Lateral Impact Loading Research Articles

The response of precast concrete segmental columns subjected to near base impact

Precast concrete segmental column has attracted many attentions for the past decades due to its unique features especially in improving the construction quality and efficiency. However, the performance of precast segmental column under lateral impact loading has been less studied. Our previous studies performed laboratory pendulum impact tests on scaled segmental columns to investigate their behaviours when impacted at mid-span of the column. This article studies the response of segmental column when impacted near the column base, which generates different response modes and failure mechanisms compared to the columns subjected to the mid-span impact. Lateral impacts are applied either to segmental joint between the two bottom segments or directly onto the centre of the base concrete segment. A detailed three-dimensional numerical model is created and validated with laboratory impact testing results on scaled segmental columns. A full-scale 3-m tall segmental column is then numerically built to study the behaviour under near base impact. The column damage and failure modes are analysed. The influences of prestress level in the post-tensioning tendon and concrete strength on the performance of segmental column subjected to near base impacts are investigated through numerical simulations.

Novel learning framework (knockoff technique) to evaluate metric ranking algorithms to describe human response to injury

Objective: The objective of this study is to present a novel framework, termed the knockoff technique, to evaluate different metric ranking algorithms to better describe human response to injury.Methods: Many biomechanical metrics are routinely obtained from impact tests using postmortem human surrogates (PMHS) to develop injury risk curves (IRCs). The IRCs form the basis to evaluate human safety in crashworthiness environments. The biomechanical metrics should be chosen based on some measure of their predictive ability. Commonly used algorithms for the choice of ranking the metrics include (a) areas under the receiver operating characteristic curve (AUROC), time-varying AUROC, and other adaptations, and (b) some variants of predictive squared error loss. This article develops a rigorous framework to evaluate the metric selection/ranking algorithms. Actual experimental data are used due to the shortcoming of using simulated data. The knockoff data are meshed into existing experimental data using advanced statistical algorithms. Error rate measures such as false discovery rates (FDRs) and bias are calculated using the knockoff technique. Experimental data are used from previously published whole-body PMHS side impact sled tests. The experiments were conducted at different velocities, padding and rigid load wall conditions, and offsets and with different supplemental restraint systems. The PMHS specimens were subjected to a single lateral impact loading resulting in injury and noninjury outcomes.Results: A total of 25 metrics were used from 42 tests. The AUROC-type algorithms tended to have higher FDRs compared to the squared error loss–type functions (45.3% for the best AUROC-type algorithms versus 31.4% for the best Brier score algorithm). Standard errors for the Brier score algorithm also tended to be lower, indicative of more stable metric choices and robust rankings. The wide variations observed in the performance of the algorithms demonstrated the need for data set–specific evaluation tools such as the knockoff technique developed in this study.Conclusions: In the present data set, the AUROCs and related binary classification algorithms led to inflated FDRs, rendering metric selection/ranking questionable. This is particularly true for data sets with a high proportion of censoring. Squared error loss–type algorithms (such as the Brier score algorithm or its modifications) improved the performance in the metric selection process. The presented new knockoff technique may wholly change how IRCs are developed from impact experiments or simulations. At the very least, the knockoff technique demonstrates the need for evaluations among different metric ranking/selection algorithms, especially when they produce substantially different biomechanical metric choices. Without recommending the AUROC-type or Brier score–type algorithms universally, the authors suggest careful assessments of these algorithms using the proposed framework, so that a robust algorithm may be chosen, with respect to the nature of the experimental data set. Though results are given for sets from a published series of experiments, the knockoff technique is being used by the authors in tests that are applicable to the automotive, aviation, military, and other environments.

Tensile Properties of a Novel Graphene Pattern Stitched Carbon/Epoxy 3D Composite

The focus of this study is on the tensile properties of a novel graphene pattern stitched carbon/epoxy 3D composite which could be considered in aerospace industry applications. Tensile modulus and strength are reduced by18-25% due to filament breakage during stitching; this reduction varies with stitching density. Fabrication induced voids and resin rich regions also contribute. However, extensive delamination observed in the tension loaded unstitched laminate is constrained by the graphene pattern stitching and the proposed 3D reinforced composite is expected to be more damage resistant under lateral impact loading.

Experimental and Numerical Studies on Concrete Filled Circular Steel Tubular (CFCST) Members Under Impact Loads

This paper presents experimental and numerical studies on the behavior of concrete filled circular steel tubular (CFCST) members under lateral impact loading. Fourteen CFCST member specimens were designed, fabricated and tested using a Drop Hammer Impact Test Machine in a simple double-supported boundary conditions. The main parameters include the outer diameter of CFCST member, the thickness of steel tube and the height of drop hammer. The failure modes, the impact force, the impact force time history curves and the strain time history curves were investigated to evaluate the behavior of CFCST member under an impact load. A finite element analysis (FEA) model of CFCST member under lateral impact loading was established using ABAQUS software, and the accuracy of the proposed model was verified by a comparison with the test results. The response of the specimen under impact loading simulated by FEA model, matches well with the test results.

Behaviour of ultra-high strength steel hollow tubes subjected to low velocity lateral impact: Experiment and finite element analysis

This paper presents experimental and numerical study on the behaviour of ultra-high strength steel (UHSS) hollow tubes under low velocity lateral impact loading. A total of six specimens were tested under lateral impact loading. The finite element (FE) model was established with the consideration of the strain rate effect and validated against test results. The parametric study showed that UHSS hollow tubes had the similar failure pattern when compared to that of normal strength steel members. The mid-span deflection and the residual deformation decreased significantly when the UHSS tube was applied.

Improved impact resistant capacity of segmental column with fibre reinforced polymer wrap

Our previous studies investigated the response of precast segmental columns subjected to lateral impact loading, and found that the columns exhibited better flexibility and impact resistance capability as compared to monolithic cast-in-place column. The damage and failure of segmental column were mainly due to flexural compression induced damages when subjected to mid-span impact, and concrete shear failure when subjected to near base impact. In this paper, we utilize FRP to wrap the concrete segments to improve its impact resistant capacity. Laboratory impact tests on scaled columns are conducted. The columns are impacted at mid-span, segmental joint near column base and directly onto the centre of the bottom concrete segment, for which the column responses are respectively associated primarily with the flexural bending mode, combined bending and shear mode, and direct shear deformation mode. The responses of the columns are examined and compared with those non-retrofitted columns. Then, a detailed three-dimensional numerical model of the segmental column is generated and validated with lab test results. The numerical model can be used to calculate the responses of the segmental columns subjected to lateral impact loading for design analyses.

Investigation of concrete-filled steel tube beams strengthened with CFRP against impact loads

As a promising strengthening solution, carbon fiber reinforced polymer (CFRP) sheets have been used to improve the structural response of concrete-filled steel tubes (CFSTs) in service loads, owing to the durability and high strength-to-weight ratio provided by CFRP. Despite the wealth of knowledge available in the literature on how CFRP sheets contribute to strengthening CFSTs under static loads, there is a research gap regarding how the strengthened structural components respond to lateral impact loads, due to vehicle and vessel collision, as well as wind and water-borne debris impact. This was the motivation of the current study to establish a computational framework supported by experimental tests to evaluate the performance of CFST beams with and without CFRP under a set of impact scenarios. For this purpose, a range of influential aspects related to CFRP, concrete, and steel, as well as impact energy, are investigated. Such a holistic assessment provides unique information to answer fundamental and practical questions regarding the use of CFRP for strengthening of CFST beams against impact loads. To further assist with the proper configuration of CFRP-strengthened CFST beams, a section analysis method is developed and validated as the outcome of this study.

Dynamic Simulation of Biomechanical Behaviour of the Pelvis in the Lateral Impact Loads.

The objective of this study was to develop and validate a novel 3D dynamic model of a pelvic side-impactor system. The biomechanical responses of a pelvic flexible model (having .mnf file suffix) under the lateral impact load for predicting the bone fracture mechanism are investigated as well. The 3D solid model of the side-impactor system was imported into MSC/ADAMS software for analyzing the dynamic model, and the pelvic flexible model was extracted from the CT images of a Chinese female volunteer. The flexible model of the pelvis system was developed considering a wide range of mechanical properties in the bone complex and soft tissue to achieve a realistic biomechanical response during a lateral impact. Good agreements were achieved between the dynamic simulations and the experimental results of pelvic side impacts, in terms of the biomechanical criteria. The dynamic model of impactor system could be employed to investigate the hip protector effectiveness, improving the vehicle safety, and biomechanical response of the other human organs.

Hybrid corrugated members subjected to impact loading: Experimental and numerical investigation

Latest development in material and manufacturing technologies make it possible to increase the yield strength of steel to more than 1200 MPa. These steel grades, suitable for structures prone to extreme loadings, give potentials for considerable weight reduction and a cost-effective way to produce energy-efficient members. Having analysed the impact behaviour of corrugated members recently, this paper now investigates the performance of hybrid corrugated (HC) sections consisting of mild-steel corrugated plates and ultra-high strength (UHS) steel tubes. Three different types of trapezoidal corrugated plates are considered so as to examine the effect of geometrical corrugation parameters on the performance of entire member. Along with this, in order to study the contribution of UHS tubes in the performance of HC members under impact loading, their performance is also examined separately. In combined lateral impact and axial loading scenario, the tube is initially compressed axially; thus an indenter perpendicularly impacts the specimen at mid-span. An advanced numerical model in which nonlinear strain-rate dependent material behaviour of steel is taken into account is also developed by using ABAQUS/Explicit. Thus, the residual deformations, time histories, global lateral deflection, and energy absorptions are discussed and compared with those of experimental results.

Experimental and numerical study on lateral impact response of concrete filled steel tube columns with end plate connections

The behaviour of concrete filled steel tube (CFST) columns has been investigated intensively against lateral and axial impact loading. However, there is a lack of knowledge on the impact response of the connection between such the column and steel beam. In order to close this gap, the most common connections with a partial depth end plate (PDEPCs), as a simple connection, and a flush plate (FPCs), as a moment resisting connection, were investigated under lateral impact loads. The long bolts were used to connect the CFST column to the beam as an alternative technique to the ordinary bolts. Here, eight specimens were tested under loading conditions with different locations and plate thicknesses. 3D finite element models were then developed and validated against the corresponding experimental results. Full range analyses of the connection response under the loading regime were then carried out using the validated FE models to examine the internal forces and the energy dissipation of the connections. The main findings are as follows: (1) the failure modes of both connection types investigated were similar at both loading locations only with slightly higher tearing fracture on the PDEPC; (2) using a thicker end plate increases the moment capacity of the connection but decreases its energy absorption; (3) the performance of long bolts provides the connection with appropriate ductility up to failure.

Experimental study on the behavior of precast segmental column with domed shear key and unbonded Post-Tensioning tendon under impact loading

Precast segmental columns have been more and more popularly used in constructions of prefabricated reinforced concrete (RC) structures in recent years. During its servicing life the precast segmental column might be subjected to lateral impact loads from hazards such as falling rock and vehicle collision etc., which however has not been well understood. It is therefore necessary to properly understand the response and vulnerability of segmental column under impact loading. A previous experimental study revealed that the trapezoidal prism shear key on concrete segment could effectively reduce lateral slippage between segments under lateral impact loading, but stress concentration near the shear key led to crushing damage to concrete segment. A new shear key design, i.e., domed shear key with smoothed curvature is proposed in this study. Precast segmental columns with domed shear key are fabricated and tested. This paper presents the test results of scaled segmental columns with this new shear key design. The performance of segmental column with the new dome shear key is compared with previously tested columns with trapezoidal shear key and plain segmental column without shear key. Furthermore, the segmental columns with the new domed shear keys were impacted at different locations along the column including the column mid-span, the segmental joint, and the bottom segment to examine the influences of different impact locations on their impact resistant capacities, and the response and failure modes.

Mechanical properties of equal-strength stainless reinforced replacement piers under lateral impact loading

Stainless reinforced equal-strength replacement piers are used to solve the problems of steel corrosion, surplus strength, and resource waste for piers in marine environments. In this study, an ultrahigh drop weight impact test system was applied for a comparative experimental model of the horizontal impacts between two groups of stainless reinforced replaced concrete piers. The impact forces and displacements, strain time–history curves, crack propagations and distributions, and concrete damages, were analyzed during the experimental test. The results showed that the original specimen had consistent change trends with the stainless reinforced equal-strength replaced specimens in regard to maximum impact, steel bar and concrete strains, displacement peaks, and other aspects. Furthermore, under equal impact energies, the relative ratios were found to all range at ±5%, and the fracture quantities and distributions, as well as the concrete damages, were approximately consistent. These research results will potentially provide technical support for the future designs of anti-impact stainless reinforced concrete piers.

Comparison of dynamic lateral resistance of railway concrete, wooden and steel sleepers subjected to impact loading

This paper was devoted to investigating and comparing the dynamic lateral resistance (DLR) of various types of sleepers under lateral impact loading conditions. In this regard, a series of impact tests were conducted on concrete, wooden and steel sleepers in the laboratory, using an inventive pendulum loading test device (PLTD). In loading tests, different masses and triggering angles for the PLTD hammer, the impact load, inertia force and lateral displacement of sleepers were recorded by instrumenting the hammer and sleepers. Furthermore, in order to compare the ballast–sleeper interaction force diagrams in dynamic and static states of loading, a number of single tie (sleeper) push tests (STPTs) were accomplished in a similar circumstance. The laboratory results showed the insufficiency of steel sleeper in providing the DLR against impact loads in comparison with concrete and wooden sleepers. Moreover, the maximum DLR of concrete, wooden and steel sleepers were calculated as 12.2, 5.1 and 2.35 kN, which were considerably higher than their static lateral resistances (SLRs) of 6.2, 3.1 and 1.75 kN, respectively. Assuming an impact coefficient as the DLR/SLR ratio, the values of 1.98, 1.65 and 1.34 were attained for the mentioned sleepers, indicating a very good agreement with the value of 200% suggested by the American Railway Engineering and Maintenance-of-Way Association [AREMA. (2006). Manual for railway engineering. Lanham, MD: Author] for a concrete sleeper.

Effects of axial load on nonlinear response of RC columns subjected to lateral impact load: Ship-pier collision

In this paper, the effects of axial load on dynamic responses and failure behaviors of reinforced concrete (RC) columns subjected to lateral impact loading are evaluated using numerical simulations in LS–DYNA. First, a series of numerical mass dropping impact tests are carried out on an axially loaded singular RC column to investigate the sensitivity of column impact response, internal force distribution, and plastic hinge location to the variability of the axial load. Also, a comparative study is done on the failure modes and impact responses of the column with different axial load ratios subjected to lateral impact loading at different elevations from the column base. It is found that the decrease of impact elevation causes the increase of initial peak impact force and changing the failure mode of the column from a global-flexure mode to the shear-flexural or global shear failure modes. In addition, a parametric study is carried out to quantify the relationships between the impact responses (including peak impact force, peak flexural moment, and plastic hinge location) and axial load ratio by varying of impact velocity for the column mid-span impacting scenarios. From the results, it is obtained that the increase of axial load ratio causes the increase of initial peak impact force and the internal forces of the column. Besides, it is found that the distance of plastic hinge locations from the column impact point (in particular, mid-span for parametric study) decreases in proportion to the increase of axial load ratio which causes the column failure localized at the impact zone. Moreover, to prove the axial load effects on the responses of an impacted structure in a realistic application, the finite element simulations of ship collision with a cable-stayed bridge pier in the cases with and without superstructure are developed in LS–DYNA. It is proved that the pier impact responses including impact force and internal forces have the greater values for the pier in the presence of the superstructure than those of isolated model. Also, The pier with superstructure tends to redistribute the impact load downward the pier substructure which leads to the increase of collision intensity, the severity of local damages, and shear failures.

Behaviour of cold-formed dimpled columns under lateral impact

The UltraSTEEL® forming process forms plain steel sheets into dimpled steel sheets. During the forming process both geometry and mechanical properties are considerably altered. This study aims to understand the response of the dimpled steel columns to low velocity lateral impact loads. Explicit finite element (FE) models were created and validated, including boundary conditions, element types and element sizes. Plain, dimpled columns and columns with dimpled geometry and plain material (DGPM) were analysed under lateral impact, to find out the difference between plain and dimpled columns, and the influence of the introduced dimpled geometry. Comparisons were made based mainly on the mean impact force, crush efficiency, and ability to maintain stability. A series of numerical analysis was carried out under different axial compressive loads. The dimpled columns have shown an up to 32.5% greater mean force and an up to 24.4% greater crush efficiency over the plain ones. The dimpled columns have also shown a better stability under axial compressive loads. A further investigation on the support conditions indicated that the dimpled geometry contributes to the reduction of the maximum impact force and therefore increasing the crush efficiency, where at least one end of the column is fully fixed.

Parameter Analysis on the Anti-Impact Behavior of Pcfst Columns under Lateral Impact Load

Concrete-filled steel tubular (CFST) structures have been widel y used in civil engineering structures, due to its good behaviors under both static and dynamic loads. In this paper, numerical studies were carried out to investigate the anti-impact behavior of partially concrete-filled steel tubular (PCFST) columns under lateral impact loads. Finite element analysis (FEA) model was established using ABAQUS. To validate the FEA model, the numerical results were compared with experimental results. Moreover, parameter analysis was carried out to further study the anti-impact behaviors of the PCFST columns. The concrete filling height, the impact energy, the impact direction, and the yield strength of steel were the main parameters considered in this study. The dynamic responses under the impact load, including the impact force, the failure mode, and the displacement response, were all analyzed. The results of parameter analysis showed that the anti-impact behaviors of the PCFST columns significantly increased when the concrete filling height or the yield strength of steel increased greatly. The impact energy and direction also greatly affected the anti-impact behaviors of the PCFST columns.

Lateral impact response of innovative hollow corrugated members

There has recently been a growing trend of replacing conventional structural elements by innovative components so as to achieve more resilient infrastructures. Owing to the recent benchmark study conducted at Monash University, it has been demonstrated that the ultimate compressive capacity of hollow box members consisting of self-strengthened corrugated plates is significantly more than those made of flat plates. However, the behaviour of hollow corrugated members subjected to lateral impact loading has never been investigated. This paper fundamentally reports the behaviour of members built up from four corrugated plates, which are butt-welded at the apexes of the section, under lateral impact loading. Three different types of corrugation profiles as well as two levels of impact energy are considered to investigate the influence of geometric parameters and impact energy level on the member behaviour. The samples are transversely hit by an indenter with defined weight dropping from desired height. It will be demonstrated that the corrugation shape may influence the peak impact force, stabilised post-peak forces, and contact duration. A numerical model is also developed and verified against the experimental results using ABAQUS. Good agreement between experimental and numerical results including recorded data histories and damage patterns is achieved.

Experimental study of CFRP strengthened steel columns subject to lateral impact loads

In both building and civil engineering structures, the occurrence of impact loading to column elements can be a significant issue, particularly in regard to disproportionate collapse. For existing structures vulnerable to impacts, the development of appropriate strengthening techniques is key to extending service life and improving robustness. In the case of structural steelwork, composites such as carbon fibre reinforced polymer (CFRP) offer a promising means of retrofitting and improving performance under impact. Towards this, the present study experimentally investigated a total of 12 square hollow section (SHS) columns under impact loads. The test series included both unstrengthened and CFRP strengthened samples with different fibre orientations with a view to finding the optimum CFRP configuration. As a means of simulating lateral impact on axially loaded elements, a purpose-built test rig was manufactured to apply a compressive preload to the samples prior to impact. Different preloading levels were applied to the samples before they were impacted transversely. The results show that the strengthening effectiveness increased with higher preloading level. The average reduction in the transverse displacement for the strengthened columns tested under 70% preloading level was around 32% compared to the unstrengthened column while this value was about 22% for the columns tested without compressive preload.

Experimental investigation and improved FE modeling of axially-loaded circular RC columns under lateral impact loading

Circular reinforced concrete (RC) columns have been widely used in the bridge structures (e.g., piers) due to their economic and functional advantages. However, RC columns are usually subjected to a lateral impact load under extreme loading conditions, especially under the collision event of an aberrant vehicle or vessel. Although a number of low-velocity impact tests on RC beams have been conducted, few experiments have been performed to clarify the dynamic behaviors of axially-loaded RC columns subjected to lateral impact loading. To this end, low-velocity impact tests on the axially-loaded circular RC columns are designed and conducted in this paper. Ten circular RC column specimens are fabricated with two different reinforcement ratios. Two out of these specimens are tested under static axial loading to determine their compressive resistances and the axial load levels applied in the impact tests. The other eight specimens with different axial load levels are tested under impact loading through the drop hammer test system at Hunan University. It is found that the applied axial loads have a great effect on the impact responses (e.g., impact forces, maximum and residual deformations) of the circular RC columns. Generally, the axial loads play a positive effect when the deformations of the column specimens are relatively small. On the contrary, the presence of an axial load exhibits catastrophic effects (e.g., complete collapse) in the case of the column with a low reinforcement ratio subjected to a high-energy impact. To further interpret the experimental data, the corresponding finite element (FE) models are developed for the impact simulation of axially-loaded RC columns. The conventional modeling used for RC beams is shown to have some disadvantages in the prediction of the impact-induced responses (e.g., resilient deformations) of the axially-loaded columns. For this reason, an improved FE modeling technique is proposed to simulate the axially-loaded RC columns subjected to impact loading. In the improved FE model, the concrete material model is modified to accurately consider the confinement effect of the spiral stirrup. The influences of both the bond-slip and crack closure behaviors on the impact-induced responses are also identified and considered in the improved FE models. The numerical results obtained from the improved models are in good agreement with the experimental data, indicating the applicability of the proposed FE modeling. These findings drawn from the experimental and numerical investigations can facilitate more reliable evaluation of a bridge structure with RC columns subjected to vehicle or vessel impacts.

Effects of load-related parameters on the response of concrete-filled double-skin steel tube columns subjected to lateral impact

Concrete-filled double-skin steel tubes (CFDSTs), which consist of two concentric steel tubes with concrete sandwiched between them, have found increasing use as a new sustainable alternative to existing structural bridge piers and building columns, over the recent years. They can hence become vulnerable to lateral impact loads such as those from collision of vehicles, vessels, barges or flying debris from a nearby explosion. This paper treats the response of such columns under a combination of static axial and dynamic lateral impact loads using a fully coupled numerical analysis with the finite element code LS-DYNA. The capability of the numerical model to trace the response and to predict the failure modes of the columns has been validated using extensive results from experiments carried out recently at Queensland university of Technology. A parametric sensitivity analysis is conducted to investigate the effects of several load-related parameters on the key response of the CFDST columns. Results provide new information on the impact response of CFDST columns and the effects of controlling parameters to form an extensive database. This can be employed to develop appropriate equations and design calculation methods for CFDST columns under lateral impact loading.