Concentration of earthquake Stresses in Structural Joints

Earthquake generates ground motion both in horizontal and vertical directions. Due to the inertia of the structure the ground motion generates shear forces and bending moments in the structural framework. In earthquake resistant design it is important ensure ductility in the structure, ie. The structure should be able to deform without causing failure. The bending moments and shear forces are maximum at the joints. Therefore, the joints need to be ductile to efficiently dissipate the earthquake forces. 

Most failures in earthquake-affected structures are observed at the joints. Moreover, due to the existing construction practice, a construction joint is placed in the column very close to the beam-column joint (fig. 1(a))

Figure 1 (a) Failure  at construction joint

This leads to shear or bending failure at or very close to the joint. The onset of high bending moments may cause yielding or buckling of the steel reinforcements.

Figure 1(b) Crushing of concrete

The high compressive stress in concrete may also cause crushing of concrete. If the concrete lacks confinement the joint may disintegrate and the concrete may spall (fig. 1(b,c)). All these create a hinge at the joint and if the number of hinges is more than the maximum allowed to maintain the stability of the structure the entire structure may collapse. If the shear reinforcement in the beam is insufficient there may be diagonal cracks near the joints (fig. 1(d)). This may also lead to failure of the joint.

Figure 1 (c) Spalling of concrete

Figure 1 (d) Diagonal shear crack

Bond failure is also observed, in case, lap splices are too close to the joints. Indian codes suggest methods that attempt to delay all these failures through a sound reinforcement detailing (IS 13920:1993). However, in many structures these details have not been followed due to perceived difficulties at site. In most of the structures in Gujarat lack of confinement and shear cracks have been found to be most common causes of failure. A rehabilitation and retrofitting strategy must alleviate these deficiencies from the structures.

How to Avoid Hurricane Damage?

Once an impending hurricane hits, there often is little that can be done. Luckily, there are preventative measures that you can take to protect your property against wind and water damage.

These steps range from those best left to professionals to those for do-it-yourselfers.

Before making structural changes to your property, check local building codes and keep in mind that not all homes require the same degree of storm protection. For example, areas with a high likelihood of hurricanes and other strong storms may benefit greatly from “hurricane straps,” while this may not be an advisable investment for other property owners.

Check with your local American Red Cross or other emergency management offices for information on the area’s flood elevation, which can help you determine how much water is likely to flow into your property.

Also, remember that homeowners insurance does not cover flooding, so it is important to purchase flood insurance. Note: It will be 30 days before the policy takes effect, so don’t wait until the storm warning appears.

Securing the Roof

High winds can cause your roofing structure to fail, if the sheathing is not properly installed.

Roofs are designed to transfer the force of high winds down to the foundation. If the roof sheathing is not nailed into the rafters or trusses of your roofing structure, then it can fail to perform as designed.

From the attic, examine the roofing boards for proper installation. When replacing your roof, make sure that the sheathing complies with the latest industry standards.

Check for proper bracing of your roof’s gables, the upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof. From inside the attic space, you should see X-shaped supports in these areas. If these supports are not in place, be sure to hire a contractor to brace them properly.

Hurricane straps, which are galvanized metal braces that keep the roof securely fastened to the walls of a home or building, are advised for properties in areas with a high hurricane risk. Installing braces should be left to a licensed professional.

Securing Windows and Doors 

Your property’s windows and doors must be properly braced to withstand the high winds of hurricanes, because, if breached, the resulting high pressure can cause serious damage to your walls and roofing structure. 

Protect your property’s vulnerable openings with storm shutters. They can be purchased for exposed windows, skylights, doors and other glass surfaces. They are available in steel, wood or aluminum. Their protection benefit can be mimicked with plywood. 

Also most bolts that come with your doors are not capable of withstanding the high winds associated with hurricanes. Reinforcing bolts to secure your doors to the top and bottom frame will ensure that your doors will be able to handle the storm.

While no amount of preparation can prevent all wind damage, you can count on the professionals at storm damage restoration Delaware to restore your property. 

Protecting Home Systems from Flooding 

Your electrical system can be ravaged by flooding. To minimize and prevent damage to this vital system, make sure that the main electrical panel board and all electrical outlets and switches are located at least 12 inches above the flood elevation for your area. If not, consider elevating all wire and service lines 12 inches above the flood elevation, but be sure that all electrical wiring is done be a licensed electrician. 

Electrically run units, such as washers, dryers, furnaces and water heaters, should be moved to a higher level or elevated at least 12 inches above the flood elevation, if possible. A base of concrete or pressure treated lumber that can hold the weight may be used to elevate the units. Consider building a flood wall around these units, if they cannot be relocated. 

To prevent floating and potential spills, anchor fuel tanks to the floor and be sure that vents and openings are above projected flood elevation. 

To protect your floor drain, install a float plug and a licensed plumber should put in a backflow valve to prevent sewage back up. 

Even after taking preventative measures to protect against flooding, water damage can result. When this happens, its best to call in the experts at flood damage restoration Delaware to remediate the situation.

Acid Washing Conrete 3.6

Concrete stain also waterproofs and protects the terrace. This do-it-your self project could possibly take two weekends to full in order to enable for sufficient drying time. Rent or invest in a pressure washer and clean up the work surface of the outdated concrete. Do a light acid wash to bond the new pavers to the present concrete. Increase muriatic acid one component to 10 parts mineral water. Spray on with a bug sprayer or use an old mop. Constantly use gloves and eye safety when utilizing chemicals. Wash the concrete with clean up normal water several times to clean the acid from the concrete.Now you really should locate the middle of the slab. Do this by measuring the sides or stringing two lines diagonally from corner to corner and marking the middle. Following, snap a chalk sections parallel to any structure you may well have up coming to the patio like a home or shed. Lay out tiles or rocks together this set to test the design. Adjust right up until it satisfies your tastes. If you're heading to use tile, use an outdoor grade tile. Usual tiles with a glossy place can become extremely slick in the rain. 

 

 

Blend normal water and latex additive appropriate for out-of-doors problems, with thin set mortar. Operate tiny locations at a time. Position tiles 1 at a time together the snapped range. Use tile spacer to preserve a continuous design. If you're employing rocks or slate, set up a pattern initial off to the side. Then as you move together transfer the routine together the thin established. Increase enough mortar to hold the rocks in position. Press tiles into site utilizing a rubber mallet to point every tile with the up coming. Use a extended point laid across the tiles to make positive just about every tile is place. Remove excessive mortar all-around the joints as you arrive to them.

Perform from the middle outwards as you spot the tile so you don't have to cross more than on them. Minimize tiles or slate with a tile wet saw and reduce stone with a cold chisel and hammer. Generally put on basic safety glasses when cutting tile or stone.

 

Combine sanded tile grout with outside sealant and distribute into the grooves with a sponge float. As it begins to established, use a fresh sponge and clear bucket of drinking water to wipe aside the grout. Modify the dirty standard water with thoroughly clean normal water as essential. Include grout in amongst stones with a margin trowel. Wipe away excessive grout with a wet sponge. 

A concrete terrace could possibly have a smooth, shiny floor that can make it slick when wet or that prevents paint or sealer from adhering. Acid washing also removes stubborn stains. Home improvement shops sell many acids for concrete etching: citric, phosphoric or muriatic. Select the safest that will get the employment accomplished. A home improvement shop could possibly also know of a reputable concrete cleaning service to do the work for you. Citric acid may perhaps not be strong enough for a extremely slick outdoor patio, but the strongest acid, muriatic, calls for cautious attention to wellbeing precautions.

W-EQ Coupling Dampers: A Unique Damper from Nippon Steel Engineering Co.

W-EQ Coupling Dampers are introduced at key locations instead of a number of coupling beams to add distributed viscous damping, which reduces wind and earthquake vibrations including accelerations, velocities and displacements (drifts) as well as the overall design forces. W-EQ Coupling Dampers lead to more efficient designs and increased safety and resilience against large hurricanes and earthquakes. 

It consists of multiple layers of viscoelastic material alternating between layers of steel plates with each consecutive plate extending out to the opposite side. The plates are then anchored into structural members using a number of different connection details. When the W-EQ Coupling Dampers are configured into the structural system (coupling beams, core walls and outriggers, amongst others) at strategic locations they can significantly increase the level of distributed damping of the building without occupying any architectural space.

 Full-scale tests of the W-EQ Coupling Damper- conducted for both wind and earthquake applications for realistic high-rise building load conditions

When viscoelastic material is deformed it provides a velocity-dependent viscous restoring force, which adds damping to the structure, as well as a displacement-dependent elastic restoring force. The W-EQ Coupling Dampers are placed horizontally between large structural walls which are extremely effective locations, because of the significant levels of shear distortions in the viscoelastic material caused by the relative motion of the walls under lateral vibrations. Also, because the W-EQ Coupling Dampers replace coupling beams they do not take up any valuable leasable space like traditional vibration absorbers.

Design Benefits 

 

Incorporating W-EQ Coupling Dampers can reduce structural materials over the height of the structure or an increase in the number of stories for a given structural configuration. As opposed to commonly used vibration absorbers, W-EQ Coupling Dampers do not take up valuable leasable space at the top of the structure and do not require monitoring, maintenance or tuning over the life of the structure to ensure adequate performance. W-EQ Coupling Dampers can also be used to reduce both wind and earthquake induced vibrations.

Positioning of W-EQ Coupling Damper

Performance against Seismic Vibrations 

W-EQ Coupling Dampers reduce earthquake induced vibrations through added damping to the lateral modes of vibration. W-EQ Coupling Dampers are capacity designed such that if predefined load levels are reached during an extreme seismic loading W-EQ Coupling Damper connecting elements act as structural fuse elements and prevent damage from occurring in adjacent structural elements. After an extreme earthquake, the W-EQ Coupling Dampers can be inspected and if the structural fuse elements were activated, they can easily be repaired or replaced. The W-EQ Coupling Dampers can enhance the dynamic performance significantly and decrease the time to occupancy or level of repair after an earthquake.

Seismic Vulnerability of Tipaimukh Dam

The Vajont dam, Italy: October 1963

An earth took place and reservoir of this dam began to fill One tremor set off landslides that plunged into the reservoir, creating a huge wave that overtopped the dam by 110 metres. About two minutes later, the town of Longarone was leveled and almost all of its 2,000 inhabitants killed. 

This example is mentioned to visualize the risk of constructing Tipaimukh Dam in the Brahmaputra valley and its adjoining hill ranges. Due to the colliding Eurasian (Chinese) and Indian tectonic plates, this region is seismically very unstable and the region has seen some major. Above example indicates that even the Tipaimukh Dam remain intact after earthquake the downstream may wash out.

Currently, the only mandatory risk assessment requirement is to conduct a ‘dam-break analysis’ which predicts the effects of flooding downstream, in case the dam actually breaks. Let us take the example of earthquakes. Currently the focus is only on whether the dam will withstand the earthquake. Occasionally, the issue of whether the water reservoir itself can induce seismic activity is discussed. While these are both very important aspects, they are not the only earthquake associated risks as far as dams are concerned.

Researchers in the Northeast have been highlighting overall impacts of earthquakes on river systems, which can increase risks to and from existing large dams. Dam engineers are quick to point out that a particular dam may survive a major earthquake, but even assuming that the actual structure is able to withstand a powerful tremor, quake-induced changes in the river system may have a serious impact on the viability of the project itself, as several basic parameters vis-à-vis the regime of rivers, and the morphology and behaviour of channels, may change. The last two major earthquakes in the region (1897 and 1950) caused landslides on the hill slopes and led to the blockage of river courses, flash floods due to sudden bursting of these temporary dams, raising of riverbeds due to heavy siltation, fissuring and sand venting, subsidence or elevation of existing river and lake bottoms and margins, and the creation of new water bodies and waterfalls due to faulting.

 Analysis of the available scientific data clearly indicates that the neotectonism of the Brahmaputra valley and its surrounding highlands in the eastern Himalayas has pronounced effects on the flooding, sediment transport and depositional characteristics of the river and its tributaries, which in turn has a bearing on the long-term viability of dams. The earthquake of 1950, for example, raised the bed level of the Brahmaputra at Dibrugarh by at least three metres (10 feet) leading to increased flood and erosion hazard potential in the river. Brahmaputra expert, Dr. Dulal Goswami, says: “A single earthquake event could cause sedimentation equivalent to several decades of normal sedimentation during the high flow period.” This could certainly render many of the proposed dams economically unviable as dam life is intricately connected with rates of sedimentation.

Seismic Performance of the Ceiling-Piping-Partition System

According to FEMA in the United States nonstructural systems represent 75% of the value of buildings exposed to earthquakes. The partial or full failure of such elements results economic loss. 

Among the various nonstructural systems, ceiling-piping-partition systems are widely used in many kinds of buildings and represent a major portion of nonstructural earthquake vulnerability. The project, Simulation of the Seismic Performance of Nonstructural Systems, was awarded after a nationwide competition among universities to conduct a NEES Grand Challenge project, and it will extend for five years.

Ceiling-piping-partition systems consist of several components and subsystems, have complex three-dimensional geometries and complicated boundary conditions because of their multiple attachment points to the main structure, and are spread over large areas in all directions. Their seismic response, their interaction with the structural system they are suspended from or attached to, and their failure mechanisms are not well understood. Moreover, their damage levels and fragilities are poorly defined due to the lack of system-level experimental studies and modeling capability. 
 

Nonstructural Systems: Ceiling-Piping-Partition Systems

Network for Earthquake Engineering Simulation (NEES) research program of the National Science Foundation has recently awarded to the University of Nevada, Reno a $3.6 million Grand Challenge grant to study the seismic performance of ceiling-piping-partition nonstructural systems. This Grand Challenge project will integrate multidisciplinary system-level studies that will develop, for the first time, a simulation capability and implementation process for enhancing the seismic performance of the ceiling-piping-partition system. A comprehensive experimental program is proposed that will use the University of Nevada, Reno (UNR) and the University at Buffalo (UB) NEES Equipment Sites to conduct subsystem and system-level full-scale experiments.

Integrated with this experimental effort will be a numerical simulation program that will develop experimentally verified analytical models; establish system and subsystem fragility functions; and, develop visualization tools that will provide engineering educators and practitioners with sketch-based modeling capabilities. Public policy investigations at the building and metropolitan level scales are designed to support the implementation of the research results.

Design Consideration for Standpipe and Hose System in Fire Protection System

In multi-story buildings a type of rigid water piping is provided to connect fire hoses. Within buildings these pipes serve the same purpose of fire hydrants. This system allows manual application of water to the fire. Dear readers, these pipe is called Standpipe. In this post I shall discuss Design consideration for Standpipe and Hose System 

1.The fire protection system shall be designed for their effective use either by amateur or trained fire fighting personnel or both. 

Building Type	Sprinkler System (l/min)*	Standpipe and Hose system (l/min)*	Duration** (min)
Light hazard - I	1000	1000	30
Light hazard - II	1900	1900	50
Ordinary hazard - I	2650	1900	75
Ordinary hazard - II	3200	1900	75
Ordinary hazard - III	4800	1900	75
Notes:
* Values will be for one riser serving floor area of 1000 m2. **These duration shall be for a building up to the height of 51 m. For greater height of 51-102 m and  above 102 m, the duration will be 1.25 times and 1.5 tomes of the specified values respectively.
Light hazard – I          : Occupancy groups, A1, A2, A4 Light hazard – II        : Occupancy groups, A3, A6, A8, B, C, D, E4, E7, F1 & F2 Ordinary hazard – I   : Occupancy groups, E1, E3, E5, F3, F4, F5, F6, F7, G1 & G4 Ordinary hazard – II  : Occupancy groups, G2 & H1 Ordinary hazard – III : Occupancy groups, G3 & H2 Extra hazard : Occupancy groups, j – pressure and flow requirement for this group shall be determined by Fire Department but shall not be less than required value for Ordinary hazard-III

2. All standpipes in standpipe system shall be sized so that they will provide a minimum flow specified in Table-1. In standpipe system with more than one standpipe, the supply piping shall be sized for the minimum flow specified in Table-1 for the first standpipe plus 1000 litre per minute for such additional standpipe. The total number of such additional standpipes shall not be more than 8. All standpipe risers shall be connected through a gate valve with a main of size equal to that of the largest riser. 

3. The minimum pressure for standpipes supplying a 50 mm or larger hose shall be at least 300 Kpa. For standpipe supplying first aid hose (38 mm nominal) may have a minimum pressure of 200 Kpa. 

4. The size (diameter) of stand pipes for various building height may be as shown in Table -2 or hydraulically designed to provide the required flow and pressure, stated above, at the topmost outlet.

Table-2 : Standpipe Sizes

No. of Storeys	Building Height(m)	Size of Stand pipe(mm)
Up to 5	UP to 17	75*
Up to 10	UP to 33	100
10 to 20	33 to 63	150
20to 54	63 to 65	200
*These pipe may be used only for occupancy groups A1, A2 and A4

5. The water supply required for combined system (for partial automatic sprinkler and Fire Department hose) shall be calculated in accordance with (2) above plus an amount equal to the hydraulically calculated sprinkler demand or 550 litre per minute for light hazard occupancy groups or 1900 litre per minute for ordinary hazard occupancy groups. 

Table-3 : Piping for Standpipe System

Materials	Standard
Copper Tube	ASTM B75, ASTM B88
Copper and Copper-Alloy Tube	ASTM B251
Steel Pipe	ASTM A55, ASTM A120, ASTM A135
Wrought Steel or Iron	ANSI B36.10

6. The size of combined system shall be at least 150 mm or hydraulically designed to provided the required flow (5) and pressure. 

7. The standpipe shall be located in noncombustible enclosure such that it will be able to provide hose stream to the most remote area of the floor served. 

Table-4 : Standpipe Fittings

Materials	Standard
Cast Iron	ANSI 616.1, ANSI B 16.4
Copper	ANSI B16.18, ANSI B16.22
Malleable Iron	ANSI B16.3
Steel	ANSI B16.5, ANSI B16.9, ANSI B16.11, ANSI B16.25, ASTM A234

8. The hose shall be connected to the standpipe within 1.5 m from the floor. Hose stations shall be easily accessible for inspection and testing.

Proposed Foundation System for So called Mile-High Tower : Tallest Building of the World to Come

The upcoming tallest building of the world is the Kingdom Tower to be built in Jeddah, Saudi Arabia. Initially building was planned to stand one mile (1.6 km) high and be called the Mile-High Tower. But the geotechnical investigation suggested the proposed area could not support a building of such height. So the building was scaled down to 0.62 miles (one kilometer) tall, which will still allow it to overshadow the 2,717 ft. (828 m) Burj Khalifa to claim the title of the world's tallest building.

Designs for the foundation were in place by early August and the contract for the piling with Langan International was being tendered. On 16 August 2011, Langan officially announced their involvement and that the foundation and piling had to be uniquely designed to overcome subsurface issues such as soft bedrock and porous coral rock, which normally could not support a skyscraper without settling. 

Kingdom Tower:The World Tallest Tower

The foundation will be similar to that of the Burj Khalifa, but larger. It is expected to be around 60 metres (197 ft) deep with a concrete pad of around 7,500 m2 (80,729 sq ft). The concrete will have to have low permeability to keep out corrosive salt water from the Red Sea, its depth and size is also considered to be an indicator of what the tower's final height will be.

Sky Terrace of Kingdom Tower: 30 m (98 ft) diameter outdoor balcony at 157 floor level

 The piles will be up to 200 metres (656 ft) deep and the pad over 300 feet (91 m) across, yet even still the building, which will weigh over 900,000 tons, is expected to settle. The idea is that it settles evenly enough so that the building doesn't tip or put undue stress on the superstructure. Computer modeling programs performed tests at the site to confirm that the foundation design would work.