Column Wall Research Articles

Computational fluid dynamics study of potential solutions to alleviate viscous heating band broadening in 2.1 millimeter liquid chromatography columns

We report on a numerical simulation study of a number of potential column technology solutions to minimize the plate height contribution (Hvh) originating from the use of ultra-high pressures and their concomitant viscous heating effect. Looking as far as possible into the future of UHPLC, all main results are obtained for the case of a 2500 bar pressure gradient. However, to generalize the result, a correlation is given that can be used to interpolate the results to lower pressures with some 10% accuracy. For the considered case of a 2.1mm column, a liquid flow rate of 0.45 ml/min, an analyte with retention factor k(25°C)=3 and a retention enthalpy chosen such that ΔHR/R= -1000 K, it is found that, in order to keep the global plate height as measured at the column outlet (Hvh,glob,out) below 1 μm, the bed conductivity would need to be raised to λbed=2.4 W/m•K, i.e., 4 times higher than a typical packed bed of fully-porous or core-shell silica particles. An equivalent effect on the band broadening could be obtained if it would be possible to replace the steel column wall with a low conductivity material. In this case, a wall conductivity of 0.25 W/m•K, i.e., 64 times smaller than the conductivity of steel, would be needed to keep Hvh,glob,out below 1 μm. Results are also interpreted based on contour plots of the axial and radial velocity variation of a retained analyte.

Energy absorption characteristics of functionally graded polymer-based lattice structures filled aluminum tubes under transverse impact loading

This paper aims to evaluate the potential use of an innovative functionally graded lattice-filled composite beam composed of axial and radial graded three-dimensional lattice cores. Graded lattice filled circular beams with different graded patterns are compared with homogenous lattice filled counterparts. Graded lattice core samples are prepared using 3D printing techniques, inserted into thin-walled tubes and subjected to three-point bending loads. Then numerical models are created in Abaqus and verified against the experiments. Parametric studies find that the novel lattice-filled structure absorbs more energy but yields larger crushing force than the uniform counterpart. In addition, various parameters, like gradient parameter and filling length, thickness and yield stress of column wall, have a considerable impact on the crashworthiness of this novel structure. Finally, multi-objective optimization is performed to maximize specific energy absorption while reducing maximum impact force. Optimization results show that graded lattice-filled structures produce superior Pareto solutions than the ordinary counterparts. Especially, the specific energy absorption can be increased to 173.9% and increasing graded lattice-filled structure has the best crashworthiness, and the least decreasing graded lattice-filled structure. The functionally graded lattice core of this study provides a novel approach to design new crash-resistant energy absorber with high energy absorption capacity.

Outcome of Open Reduction and Internal Fixation of Posterior Acetabular Fractures

Background:Acetabular fractures are a common clinical challenge. The posterior wall fractures represented 35% of all acetabular fractures and usually complexed. The curative treatment is surgical and depends on the fracture anatomy and surgeon preferences. Aim of the Work:The current study aimed to assess the short term results of posterior acetabular fractures management by open reduction and internal fixation. Patients and Methods:Thirty patients with displaced posterior wall acetabular fractures were included. They were treated by open reduction and internal fixation using neutralizing plates and screws. All patients were assessed by a pre-prepared trauma assessment sheet. Post-operative, active assisted and pain free passive range of motion exercises in all planes was advised. Functional outcome was evaluated using the Merle D'Aubinge and Postel score. Patients were followed up initially at 3 weeks intervals for first 2 months and thereafter at 6 weekly intervals for the next 6 months. Result:Patients were classified to two groups: Group [A] “70%” patients with isolated posterior wall fracture, and Group [B] “30%” of patients with posterior column plus posterior wall acetabular fracture. Both groups were comparable regarding age, gender, side and mode of trauma. The double plating fixation method was significantly increased in group B when compared to group A [77.8% vs. 0.0% respectively]. Group B was associated with significant increase of operative time than group A [164.44±13.33 vs. 128.57±27.80 minutes, respectively]. Blood loss significantly increased in group B than group A [1422.22±376.76 vs. 780.95±437.46 ml, respectively]. The excellent outcome was significantly associated with younger age, lower or absent complications, and anatomical [good quality] of direct postoperative radiological outcome. Conclusion: Most of our patients had an excellent and good outcome as a result to application of more strict selection criteria of patients and pattern.

Improving LC/MS/MS-based bioanalytical method performance and sensitivity via a hybrid surface barrier to mitigate analyte – Metal surface interactions

The accurate determination of the pharmacokinetics (PK) of a candidate drug molecule is critical in both drug discovery and development. Over the last 30 years, the sensitivity and selectivity of LC/MS has resulted in it being established as the technology of choice for these studies. However, unwanted chemical interactions between analyte(s) and the metal components in a chromatography system can result in poor peak shape and reduction in signal response, which can adversely affect the analysis of low concentrations of drugs and their metabolites in biological samples. This study evaluated the benefits of employing an inert hybrid surface technology (HST) applied to the metallic components in the LC flow path, column frits and column wall to mitigate these interactions. The results obtained were compared with that of an identical conventional LC for the bioanalysis of two steroid phosphate drugs (dexamethasone phosphate and hydrocortisone phosphate) and an epidermal growth factor receptor (EGFR) inhibitor (gefitinib) in human plasma. The results showed that for the two steroid phosphates, the peak width was reduced by 20%, peak tailing factors reduced by up to 30% and the assay sensitivity improved by factors of 7.5 and 10. This resulted in a significant improvement in the limit of detection. The new LC system also improved the reproducibility of peak integration for gefitinib, thereby reducing assay coefficients of variation (%CV) from greater than 10% to less than 5% at the lower limit of quantification.

Long-term outcome after en bloc resection and reconstruction of the spinal column and posterior chest wall in the treatment of malignant tumors

BackgroundMalignant tumors occurring around both the spinal column and posterior chest wall are uncommon. Surgical resection of chest wall tumors adjacent to the spinal column is still challenging due to the surrounding anatomical structures. The purpose of the present study was to evaluate the long-term outcomes of surgical management in malignant tumors involving the spinal column and posterior chest wall. MethodsBetween 1999 and 2007, 10 consecutive patients underwent en bloc resection combined with the posterior chest wall in the treatment of malignant tumors around the spinal column. There were 6 males and 4 females with a mean age at the surgery of 40.9 years old (range, 14–62 years old). The mean postoperative follow-up period was 159.7 months (range, 84–245 months). The clinical history, physical examination, laboratory data, radiological findings, and operative findings for each patient were retrospectively reviewed. ResultsAll surgeries were performed via a combined anterior and posterior approach. The mean numbers of partially resected vertebrae and ribs were 3.1 and 4.1, respectively. Lower or upper lobectomy was performed in four patients, and the diaphragm was partially resected in two patients. The surgical margin was wide in seven patients and marginal in two patients. Although five patients had postoperative respiratory problem, all patients improved immediately without life-threatening complications. There were no patients with respiratory insufficiency after surgery. One patient with osteosarcoma died of lung metastases 99 months after surgery. At the final follow-up, only one patient had local recurrence, five had been continuously disease-free, and three were alive with no evidence of disease. ConclusionsEn bloc resection and reconstruction in selected patients with malignant tumors involving both the spinal column and posterior chest wall demonstrated good long-term results for local control and the respiratory function.

NOVEL J-PLATE FOR ANTERIOR PELVIC RING INJURIES OSTEOSYNTHESIS

The aim of the study was to evaluate the results of anterior pelvic ring fractures and acetabular fractures fixation with the specially designed plate by miniinvasive surgical approach.
 Materials and methods. 54 patients with anterior pelvic ring fractures and antrerior acetabular column admitted in Sklifosovsky Clinical and Research Institute for Emergency Care in the period from 2012 to 2020 year were analyzed. In 12 patients of the first group Judet-Letournel surgical approach was used. In 42 patients of the second group miniinvasive suprapubic and ilial surgical approach were used. In all patients novel J-plate was implanted. Mean operative time, mean blood loss, infectious complications were evaluated. Harris Hip Score for functional assessment after pelvic fractures was used for evaluation of long-term results. 
 Results. Mean operative time in the first group was 181±25.4 min., mean blood loss amounted to 384±51.6 ml. Mean operative time in the first group was 98 ±21.5 min, blood loss - 183±59.8 ml. There were no infectious complications. The amount of good and excellent treatment results in the main group was 72%. Unsatisfied results amounted to 4%.
 Conclusion. J-plate for pelvic injuries fixation is indicated in patients with anterior column and anterior wall acetabular fractures associated with contralateral pubic bone fracture or pubic symphysis rupture. Combination of ilial and suprpubic surgical approaches can be used in less than 2 weeks after trauma to minimize operation time and blood loss.

Prospective study of functional outcome in surgical management of posterior column or posterior wall of acetabular fracture by open reduction and internal fixation

Background: Acetabular fractures remain one of the most difficult Orthopaedic injuries to treat successfully. 80% of the acetabular fractures result from high-energy trauma like motor vehicle accidents and 10% falls from a significant height. Posterior wall fracture with or without dislocation are the most common type acetabular fracture accounting for a quarter to a third of all acetabular fractures. Unsatisfactory clinical results occur in more than 80% of patients treated non-surgically. Recently it has become obvious that accurate reduction of fracture is an important factor in achieving satisfactory outcome and open reduction is better than closed reduction Operative management usually offers the best chance of preserving long-term joint function and early mobilization but only if an anatomically reconstructed acetabulum is achieved. Results: The mean follow up period ranged from 6 weeks to 18 months. All the fractures were united at an average of 16 weeks and mean Harris hip score at the end of 1 year was 85.8. There was 1 superficial wound infections which was treated with intravenous antibiotic and wound healed with secondary intention and 1 case had foot drop post-operatively treated with foot drop splint recovery occurred after 6 month postoperatively. Conclusion: Good to excellent results were achieved in 75% of total cases. Hence we conclude that management of posterior wall or posterior column of Acetabular fracture is best achieved by means surgical approach by open reduction internal fixation with plates and screws.

Axial compressive behavior of concrete filled stainless-carbon steel tube columns: Experimental investigation

This paper investigates the axial compressive behavior of concrete-filled stainless-carbon steel tube (CFSCT) stub columns, consisting of an outer stainless steel tube, an inner carbon steel tube, and infilled concrete. A total of twenty column specimens are fabricated and tested. Test parameters include column section type, strength and wall thickness of carbon steel tube, and concrete strength. Failure modes, load versus deformation relationships, ultimate strength, residual strength, ductility, elastic and elastic-plastic local buckling stress, and strain characteristics are investigated. Results show that outward local buckling of stainless steel tubes occurs in all CFSCT column specimens, and columns fail in a ductile manner. Increasing the carbon steel tube thickness can significantly improve column ultimate strength and residual strength. Compared to conventional concrete-filled stainless steel tube (CFSST) columns, the ultimate strength of CFSCT columns improved by 10.9%, 23.1%, and 27.4% on average for columns with carbon steel tube wall thickness of 2, 4, and 6 mm, respectively. The post-peak ductility behavior is also related to carbon steel tube wall thickness, increasing wall thickness can slow down the descending branch after peak load. Concrete has significant effect on the ultimate strength, when concrete strength increases, specimen ultimate strength increases by 15.1% on average. In addition, finite element model is established and analyzed based on the experimental results. Finally, ultimate strengths are compared and evaluated according to the Eurocode 4, AIJ, ACI and GB 50936.

Buried layers change soil water flow and solute transport from the Yellow River Delta, China

For the limitation of techniques on the saline soil improvement, the effect of a new method with some effective materials on saline soil improvement was studied by soil column experiment. Biochar and wood fibre were used as a buried layer to identify their effects on the saline soil reclamation. Soil samples were packed in each column (height, 130 cm; diameter, 20 cm). A tape measure (length, 100 cm) was fixed vertically to the outer wall of each soil column; it was used to record the location of the wetting front during infiltration. Biochar and wood fibre were inserted at depths of either 30 cm or 50 cm (thickness in each treatment, 2 cm). Soil columns were irrigated once with 15 L of brackish water (2 g/L). Soil water content and salt content were measured with a TRIME-PICO sensor at the 25, 60 and 100 cm layers, and Mariotte’s bottle was used at the 100-cm layer to measure the underground water level. Wood fibre and biochar used as the buried layer was found that they caused a breakdown in the continuity of capillary movement and salt reduction. Wood fibre and biochar were able to retard the rate of water infiltration at 0–30-cm depth, for high water potential created when the buried layer contained sufficient water; it improved the more water infiltration than evaporation. Thus, it could serve to increase the salt leaching efficiency during the longer time scales of soil water infiltration; results showed that the buried layer was at 30-cm depth; the desalting rates were 3.69% (biochar) and 29.38% (wood fibre); the desalting rates were 4.76% (biochar) and 17.07% (wood fibre) when buried layer at 50 cm. And, the better performance in soil water infiltration and salt reduction was caused by a higher pore width, abundant fibrous tissue and saturation moisture content (Ɵs). The buried layer can improve the soil water infiltration process, especially when the wood fibre layer was at 30 cm. Both biochar and wood fibre layers could limit salt accumulation in surface soil, indicating that the continuity of capillary movement was broken after embedding the interlayer; wood fibre was superior to biochar in this regard. This study provides a new method on the saline soil improvement that could improve the mulching development, and the effect of the evaporation could be further considered by the buried layer.

Elasto-plastic Analysis of High-strength Concrete Shear Wall with Boundary Columns Using Fiber Model

In this study, an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load. The boundary column and shear wall were divided into fiber elements, and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens. The results show that the finite element analysis results were in good agreement with the experimental results. The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall. The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters: axis compression ratio, height to width ratio, ratio of vertical reinforcement, and ratio of longitudinal reinforcement in the boundary column. The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease. The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase. The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility. The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.

CFD-PBM simulation of hydrodynamics of microbubble column with shear-thinning fluid

Abstract A numerical simulation was performed to study the hydrodynamics of micro-bubble swarm in bubble column with polyacrylamide (PAM) aqueous solution by using computational fluid dynamics coupled with population balance models (CFD-PBM). By considering rheological characteristics of fluid, this approach was able to accurately predict the features of bubble swarm, and validated by comparing with the experimental results. The gas holdup, turbulent kinetic energy and liquid velocity of bubble column have been elucidated by considering the influences of superficial gas velocity and gas distributor size respectively. The results show that with the rise of the superficial gas velocity, the gas holdup and its peak width increase significantly. Especially, the curve peak corresponding to high gas velocity tends to drift obviously toward the right side. Except for the occurrence of a smooth holdup peak at the column center under the condition of the moderate distributor size, the gas holdups for the small and large distributor sizes become flat in the radial direction respectively. The distribution of turbulent kinetic energy presents an increasingly asymmetrical feature in the radial direction and also its variation amplitude enhances obviously with the rise of gas velocity. The increase in gas distributor size can enhance markedly turbulent kinetic energy as well as its overall influenced width. At the low and moderate superficial gas velocity, the curves of the liquid velocity in radial direction present the Gaussian distributions, whereas the perfect distribution always is broken in the symmetry for high gas velocity. Both liquid velocities around the bubble column center and the ones near both column walls go up consistently with the gas distributor size, especially near the walls at the large distributor size condition.

ANALYSIS OF BEHAVIOUR OF CALCIUM SILICATE HOLLOW BLOCKS MASONRY SUBJECTED TO THE CONCENTRATED LOAD

Loading of masonry with concentrated load is a sufficiently common case of loading which occurs due to structures of various purposes and sizes which lean against masonry wall, column or partition wall. Reinforced concrete or metal beams, reinforced beams, wooden structures of roof or span are leaned against masonry structures most usually. Investigations show that masonry structures under concentrated load withstand higher loads than structures of which the whole surface area is compressed. In most cases traditional bricks’ masonry under concentrated load was investigated. Its head joints are filled with mortar. This paper describes the experimental and numerical modeling results of investigation of calcium silicate hollow blocks masonry with thin layered mortar and unfilled head joints compressed by concentrated load. The more dangerous case when the edge of masonry unit (wall) is affected by concentrated load was chosen for analysis. Preliminary investigations have shown that the bed joints transmiss horizontal stresses. The stress distribution angle is close to 60°, i.e. close to stress distribution in masonry with filled head joints.

Application of new H-shaped anatomical titanium plate for posterior wall/posterior column acetabular fractures

To explore the effectiveness of a new H-shaped anatomical titanium plate in treatment of posterior wall/posterior column acetabular fractures. Between March 2012 and April 2019, 46 patients with acetabular fractures involving posterior wall/posterior column were treated with the new H-shaped anatomical titanium plates. There were 28 males and 18 females. The age ranged from 20 to 70 years, with an average of 45.5 years. Among the patients, 34 cases were injured by traffic accidents and 12 cases by falling from height. The time from injury to operation ranged from 2 to 14 days, with an average of 7 days. According to Letournel-Judet classification, there were 12 cases of posterior wall fractures, 1 case of posterior column fracture, 3 cases of transverse fractures, 9 cases of transverse fractures involving posterior walls, 8 cases of posterior column and posterior wall fractures, 2 cases of anterior column and posterior semi-transverse fractures, 3 cases of T-shaped fractures, and 8 cases of double column fractures. Matta reduction standard was used to evaluate fracture reduction and Merle d'Aubign-Postel score was used to evaluate hip joint function. All operations were successfully completed. The time of posterior operation was 60-120 minutes, with an average of 80 minutes. The amount of intraoperative blood loss ranged from 200 to 600 mL, with an average of 300 mL. All the incisions healed by first intention and no infection, deep vein thrombosis, or sciatic nerve injury occurred. All 46 patients were followed up 6-72 months, with an average of 37 months. According to Matta reduction standard, 40 cases obtained anatomic reduction, 4 cases satisfactory reduction, 2 cases unsatisfactory reduction, and the satisfaction rate was 95.7% (44/46). All fractures healed, and the healing time was 3-6 months, with an average of 4.3 months. No internal fixation failure occurred during the follow-up. At last follow-up, the Merle d'Aubign-Postel score ranged from 6 to 18 (mean, 15.5), including 38 cases of excellent, 4 cases of good, 2 cases of fair, and 2 cases of poor, with an excellent and good rate of 91.3% (42/46). Heterotopic ossification occurred in 4 cases, traumatic arthritis in 4 cases, and osteonecrosis of femoral head in 2 cases after operation. For acetabular fractures involving posterior wall/posterior column, the new H-shaped anatomical titanium plate can provide stable fixation, satisfactory reduction, and good recovery of hip function.

Study and design of assembled CFDST column-beam connections considering column wall failure

Currently, there is a lack of research in the design approach to avoid column wall failure in the concrete filled double skin steel tubular (CFDST) column-beam connections. In this paper, a finite element model has been developed and verified by available experimental data to analyze the failure mechanism of CFDST column-beam connections. Various finite element models with different column hollow ratios () were established. The simulation result revealed that with increasing  the failure mode gradually changed from yielding of end plate, to local failure of the column wall. Detailed parametric analyses were performed to study the failure mechanism of column wall for the CFDST column-beam connection, in which the strength of sandwiched concrete and steel tube and thickness of steel tube were incorporated. An analytical model was proposed to predict the moment resistance of the assembled connection considering the failure of column wall. The simulation results indicate that the proposed analytical model can provided a conservative prediction of the moment resistance. Finally, an upper bound value of was recommend to avoid column wall failure for CFDST column-beam connections.

Mechanical Behavior of a Multisegmented Tower Anchorage Structure with an Exposed Steel Anchor Box

A tower anchorage structure with an exposed steel anchor box is commonly used for cable‐stayed bridges. Many researchers have conducted studies on this structure by considering a single segment. However, in practical engineering, the stress of multisegmented tower anchorage structure is not completely similar to that of single segment, and the forces between segments affect each other. Hence, in this study, the mechanical behavior of a multisegment anchorage structure with an exposed steel anchor box was investigated via finite element analysis. Furthermore, the load transfer path and stress distribution characteristics of the structure were investigated. The results indicate that the horizontal component of the cable force is borne by the side plate of the steel anchor box, the diaphragm, and the side wall of the concrete tower column, while the vertical component is transmitted by the steel anchor box and concrete tower column. Under the action of this cable force, the horizontal component of the cable force borne by the middle segment increases, while the components at the two end segments decrease. The vertical force is greater on the lower tower segments. The stress levels on the side plate and on the diaphragm of the steel anchor box in the middle section are high. Under the cable force load, the frame formed by the end plate and side plate of the steel anchor box expands outward. The end plate is mainly under a tensile load, and the tensile stress level on the lower section exceeds that on the upper section. A high‐stress area for the concrete tower is observed in the steel‐concrete joint. The stud group of the anchorage structure is subjected to horizontal and vertical shear forces, and no “saddle‐shaped” distribution of the stud shear is found. An optimal arrangement method for the stud group was proposed to optimize its mechanical performance.

Faktori sigurnosti u proračunu debljine zida kolona za rektifikaciju

Gas rectification columns are a very important part of each onshore plant. Their sudden failures cause huge losses on a daily basis, while fluid leakage can be very dangerous to people and environment. For that reason, the proper design of the column is of huge importance, among the others safety factors as well. In this paper, the wall thickness measure is presented with the aim to calculate corrosion rate and remaining life of rectification columns. The minimum required column wall thickness was calculated according to the most commonly used international standard and the obtained difference was analyzed.

Analysis of the estimated remaining service life of gas rectification columns

Gas rectification columns are process apparatuses which are very important part of each onshore plant. Sudden failure of these types of columns causes huge daily losses, while fluid leakage can be very dangerous for the people and hazardous for the environment. For that reason, a regular and correct examination of the column is of great importance for the continual process of leading. Together with the detailed examination of the column, a risk-based inspection was applied to maximize savings, both material, time, and costs. The expected remaining service life of rectification columns was also analyzed, while the corrosion rates were calculated according to the various international standards. The minimum required column wall thickness was calculated according to the most commonly used international standard and the obtained difference was analyzed. Detailed analysis of the total risks of the column due to potential failure is presented.

Experimental studies on T-stub to hollow section column connection bolted by T-head square-neck one-side bolts under tension

A novel T-head Square-neck One-side Bolt (TSOB) was proposed and tensile tests on the T-head Square-neck One-side Bolts bolted Connection (TSOBC) for T-stub to Hollow Square Steel Tube (HSST) were conducted. In total, six TSOBCs and three Standard High-strength Bolts bolted Connections (SHBCs) were tested. Four failure modes were found in the test, namely, (1) column wall yielding, (2) column wall yielding with bolt hole shearing, (3) T-stub flange yielding, and (4) bolt failure. Compared to the SHBC, the tensile yield strength and tensile ultimate strength of TSOBCs with vertical and horizontal slotted bolt holes both decreased if the connections encountered the column wall yielding, the column wall yielding with bolt hole shearing, or the T-stub flange yielding failure. The Gomes and Yeomans models were modified to calculate the bending yield strength of the column wall of TSOBC under the failure mode of column wall yielding with bolt hole shearing. The modified Gomes model was recommended to design TSOBC failed by column wall yielding with bolt hole shearing. Theoretical models for calculating the bending yield strength of T-stub flange with slotted bolt holes of TSOBC was also presented, and calculated values were in good agreement with test results.

Acetabular fractures: epidemiological, lesional, therapeutic and evolutionary aspects

<p class="abstract"><strong>Background:</strong> Fractures of the acetabulum are serious because they affect a deep, load-bearing joint that is difficult to repair surgically at first. They occur in a context of polytrauma. The aim of our work is to study the epidemiological, lesional, therapeutic and evolutionary aspects of acetabulum fractures.</p><p class="abstract"><strong>Methods: </strong>This is a 5-year retrospective study from January 2012 to December 2016 including 45 patients treated for acetabulum fracture.</p><p class="abstract"><strong>Results: </strong>45 patients including 38 men and 7 women with a mean age of 36 years (extremes 18 and 74). The circumstances of occurrence were dominated by road traffic accidents with 42 cases (93.3%).</p><p class="abstract">According to the Judet-Letournel classification, we observed 28 elementary fractures (16 posterior wall fractures, 11 posterior column fractures, 1 anterior column fracture) and 17 complex fractures (7 posterior column and posterior wall fractures, 6 transverse and posterior wall fractures, 3 posterior and anterior column fractures, 1 anterior column and posterior hemi-transverse fracture). The association of a dislocation with an acetabulum fracture was found in 32 cases. Associated lesions (fractures) were observed in 23 patients. One case of associated TCE was noted. Treatment was orthopedic in 18 patients, surgical in 18 patients and functional in 9 patients. According to the Matta criteria we obtained after treatment 46.7% good reduction, 51.1% satisfactory and 2.2% unsatisfactory reduction. According to the Postel-Merle D'Aubigné rating, 16 patients obtained excellent results with overall 93.3% satisfactory results. The complications found were coxarthrosis (15 cases), para-articular ossification (2 cases) and vicious callus (1 case).</p><p class="abstract"><strong>Conclusions:</strong> The treatment of acetabulum fractures depends on the type of fracture, the age and activities of the patients. Orthopedic, surgical as well as functional treatment can give good acetabular reconstructions and functional results.</p>

The Behaviour of Fresh Concrete with Varying Coarse Aggregate Content at the Concrete-Steel Wall Interface

The interaction between concrete and steel occurs during concrete mixing and finishing processes, during filling of concrete moulds, formwork, composite columns and during pumping of concrete mixtures. More experimental investigation is required to predict variations in interface friction, as a result of the composition of the lubrication layer which depends on the composition of concrete. This study provides experimental results to allow for a better understanding of friction at concrete-steel interface, with changes in the coarse aggregate (CA) content in the aggregate mixture (AM). Friction tests on fresh concrete have been carried out using the BTRHEOM tribometer (Nantes, France) and the interface parameters were calculated on the basis of the interface friction between the concrete and the steel wall, through the ADRHEO software. The roughness parameters were measured along the length of the rotary steel cylinder of the tribometer. In addition, the roughness of new and modified metal form-lining in steel composite columns was also measured. Variations in the CA content in the AM in the 42 to 52% range had minimal effects on the yield stress of the interface. The viscous constant of the interface as measured with a tribometer decreased, when the roughness parameter Rt values of the rotary cylinder wall, which refer to the absolute vertical distance between the maximum profile peak height and the maximum profile valley depth along the sampling length, were in the 17.10 to 28.73 μm range. The roughness profile peaks’ asperity recorded, was higher for the worn metal form-lining and for the steel composite columns with the inner surface covered in rust, when compared to the rotary cylinder roughness profile. The hypothesis is based on the principle that a sufficient lubrication layer, with the required thickness of fine mortar is created at the interface between the concrete and the metal form-lining or steel composite column wall, when the CA content in the AM varies in the range from 42 to 52% and the wall roughness parameters (Rt) of these elements varies in the 15.00 to 30.00 μm range.