Deflection Of Building Research Articles

Analysis of the Model Used to Predict Continuous Deformations of the Land Surface in Areas Subject to Discontinuous Deformations—A Case Study

This article analyses and evaluates the model used by the Jastrzebie Coal Company in Poland to forecast the values of continuous deformations of land surfaces caused by underground mining. Particular attention is paid to the values of terrain inclinations, which cause significant deflections of buildings located in mining areas affected by exploitation. The inclination forecasts were made using Bialek’s model, with the values of its parameters determined in situ and after completion of the exploitation of a longwall. The obtained results were compared with the values of the terrain inclinations calculated from the results of geodetic measurements carried out at observation points located near the buildings and discontinuous linear deformations (i.e., the ground steps). The conducted research shows that the correlations between the absolute values of the practical inclinations and the values of the theoretical inclinations were rather weak, as the values of their correlation coefficients did not exceed 0.24. The tested model underestimated 45.5% of the values of the inclinations observed in situ by an average of −53.5%. The model values of the inclinations for the remaining observed inclinations (54.5%) were overestimated by an average of 461.9%. The largest anomalies were obtained in the case of inclination values from points located near the ground steps. The effectiveness of predicting inclination values with a commonly used model is strongly reduced when discontinuous linear deformations appear. Nonetheless, it reflects well the mining area categories.

Formulation of Separation Distance to Mitigate Wind-Induced Pounding of Tall Buildings

Structures in proximity subjected to a substantial lateral load (e.g., wind and earthquakes) can lead to a significant hazard known as structural pounding. If not properly mitigated, such impacts can lead to local and global damage (i.e., structural failure). Mitigation approaches can include providing a suitable separation gap distance between structures, installing adequate shock absorbers, or designing the structure for the additional pounding impact loads. Wind-induced pounding of structures can be of higher risk to buildings due to large deflections developed during wind events. The current study develops various mathematical formulas to determine the suitable separation distance between structures in proximity to avoid pounding. The developed procedure relies first on wind-load evaluations using Large Eddy Simulation (LES) models. Then, the extracted wind loads from the LES are applied to finite element method models to determine the building deflections. Various building heights, wind velocities, and flexibility levels are examined to prepare a training database for developing the mathematical formulas. A genetic algorithm is utilised to correlate the required separation gap distance to the varying parameters of the tall buildings. It was found that more complex formulas can achieve better mapping to the training database.

Evaluation of Soil Structure Interaction Effects on Seismic Response of RC Framed Buildings Using Simplified Method

In the current practice for the design of the building structure is done by considering the footing as fixed based. The mid-rise buildings having variation in storey height from 3- to 10-storey were selected for the research. In this research, analysis was done to study into the interaction between the seismic response of RC-framed buildings and the soil-structure for various soil types. To study the linear responses of the structures, the model was developed in FEM software SAP2000. The underneath soil was modelled by using direct method, where the soil is considered as solid element. The considered depth of soil was considered 30 m and the viscous spring dashpot were applied to avoid the reflection of seismic waves in soil medium along the effective horizontal soil boundaries. The seismic response variables such as maximum lateral deflection, inter-storey drift and fundamental time periods have been studied. SSI amplified the lateral deflection, inter-storey drift and time period of structure shifting the performance level from life safety to near collapse level. Fundamental time period of the first mode was increased by 23 % for very soft soil. The maximum lateral deflection of 10-storey building for very soft soil was amplified up to 282 % for Kobe and the performance level was shifted from life safety (1.5 %) to collapse level for all the considered model for soil type D . The performance level of structure was checked against the different soil types on varying storey height and finally a simplified method has been proposed to incorporate the effects of SSI in fixed base structures.

Reliable Tilt of Objects Subjected to Rectification and Located in Mining Areas

Abstract Mining exploitation of hard coal is conducted in the Silesian region in Poland. As a result, the post-mining void is formed which leads to non-uniform lowering of the ground level. Consequently, thousands of buildings are vertically deflected. This type of deflection causes troublesome use of buildings, underestimates their value, and in extreme situations leads to exceeded limit states. Therefore, such buildings are rectified by non-uniform elevations by means of jacks. On the basis of the analysed rectification processes, the method of determining the deflection of a building and the height of elevating its corners were presented depending on the type of building. This paper is a review of methods of determining the deflection of buildings having different sizes: single-storey buildings, single-storey buildings with a usable attic, two-storey buildings, and 11-storey buildings. Moreover, specific situations were analysed, in which the elevation height was determined by a range of additional works performed during rectification. This review was used to develop guidelines for determining deflection values and specifying the height of non-uniform elevation of corners.

Computing the value of uneven raising of building consisting of nine segments deflected from vertical due to mining exploitation

Deflection of buildings from vertical is a common damage caused by underground mining. Its removal consists in tearing the building apart at the level of one of the storeys, most often in the basement, and then unevenly lifting a part of the building above the tearing plane with the use of piston hydraulic jacks. One of the conditions for a properly carried out rectification is the correct computing of the height of lifting the individual corners of the building. The subject of the article is the deflected from vertical building of large projection (64.0 m × 41.9 m). The building consists of nine dilated segments, which are functionally related. The width of expansion joints between segments is about 10 cm. The deflection from vertical of the building occurred as a result of deformation of the mining area. Due to the significant projection of the building, the deflection of each segment is not the same. It was decided that deflection of the building would be removed by uneven raising of the structure with jacks mounted in the walls. The method of computing the value of uneven raising of the building is presented. In the first step the deflection of each segment was identified. Than the segments were divided into groups, due to their functional solutions. Then, for each group, the average deflection was determined. On the basis of this deflection, the values of uneven raising of each segment were determined. Described procedure made it possible to minimize the number of steps that will appear between the segments. Thanks to this, the building will regain functionality after carrying out the planned renovation.

Comparative analysis of earth quake resistant building design by considering bracings and shear wall system in ETABS software

Earthquakes are one of nature's most prominent risks to life on this planet and have decimated incalculable urban areas and towns on for all intents and purposes each landmass. Earth quack resistant structure is one of the most important concept in structural engineering. According to building design codes, earth quake resistant is depending upon the seismic zones. As per IS code 1893:2015 code seismic zones are classified in to four types they are Zone V, Zone IV, Zone III and Zone II. Everyday new procedures are being produced for the advancement of living arrangements financially, rapidly and satisfying the prerequisites of the gathering specialists and creators do the crease work, arranging and design, and so on, of the developments. The bracing systems and shear wall systems are generally used for designing the earth resistant structures, due to its simple construction methods and easy to install at the site. Both bracing systems and shear wall methods reduces the deflection of building as per the considerations. In the present study a G + 12 building is modeled by using ETABS Software and analysis is carried out by using Response spectrum analysis. The results like storey drift, storey shear, storey bending, time period and frequency were compared for building models made with steel bracings and shear wall systems.

Investigation into the Performance of a Covered Top-Down Pit-in-Pit Deep Excavation in Shenzhen Soil-Rock Mixed Strata

An oversized pit-in-pit (PIP) excavation, which comprised an octagonal pit outside and two cross-shaped pits inside, was excavated in soil-rock mixed strata, Shenzhen, China. There were two shield tunnels connected to the north and south of the PIP excavation after the main structures completed. Extensive instruments were adopted throughout the construction process to guarantee the safety of the project. Based on the massive field data, the performance of the ground settlement, retaining structures and adjacent building deflection were investigated. Field data indicate that the influence zone of ground settlement in depth was above the stiff clay layer. The maximum lateral displacement (δhm) of the retaining structures occurred at 0.4 He (He is the excavation depth), and δhm decreased when the excavation depth was over 0.5 He. The maximum ground settlement δvm occurred at 0.2 He which gradually decreased with d (d is the distance from the monitoring point to the excavation edge). This large discrepancy of the ground settlement induced 3.13‰ tilting of the adjacent buildings. The ground settlement influence zone was 1.7 He away from the pit edge (d ≤ 1.7 He). A half-3D numerical model was established to investigate the influence of different excavation sequences. The results show that the maximum principal stress (σm) of the cover plate increased to peak value due to the excavation of subsoil, which indicated that the sidewall construction and subsoil excavation should be carried out simultaneously to reduce the stress concentration of the cover plate. TD excavation can effectively minimize the ground and building settlement, while the excavation may induce uneven displacement of the interior supporting columns. Push in failure of the sidewalls may occur during the construction which was the combined result of unloading and increase in the excavation depth.

A bar model of a temporary wooden support used to remove deflections of buildings

The deflection of buildings located in mining areas is removed by uneven raising of the overground part of the structure by means of supports consisting of a hydraulic piston jack and a stack of underpinning elements. Temporary supports may also consist of stacks of wooden elements only. The article presents a bar model of a temporary support consisting of a stack of elements. The model, which is described by a differential, second-order equation, allows to determine horizontal displacements. It was demonstrated that the unintended eccentricity and the initial curvature of the element have influence on such displacements. In addition, the effect of the load transmitted by the deformed adjacent supports is important. The model presented can be used to determine the limit load capacity of temporary supports due to unintended horizontal displacements of the structure. The model therefore allows to design safely the removal of building structures’ deflections.

Improvement of exploitation reliability of a magnetic-grab crane by means of removal of residual deformation in main beams

In hired results over of inspection of metal structures of main beams of bridge of magnetic-bucket crane are brought, his technical description is given. Reasons of origin of the remaining (negative) bending and his negative influence are educed on operating descriptions and safety of work of crane. The size of the negative bending of main beams of bridge is set in size of a 105 mm at the size of crane span 20 m. Such size of the building deflection resulted in rolling of two light carts of magnetic-bucket crane to the middle of span, their defect and leaning against three skating rinks. Such defect assisted strengthening of wear of flange and increased attenuation time of own vibrations. Previous repairs of beams by means of hot edit heating of areas of lateral walls to the temperature 800-900°C in future negatively affected on operating descriptions of crane metal construction. Expedient complex technology of repair of metal structures for span beams is offered technically with the purpose of extension of time of service of crane. Technology includes: method of hot edit of beam and method of preliminary tension. The sequence of works is described at implementation of repair these methods. The construction of stretching device and his bracing on main beams. In the construction of stretching device supports are included with the set tighteners (lug). Tensioning devices are fastened to the bottom belt of tension beams. In lugs the cored armature is set and she is laid on brackets. The pull of the cored armature is produced by means of hydraulic jacks, fixed by a nut and check-nut. Diagrammatized technological process of complex repair. The offered technology will allow to produce repair works without dismantling of crane and promote reliability of its exploitation

Effect of Eccentricity of Applied Force and Geometrical Imperfections on Stiffness of Stack of Cuboidal Steel Elements.

Experimental tests were performed on a stack of cuboidal steel elements and its mathematical model was developed. Each cuboidal element was made of rolled profiles. Such stacks are the part of temporary supports that can be used to eliminate deflections of buildings. Stacks were loaded eccentrically through the inaccurate position of a jack. Moreover, two types of geometrical imperfections could be noticed. They included inaccurate contact between the stack elements and initial relative displacements of profiles that formed cuboidal elements. A mathematical model was developed to describe deformations of the stack and its parameters were determined by analysing test results. The eccentricity of the applied force had a slight impact on the stack stiffness, which was considerably reduced by geometrical imperfections. The imperfection covering initial relative displacements of rolled profiles inside cuboidal elements had the greatest impact on the stiffness. It could cause even a 10-fold drop in the stack stiffness when compared with the theoretical stiffness resulting from the stiffness of the stack section, and the stiffness dropped by ca. 3.5 times when the imperfection included the inaccurate contact between the cuboidal elements. Finally, the occurrence of both types of geometrical imperfections generated the real stiffness more than ten times lower than the theoretical stiffness that did not take into account imperfections.

Evaluation of the interstorey drift performance of timber beam-hanger connection systems

This paper presents the results of a study on pre-engineered steel and aluminum, nominally “pinned”, bolted-plate (BP), staggered dovetail (S-DT), and dovetail prototype (DTP) beam-hanger connection systems for glue-laminated timber joints under a combination of shear and reversed cyclic loading. A total of seven systems were tested to observe the evolution of damage, failure modes, and moment–rotation behaviour. The interstorey drift and deflection of a building that would cause failure of each system is inferred from the ultimate rotation capacities and compared to the limit(s) prescribed by Clause 4.1.8.13.3 of the National Building Code of Canada for various building categories. The BP systems generally reached an interstorey drift exceeding 2.5%, while the S-DT and DTP systems reached drifts of 0.6% and >1.2%, respectively. The BP systems also exhibited more ductile failure modes than the S-DT and DTP systems, involving withdrawal failure of the wood screws. Recommendations are made for appropriate connectors to use in each building category considered.

Study on Methods to Control Interstory Deflections

One of the possibilities to prevent building pounding between two adjacent structures is to consider appropriate in-between separation distance. Another approach might be focused on controlling the relative displacements during seismic excitations. Although the majority of building codes around the world recommend the use of some equations of various distances between structures to avoid pounding; a lot of reports after earthquakes have obviously shown that safety situation or economic consideration is not always provided due to the collisions between buildings and high cost of land; respectively. The aim of the present paper is to focus the analysis on the properties of structures and conduct an in-depth analysis of available methods to control interstory deflections so as to prevent pounding. For this purpose, a numerical lumped mass model of the five-story building has been considered and its response under different earthquake records has been investigated. Firstly, the influence of the change in structural properties (story stiffness; mass and damping) has been examined. Then the application of tuned mass damper, base isolation and base isolation with rubber bumpers has been considered. The results of comparative analyses clearly indicate that using base isolation, with the addition of bumpers, can be selected as the best method to control building deflections and decrease absolute lateral displacement between two buildings so as to prevent their pounding during earthquakes

Charts for the mining-induced deflection of buildings

This study investigates the flexural deformations of buildings induced by mining-related subsidence. A two-stage solution (previously applied to the tunnelling problem) is used. Buildings are modelled as a beam founded on an elastic continuum that is subjected to ground subsidence. A tensionless soil–structure interface is employed. The effects of both building stiffness and self-weight on the building deflection are considered. The proposed formulation is compared with analytical solutions and empirical envelopes from previous research. A parametric study is conducted for both perfect soil–foundation bond and gap formation to relate deflection ratio modification factors and the limit radius of the greenfield settlement curve (associated with the gap formation) to relative structure–soil stiffness, building weight, foundation shape, and greenfield ground curvature (hogging or sagging) by means of dimensionless groups. Finally, a simple case study is used to demonstrate the proposed procedure. The given framework is more comprehensive than design charts provided by previous mining-related works and can be used for rapid preliminary risk assessment.

Research and Optimization of the Belt Truss Location in High-Rise RCC Structure

Rapid improvement in infrastructure to acquire the development of modern civilization is the demand of high-rise structures. As day by day, the height of structures is increasing there is problem with its stiffness which induces lateral stability and sway due to lateral forces, which has to be reduce. One more structural system has been developed to overcome problems related to lateral stability and sway of building. To reduce the lateral deflection due to earthquake or wind forces, one of the most efficient and economical structural system used to knock out these challenges is the use of belt truss and outrigger truss. It is commonly used to control the excessive drift due to lateral load, so that during minor or major earthquake, the risk of structural and non-structural damage can reduce to sufficient amount. The objective of this thesis is to optimize the location of belt truss to control the deflection or sway of building. Here, Belt truss can be shear wall, hollow steel sections, braced sections and many more. In this paper, we are going to compare the results due to different locations of shear wall and X-braced section. Structure is located in earthquake zone IV(India) on Hard rock strata. Different results to be compared are Lateral Deflection, story drift. Study provides comparison between the two, by analyzing and designing the G+24 irregular residential structure. By using belt truss at ideal location, overall lateral deflection reduces by 22%. And this ideal location is obtained when the belt truss is applied at 13th & 14th floors simultaneously. From this location of belt truss, we can conclude that the lateral deflection of the high-rise structure can be reduce by applying the belt truss in the middle floors.

Three-Dimensional Response of Neighboring Buildings Sitting on Pile Foundations to Seismic Pounding

Seismic pounding occurs when the separation gap between buildings and structures is not wide enough, particularly during major earthquake events; this can cause them to collide, causing local damage or, in extreme cases, collapse. This study investigated the impact that this separation gap has on the seismic response of midrise buildings supported on piles while considering seismic soil–pile–structure interaction (SSPSI). To achieve this aim, three 15-story reinforced concrete buildings sitting on pile foundations and with five different separation gaps under excitations from the 1994 Northridge and 1995 Kobe earthquakes were numerically simulated. This study used three-dimensional numerical modeling to simultaneously capture the effects of seismic pounding and SSPSI. Because the considered structure, pile foundation, and soil deposit are three-dimensional in nature, the adopted three-dimensional numerical modeling can provide a more realistic simulation to capture the seismic behavior of the system. The nonlinear behavior of structural elements was included, and the dynamic soil properties were obtained from field data and backbone curves. A contact pair interface with small-sliding surface-to-surface formulation between buildings was used to capture possible seismic pounding, and contact interfaces with a finite-sliding formulation were used to simulate the interaction between the piles and the soil. The results, including lateral building deflections, interstory drifts, structural shear forces, foundation rocking, lateral pile deflections, and the distributions of bending moments and shear forces of the piles, are presented and discussed. The findings of this study will give engineers a better insight into the possible effects of seismic pounding on the seismic performance of buildings, and the response of end-bearing piles in soft soils.

Measurement methods of building structures deflections

Underground mining exploitation is leading to the occurrence of deformations manifested by, in particular, sloping terrain. The structures situated on the deforming subsoil are subject to uneven subsidence which is leading in consequence to their deflection. Before a building rectification process takes place by, e.g. uneven raising, the structure's deflection direction and value is determined so that the structure is restored to its vertical position as a result of the undertaken remedial measures. Deflection can be determined by applying classical as well as modern measurement techniques. The article presents examples of measurement methods used considering the measured elements of building structures’ constructions and field measurements. Moreover, for a given example of a mining area, the existing deflections of buildings were compared with mining terrain sloping.

Deformations of temporary wooden supports used to reduce building deflections in mining areas

Temporary supports, consisting of a stack of wooden elements and a hydraulic jack, are used in the process of removing deflections in buildings with one to three aboveground floors in mining areas. During uneven raising, the supports are loaded monotonically, unloaded and loaded cyclically. Laboratory tests were designed for the supports. For the investigated range of loads of 0 to 400 kN, under a growing load, a linear relationship exists between a load and the change in the stack length, which signifies that the deformations of wooden elements and displacements related to their mutual interactions increase proportionally. A seemingly higher stack stiffness is seen at the beginning of the unloading process and for cyclical loads, meaning that in this phase of loading, the material deformation of the wooden elements and the jack is responsible for changing the jack length in this load phase, with a negligible presence of mutual displacements of wooden elements. The support, after being unloaded, returns to the initial position and its permanent deformations are not observed. The stiffness of a temporary support decreases as the height of the stack of wooden elements increases.

Methods of Removing Buildings Deflection Used in Poland

The deflection of the building in relation to the vertical is caused by its uneven lowering. The deflection hinders the use of the building and causes occurrence of the additional inner forces which the construction of the building is not designed to take. Therefore, the deflections of the buildings should be removed. Three methods of removing building deflection have been used in Poland. The first method is removing the soil from under the part of the building which is positioned too high. The second method is elevating parts of the building that are too low. The third method is simultaneous removing the soil and elevating the building. In this work all three methods are presented and analysed showing their advantages and disadvantages. Removing the soil from under the part of the building which is positioned too high can be achieved by drilling holes under the building or cutting parts of the soil under the building. After removing the soil, the building returns to the vertical. The advantage of this method is no interference in the construction of the building. The disadvantages are the lack of precise control over the process and the necessity of occupancy for the construction site the considerable area around the building. The second method to remove the deflection of building is elevating using the hydraulic jacks. These jacks are usually built-up in the openings made in the walls of the lowest level. Removing deflection through elevating is performed through inflicting shifting to the jacks. It consists of three phases: tearing the building, steady elevating and not steady elevating. In practice two types of jacks are used: hydraulic piston jacks and hydraulic diaphragm jacks. These jacks can be manually or computer controlled. The advantage of this method is full control of the levelling process. The disadvantage is the interference in the construction of the building (tearing the building). The last method is simultaneous elevating parts of the building located too low and lowering parts of the building positioned too high. Removing building deflection through non uniform elevating with the help of hydraulic piston jacks is the method being used the most often.

Damage of masonry structures relative to their properties: Development of ground movement fragility curves

The objective of this paper is to study the effect of the properties of masonry buildings on the threshold values of the deflection ratio, which is used to assess the damage category of buildings. Based on the results obtained from a sensitivity analysis, fragility curves are drawn and used to develop a probabilistic approach to help assess the damage for different structure typologies due to ground settlement.The threshold values of the building deflection ratio are primarily empirical. The analytical method of Burland et al. (1977) was used to define analytical threshold values to assess the building damage in relation to the building properties: length L, height H, equivalent Young’s modulus E and equivalent shear modulus G. This paper starts with a comparison of various empirical and analytical threshold values of the deflection ratio. Next, a sensitivity analysis is performed using the analytical method of Burland et al. (1977) and modified by Saeidi et al. (2012) to take into account the anisotropic behaviour associated to the masonry mechanical properties and the existence of openings. The investigated parameters are the E/G and L/H ratios and the position of the neutral axis of the beam simulating the building. The results show a significant influence of the E/G and L/H ratios and suggest defining a range of the threshold deflection ratio associated to different damage categories for different building typologies. Fragility curves are then developed based on the definition of the building typologies. These fragility curves are a useful tool to estimate the probability of reaching each category of damage once the deflection ratio and the properties of the relative structure are determined. To improve their accuracy, several intervals of the properties of the buildings were used to develop these fragility curves. The choice of these intervals to draw the fragility curves was based on various bibliographic studies and numerical studies in the case of E/G and statistic studies in the case of L/H.

水平・鉛直方向振動を評価可能なエレベータロープモデルの構築

Elevator ropes in a high-rise building are excited by deflection of building caused by earthquake and wind. Especially, the long-period ground motion causes the resonance between elevator ropes and building. As it causes severe damage for elevator, reducing the displacement of elevator rope is demanded. When the rope is long, it is difficult to ignore that the interaction between horizontal and vertical vibrations of rope. Currently, there are some methods to analyze the rope sway. But, the existence of universal method that can analyze the interaction between horizontal and vertical vibrations, and coincide with the experiments using actual elevator rope is very few. Therefore, in this study the new rope model is constructed as a multi rigid body pendulum, and I set the equation of motion by following the multi-body dynamics. And, the coincidence of the proposed model and the result of experiment are shown by numerical simulation. Furthermore, vertical or horizontal direction damping is added at the lower end of rope, and its effectiveness is confirmed.