Base Of Wall Research Articles

Seismic Performance Evaluation of SSMF with Simple Beam–Column Connections Under the Base Level

Simple beam–column connections are simpler and cheaper in construction than rigid beam–column connections, moreover, beams under the base level are only carrying gravity loads because of high rigidity of basement walls; therefore, seismic performance of special steel moment frame with basement wall is investigated in two cases in this paper. First, as the normal case of design, rigid beam–column connections are used under the base level, then all of the beam–column connections under the base level are changed to simple connections. The seismic performance of these two types is evaluated by FEMA P695 method. For predicting the collapse capacity of each archetype, adjusted collapse margin ratios are evaluated based on several nonlinear analyses and compared to acceptance criteria. Finally, seismic performance of these two kinds of structures is compared with each other. Despite the structural system’s change in height, seismic performance factors of special steel moment frames are considered for designing whole of the structures. Finally all two types of structures pass the acceptability checks and all the initial assumption are proved.

Impacts of multiple refurbishment strategies on hygrothermal behaviour of basement walls

The refurbishment of existing buildings to provide thermal performance comparable to new design standards can be achieved using multiple design strategies. Although high structural thermal resistance is usually considered to be of high importance, hygrothermal conditions must be taken into account. They can significantly prolong the life of the building and avoid biological growth inside the structure as well as the indoor environment. In this study, three structures from different decades are compared from the point of view of thermal insulation performance, structural drying and mould growth, which was assessed using the Finnish mould growth model. Special interest is given to structural details that are subjected to humid conditions and details characterised by a thermal bridge, where vapour condensation can occur. The numerical computation provides a risk assessment tool for the structural elements in terms of hygrothermal performance and structural health implications.

ЗАХИСТ ЖИТЛОВИХ БУДИНКІВ ВІД СЕЙСМІЧНИХ НАВАНТАЖЕНЬ ТА ДИНАМІЧНИХ ВПЛИВІВ ЗАЛІЗНИЧНОГО ТРАНСПОРТУ

В статті представлені результати експериментально-теоретичних досліджень щодо вирішення проблеми віброізоляції багатоповерхових житлових будинків у рівні пальового ростверку від потягів залізниці. Результати виконаних робіт дозволили отримати акселерограми поверхні ґрунту на будівельному майданчику; здійснити розроблення розрахункових динамічних моделей віброізольованих 6, 10 та 13-поверхових секцій житлового будинку для проведення розрахунків та розроблення рекомендацій з конструювання вузлів влаштування віброізоляторів та системи сейсмо- та віброзахисту секцій будинку з метою зниження до допустимих за Санітарними нормами динамічних впливів від потягів залізниці. Для захисту від динамічних впливів потягів залізниці за результатами чисельних досліджень та випробувань гумових віброізоляторів, проведених в ДП НДІБК та ІГТМ НАНУ, згідно патенту на оголовок кожної палі перед бетонуванням плити ростверку встановлюється гумовий ізолятор та влаштовується система віброзахисту будинку у рівні підошви плити ростверку та стін підвалу. За результатами розрахунків просторових моделей будинків обґрунтовані параметри гумових ізоляторів для віброзахисту 6, 10 та 13-поверхових секцій. Виконані випробування двох типів гумових віброізоляторів вітчизняного виробництва з зовнішнім діаметром 340 мм і товщиною 40 і 50 мм з доведенням максимального вертикального навантаження до 3200 кН. Середня жорсткість гумового ізолятора діаметром 340 мм та товщиною 50 мм на стиск (при розрахункових навантаженнях на палі до 800 кН) дорівнює Кz = 67000 кН/м; ізолятора товщиною 40 мм Кz = 105000 кН/м (при розрахункових навантаженнях на палі до 1200 кН).Розрахункові коефіцієнти запасу проти перекидання секцій висотою 13, 10 та 6 поверхів дорівнюють від 5,4 до 16,5 при інтенсивності сейсмічних впливів 6 балів. При вітрових впливах коефіцієнти запасу дорівнюють від 101,6 до 196,6.

Effect of constructing twin tunnels under a building supported by pile foundations in the Sydney central business district

In congested cities such as Sydney, competition for underground space escalates within the built environment because various assets require finite geotechnical strength and support. Specific problems such as damage to buildings may develop when high-rise buildings on piled foundations are subject to ground movements as tunnels are constructed. This paper focuses on the risks of tunneling beneath Sydney’s Martin Place and how buildings are subject to additional loads caused by tunneling. The key objective of this study is to improve the understanding of tunnel–rock–pile interactions and to encourage sustainable development. A finite element model is developed to predict the interaction between tunnel construction and piled foundations. The tunnel, rock, and pile components are studied separately and are then combined into a single model. The ground model is based on the characteristics of Hawkesbury Sandstone and is developed through a desktop study. The piles are designed using Australian Standards and observations of high-rise buildings. The tunnel construction is modeled based on the construction sequence of a tunnel boring machine. After combining the components, a parametric study on the relationship between tunnel location, basements, and piles is conducted. Our findings, thus far, show that tunneling can increase the axial and flexural loads of piles, where the additional loading exceeds the structural capacity of some piles, especially those that are close to basement walls. The parametric study reveals a strong relationship between tunnel depth and lining stresses, while the relationship between tunnel depth and induced pile loads is less convincing. Furthermore, the horizontal tunnel position relative to piles shows a stronger relationship with pile loads. Further research into tunnel–rock–pile interactions is recommended, especially beneath basements, to substantiate the results of this study.

Textile Bewehrung in der Lagerfuge von Kellermauerwerk und windbelasteten Ausfachungswänden

AbstractThe successful structural verification of basement walls under earth pressure loading with light vertical loading is often difficult. This situation is often encountered for external basement walls under terrace doors, stairs, masonry light wells, etc., where the vertical loading that is theoretically necessary is absent. This makes it impossible to resist the acting flexural forces from earth using a vertical arch model alone. In such cases the basement wall must also resist the earth pressure in a horizontal direction. However, due to the fact the bending moment capacity of unreinforced masonry parallel to the bed joint is low you have the option here of using a textile‐reinforced bed joint with longitudinal fibres of alkali‐resistant glass or carbon fibre. With an appropriately adapted textile reinforcement in the bed joints, the masonry can fulfil the requirements for load‐bearing capacity against earth pressure with a horizontal load transfer, even under a small vertical load. The same applies to infill walls subjected to high wind loads the bending moment capacities of which are also slightly parallel to and vertically to the bed joint and cannot be provably demonstrated on large infill surfaces and strong wind loads. The load‐bearing can also be increased by improving the flexural strength parallel to the bed joint. The Chair of Structural Design in the Faculty of Architecture of the Technical University (TU) Dresden was carrying out extensive numerical and experimental studies for this purpose. In the journal Mauerwerk 01/2018 [1] first findings from small trial series have already been presented. In the meantime, a series of large‐scale tests have additionally been performed to check the promising results of the small‐scale tests with respect to their real applicability. This report should provide a combined insight into the work of the concluded research project.

Assessment of The Effectiveness of Secondary Horizontal Insulation Against Rising Damp Performed by Chemical Injection

Dampness in basement walls caused by capillary rise of water from the ground, as well as possible resulting damage, is very unfavourable phenomenon. This problem mainly concerns historical buildings and other structures erected before 1920, and the destruction is caused by lack, damage or technical wear of insulation. However, it can also arise in relatively new buildings where insulation was made incorrectly (or was not made at all). Creating a barrier that interrupts the capillary rise of moisture in the existing wall, i.e. secondary horizontal hydro-insulation is perceived as one of the most difficult, from a technical point of view, tasks in the field of building protection against water and dampness. The so-called mechanical methods are seen as the safest. Assuming that the works will be flawlessly planned and executed, a durable layer, impermeable to water and thus completely inhibiting the capillary transport of moisture, is formed in the cross-section of the wall – in many cases resulting in highly efficient isolation as “in a new building” 1[1]. However, due to practical limitations, mechanical methods are used much less frequently than injection schemes. By injection, injection technology or chemical injection is meant the introduction of injection fluid into the masonry, with the following three distinguishable ways of applying an injection agent: penetration, pressure and pulse in the form of an aerosol. The technology must ensure equal distribution of an injection agent within the entire wall cross-section, and its principle of operation is to create a continuous layer interrupting capillary rising to obtain (after some time) an area with regular dump in the masonry zone above the membrane. Injection methods, although widely used, are associated with a greater risk of partial or complete failure. The universality of application combined with the risk of failure has encouraged the search for a parameter to assess the effectiveness of secondary horizontal insulation. A suitable parameter is the AQ coefficient (from German - Abdichtungs Qualität) based on the capillary water absorption coefficient, proposed by Venzmer et al3. The article presents research results on the effectiveness of chemical injections performed in reference walls made of ceramic bricks. The membrane was made using three different injection agents: formulation based on silicates (mixture of silicates and alkaline methyl silicates), silicon micro-emulsion and silane-based injection cream. In the injection zone, the drill cores were taken to perform capillary water absorption coefficient measurements. In order to obtain reference samples, additional drills were made above the impregnation zone protected with the injection agent. Both the measurements made and the calculated AQ coefficients proved the effectiveness of the abovementioned injection agents.

Earthquake design of flexible soil-retaining structures

Many soil-retaining wall structures are restrained from outward sliding movements and because of this it may not be appropriate to use the commonly applied Mononobe–Okabe (MO) method to estimate the earthquake induced pressures on them. This semi-rigid or stiff wall category includes bridge abutments, building basement walls and hydraulic structures associated with hydro-power and flood control. In the present research, finite-element analyses have been completed on cantilever walls that deform by both rotation about their base and flexure in the wall stem. The wall stiffness parameters have been varied to produce pressure distributions under earthquake and gravity loads for walls that vary from rigid to sufficiently flexible for the MO method to be applicable. The paper summarises the results of these finite-element studies. An example is presented to demonstrate how the results can be applied in the earthquake design of semi-rigid or stiff walls.

Lessons Learned from Evaluating the Responses of Instrumented Buildings in the United States: The Effects of Supporting Building Characteristics on Floor Response Spectra

Floor spectra of many instrumented buildings are evaluated to identify and quantify influential parameters on the horizontal seismic responses of acceleration-sensitive nonstructural components (NSCs). It is shown that many of these parameters are not explicitly incorporated into the American Society of Civil Engineers ASCE 7-16 design equations and are challenging to capture through numerical building models. Significant torsional responses are identified, even for nominally regular buildings, which can increase seismic demands on NSCs located at a floor periphery. For many instrumented buildings, especially single-story ones, floor diaphragms behave as flexible in their plane. This behavior, while mitigating torsional responses, can increase demands on NSCs located away from elements of the lateral-force resisting systems. An evaluation of floor acceleration responses of instrumented buildings with basements reveals that in many cases, even with the presence of perimeter concrete basement walls, accelerations at grade level could be significantly larger than those at lower basement levels. Consideration should be given to establishing the seismic base at the lowermost basement elevation.

Assessing the impact of vertical heat exchangers on the response of a retaining wall

Shallow geothermal energy systems, e.g. borehole heat exchangers or thermo-active structures, provide sustainable space heating and cooling by exchanging heat with the ground. When installed within densely built urban environments, the thermo-hydro-mechanical (THM) interactions occurring due to changes in ground temperature, such as soil deformation and development of excess pore water pressures, may affect the mechanical behaviour of adjacent underground structures. This paper investigates the effects of vertical heat exchangers installed near a deep basement by performing fully coupled THM finite element analyses using the Imperial College Finite Element Program. Different heat exchanger configurations are considered and their influence on the response of the basement wall is assessed in two-dimensional plane strain analyses, where different methods of modelling the heat sources in this type of analysis are employed to evaluate their effect on the temperature field and the non-isothermal soil response.

Molecular Characterization of Myiasis-Causing Moth Flies (Diptera: Psychodidae)

The aim of this study is to examine the molecular characterization of moth flies (Diptera: Psychodidae) based on their mitochondrial DNA sequences and determine the vectorial potential and damage caused by moth flies in future researches. A total of 240 adult moth flies were collected from toilet, bathroom, and basement walls of houses from different locations of the Kayseri region between May 2016 and April 2017. The polymerase chain reaction (PCR) analyses were performed using primer pairs, specificaly targeting the mitochondrial cytochrome oxidase c subunit I (mt-COI) gene of adult flies. In total, five isolates were gel purified and sequenced for molecular characterization and phylogenetic analyses. Two species, namely Telmatoscopus albipunctatus (ERU-Telmatos3 and ERU-Telmatos6) and Psychodidae sp. (ERU-Psycho1,4,5), were successfully identified with the sequence alignment of isolates. According to the phylogenetic analysis, it was determined that the ERU-Telmatos3 and ERU-Telmatos6 isolates are clustered in the haplogroup A, while the ERU-Psycho1,4,5 isolate was clustered within the haplogroup B. The ERU-Psycho1 isolate was characterized as a new haplotype within the haplogroup B. This study represents the first molecular characterization and phylogenetic status of moth flies in Turkey. The obtained findings should be the first step in the future investigation based on detecting the transmission of bacterial pathogens by moth flies.

The Effect of Soil around the Basement Walls on the Base Level of Braced Framed Tube System

According to the 2800 standard, the Iranian code of practice for seismic-resistant design of buildings, the base level refers to the level at which it is assumed that the horizontal movement of the ground is transmitted to the structure. In cases that there are reinforced concrete walls being run by an integrative structure in the underground perimeter, and the surrounding ground is dense and compressed, the base level is considered on the top of the basement wall. In tall structures, due to strong forces and moments at the foot of the structure, examining the location of base level and its movement becomes specially important. The aim of this study was to investigate the impact of changing the properties of the soil around the underground perimeter walls on the base level, taking into account the effects of soil-structure interaction systems. In this regard, the soil-structure system was investigated in two-dimensional models and the location of the base level was identified using shear and drift changes. The results indicated that taking into account the level of the upper stories is possible through performing appropriate walls integrated with the structure even without Compacting the soil around the structure.

Seismic ground motion induced lateral earth pressures on basement walls

Research on the dynamic lateral earth pressures acting on basement walls induced by seismic ground motions has appeared in the literature in the last few years to examine the apparent inconsistency between the theoretical pressures and the pressures suggested by basement wall good performance of during large earthquakes. This inconsistency suggested that the current methods would yield excessive lateral earth pressures. In this paper, a two dimensional plane strain finite element model of a 2-story concrete basement wall was used to examine the dynamic lateral earth pressures. The seismic ground motion was the N-S component of the 1992 Erzincan earthquake motion record. The assumed soil profile was a sands deposit overlying a reflecting bedrock layer. The observed time history outputs were the wall acceleration in horizontal direction, the lateral earth pressures, and the associated lateral thrust. The outputs were examined further to evaluate the amplification of wall acceleration, the different time history pattern of wall acceleration and lateral thrust, the influence of limiting soil tensile strength, the time difference for peak wall acceleration and peak lateral thrust, and a discussion on phase difference. The results suggested that the complex interaction could not be represented by typical simple peak input acceleration – soil pressure relationships.

Shear behavior of reinforced concrete basement walls with consecutive convexo-concave-shaped bars as shear reinforcement

ABSTRACTThis study examined the significance and shortcomings of the consecutive convexo-concave shaped shear reinforcement (CCSR) developed as an alternative for transverse crossties in basement walls. Three wall specimens prepared under a full scale were tested under constant axial load and out-of-plane lateral load. In the tests, the CCSR was classified into two types including S-type for the S-curve bending and B-type for approximately 90° bending. To investigate the shear transfer capacity of the CCSR, a mechanism model was driven on the basis of the upper-bound theorem of concrete plasticity. Test results revealed that the CCSR is more favorable to restrict the opening of the inclined cracks and enhancing the shear capacity of the basement wall when compared with the conventional crossties. Wall S (with S-type of CCSR) and Wall B (with B-type of CCSR) possessed 1.21 times and 1.12 times higher shear capacity, respectively, than wall C (with the conventional crossties). The wall S exhibited least rapid descending branch after the peak load, maintaining 80% of the peak load until the wall drift ratio reached 5.4%. The American Concrete Institute (ACI) 318-14 equations extremely underestimate the shear capacity of the basement wall, whereas the predictions obtained from the proposed mechanical model are in better agreement with the test results.

Proposal for the simplified design of basement walls under lateral earth pressure

AbstractThis paper deals with the design of basement walls subjected to lateral earth pressure. The current simplified calculation method according to DIN EN 1996‐3/NA only covers active earth pressure, which is the lower limiting value of the earth pressure. Designing according to DIN EN 1996‐1‐1/NA, higher coefficients of earth pressure (like earth pressure at rest) can be considered, with an additional verification of the shear resistance being necessary. This paper presents a theoretical model, which forms the basis for an analytical derivation of the loadbearing capacity, and explains the required minimum values of the acting normal force to ensure sufficient resistance to cover bending and shear. Based on these results, a simplified equation is proposed for the determination of the required minimum normal force, based on the design according to DIN EN 1996‐3/NA and providing identical values in case of an earth pressure coefficient of 1/3. The required minimum load resulting from this approach fulfils the described requirement to cover bending and shear. The presented solution is verified and the conditions for application are defined. Finally, the minimum required normal forces are evaluated and tabulated for common cases relevant to building practice.

Experimental investigation on the mechanical behaviour of a new superimposed RC exterior basement wall with socket base

A new superimposed RC exterior basement wall with socket base is proposed here. To investigate the mechanical behaviour and failure mode, nine such basement walls and one cast-in-place basement wall were tested under the monotonic lateral load. The test results indicated that crack distributions and the corresponding loads of the superimposed basement walls under the serviceability limit state, which is the critical state that controls the design of the basement wall, are approximately identical with those of their cast-in-place counterpart. The failure of this new basement wall is generally dominated by the failure of the diagonal compression struts in the wall embedded in the socket base, whereas the failure mode of its cast-in-place counterpart is shear-compression failure near the bottom of the wall. Furthermore, the effects of four critical parameters were investigated: embedded length, thickness of the exterior lateral wall of socket base, longitudinal reinforcement ratio and roughness of the interface. The outcome of this study will provide systematic experimental data and conceptual understanding for the design of superimposed RC exterior basement walls with socket bases.

Crack control in concrete walls through novel mixture design, full-scale testing, and finite element analysis

The research evaluates novel concrete mixtures, including crystalline admixtures, coarse ground calcium carbonate, and macro/micro-fibers, for use in basement walls that satisfy the International Residential Code with a reduction in reinforcement. The experimental investigation proved the mixture exceeds the 28-day design strength within 7 days of age with excellent long-term strength gain. Addition of the crystalline permeability-reducing admixture was found to reduce the rapid chloride permeability and hydraulic conductivity. To validate the applicability of the respective mixtures, a nonlinear finite element analysis was developed to estimate thermal stresses and cracking at the basement walls when subjected to environmental loads and thermal gain from the heat of hydration. It is concluded through the experimental and numerical efforts that the novel mixtures are capable of mitigating thermal and early-age shrinkage cracks.

Textile reinforcement in the bed joint of basement masonry – First findings from a current research project

AbstractThe successful structural verification of basement walls under earth pressure loading with light imposed loading is often difficult. This situation is often encountered for external basement walls under terrace doors, stairs, masonry light wells etc., where the theoretically necessary imposed loading is missing. This makes it impossible to resist the acting bending forces from earth pressure using a vertical arch model. In such cases, the earth pressure has to be resisted in a horizontal direction. Since however the bending moment capacity of unreinforced masonry parallel to the bed joint is low, another possibility is to use a textile‐reinforced bed joint with longitudinal fibres of alkali‐resistant glass or carbon fibre. With an appropriately adapted textile reinforcement in the bed joints, the masonry can fulfil the requirements for load‐bearing capacity against earth pressure with horizontal load transfer, even under a small imposed load. Textile reinforcement has the advantage above all of corrosion resistance compared to conventional steel reinforcement, and textiles can also be inserted into thin bed joints. The Chair of Structural Design in the Faculty of Architecture of the TU Dresden is currently carrying out extensive numerical and experimental studies for this purpose. The objective is to develop an optimal configuration of material and textile form for use as bed joint reinforcement. The investigations are concentrating on the tension strength, bonding and durability of the composite material ”textile mortar“. This report should give a brief overview of the state of the work in the currently running research project.

Room To Grow

The Victoria and Albert Museum, London’s renowned decorative arts and design museum, has unveiled a new, expansive underground exhibition gallery topped by an elegant courtyard. The need to maximize the gallery’s footprint while creating a tall, column-free space led to the use of extremely thin basement walls, a robust pile grid, and a roof strong enough to support extreme loading from both above and below. Complicating matters, the site features a high water table and adjacent buildings of great historic value.

A study of selected properties of autoclaved bricks.

This research investigated the possibility of using material with different share as an addition to prepare autoclaved bricks. Modifiers are searched, thanks to which the obtained materials will indicate potential suitability of modified products for exposure to activity of moisture and highly loaded building elements, e.g. basement walls. As the modifier was used: highly-efficient chemical agent of polymer, silicate and lithium compounds. The amount of water necessary to thicken the mixture was replaced by a modifier. Introduction of modifier in the form of chemical agent into lime-sand mixture causes the increase of the compressive strength by more than 4 MPa in relation to the reference sample, using 1% of additive. In each analyzed case it reduces the water absorption of finished products. The results of compressive strength and water absorption show different values after 21 days and 24 months from the autoclaving process, the longer the time from the moment of production of products, the better result. Regardless of the amount of applied modifier, the distribution of pores is presented in similar way, the number of macropores was noted at level of around 70%.

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ СВАЙНЫХ ФУНДАМЕНТОВ В РАСЧЕТНО-АНАЛИТИЧЕСКОМ КОМПЛЕКСЕ SCAD OFFICE

The article gives a comprehensive review of the main methods aimed at creating analytical and numerical models of slab-pile foundations in accordance with the present technical requirements using SCAD Office structural analysis software. Based on the example of a pile-and-slab foundation analysis, the authors compare the results which have been gained using analytical and numerical methods for two types of foundations, one of them has yield and the other one has rigid piling. Both foundations are ruggedized by basement walls. In order to determine the optimal analysis method for pile-and-slab foundation, three analytic methods of piling modeling are considered in accordance with SNiP 2.02.03-85 and SP 24.13330.2011. Besides, the authors have demonstrated the use of two numerical methods which are based only on the finite elements method for linear-elastic tasks solved using the widespread application sofware. The analytical modeling, which is regulated by standards, is carried out using the mathematical package SMath Studio. It is supposed that the complete analysis technology will use a standard mathematical package for import and export to and from the common data interchange format (DIF) in a structured view, which is acceptable for import and export in the SCAD system. A detailed description of the calculation technology is presented by the authors, thus indicating the applicability limits of these methods and recommendations for their use in static conditions. The demonstrated example testifies a fine precision of the considered methods. The research could be of great interest for designing engineers, university postgraduates and undergraduates.