the key parameters varied within a reasonable scope. The blast loading from blast tests and simulations were presented. On this basis, the interior blast loading could conveniently be predicted by using the method and data in this paper, which could be used in the protective design of other reticulated domes.
•Ultra-high performance concrete slabs are tested under contact explosion.•Normal strength concrete slabs are tested as control samples.•Coupled SPH and FEM model is developed to reproduce the field ...test observations.•Comparison and discussions are made regarding the slabs performance.
Dynamic performance of concrete structures under blast loading conditions is a topic of importance as such load generates severe structural damage including flexural damage, shear damage and concrete spall damage which may impose threats to the personnel and instruments shielded by the reinforced concrete structure. To mitigate blast effects on civil structures, a new kind of concrete material named Ultra-High-Performance-Concrete (UHPC) is now widely studied and applied. UHPC material is known for its high compressive and tensile strength, large energy absorption capacity as well as good workability and anti-abrasion ability. In a previous study, the performance of UHPC slab under blast loads had been investigated through free air explosion tests. The blast resistance capacity of UHPC had been demonstrated through comparison with normal strength concrete. In the present study, the dynamic performance of UHPC slab under contact charge explosion is experimentally studied and compared with normal strength concrete slab under the same loading scenario. Numerical models are established to reproduce both the previous free air explosion tests and the current contact explosion tests. In particular, finite element model is established to simulate the free air explosion test, and coupled smoothed particle hydrodynamics (SPH) method and finite element method is utilized to simulate the contact blast tests. Numerical results are compared with the experimental observations, and the feasibility and accuracy of the numerical model are validated.
•The KCC model was calibrated to effectively predict behaviors of UHPC subjected to lowvelocity impact loading.•A series of triaxial compression tests were carried out to obtain the parameters of ...three strength surfaces by experimental data fitting.•A 3D finite element model was developed based on the calibrated KCC model.•The effectiveness of the calibrated KCC model was verified by comparing the results of numerical simulations and low-velocity impact tests.
As an innovative material, UHPC (ultra-high performance concrete) is regarded as a promising material to improve dynamic resistant performance of civil engineering structures suffered from extreme loadings such as blast, shock and impact loading. The mechanical properties of UHPC members suffered from static/dynamic loading have been systematically investigated through many physical experiments. However, the rationality of the constitutive model utilized in numerical simulations (especially the finite element simulations) to precisely describe behaviors of UHPC has been little emphasized. The objective of this study, therefore, is to calibrate the KCC (Karagozian & Case Concrete) model to effectively predict behaviors of UHPC suffered from low-velocity impact loading. At the beginning, the properties of UHPC under triaxial compression were experimentally investigated by a series of triaxial compression tests to obtain the parameters of three strength surfaces by experimental data fitting. Meanwhile, EoS (equation of state) was derived by the combination of hydro-static compression test, “p-alpha equation” and Mie–Grueneisen equation of state. Moreover, suitable damage parameters were given by repeated trials, and the suitable model of strain-rate effect for UHPC was also suggested. The single element analysis results indicate that the calibrated KCC model can reasonably reflect the behaviors of UHPC under the uniaxial and triaxial stress state. Eventually, numerical results of low-velocity impact tests of UHPC columns and beams based on the calibrated KCC model agree very well with the tests results, which indicates the rationality of the calibrated KCC model for numerical simulations on low-velocity impact.
Current practice in analysis and design of structures to withhold surface explosions considers only airblast forces on structures. A surface explosion, in fact, generates both ground shock and ...airblast pressure on a nearby structure. In this paper, the influences of simultaneous ground shock and airblast forces on structural responses are investigated. Blast-induced surface ground motions and airblast pressures estimated in a previous study are employed as input in the analysis. A previously developed three-dimensional homogenized material model for a masonry wall including the equivalent elastic properties, strength envelope and damage threshold is used to model masonry wall. Another material damage model developed for reinforced concrete structures is used for modelling RC behavior due to explosive loads. These material models are programmed and linked to an available computer program LS-DYNA3D through its user subroutine capability. A one-story masonry infilled RC frame is used as an example in the study. Dynamic response and damage of the example structure to simultaneous ground shock and airblast forces, or separately to ground shock only or airblast forces only are calculated. It is found that in general, airblast load governs structural response and damage when the scaled distance is small. However, under certain conditions, structural damage will be critically underestimated if ground shock is neglected. When the scale distance increases, the relative importance of the ground shock on structure response increases, and ground shock will dominate the surface explosion effects on structures at large scaled distance. At large scaled distance, the ground shock and airblast force effects on structures decoupled and structure response and damage to ground shock and airblast force can be analyzed separately.
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