Magento – How to add shipping rate according to weight

You cannot do that using the table rates.
The table rates will always use the last available value if there is no record in the taabase for a specific configuration.
What you can do is to create your own shipping method. This is not that hard.
See a tutorial here on how to do it..
The only thing you need to customize is the collectRates method in the shipping model.
Here is how it can look in your case.

public function collectRates(Mage_Shipping_Model_Rate_Request $request)
{
    // skip if not enabled
    if (!Mage::getStoreConfig('carriers/'.$this->_code.'/active')) {
        return false;
    }


    // this object will be returned as result of this method
    // containing all the shipping rates of this method
    $result = Mage::getModel('shipping/rate_result');
    $method = Mage::getModel('shipping/rate_result_method');
    $method->setCarrier($this->_code);
    $method->setCarrierTitle('Some title here');
    $method->setMethod($this->_code);
    $method->setMethodTitle($this->getConfigData('name'));
    //get qty in cart
    $qty = $request->getPackageQty()
    //calculate the price
    $price = 2 + $qty; //3 for 1 item, 4 for 2 items and so on. You can even insert here a calculation algorithm based on config values or what ever comes to mind.
    $method->setPrice($price);
    $result->append($method);
    return $result;

}

After spending a lot of time and testing I have the solution which ultimately Magento OOTB provides, Its just a matter for how to use it.

We can ship Bundle items separately. While creating bundle products use the following option.

Along with this, we have one more setting which is based on Clients’s business logic.

The Maximum package weight will always be 150 due to UPS limitation. “Packages Request Type” has two options

• Divide to equal weight (one request): If total cart weight is for eg. 180lb, ups will calculate the rate for 180/2=90lb and if for eg. for 90lb UPS says it will cost $100, the final cost will be $100*2 = 200. i.e. two packages of 90lbs each.

• Use origin weight (few requests): If cart weight is 180lbs with one child product of 50lb and other of 130lbs, UPS will calculate the separate rate for 130lbs and 50lbs package by sending two requests to API and sum them up. For eg. of 130lbs package costs $100 and 50lbs package cost $60 the final shipping cost will be $100+$60=$160. Let me know which is suitable in our case.