Diagonal Cracks Research Articles

An experimental study on the shear strength of SFRC beams without stirrups

The use of steel fibers in reinforced concrete (RC) structural members aims at the impro- vement of mechanical properties of such members. This study focuses on shear strength characteristics of steel fiber reinforced concrete (SFRC) beams without stirrups. Test speci- mens consisting of three RC and ten SFRC beams without stirrups have been tested under three-point loading in order to investigate the effects of fiber content and shear span-to- -effective depth ratio on the shear strength. Furthermore, an equation developed previously for predicting the ultimate shear strength of SFRC beams without stirrups is proposed to predict the diagonal cracking strength of SFRC beams without stirrups.

Numerical Analysis on the High-Strength Concrete Beams Ultimate Behaviour

Development of technologies of high-strength concrete (HSC) beams production, with the aim of creating a secure and durable material, is closely linked with the numerical models of real objects. The three-dimensional nonlinear finite element models of reinforced high-strength concrete beams with a complex geometry has been investigated in this study. The numerical analysis is performed using the ANSYS finite element package. The arc-length (A-L) parameters and the adaptive descent (AD) parameters are used with Newton-Raphson method to trace the complete load-deflection curves. Experimental and finite element modelling results are compared graphically and numerically. Comparison of these results indicates the correctness of failure criteria assumed for the high-strength concrete and the steel reinforcement. The results of numerical simulation are sensitive to the modulus of elasticity and the shear transfer coefficient for an open crack assigned to high-strength concrete. The full nonlinear load-deflection curves at mid-span of the beams, the development of strain in compressive concrete and the development of strain in tensile bar are in good agreement with the experimental results. Numerical results for smeared crack patterns are qualitatively agreeable as to the location, direction, and distribution with the test data. The model was capable of predicting the introduction and propagation of flexural and diagonal cracks. It was concluded that the finite element model captured successfully the inelastic flexural behaviour of the beams to failure.

Improving Thermal Insulation Properties for Prefabricated Wall Components Made Of Lightweight Aggregate Concrete with Open Structure

Porous concrete is commonly used in civil engineering due to its good thermal insulation properties in comparison with normal concrete and high compression strength in comparison with other building materials. Reducing of the concrete density can be obviously obtained by using lightweight aggregate (e.g. pumice). The concrete density can be further minimized by using specially graded coarse aggregate and little-to-no fine aggregates. In this way a large number of air voids arise. The aggregate particles are coated by a cement paste and bonded together with it just in contact points. Such an extremely porous concrete, called ‘lightweight aggregate concrete with open structure’ (LAC), is used in some German plants to produce prefabricated wall components. They are used mainly in hall buildings, e.g. supermarkets. The need of improving thermal insulation properties was an inspiration for the prefabrication plant managers, engineers and a scientific staff of the Technical University of Kaiserslautern / Germany to realise an interesting project. Its aim was to reduce the heat transfer coefficient for the wall components. Three different wall structure types were designed and compared in full-scale laboratory tests with originally produced wall components in terms of load-carrying capacity and stiffness. The load was applied perpendicularly to the wall plane. As the components are not originally used for load-bearing walls, but for curtain walls only, the wind load is the main load for them. The wall components were tested in horizontal position and the load was applied vertically. Totally twelve wall components 8.00 × 2.00 × 0.25m (three for every series) were produced in the prefabrication plant and tested in the University of Kaiserslautern laboratory. The designed and tested components differed from each other in the amount of expanded polystyrene (EPS), which was placed in the plant inside the wall structure. The minimal amount of it was designed in the original wall component type. Besides, two improved types of prefabricated wall had built-in steel lattice girders. The failure mode was the same for all the tested components: diagonal cracks occurred on the sides of each component due to their insufficient shear-force-capacity. The span deflection was measured during all the tests by means of LVDTs. Load-carrying capacities obtained in the tests were for all wall structure types similar and much higher (many times) than internal forces (i.e. bending moments and shear forces) calculated for a wind load acting on a typical hall building according to the German codes. An increased amount of EPS (up to 30 per cent in volume) did not influence significantly the wall structural strength. The use of the steel lattice girders caused some technological problems and led to a quality loss of the produced components. The future use of the lattice girders would require a change in the production process: it would have to be more labour consuming.

Experimental investigation of high-cycle fatigue behavior for prestressed concrete box-girders

An experimental study is proposed to investigate the high-cycle fatigue behavior of prestressed concrete box-girders. Special focus is on the shear diagonal cracks in the webs of girders, which is rarely investigated in the open literature. Laboratory fatigue tests were designed and conducted to study the propagation of shear diagonal crack of PC box-girder specimens under cyclic loadings. The development of stirrup strain, propagation characteristics of diagonal crack and the related factors are discussed in detail. A finite element (FE) model for concrete damage of PC box girder under high-cycle fatigue loading is established to investigate the crack propagation behavior. Following this, a model for the calculation of diagonal crack widths of PC box-girder under fatigue loading is proposed based on the experimental observations. The calculation results are compared with experimental data for validation. It is observed that the maximum stirrup strain in crack zone increases 67.9% based on this investigation. The ratio of displacement during the last cycle and that during initial loading can research 40.3% in the current investigation. Finally, several conclusions are drawn based on the proposed study.

Experimental investigation on the behaviour of reinforced concrete slabs strengthened with ultra-high performance concrete

Nine rectangular specimens were tested to investigate the behaviour of composite reinforced concrete (RC) slabs strengthened with ultra-high performance concrete (UHPC). The specimens were two series with various UHPC strengthening configurations. The first, a rehabilitation series, tested UHPC as patch material for repairing deteriorated concrete structures. The second, a UHPC overlay series, was used to retrofit soffits of RC members. The results showed that using the rehabilitation series, the UHPC reduced diagonal cracking and developed more flexural cracks as compared to RC slabs with no UHPC strengthening. The UHPC exhibited excellent energy absorption with extensive deflection hardening and ductility during the post cracking range. In the UHPC overlay series, each slab showed diagonal shear cracks and debonding modes. The UHPC overlay delayed the development of shear cracking. As the overlay thickness increased, the ultimate load increased; but the tendency for the UHPC to undergo fracture failure also increased.

Combined shear and flexure performance of prestressing concrete T‐shaped beams: Experiment and deterministic modeling

The development of a nonlinear numerical computational model for the detailed description of destructive tests generally requires a multiple‐stage, strategic model updating procedure. In this contribution, a model updating procedure is applied to the simulation of prestressed reinforced concrete (RC) beams. The combined ultimate shear and flexure capacity of the beams is affected by many complex phenomena, such as the multi‐axial state of stress, the anisotropy induced by diagonal concrete cracking, the interaction between concrete and reinforcement (bond), and the brittleness of the failure mode. In this research, a series of material, small‐scale component fracture tests were carried out by two collaborating laboratories. These tests provided advanced statistical identification of the fracture‐mechanical parameters of the optimized concrete mixtures for the prestressed laboratory‐tested beams mentioned above (with a span of 5.00 m) and associated field‐tested, long‐span concrete TT roof elements (with a span of 30.00 m). Ten scaled laboratory‐tested beams with heights of 0.30, 0.45, and 0.60 m were used in a procedure for the comprehensive updating of the nonlinear numerical model with respect to shear resistance performance. The objectives of this research are, in addition to the analysis, the effective development of an updating process for nonlinear numerical modeling which is based on the information from different monitoring systems. Hence, this contribution focuses on the presentation of a comprehensive updating procedure for the shear capacity of nonlinear numerical models of prestressed beam elements using information about fracture‐mechanical material parameters gained from (a) different monitoring systems and (b) code‐based methods.

Shear Behavior of High Strength Self Compacting Concrete Beams

This research presents an experimental study to investigate the shear behavior of high strength self-compacting concrete slender beams. The experimental program includes testing seven beams with constant size of (150mm height ×125mm width×1000mm length) to study the effect of shear span to effective depth ratio (a/d), longitudinal reinforcement ratio (ρw) and shear reinforcement ratio (ρv) on shear behavior for these beams. The experimental results showed that, increase shear span to effective depth ratio (a/d) has pronounced effect on decreasing diagonal cracking load and ultimate shear strength and increasing the ductility ratio, as (a/d) increase from 2.5 to 3.0, the decreases in diagonal cracking load and ultimate shear strength are with percentages of 17.8% , 21.6% respectively, while the ductility ratio increase with percentage of 16.7%. Also the results showed that the longitudinal reinforcement ratio (ρw) has significant effect on the gain in shear bearing capacity and ductility ratio, as increasing of longitudinal reinforcement ratio from 3.191% to 6.383% the increases in diagonal cracking load, ultimate shear strength and ductility ratio are with percentages of 43.8%, 46.6% and 37.0% respectively. Furthermore the results revealed that the vertical shear reinforcement has the major effect in improvement the shear behavior of these beams, however, using shear reinforcement (ρv) with percentage of 0.502% results in increase diagonal cracking load, ultimate shear strength and ductility ratio with percentages 50.7%, 63.6% and 48.1% respectively as compared with beam without shear reinforcement. Also presence of vertical shear reinforcement changed the mode of failure from the brittle to ductile.

On the in-plane shear response of the high bond strength concrete masonry walls

Conventional unreinforced masonry walls subject to in-plane shear loading fail due to exceedance of shear and tensile bond strengths. This paper examines whether or not the in-plane shear capacity of masonry walls would increase with the increase in the bond strengths through experimental and numerical investigations. For these investigations, shear walls were built with high bond strength polymer cement mortar; they were applied in thin layers of 2 mm thickness each. Material tests were carried out to characterise the bond and the compressive strengths of the high bond strength thin layer mortared masonry; the bond strengths were found approximately double that of the conventional 10 mm thick cement mortars. The shear walls, however, exhibited significantly lower capacity (contrasting the expectation) and displayed base course sliding mode of failure. To ascertain the validity of the experimental results, a combined surface contact—interface element micro finite element (FE) modelling technique was formulated; the results adequately reproduced the experimental datasets. The validated FE model was then applied to examine the effect of the aspect ratios and pre-compression levels to the failure modes, deformation and strength of the high bond strength shear walls and is shown that once the pre-compression exceeds 15% of the masonry compressive strength, the base sliding failure mode changes to the diagonal cracking mode with corresponding increase in in-plane shear capacity. Therefore, it is concluded that the increase the bond strength without regard to pre-compression could adversely affect the safety of the high bond strength unreinforced masonry shear walls.

Shear strength modelling of deep beam reinforced with high-strength steel without stirrups

Non-linear finite-element analyses were performed to model the shear behaviour of deep beams with high-strength reinforcement and grade-60 conventional reinforcement, without stirrups. The FE model was compared with experimental results from recent tests of deep concrete beams reinforced with both types of reinforcement and loaded until failure. A detailed comparative study of the FE and experimental results is presented, which demonstrates the capability of the analytical model to describe the observed experimental behaviour. The shear behaviour of beams reinforced with high-strength steel (HSS) was compared with that of beams reinforced with grade-60 steel to demonstrate the benefits of using high-strength reinforcement. The shear design provisions of current codes and mechanics-based models were also compared with the results from the analytical model. The findings of the study showed that diagonal shear cracking strength is independent of the type of reinforcement, while beams reinforced with HSS exhibited higher post-cracking shear strength than beams with conventional reinforcement. Strut-and-tie modelling is recommended for the design of deep beams reinforced with HSS since this method accounts for high strains in reinforcement and accounts for large-size effects. The current code provisions are suitable for slender beams regardless of type of reinforcement.

Fissures and Fractures in the Koyna Seismogenic Zone, Western India

ABSTRACT The 1967 M6.3 earthquake near the Koyna dam produced a surface rupture zone following a NNE-SSW structural trend. The rupture zone is documented in a report by the officers of the Geological Survey of India (GSI, 1968). The surface expressions of the rupture comprising fissures, en-echelon fractures, oblique or diagonal tensional cracks and mole tracks, termed here as the Koyna Fissure Zone (KFZ), were reported over a limited area, about 1000m in length and 200 m in width, located to the southeast of the Koyna dam between Donichawadi and Kadoli. The Koyna region was revisited recently for investigating the fissures, to help in locating potential sites for scientific deep drilling. Most of the reported surface deformation features are obliterated due to intense weathering and laterization of the exposed basalt surface during the past 48 years. However, careful field investigations in the Donichawadi-Kadoli area as well as in the surrounding region show that fissures and fractures are still preserved at several locations. The fissures trend between N30°W to N50°E, similar to that reported previously. The mean orientation of these fissures is 25°/89°-E. Transposition of one set of fissures by another set provide strong evidence for repeated brittle deformation in the area. Physical and microstructural studies on core samples of granite-gneiss basement rock underlying Deccan basalt in the area, obtained from a 1522 m deep borehole at Rasati, confirm the extension of the surface fissures to depth. Occurrences of secondary mineralization along these fissures indicate the percolation of water through fractures within basement granitoids. The evidences for water channelization may have direct implications for the occurrence of reservoir triggered earthquakes in the Koyna region for the past five decades.

Structural Behavior of Simply Reinforced LRC Beams in Shear Failure

Structural behaviour of simply reinforced LRC beams in shear failure was studied to compliment other studies on the LRC as suitable material for structural use in the construction industry. A concrete mix of 1:1.35:3.5 at water cement ratio of 0.85 yielding 28days strength of 15N/mm2 was adopted for the study. Four beams were cast with three reinforced with 10mm, 12mm and 16mm bars while one beam plain. The beams were tested to failure and the experimental data were analyzed to obtain a stress-strain and load – deflection relationship of the beams. The results show that the LRC aggregates used in the experiment were well graded with a uniformity coefficient (D60/D10 = 9.63) greater than 7 and a coefficient of curvature of (D30)2/D60/D10 =0.654. It was observed that, failure of the LRC beams started by the development of inclined or diagonal cracks within the point of support and point of loading. The contribution of web reinforcement, LRC concrete and longitudinal/ interface forces were found to be 38.8%, 23.81% and 37.39% respectively in restraining the beams failing in shear.

High-cycle fatigue life prediction of reinforced concrete deep beams

Concrete elements deteriorate as a result of continuous application of compressive fatigue loads. Irreversible deformation accumulates; hence, the effect on embedded steel reinforcing bars capacity and concrete resistance should be accounted for in the fatigue analysis of concrete structures. Experimental investigations were conducted to study the fatigue behaviour of eight small-scale reinforced concrete deep beams with a shear span to effective depth ratio of 1.25. Percentages of the diagonal cracking load from monotonic tests were used as fatigue loads. The deformation evolution within the shear spans of the deep beams were obtained by estimating the average principal and shear strain evolutions from the strain transformation analysis of LVDT (Linear Variable Displacement Transformer) data. Mid-span deflections and reinforcement strain evolutions with proximity to a major concrete crack location were obtained. In all beams, failure occurred with fracture of the longitudinal reinforcement at the intersection with the major concrete crack. Maximum strain evolutions for shear reinforcement measured at regions around the bends were observed to be lower than the strain evolutions observed in the longitudinal reinforcement. This was attributed to the governing arch mechanism common with deep beams.The strut and tie method was modified to predict the fatigue life of the deep beams tested by modifying the constitutive models and effectiveness factor of concrete with fatigue damage models. To achieve this, the irreversible compressive fatigue strain in concrete is considered as a pseudo-load. The crack initiation life and the progressive crack growth of steel reinforcement are accounted for using strain-life models and linear elastic fracture mechanics, respectively. Within the developed algorithm, failure will occur when one of the evolving forces in either the concrete strut or steel reinforcement approaches the corresponding residual resistance capacity.

Experimental investigation of shear models for lightweight aggregate concrete deep beams

The strut-and-tie model has become an effective design methodology for deep beams replacing the conventional beam theory that does not apply to these members due to their geometric or static stress discontinuities. This article examines the applicability of shear models for deep beams with lightweight aggregate concrete. Eight lightweight aggregate concrete deep beams were constructed and tested to failure under concentrated loading. Tests were conducted to investigate the effects of shear span-to-effective depth ratio ( a/d), ranging from 0.26 to 1.04, and an effective span–depth ratio ( le/ h), ranging from 2 to 3, on the failure mode and shear behavior of deep beams. All specimens presented a shear compression or shear-flexure failure mode. Failure from the flexure mode showed a dominant pattern with increasing a/d. The le/ h value minimally influenced the diagonal cracking and ultimate strength of deep beams. In contrast, a/d significantly affected the beam strength. Our results were compared with predictions proposed by American Concrete Institute 318-14, Canadian Standard, EC2, the Tan and Cheng model, the softened strut-and-tie model, and the simplified softened strut-and-tie model, which are all based on the strut-and-tie model. These comparisons indicated that all of these shear methods can be used to predict the shear strength of lightweight aggregate concrete deep beams.

Supleišėjusių gelžbetoninių sijų-sienučių įtempių skaičiavimas

Straipsnyje nagrinėjamas įtempimų būvis gelžbetoninėse sijose-sienutėse. Sijos-sienutės plačiai naudojamos įrengiant bunkerius, galerijas, nuleidžiamus šulinius, rezervuarus. Sienučių aukščio ir angos santykis keitėsi nuo 0,3 iki 1,5. Sienutės apkrautos sutelktomis jėgomis, išskirstytomis nedidelėmis aikštelėmis trečdalyje angos. Sijų-sienučių įtempimų būvis nustatomas naudojantis tamprumo teorijos metodais. Praktinę reikšmę turi tiek tamprios stadijos, tiek stadijos su pirmaisiais plyšiais sienučių įtempimų nustatymas. Tai leidžia optimaliau išnaudoti medžiagų laikomąją galią ir pritaikyti praktikoje gautas priklausomybes. Tamprios stadijos įtempimai nustatyti baigtinių skirtumų metodu. Veikiant horizontaliems įtempiams, sienučių neutralinė ašis yra žemiau jų sunkio centro. Didėjant sienutės aukščiui, neutralinės ašies padėtis žemėja. Maksimalūs tangentiniai įtempiai pasislenka žemyn, palyginus juos su įtempiais, gautais pagal medžiagų atsparumo dėsnius. Gautos pradinių plyšių galimos atsiradimų zonos. Pateikiamos prielaidos atlikti supleišėjusių sijų-sienučių skaičiavimus.

Formation and Orientational Distribution of Cracks Induced by Electromagnetic Induction Soldering in Crystalline Silicon Solar Cells

Soldering technology has major influence on the performance of crystalline silicon (c-Si) solar cells in the photovoltaic (PV) module. The mechanism of formation of cracks due to soldering is still highly debatable. In this paper, the formation and orientational distribution of cracks induced by electromagnetic induction soldering were investigated. For this purpose, the numbers of cracked cells and poorly soldered cells were counted, and different types of cracks and poor soldering were compared and analyzed. The results show that the diagonal crack is predominant in mono-c-Si cells, while the short crack perpendicular to bus-bar is the main type of crack in multi-c-Si cells. Moreover, the intersect crack is common in mono-and multi-c-Si cells. Thereafter, a model was put forward to explain the formation and propagation of cracks. Finally, the quality of electromagnetic induction soldering was investigated, which established that the defective cells, including cracks or poor soldering, constituted only about 0.4% of the total soldered cells.

In-Plane Behavior of Plain and Strengthened Solid Brick Masonry Walls

Unreinforced masonry structures are generally vulnerable to earthquake actions. Brittle masonry walls are very stiff and attract considerable seismic forces which cannot be sustained without cracking. In order to enhance ductility and load bearing capacity, certain strengthening techniques need to be applied. An experimental program concerning in-plane behavior of solid clay brick masonry walls was performed at the Institute for Materials and Structures, Faculty of Civil Engineering University of Sarajevo, in cooperation with Institute for Lightweight Structures and Conceptual Design, University of Stuttgart. The physical models include two unconfined unreinforced full scale masonry walls L/H/D=233/237/25cm and two strengthened full scale walls jacketed on both sides with 5cm thick concrete and reinforced with Q196 steel mesh. Twelve reduced scale walls L/H/D = 100/100/25cm were additionally constructed in order to test different strengthening methods which include one-or two-sided jacketing and CFK 150 strips. Specimens were exposed to cyclic shear as well as to monotonic push over loading program for different vertical stress levels with the aim to quantify shear strength, stiffness and energy dissipation. For lower vertical loads the tested walls exhibit rigid body rotation in each displacement cycle. For higher precompression mixed flexural and shear failure mode was registered, characterized by toe crushing and diagonal cracking. No separation of jacketing from the masonry was detected. Numerical models of tested wall panels were developed using finite element programs.

Rocking in Presence of Cracking of Masonry Wall Piers

The wall pier represents the vertical element of multi-storey walls with openings, the main resistant structural components of a masonry building. Structural systems of wall piers and spandrels are required to sustain the in-plane seismic actions acting on the wall, opposing with their weights to the action of horizontal forces. The behavior of masonry constructions results to be very far from the one characterizing ductile structures, because of the lack of energy dissipation during the deformation. A strength resource of masonry structures, properly reinforced in order to avoid early local failures, consists in exhibiting rocking behavior, until a failure condition is attained. An investigation on the dynamic behavior of masonry wall piers is carried out by following Housner’s studies and properly introducing the effect of diagonal cracks, shown by typical post-earthquake cracking patterns. As a consequence, the system is characterized by the detachment of a lower triangular region that becomes ineffective during the development of the mechanism and does not oppose with its weight to the overturning. Finally, it is shown that the occurrence of diagonal cracks can be prevented by the execution of suitable retrofit interventions.

Compressive properties of Ti-6Al-4V lattice structures fabricated by selective laser melting: Design, orientation and density

Lattice structures have been intensively researched for their light-weight properties and unique functions in specific applications such as for impact protection and biomedical-implant. The advancement of additive manufacturing simplifies the fabrication of lattice structures as opposed to conventional manufacturing and this opens doors to create more designs. There are ample research opportunities to explore the mechanical performance of the lattice structures fabricated by this technology specific to each design. This study filled the research gap by investigating the deformation behaviour and compressive properties of Ti-6Al-4V lattice structures fabricated by a powder bed fusion method from the aspects of design, orientation and density. The results were compared between cubic and honeycomb unit designs, between two orientations and across five different densities. Results showed that both cubic and honeycomb lattice deformed in a layer-by-layer manner for the first tested orientation, where vertical struts were parallel to the compression direction. In the second tested orientation, where lattice struts were angled with respect to the direction of compression, the deformation behaviour was observed as a single diagonal shear band. As the density of the structure increased, the deformation pattern shifted towards diagonal crack similar to a solid part. Honeycomb lattice structure had the highest density efficiency for energy absorption in both orientations and for first maximum compressive strength in the second orientation. Change of orientation significantly affected the efficiency in plateau stress for cubic lattice structure, and compressive property values for honeycomb lattice structure. Comparative studies showed that the first maximum compressive strength and energy absorption of the lattice structures in the first orientation were higher than most of the lattice designs from other literature.

Effects of Structural Parameters on Seismic Behaviour of Historical Masonry Minaret

The October 23, 2011 (Mw = 7.2) and November 9, 2011 (Mw = 5.6) earthquakes increased the damage in the minaret of Van Ulu Mosque, an important historical masonry structure built with solid bricks in Eastern Turkey, resulting in significant shear cracks. It was found that since the door and window openings are not symmetrically placed, they result in unsymmetrical stiffness distribution. The contribution of staircase and the core on stiffness is ignorable but its effect on the mass is significant. The pulpit with chamfered corner results in unsymmetrical transverse displacements. Brace wall improves the stiffness however contributes to the unsymmetrical behaviour considerably. The reason for the diagonal cracks can be attributed to the unsymmetrical brace wall and the chamfered pulpit but the effect of brace wall is more pronounced. After introducing the cracks, a new model was created and calibrated according to the results of Operational Modal Analysis. Diagonal cracks were found to be likely to develop under earthquake loading. Drifts are observed to increase significantly upon the introduction of the cracks.

Response of shear-deficient reinforced circular RC columns under lateral impact loading

This paper reports the results of an extensive experimental investigation on the behavior of shear-deficient reinforced circular RC columns under lateral impact loading. First, it provides a brief literature review on studies of the dynamic response induced by vehicle collisions on RC columns highlighting the lack of experimental tests on vertical elements. In this context, a novel facility for testing of vertical elements under lateral impact loading was realized. Two different types of RC columns characterized by different hoop spacing were tested, representing a one-third scaled model of a reinforced circular bridge pier, designed with obsolete design practice with particular reference to non-seismic areas. A total of 10 specimens (5 for each type) were tested under a lateral rigid-hammer impact at different impact velocities (2.25, 3 and 4.5 m/s) and boundary conditions (cantilever and fixed-simply-supported). The impact load was applied at the typical vehicular impact location, i.e. near the base. A description of the impact and reaction forces, of the lateral displacements and accelerations, of the damage development and of the post-impact damage is given. The dynamic response and the observed damage are found to be significantly affected by the column type, the impact velocity and the boundary condition. A brittle shear-type damage was observed, characterized by one main diagonal crack originating from the base of the column to the impact point, revealing the high vulnerability of these structural elements.