Ramp Configuration Research Articles

Combined Crash Frequency–Crash Severity Evaluation of Geometric Design Decisions

This paper quantified the effects of freeway ramp spacing and auxiliary lane presence on crash frequency and crash severity. Crash frequencies were predicted with a safety performance function, and crash severities were estimated with what was termed a “severity distribution function.” The paper then demonstrated how to combine quantitative knowledge related to the effects of ramp spacing and auxiliary lane presence on both crash frequency and severity into a framework for assessing the overall crash cost for different ramp configurations. Geometric features, traffic characteristics, and crash data were collected for 404 freeway segments in California and Washington State. Negative binomial regression models and multinomial logit regression models were used to estimate the effects of ramp spacing and auxiliary lane presence on expected crash frequencies and crash severities, respectively. Results showed that expected multiple-vehicle crash frequency increased as ramp spacing decreased. Meanwhile, there was a decrease in the proportion of severe crashes (fatal, incapacitating injury) with a decrease in ramp spacing, even though the overall frequency of these severe crashes remained relatively unchanged. Providing an auxiliary lane was expected to decrease crash frequency, although this reduction appeared to be primarily in crashes that were less severe (possible injury and property damage only). The findings appeared to effectively capture the complex relationships between geometric designs and operations and the high sensitivity between speed and crash severity. The paper provided quantitative tools for making informed freeway and interchange design decisions where ramp spacing and auxiliary lanes were considerations.

Acceleration Characteristics at Metered On-Ramps

Vehicle acceleration capability is an important parameter for traffic operation analysis, traffic simulation, and transportation facilities design. Most of the existing studies on acceleration characteristics, however, do not fully represent the realistic traffic conditions or are based on outdated data; these deficiencies may result in errors in modeling vehicle acceleration capability. In this paper, actual acceleration characteristics at metered on-ramps were investigated according to field data collection and analysis. With the assumption that vehicles make uniformly accelerated motion in each short space or time interval, the entire acceleration length was partitioned into several short segments. Then, video cameras, magnetic counters, or both were used to document the spot speed at predetermined locations; accordingly, distance–acceleration profiles of various ramp configurations were determined. Results showed that the acceleration rate at metered on-ramps was not constant; vehicles usually accelerated at a higher acceleration rate when the speed was lower and vice versa, and the maximum acceleration rate usually occurred at about 50 to 100 ft downstream from the stop bar. Also, a ramp with taper merging configuration usually produced higher acceleration rates than did a parallel merging ramp. This study also pointed out that acceleration rates documented in the AASHTO Green Book, widely used by most state departments of transportation in the United States as the acceleration length design guidance for metered on-ramps, were much lower than the values measured at existing metered on-ramps.

Computer-aided analysis and evaluation on ramp spacing along urban expressways

High traffic efficiency on urban expressways and their ramps is the crucial requirement to ensure the optimum design and reliable operation of urban traffic networks in large cities. The mismatch between ramp configurations and spacing can lead to the dramatic drop of traffic capacity and efficiency. The traffic performance in different scenarios for four typical configurations along urban expressways is simulated after the calibration of simulation model. The results are then evaluated through the data envelopment analysis (DEA) and analytic hierarchy process (AHP). The traffic simulation software VISSIM is employed to calculate the critical variables and parameters able to represent traffic performance of urban expressways and their ramps in terms of traffic practice. To carry preferable multi-criteria evaluations from simulation process, the DEA and AHP method are used together to find the appropriate spacing between ramps and evaluate the effects from the different design speeds of frontage roads and opening time of ramps. The proposed method also gives the ranking of different scenarios for four configurations. The applicability and effectiveness of the proposed evaluation methods are demonstrated in case studies where some critical parameters for traffic designs and operations about ramps are practically given through field survey. The results show that the proposed methodology is vitally important for traffic planners and designers to assure an effective evaluation and decision support on complex transportation systems.

Effect of ramp configuration on easiness of handling, heart rate, and behavior of near-market weight pigs at unloading1

Three experiments, each using 280 pigs, were conducted in a simulated compartment to test the effect of angle of entrance (AOE) to the ramp (90°, 60°, 30°, or 0°), ramp slope (0°, 16°, 21°, or 26°), and an initial 20-cm step associated with 16° or 21° ramp slopes on the ease of handling, heart rate (HR), and behavior of near market-weight pigs during unloading. Heart rate (pigs and handler), unloading time, interventions of the handler, and reactions of the pigs were monitored. The results of the first experiment show that using a 90° AOE had detrimental effects on ease of handling (P < 0.05), HR of the pig (P < 0.05), and behavior (P < 0.05). The 0° and 30° AOE appeared to improve the ease of unloading, whereas the 60° AOE had an intermediate effect. The 30° AOE appeared to be preferable, because pigs moved at this angle balked less frequently (P < 0.01) and required less manipulation (P < 0.05) than pigs moved with a 0° AOE. The results of the second experiment show that the use of a flat ramp led to the easiest unloading, as demonstrated by the lower number of balks (P < 0.001) when pigs were moved to the ramp and less frequent use of paddle (P = 0.001) or voice (P < 0.001) on the ramp, compared with the other treatments. However, the flat ramp did not differ from the 21° ramp in many of the variables reflecting ease of handling, which may be explained by the difference in configuration between the ramps. The results also show that the use of the steepest ramp slope had the most detrimental effect on balking and backing up behavior of pigs (P < 0.001), and handling (touches, slaps, and pushes; P < 0.05 for all) when moved to the ramp and on unloading time (P < 0.01). No differences in pig HR (P < 0.05) and ease of handling on the ramp (P < 0.05) were found between a 26° and 16° ramp slope, suggesting that the length of the ramp may be one of the factors that make unloading more difficult. The results of the last experiment show that an initial step made unloading physically more demanding for the handler (P < 0.001) and pigs on the ramp (P < 0.05) as demonstrated by their greater HR. The greater difficulty of handling (P < 0.01) and reluctance to move (P < 0.05) of pigs moved toward the 16° ramp with a step suggest that pigs perceived this ramp as more psychologically challenging. Making a few changes in terms of the design of the ramp could improve the efficiency of handling and reduce stress in pigs.

Effects of Sidewall Compression and Relaminarization in a Scramjet Inlet

This paper presents the numerical simulations and the performance analysis of a scramjet inlet as part of a combined experimental and numerical study. A well-validated finite volume flow solver was used to simulate a scramjet inlet with a double ramp configuration for outer compression, including varying degrees of sidewall compression. The computed wall pressure and heat transfer in the symmetry plane are in close agreement with the measurements, and the numerical results indicate that the weak sidewall compression alters the inlet performance significantly. The effects of partial relaminarization over the expansion corner, before the interior part of the inlet, is isolated and investigated in both the experiment and simulation. It is shown that relaminarization of a boundary layer is predicted accurately using the current numerical methods. This work represents a contribution to the understanding of the effects of sidewall compression and relaminarization in designing a scramjet inlet.

Large-eddy simulation of a supersonic turbulent boundary layer over a compression–expansion ramp

Results of a large-eddy simulation (LES) of a supersonic turbulent boundary layer flow along a compression–expansion ramp configuration are presented. The numerical simulation is directly compared with an available experiment at the same flow conditions. The compression–expansion ramp has a deflection angle of β=25°. The flow is characterized by a free-stream Mach number of Ma∞=2.88 and the Reynolds number based on the incoming boundary layer thickness is Reδ0=132840. The Navier Stokes equations for compressible flows are solved on a cartesian collocated grid. About 32.5×106 grid points are used to discretize the computational domain. Subgrid scale effects are modeled implicitly by the adaptive local deconvolution method (ALDM). A synthetic inflow-turbulence technique is used, which does not introduce any low frequency into the domain, therefore avoiding any possible interference with the shock/boundary layer interaction system. Statistical samples are gathered over 800 characteristic time scales δ0/U∞. The numerical data are in good agreement with the experiment in terms of mean surface-pressure distribution, skin-friction, mean velocity profiles, velocity and density fluctuations. For the first time the full compression–expansion ramp configuration was taken into account. The computational results confirm theoretical and experimental findings on fluctuation-amplification across the shockwave/boundary layer interaction region and on turbulence damping through the interaction with rarefaction waves. The LES provide evidence of the existence of Görtler-like structures originating from the recirculation region and traveling downstream along the ramp. An analysis of the wall pressure field clearly shows the presence of a low frequency motion of the shock and strong influence of the Görtler-like vortices on the wall pressure spectra.

Gate Assignment to Minimize Passenger Transit Time and Aircraft Taxi Time

This research focuses on airport gates, which are limited resources in the air transportation system. In spite of its importance, ramp congestion has not been considered in traditional research on gate assignment. This research, therefore, proposes a new perspective on the gate assignment problem that accounts for ramp congestion, as well as passenger flow. The proposed gate assignment problem minimizes weighted nominal taxi time and weighted taxi delay, as well as passenger transit time in the terminal. Nominal taxi time and taxi delay are weighted by the number of passengers on board. As a result, the flow in the passenger terminal and on ramps becomes efficient. To get near-optimal solutions within a reasonable amount of time, two metaheuristic algorithms, tabu search and genetic algorithm, are implemented for two ramp configurations. Also, the tradeoff between passenger flow and ramp congestion is analyzed.

Analysis of the Weaknesses in the Present Freeway Capacity Models for Sweden

The aim of the work is to scrutinize the present Swedish capacity manual and new models from a project in the early 2000's. It only covers freeway facilities. By using new and extended empirical data the models that have to be improved can be further developed. The result shall be the freeway models in the new Swedish Capacity Manual. The manual for freeway facilities include a time-space model for bottleneck analysis of urban and rural freeways. The work has been based on the documentation for the present models. The models have also been compared to other international models to check the reasonableness. The project includes three parts, freeway mainline section, freeway weaving and freeway merging.The review of the models revealed several deficiencies.- The Swedish capacity model for main line section doesn’t take into account the gradient, which is an important factor and is one of the most significant parameters according to German experiences.- Another large knowledge gap is the fact that the capacity model doesn’t take into account lane width and distance to obstacle.- The model for weaving has one large weakness, it is based on empirical data where the on-ramp flow is almost equal with the off-ramp flow. The model has then been design with a total weaving flow, which means that the model is insensitive to flow cases where e.g. the on-ramp flow is much larger than the off-ramp flow.- The model for on-ramp merging does only take into account the on-ramp flow, other international models also have ramp length.The work with the new capacity models during 1998-2001 had a lack of empirical data, which gave the result that relation between different parameters where difficult to find. E.g. the weaving model has only 6hours empirical data. The models should preferable add the following parameters:- Gradient for main line- Lane width- Distance to obstacle- Separate on- and off-ramp flow in the weaving model- On-ramp lengthWith the data collection system STRESS new data have been analyzed and a new model for oversaturated conditions has been developed. Also a new model for capacity in weaving segments has been developed. The new model takes into account both on-ramp and off-ramp flow. The TPMA model for link capacity has been further developed with a parameter that takes into account the gradient.A time-space model for calculation and identification of bottlenecks should also be developed. The time-space model should be answering the following questions:• How to calculate the emergence of bottlenecks in a system of adjacent interchanges?• Which bottlenecks arise because of geometric design?• How to conduct an analysis of the geometric configuration's impact on the occurrence of the bottleneck?• How to model the changes in the geometric design to eliminate or reduce the bottleneck in time and/or place?The state of art shows that only one model is adequate and gives a relatively fully cover of different on-and off ramp configurations, the model is Freeval and is a part of HCM 2010. The Swedish model will use the method for time and space calculation in HCM 2010.

Effect of Stilling Basin Geometry on Clear Water Scour Morphology Downstream of a Block Ramp

The scour mechanism downstream of a block ramp in clear water conditions is quite a complex phenomenon that depends on several parameters. Majors role are played by ramp configuration, hydraulic conditions (downstream tailwater level and discharge), material granulometry, and stilling basin geometry. Previous studies analyzed both the scour phenomenon and the effects of all the parameters involved except the last one (i.e., the case in which the ramp has the same width as the downstream stilling basin) and the case of symmetrically expanding stilling basins. This last basin configuration represents an optimal equilibrium between the necessity to dissipate energy and to create a natural pool for the biological species, thus it has a prominent ecological value. The present paper aims to assess the effect of both the width and length of the downstream stilling basin on scour features and flow pattern in clear water conditions. Different scour morphology types are distinguished and classified according to hyd...

Effects of envelope discontinuities on perceptual restoration of amplitude-compressed speech

An interrupted signal may be perceptually restored and, as a result, perceived as continuous, when the interruptions are filled with loud noise bursts. Additionally, when the signal is speech, an improvement in intelligibility may be observed. The perceived continuity of interrupted tones is reduced when the signal level is ramped down and up before and after the noise burst, respectively--an effect that has been attributed to envelope discontinuities at the tone-noise interface [Bregman, A. S., and Dannenbring, G. L. (1977). Can. J. Psychiatry 31, 151-159]. The hypothesis of the present study was that the perceptual restoration of speech would also be reduced with similar envelope discontinuities that may occur in real life due to the release time constants of hearing-aid compression. In an effort to make the conditions more relevant to hearing aids, speech was amplitude-compressed and normal-hearing listeners of varying ages were recruited. Envelope amplitude ramps were placed at the onsets/offsets of speech segments of interrupted sentences and the restoration effect was measured in two ways: objectively as the improvement in intelligibility when noise was added in the gaps and subjectively through the perceived continuity measured by subjects' own reporting. Both measures showed a reduction as the ramp duration increased--a trend observed for subjects of all ages and for all ramp configurations. These findings can be attributed to envelope discontinuities, with an additional contribution from reduced speech information due to ramping and temporal masking from loud noise bursts.

Two-Level Nested Logit Model to Identify Traffic Flow Parameters Affecting Crash Occurrence on Freeway Ramps

This study analyzes the traffic flow conditions that affect crash occurrence on freeway ramps by type (on- or off-ramps) and configurations (diamond, loop, etc.). The study used the 5-min traffic flow data before the crash obtained from loop detectors to identify the traffic conditions contributing to crashes on ramps. With 5 years of ramp crash data on the Interstate 4 freeway in Orlando, Florida, a two-level nested logit model was developed to estimate the probabilities of crash occurrence for different ramp types and configurations. In the comparison of two nest structures, the traffic flow parameters contributing to crash occurrence greatly differed between on-ramps and off-ramps. The results of the model estimation suggested that the main-line speeds immediately upstream and downstream of ramps and the volume on ramps were correlated to crash occurrence on ramps. It is recommended that these traffic flow parameters be monitored in real time to detect elevated risk in traffic conditions on ramps within on-line systems for freeway traffic management.

Analysis of shock motion in shockwave and turbulent boundary layer interaction using direct numerical simulation data

Direct numerical simulation data of a Mach 2.9, 24○ compression ramp configuration are used to analyse the shock motion. The motion can be observed from the animated DNS data available with the online version of the paper and from wall-pressure and mass-flux signals measured in the free stream. The characteristic low frequency is in the range of (0.007–0.013) U∞/δ, as found previously. The shock motion also exhibits high-frequency, of O(U∞/δ), small-amplitude spanwise wrinkling, which is mainly caused by the spanwise non-uniformity of turbulent structures in the incoming boundary layer. In studying the low-frequency streamwise oscillation, conditional statistics show that there is no significant difference in the properties of the incoming boundary layer when the shock location is upstream or downstream. The spanwise-mean separation point also undergoes a low-frequency motion and is found to be highly correlated with the shock motion. A small correlation is found between the low-momentum structures in the incoming boundary layer and the separation point. Correlations among the spanwise-mean separation point, reattachment point and the shock location indicate that the low-frequency shock unsteadiness is influenced by the downstream flow. Movies are available with the online version of the paper.

Direct Numerical Simulation of Supersonic Turbulent Boundary Layer over a Compression Ramp

A direct numerical simulation of shock wave and turbulent boundary layer interaction for a 24 deg compression ramp configuration at Mach 2.9 and Re θ 2300 is performed. A modified weighted, essentially nonoscillatory scheme is used. The direct numerical simulation results are compared with the experiments of Bookey et al. at the same flow conditions. The upstream boundary layer, the mean wall-pressure distribution, the size of the separation bubble, and the velocity profile downstream of the interaction are predicted within the experimental uncertainty. The change of the mean and fluctuating properties throughout the interaction region is studied. The low frequency motion of the shock is inferred from the wall-pressure signal and freestream mass-flux measurement.

Application of PIV in a Mach 7 double-ramp flow

The flow over a two-dimensional double compression ramp configuration is investigated by means of schlieren visualization, quantitative infrared thermography and particle image velocimetry (PIV) in a short-duration facility producing a free-stream flow at Mach 7. The study focuses upon the accuracy assessment of PIV in the hypersonic flow regime including flow facility effects such as repeatability of test conditions. The solid tracer particles are characterized by means of electron microscopy as well as by measuring the dynamic response across a planar oblique shock wave with PIV. The experiments display a strong variation in the light scattering intensity of the seeded flow over the flow field, due to the large flow compressibility. The mean velocity spatial distribution allows to clearly identify the shock pattern and the main features of the flow downstream of the shocks. However, the spatial resolution is insufficient to determine the wall flow properties. Furthermore the velocity data obtained with the PIV technique allow the determination of the spatial distribution of the Mach number under the hypothesis of adiabatic flow. The double ramp configuration with a variable second compression angle exhibits shock–shock interactions of Edney type VI or V for the lowest and highest ramp angle, respectively. A single heat transfer peak is detected with infrared thermography on the second ramp in case of a type VI interaction while for the type V shock interaction a double heat transfer peak is found. Shock wave angles measured with PIV are in good agreement with theory and the overall flow topology is consistent with schlieren visualization. Also in this respect the results are in agreement with compressible flow theory.

Simulation of streamwise vortices at the flaps of re-entry vehicles

The present study investigates separated flows in the flap region of the X-38 re-entry demonstrator with respect to the heat loads downstream reattachment induced by streamwise vortices. In a first step generic numerical flow simulations of turbulent ramp configurations with artificially induced vortex disturbances are compared with wind tunnel data of the Ludwieg tube facility in Göttingen (RWG). The results allow insight into the perturbed flow field, the associated flow topology and the influence of different flow parameters that affect the perturbations. For numerical resolution of streamwise vortices in the boundary layer of re-entry vehicles local grids are generated around the flaps of the X-38 vehicle. Extensive studies of arranging and refining the local grids demonstrate good grid convergence. For laminar cases and cases with fixed transition vortex effects on the heat transfer are observed with and without artificial vortex excitation.

Comparison of some measurement techniques for shock-induced boundary layer separation

Detailed results are presented concerning the position of separation and reattachment in case of shock/boundary-layer interaction. The tests were performed with a flat plate – 24 ∘-ramp configuration mounted between the vertical walls of the Trisonic Windtunnel Munich. The quality of schlieren method, pressure measurement technique, oil-flow visualization and laser Doppler anemometry is critically reviewed. The average thickness of the fully developed turbulent boundary layer just ahead of the ramp is δ 0=13 mm. The results show the location of separation and reattachment as a function of Mach and Reynolds number, Mach numbers ranging from 2.2 to 2.9, and unit Reynolds numbers from 29·10 6 m −1 to 58·10 6 m −1.

MULTI-MODE ANALYSIS OF BEAM-LIKE STRUCTURES SUBJECTED TO DISPLACEMENT-DEPENDENT DRY FRICTION DAMPING

A multi-mode analysis of a beam-like structure undergoing transverse vibration and subjected to a displacement-dependent force is conducted. The system model uses a ramp configuration to increase the normal force of the dry friction damper proportional to the beam's transverse displacement. The system is studied by using harmonic balance as an approximate analytical solution and then by using a time integration method. Interesting findings include the appearance of internal resonance peaks when multiple beam modes are considered. Also, as with the earlier single-degree-of-freedom study, two dynamic response solutions exist at certain parameter values. It is found that the ability to control the amplitude of the response is a function of the frequency range considered. In general, near modal resonance peaks, the amplitude of the response decreases with increasing ramp angle. However, in an “overlapping” region between resonance peaks, the amplitude of the response actually increases with increasing ramp angle. It is also found that the damping contribution from the displacement-dependent dry friction damper is “linear structural-like” in nature and relatively insensitive to the amplitude of the response. This result suggests that in the case of turbine or compressor blades, this type of damping arrangement may be effective in the suppression of flutter.

Experimental and computational investigations of hypersonic flow about compression ramps

Comprehensive results of a joint experimental and computational study of the two-dimensional flow field over flat plate/compression ramp configurations at Mach 14 are presented. These geometries are aimed to simulate, in a simplified manner, the region around deflected control surfaces of hypersonic re-entry vehicles. The test cases considered cover a range of realistic flow conditions with Reynolds numbers to the hinge line varying between 4.5 × 105 and 2.6 × 106 (with a reference length taken as the distance between the leading edge and the hinge line) and a wall-to-total-temperature ratio of 0.12. The combination of flow and geometric parameters gives rise to fully laminar strong shock wave/boundary layer interactions with extensive separation, and transitional interactions with transition occurring near the reattachment point. A fully turbulent interaction is also considered which, however, was only approximately achieved in the experiments by means of excessive tripping of the oncoming hypersonic laminar boundary layer. Emphasis has been placed upon the quality and level of confidence of both experiments and computations, including a discussion on the laminar-turbulent transition process and the associated striation phenomenon. The favourable comparison between the experimental and computational results has profided the grounds for an enhanced understanding of the relevant flow processes and their modelling. Particularly in relation to transitional shock wave/boundary layer interactions, where laminar-turbulent transition is promoted by the adverse pressure gradient and flow concavity in the reattachment region, a method is proposed to compute extreme adverse effects in the interaction region avoiding such inhibiting requirements as transition modelling or turbulence modelling over separated regions.

Evolution of a Callovian-Oxfordian carbonate margin in the Neuquén Basin of west-central Argentina: facies, architecture, depositional sequences and global sea-level changes

This paper reviews a detailed stratigraphic and sedimentologic study of a carbonate complex developed on the foreland side of the Neuquén Embayment, a protected shallow-water epicratonic site behind the active edge of the South American plate. Superb outcrops at the core of basement-involved Andean structures expose the shelf-to-basin transition and reveal with clarity the external and the internal architecture of the depositional sequences and component system tracts. Platform carbonates are largely represented by ooid and mainly rhodoid grainstones, with associated patches of coral framestone. The deeper platform and slope facies are composed of oncoidal and skeletal micritic limestones with scattered coral-sponge-algal build-ups. The overall composition and facies pattern bears resemblance to other Late Jurassic carbonate complexes form Europe and with the Smackover Formation from the Gulf Coast Basin of North America.Analysis based on mapping of the stratal patterns and facies associations in outcrops allowed the recognition of four depositional sequences. Timing provided by ammonite biochronology suggests that eustatic fluctuations were a major factor influencing the carbonate-margin architecture, and regulated episodes of condensed sedimentation, shifts of the depositional belts, and development of stratigraphic discontinuities. The onset and the end of carbonate sedimentation were associated with episodes of marine retreat and accumulation of evaporites and eolian-fluvial deposits at basin-centre locations. However, most of the marine fluctuations recorded within the carbonate complex were insufficient to expose the shelf break (Type 2), and accordingly lowstand system tracts are poorly represented. On the shelf the transgressive system tracts are represented by thin grain-supported carbonate blankets. These taper out downslope into omission surfaces or are replaced by patches of small sponge buildups. Highstand system-tract organization changes through time, reflecting changes in productivity and accomodation, presumably tied to second-order sea-level changes. Callovian highstand accumulation featured a catch-up carbonate system and produced a thin-aggradational ramp configuration, whereas conditions during middle-late Oxfordian allowed a keep-up system and produced outbuilding depositional geometries with steeper slopes.

An analytical model of hanging-wall and footwall deformation at ramps on normal and thrust faults

We determine stress, strain and structural evolution for an analytical model of moderate angle (10–20 °) ramps developed on both normal faults (normal ramps) and thrust faults (thrust ramps). In the model, a frictionless sliding surface with ramp configuration separates two incompressible, isotropic, viscous half-spaces of different viscosity (η—hanging wall and η′—footwall). Ramps are planar, but ramp-flat corners are locally rounded. Deformation is due solely to translation across the ramp, and regional extension or shortening is ignored. Sliding down a normal ramp causes vertical extension and horizontal shortening in both the hanging wall and the footwall. This conforms with reverse faults seen in experimental models of normal ramps. The stress in the footwall has the same magnitude as that in the hanging wall but the footwall strain rate is reduced in magnitude by the ratio η/η′. Both a hanging-wall syncline and a footwall anticline form. The normal ramp migrates in front of the rising footwall at a rate V ss = V[ η/( η + η′)], where V is the sliding velocity. But the ramp does not change shape. The continuous ramp motion in the model may correspond to the creation of an extensional duplex or chaos zone in brittle rocks. At a normal ramp, mean compressive stress is lowered and deviatoric stress is raised, favoring local faulting and fracture. Sliding up a thrust ramp causes stresses, strain rates and strains of the opposite sign. Horizontal extension and vertical shortening in both walls is consistent with normal faulting. Both a hanging-wall anticline and a footwall syncline form passively. Although the deviatoric stress is raised at the ramp, so is the mean compressive stress, inhibiting fracturing. However, the mean compressive stress is lowered on the adjacent flats, favoring fracturing there.